Weldless vehicular suspension control arm

A vehicular suspension control arm comprises a first arm component and a second arm component formed from sheet metal, each arm component comprising an outer wall and two side walls, bushing connecting means adjacent a first end, at least one bracket receiving rivet aperture adjacent a second end, at least one component connecting rivet aperture located between the first end and the second end, a ride bushing and a handling bushing, a ball joint bracket comprising bracket rivet apertures corresponding to the at least one bracket receiving rivet aperture adjacent the second end of each of the first and second arm components and a plurality of rivets. When constructed, the ball joint bracket is riveted to both the first and second arm components adjacent the second end thereof via the at least one bracket receiving rivet aperture and the corresponding at least one bracket rivet aperture, the first arm component is riveted to the second arm component at the at least one component connecting rivet aperture, the ride bushing is connected at the first end of the first arm component and the handling bushing is connected at the first end of the second arm component.

FIELD OF THE INVENTION

This invention relates to the field of automotive components, in particular an automotive suspension control arm.

BACKGROUND OF THE INVENTION

Most modern road vehicles use some form of suspension system to isolate the passenger compartment from wheel disturbances caused by irregularities in the road surface. These suspension systems normally include some form of energy storage medium such as a spring, a device to control the spring's motion such as a damper, and a linkage arrangement to control the kinematics of the wheel movement. This combination of components is configured to allow the vehicle's wheels to move up and over road irregularities in a controlled manner. The most common form of linkage arrangement is a four-bar linkage configuration, constructed from the spindle assembly, the vehicle body, and two pivoting structural elements commonly referred to as control arms.

FIG.1illustrates a common prior art four-bar link configuration. The “A” shaped control arms1,2locate and guide the movement of the spindle assembly3relative to the vehicle body4. The spindle assembly carries the wheel, tire, bearing assembly and brake assembly, which are collectively referred to as the unsprung mass5of the vehicle. The unsprung mass also includes a portion of the control arm weight. Owing to the significant energy involved in moving the unsprung mass over road surface disturbances, it is preferable to reduce the combined weight of this subassembly as much as possible. Additionally, since the handling characteristics of the vehicle are directly dependent on the controlled movement of the unsprung components, it is imperative that the control arms have sufficient stiffness and strength to resist the substantial loadings that are imparted upon them.

It is therefore important that suspension control arms be strong and stiff to function well when loaded, as well as light in weight to reduce the unsprung mass. Reducing weight normally results in a reduction of both strength and stiffness. Great ingenuity is required to design parts with reduced weight but equivalent performance characteristics. The operational loads imparted on suspension control arms are discrete and well understood so that non-uniform structures can be developed to provide selective stiffness and strength in the directions and locations required by the application. Vehicle suspension control arms are generally configured in either an “A” or an “L” shape in plan view, depending on the configuration of the body mount to spindle relationship. In either case, the dominant induced loads are in the plane of the “A” or “L” formation and therefore require a high concentration of material to be located around the edges of the “A” or “L” formation to maximize the in-plane second moment of area values.

The requirement for optimized control arm structures to be non-uniform in shape has driven the use of a number of complex manufacturing processes. The most common manufacturing methods associated with vehicle control arm construction are casting, forging and welding of press-formed metal stampings into subassemblies. Owing to the complex shapes involved, it is difficult to manufacture an optimized vehicle control arm from simple press formed metal stampings.

FIG.2illustrates a common prior art cast or forged “L” shaped control arm6.

Casting involves high heat to create molten metal. Although precise shapes can be formed, the control arm tends to be solid with significant attendant weight. Cast control arms are strong but tend to be somewhat brittle. The casting process is more expensive than other manufacturing processes. Although aluminum is lighter than steel and corrosion resistant, it is considerably more expensive.

Forging involves heating metal to the point that it is malleable, then applying significant pressure to force the soft metal into the desired shape. As with casting, the forged part is solid. Although a forged part tends to have greater tensile strength than a cast part, the process is also expensive since significant heat is required and there tends to be a significant amount of scrap. Aluminum lends itself to forging, but the significant scrap adds to the cost, even though it is fairly easily recycled.

The majority of suspension control arms that employ press-formed metal stampings in their construction are configured as closed box sections.FIG.3illustrates a section of a typical prior art suspension control arm constructed from two U-shaped press-formed metal stampings501,502. This type of structural section typically requires a significant overlap of material to facilitate the required weld fillet joint. This material overlap is ultimately structurally redundant and may result in a heavier solution than alternative cast or forged configurations. If a butt jointed construction is used, without material overlap, the strength and integrity of the welding to create the joint is even more critical and the part is more difficult to manufacture.

Although a single piece control arm may be produced from sheet metal steel in an essentially U-shaped structure, a relatively heavy gage steel is required to handle the significant loads to which the control arm is subject. A heavier part is generally undesirable and the additional cost of material may be prohibitive. Moreover, the U-shaped structure renders it difficult to locate a high concentration of material around the edges of the “A” or “L” formation to maximize the in-plane second moment of area values.

FIG.4illustrates a typical prior art control arm with two press-formed metal stampings welded around most of the perimeter of the control arm. First stamping7and second stamping8are welded as shown inFIG.3.

Suspension control arms are subjected to two main loading directions, namely, fore-aft and cross car. To resist fore-aft loads such as acceleration and braking, the control arms generally require a set of bushings and a ball joint. It is generally desirable in modern vehicle suspension systems to have a relatively soft suspension in the fore-aft direction to allow the wheel to provide a recessional motion when, for example, impacting a curb. This cushions the impact. This is achieved by having a relatively stiff front rubber bushing and a soft rear bushing. By contrast, it is generally desirable to have a relatively stiff suspension in a cross car direction to facilitate proper tracking of the vehicle when driving around a curve. This is achieved by having a relatively stiff front bushing with the rear bushing not influencing this behaviour. The stiff front bushing is in line with a ball joint that transmits tractive loads from the wheel. The stiff front bushing is generally referred to as the handling bushing and the soft rear bushing is generally referred to as the ride bushing.

The control arms described above are typically connected to the unsprung mass and the vehicle using a ball joint mounted in a ball joint bracket9and a pair of bushings10,11. A disadvantage of most prior art control arms produced using the above described techniques is that an aperture for the ball joint at the knuckle end must be welded to the control arm, as illustrated inFIG.4, or the aperture must be stamped into the press-formed part thus creating an additional step, disruption of the sheet metal and additional scrap. Seats for the bushings must be connected to the control arm, typically by welding. This creates additional welding steps, with the opportunity for misalignment of the bushing seats or welding flaws.

The process of welding tends to disrupt the anti-corrosion coatings on the sheet metal thus exposing the part to corrosion at the weld. Although some parts may be electroplated with a protective coating post-welding, this is often difficult with larger, irregularly shaped parts. Post-welding electroplating of a part is expensive and requires extra processing time and floor space. In addition, welding may result in a joint with uneven strength at various points along the weld. Since control arms are typically subjected to continual stresses while a vehicle is in motion, welding irregularities may result in stress failure at the welds. Welded joints are generally subject to poorer fatigue performance than a jointless metal part. Moreover, the welding process produces a heat-affected zone along both sides of the weld that typically exhibits lower strength than the remainder of the sheet metal which thus reduces the overall strength of the part. Modern welding techniques involve robots, weld cells, welding wire and attendant infrastructure, including post-welding inspection, all of which contribute to the cost of manufacture. Welding also adversely affects the air quality in the welding area and consumes significant electricity.

SUMMARY OF THE INVENTION

Accordingly, it would be advantageous to create a suspension control arm that could provide high inherent stiffness and strength while maintaining relatively low mass using a low cost manufacturing technique such as sheet metal press-forming. It has been proven that for large volume applications such as those dictated by the automotive industry, sheet metal press-forming is the most cost-effective method of manufacturing structural components. Most vehicles currently produced employ a body structure and selected subframes constructed almost entirely from either aluminum or steel stampings manufactured using press-forming techniques. An aim of the present invention, therefore, is to utilize metal press-forming in the manufacture of a vehicle suspension control arm.

It would also be advantageous to produce a control arm using relatively light weight, pre-coated, sheet metal steel without the use of welding. In addition, reduced capital costs for equipment and floor space, reduced costs of materials and energy, reduced inspection costs, reduced part fatigue and improved vehicle performance and fuel efficiency owing to lighter weight parts, would all be beneficial.

In an embodiment of the present invention, a structural element comprising a vehicle suspension control arm is constructed from a pair of complex, single piece, sheet metal stamped components formed from a material of uniform thickness. The components are joined without welding to form the correct plan view shape, namely an “A”, “L” or other appropriate shape for the application.

In a principal aspect of the invention, a vehicular suspension control arm comprises a first arm component and a second arm component formed from sheet metal, each arm component comprising an outer wall and two side walls, bushing connecting means adjacent a first end, at least one bracket receiving rivet aperture adjacent a second end, at least one component connecting rivet aperture located between the first end and the second end, a ride bushing and a handling bushing, a ball joint bracket comprising bracket rivet apertures corresponding to the at least one bracket receiving rivet aperture adjacent the second end of each of the first and second arm components, and a plurality of rivets, such that when constructed, the ball joint bracket is riveted to both the first and second arm components adjacent the second ends thereof via the at least one bracket receiving rivet aperture and the corresponding bracket rivet aperture, the first arm component is riveted to the second arm component at the corresponding at least one arm component connecting rivet aperture, the ride bushing is connected at the first end of the first arm component and the handling bushing is connected at the first end of the second arm component.

In a further aspect of the invention, a vehicular suspension control arm further includes a third arm component formed from sheet metal comprising an outer wall and two side walls, two ends, each end comprising at least one third arm component rivet aperture, a ride bushing seat component and a handling bushing seat component, wherein the third arm component is adapted to be riveted to each of the first arm component and the second arm component adjacent the first ends thereof and to both the ride bushing seat component and the handling bushing seat component adjacent the respective ends of the third arm component.

In a further aspect of the invention, a vehicular suspension control arm comprises a first arm component and a second arm component formed from sheet metal, each arm component comprising an outer wall and two side walls, an integral bushing seat receiving aperture adjacent a first end, at least one bracket receiving rivet aperture adjacent a second end, at least one component connecting rivet aperture located between the first end and the second end, a rod comprising a ride bushing seat at a first end, a handling bushing seat at a second end, and first and second contacting surfaces located interiorly of the seats and along the rod adjacent the seats adapted to contact the first and second arm components when the respective seats extend through the seat receiving apertures, a ball joint bracket comprising bracket rivet apertures corresponding to the bracket receiving rivet apertures adjacent the second ends of the first and second arm components, and a plurality of rivets, such that when constructed, the ride bushing seat extends through the seat receiving aperture of the first component, the handling bushing seat extends through the seat receiving aperture of the second component, the first and second arm components contact the first and second contacting surfaces of the rod, the ball joint bracket is riveted to both the first and second arm components adjacent the second ends thereof via the bracket receiving rivet apertures and the corresponding bracket rivet apertures, and the first arm component is riveted to the second arm component at the corresponding at least one arm component connecting rivet aperture.

In a further aspect of the invention, the side walls of the first and second arm components partially overlap and remain spaced apart at the first ends thereof.

In a further aspect of the invention, at least one spacer maintains a spacing between the side walls of both the first and second arm components at the at least one arm component rivet apertures.

In a further aspect of the invention, the first and second arm components are riveted at three arm component rivet apertures.

In a further aspect of the invention, one of the three arm component rivet apertures is located adjacent the second end of the arm components, and the ball joint bracket is riveted to each of the first and second arm components at said rivet apertures.

In a further aspect of the invention, the bushing connecting means comprises an integral bushing stud receiving aperture adjacent the first end of each of the first arm component and the second arm component, and wherein the control arm further comprises a rod comprising a ride bushing stud at a first rod end, a handling bushing stud at a second rod end, and first and second seating surfaces located interiorly along the rod adjacent the studs adapted to contact the first and second arm components when the respective studs extend through the bushing stud receiving apertures, such that when constructed, the ride bushing stud extends through the bushing stud receiving aperture of the first arm component, the handling bushing stud extends through the bushing stud receiving aperture of the second arm component, and the first and second arm components respectively contact the first and second seating surfaces of the rod.

In a further aspect of the invention, the rod is tubular.

In a further of the invention, the ride bushing comprises a bracket which is riveted to the first end of the first arm component.

In a further aspect of the invention, the handling bushing is stabilized by contact with a reinforcement sheet metal stamping riveted to at least one of the first and second arm components adjacent the first end of the second arm component.

In a further aspect of the invention, the second bushing stud is interiorly threaded to accept a correspondingly exteriorly threaded fastener and comprises the exterior handling bushing seat, an exterior second contacting surface formed as a shoulder on the second bushing stud and a tapered portion, and the control arm further comprises a shaped ring which fits over and onto the second bushing stud and sits on the tapered portion to hold the second arm component against the second contacting surface when the handling bushing is fastened to the second bushing stud.

DETAILED DESCRIPTION

FIGS.5to9illustrate a preferred embodiment of the weldless vehicle suspension control arm15of the invention. A first arm component12and a second arm component14are stamped from sheet metal. The preferred material is a steel sheet pre-coated for corrosion protection. Given the nature of this construction, a lighter gage sheet metal may generally be used than with a corresponding prior art welded construction, such as illustrated inFIG.3andFIG.4.

First arm component12and second arm component14have certain common features. Each comprises an outer wall16and two side walls18. Each arm component has an integral bushing seat receiving aperture20adjacent a first end22of the arm component. With appropriate stamping, the apertures20are formed from the same material comprising the rest of the arm component without the need to weld or otherwise attach a separate component with a bushing seat to the control arm, as typical in prior art manufacture. In addition, each arm component12,14comprises at least one bracket receiving rivet aperture24adjacent a second end26of the arm component. In the preferred embodiment ofFIG.5, two aligned bracket receiving apertures24are formed during stamping in each arm component. In addition, each arm component comprises at least one component connecting rivet aperture28located between the first end22and the second end26. In the preferred embodiment ofFIG.5, each arm component12,14comprises three pairs of aligned component connecting rivet apertures28.

A rod30serves to provide a non-riveted connection between the arm components12,14. It also replaces separate components, such as bushing seats, which would otherwise have to be welded or similarly attached to the control arm, as further discussed below. The rod30is preferably tubular to decrease the weight of the control arm, although it may be solid. The rod30comprises a first stud31with a ride bushing seat32at a first end34and a second stud33with a handling bushing seat36at a second end38. These bushing seats32,36are intended to accept bushings, as further discussed below. The rod30also comprises a first contacting surface40and a second contacting surface42located interiorly from the first and second ends34,38of the rod. These contacting surfaces40,42are designed to contact the first and second arm components12,14at the bushing seat receiving apertures20when the control arm is assembled.

A ball joint bracket44is adapted to receive a ball joint, as further discussed below. The ball joint bracket44comprises bracket rivet apertures46corresponding to the bracket receiving apertures24adjacent the second ends26of the first and second arm components12,14. In the preferred embodiment illustrated inFIG.5, two exterior bracket rivet apertures46align respectively with a pair of bracket receiving rivet apertures24on each of the first and second arm components12,14. An interior bracket rivet aperture46aligns with the pairs of component connecting apertures28adjacent the second end26of the arm components12,14. Thus, the pairs of component connecting apertures28adjacent the second end26of the arm components12,14serve both in the connection of the two arm components to each other and in the connection of the ball joint bracket44to the two arm components.

A plurality of rivets48, as illustrated inFIG.6, are employed to join the various components at the various bracket receiving rivet apertures24, component connecting rivet apertures28and bracket rivet apertures46.

Spacers50may be used to maintain the stability of the arm components12,14prior to and during assembly. As illustrated inFIG.5, the spacers50are located at component connecting rivet apertures28in the first arm component12prior to assembly, although either arm component could receive them. The spacers50maintain the spacing between the side walls18of each of the arm components when the control arm is assembled.

In a preferred assembly sequence, following stamping of the first and second arm components12,14, the spacers50are installed in alignment with the centrally located component connecting rivet apertures28in the first arm component12which typically will face rearward in relation to the vehicle. The following sequence may occur simultaneously or in close sequence. The ride bushing seat32of the stud31of rod30is inserted through the bushing seat receiving aperture20of the first component12and the first contacting surface40of the rod30contacts the first arm component12. The handling bushing seat36of the stud33is inserted through the bushing seat aperture20of the second component14and the second contacting surface42contacts the second arm component14. The first and second arm components12,14are brought into overlapping alignment at the component connecting rivet apertures28. The ball joint bracket44is brought into alignment with the first and second arm components12,14at the bracket receiving rivet apertures24, the bracket rivet apertures46and the component connecting rivet apertures28adjacent the second end26of the arm components.FIG.6illustrates the partially assembled control arm at this point. The rivets48are then installed to complete the basic control arm15, as illustrated inFIG.7. An advantage of the structure of the preferred embodiment illustrated is that the rivets48may be installed in a single plane, thus simplifying the assembly significantly. A further fitting or fittings (not illustrated) may be employed to secure the rod30to the assembled control arm15.

Following construction of the basic control arm15, the ride bushing52may be installed on the ride bushing seat32and the handling bushing54may be installed on the handling bushing seat36. Installation may be by press fitting the bushings52,54onto the bushing seats32,36. This is shown pre-assembly of the bushings inFIG.8. A ball joint56may also be connected to the control arm15at the ball joint bracket44using standard methods. The fully assembled control arm including the bushings52,54and the ball joint56is illustrated inFIG.9. Clearly, other known methods may be employed as appropriate to assemble the control arm, bushings and ball joint.

A second principal embodiment of the control arm structure is illustrated inFIG.10. In this case, the rod30is eliminated. Again, a plurality of rivets is employed to join the various components. This embodiment may be beneficial in particular applications, such as where the “packaging” requirements of the control arm within the suspension system dictate a different perimeter profile for the control arm. Elimination of the rod30may also lead to reduced mass and cost of the part, which is generally desirable as long as sufficient part durability and functionality are maintained.

Referring toFIG.10-10B, the control arm115is constructed with first arm component112and second arm component114. These components are also illustrated schematically in cross-section to show the typical U-shape of the arm components with an outer wall and two side walls. The side walls of the second arm component114are spaced closer to each other than the side walls of the first wall component112to allow the second arm component114to nest partially within the first arm component112. A ball joint bracket144is adapted to receive a ball joint.

The ball joint bracket144comprises bracket rivet apertures146corresponding to the bracket receiving apertures124adjacent the second ends126of the first and second arm components112,114. Two exterior bracket rivet apertures146align respectively with a pair of bracket receiving apertures124on each end of the first and second arm components112,114, although other attachment choices could be made. Thus, the pairs of component connecting apertures128adjacent the second end126of the arm components serve both in the connection of the two arm components to each other and in the connection of the ball joint bracket144to the two arm components.

The ride bushing152comprising ride bushing bracket158is riveted to the first end122of the first component112at one or more bushing bracket apertures160and one or more first arm component bushing bracket receiving apertures162. Handling bushing154may be conventionally fastened to the first end122of the second arm component114. A reinforcement sheet metal stamping164may be riveted to the first and second component at one or more apertures166,168. The reinforcement sheet metal stamping164contacts the handling bushing154and serves to stabilize it. Of course, the reinforcement may be made by other than sheet metal stamping, but using a sheet metal stamping is consistent with the processes to create the control arm as a whole and will have benefits attendant to those processes.

A further principal embodiment of the invention is illustrated inFIGS.11A to13. This embodiment is similar to the construction of the control arm illustrated inFIGS.5to9, except that the rod joining the first and second arm components is replaced with a third arm component comprising a sheet metal stamping shaped similarly to the first and second arm components in terms of its outer wall and two side walls. Instead of forming bushing seat apertures from the sheet metal material of the first arm component and second arm component, separate bushing seat components are riveted to the first ends of the first and second arm components along with the third arm component to form a robust riveted structure ready to receive bushings. The bushing seat components may be formed from sheet metal or other convenient materials.

In the embodiments ofFIGS.11A to13, a first arm component212and a second arm component214are stamped from sheet metal. First arm component212and second arm component214have certain common features. Each arm component212,214comprises an outer wall216and two side walls218. In addition, each arm component212,214comprises at least one bracket receiving rivet aperture224adjacent a second end226of the arm component. The arm components212,214are connected both at their second ends and centrally as in the first embodiment already described in relation to the embodiment ofFIGS.5to9. The differences between the first embodiment and this further embodiment are manifest at the first ends of the arm components212,214. Each arm component212,214comprises at least one additional component connecting rivet aperture229located adjacent the first end of the first arm component and the second arm component. In the preferred embodiment ofFIGS.11A to13, each first and second arm component212,214comprises a pair of additional connecting rivet apertures229.

A third arm component230serves to provide a riveted connection to the first and second arm components212,214. Like the first and second arm components, the third arm component is constructed with an outer wall and two side walls. The third arm component230comprises at least one third arm rivet aperture231adjacent each end thereof to align with the at least one additional component connecting rivet apertures229of the first and second arm components212,214. As illustrated inFIGS.12A and12B, the third arm component230may be oriented in the reverse direction from that in the embodiment illustrated inFIGS.11A and11B. When riveted at these apertures, the first and second arm components212,214, the third arm component230and the ride and handling bushing seat components232,236are all securely connected. Cap238serves to hold the handling bushing to the handling bushing seat236when secured with a fastener. Spacers50may again be employed between the side walls of one of the first and second arm components212,214, and between the side walls of the third arm component230at the location of the various rivet apertures, to maintain the spacing between the arm components and to support the structure of the control arm.

As shown inFIG.13, as with the embodiment illustrated inFIGS.5to9, following construction of the basic control arm215, the ride bushing252may be installed on the ride bushing seat of the ride bushing seat component232, and the handling bushing254may be installed on the handling bushing seat of the handling bushing seat component236.

It is imperative that an automotive control arm be able effectively to transmit the loads to which it is subjected during operation of the suspension system. One concern with employing relatively light gage sheet metal stampings as structural elements of a control arm is the ability of the sheet metal structure to transmit such suspension loads without loss of strength over time which may result from excessive freedom of movement of the components. Particularly in the case of the first embodiment illustrated inFIGS.5to9, where the arm components themselves are stamped with bushing seat receiving apertures, it is important to ensure that the arm component material surrounding those apertures is sufficiently reinforced. Details of a preferred manner to achieve such reinforcement are illustrated inFIGS.14to16B.

FIG.14illustrates a hollow tube rod30which has previously been described. At its first end34, the rod30comprises a first bushing stud31with a ride bushing seat32leading to a tapered portion comprising the first contacting surface40. At its second end38, the rod30comprises a second bushing stud33with a handling bushing seat36, internal threading37in the second stud33and a second contacting surface42formed as a shoulder on the second stud33of the rod30. A tapered section43of the rod30lies between the handling bushing seat36and the second contacting surface42.

FIG.15illustrates a riveted control arm15. Adjacent the first end34of the rod30, the first contacting surface40abuts the first arm component12as the ride bushing seat32passes through the bushing seat receiving aperture20at the first end22of the first arm component12. Adjacent the second end38of the rod30, the second contacting surface42abuts the second arm component14as the handling bushing seat36passes through the bushing seat receiving aperture20at the first end22of the second arm component14.

As illustrated inFIGS.15to16B, a shaped ring51is fitted over the handling bushing seat36and contacts the tapered section43of the rod30and the material of the second arm component14surrounding the bushing seat receiving aperture20adjacent the first end22of the second arm component14. The handling bushing54comprises an inner sleeve55which in turn is fitted over the handling bushing seat36and contacts the shaped ring51. Finally, a fastener56with an externally threaded section59is threaded into the correspondingly internally threaded section37of the handling bushing seat36. This fastener56comprises a fastener head61which is shaped to contact the handling bushing54. The fastener head61may be shaped to allow a certain clearance from the handling bushing54at certain locations in order to act as a stop for deflection of the handling bushing54during operation of the suspension system.

When the fastener is inserted and tightened, the handling bushing54is held in place and the second arm component14is securely held to the rod30via the intermediate shaped ring51. The radial clamping force generated by this arrangement sufficiently reinforces the sheet metal material of the second arm component14surrounding the handling bushing seat receiving aperture20of the second arm component14to facilitate effective transmission of forces during operation of the suspension system and to create a robust control arm structure.

It should be understood that although particular component arrangements are disclosed in the illustrated embodiments, other arrangements will benefit from this invention. Although particular step sequences are shown and described, it should be understood that steps may be performed in any order, separated or combined unless otherwise indicated and will still benefit from the present invention.