Improved hydrostatic transmission.

Abstract

Improved hydrostatic transmission. System for driving a component (10) by means of a hydraulic circuit, comprising: a hydraulic power source (100) adapted to deliver pressure in the hydraulic circuit, a drive component (200), comprising: a housing (210), having a first port (212) and a second port (214), a primary hydraulic machine (230) housed in the housing (210) and a pressure booster (300) integrated in the housing (210), said pressure booster (300) being adapted to selectively raise the pressure, so that the pressure difference between the two ports (232, 234) of the primary hydraulic machine (230) is greater than the pressure difference between the two ports (212, 214) of the housing (210). Figure for the abstract: Fig. 1.

Description

Description Title of the invention: Improved hydrostatic transmission. Technical field

[0001] — The present invention relates to an improved hydrostatic transmission, in particular for driving axles, moving parts or for the rotational drive of more generic equipment such as a winch, a crusher, a drill. Prior art

[0002] — Hydrostatic transmissions are usually composed of a machine power transformer that converts the mechanical energy supplied by a motor primary, for example a heat engine or an electric motor, into hy- hydraulics distributed by a high-pressure pipe network, to one or more hydraulic motors driving wheels or axles. Motors can in particular be connected to the pump in series or in parallel.

[0003] — This transmission solution, however, has certain limitations, in particular: - In torque density: the pressure of the pipes commonly used being limited to values ​​below 450 bar, the maximum transmissible torque limit is the product of this pressure and the value of the displacement of the hydraulic motors. However, the cylinder capacity value directly impacts the size of the engines, as well as their cost. - In speed: for a pump displacement and a maximum engine speed primary given, a maximum flow rate is defined which then limits the speed of the vehicle.

[0004] This transmission solution typically has two operating modes very distinct: - A mode of operation that we call “work”: the load is im- bearing 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 equipment generic rotating), this particular condition is decisive for the dimen- engine displacement. - A mode of operation that we call “road” for a vehicle or “normal” mode for more generic rotating equipment, especially for the movement of the vehicle or machine between two workplaces: in this, the load is low, and the speed is high. Here we are trying to achieve the highest speed faster which will be limited by the size and bulk of the pumps and / or motors driving the pumps.

[0005] We therefore understand that these two modes of operation constrain the dimen- sioning of the hydraulic circuit; the components must be oversized to provide a power margin that is never used by the driver. Description of the invention In order to respond at least partially to these problems, the present invention relates to a system for driving a member by means of a hydraulic circuit, comprising: a hydraulic energy source suitable for delivering pressure in the hydraulic circuit, a drive unit, 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 power source, the primary hydraulic machine being housed in the housing and having a first port and a second hydraulic machine port, said system being characterized in that the drive member comprises a pressure booster integrated into 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. 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. 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. 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. 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. 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 disengage the pressure lifter when the rotational speed of the primary hydraulic machine exceeds a certain threshold. According to one example, the pressure lifter is adapted to take a flow rate QI and a pressure P1 from the first or second port of the casing, and deliver a flow rate Q2 and a pressure P2 to the first or second port of the primary hydraulic machine, such that Q2 < QI and P2 > PI. According to one example, the primary hydraulic machine may be a hydraulic machine of axial technology, for example having in particular an inclined plate on which the pistons slide. 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. According to one example, the primary hydraulic machine can be of fixed displacement. According to one example, the primary hydraulic machine can be multi-cylinder. According to one example, the primary hydraulic machine can be variable displacement or continuously variable. For example, the pressure lifter is of linear oscillating technology. 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 and the second hydraulic machine having identical displacements, said first and second hydraulic machines being configured such that one has pump operation and the other has motor operation. 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 and the second hydraulic machine having different displacements, said first and second hydraulic machines being configured such that one has pump operation and the other has motor operation. 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 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. Said machines may be hydraulic machines of radial technology, and particularly of multi-lobe cam radial technology. According to one example, the pressure lifter comprises a first hy- hydraulic machine and a second hydraulic machine rotatably connected, the first hydraulic machine and the second hydraulic machine, said first and second hydraulic machines being configured so 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. 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. 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 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. 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 second orifice of the first hydraulic machine, and the second orifice being connected to the internal orifice of the primary hydraulic machine having the highest pressure via conduits arranged in the casing. 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. 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 (100) 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 (100) having the lowest pressure when the pressure difference between the casing orifices exceeds a second calibration threshold value. 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 operating mode, 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, in which - 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 orifice and a second orifice, the first orifice being connected to the second orifice of the primary hydraulic machine, and the second orifice being connected to the first orifice 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. According to one example, the first hydraulic machine and / or the second hydraulic machine are hydraulic machines with radial pistons and multi-lobe cams. In one example, at least one of the first hydraulic machine and the second hydraulic machine is a variable displacement hydraulic machine. According to one example, the system further comprises 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. According to one example, the pressure amplification is controlled by a command external to the drive member. In one example, the primary hydraulic machine is a radial piston, multi-lobe cam hydraulic machine. The present invention 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. The present invention also relates to a drive member as defined above 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 housing 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 into 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 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. [Fig.1] [Fig.1] a schematic view of an exemplary system according to one aspect of the invention. |Fig.2] |Fig.2] represents an exemplary embodiment of a system according to one aspect of the invention. [Fig.3] [Fig.3] represents an exemplary embodiment of a system according to one aspect of the invention. [Fig.4] [Fig.4] represents another exemplary embodiment of a system according to one aspect of the invention. [Fig.5] [Fig.5] represents another exemplary embodiment of a system according to one aspect of the invention. [Fig.6] [Fig.6] represents another exemplary embodiment of a system according to one aspect of the invention. [Fig.7] [Fig.7] represents another exemplary embodiment of a system according to one aspect of the invention. [Fig.8] [Fig.8] represents a particular configuration of [Fig.6]. [Fig.9] [Fig.9] represents a particular configuration of [Fig.6]. Throughout the figures, common elements are identified by identical numerical references. Description of the embodiments A system according to one aspect of the invention is described below with reference to the figures. The circuits shown are simplified diagrams. Thus, various elements such as the feeding means and calibration means are not shown in the figures. However, those skilled in the art will understand that the figures are not limiting, and that the circuits may include such well-known elements. [Fig. 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. The hydraulic circuit as shown comprises a hydraulic energy source 100, for example a pressure source such as a pump or an accumulator, and a drive member 200. The hydraulic energy source 100 is adapted to supply the drive member 200, so that the drive member drives the member 10 in rotation. 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. The hydraulic power 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 power source may also comprise a fixed displacement hydraulic pump | 10 and a prime mover 120 adapted to drive it in rotation at a variable speed. A example of realization is illustrated in [Fig.2]. 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. The pressure elevator 300 is configured to selectively perform a pressure raising or amplifying function. Thus, for an initial pressure P1 at the inlet of the pressure elevator 300, the pressure elevator 300 will deliver a pressure P2 such that P2 > P1. Figures 3 and 4 show two examples of embodiments of the pressure elevator 300. 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. The pressure lifter 300 typically comprises a first hydraulic machine 310 and a second hydraulic machine 320 which are rotationally connected, and configured such that one operates as a pump and the other operates as a motor. In the examples illustrated, the first hydraulic machine 310 operates as a motor, and the second hydraulic machine 320 operates as a pump. By rotationally connected, 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. The first hydraulic machine 310 and the second hydraulic machine 320 are typically formed by the same hydraulic machine comprising two distinct parts. In the example illustrated in [Fig. 3], the first hydraulic machine 310 has a first orifice 312 and a second orifice 314, the first orifice 312 being connected to the first orifice 212 of the casing 210 (that is to say here to the orifice 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 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. In this embodiment, the first hydraulic machine 310 has a cylinder capacity C1 greater than the cylinder capacity 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 may 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. 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. 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 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 referred to as very high pressure, to power the primary hydraulic machine 230. In this embodiment, the pressure increase therefore depends in particular on the ratio between the displacements C1 and C2. More generally, the pressure lifter 300 thus makes it possible to sample a flow rate Q1 and a pressure Pl at an orifice of the casing 210, here the first orifice 212 of the casing 210, and 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 > P1. In the example illustrated in [Fig. 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), 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), 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. In this embodiment, the first hydraulic machine 310 typically has a displacement C1 equal or substantially equal to the displacement C2 of the second hydraulic machine 320. 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. As for the previous embodiment, the pressure elevator 300 thus makes it possible to take a flow rate Q1 and a pressure P1 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. 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. 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. The proposed structure thus makes it possible to achieve an increase in the pressure supplied to the primary hydraulic machine 230, without requiring oversizing of the various components of the hydraulic circuit. 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. [Fig. 5] schematically represents a variant of the invention in which the pressure booster 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 booster can be called a “4-line booster” to distinguish it from the other variants of pressure boosters described which comprise “3 lines”; in particular, a distinction is made between the “3-line booster with common supply” as shown in [Fig. 4] and the “3-line booster with common return” as shown in Figures 3 and 6 to 9. In the example illustrated in [Fig.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). 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. 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. A valve 243 is positioned between the first port 312 of the first hydraulic machine 310 and the hydraulic junction A. A valve 245 is positioned between the second port 314 of the first hydraulic machine 310 and the hydraulic junction B. A valve 247 is positioned between the second port 324 of the second machine hydraulic 320 and hydraulic junction C. A valve 249 is positioned between the first port 322 of the second hydraulic machine 320 and the hydraulic junction D. 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. 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. 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. 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. These valves 243, 245, 247, 249, 251 and 253 can be controlled hydraulically or electrically from inside or outside the casing 210. We now describe an example of traction operation, in a direction of travel that can be described as forward motion. 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. In this case, the first orifice 212 of the casing 210 is supplied by the pressure source 100 and therefore defines the high pressure inlet, while the second orifice 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. 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. As before, the first orifice 212 of the casing 210 is then supplied by the pressure 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 fluid high pressure 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. The pressure difference across the terminals of the first hydraulic machine 310 generates a rotational movement of this first hydraulic machine 310. The second hydraulic machine 320, being rotationally fixed to the first hydraulic machine 310, will operate as a pump to generate a pressure difference across its terminals in such a way as to generate a very high pressure (i.e. a pressure greater than the pressure supplied by the pressure 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. 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). 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. 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. 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. When the pressure lifter 300 is activated (e.g. by the user or the system control unit based on the captured data), valves 251 and 253 are non-passing while valves 243, 245, 247 and 249 are passing. 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 closed state). The pressure difference across the terminals of the second machine 320 causes it to operate as a motor.The second machine 320 which is integral in rotation with the first hydraulic machine 310 causes the latter to work as a pump to exert the retention of 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, through the hydraulic junction B, through the second orifice 214 of the casing 210 (the valve 253 being in a non-passing state) to join the pressure source 100. The line going from the first orifice 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 orifice 212 of the casing 210 and joining the pressure source 100 being at low pressure, . 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. 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. [Fig.6] schematically represents a variant of [Fig.3] to which actuators such as valves have been added to control the activation or not of the pressure elevator 300. As previously, this is a 3-line elevator with common return. 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. 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 command. internal, for example a hydraulic or pneumatic control. 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. 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. 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. 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. [Fig. 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. In this exemplary embodiment, the pressure booster 300 is of the 3-line and common return type similar to that already described with reference to [Fig. 3]. 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. For example, pilot valves can be configured to activate service the pressure lifter 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 lifter when a fluid flow rate at the orifice of the casing 210 forming the fluid inlet exceeds a flow rate threshold value, which reflects movement at high speed.Alternatively or in addition, the system may comprise 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) in such a way that the pilot valves are then controlled to disengage the pressure lifter when the speed measured by the sensor exceeds a certain threshold. 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. 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. The system also includes two calibrated valves or amplification valves, 430 and 440 respectively. The first amplification valve 430 is typically a spool-type 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 passable when the pressure difference between the first port 212 of the casing 210 and the second port 214 of the casing 210 exceeds a calibration value or engagement value. 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, ty- sting to that of said orifices 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 passing when the pressure difference between the first orifice 212 of the casing 210 and the second orifice 214 of the casing 210 exceeds said calibration value or engagement value. 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. This system structure allows for reversible operation, as described below. 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. 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]. In this configuration, we then find the operation presented with reference to [Fig.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. The circuit breaker valves 410 and 420 are then controlled to switch to their passing 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 single value, or when the rotation speed of the primary hydraulic machine 230 exceeds a threshold value, which disengages the pressure riser 300. 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. 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. 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. 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]. In this operation, the first hydraulic machine 310 is supplied by the pressure P1 at the second orifice 214 of the casing 210. It drives the second hydraulic machine 320, which delivers a pressure P2 such that P2 > Pl 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. 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 lift 300. The system as presented in the different examples thus makes it possible to achieve an increase or rise in pressure at the terminals of the hydraulic machine. primary 230 without requiring oversizing of the hydraulic circuit or an increase in pressure in the entire circuit. The pressure booster 300 as presented makes it possible to obtain a pressure difference between the two ports 232 and 234 of the primary hydraulic machine 230 which is greater than the pressure difference between the two ports 212 and 214 of the casing 210. Such local amplification of the pressure in the circuit thus makes it possible to obtain the following various advantages. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. System for driving an organ (10) by means of a circuit hydraulic, including: a hydraulic energy source (100) adapted to deliver a pressure in the hydraulic circuit, a drive member (200), comprising: - a casing (210), having a first orifice (212) and a second crankcase orifice (214) adapted to define an inlet and a re- crankcase crowding (210), - a primary hydraulic machine (230), adapted to be powered by the hydraulic power source (100), the hydraulic machine primary (230) being housed in the casing (210) and having a first orifice (232) and a second orifice (234) of hydraulic machine, said system being characterized in that the drive member (200) comprises a pressure booster (300) integrated in the casing (210), said pressure elevator (300) being adapted to selectively elevate pressure, so that the pressure difference between the two ports (232, 234) of the primary hydraulic machine (230) either su- greater than the pressure difference between the two orifices (212, 214) of the casing (210).

2. The system of claim 1, wherein the pressure lifter (300) is integrated into the housing (210) so that the elevator of pressure (300) is connected to the first port (232) and to the second port (234) from the primary hydraulic machine (230) via formed conduits in the housing (210).

3. System according to one of the preceding claims, in which the pressure lifter (300) is configured to be engaged when the pressure difference between the two orifices (232, 234) of the machine primary hydraulic (230) exceeds a threshold value.

4. System according to one of the preceding claims, comprising in besides at least one valve (242, 244, 246, 430, 440) connecting the elevator of pressure (300) at the first orifice (212) and / or at the second orifice (214) of the casing (210), said at least one valve (242, 244, 246, 430, 440) being configured for, when the pressure difference between the two orifices (212, 214) of the casing (210) is less than or equal to a value pressure threshold, disengaging the pressure elevator (300).

5. The system of one of claims 1 to 4, further comprising at at least one valve (242, 244, 246, 430, 440) connecting the pressure lifter (300) to the first orifice (212) and / or to the second orifice (214) of the casing (210), said at least one valve (242, 244, 246, 430, 440) being configured for, when the rotation speed of the hy- machine primary draulic (230) is greater than a threshold value, disengage the pressure lifter (300).

6. System according to one of claims 1 to 5, in which the elevator of pressure (300) is suitable for sampling a flow rate Q1 and a pressure P1 to the first or second orifice (212, 214) of the casing (210), and deliver a flow rate Q2 and a pressure P2 at the first or second orifice (232, 234) of the primary hydraulic machine (230), such that Q2 < Q1 and P2 >P]l.

7. System according to one of claims 1 to 6, in which the elevator of pressure (300) comprises a first hydraulic machine (310) and a second hydraulic machine (320) integral in rotation, the first hydraulic machine (310) and the second hy- hydraulic (320) having identical cylinder capacities, said first and second hydraulic machines (310, 320) being configured of so that one has a pump operation and the other has an engine operation.

8. The system of claim 7, wherein - the first hydraulic machine (310) has a first orifice (312) and a second orifice (314), the first orifice (312) being selected- tively connected to the casing port (210) having the highest pressure among the two orifices of the casing, and the second orifice (314) being se- selectively connected to the casing port (210) having the highest pressure weak among the two crankcase orifices, - the second hydraulic machine (320) has a first orifice (322) and a second port (324), the first port (322) being connected to the casing orifice (210) having the lower pressure among the two ports of the casing, and the second port (324) being connected to the port (232, 234) of the primary hydraulic machine (230) having the highest pressure raised via conduits arranged in the casing (210).

9. System according to one of claims 1 to 6, in which the elevator of pressure (300) comprises a first hydraulic machine (310) and a second hydraulic machine (320) integral in rotation, the first hydraulic machine (310) having a displacement su- superior to the second hydraulic machine (320), said system being configured so that, for a first mode of operation, the first hydraulic machine (310) has a engine operation, and the second hydraulic machine (320) has a pump operation, said second hy- machine hydraulic (320) powering the primary hydraulic machine (230).

10. | System according to claim 9, wherein - the first hydraulic machine (310) has a first orifice (312) and a second orifice (314), the first orifice (312) being selected- tively connected to the casing port (210) having the highest pressure among the two orifices of the casing, and the second orifice (314) being se- selectively connected to the casing port (210) having the highest pressure weak among the two crankcase orifices, - the second hydraulic machine (320) has a first orifice (322) and a second port (324), the first port (322) being connected to the second port (314) of the first hydraulic machine (310), and the second port (324) being connected to the port of the hydraulic machine primary (230) having the highest pressure among the two ports of the casing via conduits arranged in the casing (210).

11. The system of claim 10, wherein the second orifice (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) via a high pressure selector (450).

12. System according to one of claims 10 or 11, in which the first port (312) of the first hydraulic machine (310) is connected to a first calibrated valve (430), connected on the one hand to the first orifice (212) of casing (210) and on the other hand to the second orifice (214) of housing (210), said first calibrated valve (430) being configured to connect the first port (312) of the first hydraulic machine (310) at the casing port (210) having the highest pressure when the pressure difference between the ports of the casing (210) exceeds a first calibration threshold value, the second port (314) of the first hydraulic machine (310) is connected to a second calibrated valve (440), connected on the one hand to the first orifice (212) of casing (210) and on the other hand to the second orifice (214) of housing (210), said second calibrated valve (440) being configured to connect the first port (312) of the first hydraulic machine (310) at the casing orifice (210) having the lowest pressure when the pressure difference between the ports (212, 214) of the casing (210) exceeds a second calibration threshold value.

13. | System according to one of claims 1 to 6, in which the elevator of pressure (300) comprises a first hydraulic machine (310) and a second hydraulic machine (320) integral in rotation, the first hydraulic machine (310) having a displacement su- superior to the second hydraulic machine (320), said system being configured so that, for a first mode of operation, the first hydraulic machine (310) has a engine operation, and the second hydraulic machine (320) has a pump operation, said second hy- machine hydraulic (320) supplying the primary hydraulic machine (230), in which - the first hydraulic machine (310) has a first orifice (312) and a second port (314), the first port (312) being connected to the first orifice (212) of the casing (210), and the second orifice (314) being connected to the second orifice (214) of the casing (210), - the second hydraulic machine (320) has a first orifice (322) and a second port (324), the first port (322) being connected to the second port (234) of the primary hydraulic machine (230), and the second port (324) being connected to the first port (232) of the machine primary hydraulics (230), the system comprising a valve (251) adapted to selectively insulate the first orifice (212) of the housing (210) from the first orifice (232) of the primary hydraulic machine (230), and a valve (253) adapted for selectively isolating the second port (214) from the housing (210) of the second port (234) of the primary hydraulic machine (230).

14. | System according to one of claims 7 to 13, in which the first hydraulic machine (310) and / or the second hydraulic machine (320) are radial piston and cam hydraulic machines multilobed.

15. System according to one of claims 7 to 14, in which at least one among the first hydraulic machine (310) and the second machine hydraulic (320) is a variable displacement hydraulic machine.

16. | System according to one of the preceding claims, comprising in besides a first valve (410, 251) and a second valve (420, 253), the first valve (410, 251) being adapted to selectively connect or insulate the first port (212) of the casing (210) to the first port (232) of the primary hydraulic machine (230), and the second valve (420, 253) being adapted to selectively connect or isolate the second orifice (214) of casing (210) to the second port (324) of the hy- primary draulics (230).

17. | System according to one of the preceding claims, in which the primary hydraulic machine (230) is a hydraulic machine with radial pistons and multi-lobe cam.

18. Rolling machine comprising at least one displacement member and at least one at least one system according to one of the preceding claims adapted to selectively drive said displacement member in rotation.

19. Drive member (200) adapted to selectively drive in rotating a member (10), the drive member (200), comprising: - a casing (210), having a first orifice (212) and a second crankcase orifice (214) adapted to define an inlet and a re- crankcase crowding (210), - a primary hydraulic machine (230), adapted to be powered by a hydraulic power source (100), the hydraulic machine primary (230) being housed in the casing (210) and having a first orifice (232) and a second orifice (234) of hydraulic machine, said system being characterized in that the drive member (200) comprises a pressure booster (300) integrated in the casing (210), said pressure elevator (300) being adapted to selectively elevate pressure, so that the pressure difference between the two ports (232, 234) of the primary hydraulic machine (230) either su- greater than the pressure difference between the two orifices (212, 214) of the casing (210).

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