Motor vehicles – Steering gear – No mechanical connection between steering shaft and steering...
Reexamination Certificate
1997-08-11
2001-08-28
Hurley, Kevin (Department: 3619)
Motor vehicles
Steering gear
No mechanical connection between steering shaft and steering...
C180S405000, C180S006240, C701S043000
Reexamination Certificate
active
06279674
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to arrangements for steering a motor vehicle having at least two steerable wheels which includes steering equipment for setting the position of the steerable wheels as a function of a desired steering signal and equipment for producing a steering response of the motor vehicle in the event of a fault in the steering equipment and to a method for steering a motor vehicle in which the setting of the position of the wheels in order to produce a steering response is carried out by steering equipment as a function of a desired steering signal.
In electric steering systems for motor vehicles, the so-called steer-by-wire systems, as disclosed, for example, in U.S. Pat. No. 5,247,441, are safety-critical equipment. In order to satisfy the high safety requirements for such equipment, subassemblies, for example control equipment or actuators for setting the positions of the steerable wheels, are provided in a redundant and therefore very complicated manner. Particularly in the case of electric steering systems in which the wheels are steered independently of each other and without being connected to each other, it is difficult to implement the actuators in a redundant manner for space reasons. In addition, such redundancy is also technically difficult to realize so that redundant systems are not readily available.
U.S. Pat. No. 5,134,352 discloses a vehicle steering response control device for a motor vehicle which has anti-skid braking equipment. In this system, the control equipment responds to a signal which represents the steering condition of a turning vehicle to produce a different braking force applied to the wheels lying on the inside of the curve and on the outside of the curve with the result that a yawing moment is produced between the wheels lying on the inside and on the outside, in order to support the steering of the vehicle during a braking procedure.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide an arrangement and a method for steering a motor vehicle which overcome the disadvantages of the prior art.
Another object of the invention is to provide an arrangement and a method for steering a motor vehicle which satisfies the required safety standards and in which the use of redundant components is kept as small as possible.
These and other objects of the invention are attained by providing a braking control arrangement in which selectively different braking forces are applied to the wheels of the vehicle in response to signals representing a desired steering condition.
In accordance with the invention, therefore, braking equipment which is already present in the motor vehicle takes over the emergency function of the steering equipment thereby eliminating the necessity for redundant implementation of the actuators and control equipment for the steering system.
The equipment which takes over the emergency steering of the vehicle, is, according to the invention, braking equipment which is already present in the vehicle and which, as a function of the desired steering signal, selectively applies different braking forces to the wheels of the motor vehicle and thus, in the event of a fault in the steering equipment during a braking procedure, produces a steering response for the motor vehicle until the vehicle stops.
In order to detect the occurrence of a fault in the steering equipment, which may occur, for example, as a result of failure of individual components, provision is made for fault detection equipment which compares a desired steering signal with the position of the steerable wheels. Occurrence of a fault in the steering equipment is detected as a defined deviation of the position of at least one of the steerable wheels from the desired steering signal. The magnitude of the defined deviation is preferably dependent on the driving speed of the motor vehicle.
If an occurrence of a fault in the steering equipment is detected by the fault detection equipment, the system switches off the steering equipment. At the same time, it activates the braking equipment by applying control signals in such a way that braking forces are selectively applied to the wheels as a function of the desired steering signal to produce the steering reaction which is required by the steering equipment operated by the vehicle driver or by equipment provided for automatic guidance of the motor vehicle.
In order to be able to control the application of selective braking forces to the wheels, the instantaneous braking forces at the wheels are detected and are supplied to the braking control equipment as an actual braking parameter. For hydraulic braking equipment the braking pressures present in brake cylinders for the wheels are advantageously used as a measure of the braking forces being applied. As an alternative, the wheel speeds may be detected, from which the deceleration of each of the wheels is determined. The wheel-speed sensors which are necessary for this procedure are, for the most part, already present in motor vehicles.
The advantage of the invention is that, by using the braking equipment which is present in the vehicle to provide the emergency function of the steering equipment an increase in availability and in safety is achieved which cannot be achieved by steering equipment based on conventional redundant systems.
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Binfet-Kull Maria
Lissel Ernst
Baker & Botts LLP
Hurley Kevin
Volkswagen AG
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