Synchronizer is a part of synchromesh manual transmission that allows the smooth engagement of gears. The gear shift is accompanied by blows between the teeth of the gears, which leads to wear them.
The synchronizer’s main function is reduction of wear of gears and reducing a noise resulting from the impact of teeth when shifting gears by the alignment of the angular velocities of the gears. Synchronizers are installed on the most frequently used gears.
Gearbox Synchronizer: a – construction; b – details; 1 – gear wheel of drive shaft; 2 – tapered locking ring; 3 – coupling; 4 – synchronizer plug; 5 – spring; 6 – third gears gear wheel; 7 – slide of synchronizer; 8 – synchronizer hub; 9 – longitudinal grooves in the synchronizer hub.
How a Gearbox Synchronizer works
Synchronizer hub 8 is fixedly mounted on the splines of the driven shaft. There are teeth and three longitudinal grooves 9 on the surface of the synchronizer hub, into which are installed slides 7 having in the middle part external projections. The synchronizer coupling 3 is worn on the teeth. It moves along the hub in the longitudinal direction. The slides enter the annular recess on the inside of the coupling with the help of external projections. The slides are pressed against the inner surface of the coupling using springs 5.
Brass taper locking rings 2 are installed on both sides of the synchronizer hub, the ends of which have three rectangular grooves for the slides. On the inner conical surface of the blocking rings a thread is cut with fine pitch to increase the friction between the cones of the blocking rings 1 and 6. On the outer surfaces of the blocking rings and on the hubs of gear wheels 1 teeth are cut. The ends of the teeth of gears and locking wheels have bevels, which facilitates the introduction of their engagement.
Gear coupling and locking rings do not work in neutral position. The coupling 3 moves by the fork 4, and through the protrusions the moves the slides that press one of the locking rings to the gear cone 1, if fourth gear is engaged, or to the gear cone 6, if third gear is engaged.
Due to the friction between the conical surfaces, the gear wheel provides rotate the locking ring 2 and turns it relative to the coupling 3 at an angle, since there is a gap between the slide 7 and the groove in the end face of the locking ring 2. The face bevels of the ring teeth 2 do not allow enter the teeth and the coupling to engage with the gear ring on the gear wheel hub and press the locking ring to the wheel cone.
As a result, the rotational speed of the locking ring (and rotational speed hence the output shaft) and the gear engaged are gradually aligned. When these rotational speeds become the same, the teeth of the synchronizer coupling enter engage with the teeth of the locking ring, and then with the gear ring on the gear hub.