Pressure relief for a hydraulic compression stop device

A damper having a pressure tube, a piston, and a hydraulic compression stop assembly. The piston is arranged in sliding engagement inside the pressure tube. The piston divides the pressure tube into a first working chamber and a second working chamber and the piston is coupled to a piston rod that extends through the first working chamber. The hydraulic compression stop assembly is positioned in the second working chamber. The hydraulic compression stop assembly includes a sleeve, a plunger, a biasing member, and a pressure relief valve. The plunger is arranged in sliding engagement with the sleeve and can therefore move between an extended position and a retracted position. The biasing member biases the plunger towards the extended position and the pressure relief valve relieves excessive fluid pressure inside the hydraulic compression stop assembly.

FIELD

The present disclosure relates generally to dampers for vehicle suspension systems and more particularly to dampers with hydraulic compression stops.

BACKGROUND

In general, dampers are used to absorb and dissipate the impact and rebound movement of a vehicle's suspension system and keep the vehicle's tires in contact with the ground. Dampers are typically installed alongside a spring (as a stand-alone shock absorber) or inside a spring (as part of a coil-over shock and strut assembly) and placed in front and rear suspension systems. The damper is attached to a frame member or other sprung component of the vehicle by an upper mount and is attached to a suspension member or other unsprung component of the suspension by a lower mount.

Conventional hydraulic dampers include a pressure tube, which acts as a hydraulic cylinder. A piston is slidably disposed within the pressure tube with the piston separating the interior of the pressure tube into two fluid chambers. A piston rod is connected to the piston and extends out of one end of the pressure tube where it is adapted for attachment to a sprung or unsprung component of the vehicle. The opposite end of the pressure tube is adapted for attachment to the other sprung or unsprung component of the vehicle. A first valving system, typically incorporated within the piston, functions to create a damping load during the damper's extension (i.e., rebound stroke). A second valving system, typically incorporated within the piston in a mono-tube damper and in a base valve assembly in a dual-tube damper, functions to create a damping force during the damper's compression stroke.

Many hydraulic dampers include features designed to prevent the piston and piston rod from coming to an abrupt stop at the end of a compression stroke. In some instances, a simple bumper is used to cushion the piston and the piston rod when they reach the end of a compression stroke. More sophisticated compression stops have been developed that utilize a hydraulic plunger to slow the movement of the piston and the piston rod at the end of a compression stroke by increasing (i.e., ramping up) the damping force acting on the piston. Adding a hydraulic compression stop to a passive damper typically requires significant changes or modifications to the structure of the damper and to manufacturing and assembly processes. Accordingly, there remains a need for improved hydraulic compression stops that can be more easily incorporated into existing passive damper designs without requiring significant changes or modifications to the damper. There also remains a need for hydraulic compression stops with improved noise, vibration, and harshness (NVH) performance compared to existing designs.

SUMMARY

In accordance with one aspect of the present disclosure, a damper having a pressure tube, a piston, and a hydraulic compression stop assembly is provided. The pressure tube extends annularly about a damper axis and longitudinally between a first pressure tube end and a second pressure tube end. The piston is arranged in sliding engagement inside the pressure tube. The piston divides the pressure tube into a first working chamber and a second working chamber and the piston is coupled to a piston rod that extends through the first working chamber. The hydraulic compression stop assembly is positioned in the second working chamber. The hydraulic compression stop assembly includes a sleeve, a plunger, and a biasing member. The plunger is arranged in sliding engagement with the sleeve and can therefore move (i.e., slide) between an extended position and a retracted position. The biasing member biases the plunger towards the extended position.

The hydraulic compression stop assembly extends longitudinally between a first assembly end and a second assembly end. The second assembly end is positioned adjacent to the second pressure tube end. The plunger of the hydraulic compression stop assembly extends longitudinally between a first plunger end and a second plunger end. The first plunger end is configured to contact the piston and/or the piston rod at the end of a compression stroke of the damper. The second plunger end is arranged in sliding engagement inside the sleeve. Together, the sleeve and the plunger of the damper cooperate to define a hydraulic chamber inside the hydraulic compression stop assembly. The positive preload on the biasing member is advantageous because it provides for a more gradual increase in damping force when the piston and/or piston rod first contacts the plunger and begins to move the plunger from the extended position towards the retracted position.

A pressure relief valve is located at the second assembly end of the hydraulic compression stop assembly. The pressure relief valve is positioned to open and close one or more pressure relief passageways that are constructed to communicate fluid from the hydraulic chamber inside the hydraulic compression stop assembly to the second working chamber when fluid pressure inside the hydraulic chamber exceeds a pre-determined threshold pressure. The pressure relief valve helps prevent damage to the hydraulic compression stop assembly due to excessive internal pressure which may result in the hydraulic chamber of the hydraulic compression stop assembly during high rod speed events. Such excessive internal pressures can arise because the hydraulic compression stop assembly is designed to create a fixed-area flow restriction, so the pressure inside the hydraulic chamber of the hydraulic compression stop assembly continuously increases with the flow rate squared. By limiting the peak pressure inside the hydraulic chamber of the hydraulic compression stop assembly, the addition of the pressure relief valve allows the hydraulic compression stop assembly to be tuned to improve ride performance and quality during low and moderate rod speed events while not breaking during high rod speed events. The pressure relief valve also allows for the hydraulic compression stop assembly to be economically made, such as from relatively thin-walled plastic materials without risk of structural failure.

In accordance with another aspect of the present disclosure, the plunger of the hydraulic compression stop assembly includes a bumper cavity at the first plunger end that receives a bumper. The bumper is made of a compliant material and is configured to come into contact with and cushion the piston and/or the piston rod when the damper reaches the end of a compression stroke. The bumper cavity includes a side wall and the bumper has an outer circumferential surface that abuts the side wall of the bumper cavity. When the bumper is in an uncompressed state (i.e., before the bumper is pressed into the bumper cavity), the outer circumferential surface of the bumper is arranged at a non-parallel angle relative to the side wall of the bumper cavity. This geometry of the bumper creates radial compression in the compliant material of the bumper and an interference fit between the outer circumferential surface of the bumper and the side wall of the bumper cavity when the bumper is pressed into the bumper cavity. This feature helps retain the bumper in the bumper cavity and prevents movement of the bumper relative to the side wall of the bumper cavity during movement of the piston within the pressure tube during operation of the damper, particularly during rebound strokes.

Together, these features provide for a hydraulic compression stop assembly that can easily be incorporated into an existing passive damper without significant changes or modifications. These features also provide improved noise, vibration, and harshness (NVH) performance over traditional compression stop designs.

DETAILED DESCRIPTION

Referring to the Figures, wherein like numerals indicate corresponding parts throughout the several views, a damper20is illustrated.

With reference toFIG.1, the damper20includes a pressure tube30, a piston32, a piston rod34, and optionally, a reserve tube36and a base valve assembly38. The piston32is slidably disposed within the pressure tube30and divides the pressure tube30into a first working chamber46and a second working chamber48. A seal49is disposed between the piston32and the pressure tube30to permit sliding movement of the piston32with respect to the pressure tube30without generating undue frictional forces as well as sealing the first working chamber46from the second working chamber48. The piston rod34extends between a first piston rod end35and a second piston rod end37. The second piston rod end37is attached (i.e., coupled) to the piston32. The piston rod34extends through the first working chamber46and through a rod guide assembly50. Accordingly, the first piston rod end35is always positioned outside the pressure tube30. A seal assembly51seals the interface between the rod guide assembly50and the piston rod34.

The first piston rod end35is adapted to be secured to either a sprung or unsprung component of a vehicle (not shown). Because the piston rod34extends only through the first working chamber46and not the second working chamber48, extension and compression movements of the piston32with respect to the pressure tube30causes a difference in the amount of fluid displaced in the first working chamber46compared to the amount of fluid displaced in the second working chamber48. The difference in the amount of fluid displaced is known as the “rod volume” and during extension movements it flows through the base valve assembly38. During a compression movement of the piston32with respect to the pressure tube30, valving62within the piston32allows fluid to flow from the second working chamber48to the first working chamber46while the “rod volume” of fluid flow flows through the base valve assembly38.

The base valve assembly38is positioned at a base end26of the damper20which is adapted to be secured to either a sprung or unsprung component of the vehicle (not shown) and controls the flow of fluid between the second working chamber48and a reservoir chamber52positioned radially between the pressure tube30and the reserve tube36. When the damper20extends in length, an additional volume of fluid is needed in the second working chamber48due to the rod volume and fluid will flow from the reservoir chamber52to the second working chamber48through the base valve assembly38. When the damper20compresses in length, an excess of fluid must be removed from the second working chamber48due to the rod volume. Thus, fluid will flow from the second working chamber48to the reservoir chamber52through the base valve assembly38.

The piston32comprises a piston body60, a first compression valve assembly62, a first extension valve assembly64, and a nut66. The nut66is threaded onto the second piston rod end37to secure the first compression valve assembly62, the piston body60, and the first extension valve assembly64to the piston rod34. The piston body60defines a first plurality of compression passages68and a first plurality of extension passages70. The base valve assembly38comprises a valve body72, a second extension valve assembly74, and a second compression valve assembly76. The valve body72defines a second plurality of extension passages78and a second plurality of compression passages80.

During a compression stroke, fluid in the second working chamber48is pressurized causing fluid pressure to react against the first compression valve assembly62. The first compression valve assembly62therefore acts as a check valve between the second working chamber48and the first working chamber46. The damping characteristics of the damper20during a compression stroke can also be controlled by the base valve assembly38. The second compression valve assembly76controls the flow of fluid from the second working chamber48to the reservoir chamber52during a compression stroke. The second compression valve assembly76can be designed as a safety hydraulic relief valve, a damping valve, or the second compression valve assembly76can be removed altogether from the base valve assembly38.

During an extension stroke, the first plurality of compression passages68are closed by the first compression valve assembly62and fluid in the first working chamber46is pressurized causing fluid pressure to react against the first extension valve assembly64. The first extension valve assembly64is designed as either a safety hydraulic relief valve, which will open when the fluid pressure within the first working chamber46exceeds a predetermined limit, or as a pressure valve working to change the shape of the damping curve. The damping characteristics of the damper20during an extension stroke can be controlled by the first extension valve assembly64. Replacement flow of fluid into the second working chamber48during an extension stroke flows through the base valve assembly38. Fluid in the second working chamber48is reduced in pressure causing fluid in the reservoir chamber52to flow to the second working chamber48through the second plurality of extension passages78. The second extension valve assembly74therefore acts as a check valve between the reservoir chamber52and the second working chamber48. The damping characteristics of the damper20during an extension stroke can be controlled by the first extension valve assembly64.

Although a dual-tube damper20is illustrated inFIG.1, it should be appreciated that the subject disclosure is equally applicable to mono-tube dampers. Such mono-tube dampers lack the reserve tube36and the base valve assembly38shown inFIG.1.

The pressure tube30has a cylindrical shape, which extends annularly about a damper axis82and longitudinally between a first pressure tube end84and a second pressure tube end86. The first pressure tube end84mates with the rod guide assembly50and the base valve assembly38is positioned in the second pressure tube end86. It should be appreciated that when the terms “longitudinal” and “longitudinally” are used herein, they are meant to describe structures, dimensions, directions, or movements that are substantially parallel to the damper axis82.

With additional reference toFIGS.2-4, the damper20includes a hydraulic compression stop assembly88positioned inside the second working chamber48. The hydraulic compression stop assembly88includes a sleeve90, a plunger92, and a biasing member94. The plunger92is arranged in sliding engagement with the sleeve90and can therefore move (i.e., slide) between an extended position and a retracted position. The biasing member94biases the plunger92towards the extended position.

The sleeve90of the hydraulic compression stop assembly88is positioned inside the second pressure tube end86. The sleeve90extends longitudinally between a first sleeve end96and a second sleeve end98. The second sleeve end98is positioned adjacent to the second pressure tube end86, while the first sleeve end96is positioned closer to the piston32. The plunger92of the hydraulic compression stop assembly88extends longitudinally between a first plunger end100and a second plunger end102. The first plunger end100is configured to contact the piston32, second piston rod end37, and/or nut66during a compression stroke. The second plunger end102is arranged in sliding engagement inside the sleeve90. The plunger92also includes a spring cavity104that is open at the second plunger end102. The biasing member94of the hydraulic compression stop assembly88extends into the spring cavity104of the plunger92and applies a biasing force to the plunger92, which biases the plunger92towards the extended position (i.e., towards the piston32). Although other configurations are possible, in the illustrated embodiment, the biasing member94is a coil spring.

The hydraulic compression stop assembly88includes a base adapter106that is fixedly attached to the second sleeve end98. For example, the base adapter106may be welded to the second sleeve end98. A portion of the base adapter106is press-fit into the second pressure tube end86, which holds the hydraulic compression stop assembly88in place inside the second working chamber48. A portion of the base valve assembly38is received in the base adapter106. The base adapter106includes a plurality of bypass openings108, which allow fluid to flow freely between the second working chamber48and the base valve assembly38.

Together, the sleeve90, the spring cavity104in the plunger92, and the base adapter106cooperate to define a hydraulic chamber110inside the hydraulic compression stop assembly88. The biasing member94is positioned inside the hydraulic chamber110and extends longitudinally between a first biasing member end112and a second biasing member end114. The first biasing member end112is positioned inside the spring cavity104and is arranged in contact with the plunger92, while the second biasing member end114is arranged in contact with the base adapter106. The spring cavity104in the plunger92allows a longer, stiffer spring to be used for the biasing member94and prevents the biasing member94from compressing to its dead-length when the plunger92reaches the retracted position. This reduces shear stress in the spring. In the illustrated example, the spring cavity104has a frusto-conical shape that opens gradually with an increasing diameter moving towards the second plunger end102such that the biasing member94does not become constrained within (i.e., does not bind in) the spring cavity104when the plunger92moves to the retracted position.

As best seen inFIG.5, the second plunger end102includes a sealing surface116that is arranged in sliding contact with the sleeve90. An annular channel118is provided in the sealing surface116in the form of an annular groove. The annular channel118receives a sealing ring120, which includes an outside surface122that is arranged in contact with the inside of the sleeve90and an inside surface124that faces the spring cavity104. One or more holes126extend through the second sleeve end98and radially between the annular channel118and the spring cavity104. As a result, fluid pressure in the hydraulic chamber110of the hydraulic compression stop assembly88operates to push radially outwardly against the inside surface124of the sealing ring120, which presses and holds the outside surface122of the sealing ring120against the sleeve90.

Again referring toFIGS.2-5, the sealing surface116of the plunger92is defined by a plunger flange128that extends annularly about the second plunger end102. A top hat130is fixedly attached to the first sleeve end96. By way of example and without limitation, the top hat130may be welded to the first sleeve end96. The top hat130extends radially inwardly from the first sleeve end96. As a result, the top hat130and the plunger flange128come into contact with one another in an interleaving arrangement when the plunger92is in the extended position. Accordingly, the top hat130acts as a travel stop for the plunger92. The top hat130is placed at a location where the biasing member94is kept under a positive preload when the plunger92reaches the extended position. In other words, the biasing member94remains partially compressed even when the plunger92is in the extended position and will never reach its uncompressed, natural length after the top hat130is welded in place.

Optionally, the top hat130may also extend radially outwardly from the first sleeve end96towards the pressure tube30. In accordance with this arrangement, an outer circumference132of the top hat130will contact the pressure tube30if the hydraulic compression stop assembly88begins to tilt inside the pressure tube30. As a result, the top hat130defines a hydraulic compression stop assembly tilt limit that helps maintain the hydraulic compression stop assembly88in a substantially centered orientation within the pressure tube30.

The sleeve90of the hydraulic compression stop assembly88may also include a plurality of orifices134that are spaced longitudinally apart from one another such that the number of the orifices134that communicate fluid between the hydraulic chamber110and the second working chamber48decreases when the plunger92moves from the extended position to the retracted position. This occurs as the sealing surface116of the plunger92slides past the orifices134leaving fewer and fewer orifices134in fluid communication with the hydraulic chamber110as the plunger92approaches the retracted position. The decrease in the number of orifices134available to communicate fluid from the hydraulic chamber110to the second working chamber48, increases the flow restriction, and creates a progressive increase in damping force as the plunger92approaches the retracted position. If a progressive damping increase is not necessary or desired, the orifices134can be moved to alternative locations in the sleeve90, base adapter106, plunger92, and/or top hat130.

The hydraulic compression stop assembly88described herein reduces the end stop loads transferred to the vehicle body for improved ride comfort by hydraulically generating an additional damping force at the end of compression strokes of the damper20. Advantageously, the particular configuration of the hydraulic compression stop assembly88described herein can be constructed at a low cost and can be installed in conventional, passive dampers without requiring significant changes or modifications to the structure of the damper or to manufacturing and assembly processes. The welding of the top hat130to the first sleeve end96and the base adapter106to the second sleeve end98can be performed in an off-line manufacturing process where the hydraulic compression stop assembly88is constructed separately from the damper20. The pre-assembled hydraulic compression stop assembly88can then be press-fit into the second pressure tube end86during assembly of the damper20on an assembly line. This ability to weld the hydraulic compression stop assembly88off-line decreases manufacturing costs. Because welding operations of the hydraulic compression stop assembly88can be performed off-line, capacitive discharge (CD) welding can be used to further reduce manufacturing costs.

With additional reference toFIG.6, the first plunger end100includes a bumper cavity136. The bumper cavity136in the first plunger end100receives a bumper138that is made of a compliant material. For example and without limitation, the bumper138may be made of an elastomeric material. The bumper cavity136includes a side wall140and an end wall142. The bumper138has a ring-like shape and includes a central bore144that is arranged in fluid communication with an intake passageway146that extends longitudinally through the plunger92between the bumper cavity136and the spring cavity104.

The bumper138has an inner circumferential surface148, an outer circumferential surface150, a first abutment surface152, and a second abutment surface154. The first abutment surface152of the bumper138is configured to come into contact with and seal against the piston32, second piston rod end37, and/or nut66when the damper20approaches the end of a compression stroke. The second abutment surface154of the bumper138is arranged in contact with the end wall142of the bumper cavity136. Normally, fluid can freely flow between the second working chamber48and the hydraulic chamber110of the hydraulic compression stop assembly88via the central bore144in the bumper138and the intake passageway146in the plunger92. However, contact between the first abutment surface152of the bumper138and the piston32, second piston rod end37, and/or nut66during a compression stroke closes off the central bore144in the bumper138and therefore the intake passageway146in the plunger92. As a result, the only flow path through which fluid in the hydraulic chamber110can flow when the piston32, second piston rod end37, and/or nut66is in contact with the hydraulic compression stop assembly88during a compression stroke is through the open orifices134in the sleeve90. The bumper138cushions the impact of the piston32, second piston rod end37, and/or nut66on the first plunger end100and therefore provides improved noise, vibration, and harshness (NVH) performance.

Still referring toFIG.6, the outer circumferential surface150of the bumper138abuts the side wall140of the bumper cavity136. The outer circumferential surface150of the bumper138is arranged at a non-parallel angle156relative to the side wall140of the bumper cavity136when the bumper138is in an uncompressed state (i.e., before the bumper138is pressed into the bumper cavity136). Although other configurations may be possible, the non-parallel angle156may be in the range of a 2 to 10 degree difference between the angle156of the outer circumferential surface150of the bumper138and the side wall140of the bumper cavity136relative to the damper axis82. Because there is a difference between the angle156of the outer circumferential surface150of the bumper138and the side wall140of the bumper cavity136relative to the damper axis82, radial compression in the compliant material of the bumper138occurs when the bumper138is pressed into the bumper cavity136, which creates an interference fit between the outer circumferential surface150of the bumper138and the side wall140of the bumper cavity136. This geometry helps retain the bumper138in the bumper cavity136during operation of the damper20. Absent this geometry, the bumper138could lift out of the bumper cavity136during rebound strokes as a result of fluid flow inside the damper20and/or where the bumper138tries to stick to the piston32, second piston rod end37, and/or nut66, particularly during cold operating conditions. Line148′ illustrates the inner circumferential surface and line150′ illustrates the outer circumferential surface of the bumper138in an uncompressed state.

In the illustrated example, the side wall140of the bumper cavity136is parallel to the damper axis82and the outer circumferential surface150of the bumper138is arranged at an angle156ranging from 2 to 10 degrees relative to the damper axis82. In other words, inFIG.6, the side wall140of the bumper cavity136has a cylindrical shape and the bumper138, in an uncompressed state, has a frusto-conical (i.e., tapered) shape with an outer diameter that gradually decreases moving from the first abutment surface152to the second abutment surface154. In addition, the inner circumferential surface148of the bumper138may be arranged at the same non-parallel angle156as the outer circumferential surface150to adjust for geometric distortions caused by the radial compression of the compliant material of the bumper138when the bumper138is pressed into the bumper cavity136. This helps orient the inner circumferential surface148of the bumper138at a substantially parallel orientation to the damper axis82after the radial compression occurs. Absent this feature, the inner circumferential surface148of the bumper138could shift and reduce the diameter of the central bore144after the bumper138is pressed into the bumper cavity136, ultimately restricting the fluid flow through the intake passageway146.

Optionally, the bumper138may also include a tapered surface158extending between the inner circumferential surface148and the first abutment surface152, which may be configured to be spaced away from the second piston rod end37when the piston32and/or nut66is arranged in contact with the first abutment surface152of the bumper138. The diameter of the nut66may also be increased over those used in a conventional damper to provide more contact surface area between the nut66and the first abutment surface152of the bumper138.

While not shown, it should also be appreciated that an alternative arrangement is possible where the outer circumferential surface150of the bumper138is parallel to the damper axis82and the side wall140of the bumper cavity136is arranged at an angle156ranging from 2 to 10 degrees relative to the damper axis82. In other words, an alternative arrangement is possible where the outer circumferential surface150of the bumper138, in an uncompressed state, has a cylindrical shape and the side wall140of the bumper cavity136has an inner diameter that gradually decreases moving from the end wall142of the bumper cavity136to the first plunger end100.

FIGS.7-11illustrate another exemplary damper20′, with a hydraulic compression stop assembly88′ of an alternative configuration. Many of the elements of the damper20′ shown inFIGS.7-11are the same as the elements of the damper20shown inFIGS.1-6and therefore share the same reference numbers. The elements inFIGS.7-11that are new, different, or have been modified are labeled with reference numbers where a prime (′) annotation has been appended after the reference numeral.

Like in the previously described embodiment, the damper20′ illustrated inFIGS.7-11includes a pressure tube30, piston32arranged in sliding engagement inside the pressure tube30, and piston rod34coupled to the piston32. Although other configurations are possible, in the illustrated example, a nut66fixedly couples the piston32to the piston rod34such that the piston32, piston rod34, and nut66form a piston rod assembly67. The pressure tube30extends longitudinally between a first pressure tube end84and a second pressure tube end86. The piston32divides the pressure tube30into a first working chamber46positioned between the piston32and the first pressure tube end84and a second working chamber48positioned between the piston32and the second pressure tube end86. A reserve tube36extends annularly about the pressure tube30to define a reservoir chamber52that is positioned radially between the reserve tube36and the pressure tube30.

The hydraulic compression stop assembly88′ is positioned in the second working chamber48and extends longitudinally between a first assembly end160′ and a second assembly end162′. The second assembly end162′ is positioned closer to the second pressure tube end86than the first assembly end160′. The hydraulic compression stop assembly88′ illustrated inFIGS.7-11includes a sleeve90′, a plunger92′, a biasing member94′, a base adapter106′, and a pressure relief valve164′.

Like in the previously described embodiment, the plunger92′ is arranged in sliding engagement with the sleeve90′ for movement between an extended position and a retracted position. The plunger92′ extends longitudinally between a first plunger end100′ and a second plunger end102′. The first plunger end100′ is configured to contact the piston32and/or the piston rod34during a compression stroke and the second plunger end102′ is arranged in sliding engagement inside the sleeve90′. The sleeve90′ has a tubular shape and extends longitudinally between a first sleeve end96′ and a second sleeve end98′.

The base adapter106′ is fixedly attached to the second sleeve end98′ and includes a base adapter wall166′. Together, the sleeve90′, plunger92′, and base adapter wall166′ cooperate to define a hydraulic chamber110′ inside the hydraulic compression stop assembly88′. The base adapter wall166′ includes a first surface168′ that faces the hydraulic chamber110′ of the hydraulic compression stop assembly88′ and a second surface170′ opposite the first surface168′. Bypass openings108′ extend through the base adapter wall166′. The base adapter106′ further includes a first shoulder172′ that is fixedly attached to the second sleeve end98′ and a second shoulder174′ that is sized to mate with the second pressure tube end86in a press fit. By way of example and without limitation, the first shoulder172′ of the base adapter106′ may be welded to the second sleeve end98′.

The biasing member94′ biases (i.e., pushes) the plunger92′ towards the extended position, where the plunger92′ is positioned further from the second pressure tube end86than it is in the retracted position. The biasing member94′ extends longitudinally between a first biasing member end112′ and a second biasing member end114′. The biasing member94′ is positioned inside the hydraulic chamber110′ such that the second biasing member end114′ is arranged in contact with the base adapter wall166′.

The plunger92′ includes a spring cavity104′ that receives the first biasing member end112′. Although other shapes are possible, in the example illustrated inFIGS.7-11, the spring cavity104′ includes a first cavity portion176′ that has a first diameter178′ and a second cavity portion180′ that has a second diameter182′ that is larger than the first diameter178′. The second cavity portion180′ is positioned at the second plunger end102′ and receives the first biasing member end112′.

The plunger92′ includes an intake passageway146′ that extends through the first plunger end100′. The intake passageway146′ is constructed to openly communicate fluid between the second working chamber48and the hydraulic chamber110′ inside said hydraulic compression stop assembly88′ except when the piston rod assembly67(i.e., the piston32, piston rod34, and/or nut66) come into contact with the first plunger end100′, thereby closing off the intake passageway146′.

The sleeve90′ of the hydraulic compression stop assembly88′ may include a plurality of orifices134′ that are spaced longitudinally apart from one another such that the number of the orifices134′ that communicate fluid between the hydraulic chamber110′ and the second working chamber48decreases when the plunger92′ moves from the extended position to the retracted position. As previously explained, the decrease in the number of orifices134′ available to communicate fluid from the hydraulic chamber110′ to the second working chamber48, increases the flow restriction, and creates a progressive increase in damping force as the plunger92′ approaches the retracted position.

The first plunger end100′ includes a bumper cavity136′ that receives a bumper138′ that is made of a resilient material. The bumper138′ has a central bore144′ that is arranged in fluid communication with the intake passageway146′ of the plunger92′. As shown inFIG.9, the bumper cavity136′ has a cavity depth184′ and the bumper138′ has a bumper height186′. Although other configurations are possible, the geometry of the bumper cavity136′ and the bumper138′ may be selected such that the bumper height186′ is greater than the cavity depth184′ to limit the maximum amount the bumper138′ can be compressed before the side wall140′ of the bumper cavity136′ takes the impact load of the piston rod assembly67(i.e., the piston32, piston rod34, and/or nut66) at the end of a compression stroke. It should be appreciated that in accordance with such an arrangement, only a portion of the bumper138′ protrudes from the bumper cavity136′.

The damper20′ includes a base valve assembly38that is positioned at the second pressure tube end86. At least part of the base valve assembly38is received in the base adapter106′. Thus, an intermediate chamber188′ is created that is positioned longitudinally between the base valve assembly38and the base adapter wall166. This intermediate chamber188′ is disposed in fluid communication with the second working chamber48via the bypass openings108′. The base valve assembly38is arranged to control fluid flow between the intermediate chamber188′ and the reservoir chamber52that compensates for changes in the volume of fluid displaced by the piston rod34(i.e., rod volume) during compression and rebound strokes.

The base adapter106′ includes one or more pressure relief passageway190′ that extend through the base adapter wall166′ from the hydraulic chamber110′ to the intermediate chamber188′. The pressure relief valve164′ is located at the second assembly end162′ of the hydraulic compression stop assembly88′ and is positioned to open and close the pressure relief passageway(s)190′. The pressure relief valve164′ in the illustrate examples is a passive valve that is constructed such that the pressure relief passageway(s)190′ communicate fluid from the hydraulic chamber110′ to the intermediate chamber188′ and thus the second working chamber48when fluid pressure inside the hydraulic chamber110′ exceeds a pre-determined threshold pressure. This pre-determined threshold pressure can be tuned based on vehicle specific requirements, the type of impacts the hydraulic compression stop assembly88′ is designed to attenuate, and the geometry and strength of the hydraulic compression stop assembly88′.

In the example illustrated inFIGS.7-11, the pressure relief valve164′ includes a spring-disc stack192′ that is arranged in abutting contact with the second surface170′ of the base adapter wall166′. Although other configurations are possible, in the illustrated embodiment, a rivet194′ holds the center of the spring-disc stack192′ against the second surface170′ of the base adapter wall166′. The spring-disc stack192′ flexes away from the second surface170′ of the base adapter wall166′ at its periphery to open the pressure relief passageway(s)190′ when the fluid pressure in the hydraulic chamber110′ of the hydraulic compression stop assembly88′ exceeds the predetermined threshold pressure. The pressure relief valve164′ therefore helps prevent damage to the hydraulic compression stop assembly88′ due to excessive internal pressure in the hydraulic chamber110′. Such a condition can occur during high rod speed events because the fluid pressure inside the hydraulic chamber110′ continuously increases with the fluid flow rate squared. By limiting the peak pressure inside the hydraulic chamber110′ of the hydraulic compression stop assembly88′, the addition of the pressure relief valve164′ allows the hydraulic compression stop assembly88′ to be tuned to improve ride performance and quality during low and moderate rod speed events while not breaking during high rod speed events. The pressure relief valve164′ also allows for certain components of the hydraulic compression stop assembly88′ to be more economically made. For example, the plunger92′, sleeve90′, and base adapter106′ may be made from relatively thin-walled plastic materials without risk of structural failure.

As best seen inFIG.11, the second plunger end102′ includes a bearing surface116′ that is arranged in sliding contact with the sleeve90′. The bearing surface116′ of the plunger92′ is defined by a plunger flange128′ that extends annularly about the second plunger end102′. The first sleeve end96′ includes one or more indentations195′ that may be formed by crimping or other manufacturing operations. The indentation(s)195′ come into contact with the plunger flange128′ when the plunger92′ is in the extended position and therefore act as a travel stop that retains the second plunger end102′ in the sleeve90′. Optionally, the indentation(s)195′ may be placed at locations where the biasing member94′ is kept under a positive preload when the plunger92′ reaches the extended position. In such an arrangement, the biasing member94′ remains partially compressed even when the plunger92′ is in the extended position and will never reach its uncompressed, natural length after final assembly.

An annular channel118′ is provided in the bearing surface116′ in the form of an annular groove. The annular channel118′ receives a sealing ring120′, which includes an outside surface122′ that is arranged in contact with the inside of the sleeve90′ and an inside surface124′ that faces the spring cavity104′. One or more holes126′ extend through the second sleeve end98′ and radially between the annular channel118′ and the spring cavity104′. The hydraulic chamber110′ of the hydraulic compression stop assembly88′ is arranged in fluid communication with the spring cavity104′, so fluid pressure operates to push radially outwardly against the inside surface124′ of the sealing ring120′, which presses and holds the outside surface122′ of the sealing ring120′ against the sleeve90′.

FIG.12illustrates another exemplary hydraulic compression stop assembly88″ with a pressure relief valve164″ of an alternative configuration. Many of the elements of the hydraulic compression stop assembly88″ shown inFIG.12are the same as the elements of the hydraulic compression stop assembly88′ shown inFIGS.7-11and therefore share the same reference numbers. The elements inFIG.12that are new, different, or have been modified are labeled with reference numbers where a prime (′) annotation has been appended after the reference numeral.

The pressure relief valve164″ illustrated inFIG.12includes a poppet196″ and a spring198″. The poppet196″ extends longitudinally through a hole200″ in the base adapter wall166″ in a clearance fit such that the poppet196″ can slide longitudinally relative to the base adapter wall166″. The poppet196″ includes a first poppet end202″ that is positioned in the hydraulic chamber110′ and a second poppet end204″, opposite the first poppet end202″, that is positioned in the intermediate chamber188′. The spring198″ is positioned longitudinally between the first poppet end202″ and a first surface168″ of the base adapter wall166″ such that the spring198″ holds the second poppet end204″ in abutting contact with a second surface170″ of the base adapter wall166″ until fluid pressure in the hydraulic chamber110′ of the hydraulic compression stop assembly88″ exceeds a predetermined threshold pressure that corresponds with a biasing force of the spring198″. When the fluid pressure in the hydraulic chamber110′ of the hydraulic compression stop assembly88″ exceeds the predetermined threshold pressure, the second poppet end204″ moves away from the second surface170″ of the base adapter wall166″ to open one or more pressure relief passageways190″ that extend through the base adapter wall166″, which operates to relieve (i.e., reduce/bleed out) the fluid pressure in the hydraulic chamber110′. As shown in the illustrated embodiment, the hole200″ may form the pressure relief passageway190″ in some configurations.

Many other modifications and variations of the present disclosure are possible in light of the above teachings and may be practiced otherwise than as specifically described while within the scope of the appended claims.