EP1466092A1

EP1466092A1 - Hydraulic radial piston motor

Info

Publication number: EP1466092A1
Application number: EP02799840A
Authority: EP
Inventors: Bernard Allart; Louis Bigo
Original assignee: Poclain Hydraulics Industrie
Current assignee: Poclain Hydraulics Industrie
Priority date: 2001-12-24
Filing date: 2002-12-20
Publication date: 2004-10-13
Anticipated expiration: 2022-12-20
Also published as: JP4133828B2; FR2834011A1; US20050126387A1; DE60218351T2; FR2834011B1; WO2003056172A1; AU2002364477A1; JP2005513351A; DE60218351D1; EP1466092B1; US6978713B2

Abstract

The invention concerns a hydraulic radial piston motor comprising a cam, a distributor and a cylinder block whereof the cylinders are connected to communication orifices located in a communicating surface of the cylinder block. The directional valve has a distribution surface wherein emerge distribution orifices adapted to communicate with the communication orifices during the relative rotation of the cylinder block and of the distributor. The cam has several lobes each including two ramps (50) having each a convex portion (51) and a concave portion (52). The edge of each distribution orifice has a leading portion (B1) through which the communication of said orifice with the communication orifices is opened, and a separating portion (B2) through which said communication is closed. The leading portion and the separating portion (B1, B2) of the edge of at least some distribution orifices (21A, 23A) have each an edge fitting (53A; 53B) comprising at least a recess (54A; 54B), said edge fittings being different depending on whether they are in angular correspondence with the convex zone (51) or the concave zone (52) of the cam ramp.

Description

Radial piston hydraulic motor

The present invention relates to a hydraulic motor with radial pistons comprising a cam and a cylinder block capable of rotating relative to one another about an axis of rotation. The cylinder block has radial cylinders connected by cylinder conduits to communication ports located in a communication face of the cylinder block which is perpendicular to the axis of rotation. Pistons slidably mounted in the cylinders are able to cooperate with the cam and the latter has several lobes each having two ramps which each include a convex region and a concave region. The engine further comprises a fluid distributor having a distribution face which is perpendicular to the axis of rotation and which is able to bear against the communication face of the cylinder block, this distribution face having dispensing orifices comprising orifices suitable for being connected to a fluid supply and orifices suitable for being connected to a fluid exhaust. The fluid distributor is integral in rotation with the cam so that a ramp of the cam corresponds to each dispensing orifice (that is to say that each dispensing orifice is situated in angular correspondence with a ramp of the cam ), said dispensing orifices being able to communicate one after the other with the communicating orifices during the relative rotation of the cylinder block and the distributor, the edge of each dispensing orifice having a leading portion through which the communication between the dispensing orifice and the communication orifices opens during the relative rotation between the cylinder block and the distributor in a given relative direction of rotation, as well as a separation portion through which the communication between the The dispensing orifice and the communication orifices close during the relative rotation between the cylinder block and the distributor in the same direction of relative rotation. For an engine of this type, operating at full displacement, each communication orifice is successively opposite a distribution orifice connected to the fluid supply and opposite a distribution orifice connected to the fluid exhaust. . The connection to the dispensing orifice which is connected to the supply has the effect of pushing radially outwards the piston contained in the cylinder connected to the communication orifice considered, while the connection of the same communication orifice to a dispensing orifice connected to the fluid exhaust allows this piston to enter in its cylinder, towards the axis of the engine. Thus, each piston cooperates successively with the different parts of the cam lobes to allow the relative rotation of the cylinder block and the cam.

The spacings between the dispensing orifices and the spacings between the communication orifices are such that a communication orifice is not simultaneously connected to two dispensing orifices connected respectively to the fluid supply and to the fluid exhaust.

During the relative rotation of the cylinder block and the distributor, the working chambers of the cylinders, that is to say the parts of these cylinders delimited below the pistons, are alternately placed at high pressure and at low pressure. Pressure changes in these working chambers therefore generally take place at a very rapid rate. These pressure changes subject the pistons to proportional forces, and these forces are transmitted by the pistons to the cam. As a result, the components of the motor, in particular, its casing, are subjected to the variation in load which causes vibrations generating noise, the intensity of the noises produced mainly depending on the speed of the increases and pressure drops in the working chambers. For the engine to function properly, the pressure difference between the fluid supply and the fluid exhaust is large. When a piston contributing to the engine torque reaches the end of its stroke, towards its position furthest from the engine axis (top dead center), due to the connection of the communication port of its cylinder to an orifice distribution connected to the fluid supply, the same communication orifice is isolated from this distribution orifice and then is connected to another distribution orifice which, this time, is itself connected to the fluid exhaust. This results in an expansion phenomenon in the cylinder of the piston in question, the fluid present at a high pressure in this cylinder being suddenly put in communication with a clearly lower pressure, which is that of the fluid exhaust. Conversely, when the piston has reached bottom dead center of its stroke (its position closest to the axis of the engine), its cylinder is isolated from the fluid exhaust and is then connected to the fluid supply. to allow a new centripetal stroke of the piston. At this instant, the fluid contained in the cylinder passes from a low pressure to a much higher pressure which is that of the fluid supply. An expansion phenomenon also occurs, from the fluid supply, to the cylinder. In the previous case, the expansion occurs from the cylinder towards the fluid exhaust.

In both cases, the detents that operate generate sensations of shock or jolts, and noises such as clicks. These phenomena become all the more sensitive as the quality of the engines has been improved and the leaks in these engines have been reduced. In fact, in old engines, the leaks which reigned there made it possible to avoid too sudden pressure variations between the various enclosures.

The present invention aims to limit the phenomena of relaxation and the shock effects which result therefrom, by tending to allow the engine to operate substantially smoothly.

This object is achieved thanks to the fact that the leading portion and the edge separation portion of at least certain dispensing orifices each have an edge arrangement comprising at least one notch, said edge arrangements of a dispensing orifice being different, the edge arrangement of a dispensing orifice which is arranged in angular correspondence with the convex region of the ramp of the cam corresponding to the dispensing orifice considered being able to allow the passage of a volume of fluid pressure compensation between a communication orifice and the dispensing orifice smaller than the volume of pressure compensating fluid, the edge arrangement of the same dispensing orifice which is arranged in angular correspondence with the concave region of said ramp is suitable for allowing passage.

These volumes of compensation fluid are the volumes of fluid capable of passing through the notches of these edge arrangements as long as the communication between the dispensing orifice and a communication orifice takes place only through the notch (s) of the arrangement board considered.

To eliminate the abovementioned shock and noise phenomena, or at least to considerably attenuate them, the invention proposes to equip the attack portion and the edge separation portion with at least certain dispensing orifices each of an edge arrangement having at least one notch.

When a piston is in contact with a convex region of a ramp of the cam, it is in the low position, that is to say that it is in the vicinity of its bottom dead center. In this situation, the volume of the working chamber of the cylinder in which this piston moves is minimal. On the other hand, when the piston is in contact with the concave region of the ramp of the cam, it is in the vicinity of its top dead center and the volume of the working chamber of the cylinder in which this piston moves is maximum. With the invention, when a piston is in the vicinity of its bottom dead center, the communication orifice of the cylinder of this piston leaves the separation portion of a dispensing orifice or approaches the attack portion of the next dispensing orifice by an edge arrangement having at least one notch capable of passing a small volume of pressure compensation fluid between the orifices. When the same piston is near its top dead center, the communication orifice of the cylinder of this piston leaves the separation portion of a distribution orifice or approaches the attack portion of the neighboring distribution orifice by an edge arrangement having at least one notch capable of passing a larger volume of pressure compensation fluid between the orifices.

On the one hand, the invention allows the connection between each communication orifice and each distribution orifice to be progressive, either by means of the notch (s) of the on-board arrangement allowing the passage of a small volume disposed on one of the edges of the dispensing orifice, arrangement known as “with a small notched section”, either by means of the notch (s) of the edge arrangement allowing the passage of a large volume disposed on the other edge, arrangement said "with large notched section". This limits the relaxation phenomena mentioned above. In addition, the connection between a communication orifice and the edge arrangement with a small notched section of a dispensing orifice is made when the volume of the working chamber of the cylinder connected to the communication orifice considered is minimal, while that the connection between the same communication orifice and the edge arrangement with a large notched section of a dispensing orifice takes place when the volume of the working chamber of the cylinder associated with the same communication orifice is maximum.

By suitably choosing the dimensions and the number of the notches of the edge arrangements with small and large notched section, it is thus possible to obtain a progressivity of the pressure compensation between the communication orifice and the distribution orifices which, relative to the volume of the working chamber, being substantially the same in the two aforementioned situations. Thus, the choice of small notched sections and large notched sections for the two respective edges of each dispensing orifice makes it possible to obtain an even more homogeneous communication between the communication orifices and the dispensing orifices. This further promotes the flexibility of operation of the engine, since the phenomena of expansion are avoided in the same way (in the same proportions) as the pistons are in the vicinity at their extreme high position or in the vicinity of their extreme low position. We further limit vibrations and other unpleasant shock phenomena. According to a variant, the edge arrangement of the leading portion of at least one dispensing orifice comprises at least one notch which, relative to a notch of the edge arrangement of the separation portion of said dispensing orifice , is arranged at a different radial distance from the axis of rotation. The fact that these two notches are located at different radial distances from the axis of rotation can make it possible to make notches of different lengths. These different lengths are used to optimally define the variation in the pressure drop in the notch during the relative rotation of the fluid distributor and the cylinder block. For example, if the notch which is furthest from the axis of rotation and which belongs to the edge arrangement with a large notched section is in communication with the communication orifice over an angular sector larger than that on which the edge arrangement with a small notched section is in communication with this orifice, this arrangement makes it possible during the relative rotation of the fluid distributor and of the cylinder block to ensure that a communication orifice communicates for a period of time more large with edge arrangement with large notched section than with the other. This difference in communication time is one of the factors which make it possible to homogenize the decompression or compression of the volume of fluid contained in the working chamber of the cylinder block which communicates with the communication orifice considered.

Thus, the period of time during which the notch furthest from the axis of rotation belonging to the edge arrangement with large notched section communicates with a communication orifice is generally greater since, for a given relative angle of rotation between the cylinder block and the distributor, the distance to be covered by a point distant from the axis of rotation is greater than that which is crossed by a point closer to this axis.

Another use of the length of the notch consists, for a very long notch, in limiting the communication of this notch with a communication orifice, to only a small part of the length of the notch (i.e. -to say on a small angular sector of relative rotation between the cylinder block and the distributor), before the frank communication is established with the very edge of the dispensing orifice. In this case, this long cut constitutes a restriction of great length which only authorizes, over the small part considered, the passage of a small volume of pressure compensation fluid. This long notch therefore corresponds to the small notched section defined above. The notch on the other edge of the dispensing orifice, disposed at a smaller radial distance from the axis of rotation, has a shorter length but is used over its entire length over an angular sector substantially identical to that of the limited communication of the long notch with the communication orifice before frank communication is established with the very edge of the dispensing orifice. This short notch therefore allows the passage of a larger volume of pressure compensation and corresponds to the large notched section defined above.

In these cases, advantageously, for edge arrangements of at least one dispensing orifice, the distance of a notch of short length from the axis of rotation is less than the distance of a notch of great length from rotation axis. Advantageously, for at least one dispensing orifice, the edge arrangement which is arranged in angular correspondence with the concave region of the cam ramp corresponding to the dispensing orifice considered comprises at least one notch which extends over a sector angular, measured between two radii starting from the axis of rotation, which is larger than the angular sector, measured in the same way, over which extends the notch which is arranged in angular correspondence with the convex region of the ramp .

Advantageously, for at least one dispensing orifice, the edge arrangement which is arranged in angular correspondence with the concave region of the cam ramp corresponding to said orifice has a notched section larger than that of the edge arrangement which is arranged in angular correspondence with the convex region of the ramp. According to one embodiment, the edge arrangements of at least one dispensing orifice each have the same number of notches (advantageously only one notch), the notch (s) of one of these arrangements being different from that (s) of the other edge arrangement. According to another embodiment, the edge arrangements of at least one dispensing orifice each have similar notches, the number of notches of one of these edge arrangements being different from the number of notches of the other edge layout.

By "similar notches" means notches having substantially the same section and can be made with the same tool. For example, two similar notches respectively present on the leading portion and on the separation portion of a dispensing orifice, are such that the image of one of these notches obtained by symmetry with respect to a plane of symmetry of the dispensing orifice has an identical or almost identical conformation to that of the other notch.

We can thus use the same tool to machine all the notches and choose the number of notches on each edge to allow the passage of desired pressure compensation volume.

An advantageous variant is defined by the fact that two adjacent ramps of the cam are interconnected either by a cam top zone extending between their respective convex regions, or by a cam bottom zone extending between their regions respective concaves, and said areas of cam top and bottom of cam are substantially arcs of a circle centered on the axis of rotation, so that, when the pistons cooperate with said areas, their radial strokes are substantially zero and by the fact that the distribution orifices and the communication orifices have dimensions such that, during the relative rotation of the cylinder block and the distributor, each distribution orifice remains temporarily isolated from any communication orifice. These cam top areas and these cam bottom areas are referred to as "cam flats". Advantageously, the substantially zero stroke of a piston which cooperates with a cam plate is made to coincide with an insulation of the communication orifice of the cylinder of this piston, with respect to any distribution orifice. This avoids any significant compression or decompression of fluid in the working chamber of the cylinder block, the piston of which is in contact with a cam top region or a cam bottom region. The invention will be clearly understood and its advantages will appear better on reading the detailed description which follows, of an embodiment shown by way of nonlimiting example. The description refers to the accompanying drawings in which: - Figure 1 is an axial sectional view of a hydraulic motor whose distribution orifices can be in accordance with the invention;

- Figure 2 is a sectional view along line II-II of Figure 1;

- Figure 3 is a partial section along the arc of a circle designated by III-III in Figure 2; - Figure 4 illustrates the relative positions between a communication orifice and a dispensing orifice, during the relative rotation between the cylinder block and the distributor, this figure also shows how the dispensing orifice is arranged relative to a ramp of a cam lobe; - Figure 5 shows, according to a variant, a communication orifice disposed between two dispensing orifices during the relative rotation between the cylinder block and the distributor; and

- Figures 6 to 10 are variants each showing a dispensing orifice disposed between two communication orifices, during the relative rotation between the cylinder block and the distributor.

FIG. 1 shows a hydraulic motor comprising a fixed casing in three parts, 2A, 2B and 2C, assembled by screws 3.

Of course, the invention is not limited to hydraulic motors with fixed casing, but it also applies to hydraulic motors with rotating casing which are well known to those skilled in the art.

The part 2C of the casing is closed axially by a 2D radial plate also fixed by screws. A wavy reaction cam 4 is produced on part 2B of the casing.

The engine comprises a cylinder block 6 which is mounted for relative rotation about an axis of rotation 10 relative to the cam 4 and which comprises a plurality of radial cylinders, capable of being supplied with fluid under pressure and at inside which the radial pistons are slidably mounted

14.

The cylinder block 6 rotates a shaft 5 which cooperates with it by splines 7. This shaft carries an outlet flange 9.

The engine also includes an internal fluid distributor 16 which is integral with the casing with respect to the rotation about the axis 10. Between the distributor 16 and the internal axial face of part 2C of the casing are formed distribution grooves, respectively a first groove 18, a second groove 19 and a third groove 20. The distribution conduits of distributor 16 are distributed in a first group of conduits which, like conduit 21, are all connected to the groove 18, a second group of conduits (not shown) which are connected to the groove 19 and a third group of conduits which, like conduit 22, are connected to the groove 20. The first groove 18 is connected to a first main conduit 24 to which are therefore connected all the distribution orifices of the distribution conduits of the first group, such as the orifice 21A. The third groove 20 is connected to a second main conduit 26 to which are therefore connected all the distribution orifices of the conduits of the third group, such as the orifice 22A of the conduit 22.

Depending on the direction of rotation of the engine, the main conduits 24 and 26 are respectively an exhaust conduit and a fluid supply conduit, or the reverse.

The distribution conduits open into a distribution face 28 of the distributor 16, which bears against a communication face 30 of the cylinder block. Each cylinder 12 has a cylinder conduit 32 which opens into this communication face so that, during the relative rotation of the cylinder block and the cam, the cylinder conduits are alternately in communication with the distribution conduits of the different groups.

The motor of FIG. 1 also comprises a device for selecting the displacement which, in this case, includes a bore 40, which extends axially in the part 2C of the casing and in which there is disposed an axially movable selection slide 42 . The bore 40 comprises three communication channels, respectively 44, 46 and 48, which are respectively connected to the grooves 18, 19 and 20, by connection conduits, respectively 44 ', 46' and 48 '. The slide 42 is movable between two extreme positions inside the bore 40 in which it communicates the tracks 44 and 46 or the tracks 46 and 48 by its groove 43.

For example, as shown in FIG. 2, the distribution orifices, considered successively in the direction of relative rotation between the cylinder block and the distributor, comprise a pair of orifices 21A, 23A, respectively connected to the grooves 18 and 19, and a pair of orifices 21A, 22A, respectively connected to the grooves 18 and 20. In the position of the selector 42 shown in FIG. 1, the grooves 19 and 20 both communicate with fluid supply. It is understood that, during the relative rotation of the cylinder block and the distributor, a communication orifice 32A is successively set to high and to low pressure by communicating with the orifices of the two aforementioned pairs. When, on the other hand, the selector 42 is moved in the direction of the arrow F so as to make the grooves 18 and 19 communicate with each other, then the two distribution orifices 21A, 23A of the first aforementioned pair are both set to the same pressure. This pair is therefore deactivated since, when a communication orifice passes from one to the other of the two distribution orifices of this pair, the pressure in the cylinder duct connected to said communication orifice does not change. On the other hand, the next pair is active, since a communication orifice communicating respectively with the two orifices 21A, 22A of this pair is successively placed at high and at low pressure.

The situation shown in Figure 1 is therefore a situation of large displacement, while that in which the selector 42 is moved in the direction of the arrow F to communicate the grooves 18 and 19 is a situation of small displacement. In such a situation, the pairs of orifices 21A and 23A are inactive, while the pairs of orifices 21A and 22A are active.

When the cylinder block moves with respect to the distributor in the direction of rotation RI indicated in FIG. 2, the portions Bl of the edges of the dispensing orifices constitute attack portions, through which the communication of an orifice begins. communication with a dispensing orifice, while the portions B2 of the edges of the dispensing orifices constitute separation portions, by which this placing in communication ceases. Of course, when the relative rotation takes place in the opposite direction R2, it is the portions B2 which constitute the attack portions and the portions Bl which constitute the separation portions.

In the exemplary embodiment of FIG. 2, the leading portions B1 and the separation portions B2 of each dispensing orifice (considered in the direction of rotation RI) each have an edge arrangement, comprising a notch. We see that these notches are of different dimensions, the notches 54A of the edge arrangements 53A of the edges Bl of the distribution orifices 23A and 22A, as well as the notches 54A of the edge arrangements 53A of the edges B2 of the orifices 21A being small notches , these edges therefore having small notched sections, while the notches 54B of the edge arrangements 53B of the edges B2 of the distribution orifices 23A and 22A, as well as the notches 54B of the arrangements of edge 53B of the edges Bl of the orifices 21A being large notches, these edges therefore having large notched sections.

Insofar as the cam and the distributor are integral in rotation, the position of each dispensing orifice relative to the lobes of the cam is fixed.

Each lobe of the cam includes two ramps, which each have a convex region and a concave region. In Figure 4, we see one of these ramps 50, whose convex region, closer to the axis of rotation 10, is designated by the reference 51, and whose concave region, less close to this axis, is designated by the reference 52. A cam lobe is formed by this ramp 50, and by another symmetrical ramp of the ramp 50 with respect to the radius R passing through the axis of rotation of the engine. The adjacent cam lobe has a ramp 50 ′, symmetrical with the ramp 50 with respect to the radius RS.

A dispensing orifice is associated with each ramp of the cam. There is therefore an angular correspondence between each dispensing orifice and a ramp of the cam. Although the dispensing orifices are not in the same radial plane as the cam, FIG. 4 illustrates the angular correspondence between a dispensing orifice 23A and the ramp 50 of the cam. Furthermore, for the sake of clarity, the proportions have not been respected, the communication and distribution orifices being shown closer to the cam than in reality. Overall, the orifice 23A is arranged so that the inscribed circle passing through the end of the notches is substantially symmetrical with respect to a radius RC of the cam which intersects the latter substantially in an inflection zone between its convex regions 51 and concaves 52.

It can be seen in FIG. 4 that the notch 54A of the portion Bl of the edge of the orifice 23A is a small notch, while the notch 54B of the portion B2 of the edge of the orifice 23A is a large notch. The small notch 54A is in angular correspondence with the convex portion 51 of the cam, that is to say that a radius of the cam, extending radially from the axis of rotation 10 of the motor and passing through the notch 54A intersects the ramp 50 in the convex region 51 of the latter. On the other hand, the notch 54B is in angular correspondence with the concave region 52 of the ramp 50, that is to say that a radius of the cam extending from the axis of rotation 10 and passing by the notch 54B intersects the ramp 50 in the concave region of the latter. FIG. 4 also shows the different positions of a communication orifice relative to the distribution orifice 23A during the relative rotation of the cylinder block and the distributor. It is considered, for example, that the cylinder block rotates in the direction R2 relative to the cam, the direction for which the portions B2 and B1 of the edge of the orifice 23A respectively constitute the attack portion and the separation portion.

First there is a position 32A1 of the communication orifice 32A in which this communication orifice is isolated from any dispensing orifice. It can be seen that, in this position, the orifice 32A is separated from the tip of the notch 54B from the orifice 23A by an angular distance α1 _f for example of the order of 1 ° and that it is also isolated from the notch 54B of the preceding dispensing orifice 21A. During the rotation of the cylinder block relative to the distributor in the direction R2, the communication orifice gradually covers the notch 54B of the orifice 23A and, on an angular displacement α2, for example of the order by 2 °, it communicates with the dispensing orifice 23A only through this notch 54B, until it occupies a position 32A2.

When the rotation in the direction R2 continues, the communication orifice gradually covers the whole of the orifice 23A, and there is a position 32A3, in which the dispensing orifice 23A is completely covered by the communication orifice, the communication section between the dispensing orifice and the communication orifice then being maximum.

When the rotation in the direction R2 continues, the communication section decreases and the communication orifice reaches a position 32A4 in which it no longer communicates with the dispensing orifice 23A only by means of the notch 54A on the edge from this hole. He then has to travel an angular travel α3, for example of the order of 1 °, so that the communication with the dispensing orifice 23A ceases completely. It then remains for the communication orifice to travel an angular travel α4, for example of the order of 1 °, before communication begins with the distribution orifice 21A which is located after the distribution orifice 23A in the direction of rotation R2, by the notch 54A of this orifice 21A.

For the large notch 54B, when the communication orifice occupies its position 32A2, the total section of the communication passage between this orifice and the distribution orifice 23A is greater than the section of the communication passage which is established, by the small notch 54A, between the same dispensing orifice and the communication orifice when it occupies its position 32A4. The ratio between these passage sections is advantageously chosen as a function of the ratio between the volumes of the working chamber of the cylinder 12 supplied by the communication orifice 32A considered when the communication orifice occupies its positions 32A2 and 32A4 respectively. For example, the ratio between the communication sections authorized by the notches 54B and 54A is proportional to the ratio between the volume presented by the working chamber of the cylinder supplied by the orifice 32A when this orifice is in its position 32A2 and the volume of the same working chamber when the orifice 32A is in its position 32A4. It can be seen that the large notch 54B extends over an angular sector α2, measured between two radii starting from the axis of the engine, which is greater than the angular sector α3, also measured between two radii starting from the axis of the motor, over which extends the small notch 54A.

The ramp 50 of the cam is connected to the adjacent ramp 50 'by a cam top region 56, which extends between the convex region 51 of the ramp 50 and the convex region of the ramp 50', and it is connected to the other ramp which is adjacent to it, namely the ramp 50 ", by a cam bottom zone 58 which extends between the concave region 52 of the ramp 50 and the concave region of the ramp 50". Cam top areas are those where the radial distance from the cam to the axis of rotation is minimal, while the cam bottom areas are those where the radial distance from the cam to the axis of rotation is Max.

When we consider the orifice 32A, we see that it travels between its position 32A1 and its position 32A2 an angular displacement αl + α2 which is equal to the angle '1 corresponding to a part of the cam bottom 58 located d 'one side of the radius of symmetry R. In other words, during the relative rotation of the cylinder block and the distributor, when the communication orifice passes from its position 32A1 to its position 32A2, the piston of the cylinder supplied by this the communication orifice cooperates with the cam bottom zone 58. On part of this angular path, corresponding to the angular displacement l, the orifice 32A is isolated from any dispensing orifice. On the remaining part, corresponding to the displacement α2, it is in communication with the dispensing orifice 23A only through the groove 54B.

When a piston cooperates with the cam bottom region 58, its radial stroke is zero or substantially zero. For example, it is at most substantially equal to 0.5% of the amplitude of the piston stroke between its top and bottom dead centers. For this, the cam bottom zone 58 is substantially an arc centered on the axis of rotation. This means that this cam bottom zone is either an arc of a circle centered on the axis of rotation, or a region which, over the entire angular distance 2α'l which it covers, has a radial distance from the axis of rotation of the motor which is substantially equal to the maximum radial distance from the cam to the axis of rotation 10. Insofar as, when the communication orifice traverses the angular displacement αl, it is isolated from any distribution orifice, the pressure in the working chamber of the cylinder supplied by this orifice remains substantially constant during this movement. The conformation of the cam bottom zone then makes it possible to avoid any significant compression of fluid in this chamber. On the remaining part α2 of the stroke of the communication orifice 32A during which the piston of the cylinder supplied by this orifice cooperates with the cam bottom region 58, said communication orifice communicates with the dispensing orifice only through the notch 54B. We take advantage of this remaining part, on which the piston does not have to make a radial displacement, to vary "smoothly" the pressure in the working chamber of this piston by the communication operated by the notch 54B. In this case, the orifice 23A being connected to the fluid exhaust, the pressure then decreases very gradually in the working chamber, until reaching a value close to or equal to the pressure of the orifice 23A when the communication orifice will have exceeded its position 32A2 in the direction of rotation R2, in which case the piston of the cylinder supplied by this orifice will cooperate with the ramp 50 and will move radially towards the axis of rotation of the engine. The angle α'2 over which the part of the cam top zone 56 situated on one side of the radius of symmetry RS extends, corresponds to the path described by the communication orifice 32A between its position 32A4 and its position 32A5, in which it is ready to approach the dispensing orifice 21A which follows the orifice 23A in the direction R2, by the small notch 54A of this dispensing orifice 21A. This means that the communication orifice moves between its positions 32A4 and 32A5 while the piston of the cylinder supplied by this orifice cooperates with the cam crown zone 56. During this displacement, on the path α3, the orifice 32A communication continues to communicate with the distribution port 23A, but only by the small groove 54A, then, on the path α4, it is isolated from any distribution port. The area at the top of the cam 56 substantially describes an arc of a circle centered on the axis of rotation. It can either actually form such an arc of a circle, or present, over the entire angular distance 2α'2 which it covers, a radial distance to the axis of rotation of the motor which is substantially equal to the minimum radial distance from the cam to the axis of rotation 10, by deviating for example at most about 0.5% of this radial distance. As is the case for the cam bottom areas 58, we take advantage of this situation in which the piston supplied by the communication orifice 32A does not have to effect a notable radial displacement, in order to "smoothly" open the connection between this orifice and the next distribution orifice 21A.

In Figure 3, we see the position of a communication port 32A between two distribution ports, 23A and 21A. We see that the notches 54B are longer than the notches 54A, that is to say that they extend over angular deflections α2 (see FIG. 4) larger than those (α3) over which the notches 54A. The cuts 54B are also slightly deeper than the cuts 54A. To make the notches, one can start from a perfectly circular orifice and apply a milling cutter which extends in a diametral plane of this orifice and which is moved axially relative to the latter. If the cutter is circular, with a diameter slightly offset from the axis of the orifice considered, it is thus possible to make the notches 54B larger and deeper than the notches 54A.

In the figures which have just been described, the dispensing orifices are circular, except for the notches 54A and 54B. However, it is possible to choose distribution orifices of different shapes. Thus, FIG. 5 shows a communication orifice 32A which is circular, arranged between two distribution orifices, respectively 123A and 121A, which are non-circular. Indeed, for these dispensing orifices, the leading portion (B2, if the cylinder block rotates in the direction R2 relative to the distributor and Bl, if the direction of this relative rotation is RI), as well as the portion of separation (Bl if the relative direction of rotation is R2 and B2 if the relative direction of rotation is RI) are both generally convex, seen from the interior of the orifice. Overall, with the exception of the edge arrangements 53'A and 53'B which have the notches 54A and 54B described above, the leading portions and the separation portions form arcs of circles which, during the relative movement of the distributor and the cylinder block, cover the edge of a communication orifice, when the latter occupies a position corresponding to position 32A2 or to position 32A4 shown in FIG. 4. Thus, the dispensing orifices generally have the shapes described in patent application FR-A-2 587 761.

This arrangement makes it possible, once the communication has been established by the notches 54A or 54B, and when the relative rotation between the distributor and the cylinder block continues, very quickly increasing the communication section between the distribution orifices and the communication ports. Thus, thanks to the notches, the above-mentioned shock effects are avoided, but, thanks to the particular shape of the dispensing orifices, communication is then allowed very quickly, so that the efficiency of the engine is improved.

In FIG. 5, the communication orifice 32A has a substantially circular section, and the aforementioned convex shape of the edges of the orifices of the distributions 121A and 123A is that which makes it possible to increase the communication between the communication orifice as quickly as possible. the distribution orifices, after a first communication via the notches 54A and 54B.

In general, it is advantageous for the leading portion and the separation portion of the dispensing orifices to have shapes which are substantially complementary to the forms which the edges of the communication orifices have through which the communication between the orifices opens or closes. distribution and communication ports.

FIG. 6 shows a dispensing orifice 221A disposed, during the relative rotation of the cylinder block and the distributor, between two communication orifices, respectively 32A and 32'A, while being simultaneously isolated from these two orifices.

In FIG. 6, for the sake of clarity of the drawing, the arcs of circles C1 and C2 have been indicated between which the communication and distribution orifices are delimited. If the relative direction of rotation of the cylinder block and the distributor is such that the cylinder block rotates in the direction RI relative to the distributor, then the notch 254A is disposed on the leading portion Bl of the edge of the orifice distribution 221A, while the notch 254B is disposed on the separation portion B2 of the edge of this orifice. It can be seen that the notches 254A and 254B of the edge arrangements 253A and 253B are arranged at different radial distances from the axis of rotation. More precisely, the distance from the small notch 254A to the axis of rotation of the motor is less than the distance from the large notch 254B to this axis and the angular sector over which the large notch limits the communication between the orifices is larger than the angular sector of the small notch. This allows, during the relative rotation between the distributor cylinder block, to ensure that the period of time during which the distribution orifice 221A communicates with the communication orifice 32A only through the notch 254B is greater than that during which the dispensing orifice communicates with the communication orifice 32'A only through the notch 254A. In addition, the length of the notch 254B, measured tangentially with respect to the axis of rotation of the motor, is greater than that of the notch 254A.

In the example of FIG. 6, the notches 254A and 254B both have substantially the same thickness e, measured along a radius passing through the axis of rotation of the motor.

Figure 7 differs from Figure 6 only in that the notch 254'B of the separation portion B2 of the dispensing orifice 221A is slightly different from the notch 254B. In fact, the notch 254'B of the edge arrangement 253'B has a maximum thickness el, measured along a radius passing through the axis of rotation, which is greater than the thickness e, also measured along a radius. passing through the axis of rotation, of the notch 254A of the edge arrangement 253A. For example, the thickness el is substantially equal to twice the thickness e. Thus, the large notch 254'B forms a larger opening than the small notch 254A.

In FIGS. 6 and 7, the dispensing orifice 221A is oblong, its largest dimension being measured along a radius passing through the axis of rotation. In FIG. 8, the dispensing orifice 321A has, considering that the cylinder block rotates in the direction RI with respect to the cam, a separation portion B2 whose edge arrangement 353B comprises a notch 354B of upper section to that of the notch 354A of the edge arrangement 353A of the leading portion Bl. The separation portion B2 of the dispensing orifice has substantially the shape of an arc of a circle whose center is located at the inside this hole. The notch 354A is for example analogous to the notch 254A of FIGS. 6 and 7. This attack portion Bl has a shape substantially complementary to that of the edge C of the communication orifice 32'A by which the communication between the 'communication port and the distribution port opens when the cylinder block rotates in the direction of rotation RI relative to the distributor. It is also by this edge C that the communication between the distribution orifice and the communication orifice 32'A closes when the cylinder block rotates relative to the distributor in the direction R2 opposite to the sense RI. The leading portion B1 is convex, when viewed from the inside of the dispensing orifice 321A. It has substantially the shape of an arc of a circle capable of covering the arc of a circle formed by the portion C1 of the communication orifice 32'A. Thus, in the direction of rotation RI, the communication between the distribution orifice 321A and the communication orifice 32'A is done first by a very small section, due to the notch 354A, then it increases very quickly due to the shape of the attack portion Bl.

In the opposite direction of rotation R2, it can be seen that due to the shape of the edge B2 only part of the notch 354B will allow communication by a limited section between the orifices 321A and 32A before frank communication is established. between the holes. The section of this part of notch 354B is larger than the section of notch 354A.

Of course, one could equip dispensing orifices having generally the same shape as the orifice 321A with notches similar to any of the notches 54A, 54B, or 254A, 254B previously mentioned.

In FIG. 9, the dispensing orifice 421A generally has the shape of a circle except for its notches. It can be seen that the notches 454A of the edge arrangement 453A of its leading portion B1 and 454B of the edge arrangement 453B of its separation portion B2 (in the direction of rotation RI) are located at different radial distances the axis of rotation of the motor. In FIGS. 6 to 8, the small notch 254A or 354A is substantially situated on an arc of a circle, centered on the axis of rotation of the motor and passing through the geometric centers of the communication orifices 32A and 32'A, while the large notch 254B, 254'B or 354B is located beyond this circular arc, away from the axis of rotation.

In FIG. 9, the “small” cut 454A is the cut of greatest length and is located beyond an arc of a circle A, passing through the geometric centers of the communication orifices 32A and 32′A and centered on the axis of rotation, while the “large” notch 454B is the shortest notch and is situated below this arc of a circle. Notches 454A and 454B have identical sections.

This arrangement of the notch 454A of greater length makes it possible to limit the volume of fluid passing through the notch over the small part of its length in communication with the communication orifice, before frank communication is established with the edge. even from the dispensing opening. This volume limitation is due to the pressure drop generated by the great length of restriction that this notch achieves. The notch 454B of shorter length is used over its entire length on the same angular sector centered on the axis of rotation as that of the limited communication of the long notch 454A with the communication orifice before the open communication with the very edge of the dispensing orifice. The notch 454B therefore allows the passage of a larger volume of pressure compensation.

The advantage of this arrangement is to keep the circular communication and distribution orifices of the standard distributors (without notches) and in addition to make the notches defined for each application as a function of the working pressures, the rotation speeds and the volumes of the working chambers at top and bottom dead centers.

In the example which has just been described, the edges of all the dispensing orifices have notches, respectively on their leading portions and on their separation portions.

In addition, as seen in FIG. 2, the large notches 54B are all the same size, while the small notches 54A are all the same size.

One could choose that only certain dispensing orifices have their edges provided with notches or one could choose that, for certain dispensing orifices, the notches have given dimensions, smaller than those of the notches of other dispensing orifices.

In particular, it has been indicated by describing FIGS. 1 and 2 that the motor shown has two active operating displacements, that is to say a large displacement in which each pair of consecutive dispensing orifices (21A, 23A; 21A, 22A) comprises an orifice (22A or 23A) connected to the fluid supply and an orifice (21A) connected to the fluid exhaust. For the motor of Figure 1, this large displacement is obtained when the selector 42 is in the position shown. The motor also includes a small active operating displacement in which certain pairs of consecutive distribution orifices (21A, 22A) are active and include an orifice (22A) connected to the fluid supply and an orifice (21A) connected to the fluid escape, while other pairs of dispensing orifices (21A, 23A) are inactive and include two orifices placed at the same pressure.

When the engine operates in small active displacement, for the same flow rate of supply fluid, its speed is larger than when operating in large displacement. On the other hand, it delivers a lower torque in small displacement.

The shock or click phenomena mentioned above are even more sensitive when the engine is running at high speed. For this reason, it can be provided that only the edges of the distribution orifices of the active pairs in small displacement have edge arrangements having notches. As previously described, these notches then comprise small notches of the type of the notches 54A and large notches of the type of the notches 54B, according to their respective positions relative to the convex and concave regions of each cam ramp.

Alternatively, provision may be made for the edges of the dispensing orifices of the active pairs in small displacement to have edge arrangements having notched sections larger than those of the edge arrangements of the dispensing orifices of the inactive pairs in small displacement. Thus, the edge arrangements of the distribution orifices of the active pairs in small displacement include a small notch and a large notch respectively arranged in angular correspondence with a convex zone and with a concave zone of the cam, while the edge arrangements of the orifices inactive pairs in small displacement also include a small notch and a large notch respectively located opposite a convex zone and a concave zone of the cam, but these notches of the inactive orifices in small displacement are smaller than those of the orifices active in small displacement.

In the figures described above, each edge arrangement of a dispensing orifice has a single notch and the small or large notched sections are obtained by the choice of a small or a large notch.

In FIG. 10, the edge arrangements 553A and 553B of the dispensing orifice 521A include similar notches but in different numbers. The edge arrangement 553A thus comprises a notch 554A, while the edge arrangement 553B comprises two notches, 554B and 554'B.

The single notch 554A therefore defines, for the arrangement 553A, a smaller notched section than that which, for the arrangement 553B, define the two notches 554B and 554'B.

These notches can be made with the same tool, which is moved appropriately relative to the orifice 521A.

Claims

1. Hydraulic motor with radial pistons comprising a cam (4) and a cylinder block (6) capable of rotating relative to one another about an axis of rotation (10), the cylinder block having radial cylinders (12) connected by cylinder conduits (32) to communication ports (32A) located in a communication face (30) of the cylinder block which is perpendicular to the axis of rotation, pistons (14) slidingly mounted in the cylinders being able to cooperate with the cam (4), the latter having several lobes each having two ramps (50) which each comprise a convex region (51) and a concave region (52), the motor comprising, in further, a fluid distributor (16) having a distribution face (28), which is perpendicular to the axis of rotation and which is capable of being pressed against the communication face (30) of the cylinder block, this face dispenser having dispensing orifices (21A, 22A, 23A) comprising ant orifices suitable for being connected to a fluid supply (24) and orifices suitable for being connected to a fluid exhaust (26), the fluid distributor being integral in rotation with the cam so that a ramp of the cam corresponds to each dispensing orifice, the said dispensing orifices being able to communicate one after the other with the communication orifices during the relative rotation of the cylinder block (6) and of the distributor (16), the edge of each dispensing orifice having a leading portion (B1) through which the communication between the dispensing orifice and the communication orifices opens during the relative rotation between the cylinder block and the distributor in a direction of relative rotation given (RI), as well as a separation portion (B2) by which the communication between the dispensing orifice and the communication orifices is closed during the relative rotation between the cylinder block and the distributor in the same direction of relative rotation (RI), characterized in that the leading portion and the separation portion (Bl,

B2) of the edge of at least some dispensing orifices (21A, 22A, 23A) each have an edge arrangement (53A, 53B; 53'A, 53'B; 253A, 253B; 253'A, 253'B; 353A, 353B; 453A, 453B; 553A, 553B) comprising at least one notch, said edge arrangements of a dispensing orifice being different, the edge arrangement of a dispensing orifice which is arranged in angular correspondence with the convex region (51) of the ramp (50) of the cam (4) corresponding to the distribution orifice (21A) considered being able to allow the passage of a volume of pressure compensation fluid between a communication orifice and the dispensing orifice smaller than the volume of pressure compensating fluid whose edge arrangement of the same dispensing orifice which is arranged in angular correspondence with the concave region (52) of said ramp (50) is capable of allowing passage.

2. Motor according to claim 1, characterized in that, for at least certain distribution orifices (121A, 123A), the leading portion and the separation portion have shapes which are substantially complementary to the shapes which have the edges of the orifices of communication (32A) through which the communication between the distribution ports and the communication ports opens or closes.

3. Motor according to claim 2, characterized in that, for each distribution orifice (121A, 123A), the leading portion and the separation portion (Bl, B2) are generally convex, seen from the interior of the 'orifice.

4. Hydraulic motor according to any one of claims 1 to 3, characterized in that the edge arrangement (253A; 353A; 453A; 553A) of the leading portion (Bl) of at least one dispensing orifice (221A; 321A; 421A; 521A) has at least one notch (254A; 354A; 454A; 554A) which, relative to a notch (254B; 254'B; 354B; 454B; 554B) of the edge arrangement ( 253B; 353B; 453B; 553B) of the separation portion (B2) of the edge of said dispensing orifice is arranged at a radial distance different from the axis of rotation.

5. Motor according to claim 4, characterized in that, for the edge arrangements of at least one distribution orifice (221A; 321A; 421A), the distance from a short notch (254A; 354A; 454B) the axis of rotation is less than the distance of a very long notch (254B; 254'B; 354B; 454B) from the axis of rotation.

6. Engine according to any one of claims 1 to 5, characterized in that, for at least one distribution orifice (21A; 123A; 221A; 321A), the on-board arrangement (53B; 53'B;253B;253'B; 353B) which is arranged in angular correspondence with the concave region (52) of said ramp (50) comprises at least one notch (54B; 254B; 254'B; 354B) which extends over an angular sector ( α2) measured between two radii starting from the axis of rotation (10), which is larger than the angular sector (α3), measured in the same way, over which the notch (54A; 254A; 354A) extends who is arranged in angular correspondence with the convex region (51) of the ramp (50).

7. Engine according to any one of claims 1 to 6, characterized in that, for at least one distribution orifice, the edge arrangement (253'B; 353B; 553B) which is arranged in angular correspondence with the region concave (52) of said ramp (50) has a notched section larger than that of the edge arrangement (253A; 353A; 553A) which is arranged in angular correspondence with the convex region (51) of the ramp (50) .

8. Engine according to any one of claims 1 to 7, characterized in that, the on-board arrangements (53A; 53B; 253A; 253B; 253'A; 253'B; 353A; 353B; 453A; 453B) d ' at least one dispensing orifice each have the same number of notches, the notch or notches of one of these edge arrangements being different from that of the other edge arrangement.

9. Motor according to any one of claims 1 to 7, characterized in that the edge arrangements (553A; 553B) of at least one distribution orifice (521A) each have similar notches, the number of notches ( 554A) of one of these edge arrangements (553A) being different from the number of notches (554B, 554'B) of the other edge arrangement (553B).

10. Motor according to any one of claims 1 to 9, characterized in that two adjacent ramps (50, 50 '; 50, 50 ") of the cam are connected together either by a cam top region (56) extending between their respective convex regions (51), either by a cam bottom region (58) extending between their respective concave regions (52), in that said cam crown and cam bottom regions are substantially arcs of circles centered on the axis of rotation, so that when the pistons cooperate with said zones, their radial strokes are substantially zero and in that the distribution orifices (21A, 22A, 23A) and the orifices communication (32A) have dimensions such that, during the relative rotation of the cylinder block (6) and the distributor (16), each distribution orifice remains temporarily isolated from any communication orifice.

11. Motor according to claim 10, characterized in that the cam top zones (56) extend over angular sectors (α'2 + α'2), each measured between two radii starting from the axis of rotation. (10), which are lower than the angular sectors ('1 + α'1), measured in the same way, over which the cam bottom zones (58) extend.

12. Motor according to any one of claims 1 to 11, having two active operating displacements, ie a large displacement in which each pair of consecutive distribution orifices (21A, 22A; 21A, 23A) comprises an orifice (22A, 23A) connected to the fluid supply (26) and an orifice (21A) connected to the fluid exhaust (24), as well as a small displacement in which certain pairs (21A, 22A) of consecutive distribution orifices are active and include an orifice (22A) connected to the fluid supply (26) and an orifice (21A) connected to the fluid exhaust (24), while other pairs of distribution orifices are inactive and comprise two orifices (21A, 23A) put at the same pressure, characterized in that only the edges of the distribution orifices of the active pairs in small displacement have notches.

13. Motor according to any one of claims 1 to 11, having two active operating displacements, ie a large displacement in which each pair of consecutive distribution orifices (21A, 22A; 21A, 23A) comprises an orifice (22A, 23A) connected to the fluid supply (26) and an orifice connected to the fluid exhaust (24), as well as a small displacement in which certain pairs (21A, 22A) of consecutive distribution orifices are active and include an orifice (21A) connected to the fluid supply (26) and an orifice (21A) connected to the fluid outlet (24), while other pairs of dispensing orifices are inactive and include two orifices (21A, 23A) put at the same pressure, characterized in that the edges of the distribution orifices of the active pairs in small displacement have edge arrangements having notched sections larger than those of the edge arrangements of the distribution orifices use of inactive pairs in small displacement.