Compressor module, compressed-air supply system, method for operating a compressor module or a compressed-air supply system
Patent Information
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2024-04-24
- Publication Date
- 2026-03-18
AI Technical Summary
Compressor modules in compressed air supply systems for vehicles face challenges in maintaining efficient and reliable operation across varying operating conditions, particularly in rare high-load scenarios, where current consumption exceeds safe limits, risking electrical system overload.
A compressor module with a speed-controlled brushless electric motor, where the target speed is adjusted based on current consumption, maintaining a constant speed until maximum current is reached, then reducing speed to limit torque and current, using an electronic control unit to manage motor current and optimize performance.
This approach ensures the compressor module operates within safe current limits, maintaining performance across different load conditions while preventing electrical system overload, ensuring reliable and efficient compressed air supply.
Smart Images
Figure EP2024061316_14112024_PF_FP_ABST
Abstract
Description
[0001] Compressor module, compressed air supply system, method for operating a compressor module or a compressed air supply system
[0002] The invention relates to a compressor module, in particular for a compressed air supply system for a vehicle. The invention also relates to a compressed air supply system and a method for operating a compressor module or a compressed air supply system.
[0003] In motor vehicles, compressed air supply systems can, for example, supply compressed air to an air suspension system as a compressed air consumer and / or a pneumatic braking system as a compressed air consumer. In order to provide compressed air at a sufficiently high pressure for such compressed air consumers, compressors are required to generate compressed air. Such compressors are typically driven by electric motors that draw current during operation. Compressors and compressors are used synonymously in this description and refer to units that compress air. A compressor can be combined with a driving electric motor to form a compressor module as a structural unit.
[0004] In addition to the compressed air consumer(s), the compressor and its drive, key components of a compressed air supply system are electrically controllable valves that can be controlled by a compressed air controller – i.e., opened or closed. In this way, compressed air can be supplied to or released from the individual compressed air consumers in a compressed air supply system in a targeted manner. Depending on which compressed air consumers need to be supplied with compressed air in a given operating situation, the compression work to be performed by the compressor can vary greatly. As explained in more detail below, the torque delivered by the drive of the compressor depends on the compressed air pressure required for the respective operating situation.If the compressor or condenser is driven by an electric motor, its current consumption depends on the torque to be delivered (i.e. the operating load of the drive) at the supply voltage typically provided by the vehicle's electrical system.
[0005] Preferably, the compressor and the associated drive, in particular the associated electric motor, are combined into a single structural unit—hereinafter referred to as the compressor module. Compressor modules are used, for example, for compressed air supply systems in motor vehicles.
[0006] Brushless DC motors (BLDC motors: Brushless Direct Current motors) are preferably used as electric motors for driving compressors or condensers. A brushless DC motor, as a so-called internal rotor, typically has a stator equipped with electromagnetic coils, a rotor equipped with permanent magnets, and motor electronics. The motor electronics are configured as an electronic commutator in such a way that the motor electronics controls the power supply to the stator coils (hereinafter also referred to as stator coils) via power switches in such a way that the stator coils are periodically supplied with power in turn, creating a rotating magnetic field that, via magnetic forces, causes the synchronous rotation of the rotor equipped with permanent magnets.Such brushless DC motors with rotors fitted with permanent magnets are therefore also referred to as PMSM motors, where PMSM stands for permanent magnet synchronous motor. The abbreviation PMSM is typically used for sinusoidally commutated brushless electric motors, while the abbreviation BLDC (brushless direct current) is usually used for block-commutated brushless electric motors. With block commutation, the current supply to the (e.g. three or n times three) stator coils is digitally switched, i.e. either no current or the full current is supplied to the windings of the respective stator coil or stator coils of a phase. With sinusoidal commutation, each stator coil of the motor is supplied with a sine wave offset by 120°, resulting in a continuously rotating stator magnetic field of constant strength.
[0007] For the conventional speed control of a brushless electric motor, the motor is equipped with rotor angle detection devices, which include electronic sensors such as Hall sensors for detecting the rotor position. This also allows the phase angle between the applied rotating field and the mechanical rotation of the rotor to be detected, and the phase angle of the rotating field can be adjusted accordingly. BLDC motors thus behave similarly to mechanically commutated DC motors. However, brushless DC motors are more efficient, subject to less wear, and can be better controlled in terms of speed than electric motors with a brush commutator.
[0008] In compressor modules for compressed air generation in a compressed air supply system, for example, for motor vehicles, the compressor generating the compressed air and its electric motor, which serves as its drive, form a single structural unit. For both efficient and environmentally friendly operation, the design and operation of the electric motor – i.e., the brushless DC motor – pose a particular challenge. This includes, among other things, the compressor module's ability to provide sufficient compressed air to the respective compressed air supply system at all times, in all possible operating scenarios – even the rare ones. This means that a compressor module must provide sufficient compressed air for the compressed air supply system even under unfavorable conditions, which only occur rarely (high-case operating scenario).For this purpose, the drive, preferably a brushless DC motor, must also be designed accordingly. For a given DC motor's supply voltage, a higher mechanical load—i.e., a higher mechanical output power—inevitably leads to a higher current consumption of the DC motor. However, to protect a motor vehicle's electrical system, the maximum current consumption of a DC motor must be limited.
[0009] From WO 2020 / 225024 A1 it is known to operate a BLDC motor for driving a compressor at a constant speed and to reduce this speed depending on the load conditions of operating voltage and load (torque) in order to avoid over-dimensioning of the motor.
[0010] The invention is based on the object of ensuring reliable and environmentally friendly operation of a compressor module in the simplest possible way.
[0011] To achieve this object, the invention proposes a compressor module, in particular a compressor module for a compressed air supply system, in particular for a motor vehicle, which has at least the following components: a compressor and a speed-controlled brushless electric motor for driving the compressor, during the operation of which a motor current occurs and to which motor electronics with an electronic commutator and speed control are assigned, wherein the speed control during operation is carried out on the basis of a predetermined target speed.
[0012] The compressor module is connected to or has an electronic control unit. The electronic control unit can be provided separately or be part of the motor electronics and is designed according to the invention to specify the target speed as a function of a motor current currently consumed by the speed-controlled brushless electric motor and a predetermined maximum motor current such that the target speed corresponds to a predetermined constant speed as long as the motor current currently consumed by the speed-controlled brushless electric motor is smaller than the predetermined maximum motor current (ie n Soii = nconst, if IB < Iß max) and the setpoint speed is adjusted such that the motor current currently drawn by the speed-controlled brushless electric motor corresponds to the specified maximum motor current, as long as the motor current currently drawn by the speed-controlled brushless electric motor at least approximately corresponds - i.e., within the scope of the control or follow-up accuracy - to the specified maximum motor current (nvariabei, if IB = IB max). The variable setpoint speed is smaller than the specified constant speed.
[0013] This means that the drive motor of the compressor module, ie the brushless electric motor, operates with the - or with one of several possible - constant speed as the target speed (n Soii = nconst) as long as the current motor current IB is less than the specified maximum motor current. As soon as the value of the current intensity of the current motor current reaches or exceeds the specified maximum motor current, a current limiter takes effect which causes the speed of the brushless electric motor to decrease so that the load, i.e. the torque to be delivered by the brushless electric motor, is just large enough that the specified maximum motor current Iß max is not exceeded. This is because increasing back pressure on the pressure side of the compressor leads to increasing torque and thus to increasing motor current at constant speed, and with a speed that decreases in line with the increasing back pressure, the torque and thus the motor current can be kept constant.
[0014] Advantageous further developments of the invention, in particular of the power circuit arrangement, can be found in the subclaims and specify in detail advantageous possibilities for realizing the concept explained above within the scope of the task and with regard to further advantages.
[0015] Preferably, the brushless electric motor is speed-controlled. Preferably, a predetermined target speed for the brushless electric motor remains constant as long as the current average motor current IB is less than or equal to the predetermined maximum motor current. The target speed then corresponds to one—possibly one of several—predetermined speeds.
[0016] Preferably, the speed of the brushless electric motor is continuously adjusted according to a predefined characteristic curve or a given characteristic map depending on the load when the currently drawn average motor current IB reaches the predefined maximum motor current. Since the load, i.e., the torque to be generated by the brushless electric motor, depends on the pressure at the compressor outlet, a characteristic control can be configured such that, for a pressure as the input value, it provides a speed setpoint (here also referred to as the target speed) as the output value. If a characteristic map control is provided for the target speed, this target speed can be specified depending on several input parameter values.In addition to values for the pressure in the compressed air supply system, input parameter values can also be, for example, values for the parameters geodetic height and / or the outside air temperature, since the air density and thus also the air masses to be conveyed depend on these parameters.
[0017] In an alternative development, the brushless electric motor is current-controlled when the currently drawn average motor current IB reaches the specified maximum motor current Iß max and would exceed it at a constant speed. The setpoint for the motor current Isoii is then Iß max. This means that the brushless electric motor always delivers its maximum possible power without the average motor current IB exceeding the maximum motor current Iß max - with the exception of minor excesses within the scope of control accuracy. The brushless electric motor is current-controlled as long as the current speed nß of the brushless electric motor is lower than the specified constant speed (IB = Iß max as long as nß < nconst). The motor current used to control the speed is preferably an average motor current that is time-averaged and / or low-pass filtered in order to compensate for cyclical fluctuations in the motor current or short-term peaks in the motor current.
[0018] The control of the setpoint speed in one case (IB < Iß max) as well as the control of the motor current in the other case (ns < nconst) can be continuous, time-discrete or quasi-continuous.
[0019] The compressor module is preferably a component of a compressed air supply system, in particular a compressed air supply system for a motor vehicle. A further aspect of the invention thus relates to a compressed air supply system, in particular a compressed air supply system for a motor vehicle, with one or more compressed air consumers,
[0020] Compressed air lines, electrically controllable valves, a compressed air control for controlling the electrically controllable valves, a compressor module of the aforementioned type with a compressor or condenser and a brushless electric motor as drive, and preferably a pressure accumulator.
[0021] In a design variant with a compressed air reservoir, the compressed air consumer(s) are or can be pneumatically connected to the compressor(s) and / or the pressure reservoir via the compressed air lines and the electrically controllable valves in such a way that the compressed air supply system can be operated either in an open operating mode or in a closed operating mode. In such a compressed air supply system, the work to be performed by the compressor module—i.e., the torque to be delivered—can be reduced by, for example, switching from the closed to the open operating mode. This may allow the specified constant speed to be maintained for longer. In this respect, control of the brushless electric motor can be combined with a switching of the operating mode.
[0022] The compressed air control preferably has a current signal input connected to at least one current sensor configured to detect a motor current drawn by the electric motor driving the compressor and output a signal representing this current to the compressed air control. The current sensors of the motor electronics typically provided for each phase can serve as current sensors. The average motor current can be determined by the motor electronics on the compressor module or by the compressed air control. For example, the motor electronics can determine the average motor current from the three measured phase currents. Alternatively, an additional current sensor could also be provided.
[0023] The control signals to be output by the compressed air control system can be, for example, a target speed for a speed controller of the electric motor or control signals for activating or deactivating valves of the compressed air supply system according to an open or closed operating mode.
[0024] To specify a constant speed as the target speed for the brushless electric motor as long as the average motor current is less than the maximum motor current, the compressed air control system can be connected to a target speed data memory in which several predefined speed values are stored. The predefined fixed number of speeds is advantageous for improving acoustic behavior. These speeds can be set to operating points that provide good acoustic and / or pneumatic performance.
[0025] For a characteristic curve control or a characteristic map control of the speed in the case in which the average motor current would exceed the maximum motor current at a predetermined constant speed, a characteristic curve memory or a characteristic map memory is preferably provided.
[0026] The compressed air control can be designed to evaluate a current signal, the value of which represents the value of the current motor current IB, and, in the event that the current motor current reaches the predetermined maximum motor current, to determine a reduced target speed value such that the average motor current consumed by the brushless electric motor driving the compressor or condenser does not exceed the maximum motor current, but corresponds to the maximum motor current within the scope of a control accuracy.
[0027] Preferably, the compressed air control is designed to evaluate a current signal, the value of which represents the value of the current motor current IB, and, in the event that the current average motor current reaches the predetermined maximum motor current, to determine a reduced target speed value as a function of a pressure measured in the compressed air supply system using a stored characteristic curve or a stored characteristic map.
[0028] In addition, the compressed air control can be designed either to control the electrically controllable valves according to the open operating mode of the compressed air supply system when the current motor current is greater than or equal to the specified maximum value for the motor current, or to control the electrically controllable valves according to the closed operating mode of the compressed air supply system when the current motor current is less than the specified maximum value for the motor current.
[0029] Another aspect of the invention is a method for operating a compressor module. The method comprises the following steps:
[0030] Determining a target speed for the speed of the speed-controlled brushless electric motor in such a way that the target speed corresponds to a predetermined constant speed, as long as the motor current IB currently drawn by the speed-controlled brushless electric motor is less than the predetermined maximum motor current (if IB < Iß max) and the target speed is tracked in such a way that the motor current IB currently drawn by the speed-controlled brushless electric motor corresponds to the predetermined maximum motor current, as long as the motor current currently drawn by the speed-controlled brushless electric motor corresponds at least approximately (i.e. within the scope of the control or follow-up accuracy) to the predetermined maximum motor current (nsoii red < nconst, if IB = IB max).
[0031] The method preferably comprises determining a reduced target speed value as a function of a pressure measured in the compressed air supply system using a stored characteristic curve or a stored characteristic map if the current average motor current reaches the specified maximum motor current. The invention allows the brushless DC motor to be designed for a constant speed as standard. According to the invention, exceeding the permissible current consumption (usually 35 A) of the compressor or condenser is prevented by continuously or quasi-continuously adjusting the target speed by continuously adjusting the target speed when the permissible current consumption (ieThe compressor's or condenser's current (the specified maximum motor current) is continuously or quasi-continuously adjusted so that the actual motor current consumed corresponds to the specified maximum motor current, as long as this does not result in a target speed that is higher than the specified constant speed. For this purpose, the current current consumption of the brushless electric motor driving the compressor is determined.
[0032] In a preferred embodiment, the compressed air collector is an air suspension system of a vehicle which has one or more bellows.
[0033] Preferably, the compressor or compressor with the brushless electric motor are combined into a structural unit in the form of a compressor module and are thus optimally coordinated with each other on the one hand and easy to integrate as a unit into a compressed air supply system on the other.
[0034] The speed-controlled electric motor is preferably a speed-controlled BLDC motor, which is given at least one target speed during operation.
[0035] A further aspect relates to a method for operating a compressed air supply system, in particular for a motor vehicle, comprising: one or more compressed air consumers,
[0036] Compressed air lines, electrically controllable valves, a compressed air control for controlling the electrically controllable valves, a compressor module of the aforementioned type, with a compressor or condenser and a brushless electric motor as drive, and preferably a pressure accumulator.
[0037] According to this method, switching from a closed operating mode to the open operating mode occurs when the motor current IB absorbed by the electric motor driving the compressor or condenser reaches or exceeds the maximum motor current.
[0038] Additionally or alternatively, the operating method may include evaluating the current signal, the value of which represents the value of the current motor current, and, in the event that the current motor current reaches the predetermined maximum motor current, determining a reduced target speed value such that the motor current consumed by the speed-controlled electric motor driving the compressor or condenser does not exceed the maximum motor current, but corresponds to the maximum motor current within the scope of a control accuracy.
[0039] Embodiments of the invention are now described below with reference to the drawing. These are not necessarily intended to represent the embodiments to scale; rather, where useful for explanation, the drawing is schematic and / or slightly distorted. With regard to additions to the teachings immediately apparent from the drawing, reference is made to the relevant prior art. It should be noted that numerous modifications and changes to the form and detail of an embodiment can be made without deviating from the general idea of the invention. The features of the invention disclosed in the description, in the drawing and in the claims can be essential for the further development of the invention, both individually and in any combination.Furthermore, all combinations of at least two of the features disclosed in the description, the drawings and / or the claims fall within the scope of the invention. The general idea of the invention is not limited to the exact form or detail of the preferred embodiment shown and described below, or limited to an object that would be limited compared to the object claimed in the claims. For specified dimensioning ranges, values lying within the stated limits are also intended to be disclosed as limit values and can be used and claimed as desired. Further advantages, features and details of the invention will become apparent from the following description of the preferred embodiments and from the drawings, which show:
[0040] Fig. 1 is a circuit diagram of an example of a compressed air supply system including compressed air receiver in the form of air springs of a vehicle;
[0041] Fig. 2 Symbols for the valves shown in Fig. 1 to explain their operation;
[0042] Fig. 3 is a schematic block diagram of an electronic compressed air control system;
[0043] Fig. 4 a compressor module with compressor, electric motor and motor electronics;
[0044] Fig. 5 is a sketch illustrating the operation of a brushless electric motor;
[0045] Fig. 6 Diagrams illustrating the increase in current consumption of a DC motor with increasing back pressure
[0046] Fig. 7 is a symbolic representation of a compressor and a brushless electric motor with motor electronics driving it; and Fig. 8 is a diagram illustrating the target speed specification as a function of the motor current IB and the specified maximum motor current IB max.
[0047] The compressed air supply system 30 shown in Fig. 1 serves, for example, to supply compressed air to an air suspension system 32 comprising a plurality of air springs 34 of a vehicle. Instead of an air suspension system 32, other compressed air consumers, e.g., an air brake system, can also be pneumatically connected to the compressed air supply system 30.
[0048] The term "compressed air pickup" is used herein both for an entire air suspension system 32 or compressed air brake system and for individual bellows 34 of an air suspension system 32 or compressed air brakes of an air brake system, i.e. for any form of compressed air pickup.
[0049] Essential components of the compressed air supply system 30, in addition to the compressed air consumers 34, are a compressor or compressor 12 and its drive 14, as well as electrically controllable valves 44, 46, 48, 50, 52, and 54, which can be controlled—for example, opened or closed—by a compressed air control 56. In this way, compressed air can be specifically supplied to the individual compressed air consumers 34, or compressed air can be released. Depending on which of the compressed air consumers 34 needs to be supplied with compressed air in a given operating situation, the compression work to be performed by the compressor 12 can vary greatly. The compressed air control 56 is an electronic control system that outputs electrical control signals S1, S2, Sn to activate the individual electrically controllable valves, thus controlling the compressed air supply system 30.
[0050] To increase efficiency and ensure consistent availability, so-called "closed air spring systems" are used in car air spring systems. These are air spring systems that can be operated, for example, with a compressed air supply system 30, as shown in Figure 1, because the compressed air supply system 30 has components such as a pressure accumulator 36, which enables both an open operating mode and a closed operating mode. In contrast to "open systems" or an open operating mode, in the closed operating mode the air mass in the air springs is not reduced by venting the excess air into the environment; rather, this air is pumped into the pressure accumulator 36 using the compressor 12. The compressor 12 required for this is preferably designed for two-stage compression and driven by a BLDC motor 14.The closed operating mode by pumping is achieved via the second stage 12.2. In the open operating mode, the compressor 12 operates in two stages, with pre-compression via the first stage 12.1 and final compression via the second stage 12.2.
[0051] In order to enable a closed operating mode, the compressed air supply system 30 in the illustrated embodiment has, in addition to the pressure accumulator 36, also a return valve 48, a reservoir valve 52, a separation valve 44 and a boost valve 54.
[0052] The return flow valve 48 is pneumatically arranged between the compressed air consumer 32 and the compressor 12 such that, when the return flow valve 48 is activated - i.e., open - compressed air can flow from the compressed air consumer 32 into a boost and return flow line 76 leading to the compressor 12.
[0053] The reservoir valve 52 is pneumatically arranged between the pressure accumulator and a pneumatic main pressure line 40 such that when the reservoir valve 52 is activated - i.e. open - compressed air can flow from the pressure accumulator 36 into the pneumatic main pressure line 40.
[0054] The boost valve 54 is pneumatically arranged between the pressure accumulator 36 and a boost and return line 76 such that, when the boost valve 54 is activated—i.e., open—compressed air can flow from the pressure accumulator 36 into the boost and return line 76, which leads to the compressor 12. This allows the compressor 12 to recompress the compressed air extracted from the pressure accumulator 36 during closed operation before it is supplied to the compressed air consumer 32.
[0055] The separation valve 44 is pneumatically arranged between the main pressure line 40 and the air suspension system 32 in such a way that, when the separation valve 32 is activated - i.e., open - compressed air can flow from the main pressure line 40 into the air suspension system 32.
[0056] Due to the required compressor power or the delivery capacity derived therefrom, the torques required to drive the compressor 12 in the closed operating mode differ significantly from the torque required for the open operating mode.
[0057] As already indicated, the compressed air supply system 30 shown in Fig. 1 can be operated in an open operating mode or in a closed operating mode. In the open operating mode, outside air is drawn in from the environment and compressed (see the dashed arrow in Fig. 1), and in the closed operating mode, air is drawn from a pressure vessel 36—also referred to here as a reservoir—and compressed (see the dotted arrow in Fig. 1).
[0058] While the current consumption of the compressor drive—that is, the current consumption of the DC motor 14—(which is proportional to the required torque) is below approximately 25 A in open mode, it can rise to 50 A and more in closed mode. The closed mode is therefore the mode with the highest torque and current requirements. Both modes must be available in a vehicle.
[0059] The compressor module The compressor module 10 shown in Fig. 4 is intended for use in the compressed air supply system 30, as shown by way of example in Fig. 1 using a circuit diagram. The compressor module 10 is designed as a structural unit comprising compressor 12, electric motor 14 and motor electronics (16, see Fig. 7; not shown in Fig. 4; typically flanged directly to the electric motor 14) as well as other components such as air dryer 18 and air distributor 20, etc.
[0060] Fig. 5 shows a sketch of the stator and rotor of a brushless DC motor. The sketched brushless DC motor 14, as a so-called internal rotor, typically has a stator 14.1 equipped with electromagnetic coils, a rotor 14.2 equipped with permanent magnets, and motor electronics 16 (see Fig. 6). The motor electronics 16 are configured as an electronic commutator such that the motor electronics 16 controls the current supply to the stator coils 14.3 of the stator 14.1 via power switches and terminals A, B, and C such that the stator coils 14.3 are periodically supplied with current in turn such that a rotating magnetic field is produced, which, via magnetic forces, causes a synchronous rotation of the rotor 14.2 equipped with permanent magnets.
[0061] For the known speed control of the brushless electric motor 14, the motor comprises means for detecting the rotor angle, e.g., a Hall sensor 14.4 for detecting the rotor position. This also allows a phase angle between the applied rotating field and the mechanical rotation of the rotor 14.2 to be detected, and the phase angle of the rotating field to be adjusted accordingly. Thus, the BLDC motor 14 behaves similarly to a mechanically commutated DC motor. However, as a brushless DC motor, it is more efficient, subject to less wear, and can be better speed-controlled than electric motors with a brush commutator. To generate the rotating field by periodically energizing the stator coils 14.3 via terminals A, B, and C, the motor electronics 16 is provided, which functions as an electronic commutator; see Fig. 7.
[0062] The speed of the electric motor 14 is also controlled in a manner known per se via the motor electronics 16. For this purpose, the motor electronics 16 is given a target speed n S oii. To specify the target speed n S An electronic control unit 100 is provided for the speed-regulating motor electronics 16, to which a value for the average motor current is supplied from the motor electronics 16 or which is connected to a current sensor 102 that detects the respective motor current consumed by the electric motor 12 during operation. The electronic control unit 100 can also be part of the motor electronics 16 and is then at least indirectly connected to the current sensors 102 of the motor electronics 16 anyway.
[0063] The current consumption of the electric motor 12 can be calculated by the motor controller 16 from the measured phase currents or measured directly using the current sensor 58 or 102. In the first case, three current sensors 102 are required, which are necessary anyway for operational reliability. In the second case, an additional current sensor 58 is required in the supply branch (see Figure 1). Therefore, the variant without a separate current sensor 58 is preferred.
[0064] Compared to an unregulated DC motor, regulated, brushless DC motors offer the advantage that their speed can be continuously adjusted without additional design effort. The commutation of a brushless DC motor is electronic, whereas a DC motor with a brush-commutator system is mechanically commutated. For acoustic reasons, air spring systems require a constant speed across the entire specified load range (voltage, back pressure and boost pressure, temperature, geodetic altitude), which favors the use of a regulated DC motor.
[0065] The disadvantage of the speed specification is that the requirement of n=const results in a motor current that increases with the torque, which in individual cases can even exceed the defined maximum limit of, for example, 35 A. To comply with the maximum permissible current consumption, the compressor would have to be designed such that the current consumption is never exceeded under worst-case operating conditions within the specified application cases. One such scenario could be a loaded vehicle, twisted over terrain.
[0066] It is proposed to design the motor for a constant speed by default, and to reduce the required drive power of the compressor if the permissible current consumption (usually 35 A) is at risk of being exceeded. To this end, a compressor current consumption is predicted that is required to achieve a target state of the compressed air consumer. If the defined limit is at risk of being exceeded, a target speed and / or an operating mode (open or closed) is specified in advance, at which the maximum motor current is not exceeded until the target state of the compressed air consumer defined by the demand signal is reached.
[0067] Typically, the pneumatic performance of a compressor for an air suspension system is designed for the most common operating point. For example, a flow rate of 130 l / min at 11 bar boost pressure and 11 bar back pressure is required. The maximum current consumption of 35 A, however, applies across all operating ranges (operating and ambient pressures, voltages).
[0068] To avoid over-engineering the electric motor, it is designed for a current consumption of approximately 30 A at the specified operating point (taking into account device variations, service life influences, and slightly higher operating loads). Particularly in turbocharged operation, a sharp increase in the required drive power or current beyond 35 A (current ~ torque) is observed with increasing backpressure.
[0069] In the example shown in Fig. 6, the current increases by more than 2 A per bar of back pressure. A remedy would be to design the compressor module 10 in such a way that no current is exceeded in the defined, rather rare worst-case operating points. However, this has the disadvantage that the compressor module 10 exhibits a correspondingly reduced, non-specified performance in the frequently encountered operating ranges. A required flow rate of, for example, 130 l / min at 11 bar of inlet pressure and 11 bar of back pressure cannot be achieved in this case. The problem is exacerbated by device variation and service life influences. To avoid the high currents, the speed of the BLDC motor can be reduced. However, due to the proportionality of speed and current, this may result in an excessive, necessary speed reduction. For example, if the current consumption is to be reduced from 60 A to 35 A, the speed would have to be reduced to 58% of the original, from, for example, 2850 rpm.-1 to below 1700 min -1 This significant reduction in speed can lead to undesirable effects on airborne and structure-borne noise.
[0070] One approach is to operate the BLDC motor at a constant speed and, to avoid oversizing the DC motor, reduce this speed under certain load conditions (operating voltage and load). With correct design and correct consideration of all nominal conditions, the maximum current of, for example, 35 A will not be exceeded. However, this requires that all current-influencing factors, such as component tolerances and operating temperatures, are considered in the form of worst-case assumptions, and that the resulting early switch to a lower speed (including the resulting performance reduction) is acceptable.The aim was therefore not to design the compressor module for the rare worst-case conditions, but instead to provide a design according to the most common operating conditions in combination with a current limitation to ensure the specified current limits in conjunction with situationally maximum compressor performance.
[0071] The requirement for constant compressor speed leads to an increasing current consumption with increasing compressor drive torque (which is proportional to the required motor torque):
[0072] Formula: M x 2n xn = -qx U x I with:
[0073] M = Compressor drive torque (is constant at constant pressure) n = Compressor speed (is determined according to conventional control strategy at
[0074] BLDC kept constant)
[0075] T = efficiency
[0076] U = supply voltage (specified, between 9V and 16V as required)
[0077] / = Motor current (usually limited to 35A)
[0078] Measurements have shown that the motor current consumption of a supercharged compressor used in car air suspension systems can increase by more than 2 A / bar back pressure. Thus, when designed for the nominal point of 11 bar boost pressure and 11 bar back pressure at I = 30 A, a back pressure of only 13.5 bar would be permissible (which would then no longer cover the entire required operating range up to 18 bar, for example). Further reductions can result from: manufacturing-related device variations, running-in effects
[0079] Wear Environmental conditions Self-heating
[0080] The compressor module is advantageously designed so that it can perform the majority of usage conditions at a single one of the specified target speeds. Only when the specified maximum motor current Iß max is nevertheless reached in special load cases, the DC motor 14 is no longer assigned a predetermined, constant speed n const as the target speed n S oii is specified. Rather, the setpoint speed is adjusted in such a way that the absorbed motor current IB exactly corresponds to the specified motor current Iß max (n S oii variable, so that IB = Iß max). The continuously tracked and thus variable target speed is lower than the predetermined, constant target speed nconst. As soon as the tracked, variable target speed increases with decreasing load to such an extent that it corresponds to the predetermined, constant speed nconst, the predetermined, constant speed nconst is again specified as the target speed (n Soii = nconst). The variable target speed is smaller than the specified constant speed nconst.
[0081] The brushless electric motor 14 is thus operated with the constant speed nconst as the target speed n S oii (n S oii = nconst) as long as the current motor current IB is less than the specified maximum motor current Iß max. As soon as the value of the current intensity of the current motor current IB reaches or exceeds the specified maximum motor current Iß max, a current limit is activated which results in the speed of the brushless electric motor decreasing so that the load, i.e. the torque to be delivered by the brushless electric motor, is just large enough that the specified maximum motor current Iß max is not exceeded, the torque and thus the motor current can be kept constant.
[0082] Preferably, the brushless electric motor is speed-controlled as long as the current motor current IB is less than or equal to the specified maximum motor current Iß max. The setpoint speed then corresponds to a specified speed nconst—possibly one of several. The specified setpoint speed nsoii const is preferably stored in a setpoint speed memory 92; see Figure 3.
[0083] Preferably, the compressed air controller 56 is configured to evaluate a current signal whose value represents the value of the current motor current IB. If the current average motor current reaches the predefined maximum motor current Iß max, it determines a reduced target speed value nsoii red as a function of a pressure measured in the compressed air supply system using a stored characteristic curve or characteristic map. For this purpose, the compressed air controller 56 is connected to or contains a characteristic map or characteristic curve memory 94 (see Figure 3).
[0084] The control of the target speed as well as the control of the motor current can be continuous, time-discrete or quasi-continuous.
[0085] The result of such a determination of the target speed nsoii for the DC motor 14 as a function of the actual motor current IB and the predetermined maximum motor current Iß max is shown in Figure 8.
[0086] Furthermore, the basic design of the compressor 12 and the associated DC motor 14 - i.e. the compressor module 10 - when using the invention should not be based on worst case tolerance levels etc., but should also be analogous to the nominal values.
[0087] Advantages also arise in the event that the nominal diameters on the compressor discharge side are temporarily too small (e.g., when conveying into only one bellows 34) and excessive backpressure builds up due to the high discharge flow rate, which in turn would lead to excessive motor current. The application of the inventive control of the setpoint speed as well as the control of the motor current is not limited to compressors driven by a BLDC DC motor (although the latter are preferred), but can also be extended to compressors with other DC motors.
[0088] The electronic compressed air control
[0089] The compressed air control 56 outputs the control signals Sst to activate the electrically controllable valves - and thus to activate the open or closed operating mode - and a control signal n Soii for a target speed or one of several predetermined constant speeds nconst as a specification for the target speed of the DC motor 14; see Figure 3. The compressed air control 56 can thus switch the compressed air supply system from the closed to the open operating mode or vice versa.
[0090] This allows the compressed air control 56 to switch to open operation when the target speed of the DC motor 14 is already being variably tracked because the motor current IB has reached the maximum permissible motor current IB max. Switching to the open operating mode preferably occurs when the tracked, variable target speed becomes too low and, for example, reaches or falls below a predetermined minimum target speed nsoii min.
[0091] In addition, the compressed air controller 56 receives input signals representing the pressure value in the pressure accumulator 36 as the accumulator pressure signal PR and the pressure sensor pressure signal PAbn representing the pressure value in the compressed air sensor 32, as well as a request signal defining a desired state of the compressed air sensor 32—e.g., raised or lowered—or of the compressed air supply system. Other possible input signals of the compressed air controller 56 are a voltage signal representing the value of the available supply voltage, an ambient pressure signal representing the ambient air pressure, and / or an air temperature signal representing the ambient air temperature.
[0092] The pressure sensor pressure signal PAbn can represent the pressure in the entire compressed air sensor 32, e.g. the air spring system 32, or in the form of a vector with several components also the pressures in the individual bellows 34 of the air spring system 32.
[0093] The following describes how compressed air can be supplied to the compressed air pickup 32, for example, the air suspension system 32 of a vehicle, in open or closed operating mode. This is necessary, for example, if the vehicle is to be lifted on one side or all sides. For this lifting, compressed air must be supplied to the bellows 34. Open operating mode
[0094] Both raising and lowering of an air suspension system can take place in closed operating mode.
[0095] In the first open operating mode, e.g., for raising the air suspension system 12, compressed air is supplied from the compressor 12 via a pneumatic main pressure line 40 to the compressed air receiver 32—that is, the air suspension system 32—to supply compressed air to the compressed air receiver 32. Within the air suspension system 32, the compressed air is distributed by means of individual pressure receiver valves 46—which, in the illustrated embodiment, are bellows valves 46 of spring bellows 34 of the air suspension system 32.
[0096] In the illustrated embodiment, the compressor 12 is designed as a two-stage unit, comprising a first compressor stage 12.1 and a second compressor stage 12.2. In the open operating mode, the outside air is thus pre-compressed in two stages, first by the first compressor stage 12.1 and then post-compressed by the second compressor stage 12.2. The compressed air provided by the compressor 12 in the open operating mode can also be fed to a pressure accumulator 36 instead of a compressed air receiver 32, thus creating the conditions for a closed operating mode.
[0097] For the compressed air supply in the open operating mode, a compressor such as compressor 12 and a pneumatic main pressure line 40 are required, which supplies compressed air provided by compressor 12 to the compressed air receiver 32. Additional components such as an air dryer 38 or a separating or isolating valve 44 are optional.
[0098] In the second open operating mode, e.g., when lowering the air suspension system 12, the drain valve is opened. This opening of the drain valve 50 causes the pneumatically controlled 3 / 2-way valve 70 to move into the working position, where venting occurs. After the drain valve 50 opens, the pressure of the air to be vented acts as a control pressure, which acts on a control piston 74 of the pneumatically controlled 3 / 2-way valve 70 and moves the 3 / 2-way valve 70 into the working position against the force of its return spring 72. Throttle valves 80.1 and 80.2 as well as two check or one-way valves 42.1 and 42.2 effectively limit the control pressure for actuating the pneumatically controlled 3 / 2-way valve 70. Closed operating mode
[0099] Both raising and lowering can occur in an air spring system in the closed operating mode. In general, this means that a compressed air consumer 32 can be supplied with compressed air in a first closed operating mode and can release air in a second closed operating mode - also referred to as reflow mode. For the closed operating mode, a pressure accumulator 36, designed, for example, as a compressed air tank, a reservoir valve 52, an optional boost valve 54 and a likewise optional separation valve 44 and a likewise optional check valve 48 as well as corresponding compressed air lines are also provided. The components not required for the open operating mode for the closed operating mode - namely the pressure accumulator 36, the reservoir valve 52, the optional boost valve 54 and the check valve 48 - are shown in Fig. 1 within the dashed border 82.
[0100] In the first closed operating mode, for example, for lifting an air suspension system, air is pumped from the pressure accumulator 36 to the air suspension system 32 and into its bellows 34 by means of the compressor 12 and its second compressor stage 12.2. For this purpose, the compressor 12, the boost valve 54, and the separation valve 44 are activated, and the bellows valves 46 are opened. In this way, a vehicle can be lifted by means of the air suspension system 32 in the closed operating mode of the compressed air supply system 30 ("boost"). Since the air in the pressure vessel 36 already has a higher static pressure than the ambient outside air, the air in the closed operating mode is only recompressed by means of the second stage 12.2 of the compressor 12, and the first stage 12.1 of the compressor 12 is pneumatically ineffective in this case.
[0101] Just as in the open operating mode, in the closed operating mode the compressed air is fed via the air dryer 38 to the pneumatic main pressure line 40 and through the one-way or check valve 42.2 and is thus made available for delivery to a compressed air consumer 32.
[0102] In the second closed operating mode, for example, when lowering an air suspension system, air is pumped from the bellows 34 into the pressure accumulator 36. In this case, the compressor 12 is activated, and both the check valve 48 and the reservoir valve 52 are open, i.e., activated. Air is then pumped from the bellows 36 through the check valve 48 by means of the second stage 12.2 of the compressor 12, and through the reservoir valve 52 into the pressure accumulator 36.
[0103] Distribution of compressed air within the compressed air receiver
[0104] The compressed air is delivered to the compressed air consumer(s) 32 or the pressure accumulator 36 and distributed within the compressed air consumer 32—in the example, between the air springs 34 of the air suspension system 32—by means of electrically controlled 2 / 2-way valves 46, one of which is also shown in Fig. 2a as 2 / 2-way valve 60. In their first (rest) position, which is effected by a return spring 62, the 2 / 2-way valves 46 act as one-way or check valves. In the controlled second (activated or working) position, the 2 / 2-way valves 46 are open. The electrically controlled 2 / 2-way valves 46 are connected to an electronic compressed air control unit 56, which can be identical to an electronic control unit for controlling the compressor module 10 and can control control magnets 64 of the 2 / 2-way valves 46.The 2 / 2-way valves 46 of the compressed air collector 32 – in the example case, the air spring system 32 – correspond to the 2 / 2-way valve 60 shown in Figure 2a.
[0105] Ventilation
[0106] Regardless of whether the compressed air supply system 30 is operated in open or closed mode, venting one or more components - such as the bellows 34 - of the compressed air collector 32 may be necessary. In the case of a vehicle with an air suspension system, one or more bellows 36 of the air suspension system must be vented if the vehicle is to be lowered on one side or all sides. The venting of the compressed air collector 32 - e.g. when lowering the vehicle with an air suspension system - can also take place in open or closed mode. These variants for venting the compressed air collector 32 are explained in more detail below. In both cases, the aim is to vent the compressed air collector 32 - not to vent the compressed air supply system 30 as a whole.Venting of the compressed air supply system 30 necessarily takes place in open operation, in which air from the compressed air supply system 30 is released into the environment.
[0107] Ventilation in open operation
[0108] For venting in open operating mode, the compressed air supply system 30 in the example shown is designed as an indirectly venting compressed air supply system.
[0109] For this purpose, a drain valve 50, a pneumatically controlled 3 / 2-way valve 70, throttles 80.1 and 80.2 as well as a further check or one-way valve 42.1 are provided - see the corresponding border 84 around the components for indirect venting in Figure 1 .
[0110] Venting of the compressed air supply system 30 and one or more compressed air consumers 32 can be effected in the open operating mode by opening the drain valve 50, which is also designed as an electrically controlled 2 / 2-way valve. Opening the drain valve 50 causes the pneumatically controlled 3 / 2-way valve 70, as also shown in Fig. 2b, to be moved into the working position. The working position is the position in which venting occurs. After opening the drain valve 50, the pressure of the air to be vented acts as a control pressure, acting on a control piston 74, which moves the 3 / 2-way valve 70 into the working position against the force of its return spring 72. Throttle valves 80.1 and 80.2 as well as two check or one-way valves 42.1 and 42.2 ensure a sensible limitation of the control pressure for controlling the pneumatically controlled 3 / 2-way valve 70.
[0111] Ventilation in closed operation
[0112] In the closed operating mode, the components of the compressed air collector 32 are vented into the pressure vessel 36.
[0113] During venting in closed operating mode, the air is pumped from the 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 check valve 48 and the reservoir valve 52 are opened. This allows, for example, the air suspension system 32 to be lowered in closed operating mode. The first stage 12.1 of the compressor 12 is pneumatically ineffective in this case.
[0114] Summary of open / closed operating mode
[0115] An open operating mode occurs when the compressor 12 delivers air directly from the environment to the compressed air receivers 34, for example the bellows 34 of the air suspension system 32; then the compressor 12 is activated, the separation valve 44 is activated, the bellows valves 46 are activated => "Lift" request, the compressor 12 fills the compressed air reservoir 36 from the environment; then the compressor 12 is activated, the reservoir valve 52 is activated => "Fill reservoir" request, the air from the compressed air receivers 34 (in the example: the bellows 34 of the air suspension system 32) is vented into the atmosphere (bellows valves activated, separation valve activated, drain valve activated) => "Lower" request to the atmosphere A closed operating mode occurs when
[0116] The air is pumped from the bellows 34 into the pressure accumulator 36; then the compressor 12 is activated, the return valve 48 is activated, and the reservoir valve 52 is activated => "lower" request in closed operating mode ("reflow"). The first stage 12.1 of the compressor 12 is pneumatically ineffective in this case.
[0117] The air is pumped from the pressure accumulator 36 into the bellows 34; then the compressor 12 is activated, the boost valve 54 is activated, the separation valve 44 is activated, and the bellows valves 46 are activated => "lift" request in closed operating mode ("boost"). The first stage 12.1 of the compressor 12 is pneumatically ineffective in this case.
[0118] Reference symbol (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 Stator coil
[0127] 14.4. Hall sensor
[0128] 16 Engine electronics
[0129] 18 air dryers
[0130] 20 air distributors
[0131] 30 Compressed air supply system
[0132] 32 air suspension system
[0133] 34 bellows of the air springs
[0134] 36 pressure accumulators
[0135] 38 air dryers
[0136] 40 Main pressure line
[0137] 42 One-way valve / check valve
[0138] 44 Separation valve (electrically controlled)
[0139] 46 Pressure sensor valve (bellows valve, electrically controlled)
[0140] 48 Check valve (electrically controlled)
[0141] 50 Drain valve (exhaust valve, electrically controlled)
[0142] 52 Reservoir valve (electrically controlled)
[0143] 54 Boost valve (electrically controlled)
[0144] 56 Compressed air control
[0145] 58 Current sensor
[0146] 60 2 / 2-way valve
[0147] 62 return spring
[0148] 64 Control solenoid 3 / 2-way valve (pneumatically controlled) for venting
[0149] Return spring
[0150] control piston
[0151] Boost and return line
[0152] pressure sensor; PU converter
[0153] throttle
[0154] Components for closed operation
[0155] Components for indirect ventilation
[0156] Evaluation unit
[0157] Storage with specified target speeds
[0158] Characteristic curve memory
[0159] Control unit
[0160] Current sensor
[0161] Analog-to-digital converter
Claims
Patent claims 1. Compressor module (10), in particular for a compressed air supply system (20) of a vehicle, wherein the compressor module (10) comprises a compressor (12) and a speed-controlled brushless electric motor (14) for driving the compressor (12), during the operation of which a motor current (IB) occurs and to which a motor electronics unit (16) with an electronic commutator and speed control is assigned, wherein the speed control during operation is based on a predetermined target speed (n S oii), characterized in that the compressor module (10) is connected to or has an electronic control unit (100), wherein the electronic control unit (100) is designed to control the target speed (n S oii) depending on a motor current (IB) currently consumed by the speed-controlled brushless electric motor (14) and a predetermined maximum motor current (te max) in such a way that the target speed (nS oii) corresponds to a predetermined constant speed (nconst), as long as the motor current (IB) currently consumed by the speed-controlled brushless electric motor (14) is less than the predetermined maximum motor current (te max) and the target speed (n S oii) is adjusted in such a way that the motor current (IB) currently absorbed by the speed-controlled brushless electric motor (14) corresponds to the predetermined maximum mo- motor current (te max) as long as the motor current (IB) currently consumed by the speed-controlled brushless electric motor (14) corresponds at least approximately to the predetermined maximum motor current (IB max ).
2. Compressor module (10) according to claim 1, characterized in that the electronic control unit (100) is designed to determine the value (n Soii) for the target speed, when the currently absorbed average motor current (IB) reaches the specified maximum motor current (IB max), to be continuously adjusted in accordance with a specified characteristic curve or a specified characteristic map in a load-dependent manner.
3. Compressor module (10) according to claim 2, characterized in that the electronic control unit (100) is designed to determine the value (n S oii) for the target speed to be continuously adjusted according to the predetermined characteristic curve or the predetermined characteristic map as a function of a pressure measured in a compressed air supply system (30).
4. Compressor module (10) according to claim 2 or 3, with a characteristic curve memory (94) or a characteristic map memory which is connected to the electronic control unit (100) and in which a characteristic curve or a characteristic map is stored which represents values for the desired speed as a function of a pressure value as an input value for the characteristic curve or the characteristic map.
5. Compressed air supply system (30), in particular for a motor vehicle, comprising: one or more compressed air consumers (32; 34), compressed air lines (40), electrically controllable valves (44, 46, 48, 50, 52, 54), a compressed air control (56) for controlling the electrically controllable valves (44, 46, 48, 50, 52, 54), a compressor module (10) according to one of claims 1 to 4, and a compressed air reservoir (36), wherein the compressed air consumer(s) (32;34) are or can be pneumatically connected to the compressor or condenser (12) and / or the compressed air reservoir (36) via the compressed air lines (40) and the electrically controllable valves (44, 46, 48, 50, 52, 54) in such a way that the compressed air supply system (30) can be operated either in an open mode or in a closed mode, characterized in that the compressed air control (56) is designed to evaluate a current signal, the value of which represents the value of the current motor current (IB), and, in the event that the current motor current (IB) reaches the predetermined maximum motor current (te max), to determine a reduced target speed value (nsoii red) in such a way that the motor current (IB) consumed by the brushless electric motor (14) driving the compressor or condenser (12) does not exceed the maximum motor current (te max), but rather corresponds to the maximum motor current (IB max ) within the scope of a control accuracy. corresponds.; 6. Compressed air supply system (30) according to 5, characterized in that the compressed air supply system (30) has at least one pressure sensor (78) which is connected to the electronic control unit (100) of the compressor module (10) and which provides an input value for a characteristic curve control or a characteristic map control of the target speed (n S oii) the speed-controlled brushless electric motor (14) for driving the compressor (12) by the electronic control unit (100).
7. Compressed air supply system (30) according to claim 5 or 6, characterized in that the compressed air control (56) is designed either to control the electrically controllable valves (44, 46, 48, 50, 52, 54) in accordance with the open operating mode of the compressed air supply system (30) when the tracked, variable target speed exceeds a predetermined minimum target speed (n Soii min ) is reached or falls below, or to control the electrically controllable valves (44, 46, 48, 50, 52, 54) in accordance with the closed operating mode of the compressed air supply system (30) as long as the tracked, variable target speed exceeds the predetermined minimum target speed (nsoii min).
8. Compressed air supply system (30) according to claim 7, characterized in that the compressed air control (56) is designed to set the target speed (n S oii) depending on the motor current (IB) currently consumed by the speed-controlled brushless electric motor (14) and the predetermined maximum motor current (te max) in such a way that the target speed (n Soii) corresponds to a predetermined constant speed (nconst) as long as the motor current (IB) currently consumed by the speed-controlled brushless electric motor (14) is less than the predetermined maximum motor current (te max).
9. A method for operating a compressor module (10) according to one of claims 1 to 4 or a compressed air supply system (30) according to one of claims 5 to 7, the method comprising the steps of: Determining a target speed (n S oii) for the speed of the speed-controlled brushless electric motor (14) such that the target speed (risoii) corresponds to a predetermined constant speed (nconst), as long as the motor current (IB) currently consumed by the speed-controlled brushless electric motor (14) is less than the predetermined maximum motor current (IB max) (nconst, if IB < IB max ) and the target speed (n Soii) is tracked in such a way that the motor current (IB) currently drawn by the speed-controlled brushless electric motor (14) corresponds to the predetermined maximum motor current (Iß max), as long as the motor current (IB) currently drawn by the speed-controlled brushless electric motor (14) corresponds to the predetermined maximum motor current (Iß max) within the scope of the control or follow-up stirring accuracy.
10. The method according to claim 9, wherein the determination of a reduced target speed value (nsoii red) is carried out as a function of a pressure measured in the compressed air supply system (30) using a stored characteristic curve or a stored characteristic map when the current average motor current (IB) reaches the predetermined maximum motor current (IB max ).
11. A method for operating a compressed air supply system (30) according to at least one of claims 5 to 8, characterized by the method steps: Evaluating a current signal whose value represents the value of the current motor current (IB), and in the event that the current motor current (IB) reaches the specified maximum motor current (Iß max), determining a reduced target speed value (n S oii red) such that the speed-controlled motor driving the compressor (12) the motor current (IB) absorbed by the electric motor (14) does not exceed the maximum motor current (Iß max), but corresponds to the maximum motor current (Iß max) within the scope of a control accuracy.
12. Method according to claim 11, characterized by switching from a closed operating mode to the open operating mode when the tracked, variable target speed reaches a predetermined minimum target speed (n S oii min ) is reached or falls below.