Method for securing a vehicle at a standstill

Abstract

A vehicle includes an electromechanical braking device having an electric brake motor, at least one wheel, and a steering actuator that is operable to adjust the at least one wheel. A method for securing the vehicle at a standstill includes applying brake force via the brake motor and actuating the steering actuator to adjust the at least one wheel.

Claims

1. A method of securing a vehicle at a standstill, the vehicle including an electromechanical braking device with an electric brake motor that moves a brake piston against a brake disk to generate a brake application force, the method comprising: actuating the electric brake motor to generate the brake application force; and actuating a steering actuator to adjust a position of at least one vehicle wheel such that a lateral guiding force acts on the at least one vehicle wheel as an additional braking force, wherein the steering actuator is configured to adjust a steering angle of the at least one vehicle wheel, and wherein the steering actuator includes an electric servomotor.

2. The method of claim 1, wherein the electric brake motor and the steering actuator are each configured to act upon a same vehicle wheel.

3. The method of claim 1, further comprising: adjusting a tracking of the at least one vehicle wheel via the steering actuator.

4. The method of claim 1, the method comprising: adjusting a position of two opposite-lying vehicle wheels on a same vehicle axle via a common steering actuator.

5. The method of claim 1, further comprising: adjusting the steering angle of the at least one vehicle wheel such that the at least one vehicle wheel assumes an angle with respect to a down-hill slope force.

6. The method of claim 1, wherein the steering actuator and the electric brake motor are actuated chronologically one after the other.

7. The method of claim 1, wherein the steering actuator and the electric brake motor are actuated simultaneously.

8. A vehicle, comprising: a braking system that includes an electromechanical braking device having an electric brake motor; a steering actuator configured to adjust a positon of at least one vehicle wheel; and at least one device configured to at least one of regulate and control the braking system and the steering actuator, wherein actuation of the steering actuator enables adjustment of a toe angle of two opposite-lying vehicle wheels on a same vehicle axle, and further comprising: a respective steering track rod on each of a left-hand wheel and right-hand vehicle wheel of a vehicle axle, wherein the steering actuator is arranged between the steering track rods and is operable to adjust the steering track rods.

9. A method of securing a vehicle at a standstill, the vehicle including an electromechanical braking device with an electric brake motor that moves a brake piston against a brake disk to generate a brake application force, the method comprising: actuating the electric brake motor to generate the brake application force; and actuating a steering actuator to adjust a position of at least one vehicle wheel such that a lateral guiding force acts on the at least one vehicle wheel as an additional braking force, wherein the steering actuator and the electric brake motor are actuated chronologically one after the other.

10. A method of securing a vehicle at a standstill, the vehicle including an electromechanical parking braking device with an electric brake motor that moves a brake piston against a brake disk to generate a brake application force, the method comprising: actuating the electric brake motor while the vehicle is at a standstill to generate the brake application force; and actuating a steering actuator while the vehicle is at a standstill to adjust a position of at least one vehicle wheel such that a lateral guiding force acts on the at least one vehicle wheel as an additional braking force.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further advantages and expedient embodiments are evident in the further claims, the description of the figures and the drawings. In the drawings:

(2) FIG. 1 illustrates a section through an electromechanical braking device that is used as a parking brake in a vehicle and in which it is possible to generate the brake application force by way of an electric brake motor,

(3) FIG. 2 illustrates a chart with the time-dependent curve of the motor voltage, the motor current, the motor rotational speed and the brake application force during the brake application procedure of the electric brake motor,

(4) FIG. 3 illustrates a plan view of two wheels of a vehicle axle having a tracking adjusting device, illustrated in the starting position,

(5) FIG. 4 illustrates the wheels of the vehicle axle in accordance with FIG. 3 having an adjusted toe angle,

(6) FIG. 5, 6 illustrate one of the illustrations that correspond to FIGS. 3 and 4 of two vehicle wheels having a tracking adjusting device in a further embodiment,

(7) FIG. 7, 8 illustrate two vehicle wheels having a tracking adjusting device in a yet further embodiment.

(8) In the figures, identical components are provided with identical reference numerals.

DETAILED DESCRIPTION

(9) FIG. 1 illustrates an electromechanical parking brake 1 for securing a vehicle at a standstill. The parking brake 1 comprises a brake caliper 2 having a set of jaws 9 that grip over a brake disc 10. As an adjusting member, the parking brake 1 comprises a DC electric motor as a brake motor 3 whose rotor shaft drives a spindle 4 in a rotating manner and a spindle nut 5 is mounted on said spindle in such a manner that it can rotate. In the case of a rotation of the spindle 4, the spindle nut 5 is adjusted in an axial manner. The spindle nut 5 moves within a brake piston 6 that is the carrier for a brake pad 7 that is pushed by the brake piston 6 against the brake disc 10. A further brake pad 8 is located on the opposite-lying side of the brake disc 10, said brake pad being held on the set of jaws 9 in such a manner that it can not move.

(10) In the case of a rotational movement of the spindle 4, the spindle nut 5 can move within the brake piston 6 axially forwards in the direction of the brake disc 10 or in the case of a rotational movement of the spindle 4 in the opposite direction the spindle 4 can move axially towards the rear until reaching a stop 11. The spindle nut 5 influences the inner end face of the brake piston 6 so as to generate a brake application force, as a result of which the brake piston 6 that is mounted in the parking brake 1 can be displaced axially and is pressed with the brake pad 7 against the front end surface of the brake disc 10.

(11) The brake motor 3 is controlled by a regulating or controlling device 12 that is part of the parking brake system having the parking brake 1. The regulating or controlling device 12 provides as an output a supply voltage with which the electric brake motor 3 is influenced. A motor voltage U.sub.Mot is set in the brake motor.

(12) The parking brake can be supported if required by a hydraulic vehicle brake so that the brake application force is combined from an electromechanical portion and a hydraulic portion. In the case of the hydraulic support, the rear side of the brake piston 6 that faces the brake motor is influenced with hydraulic fluid that is under pressure.

(13) FIG. 2 illustrates a chart with the current curve I.sub.A, the motor voltage U.sub.Mot and the curve of the motor angular velocity w of the electric brake motor in dependence upon time for a brake application procedure. Furthermore, the electromechanical brake application force F.sub.KI is plotted in FIG. 2, said brake application force being generated by the electric brake motor, and also the path s that is covered during the brake application procedure by the brake motor or by an adjusting member that is influenced by the brake motor is also plotted.

(14) The brake application procedure starts at the point in time t1, the point at which an electrical voltage is applied and the brake motor is supplied with current in the case of a closed current circuit. The start phase (phase I) continues from the point in time t1 until the point in time t2. At the point in time t2, the motor voltage U.sub.Mot and the motor angle speed achieves its maximum. The phase between t2 and t3 represents the idle running phase (phase II) in which the current I.sub.A moves to a minimum level. After that point, the point in time t3, the buildup of force phase (phase III) takes place until the point in time t4 at which the brake pads lie on the brake disc and are pressed with increasing brake application force F.sub.KI against the brake disc. At the point in time t4, the electric brake motor is disconnected by means of opening the current circuit so that in the further curve, angle speed of the brake motor drops to zero.

(15) The phase of the build-up of force at the point in time t3 coincides with the point at which the force increases. The build-up of force or the curve of the brake application force F.sub.KI can be determined by way of example with reference to the curve of the current I.sub.A of the brake motor that fundamentally comprises the same curve as the electromechanical braking force F.sub.KI. Starting from the low level during the idle running phase between t2 and t3, the current curve I.sub.A increases sharply at the beginning of the point in time t3. This increase of the current can be detected and can be drawn upon so as to determine the point at which the force increases. Fundamentally, the curve of the build-up of force can however also be determined from the voltage curve or rotational speed curve or from an arbitrary combination of the signals: current, voltage and rotational speed.

(16) The electromechanical braking device 1 is actuated as a parking brake so as to secure the vehicle at a standstill. In addition, a braking force is generated by virtue of the fact that the toe angle is adjusted at two wheels of a common axle, as a result of which the lateral guidance force is increased at each wheel, which leads to the desired increase in the braking force at each vehicle wheel.

(17) FIGS. 3 to 8 illustrate various exemplary embodiments for a tracking adjusting device having a steering actuator 20.

(18) In the first exemplary embodiment in accordance with the FIGS. 3 and 4, the tracking adjusting device comprises two steering track rods 18 and 19 that are embodied as threaded rods and engage in one another with an inner and an outer thread, wherein it is possible by virtue of rotating the threaded rods to alter the spacing between the engagement points of the threaded rods 18, 19 on the opposite lying wheel suspensions 15, 16 of the vehicle wheels 13, 14. Furthermore, a steering actuator 20 that by way of example is embodied as an electric motor is associated with the tracking adjusting device and the screwing movement of the threaded rods 18, 19 is achieved by way of said steering actuator. Furthermore, the wheel suspensions 15, 16 are connected to one another by way of a transverse carrier 17 that is arranged spaced with respect to the threaded rods 18, 19.

(19) In the case of actuating the steering actuator 20, the threaded rods 18, 19 are adjusted into the position that is illustrated in FIG. 4 starting from the starting position in accordance with FIG. 3 in which no toe angle prevails at the vehicle wheels 13, 14. The threaded rods 18, 19 are rotated into one another so that the spacing between the wheel suspensions 15 and 16 is decreased at the engagement points of the threaded rods 18, 19. Furthermore, in each case a toe angle is set at the vehicle wheels 13 and 14 in relation to the longitudinal axis of the vehicle. By means of the inclined position of the vehicle wheels 13, 14 that assume a V-position, said wheels build-up a lateral guidance force when the vehicle is at a standstill or is travelling at low speeds and an additional braking force on the vehicle wheels results from said lateral guiding force.

(20) The recorded toe angle relates to the central starting position of the vehicle wheels 13, 14 without a steering angle. A toe-in setting is also possible in which a toe angle is already applied to the vehicle wheels 13, 14 in the neutral starting position. In addition to the toe-in angle, a desired toe angle can also be applied by way of actuating the steering actuator 20.

(21) A further exemplary embodiment is illustrated in the FIGS. 5 and 6 in which the tracking adjusting device comprises two steering track rods 18 and 19 so as to set the toe angle a at the vehicle wheels 13 and 14, said steering track rods being coupled by way of a steering actuator 20. The steering actuator 20 comprises a threaded nut between the steering track rods 18 and 19 that are embodied as threaded rods and also an electric motor for generating a rotational movement of the threaded nut 20 as a result of which the desired spacing alteration is caused between the engagement points of the steering track rods 18 and 19 at the wheel suspensions 15 or 16 of each vehicle wheel 13, 14.

(22) In the exemplary embodiment in accordance with FIGS. 7 and 8, the steering track rods 18 and 19 in each case are embodied as steering racks and a gear 20 is arranged between said steering racks, said gear being driven by a steering actuator. The relative position between the steering track rods 18 and 19 subsequently changes, as a result of which the spacing between the engagement points of the steering track rods 18, 19 are altered in a desired manner at the wheel suspensions 15, 16.