Device for measuring torque in a rotating shaft

Details Device for measuring torque in a rotating shaft Device for measuring torque in a rotating shaft

1998-03-31

2001-05-08

Fuller, Benjamin R. (Department: 2855)

Measuring and testing

Dynamometers

Responsive to torque

C180S193000

Reexamination Certificate

active

06227060

ABSTRACT:

The invention relates generally to a torque measurement device to be mounted on a rotating shaft used in power-assisted steering. More particularly, the invention relates to a device for measuring torque in a rotating shaft, of the type having a magnetic-field generator situated in the plane of a cross section of the shaft and a detector which delivers a signal proportional to the torque in the shaft as a result of the relative angular offset between the field generator and the detector.
The French publication “Le journal de l'Automobile” No. 510 of Dec. 1, 1995 describes a steering column for a power-assisted steering system. This column is equipped with a torque sensor device which delivers a signal proportional to the torque, fixed to an input shaft operated by the steering wheel and connected to a torsion bar. The column is also equipped with a worm carried by an output shaft operated by an electric motor driven as a function of the electrical signal delivered by the torque sensor. Additional torque-limiting means is formed between the input shaft and the output shaft, given the small cross section of the torsion bar. The torque sensor and the worm are housed in an arrangement protruding from the steering column tube. Angular displacement between the input and output shafts is converted into an axial movement of the input shaft bearing, and the displacement of this shaft is converted into a rotary movement with an electrical signal that represents the steering command torque being delivered.
The French patent publication FR-A-2692986 describes a mechanical device for measuring torque integrated into a steering column, the principle of operation of which relies on measuring microdisplacements under torsional loading, of two sections of a very rigid shaft. The entire device is located within the steering column and is associated with electronic processing circuits and with a coiled power cable which is also the output cable for the signal to the calculation unit of the power-assisted steering device. However, this compact arrangement, which allows the circuit to be produced in a number of ways, does not allow the radial size to be limited to the outside dimensions of the column tube.
The foregoing illustrates limitations known to exist in present devices and methods. Thus, it is apparent that it would be advantageous to provide an alternative directed to overcoming one or more of the limitations set forth above. Accordingly, a suitable alternative is provided including features more fully disclosed hereinafter.
SUMMARY OF THE INVENTION
In one aspect of the invention, this is accomplished by providing a device for measuring torque in a rotating shaft of a vehicle steering column. A magnetic field generator is situated in a plane of a cross section of the rotating shaft, and a first electronic circuit is fixed inside the steering column to a support that concentrates the magnetic field of the magnetic field generator and moves past the magnetic field generator together with a mechanical means for angular return of two sections of the rotating shaft. Measurement sensors are carried on the first electronic circuit and deliver a signal proportional to the torque in the rotating shaft as a result of the relative angular offset between the magnetic field generator and the measurement sensors. A second electronic circuit for processing signals from the measurement sensors is to be located outside the steering column.
The foregoing and other aspects will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawing figures.


REFERENCES:
patent: 5355315 (1994-10-01), Daido et al.
patent: 5501110 (1996-03-01), Peilloud et al.
patent: 5699874 (1997-12-01), Miyaura
patent: 5732790 (1998-03-01), Endo et al.

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