Electromechanical braking device for a vehicle

Abstract

An electromechanical braking device for a vehicle comprises an electric brake motor and a coupling device for mechanically coupling a wheel axle or a brake disc to the rotor shaft of the brake motor. The coupling device is adjustable between a coupled and a disengaged position.

Description

[0001] The invention relates to an electromechanical braking device for a vehicle with an electric brake motor which, in order to generate a braking force, adjusts a brake piston in a wheel brake device towards a brake disc. State of the art

[0002] German patent DE 10 2004 004 992 A1 describes a parking brake system in a vehicle, which includes an electric brake motor for generating a clamping force that secures the vehicle when stationary. The parking brake system with the electric brake motor is integrated into the vehicle's hydraulic brake system, with the brake motor moving a brake piston towards a brake disc. During normal braking operation, the brake piston is also actuated by the vehicle's hydraulic brake system.

[0003] A comparable state of the art is also known from DE 198 17 892 A1.

[0004] The voltage or power supply for the electric brake motor in such parking brake systems is regularly provided via the vehicle battery.

[0005] DE 10 2011 004 804 A1 discloses an electromechanical braking device for a vehicle, in whose power train a coupling device with rheological couplings is incorporated between the electric brake motor and the brake piston. When an electromagnetic field is applied, the material of the rheological coupling changes from liquid to solid depending on the field strength, so that a force can be transmitted. When the electromagnetic field is removed, the coupling opens and the force flow is interrupted. Disclosure of the invention

[0006] The electromechanical braking device according to the invention can be used in vehicles to generate a braking force. In a preferred embodiment, the electromechanical braking device is used as a parking brake to generate a parking braking force. This also allows for use in automated parking maneuvers, where the vehicle typically moves forwards and backwards at low speeds, for example, at a maximum speed of 20 km / h. However, it is also possible to use the electromechanical braking device more generally in braking operations to reduce speed, which also includes use at higher speeds and independently of parking maneuvers. It is possible to generate a braking force in the vehicle solely via the electromechanical braking device, or in combination with, or solely with, a hydraulic vehicle brake.

[0007] The electromechanical braking system comprises an electric brake motor that moves a brake piston towards a brake disc to generate braking force. The brake piston has a brake pad on its end face, which is in contact with the brake disc during braking. The brake piston is part of a wheel braking system for slowing down one wheel of the vehicle.

[0008] The electromechanical braking device according to the invention also comprises a coupling device between a wheel axle of the wheel or brake disc and a rotor shaft of the electric brake motor. The coupling device is adjustable between a coupling position with mechanical coupling of the wheel axle or brake disc to the rotor shaft and a disengaged position in which the coupling between the wheel brake or brake disc and the rotor shaft is released.

[0009] In the coupled position – while the mechanical coupling between the wheel axle or brake disc and the rotor shaft of the brake motor is active – the rotor shaft of the brake motor is mechanically driven by the rotating wheel via the coupling device during vehicle movement. This makes it possible to generate wheel braking force even if the electrical power supply to the brake motor fails. In this case, the rotor shaft of the brake motor is driven solely mechanically by the rotating wheel and moves the brake piston, including the brake pad, against the brake disc. This results in an electromechanical braking system with a mechanical fallback for generating braking force in the event of a power supply failure.

[0010] Conversely, the coupling device is in the disengaged position as long as the electrical power supply is intact, allowing the brake motor to be electrically driven and to move the brake piston and brake pad against the brake disc. In the disengaged position, the electromechanical brake device functions in a manner known per se and is actuated electromechanically. Since there is no mechanical coupling to the wheel axle or the brake disc, no components of the coupling device need to be moved in the disengaged position.

[0011] The coupling device preferably engages the brake disc, which is rigidly connected to the rotor shaft of the wheel on which the wheel brake device is mounted. It is also possible for the coupling device to engage directly on the rotor shaft in the coupling position. Furthermore, it is also possible for the coupling device to engage another component that is rotationally fixed to the rotor shaft.

[0012] In the coupled position, a component of the coupling device is preferably positively connected to the rotor shaft or the brake disc. This is achieved, for example, by a gear of the coupling device meshing with teeth on the wheel shaft or the brake disc. The teeth are located, for example, on the outside of the brake disc. Alternatively, a friction-fit connection is also possible.

[0013] According to a further advantageous embodiment, the gear rests on a connecting shaft, which is part of the coupling device and, in particular, axially adjustable along its longitudinal axis. The coupling device is moved between the coupled and uncoupled positions by adjusting the connecting shaft along its longitudinal axis.

[0014] Alternatively, the connecting shaft can also be adjusted transversely to its longitudinal axis between the coupled and uncoupled positions. The adjustment movement is generally preferably a linear, translational movement. Alternatively, a rotary movement or a combination of translational and rotary movements can also be used as the adjustment movement.

[0015] According to yet another advantageous embodiment, the coupling device comprises an actuator for adjusting a coupling element, which is also part of the coupling device, between the coupled and uncoupled positions. Advantageously, the coupling element of the coupling device is de-energized in the coupled position and energized in the uncoupled position. This creates a so-called fail-safe state in which the energized actuator—given a functioning electrical power supply—holds the coupling element in the uncoupled position. If, on the other hand, the power supply fails, the coupling element is automatically adjusted to the coupled position, so that the rotor shaft of the electric brake motor is mechanically coupled to the wheel shaft or brake disc and driven by it.

[0016] The coupling element is moved from the disengaged to the engaged position, for example, by the force of a spring element acting on it. When energized, the actuator holds the coupling element in the disengaged position against the force of the spring element.

[0017] In the transmission path between the wheel axle or brake disc and the rotor shaft of the electric brake motor, several gears may be located, which are part of the coupling device. It is generally sufficient that only a single coupling element, for example a single gear, is moved between the coupled and disengaged positions.

[0018] According to a further advantageous embodiment, the actuator that adjusts the coupling element between the coupled and uncoupled positions is designed as an electromagnetic actuator. Alternatively, actuators designed, for example, as electric motors, hydraulic or pneumatic actuators are also suitable.

[0019] According to a further advantageous embodiment, the coupling device includes an actuator for adjusting the direction of rotational support on the rotor shaft. This makes it possible to adjust the direction of rotational support of the coupling device depending on the vehicle's forward / reverse direction of travel. Thus, even if the direction of wheel rotation is reversed, the same direction of rotational support acting on the rotor shaft can be maintained via the coupling device, ensuring that the same direction of adjustment in the electromechanical braking device is maintained despite the change in direction of travel. In the event of a power supply failure, a wheel braking force can be generated via the mechanical coupling in the same wheel braking device in both forward and reverse travel.

[0020] According to a further advantageous embodiment, the electromechanical braking device on opposite wheels in the left and right side areas of the vehicle comprises an electric brake motor in the respective wheel brake assembly to generate a braking force. Each electric brake motor is also associated with a coupling device, which is designed as described above and is adjustable between disengaged and engaged positions. In a preferred embodiment, both coupling devices each have an actuator, the actuators preferably being controllable independently of one another. This embodiment has the advantage that, in the event of a power supply failure, only one coupling device is moved from the disengaged to the engaged position, depending on the direction of travel, in order to generate a braking force in the respective wheel brake assembly.It is not necessary to install an actuator in the coupling device in question to adjust the direction of the yaw assist. Rather, it is sufficient to design the coupling devices without an actuator for adjusting the direction of the yaw assist and simply to adjust the direction of the yaw assist within each coupling device to the respective direction of travel. Thus, when driving forward, only one coupling device, which is assigned to a first wheel brake device, is moved into the coupling position, and when driving in reverse, only the other coupling device, which is assigned to the second wheel brake device, is moved into the coupling position.

[0021] To increase braking force, in the event of a power supply failure, it is possible to move both coupling devices from the uncoupling position to the coupling position, so that a braking force is generated in both wheel braking devices.

[0022] Another aspect of the invention relates to a method for operating the aforementioned electromechanical braking device. In this method, when the brake motor is receiving electrical power, the coupling device is in the disengaged position. If the electrical power supply fails during vehicle operation, the coupling device automatically moves into the engaged position, whereupon the wheel rotation, due to the mechanical coupling, drives the rotor shaft of the electric brake motor and generates a braking force.

[0023] It may be advantageous to make the transition of the coupling device from the disengaged to the engaged position speed-dependent, for example, to perform this process only during parking or exiting maneuvers. In this case, a speed limit is specified, and the coupling position is only set if the vehicle speed does not exceed this speed limit.

[0024] A particularly advantageous development relates to the execution of an automated parking maneuver. In this process, the electric brake motor is controlled, assuming a functioning power supply, in such a way that a brake pad held by the brake piston is moved into a position directly in front of the brake disc. If the power supply fails in this situation, the coupling device is automatically moved into the coupling position, whereby, due to the position of the brake pad directly in front of the brake disc, a braking force is built up in the shortest possible time. In the position directly in front of the brake disc, there is still a minimal gap between the brake pad and the brake disc.

[0025] The invention further relates to a control unit for controlling the adjustable components of the aforementioned electromechanical braking device. In particular, one or more actuators of the coupling device are controlled via control signals from the control unit.

[0026] The invention further relates to a parking brake for securing a vehicle in a stationary position, wherein the parking brake comprises a previously described electromechanical braking device or is designed as such an electromechanical braking device.

[0027] Finally, the invention also relates to a braking system for a vehicle, comprising a hydraulic vehicle brake with at least one brake circuit for generating a braking force at at least one vehicle wheel, and furthermore an electromechanical braking device as described above, wherein the hydraulic brake pressure of the hydraulic vehicle brake and the electric brake motor of the electromechanical braking device act on the same brake piston of the wheel brake device.

[0028] Further advantages and practical designs can be found in the additional requirements, the figure description, and the drawings. These show: Fig. 1 a schematic representation of a vehicle brake with a hydraulic brake booster, wherein the wheel brake devices of the vehicle brake on the rear axle of the vehicle are additionally designed as an electromechanical brake device with an electric brake motor, Fig. 2 a section through an electromechanical braking device with an electric brake motor, Fig. 3 in schematic representation the electromechanical braking device with additional mechanical coupling device for coupling between brake disc and rotor shaft of the brake motor.

[0029] In the figures, identical components are labelled with the same reference symbols.

[0030] The in Fig. The hydraulic vehicle brake 1 shown in Figure 1 for a vehicle comprises a front axle brake circuit 2 and a rear axle brake circuit 3 for supplying and controlling wheel brake devices 9 at each wheel of the vehicle with pressurized brake fluid. The two brake circuits 2 and 3 are connected to a common master brake cylinder 4, which is supplied with brake fluid via a brake fluid reservoir 5. The master brake cylinder piston within the master brake cylinder 4 is actuated by the driver via the brake pedal 6, and the pedal travel exerted by the driver is measured by a pedal travel sensor 7. A brake booster 10, which includes, for example, an electric motor, is located between the brake pedal 6 and the master brake cylinder 4. This motor preferably actuates the master brake cylinder 4 via a transmission (iBooster).

[0031] The pedal travel of the brake pedal 6, measured by the pedal travel sensor 7, is transmitted as a sensor signal to a control unit 11, which generates control signals for the brake booster 10. The supply of brake fluid to the wheel brake components 9 in each brake circuit 2, 3 is provided via various switching valves, which, together with other components, form part of a brake hydraulic system 8. The brake hydraulic system 8 also includes a hydraulic pump, which is part of an electronic stability program (ESP).

[0032] In Fig. Figure 2 shows the wheel brake assembly 9, which is arranged on a wheel on the rear axle of the vehicle, in detail. The wheel brake assembly 9 is part of the hydraulic vehicle brake 1 and is supplied with brake fluid 22 from the rear axle brake circuit. The wheel brake assembly 9 also has an electromechanical braking device, which is preferably used as a parking brake to secure a stationary vehicle, but can also be used to brake the vehicle when it is moving, especially at lower vehicle speeds below a certain speed limit.

[0033] The electromechanical brake device comprises a brake caliper 12 with a caliper 19, which engages a brake disc 20. The brake device uses a DC electric motor as an electric brake motor 13, whose rotor shaft 25 drives a spindle 14, on which a spindle nut 15 is mounted to prevent rotation. When the spindle 14 rotates, the spindle nut 15 is axially adjusted. The spindle nut 15 moves within a brake piston 16, which carries a brake pad 17. The brake pad 17 is pressed against the brake disc 20 by the brake piston 16. On the opposite side of the brake disc 20 is another brake pad 18, which is held stationary on the caliper 19. The brake piston 16 is pressure-tightly sealed against the receiving housing on its outer side by a surrounding sealing ring 23.

[0034] Within the brake piston 16, the spindle nut 15 can move axially forward towards the brake disc 20 when the spindle 14 rotates, and axially backward when the spindle 14 rotates in the opposite direction until it reaches a stop 21. To generate a clamping force, the spindle nut 15 acts on the inner end face of the brake piston 16, thereby pressing the brake piston 16, which is axially displaceable within the brake device, together with the brake pad 17, against the facing end face of the brake disc 20.

[0035] The hydraulic braking force is generated by the hydraulic pressure of the brake fluid 22 from the hydraulic vehicle brake 1, acting on the brake piston 16. The hydraulic pressure can also provide support when the vehicle is stationary and the electromechanical braking device is activated, so that the total braking force is composed of the electrically applied component and the hydraulic component. While the vehicle is in motion, either only the hydraulic vehicle brake is active, or both the hydraulic vehicle brake and the electromechanical braking device, or only the electromechanical braking device, are active to generate braking force. The control signals for activating both the adjustable components of the hydraulic vehicle brake 1 and the electromechanical wheel brake device 9 are generated in the control unit 11.

[0036] Fig. Figure 3 shows a schematic representation of the electromechanical braking device 24 with one electric brake motor each in the wheel brake assembly on the left and right vehicle wheels. The diagram shows... Fig. 3 each a brake disc 20 of the respective wheel brake device in the left and right side area of ​​the vehicle and each a brake piston 16 with brake pads 17 and 18, which are acted upon by the electric brake motor, whose rotor shaft 25 is shown, against the brake disc 20.

[0037] Furthermore, the brake device 24 comprises a mechanical coupling device 26 in each wheel brake assembly, which is adjustable between a coupling position and a disengaged position. In the coupling position, there is a mechanical coupling between the brake disc 20 and the rotor shaft 25, and in the disengaged position, this coupling is released. The coupling device 26 comprises several gears via which, in the coupling position, motion is transmitted from the brake disc 20 to the rotor shaft 25. In the coupling position, a gear 27 of the coupling device 26 engages with a toothing 28 on the outside of the brake disc 20. The gear 27 is located on a connecting shaft 29, which, by means of an actuator 30, preferably an electromagnetic actuator, is axially adjustable along the longitudinal axis of the shaft between the coupling and disengaged positions, as indicated by the double arrow.In . Fig. Figure 3 shows the coupled position. In the disengaged position, the connecting shaft 29 is adjusted so that the gear 27 is not in engagement with the teeth 28 on the brake disc 20.

[0038] In the engaged position, with gear 27 engaging the teeth 28 on the brake disc 20, the rotation of the brake disc is transmitted to the rotor shaft 25 via further gears of the coupling device 26 when the vehicle is in motion. This allows the rotor shaft 25 to be mechanically driven by the brake disc 20 in the event of a power failure, rendering the electric brake motor inactive. This, in turn, presses the brake piston 16 with the brake pad 17 against the brake disc 20 to generate braking force. In the disengaged position, gear 27 is disengaged from the teeth 28 on the brake disc 20. Additionally, another gear 31 on the connecting shaft 29 is disengaged from another gear 32, which is part of the coupling device 26 and is part of the kinematic transmission chain to the rotor shaft 25.

[0039] The actuator 30 is designed such that, when the power supply is functioning, the connecting shaft 29 with the gears 27 and 31 is in the disengaged position. The generation of electromechanical braking force is achieved exclusively via the electrical actuation of the brake motor.

[0040] In the event of a power or voltage supply failure, the connecting shaft 29 with gears 27 and 31 is moved into the coupling position. This can be achieved, for example, by means of a spring element acting on the connecting shaft. A mechanical coupling now exists between the brake disc 20 and the rotor shaft 25, which, when the vehicle is in motion, drives the rotor shaft 25 and allows braking force to be generated despite the power supply failure.

[0041] The actuator 30 is controlled by control signals from the control unit 11. Input signals, such as vehicle speed, can be taken into account in the control unit 11. This allows the coupling device 26 to be adjusted between the coupled and uncoupled positions depending on the vehicle speed. For example, it may be advantageous to allow the coupling device to move from the uncoupled to the coupled position only during automated parking or exiting maneuvers at speeds below a certain limit, such as 20 km / h. Above this speed limit, the actuator 30 is in a locked position in which the connecting shaft 29 is held firmly in the uncoupled position, even in the event of a power supply failure.

[0042] Optionally, the coupling device 26 can be equipped with a further adjustable shaft 34, which is adjustable via an additional, second actuator 33. The actuator 33, which can be electromagnetic, is also controlled by the control unit 11. Gears are mounted axially spaced on the shaft 34 and lie within the kinematic transmission path between the brake disc 20 and the rotor shaft 25. The shaft 34 is adjustable between two axial positions via the second actuator 33, in which different gears lie within the kinematic transmission path. In the first axial position, a gear mounted on the shaft 34 lies within the kinematic transmission path, whereas in the second axial position, two meshing gears lie within the kinematic transmission path.This allows the direction of rotation to be reversed depending on the axial position of the shaft 34, thus accommodating the different directions of rotation of the brake disc 20 during forward and reverse travel. The adjusting mechanism with the adjustable shaft 34, actuated by the second actuator 33, ensures that the same direction of rotation support is always transmitted to the rotor shaft 25 of the electric brake motor, regardless of whether the vehicle is traveling forward or backward. Therefore, it is possible to generate braking force in both forward and reverse directions.

[0043] In the event that the vehicle is moving forward on an incline but would roll backward in the event of a fault, the signal information, with the support of an incline sensor, can be used to ensure that the correct gear(s) are selected via the actuation of actuator 33. Accordingly, if the vehicle rolls backward on an incline, the direction of rotation in the transmission path is reversed by actuating actuator 33, and braking force can be generated.

Claims

[1] Electromechanical braking device for a vehicle, comprising an electric brake motor (13) which, to generate a braking force, moves a brake piston (16) in a wheel brake device (9) to brake a wheel of the vehicle towards a brake disc (20), characterized by , that the braking device comprises a coupling device (26) which is adjustable between a coupling position with a mechanical coupling of a wheel shaft of the wheel or the brake disc (20) with a rotor shaft (25) of the electric brake motor (13) and a disengagement position in which the mechanical coupling between wheel shaft or brake disc (20) and rotor shaft (25) is removed. [2] Brake device according to claim 1, characterized by , that an actuator (30, 33) of the coupling device (26) is de-energized in the coupling position and energized in the uncoupling position, wherein the actuator (30, 33) adjusts a coupling element. [3] Brake device according to claim 1 or 2, characterized by , that the coupling device (26) has as a coupling element a gear (27) adjustable between coupling position and uncoupling position, which in the coupling position meshes with a toothing (28) on the wheel shaft or brake disc (20). [4] Brake device according to claim 3, characterized by , that the gear (27) is arranged on a connecting shaft (29) and the connecting shaft (29) is axially adjustable along its longitudinal axis. [5] Braking device according to any one of claims 1 to 4, characterized by , that the coupling device (26) in the transmission path between the wheel shaft or the brake disc (20) and the rotor shaft (25) of the electric brake motor (13) comprises several gears (31, 32). [6] Braking device according to any one of claims 1 to 5, characterized by, that the coupling device (26) includes an actuator (30, 33) for adjusting the direction of rotational support on the rotor shaft (25). [7] Braking device according to any one of claims 1 to 6, characterized by , that an electric brake motor (13) is arranged on opposite wheels in the left and right side area of ​​the vehicle to generate a braking force in a wheel brake device (9) on the respective wheel, wherein each electric brake motor (13) is assigned a coupling device (26). [8] Brake device according to claim 7, characterized by , that the actuators (30, 33) in the two coupling devices (26) can be controlled independently of each other. [9] Brake device according to claim 7 or 8, characterized by that the actuators (30, 33) in the two coupling devices (26) can be controlled simultaneously. [10] Method for operating the brake device (24) according to one of claims 1 to 9, in which, in the event of a failure of the electrical voltage supply of the brake motor (13) during a driving maneuver, the coupling device (26) is brought into the coupling position with mechanical coupling of the brake disc (20) with the rotor shaft (25) of the electric brake motor (13). [11] Method according to claim 10, characterized by , that with the start of an automated parking maneuver and with a functioning power supply the electric brake motor (13) is controlled in such a way that a brake pad (17, 18) which is held on the brake piston (16) is brought into a position immediately in front of the brake disc (20). [12] Control unit for controlling the adjustable components of the electromechanical braking device according to any one of claims 1 to 9. [13] Parking brake for securing a vehicle at a standstill, comprising an electromechanical braking device according to any one of claims 1 to 9. [14] Braking system for a vehicle, comprising an electromechanical braking device according to one of claims 1 to 9 and a hydraulic vehicle brake (1) with at least one brake circuit (2, 3) for generating a braking force on at least one vehicle wheel, wherein the hydraulic brake pressure of the hydraulic vehicle brake (1) and the electric brake motor (13) of the electromechanical braking device act on the same brake piston (16) of the wheel brake device (9).

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