AU2017206165A1

AU2017206165A1 - Shell Reservoir Damper

Info

Publication number: AU2017206165A1
Application number: AU2017206165A
Authority: AU
Inventors: Oscar Fiorinotto
Original assignee: Dynamic Engineering Solutions Pty Ltd
Current assignee: Dynamic Engineering Solutions Pty Ltd
Priority date: 2016-07-19
Filing date: 2017-07-18
Publication date: 2018-02-08

Abstract

An integrated reservoir ring piston pressurised damper as a gas pressurised hydraulic damper. The damper oil is pressurised by a charge of nitrogen gas. The Gas Chamber (8) and Oil Chamber (6) are separated by a barrier means, in particular a Gas Piston (4). In this particular design, the damper is made up of two concentric cylinders (twin tube). The Main Piston (7) moves within the Inner Cylinder (3) and the Gas Piston, which separates the gas and oil, moves within the Outer Cylinder (2). As a result of this configuration, the Gas Piston (4) is shaped like a ring and seals on both the inner wall of the Outer Cylinder (2) and the outer wall of the Inner Cylinder (3). Oil is displaced from the Inner Cylinder (3) by the volume of the Piston Rod (5) as the damper compresses, and by the thermal expansion of oil during operation. This oil is transferred to the Outer Cylinder (2) through an Exchange Port (11), not shown. This oil is transferred back into the Inner Cylinder (3) in the same manner as the damper extends.

Description

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to an Integrated Reservoir Ring Piston Pressurised Damper Discussion of the Background Art A hydraulic damper converts kinetic energy into heat using viscous friction of a non-compressible fluid. Typically, this is achieved by passing oil through an aperture with variable cross sectional area. Damping coefficient adjustments can be made by adjusting the aperture size through the piston or around the piston. A typical hydraulic damper consists of a damper cylinder, piston rod, hydraulic piston, gas reservoir and gas piston. The damper cylinder is full of hydraulic oil and sealed on both ends. The hydraulic piston is attached to the piston rod, which enters the hydraulic cylinder through rod seals. The hydraulic piston moves through the hydraulic oil when forces are applied to the piston rod. As the piston rod enters the sealed damper cylinder, the internal oil volume capacity is reduced, this volume of oil is transferred into a gas reservoir. The gas reservoir contains hydraulic oil and pressurised nitrogen, separated with a gas piston. The gas reservoir can take many different forms, depending on the damper design, such as mono-tube, twin tube or remote reservoir. A standard MacPherson strut hydraulic damper typically consists of a damper cylinder attachable to an un-sprung mass (wheel), and a piston rod attachable to a sprung mass (vehicle chassis). All forces to support the wheel position are transferred into the piston rod. For this reason, the piston rod is typically large in diameter. This inherently can reduce damping performance as large volumes of oil are transferred between the damper cylinder and gas reservoir.

Gas pressurised dampers necessitate a significant amount of space for a gas chamber. There are two designs which are most commonly used. The simplest of the two is a single damper cylinder with the oil at one end and gas at the other, with the two separated by a floating gas piston. The other design utilised an external (remote) reservoir connected to the damper cylinder via a high pressure hydraulic hose. In terms of packaging, both designs have limitations. The single cylinder design is limited in minimum compressed length by the minimum allowable length of the gas chamber. The remote reservoir design requires additional room and brackets to house the attachment (remote reservoir).

Using a gas charge to pressurise the oil in a damper has two primary functions. The first is to prevent a pressure drop on the low pressure side of the main piston that is below the vapour pressure of the oil; such a pressure drop produces cavitation resulting in hysteresis and very poor damper performance. The second is to maximise oil flow through the valves on the main piston to provide the best possible force response as the piston rod moves.

In high speed damping, oil is displaced with enough force to be passed through the main piston and shim stack on the other side. The passing of oil through the shim stack is standard technology and is not included in this application.

Hydraulic shock absorbers

Hydraulic dampers are often regarded as a poor solution, because the oil contains approximately 10% air. Under load, the air and oil molecules separate causing foaming and cavitation, which results in a noticeable drop in the damping force. Only after a break from use does the damper regain its full force and the vehicle its original driving performance.

Gas pressure shock absorbers

Loss of damping force does not occur with gas pressure shock absorbers. Nitrogen ensures that the shock absorber oil is permanently under pressure, thereby preventing foaming, even under load. Thus gas pressure shock absorbers perform more stably than hydraulic dampers. Gas pressure shock absorbers are available with either mono- or twin-tube technology. The mono-tube system, is the technology of choice in motor sports and on standard sports cars. The comparatively larger effective area of the working piston ensures greater damping force and better handling. Whereas twin tubes configurations are more compact. Optimum discharge of thermal energy into the atmosphere means consistent high performance is achieved.

Many shock absorbers contain pressurized nitrogen gas as well as the hydraulic oil. If a shock absorber has to react very rapidly to an up and down motion the hydraulic oil can begin to foam as the oil converts from liquid to gas. This foam causes the shock to lose some of its control. The purpose of the gas in the shock is to keep the oil under pressure so it is less likely to foam.

Often, dual twin tube shock absorbers are used because the suspension design does not allow a 90 degree orientation of the shock absorber to the wheel, and it allows greater movement of the oil.

OBJECT OF THE INVENTION

It is, therefore, an object of the present invention to provide a smaller length damper with an improved damper travel characteristics due to separating the oil and the gas from mixing.

On modern road vehicles, dampers commonly require small compressed lengths with large total damper travel. To solve this problem a twin tube damper is used. The twin tube design allows the gas chamber to be located around the outside of the inner damper cylinder. As a result, the compressed length is not limited by the gas chamber. Conventional twin tube dampers do not use a gas piston, the oil and gas are able to mix. As a result of this the damper can only be mounted in one vertical orientation to minimise the mixing of gas and oil. As there is no separating gas piston the oil is not pressurised. The lack of oil pressurisation results in a low force response damper, which will rapidly decrease in performance when worked hard for extended periods of time, due to oil/gas mixing and oil cavitations.

The integrated Reservoir Ring Piston Pressurised Damper has the packaging advantages of a twin tube damper as well as the performance of gas pressurised dampers.

BRIEF DESCRIPTION OF DRAWINGS FIG 1 Cutaway view of integrated reservoir Ring Piston Pressurised Damper

SUMMARY OF THE INVENTION

According to a broad form of the invention, there is provided an integrated reservoir ring piston pressurised damper, having: an outer damper cylinder, an inner damper cylinder a main piston transversely movable within the inner damper cylinder that compresses oil by force or is driven during expansion phase by heated oil expansion, a piston rod which is driven by transverse movement of the piston, a barrier means located within the two damper cylinders to separate the oil and the gas chambers, a gas chamber defined by said barrier means, an oil chamber defines by said barrier means; wherein oil and gas are separated by the barrier means and cannot mix.

Preferably said barrier means comprises a gas piston.

Preferably said gas piston is a ring type piston.

Preferably said ring piston is moveable in the piston cylinders to pressurise the oil by providing increased gas volume.

DETAILED DESCRIPTION OF THE DRAWINGS FIG 1 Shows an Integrated Reservoir Ring Piston Pressurised Damper as a gas pressurised hydraulic damper. The damper oil is pressurised by a charge of nitrogen gas. The Gas Chamber (8) and Oil Chamber (6) are separated by a barrier means, in particular a Gas Piston (4). In this particular design, the damper is made up of two concentric cylinders (twin tube). The Main Piston (7) moves within the Inner Cylinder (3) and the Gas Piston, which separates the gas and oil, moves within the Outer Cylinder (2). As a result of this configuration, the Gas Piston (4) is shaped like a ring and seals on both the inner wall of the

Outer Cylinder (2) and the outer wall of the Inner Cylinder (3). Oil is displaced from the Inner Cylinder (3) by the volume of the Piston Rod (5) as the damper compresses, and by the thermal expansion of oil during operation. This oil is transferred to the Outer Cylinder (2) through an Exchange Port (11), not shown. This oil is transferred back into the Inner Cylinder (3) in the same manner as the damper extends.

The gas piston (4) prevents gas from passing into the oil chamber (6). This ensures all the oil and gas do not mix which avoids cavitations.

Although the invention has been illustrated and described with respect to several exemplary embodiments thereof, it will be understood by those skilled in the art that the foregoing and various other changes, omissions and additions may be made to the present invention without departing from the spirit and scope thereof. Therefore, the present invention should not be understood as limited to the specific embodiment set out above but to include all possible embodiments which can be embodied within a scope encompassed and equivalents thereof with respect to the feature set out in the appended claims.

THOMPSON AND ASSOCIATES LAWYERS

Claims

The claims defining the invention are as follows:

1. An integrated reservoir ring piston pressurised damper, having: an outer damper cylinder; an inner damper cylinder; a main piston transversely movable within the inner damper cylinder; the main piston having a compressed position, and expanded position during heated oil phase; a piston rod which is driven by transverse movement of the piston; a barrier means located within the two damper cylinders to separate the oil and the gas chambers; a gas chamber defined by said barrier means; an oil chamber defined by said barrier means; wherein oil and gas are separated by the barrier means and cannot mix.
2. The integrated reservoir ring piston pressurised damper as claimed in claim 1 wherein said barrier means comprises a gas piston.
3. The integrated reservoir ring piston pressurised damper as claimed in claim 2 wherein said gas piston is a ring type piston.
4. The integrated reservoir ring piston pressurised damper as claimed in claim 3 wherein said ring type piston is moveable in the piston cylinders to pressurise the oil by providing increased gas volume.