Rotating hydrostatic machine with a drain hole in at least one cylinder

Abstract

A hydrostatic rotary machine with radial pistons 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 a stator; the internal element comprising a cylinder block (10); the external element comprising a cam track. The machine includes a drainage circuit which includes, for at least one cylinder (11), an injection conduit (26) passing through the wall of the cylinder (11), the injection conduit (26) opening at one end into the cylinder (11) through a port (27), and opening at the other end, from the cylinder block (10), into a drainage space supplied with hydraulic fluid. Figure for the abbreviation: Fig. 2

Description

Title of the invention: Rotating hydrostatic machine with a drainage port in at least one cylinder

[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 comprising a cylinder block with cylinders equipped with radially mobile pistons distributed circumferentially; - a stator comprising a cam track; the pistons being adapted to cooperate with the cam track in a manner coordinated 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, by means of a synchronizing junction forming a rotating coupling between the rotor and the stator.

[0006] Such a hydrostatic machine can be improved with regard to its efficiency. 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 being a stator; the internal element comprising a cylinder block having cylinders fitted with radially movable pistons distributed circumferentially visually; the external element comprising a cam track; 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 using a hydraulic fluid, by means of a synchronizing junction forming a rotating coupling between the rotor and the stator.

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

[0010] Preferably, all cylinders in the cylinder block have such an injection conduit.

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

[0012] In the prior art, a significant functional clearance between the pistons and cylinders ensures the absence of hot spots and wear. Hydraulic fluid leakage through this functional clearance is also drained via the drainage circuit. However, this reliability results in substantial power losses due to the significant leakage created between the cylinders and pistons. Even when this functional clearance is reduced, these engines experience a power limitation.

[0013] Thanks to the invention, the functional clearance between the pistons and cylinders can be reduced, if necessary, without negative drawbacks, but such a hydrostatic machine nevertheless pushes back the conventional power limits usually encountered for the same displacement, thanks to improved cooperation between the pistons and cylinders. A power gain of at least 30%, for the same displacement, is possible through the implementation of the invention.

[0014] The hydrostatic machine also remains compact, because the proposed drainage function is arranged 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 smaller ones with the same power output, can therefore be produced.

[0016] The invention allows for numerous variations in the arrangement of the drainage circuit. In particular, particularly advantageous variations exist in which a pressure chamber is created axially opposite the hydraulic distributor so that this pressure chamber compensates for the thrust created by the hydraulic distributor's cylinder function and thus relieves the pressure on the bearings that allow the rotor to rotate relative to the stator, resulting in a significant increase in service life or the possibility of reducing the bearing size, with the associated cost and weight savings.

[0017] The hydrostatic machine according to the invention may include the following additional features, 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 conduit and the lumen are formed from the same drilling profile of the cylinder block, substantially parallel to the axis of rotation and tangentially 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 includes a seal disposed between the piston and the cylinder, this seal having a course which is radially below or above said light;

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

[0024] - the pressure chamber is formed between a rotating seal which closes hermetically tickly 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 disposed 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 external element, the cylindrical collar being projecting from one of these collars;

[0028] - the pressure chamber and the hydraulic distributor are axially located on the and on the 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 synchronizing junction is in communication with the axial chamber, the Functional leak at Synchronization Injunction supplying the axial chamber with hydraulic fluid;

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

[0032] - the drainage circuit includes a drain inlet disposed on the external element and in fluidic communication with the pressure chamber;

[0033] - the drain inlet is connected to the pressure chamber by a drainage conduit extending axially within 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, during rotation in the normal direction of rotation. PRESENTATION OF THE FIGURES

[0036] Other features and advantages of the invention will become apparent from the following non-limiting description, with reference to the accompanying drawings in which:

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

[0038] - the [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 hydraulic machine static;

[0040] - Figures [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] - Figure 6 illustrates a second embodiment of the hydrostatic machine according to the invention;

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

[0043] - Fig. 8 is an axial section of a hydrostatic machine along a third method of implementing the invention;

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

[0045] Similar and common elements in 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 in rotation a element from a hydraulic fluid under pressure, i.e. 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 rotary joint 37.

[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] In this example, optionally, the cam track 8 is supported 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 from a grade of steel known as "bearing steel" or "carbon steel," which has a high carbon content, high resistance to wear and fatigue, but is nevertheless sensitive to shock. The cam ring's weakness with respect to shock 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 path 9, without suffering from 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 radially movable pistons 12 are mounted in a known manner.

[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 allowing rolling without slipping on the cam track 8.

[0056] The cam paths for hydrostatic machine, 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 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 a collar 46 which forms part of the second cover 7.

[0058] 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.

[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 making the 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 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.

[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 mobile 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 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.

[0065] 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, at the level of a synchronization junction 40, opposing the forces generated during the implementation of the synchronization, i.e. the selective pressurization of the cylinders 11.

[0066] The hydraulic distributor 18 acts in the main hydraulic circuit and allows to selectively put into fluidic communication, according to 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 jack thus created by the hydraulic distributor 18 has the effect of counteracting the repulsive force exerted in the synchronization junction 40, between the hydraulic distributor 18 and the cylinder block 10. This jack function of the hydraulic distributor 18 also causes an axial stress on the bearings 14, 15.

[0068] The hydrostatic machine also includes a drainage circuit allowing the hydraulic fluid bathing the internal space of the hydrostatic machine to be renewed and draining the hydraulic fluid produced by functional leaks occurring in particular at the level of the hydraulic distributor 18 and more specifically at the synchronization junction 40.

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

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

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

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

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

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

[0075] With reference to figures 1 and 2, for each cylinder 11, the drainage circuit includes 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 conduit 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 conduit 26 is represented in dotted lines because it is in the material: on Fig. 1, the angular position of the cutting plane does not pass through one of the injection conduits 26.

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

[0078] The injection channels 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 fast and inexpensive process, each injection conduit 26 is a straight bore obtained by drilling in a single operation and angularly positioned to open directly tangentially into the cylinder 11, thereby forming the port 27.

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

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

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

[0083] Each injection conduit 26 therefore opens at one of its ends into a cylinder 11. At the other of its ends, it opens from the cylinder block 10 (in this example, the injection conduit 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 refers specifically to an internal cavity of the hydraulic machine that is supplied with drainage hydraulic fluid, i.e., fluid circulating alongside the power function. When the hydraulic fluid is in the high-pressure circuit, to be supplied to the cylinders and drive the rotation of the rotor relative to the stator (in the example of a hydraulic motor), it is at a pressure of approximately 400 bar. When this fluid is in the drainage circuit (after leaking out at the synchronizing junction 40, for example), it is at a pressure of approximately 20 bar. This hydraulic fluid then circulates in the drainage spaces until it is discharged through the drain outlet 24 and returns to the main hydraulic circuit.

[0085] The drainage space 55 is therefore in fluidic 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 also regularly supplied with hydraulic fluid, the hydraulic fluid is therefore made 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 port 27, that is to say the position of the port 27 along the axis of the corresponding cylinder 11, is preferably chosen such that the port 27 is on the stroke of the piston 12. The port 27 is thus swept by the piston 12. A point of uncovering of the port 27 by the piston can also be provided so that the hydraulic fluid can open above or below the piston 12.

[0088] Figures 4 and 5 are partial radial cross-sectional views of the cylinder block 10, showing a cylinder 11 with its piston 12, as well as the corresponding portion of the cam track 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 track 9 in its exit stroke, and the roller 13 rolls on the lobe 29 driving the rotation of the rotor.

[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 ring, to limit functional leakage when the piston 12 is pushed towards its top dead center by the oil under high pressure arriving through 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 illustrated example, the direction of rotation of the cylinder block 10 (which is part of the rotor in this example) is indicated by 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 track 8 and in a hollow 30 of the cam track 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 exposed. The hydraulic fluid from the drainage circuit, which flows in the injection conduit 26, then exits freely through the port 27 and spreads into the cylinder 10, over the entire circumference of the piston head 12. This hydraulic fluid lubricates and cools the piston head 12 as well as the functional clearance between the piston and the cylinder in the first few millimeters of the piston head, this area being the most critical with regard to stress and the risk of hot spot formation.

[0094] During its stroke, from bottom dead center to top dead center, the piston 12 then sweeps the opening 27, its external cylindrical surface sweeping the cylinder 11 and covering this opening 27. The opening 27 is thus 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 light 27 and the design of the piston 12 are also chosen so that the seal 31 does not sweep the light 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 light 27.

[0096] Generally speaking, the seal 31 is designed to undergo a stroke that 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 track 8, causing the rotor to rotate relative to the stator, the opening 27 forms a film of oil under pressure in the gap between the piston 12 and the cylinder 12.

[0098] The direction of rotation indicated by arrows 33 in Figures 4 and 5 indicates the normal direction of rotation of the cylinder block 10. The normal direction of rotation refers to the only direction of rotation in the case of a hydrostatic machine with a single direction of rotation, and refers to 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 facilitate the work of the pistons 12 during the normal direction of rotation. In each cylinder 11, the port 27 is positioned diametrically opposite to the application of the drive 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 track 8, the reaction force of the cam track is oblique. For example, in [Fig. 5], when the roller 13 passes through point 34 illustrated in the figure, this reaction force at point 34 (at the point of contact between the roller 13 and the cam track 8) is an oblique force F pushing the piston 12 against the cylinder 11 with maximum stress at the area where the port 27 is located.

[0101] The pressurized hydraulic fluid film created by the light 27 is thus located at the level of the most critical area 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 addressing the most critical point, which is normally an area of ​​stress, heating, or even seizure, in the event of too little clearance.

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

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

[0105] According to a first embodiment of the supply of the drainage space 55, with reference to [Fig. 1], the drainage space 55 comprises a pressure chamber 35 designed to create sufficient pressure for the hydraulic fluid to flow through the injection conduit 26. This is not a high pressure comparable to that of the high-pressure hydraulic circuit, but rather a pressure more comparable to that of the low-pressure circuit. A pressure of a few bars is generally sufficient.

[0106] Advantageously, this pressure chamber 35 is created by a simple annular seal 36 disposed between the external element 2 and the second cover 7, and more specifically, 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 rotary joint 37 is used here for two functions: rotary joint which hermetically seals a junction between the rotor and the stator; and closure, with the annular seal 36, of the pressure chamber 35.

[0108] The annular seal 36 is not required to provide a high level of sealing, as a leak at this point does not affect the proper functioning of the hydrostatic machine. This seal 36 can therefore be chosen to exert a low constraint on rotation and simply to ensure a pressure increase in the pressure chamber 35.

[0109] The pressure chamber 35 is itself supplied by any means with hydraulic fluid from the drainage circuit. [Fig. 1] illustrates an example in which a radial drainage conduit 38 is provided between an axial chamber 39, centered on the axis of rotation R, and the pressure chamber 35. The radial drainage conduit is shown in dashed 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 formed in the internal element 1.

[0111] In the illustrated architecture, the synchronizing junction 40 generates hydraulic leaks during its operation, hereinafter referred to as functional leaks. This synchronizing junction 40 opens through one of its edges into this axial chamber 39. The axial chamber 39 will therefore fill with hydraulic fluid due 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 supplied by the leak from the synchronizing junction 40.

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

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

[0114] Figure 6 illustrates a second embodiment in which the drainage space 55 also includes a pressure chamber 35, but which provides different, alternative or complementary means for pressurizing the pressure chamber 35. Figure 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 fluidic 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 supply it to the axial chamber 39, according to the desired pressure or flow rate.

[0116] Figure 7 illustrates an example of a hydrostatic valve 41 configuration, according to a particularly advantageous embodiment. The hydrostatic valve 41 includes a three-way distributor 50 adapted to select one or the other of the chambers 22, 23 of the hydraulic distributor 18 (the one which, at any given moment, is at low pressure). The three-way distributor 50 connects this low-pressure fluid to a pressure relief valve 51 to obtain the desired pressure. No power loss in 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 restriction 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] Figure 8 illustrates a third embodiment in which the drainage space 55 also includes a pressure chamber 35, but which provides different, alternative or complementary means for pressurizing the pressure chamber 35. The hydrostatic machine here includes a drain inlet 43 on the edge of the annular housing 5, on the side of the first cover 6, i.e. on the side where all the other hydraulic fittings exit, which is an advantage for example for hydraulic motors housed in wheel hubs.

[0120] The drain inlet 43 is connected to a drainage conduit 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 opposite another drainage conduit 45 made in the second cover 7 and opening into the pressure chamber 35.

[0121] In the present example, given the construction of the hydrostatic machine with the bearings 14, 15 and the cam ring 9 mounted on several internal cylindrical supports of the annular housing 5, the drainage channel 44 of the annular housing 5 comprises a first section 44A which is formed entirely 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 support for the second bearing 15).

[0122] The drainage conduits 44, 45 do not require any 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 affect the operation of the hydrostatic machine. A fluidic 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 any functional leakage. The pressure in the pressure chamber 35 can then be regulated by any external device in the hydraulic circuit, with suitable components.

[0124] The temperature of the hydraulic drainage fluid can also be controlled. Given the additional function of the drainage circuit, which assists the operation of the pistons in the cylinders, it is advantageous here to supply the drain inlet 31 with hydraulic fluid that is preferably at a low temperature.

[0125] Figure 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 used to lower the temperature of the hydraulic fluid. The other elements of the circuit, in particular the high- and low-pressure sections that enable the mechanical function of the hydrostatic machine, are conventional and have not been shown.

[0126] The heat 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 conventionally 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, on the order of 50 °C for example, by 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 enabling this regulation.

[0129] Furthermore, pressurizing the pressure chamber 35 creates a force on the internal element 1 that opposes the force exerted by the distributor hy The hydraulic force 18 exerts pressure on this internal element 1 (and more specifically on the cylinder block 10) through the hydraulic distributor's actuator function. Since the pressure chamber 35 and the hydraulic distributor 18 are axially positioned on either side of the cylinder block 10, the latter experiences these two forces from both sides. Thus, the force exerted by the pressure chamber 35 on the cylinder block 10 is subtracted from the force exerted by the actuator function of the hydraulic distributor 18. This reduces the axial pressure exerted on the bearings 14 and 15, increasing their lifespan or allowing them to be sized accordingly.

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

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

Claims

Demands

1. A 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 distributed circumferentially; the external element (2) comprising a cam track (8); the pistons 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 using a hydraulic fluid, by means of a synchronizing junction (40) forming a rotating coupling between the rotor and the stator;this hydrostatic rotating machine being characterized in that it comprises a drainage circuit which includes, for at least one cylinder (11), an injection conduit (26) passing through the wall of the cylinder (11), the injection conduit (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 (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 along the axial direction.

3. Hydrostatic machine according to claim 2, characterized in that the injection conduit (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 tangential to the cylinder (11).

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

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

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

7. Hydrostatic machine according to any one of the preceding claims, characterized in that said drainage space (55) comprises a pressure chamber (35) supplied with hydraulic fluid and in fluidic 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 joint (37) which hermetically seals a junction between the rotor and the stator, and an annular joint (36) disposed between the external element (2) and the cylinder block (10).

9. Hydrostatic machine according to any one of claims 7 or 8, characterized in that the cylinder block (10) has 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 through the edge of the cylindrical collar (25).

10. Hydrostatic machine according to claim 9 when it depends on claim 8, characterized in that said annular seal (36) is disposed between the external element (2) and the cylindrical collar (25).

11. Hydrostatic machine according to any one of claims 9 or 10, characterized in that 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 cylindrical flange (25) being projecting from one of these flanges (17).

12. Hydrostatic machine according to any 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 any 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 any one of claims 7 to 13, characterized in that the synchronizing junction (40) is in communication with the axial chamber (39), the functional leak at the synchronizing junction (40) supplying the axial chamber (39) with hy- fluid draulique.

15. Hydrostatic machine according to any one of claims 7 to 14, characterized in that it comprises a hydrostatic valve (41) disposed 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 any one of claims 7 to 15, characterized in that the drainage circuit comprises a drain inlet (43) disposed on the external element (2) and in fluidic 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 any one of claims 16 or 17, characterized in that the drain inlet (43) is supplied with hydraulic fluid from a cooler (48) disposed on the hydraulic circuit.

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