FR3010744A1 - IMPROVED CYLINDER BLOCK FOR HYDRAULIC MACHINE HAVING OPTIMIZED RADIAL SIZE - Google Patents

Abstract

Cylinder block (1) and hydraulic machine equipped with such a cylinder block, in which the pistons (2) comprise a support element (21) is held by two shims (22, 23), one (23) of these wedges being configured so as to have a secondary section (25) extending axially to cooperate with a secondary housing (13) offset axially relative to the primary housing (11) in which is disposed the piston (2), and cooperating with a spring (4) disposed in the secondary housing (13), the shim (23) and the spring (4) thus making an angular indexing of the piston (2) and tending to take it out of its primary housing (11) for the keep in contact with a cam (3).

Description

GENERAL TECHNICAL FIELD The present invention relates to the field of hydraulic machines with radial pistons, and more specifically the means for guiding in translation the pistons of such hydraulic machines. STATE OF THE ART Hydraulic machines are known comprising a cylinder block having a plurality of housings in which pistons slide, including means for guiding pistons in their housings. Document FR 2727471 in the name of the applicant presents for example a hydraulic machine structure in which the pistons are guided in translation by a U-shaped guide piece, inserted firstly in a recess of the cylinder block, and secondly in a radial groove arranged on a wedge, commonly called lunambule, ensuring the maintenance of the piston roller.

Hydraulic machines are known in which each of the housings comprises a thrust spring arranged so as to exert a thrust force on the associated piston tending to remove it from its housing. The addition of such springs makes it possible to limit the risk of cavitation, and reduce the boost pressure required for the proper functioning of the hydraulic machine. However, the addition of thrust springs in the housing is constraining in terms of space. The present invention aims to provide a hydraulic machine structure thus achieving these guide function in translation and application of a thrust force on the springs, while improving the size resulting from these functions.

PRESENTATION OF THE INVENTION To this end, the present invention provides a hydraulic machine with radial pistons and multilobe cam, comprising a cylinder block having a plurality of primary housings in which are arranged pistons adapted to slide in their respective primary housings during the relative rotation of the cylinder block and the cam relative to each other; the pistons each comprising a support element adapted to be in contact with the cam and shims performing the axial retention of the bearing element in the primary housing, the hydraulic machine being characterized in that the cylinder block comprises a plurality radial secondary housings, each of said secondary housings being associated with a primary housing, and offset axially relative to the associated primary housing, and in that one of said shims of each piston is an indexing shim comprising a primary section forming the axial retention of the associated bearing element and linked in translation to the piston, and a secondary section configured to be aligned with the associated secondary housing, each of said secondary housing comprising a thrust spring, having a first end mounted in support in said secondary housing, and a second end coupled to the secondary section aligned with udit secondary housing, said push spring exerting a thrust force on the indexing wedge so as to tend to move the piston out of its primary housing, and cooperating with the indexing wedge to guide the piston in translation in its primary housing, so as to prevent rotation of the piston in its primary housing.

The present invention also relates to a cylinder block of hydraulic machine with radial pistons, comprising a plurality of primary housings in which are arranged pistons adapted to slide in their respective primary housings during the relative rotation of the cylinder block with respect to a machine cam hydraulic, the pistons each comprising a bearing element adapted to be in contact with said cam and shims performing the axial retention of the bearing element in the primary housing, characterized in that the cylinder block further comprises a plurality radial secondary housings, each of said secondary housings being associated with a primary housing, and offset axially relative to the associated primary housing, and in that one of said shims of each piston is an indexing shim comprising a primary section forming the axial retention of the associated bearing element and linked in translation to the piston, e a secondary section configured to be aligned with the associated secondary housing, each of said secondary housings comprising a thrust spring, having a first end mounted in abutment with said secondary housing, and a second end coupled to the secondary section aligned with said housing; secondary, said pushing spring exerting a thrust force on the indexing wedge so as to tend to move the piston out of its primary housing, and cooperating with the indexing wedge to guide the piston in translation in its primary housing, so as to prevent rotation of the piston in its primary housing. Said indexing wedges typically each have a general U shape, of which a first branch forms the primary section, and a second branch forms the secondary section and is slidably mounted in the associated secondary housing. The thrust spring is for example a spring with non-contiguous turns, and mounted so that its second end encloses a boss 30 of the secondary section of the indexing wedge.

According to a first variant, the shims are linked in translation to the piston by means of indexing elements extending from the shims in the housing of the piston support element.

According to another variant, which wedges and the piston comprise a peripheral housing adapted to receive a rod thus surrounding the wedges and the piston and thus immobilizing the wedges relative to the piston. According to yet another variant, the wedges have bosses adapted to be inserted into corresponding housings made in the piston so as to link in translation the wedges and the piston. The invention also relates to an assembly comprising a cylinder block as defined above and a multilobe cam, thus defining for the pistons of the cylinder block a top dead position and a bottom dead center position, in which the blocks are connected to the cylinders. pistons in translation in the sliding direction of the pistons in their respective primary housings by connecting means configured so as to remain in said primary housing 20 during sliding of the piston between the top dead center and the bottom dead center. PRESENTATION OF THE FIGURES Other characteristics, objects and advantages of the invention will emerge from the description which follows, which is purely illustrative and nonlimiting, and which should be read with reference to the appended drawings, in which: FIG. a partial sectional view of a cylinder block of hydraulic machine according to one aspect of the invention; Fig. 2 shows a partial side view of the piston of the cylinder block shown in Fig. 1; and - Figure 3 shows schematically the positioning of such a piston in a multilobe cam radial hydraulic machine; - Figures 4 to 8 show several advantageous piston structure variants for the implementation of the present invention. In all the figures, the elements in common are identified by identical reference numerals.

DETAILED DESCRIPTION FIGS. 1, 2 and 3 show several partial views of a hydraulic machine cylinder block according to one aspect of the invention.

A cylinder block 1 of a hydraulic machine is thus represented in these figures, having a plurality of radial primary housings 11 supplied with oil by internal conduits 12, and in which pistons 2 slide. FIG. 3 shows the axis of rotation ZZ. of the hydraulic machine, thereby defining the axial direction along this axis ZZ, and the radial direction with respect to this axis ZZ. The pistons 2 each comprise a support element 21, for example a support roller or roller, adapted to be in contact with a multilobal cam 3. The pistons 2 each advantageously comprise a bearing 14 forming a support for the associated bearing element 21. Two wedges 22 and 23, commonly called lunambules, rotate the support element 21 in rotation in the primary housing 11 of the cylinder block, thus ensuring that the support element 21 is oriented in a suitable manner to be in contact with the cam 3. The wedges 22 and 23 are linked in translation to the piston 2, for example by means of shoulders 27 made in the wedges 22 and 23 and forming a stop in translation of the wedges 22 and 23 with respect to the piston 2. The wedges 22 and 23 therefore have a single degree of freedom with respect to the piston 2, in translation in a direction perpendicular to the axis of the piston 2, to allow the insertion of the wedges 22 and 23. However, the positioning pistons 2 in their respective primary housings 11 also blocks this degree of freedom. The cylinder block 1 as shown further comprises a plurality of radial secondary housings 13, each of said secondary housing 13 being associated with a primary housing 11, and offset axially relative to the associated primary housing 11. One of the wedges of each piston, here the wedge 23, is an indexing wedge. The indexing wedge 23 has a primary section 24 axially holding the associated support member 21, and a secondary section 25 configured to be aligned with the associated secondary housing 13. In the embodiment shown, the indexing wedge 23 has a general shape of U, whose two branches form the primary section 24 and the secondary section 25, these two branches being connected by a base 26. The primary housing 11 and the secondary housing 13 are here connected by a groove opening, in which slides the indexing wedge 2, or more precisely here the base 26 of the indexing wedge 2.

Each secondary housing 13 is also equipped with a thrust spring 4, having a first end 41 mounted in abutment in the secondary housing 13, and a second end 42 coupled to the secondary section 25 of the indexing shim 23 aligned audit secondary housing 13.

In the embodiment shown, the thrust spring 4 is fitted around the second branch forming the secondary section 25 of the U-shaped indexing shim 23.

The thrust spring 4 thus exerts a thrust force on the indexing wedge 23, which, being connected in translation to the piston 11, transmits to the piston 11 the thrust force exerted by the thrust spring 4, so as to move the piston 11 in the direction of an output of its primary housing, that is to say a radial displacement in the direction of a distance from the axis ZZ of the hydraulic machine. In addition, the indexing wedge 23 also rotates the piston 2 in its housing 11, because of the secondary section 25 of the wedge 23 which is disposed in the secondary housing 13. The indexing wedge 23 is further dimensioned to allow to transmit thrust forces applied to the piston 2. Figures 4 to 8 show several piston structures that can advantageously be exploited to achieve the connection in translation between the wedges 22 and 23 and the piston 2. FIGS. 4 and 5 show two views of a piston variant 2, in which the wedges 22 and 23 are linked in translation with the piston 2 by means of a holding element 51, in this case a snap ring the shims 22 and 23 and the piston 2, and arranged in a peripheral groove formed in the piston 2 and in the shims 22 and 23. FIG. 6 shows a sectional view of another variant of the piston 2, in which the section primary 24 of the shim 23 has an indexing section 52 projecting and housed in a complementary housing 53 arranged in the bearing element 21 of the piston 2, which thus makes the connection in rotation between the piston 2 and the shim 23. FIG. 7 shows a sectional view of another variant of the piston 2, in which the connection in translation between the shim 22, the shim 23 and the support element 21 is made by means of a rod 54 arranged to extend in a transverse cavity of the piston 2, formed by two blind cavities 55 and 56 respectively provided in the wedge 22 and in the wedge 23, and by a through cavity 57 arranged in the element of support 21.

In the embodiments shown in FIGS. 5 and 6, the translational connection is made between the wedges 22, 23 and the piston 2 by means of indexing elements extending from the wedges into housings of the pistons support element.

FIG. 8 shows another variant, in which the shim 23 has a primary section 24 comprising bosses 58 adapted to be housed in corresponding housings made in the piston 2, so as to allow only one degree of freedom between the hold 23 and the piston 2, namely a translation along an axis perpendicular to the sliding direction of the piston 2. The wedge 22 may also have a similar shape. It is well understood that many patterns are possible, since they make it possible to achieve this connection in translation along the axis of sliding of the piston 2.

These different piston structures provide additional support between the wedges 22 and 23 and the piston 2 during the sliding of the piston 2 in its housing 11, and in particular when the piston 2 is partially out of its housing 11, in the so-called top dead center. Indeed, the shoulders 27 presented above are arranged near the head portion of the piston 2, and are therefore out of the housing 11 associated during certain phases of the movement of the piston 2, which can be problematic for immobilization in translation shims 22 and 23 with respect to the piston 2 in particular because of the transmission of the thrust force exerted by the thrust spring 4 on the shim 23.

The different variants presented remedy this problem by performing a translation connection between the shims 22 and 23 and the piston 2 which is not affected by the movements of the piston. The connection means presented for these different variants can thus come in addition to or replacement of the shoulders 27 presented above. More generally, considering the cylinder block 1 equipped with such pistons 2 and associated with a cam 3, a top dead center position and a bottom dead center position, corresponding to the two extreme positions of the piston when it is sliding between the two, are defined. bosses and hollows of the cam 3. The elements forming the connection in translation between the wedges 22 and 23 and the piston 2 are advantageously configured so as to remain in the primary housing 11 regardless of the position of the piston 2 between its neutral position high and his dead point down. The proposed structure thus has several advantages.

The offset of the thrust spring out of the primary housing of the piston allows a gain in radial size, because of the axial offset of the thrust springs, which is advantageous for the integration of hydraulic machines in certain systems or vehicles. This axial offset can also allow the pistons to abut against the bottom of their respective primary housing. The stroke of the pistons can be increased or the radial size of the hydraulic machine reduced. In addition, the proposed structure performs both immobilization in rotation of the pistons in their respective primary housings, and decreases the boost pressure for such a hydraulic machine due to the force applied by the thrust spring on the pistons tending to keep them in contact with the cam.

This thrust force applied to the pistons further allows immobilization in rotation of the cylinder block relative to the cam to a given torque level. Indeed, the pistons being pushed out of their housing, they perform an indexing of the cylinder block relative to the cam as the torque is not sufficient to exert a radial resultant greater than the thrust force applied by the springs of poussée.10

Claims (10)

REVENDICATIONS1. Multilink radial piston and cam (3) machine, comprising a cylinder block (1) having a plurality of primary housings (11) in which pistons (2) are arranged to slide in their respective primary housings (11) during the relative rotation of the cylinder block (1) and the cam (3) relative to each other; the pistons (2) each comprising a support element (21) adapted to be in contact with the cam (3) and shims (22, 23) providing the axial retention of the support element (21) in the primary housing (11), the hydraulic machine being characterized in that the cylinder block (1) comprises a plurality of radial secondary housings (13), each of said secondary housings (13) being associated with a primary housing (11), and offset axially relative to the primary housing (11) associated, and in that one (23) of said wedges (22, 23) of each piston is an indexing wedge comprising a primary section (24) providing the axial retention of the support member (21) associated and translationally connected to the piston (2), and a secondary section (25) configured to be aligned with the associated secondary housing (13), each of said secondary housings (13) comprising a thrust spring (4), having a first end (41) mounted in a ppui in said secondary housing (13), and a second end (42) coupled to the secondary section (15) aligned with said secondary housing (13), said push spring (4) exerting a thrust force on the wedge of indexing (23) so as to tend to move the piston (2) out of its primary housing (11), and cooperating with the indexing wedge (23) to guide the piston (2) in translation in its primary housing (11), so as to prevent rotation of the piston (2) in its primary housing (11). 2. Hydraulic machine according to claim 1, wherein said indexing wedges (23) each have a general U-shape, of which a first branch forms the primary section (24), and a second branch forms the secondary section (25). and is slidably mounted in the associated secondary housing (13). 3. Hydraulic machine according to one of claims 1 or 2, wherein the thrust spring (4) is a spring non-contiguous turns, and mounted so that its second end (42) encloses a boss of the section secondary (25) of the indexing wedge (23). 4. cylinder block (1) of radial piston hydraulic machine, comprising a plurality of primary housings (11) in which are arranged pistons (2) adapted to slide in their respective primary housings (11) during the relative rotation of the block cylinder (1) with respect to a multilobe cam (3), the pistons (2) each comprising a bearing element (21) adapted to be in contact with said multilobe cam (3) and shims (22, 23) producing the axial retention of the bearing element (21) in the primary housing (11), characterized in that the cylinder block (1) comprises a plurality of radial secondary housings (13), each of said secondary housings (13) being associated with a primary housing (11), and offset axially relative to the primary housing (11) associated, and in that one (23) of said wedges (22, 23) of each piston is an indexing wedge comprising a primary section (24) realizing the axial maintenance of the element of ap (21) associated and translationally connected to the piston (2), and a secondary section (25) configured to be aligned with the secondary housing (13) associated, each of said secondary housing (13) comprising a push spring (4), having a first end (41) supported in said secondary housing (13), and a second end (42) coupled to the secondary section (15) aligned with said secondary housing (13), said push spring (4) exerting a thrust force on the indexing wedge (23) so as to tend to move the piston (2) out of its primary housing (11), and cooperating with the indexing wedge (23) for guiding the piston (2) in translation in its primary housing (11), so as to prevent rotation of the piston (2) in its primary housing (11). 5. cylinder block according to claim 4, wherein said indexing wedges (23) each have a general shape of U, of which a first branch forms the primary section (24), and a second branch forms the secondary section (25). and is slidably mounted in the associated secondary housing (13). 6. Cylinder block according to one of claims 4 or 5, wherein the thrust spring (4) is a non-contiguous coil spring, and mounted so that its second end (42) encloses a boss of the section secondary (25) of the indexing wedge (23). 7. cylinder block according to one of claims 4 to 6, wherein the wedges (22, 23) are connected in translation to the piston (2) by means of indexing elements (52, 54) extending from wedges (22, 23) in housings (53, 57) of the support element (21) of the pistons (2). 8. cylinder block according to one of claims 4 to 6, wherein the wedges (22, 23) and the piston (2) comprise a peripheral housing adapted to receive a rod (51) thus surrounding the wedges (22, 23). and the piston (2) and thereby immobilizing the shims (22, 23) with respect to the piston (2). 9. cylinder block according to one of claims 4 to 6 wherein the wedges (22, 23) have bosses (58) adapted to be inserted into corresponding housings formed in the piston (2) so as to link in translation shims (22, 23) and the piston (2). 10. An assembly comprising a cylinder block (1) according to one of claims 4 to 9 and a multilobe cam (3), thus defining for the pistons (2) of the cylinder block (1) a top dead center position and a position bottom dead center, in which the wedges (22, 23) are connected to the pistons (2) in translation in the sliding direction of the pistons (2) in their respective primary housings (11) by connection means configured so as to remain in said primary housing (11) when sliding the piston (2) between the top dead center and the bottom dead center.