Motor vehicles – Steering gear – With electric power assist
Patent
1996-05-17
1998-09-22
Dickson, Paul N.
Motor vehicles
Steering gear
With electric power assist
B62D 504
Patent
active
058101128
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to an electrically powered drive mechanism for providing powered assistance to a vehicle steering mechanism.
According to one aspect of the present invention, there is provided an electrically powered driven mechanism for providing powered assistance to a vehicle steering mechanism having a manually rotatable member for operating the steering mechanism, the drive mechanism including a torque sensor operable to sense torque being manually applied to the rotatable member, an electrically powered drive motor drivingly connected to the rotatable member and a controller which is arranged to control the speed and direction of rotation of the drive motor in response to signals received from the torque sensor, the torque sensor including a sensor shaft adapted for connection to the rotatable member to form an extension thereof so that torque is transmitted through said sensor shaft when the rotatable member is manually rotated and a strain gauge mounted on the sensor shaft for producing a signal indicative of the amount of torque being transmitted through said shaft.
Preferably the sensor shaft is non-rotatably mounted at one axial end in a first coupling member and is non-rotatably mounted at its opposite axial end in a second coupling member, the first and second coupling members being inter-engaged to permit limited rotation therebetween so that torque under a predetermined limit is transmitted by the sensor shaft only and so that torque above said predetermined limit is transmitted through the first and second coupling members.
The first and second coupling members are preferably arranged to act as a bridge for drivingly connecting first and second portions of the rotating member to one another.
Preferably the sensor shaft is of generally rectangular cross-section throughout the majority of its length.
Preferably the strain gauge includes one or more SAW resonators secured to the sensor shaft.
Preferably the motor is drivingly connected to the rotatable member via a clutch.
Preferably the motor includes a gear box and is concentrically arranged relative to the rotatable member.
Various aspects of the present invention will hereafter be described, with reference to the accompanying drawings, in which:
FIG. 1 is a diagrammatic view of a vehicle steering mechanism including an electrically powered drive mechanism according to the present invention,
FIG. 2 is a flow diagram illustrating interaction between various components of the drive mechanism shown in FIG. 1,
FIG. 3 is an axial section through the drive mechanism shown in FIG. 1,
FIG. 4 is a sectional view taken along lines IV--IV in FIG. 3,
FIG. 5 is a more detailed exploded view of the input drives coupling shown in FIG. 3, and
FIG. 6 is a more detailed exploded view of the clutch showing in FIG. 3.
Referring initially to FIG. 1, there is shown a vehicle steering mechanism 10 drivingly connected to a pair of steerable road wheels 12.
The steering mechanism 10 shown includes a rack and pinion assembly 14 connected to the road wheels 12 via joints 15. The pinion (not shown) of assembly 14 is rotatably driven by a manually rotatable member in the form of a steering column 18 which is manually rotated by a steering wheel 19.
The steering column 18 includes an electric powered drive mechanism 30 which includes an electric drive motor (not shown in FIG. 1) for driving the pinion in response to torque loadings in the steering column 18 in order to provide power assistance for the operative when rotating the steering wheel 19.
As schematically illustrated in FIG. 2, the electric powered drive mechanism includes a torque sensor 20 which measures the torque applied by the steering column 18 when driving the pinion and supplies a signal to a controller 40. The controller 40 is connected to a drive motor 50 and controls the electric current supplied to the motor 50 to control the amount of torque generated by the motor 50 and the direction of its rotation.
The motor 50 is drivingly connected to the steering column 18 preferably via a gear
REFERENCES:
patent: 4530413 (1985-07-01), Buike et al.
patent: 4573545 (1986-03-01), Kalns
patent: 4629024 (1986-12-01), Buike et al.
patent: 4765425 (1988-08-01), Saito et al.
patent: 5299650 (1994-04-01), Wada et al.
Bailey David Alexander
Bartram Arthur Thomas
Murden Stuart James
Adwest Engineering Ltd.
Dickson Paul N.
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