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Synchronizer (12-speed) 12]S160T-1707140

Since the input and output shafts of the transmission rotate at different speeds, there is a "synchronization" problem when changing gears. When two gears with different rotational speeds try to mesh together, there will inevitably be impact and collision, damaging the gears. Therefore, in old transmissions, gear shifting was done using the "two-foot clutch" method. When upshifting, the gear should remain in the neutral position for a moment, and when downshifting, the accelerator should be pressed in the neutral position to reduce the speed difference between the gears. However, this operation is rather complicated and difficult to master precisely. Therefore, designers created "synchronizers" to enable the gears about to mesh to reach the same rotational speed and then mesh smoothly.

01.

Why use a synchronizer?

The principle that different operation steps should be taken when switching between adjacent gears also applies to the case of changing gears with moving gears. The only difference is that for the former, the rotational angular velocities of the teeth to be engaged and the engaging sleeve need to be the same, while for the latter, the linear velocities of the engaged points of the gears need to be the same. However, the speed analysis principle is the same.

The shifting operation of the transmission, especially the shift from high gear to low gear, is rather complicated and prone to cause impacts between the gear teeth or spline teeth. To simplify the operation and avoid such impacts, a synchronizer can be installed in the shifting mechanism.

The inertia-type synchronizer achieves synchronization through friction. On it, there is a specially designed mechanism to ensure that the coupling sleeve and the target coupling gear ring cannot come into contact before achieving synchronization, thereby avoiding impact between the teeth.

02.

The splined hub 7 is connected to the second shaft by splines and is axially positioned using washers and retaining rings. At both ends of the splined hub and between gears 1 and 4, there is a bronze-made locking ring (9) and 5. On the locking rings, there are short splined tooth rings. The cross-sectional contour dimensions of the splined teeth are the same as those of gears 1, 4 and the external splined teeth on the splined hub 7. On both locking rings, the splined teeth have chamfers (referred to as locking angles) at the end facing the coupling sleeve 8, and these chamfers are the same as those at the tooth ends of the coupling sleeve. The locking rings have internal conical surfaces with the same taper as the friction surfaces on gears 1 and 4. On the internal conical surfaces, fine-toothed spiral grooves are made to break the oil film and increase the friction between the conical surfaces. The three sliders 2 are respectively fitted in the three axial slots 11 of the splined hub and can slide axially along the slots. Under the action of two spring coils 6, the sliders press against the coupling sleeve, causing the sliders to cross the central raised part of the coupling sleeve and exactly fit in the central groove 10 of the coupling sleeve, serving as a gap positioning function. The two ends of the sliders 2 extend into the three notches 12 of the locking rings 9 and 5. Only when the sliders are in the center of the notches 12, can the teeth of the coupling sleeve and the locking rings possibly engage.