METHOD AND DEVICE FOR CONTROLLING A FLUID SOLENOID VALVE

Description

[0001] The invention relates to a method and a device for controlling or actuating a fluid solenoid valve in a fluid system of a vehicle.

[0002] Vehicles primarily use pneumatic and hydraulic fluid systems, in which the respective fluid is controlled and switched via fluid valves. Various settings can thus be adjusted by means of electrical control signals via fluid solenoid valves.

[0003] In fluid solenoid valves, an armature, which closes or opens various fluid outlets, is adjusted by energizing a coil assembly. The armature is held in a first switching position (home position) primarily by a spring action and, when the coil assembly is energized by a switching current (engagement current), is moved to the second switching position (actuated position). In the second switching position, the armature is generally held against the spring action by a holding current, which is generally lower than the switching current (engagement current).

[0004] The coil assembly is generally controlled by a driver circuit, particularly with double-sided driver control, i.e., via a lower driver circuit (low-side switch) and an upper driver circuit (high-side switch), between which the coil assembly is connected. This series connection of the driver circuits and the coil assembly is connected between a system voltage (supply voltage) and ground. Pulse width modulation (PWM) can be used, for example, where one of the driver circuits receives a control signal with the PWM signal and switches the coil current on and off according to the pulse width information, i.e., opens and closes an internal switch (e.g., a FET). From the applied system voltage and the set pulse width ratio (between 0% and 100%), the effective applied drive voltage can thus be set as the product of the system voltage and the relative pulse width.The coil current generated by applying the control voltage can be measured, so that information on the control voltage and the coil current is available.

[0005] Several operating modes are possible for the operation of the coil assembly or solenoid: For example, in a simple circuit, a fixed drive voltage can be applied by adjusting the pulse width depending on the system voltage. Such voltage control ensures, in particular, that a sufficient coil current is generated. However, since the ohmic resistance of the coil assembly is temperature-dependent, the coil current will vary depending on the coil temperature.

[0006] Furthermore, current control methods for the coil current are known that can be used in both switching modes, i.e., the switching process for adjusting the armature and also the holding mode for maintaining the adjusted armature. Here, the coil current is measured and controlled by adjusting the control voltage, i.e., in particular by setting a relative pulse width or the PWM ratio. This allows for a more precise adjustment of the coil current.

[0007] EP 1 291 256 A2 discloses a method in which the aim is to improve reliability. This aim is achieved by having a pull-in current la flow through the coil for a duration ti when the solenoid valve is switched on, and by operating the valve with a pulsed continuous current signal for a period t2 to ts when switching from pull-in current to holding current Ih. The pulsed continuous current signal is then slowly extinguished by means of a second switchable diode, and the current at the solenoid valve is monitored via a feedback device.

[0008] However, it turns out that the operation of a fluid solenoid valve is adversely affected at lower temperatures, especially in freezing conditions, and the switching process may be made more difficult, e.g. due to poorer sliding properties or lubrication, and furthermore, the components to be adjusted may stick to, for example, rubber seals.

[0009] The invention is therefore based on the objective of creating a method according to claim 1 and a device according to claim 10 for controlling a fluid solenoid valve, which enable safe operation under different conditions.

[0010] This problem is solved by a method and a device according to the independent claims. The dependent claims describe preferred embodiments.

[0011] Furthermore, an arrangement consisting of the device and the controlled fluid solenoid valve, as well as a fluid system with the fluid solenoid valve and the device, in particular with one or more fluid consumers such as a pneumatic brake system, and a vehicle with the fluid system are provided.

[0012] The fluid solenoid valve is, in particular, a pneumatic solenoid valve for use in a vehicle's compressed air system. According to the invention, it is recognized that current control is particularly advantageous in a higher temperature range, as it allows current consumption and thus energy consumption to be kept low, and furthermore, thermal stress caused by unnecessarily high currents can be avoided or at least minimized. A first operating mode is therefore provided for this purpose. It is also recognized that current control enables direct adjustment of the magnetic force, since the magnetic force is proportional to the current—and not the voltage. The temperature-dependent ohmic resistance of the coil assembly, as well as of corresponding other electrical components in the circuit, can be directly adjusted by regulating the coil current, so that the required coil current is always available, both for the switching process, i.e., for the operation of the solenoid.h. the starting current as well as the holding current can be set.

[0013] However, the invention also recognizes that such current control can be disadvantageous in a lower temperature range, since at low temperatures the coil current does not automatically increase due to the lower resistance, and thus no reserve is built up to compensate for temperature-related problems at low temperatures, especially freezing. For example, the poorer lubrication due to the higher viscosity of the lubricants and any sticking effects on the rubber seals may result in the armature not being adjusted, or not being adjusted quickly enough, i.e., not with sufficient reliability. Furthermore, it is also recognized that a higher coil current at lower temperatures, especially freezing, is advantageous, as it can lead to local heating and thus warming of the coil assembly, including the armature and seals adjusted by it.This allows an inner area of ​​the solenoid valve to be heated locally.

[0014] Therefore, according to the invention, in a lower temperature range, the current control is advantageously no longer performed, i.e., the first operating mode is no longer used, but a second operating mode is selected in which a suitable voltage value is set. According to a particularly preferred embodiment, the voltage value is controlled constantly, i.e., a constant voltage value is set. Thus, due to the decreasing ohmic resistance at falling temperatures, the generated coil current will increase with the falling temperature, thereby producing a stronger heating effect and also enabling greater forces for adjusting the armature.

[0015] An operating criterion is provided to decide whether to use the first or second operating mode. According to a particularly preferred embodiment, this operating criterion can be applied without directly measuring the coil temperature; that is, the choice between the operating modes can be made without using a direct measurement of the coil temperature. This approach recognizes that measuring the coil temperature is not without its problems, as direct measurements are difficult and measurements taken outside the coil are inaccurate because external temperatures differ significantly from the actual coil temperature.Rather, it is recognized that the set effective drive voltage can be used as an operating criterion: If the first operating mode of the current control is assumed to be in the upper temperature range, then at lower temperatures, the regulated drive voltage decreases along with the ohmic resistance of the coil arrangement. Thus, a limit voltage, i.e., a limit value of the drive voltage, can be used as an operating criterion; as soon as the drive voltage falls below or reaches the limit voltage, the system can switch to the second operating mode and keep this drive voltage constant.

[0016] In the second operating mode, different sub-ranges can also be set. In particular, sub-ranges with constant voltage regulation can be configured. By determining the set coil current, the respective coil temperature can be estimated, since the coil current increases at lower temperatures. This allows for different control voltages to be set within these sub-ranges, enabling adjustments to address the various adverse effects occurring in the lower temperature range, such as applying different counteracting forces. For example, sticking effects of rubber seals occur particularly at sub-zero temperatures, so a higher effective control voltage can be set in a lower temperature sub-range.

[0017] Thus, the second operating mode can also be subdivided into sub-operating modes.

[0018] According to the invention, several advantages are achieved: Advantages of current control can be realized, in particular the precise adjustment of a current value while avoiding unnecessary power consumption and unnecessary thermal stress caused by excessively high currents. Current control can be achieved over a wide upper temperature range, e.g., from a temperature above 20°C.

[0019] Furthermore, in the lower temperature range, the detrimental effects of insufficient current from current control can be avoided by selecting the second operating mode, thus achieving both adequate heating and the generation of higher forces to counteract potential friction or sticking effects. Such voltage control, particularly by setting a constant voltage value, can therefore be implemented with minimal hardware and simple control measures.

[0020] By setting a transition between the first operating mode and the second operating mode with a continuous drive voltage, i.e. without a jump in the drive voltage, no unnecessarily high or abrupt loads occur.

[0021] By defining the operating criterion solely based on the control voltage, a safe and accurate determination can be achieved, even without unnecessary measurement of the coil temperature.

[0022] This also enables a fluid system with a reliable fluid solenoid valve, allowing for low energy consumption, high temperature stability, and therefore reliable operation. This is particularly advantageous in vehicle applications, where a variable system voltage is available depending on the load and supply conditions, such as whether the generator is switched on or off and different electrical consumers are in use. Thus, the current regulation avoids the problems of uncertain system voltage in the high-temperature range and utilizes the decreasing resistance in the lower-temperature range to build up switching current reserves.

[0023] The operating criterion can also include a comparison or dependency on temperature values, such as the ambient temperature and / or a device temperature or coil temperature.

[0024] The fluid system can be, in particular, a compressed air system, i.e., with a pneumatic solenoid valve as the fluid solenoid valve. However, a design in a hydraulic system is also fundamentally possible.

[0025] The invention is explained in more detail below with reference to the accompanying drawings, which illustrate several embodiments. The drawings show: Fig. 1 Pneumatic solenoid valves as examples of a fluid solenoid valve; 1a) a 2 / 2 valve, 1b) a 3 / 2 valve and c) a section through an embodiment of a 3 / 2 valve; Fig. 2 A curve diagram of the control voltage and the coil current as a function of temperature; Fig. 3 A diagram of an embodiment with some process steps; Fig. 4 An embodiment of a hardware configuration; Fig. 5 A flowchart according to an embodiment of the method according to the invention.

[0026] A pneumatic solenoid valve 1 has, according to the block diagram of Figure 1a) and the exemplary section of theFigure 1b ) a coil assembly (solenoid) 2 with coil connections 2a, 2b and pneumatic connections 3 for pneumatic lines 4. According to the sectional view of the Figure 1c In general, an armature 5 is adjustable by energizing the coil arrangement 2, which is generally pre-tensioned to a basic position by a spring 6 and is moved to the actuated position when energized.

[0027] When the coil arrangement 2 is energized, the armature 5 is first moved from the home position (first switching position) to the second switching position against the spring tension of the spring 6 in a first switching mode S1, the switching process (pull-in) by means of a switching current IA (pull-in current); subsequently, the armature 5 is moved in a second switching mode S2, the holding mode (hold) by means of a holding current IH held, generally IH < IA.

[0028] The pneumatic solenoid valve 1 can, for example, be configured according to Fig. 1a) as a 2 / 2 valve, i.e., a shut-off valve for blocking and allowing a pneumatic flow, or for example according to Fig. 1b It can also be designed as a 3 / 2 switching valve. Solenoid valve 1 can also be designed as a hydraulic valve.

[0029] The solenoid valve 1 is controlled via a Figure 1 A general control circuit 7 is shown, which outputs an effective control voltage UA as a DC voltage using pulse width modulation (PWM). For this purpose, a system voltage Us is output in timed pulses, where the effectively applied control voltage UA is the time component or relative pulse width PW, which can be varied between 0% and 100%. Thus, UA = Us * PW.

[0030] According to Figure 2Two operating modes, BM1 and BM2, are provided for controlling the coil arrangement 2. Both operating modes, i.e., the first operating mode BM1 and the second operating mode BM2, can be used in both switching modes: the first switching mode S1 for active switching (pull-in) to pull in the armature 5, and the second switching mode S2 for holding the armature 5 in the second switching position. Accordingly, in Figure 2 Both switching modes S1 and S2 are also shown. According to Figure 2 The abscissa or horizontal axis shows the coil temperature T (increasing to the left) of the coil arrangement 2, which, preferably in the embodiments shown here, is not measured by an additional temperature sensor. Furthermore, in Figure 2 Two vertical axes or ordinates are shown: the control voltage UA, which, as explained above, is the product of the system voltage Us and the time component PW, as well as the coil current I flowing through the coil arrangement 2.

[0031] Thus, in Figure 2 For the first switching mode S1, i.e. the switching process or pulling process of the active adjustment of the armature 5, the switching current (pulling current) IA and the applied pulling control voltage UAA are shown, and for the second switching mode S2, the holding current IH and the applied holding control voltage UAH are shown accordingly.

[0032] As from Figure 2 As can be seen, the first operating mode BM1 is provided in an upper temperature range TO (upper temperature) and the second operating mode BM2 in a lower temperature range TU (lower temperature), which are separated e.g. at a limit temperature TG = 20° C, i.e. e.g. room temperature.

[0033] In the first operating mode BM1, current control is achieved, specifically by maintaining a constant current value for the switching current IA or the holding current IH. Thus, in the illustrated embodiment, the switching current IA (pulling-on current) is regulated to a current value of 1.15 mA in the first operating mode BM1. For this purpose, the control voltage UA is adjusted accordingly: The current value of 1.15 mA is set for the switching current IA, so that the control voltage UA is adjusted or regulated accordingly. The ohmic resistance R of the coil arrangement 2 is temperature-dependent, generally increasing essentially linearly with temperature, particularly in the upper temperature range TO between 20°C and 120°C. Therefore, when regulating (loop control) the coil current I, a control voltage UA is set that decreases towards lower temperatures in this temperature range or exhibits a linear increase with temperature.

[0034] In the second operating mode, BM2, the control voltage UA is set. Advantageously, it is set to a constant value, as is particularly relevant from… Figure 2 It can be seen that the effective drive voltage UA = U x PW is constant. Accordingly, the coil current I changes depending on the ohmic resistance R; thus, I = UA / R, so that in the diagram of the Figure 2 The coil current I increases in both switching modes towards lower coil temperatures T, corresponding to the linear decrease of the ohmic resistance R with low coil temperature T or the linear increase of the ohmic resistance with increasing coil temperature T.

[0035] The two operating modes BM1 and BM2 are advantageously continuously transitioned into one another, so that in particular the coil current I is continuously changed in the transition range.

[0036] In Figure 2The electrical values ​​of the first switching mode S1, i.e., the switching current IA and the switching control voltage UAA, are represented by dashed lines and are higher than the corresponding electrical values ​​of the second switching mode S2, i.e., the holding mode, which counteract the spring tension of spring 6 and are represented by solid lines as holding current IH and holding control voltage UAH.

[0037] The dimensions shown are for a pneumatic solenoid valve 1 of a pneumatic circuit in a commercial vehicle, where, in the first switching mode S1, a switching current (pulling current) IA of 1.15 mA is constantly regulated to adjust the armature 5 in the first operating mode BM1, i.e., in the upper temperature range TO between 120°C and 20°C, by adjusting the control voltage UA using pulse width modulation (PWM). The percentage values ​​or relative pulse widths PW of the PWM control depend on the respective system voltage Us; this, in turn, can depend on various influences in the vehicle, e.g., the current battery voltage, whether the generator (alternator) is currently active and feeding a high charging voltage of, for example, 28.8 V into the vehicle electrical system or not, and the ohmic resistances of the current consumption of the other consumers.

[0038] Thus, the current system voltage Us, which is available to the control circuit, is adjusted to the appropriate control voltage UA via pulse width modulation (PWM). At T = 120°C, the value UA = U x PW is 1600, and decreases linearly to, for example, UA = 1150 at T = 20°C. In the second operating mode, BM2, the control voltage UA is set to this constant value of the pull-in control voltage UAA, as described above. Accordingly, the switching current IA, which was constantly regulated in the upper temperature range TO by the first operating mode, BM1, increases from IA = 1.15 mA at 20°C (i.e., in the transition range) to, for example, IA = 1.42 mA at T = -40°C.

[0039] Adjusting or controlling the PWM signal results in, for example, the following values: At T = 120°C, a PWM width of PWM32 = 50% is set for the switching current IA = 1.15 mA at a system voltage Us = 32 V, a PWM width of PWM24 = 67% at Us = 24 V, and a PWM width of PWM16 = 100% at a system voltage of Us = 16 V; these values ​​then decrease with a correspondingly decreasing coil temperature T in the first operating mode BM1 down to the lower limit at T = 20°C to the values ​​PWM32 = 36%, PWM24 = 48% and PWM6 = 72%; in the second operating mode BM2, these pulse widths remain correspondingly constant.

[0040] In the second switching mode S2, i.e., the holding mode, at T = 120°C, PWM values ​​of PWM32 = 25%, PWM24 = 33%, and PWM16 = 50% are set to adjust the holding current IH = 0.575 mA. These values ​​are then reduced in the first operating mode BM1 to PWM values ​​of PWM32 = 18%, PWM24 = 24%, and PWM16 = 36% as the coil temperature drops to T = 20°C. These values ​​are then kept constant in the second operating mode BM2, i.e., the lower temperature range TU down to T = -40°C.

[0041] Figure 3 shows a circuit diagram of the device and method of such an embodiment; Figure 4 shows the training of Fig. 3 as a general block diagram.

[0042] According to Figure 3The current system voltage Us is determined by digitizing it via an analog-to-digital converter 12, resulting in a digital value Ub. This value is multiplied by the current PWM width PW in the computing unit 14, so that the current drive voltage UA = Ub x PW is output to a comparator 15. The comparator 15 also receives a threshold voltage TV from, for example, a storage unit 16 and compares these values ​​to determine if UA > TV. In the first case y, i.e., UA > TV, it is recognized that the circuit is in the upper temperature range TO, and therefore the first operating mode BM1 must be set. A control unit 17 then performs current control and outputs the currently set PWM width value PW back to the computing unit 14.Thus, in the first operating mode BM1, control by the closed control loop is enabled, whereby the pulse width PW calculated from the deviation of the actual current value to the target current value is then supplied to a driver circuit device 19 for controlling the coil arrangement 2.

[0043] For this purpose, the driver circuit device 19 has a lower driver circuit 20 (LSS, low side switch), which is preferably connected according to Fig. 3 the calculated pulse width PW is supplied, wherein an upper driver circuit 21 (HSS, high side switch) of the driver circuit device 19 is connected to the system voltage Us, with a freewheeling diode 24 between the output of the lower driver circuit 20 and the connection of the system voltage Us, for the freewheeling current of the coil arrangement 2.

[0044] The lower driver circuit 20 (low-side switch) and the upper driver circuit 21 (high-side switch) are designed in the usual way for controlling the coil arrangement 2 from both sides. The freewheeling path via the freewheeling diode 24 serves to feed the energy stored in the coil back into the system.

[0045] To measure the coil current I, a control output of the upper driver circuit 21 (HSS) is provided according to this embodiment. This control output provides a control current Ic, which is calculated as a partial current value of, for example, 1 / 10 of the coil current I, i.e., Ic = I / 10. This control current Ic is output to ground via a reference resistor RR. Thus, a measurement or control voltage Uc, calculated as Uc = Ic x RR, can be tapped at the control output and supplied to the control device 17. This device indirectly measures the coil current I and adjusts the pulse width PW accordingly as a relative value between 0% and 100%.

[0046] If the comparison device 15 decides on "No" in the comparison UA ​​> TV, i.e., the current drive voltage UA is less than the limit voltage TV, the second operating mode BM2 is set according to branch n below by the coil current control device 30, i.e., as control to output the pulse width PW, which is approximately inversely proportional to the system voltage, to the lower driver device 20.

[0047] As an alternative to the measuring circuit through the reference resistor RR with the output for the control current Ic, a current measurement can also be carried out using a shunt resistor, which is connected, for example, between ground and the lower driver circuit 20 (low side switch), so that the coil current I is measured as the voltage drop across the shunt resistor.

[0048] According to Fig. 3The system voltage Us is input as a digital value Ub to the control unit 18, which is in particular designed as a microcontroller, via the analog-to-digital converter 12, wherein the control unit 18 reads the value for the limit voltage TV from an internal or external storage device 16, and wherein the control unit 18 further operates according to the general block diagram of the Fig. 4 The control voltage Uc is received and, according to the operating criterion K1, subsequently sets the corresponding operating mode BM1 or BM2, whereby it either directly outputs the control voltage UA or outputs a control signal with the relative pulse width PW to the lower driver circuit 20, which then accordingly sets the coil current I between the upper driver circuit 21, the coil arrangement 2 representing the load and the lower driver circuit 20.

[0049] The inventive method is thus exemplified in Figure 5 depicted.

[0050] After starting in step St0, the switching mode is subsequently determined in step St1, i.e., whether According to the standby switching mode S0, the solenoid valve 2 is not to be actuated at all and thus remains in its unenergized basic position, or a pull-in process or switching process and thus, according to switching mode S1, an adjustment process to adjust the armature 5 is to be set, or the holding mode is present and, as switching mode S2, the coil arrangement 2 is to be actuated with a holding current IH.

[0051] In step St2, the available system parameters and measured values ​​are read in. Specifically, the system voltage Us is read in as a digital value Ub via the ADC 12. Furthermore, the limit voltage TV is read in, if applicable, and a currently set pulse width PW is also read in, if applicable. In the subsequent calculation step St3, the control voltage UA is determined from this as UA = Ub x PW. Steps St2 and St3 can also be combined.

[0052] In the subsequent decision step St4, the operating criterion K1 is checked, i.e., whether the control voltage UA is above the limit voltage TV, and depending on this, the following steps are carried out accordingly: If the limit voltage TV is exceeded in decision step St4, the first operating mode BM1 of the current control is subsequently carried out in control step St5 according to branch y, and accordingly according to Figure 3 The partial steps described there are carried out, i.e., the measurement of the current coil current I, e.g., via the voltage drop Uc = Ic*RR of the auxiliary output or a shunt resistor, with subsequent control or adjustment of the relative pulse width PW as a closed control loop; if the limit voltage TV is undershot in the decision step St4, the second operating mode BM2 is carried out according to branch n in the control step St6 and thus a constant control voltage UA is set, i.e., the relative pulse width PW is thus set as a function of the system voltage Us or its digitized value Ub.

[0053] In both cases, the coil arrangement 2 is subsequently controlled via the driver circuit device 19 in step St7. wherein the lower driver circuit 20 of the driver circuit device 19 is set by the determined relative pulse width PW, and the procedure is reset again before step St2, in particular before step St1. Reference symbol list (part of the description)

[0054] 1 Fluid solenoid valve, pneumatic solenoid valve 2 Coil assembly (solenoid arrangement) 2a, 2b Coil connections 3 Pneumatic connections 4 Pneumatic lines 5 Armature 6 Spring 7 Control circuit 12 Analog-to-digital converter 14 Computing unit 15 Comparator unit 16 Storage unit 17 Control unit 18 Control unit 19 Driver circuit unit from driver circuits 20, 21 20 Lower driver circuit 21 Upper driver circuit 24 Freewheeling diode 30 Coil current control unit 40 Fluid system, in particular compressed air system 41 Vehicle 45 Device BM1 first operating mode BM2 second operating mode Icoil current Iswitching current (pull-in current) Iholding current Ic control current K1 Operating criterion PW Time component, Pulse width Rohm resistance RR Reference resistance S1 first switching mode S1 S2 second switching mode S2 Tcoil temperature Tlimit temperature Tupper temperature range Tlower temperature range Tlimit voltage UA Effective drive voltage Us System voltage Ub Digitized value of the system voltage Us Uc Control voltage UAA Pull-in drive voltage UAH Hold drive voltage

Claims

1. Method for activating a fluid solenoid valve (1) in a fluid system (40) of a vehicle (41), in which an activation voltage (UA) is applied to a coil arrangement (2) of the fluid solenoid valve (1) in order to set a switching mode (S0, S1, S2), wherein the activation voltage (UA) is set in at least two different operating modes (BM1, BM2) depending on an operating criterion (K1), wherein, in a first operating mode (BM1), current control of the coil current (I) flowing through the coil arrangement (2) is carried out, and in a second operating mode (BM2) which is different from the first operating mode (BM1), the activation voltage (UA) is set without current control, characterized in that the operating criterion (K1) comprises a comparison of the current activation voltage (UA) with a limit voltage (TV), or is formed by the comparison, wherein in a first case, where the activation voltage (UA) exceeds the limit voltage (TV), the first operating mode (BM1) is set, and in a second case, where the activation voltage (UA) falls below the limit voltage (TV), the second operating mode (BM2) is set.

2. Method according to claim 1, characterized in that in the second operating mode (BM2), the activation voltage (UA) is set independently of the coil current (I), in particular is set to be constant.

3. Method according to either of the preceding claims, characterized in that the operating criterion (K1) is provided without measuring a current coil temperature (T).

4. Method according to any of the preceding claims, characterized in that the fluid solenoid valve (1) is adjustable between a basic position spring-preloaded by a spring (6) and an activated position, wherein the coil arrangement (2) can be activated in at least the following switching modes (S0, S1, S2): a sleep switching mode (S0) without energization of the coil arrangement (2), a first switching mode (S1) for setting a switching current (IA) for adjusting an armature (5) of the solenoid valve (1) from the basic position to the activated position, and a holding mode as a second switching mode (S2) for setting a holding current (IH) for holding the armature (5) in the activated second switching position, counter to the spring preload, wherein the switching current (IA) is greater than the holding current (IH), wherein in the first and the second switching mode (S1, S2), the coil current (I) is set depending on the operating criterion (K1) in each case.

5. Method according to any of the preceding claims, characterized in that the first operating mode (BM1) takes place in an upper temperature range (TU) and the second operating mode (BM2) takes place in a lower temperature range (TU), wherein a transition temperature or limit temperature (TG) is between 10°C and 40°C, e.g. between 15°C and 25°C.

6. Method according to any of the preceding claims, characterized in that in the second operating mode (BM2), a plurality of sub-ranges are formed, wherein in a lower sub-range, a different constant voltage value is set than in an upper sub-range with a smaller coil current (IA, IH).

7. Method according to any of the preceding claims, characterized in that the activation voltage (UA) is generated as an effective activation voltage (UA) by pulse width modulation from a present system voltage (Ub) and a relative pulse width (PW) to be set, e.g. by outputting pulse width information (PW) to a driver circuit device (19) of the coil arrangement (2), e.g. a lower driver circuit (20) or upper driver circuit (21) of the driver circuit device (19).

8. Method according to claim 7, characterized in that the effective activation voltage (UA) is determined by measuring a present system voltage (Us) by means of analog-digital conversion to a digital operating voltage value (Ub) and multiplication by the set pulse width (PW), wherein in the first operating mode (BM1), the current control is carried out by determining the effective activation voltage (UA) and setting the pulse width (PW) as well as measuring the coil current (IA), e.g. via a shunt resistor or measuring a comparison current or control current (Ic) proportional to the coil current (IA).

9. Method according to any of the preceding claims, characterized in that a pneumatic solenoid valve (1) in a compressed air system (40) of a vehicle is activated as the fluid solenoid valve.

10. Apparatus (45) for activating a fluid solenoid valve (1) in a fluid system (40), in particular a compressed air system of a vehicle (41), wherein the apparatus (45) comprises: a driver circuit device (19) for activating a coil arrangement (2) of the fluid solenoid valve (1), a control device (18) which is designed to carry out a method according to any of the preceding claims.

11. Apparatus (45) according to claim 10, wherein the control device (18) comprises: an analog-digital converter (12) for digitizing a present system voltage (Us) and determining a digital operating voltage value (Ub), and a computing device (14) and a comparison device (15) for evaluating the operating criterion (K1).

12. Apparatus (45) according to claim 10 or 11, characterized in that the control device (18) determines and sets a pulse width (PW) for activating the driver circuit device (19) to form a pulse width modulation for the coil arrangement (2).

13. Apparatus (45) according to any of claims 10 to 12, characterized in that the driver circuit device (19) comprises a lower driver circuit (20) and an upper driver circuit (21), between which the coil arrangement (2) is connected, wherein a series circuit comprising the upper driver circuit (21), the coil arrangement (2) and the lower driver circuit (20) can be connected to the supply voltage (Us).

14. Arrangement comprising an apparatus (45) according to any of claims 10 to 13, and the fluid solenoid valve (1) which has the coil arrangement (2) and is activated by the apparatus (45).

15. Fluid system (40) for a vehicle (41), which comprises an arrangement according to claim 14 and fluid consumers connected by the fluid solenoid valve (1).

16. Vehicle (41) comprising a fluid system (40) according to claim 15.