Production method, piston blank, piston and axial piston machine having said piston

Abstract

A method of producing a piston blank, comprising producing an intermediate blank of a piston for an axial piston machine by extrusion wherein the intermediate blank includes a shaft portion, a ball head portion, and a sealing portion, wherein the shaft portion connects the ball head portion to the sealing portion. The method also includes producing a piston blank of the piston from the intermediate blank and machining a through-opening in the intermediate blank, wherein the through-opening extends within the piston blank in the longitudinal direction.

Claims

1. A production method, wherein the production method comprises the following method steps: producing an intermediate blank of a piston for an axial piston machine by extrusion, wherein the intermediate blank has a shaft portion, a ball head portion and a sealing portion, wherein the shaft portion connects the ball head portion to the sealing portion, wherein the ball head portion includes an indentation and the sealing portion includes a recess, wherein the ball head portion includes a larger outside diameter than the shaft portion; and producing a piston blank of the piston from the intermediate blank, wherein a through-opening is incorporated in the intermediate blank by machining, wherein the through-opening extends within the piston blank in a longitudinal direction, wherein the indentation at the piston blank forms an outlet for the through-opening; wherein the recess and the indentation are created on the intermediate blank as a result of the extrusion, wherein the recess forms an inlet for the through-opening and the sealing portion includes a flange or collar extending with respect to a main axis in a radial direction, wherein the main axis is defined via a longitudinal axis along the shaft portion, wherein the sealing portion includes a larger diameter than the shaft portion.

2. The production method of claim 1, wherein a surface of the shaft portion with near-final contour and an end face of the sealing portion with near-final contour is created on the intermediate blank as a result of the extrusion.

3. The production method of claim 1, wherein a spherical segment geometry is created on a circumferential face of the sealing portion on the intermediate blank or on the piston blank by machining.

4. The production method of claim 1, wherein the piston is produced in a further method step, wherein the piston is produced by finishing the piston blank.

5. The production method as claimed in claim 4, wherein the finishing of the piston blank comprises the following substeps: hardening the piston blank; machining a ball geometry of the ball head portion; machining a spherical segment geometry of the sealing portion.

6. The production method of claim 1, wherein the ball head portion includes an elevation which extends peripherally with respect to a main axis defined via a longitudinal axis along the shaft portion, as a result of the extrusion, wherein the elevation is formed as a result of volume compensation during the extrusion.

7. The production method of claim 1, wherein the shaft portion is connected to the ball head portion via a first transition region via a radius.

8. The production method of claim 7, wherein a second transition region is formed where the shaft portion is connected to the sealing portion via a conical widening extending in the direction of the sealing portion and via a further radius.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further features, advantages and effects of the disclosure will emerge from the following description of exemplary embodiments of the disclosure. In the drawings:

(2) FIG. 1 shows in a sectional illustration an axial piston machine having an axial piston as one exemplary embodiment of the disclosure;

(3) FIG. 2 shows in a sectional illustration an intermediate blank of the piston from FIG. 1;

(4) FIG. 3 shows in a sectional illustration a piston blank of the piston from FIG. 1.

DETAILED DESCRIPTION

(5) FIG. 1 shows in a sectional illustration an axial piston machine 1 which is designed and/or suitable for example for an agricultural or construction machine. The axial piston machine 1 takes the form of an oblique-axis pump which may convert mechanical energy into hydraulic energy. The axial piston machine 1 has a plurality of pistons 2, a rotor 3 and a disk 4. The axial piston machine 1 has for example nine of the pistons 2, wherein the pistons 2 take the form of axial pistons. The pistons 2 are connected to the disk 4 in an articulated manner via a ball joint 5.

(6) The rotor 3 rotates during operation of the axial piston machine 1 about a first axis of rotation R1. The rotor 3 takes the form of a piston housing and has for this purpose a plurality of cylinder bores 6, wherein each piston 2 is movably arranged in one of the cylinder bores 6 and is rectilinearly guided in the axial direction with respect to the axis of rotation R. The cylinder bores 6 are arranged so as to be uniformly spaced apart from one another about the axis of rotation R.

(7) The disk 4 rotates during operation of the axial piston machine 1 about a second axis of rotation R2, wherein the first and the second axis of rotation R1, R2 intersect, with the result that the rotor 3 is arranged at an angle relative to the disk 4. A rotation of the disk 4 causes the pistons 2 to be moved back and forth in the cylinder bores 6, with the result that they deliver a hydraulic fluid, for example.

(8) FIG. 2 shows an intermediate blank 7 of the piston 2 from FIG. 1, in a longitudinal section along a main axis H. The intermediate blank 7 is produced for example from a raw part, for example from a solid material of round cross section, by extrusion with an extrusion tool. For example, the extrusion tool comprises a punch and a die. The intermediate blank 7 has a ball head portion 7a, a shaft portion 7b and a sealing portion 7c. The shaft portion 7b connects the ball head portion 7a and the sealing portion 7c directly to one another, with the intermediate blank 7 being extruded.

(9) The ball head portion 7a has an elevation which extends peripherally about the main axis H and which is illustrated in the detail view B. For example, the die of the extrusion tool has a peripheral groove which serves for volume compensation for excess material. The raw part has for example a small oversize, with it being possible during the extrusion for the excess material to escape into the groove of the die such that the elevation 9 is formed.

(10) The sealing portion 7c takes the form of a peripheral collar with respect to the main axis H and extends radially outward. The sealing portion 7c has a recess 10 which is illustrated in the detail view C. The recess 10 takes the form of a cylindrical countersink with an inwardly curved bottom region. The recess 10 is arranged coaxially and/or concentrically to the main axis H on an axial end side of the sealing portion 7c. The recess 10 serves for reducing the weight of the piston 2 and for this purpose extends over for example more than 60%, preferably more than 70%, especially more than 80%, of the end face of the sealing portion 13. The indentation 8, the elevation 9 and the recess 10 can be produced jointly as a result of the extrusion in one process step together with the shaping of the intermediate blank 7.

(11) The shaft portion 7b has a cylindrical shape, with the shaft portion 7b being connected to the ball head portion 7a in a first transition region 11a via a radius. In a second transition region 11b, the shaft portion 7b is connected to the sealing portion 7c via a conical widening extending in the direction of the sealing portion 7c and via a further radius. The first and the second transition region 11a, b and also the lateral surface of the cylindrical form a surface 12 of the shaft portion 7b with near-final contour.

(12) The ball head portion 7a has an indentation 8 which is illustrated in the detail view A. The indentation 8 takes the form of a conical countersink and is arranged coaxially and/or concentrically to the main axis H on an axial end side of the ball head portion 7a.

(13) The sealing portion 7c has on its axial end side, with respect to the main axis H, an end face 13 with near-final contour. The end face 13 takes the form of a circular ring face and is delimited by the recess 10 in the radial direction. The surface 12 with near-final contour and the end face 13 with near-final contour are created as a result of the extrusion and have, for example, the final contour of the finished piston 2 after the extrusion process. The surface 12 and the end face 13 may have a sufficiently high surface quality and/or component accuracy already after the extrusion, with the result that the surface 12 and the end face 13 no longer have to be finished.

(14) FIG. 3 shows a piston blank 14 of the piston 2 from FIG. 1, in a longitudinal section along the main axis H. The piston blank 14 has a through-opening 15 which extends within the piston blank 14 in the axial direction with respect to the main axis H. To produce the piston blank 14, the through-opening 15 is incorporated in the intermediate blank 7 by machining. The through-opening 15 is arranged coaxially and/or concentrically to the main axis H. The through-opening 15 takes the form of a stepped through-bore and extends in the direction of the indentation 8 starting from the recess 10. Here, the recess 10 forms an inlet for the through-opening 15, and the indentation 8 forms an outlet for the through-opening 15. The through-opening 15 opens within the indentation 8 or in the region of a bevel of the indentation 8, as illustrated in the detail view D. This ensures that no burr occurs on the end side of the ball portion 7a through the bore outlet.

(15) The sealing portion 7c has a spherical segment geometry 16, which is illustrated in the detail view F, on a circumferential face. The spherical segment geometry 16 serves for example to prevent the piston 2 wedging in the piston receptacle 6. For this purpose, the circumferential face of the sealing portion 7c of the intermediate blank 7 is machined such that the spherical segment geometry 16 is created. For example, the through-bore 15 and the spherical segment geometry can be created on the intermediate blank 7 in a common machining process such that the piston blank 14 is formed.

(16) To produce the piston 2, the piston blank 14 is for example hardened before the ball portion 7a, in particular a ball geometry 17, and the sealing portion 7c, in particular the spherical segment geometry 16, are machined to the final contour. For example, the ball geometry 17 and the spherical segment geometry 16 are machined in a finishing process by a hard-turning, grinding and/or superfinishing process. Here, for example, the elevation 9 is removed and/or a sealer receptacle, which is designed for example to receive at least one piston ring, is incorporated in the region of the spherical segment geometry 16.

(17) An expansion or a change in dimension of the piston blank 14 by the hardening process is already taken into account in the design of the extrusion tool. The extrusion tool or the extrusion process is correspondingly optimized such that all contours and dimensions which do not have to be finished, in particular the surface 12 with near-final contour and the end face 13 with near-final contour, correspond to the final contour after a hardening process.

LIST OF REFERENCE SIGNS

(18) 1 Axial piston machine

(19) 2 Piston

(20) 3 Rotor

(21) 4 Disk

(22) 5 Ball joint

(23) 6 Cylinder bore

(24) 7 Intermediate blank

(25) 7a Ball head portion

(26) 7b Shaft portion

(27) 7c Sealing portion

(28) 8 Indentation

(29) 9 Elevation

(30) 10 Recess

(31) 11a First transition region

(32) 11b Second transition region

(33) 12 Surface with near-final contour

(34) 13 End face with near-final contour

(35) 14 Piston blank

(36) 15 Through-opening

(37) 16 Spherical segment geometry

(38) 17 Ball geometry

(39) A-F Detail views

(40) H Main axis

(41) R1 First axis of rotation

(42) R2 Second axis of rotation