Fitting for a vehicle seat

[0001] The present application is a continuation of International Application PCT/EP2003/011780, filed Oct. 24, 2003, and which designates the U.S. The disclosure of the referenced application is incorporated herein by reference.

[0002] The present invention relates to a fitting for a vehicle seat, in particular a detent fitting for an automobile seat, which allows for the adjustment of the inclination of the backrest of the seat.

[0003] A fitting of this general type is known from EP 0 720 930 B1, and corresponding U.S. Pat. No. 5,681,086. In the fitting disclosed in these documents, three locking elements are provided, near their teeth, with abutment faces protruding laterally to their direction of movement and hemmed in by steps in the adjacent guideways. The protruding abutment faces are of a greater hardness than the guideways which receive the protruding abutment faces, and thus in the case of high load in the direction of rotation of the fitting, for example in the event of a crash when torque is applied via the back rest to the fitting part to which it is joined, these abutment faces dig into the guideways, thus preventing the respective locking element from moving.

[0004] The present invention is based on the object of improving a fitting of the type mentioned above. This and other objects and advantages of the present invention are achieved by a fitting for a vehicle seat, in particular a detent fitting for an automobile seat, having first and second fitting parts which are mounted to be rotatable relative to each other about an axis of rotation, with the second fitting part including an inwardly facing toothing which extends along at least a portion of an arc, at least one locking element positioned between the first and second fitting parts and mounted for movement between longitudinal guide surfaces formed on the first part and so that the locking element is moveable in a radial direction between a radially outward locking position and a radially inward release position, the locking element having on its radial outward side at least one tooth for engaging the toothing of the second part when the locking element is in the locking position, and the locking element further having longitudinal sides which oppose respective ones of the longitudinal guide surfaces, with at least one of the longitudinal sides including a step dividing the respective longitudinal side into a first section and an adjacent second section. The second section is between the step and the tooth. Also, the second section is set back from the first section so as to be further spaced from the associated guide surface.

[0005] The locking element thus bears only in the first section against the respective guide surface. In the event of the second fitting part receiving a high torque impact, especially in the event of a crash, the locking element can perform a tilting movement relative to the guiding surfaces, in which case the locking element is able to follow any radial expansion of the second fitting part, and the teeth remain interlocked. Thus the fitting according to the invention can withstand higher loads. The fitting according to the invention can be employed as an adjuster, for example for purposes of adjusting height or inclination, in all vehicle seats comprising adjustable component groups, such as an inclination adjustable back rest or height and/or inclination adjustable seat part.

[0006] During the tilting movement of the locking element, the edge of the step adjacent the first section preferably serves as a pivot axis. The position of the step is preferably chosen in such a way that the respective surface normal of the existing tooth flank intersects with the associated longitudinal side of the locking element in the second section. The force transmitted by the toothing of the second fitting part, whose effective curve corresponds to this surface normal, applies torque to the locking element, thereby supporting the tilting movement of the locking element.

[0007] In a preferred embodiment, the locking element is doubly supported by an eccentric acting upon the locking element from its radially inward facing side, in order to move it in a radially outward direction. Better support can then be provided for the tilting movement and, in the case of two diagonally opposed locking elements, these receive the load from the second fitting part and transmit it diagonally through the eccentric. In this way, greater forces can be transmitted and hence higher degrees of stability can be achieved.

[0015] For the purpose of adjusting the inclination of its backrest 3 with respect to its seat part 2, a vehicle seat 1 of an automobile comprises on its two sides one fitting 5 each, embodied as a detent fitting. The two fittings 5 are interconnected in gear transmission manner by means of a transmission bar 7. A hand lever 9, which is fixedly mounted to the transmission bar 7, serves to manually activate the fittings 5 concurrently. The indications of direction given below with respect to fitting 5 relate to the cylinder coordinate system defined by the transmission bar 7.

[0016] Each fitting 5 comprises a first or lower fitting part 11, and a second or upper fitting part 12, which are held together in the axial direction by retaining plates (not shown). The first fitting part 11 is connected to the seat part 2, and the second fitting part 12 is connected to the backrest 3.

[0017] The first part 11 is equipped with four guiding and bearing segments 15, which on the radially outward side form a cylindrical support surface with four sections, for a correspondingly curved, radially inward facing support surface on the second fitting part 12, which is embodied as a circle which is centered about the horizontal axis of rotation defined by the bar 7. This support surface of the second fitting part 12 further comprises a toothing 14. Each of two pairs of guiding and bearing segments 15 forms one guideway, extending radially and defined by parallel guide surfaces 17 (FIG. 4), for a movably attached toothed segment 19.

[0018] Each toothed segment 19, also referred to herein as a locking element, comprises a plurality of teeth 21 on a convexly curved side located radially further outward, which can cooperate with the toothing 14 of the second fitting part 12 in order to lock the fitting 5. The two corresponding guiding and bearing segments 15, by means of the guide surfaces 17, guide the longitudinal sides 22, which extend in the direction of movement of the toothed segment 19. A more detailed description of these longitudinal sides 22 will follow later. The radially inward side of toothed segment 19 comprises two convex locking cams 23 at a distance from one another.

[0019] In order to push the two toothed segments 19 radially outward (in the locking direction), a disc shaped eccentric 25 is provided, which is mounted on the transmission bar 7 by means of a sleeve shaped driving element 27. Whereas the driving element 27 is fixedly mounted on the transmission bar 7, a backlash in the direction of rotation is provided between the eccentric 25 and the driving element 27, which compensates for torsions in the transmission bar 7, as well as for positional differences between the two fittings 5.

[0020] The eccentric 25 is pre-loaded by two spiral springs 29 in one direction of rotation, i.e. the closing direction. On the outer circumference of the eccentric 25, four radially outward projecting eccentric cams 31 are provided with one clamping face each, the latter being eccentrically curved in relation to the transmission bar 7. In the circumferential direction between the eccentric cams 31, the eccentric 25 is sufficiently offset in a radially inward direction to accommodate the locking cams 23.

[0021] A driving plate 35, which is fixedly mounted on the eccentric 25 and cooperates in a generally known way with the two toothed segments 19 via slot-and-bolt guideways, serves to retrieve the toothed segments 19 in a radial direction inward, i.e. the unlocking process, which is initiated by rotating the transmission bar 7 by means of the hand lever 9.

[0022] The longitudinal sides 22 are not shaped uniformly in all their length. Rather, at a point about one third down their length from the teeth 21, they each comprise a step 41, which divides each of the longitudinal sides 22 into a first section 43, bearing as a contact surface against the guide surface 17, and a second section 45 being set back and being a free surface at a distance from the guide surface 17. The second section 45 extends from the step 41 to the teeth 21, and constitutes about one third of the length of the side 22, whereas the first section 43 extends from the step 41 to the locking cams 23 and constitutes about two thirds of the length of the side. The offset is achieved by cutting the toothed segment 19 in an appropriate way. The extent, i.e. the dimension of the step 41 transversally to the lengthwise extension of the toothed segment 19, is only on the order of fractions of a millimeter, with the result that the finer detail of the longitudinal sides 22 is difficult to see in the true-to-scale representation in FIG. 1. For this reason, FIGS. 4 and 5 are not true to scale.

[0023] Starting from an unlocked state, in which the two toothed segments 19 are radially located inward, the eccentric 25, by means of pre-loading the springs 29, is rotated in such a way that the eccentric cams 31 first come to bear against the locking cams 23, and then, in the course of further rotation, push the doubly supported toothed segments 19 outward via the locking cams 23. As soon as the toothed segments 19 engage the upper fitting part 12, the respective fitting 5 is locked.

[0024] If, in the locked state, high torque is applied to the second fitting part 12, for example in the event of a crash, then via the toothing 14 and the engaging teeth 21, the toothed segments 19 are tilted transversely to their direction of movement towards the guide surface 17, the edge of step 41 adjoining the first section 43 serving as a pivot axis, while on account of the lateral support of the associated locking cam 23 on the eccentric 25, an opposing locking force is built up.

[0025] The surface normal N (FIG. 4) of the impacted side of the teeth 21 intersects with the longitudinal side 22 (the one situated radially inward during the tilting movement and comprising the step 41 which serves as the pivot axis) in the second section 45 (above the step 41 as seen in FIG. 4), which means that the tilting movement is reinforced. By contrast, in the case of the known fitting described in the introduction, the surface normal would intersect with the longitudinal side below the step, which means that a moment would be exerted against the tilting movement.

[0026] In the case of a high torque load burden being put on the fitting 5, the second fitting part 12 expands radially on account of material expansion, which causes the diameter of the toothing 14 to expand. Because, on the one hand, the toothed segment 19 executes a tilting movement and, on the other hand, the locking cam 23 is resting on the eccentric cam 31, thereby holding the toothed segment 19 in the locked position and slaving it, the radial distance of the teeth 21 of the toothed segment 19 increases in relation to the median axis of the transmission bar 7, i.e. relative to the center of fitting 5. Thanks to the solution introduced by the invention, the teeth 21 follow the expansion of the toothing 14 more closely, thereby maintaining the engagement of the teeth.