Mechanical gearbox for motor vehicles

A mechanical gearbox for a motor vehicle, the gearbox comprising:

• only one primary shaft;
• only one secondary shaft adapted to transmit the motion to drive wheels;
• only one single clutch that is connected to the primary shaft and is adapted to receive the motion from a crankshaft of a thermal engine;
• a plurality of gear pairs, each of which mechanically couples the primary shaft to the secondary shaft, defines a corresponding speed and comprises a first gear mounted on the primary shaft and a second gear mounted on the secondary shaft permanently meshed with the first gear;
• a plurality of synchronizers, each of which is mounted coaxially to a respective one of the primary and secondary shaft between two gears of two gear pairs and is adapted to be actuated by a motorized actuation system to alternatively engage the two gears to the shaft, wherein for all the speeds the gear pairs of two consecutive speeds are engaged by two different synchronizers of the plurality of synchronizers;
• and
• a plurality of forks, each of which envelops a respective synchronizer, the plurality of forks to displace each synchronizer of the plurality of synchronizers alternatively, in two operational states, along its respective shaft, wherein the motorized actuation system is to actuate the plurality of forks/synchronizers in reciprocally independent manner so that each fork/synchronizer is actuated independently from the other forks/synchronizers,
• wherein the forks, during a gear shift from each current speed to a subsequent speed consecutive to the current speed, actuate the synchronizer of the gear of the current speed to disengage the first gear of the current speed from the primary shaft and contemporarily actuate the synchronizer of the gear of the subsequent speed to engage the gear of the subsequent speed onto the corresponding shaft;
• wherein the actuation system comprises:
• a third shaft parallel to and by the side of the primary and secondary shaft and supporting the forks, each of which presents an eyelet slidingly fitted along the third shaft, wherein the third shaft is split into two halves that are connected together by an elastic element and each of which supports a part of the forks;
• a plurality of circumferential cams, each of which is obtained on an external surface of the third shaft and is associated to the corresponding fork;
• a plurality of followers, each of which is integral with the eyelet of the respective fork and is inserted in the cam associated to the fork thereof;
• and
• a motor adapted to turn the third shaft about a central rotation axis thereof.