1. Field of the Invention
This invention relates to a coupling sleeve for use in an automotive vehicle power transmission.
2. Description of the Prior Art
In normal automotive vehicle power transmissions, when a driver operates a shift lever to effect a speed ratio change, the displacement of the shift lever is transmitted through a link mechanism to a shift fork engaging a coupling sleeve rotating with a drive shaft, thereby axially moving the coupling sleeve into engagement with a gear rotating freely on the drive shaft so as to lock the gear to the drive shaft. Since speed ratio changes are frequently effected during vehicle operation, the shift fork and coupling sleeve are subject to great wear at their contacting portions. This causes a reduction of displacement of the coupling sleeve, resulting in failure to effect certain and smooth speed ratio changes. In order to eliminate such difficulties, attempts have been made to harden the surface of the shift fork and to cover the contacting portion of the shift fork with the coupling sleeve with metal having a high antiwear property. However, these attempts cannot prevent the wear of the coupling sleeve although they can prevent the wear of the shift fork. Furthermore, since the contacting portion of the shift fork is smaller than the contacting portion of the coupling sleeve, the antiwear material becomes worn in a relatively short time.