Hydraulic machine comprising bearings for supporting rotating components

Abstract

The invention relates to a rotary hydraulic machine (102) comprising: - a housing (10), - a shaft (20) movably mounted relative to the housing about an axis, - a shroud (24) rigidly connected to the shaft and extending around at least a portion of the housing, - a cam (12) rigidly connected to one of the housing or the shaft, - a cylinder block (42) rotatably connected to the other one of the housing or the shaft, the cylinder block comprising a piston engageable with the cam to produce relative rotation between the shaft and the housing, - first and second guide bearings (28) each directly supported on the housing and the shroud, and - a third guide bearing (37) directly supported on the housing and the cylinder block.

Description

TECHNICAL FIELD

[0001] The present invention relates to a hydraulic machine. BACKGROUND

[0002] Many types of hydraulic machines are known. Such a machine essentially comprises, for example, five components: a housing, a shaft, a component forming a motor or a pump arranged between the housing and the shaft, bearings for guiding the relative rotation of the shaft and the housing, and a brake.

[0003] The housing is intended to be fixed to the frame of a machine or a vehicle. It comprises a multi-lobed cam clamped between two side elements of the housing.

[0004] The shaft supports a power take-off adapted to carry an accessory that must be driven in rotation, for example, in the case where the machine constitutes a motor and the accessory is a wheel or any other equipped rim on which the drive torque is transmitted. In the case where it constitutes a pump, the power take-off receives the mechanical drive motor torque applied to the machine inlet.

[0005] The component forming a motor or a pump is, for example, a radial piston assembly. It comprises a distributor, a cylinder block having radial cylinders each housing a piston, each piston carrying a roller abutting against the cam.

[0006] When the distributor cyclically applies pressurized fluid inside the cylinders, the bias of the pistons and the rollers associated on the cam drives the cylinder block in rotation relative to the cam, and therefore relative to the housing. Since the cylinder block is rotationally linked with the central element of the shaft, the shaft is driven in rotation by the fluid pressure applied by the distributor. The machine then constitutes a motor. Conversely, when the power take-off applies a mechanical force on the shaft in a direction of rotation drive relative to the housing, the displacement of the rollers and the pistons relative to the lobes of the cam causes a variation of the volume of the cylinders and therefore the application of a fluid pressure on the distributor. The machine then operates as a pump.

[0007] Such a machine is reversible, thus operating both as a pump and as a motor, and also in both directions of rotation. Therefore, such a hydraulic machine can be in four different states, the four states defining four quadrants of pressure values and flow directions: forward gear, in traction or holding state, and reverse gear, in traction or holding state.

[0008] The brake is formed by a stack of discs alternately rotationally linked, some discs being linked to the shaft and the other discs being linked to the housing. In the braking position, the discs are biased in abutment with each other by elastic members. A counterforce can be applied to the elastic members in a control chamber in order to place the brake in a brake release position.

[0009] A particular known construction is that in which the machine comprises a sleeve rigidly fixed to the shaft and extending around at least one portion of the housing. This sleeve thus forms an extension of the shaft which extends from the axial end of the shaft to surround a portion of the housing. This assembly rotates as a whole. Furthermore, the machine comprises two bearings for guiding the rotation of the shaft relative to the housing, which generally consist of opposite tapered bearings forming hubs, that is to say, allowing the bearing of radial and axial forces, each bearing abutting directly against the housing and the sleeve. When the hydraulic machine is used to drive a machine member such as a wheel or a track sprocket, the dimensions of the bearings of the motor should essentially ensure the function of torque transmission, but also the function of supporting the weight of the machine during rolling, or should cope with the tension shocks of the track. For these reasons, the dimensions of the rolling elements forming the bearings are proportional to these forces, and the rolling elements are advantageously as close as possible to the power take-off forming the wheel or track sprocket accessory. This mounting is advantageous because it is very robust to cope with the track rolling or traction forces, and it provides good resistance and good life of the hub function with respect to the track rolling or driving bias.

[0010] While this construction is interesting, it also has drawbacks.

[0011] Thus, the shaft is generally relatively long, making the shaft liable to bend.

[0012] Furthermore, the cylinder block in which the pistons move tends to bias the shaft by generating parasitic forces which disturb the rolling bearings of the motor. These parasitic forces result from the alternating thrust of the pistons on the cam and are thus perpendicular to the axis. Furthermore, particularly in the case of distributors whose distribution is planar, the distributor generates an axial thrust which is transmitted to the cylinder block and then to the shaft in the opposite direction to the cylinder block.

[0013] Thus, the parasitic forces of the pistons are transmitted to the shaft and to the rolling elements when they are bent.

[0014] The parasitic forces of the distributor are transmitted in particular to the rolling elements that are farthest from the distributor. They also tend to interfere with the clamping of the two tapered bearings, called the preload or pre-stress of the rolling elements, which serves to install the two opposing tapered bearings. This pre-stress is ensured by clamping the two inner rings of the rolling elements on the shaft, by wedging the stack elements on the side of the race opposite the distributor, the stack elements being mounted on splines and held in place by a retaining ring. This pre-stress is provided to counter the rolling forces and the driving forces, so that the rolling elements must always remain abutted. An axial force exceeding the preload would cause the rolling elements to move a distance, one of the rolling elements to lose contact, a gap to appear in the guidance of the shaft, and rapid damage to the rolling elements. The parasitic axial forces resulting from the thrust of the distributor must be compensated by increasing the pre-stress. However, an increase in pre-stress creates a jamming and thus a loss of rotational efficiency and a reduction in life.

[0015] In addition, the rolling bearings of the motor, which are normally dedicated to the transmission of the power of the machine, also receive these parasitic forces. Some parts, in particular these bearings, must therefore become more robust, which is detrimental to the overall bulk of the machine, or the performance of the machine must be reduced to avoid damaging the parts.

[0016] The aim of the present invention is to improve the aforementioned particular configuration by overcoming at least one of these drawbacks. SUMMARY

[0017] To this end, a rotary hydraulic machine is provided, comprising:

[0018] - a housing,

[0019] - a shaft rotatably mounted with respect to the housing,

[0020] - a sleeve rigidly fixed to the shaft and extending around at least a portion of the housing,

[0021] - a cam rigidly fixed to one of the housing and the shaft,

[0022] - a cylinder block rotationally fixed to the other of the housing and the shaft,

[0023] the cylinder block comprising a piston able to cooperate with the cam to generate a relative rotation between the shaft and the housing,

[0024] - a first and a second guide bearing each directly abutting against the housing and the sleeve, and

[0025] - at least one third guide bearing directly abutting against the housing and the cylinder block.

[0026] Thus, the third bearing ensures that the housing bears at least part of the forces generated or transmitted by the cylinder block. These forces are thus no longer transmitted directly to the shaft or to the first and second bearings. Depending on the configuration of the additional bearing(s), these forces are axial forces, radial forces or both with respect to the axis of the shaft. With this mounting, the first and second bearings are thus kept dedicated to the transmission forces of the machine. Since these bearings are no longer disturbed by all or part of the parasitic forces generated by the cylinder block and the distributor, the robustness of the motor is improved. In particular, the robustness of these bearings under equal volume is no longer compromised. Or their volume can be reduced and thus the space requirement of the motor without compromising its performance. Moreover, in the case of bearing of axial forces, there is no longer a need to compensate for the parasitic axial forces generated by the thrust of the distributor by increasing the prestress on the first and second bearings.

[0027] In one embodiment, the first, second and third bearings are the only bearings capable of guiding the rotation of the shaft with respect to the housing in the machine.

[0028] Thus, no additional bearings are provided in addition to these three bearings.

[0029] In another embodiment, the machine further comprises a fourth bearing directly abutting against the housing and the cylinder block.

[0030] It can be provided that the third bearing or at least one of the third and fourth bearings:

[0031] abuts against the housing and the cylinder block in a direction along the axis of the shaft;

[0032] abuts against the housing and the cylinder block in a direction radially with respect to the axis; or

[0033] abuts against the housing and the cylinder block in a direction along the axis and in a direction radially with respect to the axis.

[0034] In one embodiment, the third bearing abuts against the housing and the cylinder block in a direction along the axis of the shaft and the fourth bearing abuts against the housing and the cylinder block in a direction radially with respect to the axis.

[0035] Thus, these two bearings ensure the bearing of axial and radial forces, respectively.

[0036] It can be provided that the third bearing or at least one of the third and fourth bearings comprises rolling elements.

[0037] For example, the rolling elements are roller or needle bearings.

[0038] In one configuration, the rollers or needles extend along a plane perpendicular to the axis of the shaft.

[0039] This construction is particularly effective for bearing parasitic axial forces and is space-saving. The rolling element then forms an axial stop.

[0040] It can be provided that the third bearing or at least one of the third bearing and the fourth bearing comprises a bushing.

[0041] Unlike a rolling element, which comprises movable parts relative to each other, a bushing does not. It is solid on two main faces from which the housing and the cylinder block abut.

[0042] For example, the bushing is cylindrical.

[0043] In another example, the bushing is frustoconical.

[0044] This bushing allows axial and radial forces to be borne. When the bushing is subjected to parasitic forces, it tends to abut perpendicularly to the trajectory of the cylinder block, which allows the contact pressure of the housing and the cylinder block on the bushing to be optimized. This allows a significant reduction in axial play and makes it possible to adapt the shape of the housing and the cylinder block in order to further improve the distribution of the contact pressure on the bushing.

[0045] It can be provided that the bushing has a slot extending from a first axial end edge of the bushing to a second axial end edge of the bushing.

[0046] This slot allows the bushing to adapt well to the housing defined between the housing and the cylinder block, in particular by allowing the diameter of the bushing to be modified.

[0047] It can also be provided that the bushing comprises at least one element for preventing rotation of the bushing relative to a part of the machine.

[0048] Advantageously, the bushing has at least one recess passing through the thickness of the bushing and intercepting at most one end edge of the bushing.

[0049] This type of recess or recesses facilitates the circulation of lubricating liquid on the two faces of the bushing and its good distribution.

[0050] In one embodiment, the third bearing comprises a roller or needle bearing in which the rollers or needles extend along a plane perpendicular to the axis of the shaft, and the fourth bearing comprises a cylindrical bushing.

[0051] This embodiment thus combines an axial stop in the form of a rolling element and a bushing for bearing radial forces. It is particularly space-saving.

[0052] It can also be provided that the cylinder block, the housing and the at least one bearing are shaped so as to center the cylinder block independently of the shaft in a form-fitting manner relative to the housing.

[0053] It can be provided that the cylinder block is slidably mounted on splines of the shaft.

[0054] According to the present application, there is also provided a machine forming a vehicle or a construction machine, which machine is equipped with at least one hydraulic machine according to the present application. BRIEF DESCRIPTION OF DRAWINGS

[0055] Embodiments of the present application will now be presented by non-limiting examples, on the basis of the drawings, in which:

[0056] Figure 1 is a partial axial sectional view of a machine according to the first embodiment of the present application;

[0057] Figure 2 is Figure 1 a cross-sectional view of the machine shown in Fig. 1 in a plane perpendicular to the axis, which includes the cylinder block and the piston;

[0058] Figure 3 is Figure 1 an enlarged view of detail D of Fig. 1 ;

[0059] Figure 4 and Figure 5 is Figure 3 two perspective views of the bushing of the machine shown in Fig. 1 ;

[0060] Figure 6 is a perspective view showing the distribution of contact pressure on the bushing;

[0061] Figure 7 is a view similar to Figure 3 Fig. 1, which shows a machine according to the second embodiment of the present application;

[0062] Figure 8 and Figure 9 is a perspective view of the machine shown in the previous figure, in which the cylinder block has been removed, so that the housing can be seen therein;

[0063] Figure 10 and Figure 11 are perspective views showing two corresponding faces of the cylinder block of the machine. DETAILED DESCRIPTION

[0064] First embodiment

[0065] As shown in Figures 1 to 6 Fig. 1, the hydraulic machine 102 according to the first embodiment of the present application is rotationally symmetrical and centred on an axis O-O. It comprises a housing 10, a shaft 20, an assembly 25 forming a motor or pump arranged between the housing 10 and the shaft 20, bearings 26, 28 for guiding the relative rotation of the shaft 20 with respect to the housing 10, and a brake 30.

[0066] The casing 10 is intended to be fixed to the frame of a machine or vehicle.

[0067] The assembly 25 comprises Figure 2 The multi-lobed cam 12 shown, which is clamped between two lateral elements of the casing, one of which is located Figure 1 to the right of the other and is not visible.

[0068] The shaft 20 is arranged to support a power take-off adapted to carry an accessory that must be driven in rotation, for example, in the case of a machine constituting a motor, the accessory being a wheel or any other equipped rim. In the case of a pump, the power take-off receives the mechanical motor torque applied to the machine inlet.

[0069] The assembly 25 forming a motor or a pump is a radial piston assembly 36. It comprises a distributor 40 and a cylinder block 42 having radial cylinders 35 housing corresponding pistons 36, as Figure 2 shown. Each piston carries a roller 38 which abuts against the cam 12 fixed on the casing. The number of cylinders and of pistons is different from the number of lobes of the cam 12. Since in this type of machine the cam is radially external, the cylinders of the cylinder block located radially internal to the cam open radially outwards, facing the cam. The distributor 40 is supplied with fluid via known and not shown elements forming a cover of the casing and a fitting for supplying the distributor. As Figure 3 shown, the cylinder block 42 is rotationally linked with the shaft 20 by longitudinal splines 29 of the cylinder block and of the shaft which interengage, so that the cylinder block is slidably mounted on the shaft in this axial direction.

[0070] In a manner known per se, when the distributor 40 cyclically applies pressurized fluid inside the cylinders 35, the biasing of the pistons 36 and of the rollers 38 associated on the cam 12 causes the cylinder block 42 to rotate relative to the cam, and therefore relative to the casing. The shaft is thus driven in rotation by the pressure of the fluid. In this case, the machine constitutes a motor.

[0071] Conversely, when the power take-off applies a mechanical force on the shaft 20 in a direction of rotational drive relative to the casing 10, the displacement of the rollers and of the pistons relative to the lobes of the cam causes a variation of the volume of the cylinders and therefore the application of a fluid pressure on the distributor. The machine then operates as a pump. This machine is therefore reversible, and can thus operate both as a pump and as a motor, and also in both directions of rotation.

[0072] The shaft 20 has a central region or hub 22 intersected by the axis O-O. It also comprises an axial cylindrical extension away from the axis, which forms a sleeve 24 or crown, and is connected to the hub by radial connecting disc pieces 16 extending to the axial end of the shaft, inFigure 1 The sleeve 24 thus extends from this disc to the right in the figure.

[0073] The housing 10 itself has a cylindrical axial extension 11 which extends along the longitudinal axis O-O from the radial extension 9 connected to a cover not shown, to the left in the figure. Figure 1 This axial extension 11 extends around the hub 22 of the shaft 20 and faces it in a direction which is radial with respect to the axis. It thus intervenes between the hub 22 and the sleeve 24 in the radial direction.

[0074] It can thus be seen that, in this configuration given by way of example, the sleeve 24 is rigidly fixed to the hub 22 of the shaft and extends around the extension 11 of the housing. The cam 12 is rigidly fixed to the housing and the cylinder block 42 is rotationally fixed to the shaft 20.

[0075] The machine comprises a disc-type brake 30. It is formed by a stack of discs connected in rotation, some of the discs being connected to the shaft 20 and others being connected to the housing 10, alternately in space along the longitudinal axis O-O. Each disc is formed by a washer. Their respective rotation connections with the housing and the shaft can be formed, for example, by engaging ribs provided on the radial outer periphery or on the radial inner periphery of the discs in complementary splines or grooves formed oppositely on the sleeve 24 of the shaft 20 and on the associated extension 11 of the housing. As a variant, an intermediate rotation connection part can be provided, which intervenes between the discs and one of the housing 10 or the shaft 20.

[0076] The machine has a brake release chamber 55 which is placed opposite the cylinder block 42 in the axial direction with respect to the stack of discs. It thus lies to the left of this stack in the figure. Figure 1 In this case, the brake 30 is arranged at the axial end of the machine opposite the distributor 40 with respect to the cylinder block 42. In the rest position, the discs are biased against each other by springs so that the shaft 20 and the housing 10 are fixed with respect to each other in the braking case. If the discs are given a spacing by filling the brake release chamber 55 with fluid to oppose the biasing of the springs, rotation of the shaft with respect to the housing is allowed.

[0077] In order to limit the axial space requirement of the machine, the power take-off 13 can be arranged outside the elements radially external to the sleeve 24, as in the case of the figure. Figure 1 According to a variant, the power take-off force is applied axially on the discs transversely with respect to the axis O-O.

[0078] Figure 1The machine comprises two guide bearings, namely a first bearing 26 and a second bearing 28, which each abut directly against the extension 11 and the sleeve 24. Here, the two bearings each abut against an axial end region of the sleeve, against surfaces which are oriented in the direction of the axis and of the extension 11 of the housing. Here, they also abut against an intermediate portion of the extension 11 of the shaft, against surfaces which are oriented in the opposite direction to the axis in the direction of the sleeve 24.

[0079] Here, the bearings are truncated cone roller bearings, but as a variant, cylindrical roller bearings or ball bearings could be provided, for example. The axis of the rolling elements is inclined with respect to the axis O-O and forms a truncated cone in each rolling. Thus, for the bearing 26 closest to the brake 30, the axis intersects the main axis O-O, such that the bearing is situated between the brake 30 and this intersection point. Conversely, for the bearing 28 closest to the distributor 40, the axis of the rolling elements intersects the main axis, such that the bearing 28 is situated between the distributor 40 and this intersection point.

[0080] Each bearing comprises an inner ring 31, 32 and an outer ring 33, 34. The inner ring 31 of the left rolling body abuts axially against a retaining ring 45 fixed to the extension 11 of the housing in the direction opposite to the distributor 40, while the outer ring 33 of this left rolling body abuts axially against the shoulder of the sleeve 24 in the direction of the distributor 40. The inner ring 32 of the right bearing abuts axially against the radial extension 9 of the housing in the direction of the distributor, while the outer ring 34 of this right bearing abuts axially against the shoulder of the sleeve 24 in the opposite direction. In the configuration shown, although other configurations could be envisaged, the two bearings face each other along the axial direction.

[0081] As Figures 3 to 5 is shown, in this embodiment, the machine 102 comprises a third guide bearing 37.

[0082] The third bearing 37 comprises a truncated cone bushing. It is a solid part, which does not comprise parts mounted movably with respect to each other, unlike the rolling bodies. In particular, it has two truncated cone main faces, namely an outer truncated cone main face 21 and an inner truncated cone main face 23, which are both delimited by two common axial end circular edges, which form the small and large diameters of the cone, respectively.

[0083] This bearing 37 abuts directly against the housing 10 and the cylinder block 42 in each case in the direction of the axis O-O and in a direction which is radial with respect to the axis. In this case, it abuts against the truncated cone surface of the housing at the junction between its axial extension 11 and its radial extension 9, by its outer surface 21. Similarly, it abuts against the truncated cone surface of the cylinder block 42, by its inner surface 23.

[0084] The first bearing 26, the second bearing 28 and the third bearing 37 are the only bearings for guiding the rotation of the shaft relative to the housing in the machine. In this embodiment, these three bearings are located on the same side of the cylinder block 42 along the axial direction, i.e. on one side of the brake and on the opposite side of the distributor 40. The two bearings 26, 28 are located on the same side of the bearing 37.

[0085] The bushing 37 has a slot 39 which here extends in a plane radial relative to the axis from a first end edge to a second end edge of the bushing. It also comprises one or several elements 41 for rotationally locking the bushing relative to a part of the machine, here formed by the housing. In the present example, the one or several elements are two rectangular tabs 41 extending along the axial direction, which project from the edge of the bushing at the smallest diameter. Naturally, the number, shape, position and orientation of the rotation blocking elements can be varied.

[0086] Thanks to this arrangement by means of a frustoconical surface, the cylinder block 42, the housing 10 and the bearing 37 are shaped so as to center the cylinder block independently of the shaft in a form-fit manner relative to the housing.

[0087] The housing 10, more particularly at least the surface of which forms the conical seat which abuts against the bushing, is made of, for example, cast iron or molten steel or cast steel. The cylinder block 42 is made of, for example, machined steel, possibly after forging. The bushing 37 is, for example, statically mounted on the housing body 10, that is to say fixed relative to the housing. Conversely, it is slidably mounted in a manner relative to the cylinder block 42. Indeed, in this example, the cylinder block 42 made of machined steel is smoother and harder than the rough casting forming the extension 11 of the housing.

[0088] Furthermore, it can be provided that the smooth conical bushing 37 meets the following characteristics in terms of composition.

[0089] Firstly, the surface 23 of the bushing 37 is adapted to have a surface state with a low coefficient of friction, said surface of the bushing bearing against a counter-surface, i.e. in this case the seat of the cylinder block 42, in a relative rotational displacement. This state can be obtained by surface treatment of the surface 23 of the bushing. It can also be obtained by the choice of the material constituting this surface. To this end, it can be formed of a synthetic material with a low coefficient of friction or a material known as "sliding", for example based on polyvinylidene fluoride (PVDF) or polyether ether ketone (PEEK). This surface can also be loaded with sliding particles, such as bronze particles, or sheets of fluorinated synthetic material, for example polytetrafluoroethylene.

[0090] Second, the bushing 37 can be composed of a core, for example of steel, on which a layer of material having a low coefficient of friction, as described above, is deposited, in which an intermediate layer is inserted, where appropriate, which is adapted to ensure the adhesion of the surface layer having a low coefficient of friction. Such an intermediate layer can be formed on the basis of bronze, for example bronze spheres, or on the basis of a porous sintered material, for example an agglomerated material fixed to the core, for example by melting. The surface layer having a low coefficient of friction can be printed or impregnated on the intermediate layer, which is preferably porous. The bushing is then formed by a three-layer structure.

[0091] As a variant, the bushing 37 can be formed by depositing a material having a low coefficient of friction, or "sliding material", for example made of bronze or a synthetic material, directly on a core, for example made of metal, in particular steel. In this case, the aforementioned intermediate layer is omitted. The bushing 37 is then formed by a two-layer structure.

[0092] As another variant, it can be a solid material having a low coefficient of friction, for example solid bronze, which is single-layered.

[0093] Phosphor bronze is in particular able to slide on steel.

[0094] Preferably, the bushing 37 is formed, for example by metal sides, by conical rolling.

[0095] Once formed, the angular opening of the bushing is preferably comprised between 30° and 60°, for example approximately 45°. By "angular opening of the bushing" is meant the angle formed between the axis O-O of the machine and the frustoconical surface of the bushing.

[0096] Thanks to this arrangement, it is observed that the axial offset of the cylinder block on the shaft is significantly reduced. Moreover, the frustoconical surface abutting on the bushing allows to optimize the contact pressure on the bushing. The bushing thus oriented tends to abut normal to the trajectory of the cylinder block when subjected to parasitic forces, thus allowing to optimize the contact pressure on the bushing. Figure 6 A summary of the calculation of these contact pressures is shown when a pressure of 450 bar, i.e. 450.10 5 Pa, is applied to the machine operating as a motor. It is observed that, on more than half of the bushings, the pressure is almost zero (by defining half on either side of the radial plane), while in the other half, the pressure exceeds 50 bar (50.10 5 Pa) only on a short circumferential section of the bushing, here at the bottom of the graph. In addition, the edge effect is not very strong. Thus, the bushing is suitably subjected to the distributed forces and to the parasitic forces transmitted directly by the cylinder block, despite the sliding mounting of the cylinder block on the shaft. The two bearings 26, 28 therefore do not receive the parasitic forces of the shaft.

[0097] Such a machine can be equipped with mechanics, thus forming a vehicle or a construction machine.

[0098] As a variant, it can be provided that the bushing has at least one recess that passes through the thickness of the bushing and that intersects at most one of the end edges of the bushing. Such a recess facilitates good distribution of the lubricating fluid over the two faces 21, 23 of the bushing during operation of the machine.

[0099] Second embodiment

[0100] A second embodiment of the application based on Figures 7 to 11 will now be presented. Only the features that distinguish this embodiment from the previous one will be described, the other features remaining unchanged.

[0101] In this machine 202, the conical bushing is replaced by two bearings 43, 44.

[0102] The third bearing 43 is flat and directly axially abuts against the radially extending portion 9 of the housing and of the cylinder block 42. It is formed by a roller bearing or a needle bearing, in which the rollers or needles extend along a same plane perpendicular to the axis. In this example, the bearing 43 is received on a shoulder formed in the surface of the cylinder block 42 that is directed toward the brake and that faces the housing, the shoulder passing through the central recess of the bearing. It also axially abuts against the surface of the housing that is directed toward the cylinder block.

[0103] The fourth bearing 44 abuts against the housing 10 and the cylinder block 42 along a radial direction. It is formed by a cylindrical bushing that does not have an internal movable part. This bushing abuts against the cylindrical surface of the cylinder block by its inner surface and against the cylindrical surface of the radially extending portion 9 of the housing by its outer surface.

[0104] The third bearing 43 thus forms an axial stop and takes up the axial forces transmitted by the cylinder block. This avoids interfering with the bearings 26, 28. The choice of a roller bearing or a needle bearing does not affect the length of the motor.

[0105] The fourth bearing 44 forms a recentering stop and takes up the radial forces. It prevents the cylinder block from transmitting bending forces to the shaft, in particular in the case of a relatively long shaft.

[0106] The axial and radial abutment functions that were collectively provided by the bushing in the previous embodiment are thus ensured this time by separate members 43, 44, respectively.

[0107] This time, the four bearings 26, 28, 43 and 44 are all located on the same side of the cylinder block 42 as the brake. The two bearings 26, 28 are located on the same side as the bearings 43, 44. In this example, these two bearings terminate in the same radial plane.

[0108] Of course, many modifications can be made to the application without departing from the scope thereof.

Claims

1. A rotary hydraulic press, comprising: - Outer shell (10) - Shaft (20), which is rotatably mounted relative to the housing. - A sleeve (24), which is rigidly fixed to the shaft and extends around at least a portion of the housing. - Cam (12), which is rigidly fixed to one of the housing and the shaft, - Cylinder body (42), which is rotatably fixed to the housing and the other of the shaft. The cylinder block includes a piston (36) capable of engaging with the cam to generate relative rotation between the shaft and the housing. - First and second guide bearings (26, 28), which respectively directly abut against the housing and the sleeve, and - At least one third guide bearing, which directly abuts against the housing and the cylinder block.

2. The rotary hydraulic press according to claim 1, wherein, The first guide bearing (26), the second guide bearing (28), and the third guide bearing are the only bearings capable of guiding the shaft to rotate relative to the housing in the machine.

3. The rotary hydraulic press according to claim 1, further comprising a fourth bearing directly adjacent to and abutting the housing and the cylinder body.

4. The rotary hydraulic press according to any one of claims 1 to 3, wherein, The third guide bearing abuts against the housing and the cylinder block along the axis of the shaft.

5. The rotary hydraulic press according to claim 3, wherein, At least one of the third guide bearing and the fourth bearing abuts against the housing and the cylinder block along the axis of the shaft.

6. The rotary hydraulic press according to any one of claims 1 to 3, wherein, The third guide bearing abuts against the housing and the cylinder block in a radial direction relative to the axis of the shaft.

7. The rotary hydraulic press according to claim 3, wherein, At least one of the third guide bearing and the fourth bearing abuts against the housing and the cylinder block in a radial direction relative to the axis of the shaft.

8. The rotary hydraulic press according to any one of claims 1 to 3, wherein, The third guide bearing abuts against the housing and the cylinder block along the axis of the shaft and in a radial direction relative to the axis.

9. The rotary hydraulic press according to claim 3, wherein, At least one of the third guide bearing and the fourth bearing abuts against the housing and the cylinder block along the axis of the shaft and in a radial direction relative to the axis.

10. The rotary hydraulic press according to claim 3, wherein, The third guide bearing abuts against the housing and the cylinder body along the direction of the axis of the shaft, and the fourth bearing abuts against the housing and the cylinder body in a radial direction relative to the axis.

11. The rotary hydraulic press according to any one of claims 1 to 3, wherein, The third guide bearing includes rolling elements.

12. The rotary hydraulic press according to claim 3, wherein, At least one of the third guide bearing and the fourth bearing includes rolling elements.

13. The rotary hydraulic press according to claim 12, wherein, The rolling element is a roller bearing.

14. The rotary hydraulic press according to claim 13, wherein, The rollers of the roller bearing extend along a plane perpendicular to the axis of the shaft.

15. The rotary hydraulic press according to claim 12, wherein, The rolling element is a needle roller bearing.

16. The rotary hydraulic press according to claim 15, wherein, The needle rollers of the needle roller bearing extend along a plane perpendicular to the axis of the shaft.

17. The rotary hydraulic press according to any one of claims 1 to 3, wherein, The third guide bearing includes a bushing.

18. The rotary hydraulic press according to claim 3, wherein, At least one of the third guide bearing and the fourth bearing includes a bushing.

19. The rotary hydraulic press according to claim 18, wherein, The bushing is cylindrical.

20. The rotary hydraulic press according to claim 18, wherein, The bushing is truncated conical.

21. The rotary hydraulic press according to claim 18, wherein, The bushing has a slot extending from the first axial end edge of the bushing to the second axial end edge of the bushing.

22. The rotary hydraulic press according to claim 18, wherein, The bushing includes at least one element (41) for preventing the bushing from rotating relative to a portion of the rotary hydraulic press.

23. The rotary hydraulic press according to claim 3, wherein, The third guide bearing includes a roller bearing, wherein the rollers of the roller bearing extend along a plane perpendicular to the axis of the shaft, and the fourth bearing includes a cylindrical bushing.

24. The rotary hydraulic press according to claim 3, wherein, The third guide bearing includes a needle roller bearing, wherein the needle rollers of the needle roller bearing extend along a plane perpendicular to the axis of the shaft, and the fourth bearing includes a cylindrical bushing.

25. The rotary hydraulic press according to any one of claims 1 to 3, wherein, The cylinder body (42) is slidably mounted on the spline (29) of the shaft.

26. The rotary hydraulic press according to any one of claims 1 to 3, wherein, The cylinder block (42), the housing (10), and the at least one bearing are shaped such that the cylinder block is centered relative to the housing in a form-fitting manner, independent of the shaft.

27. A machine for forming a vehicle or construction machinery, the machine being equipped with at least one rotary hydraulic press according to any one of claims 1 to 3.

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