Schaeffler North America

Valve train & chain drive systems

Hydraulic tensioning elements

Chain drives are activated dynamically by the rotational irregularities in the drive shaft together with the mass inertia of the output shafts, and also by the changing support of moment loads on the output shafts. The latter is particularly relevant in the case of camshafts, piston pumps, etc. To ensure vibration-free, quiet, and low-wear operation despite these impulses, the chain oscillations resulting in drives such as these must be stabilized. Damping using a hydraulic chain tensioning element is ideal. The most common design is the speed-dependent leakage gap damper with directed damping. This uses oil from the engine's own reserves. The oil is sucked into the high-pressure chamber as it drains out across a non-return valve. If the tensioner is squeezed, the valve closes and the oil is pressed out through a narrow gap between the piston and the housing (the leakage gap).

Hydraulic tensioning elements are characterized by:

  • Low wear thanks to hardened steel components
  • Damping finely adjustable through leakage gap
  • Damping directed by use of non-return valve
  • Low space requirements

Many other properties and functions are also optionally available. One example is the tensioner for camshaft driving mechanisms, which integrates both the chain guide element and tensioning shoe as well as an oil injection nozzle. Our objective is to design a clamping fixture that is ideal in terms of function and cost for each application.


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