PRIORITY DOCUMENT

[0001] The present application claims priority from Australian Provisional Patent Application No. 2020903528 titled “AIR SPRING FOR A VEHICLE” and filed on 30 September 2020, the content of which is hereby incorporated by reference in its entirety.

TECHNICAL FIELD

[0002] The present invention relates to an air spring for a vehicle. In a particular form the present invention relates to a suspension strut for a vehicle comprising a hydraulic damper and an air spring.

BACKGROUND

[0003] Air springs, also known as air bags have long been known as an alternative to standard steel springs in a variety of automotive suspension applications. Air springs are sometimes favoured over steel springs due to their ease of adjustability, by simply increasing or decreasing pressure in the spring to effect a change in ride height and quality.

[0004] Air springs are also favoured by 4x4 and SUV users, where they are often used in association with towing trailers and caravans, when heavily loaded for outback or long distance travel, when requiring increased ground clearance when traveling over uneven terrain, or when requiring reduced ride height when entering height restricted areas, such as car parks.

[0005] There are however circumstances where it is not possible or practical to utilise air springs even if it is desirable. For example, vehicle packaging requirements and the need to package the air spring along with other suspension components, such as dampers, may limit the amount of space available to accommodate a suitably sized air spring for the lifting force required, such that unsafe or impractically high operating pressures are required in order to raise the vehicle to a desirable ride height.

[0006] It is against this background that the present disclosure has been developed.

SUMMARY

[0007] According to a first aspect, there is provided a suspension strut for a vehicle, comprising a hydraulic damper comprising a damper cylinder, a piston slidably retained within the damper cylinder, and a piston rod for driving the piston within the damper cylinder in compression and rebound, and an air spring comprising a diaphragm attached with respect to the damper cylinder at a first end and to the piston rod at a second end, and forming an air chamber, the air spring further comprising a coil spring located within the air chamber, wherein the coil spring assists the diaphragm in supporting the vehicle.

[0008] In one form, the suspension strut further comprises a first spring seat removably attached to the damper cylinder, to which the first end of the diaphragm is sealably attached with respect thereto, the first spring seat further providing a support surface for a first end of the coil spring.

[0009] In one form, the suspension strut further comprises a generally cylindrical rolling sleeve to which the first end of the diaphragm is sealably attached with respect thereto, and wherein the rolling sleeve is sealably attached with respect to the first spring seat.

[0010] In one form, the rolling sleeve locates around the coil spring and provides an internal guiding surface for maintaining the concentricity of the coil spring with respect to the damper cylinder, piston rod and diaphragm.

[0011] In one form, the suspension strut further comprises a second spring seat attached with respect to the piston rod, to which the second end of the diaphragm is sealably attached with respect thereto, the second spring seat further providing a support surface for a second end of the coil spring.

[0012] According to a second aspect, there is provided an air spring for a vehicle comprising a diaphragm configured to be attached with respect to the unsprung mass of the vehicle at a first end and the sprung mass of the vehicle at a second end, and forming an air chamber, the air spring further comprising a coil spring located within the air chamber, wherein the coil spring assists the diaphragm in supporting the vehicle.

[0013] According to a third aspect, there is provided a suspension system for a vehicle, comprising a plurality of suspension struts as previously described, a compressor, an accumulator, pipework, valving and a control system for selectively pressurising and depressurising the air spring of each strut.

BRIEF DESCRIPTION OF DRAWINGS

[0014] Embodiments of the present invention will be discussed with reference to the accompanying drawings wherein:

[0015] Figure 1 is a perspective view of a suspension strut, according to an embodiment;

[0016] Figure 2 is a cross-sectional view of the suspension strut of Figure 1;

[0017] Figure 3 is a detail cross-sectional view of the suspension strut of Figure 1; and [0018] Figure 4 is a detail cross-sectional view of the suspension strut of Figure 1.

DESCRIPTION OF EMBODIMENTS

[0019] Referring now to Figures 1 to 4, there is shown a suspension strut 1 for a vehicle, according to an embodiment. The strut 1 comprises a hydraulic damper 100 and an air spring 200. The hydraulic damper 100 comprises a damper cylinder 110, a piston 120 slidably retained within the damper cylinder 110 and a piston rod 130 for driving the piston within the damper cylinder 110 in compression and rebound. The air spring 200 comprises a diaphragm or airbag 210 attached with respect to the damper cylinder 110 at a first end 211 and to the piston rod 130 at a second end 212 and forming an air chamber. The air spring 200 further comprises a coil spring 250 located within the air chamber, wherein the coil spring 250 assists the diaphragm 210 in supporting the vehicle.

[0020] As best shown in Figure 2, the hydraulic damper 100 is a monotube damper featuring a gas piston 140 separating a pre-charged gas in a first end of the damper cylinder 110 from hydraulic fluid in a second end of the damper cylinder 110. The damper 100 also features a cylinder cap 150 in the second end of the damper cylinder 110, providing a fluid seal between the damper cylinder 110 and the piston rod 130. A first end 131 of the piston rod 130 is connected to the piston 120 and a second end 132 of the piston rod 130 is configured to connect with respect to the sprung mass of the vehicle.

[0021] While in the embodiment shown, a monotube damper is shown, it will be appreciated that alternative dampers could be employed without departing from the scope of this disclosure, such as twintube or remote reservoir dampers.

[0022] Referring now to Figure 3, it can be seen that the first end 211 of the diaphragm 210 is connected to a generally cylindrical rolling sleeve 230, where it is crimped between an engaging surface 232 on the rolling sleeve 230 and a crimping ring 231 to form an airtight seal. The rolling sleeve 230 is in turn connected to a first or lower spring seat 240 via grub screws 241 arranged around the perimeter of the rolling sleeve 230. An airtight seal is formed between the rolling sleeve 230 and the lower spring seat 240 by an O-ring 292. As best shown in Figure 3, the lower spring seat 240 is configured to locate over and be removably attached to the damper cylinder 110 by virtue of a bearing ring 244 and a snap ring 243 that engages with a snap ring groove 111 formed about the perimeter of the hydraulic cylinder 110. An airtight seal is formed between the lower spring seat 240 and the damper cylinder 110 by an O-ring 291.

[0023] While in the embodiment shown and described, the first end of the diaphragm is connected to the rolling sleeve by a crimping ring, it will be appreciated that alternate securing arrangements are also intended to fall within the scope of this disclosure. [0024] While in the embodiment shown and described, the lower spring seat 240 is removably secured to the damper cylinder 110 via a snap ring 243, it will be appreciated that in alternative embodiments different mounting arrangements may be employed. For instance, the position of the lower spring seat with respect to the damper cylinder may be adjustable by virtue of a threaded relationship between the damper cylinder and spring seat, alternatively, the lower spring seat may be permanently secured to the damper cylinder via welding, or removably secured to the damper cylinder via other fastening arrangements. Further still, the spring seat and damper cylinder may be formed as a unitary body.

[0025] While in the embodiment shown, the rolling sleeve 230 is removably secured to the lower spring seat 240 via grub screws 241, it will be appreciated that in alternative embodiments different securing arrangements may be employed. For instance, the rolling sleeve and spring seat could feature corresponding threaded sections, such that the two components are threadably engaged. Alternatively, the rolling sleeve and spring seat may be formed as a unitary body.

[0026] Again referring to Figure 3, it can be seen that the lower spring seat 240 comprises a spring support surface 242 with respect to which the coil spring 250 bears against. It can also be seen that the rolling sleeve 230 locates around the coil spring 250 and features an internal groove 236 in which a spring guide bush 260 is located providing an internal guiding surface, assisting in ensuring that the coil spring 250 remains concentric with respect to the damper cylinder 110, piston rod 130 and diaphragm 210.

[0027] Referring now to Figure 4, it can be seen that the second end 212 of the diaphragm 210 is connected to a second or upper spring seat 220, where it is again crimped between an engaging surface 222 on the upper spring seat 220 and a crimping ring 221 to form an airtight seal. The upper spring seat 220 features a central aperture 234 for receiving a top mount 160 which is configured to be threadingly engaged with a threaded section on the second end 132 of the piston rod 130 via a threaded bore 161. The top mount 160 and the upper spring seat 220 feature complimentary bearing surfaces 162, 233 with which the two components bear against each other. An airtight seal is formed between the top mount 160 and the upper spring seat 220 via an O-ring 293.

[0028] While in the embodiment shown and described, the second end of the diaphragm is connected to the upper spring seat by a crimping ring, it will be appreciated that alternative securing arrangements are also intended to fall within the scope of this disclosure.

[0029] As also shown in Figures 2 and 4, the top mount 160 is configured to receive an air fitting or pneumatic connector 280 and features an internal conduit 281, providing passage for air as it is supplied to and withdrawn from the air chamber formed by the diaphragm 210. [0030] While in the embodiment shown, air is supplied to and withdrawn from the air chamber via the connector and internal conduit in the top mount 160, it will be appreciated that in alternative embodiments, the location of the connector and conduit could be located elsewhere, such as the upper spring seat 220.

[0031] As shown in Figures 2 to 4, the air spring 200 further comprises a bump rubber 272 and limiter 271 located around the piston rod 130. The bump rubber 272 is secured at the second end 132 of the piston rod 130 adjacent to the upper spring seat 220, and within the coil spring 250. The limiter 271 is secured to the top of the cylinder cap 150. It will be appreciated that the bump rubber 272 and limiter 271 act as bump stops in the event that the strut 1 is heavily compressed. It will further be appreciated that the bump rubber 272 and limiter 271 may bear against each other in the event of failure of the diaphragm 210 or pneumatic system.

[0032] As best shown in Figures 1 and 2, the strut 1 also features a protective sleeve 300 which locates over the outside of the diaphragm 210, acting to protect the diaphragm 210 from accidental damage and to improve the working life and pressure rating of the diaphragm 210. The protective sleeve 300 is load bearing when the diaphragm is inflated, preventing the diaphragm from stretching or tearing due to overinflation.

[0033] Referring now to Figures 1 and 2, it can be seen that a first end of the strut 1 features a bottom mount 170 configured to engage with respect to the unsprung mass of the vehicle, such as an upright (not shown). The bottom mount 170 forms the lower part of the damper 100, engaging with or being a part of the lower part of the damper cylinder 110. It can also be seen that the second end of the strut 1 features the top mount 160 configured to engage with respect to the sprung mass of the vehicle, such as the vehicle chassis (not shown). While in the embodiment shown, the strut 1 features bottom and top mounts in the form of eye mounts, it will be appreciated that alternative mounting arrangements can be employed depending on the specific requirements of the vehicle.

[0034] While in the embodiment shown the diaphragm is a rolling sleeve type, it will be appreciated that air springs having alternative diaphragm types, such as bellows type diaphragms would also fall within the scope of this disclosure.

[0035] Assembly of the suspension strut 1 will be described below:

[0036] The air spring 200 comprising the diaphragm 210, secured to the upper and lower spring seats 220, 240 the rolling sleeve 230 and the internal coil spring 250, is pre-assembled and then slid over the lower end of a pre-assembled hydraulic damper’s cylinder 110 and piston rod 130 until the upper spring seat 220 bears against the top mount 160. [0037] The air spring 200 is then compressed so that the snap ring 243 is able to be snapped in to position around the groove in the damper cylinder 110.

[0038] It will be appreciated that by incorporating a coil spring 250 to work in parallel with the diaphragm 210, that the air spring 200 becomes mechanically assisted, and does not need to be pressurised as much as an air spring without a coil spring 250 in order to achieve the same lifting force. It will further be appreciated that the mechanically assisted air spring 200 inflates faster than an air spring without a coil spring 250, and that by locating the coil spring 250 within the air chamber created by the diaphragm 210 that the overall diameter of the strut 1 is able to be sized according to the space made available by the specific vehicle application, such that, where some vehicles were not able to be equipped with air springs due to the limited space available for a suitably sized airbag, due to the unsafe or impractical operating pressures required, the present disclosure is able to achieve this outcome.

[0039] Furthermore, it will be appreciated that the stiffness of the coil spring 250 can be varied dependent on vehicle application. For instance, the coil spring 250 could act as the primary spring, with the diaphragm 210 acting as a helper spring to increase ride height and overall spring stiffness where required. Alternatively the diaphragm 210 could act as the primary spring, with the coil spring 250 acting as a helper spring to reduce required operating pressure and to decrease inflation times. It will also be appreciated that the coil spring 250 can act as a fail-safe in the event of a failure in the diaphragm 210 or pneumatic system, where it is able to continue to offer at least some support to the vehicle load, rather than the strut relying entirely on the bump rubber and limiter.

[0040] While in the embodiment shown and described, the mechanically assisted air spring 200 is located over the damper 100 to form a suspension strut 1, it will also be appreciated that the mechanically assisted air spring 200 could be retrofitted or used as a replacement or alternative to a stand-alone coil spring not part of a suspension strut, as part of a vehicle suspension system. In such an arrangement the air spring may comprise a diaphragm configured to be attached with respect to the unsprung mass of the vehicle at a first end and the sprung mass of the vehicle at a second end, forming an air chamber. The air spring further comprises a coil spring located within the air chamber, wherein the coil spring would assist the diaphragm in supporting the vehicle.

[0041] Finally, it will be appreciated that the air spring may be used as part of a suspension system comprising one or more of the struts and/or one or more of the air springs, an air compressor, an accumulator, pipework, valving and a control system for selectively pressurising and depressurising the the or each air spring.

[0042] Throughout the specification and the claims that follow, unless the context requires otherwise, the words “comprise” and “include” and variations such as “comprising” and “including” will be understood to imply the inclusion of a stated integer or group of integers, but not the exclusion of any other integer or group of integers.

[0043] The reference to any prior art in this specification is not, and should not be taken as, an acknowledgement of any form of suggestion that such prior art forms part of the common general knowledge.

[0044] In some cases, a single embodiment may, for succinctness and/or to assist in understanding the scope of the disclosure, combine multiple features. It is to be understood that in such a case, these multiple features may be provided separately (in separate embodiments), or in any other suitable combination. Alternatively, where separate features are described in separate embodiments, these separate features may be combined into a single embodiment unless otherwise stated or implied. This also applies to the claims which can be recombined in any combination. That is a claim may be amended to include a feature defined in any other claim. Further a phrase referring to “at least one of’ a list of items refers to any combination of those items, including single members. As an example, “at least one of: a, b, or c” is intended to cover: a, b, c, a-b, a-c, b-c, and a-b-c.

[0045] It will be appreciated by those skilled in the art that the invention is not restricted in its use to the particular application described. Neither is the present invention restricted in its preferred embodiment with regard to the particular elements and/or features described or depicted herein. It will be appreciated that the invention is not limited to the embodiment or embodiments disclosed, but is capable of numerous rearrangements, modifications and substitutions without departing from the scope of the invention as set forth and defined by the following claims.