GB2096731A - Gas spring suspension units for vehicles - Google Patents

Abstract

A suspension unit for a vehicle comprises inner and outer housings 10, 12 in sliding telescopic relationship. A pair of flexible convolute hollow air spring assemblies 20 are located one above the other within the housings 10, 12 to receive gas under pressure. The pressure of the gas within the lower assembly 20 can be adjusted by the provision of inlet and outlet valve means 24, so that the stiffness of the suspension unit can be varied. The units, when fitted to a vehicle, may be operated at pre-set pressures or the pressure may be varied in response to cornering or braking of the vehicle. The pair of bellows may be replaced by a single bellows. <IMAGE>

Description

SPECIFICATION Improvements in or relating to suspension systems for vehicles Field of Invention This invention relates to suspension systems for vehicles and is concerned particularly with a suspension unit for a vehicle.

Backbround to the Invention Conventionally, vehicles incorporate suspension and shock absorber systems to permit relative movement between the wheels and body of the vehicle while damping out undue movement. Conventional systems are capable of coping adequately with most normal conditions but fail to perform adequately in certain extreme conditions, as is evidenced by load shedding from heavy goods vehicles on sharp corners, e.g.

roundabouts, and excess leaning of high-speed trains when cornering.

It is accordingly an object of the present invention to provide an improved suspension unit for vehicles, capable of coping with such extreme conditions and, in particular, of smoothing out excess tilting on cornering and dipping on braking.

The Invention According to one aspect of the present invention there is provided a suspension unit for a vehicle, comprising inner and outer housings disposed in telescopic sliding relationship, one or more air-tight flexible containers located within the housings for receiving gas under pressure, air inlet and outlet means incorporating valve means to enable adjustment of the pressure of gas in the container or containers, to provide a piston arrangement the stiffness of which is variable in dependence on the pressure of gas within the container or containers.

It is envisaged that in most cases suspension units in accordance with the present invention will normally be used in addition to conventional suspension systems, with an appropriate number of units, e,g. one for each wheel, being mounted on a vehicle in appropriate manner. It is, however, also possible that in certain cases the units in accordance with the invention may replace conventional suspension systems.

The units, when fitted to a vehicle, may be used in two main modes: 1) at pre-set, fixed pressures; and 2) at varying pressures adjusted in response to changing conditions.

The first mode of operation, with pre-set fixed pressures, is of course the simplest, and is most appropriate for relatively small vehicles, such as cars, particularly racing cars. The pressure of gas within the containers of the units fitted to such a vehicle is pre-set to an appropriate value prior to a journey. The value is determined by various factors, including the characteristics of the vehicle and the nature of the terrain to be covered. The pressures for all units fitted to the vehicle may either be equal - this will be appropriate for a vehicle intended for normal road use. However, in some cases, it may be preferable for the pressures of different units on a vehicle to be set at different values.This may be appropriate, for instance, in the case of a racing car intended to be used on, say, a righthand circuit in which cornering will be predominantly in a righthand direction: in such circumstances, it may be appropriate for the pressure of units associated with the righthand side of the car to be set at a higher value from those on the left.

Depending upon the vehicle and other factors, the pressure of gas within the units may either be reset prior to each separate journey undertaken, or else initially pre-set at an appropriate value intended to be suitable to average conditions.

The second mode of operation is more complex, requiring additional components and control equipment. For this reason, this mode is more appropriate for use with relatively large vehicles, such as heavy goods vehicles and highspeed trains, although it is through that this system might have some applicability in the case of racing cars.

For this mode of use, a vehicle fitted with appropriate units in accordance with the present invention is additionally provided with a sensitive tilt sensing mechanism, such as a suitable gyroscopic device, and control means, such as computer control means, for carying the pressure of gas within one or more of the containers in response to changing conditions of tilt of the vehicle.

In use, the tilt sensing mechanism is arranged to sense when the vehicle tilts, e.g. to one side upon cornering or in a forwards direction upon braking, and feeds appropriate signals to the control means. The control means responds to these signals, indicative of the direction and degree of tilting, by causing the pressure of air within one or more of the units to be increased or decreased as appropriate to compensate for the tendency to tilt and so restore the vehicle to an even keel.

The inner and outer housings are preferably of tubular configuration, conveniently having circular cross-sections.

The housings are conveniently formed of steel, preferably from drawn hot steel tubing with each housing provided with an appropriate endplate.

The housings may include suitable mounting means to enable the unit to be fitted to a vehicle.

For example, a respective mounting clevis may be secured to each housing, although it is clear that the details of the mounting means may be tailored as appropriate to suit the intended application of the unit.

The container or containers within the unit are conveniently in the form of airbags or airbellows.

Particularly preferred components for this purpose are convolute bellow airspring assemblies, manufactured by Dunlop. These are available in a range of different sizes including that of 42 inchs (114.3 mm), 6 ins (152.4 mm), 8 ins (203.2 mm) and 10 ins (254 mm) in diameter, and one or more such assemblies of appropriate size is selected to produce a unit of size and characteristics suited to its intended use.

For example, for a unit suitable for use on a motor car it is appropriate to use two 42 in (114.3 mm) convolute bellow airspring assemblies arranged in series, one above the other. Each such assembly comprises two bellows folds and has a fully compressed length of 2w ins (63.5 mm) with a fully extended length of 5 ins (127 mm), so that the maximum possible travel of such a unit is 5 ins (127 mm). Each such assembly may be pressurized to a value of up to 80 psi (5.62 kg/cm squared) and in use will be pressurised to a suitable value up to this maximum depending upon the proposed use.

It would of course alternatively be possible to use one similar 42 in (114.3 mm) diameter assembly having four folds for this purpose.

In a further aspect, the present invention provides a vehicle fitted with one or more suspension units in accordance with the present invention.

The invention will be further described by way of example, with reference to the accompanying drawing.

In the Drawing Figure 1 is a sectional view of a suspension unit in accordance with the present invention, illustrated in a fully collapsed condition.

Detailed Description of the Drawing Referring to the drawing, there is illustrated a suspension unit comprising two housings 10 and 12. Each housing comprising a cylindrical tubular side wall 14 of drawn hot steel tubing with an endplate 1 6 welded thereto to form a cup-shaped housing.

The lower housing 10 is slidably received in the upper housing 12 in telescopic relationship, the housings being oriented with the two endplates disposed at opposite ends so as to define a cylindrical space therebetween. The external diameter of the side wall of housing 10 is slightly less than the internal diameter of the side wall of housing 12 so there is a small clearance of about 0.015 ins (0.38 mm) therebetween.

A dust and grease seal 1 8 is located between the overlapping portion of the side walls 14 of the two housings for retaining lubricating grease between these overlapping regions and for preventing ingress of dust, dirt etc to the interior of the space between the housings.

In an alternative preferred arrangement (not shown) a grease seal is instead located adjacent to the lower end of the side wall 14 of the upper housing 12 and a separate dust seal is located slightly below the grease seal.

Two airtight, flexible containers are mounted in the space between the housings 10 and 12, the containers illustrated in this embodiment being 42 in (114.3 mm) diameter convolute bellow airspring assemblies, manufactured by Dunlop.

Each assembly 20 is secured to the adjacent endplate 1 6 and also to an intermediate guideplate 22 which is slidably located within the lower housing 1 0.

Each bellows assembly 20 includes a valved inlet/outlet 24 (in the Figure only that of the lower bellows assembly is shown) to enable the pressure of air or other gas within the bellows assembly to be adjusted.

Each bellows assembly 20 comprises two bellows folds and is movable between a fully compressed position, as illustrated, in which it has a length of 22 ins (63.5 mm) and a fully extended position in which it has a length of 5 ins (127 mm). It is clear that change in the length of the bellows assembly results in accoresponding relative movement of the housings 10 and 12 which therefore constitute a piston arrangement having a maximum travel of 5 ins (127 mm). It is to be noted that it is necessary to have a greater overlap between the cylindrical side walls of the upper and lower housings than is illustrated in order to accommodate a full 5 in (127 mm) travel of the housings.

Alternatively, instead of using two twofold bellows assemblies as illustrated, it is also possible to use a single fourfold assembly similarly having a 5 in (127 mm) maximum movement.

Further, it is also possible to use different numbers of different sizes of bellows assemblies to provide a piston assembly having a different maximum travel, the assemblies being seiected as appropriate depending upon the intended use of the unit.

The endplates 1 6 of the housings are provided with mounting means in the form of respective mounting devises 26. Alternative mounting means may also be used as appropriate depending upon the intended use of the unit.

In use, the unit is fitted to a vehicle (for example, this embodiment with a maximum travel of 5 ins (127 mm) is appropriate for use with a car) in appropriate location by use of the mounting devises 26.

An appropriate number of the units is fitted as required.

The units may then be operated in either of the two modes as discussed above, depending upon requirements.

Claims (10)

1. A suspension unit for a vehicle, comprising inner and outer housings disposed in telescopic sliding relationship, one or more air-tight flexible containers located within the housings for receiving gas under pressure, inlet and outlet means incorporating valve means to enable adjustment to the pressure of gas in the container or containers, to provide a piston arrangement the stiffness of which is variable in dependence on the pressure of gas within the container or containers.

2. A suspension unit according to claim 1, wherein the container or containers within the unit are in the form of airbags or airbellows.

3. A suspension unit according to claim 2, wherein the or each container is a convolute bellow airspring assembly.

4. A suspension unit according to claim 3, wherein the unit has two convolute bellow airspring assemblies arranged in series, one above the other.

5. A suspension unit according to any of the preceding claims, wherein the unit is operative at a pre-set, fixed container pressure.

6. A suspension unit according to any of claims 1 to 4, wherein the unit is operative at a varying container pressure adjusted in response to changing conditions.

7. A suspension unit constructed and arranged substantially as herein particularly described with reference to the accompanying drawings.

8. A vehicle fitted with one or more suspension units according to the preceding claims.

9. A vehicle according to claim 8 and additionally provided with a sensitive tilt sensing mechanism, such as a suitable gyroscopic device, and control means, such as computer control means, for varying the pressure of gas within one or more of the containers in response to changing conditions of tilt of the vehicle.

10. A vehicle according to claim 9, wherein the tilt sensing mechanism is arranged to sense when the vehicle tilts, e.g. to one side upon cornering or in a forwards directions upon braking, and feeds appropriate signals to the control means, the control means responding to these signals, indicative of the direction and degree of tilting, by causing the pressure of air within one or more of the units to be increased or decreased as appropriate to compensate for the tendency to tilt and so restore the vehicle to an even disposition.