Hydraulic machine with an improved control device

Abstract

Assembly comprising a hydraulic machine and a control device (30, 40) suitable for, in a first configuration, supplying all of the chambers of the cylinder block (230), during the relative rotation of the first assembly and the second assembly, and, in a second configuration, for a set of angular sectors of the cam (220), preventing the intake of fluid into at least one first chamber (260) of the cylinder block (230), the hydraulic machine comprising means suitable for maintaining the pistons (250) in contact with the cam (220).

Description

HYDRAULIC MACHINE WITH IMPROVED PILOTING DEVICE Description Technical Field

[0001] The present invention relates to the field of hydraulic machines with radial pistons and multi-lobe cams equipped with a control device. Prior art

[0002] Hydraulic machines such as radial piston hydraulic motors and pumps with multi-lobe cams can commonly have several displacement configurations. For example, a hydraulic machine can be put into a freewheel configuration in which it has a zero displacement. Some hydraulic machines can also have different displacement configurations, in which some of the lobes can be disengaged in order to modulate the displacement. We then say that some of the lobes are in "bypass" or "bypassed", according to a common terminology borrowed from the English language.

[0003] Conventional solutions achieve this disengagement of all or part of the cam lobes by connecting the chamber to the low pressure line for the relevant angular sectors. However, this solution generates fluid circulation in the conduits, and therefore causes pressure losses which harm the efficiency of the hydraulic machine.

[0004] Figures 1 and 2 schematically represent such a conventional solution.

[0005] These figures show a double-cylinder hydraulic machine 120. For illustration purposes, it is subdivided into two hydraulic sub-machines 120A and 120B, each having a fluid inlet and outlet, 122A, 122B, 124A and 124B respectively. In the example illustrated, the hydraulic machine 120 is a hydraulic motor. generally, and by convention, in all the figures, the sub-machines 120A and 120B are linked together in rotation on the same shaft (for example are produced by the same cylinder block).

[0006] Conventionally, one can choose to supply both hydraulic sub-machines for operation at full displacement, or only one of them to operate with reduced displacement.

[0007] The hydraulic machine 120 is connected to a pressure source, here a hydraulic pump 110. The circuit illustrated is a closed circuit. A pilot valve 130 connects the hydraulic pump 110 to the hydraulic machine 120. This pilot valve 130 defines two configurations presented respectively in Figures 1 and 2.

[0008] In a first configuration shown schematically in Figure 1, the pilot valve 130 connects the inlet ports 122A and 122B of the two hydraulic sub-machines 120A and 120B to the discharge (i.e., to the high pressure port) of the hydraulic pump 110, and the discharge ports 124A and 124B of the two hydraulic sub-machines 120A and 120B to the inlet (i.e., to the low pressure port) of the hydraulic pump 110. In this configuration, the two hydraulic sub-machines 120A and 120B are thus supplied and in operation; the hydraulic machine 120 therefore operates at its full displacement.

[0009] In a second configuration shown schematically in Figure 2, the pilot valve 130 connects the inlet port 122A of one of the hydraulic sub-machines 120A to the discharge (i.e., the high pressure port) of the hydraulic pump 110. The inlet port 122B of the other hydraulic sub-machine 120B as well as the discharge ports 124A and 124B of the two hydraulic sub-machines are connected to the inlet (i.e., the low pressure port) of the hydraulic pump 110. In this configuration, the hydraulic sub-machine 120B is then disengaged since its inlet and its discharge are at the same pressure. The hydraulic machine 120B, however, rotates, but does not produce any engine torque. hydraulic machine 120 therefore operates with a reduced cylinder capacity, equal to the cylinder capacity of the hydraulic sub-machine 120A.

[0010] However, as indicated, in this second configuration, we still observe a circulation of the fluid due to the pistons being kept in contact with the cam, which therefore generates a back and forth movement during rotation. Coming to detach the pistons from the cam causes other problems linked to the re-contact, in particular in terms of noise and wear. The work of transferring the oil generates mechanical losses, and heating of the hydraulic fluid. These losses are reported in the form of a drag torque in rotation of the hydraulic machine under hydraulic machine 120B. This drag torque reduces the efficiency of the complete hydraulic machine.

[0011] The present invention thus aims to respond at least partially to these problems. Statement of the invention

[0012] The present invention thus relates to an assembly comprising a machine and a control device, the hydraulic machine comprising: a first assembly and a second assembly, movable in rotation relative to each other along a main axis, the first assembly comprising a casing and a cam comprising at least one lobe, the second assembly comprising a cylinder block having a plurality of housings in which pistons slide, each assembly formed by a piston and a housing defining at least one first chamber defining a set of first chambers, a distributor adapted to supply and discharge fluid into said chambers, the distributor having a supply duct and a discharge duct in which the hydraulic machine includes means adapted to keep the pistons in contact with the cam the control device is adapted for, - in a first configuration, supplying all of the first chambers of the cylinder block (i.e. carrying out an admission and a discharge of fluid into said chambers), during the relative rotation between the first assembly and the second assembly, - in a second configuration, for a set of angular sectors of the cam or for a set of pistons, preventing the admission of fluid into said at least one first chamber of the cylinder block during relative rotation between the first set and the second set.

[0013] The first configuration typically corresponds to operation at a first displacement value, and the second configuration typically corresponds to operation at a second displacement value, strictly lower than the first displacement value.

[0014] The angular sectors of the cam for the second configuration comprise at least portions causing a movement of the piston in its housing. In other words, the closure of the fluid intake into the chambers in the second configuration is carried out for angular sectors of the cam comprising at least angular sectors of non-constant radius.

[0015] According to one example, the control device is configured to, in the second configuration, close the fluid intake into all of the first chambers, and connect the fluid discharge from all of the first chambers to a discharge volume via a calibrated valve.

[0016] According to one example, said means adapted to keep the pistons in contact with the cam comprise elastic return means positioned in said housings of the cylinder block, and tending to move the pistons radially outwards relative to the main axis.

[0017] In one example, the means suitable for holding the pistons in contact with the cam is an assembly of springs external to the cylinders attached to the cylinder block.

[0018] According to one example, each pair formed by a piston and a housing defines between the piston and the housing said first chamber and a second chamber which are distinct and superimposed according to a sliding direction of the piston in the housing, and in which in the second configuration, the control device is adapted to prevent the admission of fluid into the first chambers and / or into the second chambers of the cylinder block.

[0019] According to one example, the control device is adapted to, in the second configuration, for each pair formed by a piston and a housing, prevent the admission of fluid into one of the first chamber and the second chamber, and supply the other of the first chamber and the second chamber, so as to keep the pistons in contact with the cam.

[0020] According to one example, each housing has a first portion having a first section SI, and a second portion having a second section S2, the first section SI being strictly greater than the second section S2, the first portion emerging from an external surface of the cylinder block opposite the cam, and the second portion extending from the first portion.

[0021] According to one example, the control device comprises shut-off valves, positioned at the inlet and outlet of the first chambers, each shut-off valve being configured to be open when the pressure at its terminals exceeds a threshold value.

[0022] According to one example, the pilot device comprises a pilot valve, adapted to, in a first configuration, connect an inlet and a discharge of the first chambers to a pressure source, and in a second configuration, isolate the inlet and the discharge of the first chambers from the pressure source.

[0023] According to one example, the control device comprises a control valve, adapted to, in a first configuration, connect an inlet and a discharge of the first chambers to a pressure source, and in a second configuration, isolate the inlet and the discharge of the first chambers from the pressure source. Alternatively, the control device also comprises shut-off valves, positioned at the inlet and the discharge of the first chambers, between the first chambers and the control valve, each shut-off valve being configured to be open when the pressure at its terminals exceeds a threshold value.

[0024] According to one example, the pilot valve is adapted to, in its second configuration, connect the first chambers to a reservoir via the shut-off valves.

[0025] According to one example, the shut-off valves are rotationally fixed to the cylinder block.

[0026] According to one example, the shut-off valves are integral in rotation with the distributor.

[0027] According to one example, the hydraulic machine according to the invention is symmetrical. For a hydraulic machine, the term symmetrical means that it can operate in either direction without structural change. For example, a symmetrical hydraulic motor will exert torque in a different direction but will have similar behavior if the high and low pressures at its terminals are reversed. Similarly, a symmetrical pump is a pump that will have similar behavior if the direction of rotation of the input shaft is changed; only the high and low pressures will be reversed at its terminals.

[0028] According to one example, said hydraulic machine has a first operation at a first displacement value, and a second operation at a second displacement value strictly lower than the first displacement value, and in which the control device is adapted to be in the second configuration when the hydraulic machine has its second operating mode.

[0029] In one example, the second displacement value is zero displacement.

[0030] According to one example, in the second configuration, the displacement of the pistons radially outwardly relative to the main axis causes an increase in the volume of the first chambers while preventing the admission of fluid into said first chambers, so as to cause a depression or (pressure drop) in said first chambers. Brief description of the drawings

[0031] The invention and its advantages will be better understood upon reading the detailed description given below of different embodiments of the invention given as non-limiting examples.

[0032] [Fig. 1] Figure 1 shows an example of a circuit according to the prior art according to a first configuration.

[0033] [Fig. 2] Figure 2 shows an example of a circuit according to the prior art in a second configuration.

[0034] [Fig. 3] Figure 3 shows an example of an assembly according to one aspect of the invention in a first configuration.

[0035] [Fig. 4] Figure 4 shows an example of an assembly according to one aspect of the invention in a second configuration.

[0036] [Fig. 5] Figure 5 shows an example of an assembly according to an embodiment of the invention.

[0037] [Fig. 6] Figure 6 shows another example of an assembly according to one aspect of the invention in a first configuration.

[0038] [Fig. 7] Figure 7 shows another example of an assembly according to an embodiment of the invention.

[0039] [Fig. 8] Figure 8 shows another example of an assembly according to an embodiment of the invention.

[0040] [Fig. 9] Figure 9 shows another example of an assembly according to an embodiment of the invention.

[0041] Throughout the figures, common elements are identified by identical numerical references. Description of the embodiments

[0042] Figures 3 and 4 show an example of a system or assembly according to one aspect of the invention in two configurations.

[0043] These figures show a double-cylinder hydraulic machine 20. For illustration purposes, it is subdivided into two hydraulic sub-machines 20A and 20B, each having a fluid inlet and outlet port, 22A, 22B, 24A and 24B respectively. In the example illustrated, the hydraulic machine 20 is a hydraulic motor.

[0044] The hydraulic machine 20 is typically a radial piston, multi-lobe cam hydraulic machine.

[0045] The hydraulic machine 20 thus comprises a first assembly and a second assembly, movable in rotation relative to each other along a main axis, the first assembly comprising a casing and a cam comprising at least one lobe, the second assembly comprising a cylinder block having a plurality of housings in which pistons slide, each assembly formed by a piston and a housing defining at least one chamber, comprising a first chamber.

[0046] Figure 5 schematically represents such a hydraulic machine structure.

[0047] The hydraulic machine 20 comprises a first assembly and a second assembly, movable in rotation relative to each other along a main axis Z-Z.

[0048] The first set includes a 220 cam and a 210 housing.

[0049] The second assembly comprising a cylinder block 230 having a plurality of housings 240 in which pistons 250 slide, each piston 250 being positioned in a housing 240. Each pair formed by a piston 250 and a housing 240 defines a chamber 260.

[0050] The cam is positioned so as to surround the cylinder block 230 relative to the main axis ZZ. The casing 210 and the cam 220 define an internal volume in which the cylinder block 230 is housed, which is mounted to be able to rotate relative to the assembly formed by the cam 220 and the casing 210 typically by means of an axis defining the main axis ZZ. The hydraulic machine 220 is typically configured so that in operation, the pistons 250 follow the cam 220. Thus, the pistons 250 perform back and forth movements in their respective housings 240 depending on the geometry of the cam 220, while remaining in contact with the cam 220. In the example illustrated in FIG. 5, a spring 290 is positioned in the chambers 260, this spring tending to push the associated piston 250 towards the cam 220, and therefore ensuring that the piston 250 is kept in contact with the cam 220 even in the absence of an application of pressure in the chamber 260.This embodiment is not limiting, the return means can be any suitable means tending to apply the piston 250 towards the cam 220. In particular, in another embodiment not illustrated, the return means which makes it possible to keep the pistons in contact with the cam is an assembly of springs external to the cylinders attached to the cylinder block.

[0051] A distributor 280 ensures the supply and discharge of fluid to the chambers 260.

[0052] The subdivision of the hydraulic machine 20 into two hydraulic sub-machines may for example designate groups or rows of distinct pistons in the cylinder block 230, sub-assemblies corresponding to angular sectors of the cam 210 or lobes, portions of distinct lobes or half-lobes of the cam 210, or for example to distinct chambers.

[0053] In a known manner, the cam 210 may comprise portions of constant radius, defining sectors of the flat cam type. Such sectors angular sectors of constant radius do not cause displacement of the pistons in their housings. Such angular sectors can for example be interposed between different lobes, half-lobes or portions of lobes depending on the desired application. In the present disclosure, the lobes, portions of lobes or half-lobes are considered as having a non-constant radius, and therefore causing displacement of the pistons in contact with them during the relative rotation of the assemblies of the hydraulic machine. It is understood, however, that the invention also applies to a cam comprising such portions forming cam flats.

[0054] Conventionally, one can choose to supply both hydraulic sub-machines 20A and 20B for operation at full displacement, or only one of them to operate with reduced displacement.

[0055] The hydraulic machine 20 is connected to a pressure source 10, for example a hydraulic pump, an accumulator or any other means suitable for delivering hydraulic pressure. The hydraulic pump is typically set in motion by a drive motor or prime mover, for example a thermal or electric motor. The circuit illustrated is a closed circuit; it is understood, however, that the pressure source 10 can define an open circuit by drawing hydraulic fluid from a reservoir. In the example which follows, it is considered that the pressure source 10 delivers through its orifice 12, which is therefore at a pressure qualified as high pressure, and sucks or receives the fluid through its orifice 14 which is therefore at a pressure qualified as low pressure. The hydraulic machine is connected to the pressure source by hydraulic lines, which defines a high pressure line, and a low pressure line.

[0056] A pilot valve 30 connects the pressure source 10 to the hydraulic machine 20. This pilot valve 30 defines two configurations presented respectively in figures 3 and 4.

[0057] The pilot valve 30 as shown is a 7 / 2 type valve, therefore having 7 ports and two configurations.

[0058] It presents as follows: - a first orifice 33 connected to the orifice 12 of the pressure source 10, - a second orifice 34 connected to the orifice 14 of the pressure source 10, - a third port 35 connected to port 22A of the hydraulic sub-machine 20A, - a fourth port 36 connected to port 24A of the hydraulic sub-machine 20A, - a fifth orifice 37, - a sixth orifice 38, and - a seventh orifice 39.

[0059] The pilot valve 30 has: - a first configuration in which the first orifice 33 is connected to the third orifice 35, and to the seventh orifice 39, the second orifice 34 is connected to the fourth orifice 36 and to the fifth orifice 37, and in which the sixth orifice 38 is closed; - a second configuration in which the first orifice 33 is connected to the third orifice 35, the second orifice 34 is connected to the fourth orifice 36, and in which the fifth orifice 37 is connected to the sixth orifice 38 and to the seventh orifice 39.

[0060] In the illustrated example, the pilot valve 30 is controlled by means of a control 31 opposing a return means 32 such as a spring. It is understood, however, that this embodiment is only illustrative, and that any suitable control means can be used to control the passage of the pilot valve 30 from one configuration to the other.

[0061] The system as presented also includes shut-off valves 40A and 40B, which may be commonly designated by the reference 40, where appropriate accompanied by the letter A or B.

[0062] The first shut-off valve 40A has a through configuration and a non-through configuration. It has a first port 43A connected to the seventh port 39 of the pilot valve 30, and a second port 42A connected to the port 22B of the hydraulic sub-machine 20B.

[0063] It is controlled on the one hand by the pressure at the first orifice 43A and at the second orifice 42A, and on the other hand by an elastic return means 45A coupled to a control line 50.

[0064] Similarly, the second shut-off valve 40B has a through configuration and a non-through configuration. It has a first port 43B connected to the fifth port 37 of the pilot valve 30, and a second port 42B connected to the port 24B of the hydraulic sub-machine 20B.

[0065] It is controlled on the one hand by the pressure at the first orifice 43B and at the second orifice 42B, and on the other hand by an elastic return means 45B coupled to a control line 50.

[0066] The pilot line 50 is connected to the sixth port 38 of the pilot valve 30, to a reservoir R, or to any other pressure relief volume, for example an internal casing volume or a hydraulic line at ambient or zero pressure, as well as to two hydraulic controls of the shut-off valves 40A and 40B.

[0067] The pilot valve 30 and / or the shut-off valves 40 may be internal to the hydraulic machine, or external. In other words, the pilot valve 30 and / or the shut-off valves 40 may be integrated into the structure of the hydraulic machine, for example in the internal volume of the casing 210, or be elements added to the exterior of the hydraulic machine. The shut-off valves 40 may for example be integrated into the structure of the hydraulic machine, while the pilot valve 30 may be an external element, typically associated with the hydraulic machine at the level of its fluid supply and discharge conduits.

[0068] We now describe the operation when the pilot valve 30 is in its first configuration as shown in Figure 3. The pilot line 50 is at ambient pressure, or at the pressure of the reservoir R. As indicated, in the example which follows, it is considered that the pressure source 10 discharges through its orifice 12, which is therefore at a pressure qualified as high pressure, and sucks through its orifice 14 which is therefore at a pressure described as low pressure.

[0069] The high pressure line supplied by the pressure source 10 via its orifice 12 is connected to the first hydraulic sub-machine 20A via its orifice 22A, and to the orifice 43A of the first shut-off valve 40A. This causes the first shut-off valve 40A to be placed in the pass-through configuration, and therefore the supply of the second hydraulic sub-machine 20B. The second hydraulic sub-machine 20B discharges through its orifice 24B. The shut-off valve 40B is in the pass-through configuration because its orifice 43B is connected to the low pressure line 14 of the pressure source 10, and the low pressure line is at a pressure sufficient to counter the force of the spring 45B and therefore to place the valve 40B in its pass-through configuration.

[0070] The discharge pipes of the two hydraulic sub-machines 20A and 20B are therefore connected to the low pressure line connected to the orifice 14 of the pressure source 10.

[0071] Thus, in this configuration, the two hydraulic sub-machines 20A and 20B are powered; the hydraulic machine 20 operates at its full displacement.

[0072] The operation will now be described when the pilot valve 30 is in its second configuration as shown in FIG. 4.

[0073] The operation of the first hydraulic sub-machine 20A is unchanged; its inlet and outlet are connected to the pressure source 10 via the pilot valve 30.

[0074] The two shut-off valves 40A and 40B are connected to the pilot line 50 and therefore to the reservoir R via the pilot valve 30; the second hydraulic sub-machine 20B is therefore no longer supplied with pressure, and has zero displacement; the hydraulic machine 20 therefore has a reduced displacement. Due to the action of the return means 45A and 45B, the shut-off valves 40A and 40B switch to their non-passing configuration, which thus isolates the second hydraulic sub-machine 20B from the hydraulic circuit. Such a configuration thus makes it possible to avoid recirculation of the fluid associated with the second under hydraulic machine 20B when it is disengaged. In this way, the hydraulic machine can be used at reduced displacement for a long time without deteriorating the efficiency of the hydraulic machine. For example, for a vehicle or machine with a large working displacement at low speed, and a small displacement for traveling on the road at high speed, the efficiency of the transmission during travel is increased. For vehicles or machines that regulate their traction torque by permanent displacement changes, the efficiency of the transmission during work is also improved. The consumption of the vehicle or machine decreases, and there is a greater tendency to use the possibilities of changing the displacement over a long period. There is also less heating of the hydraulic fluid.

[0075] The hydraulic machine 20 typically comprises means adapted to ensure that the pistons are kept in contact with the cam during rotation, even when the pistons are not powered.

[0076] Such means may for example comprise springs or elastic means providing a force tending to push the pistons into contact with the cam.

[0077] In the presence of such means, it is understood that the rotation of the second hydraulic submachine 20B, even when not powered, causes a displacement of fluid due to the back and forth movements of the pistons in contact with the cam. As indicated previously, the cam may also have portions of constant radius not causing displacement of the pistons. The addition of such portions or angular sectors of constant radius does not impact the description of the invention for which the angular sectors considered comprise at least one portion of non-constant radius.

[0078] More precisely, the relative movement of the pistons of the second hydraulic submachine 20B will cause a suction effect when the pistons move in the direction of exit from their housings, and a discharge effect when the pistons move in the direction of withdrawal into their housings.

[0079] The suction effect occurs at the orifice 22B of the second hydraulic sub-machine 20B. However, this orifice is connected to the first shut-off valve 40A, which is in the non-passing configuration. This shut-off valve 40A remains in the non-passing state because the pressure at its terminals is low, and will not promote the movement of the shut-off valve 40A towards its passing state.

[0080] Furthermore, due to the rotation, the pistons of the second hydraulic submachine 20B continue to follow the cam while the chamber 260 is closed and no fluid can enter this chamber 260, a depression occurs. This depression, or drop in pressure, will generate a change in state of the air dissolved in the oil which will generate gaseous air bubbles in the oil. This phenomenon of air bubble generation which occurs in the face of this depression makes it possible to avoid a more damaging phenomenon for the hydraulic machine which is the change of state of the oil from liquid to gas (the subsequent implosion of the bubbles when the fluid returns to a liquid state during the pressure increase releases a high energy which can damage the metal).

[0081] When the pressure returns to normal in the chamber, for example when the volume is reduced by the movement of the piston to the next half-lobe causing the piston to withdraw into its housing, the air in gaseous form dissolves again in the oil.

[0082] The discharge effect occurs at the orifice 24B, the withdrawal of the pistons into their housings tending to expel the fluid present. This discharge causes a rise in pressure at the orifice 42B of the second shut-off valve 40B. When the pressure at this orifice exceeds a threshold value depending in particular on the calibration of the elastic return means 45B, the second shut-off valve 40B switches to its open configuration to evacuate the excess fluid to the reservoir R via the pilot valve 30 and the control line 50, then the second shut-off valve 40B switches back to its closed configuration. The shut-off valve 40B therefore has here a similar operation to a reversible calibrated valve.

[0083] In other words, it is understood that in this second configuration, the fluid intake for the second hydraulic sub-machine 20B is closed, but a discharge of the excess pressure is possible when the discharge pressure of the second hydraulic sub-machine 20B exceeds a pressure threshold value. In addition, it is seen that the second hydraulic sub-machine 20B is here isolated from the hydraulic circuit supplying the first hydraulic sub-machine 20A. More precisely, the intake and discharge of the second hydraulic sub-machine 20B are isolated from the intake and discharge of the first hydraulic sub-machine 20A and from the intake and discharge of the pressure source 10, which therefore avoids generating pressure losses in the hydraulic circuit.

[0084] The proposed system therefore creates a depression or partial vacuum at the level of the chambers of the disengaged pistons.

[0085] The system as proposed is also reversible, and can operate by reversing the direction of circulation of the fluid. The operation is then similar, the different components being symmetrical.

[0086] It is noted that the proposed system allows the displacement to be changed with high efficiency without the pistons leaving contact with the cam. The displacement changes are therefore silent, without generating shocks between the pistons and the cam, and there is an incentive to use the displacement change without restriction.

[0087] It is also noted that thanks to the shut-off valves 40A and 40B, the change in displacement can be made regardless of the angular position of the hydraulic machine, whatever the position of the pistons in relation to the cam.

[0088] The invention as proposed can also be used for freewheeling single-cylinder hydraulic machines with the pistons remaining permanently in contact with the cam.

[0089] Figure 6 schematically illustrates such an example application.

[0090] The diagram is similar to that already described with reference to Figures 3 and 4, except that the first hydraulic sub-machine 20A has been deleted, and the third and fourth ports 35 and 36 of the pilot valve 30 have therefore been deleted. The hydraulic machine 20 is therefore represented as a single hydraulic motor.

[0091] In the illustrated embodiment, the hydraulic machine 20 can be isolated from the pressure source 10 in the same manner as the second hydraulic sub-machine 20B described previously.

[0092] Such an embodiment makes it possible in particular to switch a hydraulic machine into a freewheel configuration by eliminating the pressure losses generated by a circulation of the fluid in the disengaged or “bypassed” hydraulic machine. As previously, it is understood that such a system is reversible, and can operate regardless of the direction of rotation of the hydraulic machine 20, as well as in a holding or braking operation.

[0093] This embodiment is particularly advantageous for temporary transmissions of towed axles or machines, for example non-motorized axles of vehicles or machines, or towed trailers, whose wheels are to be motorized temporarily by means of hydraulic machines such as proposed, for example to travel on difficult and slippery terrain. In these uses, it is often necessary to place the axle or wheels driven by the hydraulic machine in a freewheeling situation. This embodiment makes it possible to do this while minimizing losses, and the drag torque of the unpowered hydraulic machine, which improves the efficiency of the transmission and traction, as well as soil degradation and minimizes energy consumption, and there is a greater tendency to use the possibilities of freewheeling over a long period. Lower heating of the hydraulic fluid is also observed.

[0094] It is noted that the proposed system allows the machine to be put into freewheel with high efficiency without the pistons leaving contact with the cam. The use of the freewheel is thus done without generating shocks between the pistons and the cam, which encourages the use of freewheeling without restriction. It is also noted that thanks to the shut-off valves 40A and 40B, freewheeling can be carried out regardless of the angular position of the hydraulic machine, whatever the position of the pistons relative to the cam.

[0095] Figure 7 schematically shows another example of a hydraulic machine structure 20 that can be used in the context of the invention. In this figure, the shut-off valves 40A and 40B are not shown.

[0096] In this embodiment, each pair formed by a piston 250 and a housing 240 defines a first chamber 260 and a second chamber 270 which are distinct, isolated from each other by means of sealing elements, and defining distinct cylinder capacities. The cylinder capacity is defined as being the product of the effective section of a chamber considered by the stroke of the piston, the effective section of a piston being the total surface area of ​​the piston which participates in creating a force tending to move the piston in the desired direction. A distinction is made between the cylinder capacity for a given piston or a given piston stage (or chamber) and the cylinder capacity for a motor or a pump, which is equal to the sum of the cylinder capacity of the pistons for the motor or pump considered.

[0097] Such a structure makes it possible to define two hydraulic machines in a single 230 cylinder block.

[0098] The first chamber 260 and the second chamber 270 are typically superimposed according to the sliding direction of the piston 250 in the housing 240.

[0099] In the example illustrated, the housing 240 has two distinct portions; a first portion having a first section SI, and a second portion having a second section S2, the first section SI being strictly greater than the second section S2, the first portion extending from an external surface of the cylinder block 230 and opening opposite the cam 220, and the second portion extending from the first portion so as to form the bottom of the housing 240. The second portion is thus typically blind in the sliding direction of the pistons 250.

[0100] The piston 250 also has a first portion and a second portion adapted to slide respectively in the first portion and the second portion of the housing 240 while ensuring the sealing of the first chamber 260 and the second chamber 270.

[0101] In the illustrated example, conduits are arranged in the cylinder block, these conduits extending from the first chambers and from the second chambers and emerging from a lateral surface of the cylinder block 230. The conduits are then supplied by the distributor 280 which has suitable conduits. In the illustrated example, the conduit 265 is connected to the first chamber 260, and the conduit 275 is connected to the second chamber 270.

[0102] The set of first chambers can then, for example, define the first hydraulic machine 20A presented previously with reference to figures 3 and 4, and the set of second chambers can then, for example, define the second hydraulic machine 20B.

[0103] The operation is then typically identical to that already described with reference to the previous figures.

[0104] In such an embodiment, considering for example that the first chambers 260 can be disengaged, the second chambers 270 will then fulfill a function of maintaining the pistons 250 in contact with the cam 220 as long as the second chambers 270 are maintained in operation.

[0105] Alternatively, the first chambers 260 and the second chambers 270 may be disengaged, simultaneously or independently.

[0106] In such a case, each piston 250 is then provided with means ensuring maintenance in contact with the cam 220, typically an elastic return means such as a spring which is not shown in FIG. 7.

[0107] The shut-off valves 40A and 40B can in particular be integrated into the cylinder block 230 or into the distributor 280.

[0108] Alternatively, the shut-off valves may in particular be integrated into an additional part, called valve block 400, interposed between the cylinder block 230 and the distributor 280.

[0109] Figure 8 shows an exemplary embodiment in which the valve block carrying the shut-off valves 40A and 40B is coupled to the cylinder block 230, typically by means of screws, splines, or any other suitable means ensuring a rotational coupling between the valve block carrying the shut-off valves 40A and 40B and the cylinder block 230.

[0110] This embodiment presents a hydraulic machine with stepped pistons as already described in particular with reference to FIG. 7. The second chambers 270 are connected directly to the distributor 280, while the first chambers 260 are connected to the distributor via the shut-off valves, which are designated here by the reference 40.

[0111] In such an embodiment, the first chambers 260 can thus be disengaged as described previously, while the second chambers 270 are permanently supplied by the distributor 280, thus allowing the pistons 250 to be permanently held against the cam 220.

[0112] Such an embodiment in which the valve block carrying the shut-off valves 40A and 40B is coupled to the cylinder block 230 or integrated into the cylinder block makes it possible to minimize the volume in which the vacuum effect is achieved, which makes it possible to obtain this vacuum effect more quickly and more homogeneously. In addition, this embodiment makes it possible to eliminate a potential leakage zone which is the distribution interface.

[0113] Such an embodiment typically comprises a piston shut-off valve 40.

[0114] Figure 9 is a variation of Figure 8, in which the shutoff valves 40A and 40B are coupled to the distributor 280, typically by means of screws, studs, splines, or any other suitable means providing a rotational coupling between the shutoff valves 40A and 40B and the distributor 280.

[0115] As for the embodiment already described with reference to FIG. 8, the first chambers 260 can thus be disengaged by means of the cylinder distribution valves, while the second chambers 270 are permanently supplied by the distributor 280.

[0116] In such an embodiment, it is understood that the volume in which the vacuum effect occurs includes an interface between the cylinder block 230 and the distributor 280, which must therefore be adapted to maintain its sealing under such operating conditions.

[0117] Such an embodiment makes it possible to share the shut-off valves 40 by requiring only one valve per half-lobe of cam or per angular sector of distribution holes depending on the architecture of the distributor 280, and can therefore be advantageous in terms of size and cost.

[0118] In the embodiments of Figures 8 and 9, the control device, and in particular the shut-off valves 40 and the control valve 30 are integrated into the same hydraulic machine casing. As indicated previously, this embodiment is not limiting, the shut-off valves 40 and / or the control valve 30 may be separate components, external to the hydraulic machine, and either assembled to the hydraulic machine or connected to the hydraulic machine by means of pipes.

[0119] Although the present invention has been described with reference to specific exemplary embodiments, it is obvious that modifications and changes may be made to these examples without departing from the general scope of the invention as defined by the claims. In particular, individual features of the various illustrated / mentioned embodiments may be combined in additional embodiments. Therefore, the description and drawings should be considered in an illustrative rather than restrictive sense.

[0120] It is also obvious that all the characteristics described with reference to a method are transposable, alone or in combination, to a device, and conversely, all the characteristics described with reference to a device are transposable, alone or in combination, to a process.

Claims

Claims

1. Assembly comprising a hydraulic machine and a control device (30, 40), the hydraulic machine comprising: a first assembly and a second assembly, movable in rotation relative to each other along a main axis, the first assembly comprising a casing (210) and a cam (220) comprising at least one lobe, the second assembly comprising a cylinder block (230) having a plurality of housings (240) in which pistons (250) slide, each assembly formed by a piston (250) and a housing (240) defining at least one first chamber defining a set of first chambers (260), a distributor (280) adapted to supply and discharge fluid into said chambers, the distributor having a supply duct and a discharge duct in which the hydraulic machine comprises means adapted to keep the pistons (250) in contact with the cam (220), the control device (30,40) is suitable for, - in a first configuration, supplying all of the first chambers of the cylinder block (230), during the relative rotation between the first set and the second set, - in a second configuration, for a set of angular sectors of the cam (220) and / or for a set of pistons, preventing the admission of fluid into said at least one first chamber (260) of the cylinder block (230) during relative rotation between the first set and the second set.

2. An assembly according to claim 1, wherein the control device (30, 40) is configured to, in the second configuration, close the fluid intake into all of the first chambers (260), and connect the fluid discharge from all of the first chambers (260) to a discharge volume via a calibrated valve.

3. Assembly according to one of claims 1 or 2, in which said means adapted to maintain the pistons (250) in contact with the cam (220) comprise elastic return means (290) positioned in said housings of the cylinder block (230), and tending to move the pistons (250) radially outwards relative to the main axis (ZZ).

4. Assembly according to one of claims 1 to 3, in which each pair formed by a piston (250) and a housing (240) defines between the piston (250) and the housing (240) said first chamber (260) and a second chamber (270) distinct and superimposed according to a sliding direction of the piston (250) in the housing (240), and in which in the second configuration, the control device (30, 40) is adapted to prevent the admission of fluid into the first chambers (260) and / or into the second chambers (270) of the cylinder block (230).

5. An assembly according to claim 4, wherein the pilot device (30, 40) is adapted to, in the second configuration, for each pair formed by a piston (250) and a housing (240), prevent the admission of fluid into one of the first chamber (260) and the second chamber (270), and supply the other (230) of the first chamber (260) and the second chamber (270), so as to keep the pistons (250) in contact with the cam (220).

6. Assembly according to one of claims 1 to 5, in which the control device (30, 40) comprises shut-off valves (40), positioned at the inlet and outlet of the first chambers (260), each shut-off valve (40) being configured to be open when the pressure at its terminals exceeds a threshold value.

7. Assembly according to one of claims 1 to 6, in which the pilot device (30, 40) comprises a pilot valve (30), adapted to, in a first configuration, connect an inlet and a discharge of the first chambers (260) to a pressure source (10), and in a second configuration, isolate the inlet and the discharge of the first chambers (260) from the pressure source (10).

8. An assembly according to one of claims 1 to 6, wherein the pilot device (30, 40) comprises a pilot valve (30), adapted to, in a first configuration, connect an inlet and a discharge of the first chambers (260) to a pressure source (10), and in a second configuration, isolate the inlet and the discharge of the first chambers (260) from the pressure source (10), and wherein the pilot valve (30) is adapted to, in its second configuration, connect the first chambers (260) to a discharge volume via the shut-off valves (40).

9. Assembly according to one of claims 7 or 8, in which the valve block carrying the shut-off valves (40) is integral with the cylinder block (230), or in which the valve block carrying the shut-off valves (40) is integral with the distributor (280).

10. Assembly according to one of claims 1 to 9, in which said hydraulic machine has a first operation at a first displacement value, and a second operation at a second displacement value strictly lower than the first displacement value, and in which the control device (30, 40) is adapted to be in the second configuration when the hydraulic machine has its second operating mode.

11. Assembly according to claim 10, in which the second displacement value is a zero displacement.

12. An assembly according to one of claims 1 to 11, wherein in the second configuration, the displacement of the pistons (250) radially outwards relative to the main axis (ZZ) causes an increase in the volume of the first chambers while preventing the admission of fluid into said first chambers, so as to cause a depression in said first chambers.

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