Screw-based adjustment mechanism, rail comprising such an adjustment mechanism, and seat comprising such a rail

An adjustment mechanism the includes a screw, a support having first and second transverse walls perpendicular to the screw, a casing having first and second end faces arranged facing the first and second transverse walls and having a nut housing which opens in opposite first and second openings, a first elastomer pad interposed between the first transverse wall of the support and the first end face of the casing, a second elastomer pad interposed between the second transverse wall of the support and the second end face of the casing, a nut screwed onto the screw, a bearing engaged in the second opening of the casing and traversed by the screw. The nut is in rigid abutment against the casing in the direction of the first opening and the bearing is in elastic abutment against the second elastomer pad.

FIELD OF THE INVENTION

The present invention relates to screw-based adjustment mechanisms, rails comprising such mechanisms, and seats comprising such rails.

BACKGROUND OF THE INVENTION

More particularly, the invention relates to a screw-based adjustment mechanism comprising:a screw which extends along a longitudinal axis,a support having first and second transverse walls substantially perpendicular to the longitudinal axis,a casing mounted on the support between the first and second transverse walls of said support, said casing having first and second end faces respectively arranged facing said first and second transverse walls of said support, and said casing having a nut housing which extends along said longitudinal axis and opens at the first and second end faces of the casing in respective and opposite first and second openings, the screw passing through the first and second openings,a first elastomer pad interposed in compression between the first transverse wall of the support and the first end face of the casing,a second elastomer pad interposed between the second transverse wall of the support and the second end face of the casing,a nut screwed onto said screw, the nut being rotatably mounted in the nut housing of the casing,a bearing engaged in the second opening of the casing and traversed by the screw, the nut being in rigid axial abutment against the bearing in the direction of the second opening.

Document FR2882974A1 describes an adjustment mechanism of this type, which is entirely satisfactory in its operation. In the adjustment mechanism of document FR2882974A1, the bearing is mounted on the screw without clearance, passes through the second elastomer pad, and abuts against the second transverse wall of the support. This mechanism further comprises an additional bearing mounted on the screw without clearance, passing through the first opening of the casing and the first elastomer pad, the additional bearing being interposed between the nut and the first transverse wall of the support. The nut is mounted between the bearings without clearance.

SUMMARY

An object of the present invention is to further improve adjustment mechanisms of this type, in particular in order to reduce their complexity and cost.

For this purpose, according to an aspect of the invention, an adjustment mechanism of the type in question is characterized in that the nut is in rigid axial abutment against the casing in the direction of the first opening and the bearing is in elastic axial abutment against the second elastomer pad.

“Rigid abutment” is understood here to mean an abutment without elastic clearance compensation, possibly with rigid elements being interposed such as a washer or similar between the two rigid abutment elements.

“Elastic abutment” is understood here to mean an abutment with elastic clearance compensation, for example, due to the elasticity of the elastomer pad.

With these arrangements, all clearance compensation in the mechanism in the longitudinal direction is achieved simply and inexpensively by the first and second elastomer pads. This eliminates having to compensate for clearance between the casing and the support and clearance of the nut within the casing, by two independent clearance compensation systems.

In various embodiments of the adjustment mechanism, one or more of the following arrangements may possibly also be used:the nut and the bearing are shaped so as to fit axially into the casing through the second opening of said casing;the casing is a single piece (thus simplifying the structure of the casing and its assembly, and further decreasing the cost of the mechanism, in comparison to the mechanism of FR2882974A1);the nut comprises first and second cylindrical ends, the first cylindrical end rotating within a bore of the casing and the second cylindrical end fitting into the bearing;the bearing comprises a flange interposed between the second end face of the casing and the second elastomer pad, axial clearance being provided between said flange and the second end face of the casing;said flange has a non-circular edge which engages with a rim that is part of the second end face of the casing, in order to immobilize the bearing rotationally relative to the casing;a rigid washer is interposed axially between the nut and the bearing;the bearing is made of rigid material, for example metal.

The invention also relates to a rail comprising an adjustment mechanism as defined above, a fixed section, and a movable section integral to the support of the adjustment mechanism and mounted so as to slide relative to the fixed section in parallel to said longitudinal axis, the screw of the adjustment mechanism being integral to the fixed section.

Finally, the invention also relates to a vehicle seat comprising at least one rail as defined above and a seating portion integral to the first movable rail section member of said rail.

DETAILED DESCRIPTION

In the various figures, the same references designate identical or similar elements.

FIG. 1shows a motor vehicle seat1which comprises a backrest2supported by a seating portion3which itself is mounted on the floor4of the vehicle so as to slide in a substantially horizontal longitudinal direction X.

The seating portion3is connected to the floor4by two parallel rails5, of which only one is visible inFIG. 1.

As can be seen inFIG. 2, each of the rails5comprises first and second rail members6,7respectively formed by a fixed metal section6connected to the floor4and a movable metal section7connected to the seating portion3, which slide on one another along the longitudinal direction X.

Here, the rails5of the seats are electric motorized rails, controlled for example by means of a button8(FIG. 1), arranged for example on the side of the seating portion of the seat, which controls an electric motor9respectively driving (for example by means of lines10) the adjustment mechanisms11of the two rails5(FIG. 2).

As represented inFIGS. 3 and 4, the adjustment mechanism11of each rail is a screw-based adjustment mechanism, comprising a screw12integral to the fixed section7and extending along a longitudinal axis X0parallel to the aforementioned longitudinal direction X.

The adjustment mechanism11further comprises a transmission device13which may be arranged inside the movable section6. The transmission device13comprises a nut14screwed onto the screw12and mounted so as to rotate about the longitudinal axis X0of the screw12, as is clearly visible inFIGS. 5 to 7.

The nut14can be rotated, for example by a worm screw15which meshes with external teeth16of the nut14. The worm screw15may be rotatable about a transverse axis Y0parallel to a transverse horizontal direction Y perpendicular to the longitudinal direction X.

The worm screw15may be rotated by the motor9by means of lines10or the like, which pass through the side wall of the movable section6.

The worm screw15and the nut14may be rotatably mounted in a rigid casing17(for example of metal) carried by a rigid support18.

The support18may have a cradle shape having a horizontal base19on which the casing17rests. The horizontal base extends in the longitudinal direction X between two ends respectively extended by first and second transverse walls20a,20b. The first and second transverse walls20a,20bextend in the transverse direction Y and in a vertical direction Z. The first and second transverse walls20a,20bmay each comprise an opening traversed by the screw12.

The first and second transverse walls20a,20bmay be extended horizontally by two opposite fastening tabs22which can be fastened under the upper wall of the movable section (for example by screws22bscrewed into holes22aof the fastening tabs), as shown inFIGS. 3 to 5.

The casing17may be in one piece. In particular, it may be of metal.

As shown inFIGS. 5 to 7, the casing17may comprise a worm screw housing23within which the worm screw15is rotatably mounted.

The casing17may have first and second end faces24a,24brespectively arranged facing said first and second transverse walls20a,20bof the support18.

The casing17comprises a nut housing25which extends along the longitudinal axis X0and opens at the first and second end faces24a,24bof the casing in respective and opposite first and second openings26a,26b, the screw12passing through the first and second openings26a,26b.

The transmission device13may further comprise a first elastomer pad27ainterposed in compression between the first transverse wall20aof the support and the first end face24aof the casing (possibly in direct contact with the first transverse wall20aof the support and the first end face24aof the casing).

The transmission device13may also comprise a second elastomer pad27binterposed between the second transverse wall20bof the support and the second end face24bof the casing (possibly in contact with the second end face24bof the casing). It is possible that the second elastomer pad27bis compressed between the second transverse wall20bof the support and the second end face24bof the casing (possibly in direct contact with the second transverse wall20bof the support and the second end face24bof the casing).

Each elastomer pad27a,27bmay be in the form of an elastomer plate perpendicular to axis X0, where appropriate pierced by an opening28through which the screw12passes. Each elastomer pad27a,27bmay possibly comprise a returning wall29partially encompassing the casing17, in particular at the top.

The transmission device13may also comprise a bearing30, engaged in the second opening24bof the casing and traversed by the screw12. The bearing30may be of rigid material, in particular metal.

The bearing30may be in the form of a ring. It may comprise a cylindrical body31which penetrates the nut housing25through the second opening26b, and an enlarged flange32which is arranged opposite the second end face24bof the casing, with a certain clearance e for example of about 1 to several mm. The flange32is interposed axially between the second face26bof the casing and the second elastomer pad27b. Said flange32may have a non-circular edge33(for example rectilinear) which engages with a corresponding rim24cthat is part of the second end face26bof the casing, in order to immobilize the bearing30rotationally relative to the casing17.

The nut14is in rigid axial abutment against the free end of the cylindrical body31of the bearing (where appropriate with an interposed rigid washer34) and in rigid axial abutment against the casing in the direction of the first opening26a, while the flange32of the bearing is in elastic axial abutment against the second elastomer pad27b, which is thus compressed between the bearing30and the second transverse wall20bof the support20.

Other washers or bearing rings may be provided, in particular on each side of the nut14, in order to reduce friction and wear.

The nut14may comprise first and second cylindrical ends14a,14b. The first cylindrical end14acan rotate within a bore35of the casing. The second cylindrical end14bcan be nested in the cylindrical body31of the bearing30.

Said rigid axial abutment of the nut14against the casing17in the direction of the first opening26a, can be obtained for example by axial contact between the first cylindrical end14aand a corresponding portion of the casing, and/or axial contact between a shoulder14cdelimiting said first cylindrical end14aand a corresponding portion of the casing.

The nut14and the bearing30may be shaped to fit axially into the casing17through the second opening26bof said casing.

The transmission device13is particularly resistant due to the one-piece structure of the casing17and to the fact that the elastomer pads27a,27bcompensate both for the clearance between the casing17and the support18and the clearance between the nut14and the casing17.