EP3003824A2

EP3003824A2 - Steering knuckle comprising fibre reinforcement

Info

Publication number: EP3003824A2
Application number: EP14729302.1A
Authority: EP
Inventors: Gilbert PETERS; Richard Schaake; Edo SCHRAMM; Cornelius Petrus Antonius Vissers; Marc GOMEZ
Original assignee: Semcon Sweden AB; SKF AB
Current assignee: SKF AB
Priority date: 2013-06-07
Filing date: 2014-06-06
Publication date: 2016-04-13

Abstract

The present invention resides in a steering knuckle (100) comprising a bearing connection point (110) for connecting a bearing to the knuckle and comprising a further connection (130, 140) point for connecting the knuckle to a further component. The bearing connection point is formed by a first insert (110) and the further connection point is formed by a second insert (130, 140), which are joined via a composite body (120) comprising a fibre-reinforced material that is overmoulded to the first and second inserts. The bearing connection point and the further connection point are additionally joined by one or more continuous fibre tows that are wound around part of a radially outer surface of the first insert and of the second insert.

Description

Steering knuckle comprising fibre reinforcement

FIELD OF THE INVENTION

The present invention relates to a steering knuckle that is at least partly made from a fibre-reinforced composite material.

BACKGROUND TO THE INVENTION

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. Typically, steering knuckles are made of cast iron and consequently, there is potential for weight savings by manufacturing the knuckle from a lightweight material such as fibre-reinforced polymer. An example of such a steering knuckle is disclosed in DE102007053120 A1 . The steering knuckle is formed from a laminar textile comprising fibres bound in a matrix. A weight reduction is achieved, but the knuckle must also possess sufficient strength and stiffness to withstand the application loads. In use, the wheel bearing can experience high forces, which are transmitted to the vehicle suspension through the knuckle.

There is still room for improvement. SUMMARY OF THE INVENTION

The present invention resides in a steering knuckle as specified in claim 1 , whereby the dependent claims describe advantageous embodiments and further developments of the invention. Specifically the invention resides in a steering knuckle comprising a bearing connection point for connecting a wheel bearing to the knuckle and comprising a further connection point for connecting the knuckle to a further component. The bearing connection point is formed by a first insert and the further connection point is formed by a second insert, which are joined via a composite body comprising a fibre-reinforced material that is overmoulded to the first and second inserts. To increase strength and stiffness, the bearing connection point and the further connection point are additionally joined by one or more continuous fibre tows that are wound around part of an outer surface of the first insert and of the second insert.

The forces acting on the composite knuckle are introduced via the connection points. A force acting on one connection point results in a reaction force on the other connection point. The resulting load path runs between the connection points, meaning that a knuckle according to the invention comprises fibre- reinforcement located at, and in alignment with, the load path. As a result, the composite knuckle has improved strength and stiffness where it is needed most.

In one embodiment the first insert is formed by sleeve element which has a bore for receiving the bearing. The sleeve element can be e.g. a steel part to which an outer ring of the bearing is connected. Alternatively, the sleeve element may serve as the bearing outer ring. Preferably, the sleeve element is then made of a bearing grade steel, whereby at least a radially inner surface of the sleeve element has a hardened portion for forming a raceway for at least one row of rolling elements. A sleeve element that serves as the bearing outer ring may also be made from a suitable ceramic material or from titanium.

In a further embodiment the first insert comprises a plurality of bolt inserts, to enable a flanged bearing ring to be bolted to the composite knuckle. Typically, a flanged bearing ring has four or five bolt holes and the composite knuckle has an equal number of bolt inserts. Suitably, the bolt inserts are made of a metal such as steel and have a tubular geometry provided with an internal thread.

In one example of the further embodiment, at least one of the bolt inserts is joined to the second insert of the further connection point by a continuous fibre tow that is looped around the outer surface of the bolt insert and of the second insert. Preferably, each bolt insert is joined to the first insert in this way. In a second example of the further embodiment, the first insert comprises a plurality of bolt-inserts which are joined by a connection element. The connection element may be a ring or have another suitable geometry with a smoothly curved outer surface. The connection element may then be joined to the second insert by looping the continuous fibre tow around part of the outer surface of the connection element and of the second insert.

The second insert in a knuckle according to the invention is suitably formed by one of an upper and a lower connection point for a ball joint, which respectively connects an upper and a lower control arm of the vehicle suspension. In a preferred example, the second insert is a bracket, which has a tubular portion for receiving a stem of the ball joint. The bracket further comprises one or more stubs, arranged around the tubular portion. Preferably, each stub portion of the bracket is joined to the first insert by means of a separate continuous fibre tow. The stubs may have a cylindrical outer surface or other suitable shape, such that the continuous fibre tow is wound around part of the outer surface which has a smooth, curved surface. In a further example, the second insert comprises stub portions which are adapted for the connection of a separate ball joint bracket. Suitably, both of the upper and lower connection points for the upper and lower control arms respectively are joined to the first insert by means of a continuous fibre tow.

A steering knuckle typically comprises other connection points for e.g. a steering arm and for mounting a brake calliper device to the knuckle. In a further example of a knuckle according to the invention, one or more of the other connection points are formed by a third insert that is connected to one of the first and second inserts via a continuous fibre tow that is wound around part of the outer surface of the inserts.

As mentioned, the continuous fibre tows in a knuckle according to the invention are located within the composite body in the load path between connection points. The load path is an ideal site for measuring application loads. Thus in a further development of the invention, at least one of the continuous fibre tows that join the first and second inserts comprises a sensing fibre. An optical fibre comprising one or more fibre Bragg gratings is one example of a suitable sensing fibre. The sensing fibre may also be a piezoelectric fibre. Thus, the loads that act on the bearing, and which are transferred to the further component through the composite body of the knuckle, can be accurately measured.

The fibre-reinforced material that forms the composite body in a knuckle according to the invention is preferably a long fibre moulding compound comprising fibres with a length of 5 - 50 mm, embedded in a polymer matrix. Suitable materials for the fibres include glass, carbon, aramid, PBO (polybenzoxazole) and HDPE (high- density polyethelene). Suitable matrix materials include epoxy resin, phenolic resin, bismaleimide resin and polyimide resin.

The continuous fibre tows which connect the bearing connection point with the one or more further connection points may also be made from carbon, glass, aramid, HBO or HDPE fibres. Advantageously, different types of fibre are selected, depending on the properties requires. For example, an aramid fibre such as Kevlar® may be selected to provide energy absorption and safety in response to impact loads. A high-modulus carbon fibre may be selected to enhance stiffness. Alternatively or additionally, a high-strength carbon fibre may be selected to increase strength and load-carrying capacity.

As will be understood, the type of fibre, the number of fibres in the continuous fibre tow and the number of loops around the bearing connection point and the further connection point are selected depending on the application loads in question.

The present invention further defines a method of manufacturing a steering knuckle comprising a bearing connection point for connecting a wheel bearing to the steering knuckle and comprising a further connection point for connecting the steering knuckle to a further component, wherein:

• the bearing connection point is formed by a first insert;

• the further connection point is formed by a second insert; and

• the first and second inserts are joined by a composite body made of a fibre- reinforced matrix material. The method comprised steps of:

i. winding a continuous fibre tow around part of an outer surface of the first insert and around part of an outer surface of the second insert, thereby creating a pre-form in which the first and second inserts are connected via one or more loops of the continuous fibre tow; and

ii. overmoulding the fibre-reinforced matrix material to the pre-form.

The continuous fibre tows provide strength and stiffness in tension. Advantageously, the fibres are pre-tensioned during the winding process, to obtain optimal performance from the fibre properties. Thus, in a further development, the outer surface of at least one of the first and second inserts is provided with retaining means, and the step of winding comprises using the retaining means to pretension the continuous fibre tow.

In one example, the first and/or second insert has grooves in the outer surface with a depth and width that is essentially equal to the diameter of the fibre tow. Typically, the fibre tow has a diameter of 0.5 - 1 .5 mm. Preferably, each insert is provided with grooves. During the winding process, the fibre tow is wound around the grooves, which helps to keep the fibre tow in place, thereby facilitating pre- tensioning. In a further example, the outer surface of the first and/or second insert is provided with pegs that protrude from the outer surface, for guiding and retaining the fibre tows. After the winding process, the pre-form is placed in a mould. Advantageously, the first and second inserts are used in the step of overmoulding to support and precisely locate the preform with the mould. This also helps to ensure that fibre pretension is maintained. Other advantageous of the present invention will become apparent from the details description and accompanying drawings. DRAWINGS

The invention will now be described further, with reference to the following Figures, in which: shows a perspective view of a first embodiment of a steering knuckle according to the invention;

shows a side view of a pre-form of the steering knuckle of Fig. 1 a, prior to moulding;

shows a perspective view of a bracket used in the steering knuckle of Fig. 1 a; and

shows an example of a bearing outer ring that may be connected to a further component in a steering knuckle according to the first embodiment;

shows a second embodiment of a steering knuckle according to the invention; and

shows a front view of a pre-form of the steering knuckle of Fig. 3a, prior to moulding.

DETAILED DESCRIPTION

An example of a first embodiment of a steering knuckle according to the invention is shown in Fig. 1 a. The knuckle 100 comprises a bore for receiving a wheel bearing unit. The bore is formed in a sleeve element 1 10, to which an outer ring of the bearing unit may be mounted. In the depicted example, the sleeve element serves as the bearing outer ring and is made of a bearing-grade steel, whereby at least an inner circumference of the outer ring 1 10 comprises hardened portions to act as a raceway for a first row and a second row of rolling elements of the bearing unit.

The knuckle further comprises a composite body 120 that is made of a long fibre moulding compound comprising e.g. carbon fibres in an epoxy resin matrix. In addition to the bore for connection of the bearing unit, the knuckle 100 comprises a number of further connection points. In use, the knuckle is mounted to a vehicle suspension via an upper control arm, a lower control arm and a steering arm. The upper and lower control arms are connected via a ball joint, and the knuckle 100 comprises a corresponding upper connection point 130 and a lower connection point 140 in the form of a bracket comprising a tubular portion 147 for receiving a stem of the ball joint. The steering arm is connected to the knuckle 100 at an intermediate connection point 150. At an opposite side from the connection point 150, the knuckle further comprises first and second connection points 161 , 162 for attaching a brake calliper device to the knuckle.

In use, a variety of forces act on the knuckle. The largest forces are the wheel forces, which are transferred to the knuckle through the bearing unit. These forces are transferred to the vehicle suspension mainly through the upper and lower connection points 130, 140, via the knuckle body 120. As mentioned, the knuckle body is made from a long-fibre moulding compound. This material may not provide the knuckle with sufficient strength and stiffness to withstand the application forces.

According to the invention, the knuckle 100 further comprises continuous fibre tows which are wound around the bearing outer ring 1 10 and the upper and lower connection points 130, 140. The fibre tows are thus concentrated at, and are in alignment with, a load path that runs through the knuckle body 120 from the bearing connection point (i.e. the outer ring 1 10) to the upper and lower suspension connections points 130, 140. The optimal alignment and location of the fibres results in optimal strength and stiffness of the knuckle 100.

The winding of the continuous fibre tows takes place prior to moulding of the knuckle body 120. A pre-form is thus produced, which is then overmoulded with the long-fibre moulding compound. Fig. 1 b shows a side view of an example of the pre-form, during the winding process

The bearing outer ring 1 10 is fixed on a rig (not shown). The upper bracket 130 and the lower bracket 140 are likewise fixed to the rig, at locations relative to the bearing outer ring 120 suitable for connection of the upper and lower control arm ball joints. A perspective view of the upper bracket 130 is shown in Fig. 1 c. As mentioned, the upper bracket and the lower bracket comprise a tubular part 147 for receiving the stem of a ball joint. This part 147 may be threaded, may have a tapered bore, or may have a straight bore such that the ball joint stem can be bolted to the bracket 130, 140. A centre axis of the tubular part is perpendicular to or translationally perpendicular to a rotation axis of the bearing. To facilitate the connection of the bearing outer ring 1 10 with the upper and lower brackets via continuous fibres, each bracket 130, 140 further comprises stub portions 135 around which a continuous fibre tow may be wound. The stub portions 135 also facilitate the connection of the brackets 130, 140 to the overmoulded composite body 120, and provide locking in a radial direction. In the depicted example, each of the upper and lower bracket has three stub portions 135 with a cylindrical outer surface, which are arranged around the tubular portion 147. A radially outer part of the cylindrical surface, relative to the location of the bearing ring 1 10, forms the surface around which the continuous fibre tow is looped.

The tubular portion 147 and the stub portions 135 are joined by a connecting portion 137, such that the bracket forms a single piece. This facilitates the positioning of the bracket on the winding rig. The pre-form is made using e.g. an automated fibre placement machine or robot. In Fig.1 b, four continuous fibre tows are depicted. A first tow 171 is wound around part of an outer circumference of a first stub portion of the upper bracket 130 and then around part of an outer circumference of the bearing outer ring 1 10. A second tow 172 is wound around part of the outer circumference of a second stub portion 135 of the upper bracket and then around part of the bearing outer ring outer circumference. A third stub portion of the upper bracket 130 is connected in a similar fashion to the bearing outer ring via a further continuous fibre tow (not shown). For connecting the bearing outer ring and the lower bracket, a third tow 173 is wound around part of the outer circumference of a first stub portion 135 of the lower bracket 140 and then around part of the outer circumference of the bearing outer ring 1 10. A fourth tow 174 is wound around part of the outer circumference a second stub portion of the lower bracket 140. A further tow (not shown) connects the third stub of the lower bracket and the bearing ring in a similar fashion. Suitably, each fibre tow is looped a number of times around the bearing outer ring 1 10 and a stub 135, depending on the magnitude of the loads acting on the connection points. The thickness of the fibre tow may also vary depending on the loads. Furthermore, fibre tows made from different fibre materials may be used to impart different advantageous properties to the knuckle 100.

In a steering knuckle according to the invention, the bearing connection point 1 10 and the upper and lower suspension connection points 130, 140 serve as placeholders for the continuous fibre tows 171 , 172, 173, 174 during the winding process. Advantageously, the fibre tows are pretensioned during the winding process. To assist fibre-pretensioning and to help guide and retain the fibre tows, the outer circumference of the bearing outer ring 1 10 and of the stub portions 135 on the upper and lower brackets are preferably provided with retention means. In the example of Fig. 1 b, grooves with a depth and width essentially equal to the diameter of the fibre tows are provided in the outer surface of the bearing outer ring 1 10 and in the outer surface of the stub portions 135. The fibre tows are then provided in these grooves during the winding process.

An alternative solution for guiding and retaining the fibre tows is depicted in Figure 2, which shows a side view of a bearing outer ring suitable for use in a knuckle according to the first embodiment of the invention. The outer circumference of the bearing outer ring 210 is provided with a first row of pegs 231 and a second row of pegs 232, which are axially spaced from the first row. The pegs 231 , 232 protrude from the outer surface of the bearing outer ring and are circumferentially spaced. Adjacent pegs in a row may also have a slight axial offset relative to each other. During the winding process, one fibre tow is wound around the bearing outer ring, such that the fibre tow slaloms in and out of the first row of pegs 231 . A further fibre tow is wound around the second row of pegs 232 in a similar fashion. In addition, the outer circumference of the bearing ring 201 is provided with first and second grooves 221 , 222 for receiving a continuous fibre tow. The grooves are located in the region of the bearing raceways, which is the location where the loads on the rolling elements of the bearing are transmitted to the outer ring. The loads are thus led directly to the upper and lower suspension connection points via the continuous fibre tows. In the depicted examples, the continuous fibre tows comprise dry carbon fibres. These fibres will become impregnated with matrix material that is absorbed from the long-fibre moulding compound, when the knuckle body 120 is overmoulded. It is also possible to use pre-impregnated fibres, which may be cured prior to placing the preform in the mould or which may be cured simultaneously with the moulding compound.

When the pre-form is finished, it is placed in a mould and overmoulded with long- fibre moulding compound. Suitably, the bearing outer ring 1 10, the upper bracket 130 and the lower bracket 140 are precisely located and fixed to the mould during the moulding process. This helps to maintain the pretension in the fibre tows, which was achieved during the winding process. Maintaining fibre pretension is advantageous in terms of optimizing the fibre properties and thus the performance of the finished component.

As may be seen in Fig. 1 b, the bearing outer ring 1 10 also has a central annular groove or recessed portion 1 15. During the overmoulding process, the moulding compound flows into the recessed portion, which mechanically locks the bearing ring 1 10 to the composite body 120 in an axial direction.

After moulding and curing, the knuckle body may be machined. In the example shown in Fig. 1 a, the connection points 161 , 162 for the brake calliper and the intermediate connection point 150 for the steering arm are mounting holes machined into the knuckle body 120. As will be understood, these connection points may also be formed by inserts that are connected to the bearing outer ring and/or to the upper and lower brackets 130, 140 by continuous fibre tows.

An example of a second embodiment of a steering knuckle 300 according to the invention is depicted in Fig. 3a. The associated pre-form 305 is shown in Fig. 3b.

In the second embodiment, the bearing connection point is formed by first, second, third and fourth bolt inserts 31 1 , 312, 313, 314 for enabling a wheel bearing unit with a flanged outer ring to be bolted to the knuckle 300. The knuckle further comprises an upper bracket 330 and a lower bracket 340, for connection of the upper and lower control arms respectively. The upper and lower brackets 330, 340 are joined to the bolt inserts 31 1 , 312, 313, 314 by an overmoulded composite body 320. Again, long-fibre moulding compound is used in the depicted example to form the composite body.

In accordance with the invention, each bolt insert is additionally joined to one of the upper and lower brackets by a continuous fibre tow that is looped around the threaded insert and around a stub portion of the bracket.

With reference to Fig. 3b, a first continuous fibre tow 371 is looped around part of an outer circumference of the first bolt insert 31 1 and around part of an outer circumference of a first stub portion (not visible) on the upper bracket 330. A second continuous fibre tow 372 is looped around part of an outer circumference of the second bolt insert 312 and around part of an outer circumference of a second stub portion 332 on the upper bracket 330. A third continuous fibre tow 373 is looped around part of an outer circumference of the third bolt insert 313 and around part of an outer circumference of a third stub portion 333 on the lower bracket 340. A fourth continuous fibre tow 374 is looped around part of an outer circumference of the fourth bolt insert 314 and around part of an outer circumference of a fourth stub portion 334 on the lower bracket 340.

The steering knuckle 300 is provided with further strength and stiffness in that adjacent bolt inserts are joined to each other by a continuous fibre tow. A fifth continuous fibre tow 375 is looped around part of the outer circumference of the first and second bolt inserts 31 1 , 312. A sixth continuous fibre tow 376 is looped around part of the outer circumference of the second and third bolt inserts 312, 313. A seventh continuous fibre tow 377 is looped around part of the outer circumference of the third and fourth bolt inserts 313, 314. Finally, an eighth continuous fibre tow 378 is looped around part of the outer circumference of the first and fourth bolt inserts 31 1 , 314.

Thus, a steering knuckle according to the invention is a lightweight component that also delivers the robustness required in wheel end applications. A number of aspects/embodiments of the invention have been described. It is to be understood that each aspect/embodiment may be combined with any other aspect/embodiment. Moreover the invention is not restricted to the described embodiments, but may be varied within the scope of the accompanying patent claims.

Claims

Steering knuckle (100, 300) comprising a bearing connection point for connecting a wheel bearing to the steering knuckle and comprising a further connection point for connecting the steering knuckle to a further component, wherein:

^■ the bearing connection point is formed by a first insert (1 10, 210, 31 1 .

312, 313, 314);

^■ the further connection point is formed by a second insert (130, 140, 330, 340); and

^■ the bearing connection point and the further connection point are joined via a composite body (120, 320) comprising a fibre-reinforced material that is overmoulded to the first and second inserts; and

^■ the bearing connection point and the further connection point are additionally joined by a continuous fibre tow (171 , 172, 173, 174, 371 , 372, 273, 374) that is wound around part of a radially outer surface of the first and second inserts.

Steering knuckle according to claim 1 , wherein the second insert (130, 140, 330, 340) comprises two or more stub portions (135, 332, 333, 334) and wherein a continuous fibre tow is wound around part of the outer surface of each stub portion and of the second insert.

Steering knuckle according to claim 1 or 2, wherein the second insert is formed by an upper connection point (130, 330) for receiving a ball joint for connecting the knuckle to an upper control arm or is formed by a lower connection point (140, 340) for receiving a ball joint for connecting the knuckle to a lower control arm.

Steering knuckle according to claim 3, wherein the second insert further comprises a tubular portion (147) for receiving a stem of the ball joint, and forms a bracket (130, 140) for the ball joint.

5. Steering knuckle according to any preceding claim, wherein the first insert comprises a sleeve element (1 10, 210), whereby a bore of the sleeve element is adapted to receive an outer ring of the wheel bearing or is adapted to serve as an outer raceway of the bearing.

6. Steering knuckle according to any of claims 1 - 4, wherein the first insert comprises at least one bolt insert (31 1 , 312, 313, 314), to enable a flanged wheel bearing to be bolted to the steering knuckle (300) and wherein the continuous fibre tow (371 , 372, 273, 374) is wound around part of an outer surface of the at least one bolt insert.

7. Steering knuckle according to claim 6, wherein the first insert comprises at least two bolt inserts (31 1 , 312, 313, 314) which are joined to each other by a continuous fibre tow (375, 376, 377, 378) that is looped around a radially outer surface of the bolt inserts.

8. Steering knuckle according to any of claims 1 - 5, wherein the first insert comprises at least two bolt inserts (31 1 , 312) and further comprises a connection member that interconnects the at least two bolt inserts (31 1 , 312), and wherein the continuous fibre tow is wound around part of a radially outer surface of the connection member.

9. Steering knuckle according to any preceding claim, comprising at least one further connection point (150, 161 , 162) formed by a third insert, for enabling the connection of a steering arm and/or a brake calliper device, which third insert is connected to one or both of the first and second inserts by means of a continuous fibre tow.

10. Steering knuckle according to any preceding claim, wherein the radially outer surface of the first insert (1 10, 210, 31 1 , 312, 313, 314) and/or of the second insert (130, 140, 330, 340) is provided with retaining means (221 , 222, 231 ) for guiding and retaining the continuous fibre tow.

1 1 . Steering knuckle according to claim 10, wherein the retaining means are formed by one or more grooves (221 , 222) having a depth and width essentially equal to a diameter of the fibre tow.

12. Steering knuckle according to claim 1 1 , wherein the retaining means are formed by one or more pegs (231 ) which protrude from the outer surface of the insert.

Steering knuckle according to any preceding claim, wherein the composite body (120, 320) is made from a long fibre moulding compound.

Steering knuckle according to any preceding claim, wherein at least one of the first and second inserts comprises a recessed portion into which the overmoulded composite material flows, for mechanically locking of the insert to the composite body (120, 320).

A method of manufacturing a steering knuckle comprising a bearing connection point for connecting a wheel bearing to the steering knuckle and comprising a further connection point for connecting the steering knuckle to a further component, wherein:

• the bearing connection point is formed by a first insert (1 10, 210, 31 1 , 312, 313, 314);

• the further connection point is formed by a second insert (130, 140, 330, 340); and

• the first and second inserts are joined by a composite body (120, 320) made of a fibre-reinforced matrix material,

the method comprising steps of:

i. winding a continuous fibre tow (171 , 172, 173, 174, 371 , 372, 273, 374) around part of a radially outer surface of the first insert and around part of a radially outer surface of the second insert, thereby creating a pre-form (105, 305) in which the first and second inserts are connected via one or more loops of the continuous fibre tow; and

ii. overmoulding the fibre-reinforced matrix material to the pre-form. The method of claim 15, wherein the outer surface of at least one of the first and second inserts is provided with retaining means, and wherein the step of winding comprises using the retaining means to pretension the continuous fibre tow.

The method of claim 16, wherein the retaining means are formed by one or protruding pegs (231 ) or one or more grooves (221 , 222) with a depth and width substantially equal to that of the fibre tow.

The method of any of claims 15 - 17, wherein the first and second inserts are used in the step of overmoulding to support and precisely locate the preform within the mould.