Motor vehicles – Steering gear – With electric power assist
Reexamination Certificate
1999-12-08
2001-08-14
Johnson, Brian L. (Department: 3618)
Motor vehicles
Steering gear
With electric power assist
C180S444000, C074S3880PS
Reexamination Certificate
active
06273211
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to an electronic power-steering gear, in particular for motor vehicles.
DESCRIPTION OF THE PRIOR ART
WO 98/12097 A1 discloses an electric power-steering gear, in particular for motor vehicles, which has been used to form the generic term of the present invention.
In this known power-steering gear, an electric motor drives a harmonic drive which is arranged coaxially with respect to the steering shaft, the stator of the electric motor and the stator of the harmonic drive being secured in the motor vehicle, and the steering shaft of the input element forming the input element and at the same time the output element of the harmonic drive which passes on the amplified steering movement to a corresponding steering gear.
The known electric power-steering gear has the disadvantage that the stator of the electric motor has to be fixed in position in the vehicle and a controllable link or locking device, which may have, for example, the form of an electromagnetically controllable clutch, has to be provided in the vehicle in order to fix the stator of the harmonic drive in position.
Furthermore, the known electric power-steering gear has the further disadvantage that it makes a considerable radial installation space necessary in the area of the steering shaft of a motor vehicle owing to the design of the electric motor as a disk-type rotor motor and also of the harmonic drive as a disk-type gear mechanism.
SUMMARY OF THE INVENTION
The object of the invention is to improve an electric power-steering gear, in particular for motor vehicles, of the type described herein, in such a way that, on the one hand, it requires less radial installation space and, in addition, does not need the stator of the electric motor to be secure in the vehicle or require a controllable clutch arrangement for securing the stator of the harmonic drive.
This object is achieved according to the invention in that an electric power-steering gear, in particular for vehicles, has the features specified herein.
By virtue of the fact that the stator of the electric motor is arranged fixed in terms of rotation within the elastically deformable, externally toothed, sleeve-shaped flexible rotor of the harmonic drive which is permanently connected to the steering shaft and is connected fixed in terms of rotation to the steering element, and the fact that power is supplied to the electric motor via slip rings or the like, for example helical cables, it is possible to dispense with securing the stator of the electric motor in the vehicle, which is necessary in the known arrangement, and with the controlled clutch for securing the stator of the harmonic drive, as a result of which the installation of the electric power-steering gear is made significantly easier.
An alternative embodiment of an electric power-steering gear is also described herein, in which the functions of the stator and the output element of the harmonic drive have been interchanged.
Further details of the invention are explained in the further claims.
REFERENCES:
patent: 4770612 (1988-09-01), Teubler
patent: 4819975 (1989-04-01), Morishita et al.
patent: 5782143 (1998-07-01), Ishikawa
patent: 6050155 (2000-04-01), Tortora
patent: 6-38556 (1994-02-01), None
patent: WO98/12097 (1998-03-01), None
Boldt Ekkehard
Engels Frank Peter
Hein Paul
Lorenz Volker W.
Meckel Herbert
Johnson Brian L.
Kajander John E.
Lerner Avraham H.
Visteon Global Technologies Inc.
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