GB2442716A

GB2442716A - Independent rear suspension

Info

Publication number: GB2442716A
Application number: GB0620270A
Authority: GB
Inventors: Steve Scott Allen; Tony Adamo; Peter Joseph Jargowsky; Chris Eric Allard; Brian Miller
Original assignee: Ford Global Technologies LLC
Current assignee: Ford Global Technologies LLC
Priority date: 2006-10-13
Filing date: 2006-10-13
Publication date: 2008-04-16
Anticipated expiration: 2026-10-13
Also published as: GB2442716B; GB0620270D0

Abstract

An independent rear suspension system is provided that has a trailing arm 46 connected between a frame rail 38 and a wheel support knuckle 40. A lower control arm 42 is connected between a frame cross member 80 and the knuckle. 40 The suspension system also includes an upper link 44 that extends between the frame rail 38 and the knuckle 40, and a toe link 45 attached to a frame rail 38 below the axis of the axle and extending between a frame rail 38 and the trailing arm 46. The toe link 45 and upper link 44 are generally vertically aligned. A stabilizer bar 48 extends between the toe link 45 and upper link 44 and is connected to the lower control arm 42 outboard of a shock absorber 50 and a spring 52 to reduce space requirements for the suspension system forward of the wheel support knuckle 40. The lower control arm 42 is elongated and attached to the frame cross member 80 inboard of the frame rails 38 to improve the ratio of wheel travel to shock travel.

Description

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INDEPENDENT REAR SUSPENSION

Field of the invention

S The present invention relates to an independent rear suspension for a vehicle, such as a sport utility vehicle (SUV) having a third row of seats.

Background of the invention

Independent rear wheel suspension systems generally are comprised of shock absorbers, springs arid links between the frame of the vehicle and a wheel support knuckle. Upper and lower links, or control arms, generally form an articulated link that allows the vehicle to move vertically relative to the wheel. The shock absorbers and springs are generally provided to absorb impacts to the wheel and provide a smooth ride. Adjustable camber links and toe links are provided to permit adjustment of the wheel position. A stabilizer bar is generally provided to equalize forces laterally by coupling transversely aligned independent suspensions.

Suspension systems are designed to provide the desired ride and handling characteristics for a vehicle. Sports cars are generally provided with tight suspensions to improve handling. Luxury cars are provided with suspensions that are tuned to provide a softer ride with somewhat reduced handling performance. When designing or tuning a suspension system, fore and aft connections between the frame and the wheel support can be provided with softer elastomeric bushing connections to provide a softer ride.

Transverse connections between the frame and the wheel support can be provided with more rigid elastomeric bushings to provide improved handling characteristics.

One rating of a vehicle suspension system is the shock ratio which is defined as the ratio of wheel travel to shock travel. A shock ratio of greater than 1.3:1 results in higher loads being applied to the frame from the shock and spring. Lower loads translate into a more comfortable ride.

The length of lower control arms on full frame vehicles are limited general]y to the distance between the frame rails arid the wheel support knuckle. As Lhe length of the lower control arm is reduced, the shock ratio of the suspension system increases.

The length of the lower control arm also impacts the efflciency of the stabilizer bar ratio. Stabilizer bar ratio efficiency improvements can result in the reduction of the cost and weight of the stabilizer bar.

Shock and spring location in independent rear suspensions can result in a reduction of space available for third row passenger's feet. If the shock and spring are located near the third row passenger's feet, a higher floor may be required in front of the third row seats.

The angular orientation of suspension links such as the lower control arm and toe link can impact toe-in during braking and throttle off conditions. Increasing toe-in of vehicle wheels is preferred during such conditions.

Divergent toe links and lower control arms that may be required due to space limitations can reduce toe-in during braking and throttle off conditions.

Adjusting the wheel position toe-in and camber in prior art suspension systems generally must be performed in an iterative manner because, for example, in some suspension systems adjusting toe-in can cause the wheel camber to change, and visa versa. The camber must then be adjusted, which can affect the toe-in adiustment. This problem is referred to as confounding and occurs when either camber or toe-in are adjusted.

Suspension systems require adequate clearance for movement of the wheel and the suspension components relative to the vehicle frame and body. The location of suspension components can impact the design of the vehicle compartment S floor pan. Suspension system components must be contained within the envelope defined below the floor pan and frame.

Suspension components located forward of a seat located above the rear axle of a vehicle can result in a reduction of foot welil space available in front of the seat.

It is desirable to address the above design challenges with a compact rear suspension system that provides desirable axle, suspension system and wheel clearance while affording ample space for a third row seat and foot well space. It is also desirable to provide such a suspension system that reduces confounding between toe-in and camber adjustments. The above problems and others are addressed by applicants' invention as summarized below.

Summary of the invention

In accordance with a first aspect of the invention, there is provided an independent rear suspension for a vehicle having a body, at least two full frame rails, and at least one cross member secured to the two frame rails, the suspension comprising: a wheel support including a knuckle that is aligned wiLh an axle axis; a trailing arm extending from a point on the frame rail forward of the axle axis to the wheel support knuckle; an upper link extending from a point on the frame rail above and forward of the axle axis to the wheel support knuckle; a lower control arm extending from one of the cross members to the knuckle, the lower control arm being attached to the cross member inboard of the frame rails; a toe link attached to the frame rail below the axle axis and extending between the frame rail and the trailing arm; a stabilizer bar connected to the lower control arm by a stabilizer bar connecting link and to the suspension system of a wheel disposed on The opposite side of the vehicle, the stabilizer bar extending between the toe link and the upper link; a shock absorber secured to the lower control arm and the frame; and a spring secured to the shock absorber arid the frame.

The lower control arm may have a toe-in adjustment mechanism that allows the wheel toe-in to be adjusted and the upper link may have a camber adjustment mechanism that allows the wheel camber to be adjusted, whereby the camber adjustment and toe-in adjustments may be performed independently without confounding the other adjustment.

Conveniently, a toe-in adjustment mechanism is located on the lower control arm and the upper link and toe link are substantially vertically aligned.

A camber adjustment mechanism is preferably located on the upper link and the lower control arm and the link are substantially horizontally aligned.

Further aspects of the invention are set forth in Claims 12 and 16 of the appended claims.

In an independent rear suspension of a preferred embodiment of the invention, for a vehicle having a body that may be mounted on full frame rails, a cross member is secured between the frame rails. The suspension system has a wheel support that includes a knuckle that is aligned with an axle axis. A trailing arm extends from a point on the frame rail forward of the axle axis to the wheel support knuckle. An upper link extends from a point on the frame rail above and forward of the axle axis to the wheel support knuckle. A lower control arm is attached to the cross member inboard of the frame rails and is also connected to the wheel support knuckle. A toe link bar is attached to the frame rail below and forward of the axle axis and extends between the frame rail and the knuckle. A stabilizer bar is connected to the lower control arm by a connecting link and is connected on the opposite side of the iO vehicle to the suspension system of a wheel disposed and located on the opposite side. A spring is secured to the shock absorber that is secured between the lower control arm and the frame.

The stabilizer bar may pass between the toe link bar and the upper link. The stabilizer bar is connected on its ends to the lower control arms by stabilizer bar connecting links.

The lower control arm may be more than twice as long as the toe link. A shock ratio may be provided of less than or equal to 1.3:1 (wheel travel/shock travel) The lower control arm may be attached to the wheel support knuckle forward of the location where the lower control arm is attached to the cross member. In addition, the upper link may be attached to the knuckle above and forward of the wheel axis.

An advantage that may be achieved by the preferred embodiment of the invention, as summarized above, is that the foot well for a third row passenger seat may be enlarged due to less space being required forward of the axle for the suspension system components.

Another advantage that may be achieved is that an independent rear suspension may be provided that may be readily tuned to provide desired ride and handling characteristics.

Yet another advantage of the invention is that camber and toe-in adjustments may be performed with reduced confounding resulting from adjustment of either the camber or toe-in adjustment mechanisms.

Brief description of the drawings

The invention will now be described further, by way of example, with reference to the accompanying drawings, in which Figure 1 is a diagrammatic side elevation view of a prior art independent rear suspension and third row seat; Figure 2 is a diagrammatic side elevation view of a third row seat and independent rear suspension made in accordance with one embodiment of the present invention; Figure 3 is a side elevation view of the independent rear suspension shown in Figure 2; Figure 4 is a top plan view of the independent rear suspension shown in Figure 2; Figure 5 is a rear elevation view of the independent rear suspension shown in Figure 2; and Figure 6 is a fragmentary rear/inside perspective view of the independent rear suspension shown in Figure 2.

Detailed description of the preferred embodiment(s) Figure 1 is a diagrammatic representation of a prior art independent rear suspension system 10, similar to that disclosed in U.S. Patent No. 6,109,631. The suspension system 10 is located below the third row seat 12 of a sport utility vehicle. A wheel support knuckle 14 defines an axle bore 16 through which a rear axle of the vehicle extends.

The axle is supported by a combined shock and spring assembly 18 and is disposed rearward of the axle bore 16 and below the rear portion of the third row seat 12 that is secured to the vehicle floor pan 20. The toe link (not shown) is located rearward of the axle centre.

S Referring to Figure 2, an independent rear suspension system 30 made according to one embodiment of the present invention is shown. The suspension system 30 is located below the third row seat 32 of a sport utility vehicle. A floor pan 34 of the vehicle defines a foot well 36 forward of the third row seat 32. The vehicle is supported by the suspension system 30 on a frame rail 38 to which the floor pan 34 is secured. A wheel support knuckle 40 is connected to the frame of the vehicle by a lower control arm 42, an upper link 44, and trailing arm 46. The trailing arm 46 is is connected to the frame rail 38, the knuckle 40 and a toe link that is not shown in Figure 2, but is illustrated in Figures 3-6. A stabilizer bar 48 may form part of the suspension system 30 that equalizes forces applied to one rear wheel of a vehicle relative to the suspension system 30 to a rear wheel located on the opposite transverse side of the vehicle. Suspension system 30 also includes a shock absorber 50 and a spring 52. The shock absorber 50 is connected between the lower control arm 42 and the frame rail 38. Spring 52 is connected between the frame rail 38 and the shock absorber 50.

Referring to Figures 3 and 4, a stabilizer bar connecting pin 54 connects one end of the stabilizer bar 48 to the lower control arm 42. An upper link bushing 56 is provided between the upper link 44 and the knuckle 40. The upper link bushing 56 is an elastomeric member. Outer lower control arm bushing assembly 58 is provided between the lower control arm 42 and the knuckle 40. The bushings 56 and 58 provide a resilient connection between the upper link 44, lower control arm 42 and the wheel support knuckle 40.

It should be understood that attachments of the upper link 44 and lower control arm 42 to the knuckle 40 can be with either bushings or ball joints. A stabilizer bar bracket and bushing 60 are secured to the stabilizer bar 48 and the frame rail 38.

A toe link 45 connects the trailing arm 46 to the frame rail 38. Toe link 45 includes an outer clevis end 64 and an inner tubular end 66. The outer clevis end 64 could alternatively be a tubular end. An outer end bushing 68 is secured within the outer clevis end 64 and an inner end bushing 70 is provided in the inner tubular end 66. The upper link 44 has an outer clevis end 74 and an inner tubular end 76.

Referring to Figures 4 and 5, the suspension system 30 is shown in conjunction with cross member 80. Cross member extends between the frame rails 38 that extend longitudinally relative to the vehicle and are provided adjacent right and left sides of the vehicle.

An inner lower control arm bushing assembly 82 connects the inner end of lower control arm 42 to a frame bracket 83.

The lower control arm 42 extends from the inner bushing assembly 82 to the knuckle 40. The length of the lower control arm 42, as measured from the wheel knuckle 40 to the inner bushing assembly 82, is more than twice the length of the toe link 45. The increased length of the lower control arm 42 provides a shock ratio of less than or equal to 1.3:1 of wheel travel to shock travel. For example, movement of the wheel support knuckle of 2.6" is translated into 2" of shock movement. As a result, increased damping is obtained at the shock absorber 50 due to the effect of the lever corresponding to the lower control arm.

By comparison, the wheel travel to shock travel ratio of the attachment point to the lower control arm in U.S. Patent No. 6,109,631 is 1.33:1. As a result, improved shock absorber performance is obtained. The lower control arm 42 of the present invention is longer but less massive than the lower control arm in the 631 patent resui.tinq in weight reduction of the suspension sysLem that may contribute to added fuel efficiency improvements.

The lower control arm 42 cooperates with the trailing arm 46. Trailing arm 46 is connected to the frame rail 38 on its forward end and the wheel support knuckle 40 on its rearward end. The trailing arm 46 is also connected by the toe link 45 to the frame rail 38. In addition, the upper link 44 is secured between the frame rail 38 and the wheel support knuckle 40. Upper link 44 may also be referred to as a camber link. The frame bracket 83 of the lower control arm is mounted to the cross member 80 at a location that is further inboard than the bracket that secures the lower control arm to the frame rail as disclosed in the 631 patent.

The upper link 44 extends slightly rearwardly from its connection point to the frame rail 38 to the knuckle 40.

Conversely, the lower control arm extends forwardly from frame bracket 83 on the cross member 80 to the knuckle 40.

This arrangement may provide improved braking toe-in.

Stabilizer bar 48 is connected to the lower control arm 42 by the stabilizer bar connecting pin 54 outboard of the shock 50 and spring 52 and inboard of the knuckle 40. This spatial relationship improves the efficiency of the stabilizer bar 48 that functions as a torsion spring. The stabilizer bar 48 is more efficient in that it has reduced cost and weight. The stabilizer bar 48 extends between the toe link 45 and the upper link 44. By routing the stabilizer bar below the upper link 44 and above the toe link 45, less vertical space is required between the suspension system 30 and the compartment pan 34. In particular, the foot well 36 may be increased in size -10 -affording third row passengers more room for their feet within the Loot well 36.

The toe link 45 is secured substantially vertically below the upper link 44. The upper link 44 is secured to the knuckle less than 12 rearward of the connection point for the toe link 45, which should he understood as being substantially vertically aligned. Adjustments of toe-in with an adiustmen-L mechanism 77 (such as an elliptical washer or slot that receives a locking fastener) on the lower control arm do not confound the camber adjustment because the outer clevis end 64 of the toe link 45 and the outer clevis end 74 of the upper link 44 are substantially vertically aligned. That is, if the toe-in of the wheel is adjusted at the lower control arm, it is not normally required to also adjust the camber unless the wheel was previously out of adjustment as to camber. By horizontally aligning (within 12 of horizontal) the lower control arm 42 and the toe link 45, adjusting camber with a camber adjustment mechanism 78 (such as an elliptical washer or slot that receives a locking fastener) on the upper link 44 does not adversely effect toe-in adjustment. This simplifies adjusting the wheel position by allowing for adjustments to camber or toe-in independently without requiring compensatory adjustments.

The orientation of the lower control arm 42, upper link 44 and toe link 45 at only slight angles relative to a transverse direction provides the ability to improve vehicle handling since the bushings for these links may provide a stiffer connection between the upper links 44, toe link 45, and the lower control arm 42 relative to the frame rail 38 and knuckle 40. By providing stiffer lateral load bushings, handling can be improved without substantially reducing ride quality. The longitudinal orientation of the trailing arm 46 permits softer bushings to be provided between the trailing arm and the frame. By providing softer -11 -longitudinal load bushings for the trailing arm, a softer ride may be provided without adversely affecting vehicle handling.

Reterring to Figure 6, the location of the principle connection points between the frame of the vehicle and the knuckle 40 are shown in greater detai 1. The knuckle 40 is fixedly secured to trailing arm 46. The lower control arm 42 is connected at outer bushing 58 to the knuckle 40 at a io point that is below arid rearward of the axle axis. The lower control arm 42 is connected by an inner lower control arm bushing 82 to cross member 80 by the frame bracket 83.

Toe link 45 is connected on the outer end to the trailing arm 38 at the outer tubular or clevis end 64 of the toe link 45. The inner tubular end 66 of the toe link 45 is secured to frame rail 38. The toe link 45 is connected to the trailing arm 46 below and forward of the axle axis. Upper link 44 is connected on its outer clevis end 74 through a bushing 56 to the knuckle 40. Track 84 is provided for a brake calliper. The track 84 is integrally formed as part of the knuckle 40 when the knuckle 40 is formed in a casting operation.

Claims

-12 - CLAIMS

1. An independent rear suspension for a vehicle having a body, at least two full frame rails, and at least one S cross member secured to the two frame rails, the suspension comprising: a wheel support including a knuckle that is aligned with an axle axis; a trailing arm extending from a point on the frame rail forward of the axle axis to the wheel support knuckle; an upper link extending from a point on the frame rail above and forward of the axle axis to the wheel support knuckle; a lower control arm extending from one of the cross members to the knuckle, the lower control arm being attached to the cross member inboard of the frame rails; a toe link attached to the frame rail below the axle axis and extending between the frame rail and the trailing arm; a stabilizer bar connected to the lower control arm by a stabilizer bar connecting link and to the suspension system of a wheel disposed on the opposite side of the vehicle, the stabilizer bar extending between the toe link and the upper link; a shock absorber secured to the lower control arm and the frame; and a spring secured to the shock absorber and the frame.

2. An independent rear suspension as claimed in claim 1, wherein the lower control arm has a toe-in adjustment mechanism that allows the wheel toe-in to be adjusted and the upper link has a camber adjustment mechanism that allows the wheel camber to be adjusted, whereby the camber adjustment and toe-in adjustment may be performed independently without confounding the other adjustment.

-13 -

3. An independent rear suspension as claimed in claim 2, wherein a toe-in adjustment mechanism is located on the lower control arm and the upper link and toe link are substantially vertically aligned.

4. An independent rear suspension as claimed in claim 2 or 3, wherein a camber adjustment mechanism is located on the upper link and the lower control arm and the link are substantially horizontally aligned.

5. An independent rear suspension as claimed in any preceding claim, wherein the toe link is attached to the frame rail forward of the upper link to provide added clearance relative to a floor pan of the vehicle.

6. An independent rear suspension as claimed in any preceding claim, wherein the upper link is disposed above the toe link within 12 of a vertical line extending upwardly from the toe-in link.

7. An independent rear suspension as claimed in any preceding claim, wherein the shock absorber and spring are concentrically disposed and are located directly below a third row rear seat cushion.

8. An independent rear suspension as claimed in any preceding claim, wherein the stabilizer bar is connected to the lower control arm between the knuckle and the spring.

9. An independent rear suspension as claimed in any preceding claim, wherein the lower control arm is more that twice as long as the toe link to allow for a shock ratio (wheel travel/shock travel) of less than or equal to 1.3:1.

10. An independent rear suspension as claimed in any preceding claim, wherein the lower control arm, and the upper link are each attached to the wheel support knuckle by -14 -an elastomeric bushing that is received in a bushing receptacle farmed an the knuckle.

11. An independent rear suspensian as claimed in any preceding claim, wherein the lawer cantral arm is attached ta the wheel suppart knuckle farward af the lacatian where the lawer cantral arm is attached ta the crass member.

12. An independent rear suspensian far a vehicle having a bady, at least twa full frame rails, and aL least ane crass member secured ta the twa frame rails, the suspensian camprising: a wheel suppart including a knuckle that is aligned with an axle axis; is a trailing arm extending fram a paint an the frame rail farward af the axle axis ta the wheel suppart knuckle; an upper link extending fram a paint an the frame rail abave the axle axis ta the wheel suppart knuckle; a tae link attached ta the frame rail belaw the axle axis and extending between the frame rail and the trailing arm; a lawer cantral arm extending fram ane af the crass members ta the knuckle, the lawer cantral arm being attached ta the crass member inbaard af the frame rail nearest the wheel suppart knuckle ta the wheel suppart knuckle wherein the lawer cantral arm is mare that twice as lang as the tae link ta allaw far a shack ratia af less than ar equal ta 1.3:1; a shack absarber secured ta the lawer cantral arm and the frame; and a spring secured ta the shack absarber and the frame.

13. An independent rear suspensian as claimed in claim 12 wherein the lawer cantral arm has a tae-in adjustment mechanism that allaws the wheel tae-in ta be adjusted abaut a vertical axis defined by the upper link and tae link attachment paints ta the knuckle and the upper link has a -15 -camber adjustment mechanism that allows the wheel camber to be adjusted about a horizontal axis defined by the lower control arm and the toe link attachment points to the knuckle, wherein the camber adjustment arid toe-in adjustment may he performed independently without confounding the other adjustment.

14. An independent rear suspension as claimed in claim 12 wherein the toe link is attached to the frame rail forward of the upper link to provide added clearance relative to a floor pan of the vehicle, and wherein the upper link is disposed above and rearward of the toe link within 12 of a vertical line extending upwardly from the toe-in link.

15. An independent rear suspension as claimed in claim 12 wherein the lower control arm is attached to the wheel support knuckle forward of the location where the lower control arm is attached to the cross member.

16. An independent rear suspension for a vehicle having a body, at least two full frame rails, and at least one cross member secured to the two frame rails, the suspension comprising: a wheel support including a knuckle that is aligned with an axle axis; a trailing arm extending from a point on the frame rail forward of the axle axis to the wheel support knuckle; an upper link extending from a point on the frame rail above the axle axis to the wheel support knuckle; a lower control arm extending from one of the cross members to the knuckle, the lower control arm being attached to the cross member inboard of the frame rails and to the wheel support knuckle, wherein the lower control arm is attached to the wheel support knuckle forward of the location where the lower control arm is attached to the cross member; -16 -a toe link attached to the frame rail below the axle axis and extending between the frame rail and the trailing arm; a shock absorber secured to the lower control arm and the frame; and a spring secured to the shock absorber and the frame.

17. An independent rear suspension as claimed in claim 16 wherein the upper link is attached to the knuckle above io and forward of the wheel axis and the lower control arm is attached to the knuckle below and rearward of the wheel axis.

18. An independent rear suspension as claimed in claim is 17 wherein the upper link and lower control arms are secured to the knuckle at diametrically opposed locations relative to the wheel axis.

19. An independent rear suspension as claimed in claim 16 wherein the toe link has a toe-in adjustment mechanism that allows the wheel toe-in to be adjusted and the upper link has a camber adjustment mechanism that allows the wheel camber to be adjusted, wherein the camber adjustment may be performed independently without confounding the toe-in adjustment.

20. An independent rear suspension as claimed in claim 16 wherein the toe link is attached to the frame rail forward of the upper link to provide added clearance relative to a floor pan of the vehicle, wherein the upper link is disposed rearward and above the toe link within 12 of a vertical line extending upwardly from the toe link.

21. An independent rear suspension substantially as herein described with reference to and as illustrated in any one of Figures 2 to 6 of the accompanying drawings.