DE102009008843A1 - Method for stabilizing passenger car during drop in abrupt steering moment, involves taking back support moment of electrical or hydraulic servo device while recognizing abrupt steering moment drop - Google Patents

Abstract

The method involves taking back a support moment of an electrical/hydraulic servo device (5) while recognizing an abrupt steering moment drop. Brake interference for stabilization of a vehicle is determined during separation of the vehicle by an electronic stability program. An auxiliary moment is produced during separation of the vehicle by modifying the support moment produced by the servo device, where the auxiliary moment presets a moving direction of a steering control (2) i.e. steering wheel, for stabilization of the vehicle. An independent claim is also included for a servo-steering mechanism of a motor vehicle.

Description

The The invention relates to a method for stabilizing a Motor vehicle at an abrupt steering torque drop, the motor vehicle with a freely controllable electric or hydraulic servo device and an electronic stability program which is in a stable critical driving situation by an individual Radbremsenansteuerung a stabilization of the vehicle allows. Furthermore, the invention relates on an appropriately configured power steering for a Motor vehicle.

electronic Stability programs are based on the idea by a specific operation of individual wheel brakes stability critical Avoid driving situations and so, for example, a spin to prevent the vehicle in the border area. This will be continuous a driver-side steering command with the current driving condition adjusted. The driver-side steering command, for example, by means of a steering angle sensor be detected while the current driving condition, for example based on wheel speed sensors, which are for an anti-lock braking system be required, and a yaw rate sensor can be determined can. Is a significant deviation between steering command and driving condition determined, the electronic stability program initiates a wheel-specific brake intervention.

While electronic stability programs of the first generation only on a braking intervention to stabilize the vehicle In addition, in newer systems, an automatic Steering provided. By a steering intervention can a vehicle when braking on inhomogeneous road (μ-split) or oversteer be stabilized very efficiently. However, an active steering intervention to be able to make the vehicle must be an actively controllable Have steering system.

In overlay steering can be by means of a suitable servo device from the driver's steering command independent additional steering angle set at the vehicle wheels, as by an example integrated in the steering column planetary gear an additional degree of freedom with regard to the coupling of the steering handle with the steering gear is available.

Even with freely controllable electric or hydraulic power steering additional stabilization of the vehicle by steering intervention is possible. However, the steering angle of the front wheels can not be adjusted as in a superposition steering regardless of the driver's steering angle specification. Rather, the driver is given a steering recommendation early in power steering. For this purpose, an additional torque is generated via the servo device, which is noticeable on the steering handle and determines the direction in which the steering handle to stabilize the vehicle is to move. The driver can then perform the steering correction required for stabilization itself. The additional torque of the steering recommendation is always chosen so that the driver can hold the steering handle against the additional torque and possibly override the steering recommendation, so that it always retains full control of the vehicle. Such steering is for example in the DE 101 41 425 B4 described.

In front In this background, the invention of the following problem goes off: with a sudden loss of static friction during Driving through a curve decreases the manual steering torque abruptly. For the driver is thereby the danger, the steering handle in Direction of the curve inside to tear and so the vehicle on recovery of liability or earlier in skidding bring to. Common causes of such Static friction loss are changes in the road surface, Pollution and / or weather-related roadway inhomogeneities or road bumps.

in principle It is possible to skid the vehicle by one targeted wheel brake intervention counter. It is also possible the driver via an additional torque a haptic steering recommendation to convey, so that this in conjunction with the electronic Stability program can stabilize the vehicle.

The However, the invention starts elsewhere and strikes according to claim 1, upon detection of a abrupt decrement of the steering torque the support torque of Servo device to take back. This is already happening a tearing of the steering wheel prevented, and thus the Danger that the vehicle at all in a stability-critical Situation gets reduced. Due to the reduced support torque increases the required manual force in the direction of a potential tearing of the steering handle.

Of the This gives the driver feedback on the occurring static friction loss. On the other hand, a possible Cracking at least strongly subdued. The support moment can also be reduced such that an adjustment of the steering handle is substantially completely compensated.

If, despite everything, a stability-critical driving situation, the vehicle can in the conventional manner by means of electronic stabili and, where appropriate, stabilized by additional specification of a dynamic steering recommendation.

The inventive solution uses exclusively on the vehicle already available parameters, so that this without much effort, for example, in an electronic Stability program or a steering controller can be implemented. It covers a gap between the functions of a dynamic steering recommendation and an electronic steering Stability program low cost and increased the driving safety.

The The above object is further achieved by a power steering system according to claim 7 solved.

advantageous Embodiments of the invention are in further claims specified.

following the invention with reference to an embodiment shown in the drawing explained in more detail. The drawing shows in:

1 a schematic representation of an embodiment of a power steering according to the invention, and in

2 a schematic view of the reduction of the assist torque at an abrupt steering torque drop.

That in the 1 and 2 illustrated embodiment relates to a power steering of a passenger vehicle, which is explained in more detail by way of example below with reference to an electromechanical steering. The steering 1 includes a steering handle 2 , with the applied by the driver steering or hand torque M _H via a steering column 3 and a steering gear 4 is brought to action on the vehicle wheels. Furthermore, a is a servo device 5 provided in the form of an electric motor, via which a support torque M _{U is} generated in response to the steering or manual torque M _H to assist the driver while steering. Both moments come into effect on the steering. Since the support is continuous and steady, this is at the steering handle 2 not felt. The steering handle 2 is in the present case designed as a steering wheel. However, other input means may be provided for initiating a driver-side steering command.

The manual torque M _H is provided with a torque sensor 6 detected, preferably on the steering column 3 is appropriate. By means of a steering control unit 7 filed allocation rule, which in the following as a support characteristic 8th is designated, to the respective manual torque M _{H is} a control signal s _U for the servo device 6 generated. The extent of the steering assistance can be specified via the support characteristic curve, which may still depend on the vehicle speed v and other vehicle parameters.

In the control unit 7 The steering is a non-illustrated control circuit implemented with which the driver specified steering torque with respect to the power assistance and the steering angle are controlled. For this purpose, suitable angle sensors z. B. on the steering column 3 and / or be provided on the electric motor whose signals to the control unit 7 be transmitted.

Furthermore, a system for generating a dynamic steering recommendation is provided which, in a stability-critical driving situation, conveys to the driver a steering advice for stabilizing the vehicle at the steering handle. The steering recommendation or via the servo device 5 at the steering handle 2 According added effect to the effect is designed so that this can be overruled by the driver at any time. With the steering recommendation, the driver should only be given a tactile indication of a behavior that is correct in a stability-critical driving situation.

A signal S _E representing the steering recommendation is determined on the basis of detected vehicle parameters. The generation of this signal can be in the steering controller 7 or in an external device such as a brake control unit 9 or another computing device. For recognizing a stability-critical driving situation, the recognition and fail-safe algorithms of the electronic stability program can be used, which among other things omits vehicle data such as the steering angle δ, the yaw rate ω, the wheel speeds n _i , the vehicle lateral acceleration a _y and the vehicle speed v. The signal s _E representing the steering recommendation is used to determine the actuating signal s _U for the servo device 5 also included, with which a support torque M _{U is} generated as a function of the torque applied by the driver M _H. Will about the servo device 5 the steering 1 an additional torque generated as steering recommendation, so this torque offset on the steering handle 2 noticeable.

The above-explained steering 1 also has a facility 10 for stabilizing the motor vehicle in the event of an abrupt drop in steering torque, as occurs in the event of a sudden loss of static friction during the passage through a curve. Without additional measures there is a risk that the driver, if this is not fast enough re acts, the steering handle 2 causes the vehicle to spin. In order to reduce the risk of such a stability-critical situation and to avoid an early intervention of the electronic stability program as possible, it is provided to detect a static friction loss based on characteristic driving condition parameters and by a temporary reduction of the assist torque of the servo device 5 a tearing of the steering handle 2 to prevent, ie sudden movements of the steering handle 2 to attenuate or substantially completely compensate.

The stabilizer 10 includes detection means 11 which determine an abrupt drop in the steering torque on the basis of vehicle parameters already present on the vehicle. For this purpose, for example, the steering torque, the lateral acceleration, the steering angle and the steering angle acceleration can be evaluated. However, it is also conceivable to access other parameters which are characteristic of a static friction drop during the passage through a curve.

The stabilizer 10 is preferably in the steering control unit 7 implemented, but can also elsewhere, for example in the brake control unit 8th or another computing device. Furthermore, it is possible the function of the stabilization device 10 Software technology to integrate into the electronic stability program or in the provision of the control signal for the dynamic steering recommendation.

For example, it can then be concluded that there is an abrupt drop in the steering torque if, as the steering torque M _H and decreasing lateral acceleration a _y decrease, the steering angle δ and the steering angular acceleration ∂ ² δ / ∂t ₂ increase and, at the same time, the steering angle δ is not equal to zero.

If such a condition is detected, the servo device becomes 5 through the steering controller 7 controlled so that that of the servo device 5 as a function of the steering command provided support torque M _{U is} reduced.

For this purpose, for example, depending on the above-mentioned parameters in a signal generation unit 12 the stabilization device 10 a control signal s _{S are} generated, which corresponds to the actuating signal s _U for the servo device 5 is switched on. The control signal s _S can also be switched on the input side, that is to say before the calculation of the actuating signal s _U. Furthermore, it is possible, by means of the control signal s _S , to temporarily change the calculation rules for determining the actuating signal s _U from the signal S _H representing the manual torque M _H , in order to reduce the assist torque M _U.

The The invention has been described above with reference to an embodiment explained in more detail. However, it is not limited to but includes all defined by the claims Configurations. In particular, the principle explained above also be used with hydraulic power steering systems.

1

steering

2

Steering handle (eg steering wheel)

3

steering column

4

steering gear

5

servo (eg electric motor)

6

Steering torque sensor (Manual torque sensor)

7

Steering control unit

8th

Support characteristic

9

Brake control unit

10

stabilizing device

11

recognition means

12

Signal generation unit

a _y

lateral acceleration

_i

wheel speed

s _E

signal the steering recommendation

S _H

Signal of manual torque M _H

s _S

control signal

s _U

actuating signal

v

driving speed

M _H

driver's side manual torque

M _U

assist torque

δ

steering angle

ω

yaw rate

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 10141425 B4 [0005]

Claims (12)

Method for stabilizing a motor vehicle in the event of an abrupt drop in the steering torque, wherein the motor vehicle is provided with a freely controllable electric or hydraulic servo device ( 5 ) and an electronic stability program, which is suitable for effecting stabilization of the vehicle by an individual wheel brake control system, characterized in that the assistance torque of the servo device is withdrawn when an abrupt steering torque drop is detected. Method for stabilizing a motor vehicle according to claim 1, characterized in that an abrupt Loss of steering torque is closed when with decreasing steering torque and decreasing lateral acceleration, the steering angle and the steering angular acceleration increase and the steering angle is not equal to zero. Method for stabilizing a motor vehicle according to claim 1 or 2, characterized in that the support torque is withdrawn so far that an adjustment of a steering handle ( 2 ) is attenuated to the driver input of a steering command. Method for stabilizing a motor vehicle according to claim 1 or 2, characterized in that the support torque is withdrawn so far that an adjustment of a steering handle ( 2 ) is compensated for the driver input of a steering command. Method for stabilizing a motor vehicle according to one of claims 1 to 4, characterized that when the vehicle breaks out, the electronic stability program causes a wheel brake intervention to stabilize the vehicle. Method for stabilizing a motor vehicle according to one of claims 1 to 5, characterized that at a breaking out of the vehicle by a modification of the servo torque generated by the servo device an additional torque is generated, the steering handle as a dynamic steering recommendation is tactile and sets the direction in which the steering handle to stabilize the vehicle to move. A power steering system for a motor vehicle equipped with an electronic stability program, comprising: a steering handle (10); 2 ) for initiating a driver-side steering command, a steering gear ( 4 ) for the steering operation of the vehicle wheels, with the steering handle ( 2 ) is mechanically coupled, a freely controllable hydraulic or electrical servo device ( 5 ) for introducing an assist torque into the steering, and a steering control device ( 7 ), which in dependence on the driver-side steering command, the servo device ( 5 ) for generating an assist torque, characterized in that a stabilization device ( 10 ) is provided, which detects an abrupt steering torque drop based on detected in connection with the electronic stability program vehicle parameters and in such a case, the servo device controls such that the latter provided by this depending on the steering command assist torque is reduced. Power steering system according to claim 7, characterized in that the stabilization device ( 10 ) is configured such that it is concluded that there is an abrupt drop in steering torque when, as the steering torque decreases and the lateral acceleration decreases, the steering angle and the steering angular acceleration increase and the steering angle is not equal to zero. Power steering system according to claim 7 or 8, characterized in that the stabilization device ( 10 ) is configured such that the assist torque is decreased so far that an adjustment of a steering handle for driver input of a steering command is attenuated. Power steering system according to claim 7 or 8, characterized in that the stabilization device ( 10 ) is configured such that the assist torque is taken back so far that an adjustment of a steering handle for the driver input of a steering command is compensated. Power steering according to one of claims 7 to 10, characterized in that at a breaking out of the vehicle the electronic stability program a wheel brake intervention to stabilize the vehicle causes. Power steering system according to one of claims 7 to 11, characterized in that an additional torque is generated at a breaking of the vehicle by a modification of the assisting torque generated by the servo device, which at the steering handle ( 2 ) is perceived as a dynamic steering recommendation and specifies the direction in which the steering handle ( 2 ) to stabilize the vehicle to move.