Machine element or mechanism – Gearing – Teeth
Reexamination Certificate
1999-06-28
2001-03-27
Marmor, Charles A (Department: 3681)
Machine element or mechanism
Gearing
Teeth
C074S462000, C074S458000, C409S010000, C409S032000
Reexamination Certificate
active
06205879
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to improved helical and spur gear drives provided with meshing pinion/gear tooth surfaces that reduce vibration and noise and provide favorable bearing contact of tooth surfaces under load and, more particularly, to improved helical and spur gears wherein the pinion tooth surface is double crowned and is in mesh with a conjugated gear tooth surface.
2. Description of Related Art
Helical and spurs gears of existing design for transformation of rotation under load between parallel axes are known to be sensitive to errors in alignment such as the change of shaft angle and the lead angles of pinion/gear tooth surfaces that cause: (i) a function of transmission errors of undesirable shape and unacceptable magnitude; (ii) shift of the bearing contact, and (iii) adverse conditions of transfer of meshing between neighboring teeth accompanied by unacceptable elastic tooth deformation. The load capacity of conventional involute gearing is limited as a result of high level of contact and bending stresses.
An object of the present invention is to provide improved helical and spur gear drives that overcome the above noted deficiencies of existing helical and spur gears.
SUMMARY OF THE INVENTION
The present invention provides an improved gear drive of the helical or spur types comprising a driving gear (i.e. a pinion) with a tooth surface that is uniquely double crowned in the profile and longitudinal directions and a driven gear provided with a conjugated tooth surface that can comprise a conventional involute type tooth surface or a uniquely modified tooth surface.
The double crowned tooth surface of the driving gear is generated as (i) the envelope to a family of surfaces generated by a skew rack-cutter having a parabolic tooth profile in normal section while the rack-cutter and the driving gear perform related translational and rotational motions, respectively, and then (ii) as the envelope to a family of tool surfaces that are generated while the tool performs a plunging motion with respect to the driving gear in the direction of the shortest distance between the axes of rotation of the tool and the driving gear with tool plunging motion varied by a parabolic function. For example, the tool is translated in a direction parallel to the pinion rotational axis, and the magnitude of its plunge is executed by a parabolic function in the direction of the shortest distance between the crossed axes of the tool and the driving gear (pinion).
The driven gear of a helical gear drive includes a conjugated tooth surface defined as the envelope to a family of surfaces generated by a skew rack-cutter having a tooth surface of parabolic profile in normal section. Such a helical driven gear and double crowned helical drive pinion provide concave-convex contact of the tooth surfaces with a small difference of tooth surface curvatures that results in substantial reduction of contact stresses and increased strength to bending stresses.
Alternately, the conjugated tooth surface of the helical driven gear can comprise conventional screw involute helical teeth. The driven gear of a spur gear drive includes a conjugated tooth surface defined as the envelope to a family of a straight rack-cutter surface having a tooth surface of parabolic profile in normal section. Such a spur driven gear and double crowned helical drive pinion provide concave-convex contact of the tooth surfaces with a small difference of tooth surface curvatures that results in substantial reduction of contact stresses and increased strength to bending stresses.
Alternately, the conjugated tooth surface of the driven spur driven gear can comprise a conventional cylindrical involute spur tooth surface.
The meshing and contact of the above described tooth surfaces provide the following characteristics and advantages: (i) the driving gear/driven gear tooth surfaces are at every instant in theoretical point contact that spreads under load over an elliptical area of the tooth surfaces, (ii) a parabolic function of transmission errors of a preselected magnitude is produced during meshing of the pinion/gear tooth surfaces and is capable of absorbing discontinuous, almost linear functions of transmission errors caused by pinion/gear misalignment, (iii) a localized and stabilized bearing contact of pinion/gear tooth surfaces is provided by the instantaneous contact ellipses, and (iv) the transfer of meshing between the neighboring teeth is improved to decrease the total tooth elastic deformation, enabling increase of the contact ratio (i.e. the average number of teeth being in contact simultaneously).
REFERENCES:
patent: 4224834 (1980-09-01), Kotthaus
patent: 5083474 (1992-01-01), Rouverol
patent: 5341699 (1994-08-01), Rouverol
patent: 5823857 (1998-10-01), Tan
patent: 6080199 (2000-06-01), Umeyama et al.
Silencing high-speed gearheads, Bernd Strober, Strober Drives, Inc., Powertrain Design, pp. 33-35, Nov. 1998.
Industry in Motion, New coupling keeps up with demand, Powertrain Design, pp. 10, Nov. 1998.
Feng Pin Hao
Lagutin Sergey A
Litvin Faydor L.
Sep Thomas M
Townsend Dennis P
Marmor Charles A
Visteon Global Technologies Inc.
Waddell Tisha D.
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