PRIORITY DOCUMENTS

[0001] The present application claims priority from Australian Provisional Patent Application No. 2022900185 titled “BUMP STOP” and filed on 1 February 2022, the content of which is hereby incorporated by reference in its entirety.

TECHNICAL FIELD

[0002] The present disclosure relates to a hydraulic bump stop.

BACKGROUND

[0003] Vehicle suspension systems will typically include a bump stop, used to protect the vehicle when the suspension reaches full compression when encountering a bump or dip in the surface of the terrain the vehicle is travelling over.

[0004] In the case of heavy vehicles, most bump stops will be mounted to the chassis or frame of the vehicle, where a portion of the suspension, such as the lower control arm and/or axle will make contact with the bump stop when approaching full compression, preventing contact between suspension and vehicle components.

[0005] Hydraulic bump stops will often use an architecture similar to that of a damper and spring working in parallel, where the damper comprises a piston and piston rod that move within a volume of non-compressible fluid such as hydraulic fluid, which is charged or pressurised by a volume of compressible gas such as air or nitrogen so as to allow for thermal expansion and contraction, as well as reducing cavitation of the hydraulic fluid.

[0006] It will be appreciated that in such systems, a displacement of hydraulic fluid caused by an increase in volume of the piston rod entering the volume of hydraulic fluid during bump, causes the volume of the compressible gas to reduce and pressure to increase, creating a restorative force. It will be appreciated that the further the piston and piston rod move in bump, the greater the pressure becomes in the compressible volume, and the greater the restorative force. It will be appreciated that this increase in restorative force adds to that being provided by the spring acting in parallel with the damper, which can in some cases be undesirable.

[0007] It is against this background that the present disclosure has been developed. SUMMARY

[0008] According to a first aspect, there is provided a bump stop for a vehicle, comprising a damper cylinder having an internal volume configured to contain a liquid therein, a piston assembly comprising a damper piston and a piston rod slidingly retained within the damper cylinder, the damper piston separating the internal volume of the damper cylinder into a first fluid chamber and a second fluid chamber, the first fluid chamber defined by an inner surface of the damper cylinder and a first surface of the damper piston, the second fluid chamber defined by an annulus formed between at least an outer surface of the piston rod, an inner surface of the damper cylinder and a second surface of the damper piston, wherein the damper piston is configured to allow the flow of fluid between the first and second fluid chambers during extension and compression of the bump stop, an outer cylinder having a first end configured to slidably receive the damper cylinder and a second end configured to attach to the piston rod, such that the outer cylinder, piston rod and damper piston move in unison with respect to the damper cylinder in extension and compression of the bump stop, wherein a third fluid chamber is defined by an annulus formed between at least an outer surface of the damper cylinder and an inner surface of the outer cylinder, and a fourth fluid chamber configured to contain a compressible gas therein, is defined by an annulus formed between at least an outer surface of the piston rod and an inner surface of the outer cylinder, and wherein the second and third fluid chambers are in fluid communication with each other, and wherein the combined volume of the first, second and third fluid chambers remains substantially constant during extension and compression of the bump stop.

[0009] In one form, the damper piston comprises a compression valve arrangement for allowing the flow of fluid through the damper piston from the first fluid chamber to the second fluid chamber during compression; and an extension valve arrangement for allowing the flow of fluid through the damper piston from the second fluid chamber to the first fluid chamber during extension.

[0010] In one form, the second and third fluid chambers are connected via a plurality of apertures formed in the damper cylinder and extending between the inner and outer surface of the damper cylinder.

[0011] In one form, the piston assembly further comprises a fifth fluid chamber located within an internal volume of the piston rod, and a separator piston slidably retained within the piston rod, wherein the fifth fluid chamber is configmed to contain a compressible gas, and the separator piston separates the liquid in the damper cylinder from the gas in the fifth fluid chamber.

[0012] In one form, the fourth and fifth fluid chambers are connected via at least one gas passage formed in the piston rod. [0013] In one form, a sixth fluid chamber is formed inside the piston rod between the separator piston and the damper piston, wherein the sixth fluid chamber is in fluid communication with the first fluid chamber.

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 side view of abump stop, according to an embodiment, at rest;

[0016] Figure 2 is a cross-sectional view of the bump stop of Figure 1, at rest;

[0017] Figure 3 is a side view of the hydraulic bump stop of Figure 1, undergoing partial compression;

[0018] Figure 4 is a cross-sectional view of the hydraulic bump stop of Figure 1, undergoing partial compression;

[0019] Figure 5 is an alternate cross-sectional view of the hydraulic bump stop of Figure 1, undergoing partial compression, detailing one of a plurality of rebound valves;

[0020] Figure 6 is a side view of the hydraulic bump stop of Figure 1, at full compression;

[0021] Figure 7 is a cross-sectional view of the hydraulic bump stop of Figure 1, at full compression;

[0022] Figure 8 is a detailed cross-sectional view of a portion of the bump stop of Figure 1; and

[0023] Figure 9 is a cross-sectional view of a bump stop, according to an alternate embodiment.

DESCRIPTION OF EMBODIMENTS

[0024] Referring to Figures 1 to 7, there is shown a bump stop 1 for a vehicle. The bump stop 1 comprises a damper cylinder 100 having an internal volume configured to contain a liquid (such as hydraulic oil) therein. The bump stop 1 further comprises a piston assembly comprising a damper piston 210 and piston rod 220 slidingly retained within the damper cylinder 100. The damper piston 210 separates the internal volume of the damper cylinder 100 into a first fluid chamber 11 and a second fluid chamber 12, the first fluid chamber 11 is defined by an inner surface 110 of the damper cylinder 100 and a first surface 211 of the damper piston 210, the second fluid chamber 12 is defined by an annulus formed between at least an outer surface 222 of the piston rod 220, an inner surface 110 of the damper cylinder 100 and a second surface 212 of the damper piston 210. The bump stop 1 further comprises an outer cylinder 300 having a first end 301 configured to slidably receive the damper cylinder 100 and a second end 302 configured to attach to the piston rod 220, such that the outer cylinder 300 and piston assembly move in unison with respect to the damper cylinder 100. A third fluid chamber 13 is defined by an annulus formed between at least an outer surface 120 of the damper cylinder 100 and an inner surface 310 of the outer cylinder 300, and a fourth fluid chamber 14 configured to contain a compressible gas (such as air or nitrogen) therein, is defined by an annulus formed between at least an outer surface 222 of the piston rod 220 and an inner surface 310 of the outer cylinder 300. The second and third fluid chambers 12, 13 are in fluid communication with each other, and the combined volume of the first, second and third chambers 11, 12, 13 remains substantially constant during extension and contraction of the damper cylinder 100 with respect to the piston assembly and outer cylinder 300.

[0025] It can be seen that the damper cylinder 100 has a closed first end 101 and a second end 102 through which the piston assembly extends. It will be appreciated that fluid is prevented from leaking between the second fluid chamber 12 and fourth fluid chamber 14 via the second end 102 of the damper cylinder 100 by virtue of an end cap arrangement 130 (best shown in Figure 8). It can also be seen that the end cap 130 acts to prevent fluid leaking between the third fluid chamber 13 and the fourth fluid chamber 14 via the second end 102 of the damper cylinder 100. It will be appreciated that the end cap arrangement 130 also prevents gas leaking from the fourth fluid chamber 14 in to either of the third fluid chamber 13 or the second fluid chamber 12.

[0026] It can also be seen that the first end 301 of the outer cylinder 300 comprises a first end cap arrangement 310 through which the damper cylinder 100 extends, and prevents fluid from leaking from the third fluid chamber 13 between the damper cylinder 100 and the outer cylinder 300. The second end 302 of the outer cylinder 300 comprises a second end cap arrangement 320, configured to engage with the piston rod 220 and which prevents gas leaking from the fourth fluid chamber 14 between the outer cylinder 300 and piston rod 220.

[0027] With reference to Figures 4, 5 and 7, it can be seen that the second and third fluid chambers 12, 13 are hydraulically connected via a plurality of apertures 140 formed in the damper cylinder 100 and extending between the inner and outer surfaces 110, 120. It can also be seen that the piston rod 220 is cylindrical and has an internal volume, and the piston assembly further comprises a pneumatic spring located within the internal volume of the piston rod, the pneumatic spring comprising a fifth fluid chamber 15 configured to contain a compressible gas and a separator piston 230 slidably retained within the piston rod 220 and configured to separate the fluid from the gas.

[0028] It can also be seen that the fourth and fifth fluid chambers 14, 15 are in fluid communication via gas passages 223 within the piston rod 220, such that the combined volume of the fourth and fifth fluid chambers 14, 15 act as a pneumatic spring. The piston assembly is also provided with a charge port 240, also in fluid communication via a gas passage 223 in the piston rod 220, used to pressurise the fourth and fifth fluid chambers 14, 15 with compressed gas.

[0029] In addition to providing a restorative force (described in further detail below), the pneumatic spring also acts to reduce cavitation of the hydraulic fluid, and accommodating thermal expansion and contraction by pressurising the hydraulic fluid via the separator piston 230, which is configured to move up and down within the piston rod 220 in response to increases and decreases in the overall volume of the hydraulic fluid. As best shown in Figures 2, 4, 5 and 7, a sixth fluid chamber 16 is formed inside the piston rod 220 between the separator piston 230 and the damper piston 210, where the sixth fluid chamber 16 is in fluid communication with the first fluid chamber 11 via a low flow rate valve or aperture 214 which allows for flow between the first and sixth fluid chambers 11, 16 in response to thermal expansion and contraction.

[0030] The bump stop 1 is configured to be mounted to the chassis or frame of the vehicle via the second end 302 of the outer cylinder 300 and piston rod 220. It will be appreciated that at rest (as shown in Figure 1) the damper cylinder 100 is fully extended with respect to the outer cylinder 300 and piston assembly by virtue of the gas pressure in the fourth and fifth fluid chambers 14, 15. The first end 101 of the damper cylinder 100 is configured to be pushed or struck by a portion of the vehicle suspension, causing the damper cylinder 100 to move in compression relative to the outer cylinder 300 and piston assembly.

[0031] As the damper cylinder 100 is moved as a result of compression, hydraulic fluid in the first fluid chamber 11 is forced through a compression valve arrangement, comprising a plurality of flow control valves or apertures 213 in the damper piston 210 and in to the second fluid chamber 12, where (as best shown in Figure 4) the increase in volume of the piston rod 220 entering the internal volume of the damper cylinder 100 is compensated for by a substantially equal increase in volume of the third fluid chamber 13, such that hydraulic fluid flows from the second fluid chamber 12 to the third fluid chamber 13 via the plurality of apertures 140 formed in the damper cylinder 100. It will be appreciated that, unlike the prior art, the addition of the third fluid chamber 13 allows the volume of the piston rod 220 to be accommodated without reducing the volume of the compressible gas used to pressurize the hydraulic fluid, in other words, the position of the separator piston 230 does not move in response to compression of the bump stop 1. Instead, compression of the volume of gas is only caused by the volume of the fourth fluid chamber 14 reducing as the damper cylinder 100 is driven further in to the outer cylinder 300, with the fifth fluid chamber 15 accommodating the majority of the gas volume when the bump stop 1 reaches a fully compressed state, as best shown in Figure 7. It can also be seen that the majority of fluid has moved out of the first fluid chamber 11 and in to the second and third fluid chambers 12, 13. [0032] The compression valve arrangement is configured to have a damping effect as the hydraulic fluid flows through the damper piston 210 from the first fluid chamber 11 to the second fluid chamber 12, while preventing flow from the second fluid chamber 12 to the first fluid chamber 11.

[0033] As the damper cylinder 100 moves in extension, by virtue of the expansion of the volume of gas in the fourth and fifth fluid chambers 14, 15, the decrease in volume of the third fluid chamber 13 causes hydraulic fluid to flow from the third fluid chamber 13 to the second fluid chamber 12 via the plurality of apertures 140 formed in the damper cylinder 100, and hydraulic fluid in the second fluid chamber 12 is forced through an extension valve arrangement in the damper piston 210 and in to the first fluid chamber 11. As best shown in Figure 5, the extension valve arrangement comprises a plurality of apertures 215 in the damper piston 210 and at least one valve in the form of a shim 216, that allows for fluid to flow from the second fluid chamber 12 to the first fluid chamber 11, but not in reverse, with minimal resistance or rebound damping, allowing the bump stop 1 to return to an at rest configmation as quickly as possible, in other words. It will be appreciated that the combination of the compression and extension valve arrangement provides a bump stop which is capable of absorbing impact forces associated with being pushed or struck by a portion of the vehicle suspension, and then rapidly returning to an at rest position in order to absorb subsequent impact forces.

[0034] While in the embodiment shown a plurality of apertures 215 and a single shim 216 are used, it will be appreciated that alternative arrangements that also allow for fluid to flow from the second fluid chamber to the first fluid chamber, but not in reverse, with minimal resistance or rebound damping, are also intended to fall within the scope of this disclosure. For instance, in an alternate arrangement, the damper piston may be provided with one or more check valves.

[0035] It will be appreciated that the above described bump stop 1 provides a solution where a single gas volume can be used to pressurise the hydraulic fluid (in order to accommodate thermal expansion and reduce cavitation) and to provide a restorative force, where the volume of the gas is substantially unaffected by a displacement of hydraulic fluid caused by the volume of the piston rod 220 entering the damper cylinder 100.

[0036] It will also be appreciated that the above described bump stop 1 provides a compact and simple solution where the outer cylinder is capable of accommodating both compressible gas and non- compressible fluid.

[0037] In an alternate embodiment, such as that shown in Figure 9, the bump stop may also operate without a separator piston separating the hydraulic fluid and gas volume. It will be appreciated that without the separator piston, the pressurised gas will still accommodate thermal expansion and contraction of the hydraulic fluid. [0038] In yet a further embodiment (not shown) it is envisaged that the end cap 130 does not have to be configured to provide an internal seal between the second, third and fourth fluid chambers. Particularly in an embodiment such as that shown in Figure 9, where the hydraulic fluid and gas are already in direct communication in the fifth fluid chamber 15.

[0039] It will be appreciated that in such embodiments where the gas and hydraulic fluid are not separated, the bump stop will have to be oriented such that the gas substantially remains in the fourth and fifth fluid chambers. It will further be appreciated that such embodiments will require less components, and therefore potentially cost and weigh less, but at the expense of increased likelihood of cavitation.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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.