Hydraulic circuit using a pressure adapter

Abstract

The invention relates to a hydraulic circuit for driving a bi-directional hydraulic actuator (200), comprising: - a hydraulic energy source (100), - a hydraulic actuator (200), - a pressure adaptation module (3000), - a first supply line connecting a first terminal of the hydraulic energy source (100) to a first port of the pressure adaptation module (3000), - a second supply line connecting a second terminal of the hydraulic energy source (100) to a second port of the pressure adaptation module (3000), - a first adaptation line connecting the pressure adaptation module (3000) to a first terminal of the hydraulic actuator (230), - a second adaptation line connecting the pressure adaptation module (3000) to the other terminal of the hydraulic actuator (230), the pressure adaptation module being suitable for modifying the pressure difference across the terminals of the hydraulic actuator (230) so that the pressure difference across the terminals of the hydraulic actuator (230) is different from the pressure difference across the terminals of the hydraulic energy source (100).

Description

HYDRAULIC CIRCUIT USING A PRESSURE ADAPTER Description Technical Field

[0001] The present invention relates to a hydraulic circuit comprising a pressure adapter, in particular for driving axles, movement members, jacks, or for driving the rotation of more generic equipment such as a winch, a crusher, a drill. Prior art

[0002] Hydraulic systems usually consist of a power transformer machine that converts the mechanical energy supplied by a prime mover, for example a heat engine or an electric motor, into hydraulic energy distributed by a high-pressure pipe network to one or more hydraulic components such as cylinders or hydraulic motors driving wheels or axles.

[0003] This transmission solution, however, has certain limitations, including: - In torque density: the pressure of commonly used pipes being limited to values ​​lower than 450 bar, the maximum transmissible torque limit is the product of this pressure and the value of the displacement of a hydraulic actuator, typically hydraulic motors. However, the displacement value directly impacts the size of the motors, as well as their cost. - In speed: for a given pump displacement and maximum prime mover speed, a maximum flow rate is defined. In the case of a transmission application, this then limits the vehicle speed.

[0004] In the case of a hydrostatic transmission, there are typically two very distinct operating modes: - A mode of operation that we call “work”: the load is important and the speed is low, we are looking here for the best crossing capacity (for a vehicle) or in any case the highest torque (for more generic rotating equipment), this particular condition is decisive for the dimensioning of the engine displacement. - An operating mode that is called "road" for a vehicle or "normal" mode for more generic rotating equipment, particularly for moving the vehicle or machine between two work locations: in this mode, the load is low, and the speed is high. Here, the aim is to achieve the fastest speed, which will be limited by the size and bulk of the pumps and / or the motors driving the pumps.

[0005] It is therefore understandable that these two operating modes constrain the sizing of the hydraulic circuit; the components must be oversized to provide a power margin that is never used by the driver.

[0006] More generally, for the driving of a hydraulic organ, different drive modes may be required, involving very varied needs in terms of hydraulic power supply.

[0007] To overcome these problems, it was considered to use pressure / flow adapters within a hydraulic circuit that can be activated or deactivated on demand in order to size the hydraulic circuit for the most normal operating conditions while allowing occasional operation over more unusual operating ranges.

[0008] However, when the hydraulic consumer is bidirectional, it is interesting to be able to provide a circuit operation in four quadrants (1st quadrant: the consumer causes an action in one direction; 2nd quadrant: the consumer retains an action in this direction; 3rd quadrant: the consumer causes an action in the other direction; 4th quadrant: the consumer retains an action in this other direction) which allows pressure adaptation. Statement of the invention

[0009] In order to at least partially address these issues, the present invention relates to a hydraulic circuit for driving a bidirectional hydraulic actuator having two terminals, said circuit comprising - a hydraulic energy source suitable for delivering a flow rate in the hydraulic circuit, thus enabling in particular a pressure increase in the hydraulic circuit, - a hydraulic actuator, - a pressure adaptation module, - a first supply line connecting a first terminal of the hydraulic energy source to a first port of the pressure adaptation module - a second supply line connecting a second terminal of the hydraulic energy source to a second port of the pressure adaptation module - a first adaptation line connecting the pressure adaptation module to a first terminal of the hydraulic actuator - a second adaptation line connecting the pressure adaptation module to the other terminal of the hydraulic actuator, the pressure adaptation module being adapted to modify the pressure difference across the terminals of the hydraulic actuator so that the pressure difference across the terminals of the hydraulic actuator is different from the pressure difference across the terminals of the hydraulic energy source.

[0010] In one example, the first feed line, the second feed line, the first adaptation line, and the second adaptation line are distinct.

[0011] The circuit is typically a closed loop hydraulic circuit.

[0012] According to one example, the circuit further comprises a first branch line connecting a first terminal of the hydraulic power source to the first terminal of the hydraulic actuator, and a second branch line connecting a second terminal of the hydraulic power source to the second terminal of the hydraulic actuator, said first bypass line and second bypass line being provided with sealing means adapted to selectively seal said first bypass line and second bypass line.

[0013] According to one example, the pressure adaptation module is adapted to increase the pressure difference across the hydraulic actuator such that the pressure difference across the hydraulic actuator is greater than the pressure difference across the hydraulic power source.

[0014] According to one example, the pressure adaptation module is adapted to allow the flow rate through the hydraulic actuator to be reduced so that the flow rate through the hydraulic actuator is less than the flow rate provided by the hydraulic power source.

[0015] According to one example, the pressure adaptation module is adapted to decrease the pressure difference across the hydraulic actuator such that the pressure difference across the hydraulic actuator is less than the pressure difference across the hydraulic power source.

[0016] According to one example, the pressure adaptation module is adapted to allow the flow rate through the hydraulic actuator to be increased such that the flow rate through the hydraulic actuator is greater than the flow rate provided by the hydraulic power source.

[0017] In one example, the pressure adaptor module includes a pressure adapter including a first hydraulic machine and a second hydraulic machine rotatably interconnected, said first and second hydraulic machines being configured such that one has pump operation and the other has motor operation.

[0018] In one example, the pressure adaptor module includes a single pressure adapter.

[0019] According to one example, the first hydraulic machine has a first terminal connected to the first terminal of the hydraulic energy source, and a second terminal connected to the second terminal of the hydraulic power source, and the second hydraulic has a first terminal connected to the first terminal of the hydraulic actuator, and a second terminal connected to the second terminal of the hydraulic actuator.

[0020] According to an example, the first hydraulic machine has a first terminal and a second terminal, the second hydraulic has a first terminal and a second terminal, the first terminal of the first hydraulic machine is connected to the first terminal of the hydraulic energy source, the second terminal of the second hydraulic machine is connected to the first terminal of the hydraulic actuator (30), the second terminal of the first hydraulic machine is connected to the first terminal of the second hydraulic machine, and to the second terminal of the hydraulic energy source.

[0021] In one example, the second terminal of the first hydraulic machine is connected to the first terminal of the second hydraulic machine, and to the first terminal and the second terminal of the hydraulic power source via a low pressure selector.

[0022] According to one example, the low pressure selector is housed in a housing of the pressure matching module. By being housed in the same housing, the conduits connecting the low pressure selector to the first hydraulic machine and the second hydraulic machine can be formed directly in the housing.

[0023] In one example, the second terminal of the second hydraulic machine is connected to the first terminal and the second terminal of the hydraulic actuator via a high pressure selector.

[0024] According to one example, the high-pressure selector is housed in a housing of the pressure matching module. By being housed in the same housing, the conduits connecting the low-pressure selector to the first hydraulic machine and the second hydraulic machine can be formed directly in the housing.

[0025] According to an example, the circuit presents: - a first operating mode, in which the hydraulic actuator is powered so as to deliver mechanical power in a first operating direction, - a second operating mode, in which the hydraulic actuator delivers hydraulic power in the first operating direction, - a third operating mode, in which the hydraulic actuator is powered so as to deliver mechanical power in a second operating direction opposite to the first operating direction, and - a fourth operating mode, in which the hydraulic actuator delivers hydraulic power according to the second operating direction.

[0026] According to an example, which the hydraulic actuator is an actuator adapted to carry out a transformation of hydraulic energy into mechanical energy or vice versa, and configured so that an inversion of the pressure difference at its terminals causes a change in the direction of actuation.

[0027] In one example, the pressure lifter is configured to be engaged when the higher of the two pressures between the first supply line and the second supply line exceeds a threshold value.

[0028] This disclosure also presents a system for driving a member by means of a hydraulic circuit, comprising: a hydraulic energy source adapted to deliver pressure in the hydraulic circuit, a drive member, comprising: - a casing, having a first orifice and a second casing orifice adapted to define an inlet and a discharge of the casing, - a primary hydraulic machine, adapted to be powered by the hydraulic energy source, the primary hydraulic machine being housed in the casing and having a first orifice and a second hydraulic machine orifice, said system being characterized in that the drive member comprises a pressure booster integrated in the casing, said pressure booster being adapted to selectively raise the pressure, so that the pressure difference between the two ports of the primary hydraulic machine is greater than the pressure difference between the two ports of the casing.

[0029] In one example, the pressure lifter is integrated into the housing such that the pressure lifter is connected to the first port and the second port of the primary hydraulic machine via conduits formed in the housing.

[0030] In one example, the pressure lifter is configured to be engaged when the pressure difference between the two ports of the primary hydraulic machine exceeds a threshold value.

[0031] The system may further comprise at least one valve connecting the pressure lifter to the first orifice and / or to the second orifice of the casing, said at least one valve being configured to, when the pressure difference between the two orifices of the casing is less than or equal to a pressure threshold value, disengage the pressure lifter.

[0032] The system may further comprise at least one valve connecting the pressure lifter to the first port and / or to the second port of the casing, said at least one valve being configured to, when the rotational speed of the primary hydraulic machine is greater than a threshold value, disengage the pressure lifter.

[0033] The system may further comprise at least one valve connecting the pressure lifter to the first port and / or the second port of the housing, said at least one valve being configured to disengage the pressure lifter when the rotational speed of the primary hydraulic machine exceeds a certain threshold.

[0034] According to one example, the pressure lifter is adapted to take a flow Q1 and a pressure PI from the first or second port of the casing, and deliver a flow Q2 and a pressure P2 to the first or second port of the primary hydraulic machine, such that Q2 < Q1 and P2 > PI.

[0035] According to one example, the primary hydraulic machine may be a hydraulic machine using axial technology, for example having in particular an inclined plate on which the pistons slide.

[0036] According to one example, the primary hydraulic machine may be a radial technology hydraulic machine, for example having in particular a multi-lobed cam in contact with which the pistons slide.

[0037] According to one example, the primary hydraulic machine can be of fixed displacement.

[0038] According to one example, the primary hydraulic machine can be multi-cylinder.

[0039] According to one example, the primary hydraulic machine can be variable displacement or continuously variable.

[0040] For example, the pressure lifter is of linear oscillating technology.

[0041] According to one example, the pressure lifter comprises a first hydraulic machine and a second hydraulic machine rotatably connected, the first hydraulic machine and the second hydraulic machine having identical displacements, said first and second hydraulic machines being configured such that one has a pump operation and the other has a motor operation.

[0042] According to one example, the pressure lifter comprises a first hydraulic machine and a second hydraulic machine rotatably connected, the first hydraulic machine and the second hydraulic machine having different displacements, said first and second hydraulic machines being configured so that one has a pump operation and the other has a motor operation.

[0043] According to one example, the pressure lifter comprises a first hydraulic machine and a second hydraulic machine rotatably secured together, the first hydraulic machine and the second hydraulic machine having different displacements, said first and second hydraulic machines being configured such that one has a pump operation and the other has a motor operation. Said machines can be hydraulic machines using radial technology, and particularly multi-lobe cam radial technology.

[0044] According to one example, the pressure lifter comprises a first hydraulic machine and a second hydraulic machine rotatably interconnected, said first and second hydraulic machines being configured such that one has a pump operation and the other has a motor operation. Said hydraulic machines may be of fixed displacement, multi-displacement or variable displacement.

[0045] According to one example, - the first hydraulic machine has a first port and a second port, the first port being selectively connected to the port of the casing having the highest pressure among the two ports of the casing, and the second port being selectively connected to the port of the casing having the lowest pressure among the two ports of the casing, - the second hydraulic machine has a first orifice and a second orifice, the first orifice being connected to the orifice of the casing having the lowest pressure among the two orifices of the casing, and the second orifice being connected to the orifice of the primary hydraulic machine having the highest pressure via conduits arranged in the casing.

[0046] According to one example, the pressure lifter comprises a first hydraulic machine and a second hydraulic machine rotatably connected, the first hydraulic machine having a greater displacement than the second hydraulic machine, said system being configured such that, for a first mode of operation, the first hydraulic machine has a motor operation, and the second hydraulic machine has a pump operation, said second hydraulic machine powering the primary hydraulic machine.

[0047] According to one example, - the first hydraulic machine has a first orifice and a second orifice, the first orifice being selectively connected to the orifice of the casing having the the highest pressure of the two crankcase ports, and the second port being selectively connected to the crankcase port having the lowest pressure of the two crankcase ports, - the second hydraulic machine has a first port and a second port, the first port being connected to the second port of the first hydraulic machine, and the second port being connected to the internal port of the primary hydraulic machine having the highest pressure via conduits arranged in the casing.

[0048] In one example, the second port of the second hydraulic machine is connected to the first port and the second port of the primary hydraulic machine via a high pressure selector.

[0049] According to one example, the first orifice of the first hydraulic machine is connected to a first calibrated valve, connected on the one hand to the first casing orifice and on the other hand to the second casing orifice, said first calibrated valve being configured to connect the first orifice of the first hydraulic machine to the connection linked to the hydraulic energy source having the highest pressure when the pressure difference between the casing orifices exceeds a first calibration threshold value, the second orifice of the first hydraulic machine is connected to a second calibrated valve, connected on the one hand to the first casing orifice and on the other hand to the second casing orifice,said second calibrated valve being configured to connect the first orifice of the first hydraulic machine to the connection linked to the hydraulic energy source having the lowest pressure when the pressure difference between the orifices of the casing exceeds a second calibration threshold value.

[0050] According to one example, the pressure lifter comprises a first hydraulic machine and a second hydraulic machine which are rotationally fixed together, the first hydraulic machine having a cylinder capacity greater than the second hydraulic machine, said system being configured so that, for a first mode of operation, the first hydraulic machine has a motor operation, and the second hydraulic machine has a pump operation, said second hydraulic machine powering the primary hydraulic machine, wherein - the first hydraulic machine has a first orifice and a second orifice, the first orifice being connected to the first orifice of the casing, and the second orifice being connected to the second orifice of the casing, - the second hydraulic machine has a first port and a second port, the first port being connected to the second port of the primary hydraulic machine, and the second port being connected to the first port of the primary hydraulic machine, the system comprising a valve adapted to selectively isolate the first port of the housing from the first port of the primary hydraulic machine, and a valve adapted to selectively isolate the second port of the housing from the second port of the primary hydraulic machine.

[0051] According to one example, the first hydraulic machine and / or the second hydraulic machine are radial piston and multi-lobe cam hydraulic machines.

[0052] In one example, at least one of the first hydraulic machine and the second hydraulic machine is a variable displacement hydraulic machine.

[0053] In one example, the system further includes a first valve and a second valve, the first valve being adapted to selectively connect or isolate the first housing port to the first port of the primary hydraulic machine, and the second valve being adapted to selectively connect or isolate the second housing port to the second port of the primary hydraulic machine.

[0054] According to one example, the pressure amplification is controlled by a command external to the drive member.

[0055] In one example, the primary hydraulic machine is a radial piston, multi-lobe cam hydraulic machine.

[0056] The present disclosure also relates to a rolling machine, for example a vehicle, a construction machine or an agricultural machine, comprising at least one movement member and at least one system as defined previously adapted to selectively drive said movement member in rotation.

[0057] The present disclosure also relates to a drive member as defined previously with reference to the system. The invention thus relates in particular to a drive member adapted to selectively drive a member in rotation, the drive member, comprising: - a casing, having a first orifice and a second casing orifice adapted to define an inlet and a discharge of the casing, - a primary hydraulic machine, adapted to be powered by a hydraulic energy source, the primary hydraulic machine being housed in the casing and having a first orifice and a second hydraulic machine orifice, said system being characterized in that the drive member comprises a pressure booster integrated in the casing, said pressure booster being adapted to selectively raise the pressure, so that the pressure difference between the two orifices of the primary hydraulic machine is greater than the pressure difference between the two orifices of the casing. Brief description of the drawings

[0058] 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.

[0059] [Fig. 1] Figure 1 is a schematic view of an exemplary system according to one aspect of the invention.

[0060] [Fig. 2] Figure 2 represents an exemplary embodiment of a system according to one aspect of the invention.

[0061] [Fig. 3] Figure 3 represents an exemplary embodiment of a system according to one aspect of the invention.

[0062] [Fig. 4] Figure 4 represents another exemplary embodiment of a system according to one aspect of the invention.

[0063] [Fig. 5] Figure 5 represents another exemplary embodiment of a system according to one aspect of the invention.

[0064] [Fig. 6] Figure 6 represents another exemplary embodiment of a system according to one aspect of the invention.

[0065] [Fig. 7] Figure 7 represents another exemplary embodiment of a system according to one aspect of the invention.

[0066] [Fig. 8] Figure 8 represents a particular configuration of Figure 6.

[0067] [Fig. 9] Figure 9 represents a particular configuration of Figure 6.

[0068] [Fig. 10] Figure 10 shows another exemplary embodiment of a system according to one aspect of the invention.

[0069] [Fig. 11] Figure 11 represents a particular configuration of the system presented in Figure 10.

[0070] [Fig. 12] Figure 12 represents another particular configuration of the system presented in Figure 10.

[0071] [Fig. 13] Figure 13 represents another particular configuration of the system presented in Figure 10.

[0072] [Fig. 14] Figure 14 shows another exemplary embodiment of a system according to one aspect of the invention.

[0073] [Fig. 15] Figure 15 represents a particular configuration of the system presented in Figure 14.

[0074] [Fig. 16] Figure 16 represents another particular configuration of the system presented in Figure 14.

[0075] [Fig. 17] Figure 17 represents another particular configuration of the system presented in Figure 14.

[0076] [Fig. 18] Figure 18 shows another exemplary embodiment of a system according to one aspect of the invention.

[0077] [Fig. 19] Figure 19 shows another exemplary embodiment of a system according to one aspect of the invention.

[0078] [Fig. 20] Figure 20 represents another example of circuit embodiment according to one aspect of the invention.

[0079] [Fig. 21] Figure 21 represents another example of circuit embodiment according to one aspect of the invention.

[0080] Throughout the figures, common elements are identified by identical numerical references. Description of the embodiments

[0081] A system according to one aspect of the invention is described below with reference to the figures. The circuits presented are simplified diagrams. Thus, various elements such as the feeding means and calibration means are not shown in the figures. Those skilled in the art will understand, however, that the figures are not limiting, and that the circuits may include such well-known elements. In particular, in the embodiments described, the member 10 is represented as a hydraulic motor intended to drive an element such as a wheel in rotation. Nevertheless, the invention applies to other types of drive member, in particular translational drive members such as hydraulic cylinders.

[0082] Figure 1 is a schematic general view of a system according to one aspect of the invention. This figure shows a member 10, for example a member for moving a vehicle or machine such as a wheel, a mechanical axle or a crown of an excavator turret. This member 10 is driven by a hydraulic circuit.

[0083] The hydraulic circuit as shown comprises a hydraulic energy source 100, for example a flow source such as a pump or a accumulator, and a drive member 200. The hydraulic energy source 100 is adapted to power the drive member 200, so that the drive member drives the member 10 in rotation or translation depending on the type of member chosen. The circuit can be an open-loop or closed-loop circuit. In the case of an open-loop hydraulic circuit, the hydraulic energy source 100 typically comprises an ambient pressure reservoir, a hydraulic pump or an accumulator and a valve or valve ensuring the hydraulic connection depending on the operating mode. Conversely, a closed-loop hydraulic circuit designates a hydraulic circuit in which the fluid does not return to the reservoir. Thus, considering a hydraulic pump as the flow source, the fluid delivered by the pump flows in the circuit through various actuators and hydraulic members, then returns to the pump without passing through a reservoir.

[0084] It is understood that the system can be reversible. The description generally presents an operation in which the member 10 is driven in rotation. Since the hydraulic members have a reversible operation, an inverse operation is possible, in particular during braking phases; the member 10 then performs a drive function allowing energy recovery.

[0085] The hydraulic energy source 100 is typically a hydraulic pump, for example a variable displacement hydraulic pump 110 driven by a prime mover 120 such as a heat engine or an electric motor. The hydraulic energy source may also comprise a fixed displacement hydraulic pump 110 and a prime mover 120 adapted to drive it in rotation at a variable speed. An exemplary embodiment (with a variable displacement pump) is illustrated in FIG. 2.

[0086] The drive member 200 comprises a casing 210 in which is housed a primary hydraulic machine 230 typically adapted to have a motor operation in order to drive the member 10 in rotation. The drive member also comprises a pressure booster 300 housed in the casing 210.

[0087] The pressure elevator 300 is configured to selectively perform a pressure raising or amplifying function. Thus, for an initial pressure PI at the inlet of the pressure elevator 300, the pressure elevator 300 will deliver a pressure P2 such that P2 > PI.

[0088] Figures 3 and 4 show two examples of embodiments of the pressure elevator 300.

[0089] For the casing 210, a first orifice 212 and a second orifice 214 are defined, which form a fluid inlet and a fluid outlet according to the direction of circulation of the fluid. Similarly, for the primary hydraulic machine 230, a first orifice 232 and a second orifice 234 are defined, which form a fluid inlet and a fluid outlet according to the direction of circulation of the fluid. In the context of the description, for operation as a motor of the primary hydraulic machine 230, it will be considered that the first orifice 212 forms a fluid inlet, and therefore a high-pressure line, and that the second orifice 212 forms a fluid outlet, and therefore a low-pressure line. Unless otherwise stated, it will be considered that the operation described thus corresponds to operation in traction and forward gear. An orifice in the present text designates an orifice or a terminal adapted to make a hydraulic connection.

[0090] The primary hydraulic machine 230 may, for example, be a rotating machine, typically a hydraulic machine with radial pistons and a multi-lobe cam, or a hydraulic machine with axial pistons. The hydraulic machine may, for example, be used as a motor for driving a member such as a wheel or an axle, a coupling or an implement.

[0091] The primary hydraulic machine 230 may also be a cylinder, the two ports 232 and 234 being then typically connected to two chambers of the cylinder for the application of opposing forces. In such a case, the system then typically comprises means adapted to limit the pressure in the hydraulic circuit, for example pilot-controlled setting valves. More generally, the hydraulic machine 230 may be any actuator or hydraulic member having reversible operation. The primary hydraulic machine 230 may more generally be a bidirectional hydraulic actuator comprising two terminals and adapted to transform received hydraulic energy into mechanical energy or vice versa, and for which the inversion of the pressure difference at its terminals causes a change in the direction of operation.

[0092] The pressure lifter 300 typically comprises a first hydraulic machine 310 and a second hydraulic machine 320 which are rotationally fixed together, and configured so that one has a pump operation and the other has a motor operation, it being understood that such members are reversible and that a hydraulic motor can have a pump operation, and vice versa. In the examples illustrated, the first hydraulic machine 310 has a motor operation, and the second hydraulic machine 320 has a pump operation. By rotationally fixed together, it is meant here that the first hydraulic machine 310 and the second hydraulic machine 320 are rotationally coupled, and therefore rotate together. This rotational coupling can be achieved for example by coupling the two hydraulic machines on the same shaft, or by connecting them by a rigid mechanical link.

[0093] The first hydraulic machine 310 and the second hydraulic machine 320 are typically formed by the same hydraulic machine comprising two distinct parts.

[0094] In the example illustrated in Figure 3, the first hydraulic machine 310 has a first port 312 and a second port 314, the first port 312 being connected to the first port 212 of the casing 210 (i.e. here to the port of the casing 210 having the highest pressure), and the second port 314 being connected to the second port 214 of the casing 210 (i.e. to the port of the casing 210 having the lowest pressure), The second hydraulic machine 320 has a first port 322 and a second port 324, the first port 322 being connected to the second port 314 of the first hydraulic machine 310 and to the second port 214 of the casing 210 (i.e. to the port of the casing 210 having the lowest pressure), and the second port 324 being connected to the first orifice 232 of the primary hydraulic machine 230, (i.e. its inlet, and therefore its orifice having the highest pressure) via conduits arranged in the casing. In this embodiment, the first hydraulic machine 310 has a displacement C1 greater than the displacement C2 of the second hydraulic machine 320. Such an embodiment is referred to as a 3-line elevator with common return. The first hydraulic machine 310 and / or the second hydraulic machine 320 may, for example, have fixed or variable displacements. For example, one may have a fixed displacement and the other a variable displacement, or both may have a fixed displacement, or both may have a variable displacement.The use of at least one variable displacement hydraulic machine makes it possible to vary the amplification or pressure rise ratio by varying the displacement ratio between the first hydraulic machine 310 and the second hydraulic machine 320. The system can then, for example, comprise a controller adapted to control the variation of the displacement ratio and therefore the variation of the pressure rise ratio as a function of a setpoint or operating conditions.

[0095] The first hydraulic machine 310 and the second hydraulic machine 320 are typically identical or similar in every respect and not symmetrical, if applicable except for the displacement. The first hydraulic machine 310 and the second hydraulic machine 320 typically each have a single shaft output, these two shaft outputs being mechanically connected.

[0096] In operation, the pressure booster 300 is powered by the hydraulic energy source 100 adapted to deliver a flow rate, thus making it possible to achieve a pressure increase in the circuit. A high pressure is thus applied to the inlet 312 of the first hydraulic machine 310. The latter performs a function of driving the rotation of the second hydraulic machine 320. The second hydraulic machine is powered by the discharge of the first hydraulic machine 310. However, due to the differences in displacement, the second hydraulic machine 320 will then deliver a higher pressure, which is described as very high pressure, to power the machine primary hydraulic 230. In this embodiment, the pressure increase therefore depends in particular on the ratio between the cylinder capacities C1 and C2.

[0097] More generally, the pressure lifter 300 thus makes it possible to take a flow rate Q1 and a pressure PI from an orifice of the casing 210, here the first orifice 212 of the casing 210, and to deliver a flow rate Q2 and a pressure P2 to the inlet of the hydraulic machine 230 (here its first orifice 232), such that Q2 < Q1 and P2 > PI.

[0098] In the example illustrated in Figure 4, the first port 312 of the first hydraulic machine 310 and the first port 322 of the second hydraulic machine 320 are both connected to the first port 212 of the casing 210 (i.e. here to the port of the casing 210 having the highest pressure).

[0099] The second port 314 of the first hydraulic machine 310 is connected to the second port 214 of the casing 210 (i.e. to the port of the casing 210 having the lowest pressure),

[0100] The second port 324 of the second hydraulic machine 320 is connected to the first port 232 of the primary hydraulic machine 230 (i.e. its inlet, and therefore its port having the highest pressure) via conduits arranged in the casing. Such an embodiment is referred to as a 3-line elevator with common supply.

[0101] In this embodiment, the first hydraulic machine 310 may typically have a displacement C1 equal or substantially equal to the displacement C2 of the second hydraulic machine 320.

[0102] In operation, the pressure booster 300 is powered by the hydraulic energy source 100. A high pressure is thus applied to the inlet 312 of the first hydraulic machine 310. The latter performs a function of driving the rotation of the second hydraulic machine 320. The second hydraulic machine 320 is also powered by the hydraulic energy source 100; it will therefore perform a pressure amplification function.

[0103] As for the previous embodiment, the pressure elevator 300 thus makes it possible to take a flow rate Q1 and a pressure PI from an orifice of the casing 210, here the first orifice 212 of the casing 210, and to deliver a flow rate Q2 and a pressure P2 to the inlet of the hydraulic machine 230 (here its first orifice 232), such that Q2 < Q1 and P2 > PI.

[0104] More generally, the pressure booster 300 makes it possible to transform the high pressure at the intake of the casing 210 into a very high pressure at the intake of the primary hydraulic machine 230.

[0105] In the system according to the invention, as indicated previously, the connection between the primary hydraulic machine 230 and the second hydraulic machine 320 is formed by conduits arranged in the casing 210 of the drive member 200. Such a structure thus makes it possible to confine the very high pressure zone to a reduced space internal to the casing 210, and to avoid a rise in pressure in the entire circuit.

[0106] The proposed structure thus makes it possible to increase the pressure supplied to the primary hydraulic machine 230, without requiring oversizing the various components of the hydraulic circuit.

[0107] This function can in particular be implemented punctually, for example for obstacle clearance. The pressure elevator 300 can then be selectively activated when conditions are met.

[0108] Figure 5 schematically represents a variant of the invention in which the pressure elevator 300 is produced by a first hydraulic machine 310 and a second hydraulic machine 320 linked in rotation, in which the supply and discharge lines of the first hydraulic machine 310 and the supply and discharge lines of the second hydraulic machine 320 are, by default, isolated from each other. Such a pressure elevator can be called a “4-line elevator” to distinguish it from the other variants of pressure elevators described which comprise “3 lines”; in particular, the “3-line” elevator with common supply” as shown in Figure 4 and the “3-line with common return” pressure riser as shown in Figures 3 and 6 to 9.

[0109] In the example illustrated in Figure 5, valves allow the passage or not of fluid in the conduits depending on whether or not the pressure elevator is activated. This makes it possible to activate or not the pressure elevator in one direction of rotation or the other, either in traction or in restraint (for example for a machine equipped with a system according to the invention).

[0110] The first hydraulic machine 310 has a first orifice 312 and a second orifice 314, the first orifice 312 is connected to the conduit joining the first orifice 212 of the casing 210 to the first orifice 232 of the primary hydraulic machine 230 at a hydraulic junction A. The second orifice 314 is connected to the conduit joining the second orifice 214 of the casing 210 to the second orifice 234 of the primary hydraulic machine 230 at a hydraulic junction B.

[0111] The second hydraulic machine 320 has a first orifice 322 and a second orifice 324, the first orifice 322 is connected to the conduit joining the second orifice 214 of the casing 210 to the second orifice 234 of the primary hydraulic machine 230 at a hydraulic junction D. The second orifice 324 is connected to the conduit joining the first orifice 212 of the casing 210 to the first orifice 232 of the primary hydraulic machine 230 at a hydraulic junction C.

[0112] A valve 243 is positioned between the first port 312 of the first hydraulic machine 310 and the hydraulic junction A.

[0113] A valve 245 is positioned between the second port 314 of the first hydraulic machine 310 and the hydraulic junction B.

[0114] A valve 247 is positioned between the second port 324 of the second hydraulic machine 320 and the hydraulic junction C.

[0115] A valve 249 is positioned between the first port 322 of the second hydraulic machine 320 and the hydraulic junction D.

[0116] A valve 251 is positioned on the conduit joining the first port 212 of the casing 210 to the first port 232 of the primary hydraulic machine 230 between junction A and junction C.

[0117] A valve 253 is positioned on the conduit joining the second port 214 of the casing 210 to the second port 234 of the primary hydraulic machine 230 between junction D and junction B.

[0118] Each of these valves 243, 245, 247, 249, 251 and 253 can be controlled to switch from a passing state to a non-passing state or from a non-passing state to a passing state. Thus, the valves 243, 245, 247, 249, 251 and 253 make it possible to isolate or not the first hydraulic machine 310 and / or the second hydraulic machine 320 from each other and one and / or the other from the primary hydraulic machine 230.

[0119] It is noted that the system may have a smaller number of valves. Thus, the system comprises valves 251 and 253, as well as at least one pair of valves from among valve pairs 243 and 245 on the one hand, and 247 and 249 on the other hand.

[0120] These valves 243, 245, 247, 249, 251 and 253 can be controlled hydraulically or electrically from inside or outside the casing 210.

[0121] We now describe an example of traction operation, in a direction of travel that can be described as forward motion.

[0122] An initial situation is considered in which the pressure lifter 300 is deactivated (for example by the user or the system control unit based on captured data). Thus, the valve 251 and the valve 253 are open. The valves 243, 245, 247 and 249 are closed.

[0123] In this case, the first port 212 of the casing 210 is supplied by the hydraulic power source 100 and therefore defines the high pressure inlet, while the second port 214 of the casing 210 defines the low pressure discharge. The primary hydraulic machine 230 has a motor operation in traction mode without pressure rise. Moreover, the fluid does not circulate in the pressure riser 300.

[0124] When the pressure lifter 300 is activated (for example by the user or the system control unit based on captured data), the valves 251 and 253 are switched to the non-passing configuration while the valves 243, 245, 247 and 249 are passing.

[0125] As previously, the first orifice 212 of the casing 210 is then supplied by the hydraulic energy source 100 and therefore defines the high pressure inlet, while the second orifice 214 of the casing 210 defines the low pressure discharge. However, in this case, the valve 251 being non-passing, and the valve 243 being passing, the high pressure fluid instead of going towards the first orifice 232 of the primary hydraulic machine 230, goes towards the first orifice 312 of the first hydraulic machine 310. The second orifice 214 of the casing 210 being connected to the low pressure and the valve 253 being in a non-passing configuration while the valve 245 is in a passing configuration, the low pressure is established in the line going from the second orifice 214 of the casing 210 passing through the hydraulic junction B and up to the second orifice 314 of the first hydraulic machine 310.

[0126] The pressure difference at the terminals of the first hydraulic machine 310 generates a rotational movement of this first hydraulic machine 310. The second hydraulic machine 320, being integral in rotation with the first hydraulic machine 310, will operate as a pump to generate a pressure difference at its terminals in such a way as to generate a very high pressure (i.e. a pressure greater than the pressure supplied by the hydraulic energy source to the first orifice 212 of the casing 210 in the hydraulic line going from the second orifice 324 of the second hydraulic machine 320 to the first orifice 232 of the primary hydraulic machine 230, the valve 247 being in a passing state. In the hydraulic line going from the first orifice 322 of the second hydraulic machine 320 to the second orifice 234 of the primary hydraulic machine 230 the low pressure has been established, the valve 249 which is on this line being in a passing state.

[0127] The pressure difference at the terminals of the primary hydraulic machine 230 being greater than when the pressure booster is deactivated, the member 10 set in rotation by the primary hydraulic machine 230 can exert a greater torque (for example to allow the machine equipped with such a device to overcome an obstacle).

[0128] We now describe an example of operation in restraint, in the same direction of circulation as previously described, which can be described as forward movement.

[0129] When the pressure lifter 300 is deactivated (for example by the user or the system control unit based on sensed data), the valve 251 and the valve 253 are open. The valves 243, 245, 247 and 249 are closed.

[0130] In this case, the machine being in a restraint mode (for example what is called hydrostatic braking) although the machine is moving forward (for example driven by its inertia) the hydraulic circuit aims to create a resistive torque opposite to the direction of rotation of the member 10. In this case the second orifice 214 of the casing 210 is at high pressure, while the first orifice 212 of the casing 210 is at low pressure. Due to the restraint, the primary hydraulic machine 230 has a pump operation without pressure rise due to the pressure riser 300, in which the fluid does not circulate.

[0131] When the pressure lifter 300 is activated (for example by the user or the system control unit depending on the data captured), the valves 251 and 253 are non-passing while the valves 243, 245, 247 and 249 are passing.

[0132] The primary hydraulic machine 230 has a pump operation and a very high pressure is established on the line connecting the second orifice 234 of the primary hydraulic machine 230 to the first orifice 322 of the second hydraulic machine 320, the valve 249 being open and the valve 253 being in a non-open state. The line connecting the first orifice 232 of the primary hydraulic machine 230 to the second orifice 324 of the second hydraulic machine 320 is at low pressure (the valve 247 being in a passing state). The pressure difference across the second machine 320 causes it to operate as a motor. The second machine 320, which is rotationally fixed to the first hydraulic machine 310, causes the latter to work as a pump to exert restraint on the machine equipped with a system according to the invention by establishing a high pressure in the line going from the second orifice 314 of the machine 310, passing through the valve 245 which is in a passing state, via the hydraulic junction B, via the second orifice 214 of the casing 210 (the valve 253 being in a non-passing state) to reach the hydraulic energy source 100.The line from the first port 312 of the first hydraulic machine 310 passing through the valve 243 (which is in a passing state), through the hydraulic junction A, through the first port 212 of the casing 210 and joining the hydraulic energy source 100 being at low pressure.

[0133] The system is reversible, and has a similar operation in a reverse direction typically corresponding to reverse operation, whether in traction or in restraint, with the pressure lift 300 engaged or not.

[0134] More generally, the invention as proposed has an operation that is described as 4 quadrants, namely a possible operation in two directions of operation typically corresponding to forward and reverse movement, and in traction or in restraint.

[0135] The embodiment presented is particularly advantageous due to its structural symmetry which makes it possible to operate indifferently with the pressure lift 300 according to the invention engaged or disengaged in restraint and in traction in forward and reverse gear.

[0136] Figure 6 schematically represents a variant of Figure 3 to which actuators such as valves have been added to control the activation or not of the pressure elevator 300. As in Figure 3, this is a 3-line elevator with common return.

[0137] In this figure, the first port 232 of the primary hydraulic machine 230 is connected to the first port 212 of the casing 210 via a calibrated valve 240, which is open in the direction from the first port 212 of the casing 210 to the first port 232 of the primary hydraulic machine 230 when the pressure at the first port 212 of the casing 210 exceeds a calibration value.

[0138] It should be noted that the calibrated valve 240 can also be a piloted calibrated valve, that is to say a valve whose opening can be controlled by an external control, for example a hydraulic or pneumatic control.

[0139] This figure also shows different possible locations for a pilot valve to control the activation or not of the pressure booster 300. It is understood that the different locations indicated can be used individually or combined in the same embodiment depending on the desired control.

[0140] According to a first example, the system comprises a valve 242 positioned between the first orifice 212 of the casing 210 and the first orifice 312 of the first hydraulic machine 310, that is to say upstream of the inlet of the hydraulic motor of the pressure elevator according to the operation considered. Thus, when the valve 242 is non-passing, the pressure elevator 300 is not supplied and is therefore disengaged. By disengaged, it is meant here that the pressure elevator 300 is not functional, that is to say in particular that the pressure difference between the two orifices 232 and 234 of the primary hydraulic machine 230 is equal to the pressure difference between the two orifices 212 and 214 of the casing 210, excluding pressure losses.

[0141] According to a second example, the system comprises a valve 244 positioned between the second orifice 324 of the second hydraulic machine 320 and the first orifice 232 of the primary hydraulic machine 230. When the valve 244 is non-passing, the discharge of the second hydraulic machine 320 is closed, the first hydraulic machine 310 and the second hydraulic machine 320 are then at zero effective displacement.

[0142] According to a third example, the system comprises a valve 246 positioned between the second orifice 314 of the first hydraulic machine 310 and the first orifice 322 of the second hydraulic machine 320 on the one hand, and the second orifice of the casing 214 and the second orifice 234 of the primary hydraulic machine 230 on the other hand. This valve 246 is then typically used in conjunction with one of the valves 242 and / or 244 described previously. The valve 246 is then open when the pressure riser 300 is engaged. The valve 246 and where appropriate one and / or the other of the valves 242 and / or 244 is closed when the pressure riser 300 is disengaged.

[0143] Figure 7 shows an exemplary embodiment of a system according to one aspect of the invention. This figure shows the various elements allowing operation of the system in both directions of rotation of the primary hydraulic machine 230, whether in traction mode or in restraint mode. The particularity and the interest of such a circuit is that it makes it possible to offer the user a so-called 4-quadrant operation with a pressure booster that does not have a symmetrical diagram. In this exemplary embodiment, the pressure booster 300 is a 3-line and common return type similar to that already described with reference to Figure 3.

[0144] In the example illustrated, different pilot valves are integrated so as to control the activation or non-activation of the pressure lifter 300. These different pilot valves which are described below may or may not be integrated into the casing 210.

[0145] The pilot valves may for example be configured so as to activate the pressure booster when the pressure difference between the first orifice 212 and the second orifice 214 of the casing 210 exceeds a threshold value, and disengage it when the pressure difference between the first orifice 212 and the second orifice 214 of the casing 210 is below said threshold value. Such a type of engagement corresponds for example to crossing an obstacle. Alternatively, the pilot valves may for example be configured so as to disengage the pressure booster when a flow of fluid at the orifice of the casing 210 forming the fluid inlet exceeds a flow threshold value, which indicates movement at high speed. Alternatively or additionally, the system may include a rotation speed sensor of the member 10 or of an axle driven by the primary hydraulic machine 230 associated with a controller such as an electronic control unit or ECU (according to the acronym commonly used) such that the pilot valves are then controlled to disengage the pressure lifter when the speed measured by the sensor exceeds a certain threshold.

[0146] The system as presented comprises two circuit breaker valves 410 and 420, which are designated by first circuit breaker valve 410 and second circuit breaker valve 420. These valves are typically on / off type valves, which can be on or off. For example, they can be solenoid valves which are on by default, i.e. in the absence of control, or which are off by default.

[0147] The first circuit breaker valve 410 is positioned between the first port 212 of the housing 210 and the first port 232 of the primary hydraulic machine 230. The second circuit breaker valve 420 is positioned between the second port 214 of the housing 210 and the second port 234 of the primary hydraulic machine 230.

[0148] The system also includes two calibrated valves or amplification valves, respectively 430 and 440. In the illustrated example, these valves 430 and 440 are independent. Alternatively, these valves 430 and 440 can be mechanically linked.

[0149] The first amplification valve 430 is typically a slide valve, adapted to selectively connect the first port 312 of the first hydraulic machine 310 either to the first port 212 of the casing 210, or to the second port 214 of the casing 210, typically to the one of said ports 212 and 214 having the highest pressure. The first amplification valve 430 is by default in a non-passing configuration. It has a calibration, so that it is only passing when the pressure difference between the first orifice 212 of the casing 210 and the second orifice 214 of the casing 210 exceed a calibration value or engagement value.

[0150] The second amplification valve 440 is typically a slide valve, adapted to selectively connect the second port 314 of the first hydraulic machine 310 and the first port 322 of the second hydraulic machine 320 either to the first port 212 of the casing 210, or to the second port 214 of the casing 210, typically to the one of said ports 212 and 214 having the lowest pressure. The second amplification valve 440 is by default in a non-passing configuration. It has a calibration, so that it is only passable when the pressure difference between the first port 212 of the casing 210 and the second port 214 of the casing 210 exceeds said calibration value or engagement value.

[0151] The second port 324 of the second hydraulic machine 320 is connected to the first port 232 and to the second port 234 of the primary hydraulic machine 230 by a high pressure selector 450, adapted to connect the second port 324 of the second hydraulic machine 320 to the port of the primary machine 230 having the highest pressure.

[0152] This system structure allows for reversible operation, as described below.

[0153] A first operating mode of the system is described, corresponding to a traction mode according to a first direction of circulation which can be described as forward. In this embodiment, the first orifice 212 of the casing 210 is supplied by the hydraulic energy source 100 and therefore defines the high pressure intake, while the second orifice 214 of the casing 210 defines the low pressure discharge. The primary hydraulic machine 230 has a motor operation. The circuit breaker valves 410 and 420 are open; the primary hydraulic machine 230 is therefore supplied directly by the hydraulic energy source 100. When the pressure difference between the first orifice 212 of the casing 210 and the second orifice 214 of the casing 210 is less than the calibration value or engagement value, the pressure booster 300 is disengaged.

[0154] When the pressure difference between the first port 212 of the casing 210 and the second port 214 of the casing 210 exceeds the setting value, the amplification valves 430 and 440 are actuated. The first port 312 of the first hydraulic machine 310 is then connected to the first port 212 of the casing 210, while the second port 314 of the first hydraulic machine 310 and the first port 322 of the second hydraulic machine 320 are connected to the second port 214 of the casing 210. The circuit breaker valve 410 is then tilted so that it is no longer open. This configuration is shown in FIG. 8.

[0155] In this configuration, we then find the operation presented with reference to figure 3; the high pressure selector 450 ensures that the pressure delivered by the second hydraulic machine 320 is delivered to the inlet of the primary hydraulic machine 230, that is to say here its first orifice 232. The pressure P2 is isolated from the hydraulic circuit due to the switching of the circuit breaker valve 410 into its non-passing configuration.

[0156] The circuit breaker valves 410 and 420 are then controlled to switch to their on-off configuration when the pressure difference between the first orifice 212 of the casing 210 and the second orifice 214 of the casing 210 falls below the calibration value or engagement value, or for example when the flow rate at the first orifice 212 of the casing 210 or at the second orifice 214 of the casing 210 exceeds a threshold value, or when the rotation speed of the primary hydraulic machine 230 exceeds a threshold value, which disengages the pressure booster 300.

[0157] In a situation of operation in the same direction but in the event of braking or holding, the high pressure and low pressure branches of the hydraulic circuit are reversed.

[0158] The high pressure branch of the circuit is established at the second port 234 of the primary hydraulic machine 230, which is therefore connected to the second port 324 of the second hydraulic machine 320 via the high pressure selector 450.

[0159] If the pressure difference between the first orifice 212 of the casing 210 and the second orifice 214 of the casing 210 is less than the calibration value or engagement value, the amplification valves 430 and 440 are non-passing, and the pressure booster is disengaged.

[0160] If the pressure difference between the first port 212 of the casing 210 and the second port 214 of the casing 210 is greater than or equal to the calibration value or engagement value, the amplification valves 430 and 440 are open. The first port 312 of the first hydraulic machine 310 is then connected to the second port 214 of the casing 210, while the second port 314 of the first hydraulic machine 310 and the first port 322 of the second hydraulic machine 320 are connected to the first port 212 of the casing 210. The circuit breaker valve 420 is then switched so as to no longer be open. This configuration is shown in FIG. 9.

[0161] In this operation, the first hydraulic machine 310 is supplied by the pressure PI at the second orifice 214 of the casing 210. It drives the second hydraulic machine 320, which delivers a pressure P2 such that P2 > PI at its second orifice 324 due to the ratio between the displacements of these two hydraulic machines 310 and 320. This pressure P2 is applied to the second orifice 234 of the primary hydraulic machine 230, which accentuates the retaining effect. This pressure P2 is isolated from the rest of the hydraulic circuit due to the switching of the circuit breaker valve 420 into its non-passing configuration.

[0162] The system as presented is fully reversible, and can therefore also operate in the opposite direction for example reverse drive, whether in traction or in restraint, with or without engagement of the pressure lifter 300.

[0163] Figure 10 shows another example system according to one aspect of the invention.

[0164] In this embodiment, the pressure lifter 300 is associated with a plurality of valves and members making it possible to ensure commissioning automatic pressure lift 300 when the pressure in the hydraulic circuit exceeds a pressure threshold value.

[0165] In this embodiment, the pressure elevator 300 has a structure similar to that already described with reference in particular to FIG. 3.

[0166] In this embodiment, the valves 410 and 420 (previously shown in Figures 7, 8 and 9) are replaced by calibrated non-return valves with piloted chambers.

[0167] The first port 212 and the second port 214 of the housing 210 are connected in parallel to a high pressure selector 460 and to a low pressure selector 470.

[0168] The low pressure selector 470 is connected to the second port 314 of the first hydraulic machine 310 and to the first port 322 of the second hydraulic machine 320.

[0169] The high pressure selector 460 is connected to a pilot valve 480, as well as to a sequence valve 485 and to a first restriction 488. The first restriction 488 is connected to a relief valve 490 adapted to perform a relief when the pressure exceeds a relief threshold value, and is also connected to a hydraulic pilot line of the sequence valve 485, as well as to a hydraulic pilot line of the pilot valve 480 via a second restriction 492.

[0170] The sequence valve 485 connects the high pressure selector 460 to the first port 312 of the first hydraulic machine 310 of the pressure elevator 300.

[0171] The pilot valve 480 is connected on the one hand to the piloted chambers of the calibrated non-return valves 410 and 420, and on the other hand to the second orifice 324 of the second hydraulic machine 320.

[0172] The second port 324 of the second hydraulic machine 320 is also connected to the high pressure selector 450 and to a pressure relief valve 495. The high pressure selector 450 is connected to the two ports 232 and 234 of the primary hydraulic machine 230. It is adapted to connect the second port 324 of the second hydraulic machine 320 to the port of the primary machine 230 having the highest pressure.

[0173] The pilot valve 480 is configured to selectively connect the piloted chambers of the calibrated non-return valves 410 and 420 either to the high pressure selector 460 or to the high pressure selector 450 connected to the second port 324 of the second hydraulic machine 320. By default, the pilot valve 480 connects the piloted chambers of the calibrated non-return valves 410 and 420 to the second port 324 of the second hydraulic machine 320. When the pressure at the high pressure selector 460 exceeds by a certain threshold (determined by the stiffness of the elastic return means of the pilot valve 480) the value of the pressure at the second restriction 492 on the side of the pilot chamber 480, the latter switches to its configuration in which it connects the piloted chambers of the calibrated non-return valves 410 and 420 to the high pressure selector 460.

[0174] The sequence valve 485 is by default non-passing. It becomes passable when the difference between the pressure at its inlet and the pressure delivered to its pilot line at the outlet of the first restriction 488 exceeds a sequence threshold value. This sequence threshold value is reached when the discharge valve 490 becomes passable (because then a flow passes into the first restriction 488 thus creating a pressure difference at its terminals, the lowest pressure being at the terminal connected to the discharge valve 490). The discharge valve 490 thus determines by its setting (typically by means of a calibrated spring) the pressure value from which the sequence valve is engaged, and thus the pressure value from which the pressure booster 300 is supplied. The setting of the discharge valve 490 can be adjustable or fixed.

[0175] A first mode of operation of this system is now described, corresponding to a mode of operation in a first direction of operation, without pressure increase. This mode of operation corresponds to the configuration shown in Figure 10.

[0176] The hydraulic power source 100 delivers a supply pressure PI to the first port 212 of the casing 210.

[0177] The high pressure selector 460 then connects the pilot valve 480, the first restriction 488 and the sequence valve 485 to the first port 212 of the housing 210. The low pressure selector 470 connects the second port 314 of the first hydraulic machine 310 and the first port 322 of the second hydraulic machine 320 to the second port 214 of the housing 210.

[0178] The pressure PI as considered here is lower than the set pressure of the relief valve 490. The sequence valve 485 is in its non-passing configuration.

[0179] The pilot valve 480 is in its default configuration. It connects the piloted chambers of the calibrated check valves 410 and 420 to the second port 324 of the second hydraulic machine 320, to the pressure limiter 495 and to the high pressure selector 450.

[0180] The pressure lift 300 is therefore not put into operation.

[0181] The pressure PI delivered by the hydraulic energy source 100 supplies the primary hydraulic machine 230 via its first orifice 232. In addition, the pressure PI controls the controlled chambers of the calibrated non-return valves 410 and 420 via the high pressure selector 450. The calibrated non-return valve 420 is thus open, so as to allow the discharge of the primary hydraulic machine 230 towards the second orifice 214 of the casing 210.

[0182] A second mode of operation of this system is now described with reference to Figure 11, corresponding to a mode of operation in a first direction of operation, with pressure increase. The differences with the first mode of operation are described below.

[0183] In this second operating mode, the hydraulic energy source 100 delivers a pressure PI, greater than the setting pressure of the relief valve 490.

[0184] The discharge valve 490 is thus open, and discharges the excess pressure in the reservoir R, a flow of fluid therefore passes through this valve 490. This fluid flow generates a pressure drop in the first restriction 488 and therefore a pressure difference at its terminals (the lowest pressure being at the level of the relief valve 490).

[0185] The sequence valve 485 then switches to its on-off configuration when the difference between the pressure at its inlet and its pilot pressure exceeds the setting value applied by a return element, typically of the order of a few bars, for example 4 bars.

[0186] Likewise, the pilot valve 480 switches to its configuration in which it connects the piloted chambers of the calibrated non-return valves 410 and 420 to the high pressure selector 460 when the pressure difference between the pressure PI delivered by the hydraulic energy source 100 and the pilot pressure at the second restriction 492 exceeds a calibration value applied by the elastic return means to the pilot valve 480, typically of the order of a few bars, for example 4 bars.

[0187] The pressure booster 300 is supplied via the first orifice 312 of the first hydraulic machine 310. The latter operates as a motor, and drives the second hydraulic machine 320 in rotation, the inlet 322 of which is connected to the discharge 314 of the first hydraulic machine 310. As already described previously, due to the ratio between the cylinder capacities C1 and C2 of the first hydraulic machine 310 and the second hydraulic machine 320, the pressure delivered by the second hydraulic machine 320 to its second orifice 324 is a pressure P2 such that P2 > P1. The pressure limiter 495 defines a maximum pressure P2max, beyond which the excess pressure is returned to the return line of the hydraulic circuit.

[0188] The pressure P2 supplies the primary hydraulic machine 230 via the high pressure selector 450. The latter is in the configuration connecting the second port 324 of the second hydraulic machine 320 to the first port 232 of the primary hydraulic machine 230 due to the pressure increase, as described previously.

[0189] The calibrated non-return valve 410 is non-passing, its controlled chamber being at pressure PI while pressure P2 is applied to the first orifice 232 of the primary hydraulic machine 230.

[0190] The primary hydraulic machine 230 discharges the flow which feeds it via its second orifice 234 towards the second orifice 214, this flow passing through the calibrated non-return valve 420 which is itself passing due to the pressure PI applied to its controlled chamber.

[0191] It is therefore understood here that when the pressure delivered by the hydraulic energy source 100 exceeds a pressure threshold value, the proposed system automatically switches to an operating mode putting the pressure booster 300 into operation.

[0192] When the pressure delivered by the hydraulic energy source 100 decreases and falls below said pressure threshold value, the system switches to its first operating mode as described previously.

[0193] The system as presented is reversible. Thus, the two operating modes described with reference to figures 10 and 11 can also be applied for operation in the opposite direction, the high pressure selector 450, the high pressure selector 460 and the low pressure selector 470 allow inversion of the system while maintaining an unchanged operating principle.

[0194] The system as proposed also allows operation in hydrostatic braking or in restraint. Such operation is shown in Figures 12 and 13, respectively showing the cases in which the pressure lifter 300 is not engaged, and in which the pressure lifter 300 is engaged.

[0195] Figure 12 shows a configuration similar to that already described with reference to Figure 10, but in which the high pressure and low pressure branches of the hydraulic circuit are reversed. In a holding or braking operation, the primary hydraulic machine 230 operates as a pump; its inlet port 232 is at low pressure, while its discharge port 234 is at high pressure. Similarly, the first port 212 of the casing 210 is at a low pressure, and the second port 214 of the casing 214 is at high pressure. The operation of the system compared to that already described with reference to FIG. 10 remains unchanged. The high pressure selector 450, the high pressure selector 460 and the low pressure selector 470 ensure a reversal of the hydraulic connections to maintain an operation as already described with reference to FIG. 10.

[0196] More specifically, in this operating mode, the hydraulic energy source 100 no longer delivers power. The primary hydraulic machine 230 performs a hydraulic pump function. It delivers a pressurized flow which is applied to the controlled chambers of the calibrated non-return valves 410 and 420 via the high pressure selector 450 so that they are open.

[0197] The high pressure selector 460 and the low pressure selector 470 ensure that the high pressure line is connected in particular to the first restriction 488. As long as the pressure remains lower than the setting pressure of the relief valve 490, the pressure booster 300 is disengaged as already described with reference to FIG. 10.

[0198] Figure 13 shows a configuration for a restrained operation with the pressure lifter 300 in operation. As already described with reference to Figure 11, the pressure lifter is put into operation when the pressure at the relief valve 490 exceeds its set pressure, and the difference between the pressure at the inlet of the sequence valve 485 and the pressure between the first restriction 488 and the second restriction 492 exceeds the set value defined by the elastic return means of the sequence valve 485.

[0199] The sequence valve 485 then becomes open, which allows the rotation of the first hydraulic machine 310 and the second hydraulic machine 320 of the pressure elevator 300, allowing fluid to circulate at the first orifice 312 of the first hydraulic machine 310. The valve 480 changes position to connect the highest system pressure PI to the pilot chamber of the piloted valves 410 and 420.

[0200] Transiently, the first hydraulic machine 310 is rotated by sucking oil from its orifice 312 and discharging this oil to the orifice 314. This, in motor operation, drives the second hydraulic machine 320 into rotation, which then starts to operate as a pump discharging its oil to the orifice 324. This discharge causes the pressure to rise at the second orifice 234, the conduit at this orifice seeing the two hydraulic machines 230 and 320 discharging towards it in pump mode. The valve 420, the pilot chamber of which has been set to the highest system pressure PI by means of the high pressure selector 460, closes and becomes non-passing. The valve 410 is maintained in its passing position thanks to the pilot chamber connected to the pressure PI.

[0201] Due to the closure of the valve 420, the second hydraulic machine 320 is then supplied via its second orifice 324 by the pressure delivered by the primary hydraulic machine 230. It drives the rotation of the first hydraulic machine 310 which, due to its greater displacement, performs an additional braking function. This braking will cause a rise in pressure at the second orifice 324 of the second hydraulic machine 320 (which here forms its inlet), and therefore at the second orifice 234 of the primary hydraulic machine 230 (which here forms its discharge), which amplifies the pressure difference across the terminals of the primary hydraulic machine 230 and therefore the braking or restraining effect.

[0202] The fluid delivered by the first hydraulic machine 310 is then routed via the high pressure selector 460 to the second port 214 of the casing 210.

[0203] The traction or restraint operation thus makes it possible to automatically engage the pressure booster 300 as soon as the pressure difference at the terminals of the primary hydraulic machine 230 exceeds a threshold value.

[0204] As with traction operation, it is understood that braking or holding operation is reversible. Thus, the two operating modes described with reference to Figures 12 and 13 can also apply for reverse operation, the high pressure selector 450, the high pressure selector 460 and the low pressure selector 470 allow inversion of the system while maintaining an unchanged operating principle.

[0205] Alternatively, the relief valve 490 may be an electrically controlled valve. The setting of the relief valve 490 may thus be controlled and modified, and the opening of the relief valve 490 may be controlled. Alternatively, it may be chosen that the setting of the relief valve 490 may be adjustable by hydraulic or mechanical action.

[0206] Alternatively, the relief valve 490 can be connected at its outlet with a 2-position, 2-port distributor which makes it possible to obstruct the link to a low-pressure enclosure (crankcase or tank) and to prevent any activation of the pressure lifter 300 when this link is cut.

[0207] Alternatively, a 2-position, 2-port distributor may be mounted in parallel with the relief valve 490, so as to allow forcing the pressure booster 300 into service by forcing a leak.

[0208] As described above, the opening of the relief valve 490 controls the activation of the pressure booster 300. Thus, controlling the relief valve 490, for example using an electrical control, makes it possible to control the activation of the pressure booster 300.

[0209] Figure 14 shows another exemplary embodiment of a system according to one aspect of the invention.

[0210] Unlike the variant described previously with reference to Figures 10 to 13, this variant is a variant controlled for example using electrical controls or actuators. Thus, the commissioning or not of the pressure lifter 300 can here be chosen by a user or via a controller.

[0211] In this embodiment, we find the valves 410 and 420 which are here for example solenoid valves. It is understood that this embodiment is not limiting, and that the valves presented as solenoid valves, in particular the 410, 420 and / or 500 valves may be hydraulically piloted valves, typically displacement slide valves.

[0212] The ports 212 and 214 of the casing 210 are each connected on the one hand to the low pressure selector 470, and on the other hand respectively to one of the valves 410 and 420.

[0213] The valve 410 makes it possible to connect the first port 212 of the casing 210 as well as the low pressure selector 470 either to the first port 232 of the primary hydraulic machine 230, or to the first port 312 of the first hydraulic machine 310 of the pressure lifter 300. In its default configuration, the valve 410 connects the first port 212 of the casing 210 either to the first port 232 of the primary hydraulic machine 230.

[0214] The valve 420 makes it possible to connect the second port 214 of the casing 210 as well as the low pressure selector 470 either to the second port 234 of the primary hydraulic machine 230, or to the first port 312 of the first hydraulic machine 310 of the pressure lifter 300. In its default configuration, the valve 420 connects the second port 214 of the casing 210 either to the second port 234 of the primary hydraulic machine 230.

[0215] The low pressure selector 470 connects the pressure booster 300, in particular the second port 314 of the first hydraulic machine 310 and the first port 322 of the second hydraulic machine 320 to the port among the first port of the casing 212 and the second port of the casing 214 having the lowest pressure. The low pressure selector 470 is also connected to a pressure limiter 495 adapted to perform a pressure limiting function in the circuit. The two ports 232 and 234 of the primary hydraulic machine 230 are connected to the pressure limiter 495 via a high pressure selector 450 which makes it possible to ensure a safety function in the very high pressure branch.

[0216] A selection drawer 500 makes it possible to connect the second port 324 of the second hydraulic machine 320 either to the first port 232 or to the second port 234 of the primary hydraulic machine 230, which thus makes it possible to select the terminal of the primary hydraulic machine 230 whose pressure you want to increase.

[0217] A first operating mode is now described with reference to FIG. 14, corresponding for example to operation in forward traction, without putting the pressure lifter 300 into service.

[0218] The hydraulic power source 100 delivers a supply pressure PI to the first port 212 of the casing 210.

[0219] The valve 410 and the valve 420 are in their default configuration. The pressure PI thus supplies the first port 232 of the primary hydraulic machine 230. The fluid at the discharge 234 of the primary hydraulic machine 230 passes through the valve 420 to reach the second port 214 of the casing 210.

[0220] The pressure lifter 300 is connected to the second port 214 of the casing 210 and is not powered. The primary hydraulic machine 230 is thus powered directly by the hydraulic energy source 100.

[0221] A second operating mode is now described with reference to FIG. 15, corresponding for example to operation in forward traction, with commissioning of the pressure lifter 300.

[0222] In this operating mode, the control of the valve 410 is actuated. The pressure PI delivered by the hydraulic energy source 100 thus supplies the first orifice 312 of the first hydraulic machine 310. The latter has a motor operation, and drives the second hydraulic machine 320 in rotation. The latter is supplied via the discharge of the first hydraulic machine 320, and due to the ratio between the cylinder capacities, can deliver a pressure P2 > PI.

[0223] The pressure P2 is applied to the first port 232 of the primary hydraulic machine 230 via the selection slide 500 whose control is actuated. The discharge from the primary hydraulic machine 230 passes through its second port 234, and via the valve 420. The excess fluid from the second port 314 of the first hydraulic machine 310 of the pressure elevator 300 in the circuit passes through the low pressure selector 470 to reach the second orifice 214 of the casing 210.

[0224] It is thus understood that the pressure lifter is engaged by activating the valve 410. Conversely, the pressure lifter 300 can be disengaged by ceasing to control the valve 410.

[0225] The system presented can also perform a holding or braking function. This operation is detailed with reference to Figure 16.

[0226] In such operation, the primary hydraulic machine 230 is driven in rotation; it therefore has a pump operation. It delivers a pressure PI to its second orifice 234, which is discharged via the valve 420 by the second orifice 214 of the casing 210.

[0227] The selection slide 500 is actuated so that the port 324 of the pressure lifter is connected to the port 232 of the primary hydraulic machine so that the pump part of the pressure lifter delivers to the port 232 through which the primary hydraulic machine 230 is supplied.

[0228] For hold operation, the pressure rise function can be engaged by piloting valve 420 and returning selection spool 500 to its default configuration. Such a configuration is shown in Figure 17.

[0229] The valve 420 thus closes the discharge through the second orifice 234 of the primary hydraulic machine 230. The flow passes through the selection slide 500 to supply the second hydraulic machine 320 through the second orifice 324 of the second hydraulic machine 320, which operates as a motor and drives the first hydraulic machine 310 in rotation. The first hydraulic machine 310 then operates as a pump, and due to the difference in displacement with the second hydraulic machine 320, amplifies the pressure at the orifice 324 of the second hydraulic machine 320, and therefore at the discharge at the orifice 234 of the primary hydraulic machine 230. This increase in pressure amplifies the pressure difference across the terminals of the primary hydraulic machine 230, and therefore amplifies the braking or holding torque.

[0230] As before, controlling valve 420 allows switching to an operating mode without pressure increase.

[0231] The system as proposed is reversible, whether in traction or in retention. The operation is similar to the operation described with reference to figures 14 to 17, with inversion of the high pressure and low pressure branches at the ports 212 and 214 of the casing 210.

[0232] Figure 18 shows another embodiment of a system according to one aspect of the invention.

[0233] This embodiment includes various elements already described with reference in particular to figures 10 to 13.

[0234] In this embodiment, the pressure lifter 300 is of the 4-line type, as already described in particular with reference to FIG. 5.

[0235] This 4-line pressure lifter structure 300 requires duplicating the sequence valve 485. Thus, two sequence valves 485a and 485b are respectively connected to the first port 312 and the second port 314 of the first hydraulic machine 310, these two sequence valves 485a and 485b having an operation identical to the sequence valve 485 described previously. The two sequence valves 485a and 485b typically have the same setting. This setting may be fixed, or may be adjustable by means of a control, for example an electrical control.

[0236] The operation is essentially similar to that already described with reference in particular to figures 10 to 13.

[0237] When the pressure delivered by the hydraulic energy source 100 is lower than the setting pressure of the relief valve 490, the two sequence valves 485a and 485b are not open, and the pressure booster 300 is therefore not put into operation.

[0238] The primary hydraulic machine 230 is supplied via the valves 410 and 420 which are pass-through, either due to the direction of circulation of the fluid, or due to the control of their controlled chambers.

[0239] When the pressure delivered by the hydraulic energy source 100 is greater than the setting pressure of the discharge valve 490, the latter becomes open and discharges into the reservoir R.

[0240] The opening of the relief valve 490 causes a flow rate to pass through the restriction 488, thus creating a pressure drop generating a pressure difference at its terminals; the pressure downstream of the restriction, which is the lowest, allows the sequence valves 485a and 485b to open, which are then open, so as to allow the supply and discharge of fluid by the first hydraulic machine 310 of the pressure lifter 300. As already described previously, the first hydraulic machine 310 then operates as a motor to drive the second hydraulic machine 320, which operates as a pump, and which can deliver a pressure P2>P1 due to the ratio of the displacements between the first hydraulic machine 310 and the second hydraulic machine 320. The pressure P2 is then delivered to the primary hydraulic machine 230.

[0241] The operation in braking or holding mode is also similar to that already described with reference to Figures 12 and 13, except that the two sequence valves 485a and 485b are controlled simultaneously.

[0242] Figure 19 shows another embodiment of a system according to one aspect of the invention.

[0243] This variant is a piloted variant, with a 300 pressure lift of the 4-line type.

[0244] In the same way as for figures 14 to 17, in this embodiment, we find the valves 410 and 420 which are here for example solenoid valves, and which make it possible to connect the primary hydraulic machine 230 either to the hydraulic energy source 100, or to the pressure elevator 300.

[0245] The system can thus isolate the pressure lifter 300, for example by positioning it in a closed loop so that the pressure lifter 300 is in a freewheel configuration. The valves 410 and 420 can be controlled so that the hydraulic energy source 100 supplies the first hydraulic machine 310 at a pressure P1. The latter rotates the second hydraulic machine 320, and delivers a low pressure to the hydraulic energy source 100. The second hydraulic machine 320 delivers a pressure P2>P1 due to the ratio between the displacements of the first hydraulic machine 310 and the second hydraulic machine 320, which supplies the primary hydraulic machine 230. The second hydraulic machine 320 then forms a closed circuit with the primary hydraulic machine 230, the very high pressure P2 is thus confined in the casing 210.

[0246] The proposed system can also have a holding or braking operation, with or without activation of the pressure booster 300 via the control of the valves 410 and 420, in a similar manner in particular to the embodiment described with reference to figures 16 and 17.

[0247] Figure 20 schematically represents an example of a hydraulic circuit or hydraulic system according to one aspect of the invention.

[0248] This figure shows a hydraulic energy source 100 and the hydraulic actuator 230, here represented as being a drive member for a wheel. It is understood that this embodiment is not limiting, and that the hydraulic actuator 230 can be any hydraulic member, in particular one or more rotational or translational drive members such as bidirectional hydraulic cylinders.

[0249] The hydraulic energy source 100 is adapted to deliver pressure in the hydraulic circuit. It may for example comprise a flow source 100 as described above, for example a hydraulic pump in an open loop or closed loop circuit, or a hydraulic accumulator.

[0250] Block 3000 designates a pressure adaptation module.

[0251] The pressure adaptation module 3000 is adapted to modify the pressure difference across the hydraulic actuator 230 so as to that the pressure difference across the hydraulic actuator 230 is different from the pressure difference across the hydraulic energy source 100.

[0252] The pressure adaptation module 3000 can thus be a pressure booster, adapted so that the pressure difference across the terminals of the hydraulic actuator 230 is greater than the pressure difference across the terminals of the hydraulic energy source 100.

[0253] Conversely, the pressure adaptation module 3000 can thus be a pressure reducer, adapted so that the pressure difference across the terminals of the hydraulic actuator 230 is lower than the pressure difference across the terminals of the hydraulic energy source 100.

[0254] The pressure adaptation module 3000 typically comprises a pressure booster 300 as described above, or according to any other suitable architecture or structure, as well as, where appropriate, a set of valves, flaps, slides and hydraulic components suitable for ensuring control of the circuit.

[0255] The pressure adaptation module 3000 and the hydraulic actuator 230 typically define a drive member 200 as described previously.

[0256] The pressure adaptation module 3000 and the hydraulic actuator 230 are typically housed in the same housing 210 as described previously.

[0257] We now describe the hydraulic pipes or lines connecting these elements.

[0258] The circuit as presented includes - a first supply line 132 connecting a first terminal of the hydraulic energy source 100 to a first terminal of the pressure adaptation module 3000, - a second supply line 134 connecting a second terminal of the hydraulic energy source 100 to a second terminal of the pressure adaptation module 3000, - a first adaptation line 3100 connecting the pressure adaptation module 3000 to one of the terminals of the hydraulic actuator 230 - a second adaptation line 3200 connecting the pressure adaptation module 3000 to the other terminal of the hydraulic actuator 230.

[0259] In this embodiment, the first supply line, the second supply line, the first adapter line, and the second adapter line are distinct. By distinct, it is meant herein that the lines are not directly fluidically connected to each other, and therefore may be at distinct pressures.

[0260] In the circuit as proposed, considering a first operating mode, the hydraulic energy source 100 thus supplies the pressure adaptation module 3000, and the latter then supplies the hydraulic actuator 230. The operating direction of the circuit can be reversed in order to drive the hydraulic actuator 230 in two opposite directions.

[0261] In addition, since the various hydraulic components are typically reversible, the circuit can have a holding operation. In such an operating mode, the hydraulic actuator 230 delivers hydraulic energy and supplies the hydraulic energy source 100 via the pressure adaptation module 3000. The pressure adaptation module 3000 amplifies the pressure difference across the terminals of the hydraulic actuator 230 so as to amplify the holding effect, regardless of the direction of operation.

[0262] Such a circuit thus makes it possible to achieve 4-quadrant type operation as described previously.

[0263] The circuit as proposed can thus present: - a first operating mode, in which the hydraulic actuator 230 is powered so as to deliver mechanical power in a first operating direction, - a second operating mode, in which the hydraulic actuator 230 delivers hydraulic power according to the first operating direction, - a third operating mode, in which the hydraulic actuator 230 is powered so as to deliver mechanical power according to a second direction of operation opposite to the first direction of operation, and - a fourth operating mode, in which the hydraulic actuator 230 delivers hydraulic power according to the second operating direction.

[0264] Figure 21 schematically represents a variant of the circuit already described with reference to Figure 20.

[0265] In this embodiment, the circuit comprises: - a first branch line 142 connecting a first terminal of the hydraulic energy source 100 to the first terminal of the hydraulic actuator 230, and - a second branch line 144 connecting a second terminal of the hydraulic energy source 100 to the second terminal of the hydraulic actuator 230.

[0266] The first bypass line 142 and second bypass line 144 are typically provided with sealing means adapted to selectively seal said first bypass line 142 and second bypass line 144. In the illustrated example, these sealing means are designated by the references 143 and 145 respectively.

[0267] The bypass lines 142 and 144 thus make it possible to connect the hydraulic actuator 230 directly to the hydraulic energy source 100, bypassing the pressure adaptation module 3000.

[0268] The embodiments presented in Figures 20 and 21 contain the various elements already described with reference to the previous figures.

[0269] The system as presented in the various examples thus makes it possible to achieve an increase or rise in the pressure at the terminals of the primary hydraulic machine 230 without requiring an oversizing of the hydraulic circuit or an increase in the pressure in the entire circuit. The pressure booster 300 as presented makes it possible to obtain a pressure difference between the two orifices 232 and 234 of the primary hydraulic machine 230 which is greater than the pressure difference between the two orifices 212 and 214 of the casing 210.

[0270] Such local amplification of the pressure in the circuit thus makes it possible to obtain the following various advantages.

[0271] The primary hydraulic machine 230 can have a lower displacement for the same delivered torque, without requiring the entire hydraulic circuit to be sized to be subjected to higher pressure. The crossing capacity is thus increased without oversizing the circuit.

[0272] To obtain the same pressure and with a primary hydraulic machine of a given cylinder capacity, the hydraulic energy source 100 can then be undersized compared to a circuit without a pressure booster 300.

[0273] Furthermore, the use of a 230 primary hydraulic machine as a motor with a reduced displacement has a beneficial impact in terms of efficiency, whether the pressure raising function is engaged or not.

[0274] The system as proposed can, for example, be used in a machine, a vehicle, a construction machine, an agricultural machine, or any other equipment that can be equipped with a hydraulic drive member as proposed.

[0275] For example, such a machine may be equipped with such a system for all or part of the movement members, for example at each wheel, or on one or more axles to drive several wheels of the same axle with a single system, for example the rear axle only, the front axle only, or even at each of the wheels of the front axle or on each of the wheels of the rear axle.

[0276] Such a machine may have a circuit enabling automatic engagement of the pressure lift on the moving parts or wheels that require additional torque. This automatic activation may, for example, be controlled by an electronic control unit, which may, for example, determine activation based on data captured on the machine, or may be derived from the design of the hydraulic machine, which allows this through an appropriate hydraulic circuit.

[0277] Such a machine may have a circuit allowing the controlled engagement of the pressure lift on the wheels that need extra torque. This control is made by the user.

[0278] Considering a machine or a device comprising several drive members according to the invention, the activation of the different drive members can be done independently or combined to initiate the increase in pressure on all the drive members of the same part of the machine.

[0279] 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.

[0280] 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 method.

Claims

Claims

1. Hydraulic circuit for driving a bidirectional hydraulic actuator (200) having two terminals, said circuit comprising - a hydraulic energy source (100) adapted to deliver a flow rate in the hydraulic circuit, - a hydraulic actuator (200), - a pressure adaptation module (3000), - a first supply line (132) connecting a first terminal of the hydraulic energy source (100) to a first port of the pressure adaptation module (3000) - a second supply line (134) connecting a second terminal of the hydraulic energy source (100) to a second port of the pressure adaptation module (3000) - a first adaptation line connecting the pressure adaptation module (3000) to a first terminal of the hydraulic actuator (230) - a second adaptation line connecting the pressure adaptation module (3000) to the other terminal of the hydraulic actuator (230), the pressure adaptation module being adapted to modify the pressure difference across the terminals of the hydraulic actuator (230) so that the pressure difference across the terminals of the hydraulic actuator (230) is different from the pressure difference across the terminals of the hydraulic energy source (100).

2. The circuit of claim 1, wherein the first power supply line, the second power supply line, the first matching line, and the second matching line are distinct.

3. A circuit according to either of claims 1 or 2, wherein said hydraulic circuit is a closed-loop hydraulic circuit.

4. Circuit according to one of claims 1 to 3, further comprising a first bypass line connecting a first terminal of the hydraulic energy source (100) to the first terminal of the hydraulic actuator (230), and a second bypass line connecting a second terminal of the hydraulic energy source (100) to the second terminal of the hydraulic actuator (230), said first bypass line and second bypass line being provided with suitable closing means (143, 145) for selectively closing said first bypass line and second bypass line.

5. Circuit according to one of claims 1 to 4, in which the pressure adaptation module is adapted to allow the reduction of the flow rate passing through the hydraulic actuator (230) so that the flow rate passing through the hydraulic actuator (230) is lower than the flow rate provided by the hydraulic energy source (100).

6. Circuit according to one of claims 1 to 4, in which the pressure adaptation module is adapted to allow the increase of the flow rate passing through the hydraulic actuator (230) so that the flow rate passing through the hydraulic actuator (230) is greater than the flow rate provided by the hydraulic energy source (100).

7. A circuit according to one of claims 1 to 6, wherein the pressure adaptation module (3000) comprises a pressure adapter (300) comprising a first hydraulic machine (310) and a second hydraulic machine (320) rotationally fixed together, said first and second hydraulic machines (310, 320) being configured so that one has a pump operation and the other has a motor operation.

8. The circuit of claim 7, wherein the pressure adapting module (3000) comprises a single pressure adaptor (300).

9. Circuit according to one of claims 7 or 8, in which the first hydraulic machine has a first terminal connected to the first terminal of the hydraulic energy source (100), and a second terminal connected to the second terminal of the hydraulic energy source (100), the second hydraulic machine has a first terminal connected to the first terminal of the hydraulic actuator (230), and a second terminal connected to the second terminal of the hydraulic actuator (230).

10. A circuit according to one of claims 7 or 8, wherein the first hydraulic machine has a first terminal and a second terminal, the second hydraulic machine has a first terminal and a second terminal, the first terminal (312) of the first hydraulic machine is connected to the first terminal of the hydraulic power source (100), the second terminal of the second hydraulic machine is connected to the first terminal of the hydraulic actuator (230), the second terminal of the first hydraulic machine is connected to the first terminal of the second hydraulic machine, and to the second terminal of the hydraulic power source (100).

11. The circuit of claim 10, wherein the second terminal of the first hydraulic machine is connected to the first terminal of the second hydraulic machine, and to the first terminal and the second terminal of the hydraulic power source (100) via a low pressure selector, the low pressure selector typically being housed in a housing of the pressure adaptation module (3000).

12. Circuit according to one of claims 10 or 11, in which the second terminal of the second hydraulic machine is connected to the first terminal and to the second terminal of the hydraulic actuator (230) via a high pressure selector, the high pressure selector typically being housed in a casing of the pressure adaptation module (3000).

13. Circuit according to one of the preceding claims, adapted to present: - a first operating mode, in which the hydraulic actuator (230) is powered so as to deliver mechanical power in a first operating direction, - a second operating mode, in which the hydraulic actuator (230) delivers hydraulic power in the first operating direction, - a third operating mode, in which the hydraulic actuator (230) is powered so as to deliver mechanical power in a second operating direction opposite to the first operating direction, - a fourth operating mode, in which the hydraulic actuator (230) delivers hydraulic power according to the second operating direction.

14. Circuit according to one of the preceding claims, in which the hydraulic actuator is an actuator adapted to carry out a transformation of hydraulic energy into mechanical energy or vice versa, and configured so that an inversion of the pressure difference at its terminals causes a change in actuation direction.

15. A circuit according to any preceding claim, wherein the pressure lifter (300) is configured to be engaged when the the higher of the two pressures between the first supply line (132) and the second supply line (134) exceeds a threshold value.

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