What are thrust forces acting on gears?
When the Z-axis of the gears shown in the figure below is the gear axis, the force acting on the gears in the X-axis direction, the force acting in the Y-axis direction, and the force acting in the Z-axis direction are called the tangential force, the radial force, and the thrust (axial force), respectively. These are among the forces acting on the gears when the gear pair transmits power.
When spur gears transmit power, thrust is not generated.
On the other hand, helical gears, which are another style of parallel axis gears, have tooth flanks that are twisted, so thrust is generated in accordance with the direction of twisting and rotation. Therefore, a thrust bearing that can withstand the generated thrust is necessary when helical gears are used.
Power transmission applications using intersecting axis gears, such as straight bevel gears and spiral bevel gears, and nonparallel and nonintersecting axis gears, such as screw gears and worm gears, also generate thrust and require countermeasures.
