Land vehicles – Wheeled – Running gear
Reexamination Certificate
1999-03-29
2001-08-07
DePumpo, Daniel G. (Department: 3611)
Land vehicles
Wheeled
Running gear
C280S124104, C280S124106, C280S006155, C280S005505, C280S005507
Reexamination Certificate
active
06270098
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is generally directed to vehicle suspension systems. and in particular to a load distribution unit for a vehicle suspension system.
2. Description of the Background Art
The applicant has previously developed a vehicle fluid suspension system including a load distribution unit which performs the function of redistributing fluid between two pairs of diagonally interconnected double-acting or four single-acting rams respectively provided at each wheel assembly of the vehicle during cross-axle articulation motions, whilst opposing roll motions and introducing a controlled magnitude of pitch resilience. Such a suspension system is described in the applicant's International Application No. PCT/AU95/00096, details of which are incorporated herein by reference.
SUMMARY OF THE INVENTION
The present invention relates to an improved construction of said load distribution unit which can potentially reduce the packaging volume and weight of the original arrangement of the unit by more than 30% thereby increasing the mass production viability of the suspension system as a whole.
With this in mind, according to one aspect of the present invention, there is provided a load distribution unit for a vehicle suspension system having at least one pair of laterally adjacent forward wheel assemblies, and at least one pair of laterally adjacent rear wheel assemblies, a wheel ram associated with each said wheel assembly, each wheel ram including a major chamber therein,
wherein the load distribution unit includes two pairs of axially aligned fluid chambers, each fluid chamber being divided into two control chambers by a piston supported therein, in each pair of axially aligned fluid chambers two of the control chambers which vary in volume proportionally and in opposite senses therein with piston motion are system chambers, the remaining two chambers in each pair of axially aligned fluid chambers being bump chambers,
the piston of each said axially aligned pair of fluid chambers being interconnected by a connection means, the major chamber of each said wheel ram being in fluid communication with a respective said system chamber, such that as the vehicle suspension system provides a roll stiffness and a pitch stiffness while providing minimal cross-axle articulation stiffness,
and wherein a fluid communication is provided between pairs of the bump chambers such that the fluid pressure within the communicating bump chambers is transferable therebetween to thereby enable a pressure balance to be achieved between the system chambers.
The connection means interconnecting the pistons may be a rod member extending through the two control chambers in the middle of each pair of axially aligned fluid chambers.
A respective pair of the fluid chambers may be connected to the major chambers of the wheel rams on each side of the vehicle and the pistons located within each said respective pair of fluid chambers may be urged for movement in opposing axial directions to thereby enable the suspension system to resist roll motion by providing a roll stiffness while also providing a minimal cross-axle articulation stiffness.
Furthermore, the piston located within the pair of fluid chambers connected to the major chambers of the wheel rams at the front or rear of the vehicle may be urged for movement in opposing axial directions when the wheel assemblies are undergoing cross-axle articulation motion and may be urged for movement in the same axial direction when the vehicle is undergoing pitch motion to thereby confer minimal articulation stiffness and provide a pitch stiffness which is independent of the roll, four wheel bounce or articulation stiffnesses.
The bump chambers may be in fluid communication with accumulator means to thereby allow for a greater degree of resilience for the vehicle suspension system such that transient vertical motions of the wheel assemblies which can arise when the vehicle is travelling over a speed bump can be accommodated by the load distribution unit.
The fluid chambers may be of differing sizes to enable the pressures in the load distribution unit to be set as required during the design process. Each pair of fluid chambers may be located in parallel adjacent relation. Alternatively, each pair of chambers may be positioned in different positions in the vehicle or aligned along a common axis.
According to a second aspect of the invention there is provided a load distribution unit for a vehicle suspension system having at least one pair of laterally adjacent forward wheel assemblies, and at least one pair of laterally adjacent rear wheel assemblies, a wheel ram associated with each said wheel assembly, each wheel ram including a major chamber therein,
wherein the load distribution unit includes three fluid chambers aligned along a common axis to thereby provide opposing end chambers and a central chamber therebetween,
the end chambers being respectively divided by a piston supported therein into two control chambers, the central chamber being divided by two pistons into two control chambers and a central bump chamber,
two of the control chambers which vary in volume proportionally and in opposite senses with piston motion being separate bump chambers, the remaining four control chambers being system chambers,
respective connection means interconnecting each of the pistons in the central chamber to the piston in an adjacent said end chamber, the major chamber of each said wheel ram being in fluid communication with a respective one of the system chambers, such that the vehicle suspension system provides a roll stiffness and a pitch stiffness while providing minimal cross-axle articulation stiffness,
the two separate bump chambers of each end chamber being in fluid communication such that the fluid pressure within the communicating bump chambers is transferable therebetween to thereby enable a pressure balance to be achieved between the system chambers.
The connection means interconnecting the pistons may be a rod member extending through a said control chamber of the central chamber and a said control chamber of the end chamber adjacent thereto.
The two separate bump chambers may be in fluid communication with an accumulator means, and the central bump chamber may be in fluid communication with an accumulator means.
In devices such as rams and load distribution units described above, the problem of stationary friction or “stiction” where there is an initial resistance to movement of a stationary piston in a chamber can arise. This undesirable effect is especially prevalent in seals where there exists a large pressure difference across the seals which energises the seal firmly into the sealing surface giving high levels of friction. It is commonly found that there is only a certain reduction of the energising force possible (giving a set reduction in friction levels) whilst still maintaining a low fluid loss seal. This friction level can significantly retard the response time of the suspension system which can be detrimental to the ride comfort of the vehicle. The application seeks to overcome this problem by utilising fluid containers having at least a portion which is flexible to function as the chambers of the fluid ram. A similar problem can also arise in a load distribution unit with stiction between the piston seals and the bores, and the rod seals and the rods.
Hence, according to a further aspect of the present invention, there is provided a load distribution unit for a vehicle suspension system having at least one pair of laterally adjacent forward wheel assemblies, and at least one pair of laterally adjacent rear wheel assemblies, a wheel ram associated with each said wheel assembly, each wheel ram including a major chamber therein,
wherein the load distribution unit includes a housing divided into a pair of chamber sets, each chamber set including two axially aligned end chambers and a central chamber located and axially aligned therebetween,
pistons respectively located within the central chamber and
Heyring Christopher Brian
Monk Richard
Birch & Stewart Kolasch & Birch, LLP
DePumpo Daniel G.
Kinetic Limited
Zeender F.
LandOfFree
Load distribution unit for vehicle suspension system does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Load distribution unit for vehicle suspension system, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Load distribution unit for vehicle suspension system will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2502202