Non contacting torque sensor

• US 20020000129A1
• Filed: 08/22/2001
• Published: 01/03/2002
• Est. Priority Date: 09/07/1999
• Status: Active Grant

• Current Assignee: BEI Sensors & Systems Company Incorporated (Schneider Electric SE)
• Original Assignee: BEI Sensors & Systems Company Incorporated (Schneider Electric SE)
• Inventors: Vuong, Jim B., Madni, Asad M., Hansen, Robert K.
• Granted Patent: US 6,520,031 B2
• Time in Patent Office: Days
• US Class Current: 73/862.326
• CPC Class Codes: G01D 5/2053 by a movable non-ferromagnetic conductive element
• CPC Class Codes: G01L 3/105 involving inductive means G01L3/102, G01L3/104 take precedence
• CPC Class Codes: G01L 3/109 involving measuring phase difference of two signals or pulse trains

Abstract

A non contacting angular differential displacement torque sensor utilizes a split shaft with a connecting torsion bar with a pair of receive disks each with an intervening coupler disk carrying a conductive attenuating pattern where the inductive coupling between transmit and receive disks is individually attenuated in accordance with the angular position of the shaft on which the disks are mounted. The pair of receive disks which receive signals from a common transmitter have their angular difference taken and this is the actual torque on the shaft.

Claims

1. A non contacting torque sensor for a shaft having a torsion bar connecting two portions of said shaft comprising:

a transmit annular disk surrounding said shaft and fixed for non rotation and generating a radio frequency (RF) signal;

a pair of annular coupler disks mounted for rotation with said shaft on opposite sides of said torsion bar with said transmit disk between them;

a pair of fixed receiver annular disks surrounding said shaft with said coupler disks between them, said pair of receiver disks receiving radio frequency signals from said transmit disk through said coupler disks indicative of the rotation of said shaft;

and means for angularly comparing said respective signals from said pair of receiver disks to provide a torque signal indicative of the angular differential displacement of said shaft portions.

2. A torque sensor as in claim 1 where both of said signals received by said receiver disks have the same duty cycle with a phase shift between them proportional to the rotational differential displacement of said pair of coupler disks.

3. A torque sensor as in claim 2 where said angular comparing of said phase shifted signals provides an output signal with a changing duty cycle which is proportional to the differential displacement of one coupler disk from the other whereby said torque signal is indicated.

4. A non contacting torque sensor as in claim 3 where said angular comparison is made by an exclusive OR gate whereby for clockwise or counter-clockwise rotation of the shaft said duty cycle respectively decreases or increases with respect to increase of torque.

5. A non contacting torque sensor as in claim 1 where said shaft is an automobile steering column which is not physically connected to the wheels of the automobile and where an electric motor controls the steering which is actuated by said torque signal.

6. A non contacting torque sensor as in claim 1 including means for shifting phase of one of said receiver signals by a fixed angle before said angular comparing whereby crossover ambiguity is prevented.

7. A non contacting torque sensor as in claim 6 where said fixed angle is 90°

and a zero torque signal has a 50% duty cycle.

8. A non-contacting torque sensor as in claim 1 where said coupler disks provide a pair of RF attenuated sinusoidal waveforms to said receiver disks whose phase is proportional to the angular position of the coupler whereby the difference in positions is indicative of said angular differential displacement.