WO2019072995A1

WO2019072995A1 - Axial piston machine having a coated sliding surface

Info

Publication number: WO2019072995A1
Application number: PCT/EP2018/077788
Authority: WO
Inventors: Lennard GEISSLER
Original assignee: Liebherr Machines Bulle Sa
Priority date: 2017-10-13
Filing date: 2018-10-11
Publication date: 2019-04-18

Abstract

The invention relates to an axial piston machine comprising a barrel with cylinder bores and pistons which are received therein, which barrel is arranged between a sliding disc and a control plate, wherein the barrel is mounted such that it can rotate about a rotational axis, and wherein at least one component of the axial piston machine is coated at least in sections with an overlay-welded coating on a surface which is in contact with a sliding partner. Furthermore, the invention relates to a method for producing an axial piston machine of this type, wherein the coating is applied by way of overlay welding and preferably laser cladding.

Description

Axial piston machine with coated sliding surface

The invention relates to an axial piston machine with a drum which is arranged between a sliding disk and a control plate.

Axial piston machines are known from the prior art. They can be used as pumps for converting mechanical energy into hydraulic energy or motors for converting hydraulic energy into mechanical energy. The axial piston machines have a construction in common, wherein a drum with cylinder bores between a hydraulically arranged control plate and a mechanics side arranged sliding disc is edged. The sliding disk is oriented obliquely to the drum, slightly inclined at idle and increasingly inclined at higher load of the axial piston machine, and pistons are arranged in the cylinder bores of the drum, are attached to the sliding-disk side ends of the sliding shoes, which are supported on the sliding disk. The hydraulic side face of the drum is in direct contact with the control plate.

In operation, the drum rotates and the control plate is fixed against rotation, whereby the corresponding contact or functional surfaces of the drum and the Control plate move relative to each other. Further, during operation of the axial piston machine, the corresponding contact surfaces of the sliding shoes and the sliding disk also move relative to each other as the lateral surfaces of the piston and the cylinder bores of the drum. Corresponding contact surfaces of the sliding disk and an actuating means, such as an actuating piston or a spring for adjusting the slope of the sliding disk move relative to each other during operation.

As regards the contact area of the control plate and the drum, it has been proposed in the prior art to coat the functional surface of the drum which bears against the control plate by plating or pouring in order to minimize the friction on the functional surfaces and the life of the To improve axial piston machine, as well as to reduce the leakage in the contact area of the functional surfaces. On the one hand, however, this leads to considerable additional expenditure and considerable additional costs in production and, on the other hand, compliance with the typically varying nominal thickness of the coating over the entire course of the contact surface is difficult to realize.

The object of the invention is to keep the friction at the corresponding sliding surfaces within an axial piston machine low and thus to increase the life of the axial piston machine. At the same time production costs and production costs should be kept as low as possible.

Against this background, the invention relates to an axial piston machine comprising a drum with cylinder bores and piston therein, which is arranged between a sliding disk and a control plate, wherein the drum is rotatably mounted about a rotation axis, and wherein at least one component of the Axiaikolbenmaschine at one with a sliding partner In contact surface is coated at least in sections with an order-welded coating. The axial piston machine according to the invention may be an axial piston pump for converting mechanical energy into hydraulic energy or an axial piston motor for converting hydraulic energy into mechanical energy. In terms of rotation about their common axis of rotation, the drum and shaft are firmly coupled together. The plurality of cylinder bores are parallel to the axis of rotation of the drum and each receive a movably mounted piston. The sliding disk is inclined to the axis of rotation of the drum and the pistons are connected via articulated bearings with the sliding disk in connection. Preferably, in the axial piston machine according to the invention is a swash plate machine, wherein the drive shaft and the drum axis always run in a line and the position of the disc deviates from it. In one embodiment, it is an adjustable axial piston machine in which the angle of the sliding disk to the drum axis can be changed.

The rotatably mounted drum and fixed in order to avoid their rotation control plate move relative to each other during operation of the axial piston machines, whereby the corresponding functional surfaces of the drum and the control plate rub against each other.

In one embodiment, both the component and the coating are metallic. The opposite surface of the sliding partner can also be metallic. The coating may have a lower hardness than the underlying surface of the component and / or the surface of the sliding partner. For example, component or component surface and / or Gleitpartneroberfläche be made of steel and / or the coating of bronze. Due to different hardnesses of the two contact partners, the sliding properties can be improved and the dimensional stability of the two surfaces can be retained longer, which is essential for the required life. In the case of contact between the drum and the control plate increases, for example, by the duration of use Progressing abrasion on the two surfaces on the high pressure side, the oil leakage.

Unlike coating by, for example, plating or casting, as known in the context of the prior art drum and control plate, build-up welding is faster and less expensive and allows greater dimensional accuracy. A reworking of the coated surface is at most necessary to a small extent. In one embodiment, it is provided that the drum has on its first end face a functional surface, with which it bears against the inner surface of the control plate, wherein the drum is coated on the functional surface or the control plate on the inner surface at least in sections with an order-welded coating.

In the first variant of this embodiment, therefore, the component is the drum, with the sliding partner around the inner surface of the control plate and the surface in contact with the sliding partner around the functional surface of the drum. In this embodiment, the invention achieves a significant reduction in the manufacturing cost of the drums with at least identical and typically improved quality over prior art coatings of functional surfaces obtained by plating or casting.

The second variant relates to an alternative made easy by build-up welding, according to which the coating can also be attached to the other partner of the sliding contact, namely on the control plate. There, the component is the control plate, with the sliding partner around the functional surface of the drum and in the surface in contact with the sliding partner around the inner surface of the control plate. In one embodiment it is provided that the drum has at its first end face a trough whose surface forms the functional surface, wherein the trough is preferably trough-shaped and has a concave surface. Such geometry may generally be technically required or at least advantageous in axial piston engines. The trough is preferably formed radially symmetrically with respect to the axis of rotation of the drum. In the center of the trough is typically the center bore of the drum, so that the actual functional surface is not disk-shaped but circular or the trough-shaped trough has the shape of a trough with hole.

The control plate has in this embodiment on the inside of a corresponding with the trough molding, again typically broken from a central bore.

In one embodiment, the first end face of the drum has an annular surrounding surface which encloses the trough. Thus, in this embodiment, the trough does not occupy the entire first end face of the drum. The surrounding area is preferably also not coated with an application-welded coating in the case of a coating of the functional surface of the drum and is preferably also not applied to the control plate. The surrounding area may be in the radial plane of the drum or at an angle to it.

The shape of the trough is crucial to allow an effective escape of the welding gases during a build-up welding on the trough and thus avoid pore formation in the coating.

In one embodiment, it is provided that the inclination of the trough surface to the radial plane of the drum and / or the curvature of the trough surface changes depending on the distance, for example with increasing distance from the axis of rotation of the drum. The trough surface can theoretically be divided into a central area and an outer edge area and into these two areas have different slopes and / or curvatures. Preferably, a discontinuous change in the curvature takes place at the transition between the central region and the edge region. A discontinuity in the slope curve is preferably not provided, but a change in the curvature can cause the slope in the edge region changed more or in different ways.

In one embodiment, it is provided that the inclination and / or the concave curvature increase in an outer edge region. In the interest of a high mechanical strength of the coating, it may be advantageous that the inclination or concave curvature at the outer edge of the trough is maximum.

In one embodiment, it is provided that the inclination decreases in an outer edge region and / or that the curvature has convexly and / or at least partially no curvature in an outer edge region. A flat as possible conclusion of the trough by a smaller pitch or a convex curvature in the edge region may be advantageous to allow an effective escape of welding gases.

In one embodiment, it is provided that the inclination of the trough surface to the radial plane of the drum does not exceed an angle of 45 ° and preferably 25 ° at any point. For example, it may be provided that the inclination of the trough surface to the radial plane of the drum in the central region does not exceed an angle of 20 ° and generally an angle of 45 °. Preferably, the angle is generally at most 20 °, preferably at most 15 ° and more preferably at most 10 °. A concave shape of the trough or an inclination of the trough contour, the orientation of which approaches a concave profile instead of a convex profile, are unfavorable with regard to an effective escape of the welding gases. To avoid pore formation in the coating, however, a sufficiently effective and sufficiently rapid escape of the welding gases is essential. Taking into account preferred geometries of typical My angles can be between 10 ° and 20 °. As maximum tolerable angles of 45 ° are to be considered.

In one embodiment, it is provided that the trough surface has at least one outwardly sloping step or outer edge, preferably in an outer edge region. The step can also be rounded. Such a step or discontinuity in the corresponding area may favor the escape of welding gases. Conversely, it is preferably provided that the trough surface has no inwardly sloping step or inner edge.

As an alternative to a trough, the end face may also be flat or may have a shape with, for example, a convex surface. If the machine geometry allows such a construction, such an embodiment is advantageous because it promotes the outflow of the welding gases.

In the variant in which the control plate is coated by build-up welding, an escape of the welding gases may be favored in the case of a convex shape, which would not result in concave functional surface of the drum.

In one embodiment, it is provided that the functional surface of the drum or the inner surface of the control plate is not completely, but only partially coated with an order-welded coating.

For example, a first annular coating section may be provided, which preferably extends continuously over the circumference of the functional surface of the drum or inner surface of the control plate. The coating ring may have a narrow width of, for example, less than 0% and preferably less than 5% of the diameter of the drum and / or outside the kidney openings of the drum leading to the cylinder bores for the pistons and corresponding kidney openings of the control plate run. As an alternative or in addition to the first coating ring, a second coating ring may be provided which extends in the region of the kidney openings and has a width which is greater than the radial extent of the kidney openings. The kidney openings may be completely within the area covered by the second coating ring.

In one embodiment, instead of the second coating ring, isolated coating zones may also be provided in the region of the kidney openings, which surround, for example, a kidney opening, but are not in contact with each other.

In one embodiment, it is provided that on the sliding-disk-side ends of the pistons of the axial piston machine sliding shoes are attached, which abut with its underside on the inside of the sliding disk, wherein the underside of the sliding shoes or the inside of the sliding disk is at least partially coated with an order-welded coating. In the first variant of this embodiment, therefore, the component is the sliding shoe, in which the sliding partner is around the sliding disk and in the surface in contact with the sliding partner around the underside of the sliding shoe. In the second variant, the component is the sliding disk, with the sliding partner around the sliding block and, in the case of the surface in contact with the sliding partner, around the inside of the sliding disk.

In an embodiment it can be provided that the coating extends over the entire underside of the sliding shoes. In one embodiment, it may be provided that the coating is segmented by channel-shaped omissions or recesses, such omissions may be arranged, for example, the shape of concentric circles about a reference point in the central region of the underside of the shoe. They can be used as a maze to hold back serve oil, which can emerge from an oil channel in the middle area at the bottom of the shoe.

In one embodiment, it is provided that the coating is multi-layered. A multilayer coating can be applied in multiple layers. In this case, by deliberately changing the parameters during the production of the successive or adjacent layers, they can be specifically provided with specific properties. The individual layers may consist of the same or different materials. In addition, the influenceable parameters of the welding process, such as the temperature, the coating material inflow, etc., can be carried out while maintaining or changing the application of different layers. By a combination of these variabilities or the position-dependent adjustment of a degree of freedom, for example, certain hardness profiles can be achieved. In addition, the sweat layer applied directly to the base body can be designed as a so-called buffer layer. In this case, such a welding material and / or the influenceable variables of the welding process, for example the temperature, the feed, etc., are selected for this welding position in such a way that the highest possible bonding strength is achieved between the main body and the buffer layer. Achieving a high bond strength there is challenging, since in the deposition welding a momentarily localized energy input must be sufficient to high-strength connect the coating material with the base body, which has a very high heat capacity due to its dimensions. As mentioned, the tedious and costly heating of the body should be avoided by the coating by means of deposition welding; equally the effort to achieve such a temporal cooling - eg. By reheating with a defined temperature drop - which is expedient that the coating of the finished component of a correspondingly high quality. The upper layer of the coating is then carried out with such a welding material and / or under such welding process parameters, which lead to the best possible contact surface or the best possible functional surface. Exemplary thicknesses a single layer amount to between 0.5 to 1 mm, preferably 0.7 mm. Due to the multi-layeredness, it is also possible to achieve a specific structure of the coating in the sense of 3D printing, as already explained with reference to the example of the sliding surface of a sliding shoe.

In the context of multilayer coatings, when coating the functional surface of a drum or control plate, one or more base layers may extend over all or more of the functional surface of the drum or control plate than one or more additional layers, such as those only Areas are provided, which were mentioned above in the context of the coating rings.

In the case of a coating of the lower side of the sliding shoe, it may be provided in the context of the multilayer coatings that one or more base layers extend over the entire underside and omissions, for example in the embodiment as described above, only one or more, but at least a smaller number of Additional layers concern.

In one embodiment, one of the corresponding contact surfaces of the sliding disk and an actuating means, for example a control piston or a control spring for adjusting the slope of the sliding disk coated with an order-welded coating.

Against the background mentioned above, the invention further relates to a method for producing an axial piston machine according to the invention, wherein the coating is applied by build-up welding and preferably laser deposition welding. In build-up welding, volume build-up takes place through the application of the coating material.

Preferably, the coating material is the welding head or the active zone of the coating process', ie in the case of a laser deposition in the Laser arc fed in powder form. The powdery starting material for coating preferably has a spherical or spherical geometry. In order to favor the local melting of the individual grains, which promotes a time savings in the coating and a higher uniformity of the coating and a generally higher security of the process control; however, considering adequately the material cost, the diameters of the individual grains of the starting powdery material to be coated should have diameters between 40 microns and 160 microns. Preferably, the diameters of the individual grains have values of from 40 microns to 110 microns; more preferably, these are in the range of 40 microns to 80 microns.

Preferably, the coating material is a non-ferrous metal or such an alloy, which is commonly referred to as non-ferrous metal.

Particular preference is given to alloys which have a proportion of copper (Cu) between 50% and 80%. Equally preferred are alloys containing beryllium (Be) and in this case have a copper content of between 50% to 98%. Furthermore, alloys are preferred which have a content of tin (Sri) between 5% and 15%. Further preferred are alloys containing a content of zinc (Zn) between 5% and 45%. Equally preferred are alloys with a nickel (Ni) content of between 2% and 20%.

Concrete examples of coating materials are CuSn10Pb9Ni2 and CuZn40Al2Mn2Si as well as CuSn10Bi8Ni5.

It is known that during welding the composition of the starting material differs from the composition of the already applied material, ie that of the welding bead. One reason for this is that certain constituents or certain metals from the alloy emerge disproportionately from the starting material during the melting process or during the molten state or are less well integrated into the welding bead during solidification but exit from the material. One metal in which this phenomenon occurs is zinc. So that ultimately the welding bead has the desired material composition, it is possible to add to the starting material an excess of those components which are disproportionately not incorporated into the welding bead.

In the case of a coating of the functional surface of the drum, it can be provided, for example, that the layer application takes place from the inside to the outside. For example, the order can be carried out on sequentially applied, radially outwardly extending tracks. The areas of the functional area which are near the axis of rotation are thus coated in each working step in front of the regions remote from the axis of rotation, and the welding gases escape outward in the radial direction approximately. Feed and coating material inflow can be specified according to the radial position such that a coating with a uniform surface results.

In one embodiment, the entire component is heated before and / or during layer application, for example to a temperature of greater than 500 ° C., preferably greater than 900 ° C. Suitable temperature ranges include ranges of, for example, between 900 ° C and 1300 ° C. In one embodiment, a temperature of about 1100 ° C is preferred.

Further details and advantages of the invention will become apparent from the embodiments discussed below with reference to the figures. In the figures show:

FIG. 1 is a sectional view of an axial piston machine;

Figure 2 is a schematic sectional view through the drum of an axial piston machine; 3 shows three detailed views of an unfavorably formed edge region of the end face of such a drum;

Figure 4: a detailed view of a low-trained edge region of

End face of such a drum;

Figure 5: another two detailed views of low-trained edge regions of

End face of such a drum;

FIG. 6 shows a plan view of the functional surface of a drum with coating zones in the form of two rings;

FIG. 7 shows a top view of the functional surface of a drum with coating zones in the form of a ring and a plurality of individual coating zones;

FIG. 8 shows a perspective view of a control plate with an exemplary coating zone on the inner surface; and

Figure 9: views of a shoe of an axial piston according to the invention with a coated by cladding underside.

A longitudinal sectional view of an axial piston machine is shown in FIG. The axial piston machine comprises a housing 1 with a bore for a shaft 2, which is non-rotatably connected to a rotatably mounted in the housing 10 drum. The drum 10 comprises a plurality of axial cylinder bores 3, in which pistons 4 are received linearly displaceable. In the housing 1, a sliding disk 5 and a control plate 6 are further accommodated, between which the drum 10 is enclosed. The inclination of the sliding disk 5 relative to the drum 10 can be adjusted by means of a control piston 7. At the sliding-disk-side ends of the piston 4 sliding shoes 30 are fixed, with their underside on the inside of the Sliding disk 5 abut. The hydraulic channels 8a for low pressure and 8b for high pressure of the axial piston machine open at the control plate 6. As can be seen from the figure, the control plate 6 and the drum 10 abut each other in a contact region 9 and have contacting functional surfaces. It can be seen that the drum 10 at the corresponding end face a trough-shaped indentation and the control plate 6 has a corresponding shape.

A simplified longitudinal sectional view through a drum 10 of such or other axial piston machine is shown in FIG. The generally cylindrical drum 10 comprises a central bore 11 extending around its axis of rotation A for receiving the shaft (reference numeral 2 in the example of FIG. 1). On the front side 12, which is in the installation situation on the control plate (reference numeral 6 in the example of Figure 1), a trough-shaped indentation 13 is provided, the surface 14 forms the functional surface to the control plate. This surface is coated with an electrodeposited coating 15.

In FIG. 2, an edge region of the front side 12 is marked with dotted lines. This area is considered in more detail in Figures 3 to 5.

FIGS. 3a to 3c show detailed views of the corresponding region, wherein the depression 13 ends laterally at an inwardly sloping step 16. Such a step 16 is for the attachment of the order-welded coating 15 of disadvantage. Namely, when, as indicated in Figure 3b with reference to the arrow B, the application of the coating 15 takes place from the inside to the outside, so moves the instantaneous weld 15m from inside to outside, escapes the welding gas mainly in the area C on the outside of the current weld 15m, as indicated in Figures 3b and 3c. The arrows visible in the figure represent the main direction of flow of the convection, the length of the arrows being representative of the extent of convection at the respective point, in the region D above the immediately previously applied coating layer. 15z, only a small amount of welding gas escapes, since the convection resulting from the high heat, as indicated by the arrows, represents a barrier to the escape of the welding gases. Therefore obstructed in the welding direction, ie outwardly rising step or contour 16, the escape of the welding gases. As soon as the instantaneous weld 15 approaches step 18, as shown in FIG. 3 c, only a narrow space is available for the escape of the welding gases and pore formation occurs, which, however, must absolutely be avoided.

The inventors had already experimented for some time to coat the functional surface of the drum by build-up welding. However, a practical implementation failed because of the problem of pore formation, regardless of the specific method used, that is, regardless of whether the coating was applied by laser cladding, plasma powder build-up welding or other methods. Because the requirement of suitability for use in axial piston machines is a complete absence of pores of the coating, especially at the typical operating pressures of a few hundred bar, the hydraulic oil penetrates into any existing pore, causing an immediate onset and progressive detachment of the coating and thus a rapid total failure of the axial piston and secondary damage in the entire oil cycle can cause. In the early experiments, it was unrecognized that the main problem was insufficient drainage of the welding gases. On the basis of the measures described in the present application, it was possible to achieve that axial piston machines with job-welded coatings on the functional surface of the drum are now practically usable.

In a preferred embodiment, the invention therefore provides a special design of the trough 13, as shown schematically, for example in Figure 4. In this embodiment, an outwardly rising step on the edge of the trough 13 is deliberately avoided. Instead, the trough 13 comprises an edge zone 17 with a concave one compared to the central area 18 of the trough 13 Curvature of the surface 14. The inclination angle α of the surface 14 to the radial plane E of the drum 10 is in the central region 18 of the trough 13 at a maximum of about 10 ° (a1) and increases even in the edge zone 17 only to a maximum of 20 ° (Q2). These angles are sufficiently small to allow sufficient escape of the welding gas at each point. Also missing is the ever steady and never abrupt change of the slope on an inner edge, in which the outflow of the welding gases could be hindered and thus delayed. Furthermore, such a design contributes to increasing the mechanical strength of the coating 15. In the example shown, the surface 14 reaches its maximum slope directly at the edge point 19 of the depression 13, which is advantageous for the mechanical strength of the coating.

In the example shown, the coating 15 consists of three individual layers 15a, 15b and 15c, which were applied sequentially successively by means of laser deposition welding.

Figures 5a and 5b show further examples of how the surface 14 of the trough could be formed in the edge region in a manner favorable for build-up welding. In the case of FIG. 5a, an outwardly sloping step 20 is provided at the edge point 19 of the trough 13, through which welding gas can escape. In the edge zone 17 before no increased concave curvature is provided, but a relatively shallow fading of the trough 13 with an inclination angle α of about 10 °. In the case of FIG. 5b, an outwardly sloping step 21 is already provided within the trough 13, that is to say still in the edge zone 17 and before the edge point 19.

FIG. 6 shows a plan view of the functional surface 14 of a drum 10 in a variant in which the coating 15 is divided into a plurality of discrete zones. The functional surface 14 of the drum 10 is thus not over the entire surface coated with the coating 15, but only in sections. Namely, as the first coating section, an annular bead 151 is provided, which is continuously extending over the circumference of the functional surface 14. This coating section 151 serves as a support ring. It is thin compared to the diameter of the drum 10 and extends radially outside the kidney openings 22 which lead to the cylinder bores 3 for the pistons 4. In addition to the first coating ring 151, a coated functional surface may be provided in the form of a second, wider coating ring 152 which extends in the region of the kidney openings 22 and has a width which is greater than the radial extent of the kidney openings 22. The kidney openings 22 are completely within the area covered by the second coating ring 152. In this way, the application of coating material in a portion of it where no coating is needed _»can be avoided. As a result, a material saving and weight saving can be achieved.

FIG. 7 shows a variant, which differs from FIG. 6, of how the coating 15 on the functional surface 14 of the drum 10 can be subdivided into a plurality of discrete zones. Namely, instead of the second coating ring 152, a plurality of loop-shaped sealing zones 153a, 153b, etc. are provided which extend locally around the edges of the kidney openings 22. Thus, the feeds 151 and 153a, 153b etc. can only be found in places where they are actually or especially needed. Thus, further material savings and weight savings can be achieved.

FIG. 8 shows a perspective view of a control plate 6 with a coating zone, shown by way of example, on the inner surface 23, which faces the functional surface 13 of the drum 10 and together with the latter forms the contact zone 9. As can be seen, also includes the control plate 6 a plurality of kidney openings, namely an elongated low pressure kidney 24 and a plurality of high pressure kidneys 25, which correspond in shape to the kidney openings 22 of the drum. Further, in the control plate 6, a control notch 26 and a cutout 27, through which the control plate 6 rotatably in the housing 1 of the axial piston machine can be attached. In place of the coating on the functional surface of the drum, As is indicated only incompletely in the figure, a coating 15 may be provided on the inner surface 23 of the control plate 6. In principle, the same applies to the distribution of the coating as was explained in connection with FIGS. 6 and 7 for the functional surface of the drum, FIG. 8 showing, by way of example, a loop-shaped sealing zone 154 which extends locally around the edge of a high-pressure kidney 25 with control notch 28 ,

Finally, FIGS. 9a and 9b show a longitudinal sectional view through a sliding block 30 and a plan view of the lower surface 31 of a sliding block 30 with which it rests on the inside of the sliding plate 5 and slides along the axial piston machine during operation thereof. The lower surface 31 of the sliding shoe 30 is covered over its entire surface with an application-welded coating 32, the coating 32 being segmented by channel-shaped recesses 33. They comprise concentric circles 33 a and 33 b, which are arranged around an outlet opening 34 of an oil passage 35 in the middle of the lower surface 31 of the sliding shoe 30. Recesses 33 in the form of connecting channels 33c are provided between the exit opening 34 and the innermost circle 33a and between the outermost circle 33b and the edge of the lower surface. Thus, an optimal distribution of oil over the lower surface 31 of the sliding disk 30 is achieved. The depressions 33 are all formed by a cover layer in the otherwise multi-layer coating 32 which is missing at the corresponding locations.

Claims

claims

1. Axialkoibenmaschine with a drum with cylinder bores and received therein piston, which is arranged between a sliding disk and a control plate, wherein the drum is rotatably mounted about a rotation axis, characterized in that at least one component of the Axialkoibenmaschine in contact with a sliding partner in contact Surface is coated at least in sections with a job-welded coating.

2. Axialkoibenmaschine according to claim 1, characterized in that the drum has at its first end face a functional surface, with which it bears against the inner surface of the control plate, wherein the drum on the functional surface or the control plate on the inner surface at least partially coated with an order-welded coating is.

3. Axial piston machine according to claim 2, characterized in that the drum has at its first end face a trough, the surface forms the functional surface, wherein the trough is preferably trough-shaped and has a concave surface, wherein preferably the inclination of the trough surface to the radial plane of the drum and / or the curvature of the trough surface is varied as a function of the distance from the axis of rotation of the drum, and particularly preferably

4. axial piston machine according to claim 3, characterized in that the inclination and / or the curvature increases in an outer edge region, wherein the inclination of the trough surface to the radial plane of the drum preferably exceeds an angle of 45 ° and preferably 25 ° at any point.

5. axial piston machine according to claim 3, characterized in that the inclination or curvature decreases in an outer edge region of the first end face of the drum and / or that this curvature is convex in an outer edge region and / or the outer edge region at least partially has no curvature, wherein the inclination of the trough surface to the radial plane of the drum preferably does not exceed an angle of 45 ° and preferably 25 ° at any point.

6. Axial piston machine according to one of claims 3 to 5, characterized in that the trough surface has at least one outwardly sloping step or outer edge, preferably in an outer edge region.

7. Axial piston machine according to one of claims 2 to 6, characterized in that the functional surface of the drum or the inner surface of the control plate is not completely, but only partially coated with an order-welded coating, preferably a first annular coating portion may be provided _"the over the periphery of the functional surface of the drum or on the extending of the inner surface of the control plate, and preferably outside the kidney ports of the drum or of the control plate extends, wherein particularly preferably a second annular coating portion may be provided, of about extends the circumference of the functional surface of the drum or inner surface of the control plate and in the region of the kidney openings of the drum or the control plate and wherein particularly preferably isolated coating zones may be provided which are not in contact, for example in the region of the kidney openings,

8. Axial piston machine according to one of the preceding claims, characterized in that attached to the sliding-disk-side ends of the piston of the axial piston sliding shoes, which abut with its underside on the inside of the sliding disk, wherein the underside of the sliding shoes or the inside of the sliding disk at least in sections with a coated coating, wherein the coating preferably extends over the entire underside of the sliding shoes, wherein the coating is particularly preferably segmented by channel-shaped omissions or depressions, which further preferably run as concentric circles about a reference point in the central region of the underside of the shoe ,

9. Axial piston machine according to one of the preceding claims, characterized in that the coating is multi-layered, wherein the layers can be arranged one another in layers or side by side and wherein the coating materials have specific properties, such as degrees of hardness.

10. Axial piston machine according to one of the preceding claims, characterized in that »it is the coating material is a non-ferrous metal, preferably with a copper content of 50% to 80%.

11. Axial axial piston machine according to one of the preceding claims, characterized in that the coating material consists of CuSn10Pb9Ni2, CuZn40AI2Mn2Si or CuSn10Bi8Ni5

12. A method for producing a Äxialkolbenmaschine according to any one of the preceding claims, characterized in that the coating is applied by build-up welding and preferably laser cladding.

13. A method for producing a Äxialkolbenmaschine according to claim 12, characterized in that the coating powder is supplied to the active zone of the coating in the form of coating powder.

14. A method for producing a Äxialkolbenmaschine according to claim 12 or 13, characterized in that the pulverformige starting material has a spherical or spherical geometry.