This invention, hereafter called "Z-Lin " system relates to a vehicle suspesion system and relates particularly to the interconnect¬ ion of springing devices attached to different wheels of the vehicle, namely torsion bars including torque transmitting means from another spring, to provide a dynamic and interactive connection between the suspension for each wheel .

With the system of the invention, an upward force applied through suspension structures carrying one vehicle wheel exert a turning force on a torque transmitting member connected to another vehicle wheel. The purpose is to provide differential action by said springing devices according to load, load differences and resulting geometry changes with¬ in the Z-Link system.

According to the invention there is provided a vehicle suspens¬ ion system comprising first transmitting means to transmit relative suspension movement of one vehicle wheel, second transmitting means to transmit relative suspension movement of a second vehicle wheel, a first link connected to the first transmitting means, a second link connected to the second transmitting means, and an interconnecting link extending between the first and second links, the links having a "Z" configuration so that movement of the first transmitting means in a given rotational direction acts to move the second transmitting means in the opposite rotational direction, the geometry of the links being arranged so that the distance between the lines of action of the resp¬ ective transmitting means and the interconnecting link are a function of the forces acting on the respective wheel suspensions within pre¬ determined operating limits of movement of the interconnecting link. Preferably, the transmitting means comprise torsion bars.

The advantages of the Z-Link system are: (1) Where side loads on the vehicle occur due to cornering forces, uneven loading, the effect of external forces eg. wind, and approxim¬ ately equal load is carried by front and rear suspension means including the torsion bars, on the same side of the vehicle, the torque load transmitted by each torsion bar to the interconnecting Z-Link will be approximately equal. The point of resistance to the torque loads will at the Z-Link and each torsion bar will behave as a short firm spring

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thereby giving high roll resistance to the vehicle suspension.

(2) Where suspension loads, including torsion bar torques, are temporarily unequal on one side of the vehicle eg. when one end of the vehicle passes over a bump or hollow, the torque loads transmitted to the Z-Link system will be unequal and will meet unequal resistance according to the varying geometry of the Z-Link system. The point of resistance to the transmitted torque will be at the distal end of the torsion bar furthest from the disp¬ laced suspension member. Effectively the torsion bars will behave as one long bar thereby giving soft springing for bump absorbtion.

(3) Because both aspects (1) and (2) can happen concurrently, the overall result is high roll resistance while allowing for soft bump springing action for the vehicle suspension.

(4) Because of the varying geometric relationships between links in the Z-Link system, the resulting forces in any given load situation will balance and the mechanism will maintain its geometry until the vehicle's front to rear load relationship changes.

(5) The varying geometric relationships between the links occur with a compound rising rate of change in the relationship between torques and resulting forces. Therefore a relatively small geometric change can produce a very large change in mechanical advantage of one appl ed torque compared to the other. Therefore a said suspension will experience a rapidly rising spring resistance if displaced upwards and a rapidly reducing spring resis¬ tance if displaced downwards.

(6) Because the spring rebound rate of any displaced suspension means can vary, the need for rebound damping on the suspension may be reduced. Also varying rebound would reduce the tendancy to form corrugations on loose bearing surfaces eg. gravel roads .

(7) The Z-Link system could be used with other springing means where sp ^' ringing loads could be transmitted from the normal point of resistance eg. the end or part way along a coil spring or eg. the point of attachment

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of a leaf spring, via a lever pivoted on the body of the vehicle and causing a torque to be applied to a suitable torque transmitting device and thereby to the Z-Link interconnecting system.

(8) The Z-Link system would readily adapt to use in an "Active Suspension" format by incorporating a middle link that was extensible and reducable by hydraulic or other means.

(9) The Z-Link could be mounted in the configuration most appropriate to the vehicle, in any rotational positioning.

Description of the drawings... Figure 1 is a schematic illustration of the system of the invention, in one embodyment, Figure 2 is a view looking in the longitudinal direction, ie. viewed from

(F).,

Figure 3 is a schematic plan view,

Figures 4 to 9 show schematically various geometric relationships of the

Z-Link system and

Figure 10 is a graph indicating rate of change characteristics in the

Z-Link system.

Refering to the drawings, this invention is an interlinking system for use with a suspended vehicle eg. Fig.l, having said suspension means eg. Fig.l(A,B), and having said springing means eg. (1,7) where said springing means are interconnected front to rear via said Z-Link eg. Fig.1(C) along one side of the vehicle. A similar mirror image system would be employed on the other side of the vehicle (not shown Fig.l)

A pair of said springing members, Fig.2(1, 7), free to rotate within approp¬ riate bearings Fig.3(12, 13 respectively) which are fixed to the vehicle, both being subject to torque load about their centres (arrows 8,10 resp), being fixed to arms (2,6 resp), apply a turning force on said arms (arrows 9,11 resp) via appropriate hinging means (3,5) to a link (4).

in normal circumstances torque loads (arrows 8,10) should be equal and

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angles eg. Fig.4(a,a) also equal. Relative lengths of arms (2,6) should be such that length Fig.4(1) to (3) should equal length (5) to (7). If mean torque loads about members (1) and (7) are unequal, arms (2,6) can also be made unequal during manufacture appropriately to equalise angles Fig.4(a _s a) during normal vehicle use.

The distance between the fixed centres (1,7) and the length of link (4) ie. between centres (3) and (5) should be such that when the angle Fig.7

(f) is about 90°, angle (g) is about 0°. By making angles (a,a) less, eg. by increasing the length of l nk (4), there is a more rapid rise in the rate of change of relative torque loads and the maximum attainable angle change eg. Fig.4(a) to Fig.7(f) will be reduced.

Figure 10 (axis Y) indicates the increase in returning load eg. Fig.8(11) as a multiple of displacing load eg. Fig.8(9) according to degrees of angle change (shown axis X) of the displacing arm eg. Fig.8(2). Graph P shows approximately the rate of increase for a system having angles as indicated in Fig.4(a,a). Graphs Q and R show approximately the rate of increase for a system having angles respectively less and much less than indicated in Fig.4(a,a).

Operation Figures 4 to 7 represent the effect of a temporary increase in torque about member (1) ie. (arrow 8) relative to that about member (7) ie. (arrow 10). Angle changes eg Fig.5(b) compared to (c), Fig.6(d) compared to (e), Fig.7(f) compared to (g) indicate changes in relative mechanical advant¬ age of said torque loads as applied to member (4).

The decrease of angle between members (6,4) eg. Fig.5(c) means that any torque applied about (7), ie. (arrow 10) is effectively applied over a short distance eg. Fig.8(14) thereby increasing load Fig.2(11) applied to member (4).

Similarly, the increase of angle between members (4,2) eg.Fig.5(b) means that the load applied to member (4) is effectively applied over a longer distance eg.Fig.8(15) thereby decreasing load Fig.2(9) applied to member (4). As said angles vary by an increasing amount eg. Figs.6&7, the lesser torque applied about member (7) ie. via (arrow 10) is able to resist the

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greater torque applied about member (1) ie. (arrow 8) and prevent further rotation against the lesser torque.

In the case of Fig.7, the greater torque eg. (arrow 8) is resisted via member (4) which overlies member (6) and cannot cause further rotation against the lesser torque ie. (arrow 10). Torsion bar member then behaves as a short firm spring (1).

Conversely, eg. Fig.9 the above example is reversed but still the lesser torque (arrow 8) resists the greater (arrow 10). When the disparity between the torque loads is reduced or eliminated, the geometry of the system returns towards or to that illustrated in Fig.4.

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