Motors: expansible chamber type – Working member position feedback to motive fluid control – Follower type
Patent
1993-10-12
1995-10-31
Look, Edward K.
Motors: expansible chamber type
Working member position feedback to motive fluid control
Follower type
91380, 92DIG1, 92DIG2, 180132, F15B 910, B62D 506
Patent
active
054619645
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a roller-contact bearing device with reduced clearance for a power-assisted steering system of the type of those which comprise: the form of a cylinder of revolution about an axis; this axis, translationally fixed along this direction and rotationally driven about this axis, from the outside of the casing, by the application of an input torque on a first of its two ends; separate this volume into two sealed pressure chambers subjected to respective pressures varying as a function of the said input torque, these pressures exerting on the piston a translational force which can be converted into an output torque; and vicinity of the second end of the latter, so as to convert a rotational movement of the shaft into a translational movement of the piston, direction as a function of the input torque, and this device comprising at least a first roller-contact bearing arranged between the first end of the shaft and the casing so as to transmit to the latter the axial forces being exerted on the shaft from its second end towards the first.
Such devices are used in power-assisted steering systems of the type described for example in U.S. Pat. No. 4,128,046, and are essentially composed either of a special roller-contact bearing or one which has been the subject of a selection, or of a more ordinary roller-contact bearing whose clearance has been reduced by virtue of multiple settings.
Whatever the solution adopted, the roller-contact bearing devices with reduced clearance currently in use have the drawback of being costly, and of only showing maximum efficiency at the time of mounting, wear being likely to degrade their performance.
In this context, the object of the present invention is to provide a roller-contact bearing device of the type previously defined, but endowed with automatic clearance compensation, that is to say exempt from setting and adjustment, and having great stability over time.
To this end, the device of the invention is essentially characterized in that it further comprises a second roller-contact bearing arranged between the first end of the shaft and the casing, as well as elastic means bearing on the casing so as to exert on the shaft, via the second roller-contact bearing, an axial force directed from the second end of this shaft towards the first, and of greater intensity than the axial forces in the opposite direction to which this shaft is subjected.
The elastic means, especially for reasons of cost and bulk, may advantageously comprise a non-planar disc spring commonly referred to as a belleville washer which provides elastic resistance when forced to into a planar position.
In one possible embodiment, the shaft has in the vicinity of its first end a radial widening, the casing has at a region situated between the two ends of the shaft a radial narrowing, and the second roller-contact bearing and the said elastic means are arranged between the radial widening of the shaft and the radial narrowing of the casing, the second roller-contact bearing therefore preferably being a needle bearing.
In another possible embodiment, the shaft has, in the vicinity of its first end, an annular peripheral groove of right triangular cross section, forming two conical rolling surfaces centered on the axis, a first of these two surfaces being rather turned towards the first end of the shaft and the second surface being rather turned towards the second end of the shaft; the casing is therefore designed so as to offer, facing the first rolling surface, a third rolling surface, parallel to the first, a removable ring being arranged around the shaft in the immediate proximity of the third rolling surface so as to offer a fourth rolling surface facing the second and parallel to it; moreover, first rollers are arranged between the first and third rolling surfaces so as to roll thereon and to form the said first roller-contact bearing, second rollers are arranged between the second and fourth rolling surfaces so as to roll thereon and to form the said second roller-contact bearin
REFERENCES:
patent: 3868888 (1975-03-01), Rehfeld
patent: 4128046 (1978-12-01), Roseu
patent: 4202249 (1980-05-01), Jablonsky et al.
patent: 5205372 (1993-04-01), Kotake et al.
Bruguera Raimon Soler
Cortes Guasch Esteve
Bendix Espana S.A.
Look Edward K.
McCormick Jr. Leo H.
Nguyen Hoang
Palguta Larry J.
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