GB2254056A

GB2254056A - Vehicle suspension system

Info

Publication number: GB2254056A
Application number: GB9206036A
Authority: GB
Inventors: Richard Henry Stone; Roy Thomas Watson; Richard Walter Roberts; John Francis Kelleher
Original assignee: Norde Suspensions Ltd
Current assignee: Norde Suspensions Ltd
Priority date: 1991-03-23
Filing date: 1992-03-19
Publication date: 1992-09-30
Also published as: FR2674188A1; DE4209192A1; GB9206036D0; GB9106226D0; FR2674188B1

Description

2254056 - 1 VEHICLE SUSPENSION SYSTEM This invention relates to vehicle

suspension systems, and is particularly concerned with tandem axle vehicles.

Proposed legislation is such that with load carrying vehicles of both cab and fixed platform or tractor and articulated trailer types, the springs of the suspension system must exhibit a particular natural or bounce frequency to suit the intended ground weight of a particular vehicle such as, for example, less than 2Hz with the vehicle and load having a 19 tonne ground weight.

With conventional leaf springs, this is only achievable with springs having a considerable number of leaves, adding considerably to the cost and weight of a vehicle or a trailer at the expense of its load carrying capacity, it being the combined vehicle weight and load that must be below legislated levels before the vehicle can be used legally on public highways.

A most effective alternative to leaf spring suspensions is the so called rubber suspension of the type described in British Patent 1276352 where rubber blocks are secured to a mounting block pivotally mounted within a connected between the axles. The pivotal connection of mounting block to the beam necessitates the location of block within the beam to ensure that the line of action hence load applied to the springs is generally central of faces of the block to which the springs are secured, prevent excessive bending moments from being induced in springs and to prevent weight transfer from one axle to beam the the and the to the the 2 - other when accelerating or braking. Consequently the beams of the suspension system are relatively bulky and relatively heavy again at the expense of vehicle load.

The invention has for its objective to provide a modified version of rubber suspension system capable of meeting the proposed spring frequencies for particular vehicle ground weights, with better weight characteristics and lower cost factors.

According to the present invention, a vehicle suspension system comprises a beam connected between the axles to each side of the vehicle, a mounting block rigidly secured to each beam and extending above the beam, two rubber springs secured to each mounting block and angularly disposed and secured by their opposite ends to the load carrying platform, the angle of inclination of the springs being such that the effective centre of rotation of the beam/spring assembly is the plane of the beam to axle connections. Preferably, there are anti-roll means connected between the suspension system or axle and the vehicle frame.

With the construction of the invention, a relatively simple I-section beam can be employed combining relatively high strength and low weight, the rigid connection of the mounting block on the beam and the angular disposition of the springs combining to ensure that there is minimal weight transfer from one axle to the other during acceleration and braking, and at the same time enabling the springs to combine to serve as a pivot allowing axle articulation.

According to a further feature of the invention, a - 3 vehicle comprises a tandem axle suspension system having a beam connected between the axles to each side of the vehicle, a mounting block rigidly secured to each beam and extending above the beam, and two rubber springs secured in angular disposition to each mounting block and secured by their opposite ends to the load carrying platform, the angle of inclination of the springs of each pair being determined by the ground weight of the tandem axles to create a required natural or bounce frequency for the tandem axles at their ground weight, and to so dispose the effective centre of rotation of the beam/spring assembly in proximity to the plane of the beam-to-axle connections as to ensure minimal weight transfer from one axle to the other during acceleration and braking.

Thus, the invention permits considerable latitude in design in enabling the provision of any natural or bounce frequency for a given ground weight in a construction that combines relatively low cost, and relatively low weight with consequent enhanced load carrying capacity, and with minimal load transfer between axles. Thus, and for example, to ensure a natural or bounce frequency of 2Hz or less with a ground weight of 19 tonne, the springs should be set such that 0 0 their longitudinal axes are at an included angle of 40 -45 and to provide a natural or bounce frequency of 2.3Hz for a 0 ground weight of 26 tonne, the included angle should be 55 to 0 One embodiment of the invention is illustrated in the accompanying drawing, a schematic side elevation of a 4 suspension system.

In the drawing, a tandem axle suspension system has axles located in axle housings 1 and to which hanger brackets 2 are secured and to each of which a beam 3 is attached. Each axle housing 1 extends to and is suitably secured to, the load carrying platform 4 of the vehicle. Also attached between the beam 3 and the vehicle platform 4 are shock absorbers 5 and at one end an articulated anti-roll assembly 6 extends between the hanger bracket 2 to that side and the load carrying platform 4.

Centrally of the beam 3, a mounting block 7 is rigidly secured to the beam having angled mounting faces 8 to receive, and to which are appropriately secured, rubber springs 9, the opposite ends of which are attached to brackets 10 depending from the load carrying platform 4.

The angular disposition of the springs 9 is determined first in relation to the ground weight of the tandem axles and to generate a required natural or bounce frequency. Thus, and for example, for a ground weight of 19 tonne, and to generate a natural or bounce frequency of 1.9Hz the springs are to be 0 0 set at an included angle of 40 to 45 For a ground weight of 26 tonne, and to generate a natural or bounce frequency of 2.3Hz, the springs are set at an included angle of between 55 0 and 60 The second consideration in setting the angular disposition of the springs is to put the centre of rotation of beam/spring assembly in the plane of the beam-to-axle connections, or in close proximity thereto and whereby to ensure minimal weight transfer from one axle to the other 0 during acceleration or braking, but without inhibiting the ability of the assembly to serve as a pivot allowing axle articulation.

6 -

Claims

1. A vehicle suspension system comprising a beam connected between the axles to each side of the vehicle, a mounting block rigidly secured to each beam and extending above the beam, two rubber springs secured to each mounting block and angularly disposed and secured by their opposite ends to the load carrying platform, the angle of inclination of the springs being such that the effective centre of rotation of the beam/spring assembly is the plane of the beam to axle connections.

2. A vehicle suspension system as in Claim 1, wherein the beam is an Isection beam to which a mounting block is rigidly secured.

3. A vehicle suspension system as in Claim 1 or Claim 2, wherein an antiroll assembly is connected between one end of the suspension system and the vehicle frame.

4. A vehicle comprising a tandem axle suspension system having a beam connected between the axles to each side of the vehicle, a mounting block rigidly secured to each beam and extending above the beam, and two rubber springs secured in angular disposition to each mounting block and secured by their opposite ends to the load carying platform, the angle of inclination of the springs of each pair being determined by the ground weight of the tandem axles to create a required natural or bounce frequency for the axles at their ground weight, and to so dispose the effective centre of rotation of the beam/spring assembly in proximity to the plane of the beam-to-axle connections as to ensure minimal weight transfer - 7 from one axle to the other during acceleration and braking.

5. A vehicle as in Claim 4, wherein for a tandem axle assembly having a ground weight of 19 tonne, and to provide a natural or bounce frequency of less than 2Hz, the springs are 0 0 angularly disposed at an included angle of 40 to 45

6. A vehicle as in Claim 4, wherein for a tandem axle assembly having a ground weight of 26 tonne and to provide a natural or bounce frequency of 2.3Hz, the springs are 0 0 angularly disposed at an included angle of 55 to 60

7. A tandem axle vehicle suspension system substantially as hereinbefore described with reference to the accompanying drawings.