ARRANGEMENT FOR DRIVING AN ADJUSTING SCREW

Abstract

The present invention relates to an arrangement (31) for driving an adjusting screw (20) about a longitudinal axis (A1), comprising a reduction gear housing (30) in which a drive section (28) of the adjusting screw (20) provided with a toothed wheel (32) is rotatably mounted, the toothed wheel (32) being provided for meshing with a drive pinion (34) so ​​as to drive the adjusting screw (20) in rotation, characterized in that it comprises an intermediate gear (44) which is rotatably connected to the drive section (28) of the adjusting screw (20) and which is provided with a locking device (51), the locking device (51) having a locked state in which it prevents the transmission of a rotational movement of the adjusting screw (20) to the toothed wheel (32), and an unlocked state which allows the transmission of a rotational movement of the toothed wheel (32) to the adjusting screw (20). Figure for the summary: figure 3.

Description

Title of the invention: ARRANGEMENT FOR DRIVING AN ADJUSTING SCREW Technical field of the invention

[0001] The present invention relates to an arrangement for driving an adjusting screw of the type used in a steering column to control the movement of a movable element relative to a fixed support. Technical background

[0002] Motor vehicles are sometimes equipped with steering columns having electrical adjustment of the steering wheel position. This adjustment is provided by a mechanism generally comprising an electric motor, a worm wheel reducer and a screw-nut system ensuring the transformation of the rotational movement into a translational movement.

[0003] When the adjustment is not activated, it is the adjustment mechanism which ensures that the steering wheel is held in position, particularly when driving. This mechanism must be able to withstand the forces exerted by the driver on the steering wheel, including in extreme situations such as heavy braking or even a frontal impact where these forces can become very significant.

[0004] To satisfy this need, the adjustment mechanism is designed to be irreversible, either at the level of the screw-nut system or at the level of the wheel and worm reducer.

[0005] The irreversibility of the movement is obtained at the expense of efficiency. For example, an irreversible screw-nut system may have an efficiency of less than 50% due to friction between the nut and the screw. This leads to oversizing the adjustment motor to compensate for these losses. In addition, this friction is a source of heating which can lead to premature wear. This is particularly true when seeking to increase the adjustment speed, as for example in the case of columns with large strokes allowing retraction functions to be performed. Summary of the invention

[0006] The invention aims in particular to remedy the drawbacks mentioned above by proposing an arrangement for driving an adjustment screw around a longitudinal axis, comprising a reduction gear housing in which a drive section of the adjustment screw provided with a toothed wheel is rotatably mounted, the toothed wheel being provided to mesh with a drive pinion so as to drive the adjustment screw in rotation, characterized in that it comprises a intermediate gear which is rotatably connected to the drive section of the adjusting screw and which is provided with a locking device, the locking device having a locked state in which it prevents the transmission of a rotational movement from the adjusting screw to the toothed wheel, and an unlocked state which allows the transmission of a rotational movement from the toothed wheel to the adjusting screw, the locking device being unlocked only by rotation of the toothed wheel.

[0007] Thanks to the invention, by separating the mechanism ensuring irreversibility from the mechanism ensuring the transmission of movement, the screw-nut system and the wheel and worm reducer can be designed so as to reduce internal friction and thus maximize their efficiency.

[0008] According to other characteristics of the invention:

[0009] - the toothed wheel comprises at least one drive pallet capable of cooperating with the locking device for causing the gear wheel to switch to the unlocked state when a driving torque is applied to it;

[0010] - the locking device comprises at least one rolling element provided with a elastic return device which biases the rolling element into a locking position where the rolling element opposes by friction the rotation of the intermediate gear, the rolling element being movable towards an unlocking position under the action of the drive pallet when the toothed wheel is subjected to a driving torque;

[0011] - the locking device comprises a pair of rolling elements and the elastic return device urges the rolling elements of the pair in the direction of their movement away from each other;

[0012] - the intermediate gear comprises at least one peripheral space arranged for receive the pair of rolling elements and at least one bearing surface arranged opposite a drive pallet so as to allow the intermediate gear to be driven in rotation by the drive pallet pressing against said at least one bearing surface;

[0013] - the peripheral space is delimited radially towards the inside of the inter gear intermediate by at least one facet arranged on the intermediate gear and radially outwards by a fixed axial surface;

[0014] - the intermediate gear comprises at least three pairs of rolling elements which are received in three associated peripheral spaces;

[0015] - the intermediate gear comprises at least three fins, each fin being in sandwiched between two drive vanes, each vane having two bearing surfaces associated with two drive vanes allowing drive in both directions of rotation.

[0016] The invention also provides a steering column) comprising at least one support fixed and a movable body which are linked together by an adjusting screw and an adjusting nut, and comprising at least one motor equipped with a drive pinion which meshes with a toothed wheel, characterized in that it comprises an arrangement according to one of the preceding characteristics which makes it possible to control a movement of the movable body relative to the fixed support. Brief description of the figures

[0017] Other characteristics and advantages of the invention will appear during the reading of the detailed description which follows for the understanding of which reference will be made to the appended drawings in which:

[0018] [Fig-1] is a perspective view which schematically represents a column of steering equipped with an arrangement for driving an adjustment screw by a geared motor in accordance with the teachings of the invention;

[0019] [Fig.2] is a perspective view which partially represents the arrangement of the [Fig.l] provided with a reducer housing according to a first embodiment of the invention;

[0020] [Fig.3] is a longitudinal sectional view along plane 3-3 which represents by initially the reducer housing of [Fig.2];

[0021] [Fig.4] is an exploded perspective view showing the main elements of the reducer housing of [Fig.2];

[0022] [Fig.5] is a perspective view showing an intermediate gear fitted the reducer housing of [Fig.2] with its elastic return device and its bearings 58;

[0023] [Fig.6] is a perspective view showing a toothed wheel fitted to the housing of reducer of [Fig.2];

[0024] [Fig.7] is a cross-sectional view along plane VII-VII which represents the reducer housing in a state of rest;

[0025] [Fig.8] is a view similar to that of [Fig.7] which represents the reducer housing in an intermediate state of unlocking;

[0026] [Fig.9] is a view similar to that of [Fig.7] which represents the reducer housing in an unlocked state before rotation of the intermediate gear;

[0027] [Fig. 10] is a view similar to that of [Fig.7] which represents the housing of reducer in an unlocked state after rotation of the intermediate gear;

[0028] [Fig. 11] is a perspective view similar to that of [Fig.4] which represents a arrangement according to a second embodiment with a different intermediate gear shape;

[0029] [Fig. 12] is a cross-sectional view similar to that of [Fig.7] which re shows the arrangement of [Fig.l 1] in the resting state. Detailed description of the invention

[0030] In the following description, identical, similar or analogous elements will be designated by the same reference numbers.

[0031] [Fig. 1] shows a steering column 10 intended to be installed in a motor vehicle (not shown). The steering column 10 comprises a fixed support 12, or cap, intended to be fixed to the chassis of the vehicle and a movable body 14, or lower tube, which carries elements of the steering column 10 such as an upper tube 16 in which the steering wheel axis 18 is inserted.

[0032] The movable body 14 is for example pivotally mounted relative to the fixed support 12. The upper tube 16 is slidably mounted in a longitudinal direction A1 relative to the movable body 14 by means of an adjustment screw 20 and a geared motor 22. For this purpose, the adjustment screw 20 comprises an adjustment section 24 which is screwed into an adjustment nut 26 fixed to the upper tube 16 and a drive section 28 which is rotatably received in a reduction housing 30 belonging to the geared motor 22.

[0033] An arrangement 31 for driving the adjustment screw 20 according to a first embodiment will now be described in more detail, considering FIGS. 2 to 4. A front-to-rear orientation along the longitudinal direction A1 of the adjustment screw 20 will be used, without limitation, with reference to a left-to-right orientation in FIGS. 2 to 4.

[0034] The drive section 28 is provided with a toothed wheel 32 designed to cooperate with a drive pinion 34 mounted on the drive shaft 36 of an electric motor 38 of the geared motor 22.

[0035] According to the embodiment shown, the toothed wheel 32 has helical teeth capable of meshing with the drive pinion 34 which here has the form of a worm screw. Of course, other types of teeth could also be used. The toothed wheel 32 is here mounted freely rotatable on a first cylindrical axial wall section 39 of the drive section 28.

[0036] According to the embodiment shown, the reducer housing 30 comprises at the front a bearing 40 which receives the free end of the drive section 28. The bearing 40 is here in the form of a ball bearing.

[0037] Advantageously, an intermediate gear 44 is mounted on the drive section 28, between the toothed wheel 32 and a rear radial surface 46 arranged at the rear of the drive section 28. This intermediate gear 44 is linked in rotation to the drive section 28. It is for example force-mounted on a second cylindrical axial wall section 48 of the drive section 28 which is here adjacent to the rear radial surface 46.

[0038] A locking screw 42 is here screwed into the free end of the drive section 28 to axially retain the toothed wheel 32 and the gear on the adjusting screw 20.

[0039] The intermediate gear 44, which is shown separately in [Fig. 5], here comprises a main tubular body 50 intended to be force-fitted onto the second cylindrical axial wall section 48 and a locking device 51.

[0040] The intermediate gear 44 here comprises three fins 52 which are provided to mesh with associated drive vanes 54 carried by the rear face of the toothed wheel 32, as described below and illustrated in [Fig. 6]. The fins 52 here extend in a plane transverse to the longitudinal direction AL

[0041] The main tubular body 50 here comprises, behind each fin 52, two substantially flat facets 56 forming rolling surfaces for a pair of associated bearings 58. The bearings 58 here have the shape of rollers with axes parallel to the longitudinal axis AL.

[0042] As illustrated by Figures 7 to 10, each pair of bearings 58 is received in a radial space 60 delimited radially inwardly by the main tubular body 50 of the intermediate gear 44, and radially outwardly by a fixed axial surface 62 formed here by the internal surface of a fixed ring 64 mounted in the reduction gear housing 30.

[0043] The fins 52 each comprise two axial bearing surfaces 66, on their circumferential end edges. These two axial bearing surfaces 66 are provided to receive in circumferential support bearing edges 68 formed on the drive vanes 54.

[0044] The drive vanes 54 are here in the form of axial wall portions extending axially towards the rear of the toothed wheel 32. According to the embodiment shown, the toothed wheel 32 comprises three drive vanes 54 and the intermediate gear 44 comprises three fins 52. Each drive vane 54 is received in a circumferential space 70 delimited by two axial bearing surfaces 66 of two fins 52.

[0045] The bearing edges 68 of two contiguous drive pallets 54 circumferentially delimit between them a peripheral space 72 in which one of the pairs of bearings 58 is housed.

[0046] Advantageously, an elastic return device 74, shown in particular in [Fig. 5], is mounted on the intermediate gear 44 so as to stress the two bearings 58 of each pair in the direction of their circumferential spacing. This tends to wedge each bearing 58 between a facet 56 and a part of the fixed axial surface 62 radially opposite each other, as illustrated in [Fig. 7].

[0047] The elastic return device 74 here comprises an annular part 76 which extends in a transverse plane and which is inserted between the rear radial surface 46 and the intermediate gear 44. It also comprises three pairs of tongues 78 which are each received between two bearings 58 of the same pair to urge them in the direction of their separation.

[0048] The bearings 58 and the elastic return device 74 together form the locking device 51, the operation of which will be described in more detail in relation to FIGS. 7 to 10.

[0049] In [Fig. 7], a portion of the reducer housing 30 is shown when the elements of the arrangement 31 are in a rest state, that is to say the locking device 51 is in the locked state. This rest state also applies when the adjusting screw 20 is subjected to axial stress via the adjusting nut 26.

[0050] In this state of rest, the jamming of the bearings 58 against the facets 56 and the fixed axial surface 62 prevents any rotation of the intermediate gear 44, and therefore of the adjusting screw 20, relative to the toothed wheel 32. This blocking is active in both directions of rotation of the adjusting screw 20.

[0051] It is noted that the bearing edges 68 of the drive pallets 54 are positioned at a distance from each of the bearings 58 and at a distance from each of the bearing surfaces 66.

[0052] In the case where the adjusting screw 20 is biased longitudinally, forwards or backwards, it transmits a rotational driving torque to the intermediate gear 44. The locked state of the locking device 51 prevents any relative movement of the intermediate gear 44 with respect to the toothed wheel 32.

[0053] In the case where the electric motor 38 is actuated in order to control a longitudinal adjustment, the rotation of the drive pinion 34 causes a rotation of the toothed wheel 32 in the direction of the arrow F1, as illustrated by [Fig.8].

[0054] The rotation of the toothed wheel 32 firstly causes, as illustrated by [Fig.8], a slight circumferential displacement of each drive vane 54 until it comes into contact with the opposite bearing 58. The pressure exerted by each drive vane 54 against the associated bearing 58 causes compression of the elastic return device 74 which allows the associated bearing to move closer to the opposite bearing 58 of the same pair.

[0055] The rotation of the toothed wheel 32 causes secondly, as illustrated by [Fig.9] and by the arrow F2, a displacement of the bearing 58 which then reaches a position, in its peripheral space 72, where it has a slight freedom of movement, a clearance. This clearance is obtained by a particular configuration of the facets 56 with respect to the fixed axial surface 62, each facet 56 being inclined so that the radial dimension of the peripheral space 72 increases slightly when the bearing 58 approaches the other bearing 58 of the same pair.

[0056] By moving circumferentially, the bearings 58 allow the bearing edges 68 of each drive vane 54 to move circumferentially until it comes into contact with a bearing surface 66 of an associated fin 52. This position, illustrated by [Fig.9], allows the toothed wheel 32 to drive the intermediate gear 44 in rotation, which causes rotation of the adjusting screw 20, as illustrated by [Fig. 10] and by the arrow F3.

[0057] The operation of the arrangement according to the invention has been described in Figures 7 to 10 in the case of clockwise rotation. Of course, the operation is similar when the motor 38 drives the toothed wheel 32 in rotation in the counterclockwise direction.

[0058] In Figures 11 and 12, an arrangement 31 is shown according to a second embodiment which differs from the first embodiment mainly by the shape of the intermediate gear 44 and the drive pallets 54 of the toothed wheel 32. For the description of this second embodiment, emphasis will be placed on the differences compared to the first embodiment, the general principle of the invention and the operation being substantially identical.

[0059] As shown in Figures 11 and 12, the intermediate gear 44 comprises a smooth axial section 80 which is provided to receive the toothed wheel 32 freely rotatably and which extends from a front axial end of the main tubular body 50. The fins 52 no longer extend in a transverse plane but in a longitudinal plane. A circumferential space 70 is delimited by two contiguous fins 52 to receive both drive vanes 54 of the toothed wheel 32 and a pair of bearings 58.

[0060] According to the second embodiment, the toothed wheel 32 comprises three pairs of drive vanes 54 which are shaped so that two drive vanes 54 of a pair extend on each side of a fin 52.

[0061] The main tubular body 50 here comprises, for each pair of bearings 58, a single facet 56, or flat, which forms a rolling track.

[0062] The operation of the second embodiment is similar to that of the first embodiment.

[0063] In the two embodiments described above, the intermediate gear 44 comprises three pairs of bearings 58 and three fins 52. According to alternative embodiments, the intermediate gear 44 could comprise two pairs of bearings 58 and two fins 52, or more than three pairs of bearings 58 and more than three fins 52.

Claims

Claims

1. Steering column (10) comprising at least one fixed support (12) and a movable body (14) which are connected together by an adjusting screw (20) and an adjusting nut (26), and comprising at least one motor (38) equipped with a drive pinion (34) which meshes with a toothed wheel (32), characterized in that it comprises an arrangement (31) for driving the adjusting screw (20) about a longitudinal axis (A1), this arrangement (31) making it possible to control a movement of the movable body (14) relative to the support, in which the arrangement (31) comprises - - a reduction gear housing (30) in which a drive section (28) of the adjusting screw (20) provided with a toothed wheel (32) is rotatably mounted, the toothed wheel (32) being provided to mesh with a drive pinion (34) so ​​as to drive the adjusting screw (20) in rotation,- an intermediate gear (44) which is rotatably connected to the drive section (28) of the adjusting screw (20) and which is provided with a locking device (51), the locking device (51) having a locked state in which it prevents the transmission of a rotational movement of the adjusting screw (20) to the toothed wheel (32), and an unlocked state which allows the transmission of a rotational movement of the toothed wheel (32) to the adjusting screw (20), the locking device (51) being unlocked only by rotation of the toothed wheel (32).,

2. Steering column (10) according to the preceding claim, characterized in that the toothed wheel (32) comprises at least one drive pallet (54) capable of cooperating with the locking device (51) to cause the transition to the unlocked state when the toothed wheel (32) is subjected to a drive torque.

3. Steering column (10) according to the preceding claim, characterized in that the locking device (51) comprises at least one rolling element (58) provided with an elastic return device (74) which urges the rolling element (58) into a locking position where the rolling element (58) opposes by friction the rotation of the intermediate gear (44), the rolling element (58) being movable towards an unlocking position under the action of the drive pallet (54) when the toothed wheel (32) is subjected to a driving torque.

4. Steering column (10) according to the preceding claim, characterized in that the locking device (51) comprises a pair of rolling elements (58) and the elastic return device (74) urges the rolling elements (58) of the pair in the direction of their movement away from each other.

5. Steering column (10) according to the preceding claim, characterized in that the intermediate gear (44) comprises at least one peripheral space (72) arranged to receive the pair of rolling elements (58) and at least one bearing surface (66) arranged opposite a drive pallet (54) so ​​as to allow the intermediate gear (44) to be driven in rotation by the drive pallet (54) pressing against said at least one bearing surface (66).

6. Steering column (10) according to the preceding claim, characterized in that the peripheral space (72) is delimited radially towards the inside of the intermediate gear (44) by at least one facet (56) arranged on the intermediate gear (44) and radially towards the outside by a fixed axial surface (62).

7. Steering column (10) according to the preceding claim, characterized in that the intermediate gear (44) comprises at least three pairs of rolling elements (58) which are received in three associated peripheral spaces (72).

8. Steering column (10) according to the preceding claim, characterized in that the intermediate gear (44) comprises at least three fins (52), each fin (52) being interposed between two drive vanes (54), each fin (52) comprising two bearing surfaces (66) associated with two drive vanes (54) allowing drive in both directions of rotation.

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