A revolutionary new induction heating system is being introduced to the automotive industry for the heat treatment of crankshafts.
Crankshafts are widely used in internal combustion engines, pumps, compressors, etc., and are among the most critical auto components. A crankshaft, typically cast or forged, comprises a series of crankpins and main journals interconnected by webs/counterweights (Fig. 1). High strength, good wear resistance, geometrical accuracy and low cost are among some of the crankshaft requirements.
A majority of the existing induction crankshaft hardening machines require the crankshaft rotation during heating. Each crankpin and main journal is heated by bringing a "U-shaped" inductor close to the crankpin or main bearing surface while the crankshaft is rotated about its main axis. Since the crankpin axis is offset radially from the main axis, the crankpin will orbit around the main axis. The crankshaft's rotational speed varies between 24 and 32 rpm; consequently, the "U-shaped" inductor, as well as other massive components of the induction hardening machine including output transformer of power supply, busswork, cables, etc. (which often weight over 2,000 lbs), must travel with the orbital motion of the crankpins. The circular orbital motion of such a heavy system must be maintained precisely, resulting in the complex, sensitive, bulky, noisy and costly design of the conventional induction hardening machines.