Motor vehicle braking system with pedal fault detection and handling

Abstract

The invention relates to a motor vehicle braking system with a brake pedal unit comprising sensors for detecting a quantitative brake pedal actuation value and an electronic control unit configured to receive the brake pedal actuation value and, based on this value, to control a brake actuator to decelerate the motor vehicle. To ensure functionality in the event of a "stuck pedal" fault, the brake pedal unit has a contact sensor on a foot contact surface, and the control unit is configured to detect a pedal fault, in particular a stuck pedal, based on a signal from the contact sensor and the brake pedal actuation value, and in this case to initiate deceleration of a predetermined magnitude.

Description

[0001] The invention relates to a motor vehicle brake system with a brake pedal unit having sensors for detecting a quantitative brake pedal actuation variable and an electronic control device configured to receive the brake pedal actuation variable and to control a brake actuator based on the brake pedal actuation variable in order to decelerate the motor vehicle.

[0002] There are essentially two different types of brake pedal units known in the automotive industry. A conventional brake pedal is mechanically coupled to a hydraulic cylinder, the master cylinder. When the brake pedal is depressed, a sensor measures the master cylinder pressure and pedal deflection to determine the driver's braking input. Electronic brake pedals do not have this type of mechanical coupling, meaning that even in a fallback mode, braking force cannot be built up solely through the driver's muscle power. These systems therefore have higher demands on redundancy and the handling of errors that occur. One such error is the so-called "stuck pedal." Without movement of the pedal, most sensor systems cannot detect brake pedal operation, and the vehicle is not braked.One method for detecting or treating a stuck pedal is the integration of a force sensor that can detect the driver's foot force even when the pedal is stuck. However, such force measurements are complicated and expensive.

[0003] It is therefore an object of the present invention to provide a cost-effective motor vehicle braking system which meets the legal requirements for a minimum deceleration even in the event of a pedal fault.

[0004] The problem is solved by the brake pedal unit having a contact sensor on a foot contact surface, and the control device being configured to detect a pedal error, in particular a jammed pedal, based on a signal from the contact sensor and the brake pedal actuation value by the sensor system, and in this case to initiate a deceleration of a predetermined magnitude. The contact sensor can, for example, be arranged on the pedal plate with a rubber cap. The predetermined magnitude is then not based on the brake pedal actuation value, which cannot be correctly detected due to the pedal error.

[0005] In a preferred embodiment, the contact sensor has exactly two states, with a first state indicating an actuated brake pedal and a second state indicating an unactuated brake pedal. The contact sensor can thus be simply implemented as a push-button, which is simple, error-resistant, and cost-effective.

[0006] In a particularly preferred embodiment of the invention, the control device detects a pedal error when the contact sensor indicates that the brake pedal is actuated and there is no brake pedal actuation value, or when the brake pedal actuation value indicates that the brake pedal is not actuated. Thus, a comparison is made between the signals from the contact sensor and the actual sensor system for detecting the brake pedal actuation value. If a discrepancy occurs, this is interpreted as a corresponding error.

[0007] In a further preferred embodiment of the invention, a value for the predetermined deceleration magnitude is stored in a memory device of the control device, wherein the value is between 2.44 m / s^2 and 9.81 m / s^2, preferably 6.43 m / s^2. Thus, the legal requirements are always met.

[0008] In a further preferred embodiment of the invention, the brake pedal actuation variable includes a pedal travel, a pedal angle, and / or a pedal force. The corresponding sensor technology is precise and error-resistant.

[0009] In a further preferred embodiment of the invention, the contact sensor provides a digital or an analog signal.

[0010] In a further preferred embodiment of the invention, the contact sensor transmits the signal directly to the control device, whereby the transmission occurs independently of the remaining sensor system. This introduces further redundancy, which improves the availability of the braking system. Alternatively or additionally, the contact sensor transmits the signal via the sensor system for detecting the brake pedal actuation magnitude, which in turn forwards the signal to the control device.

[0011] In a further preferred embodiment of the invention, the control device is configured to dynamically adapt the predefined deceleration rate in the event of a pedal error, whereby an increasing deceleration ramp is implemented when the pedal is depressed and / or a decreasing deceleration ramp is implemented when the pedal is not depressed. This enormously improves the controllability of the button brake thus implemented by the driver. By alternately depressing and not depressing the jammed pedal, the driver can set the desired deceleration rate using the principle of pulse width modulation. The ramps can be selected such that safety objectives regarding underbraking / overbraking and residual braking torque are not violated.

[0012] In a further preferred embodiment of the invention, the ramp is linear and / or has a positive or negative curvature. In particular, the ramp can only rise to a maximum value. This allows the driver to better control the deceleration.

[0013] In a further preferred embodiment of the invention, the brake actuator is hydraulic and / or electromechanical.

[0014] In a further preferred embodiment of the invention, the brake pedal unit has no mechanical coupling to the brake actuator. In particular, there is no switchable hydraulic through-passage.

[0015] The object is also achieved by a method for controlling a motor vehicle brake system according to one of the preceding claims, wherein a pedal error is detected based on a signal from a contact sensor and a quantitative brake pedal actuation variable and, in this case, a deceleration of a predetermined magnitude is initiated.

[0016] Further features, advantages, and possible applications of the invention will become apparent from the following description of exemplary embodiments and the drawings. All described and / or illustrated features, both individually and in any combination, are part of the subject matter of the invention, regardless of their summary in the claims or their references. Fig. 1 shows a brake pedal unit with contact sensor, Fig. 2 shows schematically the contact sensor connection in a first embodiment, Fig. 3 shows schematically the contact sensor connection in a second embodiment, Fig. 4 shows two diagrams with measured values ​​in a fault-free case, Fig. 5 shows two diagrams with measured values ​​in a faulty case, Fig. 6 shows two diagrams of the delay control in case of fault;

[0017] As in Fig. As shown in Figure 1, a brake pedal unit 1 comprises a pedal plate 2 with a rubber cover. Integrated into this pedal plate 2 is a contact sensor 3, which is designed as a simple button that, when actuated, establishes a connection to a voltage potential, thereby generating a voltage pulse.

[0018] As in Fig. As shown in Figure 2, the contact sensor 3 is connected to the sensor system for the brake pedal actuation variables 4 via a separate line, over which the voltage pulse is transmitted. These sensors include a pedal travel sensor. This sensor system receives the voltage pulse and transmits it to a control device 5.

[0019] An alternative electronic architecture is in Fig. 3. The contact sensor 3 is connected directly to the control device 5 without having a connection to the sensor system 4.

[0020] In Fig. Figure 4 illustrates the behavior in the error-free case. As the force with which the driver presses the brake pedal increases, the sensor system generates a brake pedal actuation value, which, according to a predetermined relationship, maps a corresponding, steadily rising curve. This correspondingly leads to increasing deceleration of the vehicle. The signal from the contact sensor merely forms a step function between two possible states. As soon as this changes to a state in which the button switches and thus indicates an actuated brake pedal, the control unit checks whether sensor system 4 generates a corresponding brake pedal actuation value. If this is the case, a vehicle deceleration is implemented based on the brake pedal actuation value.

[0021] However, if the brake pedal actuation size does not match an actuated brake pedal, as in Fig. 5, it is assumed that the pedal is jammed. On the left in Fig. Figure 5 shows that the brake pedal actuation magnitude, in particular the pedal travel, does not increase with increasing pedal force. According to the invention, in this case, a deceleration of 2.44 m / s^2 is simply set or implemented by the actuator. For this purpose, hydraulic pressure can be built up in the wheel brakes, for example, using a linear actuator or a hydraulic pump. The pressure and thus the deceleration can be set fixedly and, in particular, independently of the brake pedal actuation magnitude, which, in fact, does not provide any useful information.

[0022] In Fig.6 alternatively shows that the generated braking torque does not have to be constant. Rather, if a jammed pedal is detected during the brake pedal operation, as indicated by contact sensor 3, the braking torque is slowly increased. The braking torque gradient starts at a high value and is slowly reduced so that the braking torque essentially asymptotically approaches a maximum value. If the deceleration becomes too great for the driver, they release the brake pedal, so that the contact sensor no longer indicates brake pedal operation. In this case, the braking torque is not reduced directly to zero, but gradually reduced using a falling ramp. This allows the driver to adjust the desired deceleration by alternately applying and releasing the brake pedal.

Claims

[1] Motor vehicle brake system with a brake pedal unit (1) having sensors (4) for detecting a quantitative brake pedal actuation variable and an electronic control device (5) configured to receive the brake pedal actuation variable and to control a brake actuator based on the brake pedal actuation variable in order to decelerate the motor vehicle, characterized by in that the brake pedal unit (1) has a contact sensor (3) on a foot contact surface (2) and the control device (5) is designed to detect a pedal error, in particular a jammed pedal, based on a signal from the contact sensor (3) and the brake pedal actuation variable by the sensor system (4) and, in this case, to initiate a deceleration of a predetermined magnitude. [2] Motor vehicle brake system according to claim 1 characterized bythat the contact sensor (3) has exactly two states, a first state indicating an actuated brake pedal and a second state indicating an unactuated brake pedal. [3] Motor vehicle brake system according to claim 2 characterized by that the control device (5) detects a pedal error when the contact sensor (3) indicates that the brake pedal is actuated and there is no brake pedal actuation variable or a brake pedal actuation variable which indicates that the brake pedal is not actuated. [4] Motor vehicle brake system according to one of the preceding claims characterized by that the specified deceleration value is between 2.44 m / s^2 and 9.81 m / s^2. [5] Motor vehicle brake system according to one of the preceding claims characterized by that the brake pedal actuation variable includes a pedal travel, a pedal angle and / or a pedal force. [6] Motor vehicle brake system according to one of the preceding claims characterized bythat the contact sensor (3) provides a digital or analogue signal. [7] Motor vehicle brake system according to one of the preceding claims characterized by that the contact sensor (3) transmits the signal directly to the control device (5) or via the sensor system (4) for detecting the brake pedal actuation variable, which forwards the signal to the control device (5). [8] Motor vehicle brake system according to one of the preceding claims characterized by that the control device is designed to dynamically adapt the specified deceleration in the event of a pedal error, whereby an increasing ramp of the deceleration is implemented when the pedal is actuated and / or a decreasing ramp of the deceleration is implemented when the pedal is not actuated. [9] Motor vehicle brake system according to one of the preceding claims characterized by that the ramp is linear and / or has a positive or negative curvature. [10] Motor vehicle brake system according to one of the preceding claims characterized by that the brake actuator is hydraulic and / or electromechanical. [11] Motor vehicle brake system according to one of the preceding claims characterized by that the brake pedal unit (1) has no mechanical coupling to the brake actuator. [12] Method for controlling a motor vehicle brake system according to one of the preceding claims characterized by that based on a signal from a contact sensor (3) and a quantitative brake pedal actuation variable, a pedal error is detected and in this case a deceleration of a predetermined magnitude is initiated.

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