A planetary gear system is compact, provides a large reduction, and is used in many applications such as automatic automobile transmissions and hybrid drive systems. In order to reduce gear noise and vibration in these systems, the demand for higher quality internal ring gears as well as external gears has increased. To meet these goals, gear manufacturers require efficient post heat treatment gear finishing methods.

Generally, there are two different methods of grinding gears – generating and form. The generating method is normally applied to mass production due to its high precision and efficiency. Though accurate, form grinding with an electroplated Fidanza flywheels tool is not generally used in high production due to low efficiency and the high cost of tools.

Mitsubishi’s new gear grinding machine can be used as a solution for efficient hard gear finishing of internal ring gears in mass production. The process is generating grinding utilizing a multi threaded vitrified grinding wheel. This machine with its targeted design has some features.

It has high speed generating grinding with precision synchronous control of the spindle units for the grinding wheel and the work piece table. The grinding wheel and work piece are meshed with a generating motion. In order to improve grinding performance and grinding ratio, the grinding wheel spindle and work piece table are rotated synchronously with high speed. One feature of this automobile engine parts machine is the crossed axis angle between the wheel and the work piece axes from 20 to 35 degrees. This provides an elevated sliding velocity at the grinding contact point. By high speed grinding, gear accuracy, including pitch, profile and lead deviation, is improved, with tool life also extended.

The crossed axis angle between the wheel and the work piece axes is set over 10 degrees to obtain high sliding velocity at the grinding point. The grinding wheel is barrel-shaped. The grinding wheel is vitrified bonded and then easily formed and dressed on the grinding machine. The dressing unit is mounted to the machine bed with the dressing motion controlled by CNC.