Element for the axial fastening of a wheel to the hub of a motor vehicle axle

Description

[0001] The present invention claims priority from French application No. 2100987 filed on 02.02.2021. Technical field of the invention

[0002] The invention relates to the field of fastening devices arranged for clamping a wheel axially against a hub configured for mounting on a motor vehicle axle. Such a hub is, for example, of the type equipped with a brake disc or arranged as a drum. More specifically, the invention concerns such a fastening device comprising a screw and a ring that ensure the effectiveness, quality, and durability of the wheel clamping on the hub, at a predefined and reproducible tightening threshold. Prior art

[0003] Motor vehicles are typically equipped with wheels for travel on a road. Wheels consist of a rim around which a tire is mounted and are individually attached to a vehicle axle via a hub that drives the rotating wheel. The hub may, for example, be of the type equipped with a brake disc or arranged as a drum brake, in which case the rim is bolted axially to the hub.

[0004] To hold the wheel in position on the hub, the rim is axially clamped against the hub by means of a plurality of axial extension fasteners that are identically arranged and angularly distributed around the wheel's axis of rotation. Such a fastener essentially comprises a screw which has at its proximal end a head equipped with a drive mechanism for rotating the screw and at its distal end a thread for its axial tightening to the hub.

[0005] The proximal and distal notions used here and thereafter are relative notions assessed according to the general extension axis of a said fastening member and / or the rotation axis of the hub and therefore of the rim fixed to the hub via the fastening members, with respect to the position of the screw head which is located at the proximal end of the fastening member.

[0006] To mount the wheel onto the hub, the rim is positioned in the center position on the hub. The bolts of the various fastening components are then inserted axially through smooth-faced bores in the rim, and then screwed into threaded bores in the hub. The bolts are thus tightened successively against the rim in a predetermined order, until the rim is axially clamped against the hub by the bolt heads pressing against the rim. Due to the tightening torque exerted by the bolts against the rim, each bolt exerts an axial clamping force on the rim against the hub, which ultimately secures the wheel to the hub.

[0007] To ensure reliable wheel-to-hub tightening, it is necessary to verify the correct centering of each bolt relative to the rim and hub, and to prevent spontaneous loosening of the bolts due to the stresses they undergo while the vehicle is in motion. These stresses result primarily from the multidirectional loads that the bolts cyclically bear as the vehicle moves, which are particularly significant when cornering and / or braking.

[0008] However, it appears that centering the screws on the hub and / or preventing them from loosening is difficult to achieve. This is due to the radial mounting clearance between the screw and the rim, the frequent buckling of the screw when tightening the rim axially against the hub, and / or the uneven tensile forces experienced by the screw along its axial extension.

[0009] Achieving a coaxial fit of the screws within the threaded holes of the hub is also tricky, otherwise allowing for mounting clearances that increase the risk of the screws loosening. Furthermore, it is common for the tightening force and / or the coefficients of friction between the axially contacting surfaces to be uncontrolled.

[0010] To reinforce the centering of the screws inside the hub and prevent them from loosening, it has been proposed to equip each of the fixing elements with a ring of elastically deformable shape which is interposed in axial support between the head of the screw and the rim of the wheel, as shown for example in document EP1529969-B1 (AGRATIA SPA).

[0011] According to this document, the screw head bears axially against the ring via a conical bearing surface, and the ring bears against the rim via a hemispherical bearing surface. This ensures the screw remains centered within the hub. Furthermore, the ring exhibits elasticity, giving it a spring-like structure, which reinforces the axial engagement of the screw threads against the threaded bore of the hub, thus preventing the screw from loosening while the vehicle is in motion.

[0012] However, this solution needs improvement, particularly regarding the quality of the rim's clamping force against the hub. It is essential to ensure that the rim's clamping force against the hub is consistent, guaranteeing that the bolts cannot loosen under the loads they bear while the vehicle is in motion. It is also important to ensure that the wheel's attachment to the hub via all the bolts is uniform, with a predefined tightening threshold that can be replicated for each bolt.

[0013] It is also useful that the quality of the rim clamping against the hub is not subject to the material of the rim, or in other words that the methods of fixing the wheel to the hub via the fixing devices are compatible with a rim of any metallic material, and this without affecting the quality of the contact of the fixing devices against the rim at a predefined tightening threshold. Presentation of the invention

[0014] Based on the observation just made, the invention aims to overcome the shortcomings of the state of the art at least with regard to the difficulties to be overcome previously mentioned.

[0015] To this end, the invention provides a wheel fixing device for axial application against the hub of a motor vehicle axle. By way of non-restrictive illustration, said hub may be of the type equipped with a brake disc or be arranged as a drum, for example.

[0016] The fastening element proposed by the invention is of the type comprising a screw provided with a head for axial support against a ring configured to itself axially support the rim of the wheel as a result of screwing the screw into the inside of a tapped bore that comprises the hub.

[0017] The invention essentially aims to provide such a fastening device that ensures a firm clamping of the wheel rim against the hub, provided it is axially supported.

[0018] without affecting correct centering of the screw on the hub, which is homogeneous and reproducible at a predefined clamping threshold of the rim against the hub by a plurality of such identical fixing devices which are angularly distributed around the axis of rotation of the hub, and / or which can be used regardless of the rim material without affecting the quality of their axial support against each other.

[0019] He is specifically sought after: ) to compensate as best as possible, during wheel tightening on the hub, for an initial deflection of the screws included in said fastening elements jointly used for fixing the rim to the hub, and / or ) to provide compensation for assembly clearances between the elements that are successively stacked axially during wheel tightening on the hub by the fastening elements, in particular the screw head, the ring, the rim and the hub, and / or ) to prevent a risk of spontaneous loosening of the screws included in the wheel-to-hub fastening elements, in particular by preventing slippage of the contact surfaces against each other as a result of tightening the rim to the hub and / or during vehicle movement, ) to guarantee control of the tightening force to be applied to a predefined setpoint for tightening the screws of the fastening elements,by promoting adhesion between the surfaces in contact with each other as a result of tightening the rim to the hub, ) to be able to control the achievement of elastic clamping of the rim against the hub, at least by applying elastic axial tension to the screws, and this without affecting their centering inside the hub and / or without compromising the coefficient of friction obtained between the surfaces successively brought into axial contact with each other.

[0020] It should be noted that such research is also subject to the constraint of reducing the costs associated with implementing the invention, in the context of severe economic competition in the automotive sector.

[0021] To achieve this, the invention proposes a said fixing element by providing a ball joint support for the screw head against the ring and a conical support for the ring against the rim.

[0022] The ball-and-socket joint of the screw head on the bushing allows for optimal centering of the screw relative to the hub to which it is screwed. Their contact surfaces permit multidirectional movement of the screw relative to the rim and hub, thus limiting significant bending of the screw when attached to the hub. This result is simultaneously achieved by preventing, under the effect of tightening the rim axially against the hub, relative movement between the bushing and the rim that could degrade the coefficient of friction between their contact surfaces. The bushing is structurally designed as a robust component that cannot deform under the effect of tightening applied to a minimum predetermined threshold.

[0023] This provides a firm, conical axial support for the ring against the rim, and the tightening achieved at the set point is reproducible for all the fastening components used to secure the wheel. Furthermore, during rim tightening against the hub, an elastic deformation of the rim by the ring can be exploited to reinforce—based on a localized elastic deformation of the rim caused by the rings—an elastic tightening of the rim against the hub, which is at least achieved by an elastic axial extension of the bolt under axial stress.

[0024] The rim can be made of any metallic material, provided the contact surfaces between the ring and the rim remain constant. The effects of friction between the ring and the rim are minimized by their axial contact via conical contact surfaces, which are constant and thus promote a constant coefficient of friction between the ring and the rim. Such firm and static contact of the ring against the rim also limits moisture infiltration between them, thereby reducing rim corrosion.

[0025] In the case of a rim - made of steel for example - which may be locally deformed by the ring as a result of the tightening force exerted by the screw, not only does such deformation not affect the extent of the contact surfaces between the ring and the rim but also reinforces by elasticity the support of the threads of the screw inside the tapped bore of the hub which receives it.

[0026] Furthermore, the firm and static conical bearing surface of the ring against the rim can be defined to optimize the generation of an axial thrust component of the rim acting against the hub. This allows for the generation of an axial clamping force sufficiently effective to hold the rim against the hub, while simultaneously reducing the clamping force required at the setpoint threshold—reproducible for all fasteners used to attach the wheel to the hub—without risk of loosening. The axial tension on the screw can then be limited, thus restricting significant bending of the screw due to uneven stress distribution across its threads.

[0027] Furthermore, regarding the contact surfaces between the screw head and the bushing, their spherical shape facilitates the correct application in the workshop of any treatment and / or coating to these surfaces, such as zinc plating, thus ensuring the long-term stability of the friction coefficient between the surfaces. The slight movement of the screw relative to the bushing for centering within the hub does not affect the maintenance of constant contact surfaces between the screw head and the bushing, and therefore does not affect the maintenance of the friction coefficient between the contact surfaces of the bushing and the rim.

[0028] Furthermore, this limits the axial extension of the ring towards the screw head, without affecting the desired ball joint travel of the screw for centering. This prevents the ring from protruding towards a screw rotation drive element at its proximal end, which can then be formed around the periphery of the screw head to facilitate its rotation by an operator.

[0029] Accordingly, a fastening element according to the invention is arranged for clamping a wheel rim onto a motor vehicle hub. The fastening element, which provides overall axial extension, comprises a screw with a head that bears axially against a ring threaded around a smooth face of the screw shank. This smooth face is extended axially by an external thread of the screw shank extending from its distal end. The axially opposite faces of the ring have a partially spherical shape on one face and a conical shape on the other.

[0030] According to the invention, the distal face of the screw head is arranged in a cooperating spherical cap by interlocking with a complementary spherical cap on the proximal face of the ring. The conical face of the ring is formed on its distal face, creating a conical interlocking element.

[0031] Preferably, the spherical cap of the screw head is a male spherical cap that cooperates by interlocking with the spherical cap of the ring, which is a female spherical cap. Even more preferably, the conical face of the ring is formed at the periphery of the distal face of the ring, creating a male interlocking element.

[0032] The ring material is a metallic material that can be chosen from any type of metal, such as steel or aluminum. The ring has a robust, non-deformable structure, being held in place by an axial clamping force of the rim against the hub by the fastening element, which conforms to a predefined clamping threshold of the rim to the hub.

[0033] Other characteristics of the fastening element relating to the invention as defined above are set out below.

[0034] The generatrix of the conical conformation face of the ring is advantageously oriented substantially parallel to the generatrix of the spherical cap formed on the proximal face of the ring.

[0035] The axial extension of the spherical cap included in the ring is preferably at most equal to the axial extension of the spherical cap included in the screw head.

[0036] The spherical cap of the screw head is advantageously axially extended towards its proximal end by a male drive element for screw rotation. In one variant, this drive element may be female.

[0037] Preferably, the proximal end of the male spherical cap of the screw head is flush with the smooth face of the screw shank around which the ring is threaded.

[0038] The invention also relates to a motor vehicle conventionally equipped with wheels, each fixed to its respective hub via a plurality of fastening elements angularly distributed around the hub's axis of rotation. The hubs are arranged, in particular, to allow axial clamping of the rim against the hub via the fastening elements, and may be of any type, such as a hub equipped with a brake disc or arranged as a drum, for example.

[0039] Each fastening component comprises a screw around which a bushing is threaded, bearing axially against a rim of the wheel. The respective screws of the fastening components pass through bores in the rim and are screwed to the hub by axially tightening the bushings against the rim.

[0040] Such a motor vehicle falling within the scope of the invention is principally recognizable in that said fastening elements are each in conformity with a fastening element of the invention as just described.

[0041] More specifically, the spherical caps of the screw heads of the fasteners are at least partially housed within the spherical caps of the rings. The conical faces of the rings are fitted into respective recesses in the rim, each of which has at least one conical shape complementary to the conical shape of the ring.

[0042] The rim material is in particular a metallic material chosen indifferently from any metallic material, including for example steel or aluminium. Presentation of the figures

[0043] The invention will be better understood upon reading the following detailed description of an exemplary embodiment, in relation to the following figures in the attached plates: [ Fig. 1 ] There figure 1 is a schematic axial view representation of a fastening element pertaining to an embodiment of the invention, illustrated in the position of clamping a motor vehicle wheel against a hub fitting an axle of the vehicle. Fig. 2 ] There figure 2 is an exploded axial view representation of the fastening element shown on the figure 1 . [ Fig. 3 ] There figure 3 is an assembled axial view representation of the fastening element shown on the figure 2 . Detailed description of the invention

[0044] The figures and their detailed, non-limiting descriptions illustrate the invention in specific ways that do not restrict its scope. The figures and their detailed descriptions of an example of an embodiment of the invention may serve to further define it, if necessary in relation to the general description above. Furthermore, to avoid cluttering the figures and thus facilitate their reading, the reference numbers assigned to the terms and / or concepts used to describe the invention and indicated in any one of the figures may be repeated in the description of any other figure without implying their presence in all figures.

[0045] On the figure 1 A wheel rim 1 is mounted on a hub 2 fitted to a motor vehicle axle for the rotational drive of the wheel. For example, the hub 2 may be a hub equipped with a brake disc or be arranged as a drum.

[0046] The rim 1 is fixed to the hub 2 via a plurality of fastening members 3 which are angularly distributed around the axis A1 of rotation of the hub 2 and consequently around the axis of rotation of the rim 1 mounted and fixed coaxially to the hub 2. Each of the fastening members 3 is arranged according to the fastening member 3 shown in the figures 1 à 3 and relating to an example of an implementation of the invention.

[0047] As illustrated in the figure 1 The rim 1 is fixed to the hub 2 by axial bolting. The fasteners 3 exert an axial clamping force S1 on the rim 1 against the hub 2, according to a predefined clamping threshold. The fastener 3 shown comprises an axial extension screw 4 A2 having a head 12 extended by a shank 5.

[0048] The shank 5 of screw 4 has a proximal section whose periphery has a smooth face 6. The proximal section of the shank 5 of screw 4 slides through a bore 7 with a smooth face in the rim 1. The smooth face 6 of the shank 5 of screw 4 is extended by a distal section having an external thread 8a which cooperates by screwing with a tapped bore 8b provided in the hub 2.

[0049] As shown in the figures 1 à 3, the head 12 of screw 4 has at its proximal end a male drive member 9 for rotation of the screw 4, which is arranged in a polygon whose faces are provided on the periphery of the screw 4. The drive member 9 is extended at its distal end by a male spherical cap 10a which extends from the drive member 9 towards the smooth face 6 of the rod 5 which the male spherical cap 10a is flush with.

[0050] The fastening element 3 also includes a ring 11 which is threaded around the smooth face 6 of the screw shank 4 and bears axially against the rim 1. The ring 11 is formed from any metallic material, such as steel or aluminum, for example. The ring 11 is structurally robust, preventing its deformation when the rim 1 is tightened against the hub 2 to the specified threshold.

[0051] The ring 11 has at its proximal end a proximal face shaped as a female spherical cap 10b. The axial extension E1 of the female spherical cap 10b of the ring 11 is at most equal to the axial extension E2 of the male spherical cap 10a formed at the distal end of the drive member 9. This prevents the drive member 9 from being covered by the ring 11 and thus facilitates the operation of the screw 4 in rotation by an operator via a male drive member 9.

[0052] The ring 11 has at its distal end a distal face with a conical shape 11a – more specifically, a frustoconical shape. A small radial clearance is provided between the ring 11 and the screw shank 4, allowing the shank to move relative to the fixed ring 11. This facilitates centering the screw 4 within the hub 2 without affecting the ring 11's firm contact with the rim 1. In the illustrated example, the generatrix G1 of the conical face 11a of the ring 11 is oriented substantially parallel to the generatrix G2 of the female spherical cap 10b of the ring 11.

[0053] The conical conformation face 11a of the ring 11 is at least partly housed inside a cavity 11b in the rim 1. The cavity 11a has a conical conformation complementary to that of the ring 11, so that the conical conformation face 11a of the ring 11 bears firmly axially against the rim 1 when it is clamped against the hub 2.

[0054] During the progressive tightening of screw 4 into hub 2, any misalignment of screw 4 relative to hub 2 is spontaneously corrected by the free movement of the screw head 12 within the ring 11, until the rim 1 is effectively tightened to the specified threshold (S1) against hub 2. Under these tightening conditions, the rigid ring 11 bears axially against rim 1 via the tapered interlocking joint between them. Relative movement between ring 11 and rim 1 is thus prevented to avoid variations in the coefficient of friction between the ring 11 and rim 1 during vehicle movement.

[0055] The materials used for the ring 11 and the rim 1 can be chosen interchangeably, allowing control of the coefficient of friction between them. Since the axial thickness E3 of the rim 1, considered in the areas where the wheel is clamped to the vehicle, is reduced due to the presence of the recesses 11b, an intrinsic elasticity of the rim 1 can be exploited during clamping to induce deformation under the forces exerted by the rings 11.

[0056] This localized elastic deformation, caused by the compression of the rim 1 by the rings 11, does not affect the extent of the contact surfaces between the rings 11 and the rim 1, nor the centering within the hub 2 of the screws 4, which are mounted flexibly in a ball joint relative to the ring 11. This elastic deformation of the rim 1 allows for the completion of an elastic extension of the screws 4, which are placed under axial stress when the rim is tightened against the hub. This ensures a firm grip of the threads of the screws 4 against those of the tapped holes 8b in the hub 2. Ultimately, this prevents the screws 4 from loosening due to the robust grip of the rings 11 against the rim 1, without affecting the centering of the screws 4 within the hub 2.

[0057] The dimensions and / or geometry of the fastening element 3 allow for optimal adjustment of its overall size, both diametrically and axially. This facilitates the adaptation of the fastening element 3 according to the arrangement and / or dimensions of the rim 1 in the wheel-to-vehicle clamping zones and / or according to the type of screw 4 fitted to the fastening element 3.

[0058] The robustness of the ring 11 and the limitation of the clamping force S1 do not affect the retention of the ring 11 in its clamped position between the head 12 of the screw 4 and the rim 1, and allow for a reduction in the axial stresses borne by the screw 4 without risk of loosening. The clamping of the rim 1 against the hub 2 by all the fasteners 3 is uniform, the clamping achieved via the screws 4 of each of the fasteners at the setpoint threshold being reproducible by an operator for each of the fasteners 3.

Claims

1. Fastening member (3) arranged for tightening (S1) a wheel rim (1) on a motor vehicle hub (2), the fastening member (3) of overall axial extension (A2) comprising a screw (4) provided with a head (12) for axial bearing against a ring (11) threaded around a smooth face (6) of a rod (5) of the screw (4), said smooth face being extended axially by an external thread (8a) of said rod (5) of screws (4) extending at its distal end, the axially opposite faces of the ring (11) having at one of its said faces a partially spherical shape and at the other of its said faces a conical shape, characterized in that the distal face of the screw head (12) (4) is arranged in a spherical cap (10a) cooperating by fitting with a spherical cap (10b) of complementary shape that the ring (11) has at its proximal face, the conical shaping face (1 1a) of the ring (11) being arranged at its distal face in forming a member d The nesting with conical bearing surface.

2. Fastening member (3) according to claim 1, characterized in that: - the spherical cap (10a) of the head (12) of the screw (4) is a male spherical cap cooperating by fitting with the spherical cap (10b) of the ring (11) which is a female spherical cap, and - the conical shaping face (11a) of the ring (11) is formed at the periphery of the distal face of the ring (11) forming a male fitting member.

3. Fastening member (3) according to any one of the preceding claims, characterized in that the material of the ring (11) is a metallic material chosen from any metallic material.

4. Fastening member (3) according to any one of the preceding claims, characterized in that the generatrix (G1) of the conical shaping face (11a) of the ring (11) is oriented substantially parallel to the generatrix (G2) of the spherical cap (10b) formed on the proximal face of the ring (11).

5. Fastening member (3) according to any one of the preceding claims, characterized in that the axial extension (E1) of the spherical cap (10b) comprised in the ring (11) is at most equal to the axial extension (E2) of the spherical cap (10a) comprised in the screw (4) head (12).

6. Fastening member (3) according to any one of claims 2 to 5, characterized in that the male spherical cap (10a) comprised in the head (12) of the screw (4) is extended axially towards its proximal end by a member (9) for driving the screw (4) in rotation by a male member.

7. Fastening member (3) according to claim 2 or according to any one of claims 3 to 6, caught in the dependency of claim 2, characterized in that the proximal end of the male spherical cap (10a) comprised in the screw (4) head (12) is flush with said smooth face (6) of the screw (4) rod (5) around which the ring (11) slips.

8. Motor vehicle provided with wheels each fixed to respective hubs (2) via a plurality of fixing members (3) which are angularly distributed around the axis of rotation of the hub (2), the fixing members (3) each comprising a screw (4) around which is threaded a ring (11) bearing axially against a rim (1) comprised in the wheel, the respective screws (4) of the fixing members (3) passing through the rim (1) via bores (7) comprised therein and being screwed to the hub (2) by applying the rings (11) against the rim (1) by axial clamping (S1), characterized in that the said fixing members (3) are each in accordance with a fixing member (3) pertaining to any one of claims 1 to 7.

9. Motor vehicle according to claim 8, characterized in that the spherical caps (10a) comprised in the screw (4) heads (12) of the fastening members (3) are at least partially housed inside the spherical caps (10b) of the rings (11), the conical-shaped faces (11a) comprised in the rings (11) being housed by nesting inside respective cells (11b) comprised in the rim (1) and which have at least one conical shape complementary to the conformation conical (11 a) of the ring (11).

10. Motor vehicle according to either of claims 8 and 9, characterized in that the material of the rim is a metallic material chosen equally well from any metallic material.