Control device and method for determining a dead travel of a master brake cylinder with an upstream actuator of a hydraulic brake system of a vehicle

Abstract

The present invention relates to a control device (10) for at least one hydraulic brake system of a vehicle and to a method for determining a dead travel of a master brake cylinder (16) with an upstream actuator (14) of a hydraulic brake system of a vehicle by actuating a motor of the actuator (14) in such a way that at least one piston (24) of the master brake cylinder (16) is moved into at least one intermediate position, in which a bore (22) connecting the master brake cylinder (16) to a reservoir (20) is sealed, after deactivation of the motor, transferring a brake fluid volume from at least one sub-volume of the hydraulic brake system into the master brake cylinder (16) such that the piston (24) is moved by means of an exerted pressure force from the intermediate position at least into a bore release position, in which the bore (22) is no longer sealed, and defining a current value of the dead travel.

Description

[0001] R. 414971

[0002] - 1 -

[0003] Description

[0004] title

[0005] Control device and method for determining the dead travel of a master brake cylinder with an upstream actuator of a hydraulic brake system of a vehicle

[0006] The present invention relates to a control device for at least one hydraulic braking system of a vehicle. The invention also relates to a hydraulic braking system for a vehicle. Furthermore, the invention relates to a method for determining the dead stroke of a master brake cylinder with an upstream actuator of a hydraulic braking system of a vehicle, and to a method for operating an upstream actuator of a hydraulic braking system of a vehicle.

[0007] State of the art

[0008] From the prior art, such as DE 102012 222 718 A1, control devices for hydraulic brake systems of vehicles are known, wherein by means of such a control device at least one valve of the respective hydraulic brake system can be controlled to its closed state, as well as the operation of an electric motor of a motorized brake pressure building device upstream of a master brake cylinder of the brake system can be controlled.

[0009] Disclosure of the invention R. 414971

[0010] - 2 -

[0011] The present invention provides a control device for at least one hydraulic brake system of a vehicle with the features of claim 1, a hydraulic brake system for a vehicle with the features of claim 11, a method for determining a dead travel of a master brake cylinder with an upstream actuator of a hydraulic brake system of a vehicle with the features of claim 12, and a method for operating an upstream actuator of a hydraulic brake system of a vehicle with the features of claim 13.

[0012] Preferred further training courses are the subject of the subclaims.

[0013] Advantages of the invention

[0014] The present invention provides easily implementable methods for reliably determining or measuring the current and individual value of the dead travel of a vehicle's hydraulic braking system, or of a master brake cylinder with an upstream actuator. By utilizing the present invention, the current and individual value of the dead travel can be determined / measured with relatively high accuracy and a comparatively low error rate. In addition to a control device, the present invention provides a method for determining / measuring the current and individual value of the dead travel. Furthermore, conventional electronics can be reprogrammed to execute the method for determining / measuring the current and individual value of the dead travel, as described in the invention, with relatively little effort. Therefore, the use of the present invention is comparatively cost-effective.

[0015] As will become clear from the following description, many conventional brake system types already have sensors that can be used to determine / measure the current and individual value of the dead distance in order to implement the present invention. Thus, R. 414971

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[0017] It is generally not necessary to equip the respective hydraulic braking system, in which the current and individual value of the dead distance is determined by means of the present invention, with additional sensors. This further contributes to reducing the costs of using the present invention.

[0018] According to a preferred embodiment of the control device, the electronic device is additionally designed and / or programmed such that the actuator motor and the at least one valve can be controlled by the electronic device in such a way that the brake fluid volume subsequently transferred from the at least one partial volume into the master brake cylinder can be displaced into the at least one partial volume by means of the piston of the master brake cylinder, which is adjusted to at least the intermediate position, via the at least one open-controlled valve of the hydraulic brake system, and the displaced brake fluid volume can be enclosed in the at least one partial volume by means of an effected closure of the at least one valve.that, when the piston is in the intermediate position after the engine is deactivated, the brake fluid volume can be transferred from the at least one partial volume into the master brake cylinder via the at least one valve, which is opened again by means of the at least one control signal. The ability to temporarily store a defined volume in the at least one partial volume and transfer it back into the master brake cylinder as needed eliminates the need for at least one pumping device.

[0019] According to a preferred embodiment of the control device, the electronic unit is additionally designed and / or programmed such that at least one unit isolating valve of the hydraulic brake system can be controlled by means of the at least one output control signal. Thus, a valve type suitable for the use of the embodiment of the control device described here is already present in a large number of conventional brake systems. Therefore, the use of the embodiment of the control device described here generally does not require an additional valve on the respective hydraulic brake system. R. 414971

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[0021] Alternatively, the electronic device can be additionally designed and / or programmed such that at least one pump of the hydraulic brake system can be controlled by the electronic device, acting as the at least one delivery device, via at least one control signal, in such a way that, when the piston is in the intermediate position after the motor is deactivated, the brake fluid volume can be pumped from the at least one partial volume into the master brake cylinder by means of the at least one controlled pump. This enables precise and active control over the return transfer of the brake fluid volume from the partial volume into the master brake cylinder. By utilizing the existing pump of the hydraulic brake system, additional flexibility in brake fluid manipulation is achieved without the need for additional components.

[0022] Similarly, the electronic device can be designed and / or programmed such that at least one piston-cylinder assembly of the hydraulic brake system, acting as the at least one delivery device, can be controlled by the electronic device using at least one control signal in such a way that, when the piston is in the intermediate position after the motor is deactivated, the brake fluid volume can be transferred from at least one partial volume of the at least one piston-cylinder assembly into the master brake cylinder by means of the at least one controlled piston-cylinder assembly. This also enables a precise and controlled transfer of the brake fluid volume from the partial volume of the piston-cylinder assembly into the master brake cylinder.

[0023] According to a preferred embodiment of the control device, the electronic device is additionally designed and / or programmed such that a position of the piston, into which the piston is moved from the intermediate position by means of the brake fluid volume transferred from the at least one partial volume into the master brake cylinder, and in which the piston is spaced from its rear stop for at least a predetermined minimum time, is set. 414971

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[0025] The remaining position is recognizable by the electronic device as the bore release position. This enables precise detection and definition of the piston's bore release position.

[0026] According to another advantageous embodiment of the control device, the electronic device is additionally designed and / or programmed such that, by means of the electronic device, a current temporal change of at least one operating parameter of the at least one pumping device and / or a current temporal change of a pressure present in at least one part of the hydraulic brake system can be read or determined from at least one provided sensor signal of at least one sensor of the at least one pumping device and / or at least one pressure sensor, and a position of the piston to which and / or over which the piston is moved from the intermediate position by means of the brake fluid volume transferred from the at least one partial volume into the master brake cylinder, and at which the current temporal change of the at least one operating parameter and / or the pressure is above a respective predetermined threshold value.The electronic device identifies the bore release position. This enables highly precise and dynamic detection of the piston's bore release position through continuous monitoring and analysis of operating parameters and pressure changes in the brake system.

[0027] Preferably, the electronic device is additionally designed and / or programmed such that a current measured value of the piston's travel from its rear stop can be read from at least one provided sensor signal of a rotor position sensor of the motor and / or at least one piston position and / or piston travel sensor. Direct measurement of the piston's travel from its rear stop is thus possible in real time based on the at least one sensor signal. R. 414971

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[0029] As an advantageous further development, the electronic device can be additionally designed and / or programmed such that, taking into account the defined current value of the dead travel and a predetermined or defined target value of the dead travel, a target distance of the piston from its rear stop can be determined. The motor can then be controlled by the electronic device, taking into account the defined target distance, such that the piston is held at least temporarily at the target distance from its rear stop. This enables adaptive control of the piston distance from the rear stop, leading to optimized performance and efficiency of the braking system. By considering the currently measured dead travel and a predetermined target value of the dead travel, the braking system can dynamically determine and adjust the ideal target distance of the piston.

[0030] Preferably, the electronic device is additionally designed and / or programmed such that it can determine or query whether the vehicle is stationary, and only if the vehicle is stationary, can the operation of the actuator motor be activated by means of the output of at least one engine control signal. This motor allows the piston of the master brake cylinder to be moved from its rearward stop to at least the intermediate position. By limiting the piston movement via the operation of the actuator motor to when the vehicle is stationary, unexpected braking interventions while driving are prevented, which significantly improves driving safety. Performing the calibration while stationary also minimizes external disturbances such as uneven road surfaces or dynamic load changes, thus enabling more accurate measurement results.Since calibration is only performed when stationary, the system's energy consumption can also be optimized by avoiding unnecessary activations while driving. Limiting the process to stationary states also reduces the mechanical stress on the components, potentially contributing to a longer service life for the braking system. R. 414971.

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[0032] A hydraulic braking system for a vehicle also exhibits the advantages described above, provided that the hydraulic braking system includes such a control device, the actuator whose motor can be controlled by means of at least one motor control signal output by the electronic device of the control device in such a way that, through the operation of the motor controlled by means of the at least one motor control signal, at least the piston of the master brake cylinder of the hydraulic braking system downstream of the actuator can be adjusted from the rear stop to at least the intermediate position, and the at least one delivery device and / or the at least one valve which, after deactivation of the motor, can be controlled by means of at least one control signal output by the electronic device in such a way that the brake fluid volume from the at least one partial volume connected to the master brake cylinder can be transferred into the master brake cylinder.exhibits.

[0033] Similarly, implementing a corresponding method for determining the dead travel of a master brake cylinder with an upstream actuator of a vehicle's hydraulic brake system also yields the advantages described above. It should be noted that the method for determining dead travel can be further developed according to the control device embodiments described above.

[0034] Furthermore, implementing the method for operating an actuator upstream of a master brake cylinder in a vehicle's hydraulic braking system also provides the advantages described above. It is expressly noted that the method for operating an actuator upstream of a master brake cylinder can be further developed according to the control device embodiments described above.

[0035] Brief description of the drawings R. 414971

[0036] - 8 -

[0037] Further features and advantages of the present invention are explained below with reference to the figures. They show:

[0038] Figs. 1a and 1b show schematic overall and partial representations of a hydraulic braking system of a vehicle to illustrate one embodiment of the control device;

[0039] Figs. 2a and 2b show a flowchart and a coordinate system to illustrate a first embodiment of the method for determining the dead travel of a master brake cylinder with an upstream actuator of a vehicle's hydraulic brake system; and

[0040] Fig. 3 shows a coordinate system to illustrate a second embodiment of the method for determining the dead travel of a master brake cylinder with an upstream actuator of a hydraulic brake system of a vehicle.

[0041] Embodiments of the invention

[0042] Figs. 1a and 1b show schematic overall and partial representations of a hydraulic braking system of a vehicle to illustrate one embodiment of the control device.

[0043] It is expressly pointed out that the usability of the control device 10 described below is not limited to any specific type of hydraulic brake system or to any particular vehicle type. The features of the hydraulic brake system shown in Figures 1a and 1b, described below, are to be interpreted merely as examples. It is also pointed out that R. 414971

[0044] - 9 -

[0045] The usability of the control device 10 is not limited to the interacting braking system. For example, the control device can also be used for at least one other vehicle component and / or at least one other vehicle system, such as an electric drive motor and / or a steering device. If applicable, the at least one other vehicle component and / or system can also be controlled by the control device 10.

[0046] The control device 10 has an electronic unit 10a by means of which at least one motor control signal 14s can be output to a (not shown) motor of an actuator 14 located upstream of a master brake cylinder 16 of the brake system, and at least one control signal 12s can be output to at least one pumping device 13 and / or to at least one valve 12 of the brake system. The actuator 14 can also be referred to as a motorized brake pressure build-up device. The actuator 14 can, for example, be an electromechanical brake booster, such as an iBooster, or a brake-by-wire actuator. The control device 10 can thus be used for both a brake-force-boosting hydraulic brake system and a brake-by-wire brake system, i.e., a brake system without a mechanical connection to a brake actuation device, such as a brake pedal. The brake system shown in Fig. is merely an example.1 a and 1 b the (not shown) brake actuation device can be mechanically connected to an input rod 18.

[0047] The control device 10 can, in particular, be an ESP controller, a brake booster controller, such as specifically an iBooster controller, a BWA controller (i.e., a brake-by-wire actuator controller), or a central control unit of the respective vehicle. However, the usability of the control device 10 is not limited to any specific type of controller. (See R. 414971.)

[0048] - 10 -

[0049] The training options listed for the control device 10 are therefore to be interpreted only as examples.

[0050] A reservoir 20 is typically mechanically connected to the master brake cylinder 16. The reservoir 20 can also be referred to as a brake fluid reservoir (containing atmospheric pressure). Typically, the master brake cylinder 16 has at least one bore 22 through which, if the bore 22 is not sealed, brake fluid transfer between an internal volume of the master brake cylinder 16 and the reservoir 20 is possible. The bore 22 can also be referred to as a vent bore. To ensure brake pressure build-up in at least the master brake cylinder 16, the bore 22 can be sealed by means of a piston 24 of the master brake cylinder 16, specifically a primary piston / rod piston 24.The piston 24 is adjustable from its rearward stop into the master brake cylinder 16 by means of motor force from the actuator 14 motor and / or a driver braking force applied to the (optional) brake actuation device. Typically, the piston 24 is supported by a mechanism (not shown in Figures 1a and 1b) such that, unless the motor force of the actuator 14 or the driver braking force is applied / transmitted to it, the piston 24 is in its rearward stop position. This can also be referred to as the piston 24's stop position. The travel s of the piston 24 from its rearward stop to a position in which the bore 22 is (just) sealed by the piston 24 is generally referred to as the dead travel sO.If the piston 24 is moved into the master cylinder 16 by at least the dead travel sO from its rear stop, the bore 22 is sealed by means of the piston 24, whereas if the piston 24's movement from its rear stop is less than the dead travel sO, the hydraulic connection between the interior of the master cylinder 16 and the reservoir 20 is open. If the brake system has a (not shown) rotor position sensor for the motor and / or at least one (not shown) piston position and / or piston travel sensor, see Elect. R. 414971.

[0051] - 11 -

[0052] The electronic device 10a is preferably designed / programmed such that a current measured value of the adjustment travel s of the piston 24 from its rear stop can be read by the electronic device 10a from at least one provided sensor signal of the rotor position sensor and / or the at least one piston position and / or piston travel sensor. (Based on the motor position, i.e., the current rotation angle of the motor rotor, the adjustment travel s of the piston 24 from its rear stop can optionally be calculated with high accuracy.) The at least one piston position and / or piston travel sensor can specifically be a rod travel sensor.

[0053] The master brake cylinder 16 shown in Figures 1a and 1b is merely an example; it is a so-called tandem master brake cylinder, which, in addition to the piston / primary piston 24, also has a secondary piston / floating piston 26 that is adjustable together with the piston / primary piston 24. While the piston / primary piston 24 is supported by the secondary piston / floating piston 26 by means of a first spring 27a, the secondary piston / floating piston 26 is supported by a second spring 27b against a housing of the master brake cylinder 16.

[0054] In particular, component tolerances and / or aging effects can lead to deviations of the actual value of the dead travel sO of the respective hydraulic brake system, or its master brake cylinder 16 with the upstream actuator 14, from a target value of the dead travel sO. As will become clear from the following description, the control device 10 is therefore suitable for individually determining / measuring the current value of the dead travel sO for the brake system.

[0055] For this purpose, the electronic device 10a of the control unit 10 is designed and / or programmed such that at least one motor control signal 14s can be output to the motor of the actuator 14 located upstream of the master brake cylinder 16. R. 414971

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[0057] The operation of the motor, controlled by at least one motor control signal 14s, causes at least the piston 24 of the master brake cylinder 16 to be adjustable from its rear stop to at least one intermediate position, in which the bore 22 connecting the master brake cylinder 16 to the reservoir 20 is sealed. This means that the piston can be adjusted by the controlled motor from its rear stop to the intermediate position by a travel s greater than the dead travel sO. The at least one motor control signal 14s could, for example, be a constant motor current output to the motor. Likewise, the motor actuation effected by the at least one motor control signal 14s could also be such that the motor delivers a constant motor torque or a constant motor force.

[0058] The design and / or programming of the electronic device 10a of the control device 10 also ensures that, when the piston 24 is in the intermediate position and after subsequent deactivation of the motor, at least one control signal 12s can be output to at least one pumping device 13 and / or at least one valve 12 of the brake system. By means of the at least one controlled pumping device 13 and / or the at least one controlled valve 12, a volume of brake fluid from at least one partial volume of the brake system connected to the master brake cylinder 16 can be transferred to the master brake cylinder 16 in such a way that the piston 24 is moved from the intermediate position towards the rear stop, at least into a bore release position, by means of a pressure force exerted by the transferred volume of brake fluid.The bore release position refers to a position of the piston 24 at which the seal of the bore 22 connecting the master brake cylinder 16 to the reservoir 20 ends (straight). R. 414971.

[0059] - 13 -

[0060] Furthermore, the electronic device 10a is designed and / or programmed such that it can subsequently determine / determine a current value of the dead travel sO, taking into account an estimated or measured travel s of the piston 24 between its rear stop and the bore release position. Using the electronic device 10a, the current and individual value of the dead travel sO can thus be determined / measured with relatively high accuracy and a comparatively low error rate. This can also be described as the current and individual value of the dead travel sO of the hydraulic brake system, or of the actuator upstream of the master brake cylinder, being reliably learned. Despite component tolerances and / or aging effects, the current value of the dead travel sO can therefore always be determined using the electronic device 10a.

[0061] Furthermore, the presence of piston 24 in the bore release position can be reliably detected by means of the electronic device 10a. The presence of piston 24 in the bore release position can be recognized, for example, by the fact that piston 24 remains in this position, spaced at a certain distance (non-zero) from its rear stop, for at least a predetermined minimum time, while the brake fluid volume transferred from at least one partial volume into the master cylinder is transferred further into the reservoir 20 via bore 22. The travel s of piston 24 present for at least the predetermined minimum time is thus the travel s of piston 24 between its rear stop and its bore release position, or the current value of the dead travel sO.

[0062] Alternatively or additionally, the electronic device 10a can be used to read / determine a current change in time of at least one operating parameter of the at least one conveying device 13 and / or of a pressure p present in at least one part of the brake system. If necessary, the (at least temporary) presence of the piston 24 in the bore release position can be recognized by the electronic device 10a by the fact that at this time the current change in time of the at least one operating parameter R is displayed. 414971

[0063] - 14 -

[0064] and / or the pressure p exceeds a predefined threshold value. The current change over time of at least one operating parameter and / or the pressure p can be read from at least one provided sensor signal from at least one sensor of at least one conveying device 13 and / or at least one pressure sensor 32. Typically, (almost) every hydraulic brake system has a pressure sensor 32, which can be used to measure the pressure p over time. The pressure sensor 32 can be understood to be, in particular, a pre-pressure sensor 32, which is hydraulically connected to the master brake cylinder 16.

[0065] In a preferred embodiment of the control device, prior to deactivation of the motor, the motor and the at least one valve 12 are operated by the output of control signals 12s and 14s with the aim of first displacing the brake fluid volume, which will later be transferred from the at least one partial volume to the master brake cylinder 16, from the master brake cylinder 16 into the at least one partial volume. After the brake fluid volume has been displaced from the master brake cylinder 16 into the at least one partial volume by means of the actuator 14 via the at least one at least partially open valve 12, the previously displaced brake fluid volume can be enclosed in the at least one partial volume by closing the at least one valve 12. This is schematically represented by symbol 30 in Fig. 1a.Then, with the piston 24 in the intermediate position and after the motor has been deactivated, the brake fluid volume can flow from the at least one partial volume into the master brake cylinder 16 by (re)opening the at least one valve 12. If necessary, the operation of the at least one conveying device 13, such as at least one pump 13, can be omitted for the transfer of the brake fluid volume, thereby saving energy and preventing noise generation.

[0066] In the example shown in Figs. 1a and 1b, at least one controlled valve 12 is a unit separation valve (USV) 12 of the brake system. R. 414971

[0067] - 15 -

[0068] This allows the use of a valve type already commonly employed in brake systems. However, the use of a single unit isolating valve as the at least one controlled valve 12 is only to be interpreted as an example.

[0069] As an alternative to enclosing the transferred brake fluid volume, at least one pump 13 of the brake system can also be used as the at least one pumping device 13 for transferring the brake fluid volume from the at least one partial volume into the master brake cylinder 16. When the piston 24 is in the intermediate position and after the motor has been deactivated, the brake fluid volume from the at least one partial volume can be pumped into the master brake cylinder 16 by means of the at least one controlled pump 13. The at least one pump 13 is controlled by means of the at least one control signal 12s from the electronic device 10a.

[0070] Alternatively, at least one piston-cylinder device of the brake system, which can be controlled / actuated by means of the at least one control signal 12s of the electronic device 10a, can also be used as the at least one pumping device 13. Typically, a brake system has at least one pump 13 and / or at least one piston-cylinder device, so that the control device 10 can be used for a variety of different brake system types. This allows for cost-effective and efficient adaptation to different vehicle models and brake configurations without requiring fundamental changes to the control device 10.

[0071] Preferably, the electronic device 10a of the control unit 10 can determine or query whether the vehicle is stationary. If necessary, the motor of the actuator 14 is only activated to move the piston 24 of the master brake cylinder 16 from its position by means of the output of at least one motor control signal 14s if the vehicle is stationary. 414971

[0072] - 16 -

[0073] to adjust the rear stop to at least the intermediate position. By verifying that the vehicle is stationary before activating the actuator 14 motor, it is prevented that the piston 24 of the master brake cylinder 16 is moved while driving.

[0074] As an advantageous further development of the control device 10, the electronic device 10a can also reliably maintain the specified / desired target value of the piston 24's dead travel despite component tolerances and / or aging effects. For this purpose, the electronic device 10a can be designed / programmed to define a target distance of the piston 24 from its rear stop, taking into account the current value of the dead travel sO and the target value of the dead travel sO. Subsequently, the motor can be controlled / is controlled by the electronic device 10a, taking into account the defined target distance, such that the piston 24 is held at least temporarily at the target distance from its rear stop.The control device 10 / its electronic unit 10a thus enables, in particular, a "shortening" of the dead travel sO to the target value, specifically to compensate for component tolerances and / or aging effects, which conventionally often lead to an undesirable "lengthening" of the current value of the dead travel sO. By being able to "shorten" the dead travel sO to the desired target value, the responsiveness of the braking system can be improved.

[0075] It is expressly pointed out that the control device 10 described above can be used for (almost) any hydraulic brake system for a vehicle, provided that the hydraulic brake system is equipped with the actuator 14, the downstream master brake cylinder 16, and with at least one pumping device 13 and / or at least one valve 12. Furthermore, the brake system in the example of Figs. 1a and 1b can also be equipped with pumps 13 with an associated pump motor 15, wheel brake cylinders 28, wheel inlet valves 34, wheel outlet valves 36, accumulator chambers 38, check valves 40, and high-pressure switching valves 46, optionally. R. 414971

[0076] - 17 -

[0077] The control device 10 / its electronic equipment 10a can be advantageously designed and / or programmed to perform at least some of the process steps described below.

[0078] Figs. 2a and 2b show a flowchart and a coordinate system to explain a first embodiment of the method for determining a dead travel of a master brake cylinder with an upstream actuator of a hydraulic brake system of a vehicle.

[0079] It is expressly pointed out that the feasibility of the procedure described below is not limited to any specific type of hydraulic brake system or to any particular type of vehicle.

[0080] Figure 2a shows the process steps S1 to S5 using a flowchart, whereas Figure 2b depicts the process steps S1 to S5 using a graph g in a coordinate system. In the coordinate system, the abscissa represents a current time t (in seconds), while the ordinate shows a travel s of a piston of the master brake cylinder downstream of the actuator from its rear stop (in millimeters).

[0081] In process step S1 of the method, a motor of the actuator is controlled such that at least the piston of the master brake cylinder is moved by means of the controlled motor from a rearward stop to at least one intermediate position in which a bore connecting the master brake cylinder to a reservoir is sealed. Examples of the bore and the piston of the master brake cylinder have already been given above. As shown in Fig. 2b by means of graph g, in process step S1 the piston is moved, for example, from a travel distance s equal to zero (s=0) to a travel distance s above its dead travel sO (s > sO). R. 414971

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[0083] In process step S2, the actuator's motor is deactivated or switched to passive / inactive mode. This can be achieved, for example, by outputting a signal to interrupt the motor current or by setting the current flow to the motor to zero. After the motor is deactivated (i.e., after process step S2), in process step S3, a volume of brake fluid from at least one partial volume of the hydraulic brake system connected to the master cylinder is transferred into the master cylinder. This transfer is such that the piston is moved from its intermediate position towards its rear stop, at least to a bore release position, by means of a pressure force exerted by the transferred brake fluid volume. As explained above, the bore release position is the position of the piston at which the seal of the bore connecting the master cylinder to a reservoir (immediately) ends.The bore is released by the piston. The possibilities for causing / triggering the shift of the brake fluid volume from at least one partial volume into the master brake cylinder have already been described above.

[0084] In a further process step S4, a current value of the dead travel sO is determined, taking into account the estimated or measured adjustment travel s of the piston between the rear stop and the bore release position. In the example of Figures 2a and 2b, the presence of the piston in the bore release position is recognizable by the fact that the piston remains in this position, spaced from its rear stop, for at least a predetermined minimum time, while the brake fluid volume transferred from at least one partial volume into the master cylinder flows through the bore into the reservoir.

[0085] The procedure, comprising at least steps S1 to S4, can be performed either once when the hydraulic brake system is new or multiple times throughout its entire service life, as desired. If multiple executions of R. 414971 are required...

[0086] - 19 -

[0087] If a procedure is desired during the service life of the hydraulic brake system, the procedure can be repeated optionally after predetermined time or maneuver intervals, after high loads (which may cause changes in the dead distance sO), after the occurrence of at least a predetermined minimum temperature change, after a service, after a brake fluid change, after a "reset" or a "resetting" of at least one sub-unit of the hydraulic brake system and / or after a replacement of the master brake cylinder.

[0088] Preferably, before starting the process, it is investigated whether at least one predetermined disturbance variable is present in the vehicle or at least in its hydraulic braking system. For example, if a temperature outside a predetermined normal temperature range can be detected by means of at least one temperature sensor of the vehicle, specifically of a hydraulic braking system, then it is advantageous to refrain from executing the process.

[0089] Preferably, the execution of the procedure, which comprises at least steps S1 to S4, is delayed until the vehicle is stationary. In particular, after determining that no person is in the vehicle, it can be assumed with a high degree of probability that the vehicle will remain stationary for an extended period of time, and the procedure can then be started.

[0090] If it is determined that the current value of the dead distance sO is outside a specified normal range, it can be assumed with a high degree of probability that significant aging effects or damage to the braking system have occurred. The driver may then be advised to visit a workshop. R. 414971

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[0092] As an advantageous further development, the method described above can also be part of a method for operating an actuator upstream of a master brake cylinder in a vehicle's hydraulic braking system. Optionally, the method includes a further (optional) process step S5, which is executed after determining the current value of the dead travel sO of the hydraulic braking system. In process step S5, a target distance of the master brake cylinder piston from its rear stop is first determined, taking into account the determined current value of the dead travel sO and a predetermined or defined target value for the dead travel sO. Subsequently, the actuator motor is controlled by means of at least one motor control signal, taking into account the determined target distance, such that the piston is held at least temporarily at the target distance from its rear stop.While conventionally the rear stop defines the target value, process step S5 allows the dead travel sO to be "reset" according to the target value. To compensate for an undesirably large dead travel sO, the piston can thus be "stopped" not at its rear stop, but at the target distance from it. In particular, this ensures that the "reset" dead travel sO is not so large and can therefore be quickly overcome by the actuator's motor force and / or the driver's braking force. This allows the "reset" dead travel sO to be overcome more quickly, resulting in an improved response time of the braking system. Furthermore, the actuator's motor force and / or the driver's braking force can be used more effectively, as they do not have to be expended to overcome an excessively large dead travel sO.Precise adjustment of the dead distance sO results in a more even and effective distribution of braking force, thus improving the overall braking performance of the braking system. In particular, this ensures that the vehicle can be quickly decelerated or brought to a standstill, especially in emergency braking situations.

[0093] As an alternative or supplement to process step S5, at least one R. 414971 used for the operation of the hydraulic brake system can also be used.

[0094] - 21 -

[0095] The characteristic curve is redefined taking into account the determined current value of the dead path sO.

[0096] Fig. 3 shows a coordinate system to explain a second embodiment of the method for determining a dead travel of a master brake cylinder with an upstream actuator of a hydraulic brake system of a vehicle.

[0097] In the coordinate system of Fig. 3, the abscissa represents the current time t (in seconds), while the ordinate indicates the displacement s of a piston in the master brake cylinder downstream of the actuator from its rear stop (in millimeters) and a pressure p (in bar) corresponding to the internal pressure of the master brake cylinder. By way of example only, in the embodiment of the method described here, the piston is moved by a displacement s of 12 millimeters from its rear stop (s=0) between times to and h, thereby building up a pressure p of 30 bar in the master brake cylinder. By closing at least one valve, which is at least partially open between times to and h, at time t2, a volume of brake fluid is enclosed in at least a partial volume of the brake system. This completes a preparatory phase.

[0098] At time ts, the piston is actively retracted by the actuator towards its rearward stop until it reaches an intermediate position, which is achieved at time ts. This causes the pressure p to drop. Additional brake fluid volume is supplied from the reservoir via at least one check valve, which opens under vacuum. Then, at time ts, the at least one valve opens, triggering another increase in the pressure p in the master cylinder, so that the piston is pushed further towards its rearward stop. By pushing the piston back further, at least to its bore release position (0 < s < sO) at time te, the connection to the reservoir is opened, which is why the pressure p in the master cylinder drops rapidly again at time ts. 414971

[0099] - 22 -

[0100] is being built. The position of the piston at time te is therefore its bore release position, which is why the adjustment travel s between the position of the piston at time ts and its rear stop is the current value of the dead travel sO.

[0101] Regarding further process steps of the process of Fig. 3, reference is made to the previously explained embodiment of Figs. 2a and 2b.

Claims

R. 414971 - 23 - Claims 1. Control device (10) for at least one hydraulic braking system of a vehicle with: an electronic device (10a) which is designed and / or programmed such that the electronic device (10a) can be used to: - at least one motor control signal (14s) can be output to a motor of an actuator (14) located upstream of a master brake cylinder (16) of the hydraulic brake system in such a way that, by operation of the motor controlled by means of the at least one motor control signal (14s), at least one piston (24) of the master brake cylinder (16) can be moved from a rear stop to at least one intermediate position, in which a bore (22) connecting the master brake cylinder (16) with a reservoir (20) is sealed; - after deactivation of the motor, at least one control signal (12s) can be output to at least one delivery device (13) of the hydraulic brake system and / or to at least one valve (12) of the hydraulic brake system such that a brake fluid volume from at least one partial volume of the hydraulic brake system connected to the master brake cylinder (16) can be transferred into the master brake cylinder (16) in such a way that the piston (24) is moved from the intermediate position towards the rear stop by means of a pressure force exerted by the transferred brake fluid volume, at least into a bore release position in which the sealing of the R. 414971 - 24 - The master brake cylinder (16) ends with the bore (22) connecting the reservoir (20), and is adjustable; and a current value of the dead travel (sO) can be determined taking into account an estimated or measured adjustment travel (s) of the piston (24) between its rear stop and the bore release position.

2. Control device (10) according to claim 1, wherein the electronic device (10a) is additionally designed and / or programmed such that the motor of the actuator (14) and the at least one valve (12) can be controlled by means of the electronic device (10a) in such a way that the brake fluid volume subsequently transferred from the at least one partial volume into the master brake cylinder (16) can be displaced into the at least one partial volume by means of the piston (24) of the master brake cylinder (16) adjusted to at least the intermediate position via the at least one open-controlled valve (12) of the hydraulic brake system and the displaced brake fluid volume can be enclosed in the at least one partial volume by means of an effected closure of the at least one valve (12),that when the piston (24) is in the intermediate position after the engine is deactivated, the brake fluid volume can be transferred from the at least one partial volume into the master brake cylinder (16) via the at least one valve (12) which is opened again by means of the at least one control signal (12s).

3. Control device (10) according to claim 2, wherein the electronic device (10a) is designed and / or programmed such that at least one unit isolating valve (12) of the hydraulic brake system can be controlled by means of the at least one output control signal (12s). R. 414971 - 25 - 4. Control device (10) according to claim 1, wherein the electronic device (10a) is additionally designed and / or programmed such that at least one pump (13) of the hydraulic brake system can be controlled by means of the electronic device (10a) as the at least one delivery device (13) by means of the at least one control signal (12s) such that when the piston (24) is in the intermediate position after deactivation of the motor, the brake fluid volume can be pumped from the at least one partial volume into the master brake cylinder (16) by means of the at least one controlled pump (13).

5. Control device (10) according to claim 1, wherein the electronic device (10a) is additionally designed and / or programmed such that at least one piston-cylinder device of the hydraulic brake system, as the at least one delivery device (13), can be controlled by means of the electronic device (10a) by means of the at least one control signal (12s) such that, when the piston (24) is in the intermediate position after deactivation of the motor, the brake fluid volume can be transferred from the at least one partial volume of the at least one piston-cylinder device into the master brake cylinder (16) by means of the at least one controlled piston-cylinder device.

6. Control device (10) according to one of the preceding claims, wherein the electronic device (10a) is additionally designed and / or programmed such that a position of the piston (24), into which the piston (24) is moved from the intermediate position by means of the brake fluid volume transferred from the at least one partial volume into the master brake cylinder (16) and in which the piston (24) remains spaced from its rear stop for at least a predetermined minimum time, is recognizable by means of the electronic device (10a) as the bore release position. R. 414971 - 26 - 7. Control device (10) according to any one of claims 1 to 5, wherein the electronic device (10a) is additionally designed and / or programmed such that, by means of the electronic device (10a), a current temporal change of at least one operating parameter of the at least one conveying device (13) and / or a current temporal change of a pressure (p) present in at least one part of the hydraulic brake system can be read or determined from at least one provided sensor signal of at least one sensor of the at least one conveying device (13) and / or at least one pressure sensor (32), and a position of the piston (24),in and / or via which the piston (24) is moved from the intermediate position by means of the brake fluid volume transferred from the at least one partial volume into the master brake cylinder (16) and at which the current temporal change of the at least one operating parameter and / or the pressure (p) is above a respective predetermined threshold value, is recognizable as the bore release position by means of the electronic device (10a).

8. Control device (10) according to one of the preceding claims, wherein the electronic device (10a) is additionally designed and / or programmed such that a current measured value of the adjustment travel (s) of the piston (24) from its rear stop can be read out by means of the electronic device (10a) from at least one provided sensor signal of a rotor position sensor of the motor and / or at least one piston position and / or piston travel sensor.

9. Control device (10) according to one of the preceding claims, wherein the electronic device (10a) is additionally designed and / or programmed such that, by means of the electronic device (10a), taking into account the determined current value of the dead travel (sO) and a predetermined or determined target value of the dead travel (sO), a target distance of the piston (24) from its rear stop can be determined, and the motor is controlled by means of the electronic device (10a). R. 414971 - 27 - Taking into account the specified target distance, it can be controlled in such a way that the piston (24) is held at least temporarily at the target distance from its rear stop.

10. Control device (10) according to one of the preceding claims, wherein the electronic device (10a) is additionally designed and / or programmed such that it is possible to determine or query whether the vehicle is at a standstill by means of the electronic device (10a), and only if the vehicle is at a standstill, is the operation of the motor of the actuator (14), by which the piston (24) of the master brake cylinder (16) can be adjusted from its rear stop to at least the intermediate position, activated by means of the output of the at least one motor control signal (14s).

11. Hydraulic braking system for a vehicle with: a control device (10) according to one of the preceding claims; the actuator (14), whose motor can be controlled by means of the at least one motor control signal (14s) output by the electronic device (10a) of the control device (10) such that, by the operation of the motor controlled by means of the at least one motor control signal (14s), at least the piston (24) of the master brake cylinder (16) of the hydraulic brake system downstream of the actuator (14) can be adjusted from the rear stop to at least the intermediate position; and the at least one pumping device (13) and / or the at least one valve (12), which, after deactivation of the motor, can be controlled by means of the at least one control signal (12s) output by the electronic device (10a) in such a way that the brake fluid volume from the at least one on the R. 414971 - 28 - The partial volume connected to the master brake cylinder (16) can be transferred into the master brake cylinder (16).

12. Method for determining a dead travel (sO) of a master brake cylinder (16) with an upstream actuator (14) of a hydraulic brake system of a vehicle comprising the steps: Controlling a motor of the actuator (14) such that at least one piston (24) of the master brake cylinder (16) is moved by means of operation of the controlled motor from a rear stop to at least one intermediate position in which a bore (22) connecting the master brake cylinder (16) with a reservoir (20) is sealed (S1); After deactivating the engine (S2), transferring a volume of brake fluid from at least one partial volume of the hydraulic brake system connected to the master brake cylinder (16) into the master brake cylinder (16) such that the piston (24) is moved from the intermediate position towards the rear stop by means of a pressure force exerted by the transferred volume of brake fluid, at least to a bore release position in which the sealing of the bore (22) connecting the master brake cylinder (16) with the reservoir (20) ends (S3); and Determining an actual value of the dead travel (sO) taking into account the estimated or measured adjustment travel (s) of the piston (24) between the rear stop and the bore release position (S4).

13. Method for operating an actuator (14) upstream of a master brake cylinder (16) of a hydraulic brake system of a vehicle, comprising the steps: R. 414971 - 29 - Determining a current value of a dead distance (sO) of the hydraulic braking system according to the method of claim 12; Determining a target distance of the piston (24) of the master brake cylinder (16) from its rear stop, taking into account the determined current value of the dead travel (sO) and a predetermined or determined target value of the dead travel (sO); and Controlling the motor of the actuator (14) taking into account the specified target distance by means of the at least one motor control signal (14s) such that the piston (24) is held at least temporarily at the target distance from its rear stop (S5).

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