Motor vehicles – Steering gear – With alternate emergency power means
Reexamination Certificate
1998-09-09
2001-04-03
DePumpo, Daniel G. (Department: 3611)
Motor vehicles
Steering gear
With alternate emergency power means
C180S405000, C180S403000, C180S402000
Reexamination Certificate
active
06209677
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a steering system for non-tracked motor vehicles, having a steering handle, such as a manual steering wheel, operated by the driver, a steering adjusting drive for the steering adjustment of steerable vehicle wheels, a steering-angle desired-value generator operable by the steering handle, and a steering-angle actual-value generator operable by means of the steerable vehicle wheels. An automatic control system controls the steering adjusting drive as a function of a comparison of the desired and actual values of the steering angle and continuously monitors itself as well as a sensor system interacting with it with respect to a malfunctioning. A mechanical or hydraulic forced coupling is arranged between the steering handle and the steerable vehicle wheels, and is opened up or remains open (inoperative normal condition) when the automatic control system operates correctly and is automatically closed when the automatic control system is defective (operative special condition).
Steering systems of this type, which operate according to the “steer-by-wire” concept, are basically known and are developed for future motor vehicles. These systems offer the basic advantage that they are suitable at least with respect to the automatic control system as well as the associated sensor system without any constructive changes for many different vehicles. As a result of a corresponding programming, on one hand, virtually any transmission ratio can be implemented between the adjusting stroke of the steering handle and the steering angle change of the steered vehicle wheels. Furthermore, the automatic control system can be connected with additional sensors in order to be able to automatically take into account parameters to be defined, such as cross wind influences, or control deviations with respect thereto.
In order to be able to ensure the required amount of safety in the event of the occurrence of a defect in the automatic control system or in the event of a failure of signals which are to be analyzed by the automatic control system, an operating mode can be automatically switched on for an abnormal operation or an emergency operation. In this operating mode, a forced coupling is provided between the steering handle and the steered vehicle wheels so that the steering system operates in principle in the manner of a conventional steering system. The mechanical steering column, which is customary in conventional steering systems, can be replaced, however, by other mechanical systems or by hydraulic systems, particularly hydrostatic systems.
SUMMARY OF THE INVENTION
An object of the present invention is to provide, in a steering system of the steer-by-wire type, measures which are advantageous with respect to the operational reliability of the system.
According to the invention, this object has been achieved in that the forced coupling (which was switched to be in effect) has a defined elasticity. When the forced coupling is in effect, forces and torques, which can be transmitted between the steering handle and the steered vehicle wheels, cause a relative adjustment between the desired-value generator for the steering angle and the actual-value generator for the steering angle. In the special condition (i.e., forced coupling was switched to be in effect), when the residual function of the automatic control system and the sensor system is sufficient, the steering system operates as a power steering system. That is, the automatic control system controls the steering adjusting drive analogously to the amount and the direction of the relative adjustment which can be detected from the signals of the desired-value generator for the steering angle and the actual-value generator for the steering angle, for generating a power steering force with a direction which reduces the transmitted forces and torques.
The invention is based on the recognition of the advantages of reducing, when the forced coupling is in effect, to the extent possible, the manual forces on the steering handle to be applied by the driver and, for this purpose, operating the steering system analogously to a conventional power steering system. In this context, the automatic control system is to control the steering adjusting drive for generating a power steering force reducing the manual forces.
The present invention utilizes the fact that the forced coupling, which was switched on in the event of an emergency between the steering handle and the steered vehicle wheels, may have a corresponding elastic flexibility because of elastic flexibilities of the coupling elements or coupling media. As a result, between the end or input on the steering handle side and the end or output of the forced coupling assigned to the steered vehicle wheels, during the transmission of forces and torques, more or less large relative movements occur which result in corresponding relative adjustments between the desired-value generator for the steering angle and the actual-value generator for the steering angle. According to the invention, in the special condition of the steering system, the above-mentioned desired-value and actual-value generators are now used for detecting these relative adjustments and thus for detecting the transmitted forces and torques.
Thus, while the desired-value and actual-value generators are used in the normal condition of the steering system for determining the desired-value actual-value deviation of the steering angle, in the special condition, they are also utilized for determining the forces and torques transmitted between the steering handle and the steered vehicle wheels. Because of this double function of the desired-value and the actual-value generator, the comfort of a conventional power steering system can be achieved without additional sensors in the special operation.
It is only necessary to configure the automatic control system such that it detects the relative positions of the desired-value and actual-value generators which exist immediately during the switching-on of the forced coupling. Since immediately at the point in time of the switching-on of the forced-coupling, no forces or torques are yet transmitted between the steered vehicle wheels and the steering handle, the above-mentioned relative position is characteristic of a strain-free forced coupling.
A special advantage of the invention resides in the fact that the technical construction of the forced coupling can be arbitrary. The reason is that it is of minor significance for implementing the invention whether the forced coupling takes place by mechanical elements or hydraulically. In the former, the elastic deformability of the mechanical elements is utilized. In the latter, the elastic flexibility of the walls of the hydraulic lines as well as the compressibility of the hydraulic medium are utilized.
REFERENCES:
patent: 5020618 (1991-06-01), Nagao
patent: 5050696 (1991-09-01), McGovern et al .
patent: 5056311 (1991-10-01), Tischer
patent: 5263321 (1993-11-01), Thomsen et al.
patent: 5862878 (1999-01-01), Bohner et al.
patent: 5893427 (1999-04-01), Bohner et al.
patent: 5926676 (1998-10-01), Ko
patent: 6047788 (2000-04-01), Bohner et al.
Bohner Hubert
Moser Martin
Schneckenburger Reinhold
Daimler-Chrysler AG
DePumpo Daniel G.
Evenson, McKeown, Edwards & Lenahan P.L.L.C.
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