DE102022133694A1 - Control device for a vehicle compressed air system, vehicle compressed air system and method for operating a vehicle compressed air system - Google Patents

Abstract

The invention relates to a control device (200) adapted for implementation in a vehicle compressed air system, comprising: at least one switching valve with a switching element, in particular a solenoid switching valve (43, 93) with a switching coil, which can be activated by a switching current (201), and at least one valve control (205) which is designed to provide a switching current (201) for the at least one switching valve, wherein the valve control (205) has a pulse width modulator (211) which is designed to regulate the switching current (201) for the at least one switching valve with a switching element based on a pulse width modulation and by means of a switching current setpoint value (201d) and a determined switching current actual value (201c). According to the invention, it is provided that the valve control (205) has a look-up table (230) in which a plurality of Correction factors (KF) for at least one switching current setpoint of the at least one switching valve are stored as a function of at least one operating parameter of the switching valve, wherein the correction factor (KF) represents a factor between the measured switching current (201a) and an effective value (201c) of the switching current (201), wherein the effective value (201c) of the switching current (201) represents the actual value (201c) of the switching current (201), wherein the pulse width modulator (211) is designed to carry out the control of the switching current (201) taking into account the actual switching current value (201c).

Description

The present invention relates to a control device according to the preamble of claim 1 for a vehicle compressed air system, a compressed air system and a vehicle. The invention also relates to a method for operating a vehicle compressed air system according to the preamble of claim 6.

A compressed air system such as an air suspension system for a vehicle has a compressed air supply, in particular for supplying an air suspension system of a vehicle with compressed air. Air suspension systems can also include level control devices with which the distance between the vehicle axle and the vehicle body can be adjusted.

An air suspension system can have a number of air bellows pneumatically connected to a common line (gallery), which can raise the vehicle body as they become increasingly full and lower it as they become less full. As the distance between the vehicle axle and the vehicle body or ground clearance increases, the spring travel becomes longer and larger uneven ground can be overcome without coming into contact with the vehicle body. Such systems are used in off-road vehicles and sport utility vehicles (SUVs). Especially with SUVs with very powerful engines, it is desirable to provide the vehicle with comparatively low ground clearance for high speeds on the road on the one hand and comparatively high ground clearance for off-road use on the other. It is also desirable to implement a change in ground clearance as quickly as possible, which increases the requirements in terms of speed, flexibility and reliability of a compressed air supply.

A compressed air supply for use in a compressed air system such as an air suspension system is operated with compressed air from a compressed air supply, for example within a pressure level of 5 to 20 bar. The compressed air is made available to the compressed air supply using a compressor. The compressed air supply is pneumatically connected to a compressed air connection to supply the air suspension system and is also pneumatically connected to a vent connection. The compressed air supply system can be vented to the vent connection by releasing air via a vent valve arrangement.

EP 2 651 671 B1 shows a compressed air supply for an air suspension system of a vehicle. The compressed air supply has a compressor for generating compressed air and at least one solenoid valve that serves for venting.

Such and other vehicle compressed air systems such as a compressed air supply or an air suspension system or even level control devices are controlled by one or more actuators which are designed as a solenoid valve in order to control the provision of compressed air, in particular to control a venting or filling of a compressed air system by preventing, enabling or throttling a flow of compressed air in the compressed air lines or the like - in other words, influencing a compressed air flow.

It is an object of the invention to provide a control device for a vehicle compressed air system that allows precise control without significantly increasing the processing effort.

This object is achieved by a control device according to claim 1.

• mindestens ein Schaltventil mit einem Schaltelement, insbesondere Magnet-Schaltventil mit einer Schaltspule, welches durch einen Schaltstrom aktivierbar ist, und
• mindestens eine Ventil-Steuerung, welche dazu ausgestaltet ist, einen Schaltstrom für das mindestens eine Schaltventil bereitzustellen.

The invention thus relates to a control device as mentioned above or a similar control device adapted for implementation in a vehicle compressed air system, comprising:

• at least one switching valve with a switching element, in particular a solenoid switching valve with a switching coil, which can be activated by a switching current, and
• at least one valve controller which is designed to provide a switching current for the at least one switching valve.

The solenoid valve has a magnetic part and a pneumatic part, with the magnetic part playing a special role - it forms the switching element, usually in the form of a switching coil or similar magnetic coil of the solenoid valve, in particular a magnetic switching valve, in a compressed air system of a vehicle. If the control current of the magnetic part is too low, it may not switch through; if it is too high, the magnetic part may be damaged.

It is therefore desirable that the control current of the magnetic part has a sufficiently constant value for switching. The particular problem here is that a non-resistive load of a switching element such as that of a magnet of a solenoid valve or similar switching element of an actuator requires the control current to be regulated using a low-frequency pulse width modulation (PWM), the value of which cannot be easily determined. It should then be determined for a non-resistive load of a switching element - such as that of a magnet of a solenoid valve or similar switching element - which requires computational effort, which is not always available, especially in the application case in focus.

Thus, a control device or similar control device is provided which is adapted for implementation in a vehicle compressed air system. The control device or similar control device has at least one switching valve with a switching element, in particular a solenoid switching valve with a switching coil, which can be activated by a switching current, and at least one valve control which is designed to provide a switching current for the at least one switching valve.

According to the invention, the valve control has a pulse width modulator which is designed to regulate the switching current for the at least one switching valve based on a pulse width modulation and by means of a switching current value, in particular a switching current setpoint value and a determined switching current actual value, in particular by means of an actual value and/or setpoint value comparison.

The valve control has a lookup table in which a plurality of correction factors for different measured switching currents of the at least one switching valve are stored as a function of at least one operating parameter of the switching valve.

The correction factor represents a factor between the measured switching current and an effective value of the switching current. The effective value of the switching current represents the actual value of the switching current. The pulse width modulator is designed to control the switching current taking into account the actual value of the switching current.

The concept of the invention thus provides a control device or similar control device for controlling a switching current to the most precise actual value possible, in particular to a constant value; i.e. for switching a generally non-resistive load of a switching element, in the present case a switching element in the form of a magnet of a magnetic part of a solenoid valve in a compressed air supply of a vehicle.

The problem here is determining the actual value when controlling the system when it is controlled with slow PWM (2-5kHz) and the conditions in the vehicle fluctuate with 12-48V networks (voltage fluctuations and duty cycle of the PWM modulation) - the method of choosing a "root-mean-square" averaging (average by root of the sum of the square values), which would be advisable here to determine an effective value, but would be too computationally intensive considering the non-resistive load.

The concept of the invention therefore provides for a tap at only one fixed point of the phase of the PWM signal and adjustment of the tap according to a determined, in particular previously determined, coefficient depending on the ambient conditions, to represent the controlled variable of a constant value for switching with the switching current, i.e. switching current value. This constant value proves to be easily determined and reliable for controlling a switching element of an actuator that forms a non-resistive load, in particular in the case of a magnetic coil of a switching solenoid valve. The ambient conditions in the application case that is the main, but not the only, focus are voltage fluctuations in the vehicle network and the design of the duty cycle of the PWM control.

Preferred further developments can be found in the subclaims, which further develop the subject matter of the invention with regard to further possibilities of design within the scope of the task with further advantages.

The switching current is measured only once per period of the pulse width modulated signal.

A measurement point for the switching current within the period of the pulse-width modulated signal must be constant.

The invention also relates to a method for controlling a control circuit or similar control device adapted for implementation in a vehicle compressed air system. The control device has at least one switching valve which can be activated by a switching current and at least one valve control which is designed to provide a switching current for the at least one switching valve, with the steps: A switching current for the at least one switching valve is controlled based on a pulse width modulation and by means of a switching current setpoint and a determined switching current actual value. The valve control has a lookup table in which a plurality of correction factors for different measured switching currents of the at least one switching valve are stored depending on at least one operating parameter of the switching valve. The correction factor represents a factor between the measured switching current and an effective value of the switching current. The effective value of the switching current represents the actual value of the switching current. The switching current is controlled taking into account the actual value of the switching current.

A control device can thus be provided which is used in a compressed air system in a vehicle. In particular, the control device controls the operation of at least one switching valve, in particular a solenoid valve. The switching valve is activated or deactivated via a switching current. In order to switch the switching valve on or off safely, it is important that the value of the switching current corresponds to the specifications. The effective value of the actual switching current must therefore be recorded as accurately as possible. The recorded effective value of the switching current is then taken into account when controlling the control loop. If the recorded effective value of the switching current does not correspond to the specifications, the control must intervene and adjust the value of the switching current. This can be done by means of pulse width modulation. If the recorded switching current is too small, then the duty cycle of the pulse width modulation must be increased. If the recorded switching current is too large, then the duty cycle of the pulse width modulation must be reduced.

The control device receives a setpoint value for the switching current and then controls the switching current accordingly. The determination of the actual switching current (actual value) flows into the control system as feedback.

The actual value of the switching current is determined by measuring a switching current value per PWM period. This measured current value is compared in a look-up table to determine a correction factor. The correction factor is used to determine an RMS current value from the measured current value. Thus, to determine an RMS value of the switching current, only a one-time measurement of the switching current per PWM period and determination of the associated correction factor is necessary. The current value multiplied by the correction factor then represents the RMS value of the switching current in a PWM period. This value then forms the basis for controlling the control loop.

The valve control unit can be designed as a separate control unit or as part of a control system for the air suspension system (Electronically Controlled Air Suspension, ECAS) or as part of a vehicle control unit (ECU).

The switching current value only needs to be measured once per period of the pulse-width modulated signal. This is advantageous because it enables a significant reduction in measurement and processing effort.

The measurement time for the switching current within the period of the pulse width modulated signal must be constant. This means that the switching current can always be measured at the same specified time. This simplifies the further determination of the correction factor. In particular, the control of the solenoid valve can be improved because the measurement of the switching current always takes place at the same time within the PWM period.

The frequency of the pulse width modulated signal can be 800 Hz, for example. This means that at 100 samples per second, 800,000 samples per second would have to be recorded. However, this would lead to a comparatively high effort in the measurement data acquisition and processing.

This can be avoided according to the invention, since not the entire current curve over a PWM period, but only a few measurements or just a single measurement in a period needs to be carried out. The remaining data can be determined using the information in the lookup table and the measured values determined.

The pulse width modulation of the switching current results in a periodic "ripple" in the switching current. If no suitable method is used to determine the RMS value, the measured current value is too high or too low. This means that the current value set by the control is also too high or too low.

Embodiments of the invention are now described below with reference to the drawing. This is not necessarily intended to show the embodiments to scale; rather, the drawing is, where useful for explanation, in a schematic and/or slightly distorted form. 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 a wide variety of modifications and changes can be made to the shape and detail of an embodiment 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 development of the invention both individually and in any combination. In addition, all combinations of at least two of the features disclosed in the description, the drawing and/or the claims fall within the scope of the invention. The general idea of the invention is not limited to the exact shape 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. When specifying dimensioning ranges, Values within the limits mentioned may also be disclosed as limit values and may be used and claimed as required. For the sake of simplicity, the same reference symbols are used below wherever appropriate for identical or similar parts or parts with identical or similar functions.

• 1 ein Schaltungsdiagramm eines Luftfedersystems,
• 2 einen Graphen zur Veranschaulichung eines Schaltstroms für ein Magnetventil gemäß dem Stand der Technik,
• 3 einen Graphen zur Veranschaulichung eines Schaltstroms für ein Magnetventil gemäß einem Ausführungsbeispiel,
• 4A bis 4C jeweils einen Graphen zur Veranschaulichung eines Schaltstroms für ein Magnetventil bei unterschiedlichen Parametern, und
• 5 einen Graphen zur Veranschaulichung von Korrekturfaktoren, die in der Nachschlagetabelle gespeichert ist.

Further advantages, features and details of the invention will become apparent from the following description of the preferred embodiments and from the drawing, which shows in:

• 1 a circuit diagram of an air suspension system,
• 2 a graph illustrating a switching current for a solenoid valve according to the prior art,
• 3 a graph illustrating a switching current for a solenoid valve according to an embodiment,
• 4A until 4C a graph to illustrate a switching current for a solenoid valve at different parameters, and
• 5 a graph illustrating correction factors stored in the lookup table.

1 shows an air suspension system 100 for a vehicle 1000 (not shown in detail) with a compressed air supply 10 and an air suspension system 90; this corresponds in its structure and functional principle to that shown in 1 the aforementioned EP 2 651 671 B1 with the compressed air supply 10A shown there.

A present in the 1 The embodiment of a compressed air supply 10 shown in this application can also be used as an embodiment of a compressed air supply 10B according to the 8th or a compressed air supply 10C of the 9 be designed.

The content of the EP 2 651 671 B1 and in particular the description of the compressed air supply system of the 1 and 8th or 9 the EP 2 651 671 B1 is hereby incorporated by reference into the present application. In particular, it is also part of the disclosure of this application to design the compressed air supply as a power-off closed compressed air supply, in a modification of the EP 2 651 671 B1 described normally open compressed air supplies.

The following description of a structure of a compressed air supply is to be understood only as an example for other designs of a compressed air supply as is the case with the EP 2 651 671 B1 described normally open compressed air supplies and the normally closed compressed air supplies mentioned above.

This said, the 1 The air suspension system 90 shown here, for example, has four so-called bellows 91, each of which is assigned to a wheel of a vehicle, and a reservoir 92 for storing quickly available compressed air for the bellows 91. The bellows 91 and the reservoir 92 can optionally be connected in a valve block 96 with five magnetic switching valves - each with a switching element (here the magnetic coil) as a non-resistive load - in this case each via a normally closed magnetic valve 93, 94 to a common pneumatic line forming a gallery 95, which forms the pneumatic connection between the compressed air supply 10 and the air suspension system 90. The valve block 96 can have other or fewer magnetic valves and/or magnetic valves arranged in a 2-way valve block. A gallery is generally understood to be any type of collecting line from which branch lines to bellows 91 or a line to the compressed air supply system 10 branch off.

The compressed air supply 10 itself - as shown in 1 shown here - serves to operate the air spring system 90 and supplies the gallery 95 of the same with compressed air DL via a compressed air connection 2.

The compressed air supply 10 has a vent connection 3 and an air supply 0 with an intake. The air spring system 90 with the controllable solenoid valves 93, 94 is arranged downstream of the compressed air connection 2 in the filling direction. A filter 3.1, 0.1 is arranged downstream of the vent connection 3 in the vent direction and upstream of the air supply 0.

In a pneumatic connection between the air supply 0 and the compressed air supply 1, the compressed air supply 10 also has a compressor 21 which is driven by a motor M to supply the compressed air supply 1 with compressed air. In a pneumatic connection between the compressed air supply 1 and the compressed air connection 2, an air dryer 22 and a first throttle 31, here e.g. as a regeneration throttle, are optionally arranged. The filter 0.1, the air supply 0, the compressor 21, the compressed air supply 1, the air dryer 22 and the first throttle 31 can be arranged together with the compressed air connection 2 in a compressed air supply line 20 leading to the gallery 95 in this order.

In a pneumatic connection between the compressed air supply 1 and the vent connection 3 of the compressed air supply system 10, a vent valve arrangement - in the present case, for example, in the form of a controllable, normally open solenoid valve arrangement 40 as a solenoid switching valve - with a magnetic part 43 and a pneumatic part 44 for a vent connection 3 for releasing air is provided.

The solenoid valve arrangement 40 is arranged in a vent line 30 forming the pneumatic connection with a second throttle 32, which serves here as a vent throttle, and the vent connection 3. In other words, in the case of the normally open solenoid valve arrangement 40, the pneumatic part 44 is open when the magnetic part 43 is not activated.

Specifically, the solenoid valve arrangement 40 is designed for the direct switching of a compressed air volume. The pneumatic part 44 in the vent line 30 of the compressed air supply line 20, which can be actuated directly via the magnet part 43, is open between a pressure-side valve connection and a vent-side valve connection.

A line section of the vent line 30 forming a pneumatic chamber on the compressed air connection side is connected to the compressed air supply 1 for the pneumatic connection of the solenoid valve arrangement 40 to the compressed air supply line 20. This has the consequence that in the event of venting of the compressed air supply system 10, compressed air is vented via the vent line 30, which is taken upstream of the air dryer 22, i.e., to put it simply, undried air.

Out of 1 it can be seen that the compressed air supply system 10 with a solenoid valve arrangement 40 in the form of a directly controlled venting solenoid valve arrangement - in this case as a solenoid switching valve - via a control line 68 a direct switching of the entire compressed air volume is possible; ie without a separate control valve is designed like the one according to a 1 the aforementioned EP 2 651 671 B1 which is hereby incorporated by reference into the present application.

A separate control valve (not shown here) - as a solenoid switching valve - for forming a modified magnetic part can, for example, be designed according to a 8th or 9 the aforementioned EP 2 651 671 B1 which is hereby incorporated by reference into the present application. Such a separate control valve (in the EP 2 651 671 B1 designated 40.1 B, 40.1 C) serves as a solenoid switching valve to form a modified solenoid part. In this case, the solenoid part controls a relay valve (in the EP 2 651 671 B1 designated 40.2B, 40.2C), the latter being connected in the vent line 30.

In detail, the functioning of the compressed air supply 10 is shown by 1 illustrated as follows. The compressed air supply 1 is supplied with compressed air by sucking in air via the filter 0.1 and the air supply 0, in that the compressor 21 driven by the motor M compresses the sucked-in air. The air suspension system 90 is supplied with compressed air DL from the compressed air supply 1 via the air dryer 22 and the first throttle 31. For this purpose, the compressed air supply line 20 of the compressed air supply 10 is connected to the gallery 95 of the air suspension system 90 via the compressed air connection 2.

When the final accumulator pressure is reached in the air spring system 90, in this case in a pressure range of about 15 to 20 bar in the accumulator and 5 to 10 bar in the bellows, the compressed air supply 10 is vented. For the solenoid valve arrangement 40, a larger nominal diameter can optionally be provided for the second throttle 32 than for the first throttle 31, so that the greatest possible pressure change amplitude can be created for the regeneration of the air dryer. This allows advantageous venting of the compressed air supply system 10 and/or regeneration of the air dryer 22.

Thus, to fill a reservoir 92, the vent line 30 is first closed by energizing the solenoid valve arrangement 40 with a switching current in order to enable pressure to build up in the reservoir 92. In the present case, the compressed air supply system 10 can be vented after the final reservoir pressure has been reached, i.e. when the so-called reservoir filling end has been reached, by switching off the switching current for a magnetic part 43 (in particular the switching coil thereof) of the normally open solenoid valve arrangement 40.

Venting in the event of a vehicle lowering during normal operation can be carried out without any problem by means of the already opened solenoid valve arrangement 40 - since it is open when de-energized. A suitable pressure drop across the air dryer 22 ensures regeneration of the air dryer 22 as well as flexible and rapid venting by designing the nominal diameter of the throttles 31, 32.

The compressed air supply system 10 can also optionally have a check valve 49, which in this case can have a residual pressure holding function. On the one hand, the check valve check valve 49 to prevent foreign bodies from entering the compressed air supply system 10 in addition to the filter 3.1. In addition, the residual pressure holding function of the check valve 49 serves to maintain a minimum pressure in the compressed air supply system 10. Because the compressed air supply line 20 is open to the gallery 95 via the throttle 31, the residual pressure is also present for the air suspension system 90 in the form of the air filter system. This residual pressure - in this case at 1.5 bar - prevents the bellows 91 from sticking together in the event that the compressed air supply system 10 is vented together with the air suspension system 90. In concrete terms, this prevents the bellows walls of the bellows 91 from becoming trapped or damaged.

In addition, a pressure limiter 69 of the pneumatic part 44 of the solenoid valve arrangement 40 can optionally be provided in a pneumatic part 44, in which the pressure for the solenoid valve arrangement 40 can be limited by tapping the pressure in the vent line 30. In this way, a certain variability or tolerance with regard to pressure limitation can be achieved even at a comparatively high operating pressure.

In the present case, this is achieved by the switching point of the pneumatic part 44 being variably adjustable depending on the current strength of a switching current 201 in the magnetic part 43 (in particular the switching coil thereof). Depending on the vehicle situation, the temperature of the system or other pressure-relevant system issues, the switching point of the pneumatic part 44 can be variably adjusted in terms of current strength. The current-controlled pressure limiter 69 ensures that the gallery pressure does not exceed the static opening pressure of a level control valve designed as a solenoid valve 93 and an internal pressure of a bellows 91. In addition, a pressure measurement can also be carried out in the gallery 95 or in the reservoir 92.

Normally, a bellows pressure cannot force the solenoid valves 93 open and supports a valve spring by applying a bellows pressure above a valve armature. In the event of pressure fluctuations in the bellows 91, as can occur on rough roads or other dynamic influences, this prevents the solenoid valves 93 from being forced open. In practice, only in the event of an unintentionally sustained delivery of the air compressor can a gallery pressure become so high that a bellows valve is forced open and the vehicle is unintentionally raised. This could lead to unstable driving conditions. A pressure limiter certainly prevents such a case in systems with closed vent circuits. However, in the case of a de-energized open circuit described here, such a risk is avoided per se, since a compressor would usually discharge to the outside.

Further referring to 1 of the present application is the embodiment of the 1 The compressed air supply shown as an example is controlled in a particularly advantageous manner according to the concept of the invention; this is explained below. As stated at the beginning of this description, this control by means of a control device or similar control device 200 is not limited to the 1 compressed air supply or structure of the compressed air supply shown as an example. The control device or similar control device 200 can also be used for implementation in another vehicle compressed air system.

This being said, the design of the 1 In the compressed air supply 10 shown by way of example, a control device or similar control device 200 is provided which serves to control or regulate a switching current for a switching valve with a switching element, in particular a magnetic switching valve with a switching coil, i.e. a magnetic part of a magnetic valve arrangement which can be activated as a non-resistive load element by a switching current. The control device can be designed as a control circuit.

The control device 200 has a valve control 205, which is designed to provide a switching current for the at least one switching valve; in the present case, therefore, to control the magnetic switching valve (magnet part 43) and/or the magnetic switching valves (magnet valve 93), in particular their switching coils as non-resistive load elements thereof.

In the following description, the solenoid switching valves are provided with a switching coil and are intended to be described as an example for a switching valve with a switching element; namely, in particular, a switching element of a non-resistive load as is formed by the switching coil in the solenoid switching valves 43, 93 (the magnet part 43 and/or the solenoid valves 93). For the sake of simplicity, the solenoid switching valves 43, 93 are referred to below as switching valves 43, 93.

Further referring to 1 the valve control 205 provides a switching current for the switching valve 43. For this purpose, the valve control 205 can have a control unit 210. The control unit 210 generates a switching current 201 depending on or in accordance with the requirements of the air suspension system 90 as a function of a switching current setpoint. The switching current 201 activates, for example, the switching valve 43. The control unit 210 can have a pulse width modulator 211. The pulse width modulator 211 allows the switching valve 43 to be subjected to a switching current 201 in a desired pulse sequence, ie in a duty cycle, i.e. a sequence of applied switching current (on) and missing switching current (off). Optionally, the pulse width modulator can be operated at a frequency between 600 and 1000 Hz (in particular at 800 Hz).

The control unit 205 can optionally have a current sensor 220 for detecting the switching current 201. Alternatively, the current sensor 220 can be provided outside or independently of the control unit 205 and only provide the measured current 201. The current sensor 220 provides a switching current measurement value 201a. In particular, the current sensor 200 measures PWM once per period PWMP of the PWM signal PWM. This measurement can take place at a fixed time 201b within the period PWMP of the PWM signal.

Based on this one measured value 201 a, the effective value of the switching current (i.e. root mean square RMS) is to be determined.

The control unit 205 has a look-up table or a reference table 230 for this purpose. Correction factors KF for different switching current actual values and for different operating parameters (e.g. supply voltage, duty cycle of the PWM signal, etc.) can be stored in the reference table 230. The correction factor KF represents a factor between the measured switching current and an effective value of the switching current. The effective value of the switching current 201 then represents the actual value 201 d of the switching current 201. The values of the correction factors KF can be determined by simulation or measured in a test situation.

The current sensor 220 can measure the switching current 201a once per period of the pulse width modulated signal. In particular, this measurement can be carried out at a fixed recurring point in time within the period PWMP of the PWM signal. The measurement can therefore be carried out at a fixed point in time in the PWM period.

Based on this measured switching current value and the correction factors KF stored in the lookup table 230, the valve controller 205 can determine a deviation of the effective value 201c of the switching current 201 for the present operating parameters of the solenoid switching valves 43, 93 or similar switching valve with a switching element.

The pulse width modulator 211 serves to regulate the switching current 201 taking into account the actual value 201c of the switching current 201 for such a switching element as in this case the switching coil of the solenoid switching valves 43, 93.

2 shows a graph illustrating a switching current for a solenoid valve or general switching valve with a switching element as a non-resistive load according to the prior art. In 2 the switching current 201 for a solenoid valve is plotted in amperes I over time t. To record or measure the current profile, samples 201a of the switching current are recorded at regular intervals. The more samples per period PWMP of the pulse width signal PWM are measured, the more accurately the switching current or the profile of the switching current can be recorded. However, this can lead to a disproportionate increase in the processing effort, which cannot be achieved by the available hardware resources.

3 shows a graph to illustrate a switching current for a solenoid valve according to an embodiment, for example for a switching valve with a switching element as a non-resistive load. According to this embodiment, the switching current 201 is measured only once per PWM period and preferably at a time 201b. The measured switching current 201a is multiplied by the correction factor KF in order to determine the effective value 201c of the switching current 201.

The measurement of the switching current 201 takes place at fixed times 201b in a period of the PMW signal.

4A until 4C each show a graph illustrating a switching current for a solenoid valve at different parameters.

In 4A the course of the switching current 201 is shown at a supply voltage of 9V, a duty cycle of 45%, an effective value of the switching current of 1.1 A, a measuring sample of 1.23 A and a correction factor of 0.89.

In 4B the course of the switching current 201 is shown at a supply voltage of 12 V, a duty cycle of 35%, an effective factor of the switching current of 1.1 A, a measuring sample of 1.27 A and a correction factor of 0.87.

In 4C is the course of the switching current 201 at a supply voltage of 16 V, a duty cycle of 28 %, an effective value of the switching current of 1.1 A, a measurement sample of 1.30 A and a correction factor of 0.85.

5 shows a graph illustrating a correction factor stored in the lookup table. In 5 a correction factor KF for different duty cycles PWMT for a pulse width modulation is shown. In 5 Five characteristic curves KF1 - KF5 of correction factors KF are shown.

The first characteristic curve KF1 was recorded at a supply voltage of 8 V. The second characteristic curve KF2 was recorded at a supply voltage of 10 V. The third characteristic curve KF3 was recorded at a supply voltage of 12 V. The fourth characteristic curve KF4 was recorded at a supply voltage of 14 V. The fifth characteristic curve KF5 was recorded at a supply voltage of 16 V.

Reference symbol (part of the description)

0

Air supply

0.1

filter

1

Compressed air supply

2

Compressed air connection

3

Vent connection

3.1

filter

10

Compressed air supply

20

Compressed air supply line

21

compressor

22

Air dryer

30

Vent line

31

first throttle

32

second throttle

40

Solenoid valve arrangement with solenoid switching valve

43

Magnetic part

43A

Switching coil

44

Pneumatic part

49

check valve

68

Control line

69

Pressure limiter

90

Air suspension system

91

Bellows

92

Storage

93

Solenoid switching valve

94

Solenoid switching valve

95

gallery

96

Valve block

100

Air suspension system

200

Control device

201

Switching current

201

a Switching current measurement value

201b

Switching current measurement time

201c

Switching current actual value

201d

Switching current setpoint

205

Valve control

210

Control unit

211

Pulse width modulator

220

Current sensor

230

Lookup table

1000

Vehicle

B

Operating parameters

DL

Compressed air

KF

Correction factor

KF1

first correction factor

KF2

second correction factor

KF3

third correction factor

KF4

fourth correction factor

KF5

fifth correction factor

M

engine

PWM

Pulse width modulation

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions.

Cited patent literature

• EP 2651671 B1 [0005, 0034, 0036, 0037, 0046, 0047]

Claims (6)

Control device (200) adapted for implementation in a vehicle compressed air system (100), comprising: at least one switching valve (43, 93) with a switching element (43A), in particular a solenoid switching valve (43, 93) with a switching coil (43A), which can be activated by a switching current (201), and at least one valve control (205) which is designed to provide a switching current (201) for the at least one switching valve (43, 93), characterized in that the valve control (205) has a pulse width modulator (211) which is designed to regulate the switching current (201) for the at least one switching valve (43, 93) with a switching element (43A) based on a pulse width modulation (PWM) and by means of a switching current value (201d), in particular by means of a switching current setpoint value (201d) and a determined actual switching current value (201c) or in particular by means of a switching current actual value and switching current setpoint comparison, wherein the valve control (205) has a look-up table (230) in which a plurality of correction factors (KF) for at least one switching current setpoint value (201d) of the at least one switching valve (43, 93) are stored as a function of at least one operating parameter (B) of the switching valve (43, 93), wherein the correction factor (KF) represents a factor (KF) between the measured switching current (201a) and an effective value (201c) of the switching current (201), wherein the effective value (201c) of the switching current (201) represents the actual value (201c) of the switching current (201), wherein the pulse width modulator (211) is designed to regulate the switching current (201) taking into account the switching current value (201c), in particular the actual switching current value (201c) and/or the switching current setpoint value (201d) or in particular by means of a comparison of the actual switching current value (201c) and the switching current setpoint value (201d). Control device (200) according to Claim 1 , wherein the switching current (201) is measured once per period (PWMP) of the pulse width modulated signal (PWM). Control device (200) according to Claim 2 , wherein a measuring time (201b) for the switching current (201) is constant within the period (PWMP) of the pulse width modulated signal (PWM). Vehicle compressed air system (100), in particular an air spring system (100) with an air spring system (90), for a vehicle (1000), with a control device or similar control device (200) according to one of the Claims 1 until 3 . Vehicle (1000) with a vehicle compressed air system (100), in particular an air spring system (100) with an air spring system (90), and comprising: a control device (200) according to one of the Claims 1 until 3 and/or a vehicle compressed air system (100) according to Claim 4 . Method for operating a vehicle compressed air system (100), in particular an air spring system (100) with an air spring system (90), for a vehicle (1000), by means of a control circuit (200) adapted for implementation in the vehicle compressed air system (100), wherein - the control device (200) has at least one switching valve (43, 93) with a switching element (43A), in particular a solenoid switching valve (43, 93) with a switching coil (43A), which can be activated by a switching current (201), and at least one valve control (205) which is designed to provide a switching current (201) for the at least one switching valve (43, 93), and the method comprises the steps: regulating a switching current (201) for the at least one switching valve (43, 93) based on a pulse width modulation (PWM) and by means of a comparison of the switching current setpoint (201d) and a determined actual switching current value (201c), characterized in that the valve control (205) has a look-up table (230) in which a plurality of correction factors (KF) for at least one switching current setpoint value (201d) of the at least one switching valve (43, 93) are stored as a function of at least one operating parameter (B) of the switching valve (43, 93), wherein the correction factor (KF) represents a factor (KF) between the measured switching current (201a) and an effective value (201c) of the switching current (201), wherein the effective value (201c) of the switching current (201) represents the actual value (201d) of the switching current (201).

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