The inventor has found that a double input splitter is needed to solve a major technical problem and to address important benefits to the previously innovative method of construction of multi-speed motor vehicle gearboxes.

Patent PCT/PT01/00009 presented an innovative method of gearwheels disposal inside a gearbox. That patent is centralised in a basic modules gear system, disposed in serial, hose aim is to achieve a bigger number of gear transmission ratios, then the allowed in the actual state of the art with a given number of gearwheels.

As a result of a deep research and investigation on that innovative method, patent PCT/PT01/00009, the inventor have found that a real and feasible combination between torque capacity and actuation range interval is very difficult to achieve with the previous innovative method alone. Also, it is difficult to achieve regular step transmission ratios between consecutive gearshift without the use of more then three basic modules.

In particular, the inventor have found that it is necessary to shorten the gearbox working range, between the top gear and the lowest gear of the gearbox output, in order to attain a good mechanical strength on the gearbox main components.

Both, torque capacity and wide range capacity, together are difficult to obtain. That limitation leads to difficulties in order to meet some vehicles working requirements.

Heavy-trucks and powerful engine vehicles, which need a wide range transmission and load capacity at low rotation, cannot be attained by the previous method alone, patent PCT/PT01/00009, within gearbox components strength life limits.

According to the present invention, the new herein introduced"double input splitter"solves the above mentioned main problems related to the method of construction of multi-speed motor vehicle gearboxes, patent PCT/PT01/00009.

According to the present patent, the new combination herein introduced by the double input splitter addresses several main advantages on the previous method of construction of multi- speed motor vehicle gearboxes.

The most important advantage is the fact that the double input splitter is used to increase the working range of the gearbox, making that working range wider within the torque capacity requirements needed to the gearbox components. This solves the torque capacity and wide range capacity main problems of the previous innovative method.

The second most important advantage is the fact that, the double input splitter doubles the possible number of combinations of the previous gearbox method, by means of adding only two more gearwheels and one more synchronizing tooth clutch, connected to the input plane (I) of the gearbox.

This means that, according to the present invention, a gearbox composed of three basic modules, combined with the double input splitter, doubles the previous total number of nine possible combinations to eighteen possible combinations.

Thus, using only two more gearwheels, combined with a three basic modules gearbox, more gear steps are attained, with less components, then it was possible with a simple four basic modules gearbox constructed according to patent PCT/PT01/00009.

In addition, another main advantage, introduced by the present double input splitter, is the fact that it allows the use of an important characteristic of the previous innovative method, with significant benefits.

In the previous innovative method of construction of multi-speed motor vehicle gearboxes, it was found that the characteristic trend curve of the transmission ratios is more regular on the middle transmission ratios, then in the top and lower transmission ratios. Between the middle points and the extremes, the innovative method trends to present great undesirable steps.

The aim of the double input splitter is to double the input possibilities of a previous gearbox and also to overlap two characteristic curves, by means of duplicating the characteristic curve attained by the previously innovative gearbox concept, constructed according to patent PCT/PT01/00009.

It was found that those two characteristic curves are proportional and they are at different levels, like shown in Fig. 1.

Therefore, a gearbox constructed based on a three or four basic modules in serial, according to previous patent PCT/PT01/00009, using a common double input splitter at the gearbox input level, can be designed in order to overlap two similar characteristic curves at two different levels.

Each of those two levels is a direct result of the use of two different input shaft rotations into the previous gearbox method, by means of the double input splitter.

The double input splitter works most likely the hell known"splitter"that is widely used on heavy-trucks conventional gearboxes.

The double input splitter considered alone, without being combined with patent PCT/PT01/ /00009, is not innovative.

The innovative and important improvement introduced by this present patent is the use of that well known double input splitter, called simply"splitter", in combination with patent PCT/PTO 1/00009, titled method of construction of multi-speed motor vehicle gearboxes.

That well known double input splitter incorporated within the innovative patented method, patent PCT/PT01/00009, is thus innovative and it solves a major technical problem of that previous innovative method. Also, addressing important benefits in order to build real application gearboxes based on the previous invention,"method of construction of multi- speed motor vehicle gearboxes", patent PCT/PT01/00009.

By means of a simple analyse of costs and benefits, between a three or four basic modules gearbox with double input splitter, it was found that the benefits of the four basic modules gearbox probably doesn't compensate the costs. Thus, it is expected that a three basic modules gearbox, with double input splitter, will be the most feasible and acceptable gearbox conception.

The gearbox described on this present patent is the cheaper three basic modules gearbox, constructed according to patent PCT/PT01/00009 in combination with a common double input splitter.

The inventor considers the present patent of invention the simplest combination possible of the well known"double input splitter"within the innovative"method of construction of multi-speed motor vehicle gearboxes", patent PCT/PT01/00009.

BRIEF DESCRIPTION OF THE INVENTION The present invention was found to be the best combination possible between a double input splitter and a three basic modules gearbox, constructed according to patent PCT/PTOl/ /00009.

The double input splitter is composed by two pairs of gearwheels (1,2) and (6,7), one main input shaft (3), one double synchronised tooth clutch (4) and a rigid connection between gearwheels (2,7).

Two consecutive gearwheels (6,7), bellowing to the input plane (I) of the innovative gearbox, are used to construct the double input splitter. Those two consecutive gearwheels (6,7) mean two different input levels within the three basic modules innovative gearbox.

Those two different input levels are attained as follows. If the synchronised tooth clutch (4) engages the input shaft (3) directly on to the gearwheel (6) of the input plane (I), the three basic modules gearbox is driven by a direct connection between the vehicle engine and the three basic modules gearbox, producing the"high"input and the"high"characteristic transmission ratios curve shown in Fig. 1.

If the synchronised tooth clutch (4) engages the input shaft (3) directly on to the gearwheel (1) of the splitter, the engine rotation is driven to the gearbox via the gearwheel (2). That gearwheel (2) must be bigger then the new input gearwheel (1), in order to reduce the speed rotation transmitted to gearwheel (7) of the input plane (I) of the three basic modules gearbox. That reduced rotation speed produces the"low"input and the"low"characteristic transmission ratios curve shown in Fig. 1.

In any of the cases, according to patent PCT/PT01/00009, the three basic modules gearbox will produce nine possible transmission ratios. Thus, doubling the input possibilities by means of two different input levels, the result are eighteen possible combinations of transmission ratios within the output plane (III) of the gearbox, or eighteen speed gears.

In addition, in the case of the gearbox shown in Fig. 3, there is also the possibility of a direct input/output between the main input shaft (3) and the output shaft (18), via the synchronised tooth clutches (4,19,22), leading to a direct output 1: 1 without the need of any gearwheel mesh inside the gearbox.

The direct output 1 : 1 possibility means one more additional speed, the nineteenth.

Thus, when a direct input/output is included as shown in Fig. 3, there are a total of nineteen transmission ratios available. The final result, overlapping the two characteristic curves, is a combined characteristic curve as shown in Fig. 2.

Finally it is important to notice, there are two major output possible designs. One is concerned with vehicles with longitudinal engine mounted and rear wheels drive, whose gearbox design is shown in Fig. 3. The other is concerned with vehicles with transversal engine mounted and front wheels drive, whose gearbox design is shown in Fig. 4.

Rear engine mounted vehicles and rear wheel drive vehicles can use any of those same front engine mounted gearbox type, Fig. 3 or Fig. 4, only depending on the vehicle engine orientation being longitudinal or transversal mounted onto the vehicle.

FIELD OF THE INVENTION The field of application of the present invention is strictly concerned to motor vehicle gearboxes constructed according to previous patent PCT/PT01/00009, titled"method of construction of multi-speed motor vehicle gearboxes".

Gearboxes constructed in accordance with the present invention apply to all type of motor vehicles, when a gearbox capable to provide multiple speed transmission ratios is needed.

AIM OF THE INVENTION By means of a deep research and investigation, the inventor found that the previous method of construction of multi-speed gearboxes, patent PCT/PT01/00009, have some load capacity limiting problem with the use of common gearwheels dimensions. Those load capacity limiting problems affect specially heavy-trucks and, in general, vehicles that need to transmit great amounts of power via the gearbox at low speed rotation.

The aim of this invention is to solve those above mentioned problems.

BRIEF DESCRIPTION OF THE DRAWINGS The drawings included in this patent of invention are schematic examples of a possible combination of nine gearwheels (6-14), bellowing to a"three basic modules gearbox" constructed according to patent PCT/PT01/00009.

Because any type of practical solution for the present invention demands that the profile and dimensions of all the teeth, used in the gearboxes, must be rigorously equal in all gearwheels used, the diameter of the gearwheels must be compatible with the needed number of tooth necessary to manufacture in each of the gear wheels.

Therefore, for the elaboration of the drawings included in this patent of invention, the teeth number has been rigorously fixed for each of the gearwheels.

Fig. 1 shows a graphic of the two different levels of the output range possible to attain by means of a double input splitter, with the same three basic modules gearbox plus the direct input/output option 1: 1 possible to attain in the case shown in Fig. 3.

Fig. 2 is the same as Fig. 1, but the graph values are ascending ordered.

Fig. 3 shows a highly schematic presentation of the basic working mechanism of a gearbox comprising three basic modules, according to patent PCT/PT01/00009, plus the double input splitter mechanism.

Fig. 4 is the same as Fig. 3, but the output shaft is not a shaft used within the three basic modules as in the case represented in Fig. 3. In order to meet the requirements of transversal engine mounted vehicles, the output of the gearbox is transferred directly to the crownwheel (18) of the differential system (29) of the vehicle global transmission system.

Fig. 5 shows the same gearbox of Fig. 3 in another schematic view. Fig. 5 shows the complete gearbox, with all gearwheels assembled in the final position.

Fig. 6-9 are related to the previous Fig. 5. Fig. 6-9 are included to accurately describe the real disposal of each gearwheel of the gearbox shown in Fig. 5. Fig. 6 shows the detail of the gearwheels producing the double input splitter. Fig. 7 shows a detail of the input plane (I) of the main core gearbox. Fig. 8 shows a detail of the central plane (II) of the gearbox main core, plus the input gearwheel (25) for the reverse system. Finally, Fig. 9 shows a detail of the output plane (III) of the gearbox, plus the gearwheel (26) needed for reverse.

DETAILED DESCRIPTION OF THE INVENTION Motor vehicle gearbox according to Fig. 3-9, comprising a serial association of three basic modules, according to patent PCT/PT01/00009, in combination with a double input splitter, plus a reverse system.

The double input splitter doubles the input possibilities on the previous three basic modules gearbox. The double input splitter is used to attain a low level input, and a high level input, on the three basic modules gearbox.

Those two different input levels are needed to some vehicle's applications, in order to solve the load capacity and range compatibility problems of the method of construction of multi- speed motor vehicle gearboxes, patent PCT/PT01/00009.

The double input splitter working mechanism is the same as the input splitter system commonly used on heavy-trucks gearboxes.

The double input splitter is composed by two pairs of gearwheels (1,2) and (6,7), one main input shaft (3), one double synchronised tooth clutch (4) and a rigid connection between gearwheels (2,7).

The gearwheel (1) is free to rotate on the main input shaft (3) and that same gearwheel (1) can be coupled to the main input shaft (3) by means of a coupling and uncoupling system (4).

The double input splitter comprises a main input shaft (3), whose rotation permanently transmits the vehicle engine rotation to the double synchronised tooth clutch (4). That double synchronised tooth clutch (4) splits the engine rotation via the gearwheel (1) or gearwheel (6).

The three modules gearbox is composed of nine gearwheels (6-14), three shafts (15-17) and six synchronised tooth clutch (19-24), meshing in serial according to patent PCT/PT01/ /00009, titled,"method of construction of multi-speed motor vehicle gearboxes".

By means of the double input splitter, there are two different input gear wheels, (6) or (7), on the input plane (I) of the three basic modules gearbox. This means two different input levels on the three basic modules gearbox, as follows.

The input level via the gearwheel (6) is done by means of a direct coupling between the main input shaft (3) and the gearwheel (6). This coupling produces the high level input on the three basic modules gearbox. So, the high input level on the gearbox is always a direct coupling between the main input shaft (3) and the three basic modules gearbox. That coupling is done by means of the double synchronised tooth clutch (4).

The input level via the gearwheel (7) must be a reduced input level in order to attain the lowest gearbox transmission ratio. That lowest gearbox transmission ratio is limited by the maximum admissible torque of the main gearbox components.

In order to attain the reduced input level via the gearwheel (7), the double synchronised tooth clutch (4) must be actuated in opposite direction, coupling the main input shaft (3) with the gearwheel (1) of the splitter system.

The gearwheel (1) meshes with the gearwheel (2) and, in order to reduce the main input shaft speed, the gearwheel (2) must be bigger then gearwheel (1).

The gearwheel (2) is rigidly fixed to gearwheel (7). Thus, the input transmitted to the gearwheel (7) of the three basic modules gearbox is a reduced level.

Because a low input level can be introduced on the gearbox main core, the final output can meet a wider transmission range and also a lowest gear transmission ratio.

When the main core gearbox transmission range is aimed to be shorter, one can easily find gearwheels combination which meet the torque requirements of the vehicle's engine, within the commonly used gearwheels dimension.

By means of the combination of the double input splitter with a three basic modules gearbox, it is possible to displace the characteristic transmission curve into a new one at a lower level. The low level characteristic transmission curve is aimed to adjust the final transmission range to vehicle's normal required range.

The lowest level input is achieved reducing the transmission ratio between gearwheels (1) and (2) of the splitter system, up to the limit of gearbox torque design value.

The three basic modules are the gearbox main core, according to patent PCT/PT01/00009.

It cannot be removed any component of the three basic modules gearbox without loosing several gear transmission ratios possibilities.

For instance, if any of the six coupling and uncoupling system (19-24) is removed, there are three transmission ratios loss in the gearbox main core, plus another three due to the double input splitter. Thus, if one of any of the six synchronised tooth clutch (19-24) is removed the total loss will be six gear transmission ratios, minimum.

Removing the synchronised tooth clutch doesn't mean we can remove the respective gearwheel. Only one the gearwheels (8) or (14) can be removed with the respective coupling uncoupling system (21) and (24), without loosing more then six transmission ratios.

If anything else is removed from the three basic modules main core gearbox, that will lead to a final transmission total of nine transmission ratios, maximum.

The innovative three basic modules gearbox works differently from any conventional motor vehicle gearbox.

In a conventional gearbox, the majority of the gearwheels and the majority of the synchronised tooth clutch only produce one gear transmission. If a double input splitter is used, like in the conventional heavy-trucks gearbox, each component can produce two transmission gear maximum.

A conventional motor vehicle gearbox also needs to perform a primary reduction between the input shaft and the countershaft. Like it was found to be needed for the innovative gearbox method, patent PCT/PT01/00009, as described herein.

The countershaft is always composed of several gearwheels rigidly fixed to that countershaft. Then, the countershaft rigid gearwheels drive the possible output gearwheels at different speed rotation.

In the innovative method of construction of multi-speed motor vehicle gearboxes it is a primary condition of that method that, any of the three shafts (15-17) of three basic modules cannot have more then one gearwheel rigidly fixed to that same shaft.

It is also a primary condition that the three gearwheels (9-11), rigidly fixed to the respective shafts (15-17), must lie in the same plane meshing with one another.

The above two conditions have introduced the new concept of"gearbox planes". There are always three planes in the innovative method, patent PCT/PT01/00009.

The input plane (I) is always composed of gearwheels free to rotate on the shaft. The plane (II) is always composed of gearwheels rigidly fixed to the shaft. Finally, the output plane (III) is always composed of gearwheels free to rotate on the shaft.

The difference between a conventional gearbox and the innovative gearbox is the fact that a conventional gearbox is based on the countershaft driving free gearwheels at different speeds, and the innovative gearbox is based on three gearwheels planes rotating synchronised at different speeds.

It was found that speed changes could be smooth between shifts of synchronised planes. The gear shifts are progressive enough to meet the synchronised tooth clutch requirements.

In the drawing shown in Fig. 3, the gearwheels dimension were calculated in order to meet the heavy-trucks requirements.

Heavy-trucks transmission system use a Range Section, after the main gearbox, in order to reduce the transmission ratios up to the very low transmission ratio needed for those specific type of vehicles.

The present invention doesn't exclude the Range Section need. The drawing shown in Fig. 3 was meant to produce a transmission range output equal to the transmission range output of a heavy-trucks conventional gearbox. Thus, the same Range Section is still needed to be used.

It is obvious that, if the combination shown in fig. 3 can be used in heavy-trucks then it can be used in any lighter vehicle type.

The reverse system should not be incorporated inside the gearbox main core, because we cannot eliminate any function of any component of the three basic modules without loosing at least six gear transmissions.

Nevertheless, loosing six transmission ratios leave twelve or thirteen transmission ratios available, depending on the case of Fig. 4 or Fig. 3 respectively, and that's enough for the majority of vehicle's applications. Thus, the loosing of six transmission ratios is admissible and probably it will be aimed, depending on the specific gearwheels solution.

A reverse system is also included in this patent of invention. The best solution for the reverse system, found by the inventor, is described in Fig. 3-9.

It is an additional gearwheel system, external to the main core gearbox, composed of two gearwheels (25,26), one shaft (27) and a conventional coupling and uncoupling system (28).

The two gearwheels (25) and (26) mesh with the main core gearbox via two gearwheels (10) and (12), specially chosen for the gearwheels solution shown in Fig. 3-9.

It is a main condition that the gearwheel (10) must be positioned in the central plane (II) of the gearbox and the gearwheel (12) must be positioned in the output plane (III) of the gearbox.

The gearwheel (25) meshes with the gearwheel (10) and the gearwheel (26) meshes with the gearwheel (12). It is also a main condition that the gearwheels (10) and (12) are positioned in two consecutive shafts, (16) and (17) respectively, of the three basic modules gearbox.

There is a coupling and uncoupling system (28) providing a possible direct connection between gearwheels (25) e (26). When gearwheels (25) and (26) are coupled, via the coupling and uncoupling system (28), the gearbox is in reverse mode.

In the forward mode the coupling and uncoupling system (28) must be always open.

In reverse mode, the only possible connection between the central plane (II) and the output plane (III) must be the connection of gearwheels (25) and (26), coupled via the coupling and uncoupling system (28). Thus, in reverse mode the three coupling and uncoupling systems (22-24) must be always open.

The coupling and uncoupling systems (22-24) must be always open because the output plane (III) of the gearbox will rotate in reverse sense when the coupling and uncoupling system (28) is closed.

In reverse mode, in order to shift gears, the only possible connection within the gear box are the three coupling and uncoupling systems (19-21) and the double input splitter, via the coupling and uncoupling system (4). These possible connections produce three transmission ratios at the low level input and more three at the high lever input.

In a real application only the three transmission ratios at low level input are important.

In the gearbox shown in Fig. 3-9 the first three lowest transmission ratio available forward are also available in reverse.

Finally it is important to notice, there are two major output possible designs. One is concerned with vehicles with longitudinal engine mounted and rear wheels drive, whose gearbox design is shown in Fig. 3. The other is concerned with vehicles with transversal engine mounted and front wheels drive, whose gearbox design is shown in Fig. 4.

Rear engine mounted vehicles and rear wheel drive vehicles can use any of those same front engine mounted gearbox type, Fig. 3 or Fig. 4, only depending on the vehicle engine orientation being longitudinal or transversal mounted onto the vehicle.