The present application generally relates to vehicle suspension systems. In particular, the present application relates to dampers having a system to reduce impulse forces as the vehicle suspension system experiences a jounce event or a recoil event. Dampers (i.e. dashpots, hydraulic shock absorbers, etc.) dissipate kinetic energy as part of a vehicle suspension system. Dampers often include a housing, end caps, a piston, and a rod that is coupled to the piston. Energy is dissipated as hydraulic fluid flows along a hydraulic circuit (e.g., between a first chamber within the housing to a second chamber within the housing). The piston may include a plurality of orifices that are covered with a shim stack having a plurality of compressed shims.
As the piston moves through the housing, hydraulic fluid is forced from a first chamber, through the piston, and into the second chamber. Specifically, pressurized hydraulic fluid is forced through the orifices within the piston, deflects a portion of the shims to create an opening, and flows into the second chamber by passing through the opening. Such traditional dampers provide damping forces that are constant between a first end of stroke (e.g., extension) and a second end of stroke (e.g., compression). Where the vehicle interacts with an obstacle, a force is imparted into the piston through the rod of the damper. The piston translates toward an end of the damper and may impart a large impulse force on the end cap. Such large forces may cause damage to the piston, the end cap, the walls of the housing, or still other components of the damper assembly. Large impulse forces are also transferred to occupants within the vehicle.
Traditional dampers may include a limiting system that absorbs or dissipates energy thereby reducing the impulse forces imparted on occupants of the vehicle. Some limiting systems absorb and store energy (e.g., using a spring, a gas chamber, etc.) as the piston moves toward the end of stroke. Such a spring may produce up to 30,000 pounds of force with one inch of displacement. The stored energy is thereafter transferred to another component (e.g., the piston, the rod, etc.) as the piston moves toward the opposing end of the housing. While still other limiting systems dissipate energy, such systems provide flow paths through flow orifices within the primary piston and along the damper piston. These limiting systems are susceptible to obstruction due to debris and may generate inconsistent damping forces.