Electrical generator or motor structure – Dynamoelectric – Rotary
Patent
1998-05-15
1999-11-30
Ramirez, Nestor
Electrical generator or motor structure
Dynamoelectric
Rotary
H02K 706
Patent
active
059948078
DESCRIPTION:
BRIEF SUMMARY
This is a United States national application corresponding to copending international application No. PCT/GB96/02803, filed Nov. 14, 1996, which designates the United States, the benefit of the filing date of which is hereby claimed under 35 U.S.C. .sctn. 120, which in turn claims the benefit of British application No. 9523369.8, filed Nov. 16, 1995, and No. 9615316.2, filed Jul. 22, 1996 the benefit of the filing date of which is hereby claimed under 35 U.S.C. .sctn. 119.
This invention relates to electric actuators for vehicle power steering systems of the kind comprising a combination of two component assemblies comprising an electric motor, and a gearbox.
In known electric actuators of the kind set forth such as disclosed, for example, in EP-A-0 055 870 and EP-A-0 411 600, the two component assemblies are consecutively arranged in order. A clutch, in the form of an electromagnetic friction clutch, may be disposed between the motor and the gearbox and with the assemblies coupled together but sealed from each other in terms of both magnetic shielding and sealing from dirt and lubricants. Additionally the components comprising the sub-assemblies are mounted around a shaft or shafts which, with such a consecutive approach, produces alignment and concentricity problems between the individual components of the assemblies, and between the assemblies themselves. Also arranging the assemblies consecutively produces an overall actuator package of large proportions.
We are aware of JP-A-7 137 644 which discloses an electric actuator in which a single common output shaft extends completely through a motor armature and a part of the gearbox is adopted to break when excessive torque is generated to eliminate the need for a clutch assembly. This document has been used as the basis for the pre-characterising portion of claim 1.
According to one aspect the invention provides an electric actuator adapted for use in a vehicle power steering system, comprising an electric motor and a gearbox, the electric motor comprising a stator and an armature concentric with the stator and adapted to rotate about a common axis, and in which a single common output shaft is provided, characterised, in that the output shaft extends only part of the way through the armature of the actuator from the gearbox end of the motor to transmit torque from the motor to a drive portion of the shaft and from whence torque is transmitted to the gearbox through a transmission portion of the shaft.
The output shaft may be supported in two spaced bearings which span the transmission portion of the shaft and with the armature being supported in a cantilever manner.
The use of a common shaft has the advantageous effect of reducing the mass of the motor as well as reducing the package width with a considerable reduction in cost. It also overcomes the problems of aligning the motor with the gearbox.
Preferably, the drive portion of the output shaft may extend through the armature of the motor. The output shaft can thus provide support along the axial length of the armature. Alternatively, the drive portion of the output shaft may be shorter and only extend part of the way through the armature from the gearbox end of the motor. In the latter case, the end of the armature adjacent the gearbox housing may be fixed against relative to the output shaft, and the opposite end of the armature may be supported in an end frame which is adapted to rotate around a bearing bevelled to the master casing. The end frame provides support for the end of the armature furthest from the gearbox and helps to keep the armature and motor stator concentric with one another.
Conveniently, the armature of the motor is secured on a section of the drive portion of the output shaft. The armature may preferably be splined or keyed to the output shaft so as to prevent relative rotation between the two.
Where the output shaft extends all the way through the armature, the armature may be fixed relative to the output shaft only at the end of the armature adjacent the gearbox or along the whol
REFERENCES:
patent: 3660704 (1972-05-01), Pain et al.
patent: 4808869 (1989-02-01), Kopp
patent: 4987788 (1991-01-01), Bausch
patent: 5023213 (1991-06-01), Isozumi
Coles Jeffrey Ronald
Johnson Anthony
Wilkes Mark Anthony
Lucas Industries Public Limited Company
Ramirez Nestor
Waks Joseph
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