Methods and apparatus for position sensitive suspension damping

Abstract

An apparatus and system are disclosed that provide position sensitive suspension damping. A damping unit includes a piston mounted in a fluid-filled cylinder. A vented path in the piston may be fluidly coupled to a bore formed in one end of the piston rod, creating a flow path for fluid to flow from a first side of the piston to a second side of the piston during a compression stroke. The flow path may be blocked by a needle configured to engage the bore as the damping unit is substantially fully compressed, thereby causing the damping rate of the damping unit to increase. In one embodiment, the piston includes multiple bypass flow paths operable during the compression stroke or the rebound stroke of the damping unit. One or more of the bypass flow paths may be restricted by one or more shims mounted on the piston.

1 . A vehicle suspension damper comprising:
 a cylinder having a compression chamber and a rebound chamber and containing at least a portion of a piston rod having a piston attached thereto, wherein an outer diameter of the piston engages an inner diameter of the cylinder and is relatively movable therein, and wherein the piston borders each of the compression chamber and the rebound chamber;   a damping liquid within the cylinder; and   a bypass fluid flow path connecting the compression chamber and the rebound chamber, wherein the bypass flow path comprises a fluid path extending between an inner diameter of the piston and a side surface of the piston directly bordering one of the compression or rebound chambers.   
     
     
         2 . The vehicle suspension damper of  claim 1 , wherein the bypass flow path further comprises a valve member restricting fluid flow through the piston. 
     
     
         3 . The vehicle suspension damper of  claim 2 , wherein the piston further comprises a damping flow path extending between a first side surface of the piston and a second side surface of the piston, the damping flow path comprising the valve member. 
     
     
         4 . The vehicle suspension damper of  claim 1 , wherein the piston further comprises a damping flow path extending between a first side surface of the piston and a second side surface of the piston and including a valve member. 
     
     
         5 . The vehicle suspension damper of  claim 1 , further comprising a second valve member connected to the cylinder and operable to restrict the bypass flow path at predetermined positions during a stroke of the damper and to be unrestrictive of the bypass flow path at other positions during the stroke. 
     
     
         6 . The vehicle suspension damper of  claim 5 , wherein the second valve member comprises a needle. 
     
     
         7 . The vehicle suspension damper of  claim 6 , further comprising a floating piston mounted in fluid communication with an interior of the cylinder, the floating piston separating the damping liquid from a volume of gas contained adjacent a second side of the floating piston. 
     
     
         8 . The vehicle suspension damper of  claim 7 , further comprising a reservoir, the reservoir comprising:
 a reservoir cylinder having a first end and a second end, wherein the first end of the reservoir cylinder is fluidly coupled to the cylinder; and   
       the floating piston mounted inside the reservoir cylinder and axially movable relative thereto, the floating piston forming a reserve volume of damping liquid between a first side of the floating piston and the first end of the reservoir cylinder and forming a volume of gas between a second side of the floating piston and the second end of the reservoir cylinder. 
     
     
         9 . The vehicle suspension damper of  claim 7 , wherein the floating piston surrounds and moves relative to a needle. 
     
     
         10 . The vehicle suspension damper of  claim 7 , wherein the needle restricts an opening of the bypass flow path proximate the inner diameter of the piston at predetermined positions during a stroke of the damper. 
     
     
         11 . A vehicle suspension damper comprising:
 a cylinder having a compression chamber and a rebound chamber and containing at least a portion of a piston rod having a piston attached thereto, wherein an outer diameter of the piston engages an inner diameter of the cylinder and is relatively movable therein, and wherein the piston borders each of the compression chamber and the rebound chamber; and   a damping liquid within the cylinder,   wherein the piston includes multiple flow paths that enable the damping liquid to flow from the compression chamber to the rebound chamber, the multiple flow paths including:
 a damping flow path that comprises a first fluid path extending between a first side surface of the piston directly bordering the compression chamber and a second side surface of the piston directly bordering the rebound chamber, and 
 a bypass flow path that comprises a second fluid path extending between an inner diameter of the piston and one of the first side surface of the piston or the second side surface of the piston. 
   
     
     
         12 . The vehicle suspension damper of  claim 11 , wherein the multiple flow paths further include a rebound flow path that comprises a fluid path extending between an inner diameter of the piston and one of the first side surface or the second side surface. 
     
     
         13 . The vehicle suspension damper of  claim 12 , wherein the damping liquid is forced through the damping flow path and the bypass flow path during a compression stroke of the vehicle suspension damper, and wherein the damping liquid is forced through the rebound flow path during a rebound stroke of the vehicle suspension damper. 
     
     
         14 . The vehicle suspension damper of  claim 12 , wherein the bypass flow path further comprises a valve member restricting fluid flow through the piston and a second valve member connected to the cylinder and operable to restrict the bypass flow path at predetermined positions during a stroke of the damper and to be unrestrictive of the bypass flow path at other positions during the stroke. 
     
     
         15 . A vehicle suspension system comprising:
 a first damper unit that includes:
 a cylinder having a compression chamber and a rebound chamber and containing at least a portion of a piston rod having a piston attached thereto, wherein an outer diameter of the piston engages an inner diameter of the cylinder and is relatively movable therein, and wherein the piston borders each of the compression chamber and the rebound chamber, 
 a damping liquid within the cylinder, and 
 a bypass flow path connecting the compression chamber and the rebound chamber, wherein the bypass flow path comprises a fluid path extending between an inner diameter of the piston and a side surface of the piston directly bordering one of the compression or rebound chambers. 
   
     
     
         16 . The vehicle suspension system of  claim 15 , wherein the bypass flow path further comprises a valve member restricting fluid flow through the piston. 
     
     
         17 . The vehicle suspension system of  claim 15 , wherein the piston further comprises a damping flow path extending between a first side surface of the piston directly bordering the compression chamber and a second side surface of the piston directly bordering the rebound chamber, and wherein the piston includes a valve member. 
     
     
         18 . The vehicle suspension system of  claim 15 , further comprising a spring mounted coaxially with the first damper unit. 
     
     
         19 . The vehicle suspension system of  claim 15 , wherein the first damper unit is included in a leg of a fork. 
     
     
         20 . The vehicle suspension system of  claim 15 , further comprising:
 a second damper unit substantially similar to the first damper unit; and   one or more springs mounted substantially in parallel with the first and second damper units.