Motor vehicles – Compensating devices
Patent
1991-05-02
1993-05-11
Focarino, Margaret A.
Motor vehicles
Compensating devices
192 21, 192 431, B62D 504
Patent
active
052093158
DESCRIPTION:
BRIEF SUMMARY
STATE OF THE ART
The invention is directed to an electromotive power steering. Power steering for a motor vehicle is known in many forms; the additional power, usually produced electromotively or with the aid of a pressure means, is made proportional to the angle of twist of a torsion bar in the steering column, whereby a power-assisting effect dependent on speed is also a possibility.
Electromotive power steering can for example be used with advantage as a steering aid for motor vehicles and similar, specifically in the range of speeds during parking, i.e. as parking power steering, and is usually not required at higher speeds. Such electromotive power steering is therefore suitable particularly for smaller motor vehicles and passenger cars.
In a known electromotive steering aid (SAE-Paper 851 639) a torsion sensor detects the relative twist of the steering column before the steering gear and correspondingly actuates an electric motor with varying direction of rotation which then for its part supports through a suitable reduction gear the exertion of a moment effected by the driver about the steering column. Such electromotive steering aid is also advantageous because by the appropriate actuation of the electric servo-motor certain properties of the steering aid can be obtained without difficulty, such as for example an amplification of the supplementary power delivered by the servo-motor as the speed of the vehicle is being reduced, whereby other control algorithms can also be determined. Advantages further result in respect of the energy required for the power steering as well as in the sphere of handling properties of the vehicle. If such an electromotive steering aid is used merely as a power steering for parking, it is of course necessary to provide separating means, for example a separating coupling, which uncouple the gearing engaged by the servo-motor from the steering column, in order that steering wheel movements may be made possible at all, or not be braked too strongly, when the servo-motor is not actuated.
If the moment exerted by the driver about the steering column is for example measured by a torsion bar in the steering column, the torsion bar must, when the corresponding electromotive power steering serves merely as an aid to parking, i.e. is actuated only below a speed limit of for instance 5 km/h, be blocked at higher speeds (normal driving) or its torsion effect must be substantially eliminated, since otherwise steering loses in precision during normal driving i.e. it would in a certain sense be too soft. Such blockage of the torsion bar can for example be effected by auxiliary coupling, click-and-pawl arrangements or similar, which is awkward and expensive.
The invention has the basic objective of developing an electromotive power steering specifically as an aid to parking, in such a manner that the exertion of the supplementary force ensues without difficulties in dependence on the moment exerted about the steering column by the driver from time to time, and that an influence on the behaviour of the steering, say in the direction of the steering being too soft, is eliminated when the parking aid is uncoupled or switched off.
ADVANTAGES OF THE INVENTION
The electromotive power steering in accordance with the invention has the advantage that clutch rings constructed as ring gears transfer by respectively selective friction lock the supplementary servo-force exerted by the electric motor to the steering column and from this to the steering gear connected with it, whereby the clutch engagement as well as the respective direction of rotation are determined from the moment exerted by the driver about the steering column by turning the steering wheel. It is at the same time further advantageous that the electric motor exerting the supplementary force may be of any desired construction since its own direction of rotation does not have to be reversed for the two directions of turning of the steering wheel. To that extent the actuation of the electric motor is also not critical; it can for
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patent: 3319750 (1967-05-01), Olson
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patent: 4588060 (1986-05-01), Norton
patent: 4598787 (1986-07-01), Druchas
patent: 5031714 (1991-07-01), Nishimori et al.
Linder Ernst
Rembold Helmut
Schlagmueller Walter
Boehler Anne Marie
Focarino Margaret A.
Greigg Edwin E.
Greigg Ronald E.
Robert & Bosch GmbH
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