Measuring and testing – Dynamometers – Responsive to multiple loads or load components
Reexamination Certificate
1999-02-04
2001-12-04
Fuller, Benjamin R. (Department: 2855)
Measuring and testing
Dynamometers
Responsive to multiple loads or load components
Reexamination Certificate
active
06324919
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates, in general, to apparatus for measurement of forces and/or moments acting on rotatable members, such as vehicle wheels.
2. Description of the Art
Wheel load transducers are known for attachment to a vehicle wheel to measure torque, moments and forces applied to the wheel. Such transducers, as shown in
FIGS. 16 and 17
and described in greater detail hereafter, are typically in the form of an annular member which is affixed at an outer peripheral portion to a rim adapter welded to the wheel rim. The adapter has a plurality of circumferentially spaced apertures which align with corresponding apertures in the outer periphery of the transducer for receiving bolts therethrough to fix to the transducer to the wheel rim.
The transducer also includes an inner annular portion which also has a plurality of circumferentially spaced apertures. A hub adapter containing a corresponding circumferential arrangement of apertures is mountable on the inner ring and fastened thereto. The hub adapter includes a standard hole arrangement for attachment to vehicle wheel bolt lugs.
A plurality of radial extending webs or beams interconnect the inner and outer portions of the transducer. Moments and forces exerted on the wheel are measured by sensors, such as strain gages, which are adhesively affixed to exterior surfaces of the webs or beams. Strain gages mounted on the inboard and outboard surfaces of the beams provide torque measurements. Strain gages mounted on the sides of the beams are positioned for providing steering and camber moments and lateral force measurements. This type of transducer is not capable of measuring vertical and fore and aft forces acting on the wheel.
Other more complex transducers are capable of measuring the three directional forces, torque, camber moment and steering moment. However, such wheel load transducers have required many output channels, such as up to twelve output channels to measure the three primary forces and three primary moments or torque exerted on a vehicle wheel. Further, all such transducers exhibit some degree of imperfection known as crosstalk. Crosstalk are measurement errors that occur when forces or moments are applied at directions at right angles to the desired measurement direction.
Thus, it would be desirable to provide a force and/or moment measurement device suitable for use with rotatable members, such as vehicle wheels, which is capable of obtaining force and/or moment measurements with a high degree of accuracy. It would also be desirable to provide such a measurement apparatus or transducer which minimizes crosstalk measurement errors between adjacent sensors. It would also be desirable to provide such a measurement apparatus or transducer which optimally locates the measurement devices or strain gages for more precise measurement. Finally, it would be desirable to provide such a measurement apparatus which has a minimal number of independent output data channels.
SUMMARY OF THE INVENTION
The present invention is the load transducer for measuring forces and/or moments on a rotatable member, such as a rotatable vehicle wheel.
In an exemplary embodiment, the load transducer of the present invention includes an inner ring member, means for attaching the inner ring member to a wheel hub, an outer ring member, means for attaching the outer ring member to a wheel rim, a beam connected between the inner and outer ring members, a well formed in the beam, and a sensor mounted in the well for measuring forces exerted on the beam.
Preferably, a plurality of beams, such as four by example, are formed between the inner and outer ring members circumferentially spaced ninety degrees apart. The beams are isolated from each other by apertures.
Preferably, each beam contains a stem extending from the inner ring member and a unitary crossleg which is connected to the outer ring member.
A well is formed on a first surface of the stem, preferably along the neutral or longitudinal axis of the stem. At least one and preferably a pair of wells formed around the crossleg equi-distantly spaced from the longitudinal axis of the stem. At least one sensor or strain gage is mounted in each well. Opposed, aligned wells are preferably formed on the opposite surface of the stem and the crossleg.
By example, each strain gage is in the form of a plurality of linearly arranged resistor strips. Preferably, each strain gage is formed of a pair of angularly disposed resistor strips. The strain gage sensitivity in each beam is equalized. Preferably, the sensitivity of each strain gage in each crossleg is one half of the sensitivity of the strain gage in each stem.
An electrical connector is mounted between the inner and outer ring members. Bores are formed in the stem and the crossleg of each beam from each well in the beam to provide passage for electrical conductors from each strain gage to the electrical connector. Preferably, a recess is formed along the outer ring member for carrying the wires from each beam to the connectors.
The load transducer of the present invention provides significant advantages over previously devised load transducers used for measuring forces and/or moments on rotatable members, such as vehicle wheels. The unique provision of mounting the strain gages in wells on each beam significantly reduces crosstalk between the adjacent strain gages which previously has led to inaccurate force and/or moment measurement. Equalizing the sensitivity of the strain gages mounted in the wells on each beam in the radial and tangential directions significantly enhances the force and moment measurement accuracy.
The individual sensors or strain gages in each beam may easily be connected in four arm bridge configurations on the transducer so as to provide a minimal number of separate data output channels from the transducer. This minimizes interconnection between the transducer and an external data acquisition unit.
REFERENCES:
patent: 3867838 (1975-02-01), Gerresheim
patent: 4186596 (1980-02-01), Bohringer et al.
patent: 4297877 (1981-11-01), Stahl
patent: 4640138 (1987-02-01), Meyer et al.
patent: 4748844 (1988-06-01), Yoshikawa et al.
patent: 4821582 (1989-04-01), Meyer et al.
patent: 5231374 (1993-07-01), Larsen et al.
patent: 5604317 (1997-02-01), Jachmann et al.
patent: 5817951 (1998-10-01), Cook et al.
Larsen Hugh W.
Talaski Carl E.
Davis Octavia
Fuller Benjamin R.
Michigan Scientific Corporation
Young & Basile P.C.
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