Braking system for a vehicle

Abstract

This invention relates to a braking system for a vehicle. The vehicle has at least four brakeable wheels (12, 14, 16, 18). The braking system includes at least four brake actuator units (20), each associateable with one of the wheels (12, 14, 16, 18) of the vehicle, wherein each brake actuator unit (20) is associated with an electronic control unit (24, 26, 28, 30), the electronic control unit (24, 26, 28, 30) being designed to activate the brake actuator unit (20) to apply braking force to the associated wheel (12, 14, 16, 18), wherein at least two of the control units (24, 26, 28, 30) are designed as master units, and braking signals from brake actuator units (32) are directly transmitted to each master unit, and wherein each master unit is directly connected in signaling to at least one of the control units (28, 30) designed as slave units to forward braking signals to the slave unit.

Description

Technical Field

[0001] The present invention relates to a braking system for a vehicle having at least four brakeable wheels. Background Technology

[0002] In modern vehicles, each wheel is connected to a brake actuator unit with an electromechanical brake actuator. This braking system is also known as a "brake-by-wire" system.

[0003] In this system, the brake pedal is used to simply obtain a braking request from the vehicle's driver. Based on this braking request, individual brake actuator units are then activated via one or more electronic control units. There is no mechanical connection between the brake pedal and the brake actuator units.

[0004] Because the braking system is a safety-related device in a vehicle, it is often designed with redundancy in at least some components or functions to ensure reliable operation even in the event of a malfunction or defect. In other words, redundancy is provided within the braking system to achieve a high level of operational reliability.

[0005] In previous brake-by-wire systems, for example, an additional hydraulic braking device was provided as a backup.

[0006] However, this is associated with a large amount of labor and high costs. In addition, it requires extra installation space and increases the weight of the vehicle. Summary of the Invention

[0007] Therefore, the object of the present invention is to provide an optimized braking system with particularly high operational reliability.

[0008] This objective is achieved by a braking system according to the invention for a vehicle having at least four brakeable wheels, the braking system comprising at least four brake actuator units, each brake actuator unit being associateable with one of the wheels of the vehicle, wherein each brake actuator unit is associated with an electronic control unit, the electronic control unit being designed to activate the brake actuator unit to apply braking force to the associated wheel. At least two of the control units are designed as master units, and braking signals from the brake actuator units are directly transmitted to each master unit, wherein each master unit is directly connected in signaling to at least one other control unit designed as a slave unit to forward the braking signals to the slave unit.

[0009] The presence of two master units (each receiving braking signals directly from the brake actuation unit) ensures that even if one of the control units designed as master units fails, a braking signal can still be sent, and the braking process can be initiated if necessary. Because each master unit is directly connected in signaling to at least one other control unit designed as a slave unit, at least one other wheel can be braked, thus achieving sufficient vehicle deceleration even if one control unit fails.

[0010] Specifically, the control unit, designed as a slave unit, does not receive braking signals directly from the brake actuation unit, but rather from one of the master units.

[0011] In this context, "master" and "subordinate" mean that the master unit is hierarchically higher than the subordinate unit and can give instructions to the subordinate unit. In particular, the subordinate unit can receive braking signals from the master unit. The reverse is not true.

[0012] The advantage of this braking system is that it is designed to be "fail-safe" and does not require additional mechanical or hydraulic braking devices. Therefore, the braking system according to the invention requires very little installation space and is particularly cost-effective, while ensuring a high level of operational reliability.

[0013] In this context, "fail-safe" means that if any single component of the braking system fails, the system's minimum braking performance is maintained.

[0014] Under current conditions, if a single failure occurs, for example, if one of the brake actuator units fails, the brake circuit of the intact braking system will still maintain approximately 70% of its minimum braking power.

[0015] Perfect operation is achieved when all components of the braking system are functioning correctly.

[0016] Each of the brake actuator units includes an electromechanical brake actuator. In particular, each of the brake actuator units includes an electric motor and a spindle drive, which can actuate the brake by means of the spindle drive.

[0017] The brake actuator units are particularly dry, meaning they are not hydraulically driven.

[0018] The brake actuation unit preferably includes a brake pedal that can be actuated by the driver of the motor vehicle with their foot to generate a braking signal.

[0019] According to one embodiment, the two control units, designed as slave units, are directly interconnected in signaling terms, specifically via signal lines. Therefore, the slave units can communicate with each other. If a slave unit fails to receive a braking signal from the master unit due to a transmission failure in one of the control units designed as master units, that slave unit can therefore receive a braking signal from the other slave unit. Thus, if one master unit fails, the braking signal can be transmitted to other control units, thereby ensuring good braking behavior even if one master unit fails.

[0020] The two control units designed as the main unit are preferably directly interconnected in signaling terms, particularly via signal lines. Therefore, the control units designed as the main unit can communicate with each other and coordinate braking signals. Consequently, the same braking pressure can be generated on the wheels associated with the main unit. This allows the vehicle to remain exceptionally stable during braking maneuvers.

[0021] In cases where communication occurs between at least two control units designed as master units, one of the master units is designed to act as a higher-level master unit. In this way, it can be clearly determined which braking force will be generated on the wheel.

[0022] The control unit, designed as the main unit, can be connected to the brake actuation unit in terms of signaling via separate signal lines. Using separate signal lines ensures reliable signal transmission. In particular, even if one signal line fails, the braking signal can still be transmitted. This provides an additional level of safety.

[0023] Because the two master units can communicate with each other, if one signal line fails, the braking signal can still be transmitted from one master unit to the other. Therefore, a failure in one signal line does not negatively affect the braking performance of the braking system.

[0024] Preferably, at least two sensors are provided on the brake actuation unit, which can detect brake actuation, and each sensor is directly connected to the main unit in terms of signaling. The sensors can be used to determine the driver's braking request, which is transmitted to the control unit in the form of a braking signal.

[0025] The sensors can be force sensors and displacement sensors. With the help of force sensors and displacement sensors, it is possible to specifically determine what force the driver applies when pressing the brake pedal and how far it is pressed, in order to determine the braking request from the driver.

[0026] In one implementation, each wheel is associated with a rotational speed sensor, which is connected to a control unit associated with the relevant wheel. The current vehicle speed can be determined based on the detected rotational speed. This current vehicle speed can then be used to determine the necessary braking force based on a braking request from the driver.

[0027] Each control unit may include control electronics for activating the associated brake actuator unit, wherein at least one control unit is capable of accessing the control electronics of at least one other control unit. This ensures additional redundancy in the braking system, thus ensuring a particularly high level of operational reliability. In particular, if a failure in the associated control unit does not affect the control electronics, the brake actuator unit can be activated by a control unit other than the associated control unit.

[0028] The braking system preferably includes a bus system, and at least two control units of the main unit are designed to be connected to the bus system. In this way, the main unit can receive signals from the bus system.

[0029] For example, the braking system includes an electronic parking brake, which has a parking brake actuation unit and is connected to the bus system. Therefore, when the user actuates the parking brake, the main unit can receive a signal and activate the brake actuator unit accordingly.

[0030] Furthermore, a yaw rate sensor can be connected to a bus system. The yaw rate sensor can determine the vehicle's dynamic state, specifically whether the vehicle tends to rotate about its vertical axis. Because the yaw rate sensor is connected to the bus system, information about the vehicle's tendency to rotate about its vertical axis can be forwarded to the master unit. The master unit can then activate the brake actuator unit in a manner that compensates for the vehicle's potential tendency to rotate.

[0031] According to one embodiment, the braking system has a first power supply unit and a second power supply unit, and the power supply units can be independently connected to supply power to all control units and brake actuator units. Because two power supply units are provided, the power supply is also designed to be redundant.

[0032] For example, a first subset of the brake actuator units is connected to a first power supply unit for supplying power, and a second subset of the brake actuator units is connected to a second power supply unit for supplying power. Specifically, the first and second subsets do not intersect. More precisely, the first power supply unit supplies power to two control units, and the second power supply unit supplies power to other control units.

[0033] Preferably, the power supply units are connected diagonally in the vehicle. This means that the first power supply unit supplies two control units located diagonally opposite the center of the vehicle, and the second power supply unit supplies two other control units located diagonally opposite the center of the vehicle.

[0034] If one power supply unit fails, another power supply unit can preferably take over the supply to all brake actuator units.

[0035] For example, the main unit is associated with the front wheels, which have a higher braking load, and both are directly connected to the control unit of the rear wheels, which are positioned diagonally opposite the center of the vehicle. In this way, if one main unit fails, the vehicle's braking behavior can be controlled in a stable manner.

[0036] According to one implementation, the signaling circuitry is designed so that each master unit can communicate with other control units in a signaling manner when another master unit fails. In this way, braking signals can be forwarded particularly quickly to control units that are still operating. Preferably, in this case, the master unit is directly connected in a signaling manner to each control unit that is designed as a slave unit. Attached Figure Description

[0037] Further advantages and features of the invention will become clear from the following description and the accompanying drawings.

[0038] Figure 1 A braking system according to the invention for a vehicle is illustrated schematically. Detailed Implementation

[0039] Figure 1 A braking system 10 is shown for a vehicle having four brakeable wheels 12, 14, 16, 18. In particular, the vehicle has two front wheels and two rear wheels.

[0040] The brake actuator unit 20 is associated with each of the wheels 12, 14, 16, and 18.

[0041] Each brake actuator unit 20 includes an electromechanical actuator with a motor and a spindle driver, which is not shown in the figure for simplicity. A hydraulic actuator is not provided.

[0042] With the aid of the brake actuator unit 20, the brake shoes 21 associated with each wheel 12, 14, 16, 18 can move and press against the brake disc 22 to brake the vehicle.

[0043] Each brake actuator unit 20 is also associated with electronic control units 24, 26, 28, 30.

[0044] Control units 24, 26, 28, and 30 are designed to activate brake actuator unit 20 in order to apply braking force to the associated wheels 12, 14, 16, and 18.

[0045] For this purpose, each control unit 24, 26, 28, 30 includes control electronics 31 for activating the associated brake actuator unit 20.

[0046] Specifically, when the corresponding braking signal is transmitted to control units 24, 26, 28, and 30, the brake actuator unit 20 is activated.

[0047] In order to generate a braking signal, the braking system includes a brake actuation unit 32, which includes a brake pedal 34. The braking signal is generated by the driver pressing the brake pedal 34 of the brake actuation unit 32 with their foot, thereby issuing a signal requesting braking.

[0048] In the illustrated embodiment, the brake actuation unit 32 includes four sensors capable of detecting brake actuation, specifically two force sensors 36 and two displacement sensors 38. Both the force sensors 36 and the displacement sensors 38 are directly connected to one of the main units in terms of signaling.

[0049] In principle, a single force sensor 36 and a single displacement sensor 38 would be sufficient. By providing two sensors in each case, the safety of the braking system 10 is improved because even if one sensor fails, a braking signal can still be generated and relayed.

[0050] The brake actuation unit 32 also includes a brake force simulator 40. This generates a counterforce that counteracts the pressure applied by the driver to the brake pedal 34.

[0051] In addition, rotational speed sensor 42 is associated with each wheel 12, 14, 16, 18 to detect the rotational speed of wheels 12, 14, 16, 18.

[0052] Rotation speed sensors 42 are all connected to control units 24, 26, 28, and 30 associated with the corresponding wheels 12, 14, 16, and 18.

[0053] The braking system 10 also includes a parking brake 44 with a parking brake actuation unit 46, which can be actuated by the driver to trigger the parking brake.

[0054] It also provides a yaw rate sensor 48.

[0055] The braking system has a bus system 50, and the parking brake 44 and the yaw rate sensor 48 are connected to the bus system 50.

[0056] The two control units 24 and 26, which are designed as the main units, are also connected to the bus system 50 and can receive information from them, such as information about the actuation of the parking brake 44 or the vehicle's dynamic state as determined by the yaw rate sensor 48.

[0057] In addition, the braking system 10 has a first power supply unit 52 and a second power supply unit 54, and the power supply units 52 and 54 can be connected independently of each other.

[0058] Power supply units 52 and 54 are designed to supply power to all control units 24, 26, 28, 30 and brake actuator unit 20.

[0059] In proper operation, the first power supply unit 52 supplies power to the control units 24, 26 associated with the front wheels and their corresponding brake actuator units 20, as well as to the control units 28, 30 associated with the rear wheels positioned diagonally relative to the center of the vehicle and their corresponding brake actuator units 20. Correspondingly, the second power supply unit 54 supplies power to the control units 24, 26 associated with the other front wheel and their corresponding brake actuator units 20, as well as to the control units 28, 30 associated with the rear wheels positioned diagonally relative to the center of the vehicle and their corresponding brake actuator units 20.

[0060] In other words, power supply units 52 and 54 are connected diagonally.

[0061] In this figure, the first power supply unit 52 and the second power supply unit 54 are shown twice to illustrate the type of connection.

[0062] If one power supply unit fails, it is foreseeable that another power supply unit will take over the power supply to all control units 24, 26, 28, 30 and all brake actuator units 20, at least for a short period of time.

[0063] Of the four control units 24, 26, 28, 30, two control units 24 and 26 (specifically the control units 24 and 26 associated with the front wheels) are designed as the main units.

[0064] The other two control units 28 and 30 (specifically the control units associated with the rear wheels) are designed as subordinate units.

[0065] Each master unit is directly connected in signaling to one of the control units 28, 30 that are designed as slave units in order to forward braking signals to the slave units.

[0066] More precisely, each control unit 24, 26, designed as a main unit, is specifically connected via signal lines 56, 58 directly to control units 28, 30 located diagonally opposite the center of the vehicle to the rear wheels.

[0067] The braking signal from the brake actuation unit 32 is sent directly to each main unit.

[0068] The subordinate unit indirectly receives braking signals from the master unit.

[0069] In order to send the braking signal from the brake actuation unit 32 to the control units 24, 26 which are designed as main units, the main units are connected to the brake actuation unit 32 in terms of signaling via separate signal lines 60.

[0070] In addition, the two control units 24 and 26, which are designed as the main unit, are directly interconnected in terms of signaling via signal line 62.

[0071] Therefore, the two control units 24 and 26, designed as the main unit, can communicate with each other to coordinate braking signals. This can be used, for example, to compensate for the vehicle's tendency to rotate about its vertical axis by braking the two front wheels with different braking forces.

[0072] In cases where communication takes place between at least two control units 24, 26 that are designed as master units, one of the master units is designed to act as a higher-level master unit.

[0073] Similarly, the two control units 28, 30, which are designed as slave units, are directly interconnected in terms of signaling via signal line 64.

[0074] The control units 28 and 30, which are designed as slave units, can also communicate with each other via signal line 64 in order to coordinate braking signals.

[0075] When the driver issues a braking request by actuating the brake pedal 34, the corresponding signal is sent separately to the control unit 24, 26, which is designed as the main unit, via the signal line 60.

[0076] Then, the control units 24, 26, which are designed as master units, forward the braking signal via signal lines 56, 58 to the control units 28, 30, which are designed as slave units, and in particular, in each case, to the control units 28, 30 located diagonally opposite to the center of the vehicle.

[0077] Therefore, each control unit 24, 26, 28, 30 receives the braking signal directly or indirectly and then activates the associated brake actuator unit 20.

[0078] In perfect working order, all brake actuator units 20 are activated, enabling all wheels 12, 14, 16, and 18 to be braked during the braking process.

[0079] If one of the control units 28 and 30 designed as slave units fails, the braking signal is still forwarded directly from the braking actuation unit 32 to the two control units 24 and 26 designed as master units, and indirectly from one of the two control units 24 and 26 designed as master units to the still-operating slave unit.

[0080] Therefore, three of the four wheels 12, 14, 16, and 18 can still be braked during the braking process. As a result, approximately 70% of the braking power of the intact braking system 10 can be achieved.

[0081] If one of the control units 24 and 26, which are designed as master units, fails, the braking signal is forwarded directly from the brake actuation unit 32 to the operating master unit and indirectly from the operating master unit to one of the two control units 28 and 30, which are designed as slave units.

[0082] The malfunctioning master unit can no longer forward the braking signal to the other of the two control units 28, 30 that are designed as slave units.

[0083] However, since the control units 28 and 30, which are designed as slave units, are directly interconnected in terms of signaling, the braking signal can be forwarded to another slave unit by the slave unit that receives the signal from the master unit.

[0084] Therefore, even if one of the control units 24, 26 designed as the main unit fails, the three brake actuator units 20 can still be activated, so that three of the four wheels 12, 14, 16, 18 can be braked.

[0085] Preferably, control units 24, 26, 28, and 30 can all access the control electronics 31 of at least one other control unit 24, 26, 28, and 30. Therefore, if one control unit 24, 26, 28, or 30 fails, the brake actuator unit 20 associated with the failed control unit 24, 26, 28, or 30 can still be activated, as long as the control electronics 31 remains intact, thus ensuring unrestricted braking power is available.

[0086] According to an alternative embodiment, not shown for simplicity, the signaling circuitry can be designed such that each master unit can communicate with other control units 28, 30 in a signaling manner when another master unit fails. In this way, braking signals can be directly forwarded from one master unit to the two control units 28, 30, which are designed as slave units.

Claims

1. A braking system (10) for a vehicle having at least four brakeable wheels (12, 14, 16, 18), said braking system comprising: At least four brake actuator units (20), each brake actuator unit (20) being able to be associated with one of the wheels (12, 14, 16, 18) of the vehicle. Each brake actuator unit (20) is associated with an electronic control unit (24, 26, 28, 30), which is designed to activate the brake actuator unit (20) to apply braking force to the associated wheel (12, 14, 16, 18). In this configuration, at least two of the control units (24, 26, 28, 30) are designed as master units, and the braking signal from the brake actuation unit (32) is directly sent to each master unit. Each master unit is directly connected in signaling to at least one of the control units (28, 30) that are designed as slave units, in order to forward the braking signal to the slave unit.

2. The braking system (10) according to claim 1, characterized in that, The two control units (28, 30), which are designed as slave units, are directly interconnected in terms of signaling.

3. The braking system (10) according to any one of the preceding claims, characterized in that, The two control units (24, 26), which are designed as the main unit, are directly interconnected in terms of signaling.

4. The braking system (10) according to claim 3, characterized in that, In the case of communication between the at least two control units (24, 26) that are designed as master units, one of the master units is designed to act as a higher-level master unit.

5. The braking system (10) according to any one of the preceding claims, characterized in that, The control units (24, 26), which are designed as main units, are connected to the brake actuation unit (32) in terms of signaling via separate signal lines (60).

6. The braking system (10) according to claim 5, characterized in that, At least two sensors are provided on the brake actuation unit (32) to detect brake actuation, and each sensor is directly connected to the main unit in terms of signaling.

7. The braking system (10) according to any one of the preceding claims, characterized in that, Rotation speed sensor (42) is associated with each wheel (12, 14, 16, 18) and connected to the control unit (24, 26, 28, 30) associated with the associated wheel (12, 14, 16, 18).

8. The braking system (10) according to any one of the preceding claims, characterized in that, Each control unit (24, 26, 28, 30) includes control electronics (31) for activating the associated brake actuator unit (20), wherein at least one of the control units (24, 26, 28, 30) is able to access the control electronics (31) of at least one other control unit (24, 26, 28, 30).

9. The braking system (10) according to any one of the preceding claims, characterized in that, The braking system (10) includes a bus system (50), to which at least two control units (24, 26), designed as the main unit, are connected.

10. The braking system (10) according to claim 9, characterized in that, The braking system (10) includes an electronic parking brake (44) having a parking brake actuation unit (46) and being connected to the bus system (50).

11. The braking system (10) according to claim 9 or claim 10, characterized in that, The yaw rate sensor (48) is connected to the bus system (50).

12. The braking system (10) according to any one of the preceding claims, characterized in that, The braking system (10) has a first power supply unit (52) and a second power supply unit (54), which can be independently switched on to supply power to all the control units (24, 26, 28, 30) and the brake actuator unit (20).

13. The braking system (10) according to any one of the preceding claims, characterized in that, The main unit is associated with the front wheels and is directly connected to the control unit (28, 30) located diagonally relative to the center of the vehicle.

14. The braking system (10) according to any one of the preceding claims, characterized in that, The signaling circuitry is designed to enable each master unit to communicate with other control units (28, 30) in terms of signaling when another master unit fails.

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