Piston for an axial piston machine

Abstract

A piston for an axial machine includes a piston body having a cavity that is closed in a pressure-tight way. The cavity is divided into a plurality of chambers, arranged one beside the other in cross-section.

Claims

1. A piston for an axial piston machine, comprising: a piston body, which, in its interior, includes a cavity closed in a pressure-tight way, and webs left between several chambers into which the cavity is divided, wherein the chambers are arranged about a central column of the piston body, and wherein the chambers have an arrangement that is symmetrical or asymmetrical to the middle axis of the piston body.

2. The piston according to claim 1, wherein the chambers are arranged one beside the other in cross-section of the piston body and/or extend axially in the piston body.

3. The piston according to claim 2, wherein the chambers are manufacturable by material-removing methods, wherein the chambers are bores, or wherein the piston body includes an integral base element in which the chambers are incorporated, and wherein the chambers are closed towards a working surface of the piston by one or more closure elements.

4. The piston according to claim 2, wherein the piston body includes a middle part which is connected with a base part, wherein the chambers are arranged in the middle part, wherein the middle part or elements of which the middle part is made are at least partly manufactured by a forming process or by DMLS, or wherein the middle part is made in one piece or consists of several elements.

5. The piston according to claim 2, wherein each of the chambers is closed individually by a separate closure element, and wherein the closure elements are plugs or screw elements.

6. The piston according to claim 2, wherein the chambers are closed by a common closure element, wherein the closure element is an end cap forming the working surface of the piston, and wherein the chambers reach into the end cap or are at least partly arranged in the end cap.

7. The piston according to claim 1, wherein the chambers are formed hollow and cylindrical.

8. The piston according to claim 1, wherein the chambers are manufacturable by material-removing methods, wherein the chambers are bores, or wherein the piston body includes an integral base element in which the chambers are incorporated, and wherein the chambers are closed towards a working surface of the piston by one or more closure elements.

9. The piston according to claim 1, wherein the piston body includes a middle part which is connected with a base part, wherein the chambers are arranged in the middle part, wherein the middle part or elements of which the middle part is made are at least partly manufactured by a forming process or by DMLS, or wherein the middle part is made in one piece or consists of several elements.

10. The piston according to claim 1, wherein each of the chambers is closed individually by a separate closure element, and wherein the closure elements are plugs or screw elements.

11. The piston according to claim 1, wherein the chambers are closed by a common closure element, wherein the closure element is an end cap forming the working surface of the piston, and wherein the chambers reach into the end cap or are at least partly arranged in the end cap.

12. The piston according to claim 1, wherein the piston body is axially traversed by a pressure channel, and wherein the pressure channel extends in the central column.

13. The piston according to claim 1, further comprising a slipper which is connected with the piston body via a ball joint, wherein the piston body includes a hemispherical cutout into which a partly spherical part of the slipper engages, and wherein a pressure channel ends in the hemispherical cutout or the slipper includes the pressure channel.

14. An axial piston machine comprising at least one piston according to claim 1.

15. A method for manufacturing a piston for an axial piston machine, including a piston body, which, in its interior, includes a cavity closed in a pressure-tight way, and webs left between several chambers into which the cavity is divided, comprising: making the piston by connecting a middle portion, in which the chambers are arranged, with a base part, and making a pressure channel of the piston by drilling.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows an exemplary embodiment of an axial piston machine according to the invention,

(2) FIG. 2a shows a sectional view in an axial direction through a first exemplary embodiment of a piston body of a piston according to the invention, in which the chambers are made by a material-removing method,

(3) FIG. 2b shows a sectional view in axial direction through a piston according to the invention, in which the piston body shown in FIG. 2a has been completed by a slipper,

(4) FIG. 2c shows a sectional view in radial direction through the first exemplary embodiment of a piston body as shown in FIG. 2b,

(5) FIG. 3a shows a sectional view in axial direction through a second exemplary embodiment of a piston according to the invention, in which the chambers are arranged in a middle part which has been made by a material-forming method,

(6) FIG. 3b shows a sectional view in axial direction through a piston according to the invention, in which the piston body shown in FIG. 3a has been completed by a slipper,

(7) FIG. 3c shows three sectional views in radial direction through possible designs of the second exemplary embodiment of a piston body as shown in FIG. 3a,

(8) FIG. 4a shows a perspective view of a third exemplary embodiment of a piston according to the invention, in which the chambers each are separately closed by closure elements,

(9) FIG. 4b shows a sectional view in axial direction through the third exemplary embodiment shown in FIG. 4a, and

(10) FIG. 4c shows a sectional view in radial direction through the third exemplary embodiment shown in FIG. 4a.

DETAILED DESCRIPTION OF THE INVENTION

(11) FIG. 1 shows an exemplary embodiment of an axial piston machine according to the invention, in which the pistons according to the invention are used.

(12) The exemplary embodiment relates to a swash plate machine in which the cylinder block 5 is non-rotatably connected with the drive shaft 1. The swash plate 2 is non-rotatably connected with the housing 7, i.e. it cannot rotate with the same. Since the exemplary embodiment relates to an adjustable machine, the same is pivotally mounted at the housing. The piston 4 supports on the swash plate 2. The control disk 6 likewise is non-rotatably connected with the housing 7 and is connected with the pressure line 8.

(13) When the drive shaft 1 and with the same the cylinder block 5 are rotated, the pistons perform a stroke movement. Due to a corresponding design of the control openings in the control disk 6, the same are alternately connected with the high-pressure side and the low-pressure side. By applying a sufficient oil pressure on the low-pressure side or by mounting hold-downs it is ensured that the pistons constantly rest against the swash plate. Such axial piston machines equally are usable both as hydraulic motors and as hydraulic pumps.

(14) In the exemplary embodiment, the pistons include slippers 3 which via a ball joint are connected with the piston body 4 of the pistons and via which the pistons slide on the swash plate.

(15) In FIGS. 2 to 4 three exemplary embodiments of pistons are shown, as they are used in the axial piston machine shown in FIG. 1. Each piston body 4 includes a plurality of chambers 9 closed in a pressure-tight way, which reduce the weight of the piston body without creating dead spaces. In cross-section, i.e. in a plane which is vertical to the longitudinal axis of the piston, the chambers 9 are arranged one beside the other. Thus, webs are left between the individual chambers, which stabilize the piston body.

(16) In the first exemplary embodiment of FIG. 2, the chambers are incorporated into an integral base element 24 of the piston body by a material-removing method from the working side of the piston body. The webs left between the chambers hence likewise are made of the material of the piston body. The piston body preferably is made of steel.

(17) In the exemplary embodiments the chambers each are hollow cylindrical bores with a circular base area, which extend axially in the piston body. As can be understood in particular from FIG. 2c, the bores 9 are arranged around a central column of the piston body, which thus remains connected with the outer circumference of the cylinder body via the webs left between the chambers. In the exemplary embodiment six chambers are provided, which are annularly grouped around the central column symmetrically to the middle axis.

(18) In a second exemplary embodiment, which is shown in FIG. 3, the chambers are made by forming. In axial direction, the piston 4 includes a middle part 24 which is made by a forming method, and in particular, is extrusion-molded, cold-rolled, manufactured by pilgering, forged or manufactured as rolled profile.

(19) FIG. 3c shows three exemplary cross-sections through the middle part which includes cylindrical chambers and advantageously is extrusion-molded. As shown in the figures, the base area of the chambers can be e.g. circular, kidney-shaped or oval. The middle part 24 is designed in one piece.

(20) Alternatively, the middle part 24 also can have a multipart design, wherein several elements, of which the middle part is fabricated, can engage into each other in an axial sense (e.g. T-piece in a tube) or in a radial sense (more space for longitudinal profiling), or both at the same time.

(21) The structure produced by forming can be a radial one, an axial one or a combination of a radial and axial structure.

(22) On its end surface 23 facing away from the working side of the piston, the middle part 24 is connected with a base part 25 which serves the articulation to a slipper 3 via a ball joint. The base part 25 preferably is made in one piece and furthermore advantageously includes no closed cavities.

(23) Independent of the manufacture, the piston according to the invention includes a slipper in the exemplary embodiment, wherein a ball head arranged at the slipper 3 is mounted in a hemispherical cutout 14 on the rear side of the cylinder body.

(24) Through the central column a pressure channel 11 extends, which extends from an opening 12 passing through the working surface of the pressure piston to an opening 13 arranged in the region of the bearing of the slipper and is continued by a pressure channel 15 of the slipper. This pressure channel 15 of the slipper ends in a sliding-surface-side opening 16, so that the sliding surface is connected with the cylinder chamber via the pressure channel and thus is hydrostatically relieved. Furthermore, the pressure channel serves for lubricating the slipper.

(25) The pressure channel 11 likewise can be incorporated into the cylinder body 4 by a bore. In the exemplary embodiment shown in FIG. 3 the pressure channel can be manufactured by the forming process together with the chambers 9 at least in the region of the middle part 24.

(26) The two exemplary embodiments shown in FIGS. 2 and 3 differ from the third exemplary embodiment shown in FIG. 4 with regard to the closure of the chambers 9.

(27) In the exemplary embodiments shown in FIGS. 2 and 3 an end cap 10 is provided, which is applied onto the end-face end 20 of the base element 21 or the end-face end 22 of the middle part 24, for example by welding. The end cap 10 forms the entire working surface of the piston and closes all chambers 9 as common closure element. Centrally through the closing cap 10 the pressure channel 11 is guided. In the exemplary embodiment, the chambers 9 are extended into the end cap 10, in order to further reduce the weight.

(28) In the exemplary embodiment shown in FIG. 4, on the other hand, the chambers 9 are closed individually by plugs 17 which are pressed into the end-face ends of the chambers 9. As shown in FIG. 4a, the working surface therefore is formed by the end-face end of the base element or the middle part and by the plugs arranged in this base element or middle part. Instead of plugs pressed in screw elements might also be used, for example.

(29) The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.