Gearbox unit for a farm vehicle with a wide range of speeds

A gearbox assembly that includes a system of stacked planetary gearsets; a clutch device including an input clutch shaft and an output clutch shaft; a large clutch wheel and a small clutch wheel mounted idle on the output clutch shaft; a clutch coupling device for coupling the small and large wheels with the output clutch shaft; an output shaft including a small output wheel meshing with the large clutch wheel and a large output wheel meshing with the small clutch wheel.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a 35 U.S.C. §§ 371 national phase conversion of PCT/FR2016/052593, filed Oct. 7, 2016, which claims priority to French Patent Application No. 1559579, filed Oct. 8, 2015, the contents of which are incorporated herein by reference. The PCT International Application was published in the French language.

TECHNICAL FIELD

This invention relates to a gearbox unit for a motor-driven farm vehicle.

BACKGROUND OF THE INVENTION

Motor-driven farm vehicle gearboxes can provide a large number of possible speed ratios for the vehicle so that working equipment can be carried or pulled under optimum conditions considering the nature of the ground to be worked. In other words, gearboxes can adapt the vehicle speed to match encountered variations in resistance to progress. Furthermore, recent gearboxes include at least two parallel shaft clutches to make it possible to change from one gear to another without releasing the load, in other words without the loss of driving force during the gear change.

Normal farm vehicle gearboxes also include a large number of possible speed ratios with close speed ranges.

It is now required that gearboxes should not only have a large number of possible speed ratios, but also that speed ratios should vary over a range from very slow to very fast, for example with a range from a few hundred metres per hour up to 50 km per hour.

To achieve this, it has been thought that planetary gear systems can be staged inside gearboxes. Large reduction ratios can be obtained with this mechanical transmission system, although it is relatively compact compared with normal gearboxes.

Refer to document DE 10 2013 110 709 A1 that discloses a gearbox unit designed precisely to obtain wide speed ranges. It thus includes a system of staged planetary gears coupled at the input to the drive shaft and capable of providing a plurality of first transmission ratios. The output of the planetary gear system is coupled with two parallel clutch devices. Each clutch device comprises an input shaft clutch coupled to the planetary gear system and another output shaft clutch. For each clutch device, the unit comprises a large high speed clutch wheel and a small low speed clutch wheel both installed free to rotate on the output shaft clutch to be able to provide two second transmission ratios. It also includes a clutch coupling device for each clutch device, so that either the low speed or high speed wheels can be coupled with the output shaft clutch. The unit also comprises an output shaft comprising a small high speed output wheel engaging with the large high speed clutch wheels and a large low speed output wheel engaging with small low speed clutch wheels of two clutch devices. It is understood in this case that the wheels mentioned herein are gear wheels with parallel teeth. However, the output shaft is fitted with a conical pinion engaging a conical wheel that is mechanically coupled to a differential.

With this gearbox unit, a motor-driven vehicle is obtained with a large number of speed ratios over a wide speed range. However, premature wear of the clutch wheels has been observed for some vehicles, and under some working conditions. Furthermore, the large number of successive or parallel gear trains in such gearbox units makes their mechanical efficiency poor.

Another problem that arises and that this invention is intended to solve is to provide a gearbox unit that in particular can reduce wear of its component elements and also improve the mechanical efficiency.

SUMMARY OF THE INVENTION

This can be achieved using a gearbox unit for a motor-driven farm vehicle comprising: a system of staged planetary gears to provide a plurality of first transmission ratios; a clutch device comprising a shaft clutch with input coupled to said planetary gear system and an output shaft clutch; a large high speed clutch wheel and a small low speed clutch wheel both installed free to rotate on said output shaft clutch to provide two second transmission ratios; a clutch coupling device to be able to couple one of said low and high speed wheels with said output shaft clutch; and an output shaft comprising a small high speed output wheel engaging with said large high speed clutch wheel and a large low speed output wheel engaging with said small low speed clutch wheel. The set of clutches also comprises an uncoupling device between said output shaft and said large low speed output wheel to be able to release said output shaft from the small low speed clutch wheel.

Thus, one characteristic of the invention lies in the possibility of being able to uncouple the output shaft and the large low speed output wheel, precisely when the output shaft is driven at high speed through the small high speed output wheel engaging with the large high speed clutch wheel. Because when the output shaft is driven at high speed, the large low speed output wheel starts to drive and then drives the small low speed clutch wheel at high speed, at the risk of damaging it. Uncoupling thus makes it possible to leave the large low speed output wheel and consequently the small low speed clutch wheel at rest. The small low speed clutch wheel is thus protected. Furthermore, the mechanical efficiency of the gearboxes improves since these wheels are stopped.

According to one preferred embodiment of the invention, said large low speed output wheel is installed free to rotate on said output shaft. Said decoupling device also comprises a fixed wheel fixed to said output shaft and a coupling device fixed to said fixed wheel capable of being rotated to engage said fixed wheel to said large low speed output wheel. In this way, the uncoupling device composed of several elements is reversible. In other words, the coupling device can be controlled between a coupling position in which the fixed wheel and the large low speed output wheel are coupled, and a decoupling position in which the low speed output wheel is not fixed to the fixed wheel.

The clutch device also comprises a clutch that can be controlled, for example hydraulically, located between said input shaft clutch and said output shaft clutch. Thus, the input shaft clutch and the output shaft clutch are coaxial and the controllable clutch is installed between the two.

According to one particularly advantageous embodiment of the invention, the gearbox unit also comprises: another clutch device comprising another input shaft clutch coupled to said planetary gear system and another output shaft clutch; another large high speed clutch wheel and another small low speed clutch wheel both mounted free to rotate on said output shaft clutch to be able to provide two other second transmission ratios, said other large and small high and low speed clutch wheels engaging with said small and large high and low speed output wheels respectively; and another clutch coupling device to be able to couple one of said other low and high speed wheels with said other output shaft clutch.

In other words, the gearbox unit comprises two clutch devices each comprising an input shaft clutch coupled to said planetary gear system and an output shaft clutch. Each clutch device comprises another large high speed clutch wheel and a small low speed clutch wheel both installed free to rotate on said other output shaft clutch to be able to provide two second transmission ratios, said large and small high and low speed clutch wheels engaging with said small and large high and low speed output wheels respectively. Each also includes a clutch coupling device to be able to couple either of said low and high speed wheels with said output shaft clutch.

Thus, as will be explained below, four different second transmission ratios can be obtained through the use of two parallel clutch devices and their output shaft clutch each fitted with a large high speed clutch wheel and a small low speed clutch wheel. In this way, a total of twenty-eight different speed ratios can be obtained according to one particularly advantageous embodiment of the invention in which the system of staged planetary gears includes seven first transmission ratios.

Said other clutch device also includes another controllable clutch located between said other input shaft clutch and said other output shaft clutch. The other controllable shaft performs the same role as the first in the first clutch device.

According to one particularly advantageous embodiment of the invention, the gearbox unit also comprises an inverter module located between said system of staged planetary gears and said clutch device to be able to invert the direction of rotation of said input shaft clutch. When the gearbox unit comprises two clutch devices, the inverter module is coupled parallel to the two clutch devices by means described in more detail later in the remainder of the description.

Furthermore, said inverter module also comprises firstly a receiving shaft coupled to said planetary gear system and secondly two inversion wheels installed free to rotate on said receiving shaft and two inversion clutches to be able to couple said two inversions wheels to said clutch device alternately.

According to another embodiment of the invention, the inverter module is located upstream from the system of staged planetary gears. The consequences on the layout of the different elements will be explained in more detail in the remainder of the description.

Thus, due to the two inversion clutches that drive the receiving shaft by friction with one or the other of the two inversion wheels, the direction of rotation can be changed from one direction to the inverse direction more easily, and consequently more comfortably from forward running to reverse running.

Furthermore, the gearbox unit comprises a transmission reduction module located between said system of staged planetary gears and said clutch device to be able to reduce the transmission ratios of said plurality of transmission ratios. Such a transmission reduction module can either transmit the rotation movement at the output of the system of staged planetary gears without any reduction or demultiplication at the clutch device, or it can considerably reduce the rotation movement so as to be able to obtain extremely low speeds. For example such a reduction gear can give speeds of the order of 250 m per hour.

Thus, said system of staged planetary gears comprises three sets of planetary wheels and three sets of satellite wheels installed in said three sets of planet wheels respectively. The system of staged planetary gears will be described in more detail in the remainder of the description. Such a mechanical system can give a wide range of transmission ratios for a given input speed, while being compact.

DESCRIPTION OF PREFERRED EMBODIMENTS

The single Figure shows a gearbox unit10comprising four successive subassemblies between an input shaft11coupled to the engine shaft not shown, and an output shaft13. The gearbox unit10thus comprises a system of staged planetary gears12; a transmission reducing module14; a running direction inverter module15; and two parallel clutch devices, a first16and a second18.

The input shaft11is prolonged through the system of staged planetary gears12by a first hollow shaft segment20that passes through a first inner planet gear22and is connected to a first satellite holder24. This satellite holder comprises a first set of satellites26engaging the first inner planet gear22and a first outer planet gear28. This first group forms a first planetary gear system30.

Furthermore, the system of system of staged planetary gears12comprises a first blocking device32that when in the released position, couples the first inner planet gear22with the first satellite holder24in rotation, and in an active position holds the first inner planet gear22in a fixed position while releasing the first satellite holder24.

The first outer planet gear28is fixed to an intermediate hollow shaft segment34that extends coaxially prolonging the first hollow shaft segment20and passing through a second blocking device36to join a second outer planet gear38symmetric to the first outer planet gear28. A second set of satellites40is engaged inside this second outer planet gear38, supported by a satellite holder42fixed to a last hollow shaft segment44that extends coaxially prolonging the intermediate hollow shaft segment34.

The second set of satellites40also engages a second inner planet gear46which is fixed to a third satellite holder48. The last hollow shaft segment44passes freely through the second inner planet gear46and the third satellite holder48.

The third satellite holder48supports a third satellite set50, engaging with a third inner planet gear52and a third outer planet gear54.

When in a released position, the second blocking device36couples the first outer planet gear28fixed to the second outer planet gear38and the third outer planet gear54in rotation, and in an active position, it holds the third outer planet gear54in a fixed position while the associated first outer planet gear28and the second outer planet gear38are free.

The system of staged planetary gears12comprises a third blocking device56which when in a released position couples the last hollow shaft segment44and the third inner planet gear52in rotation. In an active position, the third blocking device56holds the third inner planet gear52in a fixed position while the last hollow shaft segment44is free.

Furthermore, the first22, second46and third52inner planet gears have the same number of teeth. For example, there are between sixty-five and seventy-seven teeth. Since these are satellites of the first26, second40and third50sets of satellites, they have the same number of teeth, for example between seventeen and nineteen teeth. The first28, second38and third54outer planets gears also have the same number of teeth, advantageously between a hundred and one and a hundred and three teeth.

Thus, the three blocking devices32,36and56, each controlled by a hydraulic device can each be in one of two states, at rest or active, and consequently all of the three devices may be in eight distinct states. In practice, seven transmission ratios are used between the input shaft11and the last hollow shaft segment44.

Thus, a first first speed ratio A corresponds to a state in which the first blocking device32is at rest, while the second36and third56blocking devices are active.

A second first speed ratio B corresponds to a state in which the first32and the third56blocking devices are at rest while the second blocking device36is active.

A third first speed ratio C corresponds to a state in which the first32and the second36blocking devices are at rest while the third blocking device56is active.

A fourth first speed ratio D corresponds to a state in which the first32, second36and third56blocking devices are at rest.

A fifth first speed ratio E corresponds to a state in which the first32and the second36blocking devices are active while the third blocking device56is at rest.

A sixth first speed ratio F corresponds to a state in which the first32and the third56blocking devices are active while the second blocking device36is at rest.

And a seventh first speed ratio G corresponds to a state in which the first blocking device32is active while the second36and third56blocking devices are at rest.

The last hollow shaft segment44extends through the transmission reducing module14and terminates by a coupling end of the last segment58.

The transmission reducing module14has a hollow reduction shaft segment60that extends coaxially prolonging the last hollow shaft segment44as far as the running inverter module15that will be described below.

The hollow reduction shaft segment60has one reduction segment coupling end62extending facing the coupling end of the last segment58. Furthermore, the coupling end of the last segment58comprises a small wheel of the last reduction segment64behind it, while the coupling end of the reduction segment62comprises a large reduction segment wheel66behind it mounted free to rotate.

Furthermore, the transmission reduction module14comprises firstly a rotation coupling device68between the small wheel of the last reduction segment64and the large reduction segment wheel66, and secondly a reduction coupling device70. The rotation coupling device68comprises a reduction shaft72extending parallel to the hollow reduction shaft segment60and the last hollow shaft segment44, said reduction shaft72comprises firstly a large reduction shaft wheel74engaging the small last reduction segment wheel64and secondly a small reduction shaft wheel76engaging the large reduction segment wheel66. The reduction coupling device70when in a first position couples the coupling end of the last segment58directly with the coupling end of the reduction segment62and in a second position couples the coupling end of the reduction segment62with the large reduction segment wheel66. Also in the first coupling position of the reduction coupling device70, the coupling end of the last segment58comes into direct contact with the coupling end of the reduction segment62without a reduction in the rotation speed, while in the second coupling position, the coupling end of the reduction segment62engages with the large reduction segment wheel66. And in this second coupling position, considering the different wheel diameter ratios, or the teeth ratios in these wheels, a large speed reduction is obtained between the last hollow shaft segment44and the hollow reduction shaft segment60.

According to a first embodiment in which the gearbox unit10is made to provide twenty-one speed ratios, firstly the small wheel of the last reduction segment64comprises for example between twenty-five and twenty-seven teeth, while the large reduction segment wheel66comprises between fifty-nine and sixty-one teeth, and secondly the large reduction shaft wheel74comprises between sixty and sixty-two teeth, while the small reduction shaft wheel76comprises between thirteen and fifteen teeth.

According to a second embodiment in which the gearbox10provides twenty-eight speed ratios, firstly the small wheel of the last reduction segment64comprises for example between twenty-one and twenty-three teeth, while the large reduction segment wheel66comprises between seventy and seventy-two teeth, and secondly the large reduction shaft wheel74comprises between seventy and seventy-two teeth, while the small reduction shaft wheel76comprises between twenty one and twenty three teeth.

The hollow reduction shaft segment60is connected to the input of the running inverter module15, and is prolonged by a receiving shaft75, and it comprises two inversion output wheels, a first inversion output wheel78and a second inversion output wheel80. The two inversion output wheels78,80are driven in rotation in the same direction. On the other hand, as will be explained below, the first inversion output wheel78is directly coupled to the two parallel clutch devices16,18while the second inversion output wheel80is coupled to them through an inversion coupling device82. The latter comprises an inverse coupling input wheel91engaging with the second inversion output wheel80and an inverse coupling output wheel92.

The second inversion output wheel80for example comprises between sixty-six and sixty-eight teeth, and the first inversion output wheel78comprises between forty-six and forty-eight teeth, while the inverse coupling input wheel91comprises between thirty-three and thirty-five teeth and the inverse coupling output wheel92comprises between twenty-three and twenty-five teeth.

It will be observed that the transmission reduction module14is optional and consequently when it is not installed in the gearbox unit, the last hollow shaft segment44is prolonged by the receiving shaft75and thus joins the running direction inverter module15directly.

Furthermore, according to one variant embodiment, the running direction inverter module15is located on the input side of the system of staged planetary gears, and the input shaft then corresponds to the output from the inverter, while the receiving shaft is prolonged and terminates by a wheel corresponding to the first inversion output wheel78.

The first clutch device16comprises a first input clutch wheel84mounted on a first input shaft clutch86, a first controllable clutch88and a first output shaft clutch90. It will be observed that the first input clutch wheel84engages the first inversion output wheel78and also the inverse coupling output wheel92of the inverter coupling device82.

Furthermore, a first large high speed clutch wheel94is installed free to rotate on the first output shaft clutch90and a first small low speed clutch wheel96is also mounted free to rotate on the first output shaft clutch90. Between the two, a first clutch coupling device98is installed on the first output shaft clutch90. This first clutch coupling device98is controllable in a first position in which it couples the first output shaft clutch90in rotation with the first large high speed clutch wheel94. It can also be controlled in a second position in which it couples the first output shaft clutch90in rotation with the first small low speed clutch wheel96. It will be observed that the first clutch coupling device98is also controllable in a neutral position intermediate between the first and the second positions, in which it is free from the first large high speed clutch wheel94and the first small low speed clutch wheel96.

Furthermore, according to the first embodiment in which the gearbox10has twenty-one speed ratios, the first input clutch wheel84, the first large high speed clutch wheel94and the first small low speed clutch wheel96have for example between fifty-nine and sixty-one teeth, between forty-six and forty-eight teeth, and between twenty and twenty-two teeth respectively. In the second embodiment in which the gearbox10has twenty-eight speed ratios, the first input clutch wheel84, the first large high speed clutch wheel94and the first small low speed clutch wheel96comprise between sixty and sixty-two teeth, between thirty-six and thirty-eight teeth, and between twenty and twenty-two teeth respectively.

At the same time, the second clutch device18comprises a second input clutch wheel100mounted on a second input shaft clutch102engaging the single first inversion output wheel78, a second controllable clutch104and a second output shaft clutch106. A second large high speed clutch wheel108is mounted free to rotate on the second output shaft clutch106, while a second small low speed clutch wheel110is mounted on it free to rotate. A second clutch coupling device112located between the two is installed on the second output shaft clutch106. It can be controlled in a first position in which it couples in rotation the second output shaft clutch106in rotation with the second large high speed clutch wheel108, and in a second position in which it couples in rotation the second output shaft clutch106with the second small low speed clutch wheel110. Similarly to the first clutch device16, the second clutch coupling device112can also be controlled in a neutral position between the first and the second position, to obtain the same effects.

Furthermore, the inverse coupling output wheel92of the inverter coupling device82engages the first input clutch wheel84as shown in the Figure, but it could equally well engage the second input clutch wheel100without any modification to obtain the same function.

Furthermore, according to the first embodiment in which the gearbox10provides twenty-one speed ratios, the second input clutch wheel100, the second large high speed clutch wheel108and the second small low speed clutch wheel110have between twenty-five and twenty-seven teeth, between forty-six and forty-eight teeth, and between twenty and twenty-two teeth respectively. In the second embodiment in which the gearbox10provides twenty-eight speed ratios, the second input clutch wheel100, the first large high speed clutch wheel108and the first small low speed clutch wheel110have between twenty-four and twenty-six teeth, between forty-four and forty-six teeth and between twenty-five and twenty-seven teeth respectively.

The first embodiment in which the high speed clutch wheels94,108have the same number of teeth and low speed clutch wheels96,110have the same number of teeth in the two clutch devices16,18, is advantageous in terms of standardisation. On the other hand, the first input clutch wheel84of the first clutch device16has a different number of teeth from the second input clutch wheel100of the second clutch device18, so that the second transmission ratios are different. Such a device can be used to design a single high speed clutch wheel/clutch coupling device/small low speed clutch wheel assembly, and consequently at a more advantageous cost.

We will now describe the output shaft13and its different methods of connection with the two clutch devices16,18. Thus, a small high speed output wheel114is mounted fixed on the output shaft13, and a large low speed output wheel116is mounted free to rotate. The small high speed output wheel114engages both the second large high speed clutch wheel108and the first large high speed clutch wheel94, while the large low speed output wheel116engages both the second small low speed clutch wheel110and the first small low speed clutch wheel96. The output shaft13is also fitted with a decoupling device118comprising a fixed wheel115fixed to the output shaft13and a controllable coupling device117. The latter can be controlled between a coupling position in which it brings the fixed wheel115into contact with the large low speed output wheel116and then in which it couples the output shaft13and the large low speed output wheel116in rotation, and a decoupling position in which the fixed wheel115is free from the large low speed output wheel116and consequently in which the large low speed output wheel116is free from the output shaft13.

According to the first embodiment in which the gearbox10outputs twenty-one speed ratios, the small high speed output wheel114and the large low speed output wheel116have for example between thirty-eight and forty teeth, and between seventy-seven and seventy-nine teeth respectively. In the second embodiment in which the gearbox10provides twenty-eight speed ratios, the small high speed output wheel114and the large low speed output wheel116comprise for example forty-two and forty-four teeth, and between seventy-nine and eighty-one teeth respectively.

With the coupling/decoupling device118, the large low speed output wheel116and then the first and second small low speed clutch wheels96,110may be free from the output shaft13and consequently remain at rest when the output shaft is driven at high speed through the small high speed output wheel114. In these circumstances, the second output shaft clutch106and consequently the second large high speed clutch wheel108drive the output shaft13, since the second input clutch wheel100has a smaller number of teeth than the first input clutch wheel84. Thus, when the last hollow shaft segment44is driven in rotation at its maximum speed through the system of staged planetary gears12, the coupling reduction device70is in the first coupling position and the running direction inverter module15is in a forward running position, in other words the first inversion output wheel78is driving while the second clutch104is engaged, the speed of the output shaft13is maximum. Also, by uncoupling the large low speed output wheel116from the output shaft13, the large low speed output wheel116and the first and second small low speed clutch wheels96,110are brought to rest. If they were not at rest, their speed would be very high, of the order of 20,000 rpm. Under these circumstances, wear would be accelerated. Thus by uncoupling, the first and second small low speed clutch wheels96,110are protected from premature aging.

It is also advantageous to release the first and second small low speed clutch wheels96,110from the output shaft13before extreme speeds are reached, when the first output shaft clutch90drives the output shaft13through the first large high speed clutch wheel94. The first and the second small low speed clutch wheels96,110are thus at rest over a wider range of speeds and consequently they are better protected.

The mechanical efficiency of the gearbox unit10according to the invention is also improved due to the smaller number of moving mechanical elements.

Furthermore, the output end of the output shaft13is terminated by a bevel gear120so that it can be mechanically connected to a differential not shown. The output shaft is also fitted with an output wheel122that will be coupled in rotation to a drive shaft of other wheels124through a clutch of four driving wheels126. The latter has an input wheel125. In other words, apart from the two rear wheels of the motor-driven farm vehicle that are driven through the bevel gear120, the two front wheels of the motor-driven farm vehicle are driven through the drive shaft124of the other wheels.

According to the first embodiment in which the gearbox10provides twenty-one speed ratios, and according to a first variant, the output wheel122and the input wheel125have for example between thirty-four and thirty-six teeth, and between sixty-five and sixty-seven teeth respectively. According to a second variant, the output wheel122and the input wheel125have for example between thirty-three and thirty-five and between sixty-six and sixty-eight teeth respectively. In the second embodiment in which the gearbox10provides twenty-eight speed ratios and according to a first variant, the output wheel122and the input wheel125have for example between forty-seven and forty-nine, and between seventy-seven and seventy-nine teeth respectively. According to a second variant, the output wheel122and the input wheel125have for example between thirty-nine and forty-one, and between sixty-seven and sixty-nine teeth respectively.

Furthermore, the gearbox unit10comprises a drive shaft128for example coupled directly to the input shaft11and that axially and freely passes through the system of staged planetary gears12, the transmission reduction module14and the running inverter module15, and successively through: the first hollow shaft segment20, the intermediate hollow shaft segment34, the last hollow shaft segment44, the hollow reduction shaft segment60, to end up directly facing the two parallel clutch devices16,18. Due to the drive shaft128, hydraulic pumps in particular, not shown, can be driven through drive devices located approximately facing the controllable clutches88,104rather than along the axial prolongation of the parallel clutch devices16,18. These drive devices also comprise a pump drive wheel130coupled to the drive shaft128through a transfer wheel132mounted free to rotate on the second output shaft clutch106, between the second controllable clutch104and the second large high speed clutch wheel108, said transfer wheel132engages a transmission wheel134fixed to the drive shaft128. Thus, the gearbox is significantly shorter along the axial direction. This is possible because the second controllable clutch104is shorter than the first88and it thus releases space to install the transfer wheel132.

Furthermore, the pump drive wheel130, the transfer wheel132and the transmission wheel134have for example between twenty-four and twenty six-teeth, between fifty-three and fifty-six teeth and between thirty-four and thirty-six teeth respectively.