WO2014178769A1

WO2014178769A1 - Spring suspension

Info

Publication number: WO2014178769A1
Application number: PCT/SE2014/050402
Authority: WO
Inventors: Anders Johansson
Original assignee: Scania Cv Ab
Priority date: 2013-04-30
Filing date: 2014-04-03
Publication date: 2014-11-06
Also published as: SE540192C2; BR112015027379B1; DE112014001858T5; BR112015027379A2; SE1350525A1

Abstract

The invention relates to a spring suspension for a wheel axle for a vehicle, the spring suspension including a spring link mounted to a vehicle body on the vehicle via a spring mounting and an axle mounting. The spring link includes a leaf spring with a loop at one end and is fitted to the spring mounting via the loop. The loop on the leaf spring faces downwards in a vertical vehicular direction d_v. When the vehicle is subject to lateral forces during cornering and the force on the vehicle's wheel axle thus increases in the vertical vehicular direction d_v, the spring link will be deformed in the vertical vehicular direction d_v as well as the horizontal vehicular direction d_h, decreasing the distance between the centre of the loop and the wheel axle and bringing about an understeering effect.

Description

Spring suspension

Scope of the invention

The present invention relates to a spring suspension for a wheel axle in a vehicle according to the introduction to the independent claim.

Background to the invention

When a vehicle's wheels move vertically, for example when cornering or giving way, the vehicle can be subjected to yawing forces. As a result of these forces, the vehicle may start to veer without the driver having turned the steering wheel. If the steering effect occurs when one of the wheels lifts while the opposite wheel is pressed downwards, as when the bodywork pitches or banks sideways, for example, it is called roll steer. The inside wheel, for example, can lift when cornering hard.

In the case of roll steer a difference arises in wheel angles between the two wheels being lifted and depressed, respectively, causing the vehicle to under- or oversteer. Oversteering involves the vehicle veering more than expected in a corner. Sports cars, for instance, are often neutral to oversteered in order to react more easily to the driver's command during more advanced driving.

Understeering involves the vehicle not veering as much as expected but trying to travel straight ahead in a corner. Slight understeering is aimed for by most vehicle manufacturers, as it gives the vehicle a more predictable and easy-to-hand le behaviour in a critical situation. Overly powerful understeering, however, makes the vehicle unwieldy. Generally speaking, front-wheel-driven vehicles are more understeered than rear-wheel-driven ones.

There are a number of different solutions for making a vehicle understeered. GB- 2211473-A, for example, shows a rear wheel axle suspension for a vehicle. The suspension makes use of a tilting effect to reduce the size of forces transmitted to the vehicle body. That way, an understeering effect can be produced while simultaneously obtaining shock absorption whenever a rear wheel strikes a bump in the road.

US-20030098565-A1 shows a leaf spring suspension for a rear wheel axle. The suspension contains leaf springs fixed to the vehicle with front and rear brackets. The rear brackets are stiff in a transverse direction, the front brackets spring- cushioned in a transverse direction. When the vehicle is subjected to transverse lateral forces, a swing pole is created for the rear axle, which is positioned behind the centre of the rear axle. The wheel axle will then incline somewhat relative to the vehicle's longitudinal direction of travel and in this way create understeering of the vehicle as the vehicle proceeds through a bend. The solution uses a specially designed journal bearing, which provides scope for transverse movement.

With another type of suspension, e.g. two-air-bellow suspension, the wheels of the vehicle are suspended from the vehicle's bodywork via their own spring link linking the wheel axle with the bodywork via individual spring mountings. When loaded, the spring mounting and the spring link are pressed downwards in a vertical sense. The load brings about a change in the angle of the spring link and hence an "extension" of the spring link horizontally. The extension results in an increase in the horizontal distance between the spring mounting and the wheel axle. Since the vehicle takes on a greater load to the outer wheel when cornering, the spring link in the wheel suspension on the outer wheel becomes longer horizontally than the spring link in the wheel suspension on the inner wheel. The wheel axle is then angled and if the wheel axle is a rear axle, the vehicle can start to oversteer, which is not desirable.

The aim of the invention is thus to provide improved wheel suspension, making the vehicle's behaviour understeered when using a spring link connecting the wheel axle with the body of the vehicle. Summary of the invention

The aim described above is achieved by spring suspension for a wheel axle for a vehicle, the spring suspension containing a spring link mounted to a vehicle body on the vehicle via a spring mounting and an axle mounting. The spring link contains a leaf spring with a loop at one end and is fitted to the spring mounting via the loop. The loop on the leaf spring faces downwards in a vertical vehicular direction d_v. Whenever the vehicle is subjected to lateral forces during cornering and the force on the vehicle's wheel axle thus increases in the vertical vehicular direction d_v, the spring link will be deformed in the vertical vehicular direction d_v as well as the horizontal vehicular direction d_h. The distance between the centre of the loop and the wheel axle then decreases, generating an understeering effect.

Therefore, by turning the leaf spring with the loop to face downwards, increased understeering of the vehicle can be produced while retaining the driving height. The driving height is the distance between the bottom of the vehicle and ground level. Desired understeering properties can thus be achieved without

compromising on driving height. The existing spring mounting and axle mounting can be used without any major modifications, thereby making the solution cheap and simple to accomplish while simultaneously enhancing the driving

characteristics.

According to one embodiment the spring link includes a single-leaf spring, in which case the spring link only has one leaf spring, enabling the weight to be reduced as compared with having a two-leaf spring, for instance.

Preferred embodiments are described in the dependent claims and in the detailed description.

Brief description of the figures attached

The invention will be described below with reference to the figures attached, of which:

Fig. 1 shows a vehicle with spring suspensions for the various wheel axles. Fig. 2 shows a spring suspension according to one embodiment of the invention. Fig. 3 shows a cross-section A-A of the spring suspension in Figure 2.

Fig. 4A shows an example of a spring link with centred loop.

Fig. 4B shows an example of a spring link with overhead loop.

Fig. 4C shows an example of a spring link with underlying loop.

Fig. 5 shows an example of a spring link with a guard band.

Detailed description of preferred embodiments of the invention

Fig. 1 schematically illustrates a goods vehicle 1 with wheels 2 connected with wheel axles 4. The wheel axles 4 are suspended via spring suspensions 3 to a vehicle body 8 (Fig. 2), for example a vehicle frame. The vehicle frame can be made up of two elongated parallel frame side bars interlinked by a number of crossbeams. Fig. 2 shows a spring suspension 3 for a wheel axle 4 for the goods vehicle 1 in Fig. 1 in more detail. The spring suspension 3 can be used for vehicles other than goods vehicles, for example passenger cars, emergency call-out vehicles and so on. Fig. 2 shows only one spring suspension 3 positioned close to one end of the wheel axle 4, but it is implicit that in most cases there will be another spring suspension 3 at the other end of the same wheel axle 4.

The spring suspension 3 contains a spring link 6 extending primarily in a horizontal vehicular direction d_h and fitted to a vehicle body 8 on the vehicle 1 via a spring mounting 5 housing a bearing 13. The spring mounting 5 is secured to the vehicle body 8, more specifically the frame side bar, using bolts or rivets for example. The spring link 6 contains a leaf spring 16 with a loop 17 at one end and is fitted to the spring mounting 5 by means of a bolt 12 extending in a primarily transverse vehicular direction d_t through the bearing 13 and through the loop 17 on the leaf spring 16. The centre of the loop 9 is indicated in the figure. At the other end the spring link 6 is secured to the wheel axle 4 via an axle mounting 7. The centre 18 of the wheel axle 4 is indicated in the figure. The axle mounting 7 can be a bridge or cross-link, for instance, with yokes 28 permanently positioned above protruding pins 31 on the wheel axle 4, bracing the spring link 6 to the wheel axle 4 by screwing the yokes 28 firmly into a plate 32 with bolts or screws. Other ways of securing the spring link 6 to the wheel axle 4 are conceivable, however. The axle mounting 7 is attached to a shock absorber 10, which in turn is secured to the vehicle body 8. In the example shown in the figure the spring link 6 has an extension 22 extending behind the wheel axle 4 in the horizontal vehicular direction d_h, in close contact with the bottom of an air bellow 1 1.

As shown in the figure, the loop 17 on the leaf spring 16 faces downwards in a vertical vehicular direction d_v. Downwards here means in the direction of ground level. In other words the spring link 6 is mounted such that the loop 17 on the leaf spring 16 is an underlying loop 17. Whenever the vehicle 1 is subject to lateral forces during cornering and the force on the vehicle's wheel axle 4 thus increases in the vertical vehicular direction d_v, the spring link 6 will be deformed in the vertical vehicular direction d_v as well as the horizontal vehicular direction d_h, thus reducing the distance between the centre 9 of the loop and a through wheel axle centre 18 on the wheel axle 4 in the horizontal vehicular direction d_h as compared with when the force on the vehicle's wheel axle 4 does not increase in the vertical vehicular direction d_v. The loop 17 here is principally circular in shape.

Fig. 3 shows a cross-section of the spring mounting 5 in Fig. 2 along the line A-A. The spring mounting 5 here is designed with two yokes 33 housing the bearing 13 between them. The bolt 12 extends through the bearing 13 along an axle 15, which here again forms an axle of rotation 15 for the loop 17 (Fig. 2) through the centre of the loop 9. The bolt 12 is secured with a nut 14 and a bracing joint 35. The leaf spring 16 hugs the bearing 13 tightly and is flexible around the axle 15. Between the yokes 33 and the bearing 13 washers 34 can be arranged to assimilate forces in the transverse vehicular direction d_t, so the spring link 6 here is shown rigidly fitted to the spring mounting 5 in the transverse vehicular direction d_t. In this way no displacement of the spring length is permitted in the transverse vehicular direction d_t. The bearing 13 can be e.g. a rubber or a ball bearing. The principle underlying the way in which understeering is produced with the spring suspension 3 described above will be explained next. Figs 4A and 4B show first two examples of known spring suspensions where oversteering or inadequate understeering is obtained. The accepted way of generating understeering for a rear wheel axle 4 has been to incline the spring link 6, which inclination is illustrated in Figs 4A and 4B. However, this design does not yield the desired degree of understeering effect unless the driving height (or ground (road) clearance) is reduced, since the rotation of the loop 17 counteracts the

understeering effect, as described in more detail in connection with Fig. 4B below. Reducing the driving height means e.g. extending the spring mounting 5 downwards so as to achieve increased inclination of the spring link 6. Fig. 4C then shows the understeering according to the invention. The figures illustrate the loop 17 as a fixed point, while the axle mounting 7 shifts. In the example the axle mounting 7 is subject to an upwards vertical force F in the event of a slewing movement. The spring suspension 3, for example, is then positioned on the outer side of the vehicle 1 (Fig. 1 ) in a bend, suspending a rear wheel axle 4. It is then desirable to decrease the distance between the centre 9 of the loop and the axle mounting 7 in order to generate an understeering effect. The wheel axle 4 will then be angled and understeering can be produced, so Figs 4A-4C do not show the spring mounting 5, and the axle mounting 7 is illustrated schematically as a rectangle.

Fig. 4A schematically shows the spring suspension 3 with a spring link 6, where the spring link 6 has a centred loop 17, known as a "Berlin eyelet". A centred loop 17 results in the loop 17 being centred around a midline on the spring link 6. The spring link 6 is secured to the axle mounting 7 at an angle a from the horizontal vehicular direction d_h down to the midpoint of the loop 9. The loop 17 can twist around the midpoint 9 of the loop through the bearing 13. The dashed line shows how the spring link 6 is twisted upwards around the midpoint 9 of the loop when the axle mounting 7 is exposed to the force F. The axle mounting 7 is moved the distance dz in a vertical vehicular direction d_v by the force F. At the same time, the loop 17 is twisted around the midpoint 9 of the loop, causing the axle mounting 7 to move in the horizontal vehicular direction d_h a distance dx. The distance dx approximates to dx = a^■ dz, (1 ) and thus depends solely on the curvature dz and the inclination a. This spring suspension 3 does not provide sufficient understeering.

Fig. 4B schematically shows the spring suspension 3 with a spring link 6, where the spring link 6 has an overhead loop 17. The loop 17 then faces away from ground level. The spring link 6 is secured to the axle mounting 7 here at an angle a from the horizontal vehicular direction d_h down to a point on the spring link 6 where the loop 17 begins. The radius of the loop 17 is marked here with 'e'. The loop 17 can twist around the midpoint 9 of the loop through the bearing 13. The dashed line shows how the spring link 6 is twisted upwards around the midpoint 9 of the loop when the axle mounting 7 is subject to the force F. The axle mounting 7 is then moved the distance dz in a vertical vehicular direction d_v by the force F. At the same time, the loop 17 is twisted around the midpoint 9 of the loop at an angle φ, causing the axle mounting 7 to move a distance dx in the horizontal vehicular direction d_h away from the centre 9 of the loop. This occurs because the loop 9 unfurls as a result of the force F acting on the axle mounting 7 and pulling on the spring link 6. The distance dx approximates to: dx = · dz— e^■ φ, (2) and thus depends on both the curvature dz and the inclination a, as well as the change in angle φ and the radius of the loop 17, e. In this case e- φ dominates over a dz; as a result the distance between the centre 9 of the loop and the axle mounting 7 increases, producing undesirable oversteering. Fig. 4C schematically shows the spring suspension 3 with a spring link 6, where the spring link 6 has an underlying loop 17. The loop 17 then faces ground level. Here the spring link 6 is secured to the axle mounting 7 at an angle a from the horizontal vehicular direction d_h up to a point on the spring link where the loop 9 begins. The spring link 6 is thus mounted upwards at an angle a in a direction from the axle mounting 7 to the spring mounting 5. The radius of the loop 9 is marked here with 'e'. The loop 17 can twist around the midpoint 9 of the loop through the bearing 13. The dashed line shows how the spring link 6 is twisted upwards around the midpoint 9 of the loop when the axle mounting 7 is subject to the force F. The axle mounting 7 then moves the distance dz in a vertical vehicular direction d_v by the force F. At the same time, the loop 17 is twisted around the midpoint 9 of the loop at an angle φ, causing the axle mounting 7 to move a distance dx in the horizontal vehicular direction d_h towards the centre 9 of the loop. This occurs because the loop 9 coils inwards under the force F acting on the axle mounting 7. The distance dx approximates to: dx =—a · dz + e^■ φ, (3) and thus depends on both the curvature dz and the inclination a, as well as the change of angle φ and the radius of the loop 17, e. In this case a dz dominates over e- φ; as a result the distance between the centre 9 of the loop and the axle mounting 7 decreases, producing understeering. The spring link 6 is thus deformed in the vertical vehicular direction d_v as well as the horizontal vehicular direction d_h, thereby decreasing the distance between the centre 9 of the loop 9 and a through wheel axle centre 18 on the wheel axle 4 in the horizontal vehicular direction d_h as compared with when the force on the vehicle's wheel axle 4 or the axle mounting 7 does not increase in the vertical vehicular direction d_v. The underlying loop 17 on the spring link 6 is not locked to the spring link, therefore, but can be opened or closed, as appropriate, depending how the vehicle turns and on which wheel axle 4 and on which side of the wheel axle 4 the spring suspension 3 is mounted. Fig. 4 shows an exposed spring link 6 with a guard band 19. The guard band 19 encloses the spring link 6 at least partially in order to keep the spring link 6 together in the event of breakage. The figure shows how the guard band 19 extends from a mounting area 23 on the leaf spring 16 within which mounting area 23 the leaf spring 16 is adapted for mounting on the wheel axle 4 (Fig. 2). The guard band 19 then extends along a first side 25 on the leaf spring 16 to enclose the loop 17, and on along a second side 26 on the leaf spring 16 to the mounting area 23 on the leaf spring 16. The first and second sides 25,26 are opposite sides of the leaf spring 16. The first and second sides 25,26 also make up the outer sides of the leaf spring 16 in a vertical vehicular direction d_v(Fig. 2). The mounting area 23 includes, for example, two opposing flat faces of the leaf spring 16, on which the guard band 19 is then placed. The mounting area 23 is positioned between the extension 22 of the leaf spring 16 and the remaining part of the leaf spring 16. The guard band 19 is attached to the leaf spring 16 by securing components 21 ,24 in the mounting area 23 and/or around the loop 17. The securing components 21 ,24 can comprise e.g. rivets or screws. As shown in Fig. 2, the axle mounting 7 is then stretched across the mounting area 23, thus tightening the guard band 19 additionally between the plate 32 and the leaf spring 6, and between the wheel axle 4 and the leaf spring 16. The figure also shows the bearing 13 and the bolt 12 running through the bearing 13.

The spring link 6 can also include a clamping unit 20 linking a lower and an upper part of the guard band 19. The clamping unit 20 functions as a loop or sliding knot around the loop 17 of the spring link and is permanently connected to only one or other of the lower and upper parts of the guard band 19. Whichever of the lower or upper part of the guard band 19 is not permanently connected to the clamping unit 20 is allowed to move in the aperture of the clamping unit 20 if the spring moves or the spring link 6 breaks. The clamping unit 20 can include, for example, a yoke placed around the leaf spring 16 and the guard band 19 and locked tight using a screw joint 27 or welding. The clamping unit 20, as shown in the figures, is positioned adjacent to the loop 17. In the event of breakage to the leaf spring in the vicinity of the loop 17 the leaf spring 16 is prevented from passing over the loop 17. The leaf spring 16 is thus preventing from moving relative to the position of the loop 17 more than is permitted by any clearance between the loop 17 and the guard band 19 and any extension of the guard band 19. Essentially, the length of the spring link 6 can then be retained, as can the stability of the spring link 6 in the vertical vehicular direction d_t. These properties can be improved by designing the guard band 19 to sit tightly round the leaf spring 16, leaving no or only little play between the guard band 19 and the leaf spring 16 around the loop 17 on the leaf spring 16. An additional way of improving these properties is to position the clamping unit 20 as close as possible to the loop 17.

The guard band 19 can be made, for example, from flats, or from steel with good tensile strength, with a thickness of between 1 and 5 mm, e.g. 2, 3 or 4 mm. The width of the guard band 19 can match the width of the leaf spring 16, for example. According to one embodiment the guard band 19 is manufactured as a single unit. The leaf spring 16 can be manufactured, for example, from spring steel, steel or composite.

The present invention is not restricted to the embodiments described above.

Various alternatives, modifications and equivalents can be used. The

embodiments listed above do not, therefore restrict the scope of the invention as defined by the claims attached.

Claims

Patent claims

1. A spring suspension (3) for a wheel axle (4) for a vehicle (1 ), the spring suspension (3) including a spring link (6) extending primarily in a horizontal vehicular direction d_h and mounted to a vehicle body (8) on the vehicle (1 ) via a spring mounting (5) housing a bearing (13), the spring link (6) further including a leaf spring (16) with a loop (17) at one end, fitted to the spring mounting (5) via a bolt (12) extending in a primarily transverse vehicular direction d_t through the bearing (13) and through the loop (17) on the leaf spring (16), the spring link (6) further being secured at the other end to the wheel axle (4) via an axle mounting (7), characterized in that the loop (17) on the leaf spring (16) faces downwards in a vertical vehicular direction d_v so that, when the vehicle (1 ) is subject to lateral forces during cornering and the force on the vehicle's wheel axle (4) thus increases in the vertical vehicular direction d_v viewed from ground level, the spring link (6) will be deformed in the vertical vehicular direction d_v as well as the horizontal vehicular direction d_h so that the distance between the centre (9) of the loop and a through wheel axle centre (18) on the wheel axle (4) decreases in the horizontal vehicular direction dh as compared with when the force on the vehicle's wheel axle (4) does not increase in the vertical vehicular direction d_v.

2. The spring suspension (3) according to claim 1 , the spring link (6) being fitted stiffly to the spring mounting (5) in the transverse vehicular direction d_t.

3. The spring suspension (3) according to claim 1 or 2, the loop (17) on the leaf spring (16) being an underlying loop (17).

4. The spring suspension (3) according to any of the preceding claims, the spring link (6) including only one leaf spring (16).

5. The spring suspension (3) in accordance with any of previous claims, the spring link (6) being mounted at an upward angle in a direction from the axle mounting (7) to the spring mounting (5).

6. The spring suspension (3) in accordance with any of previous claims, the bearing (13) being a rubber bearing.

7. The spring suspension (3) in accordance with any of previous claims, the spring link (6) including a guard band (19) at least partially enclosing the leaf spring (16).

8. The spring suspension (3) according to claim 7, the spring link (7) including a clamping unit (20) connecting the guard band (19) with the leaf spring (16).

9. The spring suspension (3) in accordance with any of previous claims, the loop (17) being primarily circular in shape