FR3136520A1 - improved hydraulic pump for high speed drive - Google Patents

Abstract

Improved hydraulic pump for high-speed drive Assembly comprising a hydraulic pump (100) and an epicyclic gearbox (200), in which the hydraulic pump (100) is a hydraulic pump with radial pistons, the gearbox (200) comprising an external sun gear ( 210), an inner sun gear (220), a planet carrier (230) and a planet gear (240); characterized in that the reducer (200) being housed in the internal volume of the casing (110) of the hydraulic pump (100), the external sun gear (210) of the reducer (200) is integral with the casing (110) of the hydraulic pump (100), the internal sun gear (220) is secured to the shaft (120) of the hydraulic pump (100), and the satellite carrier (230) is secured to the cylinder block (130) of the hydraulic pump (100), so that the reducer (200) applies a reduction ratio between the shaft (120) and the cylinder block (130) of the hydraulic pump (100). Figure for abstract: Fig. 1.

Description

improved hydraulic pump for high speed drive

This presentation concerns the field of hydraulic pumps and motors with radial pistons and multilobe cams.

Multi-lobe cam radial piston hydraulic pumps and hydraulic motors are well-known hydraulic machines commonly used in various hydraulic systems.

A recurring problem with such hydraulic machines with radial pistons and multilobe cam concerns the admissible rotation speeds for such machines. In fact, known hydraulic pumps and motors with radial pistons and multilobe cams have maximum operating speeds of around 1000 revolutions per minute.

Such a limitation in terms of rotation speed is problematic in terms of integration in certain systems, in particular for coupling a hydraulic pump to a diesel or electric type motor whose rotation speeds are very significantly higher, and such hydraulic machines are therefore usually limited to applications having a drive member that is described as slow, such as wind turbines.

Thus, hydraulic machines with radial pistons are commonly used for motor operation, while hydraulic machines with axial pistons are commonly used as pumps. Hydraulic machines with axial pistons work well at relatively high rotation speeds, however with the development of the use of electric motors which can rotate at rotation speeds going beyond 5000 rpm, these types of pumps have high yields. which are not as good as in the rotation speed ranges of combustion engines. By keeping the speed of the multilobe radial piston cam pump below 1000 rpm, good efficiency is maintained by limiting viscous friction and bubbling losses linked to high speed.

It is thus known to associate a reduction gear with a hydraulic pump. The reducer is then usually associated in the axial direction, which is detrimental in terms of axial space requirements.

This presentation therefore aims to respond at least partially to these issues.

For this purpose, the present invention proposes an assembly comprising a hydraulic pump and an epicyclic gearbox,
in which the hydraulic pump is a hydraulic pump with radial pistons and a multilobe cam, comprising a casing defining an internal volume in which are housed a shaft extending in an axial direction, a cylinder block positioned around the shaft and comprising a plurality housings in which pistons are mounted sliding radially relative to the axial direction, and a multilobed cam mounted around the cylinder block 130 and secured to the casing, in which the shaft and the cylinder block define a first set, and the casing and the cam defines a second assembly, the first assembly and the second assembly being mounted movable in rotation relative to each other in the axial direction,
the reduction gear comprising an outer sun gear, an inner sun gear, a planet carrier and one or more planet gears;
characterized in that
the reducer being housed in the internal volume of the hydraulic pump casing,
the external sun gear of the gearbox is integral with the hydraulic pump casing,
the internal sun gear is integral with the shaft of the hydraulic pump, and
the satellite carrier is integral with the cylinder block of the hydraulic pump,
so that the reducer applies a reduction ratio between the shaft and the cylinder block of the hydraulic pump, so that the cylinder block has a rotation speed strictly lower than a rotation speed of the shaft.

According to one example, the external sun gear is formed by teeth formed on an internal surface of the casing.

According to one example, the internal sun gear is formed by teeth formed on an external surface of the shaft.

According to one example, the satellite carrier is formed by a plurality of rods extending from the cylinder block in the axial direction.

According to another example, the outer sun gear of the reduction gear is secured to the cylinder block, the inner sun gear is secured to the shaft, and the planet carrier is secured to the casing.

According to one example, the assembly further comprises a primary motor adapted to rotate the hydraulic pump via the reducer, in which the reducer is configured so that in operation, the rotation speed of the hydraulic pump is lower or equal to 1000 revolutions per minute.

According to one example, the first assembly is movable in rotation relative to a support, and the second assembly is fixed relative to said support.

According to one example, the second assembly is movable in rotation relative to a support, and the first assembly is fixed relative to said support.

According to one example, the hydraulic pump is a multi-displacement pump, comprising means for deactivating part of the lobes of the cam.

According to one example, the hydraulic pump is configured such that the cam and the pistons are configured so as to define a roller trajectory which has a plurality of hollows and peaks, and a plurality of lobes, each lobe being formed between two hollows or two consecutive vertices, each lobe being composed of two half-lobes, the hollows designating the portions of the lobes of the roller trajectory furthest from the axis of rotation, and the vertices being the portions of the lobes of the roller trajectory closest to the axis of rotation, and in which the cylinder block, the pistons and the cam are configured so that for each half-lobe, the flow of fluid displaced by the pistons in contact with half-lobe lobe considered is constant for a constant rotation speed between the first set and the second set.

According to one example, the lobes are grouped so as to form subgroups of at least one lobe defining hydraulic sub-pumps, the hydraulic pump comprising a distributor adapted to selectively supply, in particular distinctly, all or part of said sub-groups .

According to one example, the distributor defines a fluid circulation conduit for each half-lobe of the roller trajectory, said circulation conduits being disjoint and defining a plurality of disjoint intake and discharge conduits, the flow circulating in each of said conduits being constant for a constant rotation speed of the hydraulic pump.

In this presentation, a hydraulic machine means a hydraulic pump or a hydraulic motor, it being understood that such devices have reversible operation.

The invention and its advantages will be better understood on reading the detailed description given below of different embodiments of the invention given by way of non-limiting examples.

There is a sectional view of an assembly according to one aspect of the invention.

There is a sectional view of another example of an assembly according to one aspect of the invention.

There is a sectional view of another example of an assembly according to one aspect of the invention.

There is another sectional view of an example of an assembly according to one aspect of the invention.

There is a curve schematizing the geometry of the lobes (a half-lobe) of the cam of the hydraulic machine according to one aspect of the invention where the ordinate represents the stroke of the piston and the abscissa the angle relative to a point of reference.

There is a curve schematizing the radial speed of a piston as a function of its position in the cylinder block according to one aspect of the invention.

In all of the figures, common elements are identified by identical numerical references.

There is a sectional view of an assembly according to one aspect of the invention, comprising a hydraulic machine 100 and a reduction gear 200.

The hydraulic machine 100 is a radial piston and multi-lobe cam pump.

It comprises a casing 110 defining an internal volume in which a shaft 120 extending in an axial direction Z-Z and a cylinder block 130 are positioned. The cylinder block 130 is mounted to rotate relative to the shaft 120 via a bearing 125, and comprises a plurality of housings 132 in which pistons 140 are mounted sliding radially relative to the axial direction Z-Z. Unlike conventional hydraulic machines, the cylinder block 130 is here movable in rotation relative to the shaft 120 in order to allow a reduction ratio of the rotation speed to be applied between the shaft 120 and the cylinder block 130 as we will describe it later.

The hydraulic machine 100 also includes a multilobed cam 150 positioned around the cylinder block 130. The cam 150 defines a plurality of lobes adapted to cooperate with the pistons 140 during operation of the hydraulic machine 100. The cylinder block 130 is coupled to a distributor 160 defining fluid supply and discharge conduits linked to the different housings 132 in which the pistons 140 slide. The distributor 160 is for example connected to a hydraulic pump via a hydraulic circuit, thus defining conduits forming suction and discharge , which open onto the external surface of the second assembly of the hydraulic machine 100.

We define for the hydraulic machine 100 a first assembly comprising the cylinder block 130, and a second assembly comprising the casing 110 and the cam 150. The first assembly and the second assembly are movable relative to each other in rotation according to the axial direction Z-Z, one of these assemblies being fixed and the other mobile depending on the application considered.

The hydraulic machine 100 is typically reversible. It may operate as a hydraulic pump or hydraulic motor depending on its use, the operation of such a hydraulic machine 100 being well known.

The system as proposed associates a reducer 200 which is integrated into the structure of the hydraulic machine 100.

The reducer 200 is an epicyclic reducer, comprising an outer sun gear 210, an inner sun gear 220, a planet carrier 230 and one or more planet gears 240. The operation of an epicyclic gear reducer is well known and will not be described in detail below. ; we understand that it makes it possible to apply a reduction ratio between the rotation speed of the inner sun gear and the rotation speed of the satellite carrier so that the outer sun gear 210 has a rotation speed strictly greater than a rotation speed of the satellite carrier 230.

The outer sun gear 210 of the reducer 200 is integral with the casing 110 of the hydraulic pump 100. The outer sun gear 210 can thus be formed by a component integral with the casing 110, or be formed by teeth formed on an internal surface of the casing 110.

The inner sun gear 220 is integral with the shaft 120 of the hydraulic pump 100. The inner sun gear 220 can thus be formed by a component integral with the shaft 120, or be formed by teeth formed on an external surface of the shaft 120.

The satellite carrier 230 is integral with the cylinder block 130 of the hydraulic pump 100. The satellite carrier 230 is for example formed by a plurality of rods extending from the cylinder block 130, typically in the axial direction Z-Z, so as to form supports and rotation axes for the satellites 240.

In the example illustrated on the , we thus see that the satellites 240 are mounted to move in rotation around the satellite doors 230 which are formed by rods extending from the cylinder block 130. The satellites 240 cooperate with the external sun gear 210 formed by internal teeth arranged in the casing 110, and with the internal sun gear 220 formed by external teeth fitted on the shaft 120.

The reduction gear 200 as proposed thus applies a reduction ratio between the rotation speed W2 of the shaft 120 and the rotation speed W3 of the cylinder block 130, so that W3 is strictly less than W2.

The reducer 200 is thus housed in the internal volume of the casing 110 of the hydraulic pump 100, which makes it possible to propose a system combining a hydraulic machine 100 and a reducer 200 with minimized bulk.

The system as proposed finds a particular application in the case where the hydraulic machine 100 operates as a hydraulic pump, the shaft 120 of which is then rotated by a primary motor M.

Indeed, as mentioned in the preamble, a problem concerns the driving of hydraulic pumps with radial pistons by means of a motor having a high rotation speed, insofar as the hydraulic pumps with radial pistons have maximum operating speeds. of the order of 1000 revolutions per minute between the cylinder block and the cam.

The present invention thus responds to this problem and proposes a system which makes it possible to drive a hydraulic pump with radial pistons by means of a motor having a high rotation speed, for example a thermal type engine (petrol or diesel). ) or electric, while maintaining good efficiency and minimized bulk due to the integration of the reducer function in the internal structure of the hydraulic machine 100.

Indeed, the shaft 120 is then rotated by the motor, and the gearbox 200 will then apply a reduction ratio so that the cylinder block 130 is driven at a rotation speed W3 lower than the rotation speed W2 of the shaft 120, for example at a rotation speed W3 less than or equal to 1000 revolutions per minute, while the rotation speed W2 of the shaft 120 can be of the order of 2000 revolutions per minute in the case driven by a diesel type engine, or for example between 3000 and 7000 revolutions per minute for drive by an electric motor.

There presents another embodiment of an assembly according to the invention.

In this embodiment, the outer sun gear 210 of the reducer 200 is integral with the cylinder block 130 of the hydraulic pump 100. The outer sun gear 210 can thus be formed by a crown extending from the cylinder block 130 in the axial direction Z-Z, and having teeth on its internal surface.

The inner sun gear 220 is integral with the shaft 120 of the hydraulic pump 100. The inner sun gear 220 can thus be formed by a component integral with the shaft 120, or be formed by teeth formed on an external surface of the shaft 120.

The satellite carrier 230 is integral with the casing 110 of the hydraulic pump 100. The satellite carrier 230 is for example formed by a plurality of rods extending from the casing 110, typically in the axial direction Z-Z, so as to form supports and axes of rotation for the satellites 240.

In operation, the primary motor M rotates the shaft 120. The internal sun gear 220 secured to the shaft then rotates the satellites 240 around the fixed satellite carrier 230. The rotation of the satellites 240 rotates the outer sun gear 210 and therefore the cylinder block 130 of the hydraulic pump 130. The reduction gear 200 therefore also applies in this embodiment a reduction ratio between the rotation speed W2 of the shaft 120 and the rotation speed W3 of the cylinder block 130.

More generally, the reducer 200 applies a reduction ratio between the shaft 120 and the cylinder block 130 so that the relative rotation speed between the cylinder block 130 and the cam 150 remains less than or equal to 1000 revolutions per minute, although the rotation speed of the shaft 120 is greater than 1000 revolutions per minute.

As an example, we can use a primary motor M electric motor having the following characteristics:
- maximum rotation speed: 6500 revolutions per minute.
- maximum torque: 96 Nm.
- power: 18kW.

The reducer 200 can then have the following characteristics:
- Number of teeth of the outer sun gear 210: 67
- Number of teeth of the inner sun gear 220: 11
- Number of teeth of satellite 240: 28
- Module: 2
- Reduction ratio: R=7.1
- Number of satellite gears 240: 3

By associating such an electric primary motor M with such a reduction gear 200, it is possible for example to obtain a rotation speed of the hydraulic pump 100 of 917 revolutions per minute for a rotation speed of the electric motor of 6500 revolutions per minute, and of 423 revolutions per minute for an electric motor rotation speed of 3000 revolutions per minute.

The hydraulic machine 100 is for example a hydraulic machine with a 4-lobe cam with a single displacement and comprising 10 pistons.

The invention thus also makes it possible to reduce the noise level generated during the operation of the hydraulic machine 100, by reducing the rotation speed of the hydraulic machine 100. Furthermore, in the embodiments described all the rotating parts are guided by coaxial bearings, this also contributes to noise reduction.

The invention also makes it possible to optimize the efficiency of the hydraulic machine during its operation as a pump, by allowing its operation in an optimal value range even in the case of being driven by a motor having a higher rotation speed. high.

Optionally, the hydraulic machine can be configured so that during pump operation, the flow rate delivered is reduced. The hydraulic machine then typically has several switchable fixed displacements. To do this, the hydraulic machine is made up of several sub-pumps. If we make the multi-displacement by the cam lobes well known to those skilled in the art; for example, it is possible to deactivate a set of lobes of the cam inside the pump, which will have the effect of deactivating the sub-pump corresponding to this set of lobes by a by-pass or bypass of its supply conduits and repression. The pump thus sees, for the same input shaft speed, its flow rate decrease at its terminals defined by the intake and discharge conduit.

Optionally, the hydraulic pump can be configured so that the flow rate taken by each sub-pump (set of lobes) is constant, or optionally so that the flow rate delivered by each half-lobe of the cam 150 is constant.

We describe below with reference to Figures 3 to 6 a particular embodiment of an assembly according to the invention in which the hydraulic pump has such a characteristic.

Such an embodiment makes it possible to subdivide the pump into several sub-pumps each delivering a constant flow rate for a constant driving speed, which is advantageous in terms of compactness to the extent that a single hydraulic pump can then be used to supply different hydraulic components instead of requiring one hydraulic pump per circuit. The displacements of the sub-pumps can be equal or different. The displacements of two sub-pumps are hydraulically separated. Each flow is independent and isolated from the other flow. The distributor allows you to separate the flow rates. Machine 100 contains as many inputs and outputs as necessary. For example, for a two-displacement pump, the machine 100 can have 1 suction port and two discharge ports, or two suction ports and two discharge ports.

In the example illustrated in particular in Figures 3 and 4, the cylinder block 130 has two rows of pistons 140 in the axial direction, the pistons 140 of the two rows being typically arranged in a staggered manner and distributed in a balanced manner all around the cylinder block ( the angular distance between two pistons always being the same). Thus two adjacent pistons 140 are separated by an angle equal to 360°/NP, NP designating the number of pistons.

Each piston 140 is in contact with cam 150 via a roller. We thus define the construction of the profile of the cam 150 taking into account the radius of the roller. The cam profile 150 is a profile parallel to the profile generated by the trajectory of the centers of the rollers and spaced from this profile by the distance of a roller radius.

We define the profile parallel to a curve as being the profile which for any point of the curve, if we take the tangent at this point to the curve and draw the perpendicular to this tangent we generate a new point of the profile parallel to one side of this curve by placing this point at a distance R (which is the same for the entire generation of the profile) on this perpendicular.

According to an exemplary embodiment, the cam 50 comprises a number NC of lobes, and in which the cylinder block comprises a number of pistons NP such that NP> 2 * NC.

According to an exemplary embodiment, the cam 50 comprises a number NC of lobes, and in which the cylinder block comprises a number of pistons NP such that 2 * NC < NP < 4 * NC.

We now describe an example of a cam structure 150 of such a hydraulic pump.

The cam 150 has a plurality of lobes defining a plurality of hollows and peaks, the pistons 140 being adapted to come into contact with the lobes during operation of the hydraulic machine so as to generate a back and forth movement in the housings 132 of the cylinder block 130. We designate the hollows of the cam profile as being the portions of the lobes of the cam 150 furthest from the axis of rotation Z-Z, and the vertices of the cam profile as being the portions of the lobes of the cam 150 closest to the axis of rotation Z-Z. More generally, the lobes of the cam 150 define undulations in the distance between the cam and the axis of rotation Z-Z, these undulations defining a plurality of local maximums and minimums in terms of distance relative to the axis of rotation Z-Z , which define the troughs and peaks respectively.

In the same way, the roller trajectory therefore also presents a plurality of lobes defining a plurality of hollows and peaks. We designate the troughs of the roller trajectory as being the portions of the lobes of the roller trajectory furthest from the axis of rotation Z-Z, and the peaks of the roller trajectory as being the portions of the lobes of the roller trajectory closest to the axis of rotation Z-Z. More generally, the lobes of the roller path define undulations in the distance between the roller path and the axis of rotation Z-Z, these undulations defining a plurality of local maxima and minima in terms of distance from the axis Z-Z rotation, which define the troughs and peaks respectively.

We represent schematically on the an example of a curve Cg illustrating in dotted lines the trajectory of the roller, that is to say the trajectory of the pistons on a half-lobe of the cam 150, and in solid line a curve Cc the profile parallel to this trajectory which is the profile of the cam that the roller follows. In this figure the radius is on the ordinate, and the abscissa indicates the angular position considered around the axis of rotation ZZ from a point on the cam 150 designated as a reference.

This figure shows schematically a piston 140 coming into contact with the cam. We designate by C the hollow between two lobes and by S the vertex of a lobe, the hollows and the vertices corresponding to reversals of curvature of the surface of the lobe considered. A lobe of the cam 150 is defined as being the portion of the cam 150 between two hollows or two successive peaks. A half-lobe of the cam 150 is thus a portion of the cam between a hollow and a peak, or between a peak and a hollow. In the same way, hollows and peaks corresponding to reversals of curvature of the roller trajectory are defined for the roller trajectory. A lobe of the roller trajectory is defined as the portion of the roller trajectory between two successive troughs or two peaks. A half-lobe of the roller trajectory is thus a portion of the roller trajectory between a hollow and a peak, or between a peak and a hollow.

In the examples shown, the valleys and peaks are points. Alternatively, these may be angular sectors defining a zone in which the piston remains, despite its rotation relative to the casing 10, at zero radial speed.

The vertex S corresponds to the point of the profile considered closest to the axis of rotation Z-Z. This therefore corresponds to the point at which a piston 140 in contact with the cam is retracted into its housing 132. Conversely, the hollow corresponds to the point of the profile considered furthest from the axis of rotation Z-Z. This therefore corresponds to the point at which a piston 140 in contact with the cam has extended as far as possible from its housing 132. The maximum stroke of the pistons 140 for a lobe considered is thus defined by the radial dimension between the top and the hollow.

Between a peak and a trough of the roller trajectory, three successive portions are distinguished: a portion P1 allowing a piston passing through it to have an increasing radial speed relative to the cylinder block (for rotation of the hydraulic machine at speed constant angular), a portion P2 allowing a piston passing through it to have a constant radial speed relative to the cylinder block (for rotation of the hydraulic machine at constant angular speed), a portion P3 allowing a piston passing through it have a decreasing radial speed relative to the cylinder block (for rotation of the hydraulic machine at constant angular speed).

In the same way, between a hollow and a peak of the roller trajectory, we successively distinguish a portion P1 allowing a piston traveling through it to have an increasing radial speed relative to the cylinder block (for a rotation of the hydraulic machine at constant angular speed), a portion P2 allowing a piston passing through it to have a constant radial speed relative to the cylinder block (for rotation of the hydraulic machine at constant angular speed), a portion P3 allowing a piston to traveling to have a decreasing radial speed relative to the cylinder block (for rotation of the hydraulic machine at constant angular speed). Pistons flowing radially in a different direction between a trough and a peak compared to when they circulate between a peak and a trough.

The speeds mentioned in this presentation are considered in absolute value, therefore without taking into account the direction of movement of the piston considered.

Considering a piston movement from the top to the trough, the portion P1 allowing a piston passing through it to have an increasing radial speed relative to the cylinder block follows the top; the portion P2 allowing a piston passing through it to have a constant radial speed relative to the cylinder block follows the portion P1 allowing a piston passing through it to have an increasing radial speed relative to the cylinder block, the portion P3 allowing a piston passing through it to have a decreasing radial speed relative to the cylinder block follows the portion P2 allowing a piston passing through it to have a constant radial speed relative to the cylinder block, and the hollow makes following the portion P3 allowing a piston passing through it to have a decreasing radial speed relative to the cylinder block.

The portion P1 allowing a piston passing through it to have an increasing radial speed relative to the cylinder block is a portion of the roller trajectory in which the speed of movement of the piston 140 relative to the cylinder block 130 in contact with the cam 150 increases considering a constant rotation speed for the hydraulic machine 1.

The portion P2 allowing a piston passing through it to have a constant radial speed relative to the cylinder block is a portion of the roller trajectory in which the speed of movement of the piston 140 relative to the cylinder block in contact with the cam 150 is constant considering a constant rotation speed for the hydraulic machine.

The portion P3 allowing a piston passing through it to have a decreasing radial speed relative to the cylinder block is a portion of the roller trajectory in which the speed of movement of the piston 140 relative to the cylinder block in contact with the cam 50 is decreasing considering a constant rotation speed for the hydraulic machine 1.

Each half-lobe of the roller trajectory thus includes these different portions between a peak and a trough or between a trough and a peak.

For each half-lobe of the roller trajectory, the portion allowing a piston traveling through it to have an increasing radial speed relative to the cylinder block extends over an angular sector equal to the angular sector of the portion allowing a piston traversing it to have a decreasing radial speed relative to the cylinder block and each of these angular sectors is typically greater than or equal to a quarter of the angular sector over which the half-lobe extends.

For each half-lobe of the roller trajectory, the portion allowing a piston traveling through it to have an increasing radial speed relative to the cylinder block extends over an angular sector equal to the angular sector the portion allowing a piston the traveling to have a decreasing radial speed relative to the cylinder block and each of this angular sector is typically greater than or equal to a third of the angular sector over which the half-lobe extends.

The more the acceleration and deceleration portions are angularly extended, the less the accelerations/decelerations are strong. This limits the stress on the cam and piston components and increases their lifespan.

However, the smaller the angular portions of acceleration and deceleration, the smaller the number of pistons necessary to have a homogeneous flow. A reduced number of pistons makes it possible to reduce costs and simplify manufacturing.

The cylinder block 130 is typically dimensioned so that in operation, each half-lobe of the roller path includes:
- either a single piston, in contact with its portion P2,
- or two pistons, one in its slope portion P1 and the other in its portion P3.

Thus, when the hydraulic machine is driven at a constant rotation speed, considering a half-lobe of the roller trajectory, when a single piston is in the portion P2, the flow of fluid displaced in relation to this half-lobe is constant.

When the hydraulic machine is driven at a constant rotation speed, considering a half-lobe when two pistons are in this half-lobe, one is in its portion P1 and the other is in its portion P3.

Portion P1 and portion P3 are configured so that at each instant, the sum of the flow rates displaced by the two pistons in these two portions is constant, and equal to the flow rate displaced by a piston in portion P2 for the same rotation speed. In other words, the profile of each lobe is defined so that when a piston is on a portion P1, the flow generated by it (which is not a constant flow since it increases) is compensated by that which is in portion P3 (which is also not a constant flow rate since it is decreasing) so that the sum of the two flow rates forms a constant flow rate equal to the flow rate of a piston in contact with portion P2 for the same speed of rotation.

Thus, over the entire half-lobe considered, the flow rate delivered is constant. A distributor conduit positioned opposite this half-lobe will therefore convey a constant flow rate.

There is a graph that represents this characteristic. This figure shows the evolution of the flow rate Q delivered as a function of time, and the evolution of the radial position R of the pistons relative to a half-lobe of the cam 150. We see that when the piston PA is in the portion P2 of the half-lobe, the flow rate delivered is constant, as described previously. When the piston PA is in the portion P3, the flow delivered decreases. The piston PB is then in the portion P1, so as to compensate for this drop in flow rate, and thus maintain a constant flow rate.

The different lobes of the hydraulic machine are typically formed so as to have a geometry as described above. Thus, each of the lobes of cam 150 delivers a constant or substantially constant flow rate in the case where the hydraulic machine operates as a pump, or consumes a constant or substantially constant flow rate in the case where the hydraulic machine operates as a motor. Such a hydraulic machine for which each of the lobes of the cam 150, and therefore each of the lobes of the roller trajectory, delivers a constant flow rate is qualified as a homogeneous hydraulic machine.

A distributor typically has a distribution cover defining a conduit for the supply and a conduit for the discharge of the fluid circulating in the hydraulic machine. These two conduits each open onto grooves in the distributor which distribute the fluid in particular via an interface plane between the distributor and the cylinder block 130. The distribution cover, the distributor and the cam 150 being fixed relative to each other , the distributor conduits are distributed so as to be able to distribute the fluid to the pistons 140 of the cylinder block 130 in contact with a half-lobe of the cam 150.

In such a hydraulic machine, each conduit therefore constantly sees a constant flow rate passing through it for a constant rotational speed of the cylinder block whatever the angular position of the cylinder block.

As the flow rate of fluid circulating in each of the conduits is constant, the supply conduits also see a constant flow rate.

Such a machine could achieve similar characteristics with other types of dispensers. For example with studs or radial distributors well known to those skilled in the art.

It is also known to those skilled in the art to produce multi-displacement hydraulic machines. The hydraulic machine is then made up of several hydraulic sub-machines. When we want to put the machine at full displacement then all the sub-machines are active. When you want to reduce the displacement of the machine, you can disengage, for example via a bypass, one or more sub-machines from the hydraulic machine.

For example, we can associate a submachine with each lobe or with a group of lobes. In this case, thanks to the invention each sub-machine will be homokinetic, since each lobe generates or operates with a homogeneous flow.

The hydraulic machine can then be configured so as to be subdivided into a plurality of hydraulic sub-machines, each corresponding to one or more lobes of the cam 150, and therefore of the roller trajectory.

More precisely, the different lobes of the cam 150 (and therefore of the roller trajectory) can be subdivided into subgroups, each subgroup being connected to a separate supply and discharge conduit.

Each subgroup can then for example correspond to one or more lobes of the cam 150 (and therefore of the roller trajectory). According to one example, the hydraulic machine is subdivided into as many hydraulic sub-machines as its cam 150 has lobes, each lobe of the cam 150 then defining a hydraulic sub-machine.

The lobes are typically associated in pairs. For example, the lobes opposite to the Z-Z axis of rotation are associated. By opposite lobes we mean lobes offset by 180° relative to the axis of rotation Z-Z. Such a configuration makes it possible to obtain a better distribution of forces within the hydraulic machine. The lobes can also be associated according to other configurations, for example offset by 120° relative to the axis of rotation Z-Z, or typically according to any regular distribution relative to the axis of rotation Z-Z so that the resultant efforts are minimized, typically zero or substantially zero.

In the case where such a hydraulic machine is used as a pump, it thus makes it possible to deliver a constant flow rate to a plurality of separate hydraulic members via separate circuits. For example, we can divide the flow rates so as to always have the same ratio from one flow to another.

In the hydraulic machine operating as a motor or pump, to the extent that a constant flow circulates in the different conduits for a constant speed of rotation of the hydraulic machine, there is no acceleration or deceleration of the fluid in the conduits compared to conventional hydraulic machines in which the conduits convey a variable flow rate over time, even for a constant rotation speed of the hydraulic machine, which in particular makes it possible to reduce pressure losses.

With reference to Figures 3 and 4, the hydraulic machine as presented comprises a cam 150 having a number NC of lobes equal to 4 lobes, and a cylinder block 130 having a number NP of pistons equal to 12 pistons distributed over 2 rows. We note here that the presents in the foreground a row of pistons, that is to say 6 pistons, the second row can be seen on the also on but corresponds to pistons in a plane parallel to the cutting plane of the but offset along the axis of rotation. The second row of pistons is offset in the cylinder block as angularly relative to the first row by an angle equal to 360°/NP (quinconcus).

In such a configuration, the relation 2 * NC < NP < 4 * NC is verified.

For such a configuration, considering identical lobes, each lobe then extends over an angular sector of 90°, that is to say 360° / 4. Each half-lobe then extends over an equal angular sector at 45°.

The pistons being distributed regularly in two rows of 6 pistons arranged in a staggered pattern, the pistons are then spaced 30° apart, or 360°/12. This spacing between the pistons 140 is understood as being the angular difference between the radial axes passing through the center of each piston 140.

For such a configuration, the angular sector AP1 of the portion P1 of the roller trajectory allowing a piston traveling through it to have an increasing radial speed relative to the cylinder block for rotation of the hydraulic machine at constant angular speed and that AP3 of the portion P3 of the roller trajectory allowing a piston traveling through it to have a decreasing radial speed relative to the cylinder block for a rotation of the hydraulic machine at constant angular speed are each equal to
AP1=AP3= (Adl-AP0-AP4)-360/NP
with AP0 and AP4 designating the angular sectors of the portions P0, P4 allowing a piston passing through them to have a zero radial speed relative to the cylinder block, for rotation of the hydraulic machine at constant angular speed, commonly referred to as flats cam.

For such a configuration, we have Adl= 45° and 360/NP=30°. If we choose P0=P4=1°, we obtain AP1=AP3=13°

The angular sector AP2 of the portion P2 of the roller trajectory allowing a piston traveling through it to have a constant radial speed relative to the cylinder block for rotation of the hydraulic machine at constant angular speed is equal to
AP2= 2x(360/NP) – (ADL-AP0-AP4).

For such a configuration, we have Adl= 45° and 360/NP=30°. If we choose P0=P4=1°, we obtain AP2=17°

These formulas which make it possible to calculate the extent of the angular sector of P2 are established thanks to the fact that when a piston leaves the zone P2 (zone where there is only one piston on the half-lobe) to enter zone P3, another piston on the same half-lobe must enter zone P1 of the same half-lobe to compensate for the deceleration of the first piston and therefore the difference in flow rate that it generates.

For such a hydraulic machine, 8 distribution conduits are thus typically defined in the distributor 160, the conduits being identified by the references C1 to C8, each distribution conduit defining either an admission or a discharge of fluid for a given lobe of the cam 150. Such a hydraulic machine 1 can thus be subdivided into any number of hydraulic sub-machines between 2 and 4 hydraulic sub-machines.

It can for example be subdivided into 4 hydraulic sub-machines, each hydraulic sub-machine corresponding to a lobe of cam 150.

It can for example be subdivided into 2 sub-hydraulic machines, the conduits of opposite lobes then being grouped together, for example the conduits C1 and C5, C2 and C6, C3 and C7, C4 and C8. We can also, for example, subdivide it into 2 sub-hydraulic machines, the conduits corresponding to the lobes being grouped alternately, that is to say the conduits C1, C3, C5 and C7 on the one hand, and the conduits C2, C4 , C6 and C8 on the other hand. Such distributions make it possible to balance the forces in the hydraulic machine.

To the extent that each lobe of the cam 150 (and therefore of the roller trajectory) allows a constant flow to circulate, we understand that the lobes can be different from each other, so as to define a plurality of hydraulic submachines having different cylinder capacities. Thus, for example, the cam 150 can be made so that it has several lobe profiles, each lobe being formed so as to deliver a homogeneous flow rate as described previously, but also so that all or part of the lobes in particular have different courses, that is to say peaks and/or troughs having radii having different values. We can also modify the slope and the variations in slope between the different lobes or groups of lobes of the cam 150. Thus we can, for example, have sub-machines of different cylinder capacities due to the difference in the hollow of the lobes. The lobes can also extend over distinct angular sectors. Thus, the angular sector Adl is not necessarily constant for all the lobes of cam 150.

According to one example, when the hydraulic machine is subdivided into several hydraulic sub-machines, the different lobes associated with the same hydraulic sub-machine can have identical geometries which contributes to balancing the constraints within the hydraulic machine.

As an alternative example, the hydraulic machine presents a distributor with studs, defining a fluid circulation conduit for each half-lobe of the cam 150, said circulation conduits defining a plurality of disjoint intake and discharge conduits.

There represents such an example of a hydraulic machine comprising a distributor with studs or ice with studs.

In this embodiment, the distributor 160 connects the housings 132 of the cylinder block 130 to an orifice (here designated by 166 or 167) without requiring the production of grooves. Thus, each half-lobe is associated with an orifice of the stud distributor, which can be an inlet or outlet orifice depending on the operation of the hydraulic machine.

A counter glass 170 is interposed between the cylinder block 130 and the distributor 160, this counter glass 170 being maintained in contact with the cylinder block 130 via return means 172 such as springs in order to ensure sealing at the interface.

The use of such a distributor with studs is adapted here because the flow of fluid in each conduit and therefore at each orifice is constant.

According to one embodiment, the distributor 160 is provided with valves, typically solenoid valves, adapted to modulate the flow rate passing through the different conduits of the distributor 160, and therefore the flow rate displaced by the pistons 140. Such an embodiment makes it possible to multiply the different displacement ratios between the different lobes, and therefore between the different hydraulic submachines. The power supply to the various hydraulic sub-machines can thus be controlled, and all or part of the hydraulic sub-machines can in particular be disengaged.

The application of such a hydraulic machine having an integrated gearbox as presented with reference to Figures 1 and 2 is particularly advantageous in terms of compactness. Indeed, it is thus possible to drive with a motor, for example an electric motor, a single pump which has an operation equivalent to a plurality of hydraulic pumps in order to power a plurality of hydraulic components such as hydraulic motors.

Although the present invention has been described with reference to specific embodiments, it is evident that modifications and changes can 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 different illustrated/mentioned embodiments can be combined in additional embodiments. Therefore, the description and drawings should be considered in an illustrative rather than a restrictive sense.

It is also obvious that all the characteristics described with reference to a process can be transposed, alone or in combination, to a device, and conversely, all the characteristics described with reference to a device can be transposed, alone or in combination, to a process.

…

Claims (13)

Assembly comprising a hydraulic pump (100) and an epicyclic reducer (200),
in which the hydraulic pump (100) is a hydraulic pump with radial pistons and a multilobe cam, comprising a casing (110) defining an internal volume in which are housed a shaft (120) extending in an axial direction (ZZ), a cylinder block (130) positioned around the shaft (120) and comprising a plurality of housings (132) in which pistons (140) are mounted sliding radially relative to the axial direction (ZZ), and a cam (150) multi-lobe mounted around the cylinder block (130) and secured to the casing (110), in which the shaft (120) and the cylinder block (130) define a first assembly, and the casing (110) and the multi-lobe cam (150) define a second set, the first set and the second set being mounted movable in rotation relative to each other in the axial direction (ZZ),
the reduction gear (200) comprising an outer sun gear (210), an inner sun gear (220), a planet carrier (230) and one or more planet gears (240);
characterized in that
the reducer (200) being housed in the internal volume of the casing (110) of the hydraulic pump (100),
so that the reducer (200) applies a reduction ratio between the shaft (120) and the cylinder block (130) of the hydraulic pump (100) so that the cylinder block (130) has a speed rotation strictly lower than a rotation speed of the shaft (120). Assembly according to claim 1, in which
the external sun gear (210) of the reduction gear (200) is integral with the casing (110) of the hydraulic pump (100),
the internal sun gear (220) is integral with the shaft (120) of the hydraulic pump (100), and
the satellite carrier (230) is integral with the cylinder block (130) of the hydraulic pump (100). Assembly according to claim 2, in which the external sun gear (210) is formed by teeth formed on an internal surface of the casing (110). Assembly according to one of claims 2 or 3, in which the internal sun gear (220) is formed by teeth formed on an external surface of the shaft (120). Assembly according to one of claims 2 to 4, in which the satellite carrier (230) is formed by a plurality of rods extending from the cylinder block (130) in the axial direction (Z-Z). Assembly according to claim 1, in which
the external sun gear (210) of the reduction gear (200) is integral with the cylinder block (130),
the inner sun gear (220) is integral with the shaft (120), and
the satellite carrier (230) is integral with the casing (110). Assembly according to one of claims 1 to 6, further comprising a primary motor (M) adapted to rotate the hydraulic pump (100) via the reducer (200), in which the reducer (200) is configured so as to that in operation, the rotation speed of the hydraulic pump (100) is less than or equal to 1000 revolutions per minute. Assembly according to one of claims 1 to 7, in which the first assembly is movable in rotation relative to a support, and the second assembly is fixed relative to said support. Assembly according to one of claims 1 to 7, in which the second assembly is movable in rotation relative to a support, and the first assembly is fixed relative to said support. Assembly according to one of claims 1 to 8, in which the hydraulic pump (100) is a multi-displacement pump, comprising means for deactivating part of the lobes of the cam (150). Assembly according to one of claims 1 to 9, in which the hydraulic pump (100) is configured such that the cam (150) and the pistons (140) are configured so as to define a roller trajectory which has a plurality of hollows and vertices, and a plurality of lobes, each lobe being formed between two hollows or two consecutive vertices, each lobe being composed of two half-lobes, the hollows designating the portions of the lobes of the roller trajectory furthest from the axis of rotation (Z-Z), and the vertices as being the portions of the lobes of the roller path closest to the axis of rotation (Z-Z), and in which the cylinder block (130), the pistons (140) and the cam (150) are configured so that for each half-lobe, the flow rate of fluid displaced by the pistons (140) in contact with a half-lobe considered is constant for a constant rotation speed between the first set and the second together. Assembly according to claim 11, in which the lobes are grouped so as to form subgroups of at least one lobe defining hydraulic sub-pumps, the hydraulic pump (100) comprising a distributor (160) adapted to selectively supply, in particular distinctly, all or part of said subgroups. Assembly according to claim 12, in which the distributor (160) defines a fluid circulation conduit for each half-lobe of the roller trajectory, said circulation conduits being disjoint and defining a plurality of disjoint intake and discharge conduits , the flow rate circulating in each of said conduits being constant for a constant rotation speed of the hydraulic pump (100).