Method and apparatus for measuring torque

{
  "publication_number": "US6269702B1",
  "country": "US",
  "kind": "B1",
  "title": "Method and apparatus for measuring torque",
  "abstract": "A method and apparatus for measuring torque of a rotating shaft is provided. In one embodiment, the apparatus includes a transducer assembly that is attached to a shaft. The transducer assembly includes a first plate member, a plurality of webs extending from the first plate member and a second plate member connected to the webs. A plurality of strain gauges are mounted on the transducer assembly at selected locations and in selected patterns. As torque is applied to the shaft, the torsional load from the shaft causes stress in the first plate member, the web members, and the second plate member. The strain gauges measure this stress and generate signals that provide a measure of the stress. The signals transmitted from the sensing circuit are compared with calibration data, and the torque value is inferred. In one embodiment, the strain gauges are arranged in opposing pairs on the transducer assembly and electrically connected as a Wheatstone bridge, so that strain resulting from non-torsional loads is canceled from the measured signal, thereby improving torque measurement accuracy. In another embodiment, the strain gauges are located on thinned regions in the transducer assembly which are fashioned for the purpose of creating areas of localized high stress. In another embodiment, the transducer assembly includes a decoupling aperture. The decoupling aperture minimizes hysteresis due to warping and bending of the transducer assembly.",
  "claims": [
    "1. A transducer for sensing torque from a rotateable shaft comprising: a first planar disk extending in a first plane and having a plurality of apertures therethrough so that said disk is adapted to be coupled to the rotateable shaft; a first plurality of web members extending perpendicular from the first planar disk, in a direction away from said shaft; a second planar disk coupled to the web members, the second planar disk extending in a plane parallel to the first planar disk; a first plurality of pairs of strain gauges coupled to the second planar disk, one pair of strain gauges being positioned adjacent the coupling point between each web within the first plurality of webs and the second planar disk, with a first strain gauge within each pair being positioned on a first side of a web and a second strain gauge in the pair being positioned on an opposite side of the respective web; a series electrical connection between each first strain gauge of each pair; and a series electrical connection between each second strain gauge of each pair.",
    "2. The apparatus of claim 1 wherein the arrangement of pairs of the strain gauges is a physical arrangement, with the strain gauges of the pair physically positioned symmetrically to each other about a selected feature of the transducer assembly.",
    "3. The apparatus according to claim 1 wherein the strain gauges are thin-film gauges.",
    "4. The apparatus according to claim 1 wherein the strain gauges are thick-film gauges.",
    "5. The apparatus according to claim 1, further including a sensing circuit having a transmitting antenna.",
    "6. The transducer according to claim 1 wherein the strain gauges are coupled in a Wheatstone bridge electrical circuit configuration.",
    "7. The apparatus according to claim 6 wherein the number of strain gauges are grouped together in groups of four and each group has one strain gauge in each respective leg of the Wheatstone bridge to cancel out non-torque stresses in the transducer assembly.",
    "8. The apparatus according to claim 1 wherein the transducer assembly includes a plurality of thin regions that are thinner than other regions on the transducer assembly, the strain gauges being affixed to the thin regions.",
    "9. The apparatus according to claim 1, further comprising a power supply circuit electrically connected to the strain gauges.",
    "10. The apparatus according to claim 9 wherein the power supply circuit includes at least one first inductive element and at least one second inductive element, said second inductive element moving relative to the first inductive element when power is being transferred.",
    "11. The apparatus according to claim 1, further comprising an engine having a crankshaft, the crankshaft being rigidly attached to the first plate member.",
    "12. The apparatus according to claim 1, further comprising a drive train having a flywheel, the flywheel being rigidly attached to the second plate member.",
    "13. The transducer according to claim 6 further including: a second plurality of web members extending perpendicular from the first planar disk, in a direction away from said shaft and coupled to the second planar disk; a second plurality of pairs of strain gauges coupled to the second planar disk, one pair of strain gauges being positioned adjacent the coupling point between each web within the second plurality of webs and the second planar disk, with a first strain gauge within each pair being positioned on a first side of a web and a second strain gauge in the pair being positioned on an opposite side of the same respective web; a series electrical connection between each first strain gauge of each pair; a series electrical connection between each second strain gauge of each pair and the first pair of strain gauges of the first plurality forming a first leg of the Wheatstone bridge, the second pair of strain gauges of the first plurality forming a second leg of the Wheatstone bridge, the first pair of strain gauges of the second plurality forming a third leg of the Wheatstone bridge, and second pair of strain gauges of the second plurality forming a fourth leg of the Wheatstone bridge.",
    "14. A transducer for sensing torque from a rotateable shaft comprising: a first planar disk extending in a first plane and having a plurality of apertures therethrough so that said disk is adapted to be coupled to the rotateable shaft; a pair of web members extending perpendicular from the first planar disk, in a direction away from said shaft, the first web member in said pair being positioned at a mirror image location with respect the second web member in the pair about a central plane that is perpendicular to the first planar members and passes though the center of the first planar disk; a second planar disk coupled to the pair of web members, the second planar disk extending in a plane parallel to the first planar disk; a pair of strain gauges coupled to the second planar disk, one pair of strain gauges being positioned on the second planar disk adjacent the coupling point between each web and the second planar disk, with a first strain gauge within each pair being positioned on a first side of a web and a second strain gauge in the pair being positioned on an opposite side of the respective web; a Wheatstone bridge circuit having four legs composed of the pairs of the strain gauges, with the first strain gauge of the first web of the pair being in a leg of the Wheatstone bridge opposite the first strain gauge of the second web of the pair and the second strain gauge of the first web being in a leg of the Wheatstone bridge opposite the second strain gauge of the second member of the web, the first and second strain gauges being in adjacent legs to each other.",
    "15. The transducer according to claim 14 further including a second pair of web members that are in a mirror image position with respect to each other about a central plane that passes through the center of the first planar disk, each of the second pair having a pair of strain gauges on adjacent sides coupled to the second planar member and positioned in series to corresponding legs of the Wheatstone bridge.",
    "16. A transducer assembly for sensing torque from a rotateable shaft comprising: a first planar disk extending in a first plane and having a plurality of apertures therethrough so that said disk is adapted to be coupled to the rotateable shaft; a first plurality of web members extending perpendicularly from the first planar disk, in a direction away from said shaft; a second planar disk coupled to the web members, the second planar disk extending in a plane parallel to the first planar disk; a recessed region positioned on the second planar disk, located adjacent each side of each web member; a strain gauge positioned within the recessed regions on the second planar disk.",
    "17. The transducer according to claim 16 further including a strain relief slit adjacent each web member extending into said second planar disk.",
    "18. The transducer according to claim 17 wherein said strain relief slit extends completely through said second planar disk.",
    "19. The transducer according to claim 16 further including a decoupling aperture adjacent each web member extending into said second planar disk.",
    "20. The transducer according to claim 19 wherein said decoupling aperture extends completely through said second planar disk."
  ],
  "description_excerpt": "This invention relates to an apparatus and method for measuring torque, and more particularly, a structure and method that will measure the torque output of a rotating shaft.\n\nEngine crankshaft torque is an important factor in engine and vehicle performance. Fuel economy, drivability and operational smoothness in a vehicle driven by an automatic transmission are functions of transmission shift points and engine control parameters. Crankshaft torque is taken into account in order to optimize these shift points. The design and proper function of the drive train also must take into account crankshaft torque.\n\nCrankshaft torque has been typically measured in test cells using highly specialized expensive dynamometer equipment and setups. The equipment, however, is large and very sensitive, making it totally unsuitable for vehicular applications.\n\nAlso, other attempts to measure engine crankshaft torque were made by machining “flats” into the engine crankshaft and installing stress or strain gauges onto the flats. As torque load is applied to the crankshaft, the strain gauges sense the induced stress load at their locations on the flats. The resulting signals from the strain gauges are compared with the torque calibration data, from which the torque values are inferred.\n\nSuch torque measuring devices are plagued by several problems. Life limiting modifications to the engine crankshaft are required for their installation, in addition to the difficulties and impracticalities of having to install sensors and physically load and calibrate each individual crankshaft, thereby disqualifying their use in commercial production vehicles.",
  "cpc": [
    "G01L 3/108"
  ],
  "ipc": [
    "G01L 3/10",
    "G01L 3/14"
  ],
  "inventors": [
    "Vernon A. Lambson"
  ],
  "filing_date": "1999-10-21",
  "publication_date": "2001-08-07",
  "grant_date": "2001-08-07",
  "priority_date": "1998-10-30",
  "application_number": "US-42591099-A",
  "family_id": "22311696",
  "cited_by_count": 102,
  "citations": [
    "US4444061A",
    "US4471663A",
    "US4573362A",
    "US4640138A",
    "US4823618A",
    "US4821582A",
    "US5874682A",
    "US5648617A",
    "US5837909A"
  ]
}