What is the purpose of incorporating "scissor gear" in an engine?

Incorporating scissor gears in an engine serves multiple important purposes that contribute to the overall performance and durability of the engine's components. One of the primary functions of scissor gears is to maintain minimal or zero gear lash, which enhances the precision of power transfer between gears and helps ensure smooth operation. This is vital because excessive lash can lead to vibrations and uneven wear.

Additionally, scissor gears are designed to eliminate gear rattle, which can occur when gears are not perfectly meshed. By minimizing the free play or "lash" between the gears, these components help reduce the likelihood of rattling noises that can be indicative of poor alignment or clearance issues. This not only improves the sound quality of the engine but also ensures that the gears operate more efficiently over time.

Furthermore, scissor gears also play a role in controlling gear noise, which is an important consideration for the overall refinement of an engine. Excessive noise can be a sign of wear or can contribute to operator discomfort, so the integration of scissor gears helps mitigate these issues.

In summary, scissor gears contribute to maintaining precise gear engagement, reducing undesirable noises, and ensuring smoother operation, covering all the purposes outlined in the question.