Method for operating a braking system

Abstract

Method for operating a braking system (1) with a brake pedal (10) and with a brake force generating device (20) which can be controlled or is controlled by a first control device (21), wherein the brake pedal (10) is mechanically coupled to a pedal unit (50) which has at least one element (52) for generating a haptic brake pedal feel and at least one force- and / or displacement-measuring sensor (53) by which actuation of the brake pedal (10) can be detected or is detected, wherein the pedal unit (50) is mechanically decoupled from the brake force generating device (20) and, based on the actuation of the brake pedal (10) detected by the sensor (53), control signals can be transmitted to the first control device (21) which lead to the generation of a braking force by the brake force generating device (20), characterized in that the brake pedal (10) is decoupled when an impendingthe electric motor (51) is pulled in during the inevitable crash.

Description

[0001] The invention relates to a method for operating a braking system according to the preamble of claim 1.

[0002] A braking system is known from DE 10 2013 226 243 A1. In particular, a vehicle braking system is proposed therein in which the assistance of a driver's pedal force applied to the brake pedal to generate braking force is provided by an electric motor. The brake pedal is mechanically connected to the electric motor via a linkage, and the electric motor is in turn mechanically connected to a master brake cylinder. The electric motor can be controlled by a control unit to provide the assisting force generated by the electric motor. The control unit also includes a brake feel module to enable the realization of a specific brake pedal feel, e.g., that of a vacuum brake booster.

[0003] DE 10 2010 052 924 A1 also describes an electromechanical brake booster. Here, too, an electric motor is used to generate an amplifying force to increase the pedal force applied by a driver to the vehicle's braking system via a brake pedal. Furthermore, a pedal position sensor is provided to determine the position of the brake pedal, and a position sensor is provided to determine the position of the electric motor. A pedal force detection device is designed to determine the pedal force based on the current position of the brake pedal and the current position of the electric motor.

[0004] German patent application DE 10 2013 012 750 A1 discloses a method for operating a driver assistance system. This system is specifically designed for automated driving by intervening in the engine control, transmission, and braking system of a motor vehicle. Among other things, it is proposed that a sleep mode can be activated by the driver, in which the pedals are retracted or moved to a resting position. This is intended to increase the driver's freedom of movement in the footwell.

[0005] Furthermore, DE 10 2015 119 185 A1 describes a steering device for a motor vehicle. The steering device has two U-shaped grip areas that can be switched between an activated (separated) and a deactivated (retracted) state. An accelerator pedal, a clutch pedal, and a brake pedal are also provided. For the steering device to be activated, the pedals can be moved out of the vehicle floor. In the deactivated state, the pedals are completely recessed in the vehicle floor.

[0006] DE 199 20 848 A1, which discloses the features of the preamble of claim 1, describes a device for controlling an electromechanical operating unit of a vehicle. Specifically, the electromechanical operating unit comprises an actuating module connected to an accelerator pedal, a brake pedal, and, via a steering linkage, to a steering wheel. The actuating module is pivotally connected to the vehicle via a rocker arm. Furthermore, an adjustment motor is provided, which is connected to the actuating module on one side and to the vehicle on the other via an actuating rod. The actuating rod serves to adjust the actuating module. A control unit on the actuating module processes signals from sensors and outputs corresponding signals to a pedal motor, which also acts as a tactile feedback generator for the brake pedal. When the accelerator pedal is depressed, the brake pedal is also moved accordingly.However, a braking request is only generated purely electrically when the driver presses the brake pedal. It is also suggested that the brake pedal motor be used to adjust the brake pedal characteristics.

[0007] From DE 10 2010 025 252 A1, a method for simulating the pedal characteristics of a decoupled motor vehicle braking system is known. To carry out the method, a device with a rotatably mounted brake pedal is used, which has an active, self-locking element and a passive elastic element. The relationship between pedal travel and pedal force can be changed using the active, self-locking element, which is controlled by a pre-programmed, authentic pedal characteristic.

[0008] German patent application DE 10 2016 212 053 A1 discloses a device comprising a pedal and a brake force simulator. The pedal is connected to the brake force simulator via a transmission rod. To generate haptic feedback, the pedal is set into vibration by means of a vibration actuator. Sensors measure the actuation force applied to the brake force simulator. From this, a value for the braking effect intended by the driver is derived, which is then used to control autonomous brake actuators.

[0009] German patent DE10 2013 214 336 A1 describes a simulator device for a vehicle's power-assisted braking system, which is mechanically connected to the pistons of a master brake cylinder via an input rod. The simulator device can be controlled in a simulator mode during power-assisted braking of the vehicle. In simulator mode, the simulator device, which is attached to the power-assisted braking system, exerts a counterforce on the brake pedal when the brake pedal is actuated.

[0010] From DE 10 2006 026 873 A1, an actuating device for a vehicle braking system designed as a "by-wire" system is disclosed. The actuating device has a brake pedal which is connected to a brake pedal axle. The brake pedal axle can be moved by an electric motor, which can be controlled by a control unit. By rotating the brake pedal axle, a pulsating movement of the brake pedal can be generated. A brake control unit, which is connected to the brake pedal via a connecting rod, serves to generate the brake pedal feel required for the vehicle braking system.

[0011] German patent DE 10 2004 040 616 A1 describes a brake-by-wire braking system with an active pedal simulator, in which a characteristic curve describing the relationship between the pedal resistance applied by the pedal simulator and the pedal travel is modified to change the pedal behavior. The pedal simulator can also generate a pulsating resistance force on the brake pedal.

[0012] Finally, DE 197 23 665 A1 includes a programmable electronic pedal simulator, which allows any force-displacement characteristic and thus any pedal feel to be set when pressing down a brake pedal.

[0013] One object of the invention is to provide a suitable method for operating a braking system, which increases the possibilities of haptic feedback for the driver and the possibilities of adapting the braking system to specific driving and operating situations.

[0014] The above problem is solved by a method having the features of claim 1.

[0015] Advantageous developments or further developments of the invention can be found in the dependent claims.

[0016] The description begins with a motor vehicle's braking system, comprising a brake pedal and a brake force generation device. The brake force generation device can be controlled by a first control unit, or is controlled in such a way that a braking force can be generated or at least assisted.

[0017] It is further described that the brake pedal is mechanically coupled to a pedal unit which has at least one element for generating a haptic brake pedal feel (e.g., a spring and / or rubber-elastic element) and at least one force- and / or displacement-measuring sensor by which actuation of the brake pedal can be detected or is detected. It should be noted here that the element for generating a haptic brake pedal feel is preferably adaptable. This means that, for example, the mechanical properties of the spring and / or rubber-elastic elements can be adapted to different requirements or needs.

[0018] The pedal unit, in turn, is mechanically decoupled from the brake force generation unit. Based on the actuation of the brake pedal detected by the sensor, control signals can be transmitted to, or are transmitted to, the first control unit. These control signals cause the brake force generation unit to generate braking force. However, the brake force generation unit remains connected to the vehicle's wheel brakes via hydraulic lines.

[0019] The braking system's features described above allow for highly flexible installation within the vehicle. In particular, the pedal assembly can be mounted independently of the brake force generation unit. This means that the brake force generation unit and its associated brake control system do not necessarily have to be installed at the same height as the brake pedal in the engine compartment behind the vehicle's firewall. Furthermore, this optimizes the available space in the driver's footwell in the event of a crash. Despite this optimized installation, a minimum level of familiar brake pedal feel can still be maintained.

[0020] There is at least one electric motor which is mechanically coupled to the brake pedal and by which the brake pedal can be moved or is moved.

[0021] This creates highly flexible application possibilities for the braking system. The brake pedal can thus be adapted in its movement and / or position to different driving and operating situations.

[0022] Highly demand-oriented operation of the electric motor can be ensured if the force- and / or displacement-controlled sensor is electrically connected to a control device, through which the electric motor can in turn be controlled or is controlled.

[0023] It is proposed that at least one electric motor and the control unit operating it be integrated into the pedal unit. This would increase the compactness of the braking system and reduce its installation effort.

[0024] Particularly high flexibility in the assembly of the brake system, especially in the assembly of the pedal unit with brake pedal on the one hand and the brake force generation unit with control unit on the other, can be achieved if the first control unit, associated with the brake force generation unit, and the control unit controlling the electric motor are connected to each other via a data bus. Alternatively, an analog electrical connection is also conceivable, e.g., for transmitting measurement signals from the force and / or displacement sensor.

[0025] As already mentioned, the invention is intended to provide a suitable method for operating a braking system. The brake pedal of the braking system is actively moved, or can be actively moved, by at least one electric motor.

[0026] This creates the basic conditions for significantly improving the haptic feedback for the driver when the brake pedal is pressed and for optimally adapting the position of the brake pedal to a wide variety of situations.

[0027] The system can be designed, for example, such that in a specific operating mode of the braking system (e.g., a sport mode), selectable by the driver, the electric motor is controlled in such a way that the force-displacement curve of the brake pedal is steeper than in a conventional operating mode. Furthermore, the maximum pedal travel adjustable by the driver can be reduced. The sport mode is preferably configurable, meaning that, for example, the steepness of the force-displacement curve of the brake pedal can be adapted to different needs via software parameters in the pedal unit's control system.

[0028] This allows the driver to experience a sportier brake pedal feel. Compared to the normal operating mode, the brake force generation system produces higher brake pressures for the same pedal travel.

[0029] Furthermore, it is advantageous if, in ABS operation of the braking system, the electric motor is controlled in such a way that it moves the brake pedal rapidly up and down. In this way, the familiar behavior of the brake pedal during ABS intervention can be simulated.

[0030] In another embodiment of the method, it is proposed that if the braking effect of the braking system undesirably decreases due to brake heating (so-called fading), the electric motor is controlled in such a way that the force-displacement characteristic of the brake pedal is flatter than in a normal operating mode and the maximum pedal travel adjustable by the driver is increased. In this way, the known behavior of the brake pedal during fading can be simulated.

[0031] It is known that rapid, repeated application of the brake pedal leads to a perceived hardening of its action. To simulate this brake pedal feel, another embodiment of the method proposes that, during rapid application of the brake pedal, the electric motor is controlled in such a way that the force-displacement characteristic of the brake pedal is steeper than in a normal operating mode. Simultaneously, the maximum pedal travel adjustable by the driver is reduced.

[0032] Another refinement of the method, particularly suitable for autonomous vehicles, proposes that the electric motor move the brake pedal out of the footwell when the vehicle is driving autonomously. This movement can be achieved, for example, by pulling the brake pedal towards the firewall. However, the reverse is also conceivable: the brake pedal could be folded or moved upwards (towards the instrument panel), thus also moving it out of the footwell. This provides the driver with maximum legroom during autonomous driving.

[0033] To improve driver safety, one implementation of the invention proposes that, in the event of an impending, unavoidable crash, the brake pedal is retracted by the electric motor. In the event of a crash, the electric motor moves the brake pedal, in particular, towards the firewall (front bulkhead).

[0034] A preferred embodiment of the invention is illustrated in the figures and is explained in more detail in the following description with reference to the figures. This also highlights further advantages of the invention. Identical reference numerals, even in different figures, refer to identical, comparable, or functionally equivalent components. Corresponding or comparable properties and advantages are achieved even if no repeated description or reference is made to them. The figures are not, or at least not always, to scale. In some figures, proportions or distances may be exaggerated to more clearly emphasize features of an embodiment.

[0035] They show, each schematically Fig. 1. A representation of a braking system of a motor vehicle, Fig. 2. An enlarged signal flow diagram showing the essential components and Fig. 3. A diagram illustrating different adjustable operating modes.

[0036] First, attention will be paid to the Fig. 1. Reference is made to this figure. A brake system 1 is shown schematically in this figure. The brake system 1 has a brake pedal 10, which is connected to a pedal unit 50 via a mechanical connection 60, for example in the form of a linkage.

[0037] The pedal unit 50 serves to create a specific brake pedal feel. Furthermore, the pedal unit 50 is designed to move the brake pedal 10 into specific positions depending on certain driving or operating situations. This will be explained in more detail later.

[0038] The pedal unit 50 is supplied with the necessary electrical energy via an energy supply 80.

[0039] Furthermore, a brake force generation device 20 is visible in the figure. The brake force generation device 20 comprises a brake actuator (for example, in the form of an electric motor) which, upon actuation of the brake pedal 10, displaces hydraulic fluid in a master brake cylinder (not shown) located in the brake force generation device 20 and thus in a hydraulic connection 40 (brake lines). This results in a braking effect at the wheel brakes 30.

[0040] Furthermore, a control device 21 for controlling the brake force generation device 20 is shown schematically in dashed lines. This can preferably be an integral part of the brake force generation device 20.

[0041] In Fig. Figure 2 shows a signal flow diagram, which describes in more detail the components of the brake system 1 that are essential for the invention.

[0042] It can be seen that the pedal unit 50, which is preferably designed as a housing, accommodates an electric motor 51, a spring and / or rubber-elastic element 52, and a force- and / or displacement-measuring sensor 53. Furthermore, a control unit 54 is incorporated into the pedal unit 50.

[0043] The operation of brake system 1 now proceeds as follows: When a driver presses the brake pedal 10, the brake pedal 10 is set into a pivoting movement B about a pivot point 11. The resulting adjustment path s is shown and depicts the brake pedal 10 in a deflected position (indicated by dashed lines, see 10').

[0044] As a result, the mechanical connection 60, which is designed in the form of a linkage, acts directly on the spring- or rubber-elastic element 52. The spring- or rubber-elastic element 52 thus serves to generate a certain haptic brake pedal feel, as the driver is accustomed to with an ordinary, mechanical brake pedal.

[0045] The actuation of the brake pedal 10 can be measured by the sensor 53 based on a force measurement (measurement of the force acting on the mechanical connection 60) or based on a displacement measurement (measurement of the displacement of the connection 60). A combination of these two measurement methods is also conceivable.

[0046] Unlike conventional braking systems, in this case there is no longer a mechanical connection between the pedal unit 50 and the brake force generation unit 20. Instead, the connection between the pedal unit 50 and the brake force generation unit 20 is established solely via a data bus 70, i.e., via an electrical connection. This offers the significant advantage that the pedal unit 50, including the brake pedal 10, on one side, and the brake force generation unit 20, including the control unit 21, on the other, can be positioned independently of each other within their respective installation spaces.

[0047] If the driver wishes to brake, the actuation of the brake pedal 10 is detected by the sensor 53 and this sends corresponding sensor signals S1 to the control unit 54 of the pedal unit 50.

[0048] The sensor signals S1 are evaluated by the control unit 54, whereupon the control unit 54 transmits corresponding control signals S2 via the data bus 70 to the control unit 21 of the brake force generation unit 20, which is connected to the data bus 70. The control signals S2 correspond to the driver's braking request. The control unit 21 in turn controls the aforementioned electric motor of the brake force generation unit 20, which in turn causes a displacement of the hydraulic fluid in the brake lines (hydraulic connection 40, see Figure 40). Fig. 1) contributes.

[0049] The connection between the pedal unit 50 and the brake force generation device 20 is purely electrical, i.e., not mechanical or hydraulic.

[0050] Furthermore, a decisive advantage can be achieved through the electric motor 51, which is installed in the pedal unit 50. The electric motor 51 is operatively connected to the mechanical linkage 60, or rather to the brake pedal 10, in such a way that the linkage 60 or the brake pedal 10 can be actively moved by the electric motor 51. Thus, the movement B can be realized by the electric motor 51 without the driver having to press the brake pedal 10.

[0051] This creates the basic prerequisite for realistically simulating a pedal feel for many known operating situations of conventional braking systems.

[0052] For example, it is conceivable that the driver has preselected an operating mode M2, corresponding to a sporty operating mode, via a switch and / or a menu. After such a setting has been selected by the driver, the control unit 54 of the pedal unit 50 and the control unit 21 of the brake force generation unit 20 receive corresponding information via the data bus 70, such as "Sport mode set". Compared to a conventional ("normal") operating mode M1, higher brake pressures P are then generated via the control unit 21 for the same pedal travel S.

[0053] On the other hand, in operating mode M2, the control unit 54 of the pedal unit 50 controls the electric motor 51 in such a way that the force-displacement characteristic of the brake pedal 10 becomes steeper and the maximum pedal travel is reduced. This is evident from the Fig. Figure 3 shows a pedal force F applied by the driver or a brake pressure P generated over an adjustment range s of the brake pedal 10.

[0054] The characteristic curve for a standard (normal) operating mode M1 is shown, in which a maximum pedal force Fmax or maximum brake pressure Pmax corresponds to a maximum adjustment travel smax. If the steeper characteristic curve of a sporty operating mode M2 ​​is selected, a maximum pedal force Fmax or maximum brake pressure Pmax is achieved at a maximum adjustment travel smax' of the brake pedal 10, which is shorter than the maximum adjustment travel smax in the standard operating mode M1. This results in a sportier pedal feel.

[0055] Furthermore, in ABS operation of the brake system 1, the electric motor 51 can be controlled in such a way that the electric motor 51 moves the brake pedal 10 rapidly up and down (cf. 10'' and 10''' in Fig. 2).

[0056] Specifically, when the ABS system intervenes, the control unit 21 sends a signal, such as "ABS attack detected" (not shown), to the control unit 54 of the pedal unit 50. The control unit 54 then controls the electric motor 51 so that it moves the brake pedal 10 as described, thereby simulating the familiar behavior of a brake pedal during an ABS attack.

[0057] If the braking effect of the brake system 1 decreases undesirably due to heating of the wheel brakes 30 (so-called fading), the driver usually has to exert more travel and force on the brake pedal to achieve the same braking effect. Therefore, when fading is detected, the control unit 21 of the brake force generation unit 20 sends a signal, such as "fading detected" (not shown), to the control unit 54 of the pedal unit 50. The control unit 54 then controls the electric motor 51 so that the force-displacement characteristic of the brake pedal 10 becomes flatter and the maximum pedal travel is increased. This effectively simulates the familiar behavior of a brake pedal during fading.

[0058] This is also in the Fig. Figure 3 shows the characteristic curve of operating mode M3 during fading. It is evident that the characteristic curve of operating mode M3 is flatter, so that with the same maximum applied pedal force Fmax, the maximum travel smax'' of the brake pedal 10 is significantly longer than the maximum travel smax in normal operating mode M1.

[0059] It is also known that in conventional braking systems, the brake pedal becomes "hardened" when pressed quickly. Here, too, the control unit 54 can detect rapid actuation of the brake pedal 10 via the sensor 53. The control unit 54 then activates the electric motor 51 so that the driver must apply more pedal force F to achieve a specific pedal travel S. Simultaneously, the maximum pedal travel S that the driver can achieve is reduced. This simulated behavior of the brake pedal 10 is further enhanced by a steeper force-displacement characteristic curve of the brake pedal 10, similar to that in the sporty operating mode M2 ​​(compare Fig. 3) achieved.

[0060] It should be noted that the force characteristics in Fig. Although 3 are shown linearly for the sake of simplicity, in reality they tend to have an upward-curving, parabolic shape.

[0061] Furthermore, it is also conceivable that the brake pedal 10 is moved out of the footwell in one direction by the electric motor 51 during automatic driving of the vehicle. During automatic driving, the control unit 54 receives a signal from another control unit (not shown), such as "automatic driving mode active" (not shown). The control unit 54 then controls the electric motor 51 so that the brake pedal 10 is moved towards an end wall of the vehicle (not shown), in this case towards the pedal unit 50. However, if the driver touches the retracted brake pedal 10 and continues to depress it, the control unit 54 does not send a signal, such as "pedal actuation by driver," to the control unit 21, because the vehicle is in automatic driving mode.

[0062] Only when the automatic driving mode ends does the control unit 54 receive another signal, such as "automatic driving mode not active". The control unit 54 then controls the electric motor 51 so that the brake pedal 10 is returned to its normal position. Actuation of the brake pedal 10 by the driver is now detected by the control unit 54 via the sensor 53, which then forwards this information to the control unit 21 of the brake force generation unit 20 via the data bus 70.

[0063] Finally, it should be mentioned that the electric motor 51 also enables the brake pedal 10 to be actively retracted in the event of a crash. Specifically, pre-crash sensors 90 send (see below) Fig.2) In the event of an impending and unavoidable crash, corresponding signals are sent to a control unit (not shown) (for example, an airbag control unit). This sends a signal, such as "crash detected", to the control unit 54 of the pedal unit, which in turn controls the electric motor 51 so that the brake pedal 10 is moved towards the front wall of the vehicle (not shown).

Claims

[1] Method for operating a braking system (1) with a brake pedal (10) and with a brake force generating device (20) which can be controlled or is controlled by a first control device (21), wherein the brake pedal (10) is mechanically coupled to a pedal unit (50) which has at least one element (52) for generating a haptic brake pedal feel and at least one force- and / or displacement-measuring sensor (53) by which actuation of the brake pedal (10) can be detected or is detected, wherein the pedal unit (50) is mechanically decoupled from the brake force generating device (20) and, based on the actuation of the brake pedal (10) detected by the sensor (53), control signals can be transmitted to the first control device (21) which lead to the generation of a braking force by the brake force generating device (20), characterized by, that the brake pedal (10) will be retracted by the electric motor (51) in the event of an impending, unavoidable crash. [2] Method according to claim 1, characterized by , that the electric motor (51) in a specific operating mode (M2) of the braking system (1) selectable by a vehicle driver is controlled in such a way that a force-displacement characteristic of the brake pedal (10) is steeper than in an ordinary operating mode (M1) and a maximum pedal travel (smax) of the brake pedal (10) adjustable by the vehicle driver is shortened. [3] Method according to claim 1 or 2, characterized by , that in ABS operation of the braking system (1) the electric motor (51) is controlled in such a way that it moves the brake pedal (10) quickly up and down. [4] Method according to any one of the preceding claims, characterized by, that in the event of an undesirable decrease in the braking effect of the braking system (1) the electric motor (51) is controlled in such a way that a force-displacement characteristic of the brake pedal (10) is flatter than in a normal operating mode (M1) and a maximum pedal travel (smax) of the brake pedal (10) adjustable by the driver is increased. [5] Method according to any one of the preceding claims, characterized by , that when the brake pedal (10) is quickly actuated, the electric motor (51) is controlled in such a way that the force-displacement characteristic of the brake pedal (10) is steeper than in a normal operating mode (M1) and the maximum pedal travel (smax) of the brake pedal (10) adjustable by the driver is reduced. [6] Method according to any one of the preceding claims, characterized by , that the brake pedal (10) is moved out of the footwell by the electric motor (51) during automatic driving of the motor vehicle.

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