Bicycle suspension damping system

A bicycle including a suspension system operably positioned between the bicycle frame and at least one of the front wheel and rear wheel of the bicycle. The suspension system includes a damping system including a first valve and a second valve, which cooperate to provide desirable damping forces throughout a broad range of relative velocities of the suspension system, while also being relatively lightweight and compact. The first valve includes a first orifice and a first valve body configured to regulate fluid flow through the first orifice. The second valve includes a second orifice. In one arrangement, the second orifice is defined by the first valve body. In another arrangement, the second valve includes a second valve body configured to regulate fluid flow through the second orifice.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to vehicle suspension systems. More specifically, the present invention relates to an improved suspension damping system to be incorporated into the suspension system of a vehicle, such as a bicycle.

2. Description of the Related Art

Suspension systems, in general, produce both a spring force and a damping force in response to relative movement of movable portions of the suspension system. Suspension damping systems generally produce a damping force that varies with the relative velocity of the movable portions of the damping assembly. A goal in suspension design is to achieve desirable levels of damping force throughout the range of commonly experienced velocities of the suspension system. Attempts to fulfill this goal have met with varying degrees of success and typically include providing multiple damping circuits, each of which are primarily effective over only a portion of the total velocity range.

However, in connection with suspension damping systems applicable to bicycle suspension systems, an overriding design constraint is the relatively small physical space that is available for housing the damping system. In addition, because a bicycle generally is human-powered, another important design constraint is weight. That is, the overall size and weight of usable or marketable bicycle suspension systems are severely restricted in comparison to other vehicles, such as automobiles, for example. Due to such constraints, prior art bicycle suspension damping systems typically provide a desirable level of damping force during only a portion of the entire range of velocity of the suspension system. For example, some prior art bicycle damping systems provide a desirable level of damping force at low velocities but not at high velocities, while other prior art damping systems provide desirable damping force at high velocities but have undesirable characteristics at low velocities. Accordingly, what is needed is an improved bicycle damping system which conforms to the prevailing physical constraints of bicycle suspension systems and also provides a desirable level of damping force throughout a greater range of expected suspension system velocities than the prior art.

SUMMARY OF THE INVENTION

A preferred embodiment is a bicycle including a suspension damping assembly operably positioned between a frame of the bicycle and one of the front wheel and rear wheel of the bicycle. The suspension damping assembly includes a first fluid chamber and a second fluid chamber. A partition separates the first fluid chamber from the second fluid chamber. A first valve comprises a valve body and a first orifice defined by the partition. The first orifice is configured to permit fluid to flow between a first side of the partition and a second side of the partition. The valve body has a first position in which the valve body substantially prevents fluid flow from the first orifice between the partition and the valve body and a second position in which the valve body permits fluid flow from the first orifice between the partition and the valve body. A second valve comprises a second orifice defined by the valve body. The second valve is configured to permit fluid flow from a first side of the valve body to a second side of the valve body.

Another preferred embodiment is a bicycle including a suspension damping assembly operably positioned between a frame of the bicycle and one of the front wheel and rear wheel of the bicycle. The suspension damping assembly includes a first fluid chamber and a second fluid chamber. A partition separates the first fluid chamber from the second fluid chamber. A first valve is configured to permit fluid flow between the first fluid chamber and the second fluid chamber past the partition in a first direction. The first valve includes a first valve body and a first orifice defined by the damping assembly. The first orifice is configured to permit fluid flow between the first fluid chamber and the second fluid chamber. The first valve body is movable in response to fluid pressure between a first position in which the first valve body blocks the first orifice to substantially prevent fluid flow from the first orifice between the partition and the first valve body, and a second position in which the first valve body permits fluid flow from the first orifice between the partition and the first valve body. A second valve is configured to permit fluid flow between the first fluid chamber and the second fluid chamber past the partition in the first direction. The second valve includes a second valve body and a second orifice defined by the damping assembly. The second orifice is configured to permit fluid flow between the first fluid chamber and the second fluid chamber. The second valve body is movable in response to fluid pressure between a first position blocking the second orifice to substantially prevent fluid flow through the second orifice and a second position in which the second valve body permits fluid flow through the second orifice.

Yet another preferred embodiment is a bicycle including a suspension damping assembly operably positioned between a frame of the bicycle and one of the front wheel and rear wheel of the bicycle. The suspension damping assembly includes a first fluid chamber and a second fluid chamber. A partition separates the first fluid chamber from the second fluid chamber. A first valve is configured to permit fluid flow between the first fluid chamber and the second fluid chamber past the partition in a first direction. The first valve is movable between a first position in which fluid flow through the first valve is substantially prevented and a second position in which fluid flow through the first valve is permitted. A second valve is configured to permit fluid flow between the first fluid chamber and the second fluid chamber past the partition in the first direction. The second valve is movable between a first position in which fluid flow through the second valve is substantially prevented and a second position in which fluid flow through the second valve is permitted. The first valve is movable between the first position and the second position when the second valve is in either of the first position or the second position. Further, the second valve is movable between the first position and the second position when the first valve is in either of the first position or the second position.

Still another preferred embodiment is a bicycle including a suspension damping assembly operably positioned between the a frame of the bicycle and one of the front wheel and rear wheel of the bicycle. The suspension damping assembly includes a first fluid chamber and a second fluid chamber. A partition separates the first fluid chamber from the second fluid chamber. A first valve is configured to permit fluid flow between the first fluid chamber and the second fluid chamber past the partition in a first direction. The first valve is movable between a first position in which fluid flow through the first valve is substantially prevented, and a second position in which fluid flow through the first valve is permitted. A second valve is configured to permit fluid flow between the first fluid chamber and the second fluid chamber past the partition in the first direction. The second valve is movable between a first position in which fluid flow through the second valve is substantially prevented, and a second position in which fluid flow through the second valve is permitted. The damping assembly has at least a first mode in which the first valve is in the first position and the second valve is in the first position. The damping assembly has a second mode in which the first valve is in the first position and the second valve is in the second position. In addition, the damping assembly has a third mode in which the first valve is in the second position and the second valve is in the first position.

A further preferred embodiment is a bicycle including a suspension damping assembly operably positioned between a frame of the bicycle and one of the front wheel and rear wheel of the bicycle. The suspension damping assembly includes a tube defining a fluid chamber. A first piston is sealed with an interior surface of the tube and includes a first valve configured to selectively permit fluid flow from a first side of the first piston to a second side of the first piston. A second piston is sealed with an interior surface of the tube. The first and second pistons define a fluid chamber therebetween. The second piston defines a plurality of orifices configured to permit fluid flow from a first side of the second piston to a second side of the second piston. A movable plate is movable between a first position and a second position. In the first position, the plate does not block the plurality of orifices such that fluid flow between the first side of the second piston and the second side of the second piston is permitted at a first flow rate. In the second position, the plate blocks at least one of the plurality of orifices and does not block at least one of the plurality of orifices such that fluid flow between the first side of the second piston and the second side of the second piston is permitted at a second flow rate less than the first flow rate.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present bicycle suspension damping assembly are disclosed herein. Although the disclosed embodiments are well-suited for use in connection with bicycle suspension systems, it is contemplated that the present damping assembly may be adapted for use in other vehicles as well, such as motorcycles, automobiles, snowmobiles and all-terrain vehicles, for example. In addition, the specific embodiments of the damping assembly are often described herein using relative terms, such as “above,” “below,” “upward,” “downward,” “axial,” and “radial.” Such relative terminology is used for the convenience of describing the specific embodiments as oriented in the drawings of the present specification. Accordingly, such relative terms are not intended to limit the scope of the present invention.

FIG. 1illustrates a bicycle20including a frame assembly22. The bicycle frame assembly22includes a main frame24and a sub-frame26. The sub-frame26is pivotally supported relative to the main frame24. A shock absorber28extends between the main frame24and the sub-frame26and preferably is configured to provide both a spring force and a damping force that regulates relative movement between the main frame24and sub-frame26. The spring force tends to lengthen the shock absorber28and the damping force attenuates both compression and extension (or rebound) movement of the shock absorber28.

A forward end of the frame assembly22preferably supports a front suspension fork30for rotation about a steering axis AS. Similar to the shock absorber28, the front suspension fork30preferably provides both a spring force and a damping force, as is described in greater detail below.

A handlebar assembly32is connected to the upper end of the suspension fork30. A front wheel34of the bicycle20is rotatably supported by a lower end of the front suspension fork30. A central, upper portion of the frame assembly22supports a bicycle seat assembly36, including a seat post38and a saddle40.

A rear wheel42is rotatably supported by the sub-frame26of the frame assembly22. Thus, the rear wheel42is movable, along with the sub-frame26, relative to the main frame24. Movement of the rear wheel42and sub-frame26is regulated by the shock absorber28.

A lower, central portion of the frame assembly22supports a pedal crank assembly44for rotation about a crank axis AC. In the illustrated arrangement, the pedal crank assembly44is drivingly coupled to the rear wheel42by a chain drive transmission46. The chain drive transmission46preferably includes an endless drive chain48looped around one of a plurality of variably-sized gears, or chain rings50, of the pedal crank assembly44and one of a plurality of variably-sized gears, or cogs52, coupled to the rear wheel42.

A front derailleur54is configured to move the drive chain48to a selected one of the plurality of front chain rings50. Similarly, a rear derailleur56is configured to move the drive chain48to a selected one of the plurality of rear cogs52. By moving the drive chain48between varying combinations of the chain rings50and cogs52, a desired gear ratio may be selected from the plurality of available gear ratios. Although such a multi-speed chain drive arrangement is preferred for its efficiency and reliability, other suitable drive chain arrangements may also be used.

A front brake assembly58is configured to apply a braking force to the front wheel34. Similarly, a rear brake assembly60is configured to apply a braking force to the rear wheel42. Although disc-type brakes are shown, other suitable types of braking systems may also be used, such as cantilever-type brakes, for example. Preferably, rider controls62are provided on the handlebar assembly32to permit a rider of the bicycle20to control the front and rear derailleurs54,56and the front and rear brake assemblies58,60.

FIG. 2illustrates one fork leg assembly70of the front suspension fork30ofFIG. 1. Generally, the front suspension fork30will include a pair of fork leg assemblies70oriented to straddle the front wheel34. However, in other arrangements, only one fork leg assembly70may be provided, if desired. In addition, other suitable structures may also be employed, such as a linkage-type structure, as will be appreciated by one of skill in the art.

The illustrated fork leg assembly70includes an outer tube or fork leg72, and an inner tube or stanchion74. The fork leg72and the stanchion74are telescopically engaged with one another for relative movement along a longitudinal axis A of the fork leg assembly70. In the illustrated arrangement, the outer tube or fork leg72forms a lower end of the fork leg assembly70, while the stanchion74forms the upper end of the fork leg assembly70. In other arrangements, the relative positions may be reversed, such that the outer tube72is positioned relatively above the inner tube74.

The illustrated fork leg assembly70includes a damper assembly76positioned within an internal space defined by the fork leg72and stanchion74. The damper assembly76, as described in greater detail below, preferably is configured to provide a damping force that resists both compression movement and extension (or rebound) movement of the fork leg assembly70. In addition, preferably the front suspension fork30includes a suspension spring (not shown) configured to produce a spring force tending to extend the fork leg assembly70and resist compression of the fork leg assembly70. In some arrangements, the damping system of the front suspension fork30may be located in one fork leg assembly70, while the suspension spring may be located in the other fork leg assembly70. In alternative arrangements, each fork leg assembly70may include both a damper assembly76and a suspension spring. The suspension spring may be of any suitable construction, such as a coil spring or air spring arrangement, for example.

The damper assembly76preferably extends substantially the entire length of the fork leg assembly70and is coupled to both the fork leg72and the stanchion74. The damper assembly76may be connected to the fork assembly70by any suitable connection. For example, a lower end of the damper assembly76may be directly coupled to the fork leg72. In the illustrated arrangement, the upper end of the damper assembly76is connected to the stanchion74through a cap78. The cap78may be coupled to both the upper end of the damper assembly76and the stanchion74by a threaded connection, for example. As will be understood by those of skill in the art, the cap78may also include adjustment controls, such as adjustment levers or knobs, which permit adjustment of damping features of the damper assembly76, which are described in greater detail below.

With additional reference toFIG. 3, the illustrated damper assembly76includes a damper tube80and a piston rod82. The piston rod82and damper tube80are telescopically engaged with one another for relative compression (i.e., shortening) and extension (i.e., lengthening) movement. As described above, preferably the damper assembly76provides a damping force in response to both compression and extension movement between the damper tube80and the piston rod82. The damping force may vary for a given velocity between movement in a compression direction and movement in an extension direction.

As illustrated inFIG. 3, the piston rod82carries a damping piston assembly84on its lower end within the damper tube80. The damping piston assembly84is in a substantially sealed, sliding engagement with an interior surface of the damper tube80. Thus, the damping piston assembly84divides the interior of the damper tube80into a first fluid chamber86below the damping piston assembly84and a second fluid chamber88above the damping piston assembly84. The fluid chamber86reduces in volume in response to compression movement of the damper assembly76and is often referred to as the compression chamber. Similarly, the fluid chamber88reduces in volume in response to extension or rebound movement of the damper assembly76and is often referred to as the rebound chamber.

The damper assembly76also includes a compensator90which is configured to compensate for displacement of damping fluid within the damper tube80by an increasing volume of the piston rod82being present within the damper tube80as a result of compression of the damper assembly76. Thus, as the piston rod82occupies an increasing volume of the damper tube80upon compression, the compensator90reduces in volume, thereby increasing the volume of the compression chamber86to accommodate fluid that cannot be displaced to the rebound chamber88.

In the illustrated arrangement, the compensator90includes a bladder92which separates the compression chamber86from a gas chamber94. The gas within the gas chamber compresses such that the gas chamber94is able to reduce in volume to compensate for the damping fluid that cannot be displaced to the rebound chamber88during compression of the damper assembly76.

A valve96may be provided to provide access to the gas chamber94. The gas chamber94typically is filled with a pressurized gas, such as nitrogen, for example. Although a bladder-type compensator90is illustrated, other suitable constructions may also be used. For example, a floating piston may be provided within the damper290, which is in sealed, sliding engagement with the interior surface of the damper tube80to separate the compression chamber86from the gas chamber94. In addition, if desired, the compensator90may be located in a tube other than the damper tube80. Such reconstruction is referred to as a remote reservoir-type damping assembly.

One advantage of the illustrated construction of the damper assembly76is that the damper assembly76is a self-contained unit. That is, the damper assembly76may be removed from the fork leg72and stanchion74while remaining intact as a complete assembly. Accordingly, preferably no damping fluid is lost while removing the damper assembly76from the remainder of the fork leg assembly70thereby easing assembly and disassembly of the fork leg assembly70. However, in alternative arrangements, fluid from within the damper assembly76may communication with an interior space of the fork leg assembly70, between the fork leg72and the damper tube80. The interior space of the fork leg assembly70may be used as a reservoir for displaced damping fluid, as will be appreciated by one of skill in the art.

An additional advantage of the illustrated construction of the damper assembly76is that the damper tube80includes multiple sections. The illustrated damper tube80includes an upper section80aand a lower section80b. The upper section80adefines an entire portion of the interior surface of the damper tube80with which the damping piston assembly84engages throughout its complete range of relative movement, or suspension travel. Thus, the damping piston assembly84does not have to traverse a transition between the sections80a,80b, which may damage sealing structures between the damping piston assembly84and the damper tube80.

The lower section80bdefines a portion of the damper tube80which houses the compensator90. As described below, additional features (e.g., a base valve assembly) may be desired within the damper assembly76and may be provided within the lower section80bof the damper tube80. Thus, the upper section80a, along with the piston rod82and damping piston assembly84, may comprise a first sub-assembly and the lower section80b, along with the compensator90and/or other desired structures, may comprise a second sub-assembly. Providing separate sub-assemblies allows different upper and lower sections80a,80bto be combined together to produce different models of the damper assembly76with increased manufacturing flexibility and efficiency.

With reference toFIG. 4, the damping piston assembly84includes a damping piston100. The damping piston100is in sealed, slidable engagement with an interior surface of the damper tube80. A seal member102is interposed between a circumferential edge of the piston100and the interior surface of the damper tube80to create a substantially fluid tight seal between the piston100and the damper tube80. Accordingly, the piston100operates as a partition between the compression chamber86and the rebound chamber88.

As is described in detail below, the damping piston assembly84includes one or more fluid flow circuits which permit fluid flow between the compression chamber86and the rebound chamber88in a restricted manner to produce a damping force. Although the illustrated damping piston assembly84is supported on the piston rod82for movement within the damper tube80, in other arrangements fluid flow circuits similar to those described below may be provided within a stationary piston, or partition, between the compression chamber or rebound chamber and another fluid chamber, such as a reservoir chamber, for example.

The illustrated piston100is supported on a support shaft104, which extends along an axis of the damper assembly76. The support shaft104is coupled to a lower end of the piston rod82. The support shaft104passes through a central aperture of the piston100and includes a shoulder106which contacts a bottom surface of the piston100and supports the piston100from below.

The piston100includes one or more compression ports108extending axially through the piston100. The compression ports108preferably are orifices in the piston100which permit fluid to move through the piston from the compression chamber86to the rebound chamber88. Although two compression ports108are shown inFIG. 4, preferably a plurality of compression ports108is provided circumferentially around the piston100. For example, in one arrangement, eight such compression ports108may be equally spaced around the circumference of the piston100.

A valve body, referred to as a compression plate or first valve body110herein, is biased toward an upper surface of the piston100by a biasing arrangement112. The biasing arrangement112may comprise any suitable type of spring. In the illustrated arrangement, the biasing arrangement112is a plurality of disc springs114, also commonly referred to as Belleville washers. The disc springs114are provided in an alternating arrangement between the first valve body110and a shoulder116of the support shaft104such that the smaller diameter ends of the disc springs114are adjacent the first valve body110and shoulder116. In the illustrated arrangement, four disc springs114are provided. However, in other arrangements, a greater or lesser number of disc springs114may be provided, one or more of which may be nested within one another rather than alternating, as shown. In addition, other suitable types of springs may also be used, such as a coil spring, for example.

The first valve body110includes a substantially planar, plate-like portion118which preferably rests directly against an upper surface of the piston100. Desirably, the plate portion118has an outer diameter of a sufficient size that the plate portion118covers the compression ports108. A tubular shaft portion120of the first valve body110extends upwardly from the plate portion118and is slidably engaged with the support shaft104such that the first valve body110is configured for movement along the axis A of the piston rod82relative to the piston100.

The plate portion118of the first valve body110also defines at least one, and preferably a plurality, of orifices or flow ports122. Desirably, one port122is provided for each of the compression ports108. In addition, desirably, the ports122are aligned with the compression ports108. That is, at least a portion of the port122overlaps with the compression port108. Thus, the associated compression port108and port122are in fluid communication when the first valve body110is positioned against the piston100. Other arrangements to provide fluid communication between the ports122and the compression ports108of the piston100may also be used, such as an interconnecting channel, for example, a preferred embodiment of which is described below with reference toFIGS. 7 and 8.

The ports122are normally closed on their upper ends by a shim124, or stack comprising multiple shims, which may be referred to herein as a second valve body124. The shim or shim stack124is referred to herein in the singular, but it is to be understood that a stack of multiple shims is also covered by the singular reference, unless otherwise noted. In addition, additional shims or shim stacks discussed herein are referred to in the singular, but also encompass a stack of multiple shims.

The shim or second valve body124is configured to flex or bend about the axis A, in an upward direction from the first valve body110, to permit fluid flow through the port122in response to a pressure differential sufficient to bend the shim or second valve body124. The shim or second valve body124is held against an upper surface of the plate portion118of the first valve body110by a retention member, such as a stop126, which also defines a physical stop surface to limit upward bending movement of the shim or second valve body124, as illustrated inFIG. 5. Desirably, a retention member, such as a nut128, is engaged with the shaft portion120of the first valve body110to retain the shim or second valve body124and stop126against the upper surface of the plate portion118of the first valve body110.

Desirably, the ports122are smaller than the ports108such that fluid within the compression ports108presses against a portion of the lower surface of the first valve body110exposed to the ports108. Accordingly, if a pressure differential between the compression chamber86and the rebound chamber88is above a threshold level, the biasing force of the biasing assembly112will be overcome such that the first valve body110moves upwardly away from the piston100to permit fluid flow from the compression ports108between the piston100and the first valve body110, as illustrated inFIG. 6.

Desirably, in addition to fluid flow through the piston100, fluid flow between the compression chamber86and the rebound chamber88is also permitted through a central passage130of the support shaft104. Desirably, at its lower end, the passage130opens directly into the compression chamber86. At its upper end, the passage130communicates with the rebound chamber88through one or more radial ports132. Thus, the central passage130and radial ports132cooperate to permit fluid flow between the compression chamber86and the rebound chamber88.

Preferably, a one-way valve is provided to permit adjustment of fluid flow through the passage130in a compression direction (i.e., from the compression chamber86to rebound chamber88). In the illustrated arrangement, an adjustment shaft134extends through a hollow interior passage135of the piston rod82and through the passage130of the support shaft104. Preferably, the adjustment shaft134is connected at its upper end to the cap78(FIG. 2) of the fork leg assembly70to permit rotation of the shaft134relative to the piston rod82through a user control device, such as a lever or knob, for example. Preferably, the adjustment shaft134is configured such that rotation of the shaft134causes translation of the shaft relative to the piston rod82along the axis A.

The adjustment shaft134carries a valve body136that is configured to cooperate with a valve seat138defined at the lower end of the passage130of the support shaft104. Thus, the adjustment shaft134can be adjusted such that the valve body136restricts fluid flow from the compression chamber86into the passage130. Preferably, the valve body136is movable to a position relative to the valve seat138such that fluid flow from the compression chamber86into the passage130is completely or substantially completely prevented. Accordingly, a user of the suspension port30may adjust the compression characteristics of the damper assembly76by causing rotation of the adjustment shaft134. Those of ordinary skill in the art will appreciate that various possible user adjustment devices, such as knobs or levers, may be employed to permit external rotation of the adjustment shaft134. In addition, axial movement of the adjustment shaft134, or valve body136, may be accomplished by other suitable mechanisms, as well, which may not necessarily require rotation of the adjustment shaft134.

Desirably, the valve body136is in sliding engagement with a reduced diameter portion140of the adjustment shaft. A transition between the reduced diameter portion140and the remainder of the adjustment shaft134above the portion140defines a shoulder, which defines an upper limit for movement of the valve body136, as illustrated by the position of the valve body136inFIG. 4. A biasing member, such as a spring142is positioned between the valve body136and a stop144to normally bias the valve body136into its uppermost position. The stop144may be secured to the reduced diameter portion140of the adjustment shaft134by a retention member, such as a nut146. With such an arrangement, fluid pressure within the passage130may move the valve body136in a downward direction against the biasing force of the spring142to permit fluid flow from the rebound chamber88, past the valve body136, to the compression chamber86.

The operation of the illustrated damping piston assembly84is described with reference toFIGS. 4 through 6. As illustrated inFIG. 4, when there is no pressure differential between a compression fluid chamber86and the rebound fluid chamber88, or the pressure differential is not sufficient to overcome the biasing force of the shim or second valve body124, the shim or second valve body124remains in a position closing the ports122of the first valve body110. In addition, the first valve body110is biased against an upper surface of the piston100to close the compression ports108of the piston100. In the illustrated arrangement, the first valve body110directly contacts the piston100to close off the upper end of the compression ports108(along with the shim or second valve body124). However, in other arrangements, the compression ports108may be closed by a member other than the first valve body110, or the ports122may be defined by a member other than the first valve body110. In other words, the ports108and ports122, along with the structures that close the ports108and122may be constructed such that they do not share any common components.

With the ports108and122closed, compression fluid flow from the compression chamber86to the rebound chamber88may be permitted through the passage130of the support shaft104and the radial passages132. As described above, the adjustment shaft134may be moved along the axis A to alter a position of the valve body136relative to the valve seat138to increase or decrease a damping force provided by the damping piston assembly84at low compression velocities. Preferably, the adjustment shaft134may be adjusted such that the valve body136contacts the valve seat138to completely or substantially completely prevent fluid flow from the compression chamber86, through the passage130and radial passages132, to the rebound chamber88. If the valve body136is adjusted to prevent compression fluid flow through the passage130, compression movement of the damper assembly76will be prevented until the pressure differential between the compression chamber86and the rebound chamber88is sufficient to open the shims or second valve body124or move the compression plate first valve body110.

In addition to compression flow, the aperture120and radial ports132preferably also permit rebound fluid flow from the rebound chamber88to the compression chamber86. Desirably, the biasing force provided by the spring142against the valve body136is relatively small such that the valve body136may be pushed downwardly by fluid pressure of fluid within the passage130to permit fluid flow from the passage130into the compression chamber86with relatively little resistance provided by the valve body136. In addition, when the valve body136is positioned in contact with the valve seat138to substantially prevent compression flow through the passage130, rebound flow through to the passage130may still open the valve body136by overcoming the relatively small biasing force provided by the spring142. Thus, rebound flow through the passage130is permitted even when the adjustment shaft134is adjusted to substantially prevent compression flow through the passage130.

With reference toFIG. 5, as described above, when a compression force acting on the damper assembly76creates a pressure differential between the compression chamber86and the rebound chamber88of a threshold magnitude, the shim or second valve body124is biased away from the first valve body110to permit fluid flow from the compression fluid chamber86to the rebound fluid chamber88through the ports122of the first valve body110. At relatively low compression velocities (resulting in relatively low pressure differentials), the first valve body110remains in a position biased toward the piston100such that fluid flow between the compression plate and the piston100is completely or substantially completely prevented. In addition to fluid flow through the aperture122, as illustrated by the arrow C1, fluid flow through the passage130and radial ports132may also occur.

With reference toFIG. 6, if the pressure differential between the compression chamber86and the rebound chamber88reaches a threshold differential, the fluid pressure acting on the first valve body110and, specifically, the portion of the lower surface of the first valve body110exposed to the compression ports108, causes the first valve body110to move upward on the support shaft104against the biasing force of the disc springs114. As a result, fluid flow is permitted from the compression chamber86to the rebound chamber88through the compression ports108, as illustrated by the arrow C2. Furthermore, as illustrated inFIG. 6, when the first valve body110is lifted away from the piston100, the fluid pressure within the ports122equalizes with the fluid pressure above the shim or second valve body124such that the shim or second valve body124will move toward its closed position resting against the first valve body110. As illustrated by the arrow C2, the flow of fluid from the compression chamber86to the rebound chamber.88passes through the compression port108between the piston100and the first valve body110. In the illustrated arrangement, the fluid proceeds to flow in an upward direction between the first valve body110and the damper tube80. However, in other arrangements, other fluid flow paths may be utilized, such as through a passage between the first valve body110and support shaft104. Furthermore, although in the illustrated arrangement the first valve body110slides on the support shaft104, in an alternative arrangement the first valve body110may be configured to contact and slide along the interior surface of the damper tube80such that fluid flow may occur through an axial passage of the first valve body110, between the first valve body110and support shaft104, if provided.

As noted above, rebound fluid flow from the rebound chamber88to the compression chamber86occurs through the radial ports132and passage130. However, if desired, additional rebound fluid circuits may be provided, such as additional ports within the piston100, for example. Such an arrangement is illustrated inFIG. 8and described with reference thereto.

With the arrangement as illustrated inFIGS. 2 through 6, the damper assembly76is capable of providing a desirable level of damping force over a relatively wide range of compression velocities of the suspension fork30. Although the shim or second valve body124and first valve body110are configured to regulate compression fluid flow, in other arrangements, the same or similar elements may be provided to regulate rebound fluid flow in addition wherein the alternative to the illustrated shim or second valve body124and first valve body110. Furthermore, although the damping arrangement76has been described in connection with the front suspension fork30, the rear shock absorber28may be constructed to incorporate a damping system similar to the damper assembly76, as will be appreciated by one of skill in the art.

FIGS. 7 through 9illustrate a modification of the damping piston arrangement84ofFIGS. 2 through 6. For convenience, the same reference numerals are used inFIGS. 7 and 8to refer to the same or substantially similar components as those described above in connection withFIGS. 2 through 6. Thus, the damping piston assembly ofFIGS. 7 through 9is generally referred to by the reference numeral84and, except as noted below, is structurally and functionally similar to the damping piston arrangement84ofFIGS. 2 through 6.

Similar to the damping piston assembly84ofFIGS. 2-6, the damping piston assembly84ofFIGS. 7 and 8includes a main piston100in slidable engagement with a damper tube80. The main piston100is supported on a support shaft104, which is carried by a piston rod (not shown). The main piston100includes one or more compression ports108extending in an axial direction through the piston100.

A first valve body110is biased toward an upper surface of the piston100by a biasing arrangement112, preferably including a plurality of disc spring washers114. In the illustrated arrangement, the first valve body110rests directly on the upper surface of the piston100. The first valve body110also includes one or more ports122, which extend in an axial direction through the first valve body110. The ports122are closed at an upper end by a shim, or shim stack or second valve body124. In the illustrated arrangement, the shim or second valve body124rests directly against the upper surface of the first valve body110. A stop126retains the shim or second valve body124against the first valve body110. The stop126is secured to the first valve body110by a retention member, such as a nut128.

The support shaft104defines a central passage130, which is configured to permit fluid flow between the compression chamber86and the rebound chamber88. Radial ports132extend from an upper end of the passage130and open into the rebound chamber88. An adjustment shaft134extends through the passage130of the support shaft104and carries a valve body136which is configured to cooperate with a valve seat138at a lower end of the passage130. A spring142is supported on a stop144and biases the valve body136toward its uppermost position relative to the adjustment shaft134.

In addition, the damping piston assembly84ofFIGS. 7 and 8includes a secondary piston150, which is positioned below the piston100, also referred to as the “main” piston. The secondary piston150is supported by the support shaft104and, like the piston100, is in sliding engagement with an interior surface of the damper tube80. The secondary piston150is spaced along the axis A of the support shaft104from the main piston100such that a fluid chamber152is defined between the main piston100and the secondary piston150. Because the fluid chamber152is below the main piston100, it may be considered as a secondary compression chamber.

The secondary piston150includes a first port154, which extends axially through the secondary piston150. Preferably, multiple first ports154are provided. The secondary piston150also includes a second port156, which extends axially through the piston150and is positioned radially inward from the ports154. Preferably, multiple second ports156are provided. An upper end of the ports156are closed by one or more shims158.

With reference toFIG. 9, preferably the first ports154are relatively large compared to the second ports156. In the illustrated arrangement, each of the first ports154is elongate and arcuate in shape and extends a substantial distance around a circumference of the piston150. In the illustrated arrangement, three first ports154are provided and, together, extend around substantially the entire circumference of a periphery of the piston150.

In contrast, each of the second ports156preferably are generally circular in shape and significantly smaller than a single one of the first ports154. In the illustrated arrangement, eight of the second ports156are provided. The collective area of the second ports156is substantially less than the collective area of the first ports154. In other arrangements, a greater or lesser number of ports156may be provided. In addition, the ports156may be shapes other than circular.

In addition, the valve body136includes a plate-like portion160, which is oriented generally parallel to the secondary piston150. In the illustrated arrangement, the plate-like portion160is a unitary structure with the valve body136. However, in other arrangements, the valve body136and the plate160may be constructed from separate components.

The plate160includes one or more ports162, which extend axially through the plate160. Preferably, one port162is provided for each of the ports156of the secondary piston150. The ports162preferably are in radial alignment with the ports156of the secondary piston150. That is, preferably the ports162are located at a radius from the axis A that is the same or of a similar value as the radius of location of the ports156. In addition, the ports162may be in angular alignment with the ports156. However, in the illustrated arrangement, a lower surface of the secondary piston150defines an annular groove164which interconnects the ports156. Accordingly, fluid communication between the ports162of the plate160and the ports156is permitted regardless of the angular alignment between the ports162and156. In addition, an upper surface of the secondary piston150defines a similar groove166which interconnects upper ends of the ports156. Thus, the total area of fluid pressure acting on the shim158is generally equivalent to the area of the groove166, as opposed to simply the collective area of the ports156.

As described above, the plate160is movable along with the adjustment shaft134toward the lower surface of the secondary piston150to a position sufficient to inhibit fluid flow through the ports154, as illustrated in phantom line inFIG. 7. Preferably, the plate160may be positioned against a lower surface of the secondary piston150such that fluid flow through the ports154is substantially or completely prevented. When the plate160is moved to the closed position (as illustrated in phantom line), fluid flow is still permitted through the ports156. However, the fluid flow area of the collection of ports156is significantly less than the fluid flow area of the ports154. In addition, fluid flow through the ports156must overcome the biasing force of the shim158. As a result, for similar compression velocities of the damping piston arrangement84relative to the damper tube80, a significantly lower flow rate will occur when the plate160is in the upper or closed position compared to when it is in the lower or open position. As a result, a damper employing the damping piston arrangement84ofFIGS. 7 and 8will provide a significantly larger damping force when the plate160is in the closed position compared to when the plate160is in the open position. Because the plate160(and valve body136) is movable with the adjustment shaft134, an external user control device may be provided to permit a user of the suspension fork30to move the plate160between the open and closed position.

Preferably, an upper surface of the main piston100defines an annular groove170that is similar to the grooves164and166of the secondary piston150. That is, the groove170interconnects the plurality of compression ports108of the main piston100. As a result, fluid pressure is applied to the first valve body110over an annular area (minus the collective area of the ports122), rather than at the discrete locations of the ports108as in the arrangement ofFIGS. 2 through 6. In addition, it is not necessary for the ports122to be aligned with the compression ports108, which provides for simpler manufacturing of the damping piston arrangement84.

The damping piston arrangement84ofFIGS. 7 and 8also includes a mechanism for adjusting fluid flow through the passage130of the support shaft104. Specifically, the illustrated arrangement includes an adjustment sleeve172, which is coaxially supported on the adjustment shaft134within the passage130. The adjustment sleeve172is configured to be adjustable along the axis A to cover a selected portion of the radial ports132. The adjustment sleeve172may be coupled to an upper cap of the fork assembly to permit external adjustment by a user, as described above. Thus, the rebound fluid flow through the passage130may be adjusted to alter a rebound damping force produced by the damping piston assembly84for a given relative velocity of the piston assembly84relative to the damper tube80.

In addition to rebound fluid flow through the passage130, the main piston100preferably incorporates one or more rebound fluid flow ports174. A lower end of the ports174are normally closed by one or more shims176. The shims176are configured to prevent compression fluid flow through the ports174, but open in response to rebound fluid flow through the ports174above a threshold pressure differential between the rebound chamber88and the fluid chamber152, which in most instances will be substantially the same as the pressure within the compression chamber86.

In addition to the radial ports132, an additional set of radial ports180permit fluid communication between the passage130and the rebound chamber188. The ports180open into a generally bell-shaped housing182, which is supported on the support shaft104. An open, upper end of the housing182is substantially closed by a shim184. As illustrated, a slight gap exists between an upper end of the housing182and the shim184. However, if the pressure in the rebound chamber88is increased in comparison to the pressure within the housing82(and, thus, the pressure within the compression chamber86), the shim184deflects in a downward direction to contact the housing182and inhibit or substantially prevent fluid flow from the rebound chamber88into the interior of the housing182. In response to compression fluid flow, the shim184deflects in an upward direction to permit fluid flow from the interior of the housing182into the rebound chamber88. Thus, the shim184and housing182cooperate to form a one-way valve to permit compression fluid flow while inhibiting or at least substantially preventing rebound fluid flow.

Thus, because compression fluid flow through the passage130is not restricted by the size of the radial ports132that is exposed by the adjustment sleeve172, due to the large amount of volume flow permitted through the radial ports180, compression fluid flow through the passage130is primarily regulated by the position of the valve body136relative to the valve seat138. In contrast, because the valve body136will open against the small biasing force of the spring142, rebound fluid flow through the passage130is regulated primarily by the volume of the radial passages132exposed by the adjustment sleeve172. Accordingly, both compression and rebound fluid flow through the passage130may be individually optimized for a given set of riding conditions.

FIG. 10illustrates yet another modification of the damper assembly76ofFIGS. 2 through 6andFIGS. 7 through 9. For convenience, similar components inFIG. 10will be referred to by the same reference numeral as the corresponding components inFIGS. 1 through 9. The damping piston assembly84ofFIG. 10is substantially similar to the damping pistons84ofFIGS. 2 through 6and the damping piston assembly84ofFIGS. 7 through 9. However, the damping piston assembly84ofFIG. 10includes additional rebound damping adjustment mechanisms.

The support shaft104of the damping piston assembly84ofFIG. 10includes a central passage130which communicates with the rebound chamber88through radial ports132. An adjustment sleeve172is positioned within the passage130of the support shaft104and may be moved along the axis A of the damper assembly76to vary the area of the radial ports132exposed to the central passage130. Desirably, the adjustment sleeve172is capable of completely or substantially completely closing off the radial ports132from the central passage130.

In addition, a secondary sleeve200is positioned within the central passage130of the support shaft104. Preferably, the secondary sleeve200occupies an intermediate portion of the central passage130and fits snugly against the interior surface of the support shaft104. The sleeve200defines one or more ports202extending radially through an upper end portion of the sleeve200.

A secondary rebound adjustment rod204extends through the interior of the adjustment sleeve172. A valve body206is carried on the lower end of the adjustment rod204. In the illustrated arrangement, the valve body206is defined by a machine screw and, specifically, by a head portion of the machine screw. The machine screw is threadably engaged with the secondary adjustment rod204. The head of the machine screw206is positioned within an upper end of the sleeve200. The head of the machine screw206is sized to occupy a substantial portion of the hollow interior of the sleeve200, but to still permit fluid flow between the head of the machine screw206and the interior surface of the sleeve200.

The adjustment rod204is configured to move along the axis A such that the head of the machine screw206may be adjusted to block a desired portion of the ports202. Accordingly, adjustment of the amount of fluid flow permitted from the rebound chamber88through the radial ports132and past the machine screw206into a lower portion of the central passage130of the support shaft104is permitted. The adjustment rod204may be coupled to a user control at the cap78(FIG. 2) of the fork leg70to permit external adjustment of the position of the adjustment rod204and, thus, the machine screw206relative to the ports202. Furthermore, although not specifically illustrated, the damping piston arrangement84ofFIG. 10preferably includes rebound specific flow circuit through the main piston100similar to the rebound ports174and shim176illustrated inFIGS. 7 and 8.

A one way valve210closes a lower end of the central passage130. The valve210includes a valve body212biased against a valve seat214by a biasing member, such as a spring216. The valve body includes one or more ports218extending radially through a side wall of the valve body212. Accordingly, fluid pressure within the central passage130may overcome the biasing force of the spring216to move the valve body212in a downward direction away from the valve seat214such that fluid flow is permitted from the central passage130through the ports218and into the compression chamber86. In contrast, fluid pressure in the compression chamber86tends to push the valve body212more tightly against the valve seat214such that compression fluid flow through the central passage130is substantially or completely prevented.

In addition, the damping assembly76ofFIG. 10includes an inertia valve220, which is configured to, at least in part, regulate fluid flow from the compression chamber86to a reservoir chamber222. The reservoir chamber222is separated from the compression chamber86by a partition, or a piston224. Specifically, the piston224is disposed in the upper end of a lower portion80bof the damper tube80. As described above, the lower portion80bof the damper tube80is secured to the upper portion80aof the damper tube80. Thus, the damper tube80is in two sections,80aand80b, which permits the lower portion80bto be varied depending upon whether an inertia valve220is desired for a particular model fork, as described above. As a result, the efficiency of the manufacturing process for producing the fork leg70is enhanced.

A shaft226is supported within a central aperture of the piston224and is secured to the piston224by a nut228. The shaft226extends in a downward direction from the piston224and supports the inertia valve220, as is described in greater detail below.

The piston224includes axially-extending ports230, the lower ends of which are closed a shim232. Thus, the ports230and shim232create a one-way valve which permits fluid flow from the compression chamber86to the reservoir chamber222, but substantially or completely prevents fluid flow from the reservoir chamber222to the compression chamber86. A stop234defines a stop surface that defines an open position of the shim232.

Preferably, the piston224includes an additional one-way valve structure which permits fluid flow from the reservoir chamber222to the compression chamber86upon rebound movement of the damping assembly76. Such a one-way valve is desirable to permit fluid which has been displaced to the reservoir chamber222during compression of the damper assembly76to be able to return to the compression chamber86upon subsequent rebound motion. Such a one-way rebound valve may be constructed of rebound ports and a rebound shim closing an upper end of the rebound ports similar to the ports230and shim232, as will be appreciated by one of skill in the art. In addition, other suitable structures to permit refill flow from the reservoir chamber222to the compression chamber86may also be used.

The shaft226includes a central passage240which extends axially along the shaft226. The shaft226defines an upper set of ports242extending radially through the shaft226and a lower set of ports244extending radially through the shaft226. An inertia mass246is biased into an upward position against the stop234by a biasing member, such as a spring248, such that the inertia mass246normally blocks the ports242and244. Upon upward acceleration of the damper tube80, the inertia mass246tends to resist movement such that the damper tube and inertia valve shaft226move upwardly relative to the inertia mass246. Looked at from another perspective, in response to upward acceleration of the damper tube80, the inertia mass246moves relatively downward on the shaft226, overcoming the biasing force of the spring248, to expose the ports242and244. Thus, fluid flow is permitted from the compression chamber86into the reservoir chamber222through the inertia valve220in addition to the compression fluid flow permitted by the compression ports230of the piston224. Accordingly, when a significant bump is encountered, the inertia valve220opens to permit additional fluid flow and reduce the damping force provided by the damping assembly76. However, in response to downward movement of the damper tube80, the inertia valve220remains closed. Accordingly, downward directed forces, such as rider induced forces, do not open the inertia valve220, such that the fork30tends to resist compression in response to rider-induced forces.

Preferably, flow through the ports242and244are also controlled by a pressure regulated valve assembly250. The valve250includes a valve body252normally biased by a biasing member, such as a spring254, into an upward position such that an upper surface254of the valve body252contacts a valve seat256defined by the shaft226to close off the ports242and244. The valve body252is movable in a downward direction in response to fluid pressure from the compression chamber86to open one or both sets of ports242,244. Thus, with the illustrated arrangement, both a sufficient upward acceleration of the damper tube80and a sufficient pressure differential between the compression chamber86and the reservoir chamber222are necessary to permit fluid flow through the ports242and244.

As will be appreciated by one of skill in the art, the inertia valve220and pressure regulated valve250may be combined with the damping piston assemblies84ofFIGS. 2 through 6or7through9, instead of the damping piston assembly84ofFIG. 10. In addition, although not specifically illustrated inFIG. 10, preferably a volume compensation device (similar to the compensator90ofFIG. 2) is provided to compensate for an increasing volume of the piston rod that occupies the damper tube80during compression movement. The volume compensation device may be positioned below the inertia valve220and pressure regulated valve250.

Although this invention has been disclosed in the context of certain preferred embodiments and examples, it will be understood by those skilled in the art that the present invention extends beyond the specifically disclosed embodiments to other alternative embodiments and/or uses of the invention and obvious modifications and equivalents thereof. In particular, while the present bicycle damping system has been described in the context of particularly preferred embodiments, the skilled artisan will appreciate in view of the present disclosure that certain advantages, features, and aspects of the system may be realized in a variety of other applications, many of which have been noted above. Additionally, it is contemplated that various aspects and features of the invention described can be practiced separately, combined together, or substituted for one another, and that a variety of combination and subcombinations of the features and aspects can be made and still fall within the scope of the invention. Thus, it is intended that the scope of the present invention herein disclosed should not be limited by the particular disclosed embodiments described above, but should be determined only by a fair reading of the claims.