Motor vehicle braking system and method for operating such a system

Abstract

Motor vehicle braking system comprising an actuating device (10) with a brake pedal (11) and an electromechanical brake booster (12), which are coupled to each other in such a way that when the electromechanical brake booster (12) is actuated, the brake pedal (11) is actuated, a brake pressure generating device (31) for actively generating brake pressure independently of the actuating of the electromechanical brake booster (12) and the brake pedal (11), and a control device (50) for controlling the brake pressure generating device (31), which is configured in such a way as to cause a brake pressure build-up via the brake pressure generating device (31) when a blockage of the actuating device (10) is detected during a braking request, characterized in that a motor angle (α) is used to detect a blockage of the actuating device (10).) or a corresponding displacement and motor torque (M) of an electric motor (13) of the electromechanical brake booster (12) are related to each other and a lockup is then concluded if the motor torque (M) or the gradient of the motor torque (M) deviates from a predetermined target curve (M(μ)) in relation to the motor angle (μ) or the corresponding displacement and / or the curve of the brake pressure (pist) provided by the master brake cylinder (20) and the motor torque (M) are related to each other and a lockup is then concluded if the motor torque (M) deviates from a predetermined target curve (ΔM(p)) in relation to the brake pressure (pist).;

Description

[0001] The invention relates to a motor vehicle braking system comprising an actuating device with a brake pedal and an electromechanical brake booster, which are coupled to each other such that the brake pedal is actuated when the electromechanical brake booster is actuated; a brake pressure generating device for actively generating brake pressure independently of the actuating of the electromechanical brake booster and the brake pedal; and a control device for controlling the brake pressure generating device, which is configured to initiate brake pressure build-up via the brake pressure generating device when a blockage of the actuating device is detected during a braking request. The invention further relates to a method for operating a motor vehicle braking system.

[0002] A motor vehicle braking system of the type mentioned above is known from WO 2015 / 188958 A1.

[0003] Electromechanical brake boosters are becoming increasingly common in vehicle braking systems, particularly in passenger cars. In these systems, an electric motor provides assistance to the driver during braking. Furthermore, an electromechanical brake booster can initiate the application of the wheel brakes independently of the driver.

[0004] The present invention relates to braking systems in which the electromechanical brake booster and the brake pedal are coupled. When braking is required without the driver's input, for example, when an emergency brake assist system is activated, the brake pedal is automatically moved, i.e., pivoted towards the firewall, when the electromechanical brake booster is actuated. If the movement of the brake pedal is restricted, for example, by a driver's foot accidentally positioned underneath it or by an object under the brake pedal, sufficient brake pressure cannot be built up in the master cylinder of the braking system via the electromechanical brake booster, which is thereby blocked.In WO 2015 / 188958 A1, it is proposed that in such a case, the corresponding control of the electromechanical brake booster be deactivated or that it be returned to its initial position, and that the brake pressure required at the wheel brakes be supplied instead via the brake pressure generation unit of the ESP-ABS hydraulic system. This allows braking to be achieved despite the brake pedal and the electromechanical brake booster being locked.

[0005] Reliably detecting a brake pedal lock-up is generally difficult. Firstly, algorithms must be developed that can reliably distinguish between a locked and an unlocked state of the actuator, taking into account a multitude of eventualities. Secondly, suitable sensors must be provided that operate with sufficient reliability and are cost-effective to manufacture and install, especially for mass production. A larger number of sensors can increase the accuracy of detecting a lock-up. However, a large volume of data necessitates a correspondingly high level of processing effort. This, in addition to the cost of the sensors themselves, results in high costs. Therefore, there is a great need for a solution that is as simple and cost-effective as possible, yet still reliable.

[0006] To determine whether the brake pedal is locked, WO 2015 / 188958 A1 proposes evaluating a "deformation" of the electromechanical brake booster resulting from the tensile forces exerted on the brake pedal by the brake booster during a lockup. In one specific implementation, WO 2015 / 188958 A1 interprets this deformation as the difference in travel between a transmission component located in or on the brake booster and a transmission component located on the brake pedal. Due to system elasticities, a tensile force acting between these components when the brake pedal locks, causing a certain degree of deformation, results in a slight, measurable difference in travel. The change in this difference over time ultimately provides information about whether or not the brake pedal is locked.Specifically, WO 2015 / 188958 A1 proposes to observe the motor angle of the electric motor of the electromechanical brake booster and the pedal rod travel using a sensor and to determine a difference travel from the two quantities.

[0007] The invention is based on the objective of demonstrating technical alternatives to WO 2015 / 188958 A1.

[0008] According to claim 1, it is proposed that in a motor vehicle braking system of the type mentioned above, to detect a blockage of the actuating device, a motor angle or a corresponding displacement and a motor torque of an electric motor of the electromechanical brake booster are related to each other, and a blockage is then concluded if the motor torque or the gradient of the motor torque deviates from a predetermined target curve in relation to the motor angle or the corresponding displacement, and / or the curve of the brake pressure provided by the master brake cylinder and the motor torque are related to each other, and a blockage is then concluded if the motor torque deviates from a predetermined target curve in relation to the brake pressure.

[0009] The solution according to the invention offers the advantage over the aforementioned prior art of being insensitive to any changes in system elasticities, friction effects and the like.

[0010] In motor vehicle braking systems, where the control of the electromechanical brake booster takes into account, among other things, the pedal force applied to the brake pedal, the concept according to the invention can be implemented purely in software without any additional equipment.

[0011] A further advantage of the solution according to the invention is that it does not require the detection or interpretation of tensile forces. Therefore, it is not necessary for the corresponding pedal force sensor to also detect tensile forces. This allows the use of a sensor that is only capable of detecting compressive forces as the pedal force sensor. Such a sensor offers potential cost savings compared to a force sensor that must detect both tensile and compressive forces.

[0012] Furthermore, the solution according to the invention offers the advantage of not only being able to detect a blockage of the brake pedal, but also other blockages in the actuating device as a whole, such as a malfunction of the electromechanical brake booster due to a defect or environmental influences such as icing of the electric motor.

[0013] Advantageous embodiments of the invention are the subject of further patent claims.

[0014] In one embodiment of the invention, the control unit is configured such that a blockage is only detected if the brake pressure supplied by a master cylinder remains below a predetermined limit. This utilizes the fact that when the actuating device is blocked, the brake pressure behind the master cylinder hardly increases. This information can be used to validate the blockage signal sent to the brake pressure generation unit. Since a corresponding pressure sensor is usually present on the ESP-ABS hydraulic unit, no additional equipment is required, yet the accuracy of the algorithm implemented in the control unit is increased. This improves its robustness against false detections.

[0015] In another version, the control unit also incorporates the signal from a pedal force sensor for condition assessment. If a blockage is detected and a signal from the pedal force sensor indicating the application of a pressure force is present, a malfunction of the electromechanical brake booster can be inferred. This can be compensated for in the event of a braking demand, as explained above. Furthermore, a corresponding warning can be issued to the driver, prompting them to visit a workshop. If an object were to become trapped under the brake pedal, however, a tensile force would typically be felt at a pedal force sensor.

[0016] Furthermore, the control unit can incorporate a status signal indicating whether an autonomous braking request—that is, a braking request without the driver pressing the brake pedal—has occurred. Such a status signal can be transmitted, for example, in conjunction with the requested brake pressure or the force to be provided by the electromechanical brake booster. This type of status signal can improve the differentiation between the detection of a locked brake pedal and the detection of a locked electromechanical brake booster.

[0017] Furthermore, differentiating between a brake pedal blockage and a blockage of the electromechanical brake booster can be achieved by using different sensitivity in signal evaluation, for example, via different threshold values. In this context, threshold values ​​are understood to be both constant values ​​and functions or characteristic maps that depend on at least one parameter.

[0018] In an advantageous embodiment of the invention, the following signals are connected to the control unit as input variables: the signal from a motor angle sensor of the electromechanical brake booster, the signal from a pedal force sensor representing an actuating force applied to the brake pedal, and the signal from a pressure sensor representing the pressure supplied by the master brake cylinder to an ESP-ABS hydraulic unit. Such sensors are usually present in the braking system for controlling the electromechanical brake booster, so that the locking detection can be implemented almost entirely in software.

[0019] Furthermore, to improve the accuracy of the control unit, input variables can also include a quantity representing the motor torque or a change in the motor torque over time. This includes, in particular, the current supplied to the electric motor, which is used to adjust the torque provided by the electric motor.

[0020] Furthermore, the present invention proposes a method for operating a motor vehicle braking system according to claim 7, in which, on the motor vehicle side, at least one actuating device is provided with a brake pedal, a pedal force sensor and an electromechanical brake booster with an electric motor and a motor angle sensor, a master brake cylinder and a pressure sensor, as well as an ESP-ABS hydraulic unit with a brake pressure generating device. The method comprises, in particular, the following steps: - Activating a blockage detection system when a brake pressure request is detected, which involves actuation of the electromechanical brake booster, - Comparison of the motor torque curve and / or the time-dependent change of the motor torque (M) (13) of the electric motor as a function of the motor angle or a corresponding displacement variable with a target curve, - Performing a status assessment when blockage detection is activated by evaluating the deviation from the target behavior and outputting a status signal regarding the presence of a blockage of the actuating device, and - Activating the brake pressure generation device to generate brake pressure when the status signal indicates the presence of a blockage.

[0021] This results in the advantages already explained above. The brake pressure generation device can thus compensate for the lack of actuation by the electric brake booster.

[0022] In one embodiment of the method, if a positive status signal is received for the brake pressure generation device, i.e., if a blockage is present, the electromechanical brake booster is deactivated or returned to its initial position. This allows a trapped object or driver's foot to be released very quickly, thus clearing the blockage for a renewed braking maneuver.

[0023] In a further embodiment of the method, the pressure curve provided by the master brake cylinder and detected by the pressure sensor, as a function of the engine torque, can be compared with a target curve. This information can then be used in step c) for plausibility checks during condition assessment to further improve the accuracy of the condition detection of the actuating device. Such plausibility checks can include weighting both criteria against each other. In particular, it is also possible to assign a higher weight to the pressure-dependent criterion than to the angle- or displacement-dependent criterion.

[0024] To ensure good detection of blockages in the area of ​​the electromechanical brake booster, this can also be modified as follows. - Comparison of the motor torque curve and / or the time-dependent change of the motor torque of the electric motor as a function of the motor angle or a corresponding displacement variable with a target curve, - Comparing the pressure curve supplied by the master brake cylinder as a function of engine torque with a target curve, - Performing a condition assessment by evaluating deviations from the respective target curve and outputting a status signal regarding the presence of a blockage of the actuating device, and - Activating the brake pressure generation device to generate brake pressure when the status signal indicates the presence of a blockage.

[0025] The invention will now be explained in more detail with reference to exemplary embodiments illustrated in the drawing. The drawing shows: Fig.1 a schematic representation of a motor vehicle braking system according to an embodiment of the invention, Fig. 2. the course of the motor torque (M) as a function of the motor angle (φ) for various blockages b, c compared to a target course a, and in Fig. 3 A schematic representation of the control device.

[0026] The exemplary embodiment in Fig. Figure 1 shows a motor vehicle braking system 1 with an actuating device 10 , a master brake cylinder 20 , an ESP-ABS hydraulic unit 30, wheel brakes 40 , various sensors and a control unit 50 .

[0027] The master brake cylinder 20 It is hydraulically connected to the ESP-ABS hydraulic unit. 30 connected, which is a brake pressure generating device 31for generating brake pressure. The wheel brakes are in turn hydraulically connected to the ESP-ABS hydraulic unit. 30 connected.

[0028] The operating device 10 includes a brake pedal 11 for operation by a driver and an electromechanical brake booster 12 with an electric motor 13 . Via an actuation cable 14 are provided by the driver and / or electromechanical brake booster 12 Forces applied to the master brake cylinder 20 transmitted. Fig. Figure 1 shows an example of an actuation chain 14 , which may, for example, be in the form of a push rod or push linkage extending from the brake pedal 11 through the electromechanical brake booster 12 to the master brake cylinder 20 extends. This connection is designed in such a way that between the master brake cylinder 20and the brake pedal 11 Both compressive and tensile forces can be transmitted. How particularly Fig. The actuating train 14 with the primary piston can be removed from 1. 21 of the master brake cylinder 20 coupled.

[0029] In the illustrated embodiment, the electric motor is used for illustrative purposes. 13 of the electromechanical brake booster 12 designed as a geared motor, which is connected to the actuating train 14 is coupled. The electric motor 13 has a stator 15 and a rotor 16 up, which concentrically surround the actuating cord 14 are arranged. One is also coaxial with the actuating string. 14 The arranged spindle drive of the geared motor comprises a spindle that is mounted in a rotationally fixed but axially movable manner. 17 , which is connected to the actuation chain 14 is firmly connected. The spindle 17combs over balls with a ball screw nut 18 , which via the rotor 16 of the electric motor 13 is driven. However, instead of the geared motor type shown, other electric drives can also be used, which convert the torque of an electric motor via a rotary-translation gearbox. 13 into an axial force on the actuating cable 14 allow.

[0030] When the electric motor is activated 13 will the ball screw nut 18 set in rotation, depending on the direction of rotation on the spindle 17 and thus on the actuation cord 14 to generate a positive or negative force in the axial direction. In this context, a positive force is understood to be a force that points in the same direction as a force exerted by the driver when applying the brake pedal. 11 generated pedal force F PA negative force points in the opposite direction and thus counteracts the pedal force. F P the driver.

[0031] In amplifier mode, the actuation train 14 as a result of pedal force F P as well as one powered by an electric motor 13 provided positive force in the direction of the master brake cylinder 20 , i.e. in Fig. 1 shifted to the left. This shifts the driver's input from the brake pedal. 11 applied pedal force F P with a pedal force sensor 60 measured which one is on the actuation cord 14 is appropriate. Furthermore, the master brake cylinder 20 Pre-pressure generated by means of a pressure sensor 61 Recorded. Depending on the recorded pedal force. F P will the electric motor 13 of the electromechanical brake booster 12 Energized. As a result, the rotor begins to rotate. 15to rotate. Via the rotor 15 The ball screw nut 18, which is permanently connected or formed in one piece, and the balls of the ball screw drive move the spindle. 17 and thus the actuation chain 14 in a translational movement towards the master brake cylinder 20. The spindle 17 is rotationally fixed, but translation-free in a housing of the electromechanical brake booster which is not shown in detail here. 12 stored.

[0032] Should the electromechanical brake booster 12 If the system fails to operate or loses power, the driver can operate the brake using only their foot. To allow the brake pressure to be reduced to zero after application, the drive of the electromechanical brake booster can be... 12It must be designed to be self-locking. In particular, it can be designed so that the hydraulic back pressure in the master brake cylinder prevents it from locking. 20 provided spring system 22 and any pedal return spring that may be present 19 in the brake booster 12 a sufficient restoring force is built up, which activates the electromechanical brake booster. 12 as well as the brake pedal 11 returns to the unbraked position. This return movement can be assisted, if necessary, by the electromechanical brake booster. 12 This can be supported by reversing the direction of rotation of the electric motor. 13 Negative support forces can also be represented during braking.

[0033] Furthermore, it is possible to use the electromechanical brake booster. 12 to activate even when the driver is on the brake pedal 11 no pedal force F P is applied. In this way, for example, an autonomous braking process can be initiated as part of an emergency braking assistant, in order to apply brake pressure via the master brake cylinder. 20 to build up. Due to the mechanical coupling between the electromechanical brake booster 12 and the brake pedal 11 The brake pedal is used in this process. 11 automatically carried along, as is also the case when the brake pedal is pressed 11 would be done by the driver.

[0034] If, during a braking request, the actuating device 10 becomes blocked, regardless of whether a braking request is initiated by actuating the brake pedal 11 or is initiated autonomously, the master brake cylinder can be used. 20 No or insufficient brake pressure for the ESP-ABS hydraulic unit 30be provided. If such a situation is detected, it is possible to compensate for the missing brake pressure via the brake force generation device. 31 of the ESP-ABS hydraulic unit 30 to generate a braking force that still allows the vehicle to be decelerated. A suitable strategy for this purpose, which is used in a vehicle braking system, will be explained in more detail below. 1 of the type described above, a reliable detection of a blockage of the actuating device with as little effort as possible. 10 made possible.

[0035] It should be expressly noted at this point that the present invention does not relate to an electromechanical brake booster. 12 of type according to the specific design of Fig. 1 is limited. Rather, for the introduction of the motor torque, M of the electric motor 13 of the electromechanical brake booster 12Other designs and mechanical concepts are also used. Further examples of coupling an electric motor. 13 via a gearbox with the actuating train 14 are disclosed, for example, in DE 10 2014 226 248 A1 and DE 10 2014 226 255, the relevant content of which is hereby incorporated into the present application. As described therein, the transmission device of the geared motor can, for example, comprise a crank disk and at least one lever, preferably two levers interacting with the crank disk. Furthermore, a transmission device is possible in which an electric motor drives a cam disk, the circumference of which is connected to a section of the actuating train. 14 is engaged to direct it towards the master brake cylinder. 20 to press, for example to achieve a variable translation ratio between the translation speed of the actuating string 14and the speed of the electric motor 13 to specify.

[0036] A blockage of the operating device 10 This can have various causes. For example, it is possible that the brake pedal was pressed during operation. 11 an object under the brake pedal 11 It becomes wedged, preventing it from pivoting further towards the firewall. Furthermore, it is possible that during autonomous braking, the driver's foot could get caught under the brake pedal. 11 This occurs, thus hindering further swiveling. Due to the mechanical coupling between the brake pedal 11 and the electromechanical brake booster 12 The problem is that if the activation of the electromechanical brake booster is maintained, 12 the brake pedal 11 is carried along so that the foot remains under the brake pedal 11It can get jammed. Furthermore, the operating mechanism can become blocked. 10 due to external influences or a mechanical defect in the electromechanical brake booster 12 This can be caused, for example, by the electric motor freezing. 13 , so that above the master brake cylinder 20 Sufficient brake pressure cannot be built up.

[0037] To detect when the actuating device is blocked, the control unit 50 A corresponding algorithm is implemented. This can be achieved, among other things, by using signals that are used to control the electric brake booster. 12 and, if applicable, the brake pressure generating device 31 be available.

[0038] The control unit 50 is configured in such a way as to detect a blockage of the actuating device 10during a braking request, either by the driver via the brake pedal 11 or possibly autonomously initiated by another control unit which is connected to the first-mentioned control unit 50 connected via the vehicle bus, a brake pressure build-up via the brake pressure generating device 31 to trigger.

[0039] To determine if the operating mechanism is blocked 10 As a first step, it can be checked whether there is a brake pressure request that would trigger the activation of the electromechanical brake booster. 12 This requires. This can be recognized, for example, by the fact that the driver presses the brake pedal. 11 The braking force can be activated or, in the case of autonomous braking, detected by a corresponding status signal. Additionally, a target value for the braking force can optionally be sent to the control unit in parallel. 50be transmitted. If a brake pressure request is received, the blockage detection is carried out in the control unit. 50 activated.

[0040] In a further step, the control unit 50 a comparison of the motor torque curve M and / or the change in engine torque over time M of the electric motor 13 depending on the engine angle f or a corresponding path size with a predefined value, for example in the control unit 50 saved target curve M(φ) soll The corresponding path variable could be, for example, the position of the actuating cable. 14 can be used because of its mechanical coupling with the electric motor 13 of the electromechanical brake booster 12 in a known relationship to the engine angle f It is. In this case, however, a suitable displacement sensor is required. 63on the actuation cord 14 be provided for.

[0041] For example, if the brake pedal locks up 11 The course of the motor torque M versus the motor angle is shown. f rise more sharply than expected. Therefore, an expected correlation between actual engine torque and actual torque is not observed. M and the engine angle f If the requirements are not met, it can be assumed that the operating device 10 is mechanically blocked.

[0042] Since the pressure build-up in the master brake cylinder 20 usually directly with the movement of the electric motor 13 and the actuation cable 14 If coupled, a corresponding status detection can also be achieved using the master brake cylinder. 20 provided print p ist This occurs in vehicles equipped with an ESP-ABS hydraulic unit. 30 are equipped with a corresponding pressure sensor 61is generally known.

[0043] Alternatively or additionally, it is therefore possible to trace the path of the master brake cylinder. 20 provided and by means of the pressure sensor 61 recorded pressure p ist depending on the engine torque M to compare with a target curve M(p). If the pressure remains constant p ist If the pressure curve falls short of the expected progression, it can also be assumed that the actuating device 10 is mechanically blocked.

[0044] Subsequently, if blockage detection is activated, a status assessment is performed by evaluating the determined course and outputting a status signal. s3 regarding the presence of a blockage of the actuating device 10 towards the brake pressure generating device 31 .

[0045] The latter is controlled by the control unit 50then controlled accordingly to generate brake pressure in order to actuate the wheel brakes. 40 to enable.

[0046] In principle, it is possible to use only one of the two aforementioned criteria for blockage detection. However, combining both criteria improves the accuracy of the results and increases robustness against false positives. The two criteria can be appropriately weighted against each other for this purpose.

[0047] Furthermore, it is possible to configure the control unit 50 certain system states of the ESP-ABS hydraulic unit 30 Factors that could distort the pressure readings must be taken into account. Examples include ABS control or the pumping of brake fluid into the pressure accumulator of the ESP-ABS hydraulic unit. 30These system states are known via corresponding status information in the vehicle bus system, so that they can be taken into account accordingly.

[0048] Is there a positive status signal regarding the blockage? s3 for example, because an object or the driver's foot is under the brake pedal 11 If it is jammed, it is recommended to generate additional power through the electromechanical brake booster. 12 to end it as quickly as possible, for example by having it done by the control unit 50 It is deactivated or preferably returned directly to its starting position. This allows a driver to prevent the brake pedal from locking up. 11 to remove it so that it can then be used again in the usual way.

[0049] Is the blockage of the operating device 10 not through the brake pedal 11, but through the electromechanical brake booster 12 caused, regardless of whether the driver has pressed the brake pedal 11 activated or autonomous braking is initiated, insufficient motor angle f on the electric motor 13 set or sufficient pressure through the master brake cylinder 20 to be built up. This applies equally to the case of any stiffness in the electromechanical brake booster, regardless of the cause. 12 . Here too, a deviation from the respective target curve occurs, which serves as the reason for activating the brake pressure generating device. 31 can be used to compensate for the lack of brake pressure build-up in the master brake cylinder 20 to compensate. Such a detection system can operate continuously, independent of an activation signal.

[0050] A blockage of the electromechanical brake booster differs qualitatively. 12 from a brake pedal blockage 11 . Fig. Figure 2 shows an example of the motor torque curve. M depending on the engine angle f . a) denotes the expected target curve, which serves as the basis for assessing any deviations in the control system. 50 It may be stored and is shown here purely as an example of a tolerance band. In the event of a brake pedal blockage... 11 Due to a jammed object, as shown in the actual curve b), there is a sudden, significantly increased rise in motor torque at the beginning of the jamming. M . Stiffness in the electromechanical brake booster 12 However, this is more noticeable through an actual curve according to characteristic curve c). In the case of a frozen electric motor 13Even setting a small motor angle would be sufficient. f impossible. These different characteristics can be taken into account during the condition assessment using appropriate decision criteria, so that it is not only a matter of the presence of a blockage in the actuating device. 10 It is not only possible to conclude the cause itself, but also to differentiate the causes.

[0051] Fig. Figure 3 shows an example of a schematic representation of the control unit. 50 including the most important input and output variables as well as a possible structure of the decision algorithm.

[0052] In a first block 51 A check is performed to determine whether an autonomous braking request has been made or not. For this purpose, the control unit... 50 a corresponding status signal s1This information is received via the vehicle bus system from another control unit, such as an ESP control unit. Simultaneously, this allows information about the requested brake pressure to be transmitted. p soll be transmitted. Furthermore, the input signal from the driver at the brake pedal can be used as an additional input at this point. 11 applied pedal force F P to take into account, for example, those equipped with a pedal force sensor 60 The system records the following information. This information allows us to determine whether brake pressure is being requested and, furthermore, whether there is no or only minimal driver foot force on the brake pedal. Depending on this, a decision is made as to whether a check for a locked brake pedal is necessary. 11 whether or not this should be done. This can be indicated by a corresponding status signal. s2 be expressed.

[0053] In a second block 52The progression of the engine torque is then compared. M or its first derivative as a function of the motor angle f of the electric motor 13 or a corresponding path size with a predefined target path M(φ) soll A corresponding deviation ΔM(φ) This information is incorporated into the subsequent condition assessment. The motor current of the electric motor is used as an example of an input variable. 13 to determine the engine torque M as well as the one with an engine angle sensor 62 detected engine angles f This is taken into account. However, it is also possible to adjust the engine torque. M Capture it in a different way. Instead of the engine angle. f A corresponding path value can be determined, for example, by means of a displacement sensor. 63 on the actuation cord 14 be recorded.

[0054] In a third block 53 The progression of the engine torque is then compared.M depending on the master brake cylinder 20 provided brake pressure p ist , where the corresponding input variables are again the motor current of the electric motor 13 as well as the signal from the pressure sensor 61 be taken into account. A corresponding deviation ΔM(p) This is incorporated into the subsequent condition assessment.

[0055] The condition assessment takes place in a fourth block. 54 based on the information mentioned above s2 , ΔM(φ) and ΔM(p) A differentiation between different causes for a possible blockage of the actuating device. 10 This can be achieved, for example, using suitable threshold values, characteristic curves, or maps. The sensitivity of the detection can be adjusted, if necessary, by using applicable threshold values.

[0056] Furthermore, the fourth block includes 54a logic circuit for status generation s3 for the blockage state. For example, if it is indicated that a blockage is present, the brake pressure generating device can be activated with corresponding status information. 31 of the ESP-ABS hydraulic unit 30 to compensate for the lack of brake pressure.

[0057] Should the operating device 10 If the system is only monitored for brake pedal locking, the status signal generation can be reduced to the states "Pedal locked" and "Pedal unlocked". A status evaluation only occurs if the first block... 51 via its status signal s2 An activation has occurred.

[0058] With regard to the detection of blockages in the area of ​​the electromechanical brake booster 12 The functionalities of the second and third blocks can be used 52and 53, however, can also be continuously evaluated and the result of the condition assessment can be expressed in a correspondingly modified status signal. s3 be expressed.

[0059] The invention has been explained in more detail above with reference to exemplary embodiments and further modifications. Individual technical features, which were explained above in the context of further individual features, can be implemented both independently of these and in combination with other individual features, even if this is not expressly described, as long as it is technically possible. The invention is expressly not limited to the described exemplary embodiments and modifications, but encompasses all embodiments defined by the claims. Reference symbol list 1 Motor vehicle braking system 10 Actuating device 11 Brake pedal 12 electromechanical brake boosters 13 Electric motor 14 Actuating string (push rod) 15 Stator 16 Rotor 17 spindles 18 threaded nut 19 Return spring 20 master brake cylinders 21 Primary pistons 30 ESP-ABS hydraulic unit 31 Brake pressure generating device 40 wheel brake control unit 50 Sensor 51 first block 52 second block 53 third block 54 fourth block 60 pedal force sensor 61 Pressure sensor 62 Engine angle sensor 63 Displacement sensor p ist Pressure at the pressure sensor p soll requested brake pressure s1 status signal s2 status signal s3 status signal F P pedal power M Motor torque M(φ) soll Target progress M(p) soll Target progress ΔM(φ) deviation - angle / displacement criterion ΔM(p) deviation - pressure criterion φ Motor angle QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] WO 2015 / 188958 A1 [0002, 0004, 0006, 0007] DE 102014226248 A1

[0035] DE 102014226255

[0035]

Claims

[1] Motor vehicle braking system, comprising an actuating device (10) with a brake pedal (11) and an electromechanical brake booster (12), which are coupled to each other in such a way that when the electromechanical brake booster (12) is actuated, the brake pedal (11) is moved along with it, a brake pressure generating device (31) for actively generating brake pressure independently of the actuation of the electromechanical brake booster (12) and the brake pedal (11), and a control device (50) for controlling the brake pressure generating device (31), which is configured to initiate a brake pressure build-up via the brake pressure generating device (31) when a blockage of the actuating device (10) is detected during a brake request, characterized by , that to detect a blockage of the actuating device (10) a motor angle (φ) or a corresponding displacement and a motor torque (M) of an electric motor (13) of the electromechanical brake booster (12) are related to each other and a blockage is then concluded if the motor torque (M) or the gradient of the motor torque (M) in relation to the motor angle (φ) or the corresponding displacement deviates from a predetermined target curve (M(φ) soll ) differs and / or the course of the brake pressure (p) provided by the master brake cylinder (20) ist ) and the engine torque (M) are related to each other, and a blockage is then concluded when the engine torque (M) is in relation to the brake pressure (p). ist ) deviates from a specified target curve (ΔM(p)). [2] Motor vehicle braking system according to claim 1, characterized by, that in the control device (50) a blockage is only concluded if the motor angle (φ) or the corresponding displacement deviates from the target path and the brake pressure (p) provided by the master brake cylinder (20) is ist ) remains below a predetermined limit. [3] Motor vehicle braking system according to claim 1 or 2, characterized by , that the control unit (50) also takes into account the signal from a pedal force sensor (60) for condition assessment. [4] Motor vehicle braking system according to claim 1 or 2, characterized by , that in the control unit (50) a status signal (s1) is taken into account whether an autonomous braking request, i.e. a braking request without the need for brake pedal actuation by a driver, is present or not. [5] Motor vehicle braking system according to any one of claims 1 to 4, characterized by , that the following are connected to the control unit (50) as input variables: the signal from a motor angle sensor (62) of the electromechanical brake booster (12), the signal from a pedal force sensor (60), which represents an actuating force applied to the brake pedal (11), and the signal from a pressure sensor (61) which represents the pressure supplied by the master brake cylinder (20) to an ESP-ABS hydraulic unit (30). [6] Motor vehicle braking system according to any one of claims 1 to 5, characterized by , that the control device (50) is further supplied with a quantity representing the motor torque (M) or a time-dependent change of the motor torque as an input variable. [7] Method for operating a motor vehicle braking system with an actuating device (10) with a brake pedal (11), a pedal force sensor (60) and an electromechanical brake booster (12) with an electric motor (13) and a motor angle sensor (62) and / or displacement sensor (63), a master brake cylinder (20) and a pressure sensor (61), and an ESP-ABS hydraulic unit (30) with a brake pressure generating device (31), the procedure includes the following steps: Activating a blockage detection upon detection of a brake pressure request which involves actuation of the electromechanical brake booster (12), Matching the course of the motor torque (M) and / or the time change of the motor torque (M) of the electric motor (13) as a function of the motor angle (φ) or a corresponding displacement variable with a target course (M(φ) soll ), Performing a status assessment with blockage detection activated by evaluating the deviation (ΔM(φ)) from the target curve (M(φ) soll ) and output of a status signal (s3) regarding the presence of a blockage of the actuating device (10), and Activating the brake pressure generating device (31) to generate brake pressure when the status signal (s3) indicates the presence of a blockage. [8] Method according to claim 7, characterized by , that in the event of a positive status signal (s3), i.e., the presence of a blockage, the electromechanical brake booster (12) is deactivated or returned to its initial position. [9] Method according to claim 7 or 8, characterized by , that the course of the engine torque (M) continues to depend on the pressure (p) provided by the master brake cylinder (20). ist ) with a target curve (M(p) soll ) is compared and taken into account in the condition assessment. [10] Method for operating a motor vehicle braking system with an actuating device (10) with a brake pedal (11), a pedal force sensor (60) and an electromechanical brake booster (12) with an electric motor (13) and a motor angle sensor (62) and / or displacement sensor (63), a master brake cylinder (20) and a pressure sensor (61), and an ESP-ABS hydraulic unit (30) with a brake pressure generating device (31), the procedure includes the following steps: Matching the course of the motor torque (M) and / or the time change of the motor torque (M) of the electric motor (13) as a function of the motor angle (φ) or a corresponding displacement variable with a target course (M(φ) soll ), Comparing the pressure curve (P actual) supplied by the master brake cylinder (20) as a function of the engine torque (M) with a target curve (M(p) soll ), Performing a condition assessment by evaluating the deviations (ΔM(φ), ΔM(p)) from the respective target curve (M(φ) soll , M(p) soll ) and output of a status signal (s3) regarding the presence of a blockage of the actuating device (10), and Activating the brake pressure generating device (31) to generate brake pressure when the status signal (s3) indicates the presence of a blockage.

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