Control device and method for operating a solenoid valve

Abstract

The invention relates to a control device (24) and a method for operating at least one solenoid valve (14) of a braking system of a vehicle by increasing or decreasing the current intensity (I 14 ), the solenoid valve (14) which is initially in a first switching state is switched from the first switching state to a second switching state different from the first switching state, wherein the current intensity (I 14 ) during a transition time interval of at least 20 milliseconds, increasing or decreasing the current intensity (I 14 ), the magnitude of the slope being between 0.05 amperes per second and 5 amperes per second during said transition time interval. The invention also relates to a braking system for a vehicle.

Description

Technical Field

[0001] The invention relates to a control device for at least one solenoid valve of a brake system of a vehicle. The invention also relates to a brake system for a vehicle. Furthermore, the invention relates to a method for operating at least one solenoid valve of a brake system of a vehicle. Background Art

[0002] It is known from the prior art to equip a brake circuit of a vehicle's brake system with two wheel brake cylinders, wherein each wheel brake cylinder has a separate wheel inlet valve (Radeinlassventil) upstream and each wheel brake cylinder has a separate wheel exhaust valve (Radauslassventil) downstream. For example, DE 102013208703 A1 describes a dual-circuit brake system with two brake circuits, each of which has a first wheel brake cylinder, a first wheel inlet valve, a first wheel exhaust valve, a second wheel brake cylinder, a second wheel inlet valve and a second wheel exhaust valve. Summary of the invention

[0003] The present invention proposes a control device for at least one solenoid valve of a brake system of a vehicle having the features according to the invention, a brake system for a vehicle having the features according to the invention, and a method for operating at least one solenoid valve of a brake system of a vehicle having the features according to the invention.

[0004] The present invention proposes an improved possibility for switching at least one solenoid valve of a brake system of a vehicle when setting / maintaining a corresponding desired pressure in a master brake cylinder of the corresponding brake system and / or in at least one wheel brake cylinder of the corresponding brake system. As described in detail below, at least one solenoid valve can be operated with the aid of the present invention so that component tolerances at the corresponding solenoid valve do not (substantially) affect the setting / maintenance of the corresponding desired pressure. Furthermore, the present invention can prevent a sudden / unexpected "sinking" of a brake operating element / brake pedal of the corresponding brake system during actuation of a brake operating element by a driver of a vehicle equipped with the brake system, which "sinking" is also known by the following name: stick-slip effect or stick-slip effect. The present invention thus contributes significantly to increasing the braking comfort of the driver of the corresponding vehicle.

[0005] By varying the current intensity of the current flowing through at least one solenoid coil of the respective solenoid valve, so that the magnitude of the slope during the transition time interval is between 0.05 amperes per second and 5 amperes per second, component tolerances on the solenoid valve (which affect the interaction between the adjustable valve part of the solenoid valve and the magnetic field caused by means of the at least one solenoid coil of the solenoid valve) can be "compensated", so that despite component tolerances the solenoid valve still reliably performs its desired function. This is a major advantage compared to the prior art, in which, due to component tolerances, conventionally a limitation of the desired functional capacity of a valve constructed in this way had to be tolerated.

[0006] The invention can be applied in particular to at least one continuously adjustable / continuously switchable solenoid valve, which can be adjusted / switched to at least one partially open state in addition to its completely closed state and its completely open state. However, it should be explicitly pointed out that the feasibility of the invention is not limited to certain valve types.

[0007] In an advantageous embodiment of the control device, the actuation mechanism is designed to switch the solenoid valve, which is initially in its completely closed state as a first switching state, from the completely closed state to a partially open or completely open state as a second switching state by increasing or decreasing the current intensity of the current flowing through the at least one solenoid coil of the solenoid valve. Advantageously, by increasing or decreasing the current intensity of the current flowing through the at least one solenoid coil of the solenoid valve so that the magnitude of the current intensity during the transition time interval is between 0.05 amperes per second and 5 amperes per second, in this case, in particular component tolerances can be compensated, which reduce the interaction between the displaceable valve part of the solenoid valve and the magnetic field caused by means of the at least one solenoid coil of the solenoid valve.

[0008] Preferably, if the solenoid valve is a normally open solenoid valve, the control mechanism is designed to reduce the current intensity of the current flowing through at least one solenoid coil of the normally open solenoid valve by a slope between -0.05 amperes per second and -5 amperes per second while the normally open solenoid valve remains in its completely closed state. As described in detail below, in this way, a "sudden opening" of the solenoid valve can be avoided, which in the prior art often leads to a "sinking" of the brake operating component.

[0009] It is also advantageous if the control device is designed to switch the solenoid valve, which is initially in a partially open or fully open state as a first switching state, from the partially open or fully open state to its fully closed state as a second switching state by increasing or decreasing the current intensity of the current flowing through the at least one solenoid coil of the solenoid valve. By increasing or decreasing the current intensity of the current flowing through the at least one solenoid coil of the solenoid valve so that the magnitude of the current intensity during the transition time interval is between 0.05 amperes per second and 5 amperes per second, component tolerances can also be compensated in this case, which reduce the interaction between the displaceable valve part of the solenoid valve and the magnetic field caused by the at least one solenoid coil of the solenoid valve.

[0010] In another advantageous embodiment of the control device, the control mechanism is designed to increase or decrease the current intensity of the current flowing through at least one electromagnetic coil of the electromagnetic valve so that the electromagnetic valve, which is initially in its fully open state as the first switching state, switches from the fully open state to a partially open or fully closed state as the second switching state. Alternatively or additionally, the control mechanism can also be designed to increase or decrease the current intensity of the current flowing through at least one electromagnetic coil of the electromagnetic valve so that the electromagnetic valve, which is initially in its partially open or fully closed state as the first switching state, switches from the partially open or fully closed state to its fully open state as the second switching state. By designing the control device / its control mechanism in this way, component errors on the electromagnetic valve can also be compensated.

[0011] The aforementioned advantages are also ensured for a brake system for a vehicle, which has such a control device and at least one solenoid valve which can be controlled by the control device. The at least one solenoid valve can be, for example, at least one wheel inlet valve, at least one wheel outlet valve, at least one high-pressure switching valve and / or at least one switching valve. Thus, the invention can be implemented using a variety of valve types installed in the brake system.

[0012] Furthermore, a corresponding method for operating at least one solenoid valve of a brake system of a vehicle also provides the above advantages. It should be noted that the method for operating at least one solenoid valve of a brake system of a vehicle can be improved according to the above-described embodiment of the control device. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Other features and advantages of the present invention are described below with the aid of the accompanying drawings.

[0014] 1A and 1B show schematic diagrams of an embodiment of a control device and a brake system equipped with the control device, and show a coordinate system for introducing the working principle of the control device and the brake system; and

[0015] Figure 2 A flow chart is shown for describing one specific embodiment of a method for operating at least one solenoid valve of a brake system of a vehicle. DETAILED DESCRIPTION

[0016] 1A and 1B show schematic diagrams of one embodiment of a control device and a brake system equipped with the control device, and show a coordinate system for explaining the operating principle of the control device and the brake system.

[0017] exist Figure 1Aa and Figure 1Ba The brake system schematically shown in FIG. 1 is, for example, a dual-circuit brake system with two brake circuits 10, wherein each of the two brake circuits 10 is respectively configured with a first wheel brake cylinder 12, a first wheel inlet valve 14 disposed upstream of the first wheel brake cylinder 12, a first wheel exhaust valve 16 disposed downstream of the first wheel brake cylinder 12, a second wheel brake cylinder 18, a second wheel inlet valve 20 disposed upstream of the second wheel brake cylinder 18, and a second wheel exhaust valve 22 disposed downstream of the second wheel brake cylinder 18. For example, in Figure 1Aa and Figure 1Ba The brake system shown in has an X-brake circuit classification, wherein its two first wheel brake cylinders 12 are assigned to the rear axle and its two second wheel brake cylinders 18 are assigned to the front axle. However, it is expressly pointed out here that the usability of control device 24 described below is not limited to a certain type of brake system, not to a specific brake circuit classification and not to a specific vehicle type / motor vehicle type of vehicle / motor vehicle equipped with the brake system.

[0018] The functioning of control device 24 will be described below by way of example with reference to the actuation of the (corresponding) first wheel inlet valve 14 by control device 24. Figure 1Aa As can be seen in FIG. 1 , control device 24 has an actuation device 26 which is designed at least for adjusting the current intensity I of the current flowing through at least one electromagnetic coil of first wheel inlet valve 14. 14 , in order to switch first wheel intake valve 14 in this way. This can be understood as the current intensity I of the current flowing through the at least one electromagnetic coil of first wheel intake valve 14 14 By means of actuation device 26, it can be changed / changed so that first wheel inlet valve 14, which is initially in the first switching state, is switched by current intensity I 14As will become apparent from the following description, the first switching state (or the second switching state) may be understood as any switching state of first wheel intake valve 14 in which, due to its design, first wheel intake valve 14 is controllable and / or maintainable if the (time-averaged) current intensity I of the current flowing through at least one electromagnetic coil of first wheel intake valve 14 is 14 is equal to the value / average value corresponding to the first switching state (or the second switching state). In particular, when the current intensity I of the current flowing through the at least one electromagnetic coil of the first wheel intake valve 14 14 During the increase or decrease, the control device 26 is additionally designed to increase or decrease the current intensity I with a constant or variable slope during a transition time interval of at least 20 milliseconds. 14 The magnitude of the slope during this transition time interval is (only) between 0.05 amperes per second and 5 amperes per second. The advantages of actuating first wheel inlet valves 14 by means of control device 24 will be described below.

[0019] During the transition time interval, the magnitude of the slope of the current flowing through the at least one electromagnetic coil of first wheel intake valve 14 is (only) between 0.05 amperes per second and 5 amperes per second, which transition time interval is preferably longer than 50 milliseconds, in particular longer than 75 milliseconds, and in particular longer than 100 milliseconds. During the transition time interval, the magnitude of the (positive or negative) slope of the current flowing through the at least one electromagnetic coil of first wheel intake valve 14 is preferably (only) between 0.1 amperes per second and 5 amperes per second, for example (only) between 0.2 amperes per second and 5 amperes per second, in particular (only) between 0.2 amperes per second and 3 amperes per second, or between 1 ampere per second and 5 amperes per second. Thus, the current intensity I of the current flowing through the at least one electromagnetic coil of first wheel intake valve 14 is 14 The increase or decrease can be understood as the current intensity I 14 A continuous / linear increase or decrease during the transition time interval.

[0020] The above-described behavior of control device 24 can also be advantageously applied to all other valves 16, 20 and 22 when using it to actuate first wheel intake valve 14. Advantageously, actuation device 26 is thus designed to switch all valves 14, 16, 20 and 22 accordingly by adjusting the corresponding current intensity I of the current flowing through at least one solenoid coil of the corresponding valve 14, 16, 20 and 22. 14 ,I 16 ,I 20 and I 22In this way, each high-pressure switching valve 28 and each switching valve 30 of the brake circuit 10 of the brake system can also be controlled / switched by means of the control device 24 .

[0021] The valves 14, 16, 20, 22, 28 and 30 can be respectively referred to as solenoid valves. Each valve 14, 16, 20, 22, 28 and 30 has a displaceable valve part, wherein each displaceable valve part can be displaced by means of a magnetic field caused by energizing at least one solenoid coil of the corresponding valve 14, 16, 20, 22, 28 and 30. Each valve 14, 16, 20, 22, 28 and 30 can thus be selectively switched by energizing at least one of its solenoid coils more strongly or by reducing / interrupting the current flowing through at least one of its solenoid coils.

[0022] 1A and 1B, actuation device 26 is additionally designed to determine a first setpoint value for a first brake pressure in first wheel brake cylinder 12 and a second setpoint value for a second brake pressure in first wheel brake cylinder 18. The first setpoint value and the second setpoint value are determined, for example, taking into account the following variables: a setpoint total braking torque M to be applied to at least one wheel and / or at least one axle of the vehicle and / or a desired value requested by the driver of the vehicle and / or an automatic speed control of the vehicle; total The theoretical total braking torque value and possible values ​​for at least one engine braking torque M applied to at least one wheel and / or at least one axle gen-front and M gen-rear - For example, the engine braking torque M applied to the front axle gen-front and the engine braking torque M applied to the front axle gen-rear ——at least one engine-braking torque value. The control device 26 analyzes, for example, at least one sensor signal 32a about the actuation of the brake actuating element / brake pedal 32 by means of a driver's braking force 34 of the driver to determine the first setpoint value and the second setpoint value. In addition, the control device 26 can be designed to receive information about the current availability of the electric drive motor that can be used as a motor. The control device 26 can also be designed in particular to determine at least one applied engine-braking torque M taking into account the at least one sensor signal 32a and the received information. gen-front and M gen-rear The electric drive motor is controlled accordingly.

[0023] After determining a first theoretical value for the first brake pressure and a second theoretical value for the second brake pressure, control device 26 is designed to regulate the second brake pressure in second wheel brake cylinder 18 according to the first theoretical value at least by means of first wheel inlet valve 14 of the same brake circuit 10, and to regulate the first brake pressure in first wheel brake cylinder 12 according to the second theoretical value at least by means of first wheel exhaust valve 16 of the same brake circuit 10, when second wheel inlet valve 20 is in its open switching state and second wheel exhaust valve 22 is in its closed switching state.

[0024] As in Figure 1Aa As can be seen in , the brake system can be operated in a first operating mode by means of control device 24 / actuator 26, in which first operating mode all second wheel intake valves 20 are simultaneously in their open switching state, all first wheel exhaust valves 16 are in their open switching state, and all second wheel exhaust valves 22 are in their closed switching state, and when second wheel intake valves 20 are in their open switching state, first wheel exhaust valves 16 are in their open switching state, and second wheel exhaust valves 22 are in their closed switching state, first wheel intake valves 20 are alternately controlled either in their completely closed state or in their partially or completely open state, so that a first brake pressure present in first wheel brake cylinder 12 is adjusted to an opening pressure (Ansprechdruck) of each storage chamber 36, for example, low-pressure storage chamber 36, which is arranged downstream of second wheel exhaust valve 16, and a second brake pressure present in second wheel brake cylinder 18 is adjusted to a second brake pressure which is higher than the first brake pressure. Figure 1Aa The first operating mode shown is preferably carried out when the vehicle can be partially braked by means of the electric drive motor acting as a generator, but in order to maintain the setpoint total braking torque M total Friction-braking torque M applied to the front axle fr-front(not equal to zero) is also desirable. By executing the first operating mode, the brake fluid volume, which is moved from the connected master brake cylinder 38 into the brake circuit 10 by actuating the brake operating member 32 with the help of the driver's brake force 34, can be discharged into the respectively downstream storage chamber 36 via valves 14 and 16 as long as it is not needed to increase the second brake pressure. The deceleration of the vehicle desired by the driver can thus be carried out while using the electric drive motor used as a motor together, but without over-braking the vehicle. This allows the kinetic energy of the vehicle to be recovered by converting the kinetic energy into electrical energy, which is temporarily stored in an accumulator (not shown) and can be used when necessary, for example, for re-accelerating the vehicle. Despite the displacement of the brake fluid volume into the storage chamber 36, in order to provide the driver who actuates the brake operating member 32 with a brake operating feel / pedal feel that complies with the standard, a counterforce that reacts to the driver's brake force 34 can be induced in an optional manner with the help of an electromechanical brake force booster 40 connected to the brake operating member 32.

[0025] If with the help of Figure 1Aa As can be seen, in order to maintain the theoretical total braking torque M total For the friction-braking torque M fr-front The regulation to be performed requires reliable controllability of first wheel intake valve 14. However, solenoid valves often have component tolerances, so that the pressure-current intensity-characteristic curve of the corresponding solenoid valve often deviates from the desired standard characteristic. For example, it is possible that first wheel intake valve 14 has component tolerances that reduce the magnetic interaction between its adjustable valve part and the magnetic field caused by the current flowing through at least one solenoid coil thereof. In this case, the magnetic force acting on the adjustable valve part by the magnetic field is not sufficient, for example, so that first wheel intake valve 14, which is designed as a normally open solenoid valve, is opened only to such an extent from its completely closed state to a partially open state when the first wheel intake valve 14 is actuated, so that only the desired flow flows through first wheel intake valve 14. There is therefore the risk that too much volume flows through first wheel exhaust valve 14 and that the first wheel exhaust valve 14 is closed in the event of too low a second brake pressure in second wheel brake cylinder 18 and / or a master brake cylinder internal pressure p in master brake cylinder 38. TMC Too low a situation.

[0026] However, this problem is eliminated by the advantageous design of the control mechanism 26. Fig. 1Ab In the coordinate system of FIG. 1 , the abscissa is the time axis t, and the ordinate shows the current intensity I of the current flowing through the at least one electromagnetic coil of the first wheel intake valve 14. 14 and the master brake cylinder internal pressure p in the master brake cylinder 38 TMC which is equal to the second brake pressure in second wheel brake cylinder 18 .

[0027] The first wheel intake valve 14 which is in its fully closed state between times t0 and t1 is switched from its fully closed state to a partially open state by the actuation mechanism 26 and remains in the partially open state between times t2 and t3. During the transition time interval between times t1 and t2, the current intensity I 14 The current ramp is thus generated during the transition time interval, which has a (negative) slope whose magnitude is (only) between 0.05 amperes per second and 5 amperes per second. It can therefore also be said that a "current ramp" is generated during the transition time interval (for comparison, the dashed line shows the prior art). Due to the "current ramp" generated during the transition time interval, first wheel inlet valve 14 is only gradually converted from its completely closed state to the partially open open state. This ensures that first wheel inlet valve 14 only opens gradually, even in the event of component tolerances at first wheel inlet valve 14, which reduce the interaction between the displaceable valve element of first wheel inlet valve 14 and the magnetic field generated by means of at least one electromagnetic coil of first wheel inlet valve 14. This reliably prevents the desired flow through wheel inlet valve 14 from being exceeded.

[0028] While first wheel inlet valve 14 is in the partially open state between times t2 and t3, it is switched by actuation device 26 from the partially open state to its fully closed state and remains in its fully closed state between times t4 and t5. Also during this switching process, during the transition time interval between times t3 and t4, current intensity I14 increases with a (positive) slope, the magnitude of which during the transition time interval is (only) between 0.05 amperes per second and 5 amperes per second. This can also be referred to as another "current ramp" between times t3 and t4 for gradually closing first wheel inlet valve 14. The gradual closing of first wheel inlet valve 14 ensures a gradual reduction in the volume flow through first wheel inlet valve 14, even if component tolerances thereof weaken the interaction between the displaceable valve element of first wheel inlet valve 14 and the magnetic field caused by at least one electromagnetic coil of first wheel inlet valve 14.

[0029] The “current ramp” implemented between the times t1 and t2 and between the times t3 and t4 enables: with the aid of the internal pressure p TMC And accordingly, a predetermined setpoint pressure p is reliably maintained by means of the second brake pressure in second wheel brake cylinder 18. target Therefore, there is no need to worry about the pressure falling below the setpoint pressure p in the master brake cylinder 36. targetThe component tolerances existing in first wheel intake valve 14 thus do not / hardly impair the brake operating feel / pedal feel of the driver who operates brake operating member 32. Likewise, the component tolerances existing in first wheel intake valve 14 do not (essentially) lead to a "sinking" of brake operating member 32 or a stick-slip effect or stick-slip effect of brake operating member 32. fr-front Conventionally, it is often necessary to detect and correct the friction-braking torque M fr-front The work step of the deviation is thus eliminated.

[0030] If the driver requires the theoretical total braking torque M total It is no longer possible to use the electric drive motor as a generator and the friction braking torque M fr-front To achieve this, the braking system is Figure 1Ba Operation in the second operating mode shown can also result in a friction braking torque M acting on the rear axle. fr-rear Advantageously, when second wheel inlet valve 20 is in its open switching state and second wheel outlet valve 22 is in its closed switching state, actuation device 26 is additionally designed to actuate at least one pump motor 42 of at least one pump 44, so that brake fluid is pumped out of storage chamber 36 by means of at least one pump 44, so that the first brake pressure in first wheel brake cylinder 12 increases above the opening pressure of the respectively downstream storage chamber 36. As in Figure 1Ba , while the brake fluid is pumped by means of at least one pump 44, a second brake pressure in second wheel brake cylinder 18 is respectively adjusted by means of an associated first wheel inlet valve 14, and a first brake pressure in first wheel brake cylinder 12 is respectively adjusted by means of a downstream first wheel outlet valve 16. In particular, in this way, the first brake pressure in first wheel brake cylinder 12 can be gradually adjusted to the second brake pressure in second wheel brake cylinder 18. The counterforce to driver brake force 34 brought about by means of electromechanical brake booster 40 can be adjusted accordingly, so that the driver also does not or hardly notices this blending process.

[0031] In order to also achieve an increase in the first brake pressure in first wheel brake cylinder 12 above the opening pressure of the respectively downstream storage chamber 36, the respectively upstream first wheel inlet valve 14 is switched from its completely closed state to a partially open state. This is also done by gradually switching first wheel inlet valve 14 by means of a “current ramp”.

[0032] An advantageous development of actuation device 26 for switching first wheel inlet valve 14 in this operating situation is achieved by Figure 1Bb and Fig. 1Bc The coordinate system is shown, and its horizontal axis is the time axis t. Figure 1Bb The ordinate of the coordinate system shows the current intensity I of the current flowing through the at least one electromagnetic coil of first wheel intake valve 14 14 , and shows the first theoretical value p 1-target (as theoretical pressure value). Fig. 1Bc The ordinate of the coordinate system of φ also shows the master brake cylinder internal pressure p in the master brake cylinder 38 . TMC , the desired setpoint pressure p in the master brake cylinder 36 target and a first brake pressure p1 in first wheel brake cylinder 12 .

[0033] During time t10 and t12, first wheel intake valve 14 is controlled to its fully closed state and maintained. At time t11 between time t10 and t12, it is decided to increase the second brake pressure from time t12. As an advantageous refinement, control device 26 is designed to reduce the current intensity I of the current flowing through the at least one electromagnetic coil of first wheel intake valve 14 by a slope between -0.05 amperes per second and -5 amperes per second while first wheel intake valve 14 is maintained in its fully closed state. 14 (For comparison, Figure 1Bb 14 shows the prior art with dashed lines). In this way, a delay can be avoided when a desired increase in the first brake pressure in first wheel brake cylinder 12 is desired. Even if component tolerances exist in first wheel inlet valve 14, which reduce the magnetic interaction between the adjustable valve element of first wheel inlet valve 14 and the magnetic field caused by at least one electromagnetic coil thereof, the current intensity I 14 The previously initiated reduction in the flow rate through first wheel inlet valve 14 is prevented from being suddenly exceeded. Therefore, in this operating situation, there is no need to worry about a "sinking" of brake actuating element 32 or a stick-slip or stick-slip effect of brake actuating element 32. Time interval during which the current intensity I of the current flowing through the at least one solenoid coil of first wheel inlet valve 14, while first wheel inlet valve 14 remains in its completely closed state, is 1. 14 has decreased—can be longer than 20 milliseconds, preferably longer than 50 milliseconds, in particular longer than 75 milliseconds, and especially longer than 100 milliseconds. During this time interval, the magnitude of the (negative) slope is preferably (only) between 0.1 amperes per second and 5 amperes per second, for example (only) between 0.2 amperes per second and 5 amperes per second, in particular (only) between 0.2 amperes per second and 3 amperes per second, or between 1 ampere per second and 5 amperes per second.

[0034] Fig. 1Bd and Figure 1Be Another advantageous characteristic of the control mechanism 26 is shown. Fig. 1Bd and Figure 1Be In the coordinate system of , the abscissa is the time axis t, and the corresponding ordinate shows the current intensity I of the current flowing through at least one electromagnetic coil of the first wheel intake valve 14. 14 , the master brake cylinder internal pressure p in the master brake cylinder 38 TMC , a first brake pressure p1 in first wheel brake cylinder 12 , a second setpoint value p 2-target (as a setpoint pressure value) and a second brake pressure p2 in second wheel brake cylinder 18 .

[0035] exist Fig. 1Bd and Figure 1Be In both examples, control device 26 is designed to control first wheel inlet valve 14 from a partially open state to its fully open state at time t13, starting from an assumed commensurate first brake pressure in first wheel brake cylinder 12 and second brake pressure in second wheel brake cylinder 18, in order to facilitate a “common pressure regulation” in all wheel brake cylinders 12 and 18. However, in Figure 1Be In the example, during the transition time interval, the current intensity I is reduced at a slope 14 , the magnitude of which during the transition time interval is between 0.05 amperes per second and 5 amperes per second. By means of this "current ramp", in this case, first wheel intake valve 14 is gradually opened, rather than first wheel intake valve 14 opening suddenly. In this way, component tolerances can be compensated, which increase the magnetic interaction between the adjustable valve part of first wheel intake valve 14 and the magnetic field caused by means of its at least one electromagnetic coil. Such component tolerances at first wheel intake valve 14 slow down the increase of the flow opening at first wheel intake valve 14. By means of current intensity I 14 The sudden decrease in pressure causes a sudden opening of first wheel inlet valve 14, which can result in a sudden pressure drop in brake circuit 10. In particular, if an assumed match between the first brake pressure and the second brake pressure has not yet occurred due to a delayed increase in the flow opening at first wheel inlet valve 14, the sudden opening of first wheel inlet valve 14 can result in a sudden decrease in the second brake pressure in second wheel brake cylinder 18 and, accordingly, in master brake cylinder internal pressure p in master brake cylinder 38. TMC However, by gradually opening the first wheel intake valve 14, the friction-braking torque M applied to the front axle can be avoided. fr-front Similarly, by gradually opening the first wheel intake valve 14, it is possible to avoid the internal pressure p of the master brake cylinder TMCThe abrupt reduction in the braking force causes the brake operating component 32 to “sink”.

[0036] Here again, Figure 1Aa and Figure 1Ba The design of the brake system shown in FIG. 4 , with its components as well as pressure sensor 46 and brake fluid reservoir 48 , is to be understood only as an example.

[0037] Figure 2 A flow chart is shown for describing one specific embodiment of a method for operating at least one solenoid valve of a brake system of a vehicle.

[0038] It should be pointed out here that the feasibility of the method described below is not limited to a certain valve type of the at least one solenoid valve, not limited to a specific brake system type of the brake system, and not limited to a specific vehicle type / motor vehicle type of the vehicle / motor vehicle equipped with the brake system.

[0039] In method step S1, the solenoid valve, which is initially in a first switching state, is switched from the first switching state to a second switching state different from the first switching state. This is done by increasing or decreasing the current intensity of the current flowing through at least one solenoid coil of the solenoid valve, wherein during the increase or decrease of the current intensity of the current flowing through at least one solenoid coil of the solenoid valve, the current intensity is increased or decreased with a constant or changing slope during a transition time interval of at least 20 milliseconds, the magnitude of the slope during the transition time interval being (only) between 0.05 amperes per second and 5 amperes per second. During the transition time interval, the magnitude of the slope is (only) between 0.05 amperes per second and 5 amperes per second, the transition time interval being preferably longer than 50 milliseconds, in particular longer than 75 milliseconds, in particular longer than 100 milliseconds. During this transition time interval, the magnitude of the (positive or negative) slope is preferably (only) between 0.1 amperes per second and 5 amperes per second, for example (only) between 0.2 amperes per second and 5 amperes per second, in particular (only) between 0.2 amperes per second and 3 amperes per second, or between 1 ampere per second and 5 amperes per second.

[0040] The method presented here can also compensate for component tolerances on the solenoid valve so that they do not adversely affect the driver's brake actuation feel / brake pedal feel. In particular, "sinking" of brake actuation components of the brake system or stick-slip or stick-slip effects of brake actuation components can be prevented in this way.

[0041] As an advantageous improvement, if a normally open solenoid valve is operated as the solenoid valve, and before the normally open solenoid valve is switched from its fully closed state as the first switching state to a partially open or fully open state as the second switching state by method step S1, an (optional) method step S0 may also be performed. As method step S0, while the normally open solenoid valve remains in its fully closed state, the current intensity of the current flowing through at least one solenoid coil of the normally open solenoid valve is reduced with a slope between -0.05 amperes per second and -5 amperes per second. This leads to the above-mentioned advantages.

Claims

1. A control device (24) for at least one solenoid valve (14) of a braking system of a vehicle, comprising: An operating mechanism (26) is designed to adjust the current intensity (I 14 ), in, The current intensity (I) of the current flowing through at least one electromagnetic coil of the electromagnetic valve (14) can be varied by means of the control device (26). 14 ), so that the solenoid valve (14) which is initially in the first switching state increases or decreases the current intensity (I 14 ) and can be converted from the first switching state to a second switching state different from the first switching state; It is characterized in that In increasing or decreasing the current intensity (I 14 ), the control device (26) is additionally designed to increase or decrease the current intensity (I 14 ), the magnitude of the slope being between 0.05 amperes per second and 5 amperes per second during the transition time interval, wherein the solenoid valve (14) is a normally open solenoid valve, and wherein the control mechanism (26) is designed to reduce the current intensity (I) of the current flowing through at least one solenoid coil of the normally open solenoid valve by a slope between -0.05 amperes per second and -5 amperes per second while the normally open solenoid valve remains in its fully closed state. 14 ).

2. A control device (24) for at least one solenoid valve (14) of a braking system of a vehicle, comprising: An operating mechanism (26) is designed to adjust the current intensity (I 14 ), in, The current intensity (I) of the current flowing through at least one electromagnetic coil of the electromagnetic valve (14) can be varied by means of the control device (26). 14 ), so that the solenoid valve (14) which is initially in the first switching state increases or decreases the current intensity (I 14 ) and can be converted from the first switching state to a second switching state different from the first switching state; It is characterized in that In increasing or decreasing the current intensity (I 14 ), the control device (26) is additionally designed to increase or decrease the current intensity (I 14 ), the magnitude of the slope being between 0.05 amperes per second and 5 amperes per second during the transition time interval, wherein the control mechanism (26) is designed to increase or decrease the current intensity (I 14 ), so that the solenoid valve (14), which is initially in its fully open state as the first switching state, switches from the fully open state to a partially open or fully closed state as the second switching state.

3. A braking system for a vehicle, comprising: A control device (24) according to claim 1 or 2; and At least one solenoid valve which can be controlled by means of the control device (24).

4. The braking system according to claim 3, wherein: At least one of the solenoid valves is at least one wheel inlet valve (14, 20), at least one wheel outlet valve (16, 22), at least one high-pressure switching valve (28) and / or at least one switching valve (30).

5. A method for operating at least one solenoid valve (14) of a braking system of a vehicle, comprising the following steps: By increasing or decreasing the current intensity (I 14 ), so that the solenoid valve (14) initially in a first switching state is switched from the first switching state to a second switching state different from the first switching state; It is characterized in that In increasing or decreasing the current intensity (I 14 ), increasing or decreasing (S1) the current intensity (I 14 ), the magnitude of the slope being between 0.05 amperes per second and 5 amperes per second during the transition time interval, wherein a normally open solenoid valve is operated as the solenoid valve (14), and wherein, before the normally open solenoid valve switches from its fully closed state as the first switching state to (S0) a partially open or fully open state as the second switching state, the current intensity (I) of the current flowing through at least one solenoid coil of the normally open solenoid valve has been reduced with a slope between -0.05 amperes per second and -5 amperes per second while the normally open solenoid valve remains in its fully closed state. 14 ).

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