DE102024211061A1 - Hydrostatic rotary machine with a drainage slot in at least one cylinder - Google Patents

Abstract

A hydrostatic rotary machine with radial pistons, comprising: an inner element and an outer element, which are mounted coaxially and so as to rotate relative to one another about an axis of rotation, one of these elements being a rotor and the other of these elements being a stator; the inner element comprising a cylinder block (10); the outer element comprising a cam track.The machine comprises a drainage circuit which, for at least one cylinder (11), includes an injection line (26) which traverses the wall of the cylinder (11), the injection line (26) opening into the cylinder (11) via one of its ends through an elongated hole (27) and opening into a drainage chamber fed with hydraulic fluid from the cylinder block (10) via the other of its ends.

Description

The invention relates to the field of mechanics and hydraulics and more particularly to a hydrostatic rotary machine.

Hydrostatic rotary machines are rotating machines that have a stator coupled to a rotor, which is generally connected to a rotating drive element such as a wheel, a pinion or any transmission device.

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

The hydrostatic machine can also be used as a hydraulic pump. It receives torque transmitted from the rotating drive element and compresses the hydraulic fluid in response.

STATE OF THE ART

• - einen Rotor, der einen Zylinderblock enthält, der mit radial beweglichen Kolben versehene und umfangsmäßig verteilte Zylinder aufweist;
• - einen eine Nockenbahn enthaltenden Stator; wobei die Kolben geeignet sind, mit der Nockenbahn in mit der Rotation des Rotors bezüglich des Stators koordinierter Weise zusammenzuwirken;
• - einen hydraulischen Verteiler, der geeignet ist, die Zylinder dank einer Synchronisationsverbindung selektiv an einen ein Hydraulikfluid verwendenden Hydraulikkreis anzuschließen, die eine Drehkupplung zwischen dem Rotor und dem Stator bildet.

The patent application WO2020008145 describes a hydrostatic rotary machine that contains:

• - a rotor comprising a cylinder block having cylinders provided with radially movable pistons and distributed circumferentially;
• - a stator including a cam track; wherein the pistons are adapted to cooperate with the cam track in a manner coordinated with the rotation of the rotor relative to the stator;
• - a hydraulic distributor suitable for selectively connecting the cylinders to a hydraulic circuit using a hydraulic fluid thanks to a synchronisation connection forming a rotary coupling between the rotor and the stator.

Such a hydrostatic machine can be improved in terms of its working performance.

STATEMENT OF THE INVENTION

The invention aims to improve the hydrostatic rotary machines of the prior art.

• - ein inneres Element und ein äußeres Element, die koaxial und um eine Rotationsachse zueinander drehend montiert sind, wobei eines dieser Elemente ein Rotor und das andere dieser Elemente ein Stator ist; wobei das innere Element einen Zylinderblock enthält, der mit radial beweglichen Kolben versehene und umfangsmäßig verteilte Zylinder aufweist; wobei das äußere Element eine Nockenbahn enthält; wobei die Kolben geeignet sind, mit der Nockenbahn in mit der Rotation des Rotors bezüglich des Stators koordinierter Weise zusammenzuwirken;
• - einen hydraulischen Verteiler, der geeignet ist, die Zylinder dank einer Synchronisationsverbindung selektiv an einen ein Hydraulikfluid verwendenden Hydraulikkreis anzuschließen, die eine Drehkupplung zwischen dem Rotor und dem Stator bildet.

For this purpose, the invention relates to a hydrostatic rotary machine with radial pistons, which comprises:

• - an inner element and an outer element mounted coaxially and rotatably relative to one another about an axis of rotation, one of these elements being a rotor and the other of these elements being a stator; the inner element comprising a cylinder block having cylinders provided with radially movable pistons and distributed circumferentially; the outer element comprising a cam track; the pistons being suitable for cooperating with the cam track in a manner coordinated with the rotation of the rotor relative to the stator;
• - a hydraulic distributor suitable for selectively connecting the cylinders to a hydraulic circuit using a hydraulic fluid thanks to a synchronisation connection forming a rotary coupling between the rotor and the stator.

This hydrostatic rotary machine includes a drainage circuit comprising, for at least one cylinder, an injection line passing through the wall of the cylinder, the injection line opening into the cylinder via one of its ends through a slot, and opening into a drainage chamber fed with hydraulic fluid from the cylinder block via the other of its ends.

Preferably, all cylinders of the cylinder block contain such an injection line.

• - die Gestaltung einer hydrostatischen Maschine mit einem reduzierten Spiel zwischen den Kolben und den Zylindern, was eine Erhöhung der Leistung der Maschine bei gleichem Hubraum ermöglicht;
• - eine Erhöhung der Zuverlässigkeit und der Lebensdauer dank eines geringeren Verschleißes der Kolben und der Zylinder.

The invention makes it possible to improve the working performance of the hydrostatic machine by combining measures that are known to be incompatible:

• - the design of a hydrostatic machine with a reduced clearance between the pistons and the cylinders, which allows an increase in the power of the machine with the same displacement;
• - increased reliability and service life thanks to reduced wear on the pistons and cylinders.

In the current state of the art, a large operating clearance between the pistons and cylinders ensures the absence of hot spots and wear. Hydraulic fluid leakage through this operating clearance is also drained via the drainage circuit. However, this reliability results in significant power losses due to the size of the leak created between the cylinders and pistons. Even if this operating clearance is reduced, these engines reach a performance limit.

Thanks to the invention, the operating clearance between the pistons and cylinders can be reduced if necessary, without any negative trade-off. However, such a hydrostatic machine certainly pushes the typical performance limits normally encountered for the same displacement thanks to improved work in the area of piston-cylinder interaction. A power increase of at least 30% for the same displacement is conceivable through the application of the invention.

The hydrostatic machine also remains compact, as the proposed drainage function is implemented with few changes and without increasing the space required.

This allows for a significant increase in performance without a significant increase in production costs. This allows for the production of hydraulic motors that are more powerful or smaller in size while maintaining the same power output.

The invention allows for many variations in the design of the drainage circuit. Particularly advantageous variants include creating a pressure chamber axially opposite the hydraulic distributor. This pressure chamber compensates for the thrust generated by the hydraulic distributor's power cylinder function, thus relieving the pressure on the rolling bearings that enable the rotor to rotate relative to the stator. This significantly extends service life or allows for the possibility of downwardly sizing the rolling bearings, with the associated cost and weight savings.

• - das Langloch bildet eine Öffnung in der Wand des Zylinders, die sich im Wesentlichen gemäß der axialen Richtung erstreckt;
• - die Einspritzleitung und das Langloch werden von einem gleichen Bohrungsprofil des Zylinderblocks im Wesentlichen parallel zur Rotationsachse und tangential zum Zylinder geformt;
• - das Langloch ist auf dem Hub des Kolbens angeordnet;
• - das Langloch ist freigelegt, wenn der Kolben am unteren Totpunkt ist, und das Langloch wird vom Kolben bei seinem Hub verdeckt;
• - der Kolben enthält eine zwischen dem Kolben und dem Zylinder angeordnete Dichtung, wobei diese Dichtung einen Hub aufweist, der sich radial unter oder über dem Langloch befindet;
• - der Dränageraum enthält eine Druckkammer, die mit Hydraulikfluid gespeist wird und mit den Einspritzleitungen in Fluidkontakt steht;
• - die Druckkammer wird zwischen einer Drehdichtung, die eine Verbindung zwischen dem Rotor und dem Stator hermetisch verschließt, und einer Ringdichtung gebildet, die zwischen dem äußeren Element und dem Zylinderblock angeordnet ist;
• - der Zylinderblock enthält einen zylindrischen Bund, der koaxial mit der Rotationsachse vorsteht, wobei die Einspritzleitungen sich axial in diesem zylindrischen Bund erstrecken und über den Rand des zylindrischen Bunds münden;
• - die Ringdichtung ist zwischen dem äußeren Element und dem zylindrischen Bund angeordnet;
• - der Zylinderblock enthält zwei Kragen, die zu beiden Seiten der Zylinder angeordnet sind, mit einem Wälzlager, das zwischen jedem Kragen und dem äußeren Element montiert ist, wobei der zylindrische Bund von einem dieser Kragen vorsteht;
• - die Druckkammer und der hydraulische Verteiler befinden sich axial zu beiden Seiten des Zylinderblocks;
• - die Maschine enthält: eine auf die Rotationsachse zentrierte und mit Hydraulikfluid gespeiste axiale Kammer und eine radiale Dränageleitung, die sich zwischen der axialen Kammer und der Druckkammer erstreckt;
• - die Synchronisationsverbindung steht mit der axialen Kammer in Verbindung, wobei das Betriebsleck an der Synchronisationsverbindung die axiale Kammer mit Hydraulikfluid speist;
• - die Maschine enthält ein in der axialen Kammer angeordnetes hydrostatisches Ventil, das mit dem hydraulischen Verteiler verbunden und geeignet ist, die axiale Kammer mit Hydraulikfluid zu speisen;
• - der Dränagekreis enthält einen Dräneingang, der auf dem äußeren Element angeordnet ist und mit der Druckkammer in Fluidverbindung steht;
• - der Dräneingang ist mit der Druckkammer über eine Dränageleitung verbunden, die sich axial in der Dicke der Wand des äußeren Elements erstreckt;
• - der Dräneingang wird ausgehend von einem auf dem Hydraulikkreis angeordneten Kühler mit Hydraulikfluid gespeist;
• - das Langloch ist der Anwendung der Antriebskräfte bei der Rotation in der normalen Drehrichtung diametral entgegengesetzt positioniert.

The hydrostatic machine according to the invention may have the following additional features alone or in combination:

• - the slot forms an opening in the wall of the cylinder, which extends substantially in the axial direction;
• - the injection line and the slot are formed by a same bore profile of the cylinder block, substantially parallel to the axis of rotation and tangential to the cylinder;
• - the slot is located on the stroke of the piston;
• - the slot is exposed when the piston is at bottom dead center and the slot is covered by the piston during its stroke;
• - the piston includes a seal arranged between the piston and the cylinder, said seal having a stroke located radially below or above the elongated hole;
• - the drainage chamber contains a pressure chamber fed with hydraulic fluid and in fluid contact with the injection lines;
• - the pressure chamber is formed between a rotary seal hermetically sealing a connection between the rotor and the stator and an annular seal arranged between the outer element and the cylinder block;
• - the cylinder block comprises a cylindrical collar projecting coaxially with the axis of rotation, the injection lines extending axially in this cylindrical collar and opening over the edge of the cylindrical collar;
• - the ring seal is arranged between the outer element and the cylindrical collar;
• - the cylinder block comprises two collars arranged on either side of the cylinders, with a rolling bearing mounted between each collar and the outer element, the cylindrical collar projecting from one of these collars;
• - the pressure chamber and the hydraulic distributor are located axially on both sides of the cylinder block;
• - the machine comprises: an axial chamber centred on the axis of rotation and supplied with hydraulic fluid and a radial drainage line extending between the axial chamber and the pressure chamber;
• - the synchronization connection communicates with the axial chamber, the operating leak at the synchronization connection supplying the axial chamber with hydraulic fluid;
• - the machine includes a hydrostatic valve arranged in the axial chamber, connected to the hydraulic distributor and suitable for supplying the axial chamber with hydraulic fluid;
• - the drainage circuit includes a drainage inlet located on the outer element and in fluid communication with the pressure chamber;
• - the drainage inlet is connected to the pressure chamber via a drainage pipe extending axially in the thickness of the wall of the outer element;
• - the drain inlet is fed with hydraulic fluid from a cooler located on the hydraulic circuit;
• - the slot is positioned diametrically opposite to the application of the driving forces during rotation in the normal direction of rotation.

REPRESENTATION OF THE FIGURES

• - 1 eine axiale Schnittansicht einer hydrostatischen Maschine gemäß einer ersten Ausführungsform der Erfindung ist;
• - 2 in Perspektive den Zylinderblock der hydrostatischen Maschine veranschaulicht;
• - 3 eine schematische Draufsicht des Zylinderblocks der hydrostatischen Maschine ist;
• - 4 und 5 einen Kolben der hydrostatischen Maschine in seinem Zylinder an seinem unteren Totpunkt bzw. oberen Totpunkt veranschaulichen;
• - 6 eine zweite Ausführungsform der hydrostatischen Maschine gemäß der Erfindung veranschaulicht;
• - 7 schematisch ein hydrostatisches Ventil der hydrostatischen Maschine aus 6 veranschaulicht;
• - 8 ein Axialschnitt einer hydrostatischen Maschine gemäß einer dritten Ausführungsform der Erfindung ist;
• - 9 eine schematische Ansicht ist, die den Dränagekreis der hydrostatischen Maschine veranschaulicht.

Further features and advantages of the invention will become apparent from the following non-limiting description with reference to the accompanying figures, in which:

• - 1 is an axial sectional view of a hydrostatic machine according to a first embodiment of the invention;
• - 2 illustrates in perspective the cylinder block of the hydrostatic machine;
• - 3 is a schematic plan view of the cylinder block of the hydrostatic machine;
• - 4 and 5 illustrate a piston of the hydrostatic machine in its cylinder at its bottom dead center or top dead center;
• - 6 illustrates a second embodiment of the hydrostatic machine according to the invention;
• - 7 schematically a hydrostatic valve of the hydrostatic machine from 6 illustrated;
• - 8 is an axial section of a hydrostatic machine according to a third embodiment of the invention;
• - 9 is a schematic view illustrating the drainage circuit of the hydrostatic machine.

The same elements common to the different embodiments bear the same reference numbers in the figures.

DETAILED DESCRIPTION

1 illustrates a hydrostatic rotary machine according to the invention in section along a plane extending along its axis of rotation R.

This hydrostatic machine is either a hydraulic motor that rotates an element using a pressurised hydraulic fluid or a hydraulic pump that is capable of pressurising a hydraulic fluid using the rotation of an element.

The hydrostatic rotary machine comprises an inner element 1 and an outer element 2, which are mounted to rotate relative to each other about the rotation axis R by means of rolling bearings 14, 15.

In the present illustrative example, the hydrostatic machine is a hydraulic motor and the inner element 1 is rigidly connected to a drive element, which here consists of a splined shaft 3.

Of the inner element 1 and the outer element 2, one of these elements is a rotor, while the other is a stator. In the present example, the outer element 2 is a stator and is connected to a frame such as a fixed structure or on board a vehicle, while the inner 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 outer 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 case, is a motor housed in the hub of a drive wheel.

The outer element 2 comprises an annular housing 5, which here has the general shape of a ring, with a first cover 6 which covers one of the openings (right in 1 ) of this annular housing 5, and a second cover 7, which closes the opposite opening (left in 1 ) hermetically seals. The second cover 7 contains a rotary seal 37 at its interface with the splined shaft 3.

The outer element 2 also includes a cam track 8, which is characteristic of hydrostatic machines with radial pistons. As is known, this cam track 8 has an inner circumferential shape, with a profile formed by depressions and elevations, forming a cyclical profile with a sequence of increasing and decreasing radii, synchronized with the input and output movement of the radial pistons.

In this example, the cam track 8 is optionally carried by a cam ring 9 mounted on an inner side 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 manufactured from a steel grade called "rolling bearing steel" or "carbon steel," which has a high carbon content and high wear and fatigue resistance, but is sensitive to shocks. The cam ring's weakness with respect to shocks is compensated for by its assembly in the annular housing 5, which is ductile. The high performance of a contact pressure and fatigue-resistant material can thus be advantageous for the cam track 9. without suffering from the disadvantages normally associated with this type of material.

The inner element 1 contains a cylinder block 10, which is also specific to hydrostatic machines with radial pistons. This cylinder block 10 is provided with cylinders 11, into which radially movable pistons 12 are mounted in a known manner.

In a known manner, the cylinders 11 are radial cylinders extending over the entire circumference of the cylinder block 10, angularly uniformly distributed around the axis of rotation R, and the pistons 12 each have, on their end directed towards the cam track 8, a roller 13 which allows rolling without slipping on the cam track 8.

The cam tracks for a hydrostatic machine, the interaction with the radial pistons 12 and the synchronization methods by selectively connecting the cylinders to the hydraulic fluid circuit are also known and will not be described in more detail here.

The inner element 1 and the outer element 2 are mounted to rotate relative to each other, in this example thanks to a first rolling bearing 14 and a second rolling bearing 15, which are mounted directly between the inner element 1 and the outer element 2. These rolling bearings 14, 15 are inserted into the annular housing 5 on both sides of the cam ring 9. The example of the 1 illustrates two possible mountings of the rolling bearings 14, 15 in the annular housing 5: a direct mounting of the rolling bearing with its outer ring in contact with the annular housing 5 (this is the case for the first rolling bearing 14); and a mounting of the rolling bearing in the housing with an intermediate support ring (this is the case for the second rolling bearing 15), and in the present example, this support ring is a collar 46 which is part of the second cover 7.

The cylinder block 10 includes two collars 16, 17 arranged on either side of the cylinders 11, with a rolling bearing 14, 15 mounted between each collar 16, 17 and the outer element 2, the inner ring of each rolling bearing 14, 15 being mounted directly on the corresponding collar 16, 17.

Thus, a rolling bearing assembly is obtained which is simple and produces reduced side chains, with the cam ring 9 mounted in the annular housing 5 and the rolling bearings 14, 15 arranged on either side of this cam ring 9, forming the direct interface between the inner element 1 and the outer element 2.

The hydrostatic machine also includes devices for distributing and synchronizing the hydraulic fluid. These devices include a hydraulic distributor 18 and a distributor base 4.

The distributor base 4 contains a fluid inlet 19 and a fluid outlet 20, which are typically connected to the high-pressure part and the low-pressure part of a hydraulic circuit.

The distributor base 4 is firmly connected to the outer element 2. In this example, the distributor base 4 is firmly connected to the first cover 6.

The hydraulic distributor 18 is mounted on the distributor base 4, being axially movable with respect to the latter, the two components being rotationally coupled, for example, by means of pins allowing axial sliding.

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

Seals allow the hermetic sealing of the chambers 22, 23 while simultaneously permitting the axial movement of the hydraulic distributor 18 on the distributor base 4. As is known, these seals have different diameters with the aim of creating 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 in the area of a synchronization connection 40 by resisting the forces generated during synchronization, i.e., the selective pressurization of the cylinders 11.

The hydraulic distributor 18 acts in the main hydraulic circuit and allows, according to the rotation of the rotor with respect to the stator, the high and low pressure circuits to be selectively put into fluid communication with channels 32, each of which is connected to a cylinder 11.

The working cylinder thus generated by the hydraulic distributor 18 counteracts the repulsion force exerted in the synchronization connection 40 between the hydraulic distributor 18 and the cylinder block 10. This working cylinder function of the hydraulic distributor 18 also causes an axial load on the rolling bearings 14, 15.

The hydrostatic machine also includes a drainage circuit which allows the hydraulic fluid flowing through the interior of the hydrostatic machine to be renewed and which drains the hydraulic fluid generated by operating leaks, particularly in the area of the hydraulic distributor 18 and more precisely the synchronization connection 40.

The drainage circuit contains a drainage 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.

The hydraulic fluid involved in this drainage function is supplied in the hydraulic machine itself by the aforementioned operating leaks, in particular at the hydraulic distributor 18 and, if necessary, through an external drainage inlet intended for the drainage function, as explained below in a variant.

In the drainage circuit, the hydraulic fluid is caused to pass from one interior of the hydrostatic machine to the other, depending on the possibilities of fluid communication, until it exits via the drainage outlet 24.

The drainage circuit is designed here to perform an additional function of supporting the pistons' work in the cylinders. In the drainage circuit, the hydraulic fluid is also forced to pass through the wall of the cylinder block 10 and flow into the cylinders 11.

Of the two collars 16, 17 of the cylinder block 10, collar 17 is the one located 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 includes a collar 25 formed by a cylinder, which projects from the collar 17 toward the second cover 7 and is centered on the rotation axis R. The collar 25 and the rotor are thus coaxial.

2 is a perspective half-section view of the cylinder block 10 and the splined shaft 3 to which it is firmly connected. 2 makes this covenant 25 visible.

With reference to the 1 and 2 the drainage circuit includes for each cylinder 11 an injection line 26 which is arranged in the thickness of the wall of the collar 25, crosses the cylinder block 10 and opens into the corresponding cylinder 11.

1 schematically illustrates the path of this injection line 26 in the thickness of the wall of the collar 25 and in the material of the cylinder block 10. This path of the injection line 26 is shown in dashed lines because it runs in the material: in 1 the angular position of the cutting plane does not pass through one of the injection lines 26.

2 makes three of the injection lines 26 visible on the side where they open over the edge of the collar 25. The injection lines 26 extend in the material of the cylinder block 10 and each open into a cylinder 11 through an elongated hole 27.

The injection lines 26 can have any suitable shape until they reach the elongated hole 27. Due to manufacturing processes such as die casting or additive manufacturing, many shapes are possible.

However, according to a particularly advantageous embodiment allowing a rapid and cost-effective process, each injection line 26 is a rectilinear bore obtained by drilling in a single operation and angularly positioned to open directly tangentially into the cylinder 11, thereby forming the elongated hole 27.

3 is a schematic view illustrating the cylinder block 10, viewed from above, with a cylinder 11 at its center. A bore profile 28, delimited by dashed lines, schematically represents the bore produced by a drill capable of forming the injection line 26 and the slot 27 in a single pass, opening into the cylinder 11.

These elements are thus formed at lower cost with a single drilling operation, preferably completed by a simple operation of trimming or chamfering the sharp edges of the elongated hole 27 thus produced.

In each cylinder 11, the elongated hole 27 forms an opening in the wall of the cylinder 11, an opening that extends substantially in the axial direction. In other words, the elongated hole 27 extends perpendicular to the stroke of the piston 12 along an angular portion of the inner wall of the cylinder 11. Thus, approximately 1/4 or 1/3, or even 1/2, of the circumference of the inner wall of the cylinder can be occupied by this elongated hole 27.

Each injection line 26 thus opens into a cylinder 11 via one of its ends. Via the other of its ends, it opens from the cylinder block 10 (in this example, the injection line 26 opens from the edge of the collar 25 of the cylinder block 10) into a drainage chamber 55.

The drainage chamber 55 here precisely designates an internal cavity of the hydraulic machine supplied with drainage hydraulic fluid, i.e., a fluid flowing at the edge of the power function. When the hydraulic fluid is in the high-pressure circuit to be supplied to the cylinders and cause 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 bar. When this fluid is in the drainage circuit (after having escaped in the form of a leak, for example, at the synchronization joint 40), it is at a pressure of the order of 20 bar. This hydraulic fluid then flows in the drainage chambers until it is discharged via the drain outlet 24 and returns to the general hydraulic circuit.

The drainage chamber 55 is thus in fluid communication with a supply of hydraulic fluid from the drainage circuit.

Since the injection line 26 opens into this drainage chamber 55, and this chamber is also uniformly supplied with hydraulic fluid, the hydraulic fluid is caused to enter the injection line 26 through the edge of the collar 25, to cross the collar 25 and the wall of the cylinder block 10 by flowing through this injection line 26, and then to open into the cylinder 11 through the elongated hole 27.

The height of the elongated hole 27, i.e., the position of the elongated hole 27 relative to the axis of the corresponding cylinder 11, is preferably selected such that the elongated hole 27 is on the stroke of the piston 12. The elongated hole 27 is thus swept over by the piston 12. An exposure of the elongated hole 27 through the piston can also be provided so that the hydraulic fluid can flow above or below the piston 12.

The 4 and 5 are partial views of the cylinder block 10 in radial section, showing a cylinder 11 with its piston 12 and the corresponding part of the cam track 8. The gap 54 between the piston 12 and its roller 13 is intended for a bearing shell. In the case of a hydraulic motor, the piston 12 is pushed toward the cam track 9 during its output stroke, and the roller 13 rolls on the protrusion 29, driving the rotation of the rotor.

The piston 12 is formed by a body having a cylindrical outer surface designed to slide within the cylinder 11. The piston 12 is provided with a seal 31, which in this example is a sealing segment, to limit operating leaks when the piston 12 is pushed toward its top dead center by the high-pressure oil arriving through the channel 32.

• - Kolben 12 am unteren Totpunkt (4);
• - Kolben 12 am oberen Totpunkt (5).

The following two positions are illustrated:

• - Piston 12 at bottom dead center ( 4 );
• - Piston 12 at top dead center ( 5 ).

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

The positions of the 4 and 5 correspond to the passage of the roller over a protrusion 29 of the cam track 8 or in a recess 30 of the cam track 8.

If in this example the piston 12 is at bottom dead center ( 4 ), the outer cylindrical surface of the piston passes under the slot 27, thus exposing the latter. The hydraulic fluid of the drainage circuit, flowing in the injection line 26, then exits freely through the slot 27 and is distributed inside 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 operating clearance between the piston and the cylinder in the first few millimeters of the piston head, this zone being the most critical in terms of stresses and the risk of hot spots.

During its stroke from bottom dead center to top dead center, the piston 12 then passes over the elongated hole 27, with its cylindrical outer surface passing over the cylinder 11, covering this elongated hole 27. The elongated hole 27 is thus positioned between the cylinder 11 and the piston 12, opposite the gap zone that forms the operating clearance between these two moving components.

The position of the slot 27 and the design of the piston 12 are also selected so that the seal 31 never passes over the slot 27. In this example, the seal 31 is located at the top dead center of the piston 12 ( 5 ) directly below the slot 27.

In general, the seal 31 is designed to experience a stroke that is either radially below or radially above the elongated hole 27, but without over-sweeping it.

During the stroke of the piston 12, during which the latter exerts a large force on the cam track 8, which sets the rotor in rotation with respect to the stator, the slot 27 thus forms a Pressurized oil film in the gap between the piston 12 and the cylinder 12.

The arrows 33 in the 4 and 5 The direction of rotation indicated indicates the normal direction of rotation of the cylinder block 10. The normal direction of rotation means the only direction of rotation in the case of a hydrostatic machine with only one direction of rotation, and means the most frequently used direction of rotation in the case of a hydrostatic machine with two directions of rotation but with a preferred direction of rotation that is mainly used during the service life of the machine (this is, for example, the case of a bidirectional engine for the forward and reverse gears of a vehicle).

The hydrostatic machine is preferably designed for normal rotation, and the slot 27 is therefore positioned to favor the work of the pistons 12 during normal rotation. In each cylinder 11, the slot 27 is positioned diametrically opposite the application of the drive forces during rotation in the normal direction of rotation.

When the piston 12 is in its stroke toward its top dead center under the action of the high-pressure hydraulic circuit, and the roller 13 exerts a large force on the cam track 8, the reaction force of the cam track is an oblique force. For example, in 5 When the roller 13 passes through the point 34 illustrated in the figure, this reaction force at point 34 (at the contact between the roller 13 and the cam track 8) is an oblique force F which pushes the piston 12 back against the cylinder 11 with a maximum stress in the area in which the elongated hole 27 is arranged.

The pressurised hydraulic fluid film generated by the elongated hole 27 is thus located in the most critical zone for the operation of the piston 12 in the cylinder 11.

In the design of the hydrostatic machine, this arrangement further facilitates the possibility of reducing the cylinder/piston clearance by addressing the most critical point, which is normally a zone of stress, heating and even seizure, in the event of insufficient clearance.

The hydraulic fluid of the drainage circuit is thus used to support the piston/cylinder operation. After entering the cylinders 11, this fluid continues its path through the drainage circuit. In this example, it passes between the balls of the rolling bearing 14 toward the first cover 6 and is discharged through the drain outlet 24.

Several solutions are possible to feed the drainage chamber 55 and allow the flow of hydraulic fluid in the injection line 26. Any drainage circuit design solution that allows sufficient hydraulic fluid pressure to flow through the injection lines 26 is suitable. For example, a sufficiently high-yielding operating leak source located near the drainage chamber 55 can be channeled there.

According to a first embodiment of the supply of the drainage chamber 55, with reference to 1 , the drainage chamber 55 contains a pressure chamber 35 designed to generate sufficient pressure to force the hydraulic fluid to flow through the injection line 26. This pressure is not comparable to that of the high-pressure hydraulic circuit, but rather more comparable to that of the low-pressure circuit. In principle, a pressure of a few bars is sufficient.

Advantageously, this pressure chamber 35 is created by a simple annular seal 36 arranged between the outer element 2 and the second cover 7, and more precisely, in this example, the pressure chamber 35 is created between the collar 25 carrying the injection lines 26 and the second cover 7.

The rotary seal 37 is used here for two functions: rotary seal that hermetically seals a connection between the rotor and the stator; and closing the pressure chamber 35 with the ring seal 36.

The ring seal 36 does not need to provide a high degree of tightness, since a leak in this area will not affect the proper operation of the hydrostatic machine. This seal 36 can therefore be chosen to exert a slight restriction on rotation and simply to ensure a pressure increase in the pressure chamber 35.

The pressure chamber 35 is itself supplied with hydraulic fluid from the drainage circuit by any device. 1 illustrates an example in which a radial drainage line 38 is arranged between an axial chamber 39, centered on the rotation axis R, and the pressure chamber 35. The radial drainage line is shown in dashed lines.

The axial chamber is partially defined by the inner element 1 and partially by the outer element 2 (the hydraulic distributor 18). The radial drainage line 38 is located in the inner element 1.

In the illustrated architecture, the synchronization connection 40 generates hydraulic leaks during operation, referred to herein as operational leaks. This synchronization connection 40 opens into this axial chamber 39 through one of its edges. The axial chamber 39 thus fills with hydraulic fluid through this operational leak, and the hydraulic fluid passes through the radial drainage line 38 to the pressure chamber 35 at the same flow rate as that supplied by the leak in the synchronization connection 40.

This measure may be sufficient to pressurize the pressure chamber 35 if the operating leak is sufficiently large. If necessary, if the resulting pressure is too high, this flow rate can be calibrated, particularly by adjusting the diameter of the radial drainage pipe 38.

The hydrostatic machine thus has a drainage circuit without external supply, fed simply by the internal working leaks, while simultaneously applying the described support function of the work of the pistons.

6 illustrates a second embodiment in which the drainage space 55 also contains a pressure chamber 35, but which provides other, alternative or complementary means that allow the pressure chamber 35 to be pressurized. 6 is a half-section illustrating, in this example, a hydrostatic valve 41 mounted in a collar 42 of the hydraulic distributor 18.

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 control valves, etc. This hydrostatic valve is designed to recover hydraulic fluid from the distributor 18 and supply it to the axial chamber 39 according to the desired pressure or flow rate.

7 1 illustrates an exemplary configuration of the hydrostatic valve 41 according to a particularly advantageous embodiment. The hydrostatic valve 41 includes a three-way distributor 50 suitable for selecting one or the other of the chambers 22, 23 of the hydraulic distributor 18 (the one at low pressure at a given time). The three-way distributor 50 connects this low-pressure fluid to a pressure limiter 51 to maintain the desired pressure. Thus, no power loss is caused by the drainage circuit in the high-pressure circuit.

The hydrostatic valve may optionally have a pressure sensor 52 and thus feeds the axial chamber 39. The circuit is extended by a constriction, which may be formed by the radial drainage line 38, and thus leads to the pressure chamber 35.

The hydrostatic valve 41 makes it possible to control the pressure of the hydraulic fluid introduced through the slot 27 between the pistons 12 and their cylinders 11.

8 illustrates a third embodiment in which the drainage chamber 55 also contains a pressurization chamber 35, but which provides other, alternative or complementary means that allow the pressurization of the pressure chamber 35. The hydrostatic machine here includes a drainage 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 other hydraulic connections exit, which is an advantage, for example, for hydraulic motors housed in wheel hubs.

The drainage inlet 43 is connected to a drainage line 44 which extends in the thickness of the wall of the annular housing 5 parallel to the axis of rotation R and extends axially beyond the cam ring 9 and the second rolling bearing 15 until it opens opposite another drainage line 45 which is arranged in the second cover 7 and opens into the pressure chamber 35.

Taking into account the design of the hydrostatic machine with the rolling bearings 14, 15 and the cam ring 9 mounted on several internal cylindrical bearing surfaces of the annular housing 5, the drainage line 44 of the annular housing 5 comprises, in the present example, a first section 44A formed entirely in the material of the annular housing 5 and a second section 44B extending in an outlet groove in the annular housing 5, this groove being closed by the collar 46 of the cover 7 (the collar 46 also serving as a bearing surface for the second rolling bearing 15).

The drainage lines 44, 45 require no sealing devices other than mechanical adjustment of these components, given the low pressure involved and the fact that leaks in this area, which is the drainage circuit, do not affect the operation of the hydrostatic machine. Thus, a fluid line is formed by the drainage lines 44, 45 between the drainage inlet 43 and the pressure chamber 35.

An independent external drain inlet 43 can thus be directly connected to the pressure chamber 35, and the amount injected in the area of the drain inlet 43 is subsequently recovered at the drain outlet 24, in addition to the operating leaks. The pressure in the pressure chamber 35 can then be regulated by any device external to the hydraulic circuit with the appropriate components.

The temperature of the drainage hydraulic fluid can also be controlled. Considering the additional function of the drainage circuit, which supports the operation of the pistons in the cylinders, it is advantageous to supply the drainage inlet 31 with hydraulic fluid, preferably at a low temperature.

9 is a simplified schematic diagram illustrating the drainage circuit associated with the hydrostatic machine 53. This schematic diagram shows certain elements of the hydraulic circuit: the hydraulic tank 49 and a cooler 48, which is a heat exchanger that allows the temperature of the hydraulic fluid to be reduced. The other elements of the circuit, in particular the high- and low-pressure sections that allow the mechanical operation of the hydrostatic machine, are typical and have not been shown.

The exchanger forming the cooler 48 is generally present in most hydraulic circuits and is advantageously used here to feed a pump 47 of the drainage circuit, which itself feeds the drainage inlet 43. The drainage outlet 24 returns to the hydraulic tank 49 in the usual manner.

The piston/cylinder interface can thus be pressurised at the appropriate points and cooled by a hydraulic fluid at a low temperature of, for example, 50 °C, for example by using the drainage function.

The pump 47 can itself regulate the pressure in the pressure chamber 35 or, in a variant, can be assigned to any other known component that allows this regulation.

Furthermore, the pressurization of the pressure chamber 35 allows a force to be generated on the inner element 1 that opposes the force exerted by the hydraulic distributor 18 on this inner element 1 (and more precisely on the cylinder block 10), thanks to the working cylinder function of the hydraulic distributor 18. Since the pressure chamber 35 and the hydraulic distributor 18 are located axially on either side of the cylinder block 10, the latter sees these two forces applied to both sides. Thus, the force exerted by the pressure chamber 35 on the cylinder block 10 is subtracted from the force exerted by the working cylinder function of the hydraulic distributor 18. This equally relieves the axial pressure exerted on the rolling bearings 14, 15 and increases their service life, or allows them to be downsized.

Various design variants may be considered. Any other device that allows the drainage hydraulic fluid to be forced through the injection lines 26 may be considered.

Furthermore, the embodiments can be combined, in particular in such a way that the drainage space is supplied with hydraulic fluid from several sources.

QUOTES CONTAINED IN THE DESCRIPTION

This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• WO 2020008145 [0005, 0027]

Claims (19)

A hydrostatic rotary machine with radial pistons, comprising: - an inner element (1) and an outer element (2) mounted coaxially and rotating relative to one another about an axis of rotation (R), one of these elements being a rotor and the other a stator; wherein the inner element (1) comprises a cylinder block (10) having cylinders (11) provided with radially movable pistons and distributed circumferentially; wherein the outer element (2) comprises a cam track (8); wherein the pistons are suitable for cooperating with the cam track (8) in a manner coordinated with the rotation of the rotor relative to the stator; - a hydraulic distributor (18) suitable for selectively connecting the cylinders (11) to a hydraulic circuit using a hydraulic fluid, thanks to a synchronization connection (40) forming a rotary coupling between the rotor and the stator; this hydrostatic rotary machine being characterized in that it includes a drainage circuit comprising, for at least one cylinder (11), an injection line (26) passing through the wall of the cylinder (11), the injection line (26) opening into the cylinder (11) via one of its ends through an elongated hole (27) and opening into a drainage chamber (55) fed with hydraulic fluid from the cylinder block (10) via the other of its ends. Hydrostatic machine according to Claim 1 , characterized in that the elongated hole (27) forms an opening in the wall of the cylinder (11) which extends substantially in the axial direction. Hydrostatic machine according to Claim 2 , characterized in that the injection line (26) and the elongated hole (27) are formed by a same bore profile (28) of the cylinder block (10) substantially parallel to the axis of rotation (R) and tangential to the cylinder (11). Hydrostatic machine according to one of the preceding claims, characterized in that the elongated hole (27) is arranged on the stroke of the piston (12). Hydrostatic machine according to Claim 4 , characterized in that the elongated hole (27) is exposed when the piston (12) is at bottom dead center, and the elongated hole (27) is covered by the piston (12) during its stroke. Hydrostatic machine according to Claim 5 , characterized in that the piston (12) contains a seal (31) arranged between the piston (12) and the cylinder (11), this seal (31) having a stroke which is located radially below or above the elongated hole (27). Hydrostatic machine according to one of the preceding claims, characterized in that the drainage space (55) contains a pressure chamber (35) which is fed with hydraulic fluid and is in fluid contact with the injection lines (26). Hydrostatic machine according to Claim 7 , characterized in that the pressure chamber (35) is formed between a rotary seal (37) which hermetically seals a connection between the rotor and the stator, and an annular seal (36) which is arranged between the outer element (2) and the cylinder block (10). Hydrostatic machine according to one of the Claims 7 or 8 , characterized in that the cylinder block (10) includes a cylindrical collar (25) which projects coaxially with the axis of rotation (R), the injection lines (26) extending axially in this cylindrical collar (25) and opening over the edge of the cylindrical collar (25). Hydrostatic machine according to Claim 9 , if he Claim 8 depends, characterized in that the annular seal (36) is arranged between the outer element (2) and the cylindrical collar (25). Hydrostatic machine according to one of the 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 rolling bearing (14,15) mounted between each collar (16,17) and the outer element (2), the cylindrical collar (25) projecting from one of these collars (17). Hydrostatic machine according to one of the Claims 7 until 11 , characterized in that the pressure chamber (35) and the hydraulic distributor (18) are located axially on both sides of the cylinder block (10). Hydrostatic machine according to one of the Claims 7 until 12 , characterized in that it comprises: an axial chamber (39) centered on the axis of rotation (R) and fed with hydraulic fluid and a radial drainage line (38) extending between the axial chamber (39) and the pressure chamber (35). Hydrostatic machine according to one of the Claims 7 until 13 , characterized in that the synchronization connection (40) is connected to the axial chamber (39), the operating leak at the synchronization connection connection (40) feeds the axial chamber (39) with hydraulic fluid. Hydrostatic machine according to one of the Claims 7 until 14 , characterized in that it comprises a hydrostatic valve (41) arranged in the axial chamber (39), connected to the hydraulic distributor (18) and suitable for feeding the axial chamber (39) with hydraulic fluid. Hydrostatic machine according to one of the Claims 7 until 15 , characterized in that the drainage circuit includes a drainage inlet (43) arranged on the outer element (2) and in fluid communication with the pressure chamber (35). Hydrostatic machine according to Claim 16 , characterized in that the drainage inlet (43) is connected to the pressure chamber (35) via a drainage line (44) which extends axially in the thickness of the wall of the outer element (2). Hydrostatic machine according to one of the Claims 16 or 17 , characterized in that the drainage inlet (43) is fed with hydraulic fluid from a cooler (48) arranged on the hydraulic circuit. Hydrostatic machine according to one of the preceding claims, characterized in that the elongated hole (27) is positioned diametrically opposite to the application of the driving forces during rotation in the normal direction of rotation.

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