GB2162474A - An axle suspension for motor vehicles - Google Patents

Abstract

The suspension comprises a rigid axle 10 which is displaceable in the sense of a positive oblique springing during inward spring stroke movements, and wherein the wheel support points 18 are only slightly displaced transversely to the longitudinal direction of the vehicle during alternate spring strokes. The rigid axle 10 is articulated about an axis offset vertically to its wheel axis 41, to at least one guiding control arm 32, 34 on each side, and the straight line connecting the articulation points of the control arm to the rigid axle defines a pivot axis 42 about which the wheel axis is displaceable by means of a guide device 44 in the sense of a positive oblique springing during inward spring stroke movements. The guide device 44 comprises two mutually separate guide arms 62, 64 articulated to the vehicle body, which are arranged symmetrically to the longitudinal median vehicle plane d-d and mutually obliquely towards the rigid axle 10 so that the straight lines joining their control arms intersect 20 mutually beneath the wheel axis. <IMAGE>

Description

SPECIFICATION Axle suspension s stem for motor vehicles The invention relates to an axle suspension for motor vehicles, particularly but not exclusively motor cars, comprising a rigid axle which is braced via non-guiding spring means and guided via lateral guiding arms which are pivotable relative to the axle body and determine, for a wheel axis, a pivot axis about which the wheel axis is displaceable in the sense of a positive oblique springing during inward spring stroke movements.

An axle suspension of this type is already known (USA Patent Specification 2,226,047, Figure 5).

This axle suspension system has the advantage of a positive oblique springing, in that, due to a lateral offset of the wheel axis from a straight line joining the points of articulation of the control arms to the rigid axle, the wheels can move upwards and backwards about a pivot axis parallel to the wheel axis during inward spring strokes.

The inward spring stroke movement of the wheel axis therefore occurs in the direction of a shock produced upon a wheel by travelling over an irregularity, which is desirable for axle suspension.

A disadvantage of this known axle suspension lies in the fact that its instantaneous roll centre is located far above the wheel axis.

This is due to the fact that the bracing of the lateral forces is effected by the control arms articulated to the wheel brackets above the rigid axle body.

This position of the instantaneous centre causes the wheel support points to be displaced to a high degree transversely to the longitudinal direction of the vehicle during alternate spring strokes.

This has the result that, in icy road conditions, the wheels easily drift in the lateral direction and/or begin to float.

The invention seeks to provide an axle suspension Which is characterised by a substantially improved lateral wheel grip when on smooth ice.

According to the invention there is provided an axle suspension for motor vehicles, comprising a rigid axle which is braced via nonguiding spring means and guided via lateral guiding arms which are pivotable relative to the axle body and determine, for a wheel axis, a pivot axis about which the wheel axis is displaceable in the sense of a positive oblique springing during inward spring stroke movements, wherein the pivot axis is offset vertically relative to the wheel axis, the pivoting of the wheel axis about the pivot axis in the sense of the positive oblique springing being controlled via two mutually separate guide arms articulated to the vehicle body, which guide arms are arranged symmentrically to the longitudinal median vehicle plane and extend mutually obliquely towards the rigid axle so that straight lines projected through their articulations intersect mutually in the longitudinal median vehicle plane in a horizontal plane located beneath the wheel axis.

In this axle suspension, which is capable of oblique springing, the instantaneous roll centre is located beneath the wheel axis, since the intersection point of the straight joining lines passing through the articulation points of the two guide arms, which determines the centre, is located upon the longitudinal median vehicle plane in a plane beneath the wheel axis.

Such a displacement downwards of the instantaneous centre produces the advantage that the track curves, along which the wheel support points move during alternate inward and outward spring strokes, are given a steeper course, with the result that the strokes of the wheel support points relative to the road transversely to the longitudinal direction of the vehicle are reduced. This produces the desired improvement in the running behaviour, namely better adhesion of the wheels on icy surfaces in the lateral direction.

Another advantage further development of the invention provides that tthe guide arms are located in front of the rigid axle, considered in the longitudinal direction of the vehicles, are articulated to the vehicle body above their point of articulation to the rigid axle, and converge towards the rigid axle, whereby a desirable slight understeering effect can be achieved elastokinematically by the influence of lateral forces.

Another favourable further development of the invention can be achieved if the straight lines through the articulations of the guide arms intersect on the wheel support surface in the design position, whereby the minimum lateral offset distances of the wheels on icy surfaces can be achieved.

A further improvement in the running behaviour in the sense of the invention can be achieved if the said pivot axis is guided via the guiding control arms in a vertical plane, because then the pivot axis of the axle body is guided in a vertical plane perpendicular to the longitudinal direction of the vehicle during inward and outward spring stroke movements, and the axle body of the rigid axle will therefore execute no steering movements during alternate inward and outward spring stroke movements.

The straight guidance of the pivot axis of the rigid axle body may be achieved in this case by differently constructed control arm arrangements. Straight guides may be provided which are articulated to the rigid axle in its region near the wheel by only one control arm. The straight guidance may equally well be achieved by Watt linkages.

The axle suspension means according to the invention is suitable for a rigid axle which carries driving or non-driving wheels. At the same time it may also be constructed as a front axle suspension means or as an axle suspension means with steerable wheels.

An embodiment of the invention will now be described by way of example, the embodiment comprising an axle suspension according to the invention, constructed as a rear axle suspension means for motor cars.

In the diagrammatic drawing: Figure 1 shows a perspective view of the rear axle suspension means, viewed obliquely in plan, Figure 2 shows a side elevation of the rear axle suspension means in the design position, from which the position of its components, which serve for guidance, in an inward spring stroke and outward spring stroke position may also be seen, Figure 3 shows a rear elevation of the rigid axle of the rear axle suspension means to illustrate a first possible arrangement of the two control arms of a guide device determining the position of the instantaneous centre, the representation of the further axle guiding control arms having been omitted, Figure 4 shows a plan of the rigid axle with control arm arrangement according to Figure 3, Figure 5 shows a plan of a rigid axle to illustrate a second possible arrangement of the two control arms of the guide device, when the representation of the further axle guiding control arms have likewise been omitted, and Figure 6 shows a side elevation of the rigid axle according to Figure 5, In Figure 1 the reference numeral 10 generally designates a rigid axle, the axle body 12 of which, tubular for example, carries a journal 1 8 at each of its ends to mount vehicle wheels 14, 1 6.

Fairs of mounting brackets 20, 22, between which a bearing bolt 30 supporting a rocker arm 24 of a Watt linkage 26 and 28 respectively is retained, are respectively arranged on the axle body 1 2 above a horizontal plane passing through the wheel axis 41, that is to say at its upper circumference part, in the region near the wheel. These bearing bolts 30 are accordingly also located above a horizontal plane passing through the wheel axis 41.

In this embodiment the mounting brackets 20 22, considered in the forward travel direction, extend obliquely upwards and forwards, for example, so that the lower part of the rocker arms 24 mounted at the same radial space from the wheel axis 41 is located in front of the axle body 1 2.

The guiding control arms 32 and 34 of the Watt linkages 26 and 28, which are articulated in the region of the upper and lower end of the rocker arms 24, extend substantially horizontally away therefrom in the design position and are located parallel to the longitudinal median vehicle axis. They are articulated to the vehicle body 40 at 36 and 38. Obviously, within the context of structural conditions they could also be angled in the horizonal plane and obliquely to the longitudinal median vehicle plane, say symmetrically to the latter in V shape, because an accurate straight axle guidance is also ensured in that case.

The bearing bolts 30 provided eccentrically to the wheel axis 41 define a pivot axis 42 parallel to the wheel axis 41, about which the axle body 12 can oscillate. This is discussed further below. This horizontal pivot axis 42 is therefore located in front of a vertical transverse vehicle plane a-a passing through the wheel centre and extends perpendicularly to the longitudinal median vehicle axis (Figure 2).

In view of the fact that the upper guiding control arms 32 of the Watt linkages 26, 28 cross the axle body 12, a virtually vertical adjustment of the rocker arms 24 in the design position appears most advantageous under certain marginal conditions.

During two-sided, one-sided or alternatesided inward and outward spring stroke movements of the axle body 12, the Watt linkages 26, 28 effect a braking of the rigid axle 10, which is supported relative to the vehicle body by means of non-guiding springs, and a guidance of the pivot axis 42 defined by the rocker arm bearing bolt 30 in a vertical plane b-b, so that the axle body 1 2 cannot execute any inherent steering movements during such movements.

A guide device which fulfils a plurality of purposes is generally designated 44. By means of the latter the axle body 1 2 is pivoted about the horizontal pivot axis 42 according to Figures 1 and 2 during one-sided or two-sided inward spring strokes, so that a straight line 43 joining the wheel axis 41 to the pivot axis 42 tends to be displaced towards the horizontal position. By this means, on an inward spring stroke movement of the rigid axle 10 in the direction of a shock acting upon one or both wheels 14, 16, a so-called positive oblique springing is achieved. Considered in the longitudinal direction of the vehicle, the guide device 44 is arranged in front of the rigid axle 10, for example, and also controls the lateral guidance of the rigid axle 10.

It is therefore ensured, by the suspension and guidance of the axle body 12 by means of the Watt linkages 26 and 28 and by the use of the guide device 44, that the rigid axle 10 will not execute any kinematically dictated inherent steering movements, even with the desired oblique springing, in which the wheel axis 41 of the axle body 1 2 is required to move substantially along a flat curve c of Figure 2, for example.

In this case the oblique positioning of the guide device 44, which may be seen from Figure 2, has inter alia the effect, as already indicated above, that during inward and outward spring stroke movements and the movement of the pivot axis 42 defined by the bearing bolts 30 which occurs in the vertical plane b-b, the articulation points 48 of the guide device 44 to the axle body 12 move along a circular path 58 concentric with the pivot axis 56, which results in a pivoting of the axle body 12 counter clockwise about the pivot axis 42 parallel to its longitudinal axis and wheel axis 41 during inward spring stroke movements.

The axle body 1 2 is therefore pivoted counter to the forward travel direction indicated by an arrow in Figure 2, or backwards and upwards, whilst due to the mutually superimposed movements of the pivot axis 42 in the vertical plane b-b and of the articulation points 48 along the circular path 58, the wheel axis 41 of the axle body 12 is displaced, both during onesided and two-sided inward and outward spring strokes, parallel to itself approximately along the curve c (Figure 2) and at the same time in plan in a position in space perpendicular to the longitudinal median vehicle plane d-d.

The bearing bolts 30 of the rocker arms 24 should be provided on the axle body 1 2 so that moments which act upon the axle body 1 2 during acceleration and braking are braced by the guiding control arms 32, 34 of the Watt linkages 26, 28, and also the pivoting movement of the axle body 1 2 about the pivot axis 42 which is necessary for a desired oblique springing, can occur through the guide device 44.

Therefore the bearing bolts 30 cannot be located in a horizontal plane passing through the wheel axis 41. The position of the instantaneous centre of the rigid axle 10 is further determined by the guide device 44. For this purpose the guide device 44 has two guide arms 62, 64 articulated to the axle body 1 2 beneath the wheel axis 41 at a symmetrical interval from the longitudinal median vehicle plane d-d, which diverge towards their pivot bearings 66, 68 on the vehicle body, which are preferably located above a horizontal plane passing through the wheel axis 41.

This construction makes it possible to determine the position of the instantaneous centre beneath the rigid axle 10. Good holding of the wheels 14, 1 6 against lateral drifting (floating) on icy surfaces is thereby achieved.

Optimum facility for travel straight ahead on icy surfaces is achieved if the instantaneous centre is located in the wheel support plane, because in this case the track curve of the wheel support points is steepest.

Considered in the longitudinal direction of the vehicle, the guide device 44 may equally well be arranged behind the rigid axle, whilst in this case the articulation point of the guide arms to the vehicle body should be provided beneath their articulation point to the rigid axle and the guide arms diverge towards the rigid axle.

It is demonstrated below with reference to Figures 3 to 6, what advantageous installation possibilities are available for the guide arms 62 and 64 of the guide device 44 in the case of such a construction of the latter.

The properties of the rigid axle, such as toein, camber, small lateral offset of the wheel support points, starting compensations, braking compensation, control of lateral forces and the position of the instantaneous centre are then still largely retained in the position of the guide arms 62 and 64 of the guide device 44 relative to the rigid axle 10 according to Figures 3 and 4, for example, is modified according to a further proposal of the invention, as explained below.

The modification of the position of guide arms 62 and 64 should be made in this symmetrically in the lateral direction to the longitudinal median vehicle plane d-d, as the straight lines 72 and 74 joining the articulations starting and radiating from its pole 70 show. That is to say, the guide arms 62 and 64 should be displaced by equal distances in mutually opposite directions referred to the longitudinal median vehicle plane d-d in a transverse vehicle plane e-e parallel to the wheel axis 41, whilst this displacement should be made in a plane defined by the bearing points of the pivot bearings 66 and 68 and the pole 70.

Therefore, in every possible arm arrangement, the control arm bearings on the vehicle body and on the axle should be provided at an equal interval f or g from the wheel axis 41 and at an angle interval h or i from the wheel support surface 76. Accordingly the side elevation of the guide device 60 remains unchanged for every possible arm arranged ment according to this proposal.

The particular advantages of an axle suspension means according to Flgure 3 and 4 may be seen in the fact that the guide arms 62 and 64 can be accommodated on the chassis of a vehicle body as existing space conditions permit. Furthermore, with the position of the instantaneous centre in the wheel support plane, very short and almost symmetrical strokes of the wheel support points 78, 80 relative to the road in the lateral direction of the wheels during alternate spring strokes, and therefore excellent straight running facilitates on icy surfaces can be achieved. Morever, due to the pole 70 of the guide arms 62, 64 located behind the axle, an elastokinematically desirable slight understeering effect is achieved under the influence of lateral forces.

Figures 5 and 6 illustrates a further possible arm arrangement of the guide device 44 according to Figure 1, which may likewise find advantageous application particularly under constricted space conditions, and which furthermore presents the same advantages already explained.

According to this proposal the guide arms 62 and 64, for every possible arrangement relative to the rigid axle 10, are articulated to its axle body 12 in the same position beneath the wheel axis 41 in each case (see Figure 5).

In plan and in side elevation, on the other hand, in order to maintain a toe-in, camber, lateral offset of the wheel support points and height of the instantaneous centre virtually invariable, the arrangement of the guide arms may be made so that they radiate outwards towards their arm bearings 66 or 68 respectively remote from the rigid axle 10, starting from their point of articulation to the rigid axle 10.

Then, in this case, in spite of a modified arrangement of the guide arms, the rear elevation of the guide device 44 remains the same.

However, the starting compensation, braking compensation and the control of lateral forces then undergoes slight modifications. This is due to the fact that in the possible different arrangements of the guide arms, as Figure 5 shows, their pole 70 is displaced correspondingly along the longitudinal median vehicle plane d-d towards the rear of the vehicle, whereas this remains constant on the longitudinal median vehicle plane d-d in the case of the arm arrangement according to Figures 3 and 4.

Due to the arm arrangements according to Figures 3 to 6 which are practicable for a construction of the guide device 44 according to Figure 1, it is therefore possible to achieve axle kinematic properties in combination with a rigid axle, such as are known only in the case of highly technically developed individual wheel suspensions. Figure 6 shows an alternative arrangement of the guiding control arms 32, 34 to Figure 1.

Claims (5)

1. An axle suspension for motor vehicles, comprising a rigid axle which is braced via non-guiding spring means and guided via lateral guiding arms which are pivotable relative to the axle body and determine, for a wheel axis, a pivot axis about which the wheel axis is displaceable in the sense of a positive oblique springing during inward spring stroke movements, wherein the pivot axis is offset vertically relative to the wheel axis, the pivoting of the wheel axis about the pivot axis in the sense of the positive oblique springing being controlled via two mutually separate guide arms articulated to the vehicle body, which guide arms are arranged symmetrically to the longitudinal median vehicle plane and extend mutually obliquely towards the rigid axle so that straight lines projected through their articulations intersect mutually in the longitudinal median vehicle plane in a horizontal plane located beneath the wheel axis.

2. An axle suspension according to claim 1, wherein the guide arms are located in front of the rigid axle considered in the longitudinal direction of the vehicle, are articulated to the vehicle body above their point of articulation to the rigid axle, and converge towards the rigid axle.

3. An axle suspension according to claim 1 or 2, wherein the straight lines through the articulations of the guide arms intersect on the wheel support surface in the design position.

4. An axle suspension according to any one of the previous claims, wherein the said pivot axis is guided via the guiding control arms in a vertical plane.

5. An axle system for a motor vehicle substantially as described herein with reference to and as illustrated in the accompanying drawings.