EP3265679B1 - Pivoting-base mounting of an axial piston machine - Google Patents

Description

The present invention relates to a pivot cradle bearing of an axial piston machine.

An axial piston machine is an energy converter which, when designed as an axial piston pump, can convert the mechanical power resulting from speed and torque into hydraulic energy. As is well known, hydraulic energy results from pressure and volumetric flow.

In a further embodiment of the axial piston machine as an axial piston motor, the operating principle of an axial piston pump is reversed so that hydraulic power is correspondingly converted into mechanical energy.

There are basically three different designs of axial piston machines. Namely, swash plate machines, bent axis machines and swash plate machines. In each of these designs of an axial piston machine, the axis of rotation is surrounded by cylinders arranged like a turret. This means, the cylinders are arranged essentially parallel to the axis of rotation of an axial piston machine and rotate around the longitudinal axis of the axis of rotation when the axial piston machine is in operation. The cylinder liners, which together with the respective cylinder pistons represent important elements of the cylinder, are not displaced along their own axis of symmetry during operation of the axial piston machine, and are therefore designed to be stationary with respect to the axis of rotation of the axial piston machine. The respective cylinder pistons, on the other hand—apart from the possible case of idling operation of the axial piston machine—are forced to perform a lifting movement in the direction of the longitudinal axis of the axis of rotation. This is done by firmly connecting the various cylinder pistons with the end protruding from the cylinder liner to a plate that can be pivoted to the axis of rotation, so that if the plate is inclined relative to the axis of rotation, a cylinder whose cylinder liner is firmly connected to the axis of rotation rotates one rotation of the axis of rotation performs full stroke.

In a suction phase that lasts half a turn of the axis of rotation, the cylinder piston is pulled out of the cylinder liner, which creates a vacuum that is used to suck in a liquid. In a compression phase, which lasts the other half of a revolution, the cylinder head is pushed into the cylinder liner, forcing the intake fluid out of the cylinder. Thus, during a complete rotation of the axis of rotation, the cylinder performs an up and down stroke of the cylinder piston. In order to be able to vary the pump throughput while the rotational speed of the axis of rotation (or of the cylinder around the longitudinal axis of the axis of rotation) remains constant, it is possible to variably adjust the position of the pivoting plate, which is connected to the ends of the cylinder pistons protruding from the respective cylinder liners tilt axis of rotation. This is done with the help of a so-called swivel cradle, on which the side of the plate facing away from the cylinders is mounted.

However, since high forces occur when pushing back and lifting the cylinder head into the cylinder liner or out of it for expressing and sucking in liquid, both the storage and the Basic characteristics of a pivoting cradle, against which the forces of the cylinder heads are directed, of particular importance for an axial piston machine.

An axial piston machine having the features as defined in the preamble of claim 1 is known, for example, from document DE 10 2011 121 523 A1 known.

Due to the forces acting, the pivoting cradle and its associated bearing is subject to a high level of wear, which typically makes it necessary to replace these components at least once over the entire service life of the axial piston machine.

Accordingly, it is an aim of the present invention to improve the fatigue strength of a pivoting cradle bearing or of the pivoting cradle of an axial piston machine interacting therewith. At the same time, the manufacturing costs incurred for this purpose for the pivoting cradle bearing should not increase, and preferably should even be reduced.

The present task is solved by a pivoting cradle bearing with the features according to claim 1. According to this, the claimed swivel cradle bearing comprises a housing and a swivel cradle, which is arranged in the housing and has a through hole for a drive shaft, with a bearing surface being formed on two opposite sides of the through hole. In addition, the pivoting cradle bearing comprises two bearing shells in the housing for the pivotable mounting of the corresponding two bearing surfaces of the pivoting cradle, the two bearing surfaces of the pivoting cradle being hydrostatically mounted in the two bearing shells, and in a bearing area between the bearing surface and the bearing shell, the two bearing surfaces and/or the two Bearing shells each have a groove. Furthermore, the swivel cradle bearing is characterized in that at least one of the existing grooves comprises several sub-grooves running parallel to a swiveling movement of the swivel cradle with a sub-groove connecting them running transversely thereto and arranged at right angles to the several sub-grooves running parallel.

In this case, the component in an axial piston machine is referred to as a pivoting cradle whose inclined position to a through the longitudinal axis of the axis of rotation of the axial piston machine extending level regulates an axial stroke of the axial piston cylinder. As explained in the introductory part of the description, this takes place in interaction with the plate which is connected to the cylinder pistons. The Pivoting cradle on the side facing away from the cylinders on two bearing surfaces which are point symmetrical to a center of the through hole of the pivoting cradle. These two bearing surfaces touch the side of a respective bearing shell facing the bearing surface and can slide in it in order to enable the pivoting cradle to be pivoted. _{The axial force F A} resulting from the piston stroke of the cylinder acts through the swivel cradle against the respective bearing shell. To minimize or eliminate wear on the bearing shells, the force existing between the bearing shells and the pivot cradle is hydrostatically relieved. This also means that the pivoting cradle can be tilted without hysteresis using an adjustment system. In order to effectively implement this hydrostatic relief, a pressure field is built up between the bearing shells and the swivel cradle using a groove provided in a bearing surface and/or a bearing shell. The groove corresponds to a recess which, in contrast to the level surrounding it, is offset, ie its height is reduced.

In a further embodiment, a cavity formed by the respective groove is connected to a liquid from a high-pressure side of an axial piston machine in order to hydrostatically relieve the respective bearing shell with a specific pressure. The side of the liquid that is pressurized by the axial piston machine in the operating state is regarded as the high-pressure side. Correspondingly, there is a low-pressure side, which corresponds to the side of the liquid that is sucked in by the axial piston machine. In the special case of idling operation, both sides of the fluid interacting with an axial piston machine have identical pressure conditions. In this case, hydrostatic relief is not necessary due to the absence of a force that could act on the pivot cradle bearing.

Accordingly, there is a channel that leads from the high-pressure side of an axial piston machine to the cavity formed by the respective groove. The duct that connects the cavity formed by the groove and a boundary surface opposite the groove to the high-pressure side of an axial piston machine manufactures, can pass through the swivel cradle or through the bearing shell. The purpose of this channel, or the connection with the high-pressure side of the axial piston machine, is to supply a highly pressurized liquid into the hollow space characterized by the groove in order to relieve the frictional force acting between the pivot cradle and the bearing shells.

The pressures formed by the liquid on the high-pressure side in the various cavities of the respective grooves, which are preferably arranged point-symmetrically to the center of the through-hole, are of different magnitudes. In other words, this means that the liquid that is supplied to one of the two bearing shells differs in its pressure from the liquid that is supplied to the other bearing shell. _{This is advantageous since the axial force F A} delivered by the axial piston machine to the swivel cradle is offset from the longitudinal direction of the through hole and consequently also acts with different forces on the two bearing shells. Accordingly, the side of the pivot weighing storage, which is closer to the point of impact of the axial force F _A, a greater hydrostatic relief, which corresponds to a higher pressure of the supplied liquid need, which is than the side further away from the point of application of the axial force F _A.

Furthermore, it is advantageous if the angle of wrap β of the two bearing shells is approximately 150°, preferably approximately 165°, and particularly preferably approximately 180°.

The angle of wrap is the angle at which the bearing shell surrounds the pivoting cradle in the pivoting direction of the pivoting cradle. An angle of wrap of 180° corresponds to a semicircle in a plane spanned by the swivel angle. This is advantageous because there is enough pressure field area available to ensure good support and centering even with a maximum deflection of the pivot angle α. When the axial piston machine is idling, the swivel angle α is zero degrees.

In a further embodiment, the advantageously present connection of the respective grooves to a liquid is ensured by a system that includes a first check valve, which is connected to a first connection side of the axial piston machine and prevents backflow in the direction of the first connection side, and a second check valve, the is connected to a second connection side of the axial piston machine and prevents backflow in the direction of the second connection side. The system further includes a first nozzle located downstream of the first check valve and providing fluid to the cavity formed by the first groove and a second nozzle located downstream of the second check valve and providing fluid to the cavity formed by the second groove cavity provides on. In addition, a connection nozzle is provided which connects a point between the first check valve and the first nozzle and a point between the second check valve and the second nozzle. Flowing through the liquid through the nozzle preferably changes its pressure level.

One of the two inlet/outlet lines of an axial piston machine for a liquid is referred to as the connection side of the axial piston machine, one of which typically represents the high-pressure side and the other the low-pressure side during operation. Since the two connections of the axial piston machine can be used both as a supply line and as a discharge line, depending on the position of the pivoting weighing plate, these are referred to below as the first connection side and second connection side of the axial piston machine. There is a channel that connects the first connection side to a first check valve and a channel that connects the second connection side to a check valve. The check valve only allows flow away from the port side, thus preventing flow towards the port side. In addition, there is another channel that connects the side of the first check valve facing away from the first connection side to a first nozzle, which creates a connection to the cavity created by the groove on its side facing away from the check valve. There is also a second nozzle on the side of the check valve that faces away from the second port, the second Nozzle has a channel to the other cavity characterized by the groove. In addition, there is a channel which connects a point located between the first nozzle and the first check valve with a point located between the second nozzle and the second check valve via a connecting nozzle.

This arrangement ensures that the pivoting cradle receives different cradle pressures in its two bearing areas. In this case, a flow of the liquid through the respective nozzle preferably ensures a corresponding drop in pressure, so that the different pressures can be obtained.

Since the axial force F _A from the axial piston machine is offset from the center of the through hole of the swing cradle, the two bearing shells do not have the same force. Typically, the bearing shell on the low-pressure side is loaded with only half the force of the bearing shell on the high-pressure side. _{As a result, a lower cradle pressure P W2} than P _W1 builds up on the bearing shell on the low-pressure side. So that the pressure P _{W2 can be} higher than the low pressure P _{N of} the axial piston machine, there is a connecting channel between the low-pressure side of the pivoting cradle bearing, which is supplied from the high-pressure side and supplies a liquid at the appropriate pressure through appropriate nozzles.

Since, as explained above, the low-pressure side can also represent a high-pressure side with a corresponding position of the pivoting cradle, the symmetrical design of the liquid supply line from the first and the second connection point of the axial piston machine is advantageous. Accordingly, it is always possible that the two grooves are supplied with different pressures by a liquid on the high-pressure side. In order to achieve in an efficient way the pressure drop that is caused by a leakage loss, the various nozzles are provided, whereby the leakage loss between the pivot cradle and the bearing shell flows into the housing.

In a further advantageous embodiment, the distance between the points of the two bearing surfaces which are closest to one another is approximately equal to the outer diameter a roller bearing of a drive shaft passing through the through hole.

In other words, this means that the two bearing surfaces are directly adjacent to the through-hole of the pivoting cradle. This is advantageous in that the bearing distance _L D is an important factor in the stiffness to increase a pivoting cradle. This helps to keep the gap heights that occur between a bearing shell and a bearing surface as small as possible. Since the swing cradle cannot be prevented from being deformed under load, the size of a gap height must be kept as small as possible. The gap height ensures correspondingly high leakage values, which are equivalent to a loss of performance of the pump. This is because the leakage readings are fed from the high pressure side of the pump. The smallest possible distance between the two bearing surfaces is therefore obtained when they are directly adjacent to the through hole. This corresponds to the outside diameter of a roller bearing of a drive shaft of the axial piston machine running through the through-hole.

In a further advantageous embodiment, the bearing surface and/or the bearing shell are provided with two independent grooves in at least one of the two bearing regions between the bearing surface and the bearing shell. When viewed as a whole, the pivoting cradle bearing therefore has at least three grooves.

This arrangement helps to compensate for a radially acting actuating force F _Stell. A radial movement of the pivot cradle within a bearing clearance is automatically reduced by the gap height difference between the bearing shell and the bearing surface.

Advantageously, this embodiment has separate or dedicated connections to a pressure fluid for each of the two mutually independent grooves in at least one of the several bearing areas in order to provide specific hydrostatic relief for the respective groove during an adjustment process of the swivel cradle gain. The specific relief of the groove is advantageously achieved with the aid of a liquid flowing through a nozzle, the liquid being supplied from the high-pressure side of the axial piston machine.

It is also advantageous in this embodiment if the two mutually independent grooves in the bearing surface of the pivoting cradle are connected to a fluid connection running through the pivoting cradle. Furthermore, the fluid connection comprises a further connection with the outside of the bearing surface of the pivot cradle, which is arranged in an area which in an idle position of the pivot cradle is substantially flush with a fluid inlet from a high-pressure side of an axial piston machine through the bearing shell.

In this case, the pressure is supplied to the grooves, which are formed independently of one another, via channels introduced directly into the swivel cradle. Preferably, for each of the separate grooves there is also an associated nozzle located in the channels. The further connection to the outside of the pivot cradle bearing surface extends from a channel connecting the two nozzles to the outside. The result is an essentially T-shaped line, with the grooves being arranged at two ends and the outside of the bearing surface being located at the third end. More preferably, in an idle position of the swing cradle, i.e. in a position in which an axial piston machine is not pumping liquid, the channel leading to the outside of the bearing surface is aligned with a liquid supply from a high-pressure side leading through the bearing shell. More preferably, the two different grooves are supplied with different pressures.

In a further embodiment, there is a gap that widens in the direction of the through-hole between a bearing surface and an associated bearing shell. This is one way of reducing the leakage losses that occur with hydrostatic relief to a low level.

In the unloaded or slightly loaded state of the pivoting cradle, this creates a gap which, however, at the comparatively low pressures prevailing here, causes only a slight increase in the absolute leakage losses. However, when a load is applied to the pivot cradle, it will deform until the original gap is used up. Then, depending on the pressure, there is a gap with a very small to almost vanishing extent, so that despite the comparatively high pressures there are only small leakage losses. All in all, this leads to a significant reduction in leakage losses in the hydrostatic bearing of the pivoting cradle.

The gap that widens in the direction of the through-hole can be provided by a bevel of the respective bearing shells and/or a bevel of a housing section on which the respective bearing shell is arranged. In addition, it is possible that the gap results from a bevel of the bearing surface.

Advantageously, it is also possible that at least one of the existing grooves is designed in the form of a step, ie has at least two different depth levels. This design is advantageous with regard to less local deformation of the pivoting cradle in the area of the groove, since this is subjected to high lateral pressure.

In the preferred embodiment, at least one of the existing grooves comprises a plurality of parallel sub-grooves and a transverse sub-groove connecting them. The advantage of this implementation is that there are additional contact surfaces against the bearing shell between the multiple sub-grooves.

The invention also includes an axial piston machine with a pivot cradle bearing according to one of the preceding claims.

In addition, the invention includes an axial piston machine with a pivoting cradle bearing according to one of the preceding claims, wherein the pistons of the axial piston machine are designed as solid pistons. This has the advantage that any bearing play that may occur between the bearing shell and the bearing surface is reduced, so that a particularly effective bearing of the pivoting cradle is achieved.

Fig. 1:

einen Schnitt durch eine Axialkolbenmaschine mit einer erfindungsgemäßen Schwenkwiegenlagerung,

Fig. 2:

eine weitere Schnittansicht durch eine Axialkolbenmaschine mit der erfindungsgemäßen Schwenkwiegenlagerung,

Fig. 3:

eine weitere Schnittansicht durch eine Axialkolbenmaschine mit einer erfindungsgemäßen Schwenkwiegenlagerung,

Fig. 4:

eine Teilschnittansicht durch eine Axialkolbenmaschine, in dem eine Schwenkwiege in einem ausgelenkten Zustand zu sehen ist,

Fig. 5:

ein Prinzipbild der erfindungsgemäßen Schwenkwiegenlagerung,

Fig. 6:

zwei Prinzipbilder, die den Einfluss der Stellkraft und das Lagerspiel darstellen,

Fig. 7:

zeigt eine Ansicht einer Schwenkwiege, in der die Position einer Axialkraft einer Axialkolbenmaschine angegeben ist,

Fig. 8:

zeigt eine Teilschnittansicht einer Ausführungsform der Schwenkwiegenlagerung,

Fig. 9:

zeigt eine Teilschnittansicht einer Ausführungsform der Schwenkwiegenlagerung,

Fig. 10:

ist eine Prinzipskizze, die die Schwenkwiegenlagerung und die hierbei auftretenden Leckageverluste illustriert,

Fig. 11:

eine weitere Ausführungsform der Schwenkwiegenlagerung,

Fig. 12:

eine weitere Form der Schwenkwiegenlagerung,

Fig. 13:

verschiedene Seitenansichten der Schwenkwiege, bei der eine Nut treppenförmig ausgebildet ist,

Fig. 14:

eine Schwenkwiege in einer Perspektivansicht,

Fig. 15:

eine erfindungsgemäße Schwenkwiege in einer Perspektivansicht, und

Fig. 16:

zwei Axialkolbenmaschinen, einmal mit Hohlkolben und einmal mit Vollkolben.

In the following, a detailed description of the present invention is made based on embodiments illustrated in the drawings. This shows:

Figure 1:

a section through an axial piston machine with a pivot cradle bearing according to the invention,

Figure 2:

another sectional view through an axial piston machine with the pivot cradle bearing according to the invention,

Figure 3:

another sectional view through an axial piston machine with a pivot cradle bearing according to the invention,

Figure 4:

a partial sectional view through an axial piston machine, in which a pivoting cradle can be seen in a deflected state,

Figure 5:

a schematic diagram of the swivel cradle bearing according to the invention,

Figure 6:

two schematic diagrams that show the influence of the actuating force and the bearing clearance,

Figure 7:

shows a view of a swivel cradle in which the position of an axial force of an axial piston machine is indicated,

Figure 8:

shows a partial sectional view of an embodiment of the swivel cradle bearing,

Figure 9:

shows a partial sectional view of an embodiment of the swivel cradle bearing,

Figure 10:

is a schematic diagram that illustrates the slewing cradle bearing and the leakage losses that occur here,

Figure 11:

another embodiment of the swivel cradle bearing,

Figure 12:

another form of swivel cradle storage,

Figure 13:

various side views of the pivoting cradle, in which a groove is stepped,

Figure 14:

a swivel cradle in a perspective view,

Figure 15:

a pivoting cradle according to the invention in a perspective view, and

Figure 16:

two axial piston machines, one with hollow pistons and one with solid pistons.

1 shows a sectional view of an axial piston machine 2 with a pivot cradle bearing 1 according to the invention. The drive shaft of the axial piston machine 2 is designated by the reference numeral 6, to which the cylinder bushings 14 and the cylinder pistons 13 accommodated therein are firmly connected. When the drive shaft 6 rotates, the cylinders fixed to it are therefore also rotated. During such a revolution, the stroke of the cylinder pistons 13 depends on the position of the pivoting cradle 4. When the axial piston machine is in an idle state, there is no axial stroke of the cylinder pistons 13 during a complete revolution of the drive shaft 6. In an idling mode, the surface of the swivel cradle facing the cylinders forms a bearing surface on a plane which is essentially characterized by a normal vector parallel to the longitudinal direction of the drive shaft.

Accordingly, no liquid is sucked into the cylinder and ejected. Only when the pivoting cradle 4 is in an inclined position does the cylinder piston 13 perform a lifting movement during one revolution. This creates a suction movement for a liquid into the cylinder via a connection side of the cylinder A, B when the cylinder piston 13 moves out of the cylinder liner 14 . When the cylinder piston 13 moves in the opposite direction into the cylinder liner 14, the liquid sucked into the cylinder is pushed out in the direction of the corresponding connection point A, B. Here, the axial stroke of the cylinder piston 13 can be regulated via a position of the pivoting cradle 4 . The axial force F _A that results from the axial piston machine during this process and when a cylinder piston 13 is pushed back into the cylinder bushing 14 on the swivel cradle 4, the swivel cradle 4 presses against the bearing shell 8. This contact pressure force, which arises between the bearing shell and the swivel cradle 4, is hydrostatically relieved in order to eliminate the mechanical friction existing in the intermediate space there to be eliminated as far as possible. As a result, the tilting of the pivoting cradle 4 by the adjustment system 15 is possible without hysteresis and the wear on the bearing shells 8, which is caused by friction of the bearing surfaces 7 of the pivoting cradle 4, is reduced to a minimum or completely avoided.

The hydrostatic bearing (hydrostatic relief) takes place via the build-up of a pressure field between the bearing shell 8 and the bearing surface 7 of the pivoting cradle 4. For this purpose, the pivoting cradle 4 has a groove 9 for each of the two bearing surfaces 8 to be supported, which is connected to the high-pressure side P _H of the axial piston machine 2 via a channel 16 is connected. As a result, a pressure field, which will be specified in more detail later, is built up, the effectiveness of which is determined by the size and shape of the groove 9 .

However, the effective force of the pressure field acting in the groove 9 should be large enough to be able to completely relieve _{the axial force F A of the axial piston machine.} For this purpose, the groove 9 is designed in such a way that a pressure field that builds up there due to the liquid pressure produces a desired effective force with a pressure P _{W1 that is} slightly lower than the system pressure of the axial piston machine on the high-pressure side P _H .

Furthermore, one recognizes in the 1 the through hole 5, in which the drive shaft 6 is carried out.

2 shows one along the straight line AA in 1 indicated sectional view, in which the pivotability of the pivoting cradle in the bearing shell 8 provided for this purpose, which is arranged in the housing 3, can be better understood. It can be seen that the bearing shell 8, which is semicircular in shape in this sectional view, and the pivot cradle 4 received therein can change its position relative to the bearing shell 8, whereby the axial stroke of the respective cylinders can be adjusted. It can also be seen that a groove 9 introduced into the swivel cradle or into the bearing surface 7 of the swivel cradle 4 forms a cavity with the bearing shell 8 which is connected to a connection side A via a channel 16 . This ensures that the pressurized fluid required for hydrostatic relief can be supplied to the axial piston machine 2 via the high-pressure side.

Since the connection side A of the axial piston machine 2 does not necessarily have to match the high-pressure side of the axial piston machine 2, since the high-pressure side can be changed depending on the position of the pivoting cradle 4, a system 10 for connecting to the high-pressure side of the axial piston machine (connection point A or connection point B ) the liquid is supplied with the correspondingly high pressure.

3 shows in one in 2 indicated section through BB a part of the system that supplies the two grooves 9 via respective channels 16 with a liquid from the high-pressure side of the axial piston machine 2 (connection point A or connection point B). Here you can see the two connection points A, B, which each have a connection via a check valve 101, 102 to a corresponding groove (not in 3 shown). The groove is not shown in the drawing and is outside the plane of the drawing. In addition, a connecting nozzle 105 can be seen, which connects the respective connections of the check valve and groove 9 to one another downstream of the check valves 101, 102. The connecting nozzle 105 arranged in this connecting line ensures a certain pressure difference, so that different pressures act on the two grooves 9 or on the two swivel cradle.

In 4 is a partial view of the 2 can be seen, which shows that the wrap angle β must exceed a certain level in order to have enough pressure field area to ensure good support and centering even at a maximum to ensure deflection of the swivel cradle α. With this inclination of the pivoting cradle by the angle α, the axial stroke performed by the cylinder heads 13a, 13b and 13c can also be seen well. It can also be seen that even with a maximum deflection by the angle α, the groove 9 of the swivel cradle 4 forms a cavity with the bearing shell 8, which at every swivel angle α via a channel 16 or a system 10 for connecting the channel 16 formed by the groove 9 Cavity is in communication with a liquid on the high-pressure side of the axial piston machine 2 . This ensures that the hydrostatic bearing of the pivoting cradle 4 can also be carried out at a maximum pivoting angle α.

figure 5 shows a schematic diagram of the system 10 with which the grooves 9 are supplied with a liquid to produce the hydrostatic bearing. Some of the components shown here can already be found in the description 3 .

For the understanding of the present invention, it is important to realize that the axial force F _A acting on the swing cradle by the reciprocating movement of the pistons is offset from the center of the through hole 5 at a position different from the neutral position. figure 5 shows this by means of the black solid arrow offset from the center of the through hole 5, which _{indicates the axial force F A} and its position. Therefore, the need arises that the two bearing shells 8 do not receive the same supporting force through the hydrostatic relief.

The bearing shell lying on the low-pressure side (the bearing shell on which less force acts due to the movement of the pistons) is loaded in the present exemplary embodiment with only half the force than the high-pressure-side bearing shell 8. This is shown in FIG figure 5 represented visually by the differently sized force vectors P _W2 and P _{W1 .} As a result, a lower cradle pressure P _W2 than P _W1 builds up, which also requires a hydrostatic relief with a corresponding back pressure that is adapted to it. A different ratio of power distribution of the two pressures P _W1 and P _W2 such as 1:2, 1:3, 1:4, 2:3, 2:5, 3:4 or 3:5 can also be implemented.

So that the pressure P _{W2 is} greater than the pressure P _{N of} the low-pressure side of the piston engine, this side must also be _{supplied via the high-pressure side P H of} the piston engine 2 .

The corresponding pressures for the hydrostatic bearing are generated via nozzles 103, 104, 105 by a leakage loss that flows between the swivel cradle and the bearing shell into the housing. For example, the necessary pressure P _{W1 is} generated from the high-pressure side P _{H of} the piston engine 2 via a pressure drop at the nozzle 104 .

Since the pressure drop between the high-pressure side P _H and the necessary pressure P _W2 on the low-pressure side bearing shell 8 must be greater than that between the high-pressure side P _H and Pw1 (high-pressure side bearing shell 8), the leakage loss that occurs when P _W2 is generated , must be greater than that _occurring at P W1. However, since the pressure value is greater than P _N from the low-pressure side, an additional connection nozzle 105 is provided in the system 10, so that a connection from the high-pressure side of the axial piston machine is now via two nozzles 103, 105, so that the pressure acting on the low-pressure side bearing shell 8 acts, is less than the pressure on the high-pressure side bearing shell 8.

Since the cradle pressure P _W2 , which builds up on the low-pressure side, is at a higher value than the low pressure P _{N of} the axial piston machine, a fluid must be prevented from flowing back to the low-pressure side. To prevent this, a non-return valve 101 is also installed on the low-pressure side. Since in an axial piston machine the low-pressure side can change from connection point A to connection point B depending on the position of the pivoting cradle 4, an additional check valve 102 is necessary in the system 10 so that no fluid can flow to the low-pressure side even when there is a change from the low-pressure to the high-pressure side flows. Overall, a symmetrical construction of the system 10 is thus obtained, which supplies the grooves with liquid under pressure.

6 shows the interaction between pivot cradle 4 and bearing shell 8 as well as the effects of the axial force F _A , which is not arranged in the center of through-hole 5 of pivot cradle 4 . The drawing on the left shows an _{example of the optimal bearing force for an offset axial force F A} , which is offset by an angle γ from the axis of symmetry of the pivoting cradle 4 . The right drawing of the 6 also shows that the non-symmetrical impact of the force F _A moves the pivot cradle 4 within the bearing shell 8 in such a way that a bearing clearance e that varies along the bearing shell 8 occurs, which is represented by the illustrated values S1 and S2 of the bearing clearance e. Furthermore, the non-symmetrical course of the pressure field, which is given by the swivel cradle 4 via the bearing surface 7 of the swivel cradle 4 to the bearing shell 8, is also shown. A supply of a liquid for hydrostatic relief arranged centrally in the axis of symmetry of the bearing shell 8 cannot optimally compensate for the pressure field profile that occurs asymmetrically with respect to the axis of symmetry of the bearing shell 8 .

7 shows a perspective view of a pivoting cradle, in which the axial force F _A caused by the pistons is plotted for a specific pivoting of the pivoting cradle 4 . It can be seen that the axial force F _A is offset from the axis of symmetry or the center of the through hole 5 and is arranged closer to one of the two bearing shells.

8 shows an advantageous countermeasure to _{hydrostatically relieve the axial force F A} acting on the pivot cradle 4 as effectively as possible. There are two grooves 9a, 9b formed independently of one another in the bearing surface 7 of the swivel cradle 4 facing the bearing shell. The grooves 9a, 9b are arranged in such a way that they are each connected to a fluid supply from the high-pressure side of the axial piston machine 2. This liquid supply is formed via the bearing shell 8 in the groove 9a, 9b with the bearing shell 8 cavity supplied. Due to different nozzles 104a, 104b for each groove 9a, 9b, it is possible to have different pressure forces acting on the grooves 9a, 9b, which aim _{to eliminate the axial force F A} as effectively as possible. Here it is possible, for example, that the groove 9a that is positioned on a side with a small bearing clearance S2, i.e. on a side with a greater force F _{A ,} is subjected to a greater counter-pressure P _W ' than groove 9b, on whose side the _{pressure caused by F A} is lower. On the applied with a smaller pressure side is "tuned in. The resultant resulting bearing force caused by a superposition of the two by the hydrostatic relief forces P _W 'and P _W" accordingly from the nozzle 104b, a lesser back pressure P _W results, is optimally offset by the angle γ from the axis of symmetry of the bearing shell or the swivel cradle 4 and optimally opposes the pressure field caused _{by the axial force F A .}

9 shows a further embodiment with which the resulting bearing force can be offset by an angle γ, although the feed line of the high-pressure side of the axial piston machine 2 is arranged centrally to the axis of symmetry of the bearing shell 8. That is, the feed line is orthogonal to the rocker cradle surface on which the axial pistons act when the axial piston machine is in an idle condition. It can be seen here that the pivoting cradle 4 is provided with a line system 11 which supplies the grooves 9a, 9b, which are independent of one another, with liquid. In order to bring about different pressures in the different groove areas, corresponding nozzles 111, 112 are provided in the feed lines to the respective grooves 9a, 9b. On the side of the nozzles 111, 112 facing away from the grooves 9a, 9b, a further connection 12 extends to the bearing surface 7 of the swivel cradle. When the axial piston machine is idling, this connection 12 is aligned with the supply line, which extends through the bearing shell 8 from the high-pressure side of the axial piston machine 2 . So they are in 8 The advantages described can also be achieved with only one supply line through the bearing shell, since the different bearing forces or the different pressures P _W 'and P _W "acting on the groove areas 9a, 9b are caused by the in the swivel cradle running channel system 11 and the associated nozzles 111, 112 can be achieved.

10 shows a basic sketch that indicates the leakage losses with a hydrostatic bearing of the swivel weighing lower part. An important point in the hydrostatic pivot bearing is the achievement of a high rigidity of the pivot cradle 4. The undesirable but not entirely avoidable deformation of the pivot cradle 4 under the axial force F _A is an example in FIG 10 shown. The greater one of the gap heights 21, 22, the greater the corresponding leakage values QL ₁ and QL ₂ , which indicate a certain quantity of liquid supplied from the high-pressure side, which flows into the housing. The sum of the leakage values QL ₁ and QL ₂ is taken from the high-pressure side of the pump and accordingly represents a power loss of the pump. In order to keep these losses as low as possible, the gap heights 21, 22 must be as small as possible. It is advantageous here that the pivoting cradle 4 is designed to be particularly stiff.

Except for the thickness of the pivoting cradle 4, the in 1 The bearing distance D _{L that is drawn in is} an important factor in increasing rigidity. It is advantageous if the distance D _{L is} as small as possible. The smallest possible distance corresponds to the outer diameter of a roller bearing, which is therefore selected without an inner ring. The rolling elements of the bearing run directly on the drive shaft 6 of the axial piston machine.

To the in 10 To further reduce the leakage losses shown as an example and to make the hydrostatic bearing even more effective, it is possible, with a gap ψ that widens in the direction of the through hole 5, to chamfer the respective bearing shells 8 and/or chamfer a housing section on which the respective Bearing surface 7 is arranged to provide.

Such an embodiment is 11 shown. Here, an enlarged view of the swivel cradle bearing is shown, in which a moving in the direction of the Through hole widening gap ψ between the housing 3 and the bearing shell 8 is present.

12 shows a similar area as 11 , but in this case the gap ψ, which widens in the direction of the through-hole, is formed by a bevel of the bearing surface 7 of the swivel cradle 4, as a result of which a gap between the bearing surface 7 and the bearing shell 8 arises. In these two embodiments, the leakage losses QL ₁ and QL _{2 are} lowered to a low level.

In the unloaded state of the pivoting cradle, there is now a gap with an angle ψ, which widens in the direction of the through-hole 5 of the pivoting cradle 4 . Comparatively low pressures prevail in the unloaded state of the pivoting cradle, as a result of which the provision of a gap leads to a smaller increase in the absolute values of the leakage losses. However, when a load is applied to the rocker cradle 4, it will deform until the original gap of the tilt angle ψ is consumed. The consequence of this is that, depending on the pressure, a gap is formed with a very small to almost vanishing extent, so that a very small leakage loss occurs regardless of the comparatively high pressures.

Overall, this leads to a significant reduction in leakage losses. In order to achieve the advantageously reduced leakage losses, it is of secondary importance whether the gap between the bearing surface 7 and the bearing shell 8 is caused by a chamfering of the bearing surface 7 or a chamfering of the bearing surface 8 or even by a chamfering of the bearing surface 7 and the bearing surface 8. It is also possible for the housing 3 to be beveled in an area on which the bearing shell 8 is located. The gap then arises between the housing and the bearing shell and is reduced when the swivel cradle 4 is deformed in the direction of the beveled housing surface.

13 shows a further embodiment of the pivoting cradle 4 in which the groove 9 is stepped. The step-like design of the groove 9 leads to a greater material thickness of the pivoting cradle 4 and is advantageous with regard to less local deformation of the pivoting cradle 4 in the region of the groove 9, since this is laterally loaded with a liquid under high pressure.

14 FIG. 12 shows a perspective view of the pivoting cradle 4 in which the groove 9 is present directly in a blank of the pivoting cradle 4. FIG.

15 Figure 12 shows a perspective view of the pivot cradle of the present invention and an enlarged portion of the pivot cradle showing the groove in a somewhat enlarged view. In this embodiment of the groove 9 there are several small, preferably parallel sub-grooves 91 which can be supplied with pressure by means of a sub-groove 92 running transversely thereto. The plurality of sub-grooves 91 extending in parallel are spaced from each other and are connected to the sub-groove 92 extending across them in a state received by a bushing 8 so that liquids can flow between them. The advantage of this is that additional contact surfaces against the bearing shell 8 are present between the sub-grooves 91, 92. This special configuration of the grooves can be combined with any disclosed embodiment of the pivoting cradle and/or the pivoting cradle bearing.

The invention also includes an axial piston machine with one of the pivot cradle bearings described above.

In addition, it is also advantageous for the pivoting cradle bearing according to one of the embodiments described above if the axial piston machine 2 instead of the hollow pistons customary in the prior art (cf. 16a ) with full pistons as in Figure 16b are shown, is operated. Here, the bearing clearance e between the bearing shell 8 and the bearing surface 7 of the swivel cradle 4 is reduced, as a result of which the additional design effort for shifting the bearing force F _L does not necessarily have to be carried out.

The pivoting cradle 4 can be made of nitrided steel in order to achieve the necessary tensile strength. The transformation is done by forging. If, however, the pivot cradle dimensions are so large that forging of the blank cannot be carried out, an alternative is the use of nodular iron or the use of correspondingly nitridable materials. The machined component is nitrided or nitrocarburized, including other methods to increase surface hardness, such as case hardening. To prevent an abrasive layer from shortening the life of the slewing cradle bearing system, the compound layer is removed or polished after nitriding. The difference in hardness between the surface of the cradle (bearing surface 7) and the plain bearing (bearing shell 8) should be at least a factor of 4 to ensure wear-free operation. Typically 8 brass alloys are used for the bearing shells.

Claims (14)

1. A pivot cradle bearing (1) of an axial piston machine (2) comprising:

   a housing (3);

   a pivot cradle (4) that is arranged in the housing (3) and that has a passage hole (5) for a drive shaft (6), with a respective bearing surface (7) being formed at two oppositely disposed sides toward the passage hole (5); and

   two bearing shells (8) in the housing (3) for the pivotable support of the corresponding bearing surfaces (7) of the pivot cradle (4), wherein

   the two bearing surfaces (7) of the pivot cradle (4) are hydrostatically supported in the two bearing shells (8); and

   the two bearing surfaces (7) and/or the two bearing shells (8) each have a groove (9) in a bearing region between the bearing surface (7) and the bearing shell (8),

   characterized in that

   at least one of the grooves (9) present comprises a plurality of subgrooves (91) extending in parallel with a pivot movement of the pivot cradle and having a subgroove (92) that connects them, extends transversely thereto,

   and is arranged at a right angle to the plurality of subgrooves (91) extending in parallel.
2. A pivot cradle bearing (1) of an axial piston machine (2) in accordance with claim 1, wherein
   a hollow space formed by the respective groove (9) is in communication with a liquid from a high pressure side of an axial piston machine (2) to hydrostatically relieve the respective bearing shell (8) by a specific pressure.
3. A pivot cradle bearing (1) of an axial piston machine (2) in accordance with one of the preceding claims, wherein a wrap angle (β) of the two bearing shells (8) amounts to approximately 150°, preferably approximately 165°, and particularly preferably approximately 180°.
4. A pivot cradle bearing (1) of an axial piston machine (2) in accordance with claim 2, wherein the communication of the two grooves (9) with a liquid takes place by a system (10) that comprises:

   a first check valve (101) that is connected to a first connection side (A) of the axial piston machine (2) and that prevents a backflow in the direction of the first connection side (A);

   a second check valve (102) that is connected to a second connection side (B) of the axial piston machine (2) and that prevents a backflow in the direction of the second connection side (B);

   a first nozzle (103) that is arranged downstream of the first check valve (101) and that provides the liquid for the hollow space formed by the first groove (9);

   a second nozzle (104) that is arranged downstream of the second check valve (102) and that provides the liquid for the hollow space formed by the second groove (9); and

   a connection nozzle (105) that connects a point between the first check valve (101) and the first nozzle (103) and a point between the second check valve (102) and the second nozzle (104).
5. A pivot cradle bearing (1) of an axial piston machine (2) in accordance with one of the preceding claims, wherein the spacing of the points of the two bearing surfaces (7) that are disposed closest to one another approximately corresponds to the outer diameter of a roller bearing of a drive shaft (6) extending through the passage hole (5).
6. A pivot cradle bearing (1) of an axial piston machine (2) in accordance with one of the preceding claims, wherein the bearing surface (7) or the bearing shell (8) have two mutually independent grooves (9) in at least one bearing region between the bearing surface (7) and the bearing shell (8).
7. A pivot cradle bearing (1) of an axial piston machine (2) in accordance with claim 6, wherein the hollow spaces produced by the grooves (9) have a respectively separate communication with a liquid to achieve a hydrostatic relief specific to the respective groove (9) on an adjustment procedure of the pivot cradle (4).
8. A pivot cradle bearing (1) of an axial piston machine (2) in accordance with claim 6, wherein the two mutually independent grooves (9) in the bearing surface (7) of the pivot cradle (4) are connected to a liquid connection (11) extending through the pivot cradle (4), with the liquid connection (11) having a further connection (12) to the outer side of the bearing surface (7) that is arranged in a region that is substantially aligned in an idling position with a liquid inflow (13) from a connection side (A, B) of an axial piston machine (2) through the bearing shell (8).
9. A pivot cradle bearing (1) of an axial piston machine (2) in accordance with claim 8, wherein two nozzles (111, 112) are arranged in the liquid connection (11) extending through the pivot cradle (4) and the further connection (12) to the outer side of the bearing surface (7) exits between the nozzles (111, 112).
10. A pivot cradle bearing (1) of an axial piston machine (2) in accordance with one of the preceding claims, wherein a respective gap (ψ) that widens in the direction of the passage hole (5) is present between the two bearing surfaces (7) and associated bearing shells (8).
11. A pivot cradle bearing (1) of an axial piston machine (2) in accordance with claim 10, wherein the gap that widens in the direction of the passage hole (5) is provided by a chamfer of the respective bearing shells (9) and/or by a chamfer of a housing section on which the respective bearing surface (7) is arranged.
12. A pivot cradle bearing (1) of an axial piston machine (2) in accordance with one of the preceding claims, wherein at least one of the grooves (9) present is designed in step form, that is has at least two different depth levels.
13. An axial piston machine having a pivot cradle bearing in accordance with one of the preceding claims.
14. An axial piston machine in accordance with claim 13 whose pistons (13) are configured as plungers.

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