Gear and balance shaft for a piston engine

Abstract

Balance shaft for a piston engine comprises a bearing journal, on which the balance shaft is supported, a gear section, on which a gear is connected in a rotation-locked manner thereto via a press fit or another shaft-hub-connection, and an unbalanced section having an integrally connected unbalanced mass or an unbalanced mass fastened on this unbalanced section using machine elements or via another shaft-hub connection. The balance shaft can alternately comprise steel or cast iron material in the case of a friction mounting and its bearing journals can alternately be implemented as hardened or also unhardened. If the balance shaft is mounted in roller bearings and if the roller bodies have direct contact with the bearing surface, it is implemented in a suitable steel and the bearing journals are hardened. The gear comprises nodular cast iron and is not hardened.

What is claimed is: 
     
         1 . A gearwheel configured to be fastened to a balance shaft of a piston engine in a rotation-locked manner, the gearwheel comprising unhardened gearing and being formed from nodular cast iron having a fracture elongation of at least 4%. 
     
     
         2 . The gearwheel of  claim 1 , wherein the nodular cast iron has a carbon component of 2.9 to 3.8 mass percent. 
     
     
         3 . The gearwheel of  claim 2 , wherein the nodular cast iron has a carbon component of 3.20 to 3.70 mass percent. 
     
     
         4 . The gearwheel of  claim 3 , wherein nodular cast iron has a carbon component of 3.35 to 3.65 mass percent. 
     
     
         5 . The gearwheel of  claim 1 , wherein the nodular cast iron has a silicon component of 1.5 to 3.5 mass percent. 
     
     
         6 . The gearwheel of  claim 5 , wherein the nodular cast iron has a silicon component of 2.2 to 3.5 mass percent. 
     
     
         7 . The gearwheel of  claim 6 , wherein the nodular cast iron has a silicon component of 2.5 to 3.3 mass percent. 
     
     
         8 . The gearwheel of  claim 1 , wherein the nodular cast iron has a manganese component of less than 0.5 mass percent. 
     
     
         9 . The gearwheel of  claim 8 , wherein the nodular cast iron has a manganese component of 0.15 to 0.3 mass percent. 
     
     
         10 . The gearwheel of  claim 1 , wherein the nodular cast iron has a phosphorus component of at most 0.05 mass percent. 
     
     
         11 . The gearwheel of  claim 10 , wherein the nodular cast iron has a phosphorus component of at most 0.03 mass percent. 
     
     
         12 . The gearwheel of  claim 1 , wherein the nodular cast iron has a copper component of 0.5 to 1.1 mass percent. 
     
     
         13 . The gearwheel of  claim 1 , wherein the nodular cast iron includes spheroidal graphite particles having a microstructure in which the greatest dimension of the spheriodal graphite particles is less than 0.12 mm. 
     
     
         14 . The gearwheel of  claim 13 , wherein the nodular cast iron includes spheroidal graphite particles having a microstructure in which the greatest dimension of the spheriodal graphite particles is less than 0.08 mm. 
     
     
         15 . The gearwheel of  claim 14 , wherein the nodular cast iron includes spheroidal graphite particles having a microstructure in which the greatest dimension of the spheriodal graphite particles is less than 0.06 mm. 
     
     
         16 . The gearwheel of  claim 1 , wherein the nodular cast iron has (1) a manganese component of less than 0.5 mass percent, (2) a phosphorus component of at most 0.05 mass percent and (3) a copper component of 0.5 to 1.1 mass percent. 
     
     
         17 . The gearwheel of  claim 1 , wherein the nodular cast iron has a perlite component of at least 60% and a ferrite component of at most 40%. 
     
     
         18 . The gearwheel of  claim 17 , wherein the nodular cast iron has a perlite component of 80% to 90% and a ferrite component of 10% to 20%.