Patent Description:
Work vehicles such as agricultural vehicles comprise a power take-off (PTO) assembly provided with a powertrain configured to provide a torque at an output shaft to carry operational means of the work vehicle as shown in <CIT> and <CIT>.

Such PTO powertrain usually comprise at least one clutch, which is configured to engage and disengage two or more rotating shafts of the PTO, e.g. an input shaft to the output shaft of the PTO.

The aforementioned clutch may be a wet clutch actuated by a hydraulic signal that is modulated by a dedicated valve. Such valve is normally housed in the PTO assembly or on its housing and configured to use a portion of the oil supplied from the work vehicle to control the clutch.

Since the valve is positioned in the PTO assembly or on its housing, it is clear that there is a waste of space and that the piping that connect such valve to the clutch have a complicated topology.

Furthermore, the current designs of the hydraulic arrangement to provide the actuation signal are configured to lubricate the clutch arrangement only during its activation.

However, it is known that vehicles provided with a PTO continuously activate and deactivate the clutch. Accordingly, lamellas of the clutch tends to overheat thereby leading to increased wear and to oil degradation. Therefore, the useful life of the PTO decreases.

In view of the above, the need is felt to provide a PTO assembly comprising a hydraulic arrangement that allows to control the actuation of the clutch of the work vehicle That is compact, unexpansive and that may allow the cooling of the clutch in a continuous way.

An aim of the present innovation is to satisfy the above mentioned needs in a cost effective and optimized manner.

The aforementioned aim is reached by a power take-off assembly comprising a hydraulic arrangement and a control method as claimed in the appended independent claims.

Preferred embodiments of the innovation are realized according to the claims dependent or related to the above independent claim.

In the drawings reference number <NUM> discloses a power take-off, PTO, assembly of a work vehicle (not shown) ad configured to allow the torque transmission between a first shaft <NUM> and a second shaft <NUM>.

The PTO assembly <NUM> comprises a housing <NUM> configured to delimit an inner space <NUM> configured to house a transmission <NUM> configured to regulate the torque flow between first and second shafts <NUM>, <NUM>.

The housing <NUM> is furthermore configured to define a pair of openings 4a, 4b configured to allow the insertion of an inner portion of first and second shafts <NUM>, <NUM> inside inner space <NUM> and to allow the support of first and second shafts <NUM>,<NUM> in a rotatable free manner, e.g. via bearings.

In particular, in the disclosed embodiment, the first shaft <NUM> is an input shaft and preferably defines a seat 2a configured to allow the coupling with a torque providing element, e.g. another shaft operationally coupled to a source of torque of the work vehicle , e.g. via a splined coupling realized on the inner surface of a seat <NUM>.

Conversely, the second shaft <NUM> is an output shaft and preferably defines a coupling portion 3a configured to allow the coupling with an operational element, e.g. a working element that can be selectively attached to the work vehicle and using the provided torque. The coupling of such working element may be achieved via a splined coupling realized on the outer surface of the coupling portion 3a.

According to the shown embodiment, the first and the second shafts <NUM>, <NUM> are coaxial one with respect to the other along a longitudinal axis A that is the rotational axis of both shafts <NUM>, <NUM>.

The transmission <NUM> may comprises a plurality of different elements, such as gears, but essentially comprises, as exemplarily shown, a clutch assembly <NUM>. In the disclosed example the clutch assembly <NUM> is configured to selectively couple the first and second shafts <NUM>, <NUM>.

The clutch assembly <NUM> is interposed between a first intermediate element <NUM> fixedly carried by the first shaft <NUM> and a second intermediate element <NUM> fixedly carried by second shaft <NUM>. The clutch assembly <NUM> is realized between such first and second intermediate elements <NUM>, <NUM> and comprises a plurality of lamellas <NUM> carried from both the first and second intermediate elements <NUM>, <NUM> in an alternative way and that are configured to selectively cooperate by axial contact one with the other.

In the disclosed embodiment, the first intermediate element <NUM> has a substantial "S" shaped cross section comprising an inner annular portion 8a engaging the first shaft <NUM>, an intermediate disc portion 8b extending radially from the inner annular portion 8a inside the inner space <NUM> and an outer annular portion 8c extending cantilevered from intermediate disc portion 8b, parallel with respect to inner annular portion 8a but in an opposite direction with respect to this latter.

Instead, the second intermediate element <NUM> has a has a substantial "C" shaped cross section comprising an inner annular portion 9a engaging the second shaft <NUM>, an intermediate disc portion 9b extending radially from the inner annular portion 9a inside the inner space <NUM> and an outer annular portion 9c extending cantilevered from intermediate disc portion 9b, parallel with respect to inner annular portion 9a and extending in the same direction with respect to this latter.

In greater detail, the outer annular portion 8c of the first intermediate element <NUM> is placed and spaced radially between the inner annular portion 9a and the outer annular portion 9c of the second intermediate element <NUM>. Both the outer annular portions 8c, 9c carry the lamellas <NUM> that radially extends, alternatively along axis A, between such two outer annular portions 8c, 9c.

Lamellas <NUM> can be engaged axially in contact thanks to an actuation pressure given by an actuator element <NUM>. In the disclosed embodiment the actuator element <NUM> is slidable coupled to second intermediate element <NUM>.

In greater detail, the actuator element <NUM> is an annular body having a "C" shaped cross section similar to the cross section of the second intermediate element <NUM> and is radially and axially housed inside the latter. Accordingly, the actuator element <NUM> comprises an inner annular portion 11a engaging the inner annular portion <NUM>, an intermediate disc portion 11b extending radially from the inner annular portion 11a between the inner and outer annular portions 9a, 9c and an outer annular portion 11c extending cantilevered from intermediate disc portion 11b, parallel with respect to inner annular portion 11a and extending in the same direction with respect to this latter. The outer annular portion 11c is configured to slide in contact with the outer annular portion 9c of the second intermediate element <NUM>.

The actuator element <NUM> engages second intermediate element <NUM> in a translational free manner so as to assume a first operating condition (shown in <FIG>, <FIG>) into which he does not engage lamellas <NUM>, thereby leading rotationally free first and second intermediate elements <NUM>, <NUM> with respect to each other, and a second operating position (shown in <FIG>, <FIG>) into which he engages lamellas <NUM>, thereby rotationally coupling first and second intermediate elements <NUM>, <NUM> together.

The actuation to pass between first and second operating condition of actuator element <NUM> is given by a hydraulic fluid pressure provided by a hydraulic arrangement <NUM> as further described below.

In particular, the fluid provided by the hydraulic arrangement <NUM> is configured to selectively flow into a chamber <NUM> that is radially delimited by inner and outer portions 9a, 9c of second intermediate element <NUM> and axially delimited between the intermediate disc portion 9b and the intermediate disc portion 11b of actuator element <NUM>. Actuator element may slide between the inner and outer portions 9a, 9c in function of the fluid pressure inside chamber <NUM>. According to such pressure, chamber <NUM> may vary its axial dimension between two limit axial dimensions corresponding to the two operational conditions of actuator element <NUM>.

The chamber <NUM> is fluidly connected to clutch assembly <NUM> by a duct <NUM> that bypass actuator element <NUM> and that allows the communication between chamber <NUM> and inner space <NUM> that are otherwise fluidly separated, except for such duct <NUM>. Duct <NUM> allows the passage of an amount of fluid to vent chamber <NUM>.

The actuator element <NUM> is maintained in the first above described configuration thanks to actions of elastic means <NUM> configured to impart a force that is opposed to the force of the pressure given by the fluid in chamber <NUM>. In the described embodiment the elastic means <NUM> comprises a coil spring acting between the intermediate disc portion 11b of the actuator element <NUM> and a flanged portion 9d integral to inner annular portion 9a of the second intermediate element <NUM>.

The hydraulic clutch control arrangement <NUM> essentially comprises a valve <NUM> configured to regulate the flow coming from a source <NUM> of pressurized oil. Advantageously, such valve <NUM> is a hydraulic actuated proportional valve.

Advantageously the valve <NUM> comprises a housing <NUM> fixedly housed inside a seat <NUM> and accommodating a spool <NUM>. The seat <NUM> is realized within an inner portion 2b, 3b of one between first and/or second shafts <NUM>, <NUM>. In the disclosed example, seat <NUM> is realized within inner portion 3b of second shaft <NUM>.

Seat <NUM> is realized parallel to, and preferably concentric, to longitudinal axis A and therefore housing <NUM> is similarly realized and defines a space <NUM>' into which the spool <NUM> may move longitudinally along axis A. Always according to the disclosed embodiment, the inner portion 2b of first shaft <NUM> is housed radially, without contact, within the inner portion 3b of second shaft <NUM> in face of seat <NUM> that is opened towards first shaft <NUM>.

Masking reference to <FIG>, the housing <NUM> is substantially cylindrical and comprises a radial wall 23a and an axial wall 23b faced to first shaft <NUM>. The axial wall 23b defines respective a respective opening 23b' while the radial wall is opened from the opposite side defining an opening 23c'. The opening 23b' of axial wall 23b' has a diameter lower than the diameter of spool <NUM> while the opening 23c' has a diameter equal to the one of spool <NUM> to allow its mounting.

Valve <NUM> further comprises elastic means <NUM> configured to impart a force against the movement of spool <NUM> as described below and axially in contact with the spool <NUM> and the first shaft <NUM>. Accordingly, elastic means <NUM> are housed in space <NUM>', passes through opening 23b' and partially in inner space <NUM> till contact first shaft <NUM>. Preferably such elastic means <NUM> comprises a coil spring.

On the opposite side, the second shaft <NUM> defines a shoulder <NUM> configured to axially delimit the movement along axis A of spool <NUM>. According to the above described configuration, the spool <NUM> may move between a first position along axis A into which it is in contact with shoulder <NUM> (see <FIG>) and a second position wherein it is in contact with axial wall 23b (see <FIG>, <FIG>).

The spool <NUM> preferably comprises a head portion <NUM>, a terminal portion <NUM> and an intermediate portion <NUM> that extends between the head and terminal portions <NUM>, <NUM>. The head portions <NUM>, <NUM> have a diameter substantially equal to the diameter of space <NUM>' while the intermediate portion <NUM> has a diameter lower with respect to space <NUM>' thereby providing an annular moving chamber <NUM> between the intermediate portion <NUM> and the housing <NUM>.

The annular moving chamber <NUM>' is fluidly connected to inner space <NUM>' via a duct <NUM> realized inside the head and intermediated portions <NUM>, <NUM> while the head and terminal portions <NUM>, <NUM> moves inside the housing <NUM> in a fluid tight manner.

The head portion <NUM> is configured to selectively close opening 23c' while the terminal portion is faced to opening 23b' and defines a seat <NUM> for accommodating a terminal portion of elastic means <NUM>. Accordingly, elastic means <NUM> acts between the terminal portion <NUM> and an element fixedly carried by first shaft <NUM> and pass through opening 23b'.

Coming back to lateral wall 23a of housing <NUM>, it is provided with respective first, second and third radial openings 23a', 23a'', 23a'' realized along axis A and distanced between each other.

The first and second radial openings 23a', 23a'' are fluidly connected together and are both fluidly connected to opening 23b' of axial wall 23b thereby allowing fluidic communication within inner space <NUM> and, therefore, to lamellas <NUM> of clutch assembly <NUM>.

Each of the third radial openings 23a‴ is fluidly connected to chamber <NUM> via a respective duct <NUM> realized through the second shaft <NUM> and the second intermediate element <NUM>. In particular, such duct <NUM> is realized inclined with respect to longitudinal axis A.

In greater detail, the third radial openings 23a‴ are realized in proximity of opening 23c' while the first radial openings 23a' are realized in proximity of opening 23b'. Accordingly, second and third radial openings 23a", 23a‴ are positioned so as to be opened and/or closed partially/completely by head portion <NUM> while first and second radial openings are positioned so as to be opened and/or closed partially/completely by terminal portion <NUM>. Second radial openings 23a"' are furthermore configured to be in fluid communication with moving chamber <NUM>, according to the position of spool <NUM>.

The opening 23c' of housing <NUM> is, as said, connected to source <NUM> of fluid. In particular, the opening 23c' is fluidly connected to a channel <NUM> realized in second shaft <NUM> and preferably coaxial to axis A. In particular, making reference to <FIG>, channel <NUM> defines from one side the abode described shoulder <NUM> and from the opposite sides preferably extends through all the second shaft <NUM> till possibly allowing its fluid communication with the environment.

In detail, such fluid communication with the environment is normally avoided by a terminal plug <NUM> and permitted solely for maintenance purpose by extracting such plug from channel <NUM>.

Channel <NUM> is fluidly connected to the source <NUM> via at least a duct <NUM>. In the disclosed embodiment, duct <NUM> is inclined with respect to axis A and entirely realized in output shaft <NUM>.

The value of pressure coming from source <NUM> may be modulated by a control valve, not shown, configured to regulate the value of the pressure of fluid sent in duct <NUM> towards valve <NUM>. The pressure of the fluid may vary till reaching an engagement pressure pset configured to allow the movement of the actuator element <NUM>, i.e. the engagement of clutch <NUM>.

The operation of the PTO assembly comprising a hydraulic arrangement according to the invention and described as above is the following.

In the operating condition of <FIG>, the pressure p<NUM> in conduit <NUM>/channel <NUM> is lower than engagement pressure pset and the force exerted by the fluid to head portion <NUM> of spool <NUM> is no sufficient to overcome the force imparted by elastic means <NUM>. In such configuration, movable chamber <NUM> is isolated from inner space <NUM> and therefore the oil coming from duct <NUM> cannot flow towards this latter.

In the operating condition of <FIG>, the pressure p<NUM> in conduit <NUM>/channel <NUM> is lower than engagement pressure pset but the force exerted by the fluid to head portion <NUM> of spool <NUM> is sufficient to overcome partially the force imparted by elastic means <NUM> thereby partially moving the spool <NUM>. In such configuration a quantity of the fluid in channel <NUM> passes in duct <NUM> thereby starting to pressurize chamber <NUM> but not in a sufficient manner to move actuator element <NUM>. Another quantity of the fluid in channel <NUM> passes in duct <NUM> to mobile chamber <NUM>. Thus, fluid can pass from mobile chamber <NUM> via second and first openings 23a", 23a' towards the opening 23b' on axial wall 23b and therefore to inner space <NUM> in order to lubricate lamellas <NUM>.

In the operation condition of <FIG> the pressure p<NUM> in conduit <NUM>/channel <NUM> is equal or greater than engagement pressure pset and therefore the force exerted by the fluid to head portion <NUM> of spool <NUM> is sufficient to overcome the force imparted by elastic means <NUM> thereby moving the spool <NUM> till the terminal portion <NUM> contacts the axial wall 23b. In such configuration, a quantity of the fluid in channel <NUM> passes in duct <NUM> thereby pressurizing chamber <NUM> so that the force exerted by the fluid on disc portion 11b of actuator <NUM> moves these latter against lamellas <NUM> engaging the clutch assembly <NUM>. In this way, first and second intermediate elements <NUM>, <NUM> are engaged and therefor torque may be transmitted between first and second shafts <NUM>, <NUM>. A portion of fluid passes in inner space <NUM> by duct <NUM> to clutch assembly <NUM>. The quantity of the fluid in channel <NUM> passing in duct <NUM> and in mobile chamber <NUM> cannot pass to inner space <NUM> because second and first openings 23a'', 23a' are closed by terminal portion <NUM> and head portion <NUM>.

In view of the above operation, the present invention is also directed to a method for cooling a clutch assembly that is controlled via a pressure value p2 coming from a source <NUM> of fluid in pressure and configured to allow the engagement of the clutch assembly, and comprising the following phases:.

In particular, the method may be applied to the disclosed arrangement, i.e. to a method for lubricating/cooling lamellas <NUM> of the clutch assembly <NUM> by controlling valve means of PTO assembly <NUM> to provide a pressure of fluid towards valve <NUM> that is not sufficient to allows the actuation of clutch assembly <NUM> but grater to allow a preset movement of the spool <NUM> sufficient to allow fluidic communication between the source <NUM> and the inner space <NUM> housing the clutch assembly <NUM>.

The aforementioned method can be performed by an electronic control valve controlled by an electronic unit (not shown) upstream to the disclosed source (<NUM>) and configured to vary the value of pressure provided by this latter. The cooling is performed every time at the movement of spool <NUM> (i.e. at each engagement or disengagement of clutch assembly <NUM>) but can be requested actively, e.g. by detecting a high temperature of oil in inner space <NUM> or of lamellas via proper sensors and therefore controlling the pressure of source <NUM> to provide a suitable cooling phase.

It is clear that the oil provided to lamellas <NUM>, i.e. to inner space <NUM> flows towards a discharge, that is not shown, after having lubricated the clutch assembly <NUM>.

In view of the foregoing, the advantages of PTO assembly comprising a hydraulic arrangement according to the invention are apparent.

The proposed hydraulic arrangement <NUM> is particularly compact and does not require peculiar piping as in the known PTO assembly. Therefore, the costs for manufacturing and maintenance of such POT assembly is reduced.

Moreover, the peculiar valve assembly <NUM> provided allows both to:.

Therefore, the useful life of the clutch assembly <NUM>, and therefore of PTO assembly <NUM>, is improved.

It is clear that modifications can be made to the described PTO assembly comprising a hydraulic arrangement which do not extend beyond the scope of protection defined by the claims.

For example, it is clear that the proposed hydraulic arrangement may be realized between two shafts that are not an input shaft <NUM> and an output shaft <NUM> of a PTO assembly as described.

Furthermore, it is clear that the described intermediate elements <NUM>, <NUM> and actuator <NUM> or the geometry/ typology of clutch <NUM> and lamellas <NUM> may be varied according the dimensions of the PTO.

Claim 1:
- Power Take-off assembly, PTO assembly, (<NUM>) for a work vehicle, said PTO assembly (<NUM>) comprising a first and a second shaft (<NUM>, <NUM>) and a clutch assembly (<NUM>) comprising a plurality of lamellas (<NUM>) and configured to couple said first and second shaft (<NUM>),
said PTO assembly (<NUM>) comprising a housing (<NUM>) defining an inner space (<NUM>), said clutch assembly (<NUM>) and at least an inner portion (2b, 3b) of said shafts (<NUM>, <NUM>) being housed in said inner space (<NUM>),
said PTO assembly (<NUM>) comprising a hydraulic arrangement (<NUM>) for managing the flow of fluid from a source (<NUM>) of said work vehicle towards said clutch assembly (<NUM>), said hydraulic arrangement (<NUM>) comprising a valve (<NUM>), said valve (<NUM>) being housed in a seat (<NUM>) realized within at least one between said shafts (<NUM>, <NUM>), the source (<NUM>) being fluidly connected to said valve (<NUM>) via at least a conduit (<NUM>, <NUM>) realized within said at least one between said shafts (<NUM>, <NUM>), said PTO assembly being characterized in that said valve (<NUM>) comprises a housing (<NUM>) housed in said seat (<NUM>) and a spool (<NUM>) arranged within said housing (<NUM>) in a movable manner parallel to a longitudinal axis (A) of said at least one between said shafts (<NUM>, <NUM>), said housing (<NUM>) defining a plurality of openings (23a', 23a", 23a‴, 23c') configured to be opened or closed, partially or completely, by said spool (<NUM>) that is actuated by the pressure of fluid in said at least a conduit (<NUM>, <NUM>),
and wherein said valve (<NUM>) comprises elastic means (<NUM>) housed within said housing (<NUM>) and configured to impart a force to said spool (<NUM>) that is opposite to the force applied by the pressure applied by fluid in said at least a conduit (<NUM>, <NUM>).