Motor vehicles – Compensating devices
Patent
1993-12-28
1995-02-28
Tyson, Karin L.
Motor vehicles
Compensating devices
73862332, B62D 504
Patent
active
053928741
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a power assisted steering mechanism in which the power assistance is provided by electric power.
In a typical power assisted steering mechanism such as that disclosed in our UK patent 1299506 (to which reference should be made) the steering column turned by the driver is drivingly connected to a pinion which drives a rack connected to the steerable wheels. The pinion is formed on a sleeve in which there is housed a torsion bar. Relative rotation between the torsion bar and sleeve controls the degree of power assistance provided.
A problem that stops electric power assisted steering being used is the reliability of the sensing of the driver's requirement and the provision of power assistance in the required direction and to the required level of assistance.
The problem is recognised and several attempts have been made in the past to overcome it by using a multiplicity of sensors, comparing the results and releasing power assistance only if the results agree within a certain prescribed tolerance.
Using a multiplicity of sensors often requires that, at least on one of them, there is an electric coupling to the sensor in the form of a clockspring type wiring harness.
If the clockspring method is not adopted then some form of contact, often in the form of slip rings, has to be made to the sensor and this introduces friction into the input to the gear. Friction at this point of a steering system is not a good thing as this can introduce instability to a power steered application.
Other sensors using LVDT devices require sliding contacts to be made to the input of the gear to translate steering torque to the linear movement that such devices require.
Other methods of overcoming the dual sensor requirement involve such organising signals that ensure that the power assistance is only permitted to be available if the speed is below a very low threshold. This threshold is such that power assistance, if wrong values are released into the steering system, presents no danger to the driver or any other road user.
According to the present invention there is provided a power assisted steering mechanism for a vehicle, the mechanism including electrically powered drive means for driving the steering mechanism, the drive means including a drive shaft having an input shaft portion drivingly connected to an output shaft portion by resilient means such that rotation of the input shaft portion causes relative rotational displacement between the input shaft portion and the output shaft portion in dependence on the load applied to the output shaft portion, sensor means arranged to produce signals in response to the direction and amount of relative displacement between the input and output shaft portions and an electric motor for driving said output shaft in response to the signals produced by the sensor means, the sensor means comprises a magnetic inductance sensor including an annular core formed of a magnetic material which is arranged to be co-axial with the input and output shaft portions, the core having an annular air gap to define opposed sets of poles on opposite sides of the air gap, a magnetic generating coil operable to generate flow of magnetic flux through the core and between the opposed sets of poles, one of the sets of poles including at least two concentric sensor poles having associated inductance coils for sensing flow of magnetic flux through the associated sensor pole, and a pair of groups of radially extending vanes located within said annular air gap, one group of vanes being mounted on the output shaft portion and the other groups of vanes being mounted on the input shaft portion, the vanes being made of a magnetic material and serving to conduct magnetic flux between the opposed sets of poles, the vanes of one group being axially spaced from the vanes of the other group and being arranged such that on movement of the input shaft portion relative to the output shaft portion consequential relative movement of the groups of vanes causes the impedance across the air gap to alter
REFERENCES:
patent: 4680976 (1987-07-01), Lustenberger
patent: 4972727 (1990-11-01), Yoshimura et al.
Adwest Engineering Limited
Boehler Anne Marie
Tyson Karin L.
LandOfFree
Power assisted steering mechanism does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Power assisted steering mechanism, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Power assisted steering mechanism will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-842092