CH714404A1 - Axial piston machine with coated sliding surface. - Google Patents

Abstract

The invention relates to an axial piston machine comprising a drum (10) with cylinder bores (3) and pistons (4) accommodated therein, which is arranged between a sliding disk and a control plate, wherein the drum (10) is rotatably mounted about a rotation axis. In this case, at least one component of the axial piston machine is coated on a surface which is in contact with a sliding partner, at least in sections, with a job-welded coating. The invention further relates to a method for producing such an axial piston machine, wherein the coating is applied by deposition welding and preferably laser deposition welding.

Description

Description: 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 is enclosed with cylinder bores between a hydraulically arranged control plate and a mechanical side sliding disc. 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 end 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 to keep the friction at the functional surfaces low and To improve the life of the 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 low and so 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 axial piston on a coated with a sliding surface in contact surface is coated at least in sections with a contract 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. The axial piston machine according to the invention is preferably a swashplate machine, wherein the drive shaft and the drum axis always run in a line and the position of the disk deviates therefrom. 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 the purpose of preventing their rotation fixed control plate move during operation of the axial piston relative to each other, 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 progressing in the course of the useful life abrasion on the two surfaces on the high pressure side, the oil leakage.

In contrast to the coating by, for example, plating or pouring, as known in the context of drum and control plate from the prior art, deposition welding is faster and cheaper 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 at its first end face a functional surface, with which it rests 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, it is thus in the component to the drum, in the sliding partner about the inner surface of the control plate and in the surface in contact with the sliding in contact surface around the functional surface of the drum. In this embodiment, the invention achieves a significant reduction in the manufacturing cost of 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 easily made available by the deposition welding alternative, according to which the coating can also be attached to the other partner of the sliding contact, namely on the control panel. 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, the surface of which forms the functional surface, wherein the trough is preferably trough-shaped and has a convex 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 hole of the drum, so that the actual functional surface is not disc-shaped but circular or the trough-shaped trough has the shape of a tub 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. In the case of a coating of the functional surface of the drum, the surrounding area is preferably not covered with an application-welded coating 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 application of welding to the trough an effective escape of the welding gases and thus to avoid pore formation.

In one embodiment, it is provided that changes the inclination of the trough surface to the radial plane of the drum and / or the curvature of the trough surface in dependence of the distance, for example with increasing distance from the axis of rotation of the drum. The depression surface can theoretically be divided into a central area and an outer edge area and have different slopes and / or bends in these two areas. Preferably, at the transition between the central region and the edge region, a discontinuous change of the curvature takes place. 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 convex 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 convex 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 is convex in an outer edge region. A flat as possible conclusion of the trough by a smaller pitch or a concave 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 exceeds 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 convex course of the trough or an inclination of the trough contour whose orientation approximates a convex course instead of a concave course, are generally unfavorable for an effective escape of the welding gases. To avoid pore formation in the coating, however, sufficiently effective and sufficiently rapid escape of the welding gases is essential. Considering preferred geometries of typical tumble, angles of between 10 ° and 20 ° may be desirable. 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.

Alternatively to a trough, the end face may also be formed flat or have a shape with a concave surface, for example. If the machine geometry allows such a design, such an embodiment is advantageous because it favors the outflow of the welding gases.

In the variant in which the control plate is coated by cladding, escape of the welding gases may be favored in the case of a concave shape, which would not result in convex 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 10% 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.

Alternatively, 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 area of the kidney openings, which surround, for example, the kidney openings, but are not in contact with each other.

In one embodiment it is provided that are attached to the sliding-disk side ends of the piston of the axial piston sliding blocks, which abut with its underside on the inside of the sliding disk, the underside of the sliding shoes or the inside of the sliding disc at least partially coated with a contract welded coating is. 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 one embodiment, it may 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 serve as a labyrinth for retaining oil that can escape 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. The individual layers may consist of the same or different materials, whereby, for example, certain hardness profiles can be achieved. Exemplary thicknesses of 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.

In the context of multi-layer coatings can be provided in a coating of the functional surface of the drum or the inner surface of the control plate that one or more base layers extend over the entire functional surface or control panel inner surface or a larger part of the functional surface or control panel inner surface as a or several additional layers, which are provided for example only in those areas which have been mentioned above in the context of the coating rings.

In a coating of the underside of the sliding block may be provided in the context of multi-layer coatings that one or more base layers extend over the entire bottom and omissions, for example, in the training as described above, relate to only one or more additional layers.

In one embodiment, one of the 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 coated with a contract welded coating.

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

In the case of a coating of the functional surface of the drum, it may 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 webs. The areas near the axis of rotation of the functional surface are thus coated in each working step before 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 in accordance with the radial position such that a coating results with a uniform surface.

In one embodiment, the entire component is heated before and / or during coating, 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 shows:

Fig. 1: a sectional view of an axial piston machine;

2 shows 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;

4 shows a detailed view of a favorably formed edge region of the end face of such a drum;

5 shows further two detailed views of advantageously formed edge regions of the end face of such a drum;

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

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

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

9 shows views of a sliding block of an axial piston machine according to the invention with a underside coated by application whitening.

A longitudinal sectional view of an axial piston machine is shown in Fig. 1. 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 included, 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 pistons 4, sliding shoes 30 are fixed, which abut with their underside on the inside of the sliding disk 5. 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. 2. 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 FIG. 1), a trough-shaped indentation 13 is provided, whose surface 14 forms the functional surface to the control plate. This surface is coated with a job-welded coating 15.

2, an edge region of the end face 12 is marked with dotted lines. This area is considered in more detail in FIGS. 3 to 5.

3a to 3c show detailed views of the corresponding area, wherein the trough 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, as indicated in Fig. 3b with reference to the arrow B, the application of the coating 15 from the inside to the outside takes place, so the instantaneous welding point 15m moves from inside to outside, escapes the welding gas mainly in the area C on the outside of the current Welding point 15m, as indicated in Figs. 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 section 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, one in the direction of welding, i. Outwardly rising stage or contour 16 the escape of the welding gases. As soon as the instantaneous welding point 15m approaches step 16, as shown in FIG. 3c, only a narrow spatial area 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 means of application whitening. However, a practical implementation failed because of the problem of pore formation, regardless of the concrete method used, that is, regardless of whether the coating was applied by means of laser cladding, plasma powder deposition 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 the insufficient discharge 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 can now be used practically.

In a preferred embodiment, the invention therefore provides a special design of the trough 13, as shown schematically for example in Fig. 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 greater convex curvature of the surface 14 compared to the central region 18 of the trough 13. The angle of inclination a 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 approximately 10 ° (FIG. a1) and increases even in the edge zone 17 only up to a maximum of 20 ° (a2).

These angles are sufficiently low to allow sufficient escape of the welding gas at each point. It also lacks the ever-steady and never abrupt change in the slope of 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.

5a and 5b show further examples of how the surface 14 of the trough in the edge region could be designed in a manner favorable for the application 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 convex curvature is provided, but a relatively shallow fading of the trough 13 with an inclination angle a of about 10 °. In the case of FIG. 5b, an outwardly sloping step 21 is already provided within the trough 13, that is 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 weld 151 is provided which extends continuously over the circumference of the functional surface 14. This coating section 151 serves as a support ring. It is thin in comparison 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 that 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 is achieved.

Fig. 7 shows a different from Fig. 6 variant, as the coating 15 on the functional surface 14 of the drum 10 can be divided 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 coatings 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 forms the contact zone 9 together with it. 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 fixed. Instead 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. For the distribution of the coating is basically the same as explained in connection with Figs. 6 and 7 for the functional surface of the drum, wherein in Fig. 8 by way of example a loop-shaped sealing zones 154 is shown locally around the edge of a high pressure kidney 25 with control notch 26 runs.

Finally, FIGS. 9a and 9b show a longitudinal sectional view through a sliding shoe 30 and a plan view of the lower surface 31 of a sliding shoe 30 with which it rests on the inside of the sliding disk 5 and glides along the inner piston 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 33a and 33b 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 (16)

claims 1. 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, characterized in that at least one component of the axial piston machine in contact with a sliding partner in contact Surface is coated at least in sections with a contract welded coating. 2. Axial piston machine according to claim 1, characterized in that the drum has at its first end face a functional surface, with which it rests 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, whose surface forms the functional surface, wherein the trough is preferably trough-shaped and has a convex surface. 4. Axial piston machine according to claim 3, characterized in that the inclination of the trough surface to the radial plane of the drum and / or the curvature of the trough surface changes in dependence on the distance from the axis of rotation of the drum. 5. axial piston machine according to claim 4, characterized in that the inclination and / or the convex curvature increases in an outer edge region. 6. axial piston machine according to claim 4, characterized in that the inclination decreases in an outer edge region and / or that the curvature is convex in an outer edge region. 7. Axial piston machine according to one of claims 3 to 6, characterized in that the inclination of the trough surface to the radial plane of the drum exceeds an angle of 45 ° and preferably 25 ° at any point. 8. Axial piston machine according to one of claims 3 to 7, characterized in that the trough surface has an outwardly sloping step or outer edge, preferably in an outer edge region. 9. Axial piston machine according to one of claims 2 to 8, 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 a contract welded coating. 10. axial piston machine according to claim 9, characterized in that a first annular coating portion may be provided which extends over the circumference of the functional surface of the drum or inner surface of the control plate and preferably extends outside the kidney openings of the drum or the control plate. 11. Axial piston machine according to claim 9 or 10, characterized in that a second annular coating portion may be provided which extends over the circumference of the functional surface of the drum or inner surface of the control plate and extending in the region of the kidney openings of the drum or the control plate. 12. axial piston machine according to claim 9 or 10, characterized in that isolated coating zones may be provided which are not in contact with each other, for example in the region of the kidney openings. 13. Axial piston machine according to one of the preceding claims, characterized in that attached to the sliding-disk-side ends of the pistons of the axial piston sliding blocks, which rest 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 partially with a order-welded coating is coated. 14. Axial piston machine according to claim 13, characterized in that the coating extends over the entire underside of the sliding shoes, wherein the coating is preferably segmented by channel-shaped omissions or depressions, which further preferably as concentric circles about a reference point in the central region of the underside of the shoe run. 15. Axial piston machine according to one of the preceding claims, characterized in that the coating is multi-layered. 16. A method for producing an axial piston machine according to one of the preceding claims, characterized in that the coating is applied by deposition welding and preferably laser deposition welding.