Increasing of Seizure Durability of Shift Fork Using Surface Treatment

In line with the increase in the output of motorcycle engines, there has been an increase in incidents of the seizure between shift fork and gear because of the increased thrust force. We designed a test method that uses actual shift forks to simulate actual sliding conditions, then used that test method to evaluate the feature of the shift fork sliding and the different shift fork surface treatments. The shift fork slid against the gear not as surface contact but as tilted contact. We selected the candidates from the view that the surface treatment of the shift fork contact surface to give it higher seizure resistance when in tilted contact is required. We evaluated chromium nitride thin film, diamond-like carbon thin film, molybdenum sprayed coating, and sulphonitriding, and molybdenum sprayed coating exhibited the highest seizure resistance. The conformability plays a significant role in the sliding between the shift fork and the gear.