Hydraulic machine comprising a cylinder block having housings

Abstract

The hydraulic machine comprises: - a cylinder block (12) having housings (14), and - pistons (16) in the housings, each housing comprising a head zone (66) and a foot zone (68), the foot zone being delimited by a main face (70) and having a cavity (72): - entering the main face (70), - extending in a direction going from a bottom (48) of the housing to the head zone, and - not ensuring rotational locking of the piston. Abstract figure: Fig. 6

Description

Title of the invention: Hydraulic machine comprising a cylinder block having housings FIELD OF THE INVENTION

[0001] The invention relates to hydraulic machines, in particular their cylinder block. STATE OF THE ART

[0002] A rotating hydraulic machine generally comprises a cylinder block having housings in which movable sliding pistons are received. The latter set a fluid in motion or are set in motion by it depending on whether the machine operates as a pump or as a motor.

[0003] It is known to give the pistons a stepped shape for reasons of compactness (compared to profiled pistons with a single section). Indeed, thanks to the stepped pistons, the same effective displacement is obtained while bringing the axes of the pistons closer to each other and bringing the housings closer to the axis of rotation of the cylinder block. However, knowing that fluid supply / discharge conduits supply the housings from below in a direction radial to the axis of rotation, there is still a loss in radial compactness.

[0004] It was therefore envisaged to supply the housings not from below the housing but from the side, the conduit no longer extending along a radial axis but along an axis parallel to the axis of rotation. But then the conduit is largely obstructed by the piston when it occupies its position closest to the bottom of the housing (this position is commonly called by those skilled in the art "bottom dead center").

[0005] Housings supplied laterally at the level of the piston foot have also been imagined while providing recesses along the axis of the piston in the non-functional zone of the piston foot. Thanks to this arrangement, the fluid can arrive in the lower part of the housing to supply the entire chamber. But the fluid arriving at the bottom of the housing is still disturbed and undergoes pressure losses when filling the housing in motor mode. The same problem arises in pump mode when the fluid is evacuated from the housing by the piston.

[0006] An aim of the invention is to facilitate the filling of the housing with the fluid coming from the supply conduit, and its exit, without harming the compactness of the assembly. Description of the invention

[0007] For this purpose, a hydraulic machine is provided comprising:

[0008] - a cylinder block having housings, and

[0009] - pistons in the housings,

[0010] each housing comprising a head area and a foot area,

[0011] the foot zone being delimited by a main face and having a cavity:

[0012] - entering the main face,

[0013] - extending in a direction from a bottom of the housing to the head area, and

[0014] - not ensuring rotational locking of the piston.

[0015] Thus, the cavity makes it possible to enlarge the fluid passage section in areas where it should have had a very reduced passage section. It reduces the disturbance of the fluid flow there. The cavity thus facilitates the filling of the housing with the fluid, as well as its evacuation. The arrival of the fluid in the housing takes place without prior crushing and makes it possible to initiate the upward movement of the piston. The invention makes it possible to reduce pressure losses. Reducing pressure losses therefore makes it possible to reduce the temperature of the fluid (for the same effort and at equivalent speed). This reduction in temperature makes it possible to limit the rotation speed of the machine less. The invention also makes it possible to reduce fluid shear, which prevents premature aging.

[0016] It can be provided that the cavity opens into the head zone.

[0017] It may be provided that the cavity extends entirely at a distance from an axis of the housing less than a greater distance separating the head zone and the axis.

[0018] The cavity does not necessarily extend in the extension of a face of the head zone of the housing.

[0019] It can be provided that the cavity extends entirely at a distance from a median plane of the housing perpendicular to an axis of rotation of the machine.

[0020] Thus, the cavity extends outside the functional zone which includes zones of the piston and the housing which are in mutual support in the circumferential direction to the axis of rotation of the machine. The position of the cavity therefore preserves this zone.

[0021] It can be provided that the cavity is cylindrical.

[0022] The cylinder may have a circular, polygonal, oblong or elliptical section for example.

[0023] It can be provided that the cavity has an axis parallel to an axis of the housing.

[0024] It can be provided that the cavity has an axis perpendicular to an axis of the housing.

[0025] It can be provided that the cavity has an axis inclined relative to an axis of the accommodation.

[0026] It may be provided that a supply conduit opens into the cavity.

[0027] This arrangement further facilitates the entry of the fluid into the housing as well as its exit. In addition, it reduces the length of the supply conduit. Its machining time is therefore also shortened where appropriate, in compensation for the additional time required for machining the cavity.

[0028] It may be provided that a supply conduit of the housing extends at the height of the foot zone with reference to an axis of the housing.

[0029] This is therefore an arrangement in which the conduit does not open into a volume located under the foot zone but directly at the height of the latter.

[0030] It may be provided that the piston comprises a foot having a main face and a secondary face entering the main face of the foot of the piston, the cavity having a dimension in a direction perpendicular to an axis of the housing less than a dimension of the secondary face in the direction perpendicular to the axis.

[0031] It may be provided that the piston comprises a foot having a piston foot cavity opening onto two opposite sides of the foot at two respective ends of the piston foot cavity opposite one another along a main axis of the piston foot cavity.

[0032] Thus, the piston foot cavity allows fluid to pass from one side of the piston foot to the other through or under the latter. This further reduces the disturbance of the flow of fluid supplying the housing when leaving the supply duct. This reduces pressure losses.

[0033] It may be provided that the housing further has a groove configured to block the piston from rotating.

[0034] It can be provided that, the piston carrying a pin for locking the piston in rotation, the cavity has insufficient dimensions to accommodate the pin.

[0035] This provides a means of error correction when mounting the piston in the housing.

[0036] It can be provided that the housing does not have a plane of symmetry.

[0037] According to the invention, a cylinder block for a hydraulic machine is also provided,

[0038] the cylinder block having housings comprising a head zone and a foot zone,

[0039] the foot zone being delimited by a main face and having:

[0040] - a cavity entering the main face and extending in a direction going from a bottom of the housing to the head area, and

[0041] - a groove entering the main face and extending entirely away from the cavity and following a direction of an axis of the housing.

[0042] The invention further provides a method of manufacturing a cylinder block according to the invention in which:

[0043] - the cavity is made by removing material;

[0044] - the cavity and the groove are made by removing material using the same tool; and / or

[0045] - the cylinder block with the cavity is produced by casting.

[0046] In particular, when the cylinder block is produced by casting, it can be provided that the recesses are obtained by cores (possibly sand) before casting.

[0047] In another embodiment, the cylinder block with the cavity is produced by additive manufacturing. DESCRIPTION OF FIGURES

[0048] We will now present an embodiment of the invention by way of non-limiting example with the support of the drawings in which:

[0049] - [Fig.l] is an axial sectional view of a machine according to a first mode of realization lization of the invention;

[0050] [Fig.2]

[0051] [Fig.3]

[0052] [Fig.4]

[0053] [Fig.5]

[0054] - Figures 2 to 5 are views of one of the housings of the machine of [Fig.l];

[0055] [Fig.6]

[0056] [Fig.7]

[0057] - Figures 6 and 7 are similar views showing two positions of the piston in its cylinder block housing;

[0058] - [Fig.8] is a view similar to the previous one showing the passage of the fluid in the accommodation ;

[0059] - [Fig.9] is a perspective view of the cylinder block;

[0060] [Fig. 10]

[0061] [Fig. 11]

[0062] - Figures 10 and 11 are diagrams of the functional areas of the cylinder block and of the piston;

[0063] - [Fig.12] is a sectional view of a housing of a machine of a second embodiment;

[0064] [Fig. 13]

[0065] [Fig. 14]

[0066] [Fig. 15]

[0067] [Fig. 16]

[0068] - Figures 13 to 16 are similar views illustrating a third mode of rea lization;

[0069] - [Fig. 17] is a perspective view of a piston of a machine according to a fourth embodiment;

[0070] [Fig. 18]

[0071] [Fig. 19]

[0072] - Figures 18 and 19 are views showing two positions of this piston in its accommodation ;

[0073] - [Fig.20] is a cross-sectional view of the piston and housing, and

[0074] - [Fig.21] shows the passage of the fluid in the housing. First embodiment

[0075] Figures 1 to 11 illustrate a rotating hydraulic machine 2 according to a first embodiment of the invention.

[0076] The machine 2 comprises a fixed part and a rotating part mounted to rotate relative to the fixed part about an axis of rotation XX. It thus comprises a casing 4 and a central shaft 6, mounted to rotate relative to the casing by means of bearings 8. A cam 10 is rigidly fixed to the casing. A cylinder block 12 is rigidly fixed to the shaft 6. It has housings 14 extending in directions radial to the axis XX and receiving respective pistons 16 mounted to slide in the housings each in a direction radial to the axis XX. Each piston carries a roller 18 capable of rolling on a track of the cam 10 which has for this purpose lobes known per se and not illustrated.

[0077] The machine comprises a distributor 20 connected to a high-pressure fluid circuit and to a low-pressure fluid circuit. For each housing 14, the cylinder block 12 comprises a fluid supply and discharge conduit 22 opening into the housing. The machine is arranged so that the distributor 20 places the supply conduit 22 sometimes in communication with the high-pressure circuit, sometimes with the low-pressure circuit depending on the angular position of the cylinder block 12 (and therefore of the shaft 6) relative to the casing 4.

[0078] When the housings 14 are supplied in turn with high-pressure fluid, this pressure is communicated to the pistons 16 concerned which slide in their housing and, by rolling of the roller 18 against the multi-lobed cam 10, cause the rotating part to rotate. The machine then operates as a motor to rotate a load fixed to the shaft or to the casing. When, on the contrary, the rotating part is rotated relative to the fixed part, the cam 10 causes the pistons 16 to slide in turn, which causes the fluid from their housings 14 to be forced back into the high-pressure circuit. The machine then operates as a pump.

[0079] The invention is applicable to machines having configurations other than this one.

[0080] As illustrated in particular in Figures 6 to 8, each piston 16 comprises a head 26 and a foot or tail 28. It has a main axis PP extending from the head to the foot and which is here oriented in the radial direction to the axis XX. The piston 16 in this case has a general shape with symmetry of revolution around this axis, but this is not obligatory.

[0081] In this example, the foot 28 and the head 26 each have a generally cylindrical shape with a circular section in a plane perpendicular to the axis PP.

[0082] As illustrated in particular in [Fig.6], the foot 28 has a larger dimension Dp in a direction perpendicular to the axis PP. Similarly, the head 26 has a larger dimension Dt in this direction. In this case, these are diameters. The largest diameter Dp of the foot 28 is therefore smaller than the largest diameter Dt of the head 26. The head occupies a larger volume than the foot.

[0083] It is therefore a stepped piston 16, itself housed coaxially in the stepped housing 14 of complementary shape as illustrated in Figures 6 to 8. Such shapes provide advantages in terms of compactness compared to pistons having a general cylinder shape. Indeed, thanks to the stepped pistons, it is possible to have the same effective displacement while bringing the axes PP of the pistons closer to each other. The angle separating the axes PP of two contiguous pistons is thus reduced compared to that which would be obtained with non-stepped pistons, namely in which the piston has over its entire length the diameter of the head 26. This shape also brings the housings 14 and the axis of rotation XX of the cylinder block 12 closer together.

[0084] The head 26 carries the roller 18 coming into contact with the cam 10. For this purpose, it has, for example, a cradle 30 for receiving the roller 18. The cradle 30 has a cylindrical shape having an axis BB parallel to the axis of rotation XX of the machine and a circular section in a plane perpendicular to the axis BB. The cradle is open in the opposite direction to the foot.

[0085] Each housing 14 comprises a head zone 66 and a foot zone 68 respectively accommodating the head 26 and the foot 28 of the piston, having shapes complementary to these parts of the piston. Thus, the foot zone has a diameter in the direction perpendicular to the axis PP of the housing smaller than the diameter of the head zone 66 in the same direction.

[0086] The foot zone 68 is delimited by a main face 70, in this case cylindrical with a circular section in a plane perpendicular to the axis PP. It has a secondary cavity 72:

[0087] - entering the main face 70,

[0088] - extending in a direction from a bottom 48 of the housing to the head zone 66, and

[0089] - not ensuring rotational locking of the piston 16.

[0090] The secondary cavity 72 is cylindrical, it has an axis parallel to the axis PP of the housing and its section in a plane perpendicular to this axis is circular in this example. But this section could be rectangular, triangular or have another shape.

[0091] In this case, the secondary cavity 72 opens into the head zone 66 by one of its axial ends. It extends entirely at a distance from the axis PP of the housing 14 less than a greater distance separating the head zone 66 and the axis PP. Thus it is not in the extension of a face of the head zone.

[0092] The cavity 72 extends entirely at a distance from a median plane of the housing perpendicular to the axis of rotation XX. It is here intercepted by a plane radial to this axis. The secondary cavity 72 is therefore arranged so as not to impact the functional surfaces of the foot zone 68. It is known in fact that the piston 16 in its stroke in the housing 14 is subjected to circumferential forces 50, with reference to the axis of rotation XX, due to the rolling of the roller 18 on the cam 10, as illustrated in [Fig.9]. On the other hand, it does not undergo an axial force 52, namely in a direction parallel to the axis XX. As a result, the housing-piston assembly has a functional zone 54 which is subjected to significant circumferential forces and for which the contact surface and the quantity of material in contact between the cylinder block 12 and the piston 16 must be preserved.This is an area extending in the circumferential direction on the housing and the piston as illustrated in Figures 10 and 11. This functional area 54 shown in the drawing for the top of the housing 14 is also true for the piston foot 28. For this reason, the foot 28 allows in its areas oriented in the circumferential direction a longer guidance of the piston along the PP axis to counter the circumferential forces.

[0093] With reference to the figures, in the cylinder block 12, the supply ducts 22 have an end 46 forming a mouth opening into the respective housings 14. In this case, each duct 22 has a rectilinear shape and extends in a direction parallel to the axis of rotation XX. The supply duct 22 opens into the secondary cavity 72 and extends at the height of the foot zone with reference to the axis PP of the housing.

[0094] Figures 6 and 7 illustrate respectively the low and high positions of the piston 16 in the housing 14. As seen in [Fig.6], in the low position, which is the position of the piston closest to the bottom 48 of the housing, the foot 28 of the piston extends away from the mouth 46 of the supply duct 22, which it leaves clear, in particular due to the presence of the secondary cavity 72. The latter allows the fluid arriving in the foot zone 68 in motor mode to fill the housing and reach the head 26 of the piston with reduced disturbances and therefore little pressure loss. This is the case even if the foot of the piston occupies the entire foot zone 68 as illustrated in the variant of [Fig.8] which shows the fluid flow. The fluid passage section is larger near the supply duct 22. This reduces pressure losses during filling and discharge.Indeed, the same advantage exists in pump mode when the piston propels the fluid out of the housing into the conduit 22, which then serves for discharge.

[0095] The cylinder block 12 can be manufactured by giving it its general shape using conventional methods, in particular by forging or casting then machining. In one mode of implementing the manufacturing process, each secondary cavity 72 is produced by removing material, by machining using a tool such as a milling cutter.

[0096] During the manufacture of the piston, for example by machining, a centering point 76 can be made to allow cylindrical grinding of the piston if necessary. This point, visible in Figures 4, 6 and 7, has the shape of a blind cavity penetrating into the foot 28 from the face 36 and following the axis PP of the piston. It offers a grip for housing a tip making it possible to immobilize the piston between this tip and another grip (for example another tip housed in the cradle or on the head 26 before production of the cradle). Second embodiment

[0097] We will describe other embodiments in the following. The characteristics in common with the first embodiment are not described again.

[0098] In the machine constituting the second embodiment of [Fig. 12], each secondary cavity 72 does not have a cylindrical shape, which makes it more difficult to produce by machining. It even has a greater depth as one approaches the bottom 48 of the housing 14. This thus makes it possible to reduce the length of the drilling of the conduit 22.

[0099] This time, the cylinder block 12 is given its general shape by casting and the secondary cavity 72 of each housing is produced by casting on this occasion, therefore during the same step. Third embodiment

[0100] In the third embodiment illustrated in Figures 13 to 17, the housing 14 further has a groove 62 configured to lock the piston 16 in rotation relative to the housing 14 around the axis PP. The groove 62 enters the main face 70 of the foot zone 68 and extends rectilinearly in a direction going from the bottom 48 of the housing to the head zone 66. It reaches the head zone but not the bottom. The groove 62 has in this case a generally cylindrical shape, the axis of the cylinder being parallel to the axis PP.

[0101] In addition, the piston 16 carries a pin 60 for locking the piston from rotating. When the piston 16 is received in its housing 14, the pin is received in the groove 62, the two cooperating to lock the piston from rotating as it slides in the housing.

[0102] Unlike the groove 62, the secondary cavity 72 has dimensions, in particular a depth in a plane perpendicular to the axis PP, insufficient to accommodate the pin 60, which provides a foolproofing when receiving the piston in its housing. Indeed, the operator cannot place the piston in its housing while attempting to insert the pin into the secondary cavity.

[0103] As illustrated in [Fig.14], just like the secondary cavity 72, the groove 62 extends outside the functional zone 54. The groove 62 and the cavity 72 are located on either side of the median plane of the cylinder block 12 but are not diametrically opposed on either side of the axis PP. Thus, the foot zone 68 does not have a plane of symmetry. Their position around the axis here forms an angle α of approximately 150°.

[0104] For the manufacture of the cylinder block 12, in this case, the secondary cavity 72 and the groove 62 are produced in the foot zone by removing material using the same tool, for example the same milling cutter. Fourth embodiment

[0105] In the fourth embodiment of the machine illustrated in Figures 17 to 21, the machine is identical to that of the first embodiment except for the characteristics which follow.

[0106] The foot 28 of the piston has a cavity 32 having a main axis CC. The cavity opens onto two opposite sides of the foot of the piston at two respective ends 34 of the cavity opposite each other along the axis CC. In this case, the main axis CC of the cavity 32 is parallel to the axis XX of rotation of the machine. In this case, the cavity is open in the opposite direction to the head 26. It extends to a free end of the foot 28 which is opposite the head and is delimited by a cylindrical face 36 oriented in the opposite direction to the head 26. The face 36 has generatrices parallel to the axis CC and perpendicular to the axis PP of the piston 16. It has a circular section in this case.

[0107] In this case, the foot 28 has a lateral face 40 divided into two cylindrical portions of different diameters along the axis PP since the portion of the foot closest to the head 26 has a reduction in diameter. This face 40 is cut into by two lateral faces 42 located on either side of the axis PP. These lateral faces 42 form lateral cavities in this example. Each of them here has a cylindrical shape with generatrices parallel to the axis PP (shape not visible in [Fig.20]). They each extend from the free end of the foot 28 to the head 26.

[0108] In this case, the free end of the foot 28 has a flat face 44 perpendicular to the axis PP and divided into two portions on either side of the cavity 32. The piston 16 here has two planes of symmetry passing through its axis PP and perpendicular to each other (apart from the pin when it is present).

[0109] The machine 2 is configured so that, in the position of the piston 16 closest to the bottom 48 of the housing 14, the piston leaves free at least 50% of a section of the mouth 46 of the conduit 22. As can be seen in FIGS. 18 and 21, in this low position of the piston 16, the foot 28 provides a passage from one side to the other of the foot having over the entire length of the passage a section greater than or equal to 50% of the section of the supply conduit 22 opening into the housing 14. In this case, this section of the passage is greater than or equal to the section of the conduit 22. As the cavity 32 has a cylindrical shape, the fluid does not undergo a reduction in passage section when passing from one side to another of the foot 28 in this position of the piston 16. The cross section crossed by the part of the fluid intended to fill the bottom of the housing 14 does not see in its stroke a reduction in section which could cause pressure losses. On the contrary, the corresponding passage section is never less than the relevant passage section of the conduit 22. The flow is therefore improved and flows at this location along an axis parallel to the axis of rotation XX.

[0110] The cavity 32 is arranged so as not to impact the functional surfaces of the piston foot 28. As already indicated, the housing-piston assembly has a functional zone 54 which undergoes significant circumferential forces. The other zones of the foot 28, oriented in the direction parallel to the axis XX and undergoing less forces, can withstand a release of material. The main cavity 32 and the lateral cavities formed by the secondary faces 42 are located outside this functional zone 54 and therefore do not compromise performance in this regard.

[0111] The cavity 32 also allows the piston foot 28 to deform more easily. Indeed, in addition to the pressure losses, the releases of material in the non-functional areas of the piston foot give it flexibility. This reduces the concentration of stresses on the lower part of the foot 28. We thus distinguish a zone of favorable deformation in the middle part of the face 36 closest to the head 26 of the piston, and a zone of concentration of stresses at the ends of this face.

[0112] The cavity 32 is produced for example by milling.

[0113] As illustrated in [Fig.20], each lateral cavity formed by the lateral face 42 of the piston has a dimension lp, in a direction perpendicular to the axis PP of the housing, greater than the dimension lc, in the same direction, of the secondary cavity 72 of the housing located opposite. This arrangement makes it possible to avoid, during the machining of the secondary cavity 72, generating a burr in a functional sliding zone of the piston foot 28. This also allows simpler milling, if necessary.

[0114] Of course, numerous modifications can be made to the invention without departing from its scope.

[0115] The cylinder block 12 with the secondary cavity 72 can be produced by casting, forging or additive manufacturing. This cavity can also be produced by removing material, by drilling, milling, drawing or contouring.

Claims

Claims

1. Hydraulic machine (2) comprising: - a cylinder block (12) having housings (14), and - pistons (16) in the housings, each housing comprising a head zone (66) and a foot zone (68), the foot zone being delimited by a main face (70) and having a cavity (72): - entering the main face (70), - extending in a direction going from a bottom (48) of the housing to the head zone, and - not ensuring rotational locking of the piston, the housing (14) further having a groove (62) configured to lock the piston in rotation.

2. Machine according to the preceding claim in which the cavity (72) opens into the head zone (66).

3. Machine according to at least one of the preceding claims in which the cavity (72) extends entirely at a distance from an axis (PP) of the housing (14) less than a greater distance separating the head zone (66) and the axis.

4. Machine according to at least one of the preceding claims in which the cavity (72) extends entirely at a distance from a median plane of the housing (14) perpendicular to an axis (XX) of rotation of the machine.

5. Machine according to at least one of the preceding claims in which the cavity (72) is cylindrical.

6. Machine according to at least one of the preceding claims in which the cavity (72) has an axis parallel to an axis of the housing (14).

7. Machine according to at least one of the preceding claims in which a supply conduit (22) opens into the cavity (72).

8. Machine according to at least one of the preceding claims in which a supply duct (22) of the housing extends at the height of the foot zone (68) with reference to an axis (PP) of the housing (14).

9. Machine according to at least one of the preceding claims in which the piston comprises a foot (28) having a main face (40) and a secondary face (42) entering the main face of the foot of the piston, the cavity (72) having a dimension (lc), in a direction perpendicular to an axis (PP) of the housing (14), less than a dimension (lp) of the secondary face in the direction perpendicular to the axis.

10. Machine according to at least one of the preceding claims in which the piston comprises a foot (28) having a piston foot cavity (32) opening onto two opposite sides of the foot at two respective ends (46) of the piston foot cavity opposite each other along a main axis (CC) of the piston foot cavity.

11. Machine according to at least one of the preceding claims in which, the piston carrying a pin (60) for locking the piston in rotation, the cavity (72) has dimensions insufficient to accommodate the pin.

12. Machine according to at least one of the preceding claims in which the housing (14) does not have a plane of symmetry.

13. Cylinder block (12) for a hydraulic machine, the cylinder block (12) having housings (14) comprising a head zone (66) and a foot zone (68), the foot zone being delimited by a main face (70) and having: - a cavity (72) entering the main face and extending in a direction from a bottom of the housing (14) to the head zone, and - a groove (62) entering the main face and extending entirely at a distance from the cavity (72) and in a direction of an axis (PP) of the housing (14).

14. Method of manufacturing a cylinder block (12) according to the preceding claim in which the cavity (72) is produced by removing material.

15. A method of manufacturing a cylinder block (12) according to claim 13, in which the cavity (72) and the groove (62) are produced by removing material using the same tool.

16. A method of manufacturing a cylinder block (12) according to claim 13, wherein the cylinder block with the cavity (72) is produced by casting.

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