Classification by the relative position of the two shafts
This is the most common basic classification method in the industrial sector, covering the vast majority of application scenarios.
- Parallel-axis gear drives: The two shafts operate in parallel. Representative types include spur gears, helical gears, and double-helical (herringbone) gears. They offer high transmission efficiency and simple construction, making them widely used in standard gearboxes.
- Intersecting-axis gear drives: The axes intersect at an angle (typically conical). Examples include straight bevel gears and spiral bevel gears. They enable right-angle power transmission and serve as core components in automotive differentials.
- Skew-axis (crossed-axis) gear drives: The axes neither intersect nor run parallel. Worm gear sets are the classic example; they allow for high reduction ratios in a single stage and possess self-locking characteristics, making them common in systems with strict safety requirements, such as elevators.
Classification by tooth profile shape
This categorizes gear types based on performance characteristics derived from tooth profile design.
- Involute gears: The most mainstream gear type. They are easy to manufacture, offer good interchangeability, and provide smooth, reliable transmission, making them suitable for the vast majority of high-speed, heavy-load industrial applications.
- Cycloidal gears: These offer higher transmission efficiency and load-bearing capacity with minimal frictional loss. They are frequently used in high-precision, high-efficiency transmission systems, though manufacturing costs are relatively high.
- Circular-arc gears: Characterized by high tooth-surface contact strength, excellent wear resistance, and low operating noise. They are well-suited for high-power, low-speed operating conditions subject to impact loads.
