Schaeffler North America

Belt-driven starter generator

Hydraulic generator tensioning system

A very promising approach to the problem of a starter generator belt drive is the use of the generator itself as a tensioning system. The basic idea is a rotating bearing arrangement for the generator supported by a hydraulic tensioning element. The advantages lie in the comparative ease of implementation, small space requirement and almost universal applicability.


  • M Housing (1)
  • M Starter (2)

  • Increased preload (A)
  • Optimised starting behaviour (B)


  • M Housing (1)
  • M Generator (2)

  • Reduced preload (A)
  • Optimised belt life (B)


During the startup process, the torque on the generator pulley introduced into the belt drive acts on the generator housing as an equivalent countertorque. This countertorque can result, with an appropriate arrangement of the rotation point, in an automatic increase in the preload. This effect supports torque transmission during engine startup. In generator operation, this effect is reversed, the preload is reduced and the belt life is increased.


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