VARIABLE DISPLACEMENT PUMP AND METHOD FOR REGULATING SUCH PUMP

Abstract

Variable displacement pump including: i) a pumping piston for pumping the fluid; ii) a sliding seat along which a stroke of the piston takes place; a sliding of the piston along the seat corresponding to a rotation of the seat; iii) a system for regulating the torque absorbed by the pump, in turn including a means for regulating a displacement of the pump as a function of an electrical signal. The regulating means in turn including: - a structure with variable inclination for regulating the stroke length of the pumping piston and thus the displacement of the pump; - a fluid-dynamic actuator for regulating the inclination of the structure; - a control means for controlling the actuator as a function of an electrical signal.

Claims

1. A variable displacement pump allowing the passage of a fluid from a zone with a lower pressure to a zone with a higher pressure; said pump comprising: i) a pumping piston for pumping the fluid; ii) a sliding seat along which a stroke of the piston takes place; a sliding of the piston along the seat corresponding to a rotation of said seat about a rotation axis that is eccentric relative to the seat; iii) a system for regulating the torque absorbed by the pump, comprising a means for regulating a displacement of the pump as a function of an electrical signal; said displacement regulating means in turn comprising: a structure with variable inclination for regulating the stroke length of the pumping piston and thus the displacement of the pump; a fluid-dynamic actuator for regulating the inclination of said structure, a corresponding displacement of the pump being associated with every inclination of the structure; a control means for controlling the actuator which takes on at least one unbalanced configuration, in which it induces a movement of said actuator, and a balanced configuration in which it does not induce a movement of the actuator, said control means in turn comprising: a) a slider movable at least between said balanced configuration and said unbalanced configuration; in said unbalanced configuration the slider being able to take on at least a first position in which it allows the communication of a chamber acting on said actuator with a first zone and a second position in which it allows the communication of the chamber with a second zone; in an operating configuration the first zone being subject to a pressure dependent on the pressure downstream of the piston, whereas the second zone is in a zone with a lower pressure than the first zone; in said balanced configuration the slider taking on a third position in which: *) the fluid communication between the chamber and the first zone is prevented/restricted if evaluated compared to the first position; and **) the fluid communication between the chamber and the second zone is prevented/restricted if evaluated compared to the second position; b) a sliding element slidable relative to the slider, said sliding element being distinct from said actuator and being mechanically actuated as a consequence of a variation in the inclination of said structure; an element constrained to the structure with variable inclination and connected to the sliding element so as to bring the control means back from the unbalanced configuration to the balanced one; wherein said slider comprises a first pushing surface which, in the balanced configuration, is in communication with the first zone and on which the pressure pushes the slider from the third towards the first position.

2. The pump according to claim 1, wherein the slider comprises a second pushing surface which, in the balanced configuration, is in communication with the first zone and on which the pressure pushes the slider in an opposite direction relative to the first surface; the first pushing surface being larger than the second pushing surface.

3. The pump according to claim 2, wherein the first and the second pushing surface are opposite and connected by a portion of the slider interposed between them; the first pushing surface having a larger outer diameter than the second pushing surface.

4. The pump according to claim 1, wherein it comprises an elastic regulating means which exerts a force that opposes the passage of the slider from the balanced configuration to the unbalanced configuration.

5. The pump according to claim 4, wherein said elastic means comprises a first and a second spring; only the first spring intervening for one portion of the stroke of the slider, and both the first and the second spring intervening for another portion of the stroke of the slider.

6. The pump according to claim 4, wherein the first surface is closer to the elastic regulating means than the second surface.

7. The pump according to claim 1, wherein the structure with variable inclination, in order to allow a variation of the displacement, rotates about a regulation axis; said element integral with the structure with variable inclination being partially inserted in a seat obtained on the sliding element.

8. The pump according to claim 1, wherein said sliding element comprises/is a jacket of said slider.

9. The pump according to claim 8, wherein said jacket comprises a first port connected to the first zone, a second port connected to the second zone and a third port connected to the chamber; the third port being interposed between the first and the second port.

10. A method for automatically regulating a displacement of a pump according to claim 1, said method being aimed at maintaining constant/minimising a variation in the absorption of torque as an outlet pressure of the pump varies; said torque being set as a function of an electrical control current; said method comprising the steps of: i) modifying the inclination of the structure with variable inclination; the step of modifying the inclination of the structure with variable inclination being determined by a variation in the outlet pressure which gives rise to a force that moves the slider relative to the sliding element in order to pass from the balanced configuration to the unbalanced configuration; on passing from the balanced configuration to the unbalanced one, the slider moves, removing an obstruction that blocks the fluid communication between the chamber pushing the actuator and the first zone, if the variation in the outlet pressure corresponds to an increase in the outlet pressure, or removing an obstruction that blocks the fluid communication between the pushing chamber and the second zone if the variation in the outlet pressure corresponds to a decrease in the outlet pressure; the first and the second zone being at different pressures compared to the pushing chamber, determining a movement of the actuator and thus of the structure; a communication of the pushing chamber with the first zone determining an increase in the pressure in the pushing chamber, corresponding to which there is a movement of the structure with variable inclination to induce a reduction in displacement; a communication of the pushing chamber with the second zone determining a reduction in the pressure in the pushing chamber, corresponding to which there is a movement of the structure with variable inclination to induce an increase in displacement; ii) modifying the position of said sliding element to allow for restoring said balanced configuration; the step of modifying the position of the sliding element being determined by the step of modifying the inclination of the structure, which in turn determines the movement of an element constrained to said structure and connected to said sliding element.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Further features and advantages of the present invention will become more apparent from the indicative and thus non-limiting description of a preferred but non-exclusive embodiment of a pump and a method for regulating the displacement thereof, as illustrated in the appended drawings, in which:

[0012] FIG. 1 shows a perspective view of a pump according to the present invention;

[0013] FIG. 2 shows a sectional view of the pump of FIG. 1;

[0014] FIG. 3 shows a component of FIG. 1;

[0015] FIGS. 4, 5, 6, 7 show the operation of the pump according to the present invention in different operating steps;

[0016] FIG. 8 shows the regulation curve of a torque regulation system in the displacement-pressure diagram (the pump outlet pressure P is shown in the abscissa and the pump displacement is shown in the ordinate);

[0017] FIG. 9 shows the fluid-dynamic diagram of the pump according to the present invention.

DESCRIPTION OF EXAMPLE EMBODIMENTS

[0018] In the appended figures, reference number 1 indicates a variable displacement pump. Such a pump 1 is of the type known in the art as oscillating plate pump.

[0019] The pump 1 comprises: [0020] i) at least one pumping piston 10 for pumping a fluid to be treated (typically there are a plurality of pistons 10 and suitably they are movable along parallel lines); [0021] ii) a sliding seat 2 (schematically depicted with a dashed line in FIG. 2) along which the stroke of the piston 1 takes place. If there is more than one piston 10, there are corresponding seats 2.

[0022] Advantageously, this plurality of seats is obtained in a guide support 39 of the pistons 10.

[0023] Usually the guide support 39 is set in rotation about a rotation axis 390 which is offset relative to the seats 2 considered individually.

[0024] Such rotation, at least in an operating configuration, corresponds to a sliding of the piston 10 along the seat 2 (or more generally of the pistons 10 along the corresponding seats 2). As better explained below, it should be noted that at zero flow rate (non-operating configuration) a rotation of the support 39 does not correspond to a sliding of the piston 10 along the seat 2 (or of the pistons 10 along the corresponding seats 2).

[0025] The seats 2 are typically side by side along an imaginary line closed on itself (typically a circle). Such an imaginary line surrounds the rotation axis 390 of the guide support 39.

[0026] The pump 1 comprises a system 400 for regulating the torque absorbed by the pump 1. The system 400 comprises a means 4 for regulating the displacement of the pump 1 as a function of an electrical signal.

[0027] The regulation means 4 in turn comprises a structure 41 with variable inclination for regulating the stroke length of the pumping piston 10 and thus the displacement of the pump 1; an end of the piston 10 is placed at the structure 41 with variable inclination. In technical jargon, the structure 41 with variable inclination is also known as oscillating plate (even if the geometry is more complex than that of a plate). Pumps of this type are well known in the field as variable displacement axial piston pumps with oscillating plate.

[0028] If there are several pistons 10, the structure 41 with variable inclination simultaneously regulates the stroke of all the pumping pistons 10. In particular, an end of each pumping piston 10 is placed at the structure 41.

[0029] The structure 41 with variable inclination allows to move the pistons 10 back and forth relative to the seats 2 (whose position is instead not modified by the structure 41).

[0030] The structure 41 has a variable inclination relative to a rotation axis 390 of the piston or pistons 10. In the specific case reference is made to a variation of the inclination relative to the rotation axis 390, but it would be equivalent to refer to a variation of the inclination relative to an imaginary plane orthogonal to such an axis 390 or a vertical imaginary plane.

[0031] Typically a variation of the inclination of the structure 41 relative to the rotation axis 390 involves rotating the structure 41 about a regulation axis 411. Such an axis 411 suitably extends along a direction orthogonal to that of the rotation axis 390 (suitably the regulation axis 411 is orthogonal to the rotation axis 390). As mentioned above, the greater or lesser inclination of the structure 41 results in a greater or lesser stroke of the pistons 10 and thus the displacement of the pump 1 (hence the correlation between the inclination angle of the structure 41 and the displacement). If the structure 41 extends orthogonally to the rotation axis 390, the flow rate is zero. By increasing the inclination (for example, see the dashed arched arrow in FIG. 2), the flow rate increases.

[0032] Advantageously, the pistons 10 are indirectly associated with the structure 41 by means of a piston-guide plate which is rotatable about the rotation axis 390 together with the pistons 10. By way of non-limiting example, the piston-guide plate could be pushed towards the structure 41 by means of a spring (what is described with reference to the solution with several pistons 10 can be extended to the theoretical solution in which even only one piston 10 is present). The regulation means 4 also comprises a fluid-dynamic actuator 42 for regulating the inclination of said structure 41. Such a fluid-dynamic actuator 42 is a plunger.

[0033] The regulation means 4 comprises a control means 43 for controlling the actuator 42 as a function of an electrical signal (suitably an electrical signal corresponds to each combination of pump outlet pressure-position of the actuator 42). The regulation means 4 takes on at least one unbalanced configuration in which it induces a movement of said actuator 42 (the unbalanced configuration is exemplified in FIGS. 5, 7) and a balanced configuration in which it does not induce a movement of the actuator 42 (see FIG. 4 or 6). Considering how the means 4 is structured, the balanced configuration is the starting and arrival point of a possible unbalanced configuration.

[0034] The control means 43 in turn comprises a slider 431 movable at least between said balanced configuration and said unbalanced configuration; in said unbalanced configuration the slider 431 can take on at least a first position (see FIG. 5) in which it brings a chamber 420 acting on said actuator 42 in communication with a first zone 31. During the present discussion, the slider 431 can also be defined as a slide. In fact, it allows or prevents putting several ports with different pressure in fluid communication.

[0035] In the unbalanced configuration, the slider 431 can also take on a second position (see FIG. 7) in which it brings the chamber 420 acting on said actuator 42 in communication with a second zone 32.

[0036] In the first position the chamber 420 is not in communication with the second zone 32 (unless there is negligible and unwanted leakage related to the greater or lesser precision of the mechanical couplings); in the second position the chamber 420 is not in fluid communication with the first zone 31 (unless there is negligible and unwanted leakage related to the greater or lesser precision of the mechanical couplings).

[0037] In an operating configuration, the first zone 31 is affected by a pressure dependent on the pressure downstream of the piston 10 (typically the first zone 31 is affected by the outlet pressure possibly net of the pressure drops) while the second zone 32 is at a lower pressure than the first zone 31. For example, the pressure in the second zone 32 could be the ambient pressure outside the pump 1 or the pressure upstream of the piston 10 (or more generally of the pump 1). The second zone 32 is preferably at atmospheric pressure or at suction pressure. In more detail, the second zone 32, preferably coinciding with a zone of the pump where the drains are collected, is in communication with a fluid tank or is connected to the pump suction (as schematically depicted in FIG. 9). The tank can be at ambient pressure or slightly pressurised.

[0038] In the balanced configuration, the slider 431 can take on a third position (see FIG. 4 or 6) in which: [0039] *) the fluid communication between the chamber 420 and the first zone 31 is prevented/restricted if evaluated compared to the first position; and [0040] **) the fluid communication between the chamber 420 and the second zone 32 prevented/choked if evaluated compared to the second position.

[0041] If the indicated fluid communication is completely prevented, the system could be unstable (it continues to close and open) and therefore choking may be preferable, allowing a minimum passage to the benefit of stability.

[0042] The fluid-dynamic actuator 42 is associated with a first end of the structure 41 with variable inclination. In the solution exemplified in FIG. 2, the actuator 42 is hinged (advantageously at a first end) to the structure 41 with variable inclination. In other solutions not illustrated, there is only one mechanical abutment between the fluid-dynamic actuator 42 and the structure 41 with variable inclination. In a second end, the actuator 42 comprises a pushing surface which opens into the chamber 420.

[0043] With reference to FIG. 2, if the pressure in the chamber 420 increases, the structure 41 reduces its own inclination, the stroke of the pistons 10 decreases and thus the displacement decreases. If the pressure in the chamber 420 decreases, the structure 41 increases its own inclination (up to a maximum value), the stroke of the pistons 10 increases and thus the displacement increases.

[0044] The control means 43 comprises a sliding element 432 slidable relative to the slider 431 for restoring said balanced configuration (see FIG. 4). The sliding element 432 is distinct from the actuator 42 and is mechanically actuated by a variation of the inclination of said structure 41. The sliding element 432 is movable along the same direction as the slider 431. In particular, it is movable only along such a direction. The slider 431 is moreover movable back and forth only along one direction. In particular, the slider 431 and the sliding element 432 are intended to translate.

[0045] The sliding element 432 comprises/is a jacket 433 of said slider 431. The jacket 433 at least partially wraps around the slider 431. The jacket 433 can translate relative to the slider 431. In the imbalanced configuration, the fluid communication between the chamber 420 and the first zone 31 takes place through a path comprising a gap 6 interposed between the jacket 433 and the slider 431.

[0046] The jacket 433 comprises a first port 437 connected to the first zone 31, a second port 438 connected to the second zone 32 and a third port 439 connected to the chamber 420. The third port 439 is interposed between the first and the second port 437, 438.

[0047] In the balanced configuration (see FIG. 4) the slider 431 obstructs (preferably partially or at the limit completely) the third port 439 (or in any case a first channel 50 in communication with said chamber 420). Suitably, the first channel 50 passes through a wall of the jacket 433 (in particular it allows to pass through the thickness of the jacket 433). The first channel 50 extends from the third port 439. As explained above in the balanced configuration, the slider 431 could possibly allow a minimum passage of fluid from/to the first and the second zone 31, 32 (this allowing a more stable operating situation).

[0048] The slider 431 has a first groove 510 which in the first position is part of a path which puts said first channel 50 in communication with the first zone 31 (in particular puts the first channel 50 in communication with a second channel 501 leading to the first zone 31). In this regard, see FIG. 5. The first groove 510 is part of the gap 6 described above.

[0049] The slider 431 has a second groove 520 which in the second position is part of a path which puts said first channel 50 in communication with the second zone 32 (in particular the second groove 520 puts the first channel 50 in communication with a third channel 500 which passes through the wall of the jacket 433 and leads to the second zone 32). In this regard, see FIG. 7.

[0050] The slider 431 comprises a first pushing surface 33 which, in the balanced configuration, is in communication with the first zone 31 and on which the pressure pushes the slider 431 from the third towards the first position.

[0051] The first pushing surface 33 is advantageously obtained (suitably it is entirely obtained) along a side surface of the slider 431.

[0052] The slider 431 can also comprise a second pushing surface 34 which, in the balanced configuration, is in communication with the first zone 31 and on which the pressure pushes the slider 431 in the opposite direction relative to the first surface. The second pushing surface 34 is advantageously obtained (suitably it is entirely obtained) along a side surface of the slider 431.

[0053] The first pushing surface 33 is larger than the second pushing surface 34, so that the pressure acts on a differential area (between the first surface 33 and the second surface 34) which pushes the slider 431 from the third towards the first position. The first surface 33 and/or the second surface 34 are suitably annular. In an exemplary and non-limiting configuration, the difference in diameter between the first surface 33 and the second surface 34 is less than 1 mm. The first and/or the second surface 33, 34 extend transversely to a movement direction of the slider 431. Preferably, the first and second surface 33, 34 are coaxial. The second surface 34 could also be absent, i.e., with zero area. In this case, the pressure acts on the first surface 33 to push the slider 431 from the third towards the first position.

[0054] The slider 431 hinders or prevents the communication of the first and the possible second pushing surface 33, 34 with the second zone 32.

[0055] As mentioned above, there are three different pressure zones within the control means 43: [0056] P) high pressure (zone connected to the outlet pressure of the pump); [0057] T) low pressure (zone connected to the pump body, but it could also be connected to the pump suction); [0058] A) regulated pressure (which acts in the chamber 420).

[0059] Such zones with different pressures are highlighted at the control means 43 in FIG. 4 and FIG. 9. In the fluid-dynamic diagram of FIG. 9, the torque regulation system 400 and a pressure regulator 16 are depicted: the latter is not necessary for the operation of the pump 1, it may be absent, but it is generally present.

[0060] The zone subject to high pressure P has a difference in diameter, whereby the pressure acts on a differential area, generating a thrust in the same direction as the electromagnet described below.

[0061] In fact, the control means 43 comprises an electrically driven regulator 8 which moves (in particular pushes) said slider 431 to pass from the balanced configuration to the unbalanced configuration. The current input takes place through the input port 800. Such a regulator 8 comprises/is an electromagnet comprising a moving device 80 of said slider 431. It allows the electrical control signal to be translated into a physical movement. In particular, the electromagnet generates a thrust proportional to the intensity of the input current. The moving device 80 is typically a pusher.

[0062] The moving device 80 is substantially coaxial with the slider 431. The moving device 80 moves along a translation direction of the jacket 433 relative to the slider 431. The regulator 8 exerts a force along a movement direction of the slider 431. The regulator 8 is typically capable of exerting the force only in one direction (possibly it can exert it in both directions).

[0063] The slider 431 is subject to contrasting forces exerted at least by said moving device 80 and by an elastic feedback (exerted by the elastic regulation means 3, as will be better clarified below). The moving device 80 therefore exerts a force on the slider 431 which is countered by the elastic feedback of a spring.

[0064] Suitably, but not necessarily, an increase in current in the regulator 8 determines a reduction in the displacement of the pump 1.

[0065] The control means 43 comprises an elastic regulation means 3 which exerts a force that opposes the movement of the slider 431 from the balanced configuration to the unbalanced one. The elastic means 3 exerts a force on the slider 431 contrasting that of the regulator 8 and of the high pressure P. The elastic means 3 exerts a force along a movement direction of the slider 431.

[0066] Suitably, the elastic regulation means 3 has different stiffness in at least two zones of the possible stroke of the slider 431. It is thereby possible to approximate a hyperbolic trend of the stiffness of the elastic means 3. Such a hyperbolic trend has its usefulness. In fact, to have a constant absorbed torque, the product of the displacement and of the outlet pressure must be constant. In this regard, it is useful to have elastic means 3 having a variable stiffness according to a curve approximating a hyperbole. In fact, in a displacement-pressure graph the iso-torque curves are substantially hyperbolic. Therefore the movement of the slider 431 must be guided by an elastic regulation means 3 which approximates a hyperbolic trend. Alternatively, if there were only one elastic spring with constant stiffness, there would be a linear movement that would not be able to approximate the hyperbolic trend.

[0067] The elastic regulation means 3 can comprise a first and a second spring 301, 302. Only the first spring 301 intervenes for one portion of the stroke of the slider 431, and both the first and the second spring 301, 302 intervene for another portion of the stroke of the slider 431.

[0068] Suitably, the first and second spring 301, 302 may have different stiffness.

[0069] In particular, the first and second spring 301, 302 are helical springs.

[0070] Advantageously, the first spring 301 is placed outside the second spring 302 and is less stiff than the second spring 302.

[0071] One or more springs with variable stiffness (e.g., with variable pitch or variable diameter coils) could also be used to approximate the hyperbola (in which case even only one spring could be used).

[0072] FIG. 8 shows in continuous line (curve 90) a possible regulation curve of the torque regulation system in the diagram of pump displacement (ordinate)outlet pressure (abscissa). The pump displacement (in the ordinate) is expressed as a percentage relative to the maximum value.

[0073] In this diagram, the theoretical (ideal) curves at constant torque are hyperbolas (see for example the three curves 910, 920, 930).

[0074] In the first portion 91 of the regulation curve 90, the pump 1 is at maximum displacement (100%), but the outlet pressure is contained and therefore the absorbed torque is lower than the regulation torque. In fact, since the pressure is contained, the thrust of the regulator 8 (the electromagnet) on the slider 431 is not sufficient to overcome the pre-load of the elastic regulation means 3, and therefore the slider 431 is in the position closest to the regulator 8 (see configuration of FIG. 7), closing the passage between the first zone 31 and the chamber 420; at the same time the slider 431 keeps the passage between the chamber 420 and the second zone 32 open. As the chamber 420 is connected to the second zone 32 (low pressure), the pump 1 maintains the maximum possible displacement.

[0075] As the outlet pressure increases, the thrust on the slider 431 increases, until it becomes sufficient to compress the elastic regulation means 3. At this point, the displacement regulation means 4, as described above, reduces the displacement: the regulation curve 90 then follows the portion 92. As explained above, the reduction in displacement with increasing pressure is approximately linear, therefore it does not exactly follow the ideal regulation curve at constant torque (curve 91) but approximates it.

[0076] In order to be able to better approximate the theoretical (ideal) curve 910, the two springs 301, 302 are used (at least) instead of just one. The first and second spring 301, 302 have different free lengths. Only one of the first and second spring 301, 302 is initially pre-loaded. Therefore, upon reaching a second pressure level, the compression of the first spring 301 is such as to begin to pre-load the second spring 302, as well. At this point, both being pre-loaded, the equivalent stiffness will be greater, and the regulation curve 90 follows the portion 93. Thereby, the regulation curve 90 is again brought close to the theoretical (ideal) curve 910 at constant torque.

[0077] Increasing the control current to the electromagnet (electro-proportional magnet), the regulation curve 90 will move downwards, leading towards the theoretical curve 920, vice versa reducing the control current, the regulation curve 90 will move upwards, leading towards the theoretical curve 930.

[0078] The pump 1 comprises an element 410 constrained to (typically integral with) the structure 41 with variable inclination to induce the passage from the imbalanced configuration to the balanced configuration. Such an integral element 410 can therefore be defined as a member for restoring said balanced configuration. The element 410 can also be defined as an eccentric pin.

[0079] The element 410 constrained to the structure 41 with variable inclination engages at least partially in a seat 434 obtained on the jacket 433.

[0080] To allow the variation of the displacement, the structure 41 with variable inclination rotates about the regulation axis 411. Such a regulation axis 411 extends along a direction which is orthogonal to that of the axis about which the pistons 10 rotate. Advantageously, the axis 411 is fixed relative to an outer casing of the pump 1.

[0081] The element 410 integral with the structure 41 with variable inclination rotates about said regulation axis 411 and is/comprises an insert which engages in the jacket 433 (inside the seat 434) and which is eccentric relative to said regulation axis 411. A rotation of the structure 41 corresponds to an arched trajectory of the element 410.

[0082] The jacket 433 is pre-tensioned by an elastic positioning means 7 which exerts a force in a predetermined direction. In the exemplified solution, the elastic positioning means 7 comprises a helical spring that can at least partially wrap around the slider 431. The elastic positioning means 7 holds the jacket 433 in abutment against the element 410.

[0083] A method for automatically regulating a displacement of a pump 1 is also an object of the present invention. Such a pump 1 has one or more of the features described above. The method is aimed at maintaining constant/minimising a variation in the absorption of torque as an outlet pressure of a pump varies. The value of the torque to be maintained constant/minimise variation is regulated by means of an electrical signal, i.e., a control current. The method comprises the step of modifying the inclination of the structure 41. The step of modifying the inclination of the structure 41 is determined by a variation in the outlet pressure which determines a force which moves the slider 431 relative to the sliding element 432 (typically the jacket 433) in order to pass from the balanced configuration to the unbalanced configuration. The balanced and unbalanced configuration has been extensively described previously. Moving from the balanced configuration to the unbalanced configuration, the slider 431 places the pushing chamber 420 of the actuator 42 in fluid communication/more in fluid communication (taking into account that small fluid passages can also be present in the balanced configuration): [0084] with the first zone 31 if the variation in outlet pressure corresponds to an increase in outlet pressure; or [0085] with the second zone 32 if the variation in outlet pressure corresponds to a decrease in outlet pressure.

[0086] The first and the second zone 31, 32 are at different pressures compared to the pushing chamber 420. They consequently determine a variation of the force on the actuator and thus a movement of the actuator 42. A movement of the actuator 42 corresponds to a movement of the structure 41 and thus a variation of the displacement. More in particular: [0087] a communication of the pushing chamber 420 with the first zone 31 determines an increase in the pressure in the pushing chamber 420, corresponding to which there is a movement of the structure 41 such as to induce a reduction in displacement; [0088] a communication of the pushing chamber 420 with the second zone 32 determines a reduction in the pressure in the pushing chamber 420, corresponding to which there is a movement of the structure 41 such as to induce an increase in displacement. It is thereby possible to regulate the movement of the structure 41 in one direction or the other which corresponds respectively to a reduction or an increase in the displacement of the pump.

[0089] The method then comprises the step of modifying the position of said sliding element 432 to allow the restoration of the balanced configuration.

[0090] The step of modifying the position of the sliding element 432 is determined by the step of modifying the inclination of the structure 41, which in turn determines the movement of an element 410 constrained to said structure 41.

[0091] The step of moving the element 410 integral with the structure 41 determines alternatively (as a function of the direction in which the inclination of the structure 41 is modified): [0092] i) a movement of the sliding element 432 against the force exerted by elastic positioning means 7 acting on the sliding element 432; in this case the element 410 overcomes the force of the elastic positioning means 7; [0093] ii) a movement of the sliding element 432 along the same direction of the force exerted by the elastic means 7; in this case, the elastic positioning means 7, having ceased the abutting action exerted by the element 410, pushes the sliding element 432.

[0094] With explicit reference to FIGS. 4 to 7, the operation of the invention can be summarised as follows: [0095] FIG. 4: the slider 431 blocks (typically with two regulation edges 436) the port in the jacket 433 connected to the chamber 420, and the control means 43 is in the balanced configuration; in this case the pressure in the chamber 420 is intermediate between the pressures in the first and second zone 31, 32; [0096] FIG. 5: it is assumed to maintain the current command constant, so that the regulator 8 (e.g., the electromagnet) exerts a constant force on the slider 431 and it is assumed that the outlet (working) pressure of the pump 1 increases (this could take place due to an increase in the load): the differential area on which the outlet pressure of the pump acts therefore exerts an increase in force on the slider 431, further compressing the elastic regulation means 3. The slider 431 consequently moves towards the elastic regulation means 3 (moves downwards with reference to FIG. 5), consequently the connection between the first zone 31 (high pressure) and the chamber 420 opens/further opens (in particular through the regulation edges 436) and the connection between the second zone 32 (low pressure) and the chamber 420 closes. Thereby, the pressure in the chamber 420 increases, and thus the displacement of the pump decreases. [0097] FIG. 6: starting from the configuration of FIG. 5, when the displacement decreases, that is, the inclination of the structure 41 with variable inclination decreases, the element 410 integral with the structure 41 moves downwards. The jacket 433, held in abutment on the element 410 by the positioning spring 7, also moves downwards, until it is brought back into the balanced configuration (in particular with the regulation edges 436 at the port 439 in the jacket 433). Ultimately, the pump 1 and the torque regulation system 400 will be in a new balanced configuration relative to that of FIG. 4, characterised, in the face of an equal control current and a higher pressure, by a smaller displacement. Ultimately, following an increase in pressure, the pump reduces the displacement, maintaining the product approximately constant between pressure and displacement, that is, the torque. [0098] FIG. 7: if the outlet pressure of the pump 1 decreases, the slider 431 undergoes a smaller force on the differential area, it then compresses the elastic regulation means 3 less and moves towards the regulator 8 (in particular the electromagnet). Consequently, the slider 431 (in particular the regulation edges 436) closes the connection between the first zone 31 and the chamber 420 and opens/further opens the connection between the second zone 32 and the chamber 420. Thereby, the pressure in the chamber 420 decreases, and thus the displacement of the pump increases. Consequently, the element 410 will move towards the regulator 8 (typically the electromagnet), and the jacket 433 will follow it, until it is brought into a new balanced configuration (not depicted). The new balanced configuration, in the face of an equal control current and a lower pressure, will be characterised by a larger displacement, thus maintaining approximately constant the product between pressure and displacement, that is, the torque.

[0099] With the same pressure, the increase in the control signal of the regulator 8 (the electromagnet) will have the same effect as an increase in pressure (see FIG. 5), generating a reduction in displacement. Therefore, the new balanced condition, in the face of an increase in the control, will be characterised by equal pressure and a smaller displacement, therefore by a smaller absorbed torque. Conversely, a reduction in the control signal of the regulator 8 (the electromagnet) will have the same effect as a pressure reduction (see FIG. 7), generating an increase in displacement at the same pressure, and therefore an increase in torque.

[0100] Ultimately the torque absorbed by the pump 1 will decrease proportionally to the control signal to the regulator 8.

[0101] The present invention achieves several advantages.

[0102] First of all, it allows to provide a stable device not subject to particular oscillations of the absorbed torque as the load varies. This is thanks to the mechanical connection between the oscillating plate and the jacket and a system in which the slider 431 is sensitive to the outlet pressure.

[0103] The invention thus conceived is susceptible to numerous modifications and variants, all falling within the scope of the inventive concept that characterises it. Moreover, all the details may be replaced by other technically equivalent elements. All the materials used, as well the dimensions, may in practice be any whatsoever, according to needs.