GB2162473A - Axle suspension for motor vehicles - Google Patents

Abstract

In an axle suspension the guide means of its rigid axle 10 is constructed so that the latter changes its position in the sense of a positive oblique springing during inward spring stroke movements, and executes no inherent steering movements during one-sided and alternate-sided inward and outward spring strokes. The rigid axle 10 is guided on each side by a pair of guiding control arms 32, 34 which determine for its wheel axis, a pivot axis 42 about which the wheel axis 41 is movable by means of a guide arm 46 retained on the vehicle body in the sense of the positive oblique springing during inward spring stroke movements. Simultaneously, the two pairs of guiding control arms, 32, 34, each in common with a rocker arm 24 mounted on the rigid axle 12 pivotably about the pivot axis 42 which is offset vertically to its wheel axis 41, from straight guides guiding the pivot axis 42 in a vertical plane during inward spring stroke movements, whereby inherent steering movements of the rigid axle 10 are prevented. <IMAGE>

Description

SPECIFICATION Axle suspension system for motor vehicles The invention relates to an axle suspension system for motor vehicles, particularly, but not exclusively motor cars, with a rigid axle braced through nonguiding spring means, the axle being guided on each side of the vehicle by two mutually vertically staggered guiding control arms which are pivotable relative to the axle body and each articulated at one of their ends to the vehicle body, which extend in mutually opposite directions transversely to a wheel axis.

An axle suspension of this type is known (US patent No. 2,226,047 Figure 5). In the construction shown in the Figure 5 referred to, the rigid axle, which is in the form of a de Dion tube, carries, at each end face of its axle body, a wheel bracket, to which one of the guiding control arms is articulated respectively above and below the axle body.

Each wheel bracket is equipped with a journal for mounting a wheel. The journals are provided on the wheel brackets offset laterally relative to the axle body so that the wheel axis defined by them, considered in the longitudinal direction of the vehicle, is located at a radial interval in front of the axle body. The journals are therefore arranged, relative to the axle body, on a lever, the length of which corresponds to the spacing of the wheel axis from the straight line joining the two articulation points of the control arms to the rigid axle.

This axle suspension has the advantage of a positive oblique springing, in which, due to the explained lateral offset of the wheel axis relative to the straight line joining the control arm articulation points to the rigid axle, during inward spring strokes the wheels move upwards and to the rear about a pivot axis parallel to the wheel axis, relative to that part of the rigid axle which is guided by the guiding control arms.

The inward spring stroke movement of the wheel axis therefore takes place in the direction of a shock upon a wheel generated by passing over an irregularity, which is desirable for axle suspension means.

The value of the pivot angle of the axle body and of its wheel brackets which produces the positive oblique springing is then determined by the length of the control arms and the distance of the wheel axis from the straight line joining the control arm articulation points to the rigid axle.

In this context, in order to achieve the path of the wheel axis which is required for a customary oblique springing of 3" to 6 , the length of the control arms to be arranged above the wheel axis. However, this results in the disadvantage that the axle body executes steering movements during one-sided and alternate-sided inward and outward spring strokes, and is additionally also subject to a torsional stress during one-sided inward and outward spring strokes.

It is consequently the underlying object of the invention to disclose an axle suspension the axle body of which remains substantially free of steering movements and in which torsional stresses during one-sided and alternatesided inward and outward spring strokes are reduced.

According to the present invention there is provided an axle suspension for motor vehicles with a rigid axle braced through nonguiding spring means, the axle being guided on each side of the vehicle by two mutually vertically staggered guiding control arms which are pivotable relative to the axle body and each articulated at one of their ends to the vehicle body, which extends in mutually opposite directions transversely to a wheel axis and determine a pivot axis offset from the wheel axis about which the wheel axis is movable in the sense of a positive oblique springing during inward spring stroke movements, wherein the other ends of the guiding control arms of each pair of control arms are connected to opposed ends of respective rocker arms mounted on the rigid axle so as to be pivotable intermediate its length about said pivot axis, which pivot axis is offset vertically to wheel axis, the arrangement serving to guide the pivot axis in a vertical plane, the pivoting of the wheel axis about the pivot axis being controlled in the sense of the positive oblique springing through an additional guide arm.

The movement of the axle body which produces a positive oblique springing is achieved by the guide arm, in that the axle body is pivoted about the pivot axis by the latter in a direction opposite the forward travel direction during inward spring stroke movements, and in a direction opposite thereto during outward spring stroke movements.

The movement of the rigid axle during inward and outward strokes is therefore composed, in the construction according to the invention, of mutually superimposed partial movements, whilst one partial movement consists of the vertical displacement of the pivot axis, and another of the pivot movement of the axle body about the pivot axis caused by the guide arm.

Preferably, the rocker arms on the rigid axle, considered in the longitudinal direction of the vehicle, are mounted pivotably in front of the rigid axle and above a horizontal plane passing through the wheel axis.

The guide arm, which may simultaneously form a lateral guide device for the rigid axle, may be arranged, advantageously, in front of the axle, considered in the longitudinal direction of the vehicle. Preferably, the guide arm comprises a triangulated link, of which the apex is articulated to the rigid axle and is located substantially on the longitudinal median vehicle axis in plan.

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, which is illustrated in the drawing.

In the accompanying diagrammatic drawing: Figure 1 shows a perspective view of the rear axle suspension means, viewed obliquely from above, Figure 2 shows a side elevation of the rear axle suspension means in the design position, from which the position of its components serving for guidance is also visible in a position after an inward and outward spring stroke.

In Figure 1, a rigid axle is generally designated 10, and its, for example tubular, axle body 1 2 carries a journal 18 at each of its ends for mounting vehicle wheels 14, 16.

On the axle body 1 2 mounting brackets 20, 22 are arranged in a region near each wheel above a horizontal plane passing through the wheel axis, that is to say at its upper circumferential part, between which brackets a bearing bolt 30 supporting a rocker arm 24 of a Watt linkage 26 or 28 respectively is retained in each case.

The bearing bolts 30 are accordingly also located above a horizontal plane passing through the wheel axis 41.

In this exemplary embodiment the brackets 20, 22, considered in the forward travel direction, extend obliquely forwards and upwards for example, so that the lower part of the rocker arms 24 mounted at equal radial intervals from the wheel axis 41 is located in front of the axle body 12.

In the design position, the control arms 32 and 34 of the Watt linkages 26 and 28, which are articulated in the region of the upper and lower ends of the rocker arms 24, extend substantially horizontally away from the linkages and are located parallel to the longitudinal median axis of the vehicle. They are articulated to the vehicle body 40 at 36 and 38. They may obviously also be angled obliquely to the horizontal in the design position within the context of structurai considerations.

The rocker arm bearing bolts 30 provided eccentrically to the wheel axis 41 define a pivot axis 42 extending in the direction of the wheel axis 41 and parallel thereto, about which the axle body 1 2 can oscillate. This is discussed further below. This horizontal pivot axis 42 is therefore located in front of a vertical plane a-a passing through the wheel centre and extends perpendicularly to the longitudinal median vehicle plane d-d.

The pivot axis 42 is located above the wheel axis 41 in the exemplary embodiment illustrated. It may equally well be provided below the latter. However, it may also equally well be located behind the vertical plane a-a.

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

In the case of two-sided, one-sided or alternate-sided inward and outward spring stroke movements of the axle body 12, the two Watt linkages 26, 28 effect a support for the rigid axle 10, which is braced relative to the vehicle body 40 by means of non-guiding springs, and a guidance of the pivot axis 42 defined by the rocker arm bearing bolts 30 along a vertical plane b-b perpendicular to the longitudinal direction of the vehicle, so that the axle body 12 cannot execute any inherent steering movements during such movements.

The reference numeral 46 designates generally a guide arm, by means of which the axle body 1 2 is pivotable about the horizontal pivot axis 42 according to Figures 1 and 2, during an inward spring stroke, so that a connecting straight line 43 joining the wheel axis 41 to the pivot axis 42 tends to a displacement towards the horizontal position.

By this means an inward spring stroke movement of the rigid axle 10 in the direction of a shock acting upon one or both wheels, a socalled positive oblique springing, is achieved.

Advantageously, the guide arm 46 simultaneously performs the lateral guidance of the rigid axle 10 and accordingly, in the exemplary embodiment according to Figures 1 and 2, also forms a lateral guide member in the fashion of a wishbone known per se. The latter is articulated universally at 48 by its pointed end in the centre of the length of the axle body 12, particularly beneath its wheel axis 41, whereas its two members 47 and 49 diverging mutually from the articulation point 48 are mounted pivotably by their free end, on the vehicle body 40 at a distance in front of the pivot axis 42, considered in the longitudinal direction of the vehicle, about a pivot axis 56 parallel to the pivot axis 42. In this case the articulation point 48 to the rigid axle is located lower than its pivot axis 56 attached to the vehicle body.

It is therefore ensured, by the suspension and guidance of the axle body 12 by means of the Watt linkages 26 and 28, and also by the use of the guide arm 46, that the rigid axle 10 will not execute any kinematically dictated inherent steering movements, even in the case of a desired oblique springing, in which the longitudinal axis 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 position of the wishbone 46, which may be seen from Figure 2, has the effect, as already indicated above, that during the inward and outward spring strokes and the concomitant movement of the pivot axis 42 defined by the bearing bolts 30 along the vertical plane b-b, the articulation point 48 to the axle body moves along a circular path 58 concentric to the pivot axis 56, whereby a pivoting of the axle body 1 2 counterclockwise about the pivot axis 42 parallel to its longitudinal axis results during inward spring strokes.

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 along the vertical plane b-b and of the articulation point 48 along the circular path 58, the longitudinal axis of the axle body 1 2 or the wheel axis 41 will be displaced in space parallel to itself approximately along the curve c (Figure 2), and at the same time in plan in a position perpendicular to the longitudinal median vehicle plane d-d, both during one-sided and two-sided inward and outward spring strokes.

The brackets 30 of the rocker arms 24 are advantageously provided on the axle body 1 2 so that not only can moments acting upon the axle body 1 2 during acceleration and braking be braced by the control arms 32, 34 of the Watt linkages 26, 28, but 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 by the guide device 46.

The bearing bolts 30 may therefore not lie in a horizontal plane passing through the wheel axis 41. In this case the instantaneous centre of the rigid axle 10 is determined simultaneously by the articulation point 48 forming the intersection of the members 47, 49.

In the described axle suspension means with non-steering rigid axle, the kinematic characteristics of rigid axle, such as toe-in camber starting compensation, braking compensation, lateral force control and the position of the instantaneous centre of the rigid axle remain substantially unchanged.

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

Claims (6)

1. An axle suspension for motor vehicles with a rigid axle braced through non-guiding spring means, the axle being guided on each side of the vehicle by two mutually vertically staggered guiding control arms which are pivotable relative to the axle body and each articulated at one of their ends to the vehicle body, which extend in mutually opposite directions transversely to a wheel axis and determine a pivot axis offset from the wheel axis about which the wheel axis is movable in the sense of a positive oblique springing during inward spring stroke movements, wherein the other ends of the guiding control arms of each pair of control arms are connected to opposed ends of respective rocker arms mounted on the rigid axle so as to be pivotable intermediate its length about said pivot axis which pivot axis is offset vertically to wheel axis, the arrangement serving to guide the pivot axis in a vertical plane, the pivoting of the wheel axis about the pivot axis being controlled in the sense of the positive oblique springing through an additional guide arm.

2. An axle suspension according to Claim 1, wherein the rocker arms on the rigid axle, considered in the longitudinal direction of the vehicle, are mounted pivotably in front of the rigid axle and above a horizontal plane passing through the wheel axis.

3. An axle suspension according to Claim 1 or 2, wherein the guide arm, considered in the longitudinal direction of the vehicle, is arranged in front of the rigid axle.

4. An axle suspension according to any of the previous claims, wherein the guide arm simultaneously forms a lateral guide device for the rigid axle

5. An axle suspension according to any one of the previous claims, wherein the guide arm comprises a triangulated link of which the apex is articulated to the rigid axle and is located substantially on the longitudinal median vehicle axis in plan.

6. An axle suspension for motor vehicles substantially as described herein with reference and as illustrated in the accompanying drawings.