HAIRE, William (9B Moloney Drive, Wodonga, VIC 3690, AU)
CLAIMS:
1. An air suspension system for the front, steer axle of a vehicle comprising: a pair of rearwardly extending leaf springs associated at their rear ends with the axle, a forward end of each spring being mounted to chassis frame members of the vehicle, a pair of clamp blocks engaged about each spring rearwardly of the forward end, one of the clamp blocks of each pair having a transversely extending channel forming a seat for an axles thereby locating the axle relative to each spring, the leaf springs extending rearwardly of the axle to form mountings for airbags which extend between the spring and a respective vehicle chassis frame member, at least one air bag operatively associated with each spring to control relative movement between the axle and the respective vehicle chassis frame member, a high flow-rate air tube connected to the at least one air bag, air flow controlling means between the high flow-rate air tube and the air bag, the high flow-rate air tube forming a manifold to which air is passed in a manner that is substantially un-regulated by the air-flow controlling means when air pressure in the air bag increases above that in the manifold, and air pressurising/exhausting means connected to the manifold through a low flow-rate air tube to maintain a required pressure therein to thereby maintain a selected, predetermined vehicle ride height.
2. A system according to claim 1, wherein the forward end of each said spring is mounted to said vehicle chassis by a box hanger integral or attached to said chassis.
3. A system according to claim 1 or 2, wherein each set of said clamp blocks are secured to said axle and the respective spring by one or more bolts passing therethrough.
4. A system according to any one of claims 1 to 3, wherein said airflow controlling means regulates the air flow from said high flow rate air tube into said airbag fractionally proportional to a pressure differential between said high flow rate air tube and said airbag whereby said airflow rate increases at a lesser rate than an increase in differential pressure.
5. An air suspension system for the steer axles of a double steer axle vehicle comprising: a pair of rearwardly extending leaf springs associated with each axle, a forward end of each spring being mounted to chassis frame members of the vehicle, a pair of clamp blocks engaged about each spring rearwardly of the forward end, one of the clamp blocks of each pair having a transversely extending channel forming a seat for an axles thereby locating the axle relative to each spring, the leaf springs extending rearwardly of the axle to form mountings for airbags which extend between the spring and a respective vehicle chassis frame member, at least one air bag operatively associated with each spring to control relative movement between the axle and the respective vehicle chassis frame member, a high flow-rate air tube connected to the at least one air bag, air flow controlling means between the high flow-rate air tube and the air bag, the high flow-rate air tube forming a manifold to which air is passed in a manner that is substantially un-regulated by the air-flow controlling means when air pressure in the air bag increases above that in the manifold, and air pressurising/exhausting means connected to the manifold through a low flow-rate air tube to maintain a required pressure therein to thereby maintain a selected, predetermined vehicle ride height.
6. A system according to claim 5, wherein the forward ends of each pair of said springs are mounted to said vehicle chassis by two pairs of box hangers integral or attached to said chassis at longitudinally spaced locations.
7. A system according to claim 6, wherein said airflow controlling means comprises a reduced diameter connection at one or each end of said manifold which is shaped to provide proportional control of air flow.
8. A system according to any one of claims 5 to 7, said air flow controlling means comprises the end wall of said manifold defining a shoulder between the manifold wall and the connection to a respective air bag.
9. A system according to any one of claims 1 to 8, wherein said pressurising/exhausting means includes a height valve to admit pressurised air to said air bags or exhaust air from said air bags.
10. A system according to any one of claims 1 to 9, further including a height regulating valve activated by a link connected to a rocker member extending between said front and rear axles of a double steer axle set of said vehicle.
11. A system according to claim 10, wherein said link is connected to said rocker member at a point part-way along its length.
12. A system according to any one of claims 1 to 11, substantially as hereinbefore described with reference to the figures. |
SUSPENSION WITH HIGH-FLOW AIR MANIFOLDS AND LEAF SPRINGS
Cross-Reference to Related Applications
The present application claims priority from Australian Provisional Patent Application No 2006903231 filed on 15 June 2006, the content of which is incorporated herein by reference.
This invention relates to a suspension system for the steer axle of a transport vehicle or other vehicle having a solid front axle carrying steerable wheels and relates particularly to a suspension system incorporating linked airbags.
Most large vehicles, particularly road transport vehicles, such as trucks, trailers, coaches and other road vehicles, utilise a solid front axle carrying steerable front wheels. Many such vehicles have a double-steer axle arrangement whereby two forward axles of the vehicle carry steerable wheels. It is usual practice for those vehicles to utilise leaf spring suspension with attendant shock absorbers. However, such a leaf spring suspension system is relatively harsh as the spring rates necessary to support the vehicle load are relatively high. Such suspensions are unsophisticated in their design and operation so that the vehicle cabin occupants are jolted and bumped around during vehicle movement leading to high fatigue and potential accidents. Such is the rough ride provided by the relatively crude, leaf spring suspension that many cabin structures are separately suspended on the vehicle chassis, and may include special designs of suspension seats to minimise the effect of the rough ride provided by the vehicle suspension system.
It is known to use airbags on vehicle front suspensions. However, such systems require additional structures to limit relative transverse movement between the vehicle axle and the vehicle chassis. It has not previously been proposed to use air suspension systems on double-steer axle vehicles without transverse rods.
With many suspension systems, the steerable axle of a transport vehicle is guided in its vertical movement both by the connecting springs as well as at least one transverse rod or an angled torque rod or tube whereby relative lateral movement of the axle is prevented or minimised. The use of transverse locating rods or tubes or other structures adds to a suspension systems complexity and provides additional stress points along the axle and the vehicle chassis where the rods or tubes are mounted. Additional costs are also experienced.
When multiple airbags have been used in conjunction with single steerable axles on vehicles, it has previously been proposed to provide airbags on each side of the vehicle with the airbags connected by a tube or other connector of relatively small cross sectional area restricting the flow of air between the tubes to a relatively low flow
rate. The tube enables the airbags to be inflated relatively equally to provide an even height for the suspension of the vehicle above the ground. However, use of such a system on a double-steer axle vehicle does not provide the necessary cooperation between the two steer axles, particularly when the vehicle is being driven over rough terrain.
Various proposals have been made with regards to utilising air suspension systems for dual axle and tri-axle rear wheels of a transport vehicle. However, such suspension systems cannot automatically be adopted for the single and double-steer axles of such vehicles due to the nature of engine and suspension mounting points, the need for transverse control, and space requirements beneath the front end of a vehicle.
It is therefore desirable to provide an improved suspension system adapted for use with the steer axles of a vehicle.
It is also desirable to provide an air suspension system for the steered axle(s) of a single or double-steer axle vehicle which obviates the need for transverse stability rods or tubes.
It is also desirable to provide an air suspension system for the steer axle(s) of a single or double-steer axle vehicle which is relatively simple and economical to incorporate in an existing vehicle.
According to one aspect of the invention there is provided an air suspension system for the front, steer axle of a vehicle comprising: a pair of rearwardly extending leaf springs associated at their rear ends with the axle, a forward end of each spring being mounted to chassis frame members of the vehicle, a pair of clamp blocks engaged about each spring rearwardly of the forward end, one of the clamp blocks of each pair having a transversely extending channel forming a seat for an axles thereby locating the axle relative to each spring, the leaf springs extending rearwardly of the axle to form mountings for airbags which extend between the spring and a respective vehicle chassis frame member, at least one air bag operatively associated with each spring to control relative movement between the axle and the respective vehicle chassis frame member, a high flow-rate air tube connected to the at least one air bag, air flow controlling means between the high flow-rate air tube and the air bag, the high flow-rate air tube forming a manifold to which air is passed in a manner that is substantially un-regulated by the air-flow controlling means when air pressure in the air bag increases above that in the manifold,
and air pressurising/exhausting means connected to the manifold through a low flow-rate air tube to maintain a required pressure therein to thereby maintain a selected, predetermined vehicle ride height. Preferably, the forward end of each spring is mounted to the vehicle chassis frame members by a box hanger integral or attached to the chassis frame member so that the respective rearwardly extending leaf spring is moveable in a vertical plane, but the axle to which the spring is mounted is restricted from lateral movement by the box hanger mounting. With this arrangement, therefore, there is no requirement or need for a transverse control rod or tube (Panhard rod) or other lateral control structure.
Preferably, each set of clamp blocks is secured to the axle and the respective spring by one or more bolts passing therethrough. The bolts thereby prevent any longitudinal relative movement between the clamp blocks and the spring and, at the same time, prevent any lateral movement of the clamp blocks relative to the axle.
Preferably, the air flow controlling means regulates air flow from the high flow rate air tube into the airbag generally fractionally proportional to a pressure differential between the high flow rate air tube and the airbag whereby air flow rate increases at a lesser rate than an increase in differential pressure. Such air flow controlling means, therefore, controls the rate of air pressure build-up in the airbag when air flows into the airbag.
In one embodiment of the invention, each spring is formed with an eye at its forward end, the eye constituting the mounting for a rubber or other resilient bush by which the spring is supported in the box hanger. In preferred embodiments, when a vehicle wheel carried by a steer axle encounters a road bump or hole in a road surface, the relative movement is transferred to the airbags associated with the axle. Air is able to flow to and from the air bags to the manifold as a result of a sudden pressure increase in a respective air bag resulting from a vehicle wheel encountering the bump. Such sudden pressure increase, however, is not passed from one manifold on one side of the vehicle to the other due to the low flow rate connection restricting air flow between manifolds.
According to another aspect of the invention there is provided an air suspension system for the steer axles of a double steer axle vehicle comprising: a pair of rearwardly extending leaf springs associated with each axle, a forward end of each spring being mounted to chassis frame members of the vehicle,
a pair of clamp blocks engaged about each spring rearwardly of the forward end, one of the clamp blocks of each pair having a transversely extending channel forming a seat for a respective one of the steer axles thereby locating the axle relative to each spring, the leaf springs extending rearwardly of the respective axles to form mountings for airbags which extend between the spring and a respective vehicle chassis frame member, at least one air bag operatively associated with each spring to control relative movement between the respective axle and the respective vehicle chassis frame member, a high flow-rate air tube connected to the at least one air bag, air flow controlling means between the high flow-rate air tube and the air bag, the high flow-rate air tube forming a manifold to which air is passed in a manner that is substantially un-regulated by the air-flow controlling means when air pressure in the air bag increases above that in the manifold, the airbags on each side of the vehicle being connected to a common manifold, and air pressurising/exhausting means connected to the manifold through a low flow-rate air tube to maintain a required pressure therein to thereby maintain a selected, predetermined vehicle ride height.
With a double-steer axle suspension system, four leaf springs are used, the forward ends of each pair of springs being mounted to the vehicle chassis frame members by two pair of box hangers integral or attached to the chassis frame members at longitudinally spaced locations so that the respective rearwardly extending leaf spring is moveable in a vertical plane, but the axle to which the respective spring is mounted is restricted from lateral movement by the box hanger mountings.
With this arrangement, therefore, there is no requirement or need for a transverse control rod or tube (panhard rod) or other lateral control structure.
Preferably, in accordance with this aspect of the invention, the air flow controlling means comprises a reduced diameter connection at one end, or each end, of the manifold which is shaped to provide proportional control of air flow. In a particular form, the air flow controlling means comprises the end wall of the manifold defining a shoulder between the manifold wall and the connection to the respective air bag. Such a shoulder acts to regulate the flow of air entering the connection from the manifold. It is believed that the regulation is as a result of turbulence developed, and the turbulence is fractionally proportional to the pressure differential that gives rise to the flow rate of
air into the respective connection such that the regulation is proportional to the pressure difference between that of the air bag to which air is flowing and the manifold. Such regulation enables the system of the invention to react appropriately to road surface irregularities at any given vehicle speed. It is found that the rate of increase in pressure in one air bag and the transference of air from that air bag to the manifold and thus to the other air bag together with the controlled rate of flow of the air to the other air bag stabilises the rate of inflation of the other air bag to either totally obviate tramp or to substantially minimise rebound. Still further, it is found that the controlled rate of transference of air from the manifold to an air bag avoids development of suspension harmonic vibrations and/or oscillations which can give rise to unstable vehicle operation.
In one form of the invention, the pressurising/exhausting means includes a height valve to admit pressurised air from a tank, air pump or the like, to the air bags or to exhaust air from the air bags to maintain an air pressure in the manifolds commensurate with maintaining a selected predetermined vehicle ride height when the vehicle is stationery. The pressurising means is unresponsive to sudden pressure changes in the manifold pressures during vehicle operation, and is used primarily to control the ride height of the vehicle and its load within predetermined limits. Thus, when the vehicle is lightly loaded, the ride height of the vehicle is maintained at a predetermined height by reducing the pressure in the manifolds to that which will enable the air bags to support the vehicle at the desired, predetermined height. When a load is added to the vehicle, and the vehicle height lowers as a result of the load compressing and increasing the pressure in the air bags, the vehicle height is restored to the selected, predetermined level by increasing the air pressure in the system to that pressure that gives the required ride height. The ride height may be relatively fixed, or it may be able to be changed by the vehicle operator changing the height valve actuating system.
In a preferred form of the invention used with a double steer axle vehicle, the height valve is actuated by a link connected to a rocker member which extends between front and rear axles of the double steer axle set of the vehicle. The link is connected to the rocker member at a point part-way along its length, preferably approximately mid way along the length of the rocker member whereby only relative movement between the midway connection point and the vehicle supporting frame structure causes actuation of the valve. This means that normal movement of the suspension during vehicle operation will generally not result in operation of the height valve.
The air suspension system of the present invention is adapted to be installed in existing vehicles as well as being incorporated into vehicles during manufacture. For incorporation into existing vehicles, an air suspension kit is provided comprising the necessary number of air bags, the appropriate high flow rate air tubes to connect to the respective air bags, the connectors to connect the high flow rate air tubes to the air bags, and system pressurising means incorporating an air tank or the like and a height control valve.
Preferably, the height control valve and linkage is mounted to one side of the vehicle to avoid engine and gear box components that are present at the front end of a transport vehicle.
Throughout this specification the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps. In order that the invention may be fully understood embodiments thereof will now be described with reference to the accompanying drawings and legend wherein:
Figure 1 is a schematic side view of a vehicle structure fitted with an air suspension system in accordance with a first embodiment of the invention;
Figure 2 is a schematic side view showing a height control valve of the air bag suspension system embodiment of Figure 1;
Figure 3 is a schematic longitudinal sectional view of a high flow rate air tube for use with embodiments of the invention, and
Figure 4 is a schematic side view of a vehicle structure fitted with an air suspension system in accordance with a second embodiment of the invention. Figure 5 shows side and perspective views of the suspension system fitted to a chassis.
Figure 6 shows side and perspective views of the suspension system incorporating a standard shock absorber mounting.
Figure 7 shows side and perspective views of the suspension system incorporating a bottom shock absorber mounting.
Figure 8 shows a side and perspective view of the suspension system incorporating a front shock absorber mounting.
Figure 9 shows a side and perspective view of the suspension system incorporating a back shock absorber mounting.
Leεend
10. Chassis
10(a). Bracket
12. Front steering wheel
14. Rear steering wheel
16. Suspension mount
18. Suspension spring
20. Pin
21. Eye
22. Axles
24. Air bag
26. High flow rate air tube
27. Connector tube
28. Clamp block
29. Clamp block
30. Channel
31. Bolts
32. Rocker member
33. Vertical link
34. Shock absorbers
38. Low flow rate air tube
39. Height valve
50. Manifold
52. High flow rate air tube
53. Shoulder
56. Port
58. Flow indicator lines
59. Flow back indictor lines
Referring to the drawings, Figure 1 shows one embodiment of the present invention for use with a vehicle having a pair of steer axles 22 mounting front steering wheels 12 and rear steering wheels 14. The vehicle incorporates a chassis member 10 on each side of the vehicle carrying a suspension mounting 16 in the form of a box hanger for each of the front and rear steer axle and wheel sets. A trailing suspension spring 18 is mounted to each box hanger 16 by respective pins 20 that engage through eyes 21 in each spring 18. The axle 22 of each wheel set is mounted to the respective
spring 18 by a pair of clamp blocks 28 and 29. Each lower clamp block 29 has a channel 30 to seat the respective axle 18. One or more bolts 31 are pass through the axle and the clamp blocks 28 and 29 to securely bolt the axle to the blocks 28 and 29.
Each spring 18 extends rearwardly from the axle mounting to form a mounting for respective front and rear air bags 24 and 25 which engage between the spring 18 and the chassis member 10. The nature and operation of air bags in vehicle suspensions is well known and will not be described in further detail.
The structure of the box hangers 16 and springs 18 taken together with the clamping blocks 28 and 29 avoids the need to provide additional lateral support to the respective axles 22 such as through the use of transverse rods or tubes or anti-roll bars or the like.
A high flow rate air tube 26 extends between the respective front and rear air bags 24 and 25 and is connected thereto by connectors 27. The high flow rate air tubes 26 on each side of the vehicle enable air to be transferred between the respective front and rear air bags in the event that the front and rear steered wheels 12 and 14 move upwardly or downwardly with respect to the chassis 10. Thus, if the front wheel 12 moves upwardly relative to the chassis 10, through the tire encountering a bump in a road surface, the air bag 24 is compressed increasing the pressure of air in that air bag. Air is then able to move from that air bag to the rear air bag 25 through the high flow rate air tube 26. Similarly, if the rear wheel 14 moves upwardly relative to the chassis 10 increasing the pressure in the rear air bag 25, air moves through the high flow rate air tube 26 into the front air bag 24.
This movement of air between the respective front and rear air bags is independent on each side of the vehicle, and enables all four steered wheels of the vehicle structure to carry loads substantially equally, even when wheels are moving upwardly and downwardly relative to the chassis due to road irregularities and the like.
The high flow rate air tube 26 is capable of transferring a relatively large volume of air relatively quickly between the respective front and rear air bags 24 and 25, thereby decreasing load on the vehicle chassis and suspension system, including vehicle shock absorbers, if fitted.
As indicated, the passage of air through the high flow rate air tube 26 occurs in both directions, depending on which of the front and rear air bags 24 and 25 has the greater or lesser internal pressure resulting from relative movement of the vehicle wheels 12 and 14. The high flow rate air tube 26 is connected to the respective air bags by connectors 27 which, together with the high flow rate air tube 26, controls the rate of flow through the high flow rate air tube 26. In this embodiment, the diameter of the
high flow rate air tube 26 is approximately 2 inches and the diameter of the connectors 27 is between one half inch and one and one half inches. These relative dimensions, however, will vary with different embodiments of the invention, different air bag structures and sizes and the number of air bags used in an air suspension system. The high flow rate air tubes 26 on each side of the vehicle are interconnected by a low flow rate air tube 38 which is connected via low flow rate tube (not shown) to a height valve 39 mounted on the vehicle chassis 10, as shown in Figure 2. A rocker member 32 extends between the front and rear axles 22, and a vertically extending link 33 is connected between the rocker member 32 and the height valve 39. With this arrangement, any change in height between the mid point of the rocker member, to which the link 33 is connected, and the height valve 39 results in movement of the link 33 to actuate the height valve. An air tank (not shown), supplied with air from an air pump (not shown) contains air under pressure for pressurising the air bags. Movement of the link 33 causes the height valve 39 to either admit air into the air bag system through the low flow rate interconnecting tube 38, or to exhaust air from the system. Thus, if the height between the mid point of the rocker member 32 and the valve 39 decreases, as a result of an increase in load on the vehicle chassis 10, the valve actuates to increase the pressure in the air bags 24 to restore the height to the predetermined set position. The pressure in the air bags 24 and 25 is, therefore, automatically adjusted in accordance with the vehicle mass and load to that required to maintain the selected vehicle ride height. However, because the low flow rate air tube 38 conveys air at a low flow rate, minimal transference of air occurs between the high flow rate air tubes 26 on opposite sides of the vehicle due to relative movement of the vehicle wheels and chassis during operation of the vehicle. Further, by placing the connection of the link 33 to substantially the mid point along the rocker member 32, up and down movements of the front and rear wheel sets over a road bump or the like does not effect the relative position of the mid point link connection sufficiently to cause actuation of the valve 39. Referring to Figure 3, there is illustrated a high flow rate air tube 52 which is adapted to be used with any of the embodiments of the invention but which will be described with reference to its use in the embodiment shown in Figures 1 and 2.
The high flow rate air tube 52 of this embodiment is formed from a relatively flexible, pressure hose, such as a hydraulic hose. In the embodiment illustrated, the hydraulic hose is of about two to two and one half inches (approximately 50 to 60 millimetres) in diameter and is preformed with crimped ends joined to the connector tubes 27 which connect the high flow rate air tube 52 to the respective front and rear air bags 24 and 25 on each side of the vehicle. The connector tubes 27 may have a
diameter of between about 0.25 and 0.8 times the diameter of the high flow rate air tube. A hydraulic hose is a preferred form of high flow rate air tube as it is designed and constructed to resist collapsing if the outside pressure exceeds the inside pressure.
The hydraulic hose, being flexible, is also able to be located relative to a vehicle 5 chassis 10 so as to be positioned over and around structural members, suspension arms and the like. The relatively large diameter, high flow rate air tube 52 constitutes a manifold 50 with the smaller diameter end connectors 27 through which air is passed from one or other of the air bags 24, 25 during vehicle operation. The change in diameter between the large diameter manifold 50 and the smaller diameter connections 10 27 forms a shoulder 53 at each end of the manifold 50. Air flow through the manifold, indicated by flow lines 58, becomes turbulent where it strikes a shoulder 53 and the air is forced to flow back on itself as it abuts the shoulder 53, as indicated at 59. This air flow back 59 results in a control or regulation of the air flow from the manifold 50 into the end connector 27 and the air bag 25, when air is flowing in the direction as shown. 5 The control or regulation of the air flow is generally fractionally proportional to the rate at which the air pressure differential changes whereby the air flow rate increases at a lesser rate than an increase in pressure differential. Thus, as the air flow rate increases with increasing pressure differential, the flow back also increases to effectively restrict the rate of increase in the air flow. However, the flow of air out of an air bag into the 0 manifold is substantially unregulated and is more or less directly proportional to the pressure differential.
Further, the air flow through the manifold 50 is generally proportional to the pressure difference between the air bags 24 and 25, such as that caused by the front vehicle wheels 12 moving upwardly relative to the chassis 10 as a result of a bump in 5 the road surface. However, the flow rate through the manifold 50 and out into the air bag 25 is regulated by the back flow of air impeding the flow of air out of the manifold
50, as described above. Such impeding of the flow of air flowing into the air bag 25 prevents rapid transferral of air from one air bag to the other and therefore provides a damping effect to significantly reduce or eliminate tramping by reducing the rate of rise 0 of pressure in air bag 25. The control or regulation also prevents over transfer of air between air bags that could otherwise result in the air pressure in the air bag to which air is transferred rising above that of the other air bag. Such over transfer can give rise to oscillations, whereby air moves backward and forward between the air bags through the high flow air tube which sometimes resonates causing uncontrolled vehicle 5 pitching.
It will be understood that when the air pressure in the air bag 25 becomes greater than that in the air bag 24, air flows in the reverse direction to that shown in Figure 3. It will also be understood that the back flow of air caused by the shoulder 53 when air flows out of the manifold 50 in one direction or the other provides a variable regulation of the air flow in accordance with the air flow rate through the manifold. The regulation enables the system of the invention to react appropriately to road surface irregularities at any given vehicle speed. The rate of increase in pressure in one air bag and the rate of transference of air from that air bag to the manifold and thus to the other air bag together with the controlled rate of flow of the air to the other air bag stabilises the rate of inflation of the other air bag to either totally obviate tramp or to substantially minimise rebound.
A port 56 may be formed at one or other end of the high flow rate air tube 52 to facilitate connection of the tube 52 with the low flow rate air tube 38 providing pressurised air to the system. Alternatively, such a port may be positioned approximately centrally along the length of the flexible high flow rate tube 52.
Referring to Figure 4, a second embodiment of the present invention for use with a vehicle having a single steer axle 22 mounting front steering wheels 12 is shown. As with the first embodiment, the vehicle incorporates a chassis member 10 on each side of the vehicle each carrying a suspension mounting 16 in the form of a box hanger 16 for the front steer axle and wheel sets. The trailing suspension spring 18 is mounted to each box hanger 16 in the same manner as previously described, and the axle 22 of each wheel set is mounted to the respective spring 18 as previously described..
A high flow rate air tube 126 is connected to one of the air bags 24 and a second high flow rate air tube (not shown) is connected to the other air bag 24. The two high flow rate air tubes are connected together at their respective free ends by a low flow rate connection whereby air pressure in the two high flow rate air tubes is able to equalise but the restrictive connection minimises air transfer due to differing pressures resulting from one or other wheel 12 encountering a bump or depression independently of the other. The high flow rate air tubes 26 on each side of the vehicle enable air to be transferred between the respective air bags and high flow rate air tubes, or manifolds, in the event that the front steered wheels 12 move upwardly or downwardly with respect to the chassis 10. Thus, if the front wheel 12 moves upwardly relative to the chassis 10, through the tire encountering a bump in a road surface, the air bag 24 is compressed increasing the pressure of air in that air bag. Air is then able to move from that air bag to the high flow rate air tube 26.
This movement of air between the respective air bags and high flow rate air tube is independent on each side of the vehicle, and enables both steered wheels of the vehicle structure to carry loads substantially equally, even when wheels are moving upwardly and downwardly relative to the chassis due to road irregularities and the like. The high flow rate air tube 26 is capable of transferring a relatively large volume of air relatively quickly between the respective front air bag 24 and high flow rate air tube 26, thereby decreasing load on the vehicle chassis and suspension system, including vehicle shock absorbers, if fitted.
As indicated, the passage of air through the high flow rate air tube 26 occurs in both directions, depending on the pressure differential between the respective air bag and high flow rate air tube 26. The connection between the high flow rate air tube 26 and the air bag is substantially similar to that described above with reference to Figure 3 to provide a controlled or regulated air flow into the air bag, while air flow out of the air bag is substantially un-regulated. With embodiments of the present invention, it may be possible to use an air bag suspension system without the use of normal dampers or shock absorbers. Alternatively, reduced capacity dampers or shock absorbers 34 (Figure 4) may be used thus significantly reducing costs of suspension components. The damping effect resulting from use of embodiments of the present invention dramatically reduces suspension oscillation or resonance. Therefore, suspension components, including springs, mounting points and the like are subjected to less stress than would otherwise occur over the life of a vehicle.
Referring now to Figure 5, one example of the suspension system of the invention used in conjunction with shock absorbers shown as applied to a vehicle chassis 10 with the shock absorbers positioned between the axle clamp block 28 and the chassis.
Particular examples of a range of specifications and mounting options for shock absorbers is shown at Figures 6 through to 9 where the shock absorbers can be placed in a range of configurations between the vehicle wheels and the chassis.
TEST RESULTS
It has been found in tests carried out on suspension systems of the type herein described that vehicles incorporating such a system impose substantially reduced impact on road surfaces. In some tests, up to 50% reduction in road impact has been measured using the system of the invention. The test data was obtained by driving a truck over test speed bumps.
The test results further show us a substantial reduction in vehicle damage as a result of the reduced vibrations and space a substantial increase in driver comfort and stability. The use of the suspension system of the invention substantially reduced whole body vibration and increases stability by up to 17%. In addition, the suspension system of the invention applies with ISO 2631-1 standards for mechanical vibration and shock to the human body thereby reducing driver fatigue.
It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.