Method for determining a lower current threshold of a strip conductor of a solenoid coil of a solenoid valve for a valve unit which is fluidically connected to a pressurized fluid reservoir, device, and vehicle

Abstract

The invention relates to a method for determining the lower current threshold (US) of a strip conductor (B) of a solenoid coil (2) of a solenoid valve, said method having the steps of: - actively energizing the solenoid coil (2) of the solenoid valve, wherein the process of actively energizing the solenoid coil (2) of the solenoid valve is deactivated upon detecting an electric current flowing through the solenoid coil (2) at the level of an upper current threshold (OS) of the strip conductor (B), and actively energizing the solenoid coil (2) of the solenoid valve again using the electric power source upon detecting an electric current flowing through the solenoid coil (2) at the level of an ascertainable modifiable current threshold, - changing (10) the level of the ascertainable modifiable current threshold, - continuously measuring (20) a measurement signal in order to detect a change in the state of the armature of the solenoid valve between the at least one movement state and the rest state of the armature, and - determining (40) the lower current threshold (US) of the strip conductor (B) on the basis of the ascertainable modifiable current threshold when the change in state of the armature of the solenoid valve is detected (30) on the basis of the change of the ascertainable modifiable current threshold.

Description

State of the art

[0001] To store hydrogen for vehicle operation, several compressed gas tanks can be installed in the vehicle. Each of these compressed gas tanks is equipped with a multifunctional valve unit whose main function is to shut off the respective tank when the vehicle is not in use. For this purpose, the valve units are typically equipped with a self-closing solenoid valve. If no current flows through the solenoid coil of the valve, the solenoid valve closes automatically, for example, due to spring force. This behavior is necessary for safety reasons, but has the disadvantage that current must continuously flow through the solenoid coil during driving to keep the solenoid valve open.

[0002] This results in a constant, small amount of electrical energy consumption. There is a continuous effort to keep the actual electrical power required by a component as low as possible. Furthermore, valve units and solenoid valves within these units are subject to technical tolerances, meaning that the current required to flow through the solenoid coil to keep the solenoid valve open can vary.

[0003] WO2009105415 discloses a method for efficiently controlling a solenoid valve, wherein the voltage is monitored during a hold state of the solenoid in order to detect an accidental movement of the armature and to respond to this by increasing the holding current.

[0004] EP3628902 discloses a method for controlling a solenoid valve, wherein certain operating parameters of the solenoid valve can be calibrated, e.g. the time during which it is kept open, and wherein the operation of the solenoid valve is monitored.

[0005] DE102018209216 discloses a method for determining the position of an electromagnetic actuator with an armature movable by a coil between a rest position and an active position, wherein a hysteresis range with an upper current limit and a lower current limit for an operating current of the actuator is selected depending on an operating state of the actuator; the coil of the actuator is energized with a two-point controller which switches a voltage of the actuator such that the operating current remains within the hysteresis range; a frequency of the operating current is determined; and the position of the actuator is determined from the frequency of the operating current and the operating state.

[0006] DE19533452 and DE102019217405 disclose further methods for controlling a solenoid valve, whereby the power consumption of the solenoid valve is reduced during the holding phase. Disclosure of the invention

[0007] The present invention discloses a method according to the features of claim 1, a device according to the features of claim 10, and a vehicle according to the features of claim 11.

[0008] Further features and details of the invention will become apparent from the dependent claims, the description, and the drawings. Features and details described in connection with the method according to the invention naturally also apply in connection with the device and vehicle according to the invention, and vice versa, so that the disclosure regarding the individual aspects of the invention always refers, or can refer, to each other.

[0009] According to a first aspect, the present invention discloses a method for determining (at least) a lower current threshold of a current band of a solenoid coil of a solenoid valve for a valve unit, in particular of a vehicle, which communicates fluidly with a pressure fluid accumulator, wherein when an electric current at the level of the current band flows through the solenoid coil, an armature of the solenoid valve movable by the solenoid coil is held in a fully open position, wherein the movable armature, when transitioning between a closed position of the armature and the fully open position of the armature, comprises at least one state of movement and, in the fully open position, a state of rest.The method comprises, as a step, actively energizing the solenoid coil of the solenoid valve, wherein the active energizing of the solenoid coil of the solenoid valve is switched off upon detection of an electric current flowing through the solenoid coil at a level exceeding an upper current threshold of the current band. Furthermore, the method comprises, as a step, actively energizing the solenoid coil of the solenoid valve again by the electrical energy source upon detection, in particular upon detection of a current flowing through the solenoid coil falling below a definable, variable current threshold, which is lower than the upper current threshold. A further step of the method according to the invention is changing the level of the definable, variable current threshold, or changing the level of the definable, variable current threshold and (additionally) changing the level of the upper current threshold.Furthermore, a further step of the method is the continuous measurement of a measurement signal, in particular the continuous measurement and evaluation of a measurement signal, to detect a change in the state of the solenoid valve armature between at least one moving state and the rest state of the armature. The method also includes, as a step, determining (at least) the lower current threshold of the current band based on the definable, variable current threshold, when the change in the state of the solenoid valve armature due to the change in the definable, variable current threshold is detected, in particular when it has been detected (in advance).

[0010] The process steps described above and below can be carried out individually, together, simply, multiple times, in parallel and / or sequentially in any order, provided it is technically feasible.

[0011] In particular, it is also conceivable that the inventive method and / or the inventive device is used to determine (at least) a lower current threshold of a current band of a solenoid coil of a solenoid valve for a valve unit of a stationary energy unit, e.g. a generator or a fuel cell heater, which communicates fluidly with a pressure fluid storage tank.

[0012] The valve unit can be fluidically connected or is connected to at least one pressure fluid accumulator, e.g., of the vehicle or a stationary energy unit.

[0013] The fully open position of the armature is understood to be, in particular, a position of the armature in which the flow of a fluid through the valve unit, especially through a fluid channel of the valve unit, is at its maximum. In the fully open position, the solenoid valve armature is at rest, i.e., at rest or essentially at rest. The solenoid valve armature can also be understood as a magnetic armature. The moving position of the armature is understood to be a state in which the armature is moving, especially along an axis of the armature, e.g., from the closed position to the fully open position. In other words, the armature is not at rest in the moving position. The closed position of the armature is understood to be, in particular, a position of the armature in which the flow of a fluid through the valve unit, especially through a fluid channel of the valve unit, is not at its maximum, e.g., at its minimum.

[0014] If a change in the state of the solenoid valve armature is detected, resulting from a change in the configurable, variable current threshold, the lower current threshold is determined, in particular based on this configurable, variable current threshold, such that the movable armature is held in the fully open position at the lower current threshold determined from this threshold. The term "based on" in "the lower current threshold is determined, in particular based on this configurable, variable current threshold" is intended to indicate, for example, that this configurable, variable current threshold is multiplied by a factor, an offset is added, or the previous configurable, variable current threshold is used as the lower current threshold.

[0015] The active energizing of the solenoid coil of the solenoid valve, the switching off of the active energizing of the solenoid coil upon detection of the upper current threshold of the current band, and the renewed active energizing of the solenoid coil upon detection of the definable, variable current threshold, is a particularly repetitive process of the method according to the invention. In other words, the solenoid coil of the solenoid valve can be actively energized in a pulsating manner. Thus, a dynamic change in the inductance of the solenoid coil can be caused when the armature starts to move. The electric current flowing through the solenoid coil can have a periodic waveform during pulsating active energizing, in particular a sawtooth or substantially sawtooth waveform, or a sinusoidal waveform.The pulsating, active current flow to the solenoid coil of the solenoid valve is carried out in particular to determine the lower current threshold using the method according to the invention (calibration operation).

[0016] The solenoid coil of the solenoid valve can also be actively energized in pulses during normal operation to hold the movable armature of the solenoid valve in the fully open position. Advantageously, this pulsed energizing of the solenoid coil allows for a particularly simple implementation of a moderately rated current for the coil. The electrical energy for this active energizing can be supplied by an electrochemical storage device, such as a vehicle battery.

[0017] The active current supply to the solenoid coil of the solenoid valve can be switched on and off by controlling an electrical switch, e.g. a field-effect transistor.

[0018] The method according to the invention allows for the particularly simple, rapid, and / or reliable determination of at least the respective lower current threshold of a current band required to keep a solenoid valve of a plurality of solenoid valves fully open. With the respective determined lower current threshold, the current consumption of each solenoid valve of a plurality of solenoid valves, e.g., solenoid valves on hydrogen cylinders of a fuel cell vehicle, can be particularly advantageously low, preferably minimized. In particular, each solenoid valve is energized only with the necessary lower minimum electrical current (or lower minimum current intensity) of the current band.Preferably, the lower current threshold of the current band for a solenoid coil is a lower minimum current threshold of the current band or a substantially lower minimum current threshold of the current band at which the armature of the solenoid valve can (just barely) be held in the fully open position.

[0019] With the method according to the invention, in addition to the lower current threshold, the upper current threshold can also be determined, particularly as a function of the determined lower current threshold. Thus, the current consumption of each individual solenoid valve, for example, solenoid valves on hydrogen cylinders of a fuel cell vehicle, for keeping the respective armatures (fully) open can be particularly low, especially if the solenoid coils of the solenoid valves are pulsatingly and actively energized during normal operation.

[0020] The change of state of the anchor between the moving state and the resting state can also be understood as a state transition. It can be advantageous if, in a method according to the invention, the change of state of the anchor is a change of the anchor from the resting state to the moving state or a change of the anchor from the moving state to the resting state.

[0021] In particular, the definable, variable current threshold can be understood as a temporary lower current threshold of the current band in order to determine the lower current threshold of the current band for normal operation of the solenoid valve.

[0022] In addition to switching off the active current supply to the solenoid coil of the solenoid valve upon detection of an electric current flowing through the solenoid coil at the upper current threshold of the current band, a freewheeling circuit connected in parallel to the solenoid coil can be switched to conducting ("closed") simultaneously or essentially simultaneously, so that the electric current flowing through the solenoid coil of the solenoid valve can dissipate particularly advantageously due to the ohmic resistance of the solenoid coil. The freewheeling circuit includes, for example, a "freewheeling transistor" for switching the circuit to conducting. In particular, the freewheeling circuit is switched to non-conductive ("open") during the active current supply to the solenoid coil of the solenoid valve. A device according to the invention can include such a freewheeling circuit.

[0023] The time interval during which the solenoid coil of the solenoid valve is actively energized is also referred to as the rise interval. The time interval from when the active energization of the solenoid coil is switched off, once the upper current threshold has been detected, until the active energization of the solenoid coil is resumed, once the adjustable current threshold or the lower current threshold has been detected, is also referred to as the fall interval. The fall interval can also be called the freewheel interval if a freewheeling circuit is used.

[0024] Over the lifespan of a solenoid valve, its properties can change, necessitating adjustments to the lower and / or upper current thresholds (i.e., the current band) used for its operation. This allows the solenoid valve or valve assembly to operate particularly efficiently and with minimal energy consumption. Advantageously, a device according to the invention can be configured to determine and, if necessary, adjust a particularly advantageous lower and / or upper current threshold at regular intervals. In other words, self-calibration can occur.

[0025] Advantageously, the inventive method takes advantage of the fact that a change in the state of the armature between its moving and resting state causes a change in the inductance of the solenoid coil, since the inductance of the solenoid coil depends, among other things, on the distance between the armature and the solenoid coil. Movement of the armature can thus itself cause a change in the current waveform of the electric current flowing through the solenoid coil compared to the stationary armature. In particular, the change in the state of the solenoid valve armature between at least one moving state and the resting state of the armature can be detected based on the change in the current waveform. The change in the current waveform can be used as an indicator of the movement of the armature.

[0026] It can be advantageous if, in a method according to the invention, the level of the definable, variable current threshold is temporarily increased stepwise and / or decreased stepwise to change the level of the definable, variable current threshold for determining the lower current threshold. This allows a change in the state of the solenoid valve armature between at least one moving state and the rest state of the armature to be triggered in a particularly simple manner, thus enabling the detection of armature movement. In addition to the at least temporary stepwise increase of the level of the definable, variable current threshold, the upper current threshold can also be increased stepwise simultaneously to determine the lower current threshold.In addition to at least temporarily decreasing the level of the definable, variable current threshold in a stepwise manner, the upper current threshold can also be gradually reduced simultaneously to determine the lower current threshold. In other words, a shift in the current band can be used, in particular, to determine the lower current threshold. This allows for a particularly fast determination of the lower current threshold.

[0027] Advantageously, in a method according to the invention for detecting the change in state of the solenoid valve armature between at least one moving state and the rest state of the armature, the electric current flowing through the solenoid coil can be considered the measurement signal. In other words, the current waveform of the electric current flowing through the solenoid coil can be observed. Thus, a change in the current waveform of the electric current flowing through the solenoid coil can be used to easily infer a change in the state of the solenoid valve armature. The electric current flowing through the solenoid coil can be understood, in particular, as the electric current flowing directly through the solenoid coil. However, it is also conceivable that a current dependent on the electric current flowing through the solenoid coil is considered the measurement signal.

[0028] Advantageously, in a method according to the invention for detecting the change in the state of the armature, a time constant of the current flowing through the solenoid coil of the solenoid valve can be considered. The decay of the electric current flowing through the solenoid coil after the electric current flowing through the solenoid coil is switched off (upon detection of the upper current threshold) follows an exponential curve. The time constant for the exponential curve can be determined from the ratio of the ohmic resistance, in particular the ohmic resistance of the solenoid coil, to the inductance of the solenoid coil of the solenoid valve. If the inductance decreases, for example, because the armature releases from the stop of the valve unit, the time constant of the exponential decay also decreases. This time constant can be determined, for example, by a suitable filter routine, e.g., using a Taylor series.Thus, a change in the state of the anchor between the rest state and the motion state can lead to a noticeable change in the time constant.

[0029] A particular advantage of a method according to the invention for detecting the change in the state of the armature is that the current frequency of the current flowing through the solenoid coil of the solenoid valve can be considered. For example, the time elapsed between the active energizing of the solenoid coil of the solenoid valve by the electrical energy source upon detection of an electric current flowing through the solenoid coil at a definable, variable current threshold, and the subsequent active energizing of the coil upon detection of another electric current flowing through the solenoid coil at a definable, variable current threshold, can be determined. In other words, the period can be determined and analyzed, in particular the period of a sawtooth-shaped or substantially sawtooth-shaped current waveform of the electric current flowing through the solenoid coil.For example, if the time constant of the exponential curve of the electric current flowing through the magnetic coil decreases, this leads to a shortening of the decay interval, particularly the freewheeling interval. Thus, a change in the state of the armature between the resting and moving state can advantageously result in a noticeable change in the current frequency.

[0030] According to a further preferred embodiment, in a method according to the invention for detecting the change of state of the armature, a frequency spectrum of the current flowing through the solenoid coil of the solenoid valve can be considered. For example, the current waveform of the electric current flowing through the solenoid coil will exhibit strictly exponential behavior when the armature is at rest, whereas movement of the armature will lead to a deviation from this exponential behavior. Thus, a change of state of the armature between the rest state and the moving state can advantageously lead to a detectable change in the frequency spectrum of the current waveform.

[0031] Advantageously, in a method according to the invention, the upper current threshold of the current band can be adapted to the determined lower current threshold of the current band of the solenoid valve. Thus, the energy consumption of a solenoid coil that is pulsating and actively energized during normal operation of the solenoid valve can be particularly low. For example, the upper current threshold can be determined such that a desired, average current value permissible for the solenoid coil is obtained.

[0032] A particular advantage of a method according to the invention for detecting the change in state of the solenoid valve armature is that a value based on the measurement signal can be compared with a limit value. The limit value can also be understood as a threshold value.

[0033] According to a further preferred embodiment, a classification method can be applied in a method according to the invention for detecting the change in state of the solenoid valve's armature. This classification method can be understood, in particular, as machine learning. For this purpose, training data can be collected. Specifically, a statistical model is built using an algorithm based on the training data. Thus, patterns and regularities in the training data can be recognized, and even unknown data can be evaluated.

[0034] According to a second aspect, the present invention discloses a device for determining (at least) a lower current threshold of a current band of a solenoid coil of a solenoid valve for a valve unit, particularly of a vehicle, that communicates fluid-wise with a pressure fluid reservoir. The device comprises an electrical power source for providing electrical energy for actively energizing the solenoid coil of the solenoid valve. Furthermore, the device includes a sensor for detecting an electric current flowing through a solenoid coil of the solenoid valve. The device also includes a control unit for switching off the electric current flowing through the solenoid coil of the solenoid valve when an upper current threshold of a current band of the solenoid valve is exceeded, and for actively energizing the solenoid coil of the solenoid valve when a definable, variable current threshold is undershot.The device further comprises a current modulation unit for changing the level of the definable, variable current threshold, and a measuring unit for measuring a signal to detect a change in the state of the solenoid valve armature between at least one moving state and a resting state. The device also includes a determination unit for determining (at least) the lower current threshold of the current band based on the definable, variable current threshold when the change in the state of the solenoid valve armature is detected due to the change in the definable, variable current threshold. Furthermore, the device is configured to perform a method according to the invention for determining at least the lower current threshold of the current band for the solenoid coil of the solenoid valve of the pressure fluid accumulator valve unit, particularly in the vehicle.

[0035] The valve unit includes, in particular, a housing for accommodating the solenoid valve. Furthermore, the valve unit includes, in particular, a fluid inlet and a fluid outlet, wherein the fluid inlet can be fluidically connected to the fluid outlet via a fluid channel using the solenoid valve. In particular, the solenoid valve is also self-closing, i.e., when no current flows through a solenoid coil of the solenoid valve, the solenoid valve closes automatically, e.g., by means of a spring force.

[0036] The electrical energy source is, in particular, a battery, e.g., a vehicle battery.

[0037] The sensor for detecting the electrical current flowing through the solenoid coil of the solenoid valve can, for example, be a current sensor.

[0038] The control unit is specifically designed to actively switch the electrical current flowing through the solenoid coil of the solenoid valve on and / or off. Furthermore, the control unit can additionally be designed to switch a freewheeling circuit between electrically conductive and / or electrically non-conductive.

[0039] Furthermore, the device may have a memory, in particular a non-volatile memory, for storing lower current thresholds and / or for storing upper current thresholds and / or for storing (the) definable, variable current threshold(s).

[0040] In particular, the device according to the invention is used to determine the lower current threshold and / or the upper current threshold of the current band of the solenoid coil of the solenoid valve for at least one valve unit communicating with a pressure fluid storage device, e.g. a high-pressure hydrogen tank.

[0041] The device according to the second aspect of the invention thus has the same advantages as those already described for the method according to the first aspect of the invention.

[0042] According to a third aspect, the present invention relates to a vehicle, wherein the vehicle has at least one pressure fluid reservoir with a valve unit comprising a solenoid valve for controlling the flow of a pressure fluid that can be stored in the pressure fluid reservoir, and in particular a plurality of pressure fluid reservoirs, each with a valve unit comprising a solenoid valve for controlling the flow of a pressure fluid that can be stored in a respective pressure fluid reservoir of the plurality of pressure fluid reservoirs. Furthermore, the vehicle comprises a device designed according to the invention, wherein the device is further configured to determine at least the lower current threshold for the solenoid valve of the valve unit for the at least one pressure fluid reservoir.In particular, the device according to the invention is designed, in the case of several pressure fluid accumulators, to determine (at least) the lower current threshold for the solenoid valve of the respective valve unit for at least two pressure fluid accumulators of the plurality of pressure fluid accumulators.

[0043] The vehicle can also be understood as a stationary energy unit.

[0044] The stored pressure fluid can be, for example, gaseous hydrogen. Specifically, the pressure fluid is stored under high pressure in the pressure fluid storage tank. Furthermore, the valve unit is arranged directly on the pressure fluid storage tank, for example, at a bottleneck of the pressure fluid storage tank. The valve unit can also be used as a system isolation valve unit or as a valve unit for a fuel cell system.

[0045] The vehicle according to the third aspect of the invention thus has the same advantages as those already described for the method according to the first aspect of the invention or the device according to the second aspect of the invention.

[0046] Further improvements to the invention will become apparent from the following description of some exemplary embodiments of the invention, which are schematically illustrated in the figures. All features and / or advantages arising from the claims, the description, or the drawings, including design details, spatial arrangements, and process steps, can be essential to the invention, both individually and in various combinations. It should be noted that the figures are for descriptive purposes only and are not intended to limit the invention in any way.

[0047] They show schematically: Fig. 1 a flow diagram, Fig. 2 a device, Fig. 3 a sawtooth current profile, Fig. 4 a current waveform through a magnetic coil before, during and after determining the lower current threshold, and Fig. 5 a vehicle.

[0048] In the following figures, identical reference numerals are used for the same technical features even for different embodiments.

[0049] Figure 1 schematically reveals a flowchart of a procedure for determining a lower current threshold US or a lower current threshold US and an upper current threshold OS of a current band B (see e.g. Figure 3 ) a solenoid coil 2 of a solenoid valve for a fluid-communicating valve unit 100 with a pressure fluid accumulator 210a, 210b, e.g. of a vehicle 200 (see e.g. Figure 4), wherein when an electric current at the level of the current band B flows through the solenoid coil 2, an armature of the solenoid valve movable by the solenoid coil 2 is held or is held in a fully open position, wherein the movable armature, when moving between a closed position of the armature and the fully open position of the armature, comprises at least one state of movement and, in the fully open position, a state of rest.The method for determining the lower current threshold US or the lower current threshold US and the upper current threshold OS of the current band B further comprises, as steps, in particular as repetitive steps, actively energizing the solenoid coil 2 of the solenoid valve, wherein the active energizing of the solenoid coil 2 of the solenoid valve is switched off upon detection of an electric current flowing through the solenoid coil 2 at the level of an upper current threshold OS of the current band B, and a renewed active energizing of the solenoid coil 2 of the solenoid valve by the electrical energy source upon detection of an electric current flowing through the solenoid coil 2 at a definable, variable current threshold which is lower than the upper current threshold OS. Furthermore, for determining the lower current threshold US or for determining the lower current threshold US and the upper current threshold OS, a measurement signal, e.g.,The electric current flowing through the solenoid coil 2 is continuously measured to detect a change in the state of the solenoid valve armature between at least one moving state and the resting state of the armature for the duration of the determination of the lower current threshold US or for the duration of the determination of the lower current threshold US and the upper current threshold OS 20. In this example, it is assumed that the movable armature of the solenoid valve is initially (at start-up), i.e., for the current band B resulting from the upper current threshold OS and the current, definable, variable (start-up) current threshold, held in a fully open position. As shown in the flowchart, the lower current threshold US is determined, or the upper current threshold OS is determined.To determine the lower current threshold US and the upper current threshold OS, the level of the definable, variable current threshold is now reduced by one (current) step 10 so frequently, in particular repeatedly, until the change in state of the solenoid valve armature, in this example a change in the state of the armature from the rest state to the moving state, due to the change in the definable, variable current threshold, is (positively) detected 30. However, it is also conceivable that the upper current threshold is also successively changed, in particular decreased or increased.If the change in state of the solenoid valve armature is detected due to a change in the definable, variable current threshold, then the lower current threshold US of current band B is determined based on the definable, variable current threshold 40, whereby the upper current threshold OS can also be determined or adjusted. In particular, the upper current threshold OS is adjusted to the determined lower current threshold US of current band B of the solenoid valve. For example, the previous definable, variable current threshold can be determined as the lower current threshold US of current band B 40. Furthermore, in the method according to the invention, the determined lower current threshold US and / or the determined upper current threshold OS are stored in a memory in one step 50. Advantageously, for the detection of the change in state of the armature, for example,A time constant and / or a frequency spectrum and / or a current frequency of the current flowing through the solenoid coil of the solenoid valve can be considered. Additionally, in an optional step, upon detection of reaching a definable minimum threshold, e.g., 0 amperes, the determination of the lower current threshold US or the determination of the lower current threshold US and the upper current threshold OS can be aborted and an error entry can be made.

[0050] Figure 2 Disclosing a device 220 for determining at least a lower current threshold US or a lower current threshold US and an upper current threshold OS of a current band B of a solenoid coil 2 of a solenoid valve for a valve unit 100 fluid-communicating with a pressure fluid accumulator 210a, 210b, e.g. of a vehicle 200 (see e.g. Figure 4The device 220 has an electrical energy source 222, e.g., 12 volts – the vehicle's on-board voltage – for providing electrical energy to actively energize the solenoid coil 2 of the solenoid valve. The solenoid coil 2 is in Figure 2The device 220 is represented by an ohmic resistor and an (electrical) coil. Furthermore, the device 220 includes an ammeter as a sensor 224 for detecting an electric current flowing through a solenoid coil 2 of a solenoid valve. The device 220 also includes a control unit 226 for switching off the electric current flowing through the solenoid coil 2 of the solenoid valve when an upper current threshold OS of a current band B of the solenoid valve is exceeded, and for actively energizing the solenoid coil (2) of the solenoid valve when a definable, variable current threshold is undershot. For example, the control unit 226 controls a field-effect transistor 241 to switch off or switch on (actively energize) the electric current flowing through the solenoid coil 2 of the solenoid valve.Additionally, during the period when the electric current flowing through the solenoid coil 2 of the solenoid valve is switched off, a "freewheeling transistor" 242 connected in parallel to the solenoid coil 2 can be switched to conduction, e.g., by the control unit 226, so that the electric current flowing through the solenoid coil 2 of the solenoid valve is particularly advantageously reduced due to its ohmic resistance. Furthermore, the device 220 comprises a current-varying unit 228 for changing at least the magnitude of the definable, variable current threshold value, and a measuring unit 230 for measuring and evaluating a measurement signal acquired by the sensor 224 to detect a change in the state of the solenoid valve armature between at least one moving state and a rest state of the armature. To detect the change in the state of the solenoid valve armature, a value based on the measurement signal can, for example, be compared with a limit value.To detect the change in state of the solenoid valve's armature, a classification method (machine learning; e.g., a neural network) can be used as an alternative or additional measure to comparison with a limit value. Furthermore, the device 220 includes a determination unit 232 for determining at least the lower current threshold US of current band B based on the definable, variable current threshold. The device 220 is configured to perform a method according to the invention for determining at least the lower current threshold US of current band B for the solenoid coil 2 of the solenoid valve. In particular, the sensor 224 and / or the current change unit 228 and / or the measuring unit 230 and / or the determination unit 232 can also be part of the control unit 226.Furthermore, the device 220 can have a memory, in particular a non-volatile memory, for storing lower current thresholds US and / or for storing upper current thresholds OS and / or for storing (the) definable, variable current threshold(s).

[0051] Figure 3 The diagram reveals a sawtooth current profile of an electric current flowing through a solenoid coil 2 of a solenoid valve over time t. When the electric current flows through the solenoid coil 2 at the level of a current band B defined by an upper current threshold OS and a lower threshold US, an armature of the solenoid valve, movable by the solenoid coil 2, can be held in the fully open position by pulsating the current through the solenoid coil of the solenoid valve, while simultaneously and easily achieving a mean current permissible for the solenoid coil without damaging the solenoid coil.

[0052] Figure 4 discloses a temporal profile of a (sawtooth) electric current flowing through a magnetic coil 2 before (see section (1)), during (see section (2)) and after (see section (3)) the determination of a (adapted) lower current threshold US by means of a method or device 220 according to the invention.

[0053] The current im, min here denotes a lower minimum current threshold of the current band B of the solenoid coil 2 of the solenoid valve at which the armature of the solenoid valve can (just barely) be held in the fully open position. Over the course of its service life, particularly at the beginning of its service life, the properties of a solenoid valve can change, so that the lower current threshold US and / or the upper current threshold OS used for the operation of the solenoid valve or the solenoid coil 2, i.e., the current band B, must also be adjusted so that the solenoid valve or a valve unit 100 with such a solenoid valve can operate particularly efficiently and the energy consumption is particularly low. In section (1) of the in Figure 4According to the current waveform shown, the lower current threshold US of the current band B of the solenoid coil 2 of the solenoid valve is higher than the lower minimum current threshold im, min of the solenoid coil 2 of the solenoid valve, so that electrical energy is unnecessarily consumed to hold the armature of the solenoid valve in a fully open position. In section (2), the level of the definable, variable (lower) current threshold is gradually reduced by means of the method or device 220 according to the invention in order to change the level of the definable, variable (lower) current threshold for determining a (new, adapted) lower current threshold US (see section (3) of the current waveform).In addition to the stepwise reduction of the level of the definable, variable (lower) current threshold, the upper current threshold OS is also simultaneously reduced stepwise, in particular by the same value as the definable, variable (lower) current threshold US. In section (2) of the in . Figure 4According to the current profile shown, the armature of the solenoid valve releases from a rest state in the fully open position when the definable, variable (lower) current threshold is lower than the lower minimum current threshold im, min of the solenoid coil 2 of the solenoid valve (see circumscription). According to the invention, the release of the armature is detected as a change in the state of the armature, and based on the definable, variable current threshold at which the change in the state of the armature is detected, a new lower current threshold US of the current band B and a new upper current threshold OS are determined, in particular such that when the solenoid coil 2 of the solenoid valve is energized with a current at the level of the current band B, the armature of the solenoid valve is held in the fully open position (see section (3) of the in Figure 4(shown current waveform). In this example, the determined, adapted lower current threshold US in section (3) is greater than the definable, variable (lower) current threshold at which the change of state of the armature has been detected.

[0054] Figure 5Figure 1 schematically discloses a vehicle 200, wherein the vehicle 200 comprises two pressure fluid accumulators 210a, 210b, each with a valve unit 100 having a solenoid valve for controlling the flow of a pressure fluid that can be stored in the respective pressure fluid accumulator 210a, 210b. Furthermore, the vehicle 200 has a device 220 designed according to the invention, wherein the device 220 is further configured to determine at least the lower current threshold US for the solenoid valve of the respective valve unit 100 for each of the two pressure fluid accumulators 210a, 210b. In particular, the respective lower current threshold required for keeping the respective solenoid valve (fully) open, and especially the lower minimum current threshold, can thus be determined by means of the method according to the invention. The vehicle 200 can also be understood as a stationary energy unit, e.g., a generator or a fuel cell heater.

Claims

1. Method for determining at least a lower current threshold value (US) of a current band (B) of a solenoid coil (2) of a solenoid valve for a valve unit (100) fluidically connected to a pressurized fluid reservoir (210a, 210b), in particular of a vehicle (200), wherein, when an electrical current flows through the solenoid coil (2) at the level of the current band (B), an armature of the solenoid valve, which is able to be moved by the solenoid coil (2), is able to be held in a fully open position, wherein the movable armature, when being transferred between a closed position of the armature and the fully open position of the armature, comprises at least one moving state and, in the fully open position, an idle state, wherein the method comprises: - actively energizing the solenoid coil (2) of the solenoid valve, wherein the active energization of the solenoid coil (2) of the solenoid valve is switched off when an electrical current flowing through the solenoid coil (2) at the level of an upper current threshold value (OS) of the current band (B) is detected, and actively energizing the solenoid coil (2) of the solenoid valve again by way of the electrical energy source when an electrical current flowing through the solenoid coil (2) at the level of a definable, changeable current threshold value which is less than the upper current threshold value (OS) is detected, - changing (10) the level of the definable, changeable current threshold value, - continuously measuring (20) a measurement signal in order to detect a change in state of the armature of the solenoid valve between the at least one moving state and the idle state of the armature, - determining (40) at least the lower current threshold value (US) of the current band (B) on the basis of the definable, changeable current threshold value when the change in state of the armature of the solenoid valve is detected (30) due to the change in the definable, changeable current threshold value.

2. Method according to Claim 1, characterized in that the level of the definable, changeable current threshold value is temporarily incrementally increased and / or temporarily incrementally decreased in order to change (10) the level of the definable, changeable current threshold value for determining (40) the lower current threshold value.

3. Method according to either of the preceding claims, characterized in that the electrical current flowing through the solenoid coil (2) is considered as the measurement signal for detecting (30) the change in state of the armature of the solenoid valve between the at least one moving state and the idle state of the armature.

4. Method according to one of the preceding claims, characterized in that a time constant of the current flowing through the solenoid coil (2) of the solenoid valve is considered for detecting (30) the change in state of the armature.

5. Method according to one of the preceding claims, characterized in that a current frequency of the current flowing through the solenoid coil (2) of the solenoid valve is considered for detecting (30) the change in state of the armature.

6. Method according to one of the preceding claims, characterized in that a frequency spectrum of the current flowing through the solenoid coil (2) of the solenoid valve is considered for detecting (30) the change in state of the armature.

7. Method according to one of the preceding claims, characterized in that the upper current threshold value of the current band (B) is adjusted to the determined lower current threshold value of the current band (B) of the solenoid valve.

8. Method according to one of the preceding claims, characterized in that a value based on the measurement signal is compared with a limit value in order to detect (30) the change in state of the armature of the solenoid valve.

9. Method according to one of the preceding claims, characterized in that a classification method is used in order to detect (30) the change in state of the armature of the solenoid valve.

10. Device (220) for determining at least a lower current threshold value (US) of a current band (B) of a solenoid coil (2) of a solenoid valve for a valve unit (100) fluidically connected to a pressurized fluid reservoir (210a, 210b), in particular of a vehicle (200), wherein the device (220) comprises: - an electrical energy source (222) for providing electrical energy for actively energizing the solenoid coil (2) of the solenoid valve, - a sensor (224) for detecting an electrical current flowing through a solenoid coil (2) of a solenoid valve, - a control unit (226) for switching off the electrical current flowing through the solenoid coil (2) of the solenoid valve when an upper current threshold value (OS) of a current band (B) of the solenoid valve is exceeded, and for actively energizing the solenoid coil (2) of the solenoid valve when a definable, changeable current threshold value is fallen below, - a current-changing unit (228) for changing the level of the definable, changeable current threshold value, - a measuring unit (230) for measuring a measurement signal in order to detect a change in state of the armature of the solenoid valve between at least one moving state and an idle state of the armature, - a determination unit (232) for determining at least the lower current threshold value (US) of the current band (B) on the basis of the definable, changeable current threshold value when the change in state of the armature of the solenoid valve is detected due to the change in the definable, changeable current threshold value, wherein the device (220) is designed to carry out a method according to one of the preceding claims.

11. Vehicle (200), wherein the vehicle (200) comprises: - at least one pressurized fluid reservoir (210a, 210b) having in each case a valve unit (100) having a solenoid valve for controlling a flow of a pressurized fluid which is able to be stored in the pressurized fluid reservoir (210a, 210b), - a device (220) designed according to Claim 10, wherein the device (220) is further designed to determine, for the at least one pressurized fluid reservoir (210a, 210b), at least the lower current threshold value (US) for the solenoid valve of the valve unit (100).

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