Hydraulic motor for vehicle wheel

A hydraulic motor for vehicle wheel includes a hydrodynamic element, a reaction element, an oil distributor rotating as one with the reaction element, and a brake mounted between the two elements to oppose the rotational movement. The hydrodynamic element has a flange that surrounds the oil distributor. On its radially exterior face, it has means for rotationally coupling with the rotary discs of the brake. The brake is thus positioned around the distributor.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a National Stage of International Application No. PCT/EP2015/080483 filed on Dec. 18, 2015, which claims priority to French Application No. 1462934 filed on Dec. 19, 2014, the contents of which are hereby incorporated by reference in their entirety.

INTRODUCTION

The invention relates to a hydraulic motor for a vehicle wheel.

PRIOR ART

The invention belongs to the field of hydraulic motors for vehicle wheels. The vehicles in question are notably construction site vehicles, agricultural tractors or other self-propelled agricultural machines, etc., for which it is difficult or impossible to provide a mechanical transmission between the combustion engine and the wheels. This situation is encountered notably with vehicles that have to have a large ground clearance, this being incompatible with the presence of drive shafts connecting the axle of the driving wheels. The combustion engine drives an oil pump which supplies the hydraulic motor with hydraulic energy in the form of high-pressure oil. The main function of this hydraulic motor is to convert the hydraulic energy into mechanical energy for rotating the wheel.

A hydraulic motor for a vehicle wheel is known, comprising:a hydrodynamic element having:i) cells,ii) pistons mounted so as each to slide in a respective cell, defining a variable-volume chamber therein, andiii) ducts connected to the chambers,a reaction element comprising an annular cam on which an active face of each piston acts,a front bearing and a rear bearing, by way of which, at least indirectly, the reaction element and the hydrodynamic element are rotatable with respect to one another,a support rotationally linked to one of the elements, the vehicle wheel being rotationally linked to the other element when in use,an oil distributor that rotates as one with the reaction element and brings the ducts selectively into communication with an oil supply line and return line depending on its angular position relative to the hydrodynamic element, anda brake mounted between the two elements in order to selectively prevent said rotational movement, the brake having at least one first braking surface rotationally coupled to the hydrodynamic element, and a second braking surface rotationally coupled to the reaction element.

A motor that complies with this definition will be known as “motor of the specified type” below.

In general, the reaction element and the distributor are rotationally linked to the support, while the hydrodynamic element turns with the wheel with respect to the support.

The side adjacent to the wheel will be known as the “front” of the motor, and the side away from the wheel will be known as the “rear” of the motor.

Conventionally, on the rear side, the support is fixed to the chassis, optionally by way of a suspension, and on the front side, the hydrodynamic element is directly or indirectly fixed to the wheel. In this case, bearings provided directly or indirectly between the two elements for the relative rotation thereof serve at the same time as load bearings that transmit forces between the chassis of the vehicle and the wheel and also moments about axes transverse to the axis of the motor.

Typically, the brake is at the rear of the motor while the distributor is located between the brake and the two elements per se.

A drawback of the motors according to the prior art is the lack of compactness.

Another drawback of the motors according to the prior art is that it is not possible to supply them from the rear.

Another drawback of the known motors is that they consist of numerous parts.

Yet another drawback of the known motors is that they need to be completely disassembled for most repairs, for example the restoration of the friction parts of the brake, the restoration of particular seals, etc.

The known motors have a long axial length which has the double drawback of impinging laterally on the maximum ground clearance region of the vehicle and of increasing bending moments undergone by the motor on account of the forces to be transmitted between the wheel and the chassis.

An aim of the invention is to remedy all or some of the drawbacks of the prior art and/or to improve the flexibility and simplicity of manufacturing such a motor while retaining or improving the robustness and cost of this manufacture, the maintenance and/or the operation of the means by which a driving wheel hydraulic motor is manufactured.

SUMMARY OF THE INVENTION

At least one aim is achieved with a hydraulic motor for a vehicle wheel of the type specified, in which, according to a first aspect of the invention, the hydrodynamic element is secured to a collar which surrounds the oil distributor and bears, on its radially outer face, means for rotationally coupling to the at least one first braking surface, the brake thus being disposed around the distributor.

Thus, by positioning the brake around the distribution, it is possible to manufacture a motor more compact than those in the prior art. In particular, the motor has a shorter axial length. The motor comprises fewer parts than other known motors, since the collar at the same time forms a sort of casing for the distribution and a brake element.

Moreover, since the brake is no longer positioned behind but around the distributor, the distributor is located close to the rear side of the motor, such that the motor can be supplied from the rear in a manner that is very favorable for the reliability of the connections.

In particular, the supply can be central or substantially central, this being very favorable for reliability and the reduction in pressure drops, since the oil makes a minimum number of turns before reaching the hydrodynamic element.

Typically, the reaction element surrounds the hydrodynamic element.

In a preferred embodiment, the reaction element is fixed at least indirectly to the support and the hydrodynamic element is able to rotate with respect to the support.

According to one particular feature, the brake is of the multi-disk type, and the coupling means are splines formed on the collar. By virtue of the invention, it is possible to benefit from the very advantageous characteristics of this type of brake without suffering the drawback of its long axial length, since the latter is essentially superposed on that of the distributor.

In one embodiment, the oil distributor and the brake have substantially the same axial length.

Given the brake torque that is required by standards, in particular for it to be possible to brake the vehicle even if the hydraulic motor is providing its maximum torque, a brake, in particular of the multi-disk type, has to have a particular axial length depending on its diameter. It has been found according to the invention that these conditions could be realized with a brake surrounding the distributor and having an axial length similar to that of the distributor.

Advantageously, the collar is integral with the hydrodynamic element. In this way, the number of parts is reduced further.

Advantageously, in one embodiment, the hydrodynamic element has, radially on the inside of the collar, a recess delimited by the inner face of the collar and by a shoulder of the hydrodynamic element through which the ducts lead, the oil distributor being essentially housed in the recess and having a polished end face which is in sliding contact with the shoulder and has distribution orifices which communicate selectively with the ducts, depending on the relative angular position of the hydrodynamic element and of the oil distributor.

In one advantageous embodiment, the support is a rear cover of the hydraulic motor, and the collar is directed axially toward the support.

According to a second aspect of the invention, in a hydraulic motor of the specified type that may be in accordance with the first aspect or the improvements thereof, the support is a rear cover of the motor and has a central column about which the oil distributor is mounted, and channeling ducts formed in the column lead through a lateral surface of the column in order to communicate with corresponding manifolds adjacent to a radially inner surface of the oil distributor.

According to one particular feature, at least one distribution slide valve is mounted in a movable manner in the central column in order to control the operating conditions of the hydraulic motor.

Advantageously, in one embodiment, the reaction element has a tubular extension surrounding the brake.

The tubular extension may be integral with the reaction element.

The reaction element may be secured to the support by way of the tubular extension.

The tubular extension and the preferred particular features thereof contribute toward the robustness, simplicity and precision of the assembly.

Preferably, the tubular extension is equipped with coupling means, in particular splines, in order to be coupled to the at least one second braking surface.

In one advantageous embodiment, the rear bearing is fitted directly on a bearing surface formed on the element secured to the tubular extension, and the outside diameter of the rear bearing is smaller than an inside diameter of the coupling means of the extension.

According to a third aspect of the invention, in a hydraulic motor of the specified type, which may be in accordance with one or more of the above aspects or with all or some of the improvements thereof, the two bearings are fitted directly on bearing surfaces formed on the element secured to the collar, and the two bearings each have an inside diameter larger than an outside diameter of the coupling means of the collar.

Advantageously, the two bearings are fitted directly on bearing surfaces formed on each of the two elements.

By virtue of this arrangement, the two bearings ensure excellent coaxiality of the two elements. This reduces operating noise and also the risks of cavitation or overpressure in the volumes taken up by the working oil.

According to a fourth aspect of the invention, in a hydraulic motor of the specified type, which may be in accordance with one or more of the above aspects or with all or some of the improvements thereof, in the support forming a rear cover for the hydraulic motor, brake actuating means are mounted, the brake being disposed axially between the support for the one part and the cam for the other.

In one embodiment, the actuating means comprise an annular piston situated around the other, subjected to the action of a spring in the direction of activation of the brake and adjacent to a hydraulic chamber for deactivation of the brake against the action of the spring.

In one embodiment, the actuating means comprise two annular pistons situated one around the other, one adjacent to a service braking hydraulic chamber in order to activate the brake by application of a hydraulic pressure, the other being subjected to the action of a spring in the direction of activation of the brake and adjacent to a hydraulic chamber for deactivation of the brake against the action of the spring.

Advantageously, the brake actuation means comprise a piston that is urged by a spring in the direction of activation of the brake and is adjacent to a hydraulic chamber for deactivation of the brake against the action of the spring, and the hydraulic motor according to the invention comprises mechanical deactivation means which can be actuated from an outer face of the support in order to move the piston against the action of the spring.

Advantageously, the mechanical deactivation means are axially linked to a service brake annular piston in the direction of deactivation of the brake, and mutual axial supporting means between the two pistons are provided to transmit the deactivation movement generated by the mechanical deactivation means to the piston subjected to the action of the spring.

According to a fifth aspect of the invention, in a hydraulic motor of the specified type, which may be in accordance with one or more of the above aspects or with all or some of the improvements thereof, the hydrodynamic element situated radially inside the reaction element has two successive, rearwardly facing shoulders which progressively reduce the outside diameter of the hydrodynamic element from front to rear, each bearing being mounted on the hydrodynamic element in the vicinity of a respective one of the two shoulders, the two bearings having different inside diameters.

According to a sixth aspect of the invention, in a hydraulic motor of the specified type, which may be in accordance with one or more of the above aspects or with all or some of the improvements thereof, the two elements have an annular interface between one another, along which the annular cam is situated axially between the two bearings.

Preferably, at least one of the two bearings butts against a respective shoulder delimiting the annular cam at one of its annular ends.

According to a seventh aspect of the invention, in a hydraulic motor of the specified type, which may be in accordance with one or more of the above aspects or with all or some of the improvements thereof, the two elements have an annular interface between one another, along which the following are found in the following order, relative to the axial direction:the front bearing;the annular cam;the rear bearing;the brake.

According to one particular feature, the motor comprises a dynamic seal closing the annular interface between the two elements, the front bearing being situated between the annular cam and the dynamic seal.

In one embodiment, the dynamic seal is removable from a front face of the motor without the hydrodynamic element or reaction element being removed.

According to an eighth aspect of the invention, in a hydraulic motor of the specified type, which may be in accordance with one or more of the above aspects or with all or some of the improvements thereof, in order to access the brake, the two elements are removable as a single assembly, without impairing a dynamic seal which closes the interface on the front side of the hydrodynamic motor. In order to access the brake, the two elements are removable as a single assembly, the hydraulic motor comprising a dynamic seal designed to close the interface on the front side of the hydraulic motor and not to be impaired by removal of said single assembly.

Preferably, notably in the seventh and eighth aspects, the dynamic seal comprises a ring having a polished face which is in sealed and sliding contact with a polished face of one of the elements under a contact pressure generated by an elastic means pressed against a support mounted in a removable manner on the other element.

According to a ninth aspect of the invention, in a hydraulic motor of the specified type, which may be in accordance with one or more of the above aspects or with all or some of the improvements thereof, the hydrodynamic element has, on its radially outer face, a spacer, one side of which can press against the rear bearing and the other side of which has a reaction face for the brake.

Preferably, the spacer is held axially between the rear bearing and an attached ring in a peripheral groove of the hydrodynamic element.

According to a tenth aspect of the invention, in a hydraulic motor of the specified type, which may be in accordance with one or more of the above aspects or with all or some of the improvements thereof, the reaction element may be fixed in at least two different angular positions with respect to the oil distributor, each corresponding to a respective direction of rotation of the hydraulic motor.

This aspect of the invention makes it possible to produce identical motors for the left-hand and right-hand wheels of a vehicle and these intrinsically identical motors are given different directions of rotation through the judicious choice, for each one, of the angular position of the reaction element with respect to the distributor.

Preferably, the reaction element is fixed to the support by screws distributed angularly about an axis of the motor at a regular spacing chosen with respect to a succession spacing of lobes of the annular cam in order to allow the two different angular positions mentioned above.

According to an eleventh aspect of the invention, in a hydraulic motor of the specified type, which may be in accordance with at least one of the above aspects or with all or some of the improvements thereof, the oil distributor is adjacent to an interface defining at least one annular manifold, the interface having different diameters on either side of the manifold in order that the pressurized oil generates a differential axial thrust force on the oil distributor.

DESCRIPTION OF THE INVENTION

Because these embodiments are entirely nonlimiting, it is notably possible to realize variants of the invention that comprise only a selection of features described below, as described or generalized, in isolation from the other features described, if this selection of features is sufficient to confer a technical advantage or to differentiate the invention from the prior art.

FIG. 1illustrates a hydraulic motor1for a vehicle wheel that rotates about an axial direction X which constitutes at the same time the axis of the hydraulic motor1.

The motor comprises a stator101and a rotor102which rotate with respect to one another about the axis X. The rotor102comprises, at the front of the motor, a flange103provided for fastening the wheel by virtue of threaded holes55. The stator101comprises a support8which is a rear cover of the hydraulic motor1and which is fixed to the chassis of the vehicle, optionally by way of a suspension and/or a steering pivot pin.

In the embodiment described, the hydraulic motor1is designed to be the only mechanical link between the wheel and the chassis or the suspension of the vehicle, and as such it transmits all of the forces and moments between the chassis and the wheel.

The hydraulic motor1has the function of converting hydraulic energy into mechanical rotation energy of the rotor102with respect to the stator101. To this end, it comprises two interactive elements that rotate with respect to one another about the axis X, namely a hydrodynamic element2on which the pressurized oil acts, and a reaction element6, one of which is secured to the stator101so as to rotate therewith and the other of which is secured to the rotor102so as to rotate therewith, and which are disposed around one another.

In the embodiment shown, the hydrodynamic element2is secured to the rotor102and the reaction element6is secured to the stator101. In a typical embodiment, as shown, the reaction element6surrounds the hydrodynamic element2.

The hydrodynamic element2comprises an external cylindrical wall114in which cells Ai have been bored along a radial axis with respect to the axis X, as illustrated inFIG. 2. Pistons4are mounted so as each to slide radially in one of the cells Ai in each case and define a variable volume chamber3radially on the inside therein.

As also shown inFIG. 3, each piston4has, on an active face opposite the chamber3, thus radially facing the reaction element6, a roller104which rolls on an annular cam7having multiple lobes regularly distributed angularly about the axis X. The cam7is formed on the radially inner face of the reaction element6.

In a manner not shown any further, the roller104is rotationally supported on the piston4by way of a pad such that, in service, the roller104turns virtually without friction with respect to the piston4and rolls without sliding on the annular cam7.

Each chamber3is connected to an oil distributor9by a respective duct5formed in the hydrodynamic element2. The oil distributor9is secured to the reaction element6so as to rotate therewith.

At an interface34,35between the hydrodynamic element2and the distributor9, each duct5communicates selectively with a high-pressure oil inlet manifold22, an oil return manifold21, an intermediate manifold20, or none of the three manifolds20,21,22, depending on the relative angular position of the two elements2and6. The interface34,35is made up of a shoulder34of the rotor102and by an adjacent face35of the distributor.

The shoulder34and the adjacent face35of the distributor are flat faces, perpendicular to the axis X, provided with a mirror polish, which are in sealed contact with one another with regard to the working oil even at high pressure, and which slide against one another when the hydrodynamic element2is rotating with respect to the distributor9secured to the stator102. The ducts5connected to the chambers3lead through the shoulder34and, depending on the relative angular position of the stator101and of the rotor102, communicate selectively with orifices36of the ducts123,124,125formed in the oil distributor9. Some123of the ducts are connected to the low-pressure manifold21, others124to the high-pressure manifold22, and yet others125to the intermediate manifold20, depending on the respective angular position of the orifices36with respect to the lobes of the cam7.

In operation, the motor has the function of generating a torque in the direction of relative movement of the two elements2,6. To this end, the duct5associated with each piston4communicates with the high-pressure manifold22when, as shown inFIG. 3, depending on the direction of rotation of the hydrodynamic element2indicated by the arrow F, the roller104moves from the top of one lobe to the cavity between two lobes. In this case, the piston subjected to the radial force, with respect to the axis X, generated by the high-pressure oil exerts, on the oblique face of the cam, a force having a circumferential component that contributes to the motor torque. When, by contrast, the roller104is in the process of rising toward the top of a lobe, the duct5communicates with the oil return manifold21. The oblique face of the lobe pushes the piston back toward the end of the chamber3and, as a result, returns depressurized oil toward the intake of the pump situated on the vehicle. When the roller104is at the top of a lobe or in the cavity between two lobes, the duct5does not communicate with the high-pressure oil or with the oil return.

The above relates to the operation of a single-speed motor, or low-speed and high-torque operation in a two-speed motor, such as the one shown inFIG. 1. These motors having at least two speeds are capable of at least one operating condition in which the pistons4are deactivated and to this end communicate with the oil return while their roller moves from the top to the cavity of certain lobes of the cam. This has the aim of reducing the torque and increasing the speed of rotation of the rotor101, with the flow of high-pressure oil being distributed to a smaller number of pistons4. In order that the pistons4are selectively active or inactive on a lobe, the orifice36which communicates with the chamber3when the piston4descends from the top to the cavity of this lobe is connected to the intermediate manifold20by a duct125. The intermediate manifold20is selectively connected to the high-pressure manifold22or to the oil return manifold21by virtue of a slide valve24.

InFIG. 1, the slide valve24is shown in its two possible positions, namely with active lobes above the axis X and inactive lobes below the axis X. The slide valve24is controlled by the driver of the vehicle, by a single-acting hydraulic control that arrives through a connector126and is returned by a spring127.

In a motor having only one operating condition, there would be no intermediate manifold20or slide valve24and all of the orifices36would be connected either to the high-pressure manifold such as22or to the oil return manifold such as21.

In order to increase the number of pistons and thus the torque and the power of the motor to a reasonable extent, there are two rows of pistons in adjacent radial planes (FIGS. 1 and 2). In order to smooth the torque produced by the motor, the pistons of each row are in two intermediate angular positions between those of the pistons of the other row. The pistons of one row are partially interlocked between the pistons of the other row, for the purpose of spatial optimization. In a variant of the invention, there could be only one row of pistons, or more than two rows.

The hydraulic motor1also comprises a brake12mounted functionally between the reaction element6and the hydrodynamic element2.

The brake12selectively opposes the rotational movement of the hydraulic motor1and has at least one second braking surface rotationally coupled to the reaction element6and at least one first braking surface rotationally coupled to the hydrodynamic element2.

In the embodiment shown, the brake12is of the oil bath multi-disk type comprising an alternating stack of thin steel disks13rotationally coupled to one of the elements, in this case the hydrodynamic element2, and thicker disks14rotationally coupled to the other element, in this case the reaction element6. The disks14are formed of a metal core, the two opposite faces of which are lined with a friction material combined with the steel of the disks13. The braking surfaces are the faces of these disks13,14. The means for activation and deactivation of the brake12are described below.

According to one aspect of the invention, the hydrodynamic element2is secured to and integral with a collar15that has a cylindrical overall shape about the axis X and is directed axially rearward, in particular toward the support8. The collar15surrounds the oil distributor9.

At its front end, the radially inner face of the collar15is connected to the above-described shoulder34, which is thus one face of the hydrodynamic element2and which defines, with said radially inner face of the collar, a recess33housing the distributor9.

The collar15is surrounded by the brake12. In particular, the collar15bears, on its radially outer face, means16for rotationally coupling to one of the sets of disks13,14, in this case the steel disks13. The coupling means16are axial splines formed on the collar15, which engage with teeth formed along the radially inner edge of the disks13, such that the disks13are rotationally linked to the hydrodynamic element2while being able to slide axially with respect thereto.

The reaction element6has a tubular extension37secured to and integral with the cam7. The extension37secures the reaction element6to the support8by means of screws54distributed angularly about the axis of rotation X of the hydraulic motor1. The reaction element6can be fixed in at least two different angular positions with respect to the oil distributor9, each corresponding to a respective direction of rotation of the hydraulic motor1. To this end, as illustrated inFIG. 3, the distribution spacing of the screws is equal to (n−0.5) times the succession spacing of the lobes of the cam7, n being an integer which, in the example shown, is equal to 1. Thus, with a minor adaptation to the design, consisting in choosing the angular position of the reaction element6with respect to the support8to which the distributor9is secured, it is possible to produce motors that turn in one direction or the other, for the right-hand and left-hand driving wheels of a vehicle.

The tubular extension37surrounds the collar15, with the brake12being interposed. The tubular extension37is equipped with coupling means38for coupling it to the other set of disks, in this case the thicker disks14. The coupling means38are axial splines formed on the radially inner face of the extension37, which engage with teeth formed along the radially outer edge of the disks14, such that the disks14are rotationally linked to the reaction element6but are able to slide axially with respect thereto.

The axial length of the brake12is similar to the axial length of the oil distributor9.

The support8has a central column17extending along the axis X, about which the distributor9is arranged, which has an annular shape. The distribution slide valve24is mounted in a movable manner in the central column17so as to control the operating conditions of the hydraulic motor1.

The central column17is pierced by a high-pressure oil supply duct18and an oil return duct19which lead through a lateral surface of the central column17so as to communicate with the manifolds22and21, respectively, which are formed at the interface between a radially inner surface of the oil distributor9and the radially outer surface of the central column17.

The ducts18and19are intended to be connected permanently to the delivery orifice and to the intake orifice, respectively, of an oil pump mounted on the chassis of the vehicle.

In order to selectively connect the intermediate manifold20to one or the other of the manifolds21,22, the manifolds20,21and22are connected to the housing of the slide valve24by ducts18and19, or130,131,132, respectively, formed inside the column.

According to one particular feature, the manifolds20,21,22are formed by peripheral grooves at the interface with the column17. The column17has a diameter that increases toward the rear, such that the interface diameter is greater at the rear of each manifold20,21or22than at the front of this manifold. This results in a differential axial thrust force on the oil distributor9, directed toward the front, which presses together the faces34and35with a force proportionate to the oil pressure. In particular, the axial force thus produced balances the thrust force in the opposite direction that is exerted by the pressurized oil in the orifices36.

The hydraulic motor also comprises a front bearing41and a rear bearing42, by way of which the stator102and the rotor101are rotatable with respect to one another.

The bearings41,42transmit the forces between the wheel and the chassis. The cam7and the hydrodynamic element2per se, that is to say the region in which the pistons3and the chambers5are located, are situated axially between the front bearing41and the rear bearing42.

According to one aspect of the invention, the bearings41,42are mounted directly between the hydrodynamic element2and the reaction element6. More specifically, the body of the hydrodynamic element2comprises two outer bearing surfaces44on which inner rings of the two bearings41,42are directly fitted, and the reaction element6comprises two inner bearing faces45in which outer rings of the two bearings41,42are directly fitted.

In one embodiment, the two bearings41,42are of the tapered roller type mounted head to tail so that each bearing resists the axial forces in a respective direction.

The rear bearing42is mounted axially between the cam7and the brake12.

The hydrodynamic element2has two successive shoulders39,40that face rearward and progressively reduce the outside diameter of the hydrodynamic element from the front to the rear.

The front bearing41is mounted so as to transmit the rearwardly directed axial forces from the hydrodynamic element2to the reaction element6. To this end, the inner ring of the front bearing41butts against the shoulder39.

The rear bearing42is mounted so as to transmit the forwardly directed axial forces from the hydrodynamic element2to the reaction element6. The inner ring of the rear bearing42is adjacent to the shoulder40without butting against it.

Since the shoulder40brings about a smaller diameter of the rear bearing surface44compared with the front bearing surface44, the two bearings have different inside diameters.

These two diameters are both greater than the outside diameter of the splines16formed on the collar15in order to allow the bearings41,42to be mounted on the hydrodynamic element2from the rear. On its outer face, the hydrodynamic element2has an annular spacer51, a front face107of which axially positions the rear bearing42and the rear face108of which constitutes a reaction face for the brake12. The annular spacer51is kept axially in position between the inner ring of the rear bearing and a removable ring109inserted into a peripheral groove in the hydrodynamic element2. The removable ring109can be an open ring, the diameter of which can be increased by elastic deformation so as to allow the ring109to be inserted into the groove. The ring109can also be formed by two half-rings joined together along an axial joint face by removable connecting means.

On the radially inner side of the reaction element6, the cam7protrudes radially between two shoulders119,121, against each of which the outer ring of the one of the bearings41,42, respectively, butts.

The inside diameter of the splines38of the reaction element6is greater than the outside diameter of the rear bearing42, so as to allow the bearing42to be mounted from the rear of the reaction element6.

In order to repair the brake, the removal of the screws54makes it possible to separate the rear support8from the two elements2,6, which remain joined together by virtue of the spacer51and the ring109that locks the latter. The brake disks can then be replaced.

If the motor per se has to be disassembled, this is possible, after the screws54have been removed, by removing the brake disks from the rear and by removing the ring109, thereby making it possible withdraw the hydrodynamic element by way of an axial movement toward the front (the right inFIG. 1) relative to the reaction element6.

Actuating means25for the brake12are mounted in the support8forming a cover. The actuating means25comprise two annular pistons26,27situated one around the other, and a mechanical deactivation means31in thread engagement with the support8.

The annular piston26is adjacent to a service braking hydraulic chamber28for activating the brake12by application of a hydraulic pressure. Thus, the pressurization of the hydraulic chamber28causes service braking, which the driver of the vehicle actuates in order to slow the vehicle down or bring it to a standstill when it is moving or stopped for a short period.

When the annular chamber28is subjected to an oil pressure, the piston26pushes the stack of disks13,14against the spacer51, which is pressed axially onto the reaction element6by way of the rear bearing41, which transmits the axial forces toward the front given the direction of its cone shape.

The annular piston27is a parking brake piston and is subjected to the action of a spring29, in the example a Belleville washer, in the direction of activation of the brake12. The piston27is adjacent to a hydraulic chamber30for deactivating the brake12against the action of the spring29.

When the vehicle is at a standstill for a certain period, for example when its engine is stopped, the deactivation chamber30is depressurized and the spring29pushes the piston27in the direction of clamping the stack of disks against the spacer51. When the vehicle is started up, the chamber30is, automatically or manually, resupplied and the oil pressure in the chamber30inhibits the piston27, allowing the brake12to be controlled only by the service brake piston26.

In the embodiment shown, for parking braking, the parking brake piston27does not act directly on the stack of disks but by way of the piston26, which, to this end, has a rearwardly directed shoulder32.

According to one embodiment, the hydraulic motor comprises means for mechanically deactivating the parking brake so as to make it possible to release the rotor102when there is no pressure in the chamber30, notably in the event of damage to the vehicle. The mechanical deactivation means comprise screws31, the heads of which are accessible from the rear of the support8. The screws pass through plain holes111in the support and are in thread engagement with tapped holes112formed in a flange113of the piston26. By turning the screws31in the screwing direction, the piston26is pulled toward the rear, which, by way of its shoulder32, drives the piston27against the action of the spring29.

Axially along the annular interface43between the hydrodynamic element2and the reaction element6, from the front to the rear, there are a dynamic seal46which closes the interface in a sealed manner at its front end, the front bearing41, the cam7next to the cylindrical wall114of the hydrodynamic element, the rear bearing42, the brake12, and a part of the brake actuating means25.

The dynamic seal46comprises a ring48that is secured to the hydrodynamic element2so as to rotate therewith and which has a rear face49pressed against a front face50of the reaction element6. The faces49and50are flat, perpendicular to the axis X, and machined with a mirror polish. The mutual axial pressing force of the two surfaces is generated by the deformation of an O-ring53inserted between the ring48and the flange103. At the same time, the O-ring3ensures sealing between the ring48and the body of the hydrodynamic element2and, by friction, the driving of the ring48in rotation by the hydrodynamic element2.

In a variant embodiment shown inFIG. 4, the dynamic seal46comprises a cup52fastened removably to the hydrodynamic element2by screws116. Instead of pressing directly on the element2, the O-ring53is pressed against the cup52. In order to restore the dynamic seal46, all that is necessary is to remove the cup52and replace the ring48and/or the O-ring52, which have an inside diameter greater than the outside diameter of the flange103, without having to further disassemble the hydraulic motor1.

In the embodiment inFIG. 5, the spacer51is interposed between the disk pack13,14and the radially outer ring of the rear bearing42, itself butting against the shoulder121of the reaction element6. In other words, the reaction force that the shoulder121sets against the braking force if the brake is activated is no longer transmitted through the rolling bodies (rollers) of the bearing. The removable ring109now only serves to stop the inner ring of the rear bearing42axially toward the rear. It is now located in front of the spacer51and not behind the latter. After the disks have been removed, the spacer51is able to be withdrawn toward the rear and there is then access to the ring109for the removal of the latter so that the element2can be withdrawn by an axial forward movement with respect to the reaction element6. Otherwise, this embodiment is identical to the one inFIGS. 1 to 3or to the one inFIG. 4.

FIG. 6shows a view in axial section of a variant of a hydraulic motor according to the invention. Only the differences between the above-described motor and this variant will be described here. Above-described elements have references increased by 200 inFIGS. 6 and 7.FIG. 7is a view in axial section through the column217.

The central column217is furthermore pierced by a pressurized oil supply duct256for supplying high-pressure oil, which leads through a lateral surface of the central column217in order to communicate with a manifold257. The manifold257is formed at the interface between a radially inner surface of the oil distributor209and the radially outer surface of the central column217.

The duct256is intended to be connected permanently to an orifice for delivering pressurized oil coming from the vehicle that is intended to deactivate the brake212.

Actuating means225for the brake212are mounted in the support208forming a cover. The actuating means225comprise an annular piston227.

The annular piston227is a parking brake piston and is subjected to the action of a spring229, in the example a Belleville washer, in the direction of activation of the brake212. The piston227is adjacent to a hydraulic chamber230for deactivating the brake212against the action of the spring229.

When the vehicle is at a standstill for a certain period, for example when its engine is stopped, the deactivation chamber230is depressurized and the spring229pushes the piston227in the direction of clamping the stack of disks. When the vehicle is started up, the chamber230is, automatically or manually, resupplied and the oil pressure in the chamber230inhibits the piston227.

Of course, the invention is not limited to the examples that have just been described and numerous variations may be made to these examples without departing from the scope of the invention. In addition, the various features, forms, alternatives and embodiments of the invention may be combined with one another in various combinations insofar as they are not mutually incompatible or mutually exclusive.

NOMENCLATURE

1,201Hydraulic motor2Hydrodynamic element3Chamber4Piston5Duct6,206Reaction element7,207Annular cam8,208Support9,209Oil distributor12,212Brake13,14Disks15Collar16Means for rotationally coupling17,217Central column18,218High-pressure oil supply duct19,219Oil return duct20,220Intermediate manifold21,221Oil inlet manifold22,222Oil return manifold24Distribution slide valve25Brake actuating means26Service brake piston27Parking brake piston28Service braking hydraulic chamber29Spring30Hydraulic chamber for deactivating the brake31Screw32Mutual axial supporting shoulder33Recess34Shoulder35Face adjacent to the shoulder36Orifices37,237Tubular extension of the reaction element38Coupling means of the tubular extension39,40Successive shoulders of the hydrodynamic element41Front bearing42Rear bearing43,243Annular interface44,45Bearing surfaces of rolling bearings46Dynamic seal48Dynamic seal ring49Polished face of the ring50Polished face of one of the elements51Spacer52Cup53Elastic means54Fastening screw of the reaction element55Threaded holes in the hydrodynamic element101Motor stator102Motor rotor103Flange104Piston roller107Front face of the spacer108Rear face of the spacer109Ring111Plain holes in the support112Tapped holes113Flange of the piston26114External cylindrical wall116Screw119,121,319,321Shoulders123,124,125Ducts in the distributor126Hydraulic connectors127Spring130,131,132Ducts in the columnAi CellsF Direction of rotation of the element2X Axis of rotation of the hydraulic motor