Sensor concept for an electrically operated brake

Abstract

Braking device comprising a brake pedal sensor (6a, 6b) for detecting a braking request exerted on a brake pedal (1) and a control unit (4a, 4b) connected to the brake pedal sensor (6a, 6b), wherein at least two brake pedal sensors (6a, 6b) are provided, wherein the brake pedal sensors (6a, 6b) are each assigned to their own control unit (4a, 4b), and that the control units (4a, 4b) are connected to each other via a data connection (8), characterized in that an additional brake pedal state sensor (7a, 7b) is provided on at least one of the control units (4a, 4b) which can detect at least two different braking states, and that the at least one brake pedal state sensor (7a, 7b) is implemented as a brake light switch.

Description

State of the art

[0001] The invention relates to a motor vehicle brake, in particular an electrically operated brake, according to the preamble of claim 1.

[0002] In vehicles with a conventional hydraulic or pneumatic braking system, there is a mechanical link between the brake pedal and the individual wheel brakes. In contrast, electrically actuated braking systems detect the driver's braking request via sensors and evaluate it with a control unit, which then activates the brake actuators, such as electric motors mounted on the brake caliper (motor on caliper), according to the driver's request. For safety reasons, redundant sensors are mandatory. However, even with redundant sensors, the braking system can fail because the control unit has limited ability to distinguish between correct and incorrect readings. Furthermore, in the worst-case scenario, the control unit itself can malfunction and fail. Currently available braking systems are not capable of handling such malfunctions without problems.

[0003] Documents DE 199 04 721 A1 and DE 197 42 988 C1 disclose a braking device comprising a brake pedal sensor for detecting a braking request exerted on a brake pedal and a control unit connected to the brake pedal sensor, wherein at least two brake pedal sensors are provided, wherein the brake pedal sensors are each assigned to their own control unit, and that the control units are connected to each other via a data connection. Disclosure of the invention

[0004] It is therefore the object of the present invention to further improve the interference immunity of an electrically operated vehicle braking system.

[0005] This problem is solved according to the invention by the features specified in claim 1. Further embodiments of the invention are described in the dependent claims.

[0006] A key aspect of the invention is to provide multiple brake pedal sensors, each of which detects the braking request, and to assign these sensors to different control units that are interconnected via a data link. This allows information regarding the braking request or the functionality of the sensors to be exchanged between them. If one sensor fails, the corresponding control unit still has access to information from another sensor connected to a different control unit. Furthermore, if one control unit fails, the entire braking system is not affected. The reliability of the braking system can thus be significantly improved. According to the invention, at least one of the control units is equipped with an additional brake pedal state sensor capable of detecting at least two different braking states, such as "brake applied" and "brake not applied."According to the invention, the condition sensor is a brake light switch. Preferably, an additional brake pedal condition sensor is connected to all control units.

[0007] The data connection between the individual control units is preferably implemented as a data bus.

[0008] Each of the control units is preferably assigned to a brake circuit with one or more brake actuators.

[0009] The brake pedal sensors according to the invention preferably measure different physical quantities, such as pedal force and pedal travel. That is, the sensor connected to a first control unit measures, for example, the force, and the sensor connected to another control unit measures, for example, the travel. Alternatively, an angle or another physical quantity characteristic of the brake pedal actuation could also be measured.

[0010] According to a specific embodiment of the invention, the brake pedal sensors assigned to a control unit are redundantly configured, with at least two brake pedal sensors being connected to a single control unit. This further improves the reliability of the system. The redundant sensors can also measure different physical quantities.

[0011] The brake pedal sensors are preferably implemented as Hall sensors. This design is particularly simple and cost-effective.

[0012] The individual control units preferably perform a plausibility check of the individual sensor signals. This can be done using a known method of absolute value or gradient verification. The sensor signals of the sensors connected to a single control unit are preferably also compared with each other. That is, the signal of the brake pedal sensor is compared, for example, with the signal of the brake pedal position sensor. If a fault is detected, the corresponding measured value can be read from one of the other control units via the data connection. This makes it possible to maintain the braking function. Furthermore, it is also possible in most cases to precisely locate the defective sensor. This is particularly true if only a single sensor is defective.

[0013] A switch is preferably provided in the power supply path of the brake pedal sensors, by means of which the sensors can be de-energized when the vehicle is stationary. This significantly reduces the quiescent load.

[0014] The signal from the brake pedal position sensors is preferably used as a wake-up signal to activate the associated control unit. If other wake-up signals, such as those from a remote control, door contact, or ignition, have not already woken the control unit, it is woken up by the brake pedal position sensor upon the first application of the brake pedal. If this brake pedal position sensor is defective and the fault has been detected, the associated control unit is preferably woken up by another control unit. Brief description of the drawings

[0015] The invention is explained in more detail below with reference to the accompanying drawings. These show: Fig. 1 a schematic block diagram of an electrically operated braking system; Fig. 2 a schematic block diagram of an electrically operated braking system according to an embodiment of the invention; Fig. 3 a schematic block diagram of an electrically operated braking system with two brake circuits in a more detailed view, and Fig. 4 A schematic block diagram of an electrically operated braking system with three brake circuits. Embodiments of the invention

[0016] Fig. Figure 1 shows an electrically operated vehicle braking system with two brake circuits 9a, 9b. The braking system shown includes a foot brake pedal 1 and two sensor devices 2a, 2b, which detect the pedal actuation. Each sensor device 2a, 2b can include one or more sensors. Each sensor device 2a, 2b is assigned its own control unit 4a, 4b, to which the sensor signals are forwarded.

[0017] The braking system further comprises several brake actuators 5a, 5b and 5c, 5d, which are controlled and regulated by the control units 4a, 4b according to the driver's braking request. Two actuators 5a, 5b and 5c, 5d belong to each brake circuit 9a and 9b, respectively. The two brake circuits 9a, 9b can, for example, be arranged in an X configuration.

[0018] The sensors 2a, 2b and the associated control units 4a and 4b are supplied with electrical power by different vehicle electrical systems 3a, 3b. Each of the vehicle electrical systems 3a, 3b preferably includes its own energy storage device, such as a battery, which ensures a sufficient power supply even in emergencies.

[0019] The two control units 4a and 4b are connected via a data bus 8, which is used to exchange sensor signals and related information. Information about the functionality of sensors 2a and 2b can also be transmitted. If one sensor (e.g., 2a) malfunctions, the sensor signals from the other sensor (2b) are available to the affected control unit 4a. The brake circuit (9a) affected by the fault therefore does not fail and can continue to operate. Furthermore, the additional sensor information received via data bus 8 makes it possible in most cases to locate the faulty sensor (2a).

[0020] Fig. 2 shows the braking system of Fig. 1 with further details. The braking system comprises two brake circuits 9a, 9b, each of which is assigned a brake pedal sensor 6a, 6b, as well as an additional brake pedal status sensor 7a, 7b. The brake pedal sensors 6a, 6b measure a physical quantity that characterizes the extent of pedal actuation (quantitative measurement). This could be, for example, the distance, an angle, a force, or another suitable physical quantity. It has been shown that the reliability of the sensors can be further improved if the sensors 6a, 6b measure different quantities, such as force and angle.

[0021] The brake pedal state sensors 7a and 7b are sensors that can distinguish between at least two different braking states, such as "braking" and "not braking". In the simplest case, these sensors 7a and 7b are therefore implemented as switches.

[0022] During operation, the control units 4a and 4b regularly perform plausibility checks of the sensor signals. This can involve, for example, checking the absolute value of the signals or performing gradient monitoring of the individual signals, as is known. The sensors 6a and 7a, respectively, assigned to control units 4a and 4b, are preferably also compared with each other (i.e., the signal of sensor 6a with that of sensor 7a). This allows for the detection of further sensor errors.

[0023] Furthermore, it is possible to compare the signals of sensors 6a, 7a and 6b, 7b connected to control unit 4a and 4b, respectively, with those of sensors 6b, 7b connected to the other control unit (e.g., 4b). This allows for the detection of further sensor faults or signal drift. Additionally, the sensor signals from the other brake circuit (e.g., 9b) are still available to the brake circuit 9a or 9b affected by the fault, thus preventing that brake circuit from failing.

[0024] Furthermore, by using a majority decision—that is, comparing the sensor signals of three sensors (e.g., 7a, 6b, 7b) with that of a fourth sensor (e.g., 6a)—the defective sensor can be located relatively accurately. The same applies, of course, to brake systems with three or more than four sensors.

[0025] If a fault is detected, a warning signal is preferably generated and the driver is informed of the fault by means of a suitable indicator device, such as a warning light. The fault can then be rectified quickly in a workshop.

[0026] In the illustrated embodiment, the brake pedal status sensors 7a and 7b also have a wake-up function, which allows the associated control unit 4a to be switched from a standby state to its normal operating state. In modern vehicles, many electronic components are switched to a sleep or standby state when the vehicle is stationary. These components are then switched back to their normal operating state by a specific activation process, such as pressing the remote control for the central locking system, opening a door, starting the engine, etc. The "wake-up signal" for the control unit 4a is generated here by pressing the brake pedal when sensor 7a changes its signal state. If status sensor 7a is defective, the control unit 4a can also be woken up by a signal transmitted via the data bus 8.

[0027] Fig. 3 shows the braking system of the Fig. 1 and Fig. Figure 2 provides further details. As can be seen, each brake circuit comprises two redundant brake pedal sensors 6a, 6a' and 6b, 6b', respectively. Sensors 6a, 6a' are Hall effect sensors that measure an angle in this example. The corresponding sensor, a permanent magnet 12, is attached to the brake pedal 1. Sensors 6b, 6b' are force sensors and measure the braking force, which is transmitted to sensors 6b, 6b' via a spring-damper system with springs 13 and dampers 14. Each brake circuit also includes a switch 7a, 7b, which changes its state when the brake pedal 1 is actuated. A switch 10 is provided in the power supply path of each brake pedal sensor 6. This switch serves to deactivate the sensors when the vehicle is stationary, thus reducing the quiescent current. The switches 10 can be controlled, for example, by the associated control units 4a, 4b.Furthermore, an amplifier 11 is provided in the signal output 15 of the sensors, by means of which the respective sensor signal is amplified.

[0028] Fig. Figure 4 shows a different brake system, which is divided into three brake circuits 9a-9c. Each brake circuit 9a-9c in turn comprises a control unit 4a-4c and one or more brake actuators (not shown). A brake pedal sensor 6a is connected to control unit 4a, a brake pedal sensor 6b to control unit 4b, and a brake pedal status sensor 7a to control unit 4c. Each of the control units 4a-4c is connected to every other control unit via its own data bus 8a-8c. This makes it possible to compare the signals between them and thus detect sensor faults. If a fault exists, the signals from the functioning sensors can also be used.

Claims

[1] Braking device comprising a brake pedal sensor (6a, 6b) for detecting a braking request applied to a brake pedal (1) and a control unit (4a, 4b) connected to the brake pedal sensor (6a, 6b), wherein at least two brake pedal sensors (6a, 6b) are provided, wherein the brake pedal sensors (6a, 6b) are each assigned to a separate control unit (4a, 4b), and that the control units (4a, 4b) are connected to each other via a data connection (8), characterized by , that at least one of the control units (4a , 4b) has an additional brake pedal state sensor (7a , 7b) which can detect at least two different brake states, and that the at least one brake pedal state sensor (7a , 7b) is implemented as a brake light switch. [2] Brake device according to claim 1, characterized by, that the control units (4a , 4b) are designed to exchange information concerning the braking request or the functionality of the sensors (6 , 7) via the data connection (8). [3] Brake device according to claim 1 or 2, characterized by , that the data connection (8) is a data bus. [4] Brake device according to one of the preceding claims, characterized by , that several brake pedal status sensors (7a , 7b) are provided, each of which is assigned to a control unit (4a , 4b). [5] Brake device according to one of the preceding claims, characterized by that the control units (4a , 4b) are each assigned to a brake circuit. [6] Brake device according to one of the preceding claims, characterized by , that the brake pedal sensors (6a , 6b) are implemented as Hall sensors. [7] Brake device according to one of the preceding claims, characterized by, that the brake pedal sensors (6a , 6b) of at least one control unit (4a , 4b) are designed redundantly. [8] Brake device according to one of the preceding claims, characterized by , that the brake pedal sensors (6a , 6b) measure different physical quantities. [9] Brake device according to one of the preceding claims, characterized by , that the control units (4a , 4b) perform a plausibility check of the sensor signals of the brake pedal sensors (6a , 6b) and / or the brake pedal status sensors (7a , 7b). [10] Brake device according to claim 9, characterized by , that a comparison is made with the sensor signal of another sensor (6 , 7) connected to the other control unit (4a , 4b). [11] Brake device according to claim 9, characterized by , that when an error is detected, the corresponding measured value is read from another control unit (4a , 4b) via the data connection (8). [12] Brake device according to claim 9 or 11, characterized by , that as part of the plausibility check the measurement signal of one sensor (6,7) is compared with the signal of another sensor (6,7) connected to the same control unit (4a , 4b). [13] Brake device according to one of the preceding claims, characterized by , that the control units (4a , 4b) are supplied with electrical power from different networks (3a , 3b). [14] Brake device according to claim 13, characterized by that the networks (3a , 3b) each have a separate energy storage system. [15] Brake device according to any one of the preceding claims, characterized by , that at least one brake actuator (5a -5d) is included, which is controlled by the control unit (4a , 4b) according to the braking request. [16] Brake device according to claim 1, characterized by that the braking device is an electrically operated braking device for motor vehicles.

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