Lightweight suspension upright or knuckle

A lightweight suspension upright or knuckle including: a bearing connection interface having a first sleeve element and a second, radially outer, sleeve element and further including a BMC/LFT/DLFT annular body; at least one attachment interface configured to connect the suspension upright or knuckle to a respective control or support element; and a supporting structural body mechanically connecting the bearing connection interface with the at least one attachment interface. The supporting structural body is shaped as a reticular frame including first blade elements chemically and mechanically interconnected to each other and to the outer lateral surface; each blade element consisting in one or more mats or plies of continuous fibers embedded in a polymer matrix, stacked onto one another and that have been compression molded together and with the annular body. Also, a method for obtaining a lightweight suspension upright or knuckle for a vehicle providing a bearing connection interface.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Italian patent application no. 102018000007978 filed on Aug. 8, 2018, the contents of which are fully incorporated herein by reference.

FIELD OF THE INVENTION

The present invention concerns a lightweight suspension upright or knuckle, in particular a steering knuckle, for a vehicle, the lightweight suspension upright or knuckle integrating a wheel hub bearing module.

BACKGROUND OF THE INVENTION

As it is known, e.g. from US2016121927A1, in the interests of fuel economy there is an increasing drive within the automotive industry towards weight reduction of the component parts of vehicles. One such component is the steering knuckle, which connects the wheel bearing to the vehicle suspension and, more in general, such components include all the uprights of the vehicle suspension. Typically, uprights and steering knuckles are made of cast iron or of a light alloy and there is still potential for weight savings by manufacturing the knuckle/upright from a more lightweight material, such as fiber-reinforced polymer.

However, a problem there exists in joining the wheel bearing to the composite material of the 201 upright/knuckle. Another problem is that is rather difficult to deploy continuous fibers into a composite material in a part like a vehicle knuckle due to the geometrical complexity of the part, having branches in different directions, and due to the complex loading conditions.

According to US2016121927A1 a whole steering knuckle composite body comprising a fiber-reinforced polymeric material is overmolded onto a sleeve element acting as a bearing connection interface and consisting of the outer ring of the rolling bearing unit constituting the wheel hub, or of a metal ring designed to be connected with the rolling bearing.

The fiber-reinforced material comprises a long-fiber molding compound that is overmolded to a first joining surface on the sleeve element, whereby the first joining surface is a radially outer surface of the sleeve element. In addition, the first joining surface is provided with a recessed portion into which the long-fiber molding compound flows, for mechanically locking the sleeve element to the composite body in an axial direction.

However, to mold a whole knuckle body (or a whole suspension upright) onto a rolling bearing, or anyway even onto a connection interface consisting of a metal sleeve, may be not a simple and cheap operation. Moreover, the transmission of forces between the bearing and the knuckle body may be not always optimized, in particular during cornering. Finally, the steering knuckle according to US2016121927A1, though lighter than a traditional metal alloy steering knuckle, may result to be still too heavy for the majority of the applications and, above all, in a waste of precious composite material, since at least a good part of it is not arranged in optimal manner to receive the working loads.

BRIEF SUMMARY OF THE INVENTION

The object of the present invention is to provide a suspension upright or knuckle, in particular a steering knuckle, for a vehicle, including a hub bearing unit and which is easy and economical to be manufactured, though ensuring an optimized transmission of forces between the hub bearing unit and the knuckle/upright body and a low weight.

According to the invention, a suspension upright or knuckle for a vehicle is therefore provided having the features described in the appended claims.

DETAILED DESCRIPTION OF THE INVENTION

With reference toFIGS. 1, 2, 3 and 9, the number1indicates as a whole a lightweight suspension upright or knuckle (a steering knuckle in the non-limitative embodiment shown) for a vehicle, the latter being not shown for sake of simplicity.

The lightweight suspension upright or knuckle1is represented in a schematic, non-limitative manner only, in order to make clearer the concept on which the invention is based. It is therefore clear that it may have any suitable different shape, so that the invention is not limited in any manner to the specific embodiment shown.

According to one aspect of the invention, the suspension upright or knuckle1is made, in a manner that will be described in details herein below, in a composite material, e.g. a fiber reinforced synthetic plastic resin.

Contrary to the teachings of US2016121927A1, however, it is not molded in one piece over a bearing interface constituted by a metallic sleeve.

The suspension upright or steering knuckle1comprises in fact a bearing connection interface2for receiving a wheel rolling bearing3, the latter being an HBU (Hub Bearing Unit) well known in the art and accordingly not shown and described in details for sake of simplicity.

The bearing connection interface2includes a first sleeve element4having a cylindrical shape and an axis of symmetry A (FIG. 1) constituting a first axis of the knuckle1and coinciding in use with a rotation and symmetry axis of the wheel bearing3. In the non-limiting example shown, the first sleeve element4is metallic and preferably consists of a steel outer ring of the wheel rolling bearing or HBU3; the outer ring or first sleeve element4is shown in a schematic way only, for sake of simplicity, so e.g. the tracks for the rolling bodies are not shown. Alternatively, the first sleeve element4may be configured to receive in known manner, e.g. by interference fitting, the wheel bearing3and may be, in this case, made either of a metal alloy or of a fiber reinforced synthetic plastic.

According to one aspect of the invention, the bearing connection interface2also comprises a second sleeve element5(FIG. 3B) arranged radially outside the first sleeve element3and an annular body6arranged, in the non-limiting example shown, radially inside the second sleeve element5; the bearing connection interface2has a radially outer lateral surface7and a radially inner lateral surface8(FIG. 3C).

The annular body6is made of a composite material, which, according to a preferred aspect of the invention, is selected from the group consisting of BMC (Bulk Molding Compound), LFT (Long Fiber Thermoplastic) and DLFT (Direct In-Line Long Fiber Thermoplastic).

BMC, as well as LFT/DLFT, are synthetic plastic materials in which individual reinforcing fibers of considerable length (usually ½ inch or 12 mm) are uniformly dispersed within a synthetic plastic matrix without a specific orientation (or oriented by the flow during the compression but never arranged in layers) while, e.g., in SMC materials the fibers are disposed in layers. In BMC materials the synthetic plastic matrix is generally formed by a thermosetting resin and such materials are adapted to be formed, generally, by compression molding; in LFT/DLFT materials the synthetic plastic matrix is formed by a thermoplastic resin and such materials are adapted to be formed by injection molding. Moreover, in both the BMC and LFT materials the reinforcing fibers are of uniform length.

Preferably, in the final, molded material the individual reinforcing fibers form groups of fibers aligned with respect to each other, and the groups are uniformly dispersed randomly in the matrix, in order to give rise to a nearly isotropic or isotropic material.

The annular body6is coaxial with the first sleeve element4.

The radially inner lateral surface8is mechanically coupled to the first sleeve element4in any know manner, e.g. by chemical and/or mechanical (e.g. by friction) adhesion and/or owing to interlocking mechanical means, known and not shown for sake of simplicity: for example, the outer lateral surface of the first sleeve element4is knurled or lettered or otherwise machined using mechanical, chemical or optical processes, such as to create thereon a surface texture and/or it is provided with grooves, ribs or pins which may receive/be embedded in the composite material of the annular body6.

According to a further and fundamental aspect of the invention, the lightweight suspension upright or knuckle1further comprises at least one first attachment interface9(four in the non-limitative example shown) and at least one second attachment interface10, configured to connect in use the suspension upright or knuckle1to a respective control or support element therefor, known and not shown for sake of simplicity, and a supporting structural body11mechanically connecting the bearing connection interface2with the at least one and second attachment interfaces9,10.

The supporting structural body11is made of a fiber reinforced composite material realized in a peculiar and innovative way.

In particular, the supporting structural body11is shaped as a reticular frame comprising a plurality of first blade elements12chemically and mechanically interconnected to each other, at least one first blade element being also chemically and mechanically directly bound to the outer lateral surface7of the annular body6of the bearing connection interface2, so as to join integral in one piece therewith.

Each first blade element12consists in one or more plies13of continuous fibers embedded in a polymer matrix, which plies13are stacked onto one another when the blade elements12are formed by more than one plie13.

According to a feature of the invention the plies13forming the first blade elements12are configured and arranged such that the continuous fibers contained therein (known and not shown for sake of simplicity) are all contained, i.e. all lie, in planes which are all perpendicular or at least nearly perpendicular to the axis A, i.e. are parallel or nearly parallel to the drawing sheet inFIG. 3.

The fibers of each plie13forming the first blade elements12are in fact mono-directionally oriented.

To obtain the blade elements12, as it will be seen, the plies13have been compression molded to one another and at least one of the blade elements12has been compression molded to the outer surface7.

In fact, the plies13forming the first blade elements12are all wound in a ring shape around the annular body6of the bearing connection interface2and, progressively radially outwards, around one another, as it is schematically illustrated inFIGS. 4F-4IandFIG. 5L, M. In this manner, wound after wound, the plies13form progressively radially wider annular layers14of continuous fibers embedded in a polymer matrix, each plie13having been circumferentially clamped against, and chemically and mechanically bound to, the plie13arranged immediately radially inwards to form the blade elements12and each blade element12is chemically and mechanically bound to any other blade element12radially in direct contact therewith to form the supporting structural body11.

In the non-limiting embodiment ofFIGS. 1 and 2, the supporting structural body11further comprises a three dimensional, reinforcing frame structure15, which is arranged radially outside a first ring structure16(FIG. 2) defined by one or more first blade elements12.

The three dimensional, reinforcing frame structure15bears partly radially on the inside and partially radially on the outside thereof a second ring structure17(FIG. 2) formed by one or more further first blade elements12different from those forming the ring structure16.

The blade element/s12defining the ring structure17is/are wound onto the frame structure15so as to rest therein.

Moreover, the blade element/s12defining the ring structure16is/are also wound onto the frame structure15, but solely radially on the inside thereof, so as to be supported thereby.

According to a one preferred embodiment, the first and/or second ring structure16and17(in the example shown the ring structure17only) define respective first radial support arms18for the first attachment interfaces9and second radial support arms19(one single support arm19in the embodiment shown) for the second attachment interface10(FIGS. 8 and 9).

Preferably, at least one respective support arm18,19, in the example shown the arm19only, supporting the at least one second attachment interface10, is formed either by a circumferential section20(FIGS. 8 and 9) of the second ring structure17or by at least one second blade element21(FIGS. 1 and 2) also formed by one or more plies13of continuous fibers embedded in a polymer matrix and oriented as the mats or plies of the blade elements12, and by at least one further second blade element21b(still formed by one or more plies13of continuous fibers embedded in a polymer matrix) arranged at right angle with the plies13forming the first blade elements12.

The three dimensional, reinforcing frame structure15comprises (FIGS. 1 and 2) two rings22, in the non limiting example shown squared, and a plurality of tightening rods23arranged parallel to the axis A and engaged radially by the two rings22, by which they are radially compressed; the first and/or second blade elements12,21forming the radial support arms18,19are at least partially wound upon the rings22and/or the tightening rods23, so as to be supported by them and to be pre-tensioned by them.

Independently of how the arms18,19are obtained, the arms18and19are configured to radially project in cantilever fashion from the supporting structural body11, preferably on opposite sides thereof.

The attachment interfaces9,10comprise metallic pins24or bushings25connected integral with the first blade elements12and/or the second blade elements21.

As it will be seen, the attachment interfaces9,10also comprise cushions26made in a BMC/LFT/DLFT composition which are bonded to and are integral part of the blade elements12,21and in which the pins24and/or bushing25are embedded.

The use of selected composite materials in a specifically selected arrangement, as described above, allows to achieve the highest strength to weight and stiffness to weight ratios, since the fibers of the mats or plies13are placed in appropriate directions, depending on the loading condition of the structure. Main loading of the knuckle is generally acting in vertical and transversal direction with respect to car motion, so by placing the fibers in two plane structures (blades) running from lower to upper joints (attachment interfaces9) for connection with suspension arms and passing on the two sides of the hub bearing unit3, it is possible to sustain and transmit the main load in a very effective way taking full advantage of the composite material performance.

The described shape allows also to realize an effective connection to the hub bearing unit3itself having a large contact surface available, the HBU3being hosted in a large diameter composite tube6(or similar shape) that allows the transition from the circular shape of bearings3to the flat surface of the blades12,21. These latter are also particularly effective in easing the connection with upper and lower joints/interfaces9as long as by the introduction of specific metallic clamping like pins24and bushing25an effective load transfer can be obtained.

In a similar way to the main blades12, lateral blades12,21are put in place to connect the main structure with brake caliper joints and the steering arm joint, respectively. Orientation of these lateral structure is made according to the specific load paths.

As it has been seen, the structures of the blade elements12,21are preferably made in unidirectional (UD) composite material having fibers mainly oriented in the load direction (parallel to the blade direction) to obtain maximum performance of the composite material.

In the embodiment ofFIGS. 1 and 2, the sleeve element5which is part of the connection interface2designed to host the HBU3forms a central tube hosting the hub bearing unit3and made in UD plies as well, while the material of the annular body6also hosted within the tube5but packed between the latter and the sleeve4connects this “tube”5to the outer ring of the bearing3and is made in a nearly isotropic composite material like BMC/LFT/DLFT.

The central tube or sleeve5is in this embodiment shaped so to allow the four metallic rods23to be compressed in the so defined recess. In between the rods23and the central tube5, the main vertical first blades elements12are interposed, so allowing the required load transfer between these two structures that cannot be purely based on the resin performance. The four rods23are kept in a compressed state with the main central tube/sleeve5by mean of the squared rings22made by fibers in the rowing or tow form.

The connection of the blade12to form the main body11is arranged in two ways: one is by mean of the four rods23as the main blades12and the other one is due to the joints that connect the knuckle1to the suspension arms, i.e. in the example shown the attachment interfaces9.

The knuckle1is connected to suspension arms and brake caliper by mean of metallic inserts like pins24and bushings23, which are realized at least in two parts, an inner part and an outer part on the two sides of the blades12,21in composite material they are connected to. The two parts are preferably compressed against an intermediate bulky composite material (like BMC) forming the cushions26which is then in direct contact with the surfaces of the blades12,21so to allow the proper load transfer to the laminate and preventing it to fail because of the transversal stresses. The surfaces of these joints are designed so to match the shape of the blade12,21. Compression may be obtained by e.g. a screwed connection.

Regarding the steering arm19, the blade21in this case is positioned to have the higher stiffness while solicited in the steering action, so in a transversal direction to the vehicle motion. The composite blade21is in this case realized by mean of an additional cleat that enables the transfer of the load to the main blades12.

From what has been described up to now, it is clear that the present invention also relates to a method for obtaining a lightweight suspension upright or knuckle1for a vehicle comprising a bearing connection interface2for receiving a wheel bearing, the bearing connection interface including a first sleeve element4. Such method comprises, not necessarily in sequence, the steps of:

i)—providing the bearing connection interface2with a second sleeve element5arranged radially outside the first sleeve element4and comprising an annular body6, having a radially outer lateral surface7and a radially inner lateral surface8, the annular body6being formed by injection or compression molding a composite material selected from the group consisting of BMC (Bulk Molding Compound) and LFT (Long Fiber Thermoplastic) and DLFT (Direct Long Fiber Thermoplastic) directly upon a radially outer lateral surface of the first sleeve element4so as to mechanically couple the second sleeve element5to the first sleeve element4;

ii)—forming around the annular body6a supporting structural body11shaped as a reticular frame by coupling together and with the annular body6at least a plurality of first blade elements12, each first blade12element consisting in one or more plies13of continuous fibers embedded in a polymer matrix, which plies13are stacked onto one another when the first blade elements12are formed by more than one plie13;

iii)—compression molding the plies13against one another and onto the second sleeve element5and/or the annular body6thereof pertaining to the bearing connection interface2up to completely cure the plies13so as to chemically and mechanically interconnect them to each other and also chemically and mechanically directly bound at least one first blade element12to the outer lateral surface7of the bearing connection interface2;

iv)—applying to selected portions of at least some of the first blade elements12at least one first and one second attachment interface9,10configured to connect in use the suspension upright or knuckle1to respective control or support elements therefor, so as to make the bearing connection interface2integral with the at least one first and one second attachment interface9,10via the supporting structural body11.

The continuous fibers of the plies13forming the first blade elements12are arranged such that they are all contained in planes which are all essentially perpendicular to a first axis of symmetry A of the first sleeve element4.

Moreover, as schematically shown inFIGS. 3-5, the above steps are carried out so that the plies13forming the first blade elements12when in a non-cured or only partially cured state are wound in a ring shape, one after the other, in sequence, around the annular body6/second sleeve element5of the bearing connection interface2and, progressively radially outwards, around one another, by using a plurality of core templates27(FIGS. 3-5) to support the plies13, which in that state are not self-supporting, such as to form progressively radially wider annular layers14of continuous fibers embedded in a polymer matrix, each plie13being circumferentially clamped against the plie13arranged immediately radially inwards and against the core templates27and the annular body6/sleeve element5of the bearing connection interface2.

Following the sequence shown inFIGS. 3-6, firstly it is formed a unit joining the wheel bearing3with the connection interface2, e.g. by molding directly upon the sleeve element4the annular body6and/or the sleeve element5, which are however kept preferably in a non-completely cured state (FIGS. 3A-B).

Then a first template27is arranged radially outside the connection interface2so formed, and an eventual cushion26is arranged upon a radially outer end of the template27; then a first plie13is strictly wound around the bearing connection interface2, so as to be in contact with surface7, and the template27; in this manner, the template27is also blocked against the surface7(FIGS. 3D-E).

Thereafter, a second template27, e.g. identical to the first, is arranged against the first plie13on the opposite side of the first template27, it receives a further cushion26on its free radial end, and a second plie13is strictly wound around and against such second template27and the first plie13, in direct contact therewith, so also blocking the second template27in position (FIGS. 4F-H).

At this point further template27of different shape are arranged radially outside the second plie13(FIG. 4I) and radially projecting therefrom, and receive on their free radial ends further cushions26(FIG. 5L) and then a third plie13is strictly wound around and against the further templates27and the first and second plies13(FIG. 5M) so also blocking the further templates27in position.

At this point a self-supporting composite structure T is obtained, wherein the template27are all arranged parallel to axis A. Such structure T is placed in a mold28and the plies13, as well as the incompletely cured components of the connection interface2(body6and/or sleeve5) are compression molded and completely cured, so as to become rigid. This completes the compression molding step.

Thereafter, the mold28is opened and the core templates27are removed in the direction of the first axis A after the end of the compression molding step, so leaving a finished reticular body11(FIG. 7).

Thereafter, holes may be provided to complete the attachment interfaces9,10(FIG. 8) and the pins24and bushing25are arranged in place. The knuckle1is so completed.

Of course, the attachment interfaces9,10may be obtained in a different manner, e.g. the pins24and/or bushing25may be co-molded with the cushions26and the mats or plies13. Preferably, as previously described, the metallic clamping24,25may be formed in two parts screwed together.

From the above, it is clear that the suspension uptight/knuckle1described is relatively simple and economic to be obtained, extremely light and performant. Moreover, it may be shaped according to the necessity in a simple manner.

All the objects of the invention are therefore achieved.