Hydrostatic rotating machine with a drainage port in at least one cylinder

Abstract

Hydrostatic radial piston rotation machine comprising: an internal element and an external element coaxial and mounted to rotate relative to each other about 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 (10); the external element comprising a cam track. The machine comprises a drainage circuit which comprises, for at least one cylinder (11), an injection duct (26) passing through the wall of the cylinder (11), the injection duct (26) opening at one of its ends into the cylinder (11) through a port (27), and opening at the other of its ends, from the cylinder block (10), into a drainage space supplied with hydraulic fluid. Figure for the abstract: Fig.2

Description

Title of the invention: Hydrostatic rotating machine with a drainage port in at least one cylinder

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

[0002] Hydrostatic rotation 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 powered by a pressurized hydraulic fluid and in response drives the rotating drive element.

[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. PRIOR ART

[0005] Patent application WO2020008145 describes a hydrostatic rotation machine comprising: - a rotor comprising a cylinder block having cylinders fitted with radially movable pistons distributed circumferentially; - a stator comprising a cam path; the pistons being adapted to cooperate with the cam path 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 using a hydraulic fluid, thanks to a synchronization junction forming a rotating coupling between the rotor and the stator.

[0006] Such a hydrostatic machine can be improved with respect to its efficiency. Statement of the invention

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

[0008] To this end, the invention relates to a hydrostatic rotation 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 provided with radially movable pistons distributed circumferentially cially; the external element comprising a cam path; the pistons being adapted to cooperate with the cam path 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 using a hydraulic fluid, thanks to a synchronization junction forming a rotating coupling between the rotor and the stator.

[0009] This hydrostatic rotation machine comprises a drainage circuit which comprises, for at least one cylinder, an injection conduit passing through the wall of the cylinder, the injection conduit opening through one of its ends into the cylinder through a port, and opening through the other of its ends, from the cylinder block, into a drainage space supplied with hydraulic fluid.

[0010] Preferably, all the cylinders of the cylinder block comprise such an injection duct.

[0011] The invention makes it possible to improve the efficiency of the hydrostatic machine, by combining measures which are known to be irreconcilable: - the design of a hydrostatic machine with reduced clearance between the pistons and cylinders, which allows an increase in the power of the machine with equal displacement; - increased reliability and lifespan, thanks to reduced wear on pistons and cylinders.

[0012] In the prior art, a large functional clearance between the pistons and the cylinders ensures the absence of hot spots and wear. Hydraulic fluid leakage, through this functional clearance, is also evacuated by the drainage circuit. However, significant power losses are the result of this reliability, because of the importance of this leak created between the cylinders and the pistons. Even when this functional clearance is reduced, these engines encounter a power limitation.

[0013] Thanks to the invention, the functional clearance between the pistons and the cylinders can be possibly reduced, without negative compensation, but such a hydrostatic machine pushes back in any case the classic limits of power that are usually encountered at equal cylinder capacity, thanks to improved work at the level of the cooperation of the pistons in the cylinders. A gain of at least 30% of power, at equal cylinder capacity, is possible by implementing the invention.

[0014] The hydrostatic machine also remains compact, because the proposed drainage function is implemented with few modifications and without increasing the size.

[0015] A significant increase in power is thus obtained without a notable increase in production cost. More powerful hydraulic motors, or those of reduced size with equal power, can thus be produced.

[0016] The invention allows for numerous variants in the arrangement of the drainage circuit. In particular, particularly advantageous variants, in which a pressure chamber is created axially opposite the hydraulic distributor so that this pressure chamber compensates for the thrust created by the cylinder function of the hydraulic distributor and thus relieves the pressure on the bearings which allow the rotor to rotate relative to the stator, which provides a significant extension of the service life or a possibility of reviewing the dimensioning of the bearings downwards, with the associated cost and weight savings.

[0017] The hydrostatic machine according to the invention may include the following additional characteristics, alone or in combination:

[0018] - said light forms an opening in the wall of the cylinder, which extends sen possibly along the axial direction;

[0019] - the injection duct and the light are formed from the same drilling profile of the cylinder block, substantially parallel to the axis of rotation and tangential to the cylinder;

[0020] - said light is arranged on the stroke of the piston;

[0021] - said light is uncovered when the piston is at bottom dead center, and the light is blocked by the piston during its stroke;

[0022] - the piston comprises a seal arranged between the piston and the cylinder, this seal having a race which is radially below or above said light;

[0023] - said drainage space comprises a pressure chamber supplied with hygienic fluid hydraulic and in fluid contact with the injection conduits;

[0024] - the pressure chamber is formed between a rotating joint which hermetically closes specifically a junction between the rotor and the stator, and an annular seal disposed between the external element and the cylinder block;

[0025] - the cylinder block has a cylindrical collar projecting coaxially with the axis of rotation, the injection conduits extending axially in this cylindrical collar and opening through the edge of the cylindrical collar;

[0026] - said annular seal is arranged between the external element and the cylindrical collar;

[0027] - the cylinder block has two collars arranged on either side of the cylinders, with a bearing mounted between each collar and the outer member, the cylindrical collar projecting from one of these collars;

[0028] - the pressure chamber and the hydraulic distributor are axially located on either side and other side of the cylinder block;

[0029] - the machine comprises: an axial chamber centered on the axis of rotation, and supplied with hydraulic fluid; and a radial drainage conduit extending between the axial chamber and the pressure chamber;

[0030] - the synchronization junction is in communication with the axial chamber, the functional leak at synchronization injunction supplying the axial chamber with hydraulic fluid;

[0031] - the machine comprises a hydrostatic valve arranged in the axial chamber, connected to the hydraulic distributor, and adapted to supply the axial chamber with hydraulic fluid;

[0032] - the drainage circuit comprises a drain inlet arranged on the external element and in fluid communication with the pressure chamber;

[0033] - the drain inlet is connected to the pressure chamber by a drainage conduit extending axially in the thickness of the wall of the external element;

[0034] - the drain inlet is supplied with hydraulic fluid from a cooler arranged on the hydraulic circuit;

[0035] - said light is positioned diametrically opposite to the application training efforts, when rotating in the normal direction of rotation. PRESENTATION OF FIGURES

[0036] Other characteristics and advantages of the invention will emerge from the non-limiting description which follows, with reference to the appended drawings in which:

[0037] - [Fig. 1] is an axial sectional view of a hydrostatic machine according to a first embodiment of the invention;

[0038] - [Fig.2] illustrates in perspective the cylinder block of the hydrostatic machine;

[0039] - [Fig.3] is a schematic top view of the cylinder block of the hydro machine static;

[0040] - [Fig.4] and [Fig.5] illustrate a piston of the hydrostatic machine in its cylinder, respectively at bottom dead center and top dead center;

[0041] - [Fig.6] illustrates a second embodiment of the hydrostatic machine according to the invention;

[0042] - [Fig.7] schematically illustrates a hydrostatic valve of the hydro machine static of [Fig.6];

[0043] - [Fig.8] is an axial section of a hydrostatic machine according to a third embodiment of the invention;

[0044] - [Fig.9] is a schematic view illustrating the drainage circuit of the machine hydrostatic.

[0045] Elements similar and common to the various embodiments bear the same reference numbers in the figures. DETAILED DESCRIPTION

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

[0047] This hydrostatic machine is either a hydraulic motor rotating a element from a pressurized hydraulic fluid, or a hydraulic pump adapted to put a pressurized 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] Among the internal element 1 and the external element 2, one of these elements is a rotor while the other of these elements 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 is in this example 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 which hermetically closes one of the openings (on the right of [Fig.l]) of this annular housing 5, and a second cover 7 which hermetically closes the opposite opening (on the left of [Fig.l]). The second cover 7 comprises at its interface with the splined shaft 3, a rotating joint 37.

[0052] The external element 2 further comprises a cam path 8 characteristic of hydrostatic machines with radial pistons. In a known manner, this cam path 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] In this example, optionally, the cam path 8 is carried by a cam ring 9 mounted on an internal face of the annular housing 5, with the same advantages as those described in the patent application WO2020008145. In particular, the cam ring 9 can be made from a grade of steel called “bearing steel”, or “carbon steel”, which has a significant proportion of carbon, high resistance to wear and fatigue, but which is however sensitive to impacts. The weakness of the cam ring with respect to impacts is compensated by its mounting in the annular housing 5, which is ductile. The high performance of a material resistant to contact pressure and fatigue can thus benefit the cam track 9, without suffering the disadvantages 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 are mounted, in a known manner, radially movable pistons 12.

[0055] In a known manner, the cylinders 11 are radial cylinders which extend over the entire circumference of the cylinder block 10, angularly distributed in a regular manner around the axis of rotation R, and the pistons 12 each comprise, on their end facing the cam path 8, a roller 13 allowing rolling without sliding on the cam path 8.

[0056] The cam paths for hydrostatic machines, the cooperation with the radial pistons 12, 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 internal element 1 and the external element 2 are mounted to rotate relative to each other thanks, in this example, to a first bearing 14 and a second bearing 15 directly mounted between the internal element 1 and the external element 2. These bearings 14, 15 are inserted into the annular housing 5 on either side of the cam ring 9. The example of [Fig.l] illustrates two possible assemblies of the bearings 14, 15 in the annular housing 5: a direct assembly of the bearing with its external ring in contact with the annular housing 5 (this is the case of the first bearing 14); and an assembly 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 a collar 46 which is part of the second cover 7.

[0058] The cylinder block 10 comprises two collars 16, 17 arranged on either side of the cylinders 11, with a bearing 14, 15 mounted between each collar 16, 17 and the external element 2, the internal ring of each bearing 14, 15 being directly mounted on the corresponding collar 16, 17.

[0059] 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, forming a direct interface between the internal element 1 and the external element 2.

[0060] 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.

[0061] The distribution base 4 comprises 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.

[0062] 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.

[0063] The hydraulic distributor 18 is mounted on the distribution base 4, being axially movable relative to the latter, the two parts being coupled in rotation for example by means of pins allowing axial sliding.

[0064] The hydraulic distributor 18 of the present example comprises a central chamber 22 and a peripheral chamber 23 each connected to the fluid inlet 19 or fluid outlet 20. [Fig.l] illustrates the connection of the chambers 22, 23 to the fluid inlets / outlets 19, 20 according to the present example.

[0065] Seals allow the hermetic partitioning of the chambers 22, 23, while allowing the 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, at a synchronization junction 40, by opposing the forces generated during the implementation of the synchronization, that is to say the selective pressurization of the cylinders 11.

[0066] The hydraulic distributor 18 acts in the main hydraulic circuit and makes it possible to selectively put into fluid communication, depending on the rotation of the rotor relative to the stator, the high and low pressure circuits with channels 32 each connected to a cylinder 11.

[0067] The cylinder thus created by the hydraulic distributor 18 has the effect of countering the repulsion force exerted in the synchronization junction 40, between the hydraulic distributor 18 and the cylinder block 10. This cylinder function of the hydraulic distributor 18 also causes axial stress on the bearings 14, 15.

[0068] The hydrostatic machine further comprises a drainage circuit making it possible to renew the hydraulic fluid bathing the internal space of the hydrostatic machine and draining the hydraulic fluid produced by functional leaks occurring in particular at the hydraulic distributor 18 and more precisely at the synchronization junction 40.

[0069] The drainage circuit comprises a drain outlet 24 which is connected to the external hydraulic circuit and through which the hydraulic fluid in the drainage function is discharged, with a relatively reduced flow rate.

[0070] The hydraulic fluid participating in this drainage function is supplied within the hydraulic machine itself, by the functional leaks mentioned, in particular to the hydraulic distributor 18, and possibly by an external drain inlet dedicated to the drainage function as explained later as a variant.

[0071] In the drainage circuit, the hydraulic fluid is caused to pass from a space internal of the hydrostatic machine to the other, depending on the possibilities of fluid communication, until exiting through the drain outlet 24.

[0072] The drainage circuit is here arranged to perform an additional function of assisting the work of the pistons in the cylinders. In the drainage circuit, the hydraulic fluid is thus caused to further pass through the wall of the cylinder block 10 and to flow into the cylinders 11.

[0073] Of the two collars 16, 17 of the cylinder block 10, the collar 17 is the one arranged opposite the hydraulic distributor 18 and the drain outlet 24. This collar 17 and the distributor 18 are thus placed axially on either side of the cylinders 11. This collar 17 comprises a collar 25 formed by a cylinder projecting from the collar 17 in the direction of the second cover 7 and centered on the axis of rotation R. The collar 25 and the rotor are thus coaxial.

[0074] [Fig. 2] is a perspective view, in half-section, of the cylinder block 10 and the splined shaft 3 to which it is attached. [Fig. 2] shows this collar 25.

[0075] With reference to figures 1 and 2, for each cylinder 11, the drainage circuit comprises an injection conduit 26 made in the thickness of the wall of the collar 25, passing through the cylinder block 10, and opening into the corresponding cylinder 11.

[0076] [Fig. 1] schematically illustrates in dotted lines the path of this injection duct 26 in the thickness of the wall of the collar 25 and in the material of the cylinder block 10. This path of the injector duct 26 is shown in dotted lines, because it is in the material: in [Fig. 1], the angular position of the section plane does not pass through one of the injection ducts 26.

[0077] [Fig. 2] shows three of the injection conduits 26 on the side where they open through the edge of the collar 25. The injection conduits 26 extend into the material of the cylinder block 10 and each open into a cylinder 11 through a port 27.

[0078] The injection conduits 26 can have any suitable shape, up to reaching the light 27. Many shapes are possible thanks to manufacturing processes such as molding or additive manufacturing.

[0079] However, according to a particularly advantageous embodiment allowing a rapid and inexpensive process, each injection conduit 26 is a rectilinear bore obtained by drilling in a single operation and angularly positioned to directly open tangentially into the cylinder 11, thereby forming the port 27.

[0080] [Fig. 3] is a schematic view illustrating the cylinder block 10 seen from above with a cylinder 11 in the center, seen from above. A drilling profile 28, delimited by dotted lines, schematizes the bore produced by a drill adapted to form in a single pass the injection conduit 26 and the port 27 opening into the cylinder 11.

[0081] These elements are thus formed at lower cost with a single drilling operation, preferably completed by a simple operation of deburring or chamfering the sharp edges of the light 27 thus created.

[0082] In each cylinder 11, the light 27 forms an opening in the wall of the cylinder 11, an opening which extends substantially in the axial direction. In other words, the light 27 extends perpendicular to the stroke of the piston 12, along an angular portion of the internal wall of the cylinder 11. Of the order of 1 / 4 or 1 / 3, or even 1 / 2, of the circumference of the internal wall of the cylinder can thus be occupied by this light 27.

[0083] Each injection duct 26 therefore opens through one of its ends into a cylinder 11. Through the other of its ends, it opens from the cylinder block 10 (in this example, the injection duct 26 opens from the edge of the collar 25 of the cylinder block 10) into a drainage space 55.

[0084] The drainage space 55 here specifically designates an internal cavity of the hydraulic machine which is supplied with drainage hydraulic fluid, that is to say with fluid circulating on the margin of the power function. When the hydraulic fluid is in the high pressure circuit, to be supplied to the cylinders and to drive the rotation of the rotor relative to the stator (in the example of a hydraulic motor), it is at a pressure of the order of 400 bars. When this fluid is in the drainage circuit (after having exited in the form of a leak at the synchronization junction 40, for example), and is at a pressure of the order of 20 bars. This hydraulic fluid then circulates in the drainage spaces, until being evacuated via the drain outlet 24 and returning to the general hydraulic circuit.

[0085] The drainage space 55 is therefore in fluid communication with a supply of hydraulic fluid from the drainage circuit.

[0086] The injection conduit 26 opening into this drainage space 55, and this space being moreover regularly supplied with hydraulic fluid, the hydraulic fluid is therefore caused to enter the injection conduit 26 through the edge of the collar 25, to pass through the collar 25 and the wall of the cylinder block 10 by traveling through this injection conduit 26, and then to open through the port 27 into the cylinder 11.

[0087] The height of the light 27, that is to say the position of the light 27 along the axis of the corresponding cylinder 11, is preferably chosen such that the light 27 is on the stroke of the piston 12. The light 27 is thus swept by the piston 12. A point of uncovering of the light 27 by the piston can also be provided so that the hydraulic fluid can emerge above or below the piston 12.

[0088] Figures 4 and 5 are partial views, in radial section, of the cylinder block 10 showing a cylinder 11 with its piston 12, as well as the corresponding portion of the cam path 8. The gap 54 between the piston 12 and its roller 13 is intended for a bearing. In the case of a hydraulic motor, the piston 12 is pushed in the direction of the cam path 9 in its output stroke, and the roller 13 rolls on the lobe 29, causing the rotor to rotate.

[0089] The piston 12 is formed of a body having an external cylindrical surface intended to slide in the cylinder 11. The piston 12 is provided with a seal 31, which in this example is a sealing segment, to limit functional leaks when the piston 12 is pushed towards its top dead center by the high-pressure oil arriving via the channel 32.

[0090] The following two positions are illustrated: - piston 12 at bottom dead center ([Fig.4]); - piston 12 at top dead center ([Fig.5]).

[0091] In the example illustrated, the direction of rotation of the cylinder block 10 (which is part of the rotor in this example) is indicated by the arrow 33.

[0092] The positions of [Fig.4] and 5 correspond respectively to the passage of the roller over a lobe 29 of the cam path 8 and in a hollow 30 of the cam path 8.

[0093] In the present example, when the piston 12 is at bottom dead center ([Fig.4]), the external cylindrical surface of the piston passes under the port 27, and the latter is therefore uncovered. The hydraulic fluid of the drainage circuit, which circulates in the injection conduit 26, then exits freely through the port 27 and spreads into the cylinder 10, over the entire circumference of the head of the piston 12. This hydraulic fluid lubricates and cools the head of the piston 12 as well as the functional clearance between the piston and the cylinder over the first few millimeters of the piston head, this zone being the most critical with regard to stresses and the risk of hot spots forming.

[0094] During its stroke, from bottom dead center to top dead center, the piston 12 then sweeps the port 27, its external cylindrical surface sweeping the cylinder 11, covering this port 27. The port 27 is therefore positioned between the cylinder 11 and the piston 12, opposite the interstitial zone forming the functional clearance between these two moving parts.

[0095] The position of the port 27 and the design of the piston 12 are also chosen so that the seal 31 does not sweep the port 27 at any time. In this example, at the top dead center of the piston 12 ([Fig.5]), the seal 31 is located just below the port 27.

[0096] Generally speaking, the seal 31 is designed to undergo a stroke which is either radially below or radially above the light 27, but without sweeping it.

[0097] Thus, during the stroke of the piston 12, during which the latter exerts a significant force on the cam path 8, driving the rotor in rotation relative to the stator, the port 27 forms a film of pressurized oil in the gap between the piston 12 and the cylinder 12.

[0098] The direction of rotation indicated by the arrows 33 in Figures 4 and 5 indicates the normal direction of rotation of the cylinder block 10. The normal direction of rotation designates the single direction of rotation in the case of a hydrostatic machine with a single direction of rotation, and designates the most used direction of rotation in the case of a hydrostatic machine with two directions of rotation but with a preferred direction of rotation which will be mainly implemented during the life of the machine (this is the case, for example, of a motor with two directions of rotation for the forward and reverse movement of a vehicle).

[0099] The hydrostatic machine is preferably adapted to the normal direction of rotation and the port 27 is thus positioned to promote the work of the pistons 12 during the normal direction of rotation. In each cylinder 11, the port 27 is positioned diametrically opposite the application of the driving forces, during rotation in the normal direction of rotation.

[0100] When the piston 12 is in its stroke towards its top dead center, under the effect of the high pressure hydraulic circuit, and the roller 13 exerts a significant force on the cam path 8, the reaction force of the cam path is oblique. For example, in [Fig. 5], when the roller 13 passes the point 34 illustrated in the figure, this reaction force at the point 34 (during contact between the roller 13 and the cam path 8) is an oblique force F pushing the piston 12 against the cylinder 11 with a maximum stress at the area where the port 27 is arranged.

[0101] The film of pressurized hydraulic fluid created by the light 27 is thus located at the level of the most critical zone for the work of the piston 12 in the cylinder 11.

[0102] This arrangement further promotes, in the design of the hydrostatic machine, the possibility of reducing the cylinder / piston clearance by treating the most critical point, which is normally a zone of stress, heating, or even tightening, in the event of too little clearance.

[0103] The hydraulic fluid in the drainage circuit is thus used to assist the piston / cylinder work. After passing through the cylinders 11, this fluid continues its path in the drainage circuit. In this example, it passes between the balls of the bearing 14 towards the first cover 6 and is evacuated through the drain outlet 24.

[0104] To supply the drainage space 55, and allow the circulation of the hydraulic fluid in the injection conduit 26, several solutions are possible. Any solution for arranging the drainage circuit allowing sufficient pressure of the hydraulic fluid to make it travel through the injection conduits 26 is suitable. For example, a sufficiently abundant functional leak source, located near the drainage space 55, can be channeled there.

[0105] According to a first embodiment of the supply of the drainage space 55, with reference to [Fig.l], the drainage space 55 comprises a pressure chamber 35 intended to create sufficient pressure so that the hydraulic fluid tends to flow through the injection pipe 26. This is not a high pressure comparable to that of the high-pressure hydraulic circuit, but a pressure rather comparable to that of the low-pressure circuit. A pressure of a few bars is sufficient a priori.

[0106] Advantageously, this pressure chamber 35 is created by a simple annular seal 36 arranged between the external element 2 and the second cover 7, and more precisely, in this example, the pressure chamber 35 is created between the collar 25 which carries the injection conduits 26 and the second cover 7.

[0107] The rotating joint 37 is used here for two functions: rotating joint which hermetically closes a junction between the rotor and the stator; and closing, with the annular joint 36, of the pressure chamber 35.

[0108] The annular seal 36 is not required to have a high level of sealing, since a leak at this level has no impact on the proper functioning of the hydrostatic machine. This seal 36 can therefore be chosen to exert a low constraint on the rotation, and to simply ensure a rise in pressure of the pressure chamber 35.

[0109] The pressure chamber 35 is itself supplied by any means with hydraulic fluid from the drainage circuit. [Fig.l] illustrates an example in which a radial drainage conduit 38 is formed between an axial chamber 39, centered on the axis of rotation R, and the pressure chamber 35. The radial drainage conduit is illustrated in dotted lines.

[0110] The axial chamber is delimited partly by the internal element 1, and partly by the external element 2 (the hydraulic distributor 18). The radial drainage conduit 38 is made in the internal element 1.

[0111] In the illustrated architecture, the synchronization junction 40 generates hydraulic leaks during its operation, here called functional leaks. This synchronization junction 40 opens through one of its edges into this axial chamber 39. The axial chamber 39 will therefore fill with hydraulic fluid thanks to this functional leak and the hydraulic fluid will pass through the radial drainage conduit 38 to the pressure chamber 35 at the same flow rate as that provided by the leak from the synchronization junction 40.

[0112] This measurement may be sufficient for pressurizing the pressure chamber 35 if the functional leak is sufficiently abundant. If necessary, if the pressure obtained is too high, this flow rate can be calibrated, and in particular by the diameter of the radial drainage conduit 38.

[0113] The hydrostatic machine thus has a drainage circuit without external power supply, supplied simply by the internal functional leaks, while implementing the described function of assisting the work of the pistons.

[0114] [Fig.6] illustrates a second embodiment in which the drainage space 55 also comprises a pressure chamber 35, but which provides different, alternative or complementary means, allowing the pressure chamber 35 to be pressurized. [Fig.6] is a half-section illustrating in this example a hydrostatic valve 41 which is mounted in a collar 42 of the hydraulic distributor 18.

[0115] The hydrostatic valve 41 is in fluid communication with the hydraulic distributor 18. This hydrostatic valve 41 can perform any desired function, using elements known in hydraulics, such as hydrostatic distributors, flow or pressure regulating valves, etc. This hydrostatic valve is intended to recover hydraulic fluid from the distributor 18 and to supply it into the axial chamber 39, according to the desired pressure or flow rate.

[0116] [Fig.7] illustrates an example of the construction of a hydrostatic valve 41, according to a particularly advantageous embodiment. The hydrostatic valve 41 comprises a three-way distributor 50 adapted to select one or other of the chambers 22, 23 of the hydraulic distributor 18 (the one which, at a given moment, is at low pressure). The three-way distributor 50 puts this low-pressure fluid in communication with a pressure limiter 51 to obtain the desired pressure. No loss of power at the high-pressure circuit is thus caused by the drainage circuit.

[0117] The hydrostatic valve may optionally include a pressure sensor 52 and thus supplies the axial chamber 39. The circuit is extended by a constriction which may be formed by the radial drainage conduit 38, and thus leads to the pressure chamber 35.

[0118] With the hydrostatic valve 41, it is possible to control the pressure of the hydraulic fluid which will be inserted between the pistons 12 and their cylinder 11, through the port 27.

[0119] [Fig.8] illustrates a third embodiment in which the drainage space 55 also comprises a pressurization chamber 35, but which provides different, alternative or complementary means, allowing the pressurization of the pressure chamber 35. The hydrostatic machine here comprises a drain inlet 43 on the edge of the annular housing 5, on the side of the first cover 6, that is to say on the side where all the other hydraulic connections exit, which is an advantage for example for hydraulic motors housed in wheel hubs.

[0120] The drain inlet 43 is connected to a drainage duct 44 extending in the thickness of the wall of the annular housing 5, parallel to the axis of rotation R and extending axially beyond the cam ring 9 and the second bearing 15 until it opens out opposite another drainage duct 45 made in the second cover 7 and opening out into the pressure chamber 35.

[0121] In the present example, taking into account the construction of the hydrostatic machine with the bearings 14, 15 and the cam ring 9 mounted on several internal cylindrical bearing surfaces of the annular housing 5, the drainage conduit 44 of the annular housing 5 comprises a first section 44A which is formed integrally in the material of the annular housing 5, and a second section 44B which extends in a groove opening into the annular housing 5, this groove being closed by the collar 46 of the cover 7 (the collar 46 which also serves as a bearing surface for the second bearing 15).

[0122] The drainage conduits 44, 45 do not require sealing means other than the mechanical adjustment of these parts, given the low pressure involved and the fact that leaks at this level, with regard to the drainage circuit, do not impact the operation of the hydrostatic machine. A fluid conduit is thus formed by the drainage conduits 44, 45 between the drain inlet 43 and the pressure chamber 35.

[0123] An independent external drain inlet 43 can thus be directly connected to the pressure chamber 35 and the flow injected at the drain inlet 43 will then be recovered at the drain outlet 24, in addition to the functional leaks. The pressure in the pressure chamber 35 can then be regulated by any external device of the hydraulic circuit, with the appropriate components.

[0124] The temperature of the drainage hydraulic fluid can also be controlled. Considering the additional function of the drainage circuit enabling assistance to the work of the pistons in the cylinders, it is advantageous here to supply the drain inlet 31 with hydraulic fluid preferably at low temperature.

[0125] [Fig.9] is a simplified diagram illustrating the drainage circuit associated with the hydrostatic machine 53. This diagram represents certain elements of the hydraulic circuit: the hydraulic reservoir 49 and a cooler 48, which is a heat exchanger for lowering the temperature of the hydraulic fluid. The other elements of the circuit, in particular the high and low pressure portions allowing the mechanical function of the hydrostatic machine are conventional and have not been shown.

[0126] The exchanger constituting the cooler 48 is generally present in most hydraulic circuits, and is advantageously used here to supply a pump 47 of the drainage circuit which itself will supply the drain inlet 43. The drain outlet 24 returns in a conventional manner to the hydraulic reservoir 49.

[0127] The piston / cylinder interface can thus be pressurized at the appropriate locations, and cooled by a low-temperature hydraulic fluid, of the order of 50°C for example, taking advantage of the drainage function.

[0128] The pump 47 can itself regulate the pressure in the pressure chamber 35, or alternatively be associated with any other known component allowing this regulation.

[0129] Furthermore, the pressurization of the pressure chamber 35 makes it possible to create on the internal element 1 a force opposing the force exerted by the distributor hy hydraulic 18 on this internal element 1 (and more precisely on the cylinder block 10) thanks to the cylinder function of the hydraulic distributor 18. As the pressure chamber 35 and the hydraulic distributor 18 are axially located on either side of the cylinder block 10, the latter has these two forces applied to it on either side. Thus, the force exerted by the pressure chamber 35 on the cylinder block 10 is subtracted from the force exerted by the cylinder function of the hydraulic distributor 18. This relieves the axial pressure exerted on the bearings 14, 15 and increases their service life, or allows them to be reduced in size.

[0130] Alternative embodiments may be envisaged. Any other means for forcing the passage of the hydraulic drainage fluid into the injection conduits 26 may be envisaged.

[0131] Furthermore, the embodiments can be combined, in particular so that the drainage space is supplied with hydraulic fluid from several sources.

Claims

Claims

1. 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) having cylinders (11) provided with radially movable pistons and distributed circumferentially; the external element (2) comprising a cam path (8); the pistons being adapted to cooperate with the cam path (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 using a hydraulic fluid, by means of a synchronization junction (40) forming a rotating coupling between the rotor and the stator;this hydrostatic rotation machine being characterized in that it comprises a drainage circuit which comprises, for at least one cylinder (11), an injection conduit (26) passing through the wall of the cylinder (11), the injection conduit (26) opening through one of its ends into the cylinder (11) through a port (27), and opening through the other of its ends, from the cylinder block (10), into a drainage space (55) supplied with hydraulic fluid.;

2. Hydrostatic machine according to claim 1, characterized in that said light (27) forms an opening in the wall of the cylinder (11), which extends substantially in the axial direction.

3. Hydrostatic machine according to claim 2, characterized in that the injection duct (26) and the light (27) are formed from the same drilling profile (28) of the cylinder block (10), substantially parallel to the axis of rotation (R) and tangentially to the cylinder (11).

4. Hydrostatic machine according to one of the preceding claims, characterized in that said light (27) is arranged on the stroke of the piston (12).

5. Hydrostatic machine according to claim 4, characterized in that said port (27) is uncovered when the piston (12) is at bottom dead center, and the port (27) is closed by the piston (12) during its stroke.

6. Hydrostatic machine according to claim 5, characterized in that the piston (12) comprises a seal (31) arranged between the piston (12) and the cylinder. (11), this seal (31) having a stroke which is radially below or above said light (27).

7. Hydrostatic machine according to one of the preceding claims, characterized in that said drainage space (55) comprises a pressure chamber (35) supplied with hydraulic fluid and in fluid contact with the injection conduits (26).

8. Hydrostatic machine according to claim 7, characterized in that the pressure chamber (35) is formed between a rotating seal (37) which hermetically closes a junction between the rotor and the stator, and an annular seal (36) arranged between the external element (2) and the cylinder block (10).

9. Hydrostatic machine according to one of claims 7 or 8, characterized in that the cylinder block (10) comprises a cylindrical collar (25) projecting coaxially with the axis of rotation (R), the injection conduits (26) extending axially in this cylindrical collar (25) and opening out through the edge of the cylindrical collar (25).

10. A hydrostatic machine according to claim 9 when dependent on claim 8, characterized in that said annular seal (36) is arranged between the external element (2) and the cylindrical collar (25).

11. Hydrostatic machine according to one of claims 9 or 10, characterized in that the cylinder block (10) comprises two collars (16, 17) arranged on either side of the cylinders (11), with a bearing (14, 15) mounted between each collar (16, 17) and the external element (2), the cylindrical collar (25) projecting from one of these collars (17).

12. Hydrostatic machine according to one of claims 7 to 11, characterized in that the pressure chamber (35) and the hydraulic distributor (18) are axially located on either side of the cylinder block (10).

13. Hydrostatic machine according to one of claims 7 to 12, characterized in that it comprises: an axial chamber (39) centered on the axis of rotation (R), and supplied with hydraulic fluid; and a radial drainage conduit (38) extending between the axial chamber (39) and the pressure chamber (35).

14. Hydrostatic machine according to one of claims 7 to 13, characterized in that the synchronization junction (40) is in communication with the axial chamber (39), the functional leak at the synchronization junction (40) supplying the axial chamber (39) with hy- draulic.

15. Hydrostatic machine according to one of claims 7 to 14, characterized in that it comprises a hydrostatic valve (41) arranged in the axial chamber (39), connected to the hydraulic distributor (18), and adapted to supply the axial chamber (39) with hydraulic fluid.

16. Hydrostatic machine according to one of claims 7 to 15, characterized in that the drainage circuit comprises a drain inlet (43) arranged on the external element (2) and in fluid communication with the pressure chamber (35).

17. Hydrostatic machine according to claim 16, characterized in that the drain inlet (43) is connected to the pressure chamber (35) by a drainage conduit (44) extending axially in the thickness of the wall of the external element (2).

18. Hydrostatic machine according to one of claims 16 or 17, characterized in that the drain inlet (43) is supplied with hydraulic fluid from a cooler (48) arranged on the hydraulic circuit.

19. Hydrostatic machine according to one of the preceding claims, characterized in that said light (27) is positioned diametrically opposite to the application of the driving forces, during rotation in the normal direction of rotation.

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