EP3676495B1 - Production method, piston blank, piston and axial piston machine having said piston - Google Patents

Description

The invention relates to a manufacturing method with the features of the preamble of claim 1. Furthermore, the invention relates to a piston blank, a piston and an axial piston machine with the piston.

Axial piston machines are known which work as a pump and / or as a motor. Such axial piston machines have a plurality of so-called axial pistons. For example, the axial pistons are machined.

The pamphlet DE 10 2004 061 863 A1 , which probably describes the closest prior art, discloses a piston for a piston machine, in particular for an axial piston machine in bent axis design, comprising a conical section, a neck area and a ball head formed on the neck area, a recess formed in the piston and one in the recess trained cones. The document also discloses a method for producing the piston, the method comprising the steps of parting round material to the desired length, producing an inner contour by cold extrusion, preparing the outer contour by pre-turning, producing the outer contour by rotary kneading and reworking.

The DE 20 2007 017 659 U1 describes a hydrostatic displacement unit with longitudinally displaceable pistons. Such a piston has a piston head, a piston skirt and a piston base. This piston has a through-hole and is manufactured using powder metallurgy.

The DE 199 34 216 A1 discloses a hollow piston with an annular cavity for a piston engine and a method for its manufacture.

The DE 10 2006 060015 A1 describes a hollow piston with an annular cavity for an axial piston machine,

The KR 2012 0037241 A discloses a piston with a ball head and a through hole.

The invention is based on the object of proposing a production method which is characterized by inexpensive production of a piston blank or a piston. It is also an object of the invention to propose a corresponding piston blank, a piston and an axial piston machine with the piston.

This object is achieved by a manufacturing method with the features of claim 1, a piston blank with the features of claim 7, a piston with the features of claim 8 and an axial piston machine with the features of claim 9. Preferred embodiments of the invention are disclosed in the subclaims, the following description and the figures.

The invention relates to a production method which is used in particular to produce a piston blank for a piston and / or the piston. The piston blank is preferably an intermediate product and can be produced in further process steps to form the piston. The piston is preferably designed and / or suitable for an axial piston machine. The piston is particularly preferably designed as an axial piston and / or the axial piston machine is designed as an axial piston pump. In particular, the axial piston machine is designed and / or suitable for an agricultural machine. In particular, the axial piston machine is designed as an axial piston motor and can, for example, be integrated into a wheel hub of the agricultural machine. The piston can be accommodated in a cylinder bore of the axial piston machine and / or guided in a straight line. In the context of the invention it is proposed that in a method step, preferably in a first method step, of the manufacturing method, an intermediate blank is manufactured by extrusion. In particular, for this purpose a blank, preferably a solid body, is reshaped by means of an extrusion tool. A shaft section and / or a spherical head section and / or a sealing section are preferably produced by the extrusion, so that the intermediate blank is formed. In particular, the extrusion produces a basic shape of the finished piston. Optionally, an elevation running around the main axis in relation to the main axis is generated on the spherical head section by the extrusion. The elevation is formed in particular due to volume compensation during extrusion.

The intermediate blank has the shaft section, the spherical head section and the sealing section. The spherical head section serves in particular for an articulated connection to a disk of the axial piston machine. The sealing section serves in particular to receive a sealant and / or to seal the piston against the cylinder bore. The shaft section connects the spherical head section with the sealing section. In particular, the spherical head section and the sealing section are molded directly onto the shaft section. The shaft section defines a main axis with its longitudinal axis and / or its axis of symmetry. The sealing section is preferably designed as a type of flange or collar which extends in the radial direction with respect to the main axis. The sealing section and / or the spherical head section can have a larger outer diameter than the shaft section. The shaft section preferably has a conical or cylindrical shape.

In a further process step, preferably in a second process step, of the production process, a piston blank is produced. For this purpose, a through opening is made in the intermediate blank by machining. The through opening can be made in the intermediate blank by a cutting tool. The through opening is preferably made in the intermediate blank by milling or by drilling. For this purpose, the The cutting tool is moved in the axial direction with respect to the main axis through the sealing section, the shank section and the ball section with a feed rate, while the cutting tool rotates.

The through opening extends within the piston blank in the longitudinal direction. The through opening is preferably designed as a through bore and / or a longitudinal bore and / or as a stepped bore. The through opening is particularly preferably arranged coaxially and / or concentrically to the main axis. The through opening preferably extends in the axial direction with respect to the main axis between the spherical section and the sealing section. In particular, the through opening penetrates the piston blank. The through opening can serve, for example, as a hydraulic relief.

The advantage of the invention is that the extrusion of the intermediate blank significantly reduces the cost of post-machining to the finished part, in particular the piston. As a result of the extrusion, the piston blank already has a high surface quality and high component accuracy. Furthermore, a directed fiber course is established in the piston produced by flow process technology, which has a positive effect on the component properties, for example the component strength. Another advantage is that the piston blank can be manufactured inexpensively by means of the manufacturing method according to the invention.

According to the invention, an impression is produced in the spherical head section by the extrusion. In particular, the impression is designed as a countersink. The impression is preferably arranged coaxially and / or concentrically to the main axis. In particular, the embossing is attached to an axial end face of the spherical head section and preferably extends axially in the direction of the shaft section.

The impression forms an exit for the through opening. In particular, the through opening is made separately in a subsequent machining process introduced into the intermediate blank. The embossing preferably has a larger diameter than the through opening, so that the embossing preferably forms a bevel on the through opening. Particularly preferably, the through opening of the piston blank opens inside the impression. This ensures that no burr occurs or is present on the axial end face of the spherical head section.

In a further preferred embodiment of the invention, the extrusion creates a recess in the sealing section. The recess is used in particular to reduce the weight of the piston. The shape of the intermediate blank and the recess and / or the embossing are preferably produced in one process step. In particular, the recess is designed as a conical and / or a cylindrical and / or a concave and / or a hemispherical depression. The recess is preferably arranged coaxially and / or concentrically to the main axis. In particular, the recess is attached to an axial end face of the sealing section and preferably extends axially in the direction of the shaft section.

The recess forms an entry for the through opening. The recess preferably has a larger diameter than the through opening. Particularly preferably, the through opening is made in the intermediate blank in a bottom area of the recess. The advantage of the recess is preferably that a smaller mass has to be moved in the later application through the recess. As a result, the operating behavior of the axial piston machine in particular can be improved.

In a further preferred implementation, a near net shape surface of the shaft section is produced by the extrusion on the intermediate blank. In particular, the near net shape surface is formed by a jacket surface of the shaft section. Alternatively or optionally in addition, the near net shape surface is provided by a transition area between the shaft section and the sealing section and / or between the shaft section and the spherical head section educated. The transition area is preferably designed as a radius and / or a cone with which the shaft section merges onto the spherical head section and / or the sealing section.

Alternatively or optionally in addition, a near net shape end face of the sealing section is produced. In particular, the near-net-shape end face in relation to the main axis is formed by an axial end face of the sealing section. The end face is preferably designed as a circular ring surface.

In particular, the extrusion produces a surface quality of the near net shape surface or end face which corresponds to the surface requirements of the finished piston. The near-net shape surface or end face therefore does not have to be reworked in the further machining processes, as a result of which the production costs of the piston are significantly reduced. Furthermore, the surface properties of the near-net-shape surfaces and the fiber orientation in the interior of the piston blank or piston form clear identifying features for a piston produced by extrusion.

In a further embodiment, a spherical cap geometry is produced on a circumferential surface of the sealing section by machining on the intermediate blank or on the piston blank. In particular, the spherical cap geometry prevents the piston from wedging in the cylinder bore of the axial piston machine. The dome geometry is preferably designed as a rotationally symmetrical outer surface of a spherical segment. The spherical cap geometry is particularly preferably manufactured by turning. In particular, the spherical cap geometry and the through opening are produced in a common machining process.

In a further specification of the invention, a piston is produced in a further method step. In particular, the piston is designed as the axial piston for the axial piston machine. The piston is manufactured by reworking the piston blank. The post-processing is preferably used to change the material properties and / or the geometrical properties Properties and / or the surface quality of the piston blank, so that the piston is formed.

In a specific implementation, the piston blank is hardened in a first sub-step of the further process step. In particular, a tolerance compensation, for example an opening or a change in dimension of the piston blank due to the hardening process, is already taken into account during the production of the intermediate blank. The extrusion tool is preferably designed in accordance with the tolerance compensation. The surfaces not to be reworked, preferably the near net shape surface of the shaft section and / or the near net shape end face of the sealing section, are undersized so that the areas not to be reworked correspond to the final contour after the hardening process.

In further sub-steps, the spherical geometry of the spherical head section and the dome geometry of the sealing section are machined. The dome geometry and the spherical geometry are preferably machined in a common machining process. Alternatively, the spherical shape and the spherical shape are machined in two separate machining processes. In particular, the spherical geometry and / or the dome geometry are machined by hard turning and / or by grinding and / or by superfinishing. For example, the circumferential elevation of the spherical head section is removed. For example, at least one groove running around the axis of rotation for receiving the sealing means is made in the sealing section.

Another object of the invention relates to a piston blank according to claim 7 or as described above. The piston blank is extruded and has the shaft section, the spherical head section and the sealing section, the shaft section connecting the spherical head section to the sealing section and an impression in the spherical head section being produced by the extrusion. Furthermore, the piston blank has the through-opening introduced by machining, the through-opening being inside of the piston blank extends in the longitudinal direction and wherein the indentation forms an outlet for the through opening. Alternatively or optionally in addition, the piston blank is produced according to the production method as already described above. Optionally in addition, the piston blank can have the recess and / or the spherical cap geometry and / or the near-net-shape surface of the shaft section and / or the near-net-shape end face of the sealing section.

Another object of the invention relates to a piston according to claim 8 or as described above. The piston is designed and / or suitable for an axial piston machine. The piston is hardened. In particular, the surface of the shaft section and / or the end face of the sealing section correspond to the final contour of the piston after the hardening process. The spherical geometry of the spherical head section and the spherical geometry of the sealing section are machined. Alternatively or optionally in addition, the piston blank is produced according to the production method as already described above. Optionally in addition, the piston can have the impression and / or the recess and / or the spherical cap geometry.

Another object of the invention relates to an axial piston machine with the piston according to claim 9 or as this is described above. The piston is designed as an axial piston. In particular, the axial piston machine is designed as an axial piston pump or an axial piston motor. The axial piston pump converts mechanical energy into hydraulic energy in particular. The axial piston motor converts hydraulic energy into mechanical energy in particular. These axial piston machines can comprise a housing in which a rotor and a disk each rotate about an axis of rotation, the two axes of rotation forming an angle so that the rotor is angled relative to the disk. The rotor each has one or more cylinder bores for receiving the piston. The piston is, on the one hand, received in an articulated manner with the disk, for example via a ball head, and, on the other hand, guided in the receptacle of the piston. When the rotor rotates with respect to the housing, it moves each piston is located axially in the receptacle. The axial piston machine is preferably designed as a bent axis machine or a swash plate machine or a swash plate machine. In particular, the axial piston machine has more than two, preferably more than four, especially more than eight of the pistons. The axial piston machine preferably has an odd number of pistons.

Figur 1

in einer Schnittdarstellung eine Axialkolbenmaschine mit einem Axialkolben als ein Ausführungsbeispiel der Erfindung;

Figur 2

in einer Schnittdarstellung einen Zwischenrohling des Kolbens aus der Figur 1;

Figur 3

in einer Schnittdarstellung einen Kolbenrohling des Kolbens aus der Figur 1.

Further features, advantages and effects of the invention emerge from the following description of preferred exemplary embodiments of the invention. Show:

Figure 1

in a sectional view an axial piston machine with an axial piston as an embodiment of the invention;

Figure 2

in a sectional view an intermediate blank of the piston from FIG Figure 1 ;

Figure 3

in a sectional view a piston blank of the piston from FIG Figure 1 .

Figure 1 shows in a sectional view an axial piston machine 1, which is designed and / or suitable for an agricultural or construction machine, for example. The axial piston machine 1 is designed as a bent axis pump, which preferably converts mechanical energy into hydraulic energy. The axial piston machine 1 has several pistons 2, a rotor 3 and a disk 4. The axial piston machine 1 has, for example, nine of the pistons 2, the pistons 2 being designed as axial pistons. The pistons 2 are articulated to the disk 4 via a ball joint 5.

When the axial piston machine 1 is in operation, the rotor 3 rotates about a first axis of rotation R1. The rotor 3 is designed as a piston housing and for this purpose has a plurality of cylinder bores 6, each piston 2 being movably arranged in one of the cylinder bores 6 and in the axial direction with respect to the Axis of rotation R is straight. The cylinder bores 6 are arranged at a uniform distance from one another around the axis of rotation R.

When the axial piston machine 1 is in operation, the disk 4 rotates about a second axis of rotation R2, the first and second axes of rotation R1, R2 intersecting, so that the rotor 3 is arranged at an angle relative to that of the disk 4. By rotating the disk 4, the pistons 2 are moved back and forth in the cylinder bores 6, so that they convey a hydraulic fluid, for example.

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

The spherical head section 7a has an indentation 8, which is shown in the detail view A. The indentation 8 is designed as a countersink and is arranged coaxially and / or concentrically to the main axis H on an axial end face of the spherical head section 7a.

The spherical head section 7a has an elevation running around the main axis H, which is shown in the detail view B. For example, the die of the extrusion tool has a circumferential groove, which serves as a volume compensation for excess material. The blank has, for example, a slight oversize, with the excess material being able to escape into the groove of the die during extrusion, so that the elevation 9 is formed.

The sealing section 7c is designed in relation to the main axis H as a circumferential collar which extends radially outward. The sealing section 7c has a recess 10, which is shown in the detailed view C. The recess 10 is designed as a cylinder countersink with an inwardly curved base area. The recess 10 is arranged coaxially and / or concentrically to the main axis H on an axial end face of the sealing section 7c. The recess 10 serves to reduce the weight of the piston 2 and for this purpose extends over, for example, more than 60%, preferably more than 70%, in particular more than 80% of the end face of the sealing section 13. The embossment 8, the elevation 9 and the recess 10 can can be produced together by the extrusion in one process step together with the shaping of the intermediate blank 7.

The shaft section 7b has a cylindrical shape, the shaft section 7b being connected to the spherical head section 7a in a first transition region 11a via a radius. In a second transition region 11b, the shaft section 7b is connected to the sealing section 7c via a conical widening running in the direction of the sealing section 7c and via a further radius. The first and the second transition area 11a, b and the outer surface of the cylindrical form a near net shape surface 12 of the shaft section 7b.

The sealing section 7c has a near-net-shape end face 13 on its axial end face in relation to the main axis H. The end face 13 is designed as a circular ring surface and is delimited in the radial direction by the recess 10. The near-net-shape surface 12 and the near-net-shape end face 13 are produced by extrusion and, for example, have the final contour of the finished piston 2 after the extrusion process. The surface 12 and the end face 13 preferably already have a sufficiently high surface quality and / or component accuracy after the extrusion, so that the surface 12 and the end face 13 no longer have to be reworked.

The Figure 3 shows a piston blank 14, the piston 2 from FIG Figure 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 machined into the intermediate blank 7. The through opening 15 is arranged coaxially and / or concentrically to the main axis H. The through opening 15 is designed as a stepped through hole and extends from the recess 10 in the direction of the embossing 8. The recess 10 forms an entry and the embossing 8 an exit for the through opening 15. The through opening 15 opens within the embossing 8 or in the area of a bevel of the embossing 8, as shown in the detail view D. This ensures that there is no burr on the end face of the spherical section 7a through the bore exit.

The sealing section 7c has a spherical cap geometry 16 on a circumferential surface, which is shown in the detailed view F. The dome geometry 16 is used, for example, to prevent the piston 2 from wedging in the piston receptacle 6. For this purpose, the circumferential surface of the sealing section 7c of the intermediate blank 7 is machined so that the spherical cap geometry 16 is generated. For example, the through hole 15 and the spherical cap geometry can be produced in a common machining process on the intermediate blank 7, so that the piston blank 14 is formed.

To produce the piston 2, the piston blank 14 is hardened, for example, before the spherical section 7a, in particular a spherical geometry 17, and the sealing section 7c, in particular the spherical cap geometry 16, are machined to their final contour. For example, in a post-processing process, the spherical geometry 17 and the spherical cap geometry 16 are processed by a hard turning, grinding and / or superfinishing process. For example, the elevation 9 is removed and / or a sealant receptacle, which is designed to receive at least one piston ring, for example, is introduced in the area of the spherical cap geometry 16.

An expansion or a change in dimension of the piston blank 14 as a result of the hardening process is already taken into account in the design of the extrusion tool. The extrusion tool or process is optimized accordingly so that all Contours and dimensions not to be reworked, in particular the near-net-shape surface 12 and the near-net-shape end face 13, correspond to the final contour after a hardening process.

List of reference symbols

1

Axial piston machine

2

piston

3

rotor

4th

disc

5

Ball joint

6th

Cylinder bore

7th

Intermediate blank

7a

Ball head section

7b

Shaft section

7c

Sealing section

8th

Imprint

9

Elevation

10

Recess

11a

first transition area

11b

second transition area

12th

Near net shape surface

13th

Near net shape face

14th

Piston blank

15th

Through opening

16

Dome geometry

17th

Spherical geometry

A-F

Detailed views

H

Main axis

R1

first axis of rotation

R2

second axis of rotation

Claims (9)

1. A production method, wherein the production method comprises the following method steps:

   - production of an intermediate blank (7) from a piston (2) for an axial piston machine (1) by means of extrusion, wherein the intermediate blank (7) has a shaft section (7b), a ball head section (7a) and a sealing section (7c), wherein the shaft section (7b) connects the ball head section (7a) to the sealing section (7c) and wherein on the intermediate blank (7) an impression (8) is produced in the ball head section (7a) by the extrusion;

   - production of a piston blank (14) from the piston (2) from the intermediate blank (7), wherein a through opening (15) is machined into the intermediate blank (7), wherein the through opening (15) extends within the piston blank (7) in the longitudinal direction, wherein the impression (8) forms an outlet for the through opening (15).
2. The production method according to claim 1, characterised in that a recess (10) in the sealing section (7c) is produced on the intermediate blank (7) by the extrusion, wherein the recess (10) forms an inlet for the through opening (15).
3. The production method according to one of the preceding claims, characterised in that a near-net-shape surface (12) of the shaft section (7b) and/or a near-net-shape end face (13) of the sealing section (7c) is/are generated on the intermediate blank (7) by the extrusion.
4. The production method according to one of the preceding claims, characterised in that a dome geometry (16) is produced on a peripheral surface of the sealing section (7c) on the intermediate blank (7) or on the piston blank (14) by machining.
5. The production method according to one of the preceding claims, characterised in that the piston (2) is generated in a further method step, wherein the piston (2) is produced by reworking the piston blank (14).
6. The production method according to claim 5, characterised in that the reworking of the piston blank (14) comprises the following sub-steps:

   - curing the piston blank (14);

   - machining of a spherical geometry (17) of the ball head section (7a);

   - machining of the dome geometry (16) of the sealing section (7c).
7. A piston blank (14), wherein the piston blank (14) is extruded, wherein the piston blank (14) has a shaft section (7b), a ball head section (7a) and a sealing section (7c), wherein the shaft section (7b) connects the ball head section (7a) to the sealing section (7c) and wherein an impression (8) is generated in the ball head section (7a) by the extrusion; and that the piston blank (14) has a through opening (15) introduced by machining, wherein the through opening (15) extends within the piston blank (14) in the longitudinal direction, wherein the impression (8) forms an outlet for the through opening (15).
8. A piston (2) for an axial piston machine (1), characterised in that the piston (14) is produced according to the production method according to claim 6.
9. An axial piston machine (1) having the piston (2) according to claim 8, characterised in that the piston (2) is designed as an axial piston.

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