EP3676495A1

EP3676495A1 - Production method, piston blank, piston and axial piston machine having said piston

Info

Publication number: EP3676495A1
Application number: EP18764996.7A
Authority: EP
Inventors: Reinhard Kick-Rodenbücher; Lukas Kuhn; Horst Hartmann
Original assignee: Schaeffler Technologies AG and Co KG
Current assignee: Schaeffler Technologies AG and Co KG
Priority date: 2017-08-31
Filing date: 2018-08-22
Publication date: 2020-07-08
Anticipated expiration: 2038-08-22
Also published as: EP3676495B1; DK3676495T3; BR112019004951B1; CN111033037A; WO2019042495A1; US20200346278A1; CN111033037B; US11213880B2; BR112019004951A2; DE102017119967A1

Abstract

Axial piston machines are known that work as a pump and/or motor, wherein the axial piston machines have at least one axial piston. In relation to this, a production method is proposed comprising the method steps: producing an intermediate blank (7) of a piston (2), in particular an axial piston, 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 producing a piston blank (14) from the intermediate blank (7), wherein a through opening (15) is introduced into the intermediate blank (7) by means of machining, wherein the through opening (15) extends within the piston blank (7) in the longitudinal direction.

Description

Manufacturing process, piston blank, piston and axial piston machine with the piston

The invention relates to a manufacturing method having 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 operate as a pump and / or as a motor. Such axial piston machines have a plurality of so-called axial pistons. For example, the axial piston are machined.

Document DE 10 2004 061 863 A1, which describes the closest prior art, discloses a piston for a piston machine, in particular for a bent axis axial piston machine, comprising a conical portion, a neck portion and a ball head formed on the neck portion, one in the Piston formed recess and a recess formed in the pin. Furthermore, the document discloses a method for producing the piston, wherein the method comprises the steps of parting off round material to desired length, producing an inner contour by cold extrusion, preparing the outer contour by pre-turning, producing the outer contour by rotary swaging and reworking.

The invention has for its object to propose a manufacturing method, which is characterized by a cost-effective production of a piston blank or a piston. It is a further 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 having the features of claim 1, a piston blank having the features of claim 8, a piston with the features of claim 9 and an axial piston machine having the feature of claim 10 solved. Preferred embodiments of the invention are disclosed in the subclaims, the following description and the figures.

The invention relates to a manufacturing method, which is used in particular for producing a piston blank for a piston and / or the piston. The piston blank is preferably an intermediate product and can be manufactured in further process steps to the piston. Preferably, the piston is designed and / or suitable for an axial piston machine. Particularly preferably, the piston is designed as an axial piston and / or the axial piston machine 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 may for example be integrated in a wheel hub of the agricultural machine. The piston can be received in a cylinder bore of the axial piston and / or straight.

In the context of the invention, it is proposed that in one process step, preferably in a first process step, of the production process, an intermediate blank is produced by extrusion. In particular, this is a blank, preferably a solid body, formed by means of an extrusion tool. Preferably, a shaft section and / or a ball head section and / or a sealing section are produced by extrusion, so that the intermediate blank is formed. In particular, a basic shape of the finished piston is produced by extrusion. Optionally, an elevation, which revolves with respect to the main axis, on the ball head section is produced by extrusion. The survey is formed in particular due to a volume balance during extrusion. The intermediate blank has the shank portion, the ball head portion and the sealing portion. The ball head portion is used in particular for articulated connection with a disc of the axial piston machine. The sealing section is used in particular for receiving a sealing means and / or for sealing the piston with respect to the cylinder bore. The shank portion connects the ball head portion with the sealing portion. In particular, the ball head portion and the sealing portion are formed directly on the shaft portion. The shank portion defines with its longitudinal axis and / or its axis of symmetry a major axis. Preferably, the sealing portion is formed as a kind of flange or collar, which extends in the radial direction with respect to the main axis. The sealing portion and / or the ball head portion may have a larger outer diameter than the shaft portion. Preferably, the shank portion has a conical or a cylindrical shape.

In a further method step, preferably in a second method step, of the production method, a piston blank is produced. For this purpose, a passage opening is introduced by machining in the intermediate blank. The passage opening can be introduced by a cutting tool in the intermediate blank. Preferably, the passage opening is introduced by milling or by drilling in the intermediate blank. For this purpose, the cutting tool is moved in the axial direction with respect to the main axis by the sealing portion, the shaft portion and the ball portion with a feed, while the cutting tool rotates.

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

The advantage of the invention is that by the extrusion of the intermediate blank, the expense of machining to the finished part, especially the piston, is significantly reduced. By extrusion, the piston blank already has a high surface quality and a high component accuracy. Furthermore, a directional fiber profile arises in the piston which is produced by the process flow, which has a positive effect on the component properties, for example the component strength. Another advantage is that the piston blank can be produced inexpensively by means of the manufacturing method according to the invention.

In a preferred implementation of the invention, an impression is produced in the ball head section by extrusion. In particular, the imprint is designed as a countersink. The embossment is preferably arranged coaxially and / or concentrically with the main axis. In particular, the indentation is attached to an axial end face of the ball head portion and preferably extends axially in the direction of the shaft portion.

The imprint forms an outlet for the passage opening. In particular, the passage opening is introduced separately in a subsequent machining process in the intermediate blank. Preferably, the indentation has a larger diameter than the passage opening, so that the indentation preferably forms a chamfer at the passage opening. Particularly preferably, the passage opening of the piston blank opens within the impression. This ensures that no burr arises or is present on the axial end face of the ball head section. In a further preferred embodiment of the invention, a recess in the sealing section is produced by extrusion. The recess is used in particular to reduce the weight of the piston. Preferably, the shape of the intermediate blank as well as the recess and / or the impression are produced in one process step. In particular, the recess is formed as a conical and / or a cylindrical and / or a concave and / or a hemispherical recess. The recess is preferably arranged coaxially and / or concentrically with the main axis. In particular, the recess is on an axial end face of the sealing portion and preferably extends axially in the direction of the shaft portion.

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

In a further preferred realization, a near-net shape surface of the shaft section is produced by the extrusion molding on the intermediate blank. In particular, the near net shape surface is formed by a lateral surface of the shaft portion. Alternatively or optionally in addition, the surface near the final contour surface is formed by a transition region between the shaft section and the sealing section and / or between the shaft section and the ball head section. Preferably, the transition region is formed as a radius and / or a cone, with which the shaft portion merges with the ball head portion and / or the sealing portion.

Alternatively or optionally additionally, an end-face-near end face of the sealing section is produced. In particular, the end contour near end face is formed with respect to the main axis by an axial end face of the sealing portion. Preferably, the end face is formed as a circular ring surface.

In particular, a surface quality of the surface near the final surface or end face is produced by extrusion, which corresponds to the surface requirements of the finished piston. Thus, the near final surface or end face need not be reworked in the further processing processes, whereby the manufacturing cost of the piston are significantly reduced. Furthermore, the surface texture of the near net shape surfaces as well as the fiber flow in the Inside the piston blank and the piston unique identification features for a piston produced by extrusion.

In a further embodiment, a Kalottengeometrie is generated at a peripheral surface of the sealing portion by machining on the intermediate blank or on the piston blank. The Kalottengeometrie prevents in particular a wedging of the piston in the cylinder bore of the axial piston machine. Preferably, the Kalottengeometrie is formed as a rotationally symmetrical lateral surface of a spherical segment. Particularly preferably, the Kalottengeometrie is made by turning. Specifically, the dome geometry and the through hole are created in a common machining process.

In a further concretization 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 made by reworking the piston blank. The post-processing is preferably used to change the material properties and / or the geometric properties and / or the surface quality of the piston blank, so that the piston is formed.

In a concrete implementation, the piston blank is hardened in a first substep of the further method step. In particular, a tolerance compensation, for example, a rising or a dimensional change of the piston blank by the hardening process, already taken into account in the production of the intermediate blank. Preferably, the extrusion tool is designed according to the tolerance compensation. Preferably, the non-reworked surfaces, preferably the near net shape surface of the shank portion and / or the endkontaunahe end face of the sealing portion, an undersize, so that the non-nachzubearbeitenden surfaces after the hardening process of the final contour. In further sub-steps, the ball geometry of the ball head section and the Kalottengeometrie the sealing section are machined. Preferably, the Kalottengeometrie and the ball geometry are processed in a common machining process. Alternatively, the calotte geometry and the ball geometry are machined in two separate machining processes. In particular, the ball geometry and / or the Kalottengeometrie be processed by hard turning and / or by grinding and / or by superfinishing. For example, the circumferential elevation of the ball head section is removed. For example, at least one circumferential groove with respect to the axis of rotation for receiving the sealant is introduced into the sealing section.

Another object of the invention relates to a piston blank according to one of the preceding claims or as has been previously described. The piston blank is extruded and has the shaft portion, the ball head portion and the sealing portion, wherein the shaft portion connects the ball head portion with the sealing portion. Furthermore, the piston blank has the machining opening introduced through, wherein the passage opening extends in the longitudinal direction within the piston blank. Alternatively or optionally in addition, the piston blank is produced by the production method as already described above. Optionally additionally, the piston blank may have the impression and / or the recess and / or the calotte geometry and / or the surface near the end contour of the shaft section and / or the end-face-near end face of the sealing section.

Another object of the invention relates to a piston according to one of the preceding claims or as has been previously described. 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 after the hardening process correspond to the final contour of the piston. The ball geometry of the ball head section and the Kalottengeometrie the sealing section are machined. Alternatively or optionally complementing the piston blank according to the manufacturing method, as already described above, manufactured. Optionally additionally, the piston can have the impression and / or the recess and / or the calotte geometry. Another object of the invention relates to an axial piston machine with the piston according to one of the preceding claims or as 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 in particular converts mechanical energy into hydraulic energy. In particular, the axial piston motor converts hydraulic energy into mechanical energy. These axial piston machines may include a housing in which a rotor and a disk each rotate about a rotation axis, the two rotation axes forming an angle such that the rotor is angled relative to the disk. The rotor has in each case one or more cylinder bores for receiving the piston. The piston is on the one hand, for example, a ball head, articulated with the disc and on the other hand taken in the recording of the piston. As the rotor rotates with respect to the housing, each piston moves axially in the receptacle. Preferably, the axial piston machine is 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, in particular more than eight of the pistons. Preferably, the axial piston machine has an odd number of pistons. Further features, advantages and effects of the invention will become apparent from the following description of preferred embodiments of the invention. Showing:

Figure 1 in a sectional view of an axial piston machine with a

Axial piston as an embodiment of the invention; Figure 2 is a sectional view of an intermediate blank of the piston of Figure 1;

Figure 3 is a sectional view of a piston blank of the piston from the

FIG. 1

1 shows a sectional view of an axial piston machine 1, which is designed and / or suitable, for example, for an agra or construction machine. 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 a plurality of pistons 2, a rotor 3 and a disk 4. The axial piston machine 1, for example, nine of the piston 2, wherein the piston 2 are formed as axial piston. The pistons 2 are articulated via a ball joint 5 with the disc 4.

The rotor 3 rotates in an operation of the axial piston machine 1 about a first rotation axis R1. The rotor 3 is designed as 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 guided straight in the axial direction with respect to the axis of rotation R. The cylinder bores 6 are uniformly spaced from each other about the axis of rotation R.

The disc 4 rotates in an operation of the axial piston machine 1 about a second rotation axis R2, wherein the first and the second rotation axis R1, R2 intersect, so that the rotor 3 is arranged angled relative to the disc 4. By a rotation of the disc 4, the piston 2 are moved back and forth in the cylinder bores 6, so that they promote, for example, a hydraulic fluid.

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 blank, for example from a solid material with a round cross-section, by extrusion molding with an extrusion tool. For example, this includes Extrusion tool a punch and a die. The intermediate blank 7 has a ball head section 7a, a shaft section 7b and a sealing section 7c. The shaft portion 7b directly connects the ball head portion 7a and the sealing portion 7c with each other, whereby the intermediate blank 7 is extruded.

The ball head portion 7a has an impression 8, which is shown in detail view A. The indentation 8 is designed as a countersink and is arranged coaxially and / or concentrically to the main axis H at an axial end side of the ball head portion 7a.

The ball head portion 7a has a circumferential around the main axis H elevation, which is shown in the detail view B. For example, the die of the extrusion tool on a circumferential groove, which serves as a volume compensation for excess material. The blank has, for example, a slight oversize, wherein during extrusion, the excess material can escape into the groove of the die, so that the elevation 9 is formed.

The sealing portion 7c is formed with respect to the major axis H as a circumferential collar which extends radially outwardly. The sealing portion 7c has a recess 10, which is shown in the detail view C. The recess 10 is formed as a cylinder counter with an inwardly curved bottom portion. The recess 10 is arranged coaxially and / or concentrically to the main axis H at an axial end face of the sealing portion 7c. The recess 10 serves to reduce the weight of the piston 2 and extends for this purpose, for example, more than 60%, preferably more than 70%, in particular 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 together by the extrusion in a process step together with the shaping of the intermediate blank 7.

The shaft portion 7b has a cylindrical shape, wherein the shaft portion 7b with the ball head portion 7a in a first transition region 1 1 a via a Radius is connected. In a second transition region 11 b, the shaft section 7b is connected to the sealing section 7c via a cone-shaped widening running in the direction of the sealing section 7c and via a further radius. The first and the second transition region 1 1 a, b and the lateral surface of the cylindrical form a near net shape surface 12 of the shaft portion 7 b.

The sealing portion 7c has, at its axial end face with respect to the main axis H, an end-face-shaped end face 13. The end face 13 is formed as an annular surface and is bounded by the recess 10 in the radial direction. The near-net-shape surface 12 and the near-net-shape end face 13 are produced by the extrusion molding and have, for example after the extrusion process on the final contour of the finished piston 2. The surface 12 and the end face 13 preferably already fulfill 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.

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 inside the piston blank 14 in the axial direction with respect to the main axis H. To produce the piston blank 14, the passage opening 15 is machined into the intermediate blank 7. The passage opening 15 is arranged coaxially and / or concentrically with the main axis H. The passage opening 15 is formed as a stepped through hole and extends from the recess 10 in the direction of the indentation 8. The recess 10 forms an inlet and the indentation 8 forms an outlet for the passage opening 15. The passage opening 15 opens inside the indentation 8 or 8 in the area of a chamfer of the imprint 8, as shown in the detailed view D. This ensures that no burr on the front side of the ball portion 7a is formed by the hole exit.

The sealing portion 7c has on a peripheral surface a Kalottengeometrie 16, which is shown in the detailed view F. The calotte geometry 16 is used For example, to prevent wedging of the piston 2 in the piston seat 6. For this purpose, the peripheral surface of the sealing portion 7c of the intermediate blank 7 is machined, so that the Kalottengeometrie 16 is generated. For example, the through-hole 15 and the calotte geometry can be generated 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 ball section 7a, in particular a ball geometry 17, and the sealing section 7c, in particular the calotte geometry 16, are machined to the final contour. For example, in a post-processing process, the ball geometry 17 and the spherical geometry 16 are machined by a hard turning, grinding and / or superfinishing process. In doing so, e.g. the survey 9 removed and / or a Dichtmittelaufnahme, which is formed for example for receiving at least one piston ring, introduced in the region of the Kalottengeometrie 16.

A rising or a dimensional change 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 process is optimized accordingly, so that all contours and dimensions not to be reprocessed, in particular the surface near the final contour 12 and the end contour near the end face 13, correspond to the final contour after a hardening process.

LIST OF REFERENCES

1 axial piston machine

piston

3 rotor

disc

5 ball joint

6 cylinder bore

7 intermediate blank

7a ball head section

7b shaft section

7c sealing section

8 imprint

9 survey

10 recess

1 1 a first transition area

1 1 b second transition area

12 near net shape surface

13 endkontor close face

14 piston blank

15 passage opening

16 dome geometry

17 sphere geometry

A-F detailed views

H main axis

R1 first axis of rotation

R2 second axis of rotation

Claims

claims

1 . Manufacturing method, wherein the manufacturing method comprises the following method steps:

- Producing an intermediate blank (7) from a piston (2) for an axial piston machine (1) by extrusion, wherein the intermediate blank (7) has a shank portion (7b), a ball head portion (7a) and a sealing portion (7c), wherein the shank portion (7b) connects the ball head portion (7a) with the sealing portion (7c);

- Producing a piston blank (14) from the piston (2) from the intermediate blank (7), wherein in the intermediate blank (7) a through hole (15) is introduced by machining, wherein the through hole (15) within the piston blank (7) extends in the longitudinal direction.

2. A manufacturing method according to claim 1, characterized in that on the intermediate blank (7) an impression (8) in the ball head portion (7a) is produced by the extrusion, wherein the indentation (8) forms an outlet for the passage opening (15).

3. A manufacturing method according to claim 1 or 2, characterized in that on the intermediate blank (7) has a recess (10) in the sealing portion (7c) is produced by the extrusion, wherein the recess (10) has an entrance for the passage opening (15). forms.

4. Manufacturing method according to one of the preceding claims, characterized in that on the intermediate blank (7) a near net shape surface (12) of the shank portion (7b) and / or a near-net shape end face (13) of the sealing portion (7c) is generated by the extrusion.

5. Manufacturing method according to one of the preceding claims, characterized in that on the intermediate blank (7) or on the piston blank (14) a Kalottengeometrie (16) on a peripheral surface of the sealing portion (7c) is produced by machining.

6. Production method according to one of the preceding claims, characterized in that in a further method step, the piston (2) is produced, wherein the piston (2) by reworking of the piston blank (14) is produced.

7. Production method according to claim 6, characterized in that the reworking of the piston blank (14) comprises the following sub-steps:

- hardening of the piston blank (14);

- Machining a spherical geometry (17) of the ball head portion (7a);

- Machining the Kalottengeometrie (16) of the sealing portion (7c).

8. piston blank (14), characterized in that the piston blank (14) is extruded, wherein the piston blank (14) has a shank portion (7b), a ball head portion (7a) and a sealing portion (7c), wherein the shank portion (7b) the ball head portion (7a) connects with the sealing portion (7c); and that the piston blank (14) has a machined through hole (15), the through hole (15) extending longitudinally within the piston blank (14); and / or that the piston blank (14) is made according to the manufacturing method of the preceding claims.

9. piston (2) for an axial piston machine (1), characterized in that the piston (2) is hardened; and that the ball geometry (17) of the ball head portion (7a) and the spherical geometry (16) of the seal portion (7c) are machined, and that the shaft portion (7b) is made by extrusion; and / or that the piston (14) is manufactured according to the manufacturing method according to claim 7.

10. Axial piston machine (1) with the piston (2) according to claim 9, characterized in that the piston (2) is designed as an axial piston.