The manual transmission ( mechanical boxes ) and Manual transmission ( AMT, robotic boxes ) are synchronized CPR. Put, to achieve the most smooth and “soft” gear shifting, the speed of the shaft and the corresponding gear in the gearbox is aligned.
How the gearbox synchronizer works
To begin with, synchronizers are often installed in all gears in modern passenger cars. Reverse gear is also synchronized.
An exception can be considered only budget cars, in which the first gear can be without a synchronizer, as well as some trucks, old models of cars, etc.
The gearbox synchronizer itself works by using the frictional force at the time of equalizing the speeds, depending on the difference in the frequency of rotation of the shaft and gear, the frictional force for synchronization changes.
In other words, effective synchronization is achieved by increasing the contact surface area. To solve the problem, special friction rings are integrated into the gearbox design.
The synchronizer device assumes the presence of the following elements:
- hub and “crackers.”
- engagement clutches
- locking rings
- gears that have a friction cone
As a rule, one synchronizer in the gearbox synchronizes 2 gears; it works with two gears. The basis of the synchronizer is the hub, which has splines (internal and external).
Utilizing internal splines, the connection with the secondary shaft of the box is realized, and there is also the possibility of axial movement along the shaft. The outer splines are responsible for achieving the connection of the hub with the engagement clutch.
Also, grooves (three grooves) are made around the circumference of the hub. “Crackers” are placed in these grooves, which are additionally spring-loaded. The specified crackers of the synchronizer press the locking ring when the gear is engaged and block the clutch during synchronization.
The synchronizer clutch (engagement clutch) allows achieving a rigid connection between the gear and the shaft. This clutch is fixed on the hub and has internal splines, while the splines receive an annular groove. In this groove are the protrusions of the crackers. Also, a gearbox fork is attached to the synchronizer clutch.
The locking ring (synchronizer locking ring) is responsible for synchronization, preventing the clutch closing until the shaft and gear speed is equalized.
Such a ring has a conical surface on the inside. This surface is in contact with the friction cone of the gear. The outer side of the ring also has splines that block the engagement clutch.
The end surface of the ring (from the hub side) has 3 grooves. The rusks of the hub enter these grooves. The grooves themselves do not allow the ring to rotate due to contact with the friction cone since the grooves are actually a stop for the crackers.
Also, some gearboxes may have synchronizers when the protrusions are made on the locking ring, and the grooves are made in the hub itself. Synchronizers with multiple cones are used to increase the contact surface: 2 or 3 cones (double cone and triple cone synchronizer).
As an example, a 3-cone synchronizer, in addition to an outer locking ring, also has an inner ring and an intermediate ring. To prevent these rings from turning, there are protrusions on the rings themselves. Such protrusions allow the ring to be fixed in the corresponding grooves of the gear and the locking ring.
It turns out that a 3-cone synchronizer has as many as three friction surfaces. The first is between the pinion cone and the inner ring, the second is between the inner and intermediate ring, and the third is between the intermediate and locking ring. We also add that both double-cone and three-cone synchronizers can be installed in the checkpoint simultaneously.
The principle of operation of the gearbox synchronizer
If the gear lever is neutral, power from the internal combustion engine is not transmitted to the gearbox. In this case, the synchronizer couplings occupy the middle position, and the gears fixed on the driven shaft rotate freely.
However, when the gear is engaged, the fork moves the synchronizer clutch, displacing the clutch from the middle position towards the gear. Together with the clutch itself, the crackers are also shifted, which act on the locking ring.
The specified locking ring is pressed against the pinion cone, resulting in a frictional force. Under the influence of this force, the ring turns until the crackers stop in the grooves of the ring. The ring locks. That is, it does not turn further.
Also, the locking ring prevents the synchronizer sleeve from moving along the shaft axis. This becomes possible because the ends of the splines of the locking ring are located just opposite the ends of the splines of the coupling itself.
Then, under the action of the friction force, the speeds of the gear and the driven shaft are synchronized. After the speeds are equalized, the locking ring rotates from pressing the clutch splines in the opposite direction.
This means that the clutch stops blocking, and its splines mesh without restriction with the gear rim. As a result, a rigid connection of the secondary shaft of the gearbox and the gear is provided.
At the same time, the engagement occurs smoothly; there is no need to perform double squeezing of the clutch on the manual transmission, which greatly facilitates driving a car with a synchronized gearbox and increases the resource of the gearbox.
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