A hydraulic machine including a stack of disks acted upon by a push rod

Abstract

The hydraulic machine comprises a fixed part; a part mounted for rotation about an axis (OO) relative to the fixed part; and a stack (50) of discs (53, 54) forming a brake or clutch, the discs having a mean radius of friction (R f a push rod (80) that can press the disks against each other in a direction parallel to the axis on a thrust surface (4), the thrust surface having a mean thrust radius (R p ) and the mean friction radius (R f ) or within the average friction radius (R f The push rod (80) extends beyond a mean thrust radius (R p ) is the average friction radius (R f ), which recesses the push rod from the side of the push rod closest to the axis (OO), and from the opposite side of the push rod from the axis (OO) otherwise.

Description

Technical Field

[0001] The present invention relates to a hydraulic machine, and more particularly, but not limited to, a hydraulic machine having a radial piston.

Background Art

[0002] Already many types of hydraulic machines have been proposed. An embodiment of this type of machine is reproduced and shown in FIGS. 1 and 2. The machine essentially includes five assemblies, namely a housing 10, a shaft 20, an assembly 30 forming a motor or a pump disposed between the housing and the shaft, bearings or rolling element bearings 42, 43 for guiding the shaft rotating with respect to the housing, and a brake 49.

[0003] The housing 10 is intended to be attached to the chassis of a machine or a vehicle. The housing includes a cam 12 having a plurality of lobes sandwiched between two side elements of the housing.

[0004] The shaft 20 supports an accessory, such as a wheel rim or any other machine, which must be rotationally driven when the machine constitutes a motor and supplies driving torque to the motor. When the machine constitutes a pump, the power take-off receives the motor torque of the driving machine applied to the inlet of the machine.

[0005] The assembly 30 forming the motor or pump has a radial piston. The assembly includes a distributor 32 and a cylinder block 34 including a plurality of radial cylinders 35, each cylinder housing a piston 36 and each cylinder carrying a roller 38 that abuts a cam 12 integral with the housing. When the distributor 32 periodically supplies fluid under pressure inside the cylinder 35, the force acting on the piston 36 and the associated roller 38 on the cam 12 rotates the cylinder block 34 relative to the cam and, as a result, relative to the housing 10.

[0006] The cylinder block 43 is rotationally connected to the central element 22 of the shaft, in which case the shaft is driven to rotate by the fluid pressure applied by the distributor. In that case, the hydraulic machine constitutes a motor.

[0007] Conversely, when machine force is applied to the shaft 20 by a power take-off device in the direction of rotationally driving the housing 10, the movement of the roller and the movement of the piston relative to the cam lobe induce a change in the volume of the cylinder, resulting in fluid pressure being applied to the distributor. In that case, the machine functions as a pump.

[0008] Since this machine is reversible, it operates equivalently as a pump or a motor and can also rotate in both directions. Therefore, this type of hydraulic machine can be found in four different situations defining four quadrants of values of pressure and flow direction: forward movement of traction or holding, and backward movement of traction or holding.

[0009] The brake 49 is formed from a stack of disks connected to rotate alternately, some connected to the shaft and others to the housing. The disks abut each other by elastic elements 56 such as Belleville washers and thus act in the braking position.

[0010] This member 56 is arranged between, on the one hand, an element of the housing and, on the other hand, a longitudinal piston 51 which abuts against a stack of disks. In order to position the brake in the de-braking position, a force can be applied in a control chamber 58 arranged between the stack of disks and the piston, against the elastic member.

[0011] What needs to be considered here is, necessarily, an explanation associated with the rubbing or friction surface of the disk. This is the surface of the disk where the disks come into contact with each other and generate the friction that causes braking. Therefore, its rubbing or friction surface needs to be distinguished from the surface of the disk that does not provide this friction. The thrust surface is also considered, and the thrust surface is the surface of the longitudinal piston 51 and the first disk of the stack where these two members (piston 51 and the first disk of the stack) come into contact with each other for the transmission of the thrust force.

[0012] In many machines, the friction surface and the thrust surface do not coincide when considered as respective surfaces perpendicular to the axis. In other words, they are not locally centered relative to each other (although the longitudinal piston and the disk are coaxial). This is, for example, a situation where the friction surface is radially offset on the side opposite the shaft with respect to the thrust surface. In some cases, the opposite is confirmed. In other words, this is a situation where the respective radial positions of the friction surface and the thrust surface do not coincide, and the friction surface can be arranged higher radially than the thrust surface, and vice versa.

[0013] In both cases, it means that the thrust of the piston is not applied to align the position of the largest part of the friction surface, or is not properly centered locally with respect to the friction surface. As a result, the thrust is not optimally transmitted to the disc, and a non-uniform contact pressure occurs on the friction surface. As a result, the thrust is not sufficiently dispersed within the disc and becomes very high especially at specific locations. A possible consequence is that there is a tendency for excessive torque or seizure to occur. Excessive torque is defined as the temporary provision of additional torque, but its strength cannot be predicted. In that case, for example, a significant torque difference may occur between two brakes attached to the same axle, and the machine may become unstable during braking operation. It can also be confirmed that vibrations appear. If an attempt is made to compensate for this, the dimensions of a series of components through which the brake torque passes become too large. For example, the discs forming the brake need to be made thicker in order to pass this additional torque in the spline connection between these discs and their respective facing parts. However, these two situations need to be avoided. As an example, brakes using nitride discs are particularly subject to excessive torque. SUMMARY OF THE INVENTION

[0014] One object of the present invention is to avoid excessive dimensions of the components of the brake torque transmission chain (in particular, to avoid increasing the thickness of the discs, their diameters, and the number of their splines), and to avoid the risk of excessive torque or seizure of the machine.

[0015] For this purpose, a hydraulic machine is provided, which comprises a fixed part; a part rotatably mounted about an axis relative to the fixed part; a stack of disks forming a brake or a clutch, the disks being able to abut against each other by friction surfaces having an average friction radius measured from the axis; a push rod able to press the disks against each other and into abutment in a direction parallel to the axis on a thrust surface, the thrust surface having an average thrust radius measured from the axis and extending within or beyond the average friction radius, the push rod having a radial annular notch (90) that recesses the push rod from the side of the push rod opposite the axis when the average thrust radius extends beyond the average friction radius and otherwise recesses the push rod from the side of the push rod closest to the axis.

[0016] In other words, the notch is located on the side of the gap between the location where the thrust acts and the line of the average radius of the friction surface of the disk. Thus, when there is an offset between the friction surface and the thrust surface, the notch makes it possible to bend the push rod in order to return the thrust force to the center of the friction surface. As a result, the thrust force is applied more orthogonally to the friction surface. For example, when the pressure is too high on the side closest to the outside of the stack of disks, the presence of the notch can relieve this part. Thus, the pressure is more evenly distributed. Thus, the absence of a strong contact pressure avoids the occurrence of a lubrication state called "dry", i.e., a state in which excessive torque occurs. The braking operation is improved and becomes more regular. Furthermore, it is not necessary to make the dimensions of the transmission components of the brake torque chain excessively large. In summary, the present invention enables better distribution of the thrust force with respect to the stack of disks in order to avoid the phenomena of seizure and excessive torque. Furthermore, this solution implements a single part instead of a plurality of parts movable relative to each other, simplifies assembly and manufacturing, and in particular reduces the risk of forgetting parts during the assembly of the machine.

[0017] It can be confirmed that the notch extends to a part of the push rod that transmits the pressing force to the disk.

[0018] It is possible for the bottom of the notch to extend adjacent to the thrust surface. In other words, the radius of the notch at the bottom of the notch is included between the smaller radius and the larger radius of the thrust surface.

[0019] It is possible for the bottom of the notch to extend adjacent to the friction surface. In other words, the radius of the notch at the bottom of the notch is included between the smaller radius and the larger radius of the friction surface.

[0020] The machine is configured such that the member exerts a braking force on the push rod across a receiving zone having an average receiving radius measured from the axis, and the receiving zone extends beyond the average thrust radius when the average thrust radius extends beyond the average friction radius, and otherwise extends within its average friction radius.

[0021] The receiving zone can be made to have a smaller radius that extends beyond the larger radius of the thrust surface or the friction surface when the average thrust radius extends beyond the average friction radius, and otherwise extends within the larger radius.

[0022] The receiving zone can be made to have a smaller radius that extends beyond the smaller radius of the notch when the average thrust radius extends beyond the average friction radius, and otherwise extends within the smaller radius.

[0023] The push rod can be made to have a radius larger than the larger radius of the friction surface.

[0024] In this configuration, the push rod has a dimension that exceeds the friction surface of the stack of disks when viewed from the axial direction of the machine. The radius of the push rod has a radius outside the friction surface.

[0025] Preferably, the notch is dimensioned such that the average friction radius is included between the larger radius and the smaller radius of the notch.

[0026] Thus, the notch extends until it is orthogonal to the average radius of the friction surface.

[0027] It is possible for the larger radius of the friction surface to be greater than the smaller radius of the notch, or for the smaller radius of the friction surface to be smaller than the larger radius of the notch.

[0028] It is possible to configure the machine such that at least a part of the push rod gradually bends as the pressing force of the push rod against the stack increases.

[0029] Thus, this bending can reduce the contact pressure in the zone of the thrust surface that is not centered with respect to the friction surface. This part of the push rod can be the part closest to the stack or the part farthest from the stack.

[0030] In one embodiment, a part of the push rod has an axial dimension that decreases in the direction of the free end of this part.

[0031] This configuration makes it possible to control the deformation of this deformable part of the push rod and thus control the distribution of the contact pressure.

[0032] This part of the push rod can be the part closest to the stack or the part farthest from the stack.

[0033] It is possible to provide a notch having two main faces facing each other, and one of these main faces is inclined in the direction outside the push rod.

[0034] This inclined surface acts favorably on the bending of the push rod. Furthermore, by simplifying access to the bottom of the notch, machining can be facilitated as needed.

[0035] Advantageously, the inclined surface extends from one side of the notch closest to the stack.

[0036] This configuration constitutes a means of generating a deformable portion of the push rod while still controlling deformation and the generation of contact pressure.

[0037] It is possible for the push rod to have a push rod guide surface axially with respect to the support.

[0038] Preferably, the guide surface extends completely from one side of the notch furthest from the stack.

[0039] In this way, there is no interference between the zone assigned to deform upon pushing in the push rod and the zone functioning as a guide.

[0040] The machine can be made to include a calibrated spring that can press the push rod against the stack.

[0041] What this means is that, in the absence of other loads, the spring supplies a constant braking load. Next, the dimensions of the notch can be determined according to the strength of this spring to obtain a desired stress distribution. In this way, the bending dimensioning of that part can be carried out as needed.

[0042] The machine can further include at least any of the following functions. It includes a spring that can press the push rod against the stack and a brake release chamber arranged to apply a force against the brake to the spring by hydraulic pressure in the chamber. The stack is in an oil bath. The disc is made of nitrided steel. The disk includes a lining of friction material. The lining has grooves. The stack forms a brake or a clutch.

[0043] Thus, the grooves help to pass oil if necessary.

[0044] The brake can provide at least one function of a motor, an emergency brake, a safety brake (to prevent the machine from moving by the brake when the machine fails), and a parking brake if necessary.

Brief Description of the Drawings

[0045] Here, referring to the drawings, embodiments of the present invention are presented as non-limiting examples.

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Modes for Carrying Out the Invention

[0046] Similar to the machines of FIGS. 1 and 2, the hydraulic machine 2 according to the present embodiment of the machines shown in FIGS. 3 and 4 is centered on the axis O-O and essentially has five complementary assemblies, namely the housing 10, the shaft 20, an assembly forming a motor or a pump (not shown) positioned between the housing 10 and the shaft 20, means (not shown) forming bearings for guiding the shaft 20 relative to the housing 10 in relative rotation, and a brake 49.

[0047] The housing 10 is intended to be attached to the chassis of a machine or a vehicle. The housing includes a cam having a plurality of lobes (not shown) sandwiched between two side elements of the housing.

[0048] The shaft 20 supports accessories that must be rotationally driven if the machine constitutes a motor, such as the rim of a wheel or a power take-off device suitable for carrying any other machine. When the machine constitutes a pump, the power take-off device receives the motor torque of the machine applied to the inlet of the machine.

[0049] The assembly forming the motor or the pump has radial pistons. The assembly essentially includes a distributor and a cylinder block including radial cylinders, each cylinder accommodating a piston, and each cylinder carrying a roller that abuts against a cam integral with the housing. The number of cylinders, that is, the number of pistons in the cylinder block, is different from the number of lobes of the cam. Similar to the machines of FIGS. 1 and 2, the cam is radially outward, and the cylinder block positioned radially inward of the cam has cylinders that open radially outward and face the cam. The distributor is provided via elements forming a cover and a connector for supplying the distributor.

[0050] In a known manner, when a distributor periodically applies fluid under pressure inside a cylinder, the load on the piston and the associated roller on the cam causes the cylinder block to rotate relative to the cam, and as a result, to rotate relative to the housing. The cylinder block is connected to rotate with the central element of the shaft 20 by means of a longitudinal spline system, and the shaft is driven to rotate by the pressure of the fluid. In this case, the machine constitutes a motor. Conversely, when a machine force is applied to the shaft 20 by a power take-off device in the direction of rotation driving relative to the housing 10, the movement of the roller and the movement of the piston relative to the lobe of the cam induce a change in the volume of the cylinder, and as a result, a fluid pressure is applied to the distributor. In that case, the machine functions as a pump. Thus, since this machine is reversible, it functions equally as a pump or a motor and can rotate in two directions.

[0051] In order to limit the axial volume of the machine, the power take-off device can be provided outside the radially outer element, as in the case of FIG. 3. According to a variant embodiment, the power take-off device is arranged transversely with respect to the O - O axis and axially with respect to the disk, as in the case of FIG. 1.

[0052] The fixed part associated with the housing 10 and the rotating part including the shaft 20 are shown in FIG. 3. The means for forming bearings (not shown) includes two rolling element bearings having rollers sandwiched between the shaft 20 and the housing 10.

[0053] The shaft 20 has a central zone or hub 22 delimited by the axis O - O and a cylindrical extension 24 remote from the axis, and the extension forms a ring gear and is connected to the central zone by a connecting disk 16.

[0054] The housing 10 has a cylindrical axial extension 11.

[0055] The brake 49 is of the disc brake type. The brake is formed from a stack of discs 52, 54 connected to rotate alternately, some being connected to the shaft 20 and others to the housing 10. Thus, the discs are spatially alternately connected to the fixed part 10 and the rotating part 20 along the longitudinal axis O - O.

[0056] Each of the discs 52, 54 is formed by a washer. The connection of these discs to the housing and the shaft during rotation can be formed, for example, by engaging ribs provided on the outer radius or alternatively on the inner circumference of the discs 52, 54 with complementary splines or grooves formed facing these discs 52, 54 on the ring gear 24 of the shaft and the extension 11 of the respective associated housing. As a variant, it is possible to provide an intermediate part for the connection during rotation, sandwiched between one of the discs 52 or 54 and one of the housing 10 or the shaft 20.

[0057] This machine has a brake chamber 55 arranged axially opposite the cylinder block with respect to the stack of discs. Thus, in Figure 3, the chamber is arranged on the right side of this stack. In this case, the brake 49 is arranged axially at the end of the machine adjacent to the power take - off device, i.e., near the power take - off device, on the side opposite the distributor with respect to the cylinder block.

[0058] Here, "proximal" refers to the part of the brake part 49 facing towards the assembly forming the motor or the pump and thus directed towards the left side in Figure 3, and "distal" refers to the part on the right side of the figure, facing away from this assembly and towards the outside of the machine.

[0059] Furthermore, the brake chamber 55 is radially sandwiched between the central zone 22 of the shaft 20 and the ring gear 24, similar to the axial extension 11 of the housing 10. In this case.

[0060] Here too, the stack 50 of disks is arranged between two axially abutting parts. One is similar to the abutting part 17 in FIG. 1 and is not shown in FIG. 3. The other is the push rod 80, which will be described later. The disks arranged alternately abut against each other, for example, by elastic elements 56 of the Belleville washer type and thus act in the braking position. In this case, the Belleville washer has a concave surface facing the stack 50. The washer preferably abuts against the longitudinal annular piston 51 acting on the stack 50 during the braking operation at its radially outer periphery according to the illustrated embodiment.

[0061] A stop ring 85 received in the annular recess of the extension 11 and a wedge 89 axially sandwiched therebetween are associated with the spring 56 on the side of the spring opposite to the piston in the axial direction. The ring and the wedge ensure an axial block (stop) of the edge of the spring closest to the axis O - O.

[0062] To place the brake 49 in the released position, a force opposing the elastic member 56 can be applied to a control or release chamber 58 located between the stack of disks 50 and the longitudinal piston 51. The piston 51 defining the release chamber 58 is movable by sliding along the axis O - O with respect to the housing 10.

[0063] The piston includes a portion that forms a cylindrical sheath 62 axially sandwiched between a stack of disks 50 and a spring 56. The sheath 62 is extended by a portion in the form of a washer 64 that crosses the axis O-O and is associated with a gasket 68 regarding the extension 11, and constitutes the wall of the brake release chamber 58. The sheath 62 functions as a load element adjacent to the stack of disks 52, 54 at its proximal end. The parts 62 and 64 are assembled with each other in a tightly sealed manner, for example, by screwing and by incorporating static sealing means such as seals, or are related to a single block as shown. Thus, the piston 51 has an "L"-shaped half-section with a lateral branch 64 with respect to the axis and a longitudinal branch (corresponding to the sheath 62) parallel to this axis. Thus, when pressure is applied to the brake release chamber 58 and the chamber expands, the piston 51 can apply a force against the brake to the spring 56. Other modes of positioning and cooperation between the piston 51 and the spring 56 are possible.

[0064] This machine includes a ring 70 arranged between the stack of disks 50 and the washer 64 of the piston and lateral to the axis O-O. The ring 70 forms one of the transverse walls of the brake release chamber 58. The ring 70 is radially accommodated between the sheath 62 and the extension 11 facing this sheath, and has a radial dimension smaller than the clearance for sliding with respect to the piston 51, that is, the radial gap existing between these parts, enabling at least a slight axial relative movement between the ring 70 and the piston 51. The ring 70 is associated with two seals 72, 74, and these seals cooperate with the piston 51 and the housing element 11 respectively. The sheath portion 62 can slide with respect to the ring 70.

[0065] Thus, the brake release chamber 58 has an annular shape and is axially delimited by the piston washer 64 and the ring 70, and radially delimited by the sheath 62 and the extension 11.

[0066] The brake release chamber 58 is closed by three seals 68, 72, and 74.

[0067] The seal 68 associated with the piston 51 is of the type called "joint D-ring" conforming to the standard DIN 11850, including a semi-circular face and a flat face. The seal is preferably received in a groove of complementary width formed in the washer 64 or formed as a deformation of the housing element 11 facing the washer. The flat face of the seal 68 is disposed at the bottom of the groove. Its semi-circular face bears against a facing element that can move relatively along the axis O-O.

[0068] In this case, the seal 72 providing a seal between the ring 70 and the piston 51 is of the same type.

[0069] The seal 74 providing a seal between the ring 70 and the housing element 11 facing this ring is preferably an O-ring seal or a "D-ring" D-shaped ring. When placing the seal on the washer 70 as shown in the figure, using a D-ring enables proper handling of the seal during assembly.

[0070] The brake release chamber 58 is provided by at least one channel 13 that is at least partially longitudinal and formed in the extension 11 of the housing for opening into the chamber 58. Without being limited thereto, the channel 13 can open, for example, at a step formed around the longitudinal extension 11 as shown in FIG. 3. The channel 13 is connected to the brake release control line of the hydraulic machine.

[0071] The push rod 80 is axially sandwiched between the stack of disks 50 and the ring 70.

[0072] Thus, the machine is, here, in the axial longitudinal direction, from proximal to distal, in particular, a stack of disks 50, A push rod 80 that directly abuts axially against the first disk of the stack, A ring 70 that directly abuts axially against the push rod 80, A sheath 62 that itself also abuts axially against the push rod 80 around the ring 70, A brake release chamber 58, A washer 64 of the piston 51, A spring 56, A wedge 89, and A stop ring 85 are included.

[0073] The wedge 87 is axially sandwiched between the shoulder of the extension 11 of the housing and the portion of the ring 70 closest to the axis.

[0074] At rest, the spring 56 acts on the sheath 62 and the push rod 80, axially abutting against the stack of disks 52, 54, and thus acting on the disks to cause them to abut against each other. At this time, the brake 49 is in the brake position. The shaft 20 is firmly fixed to the housing 10.

[0075] On the other hand, assuming that fluid pressure is applied into the brake release chamber 58 and an axial force is generated that counteracts the spring 56 and is greater than the braking force generated by the spring 56. Since the axial abutment 87 restricts the movement of the ring 70, the increase in the volume of the brake release chamber leads to the movement of the piston 51 in the direction of the spring 56, and thus, between the piston 51 and the wedge 89, it leads to a decrease in the free space of the spring 56, and therefore, invalidates the force exerted by the spring 56 on the stack of disks 52, 54 in the brake position. That force does not act when they abut against each other, and the brake is placed in the brake release position. The shaft can rotate relative to the housing.

[0076] Before describing the details of the push rod 80, it is important to emphasize that the general configuration of the presented machine is given as an example and that a very large number of other configurations are possible. Thus, this configuration of the machine and its various features are not relevant to the present invention. These belong only to this embodiment. For example, the present invention is compatible with the general configuration of the prior art machines of FIGS. 1 and 2.

[0077] Referring particularly to FIGS. 3 and 4, the wedge 80 has a generally annular shape. The wedge has a flat front annular proximal surface 82 that is orthogonal to the axis O-O and can contact the first disk 54 of the stack in the axial direction. On the other hand, at this surface, an annular thrust zone 84 that can effectively contact this disk and an inert or inactive zone 86 that does not contact this disk when the thrust zone is in contact are distinguished. It can be seen that the thrust zone 84 faces the disk, unlike the inert zone 86.

[0078] The thrust zone 84 has an average radius R measured with respect to the axis p This average is calculated, for example, as the arithmetic mean of the radius at the very end of the thrust zone, i.e., the minimum R m and the maximum R1. Other calculation means are possible, for example, by taking into account the integral of the radius of the thrust zone.

[0079] The disks 52, 54 can be abutted against each other by friction surfaces. Thus, similarly, an annular friction zone 88 that can effectively contact an adjacent disk in the braking position and an inert or inactive zone 79 that does not contact this disk in the braking position can be distinguished on each disk. The friction zone 88 is arranged facing the adjacent disk, unlike the inert zone 79.

[0080] The friction zone 88 has an average radius R with respect to the axis fIt has this. Here too, the average is calculated, for example, as the arithmetic mean of the radius at the very end of the friction zone, that is, the minimum R2 and the maximum R1. For example, other calculation modes are possible by considering the integral of the radius of the zone.

[0081] The disks 52 that directly engage with the ring gear 24 are identical to each other. Similarly, the disks 54 that directly engage with the housing 10 are identical to each other. Since the friction zones 88 of all the disks are axially aligned, the average radius R f is the same throughout the stack.

[0082] In the configuration shown in FIG. 3, the average thrust radius R p extends beyond the average friction radius R f That is to say, the average thrust radius is larger than the average friction radius. This means that the thrust zone 84 of the push rod 80 is displaced in the radial direction opposite to the axis O - O with respect to the friction zone 88.

[0083] Here, the push rod 80 has a larger radius R M measured at the rear surface in contact with the sheath and the cylindrical surface outside it, and it is also possible to confirm that the radius R M is larger than the larger radius R1 of the friction surface 88. Here, the front surface 82 of the push rod has a larger radius R a that is larger than the larger radius R1 of the friction surface 88. Its front surface further has a smaller radius R m that is larger than the smaller radius R2 of the friction surface 88.

[0084] The push rod 80 has an annular radial notch 90 that recesses the push rod from the circumferential side of the push rod on the side opposite to the axis O - O, considering that the average thrust radius R p here extends beyond the average friction radius R f This notch has a substantially annular shape and extends substantially along a plane perpendicular to the axis. The notch 90 extends to a part of the push rod that transmits the thrust to the disk.

[0085] Here, the notch has a "U"-shaped profile in the circumferential direction and has two main surfaces 91, 92 facing each other. The rear surface 92 is flat and orthogonal to the axis.

[0086] The notch extends, for example, over at least half of the total thickness of the push rod measured in the radial direction. However, the notch may also exceed 2 / 3, and even 3 / 4 of this dimension, and can take any value included between these limits, including the limits.

[0087] In this case, the notch 90 has an average friction radius R f which is dimensioned to be included between the larger radius R a of the notch and the smaller radius R e of the notch. Thus, the bottom of the notch extends here to the end of the average friction radius R f and moves radially towards the axis slightly beyond that end.

[0088] Thus, the notch 90 delimits a front portion 81 of the push rod 80 that can contact the stack 50 and a rear portion 83 that cannot contact the stack and, in the current configuration, can contact the ring 70.

[0089] The bottom of the notch 90 extends adjacent to the thrust zone 84 with respect to the axis. In other words, the radius R e of the notch at the bottom of the notch is included between the smaller radius R M of the thrust zone 84 and the larger radius R1 of the thrust zone.

[0090] The bottom of the notch extends adjacent to the friction surface 88. In other words, the radius R e of the notch at the bottom of the notch is included between the smaller radius R2 of the friction surface 88 and the larger radius R1 of the friction surface. In particular, the larger radius R1 of the friction surface 88 is larger than the smaller radius of the notch.

[0091] The radius R MIn this case, the radius R of its front part 81 a is larger. Here in particular, the sheath 62 applies an axial pressure to the part of the rear part 83, and the rear part 83 has a larger radius and there is no opposing part to the front part 81 of the push rod.

[0092] The machine is configured such that, as shown in FIG. 3, the sheath 62 exerts a braking force on the push rod 80 across the receiving zone 78 of the push rod having an average receiving radius Rr measured from the axis. This radius, as in this case, is such that when the average thrust radius R p extends beyond the average friction radius R f , the average thrust radius R p is larger.

[0093] In this case, the receiving zone 78 has a smaller radius R that is larger than the smaller of the larger radii R1 of the thrust surface or the friction surface. This smaller radius R c is larger than the smaller radius R of the notch measured at the bottom of the notch c e e is larger.

[0094] Like most parts, the push rod 80 is made of metal. The notch 90 gives the possibility of bending in order to approach the free end of the front part 81 in the direction of the rear part 83 and / or to approach the free end of the rear part in the direction of the front part. This bending occurs when the push rod is in contact with the stack 50 in the braking position. This bending is shown in a very exaggerated way by the solid line compared to the non-bent configuration shown by the dotted line in FIG. 5. This figure shows, as an example, the case where the free end of the front part 81 approaches the rear part 83, and it is understood that not only the combination of the two movements is possible, but also the reverse.

[0095] In the example of bending shown in Fig. 5, when bending occurs, the portion of the front part 81 closest to its free end bends first and bends more than the remaining portion of this front part. This bending can reduce the contact pressure of a part of the contact surface. Also, the contact pressure can be dispersed in a determined manner. Therefore, the thrust surface 84 in contact with the disk stack 50 tends to be reduced to bring it to the portion of that thrust surface closest to the axis O-O. In particular, the pressing force (trust) applied to the stack by the push rod 80 tends to concentrate on the portion of the thrust surface 84 closest to the axis so as to better match the friction surface 88. Therefore, this dispersion of the load compensates for the difference between the average thrust radius R p and the friction radius R f .

[0096] This bending shows the influence of the notch 90, causes weakening of the push rod 80, and tends to return the eccentric force to RM around the radius R e . Next, force diffusion occurs concentrating on R e and towards the surface 84. This diffusion is a function of the thickness of the front part 81 indicated by e. This accurately determined thickness ensures the diffusion of the pressing force F in as uniform a manner as possible.

[0097] Ideally, the contact surfaces 82 and 88 are congruent. That is, R m = R2; R a = R1, and thus R f = R p .

[0098] The push rod 80 has a guide surface 96 here for axially sliding the push rod with respect to the support formed by the shoulder 98 of the ring 70. For this purpose, the ring has a cylindrical surface 100 that achieves the surface in contact with the surface 96. The guide surface 96 ensures the centering of the push rod in the machine.

[0099] As shown in FIG. 4, the guide surface 96 extends completely from one side of the notch 90 farthest from the stack, i.e., the rear distal portion 83. Thus, in the situation of the brake, the risk of interference with the guiding function during thrust (pressing) and bending is avoided. In FIGS. 3 and 5, the push rod is shown without showing this feature.

[0100] The contact pressure is transmitted from the piston 51 to the stack only by the push rod 80, and it is confirmed that the push rod 80 constitutes a rigid assembly that can be formed as a single part.

[0101] As a variant, in the opposite situation, the thrust surface 84 has an average thrust radius R f with respect to the axis extending therein. In other words, the average thrust radius is smaller than the average friction radius. This means that the thrust zone of the push rod 80 is axially offset with respect to the friction zone 88. p Furthermore, independently of this aspect, it is confirmed in FIG. 4 that one of the main surfaces 91 of the notch 90 is inclined so as to face in the direction outside the push rod. Here, this inclined portion is the front proximal surface and is thus located at the portion 81 on the side of the stack 50. This inclined portion facilitates access to the bottom of the notch, especially during the manufacture of the notch by machining.

[0102] Regarding the surface extending to the side closest to the stack of the notch, since the thrust surface 84 is flat, the proximal portion 81 of the push rod closest to the stack has an axial dimension e, and this axial dimension e decreases in the direction of the free end of this portion. In FIG. 4, this dimension is shown exaggerated. With this configuration, in this example, the part 81 gradually bends as the pressure of the push rod against the stack increases. Thus, with this configuration, the amplitude of bending can be well controlled as a function of the thrust force.

[0103]

[0104] ​However, other portions 83 of the push rod can be given a similar shape, and the same characteristics can be obtained in these other portions, either in combination with or without combination with this configuration of the proximity portion 81.

[0105] Therefore, the push rod 80 forming the wedge portion has a shape optimized for the diffusion and distribution of the contact pressure to the stack of disks.

[0106] This is shown by FIGS. 6 and 7 showing the digital simulation of the force distribution within the machine. In this simulation, only the sheath 62, the push rod 80, the stack 50 shown here as a single block, and the wedge 17 located on the opposite side of the stack are considered. Here, the push rod 80 has the same configuration as that in FIG. 3, and the notch 90 recesses the push rod from the side farthest from the axis.

[0107] The two figures show the force distribution within the stack of disks. It can be seen that this distribution is good. In fact, the pressure generated at the contact interface between the sheath 62 and the push rod 80 is close to 6 MPa. This is the same pressure value seen from the bottom of the notch 90 to the contact interface with the stack 50 throughout the central portion of the push rod 80. On the one hand, inside the stack, the local pressure rapidly decreases as it moves away from the push rod and reaches a value of 3 - 4 MPa or less. Therefore, in this example, the pressure generated on the side of the sheath decreases by only 2 MPa when transmitted to the stack. Furthermore, the average pressure measured inside the stack remains relatively constant. Therefore, a good compromise is achieved between, on the one hand, the distribution of the contact pressure within the stack of disks and, on the other hand, the mechanical resistance of the push rod and the constraints of machine processing.

[0108] The stack of disks 50 is in a lubricating oil and a cooling bath. The disks are made of, for example, steel nitride. The disks can be equipped with a lining of friction material, and the lining is provided with grooves, for example, to allow the passage of oil between the disks. Thus, the disks can include perforations or through grooves for the same reason.

[0109] Of course, numerous modifications can be made to the present invention without departing from the scope of the present invention.

[0110] For example, the stack of disks can function as a clutch of a rotating machine.

[0111] The guidance of the push rod 80 can be performed by the surface of the push rod facing in the direction opposite to the axis.

Claims

1. A hydraulic machine (2), the hydraulic machine comprising: A fixed part (10), A part (20) rotatably attached around an axis (O - O) with respect to the fixed part, and A stack (50) of disks (52, 54) forming a brake or a clutch, the disks being able to abut against each other by friction surfaces (88) having an average friction radius (R ｆ ) measured from the axis, the stack, A push rod (80) capable of pressing and abutting the disks against each other in a direction parallel to the axis on the thrust surface (84), wherein the thrust surface (84) has an average thrust radius (R measured from the axis ｐ ), and a push rod extending within or beyond the average friction radius (R ｆ ), including the average friction radius (R ｆ ), The push rod (80) is concave from the side of the push rod on the side opposite to the axis (O - O) when the average thrust radius (R ｐ ) extends beyond the average friction radius (R ｆ ), and has a radial annular notch (90) that concaves the push rod from the side of the push rod closest to the axis in other cases. A hydraulic machine.

2. The push rod (80) has a radius (R １ ) larger than the larger radius of the friction surfaces (R ａ , R Ｍ ), the hydraulic machine according to claim 1.

3. The annular notch (90) has the average friction radius (R ｆ ) that is dimensioned to be included between the larger radius (R ａ ) and the smaller radius (R ｅ ) of the annular notch, the hydraulic machine according to claim 1 or 2.

4. The hydraulic machine according to any one of Claims 1 to 3, wherein at least a part (81, 83) of the push rod (80) is configured to gradually bend as the pressing force of the push rod against the stack increases.

5. The hydraulic machine according to any one of Claims 1 to 4, wherein at least a part (81) of the push rod (80) has an axial dimension (e) that decreases in the direction of the free end of this part.

6. The hydraulic machine according to any one of Claims 1 to 5, wherein the annular notch (90) has two main surfaces (91, 92) facing each other, and one (91) of these main surfaces is inclined in the direction outside the push rod.

7. The hydraulic machine according to Claim 6, wherein the inclined main surface (91) extends from one side of the annular notch (90) closest to the stack (50).

8. The hydraulic machine according to any one of Claims 1 to 7, wherein the push rod (80) has a push rod guide surface (96) in the axial direction with respect to the support (70).

9. The hydraulic machine according to any one of Claims 1 to 8, wherein the guide surface (96) extends completely from one side of the annular notch (90) farthest from the stack (50).

10. A spring (56) capable of pressing the push rod (80) against the stack, and A brake release chamber (58) arranged to apply a force against the brake to the spring by the hydraulic pressure in the chamber, the hydraulic machine according to any one of Claims 1 to 9.

11. The hydraulic machine according to any one of Claims 1 to 10, wherein the stack (50) is in an oil bath.

12. The hydraulic machine according to any one of Claims 1 to 11, wherein the disks (52, 54) are made of nitrided steel.

13. The hydraulic machine according to any one of Claims 1 to 12, wherein the disks (52, 54) include a lining of friction material.

14. The hydraulic machine according to any one of Claims 1 to 13, wherein the lining has grooves.

15. The hydraulic machine according to any one of claims 1 to 14, wherein the stack (50) forms a brake.

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