WO2019159031A1

WO2019159031A1 - Transmission

Info

Publication number: WO2019159031A1
Application number: PCT/IB2019/050855
Authority: WO
Inventors: Claudio Benassi
Original assignee: Arbos Group S.P.A.
Priority date: 2018-02-14
Filing date: 2019-02-04
Publication date: 2019-08-22
Also published as: CN110159734A; IT201800002670A1

Abstract

The invention describes a transmission (100) comprising at least: a plurality of rotating shafts having mutually parallel rotation axes, including at least one first shaft (105), a second shaft (110), a third shaft (115) and a fourth shaft (120); a first toothed wheel (140) rotatably coupled with the first shaft (105); a first toothed wheel (145) fitted to the fourth shaft (120) and meshing with the first toothed wheel (140) of the first shaft (105), so as to define a reverse gear; a first engaging apparatus adapted for selectively engaging the first shaft (105) with the first toothed wheel (140) rotatably coupled with it or with the second shaft (110); at least one first and a second toothed wheel (165, 170) fitted to the second shaft (110); at least one first and a second toothed wheel (175, 180) rotatably coupled with the third shaft (115) and singularly meshing respectively with the first and with the second toothed wheel (165, 170) of the second shaft (110), so as to respectively define a first and a second gear; a second engaging apparatus adapted for selectively engaging the third shaft (115) with the first or with the second toothed wheel (175, 180) rotatably coupled with it; and a second toothed wheel (190) fitted to the fourth shaft (120) and meshing with the first toothed wheel (175) of the third shaft (115).

Description

TRANSMISSION

Technical field

The present invention concerns a transmission adapted for transferring torque from a power unit, for example from an internal combustion engine, to the traction members of a vehicle, for example to the drive wheels. More specifically, the present invention con cerns a transmission adapted for being installed on a farming vehicle, for example on a tractor.

State of the art

As known, most tractors generally comprise an internal combustion engine, at least two drive wheels and a transmission adapted for transferring the torque generated by the internal combustion engine to the drive wheels and possibly to a power take-off adapted for actuating the operating machines that can be connected to the tractor.

As well as transferring the torque, the transmission must be capable of changing the gear ratio between the angular speed of the drive shaft and the angular speed of the drive wheels, selecting it on each occasion among a plurality of available gears.

In order to allow this change of speed, a conventional transmission generally comprises an input shaft connected to the drive shaft, for example through a clutch, an output shaft connected to the drive wheels and/or to the power take-off, for example through a differ ential and/or other transmission members, and a plurality of gears adapted for kinemati cally connecting the input shaft with the output shaft.

Each of these gears normally comprises a first toothed wheel fitted to the input shaft and a second toothed wheel rotatably coupled on the output shaft and arranged meshed with the corresponding first toothed wheel.

The transmission also comprises engaging members, for example synchronizers, which can be actuated manually or in an automated manner to selectively engage only one of the aforementioned second toothed wheels, making it rotate as a unit with the output shaft and thus allowing the transmission of motion through the corresponding gear.

In order to ensure optimal operation of the engine in any operative condition of the tractor, for example during farming work, during travel on asphalt or during travel over soil, the transmission nevertheless has the need to provide a very high number of different gears. In order to respect this requirement with the conventional architecture it is therefore nec essary to significantly multiply the number of gears of the transmission, with the result of obtaining an extremely bulky and heavy transmission that often introduces very substan tial constructive constraints in the farming tractor as a whole.

Presentation of the invention

In light of what has been outlined above, a purpose of the present invention is to provide a transmission capable of providing numerous different gears, remaining a compact and therefore low-bulk constructive solution.

Another purpose of the present invention is to provide a transmission that can be config ured or reconfigured in a modular manner according to the specific applications for which it is intended, without substantially increasing its total bulk.

A further purpose of the present invention is to provide a transmission that can be coupled not only with an internal combustion engine but also with a hybrid system comprising an internal combustion engine and an electric motor.

Another purpose of the present invention is finally that of achieving the aforementioned purposes in a simple, rational and relatively low-cost solution.

Such and other purposes are accomplished thanks to the characteristics of the invention that are given in the independent claim 1 . The dependent claims outline preferred or par ticularly advantageous aspects of the invention.

In particular, an embodiment of the present invention provides a transmission comprising:

- a plurality of rotating shafts having mutually parallel rotation axes, including at least one first shaft, a second shaft that can for example be arranged coaxial to the first shaft, a third shaft and a fourth shaft,

- a first toothed wheel rotatably coupled with the first shaft,

- a first toothed wheel fitted to the fourth shaft and meshing with the first toothed wheel of the first shaft, so as to define a reverse gear,

- a first engaging apparatus adapted for selectively engaging the first shaft with the first toothed wheel rotatably coupled with it or with the second shaft (i.e. for making them rotate as a unit),

- at least one first and a second toothed wheel fitted to the second shaft,

- at least one first and a second toothed wheel rotatably coupled with the third shaft and singularly meshing respectively with the first and with the second toothed wheel of the second shaft, so as to respectively define a first and a second gear,

- a second engaging apparatus adapted for selectively engaging the third shaft with the first or with the second toothed wheel rotatably coupled with it (i.e. for making them rotate as a unit), and

- a second toothed wheel fitted to the fourth shaft and meshing with the first toothed wheel of the third shaft.

Thanks to this solution, a transmission is provided that is extremely simple, cost-effective and compact, which is effectively capable of mechanically providing at least two splitters, including at least one direct forward splitter and a reverse splitter, able to be selected through the first engaging apparatus and, for each of these splitters, at least two different gear ratios able to be selected through the second engaging apparatus and that, depend ing on the specific applications for which the transmission is intended, can be configured as two gears or as two ranges.

In this way, the transmission outlined above can be advantageously used as base module both for the development of mechanical or hydraulic-mechanical transmissions with a greater number of gear ratios, and for making transmissions of the CVT ( Continuous Var iable Transmission) type having a wider range of operativity with respect to those that are currently known.

According to an aspect of the invention, the distance between centres between the sec ond shaft and the third shaft can be greater with respect to the distance between centres between the second shaft and the fourth shaft.

In this way, it is advantageously possible to optimise the sizing of the parts and, conse quently, the bulk, weight and cost of the transmission as a whole.

Substantially for the same reason, it is also preferable for the half-plane containing the rotation axes of the second and of the fourth shaft to be able to be inclined with respect to the half-plane containing the rotation axes of the second and of the third shaft, for example by an angle of less than 90 sexagesimal degrees.

According to another aspect of the present invention, the first engaging apparatus can comprise a synchronizer adapted for engaging the first shaft alternatively with the first toothed wheel rotatably coupled on it or with the second shaft.

Similarly, the second engaging apparatus can comprise a synchronizer adapted for en gaging the third shaft alternatively with the first or with the second toothed wheel rotatably coupled on it.

These solutions have the advantage of being very cost-effective and not very bulky. In some embodiments, the first engaging apparatus can however comprise two clutches, for example two hydraulic clutches, respectively adapted for engaging/disengaging the first shaft with/from the second shaft and for engaging/disengaging the first shaft with/from the first toothed wheel rotatably coupled on it.

Although generally more expensive than the previous one, this second solution has the advantage of having better performance.

According to another aspect of the invention, the transmission can also comprise:

- a fifth rotating shaft having rotation axis parallel to the rotation axes of the other rotating shafts, for example arranged coaxial to the third shaft, and

- a planetary gear arranged to kinematically connect the fifth shaft to the third shaft. In this way, it is advantageously possible to obtain a significant change of speed between the third and the fifth shaft, with a high-performance and low-bulk gear mechanism. According to a further aspect of the invention, the transmission can also comprise:

- a further toothed wheel fitted to the second shaft,

- a further toothed wheel rotatably coupled with the third shaft and meshing with said further toothed wheel of the second shaft, so as to define a further gear, and

- a further engaging apparatus adapted for selectively engaging the third shaft with said further toothed wheel rotatably coupled with it (i.e. for making them rotate as a unit).

Also in this case, the further engaging apparatus can for example comprise a synchro nizer adapted for engaging/disengaging the third shaft with/from the further toothed wheel rotatably coupled with it.

Thanks to this solution, the transmission outlined above is added to with a further gear ratio, able to be used both in the forward splitter and in the reverse splitter, which advan tageously increases the field of application of the transmission.

In particular, this type of solution can be useful as base for making a CVT transmission. An embodiment of the present invention indeed foresees that the transmission can also comprise:

- a hydraulic motor having a drive shaft kinematically connected to a crown gear of the planetary gear so as to be adapted to set it in rotation, and

- a hydraulic pump having an actuation shaft kinematically connected with the first shaft and hydraulically connected to the hydraulic motor. In this way, a CVT transmission is obtained in which, for every split and range available mechanically, it is possible to continuously vary the gear ratio between the first shaft and the fifth shaft thanks to the setting in rotation of the crown gear of the planetary gear, remaining an extremely simple and compact solution.

In accordance with another embodiment of the present invention, the transmission can comprise:

- a sixth rotating shaft having rotation axis parallel to the rotation axes of the other rotating shafts,

- at least one first and a second toothed wheel rotatably coupled with the sixth shaft and singularly meshing respectively with the first and with the second toothed wheel of the second shaft, so as to respectively define a third and a fourth gear,

- a third engaging apparatus adapted for selectively engaging the sixth shaft with the first or with the second toothed wheel rotatably coupled with it (i.e. for making them rotate as a unit), and

- a fifth gear adapted for kinematically connecting the sixth shaft to the third shaft. Thanks to this solution an extremely compact transmission is provided that, mechanically, is effectively capable of supplying at least four gears for each splitter.

Also in this case, the third engaging apparatus can comprise a simple synchronizer adapted for engaging the sixth shaft alternatively with the first or with the second toothed wheel rotatably coupled on it (i.e. for making them rotate as a unit).

In order to optimise the sizing of the parts and, consequently, the bulk, weight and cost of the transmission, it is preferable for the distance between centres between the second shaft and the sixth shaft to be less with respect to the distance between centres between the second shaft and the third shaft.

For example, the distance between centres between the second shaft and the sixth shaft can have a value comprised between that of the distance between centres between the second shaft and the fourth shaft and that of the distance between centres between the second shaft and the third shaft.

Another preferred aspect of the invention is the fact that the half-plane containing the rotation axes of the second and of the sixth shaft can be inclined with respect to the half plane containing the rotation axes of the second and of the third shaft, for example by an angle of less than 90 sexagesimal degrees and, for example, greater than the angle formed between the half-plane containing the rotation axes of the second and of the fourth shaft and the half-plane containing the rotation axes of the second and of the third shaft. According to an aspect of this embodiment, the aforementioned fifth gear can comprise a third and a fourth toothed wheel rotatably coupled with the second shaft and rotating as a unit with each other, a third toothed wheel fitted to the third shaft and meshing with the third wheel of the second shaft, a third toothed wheel fitted to the sixth shaft and meshing with the fourth toothed wheel of the second shaft, and a fourth engaging apparatus for selectively engaging the second shaft with the third and fourth toothed wheel rotatably coupled on it (i.e. for making them rotate as a unit).

Also in this case, the fourth engaging apparatus can comprise a synchronizer adapted for engaging/disengaging the second shaft with/from the third toothed wheel rotatably cou pled with it.

In this way, it is advantageously also possible to add to the transmission a fifth gear for each available splitter, consequently increasing the field of application of the transmission without significantly modifying the total bulk thereof.

The third and the fourth toothed wheel of the second shaft preferably have the same number of teeth but they can possibly have toothings with different profile, for example applying different corrections relative to the displacement factor of the profile and to the addendum correction factor.

In this way, it is advantageously possible to optimise the tensions that discharge on the toothed wheels during the different operating steps, consequently optimising their sizing and therefore the bulk, the weight and the connected costs.

Returning to the relative position of the shafts, here it should be emphasised that the distance between centres between the second and the sixth shaft, as well as the angle formed between the half-plane containing the rotation axes of the second and of the sixth shaft and the half-plane containing the rotation axes of the second and of the third shaft, can be unequivocally determined as a function of the maximum transversal bulk of the transmission (which can be a fixed design parameter) and of the number of teeth of the wheels that they mesh between the second and the sixth shaft. In other words, once the transversal bulk and the number of teeth have been fixed, the angle formed between the half-planes and the distance between centres is unequivocally determined, therefore al lowing it to be different from those previously indicated, for example allowing the angle between the half-planes to be greater than 90°.

According to another aspect of the invention, the transmission can also comprise a fifth engaging apparatus adapted for selectively engaging the fifth shaft with a planet carrier of the planetary gear or directly with the third shaft (i.e. making them rotate as a unit). Thanks to this solution it is advantageously possible to add to the transmission with two ranges, able to be selected through the fifth engaging apparatus, which make it possible to multiply the number of gear ratios that can be obtained with the transmission.

According to a further aspect of the invention, the transmission can also comprise:

- a sixth engaging apparatus adapted for selectively engaging a first portion of the third shaft, with which the respective first, second and third toothed wheel are cou pled, with a second portion of the third shaft (i.e. making them rotate as a unit),

- a fifth toothed wheel rotatably coupled with the second shaft and rotating as a unit with the third and fourth toothed wheel of said second shaft,

- a fourth toothed wheel rotatably coupled with the second portion of the third shaft and meshing with the fifth toothed wheel of the second shaft, and

- a seventh engaging apparatus adapted for selectively engaging said second por tion of the third shaft with the fourth toothed wheel rotatably coupled on it.

This solution makes it possible to add to the transmission with two further ranges, able to be selected through the sixth and the seventh engaging apparatus, which further multiply the number of available gear ratios. For example, it is possible to obtain four ranges, including a creeper, a mini-creeper, a medium and a high.

In this case, the sixth engaging apparatus can comprise a reconfigurable joint adapted for selectively engaging/disengaging the first portion of the third shaft with/from the sec ond portion.

The seventh engaging apparatus can in turn comprise a further reconfigurable joint adapted for selectively engaging/disengaging the second portion of the third shaft with/from the fourth toothed wheel rotatably coupled on it.

A further embodiment of the present invention foresees that the transmission can also comprise:

- a second toothed wheel fitted on the first shaft,

- a seventh rotating shaft having rotation axis parallel to the rotation axes of the other rotating shafts, - at least one first toothed wheel rotatably coupled with the seventh shaft and mesh ing with the second toothed wheel of the first shaft,

- a second toothed wheel fitted on the seventh shaft and meshing with the second toothed wheel fitted on the second shaft, and

- an eighth engaging apparatus adapted for selectively engaging the seventh shaft with the first toothed wheel rotatably coupled with it (i.e. making them rotate as a unit).

In this way, it is advantageously possible to add to the transmission with a further splitter, in addition to the direct forward one and the reverse one, for example a forward low-speed splitter (low).

The eighth engaging apparatus can comprise a clutch, for example a hydraulic clutch, adapted for engaging/disengaging the seventh shaft with/from the first toothed wheel ro tatably coupled with it.

In order to optimise the sizing of the parts and, consequently, the bulk, weight and cost of the transmission, it is preferable for the distance between centres between the second shaft and the seventh shaft to be substantially equal to or (slightly) greater than the dis tance between centres between the second shaft and the third shaft.

It is also preferable for the half-plane containing the rotation axes of the second and of the seventh shaft to be able to form, with the half-plane containing the rotation axes of the second and of the fourth shaft, an angle substantially equal to 180 sexagesimal de grees.

In other words, it is preferable for the rotation axes of the second, of the fourth and of the seventh shaft to be able to lie in a common plane, wherein the rotation axis of the second shaft is arranged between the rotation axes of the fourth and of the seventh shaft.

According to an aspect of this embodiment, the transmission can also comprise:

- a third toothed wheel fitted on the first shaft,

- a third toothed wheel rotatably coupled with the seventh shaft and meshing with the third toothed wheel of the first shaft, and

- a ninth engaging apparatus adapted for selectively engaging the seventh shaft with the third toothed wheel rotatably coupled with it (i.e. making them rotate as a unit).

This ninth engaging apparatus can also comprise a clutch, for example a hydraulic clutch, adapted for engaging/disengaging the seventh shaft with/from the third toothed wheel rotatably coupled with it.

Thanks to this solution, a further splitter, for example a high-speed forward splitter (high) is advantageously added, further multiplying the number of gear ratios available.

Brief description of the drawings

Further characteristics and advantages of the invention will become clearer from reading the following description provided as a non-limiting example, with the help of the figures illustrated in the attached tables.

Figure 1 is the diagram of a transmission according to a base embodiment of the present invention.

Figure 2 is the view A indicated in figure 1 that shows only the arrangement of the rotating shafts.

Figure 3 is the diagram of a transmission in accordance with a second embodiment of the present invention.

Figure 4 is the diagram of a transmission in accordance with a third embodiment of the present invention.

Figure 5 is the view A indicated in figure 4 that shows only the arrangement of the rotating shafts.

Figure 6 is the diagram of a transmission in accordance with a fourth embodiment of the present invention.

Figure 7 is the diagram of a transmission in accordance with a fifth embodiment of the present invention.

Figure 8 is the view A indicated in figure 7 that shows only the arrangement of the rotating shafts.

Figure 9 is the diagram of a transmission in accordance with a sixth embodiment of the present invention.

Detailed description

With the help of the aforementioned figures, multiple embodiments of a transmission 100 that is generally adapted for transferring torque from a power unit to one or more mem bers to be actuated are now described.

For example, the transmission 100 can be installed on-board a motor vehicle, typically but not exclusively on-board a farming vehicle like a tractor, in order to transfer the torque generated by the power unit to the traction members of the vehicle, for example to the drive wheels, and possibly to an operating machine that can be installed on the vehicle itself or connected to it, for example through a power take-off.

The power unit for which the transmission 100 is intended can be any device capable of generating torque. For example, the power unit can comprise simply an internal combus tion engine, like a Diesel engine, or it can be a hybrid power unit, comprising both an internal combustion engine and an electric motor connected to a battery.

According to a base embodiment, illustrated in figure 1 , the transmission 100 can com prise a plurality of rotating shafts having mutually parallel rotation axes, including at least one first shaft 105, a second shaft 1 10, a third shaft 1 15, a fourth shaft 120 and a fifth shaft 125.

The first shaft 105 is adapted for being connected to the power unit, so as to receive the torque and be set in rotation by it. For example, the first shaft 105 can be directly con nected to the drive shaft of the internal combustion engine and/or of the electric motor. The fifth shaft 125 is adapted for being connected to the members to be actuated, for example to the drive wheels of the vehicle, so as to transmit to them the torque generated by the power unit and set them in rotation.

For example, the fifth shaft 125 can be connected to the members to be actuated through one or more transmission systems, including for example a conical wheel gear 130 and/or a planetary gear 135.

The second, third and fourth shaft 1 10, 1 15 and 120 of the transmission 100 are kinemat ically arranged between the first shaft 105 and the fifth shaft 125, so as to transmit the motion from one to another.

Preferably, the second, third and fourth shaft 1 10, 1 15 and 120 are parallel to one another and spaced apart, with the second shaft 1 10 that can be arranged coaxial to the first shaft 105 and the third shaft 1 15 that can be arranged coaxial to the fifth shaft 125.

As illustrated in figure 2, for reasons of constructive compactness and of optimisation of the stresses and of the masses, the distances between centres between the second, the third and the fourth shaft 1 10, 1 15 and 120 can be different and their rotation axes can be not perfectly coplanar.

For example, the distances between centres D3 between the second shaft 1 10 and the third shaft 1 15 can be greater than the distance between centres D4 between the second shaft 1 10 and the fourth shaft 120. Moreover, the half-plane S4 containing the rotation axes of the second and of the fourth shaft 1 10 and 120 can be inclined with respect to the half-plane S3 containing the rotation axes of the second and of the third shaft 1 10 and 1 15, for example by an acute angle of less than 90 sexagesimal degrees and preferably comprised between 60 and 70 sexa gesimal degrees.

Going back to figure 1 , the transmission 100 can comprise a first toothed wheel 140 ro tatably coupled with the first shaft 105 and meshing with a first toothed wheel 145 fitted on the fourth shaft 120, so as to define a reverse gear.

It should be emphasised here that, in the present description, the term“rotatably coupled” indicates that the toothed wheel is coaxially slotted and supported on the relative shaft, with respect to what it is nevertheless free to rotate around the common axis, whereas the term“fitted” generally indicates that the toothed wheel rotates as a unit with the rela tive shaft, irrespective of whether the connection between these two components is ob tained through fitting or any other known system.

The reverse gear defined by the wheels 140 and 145 can be configured to define a slight speed multiplication between the first shaft 105 and the fourth shaft 120.

For example, the first wheel 145 of the fourth shaft 120 can have 23 teeth and the corre sponding first wheel 140 of the first shaft 105 can have 28 teeth, defining a gear ratio equal to about 0.82.

The transmission 100 can also comprise a first engaging apparatus, which is adapted for selectively engaging the first shaft 105 with the first toothed wheel 140 or directly with the second shaft 1 10.

In the present document, the term“engage” should also be generically interpreted as the ability of an engaging apparatus to make two component rotate as a unit, irrespective of the specific ways used to obtain this effect.

In the example illustrated in figure 1 , the first engaging apparatus comprises two clutches, for example two hydraulic clutches, including a clutch 150 adapted for engaging/disen gaging the first shaft 105 with/from the second shaft 1 10, and a clutch 155 adapted for engaging/disengaging the first shaft 105 with/from the first toothed wheel 140.

In other embodiments, like for example that illustrated in figure 4, the first input apparatus could however comprise a synchronizer 160 adapted for engaging the first shaft 105 al ternatively with the first toothed wheel 140 or with the second shaft 1 10. For example, the synchronizer 160 can comprise a mobile member, typically sliding axi ally along the first shaft 105, between a first engaging position in which it engages the first shaft 105 with the toothed wheel 140 and a second engaging position in which it engages the first shaft 105 directly with the second shaft 1 10, passing through an inter mediate or neutral position, wherein the first shaft 105 is rotatably unconstrained both from the toothed wheel 140 and from the second shaft 1 10. The movement and locking of this mobile member in the three positions outlined above can be obtained through suit able mechanical members, for example forks and lever mechanisms, which can be actu ated manually or in an automated manner.

The transmission 100 illustrated in figure 1 also comprises at least one first and a second toothed wheel, respectively indicated with 165 and 170, which are fitted on the second shaft 1 10.

The first toothed wheel 165 is arranged meshed with a corresponding first toothed wheel 175 rotatably coupled with the third shaft 1 15, so as to make a first gear.

Similarly, the second toothed wheel 170 is arranged meshed with a corresponding sec ond toothed wheel 180 rotatably coupled with the third shaft 1 15, so as to make a second gear.

A second engaging apparatus is foreseen to selectively engage the third shaft 1 15 with the first or with the second toothed wheel 175 or 180, so that the second and the third shaft 1 10 and 1 15 are kinematically coupled through the first or the second gear.

In the illustrated example, this second engaging apparatus can comprise a synchronizer 185 adapted for engaging the third shaft 1 15 alternatively with the first toothed wheel 175 or with the second toothed wheel 180.

For example, the synchronizer 185 can comprise a mobile member, typically sliding axi ally along the third shaft 1 15, between a first engaging position in which it engages the third shaft 1 15 with the first toothed wheel 175 and a second engaging position in which it engages the third shaft 1 15 with the second toothed wheel 180, passing through an intermediate or neutral position, wherein the third shaft 1 15 is rotatably unconstrained both from the first toothed wheel 175 and from the second toothed wheel 180. The move ment and the locking of this mobile member in the three positions outlined above can be obtained through suitable mechanical members, for example forks and lever mecha nisms, which can be actuated manually or in an automated manner. The aforementioned first and second gears can be configured so as to both define a reduction of speed between the second shaft 1 10 and the third shaft 1 15 but with a dif ferent gear ratio, for example greater for the first gear and lower for the second gear.

For example, the first wheel 175 of the third shaft 1 15 can have 47 teeth and the corre sponding first wheel 165 of the second shaft 1 10 can have 23 teeth, defining a gear ratio equal to about 2.04.

The second wheel 180 of the third shaft 1 15 can have 35 teeth and the corresponding second wheel 170 of the second shaft 1 10 can have 34 teeth, defining a gear ratio equal to about 1 .03.

The transmission 100 also comprises a second toothed wheel 190 fitted to the fourth shaft 120 and also meshing with the first toothed wheel 175 of the third shaft 1 15, so that the reverse gear can set the second shaft 1 10 in rotation.

It should be observed here that in figure 1 , although the toothed wheel 175 is represented as a thin body, in reality it has an axial extension (i.e. a thickness) sufficient to mesh both with the toothed wheel 190 and with the toothed wheel 165, although these are offset from one another in the axial direction.

The number of teeth of the second toothed wheel 190 is preferably selected so that the overall gear ratio between the first shaft 105 and the second shaft 1 10, when the reverse gear is engaged, is substantially equal to 1 .

For example, the number of teeth of the second toothed wheel 190 can be equal to 19. The transmission 100 according to the embodiment illustrated in figure 1 can finally com prise a planetary gear, globally indicated with 195, which is adapted for kinematically connecting the third shaft 1 15 with the fifth shaft 125.

Preferably, the planetary gear 195 is configured to obtain a reduction of speed between the third shaft 1 15 and the fifth shaft 125.

This planetary gear 195 can comprise a solar toothed wheel 200 fitted to the third shaft 1 15, a crown gear 205 having internal toothing, a plurality of planetary toothed wheels 210 singularly meshing with the solar toothed wheel 200 and with the crown gear 205, and a planet carrier 215 associated with the fifth shaft 125.

In the example illustrated in figure 1 , the crown gear 205 is fixed and the planet carrier 215 is fitted to the fifth shaft 125, so that the planetary gear defines a constant gear ratio between the third shaft 1 15 and the fifth shaft 125. In order to increase the freedom of variation of the gear ratio, other embodiments, some of which will be described hereinafter, nevertheless foresee that the crown gear 205 can be set in rotation around its axis and/or that the fifth shaft 125 can be selectively engaged with the planet carrier 215 or directly with the third shaft 1 15.

Thanks to the constructive architecture described above, the transmission 100 according to the embodiment of figure 1 is capable of mechanically supplying two splitters, including at least one direct forward splitter and a reverse splitter.

The direct forward splitter is configured when the first shaft 105 is directly engaged with the second shaft 1 10, for example closing the clutch 150 and opening the clutch 155. The reverse splitter is, on the other hand, configured when the first shaft 105 is engaged with the first toothed wheel 140, for example opening the clutch 150 and closing the clutch 155.

In this second case, the rotation of the first shaft 105 is transmitted to the fourth shaft 120 through the reverse gear and from here to the second shaft 1 10 through the toothed wheels 190, 175 and 165, so that the second shaft 1 10 rotates in the opposite direction with respect to the first shaft 105.

For each of these splitters, the transmission 100 of figure 1 then provides two different gear ratios between the first shaft 105 and the fifth shaft 125, which depend on the fact that the third shaft 1 15 is engaged with the toothed wheel 175 or with the toothed wheel 180.

From this base configuration, the transmission 100 can be developed in different ways, significantly increasing the number of gear ratios available and the field of application, whilst still remaining a compact and relatively cost-effective solution.

A possible development is shown for example in figure 3, wherein the transmission 100 can be configured like a transmission of the CVT ( Continuous Variable Transmission) type.

In addition to what has already been described in relation to the base embodiment, the transmission 100 in accordance with this second embodiment can comprise a further toothed wheel 220 fitted to the second shaft 1 10, which is arranged meshed with a further toothed wheel 225 rotatably coupled with the third shaft 1 15, so as to define a further gear.

This further gear can be configured to define a speed multiplication between the second shaft 1 10 and the third shaft 1 15.

For example, the further toothed wheel 225 can have 18 teeth and the corresponding toothed wheel 220 can have 37 teeth, defining a gear ratio equal to about 0.49.

A further engaging apparatus is foreseen to selectively engage the third shaft 1 15 with the further toothed wheel 225 or to leave it rotatably idle.

In the illustrated example, this further engaging apparatus can comprise a synchronizer 230, which can comprise for example a mobile member, typically sliding axially along the third shaft 1 15, between an engaging position in which it engages the third shaft 1 15 with the further toothed wheel 225 and a neutral position, wherein the third shaft 1 15 is rotat ably unconstrained from the further toothed wheel 225. The movement and the locking of this mobile member in the two positions outlined above can be obtained through suitable mechanical members, for example forks and lever mechanisms, which can be actuated manually or in an automated manner.

In this way, for each forward and reverse splitter, the transmission 100 also mechanically provides a further gear ratio, in addition to the two described with reference to the first embodiment, which is obtained when the synchronizer 185 is in neutral position while the synchronizer 230 is in engaging position.

These three gear ratios can be configured like three different operative ranges of the transmission 100, wherein the gear ratio defined by the wheels 165 and 175 can repre sent a low speed range (low), the gear ratio defined by the two wheels 170 and 180 can represent a medium speed range (medium), and the gear ratio defined by the wheels 220 and 225 can represent a high speed range (high).

The transmission 100 in accordance with this second embodiment can also comprise a hydraulic motor 235 and a hydraulic pump 240 hydraulically connected to the hydraulic motor 235.

The hydraulic pump 240 comprises an actuation shaft 245, which is adapted for being set in rotation to allow the operation of the hydraulic pump 240 and, therefore, the pumping under pressure of an operating fluid (typically oil) towards the hydraulic motor 235.

In order to allow the rotation of the actuation shaft 245, the latter can be kinematically connected to the first shaft 105, for example through a toothed wheel 250 fitted onto the actuation shaft 245 and arranged meshed with a toothed wheel 255 fitted directly on the first shaft 105. On the other hand, the hydraulic motor 235 comprises a drive shaft 260 and exploits the pressure of the operating fluid coming from the hydraulic pump 240 to set the aforemen tioned drive shaft 260 in rotation.

The drive shaft 260 can be kinematically connected to the crown gear 205 of the planetary gear 195 that, in this embodiment, is not fixed but is free to rotate around its axis, coin ciding with the axis of the third shaft 1 15 and of the fifth shaft 125.

This kinematic connection can be obtained through a toothed wheel 265 fitted onto the drive shaft 260 and meshing for example with an outer toothing directly formed in the crown gear 205.

Thanks to this solution, for each splitter (forward and reverse) and for each operating range (low, medium and high) set mechanically, the hydraulic motor 235, actuated by the pressure of the operating fluid pumped by the hydraulic pump 240, is adapted for setting the crown gear 205 in rotation at different speeds, continuously varying the gear ratio generated by the planetary gear 195 and therefore the speed of the fifth shaft 125 with respect to the speed of the first shaft 105.

A different development of the base transmission described earlier is illustrated in figure 4.

In addition to what has already been described in relation to the base embodiment, the transmission 100 in accordance with this third embodiment comprises a sixth rotating shaft 270 having rotation axis parallel to the rotation axes of the other shafts.

As illustrated in figure 5, the distances between centres D6 between the second shaft 1 10 and the sixth shaft 270 can be less than the distance between centres D3 between the second shaft 1 10 and the third shaft 1 15.

For example, the distances between centres D6 can have a value comprised between that of the distance between centres D3 and that of the distance between centres D4. Moreover, the half-plane S6 containing the rotation axes of the second and of the sixth shaft 1 10 and 270 can be inclined with respect to the half-plane S3, for example by an acute angle of less than 90 sexagesimal degrees.

Preferably, the angle of inclination of the half-plane S6 with respect to the half-plane S3 can be greater than the angle of inclination between the half-plane S4 and the half-plane S3, for example comprised between 75 and 85 sexagesimal degrees.

Going back to figure 4, the sixth shaft 270 is rotatably coupled with at least one first and a second toothed wheel, respectively indicated with 275 and 280, which are arranged meshed respectively with the first and the second toothed wheel 165 and 170 of the sec ond shaft 1 10, so as to define a third and a fourth gear.

The third gear (wheels 165 and 275) can be configured to define a reduction of speed between the second shaft 1 10 and the sixth shaft 270, preferably with a gear ratio com prised between that defined by the first gear (wheels 165 and 175) and that defined by the second gear (wheels 170 and 180) that connect the second and the third shaft 1 10 and 1 15.

For example, the first toothed wheel 275 of the sixth shaft 270 can have 33 teeth, defining with the first wheel 165 of the second shaft 1 10 a gear ratio equal to about 1 .43.

Differently, the fourth gear (wheels 170 and 280) can be configured to define a speed multiplication between the second shaft 1 10 and the sixth shaft 270.

For example, the second toothed wheel 280 of the sixth shaft 270 can have 24 teeth, defining with the second wheel 170 of the second shaft 1 10 a gear ratio equal to about 0.71 .

The transmission 100 can also comprise a third engaging apparatus to selectively engage the sixth shaft 270 with the first or with the second toothed wheel 275 or 280.

In the illustrated example, this third engaging apparatus can comprise a synchronizer 285 adapted for engaging the sixth shaft 270 alternatively with the first toothed wheel 275 or with the second toothed wheel 280.

For example, the synchronizer 285 can comprise a mobile member, typically sliding axi ally along the sixth shaft 270, between a first engaging position in which it engages the sixth shaft 270 with the first toothed wheel 275 and a second engaging position in which it engages the sixth shaft 270 with the second toothed wheel 280, passing through an intermediate or neutral position, wherein the sixth shaft 270 is rotatably unconstrained both from the first toothed wheel 275 and from the second toothed wheel 280. The move ment and the locking of this mobile member in the three positions outlined above can be obtained through suitable mechanical members, for example forks and lever mecha nisms, which can be actuated manually or in an automated manner.

In accordance with this third embodiment, the transmission 100 can also comprise a fifth gear adapted for kinematically connecting the sixth shaft 270 to the third shaft 1 15, pref erably so as to define a unitary gear ratio between these two shafts. This fifth gear can comprise a third and a fourth toothed wheel, respectively indicated with 290 and 295, which are rotatably coupled with the second shaft 1 10 and rotate as a unit with each other.

For example, the toothed wheels 290 and 295 can be made in a single body or in separate bodies but joined together.

The third toothed wheel 290 is arranged meshed with a third toothed wheel 300 fitted to the third shaft 1 15, whereas the fourth toothed wheel 295 is arranged meshed with a third toothed wheel 305 fitted to the sixth shaft 270.

In order to obtain a unitary gear ratio between the sixth shaft 270 and the third shaft 1 15, the toothed wheel 290 can have the same number of teeth of the toothed wheel 295, whereas the toothed wheel 300 can have the same number of teeth of the toothed wheel 305.

A fourth engaging apparatus is also foreseen to selectively engage the second shaft 1 10 with the third and fourth toothed wheel 290 and 295 or to leave them rotatably idle.

In the illustrated example, this fourth engaging apparatus can comprise a synchronizer 310, which can comprise for example a mobile member, typically sliding axially along the second shaft 1 10, between an engaging position in which it engages the second shaft 1 10 with the toothed wheels 290 and 295 and a neutral position, wherein the second shaft 1 10 is rotatably unconstrained from the toothed wheels 290 and 295. The movement and the locking of this mobile member in the two positions outlined above can be obtained through suitable mechanical members, for example forks and lever mechanisms, which can be actuated manually or in an automated manner.

When the toothed wheels 290 and 295 are engaged on the second shaft 1 10, the latter is kinematically connected to the third shaft 1 15 by meshing the wheels 290 and 300, which are preferably configured so as to provide a speed multiplication, for example with a lower gear ratio with respect to that defined by the wheels 170 and 280.

As an example, the toothed wheel 300 can have 18 teeth and the corresponding toothed wheel 290 can have 37 teeth, defining a gear ratio equal to about 0.49.

In accordance with this third embodiment, the transmission 100 can also comprise a fifth engaging apparatus adapted for selectively engaging the fifth shaft 125 with the planet carrier 215 of the planetary gear 195 or directly with the third shaft 1 15. This fifth engaging apparatus can comprise for example a joint 315, which can be modi fied between a first configuration, wherein it engages the fifth shaft 125 directly with the third shaft 1 15, for example with frontal coupling, and a second configuration, wherein it engages the fifth shaft 125 with the planet carrier 215.

In this way, when the joint 315 is in the first configuration, the fifth shaft 125 rotates as a unit with the third shaft 1 15 and is therefore forced to rotate with it at the same speed, whereas when the joint 315 is in the second configuration, between the third shaft 1 15 and the fifth shaft 125 a definite speed reduction of the gear ratio of the planetary gear 195 is introduced.

In this case, the crown gear 205 of the planetary gear 195 is preferably kept fixed.

Thanks to this constructive architecture, the transmission 100 in accordance with the third embodiment of figure 4 is capable of providing the two forward and reverse splitters, able to be selected, like for the base embodiment, through the first engaging apparatus, in this case through the synchronizer 160.

For each of these splitters, the transmission 100 of figure 4 also provides two ranges, which can be selected through the fifth engaging apparatus, in this case through the joint 315, including for example a faster range (high), able to be obtained when the fifth shaft 125 is directly engaged with the third shaft 1 15, and a slower range (e.g. medium), able to be obtained when the fifth shaft 125 is connected to the third shaft 1 15 through the planetary gear 195.

For each splitter and each range, the transmission 100 of figure 4 also mechanically pro vides five gears, defined by the five gears that connect together the second, the third and the sixth shaft 1 10, 1 15 and 270.

In particular, a first gear is obtained when the second engaging apparatus, in this case the synchronizer 185, is in the position in which it engages the third shaft 1 15 with the toothed wheel 175, whereas the third engaging apparatus and the fourth engaging appa ratus, in this case the synchronizers 285 and 310, are both in neutral position. In this way, the rotation of the second shaft 1 10 (both in forward gear and in reverse gear) is trans mitted to the third shaft 1 15, and from here to the fifth shaft 125, through the toothed wheels 165 and 175.

A second gear is obtained when the third engaging apparatus, in this case the synchro nizer 285, is in the position in which it engages the sixth shaft 270 with the toothed wheel 275, whereas the second and the fourth engaging apparatus, in this case the synchroniz ers 185 and 310, are both in neutral position. In this way, the rotation of the second shaft 1 10 (both in forward gear and in reverse gear) is transmitted firstly to the sixth shaft 270 through the toothed wheels 165 and 275, and then from the sixth shaft 270 to the third shaft 1 15, and from here to the fifth shaft 125, through the toothed wheels 305, 295, 290 and 300.

A third gear is obtained when the second engaging apparatus, in this case the synchro nizer 185, is in the position in which it engages the third shaft 1 15 with the toothed wheel 180, whereas the third engaging apparatus and the fourth engaging apparatus, in this case the synchronizers 285 and 310, are both in neutral position. In this way, the rotation of the second shaft 1 10 (both in forward gear and in reverse gear) is transmitted to the third shaft 1 15, and from here to the fifth shaft 1 25, through the toothed wheels 170 and 180.

A fourth gear is obtained when the third engaging apparatus, in this case the synchronizer 285, is in the position in which it engages the sixth shaft 270 with the toothed wheel 280, whereas the second and the fourth engaging apparatus, in this case the synchronizers 185 and 310, are both in neutral position. In this way, the rotation of the second shaft 1 10 (both in forward gear and in reverse gear) is transmitted firstly to the sixth shaft 270 through the toothed wheels 170 and 280, and then from the sixth shaft 270 to the third shaft 1 15, and from here to the fifth shaft 125, through the toothed wheels 305, 295, 290 and 300.

A fifth gear is finally obtained when the fourth engaging apparatus, in this case the syn chronizer 310, is in the position in which it engages the second shaft 1 10 directly with the wheels 290 and 295, whereas the second and the third engaging apparatus, in this case the synchronizers 185 and 285, are both in neutral position. In this way, the rotation of the second shaft 1 10 (both in forward gear and in reverse gear) is transmitted to the third shaft 1 15, and from here to the fifth shaft 125, through the toothed wheels 290 and 300. Thanks to this solution a transmission 100 is thus obtained that is capable of mechanically providing two ranges and five gears for each range, for a total of ten gear ratios both for the forward splitter and for the reverse splitter.

A further variant of the transmission 100 is illustrated in figure 6 and totally analogous to the one just described, with the exception of the aspects that will be described hereinafter. The transmission 100 in accordance with this fourth embodiment foresees that the third shaft 1 15 is divided into two mutually coaxial but independent portions, respectively indi cated with 1 15A and 1 15B.

These two portions 1 15A and 1 15B can be made to rotate as a unit with one another in a selective manner through a sixth engaging apparatus, for example through a joint 320 that can alternatively be arranged in an engagement configuration, wherein it makes the two portions 1 15A and 1 15B fixedly connected to one another, and a disengagement configuration, wherein the two portions 1 15A and 1 15B are free to rotate independently. The first portion 1 15A is coupled with the toothed wheels 175, 180 and 300, according to the ways already described earlier for the third embodiment of figure 4.

The second portion 1 15B is rotatably coupled with a fourth toothed wheel 325, which is arranged meshed with a fifth toothed wheel 330 rotatably coupled with the second shaft 1 10, so as to define a further gear.

This further gear can be configured so as to obtain a speed reduction between the second shaft 1 10 and the second portion 1 15B of the third shaft 1 15.

For example, the toothed wheel 325 can have 44 teeth whereas the toothed wheel 330 can have 14 teeth, defining a gear ratio equal to about 3.14.

The toothed wheel 330 preferably rotates as a unit with the toothed wheels 290 and 295, for example it can be formed in a single body with them or in separate bodies but con nected together.

A seventh engaging apparatus is also present to selectively connect the second portion 1 15B of the third shaft 1 15 to the fourth toothed wheel 325 rotatably coupled on it.

In the illustrated example, this seventh engaging apparatus can comprise a joint 335, which can be arranged in an engagement configuration in which it engages the second portion 1 15B with the toothed wheel 325 and in a disengagement configuration, wherein the second portion 1 15B is rotatably unconstrained from the toothed wheel 325.

Thanks to these modifications a transmission 100 is provided that, in addition to the usual two forward and reverse splitters, is capable of providing, for each of these splitters, four ranges, able to be selected through the fifth, the sixth and the seventh engaging appa ratus.

In particular, a first and faster range (e.g. high) can be obtained when the fifth engaging apparatus, in this case the joint 315, is configured so as to directly engage the fifth shaft 125 with the second portion 1 15B of the third shaft 1 15; the sixth engaging apparatus, in this case the joint 320, is configured to engage together the first and the second portion 1 15A and 1 15B of the third shaft 1 15; and the seventh engaging apparatus, in this case the joint 335, is in the disengagement configuration.

A second range (e.g. medium), slower than the previous one, can be obtained when the fifth engaging apparatus, in this case the joint 315, is configured so as to engage the fifth shaft 125 with the second portion 1 15B of the third shaft 1 15 through the planetary gear 195; the sixth engaging apparatus, in this case the joint 320, is again configured to en gage together the first and the second portion 1 15A and 1 15B of the third shaft 1 15; and the seventh engaging apparatus, in this case the joint 335, is again in the disengagement configuration.

A third range (e.g. mini-creeper), slower than both of the previous ones, can be obtained when the fifth engaging apparatus, in this case the joint 315, is configured so as to engage the fifth shaft 125 directly with the second portion 1 15B of the third shaft 1 15; the sixth engaging apparatus, in this case the joint 320, is in decoupled configuration to uncon strain the first and the second portion 1 15A and 1 15B of the third shaft 1 15; and the seventh engaging apparatus, in this case the joint 335, is in the configuration in which it engages the second portion 1 15B of the third shaft 1 15 with the toothed wheel 325.

A fourth range (e.g. creeper), slower than all of the previous ones, can finally be obtained when the fifth engaging apparatus, in this case the joint 315, is configured so as to engage the fifth shaft 125 with the second portion 1 15B of the third shaft 1 15 through the planetary gear 195; the sixth engaging apparatus, in this case the joint 320, is again in the decou pled configuration to unconstrain the first and the second portion 1 15A and 1 15B of the third shaft 1 15 from one another; and the seventh engaging apparatus, in this case the joint 335, is again in the position in which it engages the second portion 1 15B of the third shaft 1 15 with the toothed wheel 325.

For each splitter and for each of these four ranges, the transmission 100 in accordance with this fourth embodiment also provides the five mechanical gears that can be selected through the second, the third and the fourth engaging apparatus, as already described with reference to the third embodiment.

However, it is worth highlighting that, whereas the operation of the transmission 100 in the aforementioned first two ranges (high and medium) is totally analogous to what is described with reference to the third embodiment, in the other two ranges (mini-creeper and creeper) the transmission of the torque takes place in a different way.

Indeed, in each of these last two ranges (mini-creeper and creeper), the first portion 1 15A of the third shaft 1 15 rotates independently with respect to the second portion 1 15B, which is fixedly connected to the wheel 325.

Therefore, when the first gear is engaged, according to the ways described earlier, the rotation of the second shaft 1 10 is transmitted firstly to the first portion 1 15A of the third shaft 1 15 through the wheels 165 and 175, and then to the second portion 1 15B and then to the fifth shaft 125 through the wheels 300, 290, 330 and 325.

When the second gear is engaged, again according to the ways described earlier, the rotation of the second shaft 1 10 is transmitted firstly to the sixth shaft 270 through the wheels 165 and 275, and then to the second portion 1 15B of the third shaft 1 15 and then to the fifth shaft 125 through the wheels 305, 295, 330 and 325.

When the third gear is engaged, again according to the ways described earlier, the rota tion of the second shaft 1 10 is transmitted firstly to the first portion 1 15A of the third shaft 1 15 through the wheels 170 and 180, and then to the second portion 1 15B and then to the fifth shaft 125 through the wheels 300, 290, 330 and 325.

When the fourth gear is engaged, again according to the ways described earlier, the ro tation of the second shaft 1 10 is transmitted firstly to the sixth shaft 270 through the wheels 170 and 280, and then to the second portion 1 15B of the third shaft 1 15 and then to the fifth shaft 125 through the wheels 305, 295, 330 and 325.

Finally, when the fifth gear is engaged, again according to the ways described earlier, the rotation of the second shaft 1 10 is transmitted directly to the second portion 1 15B of the third shaft 1 15 and then to the fifth shaft 125 through the wheels 330 and 325.

Thanks to this solution a transmission 100 is thus obtained that is capable of mechanically providing four ranges and five gears for each range, for a total of twenty gear ratios both for the forward splitter and for the reverse splitter.

A further variant of the transmission 100 is illustrated in figure 7 and is totally analogous to the fourth variant just described, with the exception of the aspect that will be illustrated hereinafter.

A first aspect of difference consists of the fact that the first engaging apparatus can com prise the two clutches 150 and 155 already described in relation to the base embodiment shown in figure 1 .

A second, more relevant aspect of difference, on the other hand, consists of the fact that the transmission 100 can comprise a seventh rotating shaft 340 having rotation axis par allel to the rotation axes of the other rotating shafts.

As illustrated in figure 8, the distances between centres D7 between this seventh shaft 340 and the second shaft 1 10 can be substantially equal to or (slightly) greater than the distance between centres D6 between the second shaft 1 10 and the sixth shaft 270. Moreover, the seventh shaft 340 can be arranged so that the half-plane S7 containing the rotation axes of the second and of the seventh shaft 1 10 and 340 can form, with the half plane S4 containing the rotation axes of the second and of the fourth shaft 1 10 and 120, an angle substantially equal to 180 sexagesimal degrees. In other words, the rotation axes of the second, of the fourth and of the seventh shaft 1 10, 120 and 340 can lie in a common plane, wherein the second shaft 1 10 is arranged between the fourth and the seventh shaft 120 and 340.

Going back to figure 7, the seventh shaft 340 can be rotatably coupled with a first toothed wheel 345, which is arranged meshed with a second toothed wheel 350 directly fitted on the first shaft 105.

The gear defined by the two toothed wheels 345 and 350 can be configured to make a speed reduction between the first shaft 105 and the seventh shaft 340.

For example, the toothed wheel 345 can have 44 teeth whereas the toothed wheel 350 can have 31 teeth, defining a gear ratio equal to about 1 .42.

An eighth engaging apparatus is foreseen to selectively engage the seventh shaft 340 with the first toothed wheel 345 or to leave it rotatably idle with respect to it.

In the illustrated example, this further engaging apparatus can comprise a clutch 355, for example a hydraulic clutch, which is adapted for engaging/disengaging the toothed wheel 345 with/from the seventh shaft 340.

The seventh shaft 340 can also have a second toothed wheel 360 fitted to it which is arranged meshed with the second toothed wheel 170 that is fitted on the second shaft 1 10.

It should now be observed that in figure 7 the toothed wheel 360 is shown offset with respect to the toothed wheel 170 only for reasons of clarity, so that such two wheels in reality lie on a same transversal plane and can mesh with each other without interfering with the toothed wheel 280, thanks to the fact that the sixth and the seventh shaft 270 and 340 are angularly offset with respect to the second shaft 1 10 as illustrated in figure 8.

The number of teeth of the toothed wheel 360 is preferably selected so as to define a (slight) multiplication of speed between the seventh shaft 340 and the second shaft 1 10, but in any case such that the overall gear ratio between the first shaft 105 and the second shaft 1 10 is greater than 1 . For example, the toothed wheel 360 can have 40 teeth. Thanks to these modifications, the transmission 100 according to the embodiment illus trated in figure 7 comprises three splitters, including the direct forward splitter, which are configured when the first shaft 105 is directly engaged with the second shaft 1 10, for example thanks to the closing of the clutch 150 and simultaneous opening of the clutches 155 and 355, a reverse splitter, which is configured when the first shaft 105 is connected to the second shaft 1 10 through the fourth shaft 120, for example thanks to the closing of the clutch 155 and simultaneous opening of the clutches 150 and 355, and finally a slow forward splitter (low), which is configured when the first shaft 105 is connected to the second shaft 1 10 through the seventh shaft 340, for example thanks to the closing of the clutch 355 and simultaneous opening of the clutches 150 and 155.

For each of these three splitters, the transmission 100 then provides the four ranges and the five gears already described with reference to the fourth embodiment.

A last variant of the transmission 100 is illustrated in figure 9. This last embodiment is totally analogous to the previous one, with the difference of comprising a third toothed wheel 365 rotatably coupled with the seventh shaft 340, which is arranged meshed with a third toothed wheel 370 fitted on the first shaft 105.

The gear defined by the two toothed wheels 365 and 370 can be configured to make a speed multiplication between the first shaft 105 and the seventh shaft 340.

For example, the toothed wheel 365 can have 37 teeth whereas the toothed wheel 370 can have 38 teeth, defining a gear ratio equal to about 0.97.

A ninth engaging apparatus is foreseen to selectively engage the seventh shaft 340 with the third toothed wheel 365 or to leave it rotatably idle with respect to it.

In the illustrated example, this further engaging apparatus can comprise a clutch 375, for example a hydraulic clutch, which is adapted for engaging/disengaging the toothed wheel 365 with/from the seventh shaft 340. Thanks to this provision, the transmission 100 is provided with a fourth splitter, in addition to those already described with reference to the previous embodiment.

This fourth splitter can be a high speed forward splitter (high) and is configured when the clutch 375 is closed, whereas the clutches 150, 155 and 355 are all left open, so that the rotation of the first shaft 105 is transmitted to the second shaft 1 10 through the wheels 370, 365, 360 and 170.

Also in this case, for each of these four splitters, the transmission 100 then provides the four ranges and the five gears already described with reference to the fourth embodiment, for a total of eighty gear ratios globally available.

Of course, those skilled in the art can bring numerous technical-applicational modifica tions to the transmissions 100 described above, without for this reason departing from the invention as claimed below.

Claims

1. A transmission (100) comprising:

- a plurality of rotating shafts having mutually parallel rotation axes, including at least one first shaft (105), a second shaft (1 10), a third shaft (1 15) and a fourth shaft (120),

- a first toothed wheel (140) rotatably coupled with the first shaft (105),

- a first toothed wheel (145) fitted to the fourth shaft (120) and meshing with the first toothed wheel (140) of the first shaft (105), so as to define a reverse gear,

- a first engaging apparatus adapted for selectively engaging the first shaft (105) with the first toothed wheel (140) rotatably coupled with it or with the second shaft (1 10),

- at least one first and a second toothed wheel (165, 170) fitted to the second shaft

(1 10),

- at least one first and a second toothed wheel (175, 180) rotatably coupled with the third shaft (1 15) and singularly meshing respectively with the first and with the second toothed wheel (165, 170) of the second shaft (110), so as to respectively define a first and a second gear,

- a second engaging apparatus adapted for selectively engaging the third shaft (1 15) with the first or the second toothed wheel (175, 180) rotatably coupled with it, and

- a second toothed wheel (190) fitted to the fourth shaft (120) and meshing with the first toothed wheel (175) of the third shaft (1 15).

2. A transmission (100) according to claim 1 , comprising;

- a fifth rotating shaft (125) having rotation axis parallel to the rotation axes of the other rotating shafts, and

- a planetary gear (195) arranged to kinematically connect the fifth shaft (125) to the third shaft (115).

3. A transmission (100) according to claim 1 or 2, comprising:

- a further toothed wheel (220) fitted to the second shaft (1 10),

- a further toothed wheel (225) rotatably coupled with the third shaft (115) and mesh ing with said further toothed wheel (220) of the second shaft (1 10), so as to define a further gear, and - a further engaging apparatus adapted for selectively engaging the third shaft (1 15) with said further toothed wheel (225) rotatably coupled with it.

4. A transmission (100) according to claim 2 or 3, comprising:

- a hydraulic motor (235) having a drive shaft (260) kinematically connected to a crown gear (205) of the planetary gear (195) so as to be adapted for setting it in rotation, and

- a hydraulic pump (240) having an actuation shaft (245) kinematically connected with the first shaft (105) and hydraulically connected to the hydraulic motor (235).

5. A transmission (100) according to any one of the previous claims, comprising:

- A sixth rotating shaft (270) having rotation axis parallel to the rotation axes of the other rotating shafts,

- at least one first and a second toothed wheel (275, 280) rotatably coupled with the sixth shaft (270) and singularly meshing respectively with the first and with the second toothed wheel (165, 170) of the second shaft (1 10), so as to respectively define a third and a fourth gear,

- a third engaging apparatus adapted for selectively engaging the sixth shaft (270) with the first or with the second toothed wheel (275, 280) rotatably coupled with it, and

- a fifth gear adapted for kinematically connecting the sixth shaft (270) to the third shaft (1 15).

6. A transmission (100) according to claim 5, wherein said fifth gear can comprise a third and a fourth toothed wheel (290, 295) rotatably coupled with the second shaft (1 10) and rotating as a unit with each other, a third toothed wheel (300) fitted to the third shaft (1 15) and meshing with the third wheel (290) of the second shaft (1 10), a third toothed wheel (305) fitted to the sixth shaft (270) and meshing with the fourth toothed wheel (295) of the second shaft (1 10), and a fourth engaging apparatus to selectively engage the second shaft (1 10) with the third and fourth toothed wheel (290, 295) rotatably coupled on it.

7. A transmission (100) according to any one of claims 2 to 6, comprising a fifth en gaging apparatus adapted for selectively engaging the fifth shaft (125) with a planet car rier (215) of the planetary gear (195) or directly with the third shaft (1 15).

8. A transmission (100) according to claim 6 or 7, comprising:

- a sixth engaging apparatus adapted for selectively engaging a first portion (1 15A) of the third shaft (1 15), with which the respective first, second and third toothed wheel (175, 180, 300) are coupled, with a second portion (1 15B) of the third shaft (1 15),

- a fifth toothed wheel (330) rotatably coupled with the second shaft (1 10) and rotat ing as a unit with the third and fourth toothed wheel (290, 295) of said second shaft (1 10),

- a fourth toothed wheel (325) rotatably coupled with the second portion (1 15B) of the third shaft (1 15) and meshing with the fifth toothed wheel (330) of the second shaft (110), and

- a seventh engaging apparatus adapted for selectively engaging said second por tion (1 15B) of the third shaft (1 15) with the fourth toothed wheel (325) rotatably coupled on it.

9. A transmission (100) according to any one of the previous claims, comprising:

- a second toothed wheel (350) fitted on the first shaft (105),

- a seventh rotating shaft (340) having rotation axis parallel to the rotation axes of the other rotating shafts,

- at least one first toothed wheel (345) rotatably coupled with the seventh shaft (340) and meshing with the second toothed wheel (350) of the first shaft (105),

- a second toothed wheel (360) fitted on the seventh shaft (340) and meshing with the second toothed wheel (170) fitted on the second shaft (1 10), and

- an eighth engaging apparatus adapted for selectively engaging the seventh shaft (340) with the first toothed wheel (345) rotatably coupled with it.

10. A transmission (100) according to claim 8, comprising:

- a third toothed wheel (370) fitted on the first shaft (105),

- a third toothed wheel (365) rotatably coupled with the seventh shaft (340) and meshing with the third toothed wheel (370) of the first shaft (105), and

- a ninth engaging apparatus adapted for selectively engaging the seventh shaft (340) with the third toothed wheel (365) rotatably coupled with it.