A hydraulic tensioner includes a cylindrical center member or mass to counteract the resonance of the piston. The center member is located between a pair of piston springs inside the fluid chamber. The mass of the center member is selected, along with the spring rates of the piston springs, so that the resonant frequency of the center member matches the resonant frequency of the piston and timing drive. Since the center member moves in the opposite direction from the piston, the center member counteracts or damps the movement of the piston at resonant frequencies.
A chain drive having a phaser such as a hydraulic vane phaser interposed between a timing chain and a driving or driven shaft is provided. The phaser or the vane are controlled to oscillate more at certain engine speeds to thereby reduce the tensioning force on the chain at the certain engine speeds.
A hydraulic tensioner having a piston slidably fitted in a bore in a housing forming a fluid chamber. The piston is biased in a protruding direction by a spring and fluid. A check valve permits flow of fluid into the fluid chamber and prevents flow of fluid in the reverse direction. A pressure relief valve is provided in the fluid chamber. The pressure relief valve works with a vent disc having two separate vent paths. The pressure relief valve and vent disc provide controlled venting of fluid from the fluid chamber during both conventional operation and during periods of excessive pressure and thus, prevent collapse of the tensioner.
