Control device and method for at least partially emptying a fluid reservoir of a braking system of a vehicle

Description

[0001] The invention relates to a control device for a vehicle's braking system with at least one brake circuit comprising a fluid reservoir. The invention also relates to a braking system for a vehicle. Furthermore, the invention relates to a method for at least partially emptying a brake fluid reservoir of a vehicle's braking system. State of the art

[0002] Various types of brake systems are known from the prior art, such as DE 10 2019 211 236 A1, whereby such a brake system has at least one brake circuit with a fluid reservoir.

[0003] German patent application DE 10 2019 207 608 A1 discloses a control device for a vehicle's braking system, designed to detect or estimate, based on at least one sensor signal provided to the control device, whether a driver braking force applied to a brake actuation element connected to a master brake cylinder of the braking system decreases over time. The control device is also designed to control and / or hold in its open state, at least temporarily during a detected or estimated decrease in the driver braking force, a high-pressure switching valve of a brake circuit connected to the master brake cylinder with at least one wheel brake cylinder, via which a brake circuit storage chamber is connected to the master brake cylinder, so that brake fluid can be transferred from the storage chamber to the master brake cylinder via the high-pressure switching valve in its open state. Disclosure of the invention

[0004] The invention provides a control device for a braking system of a vehicle with at least one braking circuit comprising a fluid reservoir with the features of claim 1, a braking system for a vehicle with the features of claim 4 and a method for at least partially emptying a fluid reservoir of a braking system of a vehicle with the features of claim 8. Advantages of the invention

[0005] The present invention provides advantageous methods for at least partially emptying a fluid reservoir of a vehicle's brake system while simultaneously limiting or preventing brake fluid flow through the single wheel outlet valve or all wheel outlet valves of a brake circuit of the brake system formed with the at least partially emptied fluid reservoir. This eliminates the conventional need to equip the at least one wheel outlet valve of the brake circuit formed with the fluid reservoir to be emptied with its own filter for brake fluid transfer from the fluid reservoir through the respective valve, such as a mesh filter. This enables more cost-effective manufacturing of the at least one wheel outlet valve of the brake circuit formed with the fluid reservoir to be emptied.The use of the present invention thus increases design freedom for the at least one wheel outlet valve of the brake circuit formed with the fluid reservoir. Additionally, this can contribute to a reduction in the types of outlet valves used when manufacturing a brake system employing the present invention.

[0006] In an advantageous embodiment of the control device, the electronic unit is designed and / or programmed to control or maintain the brake circuit's changeover valve in its closed state throughout the entire opening time. Controlling or maintaining the closed position of the changeover valve advantageously prevents the undesirable transfer of brake fluid from the fluid reservoir through the brake circuit's at least one wheel outlet valve during the opening time.

[0007] Alternatively or additionally, the electronic device can also be designed and / or programmed to control and / or maintain the closed state of the single wheel outlet valve of the brake circuit, or of at least one of the wheel outlet valves of the brake circuit, which, due to its design and orientation, is permeable to brake fluid from the fluid reservoir in a partially open state, for the entire opening time. By means of such a design / programming of the control device / its electronic component, the unwanted transfer of brake fluid from the fluid reservoir through the at least one wheel outlet valve can also be prevented for the entire opening time.

[0008] The advantages described above are also guaranteed in a braking system for a vehicle which is equipped with a corresponding control device and at least the brake circuit connected to the master brake cylinder of the braking system with the fluid reservoir and the high-pressure switching valve which can be controlled by means of the electronic device of the control device, wherein the brake circuit additionally includes the changeover valve, the single wheel outlet valve and / or the wheel outlet valves, and wherein the changeover valve, the single wheel outlet valve and / or the wheel outlet valves can be controlled by means of the electronic device.

[0009] Preferably, the single wheel outlet valve or valves each have only one filter for brake fluid transfer from a wheel brake cylinder associated with the respective valve to the fluid reservoir. Preferably, the single wheel outlet valve or valves are thus filterless for brake fluid transfer from the fluid reservoir through the respective valve. This contributes to reducing the manufacturing costs of the at least one wheel outlet valve of the brake circuit formed with the fluid reservoir to be emptied, and thus makes the brake system more cost-effective.

[0010] For example, the brake circuit can comprise a first wheel outlet valve and a second wheel outlet valve as its wheel outlet valves, wherein a first line section of the brake circuit opening at the master brake cylinder branches off to the changeover valve and the high-pressure switching valve, a second line section of the brake circuit opening at the changeover valve branches off to a first wheel inlet valve and a second wheel inlet valve, a first wheel brake cylinder is connected or connectable to a third line section of the brake circuit which branches off to the first wheel inlet valve and the first wheel outlet valve, and a second wheel brake cylinder is connected or connectable to a fourth line section of the brake circuit which branches off to the second wheel inlet valve and the second wheel outlet valve.A fifth line section of the brake circuit, opening onto the intake side of a pump unit of the brake circuit, branches off to the first wheel outlet valve and the second wheel outlet valve, the fluid reservoir is connected to the fifth line section, a sixth line section of the brake circuit, opening onto the delivery side of the pump unit, opens onto the second line section, and a seventh line section of the brake circuit, opening onto the high-pressure switching valve, opens onto the fifth line section. The present invention is thus applicable to a multitude of brake system types, which are conventionally frequently used on various vehicle types. However, it should be noted that the hydraulic configuration of the brake circuit equipped with the fluid reservoir described here is only to be interpreted as an example.

[0011] The advantages described above are also achieved by implementing a corresponding method for at least partially emptying a fluid reservoir of a vehicle's braking system. It is expressly noted that the method for at least partially emptying a fluid reservoir of a vehicle's braking system can be further developed according to the embodiments of the control device and / or the braking system described above. Brief description of the drawings

[0012] Further features and advantages of the present invention are explained below with reference to the figures. They show: Fig. 1 a schematic representation of an embodiment of the control device, or of a braking system interacting with it; Figs. 2a to 2 a flowchart, a timing diagram and schematic partial representations of a braking system to explain a first embodiment of the method for at least partially emptying a fluid reservoir of a vehicle's braking system; and Figs. 3a to 3 a flowchart, a timing diagram and schematic partial representations of a braking system to explain a second embodiment of the method for at least partially emptying a fluid reservoir of a vehicle's braking system. Embodiments of the invention

[0013] Fig. 1 shows a schematic representation of an embodiment of the control device, or of a braking system interacting with it.

[0014] The control device 10 described below can interact with (almost) any brake system that has at least one brake circuit 12a and 12b connected to a master brake cylinder 14 of the brake system, equipped with a fluid reservoir 16a or 16b and a high-pressure switching valve 18a or 18b, and which additionally includes a changeover valve 20a or 20b and / or at least one wheel outlet valve 22a, 22b, 24a and 24b. Likewise, the use of the control device 10 is not limited to any specific vehicle type equipped with the respective brake system.

[0015] The control device 10 has an electronic unit 26 which is designed and / or programmed to switch the high-pressure switching valve 18a or 18b of the brake circuit 12a or 12b, which is equipped with the fluid reservoir 16a or 16b to be emptied, into a state that is at least partially open for a predetermined or fixed opening time by means of at least one control signal 18s. In this way, the control device 10 / its electronic unit 26 ensures that, during the opening time, brake fluid from the fluid reservoir 16a or 16b can be transferred / flows into the master brake cylinder 14 via the at least partially open high-pressure switching valve 18a or 18b of the same brake circuit 12a or 12b. The volume balance of the brake system can thus be balanced by means of the control device 10 / its electronic unit 26 by at least partially emptying the fluid reservoir 16a or 16b.

[0016] Furthermore, the electronic device 26 is additionally designed and / or programmed to control and / or maintain the changeover valve 20a or 20b of the brake circuit 12a or 12b formed with the fluid reservoir 16a or 16b to be emptied, the single wheel outlet valve of the respective brake circuit 12a or 12b and / or all wheel outlet valves 22a, 22b, 24a and 24b of the respective brake circuit 12a or 12b during the entire opening time by means of at least one control signal 20s and 22s in a state in which a brake fluid transfer from the respective fluid reservoir 16a or 16b through the respective valve 20a, 20b, 22a, 22b, 24a and 24b is blocked. The control device 10 / its electronic device 26 thus limits at least one unwanted brake fluid flow from the fluid reservoir 16a or 16b through the at least one wheel outlet valve 22a, 22b, 24a and 24b of the respective brake circuit 12a or 12b.If the electronic device 26 is designed and / or programmed to control and / or maintain the single wheel outlet valve of the respective brake circuit 12a or 12b or all wheel outlet valves 22a, 22b, 24a and 24b of the respective brake circuit 12a or 12b in the state blocking brake fluid transfer from the respective fluid reservoir 16a or 16b through the respective valve 22a, 22b, 24a and 24b for the entire opening time, the unwanted brake fluid flow from the fluid reservoir 16a or 16b through the at least one wheel outlet valve 22a, 22b, 24a and 24b can also be (almost) completely prevented.

[0017] In both cases of limiting and (almost) completely preventing the unwanted flow of brake fluid from the fluid reservoir 16a or 16b through the at least one wheel outlet valve 22a, 22b, 24a or 24b, there is no conventional need to design / equip the at least one wheel outlet valve 22a, 22b, 24a and 24b with its own filter for brake fluid transfer from the fluid reservoir 16a or 16b through the respective valve 22a, 22b, 24a and 24b, such as a corresponding mesh filter or net filter. It is therefore preferred that the single wheel outlet valve or the wheel outlet valves 22a, 22b, 24a and 24b each have only one filter 23a, 23b, 25a and 25b for a brake fluid transfer from a wheel brake cylinder 28a, 28b, 30a and 30b assigned to the respective valve 22a, 22b, 24a and 24b to the fluid reservoir 16a or 16b.This can also be described as follows: the single wheel outlet valve or the wheel outlet valves 22a, 22b, 24a and 24b are each filterless for the brake fluid transfer from the fluid reservoir 16a or 16b through the respective valve 22a, 22b, 24a and 24b. This reduces the manufacturing costs for the at least one wheel outlet valve 22a, 22b, 24a or 24b of the brake system interacting with the control device 10 and facilitates its manufacture.

[0018] Eliminating the need for a separate filter for brake fluid transfer from the fluid reservoir 16a or 16b through the respective wheel outlet valve 22a, 22b, 24a or 24b allows for greater design freedom in the respective wheel outlet valve 22a, 22b, 24a or 24b of the brake circuit 12a or 12b formed with the fluid reservoir 16a or 16b. This can be used to reduce the number of outlet valve types used in the manufacture of the respective brake system.

[0019] To achieve the advantages described above, it is sufficient if the electronic device 26 is designed and / or programmed to control or maintain the changeover valve 20a or 20b of the brake circuit 12a or 12b in its closed state for the entire opening time of the high-pressure switching valve 18a or 18b of the same brake circuit 12a or 12b. (The changeover valve 20a or 20b, controlled or maintained in its closed state, is understood to be a valve 20a or 20b which, due to its design and orientation, is at least partially open to allow brake fluid from the fluid reservoir 16a or 16b and through at least one wheel outlet valve 22a, 22b, 24a and 24b of the brake circuit 12a or 12b.)) Likewise, the advantages described above are ensured if the electronic device 26 is designed and / or programmed to control and / or keep in its closed state the single wheel outlet valve of the brake circuit 12a or 12b or at least one of the wheel outlet valves 22a, 22b, 24a and 24b of the brake circuit 12a or 12b, which, due to its design and orientation, is permeable to brake fluid from the fluid reservoir 16a or 16b in a state that is at least partially open, during the entire opening time of the high-pressure switching valve 18a or 18b of the same brake circuit 12a or 12b.

[0020] The opening time during which the high-pressure switching valve 18a or 18b of the brake circuit 12a or 12b is controlled to its at least partially open state with respect to the fluid reservoir 16a or 16b to be emptied can be (fixed) predefined by the electronic device 26. As an advantageous further development, the electronic device 26 can also be designed and / or programmed to determine the opening time (itself), for example, taking into account the reservoir pressure present in the fluid reservoir 16a or 16b to be emptied. The determination of the opening time by the electronic device 26 can also be understood as waiting until a predetermined event that terminates the opening time occurs.In particular, the electronic device 26 can be designed and / or programmed to "wait" for the opening time until the driver again presses the brake pedal harder and / or until the storage pressure in the fluid reservoir 16a or 16b is reduced to less than or equal to the response pressure of the respective fluid reservoir 16a or 16b by the flow of brake fluid from the fluid reservoir 16a or 16b via the at least partially opened high-pressure switching valve 18a or 18b of the same brake circuit 12a or 12b into the master brake cylinder 14.

[0021] As in Fig. 1 As illustrated, the fluid reservoir 16a or 16b to be emptied can be a storage chamber 16a and 16b integrated into the hydraulics of the respective brake system, specifically a low-pressure storage chamber 16a and 16b. However, the use of the control device 10 is not limited to any specific type of fluid reservoir. As shown in Fig. 1 As also shown in the illustration, the control device 10 / its electronic device 26 can also be designed for the simultaneous emptying of several fluid reservoirs 16a and 16b of several brake circuits 12a and 12b of the same brake system.

[0022] The braking system of the Fig. 1 Two brake circuits 12a and 12b, each with a first wheel brake cylinder 28a or 28b and a second wheel brake cylinder 30a or 30b. Additionally, each brake circuit 12a and 12b is equipped with a first wheel outlet valve 22a or 22b and a second wheel outlet valve 24a or 24b as its wheel outlet valves 22a, 22b, 24a and 24b. Each brake circuit 12a and 12b has a first line section 32a or 32b opening at the master brake cylinder 14, which branches off to its changeover valve 20a or 20b and its high-pressure switching valve 18a or 18b. A second line section 34a or 34b of the respective brake circuit 12a or 12b, opening at the switching valve 20a or 20b, branches off to form a first wheel inlet valve 36a or 36b and its second wheel inlet valve 38a or 38b.The first wheel brake cylinder 28a or 28b is connected / connectable to a third line section 40a or 40b of the respective brake circuit 12a or 12b, which branches off to the first wheel inlet valve 36a or 36b and the first wheel outlet valve 22a or 22b. Similarly, the second wheel brake cylinder 30a or 30b is connected / connectable to a fourth line section 42a or 42b of the same brake circuit 12a or 12b, which branches off to the second wheel inlet valve 38a or 38b and the second wheel outlet valve 24a or 24b.

[0023] A fifth line section 46a or 46b, opening onto the intake side of a pump unit 44a or 44b of the respective brake circuit 12a or 12b, branches off to the first wheel outlet valve 22a or 22b and the second wheel outlet valve 24a or 24b, with the fluid reservoir 16a or 16b of the respective brake circuit 12a or 12b being connected to the fifth line section 46a or 46b. A sixth line section 48a or 48b of the respective brake circuit 12a or 12b, opening onto a delivery side of the pump unit 44a or 44b, also opens onto the second line section 34a or 34b. Furthermore, a seventh line section 50a or 50b of the respective brake circuit 12a or 12b connects to the high-pressure switching valve 18a or 18b and to the fifth line section 46a or 46b.

[0024] As an optional further development, at least one pressure relief valve 52a or 52b can be installed between the fluid reservoir 16a or 16b and the pump unit 44a or 44b in the fifth line section 46a or 46b. Likewise, a filter 54a or 54b, a throttle 56a or 56b, and / or a check valve 58a or 58b can be arranged in the sixth line section 48a or 48b. Preferably, a brake fluid reservoir 60 is connected to the master brake cylinder 14. Optionally, a brake booster 62 can also be located upstream of the master brake cylinder 14. Furthermore, at least one pre-pressure sensor 64 and / or a pressure sensor can be connected to at least one of the brake circuits 12a and 12b.

[0025] Fig. 2a bis 2d Figure 1 shows a flowchart, a time diagram and schematic partial representations of a braking system to explain a first embodiment of the method for at least partially emptying a fluid reservoir of a braking system of a vehicle.

[0026] The method described below can be implemented on (almost) any brake system that has at least one brake circuit 12a connected to a master brake cylinder 14 of the brake system, equipped with a fluid reservoir 16a and a high-pressure switching valve 18a, and which additionally includes a changeover valve 20a and / or at least one wheel outlet valve 22a and 24a. Likewise, the method is not limited to any specific vehicle type equipped with the respective brake system. The "graphic representation" of the method using at least the first brake circuit 12a and the master brake cylinder 14 of the brake system of the Fig. 1 This is only for better understanding.

[0027] In the embodiment described here, the emptying of the fluid reservoir is preceded by an optional process step S1, which can also be omitted. In process step S1, it is investigated whether the adjustment travel x of a brake pedal 66 connected to the master brake cylinder 14, caused by a driver braking force F, is not equal to zero from its unactuated initial position, whether the time derivative of the adjustment travel x is greater than or equal to zero, and whether a target braking torque M 0 corresponding to the adjustment travel x can be achieved as a generator braking torque M gen by means of at least one recuperatively operated electric motor of the vehicle. The adjustment travel x can be measured, for example, by means of a rod travel sensor 68.

[0028] In the time diagram of the Fig. 2b are represented along a time axis t the target braking torque M 0 , the generator braking torque M gen , a volume V present in a fluid storage tank 16a of the first brake circuit 12a , an opening state of a first wheel outlet valve 22a of the first brake circuit 12a and an opening state of a high-pressure switching valve 18a of the first brake circuit 12a .

[0029] From a time t0, the driver depresses the brake pedal 66. As long as the adjustment travel x is not equal to zero, the time derivative of the adjustment travel x is greater than or equal to zero, and the target braking torque M 0 corresponding to the adjustment travel x can be implemented as a generator braking torque M gen, a process step S2 is executed, which in Fig. 2c The process is shown schematically. In process step S2, a switching valve 20a of the first brake circuit 12a, a first wheel inlet valve 36a assigned to a first wheel brake cylinder 28a of the first brake circuit 12a, and the first wheel outlet valve 22a assigned to the first wheel brake cylinder 28a are controlled and / or held in an at least partially open state Φo such that, as illustrated by arrows 70, the brake fluid forced out of the master brake cylinder 14 by the driver's braking force F is moved via the switching valve 20a, the first wheel inlet valve 36a, and the first wheel outlet valve 22a into the fluid reservoir 16a.Preferably, a second wheel inlet valve 38a, associated with a second wheel brake cylinder 30a of the first brake circuit 12a, and a second wheel outlet valve 24a, also associated with the second wheel brake cylinder 30a of the first brake circuit 12a, are simultaneously controlled and / or held in a closed state, thereby preventing brake fluid transfer into the second wheel brake cylinder 30a. While a first brake pressure equal to the response pressure of the fluid reservoir 16a is present in the first wheel brake cylinder 28a, a second brake pressure present in the second wheel brake cylinder 30a can be held (almost) equal to atmospheric pressure. The high-pressure switching valve 18a is also controlled / held in its closed state Φc. Process step S2 continues even after the time derivative of the adjustment travel x becomes zero at time t1.

[0030] As soon as it is determined at time t2 that the time derivative of the adjustment travel x of the brake pedal 66 becomes less than zero (although the target braking torque M 0 corresponding to the adjustment travel x can still be implemented as a generator braking torque M gen), a further optional process step S3 is performed to investigate whether at least partial emptying of the fluid reservoir 16a is desirable. This can be done, for example, by determining whether the initial brake pressure present in the first wheel brake cylinder 28a is lower than the storage pressure present in the fluid reservoir 16a. If this is not the case, process step S2 is continued. Otherwise, the fluid reservoir 16a is at least partially emptied.

[0031] In the embodiment described here, the at least partial emptying of the liquid reservoir 16a begins at time t2: As process step S4, the high-pressure switching valve 18a is controlled for a predetermined or fixed opening time to an at least partially open state Φo such that, as indicated by an arrow 72 in Fig. 2d This is illustrated in the image showing that during the opening time, brake fluid flows from the fluid reservoir 16a into the master brake cylinder 14 via the at least partially open high-pressure switching valve 18a.

[0032] Simultaneously with process step S4, a process step S5 is also executed, in which the switching valve 20a of the first brake circuit 12a, the single wheel outlet valve of the first brake circuit 12a, and / or all wheel outlet valves 22a and 22b of the first brake circuit 12a are controlled or held in a state during the entire opening time in which brake fluid transfer from the fluid reservoir 16a through the respective valve 20a, 22a, and 24a is blocked. By way of example, in the embodiment described here, process step S5a of the process involves controlling the first wheel outlet valve 22a of the first brake circuit 12a, which, due to its design and orientation, is permeable to brake fluid from the fluid reservoir 16a in an at least partially open state Φo, into its closed state Φc during the entire opening time.Furthermore, the second wheel outlet valve 24a of the first brake circuit 12a is held in its closed state Φc throughout the entire opening time. This can be seen from the... Fig. 2d By executing process step S5a, brake fluid transfer from the fluid reservoir 16a through the outlet valves 22a and 24a of the brake circuit 12a is completely prevented. Therefore, by carrying out the process described here, the advantages explained above can also be utilized for the brake system used.

[0033] The opening time can be understood as a fixed, predetermined opening time. It can also be self-determined. For example, the opening time can be determined by taking into account a pressure difference between the storage pressure in the fluid reservoir 16a and the initial brake pressure in the first wheel brake cylinder 28a. Alternatively, the opening time can be "waited" until at least one predetermined event occurs. In particular, the opening time can be "waited" until the time derivative of the adjustment travel x of the brake pedal 66 becomes greater than or equal to zero and / or until the storage pressure in the fluid reservoir 16a becomes less than or equal to the response pressure.

[0034] The time diagram clearly shows the Fig. 2b , that if the travel x of the brake pedal 66 increases at a later time t3, the first wheel outlet valve 22a will reopen, while the high-pressure switching valve 18a can remain in its at least partially open state Φo. As soon as the travel x of the brake pedal decreases again at time t4, the volume V in the fluid reservoir 16a can be transferred back from the fluid reservoir 16a to the master brake cylinder 14 via the high-pressure switching valve 18a, which is in its at least partially open state Φo, by once again controlling the first wheel outlet valve 22a to its closed state Φc.

[0035] Fig. 3a bis 3d Figure 1 shows a flowchart, a time diagram and schematic partial representations of a braking system to explain a second embodiment of the method for at least partially emptying a fluid reservoir of a vehicle's braking system.

[0036] Regarding the feasibility of the method described below, reference is made to the explanations of the preceding embodiment.

[0037] As shown in the flowchart of the Fig. 3a As can be seen, the procedure described here has the process steps S1 to S5 already explained above. In the time diagram of the Fig. 3b The target braking torque M0, the generator braking torque Mgen, the volume V present in the fluid reservoir 16a of the first brake circuit 12a, the opening state of the first wheel outlet valve 22a of the first brake circuit 12a, the opening state of the high-pressure switching valve 18a of the first brake circuit 12a, an opening state of a changeover valve 20a of the first brake circuit 12a, and an opening state of a check valve 21a arranged parallel to the changeover valve 20a are represented along a time axis t. The times t1 to t4 correspond to the description of the preceding embodiment.

[0038] In contrast to the preceding embodiment, in the method described here, process step S5b is executed as process step S5 starting at time t2, in which the changeover valve 20a of the first brake circuit 12a is controlled or held in its closed state Φc for the entire opening time. (The changeover valve 20a, controlled or held in its closed state, is understood to be a valve 20a which, due to its design and orientation, is at least partially open Φo and permeable to brake fluid from the fluid reservoir 16a and through the at least one wheel outlet valve 22a and 24a.) Simultaneously, the first wheel outlet valve 22a is held in its at least partially open state Φo for the entire opening time. As can be seen from the Fig. 3c As can be seen, despite the presence of the first wheel outlet valve 22a in its at least partially open state Φo, the closed state of the changeover valve 20a of the first brake circuit 12a ensures that the unwanted brake fluid flow from the fluid reservoir 16a through the at least one wheel outlet valve 22a and 24a is limited to a brief and negligibly weak flow through the first wheel outlet valve 22a. The advantages explained above can therefore also be used for the brake system by carrying out the procedure described here. During the process indicated by arrow 72 in Fig. 3c During the at least partial emptying of the liquid reservoir 16a, the check valve 21a, arranged parallel to the switching valve 20a, remains in its closed state Φc.

[0039] As in Fig. 3d As illustrated by arrow 74, the driver, by applying their braking force F, can, from time t3 onwards, despite the changeover valve 20a being in its closed state Φc, move the brake fluid forced out of the master brake cylinder 14 via the check valve 21a (arranged / designed parallel to the changeover valve 20a), the at least partially open first wheel inlet valve 36a, and the at least partially open first wheel outlet valve 22a into the fluid reservoir 16a. Thus, it is not necessary to switch the changeover valve 20a back to its at least partially open state Φo at time t3. Therefore, after closing at time t2, the changeover valve 20a can remain open for the entire duration of the changeover valve's operation, as illustrated by the flow diagram. Fig. 3b The first wheel exhaust valve 22a can remain in its closed state Φc during the braking process. Similarly, after opening at time t0, it can remain in its at least partially open state Φo throughout the entire braking process.

[0040] Therefore, when carrying out the embodiment described here, no / hardly any valve switching noises occur. Furthermore, to carry out the embodiment described here, the following is required: Fig. 3b During the simulated braking maneuver, a rapid opening of the first wheel exhaust valve 22a is not necessary in the event of a sudden increase in the travel x of the brake pedal 66. Therefore, no undesirable pressure buildup at the delayed opening of the first wheel exhaust valve 22a is to be expected.

[0041] Regarding further steps in the process of Fig. 3a bis 3d refers to the previously described embodiment of the Fig. 2a bis 2d referred to.

Claims

1. Control device (10) for a brake system of a vehicle with at least one brake circuit (12a, 12b) comprising a fluid reservoir (16a, 16b), comprising: an electronic unit (26), which is designed and / or programmed to switch a high-pressure switching valve (18a, 18b) of the brake circuit (12a, 12b) into an at least partially open state for a predetermined or fixed opening time such that, during the opening time, brake fluid is transferable from the fluid reservoir (16a, 16b) via the at least partially open high-pressure switching valve (18a, 18b) into a master brake cylinder (14) of the brake system with the brake circuit (12a, 12b) connected thereto; characterized in that the electronic unit (26) is additionally designed and / or programmed to direct a switch-over valve (20a, 20b) of the brake circuit (12a, 12b), the single wheel outlet valve of the brake circuit and / or all of the wheel outlet valves (22a, 22b, 24a, 24b) of the brake circuit (12a, 12b) during the entire opening time into a state in which a brake fluid transfer from the fluid reservoir (16a, 16b) is blocked by the respective valve (20a, 20b, 22a, 22b, 24a, 24b) and / or to keep said valves in said state.

2. Control device (10) according to Claim 1, wherein the electronic unit (26) is designed and / or programmed to direct the switch-over valve (20a, 20b) of the brake circuit (12a, 12b) during the entire opening time into its closed state or to keep said valve in said state.

3. Control device (10) according to Claim 1 or 2, wherein the electronic unit (26) is designed and / or programmed to direct the only wheel outlet valve of the brake circuit or the at least one of the wheel outlet valves (22a, 22b, 24a, 24b) of the brake circuit (12a, 12b) that, owing to its design and its orientation in an at least partially open state is permeable to brake fluid from the fluid reservoir (16a, 16b), during the entire opening time into its closed state and / or to keep said valve in said state.

4. Brake system for a vehicle, having: a control device (10) according to one of the preceding claims; and at least the brake circuit (12a, 12b) which is connected to the master brake cylinder (14) of the brake system and has the fluid reservoir (16a, 16b) and the high-pressure switching valve (18a, 18b) which is activatable by means of the electronic unit (26) of the control device (10), wherein the brake circuit (12a, 12b) additionally also comprises the switch-over valve (20a, 20b), the single wheel outlet valve and / or the wheel outlet valves (22a, 22b, 24a, 24b), and wherein the switch-over valve (20a, 20b), the single wheel outlet valve and / or the wheel outlet valves (22a, 22b, 24a, 24b) are activatable by means of the electronic unit (26).

5. Brake system according to Claim 4, wherein the single wheel outlet valve or the wheel outlet valves (22a, 22b, 24a, 24b) have only one filter (23a, 23b, 25a, 25b) each for transfer of brake fluid from a wheel brake cylinder (28a, 28b, 30a, 30b) assigned to the respective valve (22a, 22b, 24a, 24b) to the fluid reservoir (16a, 16b).

6. Brake system according to Claim 4 or 5, wherein the single wheel outlet valve or the wheel outlet valves (22a, 22b, 24a, 24b) is / are in each case filterless for the transfer of brake fluid from the fluid reservoir through the respective valve.

7. Brake system according to any one of Claims 4 to 6, wherein the brake circuit (12a, 12b) comprises a first wheel outlet valve (22a, 22b) and a second wheel outlet valve (24a, 24b) as its wheel outlet valves (22a, 22b, 24a, 24b), and wherein a first line section (32a, 32b) of the brake circuit (12a, 12b) opening at the master brake cylinder (14) forks to the switch-over valve (20a, 20b) and to the high-pressure switching valve (18a, 18b), a second line section (34a, 34b) of the brake circuit (12a, 12b) opening at the switch-over valve (20a, 20b) forks to a first wheel inlet valve (36a, 36b) and to a second wheel inlet valve (38a, 38b), a first wheel brake cylinder (28a, 28b) is connected or connectable to a third line section (40a, 40b) of the brake circuit (12a, 12b), which third line section forks to the first wheel inlet valve (36a, 36b) and to the first wheel outlet valve (22a, 22b), a second wheel brake cylinder (30a, 30b) is connected or connectable to a fourth line section (42a, 42b) of the brake circuit (12a, 12b), which fourth line section forks to the second wheel inlet valve (38a, 38b) and to the second wheel outlet valve (24a, 24b), a fifth line section (46a, 46b) of the brake circuit (12a, 12b) opening at a suction side of a pump unit (44a, 44b) of the brake circuit (12a, 12b) forks to the first wheel outlet valve (22a, 22b) and to the second wheel outlet valve (24a, 24b), the fluid reservoir (16a, 16b) is connected to the fifth line section (46a, 46b), a sixth line section (48a, 48b) of the brake circuit (12a, 12b) opening at a delivery side of the pump unit (44a, 44b) opens at the second line section (34a, 34b), and a seventh line section (50a, 50b) of the brake circuit (12a, 12b) opening at the high-pressure switching valve (18a, 18b) opens at the fifth line section (46a, 46b).

8. Method for at least partially emptying a fluid reservoir (16a, 16b) of a brake system of a vehicle, having the following steps: directing a high-pressure switching valve (18a, 18b) of a brake circuit (12a, 12b) of the brake system, which brake circuit is equipped with the fluid reservoir (16a, 16b), for a predetermined or fixed opening time into an at least partially open state such that, during the opening time, brake fluid flows from the fluid reservoir (16a, 16b) via the at least partially open high-pressure switching valve (18a, 18b) into a master brake cylinder (14) of the brake system with the brake circuit (12a, 12b) connected thereto (S4); characterized by directing a switch-over valve (20a, 20b) of the brake circuit (12a, 12b), the single wheel outlet valve of the brake circuit and / or all of the wheel outlet valves (22a, 22b, 24a, 24b) of the brake circuit (12a, 12b) during the entire opening time into a state in which a brake fluid transfer from the fluid reservoir (16a, 16b) is blocked by the respective valve (20a, 20b, 22a, 22b, 24a, 24b) or keeping said valves in said state (S5).

9. Method according to Claim 8, wherein the switch-over valve (20a, 20b) of the brake circuit (12a, 12b) is directed during the entire opening time into its closed state or is kept therein (S5b).

10. Method according to Claim 8 or 9, wherein the single wheel outlet valve of the brake circuit and / or the at least one of the wheel outlet valves (22a, 22b, 24a, 24b) of the brake circuit (12a, 12b) that, owing to its design and its orientation in an at least partially open state is permeable to brake fluid from the fluid reservoir (16a, 16b), is directed during the entire opening time into its closed state or is kept therein (S5a).