Hydrostatic machine with assembled cam ring and annular housing

Abstract

Hydrostatic radial piston rotation machine comprising an internal element (1) and an external element (2) coaxial and mounted to rotate relative to each other about an axis of rotation (R), one of these elements being a rotor and the other of these elements being a stator; the internal element (1) comprising a cylinder block (10); the external element (2) comprising an annular housing (5) surrounding the cylinder block (10), and a cam ring (9) mounted in the annular housing (5). The cam ring (9), on its outer circumference, and the annular housing (5), on its inner face, each have a fit profile, one of these fit profiles being a concave, and the other a convex (38), the two fit profiles being of complementary shapes and being nested one inside the other. Figure for the abbreviation: Fig. 1

Description

Title of the invention: Hydrostatic machine with assembled cam ring and annular housing

[0001] The invention relates to the field of mechanics and hydraulics and relates more particularly to a hydrostatic rotation machine.

[0002] Hydrostatic rotary machines are rotating machines comprising a stator coupled with a rotor which is generally connected to a rotating drive element such as a wheel, a pinion or any transmission device.

[0003] Such a hydrostatic machine can be used as a hydraulic motor. It is then supplied with a pressurized hydraulic fluid and drives the rotating drive element in response.

[0004] The hydrostatic machine can also be used as a hydraulic pump. It then receives a torque transmitted by the rotating drive element and compresses the hydraulic fluid in response. PREVIOUS ART

[0005] Patent application WO2020008145 describes a hydrostatic rotating machine comprising: - a rotor and a stator mounted to rotate relative to each other around an axis of rotation, the rotor comprising a cylinder block having radial cylinders fitted with radially movable pistons distributed circumferentially; the stator comprising a housing and a cam ring mounted in the housing; the pistons being adapted to cooperate with the cam track in a coordinated manner with the rotation of the rotor relative to the stator; - a hydraulic distributor adapted to selectively connect the cylinders to a hydraulic circuit, by means of a synchronizing junction forming a rotating coupling between the rotor and the stator.

[0006] Although the implementation of the cam ring in this hydrostatic machine has advantages in several respects, it can still be improved with regard to the arrangement of this cam ring. Description of the invention

[0007] The invention aims to improve prior art hydrostatic rotation machines.

[0008] To this end, the invention relates to a hydrostatic rotating machine with radial pistons comprising: - an internal element and an external element coaxial and mounted to rotate relative to each other around an axis of rotation, one of these elements being a rotor and the other of these elements being a stator; the internal element comprising a cylinder block having cylinders fitted with radially movable pistons distributed circumferentially; the external element comprising an annular housing surrounding the cylinder block, as well as a cam ring mounted in the annular housing and comprising a cam track on its internal circumference; the pistons being adapted to cooperate with the cam track in a coordinated manner with the rotation of the rotor relative to the stator; - a hydraulic distributor adapted to selectively connect the cylinders to a hydraulic circuit, by means of a synchronizing junction forming a rotating coupling between the rotor and the stator.

[0009] In this hydrostatic rotation machine, the cam ring, on its outer circumference, and the annular housing, on its inner face, each have a nesting profile, one of these nesting profiles being a concavity, and the other of these nesting profiles being a convexity, the two nesting profiles being of complementary shapes and being nested one inside the other.

[0010] The invention benefits from the advantages associated with mounting a cam ring in the annular housing of the external element, such as, for example, the possibility of using an advantageous combination of different materials, more suited to the function of each, a simplification of the architecture, and a reduction in cost.

[0011] The rotational coupling of the cam ring and the external element is achieved directly by mounting the cam ring in the annular housing, thanks to the interlocking profiles, without resorting to through holes, fastening means and other added parts, and therefore without affecting the rigidity of the parts or creating additional risks of leakage.

[0012] This rotational coupling is both simpler and more efficient than the couplings observed in the prior art.

[0013] The invention guarantees that there will be no leaks related to the connection between the cam ring and the annular housing. Furthermore, the assembly of the hydrostatic machine is simplified, with a reduced risk of error. During the corresponding process for manufacturing the hydrostatic machine, no alignment of fasteners or ports is necessary.

[0014] The concavities and convexities of the cam ring and the annular housing can also be used to accommodate additional functions, such as drainage channel passages allowing communication between the two faces of the engine so that its construction can be further simplified, without any additional seal.

[0015] In this context, the engine also exhibits increased performance thanks to the possibility of cooling and lubricating the cylinders with a higher-density hydraulic fluid viscosity, thanks to an adaptation of the drainage function.

[0016] Hydraulic drainage fluid can thus be supplied to the cylinders at the appropriate locations, facilitating starts (particularly hot starts, the most critical situations where the hydraulic fluid viscosity is low), as well as reducing wear on the cylinders and pistons. Furthermore, no additional seals are required, and the hydraulic connections can all be located on the same side of the hydrostatic machine, making it particularly suitable for wheel hub arrangements.

[0017] The manufacturing process made possible by such a hydrostatic machine architecture involves even fewer steps than in the prior art, as well as fewer elements, which implies gains in time and cost.

[0018] The hydrostatic machine according to the invention may include the following additional features, alone or in combination:

[0019] - the cam ring's socket profile is a concavity, and the profile The fit of the annular housing is a convexity;

[0020] - the cam ring and the annular housing comprise a plurality of profiles circumferentially interlocking parts distributed in a regular manner;

[0021] - said concavity is a recess with curved lateral edges, and said convexity is a bulge with curved lateral edges;

[0022] - the interlocking profiles of the cam ring and the annular housing have the same axial dimension, this axial dimension being equal to the axial thickness of the cam ring;

[0023] - the cam track comprises a succession of lobes and recesses, and the ring of The cam has as many interlocking profiles as there are lobes in the cam track;

[0024] - the cam ring's interlocking profiles are radially centered with the lobes of the cam path;

[0025] - the inner face of the annular housing comprises: an internal cylindrical bearing surface for a bearing disposed between the rotor and the stator; and an internal bearing surface for the cam ring; these two internal bearing surfaces being formed from the same internal cylindrical surface which supports the interlocking profiles of the annular housing on its axial portion receiving the cam ring. Said bearing disposed between the rotor and the stator may be mounted directly or indirectly on its internal bearing surface, in particular it may be mounted indirectly with an intermediate support ring which forms part of a cover closing the annular housing;

[0026] - the cam ring is axially stopped by an internal shoulder of the housing annular, this shoulder also defining an internal cylindrical bearing surface for a bearing positioned between the rotor and the stator;

[0027] - the cam ring is axially fitted by clamping into the annular housing, with interlocking of the interlocking profiles;

[0028] - the hydrostatic machine includes at least one drainage conduit made in the thickness of the wall of the annular housing, substantially parallel to the axis of rotation R, and passing through the interlocking profile of the annular housing;

[0029] - the drainage conduit opens outside the annular housing via an outlet of drain, on the same side of the hydrostatic machine as all the other hydraulic conduits of the hydrostatic machine;

[0030] - the drainage conduit opens into the inside of the annular housing, axially in vis-à-vis the cylinders;

[0031] - the drainage conduit opens onto a lateral face of the interlocking profile which it traverse;

[0032] - the drainage conduit opens axially opposite at least one gap broadcasting;

[0033] - said diffusion gap comprises a diffusion notch made in a cover which is positioned opposite the cam ring and which hermetically seals one side of the hydrostatic machine;

[0034] - said diffusion gap has a functional clearance between the cam ring and the inner ring of a bearing positioned between the rotor and the stator;

[0035] - the cylinder block has a collar centered on its outer circumference, this collar being adapted to form an axial stop for two bearings disposed between the rotor and the stator, this collar having an axial dimension equal to the axial thickness of the cam ring plus a functional clearance;

[0036] - the axial distance between the two inner rings of the bearings is equal to the axial width of the piston rollers plus a functional clearance;

[0037] - the drainage conduit is supplied with hydraulic fluid from a cooler arranged on the hydraulic circuit. PRESENTATION OF THE FIGURES

[0038] Other features and advantages of the invention will become apparent from the following non-limiting description, with reference to the accompanying drawings in which:

[0039] - [Fig.1] is a cross-sectional figure of a hydrostatic machine according to the invention;

[0040] - [Fig.2] illustrates the annular housing of the hydrostatic machine of [Fig.1];

[0041] - [Fig.3] illustrates the cam ring of the hydrostatic machine of [Fig.1];

[0042] - [Fig.4] illustrates the cylinder block of the hydrostatic machine of [Fig.1];

[0043] - [Fig.5] is a detail view of [Fig.1];

[0044] - Figure 6 illustrates an example of a drainage circuit for the hydrostatic machine of the [Fig.l].

[0045] The similar and common elements of the various embodiments bear the same reference numbers to the figures. DETAILED DESCRIPTION

[0046] Fig. 1 illustrates a hydrostatic rotation machine according to the invention, seen in cross-section along a plane extending along its axis of rotation R.

[0047] This hydrostatic machine is either a hydraulic motor driving an element in rotation from a hydraulic fluid under pressure, or a hydraulic pump adapted to pressurize a hydraulic fluid from the rotation of an element.

[0048] The hydrostatic rotation machine comprises an internal element 1 and an external element 2 which are mounted to rotate relative to each other around the axis of rotation R by bearings 14, 15.

[0049] In the present illustrative example, the hydrostatic machine is a hydraulic motor and the internal element 1 is integral with a drive element which here consists of a splined shaft 3.

[0050] Of the internal element 1 and the external element 2, one is a rotor and the other is a stator. In the present example, the external element 2 is a stator and is connected to a frame such as a fixed structure or one mounted on a vehicle, while the internal element 1 is a rotor and the splined shaft 3 is connected, for example, to a wheel or a pinion. According to an application for which the invention is particularly advantageous, the external element 2 is mounted on the chassis of a vehicle, and the splined shaft is connected to a wheel whose rim surrounds the hydrostatic machine. The hydrostatic machine in this example is a motor housed in the hub of a drive wheel.

[0051] The external element 2 comprises an annular housing 5, which here has a general ring shape, with a first cover 6 that hermetically seals one of the openings (on the right of [Fig. 1]) of this annular housing 5, and a second cover 7 that hermetically seals the opposite opening (on the left of [Fig. 1]). The second cover 7 has, at its interface with the splined shaft 3, a lip seal 30.

[0052] The external element 2 further comprises a cam track 8 characteristic of hydrostatic machines with radial pistons. In a known manner, this cam track 8 has an internal circumferential shape, with a path formed of hollows and lobes, constituting a cyclic path with a succession of increasing and decreasing radii, synchronized with the entry and exit movement of the radial pistons.

[0053] The cam track 8 is carried by a cam ring 9 mounted on an inner face of the annular housing 5, with the same advantages as those described in patent application WO2020008145. In particular, the cam ring 9 can be made The cam is made from a grade of steel known as "bearing steel" or "carbon steel," which has a high carbon content, excellent resistance to wear and fatigue, but is nevertheless sensitive to impacts. The cam ring's vulnerability to impacts is compensated for by its mounting in the ductile annular housing 5. The high performance of a material resistant to contact pressure and fatigue can thus benefit the cam track 9, without suffering the drawbacks normally associated with this type of material.

[0054] The internal element 1 comprises a cylinder block 10 which is also specific to hydrostatic machines with radial pistons. This cylinder block 10 is provided with cylinders 11 in which radially movable pistons 12 are mounted in a known manner. A piston 12 is shown [Fig. 5]. In [Fig. 1], the pistons, which are known from other sources, have not been shown to simplify the figure.

[0055] In a known manner, the cylinders 11 are radial cylinders which extend over the entire circumference of the cylinder block 10, angularly distributed regularly around the axis of rotation R, and the pistons 12 each have, on their end turned towards the cam track 8, a roller 13 (see [Fig.5]) allowing rolling without slipping on the cam track 8.

[0056] The cam paths for hydrostatic machine, the cooperation with radial pistons, and the synchronization methods by selectively connecting the cylinders with the hydraulic fluid circuit, are otherwise known and will not be described in more detail here.

[0057] The inner element 1 and the outer element 2 are mounted to rotate relative to each other by means, in this example, of a first bearing 14 and a second bearing 15 directly mounted between the inner element 1 and the outer element 2. These bearings 14, 15 are inserted in the annular housing 5 on either side of the cam ring 9. The example in [Fig. 1] illustrates two possible mountings of the bearings 14, 15 in the annular housing 5: a direct mounting of the bearing with its outer ring in contact with the annular housing 5 (this is the case of the first bearing 14); and a mounting of the bearing in the housing with an intermediate support ring (this is the case of the second bearing 15), and in the present example this support ring is part of the second cover 7.

[0058] This arrangement allows for assembly that combines compactness and simplified manufacturing operations, with a reduction in associated cost. Indeed, in the present example, the annular housing 5 has, on its inner face, three cylindrical bearing surfaces whose diameter increases axially (in the direction from the first cover 6 to the second cover 7): - a first internal bearing surface 24, which is cylindrical and in which the first bearing 14 is mounted, this first internal bearing surface 24 being axially delimited by a first shoulder 25 and a second shoulder 27 of the annular housing 5, the second shoulder 27 being radially outside with respect to the first shoulder 25; - a second internal bearing surface 26 in which the cam ring 9 is mounted, this second internal bearing surface 26 being axially delimited by the second shoulder 27 and a third shoulder 28 of the annular housing 5, the third shoulder 28 being radially outside with respect to the second shoulder 27; - a third internal bearing surface 36, which is cylindrical and in which the second bearing 15 is mounted, via the second cover 7, this third internal bearing surface 36 being axially delimited by the third shoulder 28 and by an axial retaining element 29 of the external element. In the present example, this axial retaining element 29 is a large-diameter retaining ring, mounted on the inner face of the annular housing 5 and adapted to the axial retention of the second cover 7.

[0059] The diameters thus formed allow successive fitting of the internal elements into the annular housing 5, which facilitates the manufacturing process.

[0060] The cylinder block 10 has two flanges 16, 17 arranged on either side of the cylinders 11, with a bearing 14, 15 mounted between each flange 16, 17 and the external element 2, the inner ring of each bearing 14, 15 being directly mounted on the corresponding flange 16, 17.

[0061] A simple bearing assembly generating reduced dimension chains is thus obtained, with the cam ring 9 mounted in the annular housing 5 and the bearings 14, 15 arranged on either side of this cam ring 9 making the direct interface between the internal element 1 and the external element 2.

[0062] The hydrostatic machine further comprises means for distributing and synchronizing the hydraulic fluid. These means comprise a hydraulic distributor 18 and a distribution base 4.

[0063] The distribution base 4 has a fluid inlet 19 and a fluid outlet 20 which are connected in a conventional manner to the high pressure and low pressure portions of a hydraulic circuit.

[0064] The distribution base 4 is integral with the external element 2. In this example, the distribution base 4 is integral with the first cover 6.

[0065] The hydraulic distributor 18 is mounted on the distribution base 4, being axially mobile relative to the latter, the two parts being coupled in rotation for example by means of pins allowing axial sliding.

[0066] The hydraulic distributor 18 of this example comprises a central chamber 22 and a peripheral chamber 23, each connected to the fluid inlet 19 or fluid outlet 20. [Fig.1] illustrates the connection of the chambers 22, 23 to the fluid inlets / outlets 19, 20 according to this example.

[0067] Seals allow the hermetic partitioning of chambers 22, 23, while allowing axial movement of the hydraulic distributor 18 on the distribution base 4. In a known manner, these seals have different diameters in order to create an axial cylinder function for the hydraulic distributor 18. This axial cylinder function makes it possible to hold the hydraulic distributor 18 against the cylinder block 10, opposing the forces generated during the implementation of the synchronization, i.e. the selective pressurization of the cylinders 11.

[0068] The cylinder thus created by the hydraulic distributor 18 has the effect of counteracting the repulsive force exerted in the interface (the synchronization junction) between the hydraulic distributor 18 and the cylinder block 10.

[0069] The hydrostatic machine further comprises drainage means including a drain inlet 31 and a drain outlet 32. The drain inlet 31 is advantageously positioned on the edge of the annular housing 5. The drain outlet 32 ​​therefore opens onto a surface 33 perpendicular to the axis of rotation R.

[0070] The drain outlet 32 ​​opens onto the first cover 6, onto a surface 34 also perpendicular to the axis of rotation R.

[0071] The drain inlet 31 and drain outlet 32 ​​thus open onto the same face of the hydrostatic machine, the same face which also includes the fluid inlet 19 and fluid outlet 20. This face corresponds to the rear face for a hydraulic motor located in a vehicle wheel hub, as it is from this rear face that the hydraulic connections are most easily managed. The invention allows all the hydraulic connections to be located on this rear face, so that the hydraulic hoses connected to them can run along the vehicle chassis.

[0072] All the hydraulic fittings intended for the operation of the hydrostatic machine are thus protruding from one and the same side of this machine.

[0073] Fig. 2 is a perspective view of the annular housing 5, seen in the direction of arrow 35 of Fig. 1.

[0074] The first internal span 24, the second internal span 26 and the third internal span 36 are visible in this view.

[0075] The annular housing 5 also includes another internal bearing surface 37, visible in figures 1 and 2, intended for mounting and securing the first cover 6 to the annular housing 5. Alternatively, these two elements 5, 6 can be made in one piece, by turning with a single workpiece clamping, and therefore with a common reference and very low manufacturing variation, for the following machining operations: - the distribution base 4; - the lid 6; - the annular housing 5 and all its bearing surfaces 24, 26, 36 and all its shoulders 25, 27, 28; - the interlocking profiles of the annular housing 5, described below.

[0076] The cam ring 9, on its outer circumference, and the annular housing 5, on its inner face, each have a fit profile, one of these fit profiles being a concave shape, and the other of these fit profiles being a convex shape, the two fit profiles being of complementary shapes and being nested one inside the other. In other words: - the cam ring 9 has a convexity on its outer circumference, and the annular housing 5 has a concaveness on its inner face; or - the cam ring 9 has a concavity on its outer circumference, and the annular housing 5 has a convexity on its inner face.

[0077] In the present example, the interlocking profile of the annular ring 5 is formed by a convexity. The annular ring 5 thus has at least one convexity 38 on its inner face, and more precisely on the second inner bearing surface 26. In the present example, the annular housing 5 has six convexities 38 angularly distributed regularly around the entire inner circumference of the second inner bearing surface 26. These convexities 38 constitute an interlocking profile and can be formed by any protrusion of material from the second inner bearing surface 26 extending radially in the direction of the axis of rotation R.

[0078] The convexities 38 constitute, by one of their lateral faces (that is to say one of their faces perpendicular to the axis of rotation R), the third shoulder 28.

[0079] In the present example, the convexities 38 are made in the form of projecting bulges from the second internal span 26, and presenting a contour, with curved lateral edges, that is to say that the internal diameter of the internal span 26 has smooth and regular changes in radius, without abrupt change.

[0080] The internal bearing surface 26 thus has a wavy internal contour, which is easier and less expensive to machine. The convexities 38 are created during the machining of the second internal bearing surface 26, by a toolpath adapted to this undulation.

[0081] The convexities 38 can also be made according to any other variant of shape, for example with facets.

[0082] In a particularly advantageous manner, the second internal bearing surface 26 and the third internal bearing surface 36 are formed from the same internal cylindrical surface, which supports the interlocking profiles of the annular housing 5 (the convexities 38 in this example) on its axial portion receiving the cam ring 9. In other words, the second internal bearing surface 26 is formed from a cylindrical bearing surface of the same diameter as the third internal bearing surface 36 to which the convexities 38 are added.

[0083] Fig. 3 is a perspective view of the cam ring 9 shown alone.

[0084] The cam ring 9 conventionally comprises on its inner circumference the cam track 8. This cam track 8 is formed of a succession of hollows 39 and lobes 40, intended to form a path for the rollers 13 of the pistons 12. The thrust of a piston when its roller 13 is between a lobe 40 and a hollow 39 causes the rotation of the rotor.

[0085] During the relative rotation of the cylinder block 10 with respect to the cam ring 9, the pistons are caused to exert a force on an oblique surface of the cam track 8, resulting in localized forces on certain regions of the interface of each piston with its cylinder.

[0086] In the present example, the interlocking profile of the cam ring 9 is formed by a concavity. The cam ring 9 thus has at least one concavity 41 on its outer circumference. These concavities 41 constitute an interlocking profile and can be formed by removing material from the contour of the cam ring 9, in the direction of the axis of rotation R.

[0087] The number of concavities 41 corresponds to the number of convexities 38 of the annular housing 5 and their shapes are corresponding.

[0088] The cam ring 9 therefore has six concavities 41 which are formed by recesses whose profile corresponds precisely to the bulges forming the convexities 38 of the annular housing 5. The concavities 41 are recesses with curved lateral edges, without abrupt change of shape.

[0089] The concavities 41 can also be made according to any other variant of shape, for example with facets.

[0090] The outer contour of the cam ring 9 is thus designed to fit into the inner contour of the second inner bearing surface 26 of the annular housing 5. The mechanical fit chosen for these two parts can, for example, be a slight clamping, allowing the cam ring 9 to be inserted into the annular housing 5 using standard production tools. The cam ring 9 is thus axially fitted into the annular housing 5 by clamping, which results in the interlocking of the various interlocking profiles.

[0091] The interlocking profiles of the cam ring 9 (the concavities 41 in this example) and the interlocking profiles of the annular housing 5 (the convexities 38 in this example) have the same axial dimension, i.e. the same width along the axis of rotation R. These interlocking profiles also extend over the entire axial thickness of the cam ring 9, i.e. the concavities 41 are formed over the entire width (along the axis of rotation R) of the cam ring 9. This facilitates the interlocking of the cam ring 9 in the annular housing 5 and its retention.

[0092] Particularly advantageously, the number of convexities 38 of the annular housing 5, the number of concavities 41 of the cam ring 9, and the number of lobes 40 of the ring 9 are equal.

[0093] Furthermore, the concavities 41 on the outer contour of the cam ring 9 and the lobes 40 on the inner contour of the cam ring 9 are angularly indexed. In other words, each lobe 40 is radially aligned with a concavity 41, and each recess 39 is radially aligned with the normal circular contour (i.e., without concavities) of the cam ring 9. A concavity 41 and a lobe 40 are therefore angularly centered on the same radius of the cam ring 9.

[0094] Thus, the radial thickness of the cam ring 9 remains relatively constant, although oscillating around a median diameter illustrated by circle 42. The rigidity of the cam ring 9 is thus reinforced, and the latter can be dimensioned to save material and therefore reduce weight, without impacting the rigidity of the part.

[0095] In the present example, the convexities 38 are arranged in the annular housing 5, and the concaveities 41 are arranged on the cam ring 9. This version is more advantageous and easier to machine. However, this arrangement can be reversed: the cam ring 9 can be provided with convexities while the inner face of the annular housing 5 would then be provided with concaveities. The convexities of the cam ring 9 would then be radially aligned with the recesses 39 of the cam ring 9.

[0096] Advantageously, the assembly of the cam ring 9 and the annular housing 5 also contributes to the drainage function. Figure 2 shows an injection orifice 43 in fluidic communication with the drain inlet 31.

[0097] With reference to [Fig.1], the drain inlet 31 extends into a drainage channel 44 which extends into the thickness of the wall of the annular housing 5, in a direction substantially parallel to the axis of rotation R. This drainage channel 44 thus extends axially along the first internal bearing surface 24 and the second internal bearing surface 26.

[0098] The drainage conduit 44 is arranged so that it passes through a socket profile, i.e., in this example, one of the convexities 38 of the annular housing 5, and opens through the injection port 43 into the internal space of the annular housing 5. The injection port 43 is located on a lateral face of the convexity 38 through which it passes. The drainage conduit 44 thus opens onto a lateral face of the socket profile through which it passes.

[0099] The injection port 43 is intended to deliver the hydraulic drainage fluid in a localized manner to each cylinder 11. The injection port 43 thus opens axially opposite the cylinders, that is to say, it opens at an axial position which is included in the axial width of the cylinders 11.

[0100] Various arrangements allow for the promotion of the diffusion of the hydraulic drainage fluid. The injection orifice 43 is thus arranged radially opposite angular diffusion gaps, of small axial width and adapted to diffuse the hydraulic fluid angularly.

[0101] In the present example, the injection orifice 43 is arranged opposite such a gap formed by a diffusion notch 45 made in the second cover 7, the latter being opposite the cam ring 9. This diffusion notch 45 is preferably made over a large angular amplitude of the second cover 7, or even over its entire circumference.

[0102] Similarly, the injection port 43 is also arranged radially opposite another gap formed by a functional clearance 47 between the inner ring of the second bearing 15 and the cam ring 9. This functional clearance 47 has the advantage of being an interface between a part of the stator and a part of the rotor, promoting the diffusion of the hydraulic fluid.

[0103] The drain inlet 31 is for example a threaded bore adapted to be connected by a flexible hose, in a conventional manner, to a low pressure branch of the hydraulic circuit, so that the hydraulic fluid bathes all the engine components and is regularly renewed, also draining internal leaks (at the level of the hydraulic distributor 18 and the cylinders 11).

[0104] The drain outlet 32 ​​is connected to this drainage circuit to evacuate the hydraulic drainage fluid which has been brought in by the drainage conduit 44 and by internal leaks.

[0105] The hydraulic fluid, in this drainage branch, thus flows into the drainage conduit 44, opens through the injection port 43, and passes into the angular diffusion gaps 45, 47, and is then directly diffused into the cylinders 11.

[0106] Thanks to the rotation of the rotor relative to the stator, the hydraulic drainage fluid is diffused alternately to each of the cylinders 11, during this rotation.

[0107] Although the drain inlet 31 and the drain outlet 32 ​​are arranged on the same face of the hydrostatic machine (its rear face in this example), the path taken by the hydraulic fluid crosses the hydrostatic machine from one side to the other of the median plane of the cylinder block 10. The drain outlet 32 ​​is also diametrically opposite to the drain inlet 31.

[0108] The hydraulic drainage fluid is thus supplied, in a localized manner, to the points most stressed by the forces induced at the cylinder / piston interface by the work of the pistons 12 in the cylinders 11, taking into account the pressure exerted by the pistons on the camshaft 8, with oblique forces. This hydraulic fluid, in addition to its drainage function, is thus used to lubricate and cool this stressed interface in a very localized manner. The drained hydraulic fluid is also cooler than the high-pressure hydraulic fluid, and is therefore more viscous, which improves hot starts where, without the invention, the hydraulic fluid would be too hot and too viscous to ensure optimal piston operation in the cylinders.

[0109] This arrangement allows for a reduction in the clearance between the cylinders and pistons during the design phase, thereby increasing the power of the hydrostatic machine for the same volume, while reducing the risk of premature wear or even seizing, and increasing longevity. In particular, the start-up phases are thus less damaging, as these are the most critical phases.

[0110] Figure 4 is a partial perspective view illustrating the cylinder block 10, seen alone.

[0111] The cylinder block 10 has a collar 46 centered on the cylinders 11 and forming an axial support ring for mounting the two bearings 14, 15.

[0112] Fig. 4 illustrates that the hydraulic drainage fluid reaching the level of the second bearing 15 (and the functional clearance 47) flows directly into the cylinders 11. The cylinders 11 receiving the pistons (not shown), this hydraulic drainage fluid spreads around the circumference of the piston head, and lubricates the interface between the piston and its cylinder 11 at the point where this work generates the most stress, i.e. radially near the piston head.

[0113] Fig. 5 is a detail view of Fig. 1, illustrating a piston 12 in its cylinder 11. The collar 46 has an axial dimension (i.e. a width along the axis of rotation R) which is slightly greater than the axial thickness of the cam ring 9, so that the two bearings 14, 15 are as close as possible to the cam ring 9, with a functional clearance allowing rotation of the rotor relative to the stator, and the diffusion gap function described previously.

[0114] Furthermore, given the diffusion gap function (between the cam ring 9 and the inner ring of the bearing 15), this proximity between the bearings 14, 15 and the cam ring 9, achieved by the collar 46, can be used for an additional function: providing axial guidance for the roller 13. Thus, the axial retention of the roller 13 in its housing in the piston 12 is ensured (laterally in [Fig. 6], at the two arrows 52) by the inner rings of the bearings 14, 15. For this purpose, the axial distance between the two inner rings of the bearings 14, 15 is equal to the axial width of the rollers 13 of the pistons 12 plus a functional clearance. This functional clearance allows the roller 13 to slide between the inner rings of the bearings 14, 15 while axially guiding the roller 13.Such a functional clearance can be, for example, on the order of 0.1 mm to 1 mm, or even several millimeters, depending on the materials used, the operating temperature, etc.

[0115] In this context, an "X-shaped" bearing arrangement is then permitted, which is clearly advantageous in terms of cost. Given the additional function thus given to the hydraulic fluid used in the drainage function, it is also advantageous to supply the drain inlet 31 with hydraulic fluid preferably at a low temperature.

[0116] Figure 6 is a simplified diagram illustrating the drainage circuit associated with the Hydrostatic machine 48. This diagram represents some elements of the hydraulic circuit: the hydraulic reservoir 51 and a cooler 50, which is a heat exchanger used to lower the temperature of the hydraulic fluid. The other elements of the circuit, particularly the high- and low-pressure sections that perform the mechanical function of the hydrostatic machine, are conventional and have not been shown.

[0117] The heat exchanger constituting the cooler 50 is generally present in most hydraulic circuits, and is advantageously used here to supply a pump 49 of the drainage circuit which itself will supply the drain inlet 31. The drain outlet returns in a conventional manner to the hydraulic reservoir 51.

[0118] The piston / cylinder interface can thus be lubricated and cooled by a low temperature hydraulic fluid, on the order of 50 °C for example, and which therefore has a higher viscosity, by taking advantage of the drainage function.

[0119] An extremely simplified arrangement of the hydrostatic machine is thus obtained, with increased compactness using only two bearings 14, 15 mounted on the flanges 16, 17 of the cylinder block 10, a single rotating joint (the lip seal 30) between the rotor and the stator, with all the hydraulic fittings protruding from the same face of the hydrostatic machine.

[0120] Alternative embodiments may be envisaged. In particular, the hydrostatic machine may include several drainage conduits 44 distributed circumferentially on the annular casing 5.

Claims

Demands

1. Hydrostatic rotating machine with radial pistons comprising: - an internal element (1) and an external element (2) coaxial and mounted to rotate relative to each other about an axis of rotation (R), one of these elements being a rotor and the other of these elements being a stator; the internal element (1) comprising a cylinder block (10) having cylinders (11) equipped with radially movable pistons (12) distributed circumferentially; the external element (2) comprising an annular housing (5) surrounding the cylinder block (10), as well as a cam ring (9) mounted in the annular housing (5) and comprising a cam track (8) on its internal circumference; the pistons (12) being adapted to cooperate with the cam track (8) in a coordinated manner with the rotation of the rotor relative to the stator;- a hydraulic distributor (18) adapted to selectively connect the cylinders (11) to a hydraulic circuit, by means of a synchronizing junction forming a rotating coupling between the rotor and the stator; this hydrostatic rotating machine being characterized in that the cam ring (9), on its external circumference, and the annular housing (5), on its internal face, each have a nesting profile, one of these nesting profiles being a concavity (41), and the other of these nesting profiles being a convexity (38), the two nesting profiles being of complementary shapes and being nested one inside the other.;

2. Hydrostatic machine according to claim 1, characterized in that the cam ring's socket profile (9) is a concavity (41), and the annular housing's socket profile (5) is a convexity (38).

3. Hydrostatic machine according to any one of the preceding claims, characterized in that the cam ring (9) and the annular housing (5) have a plurality of circumferentially regularly distributed interlocking profiles.

4. Hydrostatic machine according to any one of the preceding claims, characterized in that said concavity (41) is a recess with curved lateral edges, and said convexity (38) is a bulge with curved lateral edges.

5. Hydrostatic machine according to any one of the preceding claims, characterized in that the cam ring (9) and of the annular housing (5) have the same axial dimension, this axial dimension being equal to the axial thickness of the cam ring (9).

6. Hydrostatic machine according to any one of the preceding claims, characterized in that the cam track (8) comprises a succession of lobes (40) and hollows (39), and the cam ring (9) comprises as many interlocking profiles as there are lobes (40) of the cam track (8).

7. Hydrostatic machine according to claim 6, characterized in that the cam ring (9) interlocking profiles are radially centered with the lobes (40) of the cam track (8).

8. Hydrostatic machine according to any one of the preceding claims, characterized in that the inner face of the annular housing (5) comprises: an internal cylindrical bearing surface (36) for a bearing (15) disposed between the rotor and the stator; and an internal bearing surface (26) for the cam ring (9); these two internal bearing surfaces (26,36) being formed of the same internal cylindrical surface which supports the interlocking profiles of the annular housing (5) on its axial portion receiving the cam ring (9).

9. Hydrostatic machine according to any one of the preceding claims, characterized in that the cam ring (9) is axially stopped by an internal shoulder (27) of the annular housing (5), this shoulder (27) further defining an internal cylindrical bearing surface (24) for a bearing (14) disposed between the rotor and the stator.

10. Hydrostatic machine according to any one of the preceding claims, characterized in that the cam ring (9) is axially fitted by clamping into the annular housing (5), with interlocking of the interlocking profiles.

11. Hydrostatic machine according to any one of the preceding claims, characterized in that it comprises at least one drainage conduit (44) made in the thickness of the wall of the annular casing (5), substantially parallel to the axis of rotation (R), and passing through the interlocking profile of the annular casing (5).

12. Hydrostatic machine according to claim 11, characterized in that the drainage conduit (44) opens outside the annular housing (5) by means of a drain outlet (31), on the same side of the hydrostatic machine as all the other hydraulic conduits of the hydrostatic machine.

13. Hydrostatic machine according to any one of claims 11 to 12, characterized in that the drainage conduit (44) opens inside the annular casing (5), axially opposite the cylinders (11).

14. Hydrostatic machine according to claim 13, characterized in that the drainage conduit (44) opens onto a lateral face of the interlocking profile which it crosses.

15. Hydrostatic machine according to claim 13, characterized in that the drainage conduit (44) opens axially opposite at least one diffusion gap (45,47).

16. Hydrostatic machine according to claim 15, characterized in that said diffusion gap comprises a diffusion notch (45) made in a cover (7) which is arranged opposite the cam ring (9) and which hermetically closes one side of the hydrostatic machine.

17. Hydrostatic machine according to any one of claims 15 or 16, characterized in that said diffusion gap has a functional clearance (47) between the cam ring (9) and the inner ring of a bearing (15) disposed between the rotor and the stator.

18. Hydrostatic machine according to any one of claims 11 to 17, characterized in that the cylinder block (10) has a collar (46) centered on its outer circumference, this collar (46) being adapted to form an axial stop for two bearings (14,15) disposed between the rotor and the stator, this collar (46) having an axial dimension equal to the axial thickness of the cam ring (9) plus a functional clearance.

19. Hydrostatic machine according to claim 18, characterized in that the axial distance between the two inner rings of the bearings (14, 15) is equal to the axial width of the rollers (13) of the pistons (12) plus a functional clearance.

20. Hydrostatic machine according to any one of claims 11 to 19, characterized in that the drainage conduit (44) is supplied with hydraulic fluid from a cooler (50) disposed on the hydraulic circuit.

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