Machine element or mechanism – Gearing – Directly cooperating gears
Patent
1986-03-28
1989-03-28
Arola, Dave W.
Machine element or mechanism
Gearing
Directly cooperating gears
74498, F16H 104
Patent
active
048153290
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
In rack and pinion steering, commonly used in passenger cars, e.g., as shown in British Pat. No. 2,037,931A of July 16, 1980 a rack is spring biased against a steering spindle pinion. Such arrangement suffices to maintain constant tooth engagement between rack and pinion, avoiding clattering noises. Also, the arrangement effects damping of axial vibration of the rack and thus avoids torsional oscillation of the steering spindle. Such oscillations cause imprecise steering due to so called steering wheel shimmy, an effect occurring at certain speeds caused by movement of unbalanced mass. The almost undamped shimmy effect makes for steering discomfort to the driver of the vehicle and also causes increased wear of the steering elements. Ordinarily, to correct such a condition, would be obvious to merely increase the spring pressure of the rack against the pinion by suitable adjustments. However, such expedient is impractical because the increase of frictional engagement between the meshed teeth of rack and pinion on unworn tooth areas would cause much too stiff steering in addition to increased tooth wear.
BRIEF DESCRIPTION OF THE INVENTION
The present invention provides an arrangement for effecting a torsional frictional load on the steering spindle to damp torsional oscillation while not causing any tooth wear of the rack and pinion nor steering stiffness due to forced tooth engagement.
Various embodiments of the invention are disclosed, but the general principle is to provide coacting friction members maintained in frictional engagement by a spring the pressure of which can be predetermined to precisely meet and overcome shimmy tendency. The friction members are located close to an antifriction bearing adjacent the pinion, and in one embodiment comprises a rotary friction member fixed to the steering spindle and abutting a part of the antifriction bearing. A friction plate is carried non-rotatively in a counter bore of a sleeve threaded into the steering housing. The sleeve has a disc spring therein that biases the non-rotative friction plate against the friction member fixedly carried on the steering spindle.
The non-rotative friction plate may be steel, or plastic preferably with a wear plate between it and the disc spring. The friction member fixed to the spindle may be a radial flange on the inner race of a ball bearing.
A further embodiment utilizes a roller thrust bearing between the two frictional elements wherein the thrust bearing has rollers which are slanted, i.e., not radially oriented but chordally disposed.
The invention as described above makes it possible to provide for frictional damping against spindle oscillation to minimize the effect of axial vibration of the steering rack in a manner not possible by the spring bias arrangement of rack against pinion. Also, the fictionally active engaged surfaces of the frictional members can be chosen for optimum results, not possible with rack and pinion type of spring bias. Further, where conventional ball bearings are used of the kind wherein balls run in the grooves of races, axial play is minimized to thus minimize wear.
A detailed description of the invention now follows in conjunction with the appended drawing in which:
FIG. 1 is a longitudinal section through a rack and pinion steering mechanism which illustrates one form of the invention;
FIG. 2 is a fragmentary longitudinal section illustrating a variation;
FIG. 3 is a fragmentary longitudinal section illustrating another variation; and
FIG. 4 is a plan view showing a thrust bearing having slanted rollers as used in FIG. 3.
Referring to FIG. 1, there is shown a steering spindle pinion 2 in a housing 1, in engagement with rack 3. Pinion 2 is integral with, or secured to, steering spindle 4. A pressure member 6 biased by spring 5 effects tooth engagement between rack 3 and pinion 2. The spring pressure is adjustable as by a shim 7, in a known manner or by means of an adjustable screw, likewise known. Pinion 2 is supported at both ends by antifriction ball bearing
REFERENCES:
patent: 3745850 (1973-07-01), Bayle
patent: 3844182 (1974-10-01), Bradshaw et al.
patent: 4016774 (1977-04-01), Baker et al.
patent: 4487281 (1982-11-01), Cordiano
Ansgar Betz
Gerhard Hagele
Arola Dave W.
Zahnradfabrik Friedrichshafen AG.
Zalkind Albert M.
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