Hydraulic machine provided with a direction changing drawer

Abstract

The invention relates to a hydraulic machine (100) comprising: - a distribution cover (2.3); - a distributor (16); - a displacement selection drawer (35) mounted so as to slide between a first position in which the machine is configured to operate with a first displacement and a second position in which the machine is configured to operate with a second displacement different from the first displacement; and - a direction changing drawer (26) mounted so as to slide between a first position in which the machine is configured to exert a torque in a first direction about an axis of rotation (10) and a second position in which the machine is configured to exert a torque in a second direction, the direction changing drawer (26) being mounted so as to slide along an axis (42) at a distance from the axis of rotation (10), the direction changing drawer extending: - in a wall of the distributor (16); or - in a wall of the distribution cover and outside the displacement selection drawer (35).

Description

[0001] Hydraulic machine equipped with a direction change drawer

[0002] FIELD OF THE INVENTION

[0003] The invention relates to hydraulic machines.

[0004] STATE OF THE ART

[0005] Document FR-3 024 503 discloses a hydraulic machine comprising a casing, radial pistons, a multi-lobed cam and a distributor. The machine comprises several sub-motors. A displacement selection slide is mounted to slide between a first position associated with a first displacement and a second position associated with a second displacement. Controlling the position of the slide therefore makes it possible to select the displacement of the machine. The slide is coaxial with the machine and is located in the distributor.

[0006] A direction change spool is also provided which is slidably mounted between first and second positions associated with two pressure configurations. This spool is controlled by the pressure difference at the machine terminals. It allows, when the motor configuration is changed (i.e. the low pressure and high pressure are reversed), to be sure that the sub-motor put in bypass or bypassed does not have a groove supplied with high pressure. This direction change spool in fact forms a selection spool for the lowest pressure. This second spool extends inside the first, coaxially with the latter. In the term "direction change spool", it must be kept in mind that it is not always the direction of rotation of the hydraulic machine that is changed but rather the direction of the torque exerted on the shaft by the hydraulic machine.Indeed, we can imagine different configurations of the drawer where, while the machine shaft rotates in the same direction, the machine can operate either as a pump or as a motor (this is for example the case when a hydraulic motor is used in pump mode to perform hydrostatic braking).

[0007] However, this arrangement complicates the manufacturing of the machine. One could attempt to remedy this by miniaturizing the direction change slide, but this reduction in dimensions makes manufacturing more expensive and has its limitations. Indeed, the two slides must occupy a certain volume to avoid internal leaks between the high and low pressure lines or circuits. It is therefore necessary to associate them with a certain quantity of material or a certain quality of materials and great precision in the production of the parts involved.

[0008] An aim of the invention is to facilitate the production of a hydraulic machine comprising such drawers.

[0009] STATEMENT OF THE INVENTION

[0010] For this purpose, according to the invention, a hydraulic machine is provided comprising:

[0011] - a distribution cover,

[0012] - a distributor,

[0013] - a displacement selection drawer slidably mounted between a first position in which the machine is configured to rotate with a first displacement and a second position in which the machine is configured to rotate with a second displacement different from the first displacement; and

[0014] - a direction change drawer slidably mounted between a first position in which the machine is configured to exert a torque in a first direction around an axis of rotation and a second position in which the machine is configured to exert a torque in a second direction, the direction change drawer being slidably mounted along an axis distant from the axis of rotation, the direction change drawer extending:

[0015] - in a wall of the distributor or

[0016] - in a wall of the distribution cover and outside the cylinder selection drawer.

[0017] Thus, by means of these positions of the direction change slide, the constraints related to the space requirement are reduced, which facilitates manufacturing. It is then easy to produce a high-performance two-cylinder machine. The positions provided for the direction change slide do not impact performance.

[0018] The displacement selection slide valve sees a large flow rate, especially when the machine is in small displacement mode, knowing that there is a recirculation of the fluid from the part of the machine in bypass or derivation. On the other hand, the direction change slide valve does not see any flow rate once it is set in one of the two operating positions (apart from a leakage flow rate which is minimized by enlarging this slide valve).

[0019] The invention allows, if necessary, to keep the displacement selection slide in the center of the distributor so that the circulation of the fluid takes place as close as possible to the grooves of the high and low pressure lines. But it leads to moving the direction change slide away from the axis of rotation. In the case where the latter extends outside the displacement selection slide, this simplifies the manufacture of the latter, knowing that the direction change slide does not see a large flow of fluid pass through.

[0020] Compared to the prior art, having two separate drawers makes it possible to have drawers with less compact constraints.

[0021] This technology is applicable to all hydraulic machines, whether used in motor or pump mode.

[0022] Again, in the expression "direction change slide", it is not necessarily the direction of rotation of the machine that is changed but rather the direction of the torque exerted on the shaft by the machine. Indeed, there are different configurations of the slide where, while the shaft rotates in the same direction, the machine can operate either as a pump or as a motor (this is for example the case when a motor is used in pump mode to perform hydrostatic braking).

[0023] In one embodiment, the displacement selector spool extends into the distributor.

[0024] Knowing that this drawer sees a large flow rate when the machine is in small displacement (recirculation of the fluid from the bypassed sub-engine), this configuration shortens the oil paths in order to limit pressure losses.

[0025] The displacement selection slide can be provided to be coaxial with the rotation axis.

[0026] Again, knowing that the displacement selection slide sees a large flow rate when the machine is in small displacement (i.e. when one of the sub-machines is bypassed), this axial configuration shortens the oil paths as much as possible and limits pressure losses to a minimum.

[0027] The direction change slide may be provided to extend outside the displacement selection slide.

[0028] It can be provided that the direction change drawer is mounted to slide in a direction parallel to the axis of rotation.

[0029] It is also possible to provide that the direction change drawer is mounted to slide in a direction not parallel to the axis of rotation.

[0030] The machine may be provided with a high pressure line and a low pressure line and is configured so that the change-over spool moves under the effect of pressure from the high pressure line. The hydraulic machine only operates if a pressure difference is established across its terminals. Depending on which "terminal" the high pressure is located at, the spool is placed in one configuration or another. The change-over spool is placed in a housing which has a chamber at each end, each chamber being connected to one or other of the high pressure and low pressure lines respectively.

[0031] It can be provided that, the second displacement being less than the first displacement, the second displacement is implemented by a group of pistons or lobes of a cam, the group forming a regular polygon centered on the axis of rotation.

[0032] We can also predict that the group forms a figure presenting a symmetry of revolution and / or a central symmetry.

[0033] This avoids the occurrence of unwanted forces and moments.

[0034] The invention also provides a subassembly for a hydraulic machine, the subassembly comprising:

[0035] - a distributor, - a displacement selection slide mounted in the distributor between a first position in which the machine is configured to rotate with a first displacement and a second position in which the machine is configured to rotate with a second displacement different from the first displacement; and

[0036] - a direction change drawer slidably mounted in the distributor between a first position in which the machine is configured to exert a torque in a first direction around an axis of rotation and a second position in which the machine is configured to exert a torque in a second direction, the direction change drawer being slidably mounted along an axis distant from the axis of rotation.

[0037] For example, the displacement selection slide is coaxial with the main axis.

[0038] A fluid path from a machine inlet to the displacement change slide can be expected to be shorter than a fluid path from the inlet to the direction change slide.

[0039] It can also be provided that, the cover forming annular grooves, the distributor forming grooves, the grooves of the cover and the grooves of the distributor forming a volume having a barycenter, the displacement selection slide is positioned so as to be closer to the barycenter than the direction change slide.

[0040] The invention also provides a device comprising at least one machine according to the invention.

[0041] Finally, according to the invention, a method of controlling a hydraulic machine is provided, in which:

[0042] - a displacement selection slider slides between a first position in which the machine is configured to operate with a first displacement and a second position in which the machine is configured to operate with a second displacement different from the first displacement; and - a direction change slider slides between a first position in which the machine is configured to exert a torque in a first direction around an axis of rotation and a second position in which the machine is configured to exert a torque in a second direction, the direction change slider sliding along an axis distant from the axis of rotation, the direction change slider extending:

[0043] - in a wall of a distributor or

[0044] - in a wall of a distribution cover and outside the cylinder selection drawer.

[0045] The invention also provides a method for controlling a hydraulic machine, in which:

[0046] - a displacement selection slider slides between a first position in which the machine is configured to operate with a first displacement and a second position in which the machine is configured to operate with a second displacement different from the first displacement, the displacement selection slider being controlled by the pressure of a pilot conduit exerting a thrust against a spring; and

[0047] - a direction change slider slides between a first position in which the machine is configured to exert a torque in a first direction around an axis of rotation and a second position in which the machine is configured to exert a torque in a second direction around the axis, the direction change slider sliding along an axis distant from the axis of rotation, the direction change slider being moved according to the supply or discharge conduit where the high pressure is established in the machine, the direction change slider extending:

[0048] - in a wall of a distributor, or

[0049] - in a wall of a distribution cover and outside the cylinder selection drawer.

[0050] DESCRIPTION OF FIGURES

[0051] We will now present embodiments of the invention by way of non-limiting examples in support of the drawings in which: - figure 1 is an axial sectional view of a hydraulic machine according to a first embodiment of the invention;

[0052] - Figures 2 to 5 are axial sectional views showing four operating configurations of the machine of Figure 1;

[0053] - Figure 6 is a cross-sectional view of the machine; Figures 7 to 10 are views similar to Figures 2 to 5 showing a machine according to a second embodiment;

[0054] - figure 11 is an axial sectional view of the distributor of the machine according to the second mode;

[0055] - figure 12 is a view of the direction change drawer of this machine; and figures 13 and 14 illustrate alternative embodiments of the ends of the direction change drawer.

[0056] I. First embodiment

[0057] We will describe a first embodiment of the hydraulic machine of the invention with reference to figures 1 to 6.

[0058] 1. Presentation of the machine

[0059] We present mainly the aspects of the machine 100 which concern the invention. Additional details on the machine, known per se, can be obtained from the document FR-3 024 503 already cited.

[0060] With reference to Figure 1, the machine 100 comprises a fixed casing, in this case in three parts 2.1, 2.2 and 2.3, following one another along the axis of rotation 10 and assembled for example by screws (not shown in the sectional plane). It comprises a corrugated or multi-lobed reaction cam 4 rigidly secured to the central part 2.2 of the casing, and for example made in the latter. The lobes of the cam are visible in Figure 6.

[0061] The machine comprises a cylinder block 6 mounted to rotate relative to the casing and the cam 4 around the main axis 10 and which has a plurality of cylindrical housings 12, radial in the present example, capable of being supplied with pressurized fluid and inside which pistons 14 are slidably mounted. In this case, the cylinder block 6 drives a shaft 5 in rotation which cooperates for this purpose with grooves (not shown) of the cylinder block 6. This shaft carries in this example an output flange 9. Each piston 14 carries a roller 7 by means of which it rests on the cam and rolls on it.

[0062] The machine 100 is of the type with a fixed casing and a rotating cylinder block. However, the invention also applies to a machine with a rotating casing and a fixed cylinder block. The machine 100 can operate as a motor or as a pump.

[0063] As illustrated in Figure 2, the machine 100 comprises an internal distributor 16 which is integral with the casing 2.1, 2.2, 2.3 with respect to rotation about the axis 10. In other words, the distributor 16 and the cam 4 do not rotate relative to each other. The distributor 16 is housed inside the rear part 2.3 of the casing, which is also designated here by the term "distribution cover". This part 2.3 can be in one piece having a bell shape as illustrated in Figure 2 or be closed at its axial end opposite the cylinder block by an attached plate. This end is here considered as the rear part of the machine and the flange 9 as its front part.

[0064] The distributor 16 has the function of supplying pressurized fluid to the piston housings when the machine is operating in engine mode. The pressure of the pistons on the cam causes, given its multi-lobed shape, the rotation of the shaft 5 relative to the casing and therefore the driving of the load by the flange 9. In pump mode, the rotation of the shaft causes the rollers 7 to roll on the cam 4 and the pistons to move back and forth in their housings. This causes the fluid to be forced out of these housings and the high-pressure line to be pressurized via the distributor.

[0065] The distributor 16 has a flat front external face 18 extending in a plane perpendicular to the axis 10 and into which distribution conduits 34 open. These conduits extend in particular in a direction parallel to the axis 10.

[0066] The distributor also has an external circumferential side face 19 which has four annular circular grooves 16eA, 16eB, 16eC and 16eD. The grooves follow one another in this order along the direction of the axis 10 between the cylinder block whose groove 16eA is closest and the rear end whose groove 16eD is closest (closest to the rear end).

[0067] The distribution cover 2.3 has an internal lateral face 20 which forms a cavity housing the distributor 16 so that the two faces 19 and 20 are opposite each other and in contact with each other following a male-female assembly. The face 20 of the distribution cover has annular circular main grooves 2A, 2B, 2C and 2D respectively opposite the grooves 16eA, 16eB, 16eC and 16eD of the distributor 16.

[0068] The grooves 2B and 2D communicate with main supply or exhaust pipes, respectively R and L, which are drilled in the wall of the distribution cover 2.3. The pipes R and L, and therefore the high and low pressure lines, are connected to a hydraulic circuit. In a preferred direction that is chosen arbitrarily for the description, the fluid supply in forward gear is via the pipe L and the groove 2D while the discharge takes place via the pipe R and the groove 2B. Conversely, in reverse gear, the supply is via the pipe R and the groove 2B while the discharge is via the pipe L and the groove 2D.

[0069] With reference to figures 2 to 5, the distributor 16 has a central cylindrical housing 33 with axis 10. The housing here is through and opens at both ends of the distributor. However, on the cylinder block side, there is a spring retaining plate.

[0070] In the internal face of this housing are provided annular grooves 16iB, 16iA, 16iC and 16iD following one another in this order along the axis from front to back.

[0071] These grooves are open in their zone directed towards the axis by opening into the central housing 33. They are spaced from each other along the axis so that they are not contiguous. The grooves form with the conduits 34 four respective enclosures for the fluid which we designate here by the same references 16iB, 16iA, 16iC and 16iD as the grooves.

[0072] The machine here has two active operating cylinder capacities. For this, the conduits 34 form two respective sets each comprising a first group of conduits and a second group of conduits. All these conduits 34 make it possible to supply the piston housings 12 and are arranged in the distributor.

[0073] In the first set, the first group of conduits 34 is connected to the first enclosure 16iB. These conduits 34 are here four in number and form the diagonals of a rectangle as illustrated in Figure 6. The second group of conduits is connected to a second 16iD of the enclosures. These conduits are here also four in number and form the diagonals of a rectangle identical to the previous one but angularly offset from it around the axis. These two groups form a main sub-machine.

[0074] In the second set, the first group of conduits is connected to a third of the 16iA enclosures. The conduits are here two in number and are diametrically opposed on either side of the axis 10. The second group of conduits is connected to the fourth 16iC enclosure. The conduits are also here two in number and diametrically opposed on either side of the axis 10, this diameter being angularly offset from the previous one around the axis. These two groups form a secondary sub-machine which is sometimes bypassed or put into derivation so as to operate the machine with the smallest displacement, namely only with the main sub-machine.

[0075] For example, each sub-engine or sub-machine corresponds to a distribution of a certain number of lobes or to a row of pistons of the cylinder block.

[0076] The details of the configuration of all the conduits 34 are not set out here, knowing that it is within the reach of those skilled in the art to determine this configuration according to the specificities of the machine, in particular the number of pistons.

[0077] With reference to Figure 2, the machine 100 comprises a displacement selector formed by a slide 35 and capable of being controlled to give the machine a choice of a large displacement configuration and a small displacement configuration.

[0078] In the large displacement configuration, the first enclosure 16iB and the third enclosure 16iA are connected to one of the main lines R, L, while the second and fourth enclosures 16iD and 16iC are connected to the other main line R, L. For example, in the case of the operating modes described later in forward gear, the second and fourth enclosures 16iD and 16iC are connected to each other and to the high pressure main line while the first and third enclosures 16iB and 16iA are connected to each other and to the other low pressure main line.

[0079] In the small displacement configuration:

[0080] - either the first, third and fourth enclosures 16iB, A and C are connected to one of the main lines (low pressure), while the second enclosure 16iD is connected to the other main line (high pressure). This corresponds to forward motion;

[0081] - either the second, third and fourth enclosures 16iD, A and C are connected to one of the main lines (low pressure), while the first enclosure 16iB is connected to the other main line (high pressure). This corresponds to reverse gear.

[0082] The first and second groups of distribution conduits 34 thus respectively define the first and second sub-machines. In large displacement, both sub-machines are active because their two corresponding groups of distribution conduits 34 are respectively connected to the supply and the exhaust. In small displacement, only the first sub-machine is active, the two groups of distribution conduits 34 of the second set, that is to say of the second sub-machine, being connected to the same main pipe at low pressure.

[0083] To change the engine displacement, the displacement selection slide 35 is controlled to switch the machine from one configuration to the other. For this purpose, the slide 35 is received coaxially in the central housing 33 of the distributor 16. It is slidably mounted relative to the latter in the axial direction.

[0084] Thus the slide valve 35 can be moved between a first position corresponding to the large displacement configuration in which it connects the first and third enclosures 16iB and A together, isolating them from the second and fourth enclosures 16iD and C (the latter also being connected to each other by the slide valve 35), and a second position which corresponds to the small displacement configuration in which it allows, combined with the slide valve for selecting the lowest pressure 26, to connect three enclosures together, isolating them from the last one.

[0085] With particular reference to Figure 2, the machine 100 further comprises a direction change slide 26. In this embodiment, this slide extends into the wall 2.3 of the distribution cover and outside the displacement selection slide 35. The distribution cover comprises for this purpose a cylindrical housing 39 having an axis 42 parallel to the axis 10 and distant from the latter. The housing 39 is entirely distant from the axis 10 and from the housing 33 of the displacement selection slide 35 as well as from the latter. The housing 39, in this example, opens out of the machine on the rear side. It is closed by a screwed plug 46. The direction change slide 26 is received coaxially in the housing 39 of the distribution cover.It is slidably mounted relative to the latter along the axis 42 between a first position in which the machine is configured to exert a torque in a first direction and a second position in which it is configured to exert a torque in a second direction opposite to the first. The machine is configured so that the direction change slide 26 moves under the effect of pressure coming from the high pressure line, as will be seen below.

[0086] The two drawers 35, 26 have grooves on their lateral face and the direction change drawer 26 has internal conduits illustrated in Figure 2 and arranged to allow the operation presented later. In Figure 1, the drawers are not illustrated.

[0087] We will now present the operating modes of the machine according to the cylinder capacities.

[0088] 2. In large displacement.

[0089] Figure 2 corresponds to the forward movement for the machine operating as a motor. Therefore, the conduit L corresponds to the supply and receives a high pressure communicated to the groove 2D of the distribution cover. The groove 2D being a groove of revolution (it goes all the way around the distributor 16), the high pressure is also established in a conduit 22 which extends from the groove 2D to a groove 50 of the housing 39. The pressurized fluid then passes through an internal conduit 27 of the slide 26 connecting its side wall opposite the groove 50 and its right axial end face oriented towards the rear. Therefore, whatever the initial position of this slide 26, the pressurized fluid passing through the conduit 27 exerts a thrust in a chamber 28 extending in the housing 39 between this face and the plug 46 so as to place this slide in the forward movement configuration of Figure 2, namely its most forward position, here the most to the left.

[0090] Figure 3 corresponds to reverse gear for this engine. This means that the duct R corresponds to the supply and receives a high pressure which is communicated to the groove 2B. This groove being of revolution, the high pressure is also established in a duct 24 which extends in the distribution cover, from the groove 2B to a groove 54 of the slide 26. The pressurized fluid then passes through an internal duct 29 of the slide 26 connecting its groove 54 and its left axial end face oriented towards the cylinder block 6. Therefore, whatever the initial position of the slide 26, the pressurized fluid passing through the duct 29 exerts a thrust in a chamber 31 extending in the housing 39 between this face and the bottom of the housing so as to place this slide in the reverse gear configuration of Figure 3, namely its rearmost position, in abutment against the plug 46.

[0091] As illustrated in Figure 2, it is worth noting that in distributor 16:

[0092] - the external groove 16eA is permanently in communication via a conduit 64 with the internal groove 16iA,

[0093] - the external groove 16eB is permanently in communication via a conduit 63 with the internal groove 16iB,

[0094] - the external groove 16eC is permanently in communication with the internal groove 16iC by a conduit 65, and

[0095] - the external groove 16eD is permanently in communication via a conduit 66 with the internal groove 16iD.

[0096] These internal conduits are shown in the section plane of Figure 2 but may in fact be in different planes from each other.

[0097] The displacement selection slide 35 is controlled by a hydraulic pilot conduit P opening into a chamber 21 located at the end of the housing 33. The pilot conduit P is connected to a pilot conduit where a pilot pressure will be applied or not depending on the desired displacement. By default, this slide is in the configuration of figures 2 and 3, where no pressure is exerted by the pilot conduit P in the chamber 21. A spring 30 exerting a return force on the slide, the latter is then urged in the direction of the pilot conduit. This configuration allows a connection of the groove 16iB with the groove 16iA via a first annular lateral groove 56 of the slide 35 and that of the groove 16iC with the groove 16iD by a second annular lateral groove 58 of the slide.

[0098] So, in forward or reverse gear, we have two internal grooves connected to the high pressure and two internal grooves connected to the low pressure. a) In forward gear

[0099] With reference to Figure 2, in forward motion, the high pressure arrives via the supply duct L which arrives in the groove 2D connected to the internal groove 16iD by the duct 66. Via the displacement selection slide 35, the internal groove 16iD is in fluidic relation with the internal groove 16iC. These two grooves are therefore at high pressure. They correspond to the supply of two sub-engines.

[0100] The discharge duct R is connected to the groove 2B which is connected to the groove 16iB by the duct 63. By the displacement selection slide 35, the internal groove 16iB is in fluidic relation with the internal groove 16iA. These two grooves are at low pressure and correspond to the discharge of two active sub-engines.

[0101] The engine formed by the machine therefore operates at full displacement with the two sub-engines each supplied with high pressure and discharging at low pressure. b) In reverse gear

[0102] With reference to Figure 3, in reverse gear, the high pressure arrives via the supply duct R which arrives in the groove 2B connected to the internal groove 16iB by the duct 63. Via the displacement selection slide 35, the internal groove 16iB is in fluidic relation with the internal groove 16iA: these two grooves are therefore at high pressure.

[0103] The discharge duct L is connected to the groove 2D which is connected to the groove 16iD by a duct 66. By the slide valve 35, the internal groove 16iD is in fluidic relation with the internal groove 16iC: these two grooves are at low pressure and correspond to the discharge of a sub-engine.

[0104] Here too, the engine operates at full capacity with the two sub-engines each supplied with high pressure and discharging at low pressure.

[0105] 3. In small displacement

[0106] When pressure is applied through the pilot duct P in the chamber 21, the displacement selection slide 35 is pressed to counteract the force exerted by the spring 30. It then moves into a small displacement configuration, to the left, where a sub-motor is deactivated, as illustrated in Figures 4 and 5. The position of the slide 35 therefore isolates each of the internal grooves 16iB and 16iD from the other grooves. The internal grooves 16iA and 16iC are put into communication with each other. a) In forward gear

[0107] In forward motion, with reference to Figure 4, the pressurized fluid arrives via the conduit L which corresponds to the supply. The high pressure is then established in the groove 2D and also in the internal groove 16iD by the fluid communication provided by the conduit 66. The displacement selection slide 35 is arranged in this configuration so as to isolate the internal groove 16iD from the other internal grooves. The high pressure is also established in the conduit 22 via the groove 2D and as previously described it is also established in the conduit 27, thus placing the chamber 28 under high pressure so as to place the direction change slide 26 in the configuration of Fig. 4, on the left. This slide in this configuration does not allow a fluidic relationship of the high pressure of the conduit 22 to another enclosure (in particular no fluidic relationship with the conduit 23). There is therefore only one enclosure subjected to high pressure.This corresponds to the power supply of a single sub-motor.

[0108] The discharge which is done by the conduit R is at low pressure. The groove 2B is therefore at low pressure and the internal groove 16iB also due to the existence of the conduit 63. Given the configuration of the displacement selection slide 35, the internal groove 16iB seems isolated from the other enclosures. However, by the groove 2B, the conduit 24 is also connected to the low pressure and given the position of the direction change slide 26, the conduits 24 and 25 are connected by the groove 54. The conduit 25 is connected to the conduit 64 which allows the internal groove 16iA to be put at low pressure. However, this is connected to the internal groove 16iC by the position of the displacement selection slide 35.

[0109] In summary, in the configuration of Figure 4, the enclosure connected to groove 2D is at high pressure and all the other enclosures connected to grooves 2B, 2A and 2C are at low pressure. One of the sub-engines is in bypass or by-pass: it is not pressurized. Its intake and discharge are at low pressure. b) In reverse gear

[0110] In reverse gear, with reference to Figure 5, the pressurized fluid arrives via the conduit R which corresponds to the supply. The high pressure is then established in the groove 2B. It is also established in the internal groove 16iB by the fluid communication provided by the conduit 63. The displacement selection slide 35 is arranged in this configuration so as to isolate the internal groove 16iB from the others. The high pressure is also established in the conduit 24 via the groove 2B. As described previously, this high pressure is also established in the conduit 29 of the slide 26, thus putting the left chamber 31 under high pressure so as to place this slide on the right, in the configuration of Figure 5 as close as possible to the plug 46. This slide in this configuration does not allow a fluidic relationship of the high pressure of the conduit 24 to another enclosure (in particular no relationship with the conduit 25). Again, there is only one enclosure subjected to high pressure.This corresponds to the power supply of a single sub-motor.

[0111] The discharge which is done by the conduit L is at low pressure. The groove 2D is therefore at low pressure and the internal groove 16iD also due to the existence of the conduit 66. Given the configuration of the slide valve 35, the internal groove 16iD seems isolated from the other enclosures. Nevertheless, by the groove 2D, the conduit 22 is also connected to the low pressure and given the position of the direction change slide valve 26, the conduits 22 and 23 are connected by the groove 50. The conduit 23 is connected to the conduit 65 which allows the internal groove 16iC to be put at low pressure. However, the latter is connected to the internal groove 16iA by the position of the displacement selection slide valve 35.

[0112] In summary, in the configuration of Figure 5, the enclosure connected to groove 2B is at high pressure and all the other enclosures connected to grooves 2D, 2C and 2A are at low pressure. Here too, one of the sub-motors is in bypass or bypass: it is not pressurized. Its inlet and outlet are at low pressure.

[0113] The sub-driver that is sometimes disabled corresponds to the speakers connected to grooves 2A and 2C. The sub-driver that is never disabled corresponds to the speakers connected to grooves 2B and 2D.

[0114] When an engine is bypassed, the pistons 14 associated with it continue to follow the profile of the cam 4 (except in the case where the pistons are retracted by free-wheeling springs). This continues to generate a recirculation of fluid in the bypassed sub-engine. This recirculation is done in our case by means of the displacement selection slide 35 between the enclosures of the grooves 2A and 2C.

[0115] In the machine of this embodiment, it is observed that a fluid path from an inlet of the machine to the displacement change slide 35 is shorter than a fluid path from the inlet to the direction change slide 26. In this example, this is achieved by the fact that the displacement selection slide 35 extends into the distributor while being coaxial with the axis of rotation while the direction change slide 26 is located in a wall of the distribution cover and outside the displacement selection slide 35.

[0116] But this arrangement can also be obtained, by considering that the grooves 2A, 2B, 2C and 2D of the cover and the grooves of the distributor 16eA, 16eB, 16eC and 16eD form a volume having a barycenter, by the fact that the displacement selection slide 35 is positioned so as to be closer to this barycenter than the direction change slide 26. With reference to the embodiments described in figures 1 to 5 and 11, the barycenter is coincident with the axis 10. II. Second embodiment

[0117] We will now describe a second embodiment with reference to Figures 7 to 12. Certain characteristics common to the first embodiment will not be presented again.

[0118] The main difference between this machine 200 and that of the first mode is that this time the direction change slide 26 and its housing 39 extend into a wall of the distributor 16. This appears in figures 7 and 11, the latter representing the distributor alone. However, as in the first mode, this housing and the slide 26 are entirely outside the displacement selection slide 35 and at a distance from it.

[0119] The structure of the machine is generally the same, as is its operation, the configuration of certain conduits being modified to take into account the position of the drawer 26 in the distributor 16.

[0120] This embodiment allows in particular a saving of space in the cover.

[0121] Figure 7 corresponds to the forward movement for this engine. This means that the conduit L corresponds to the supply and receives a high pressure, which is communicated to the groove 2D. The groove 2D being of revolution, the high pressure is also established in the conduit 222 which communicates with it. Whatever the initial position of the direction change slide 26, the pressurized fluid arrives in the chamber 28 thanks to the end section of the slide 26 which has opposite this conduit 222 a reduced diameter compared to the adjacent section. The fluid exerts an axial thrust on this section and places this slide in the configuration of figure 7, on the left, as close as possible to the cylinder block, which is also the position that the slide takes in the forward movement configuration of figure 9.

[0122] Figure 8 corresponds to reverse gear for this engine. This means that duct R corresponds to the supply and receives a high pressure communicated to groove 2B. This being of revolution, the high pressure is also established in duct 224 which communicates with groove 2B. Here again, whatever the initial position of the direction change slide 26, the pressurized fluid arrives in chamber 37 via duct 225 opposite the left axial end section of slide 26 which has a reduced diameter compared to the adjacent section. The fluid exerts an axial thrust on this section and places this slide in the configuration of figure 8, which is also the configuration of figure 10, therefore on the right.

[0123] With reference to Figure 7, it is worth noting that:

[0124] - groove 2A is permanently in communication (via conduit 64) with the inner groove 16iA,

[0125] - groove 2B is permanently in communication (via conduit 63) with groove 16iB,

[0126] - throat 2C is permanently in communication with throat 16iC (via conduit 65) and

[0127] - the 2D groove is permanently in communication (via conduit 66) with the 16iD groove.

[0128] These internal ducts are shown in the section plane but may be in different respective planes.

[0129] The displacement selection slide 35 is controlled by the hydraulic pilot conduit P. By default, this slide is in the configuration of figures 7 and 8 where no pressure is exerted by the pilot conduit P in the chamber 21. The spring 30 exerting a return force on the slide 35, the latter is then pressed in the direction of the pilot conduit. This configuration allows the connection of the groove 16iB with the groove 16iA and also the connection of the groove 16iC with the groove 16iD. We therefore have in forward or reverse gear two internal grooves connected to the high pressure and two internal grooves connected to the low pressure.

[0130] 4. In large displacement a) In forward gear

[0131] With reference to Figure 7, in forward motion, the high pressure arrives via the supply duct L in the groove 2D connected to the internal groove 16iD by the duct 66. Via the groove 58 of the slide valve 35, the internal groove 16iD is in fluidic relation with the internal groove 16iC. They are therefore at high pressure and correspond to the supply of the two sub-engines. The discharge duct R is connected to the groove 2B which is connected to the groove 16iB by the duct 63. Via the groove 56 of the displacement selection slide valve, the internal groove 16iB is in fluidic relation with the internal groove 16iA: these two grooves are at low pressure and correspond to the discharge of the two sub-engines.

[0132] The engine therefore operates at full displacement with the two sub-engines each supplied with high pressure and discharging at low pressure. b) In reverse

[0133] With reference to Figure 8, in reverse gear, the high pressure arrives via the supply duct R in the groove 2B connected to the internal groove 16iB by the duct 63. Via the groove 56, the internal groove 16iB is in fluidic relation with the internal groove 16iA: these two grooves are therefore at high pressure.

[0134] The discharge duct L is connected to the groove 2D which is connected to the groove 16iD by the duct 66. By the groove 58, the internal groove 16iD is in fluidic relation with the internal groove 16iC: these two grooves are at low pressure and correspond to the discharge of the two sub-motors.

[0135] Here too, the engine operates at full capacity with the two sub-engines each supplied with high pressure and discharging at low pressure.

[0136] 5. In small displacement

[0137] In small displacement, when pressure is applied by the pilot duct P in the chamber 21, the displacement selection slide 35 is biased against the force exerted by the spring 30. It then comes to be placed on the left in a small displacement configuration where a sub-engine is deactivated, as in figures 9 and 10. It is moved towards the cylinder block and compresses the spring. The position of this slide 35 therefore isolates the internal groove 16iB from the other grooves and also isolates the internal groove 16iD from the other grooves while the internal grooves 16iA and 16iC are put in communication with each other. a) In forward gear

[0138] Figure 9 corresponds to the forward movement. This means that the conduit L corresponds to the supply and receives a high pressure which is communicated to the groove 2D. The high pressure is also established in the conduits 222 and 223 which communicate with the groove 2D. And whatever the initial position of the direction change slide 26, the pressurized fluid arrives in the right chamber 28 via the conduit 222 of reduced diameter thanks to the end section 31 of reduced diameter of the slide. The fluid exerts an axial thrust on this section 31 and places the slide 26 in the configuration of figure 9, on the left. This slide then does not allow a fluidic relationship of the high pressure of the conduit 222 (or 223) to another enclosure.

[0139] The high pressure in the 2D groove is also established in the internal groove 16iD by the fluid communication provided by the conduit 66. The displacement selection slide 35 is arranged in this configuration so as to isolate the internal groove 16iD from the other internal grooves. Only one enclosure associated with the grooves, namely the enclosure of the 2D groove, is therefore subjected to high pressure. This corresponds to the supply of a single sub-engine.

[0140] The discharge through the conduit R is at low pressure. The groove 2B is therefore at low pressure and the internal groove 16iB also due to the existence of the conduit 63 (see figure 7). Given the configuration of the displacement selection slide 35, the internal groove 16iB seems isolated from the other enclosures. However, through the groove 2B, the conduit 224 is at low pressure. Given the position of the direction change slide 26 and its groove 54, the conduits 224 and 27 are connected. As the conduit 27 is connected to the internal groove 16iA, the latter is also put at low pressure. However, the internal groove 16iA is connected to the internal groove 16iC by the position of the displacement selection slide 35.

[0141] In summary, in the configuration of Figure 9, the enclosure connected to throat D is at high pressure and all the other enclosures B, A and C are at low pressure. A sub-engine is bypassed and is not pressurized: its intake and discharge are at low pressure. b) In reverse gear

[0142] Figure 10 corresponds to the reverse gear for the small displacement. This means that the conduit R corresponds to the supply and receives a high pressure communicated to the groove 2B. The high pressure is also established in the conduit 225 which communicates with the groove B. Here again, whatever the initial position of the slide 26, the pressurized fluid arrives in the left chamber 37 thanks to the end section 32 of reduced diameter of the slide, by the conduit 224 of reduced diameter. The fluid exerts an axial thrust on this section and places this slide 26 in the configuration of figure 10, at the end stop in the rearward direction, to the right.

[0143] The high pressure in the groove 2B is also established in the internal groove 16iB by the fluid communication provided by the conduit 63. The displacement selection slide 35 is arranged in this configuration so as to isolate the internal groove 16iB from the other internal grooves. The high pressure is also established in the conduit 224 by the groove B and, as previously described, this high pressure is also established via the diameter reduction 32 in the chamber 37 so as to place the direction change slide 26 in the configuration of FIG. 10. This slide in this configuration does not allow a fluid connection of the high pressure from the conduit 224 or 225 to another.

[0144] A single enclosure is therefore subjected to high pressure. This corresponds to the supply of a single sub-engine.

[0145] The discharge which is done by the conduit L is at low pressure. The groove 2D is therefore at low pressure and the internal groove 16iD also due to the existence of the conduit 66 (see figure 7). Given the configuration of the displacement selection slide 35, the internal groove 16iD seems isolated from the other enclosures. However, by the groove 2D, the conduit 222 is also connected to the low pressure. Given the position of the direction change slide 26, the conduits 223 and 36 are in connection by the reduced diameter section 55 of the slide 26. The conduit 36 ​​makes it possible to put the internal groove 16iC at low pressure. However, this is connected to the internal groove 16iA by the position of the displacement selection slide 35.

[0146] In summary, in the configuration of Figure 10, the enclosure connected to groove 2B is at high pressure and all the other enclosures associated respectively with grooves 2D, 2C and 2A are at low pressure. Here too, a sub-motor is bypassed: its inlet and outlet are at low pressure. In this embodiment, we therefore identify a sub-assembly for a hydraulic machine which comprises the distributor 16, the displacement selection slide 35 and the direction change slide 26.

[0147] The reduced diameter of the conduits 222, 225 serves to dampen the movement of the direction change slide 26 or shuttle valve. In fact, they form nozzles, or restrictions, which have the effect of limiting the flow rate and prevent the slide from tilting too quickly from one position to another. In the figures, it can be seen that the nozzles are produced by reducing the diameter of the bore 222, 224. Alternatively, it could be imagined that this is achieved, for example, by a pierced plug which would be forced into the constant-section conduit.

[0148] Many modifications can be made to the invention without departing from its scope.

[0149] In the second embodiment, the reduced diameter sections of the direction change drawer 26 are produced by annular grooves. In the variant of Figure 13, it is possible to provide for the same function with a groove 60. In the variant of Figure 14, this function is provided by a flat 62. In the first embodiment, this function is performed by conduits internal to the direction change drawer 26.

[0150] As shown in Figure 12, the direction change slide is symmetrical. This facilitates industrialization and avoids problems when mounting (assembling) the hydraulic machine.

Claims

DEMANDS 1. Hydraulic machine (100; 200) comprising: - a dispensing cover (2.3), - a distributor (16), - a displacement selection drawer (35) mounted to slide between a first position in which the machine is configured to run with a first displacement and a second position in which the machine is configured to run with a second displacement different from the first displacement; and - a direction change slider (26) mounted to slide between a first position in which the machine is configured to exert a torque in a first direction about an axis of rotation (10) and a second position in which the machine is configured to exert a torque in a second direction, the direction change slider (26) being mounted to slide along an axis (42) distant from the axis of rotation (10), the direction change slider extending: - in a wall of the dispenser (16) or - in a wall of the distribution cover and outside the displacement selection drawer (35).

2. Machine (100; 200) according to the preceding claim in which the displacement selection spool (35) extends into the distributor (16).

3. Machine (100; 200) according to any one of the preceding claims wherein the displacement selection drawer (35) is coaxial with the axis of rotation (10).

4. Machine (100; 200) according to any one of the preceding claims wherein the direction change slide (26) extends out of the displacement selection slide (35).

5. Machine (100; 200) according to any one of the preceding claims in which the direction change slider (26) is mounted to slide in a direction parallel to the axis of rotation (10).

6. Machine according to any one of claims 1 to 4 in which the direction change slider (26) is mounted to slide in a direction not parallel to the axis of rotation (10).

7. Machine (100; 200) according to any one of the preceding claims which includes a high-pressure line and a low-pressure line and is configured so that the direction-change spool (26) moves under the effect of pressure from the high-pressure line.

8. Machine (100; 200) according to any one of the preceding claims in which, the second displacement being less than the first displacement, the second displacement is implemented by a group of pistons (14) or lobes of a cam (4), the group forming a regular polygon centered on the axis of rotation (10).

9. Machine according to any one of the preceding claims wherein a fluid path from a machine inlet to the displacement change spool (35) is shorter than a fluid path from the inlet to the direction change spool (26).

10. Machine (100; 200) according to any one of the preceding claims in which, the cover forming annular grooves (2A, 2B, 2C and 2D), the distributor forming grooves (16eA, 16eB, 16eC and 16eD), the grooves of the cover and the grooves of the distributor forming a volume having a centroid, the displacement selection spool (35) is positioned so as to be closer to the centroid than the direction change spool (26).

11. Device comprising at least one machine (100; 200) according to any one of the preceding claims.

12. Subassembly for hydraulic machine, the subassembly comprising: - a distributor (16), - a displacement selection drawer (35) mounted to slide within the distributor between a first position in which the machine is configured to run with a first displacement and a second position in which the machine is configured to run with a second displacement different from the first displacement; and - a direction change spool (26) mounted to slide in the distributor between a first position in which the machine is configured to exert a torque in a first direction around an axis of rotation (10) and a second position in which the machine is configured to exert a torque in a second direction, the direction change spool (26) being mounted to slide along an axis distant from the axis of rotation.

13. Method for controlling a hydraulic machine (100; 200), wherein: - a displacement selector drawer (35) slides between a first position in which the machine is configured to operate with a first displacement and a second position in which the machine is configured to operate with a second displacement different from the first displacement; and - a direction change slider (26) slides between a first position in which the machine is configured to exert a torque in a first direction around an axis of rotation and a second position in which the machine is configured to exert a torque in a second direction around the axis, the direction change slider (26) sliding along an axis distant from the axis of rotation, the direction change slider (26) extending: - in a wall of a dispenser (16), or - in a wall of a distribution cover and outside the displacement selection drawer.

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