DE102019200829A1 - Rotation tool to create a honey entrance - Google Patents

Abstract

The invention relates to a rotary tool for generating a honing access (5) in a cylinder bore (3) of a workpiece (1) which is larger in diameter than the cylinder bore (3), the honing access (5) having a predefined cross section in cross section Has surface roughness, in order to produce the honing access (5) the rotary tool is lowered into the cylinder bore (3) in a lowering direction (I) until the desired drilling depth (t _B ) is reached, and the rotating tool is radially controlled in a circular milling step and is guided in a circular path around the axis of the bore (B), the tool having at least one cutting element (S1 to S7) with a radially outwardly curved round-profile cutting edge (15) which has a cutting edge () leading in the lowering direction (I) 25), in which at least one radially protruding cutting corner (E1 to E5) is formed, which in the circular milling step has the surface roughness (Rz) in the honing passage ( 5), and the circular milling step is preceded by a drilling step in terms of process technology, in which a smaller-diameter workpiece pre-drilling (33) is drilled out to the larger-diameter cylinder bore (3). According to the invention, the rotary tool carries out both the boring step and the circular milling step.

Description

The invention relates to a rotary tool for generating a honing entrance in a cylinder bore of a workpiece according to the preamble of claim 1, a method for generating the honing entrance according to claim 8 and a workpiece according to claim 9.

The cylinder raceway in an aluminum cylinder crankcase of a motor vehicle can be produced in a process chain in which the cylinder crankcase is initially provided with a, for example, conical pilot hole in a delivery state. In a drilling step, the pilot hole is drilled out to the larger-diameter cylinder bore. This is followed by a circular milling step, in which a honing pass is created at the bottom of the hole. Then, in a roughening step, the inner wall of the cylinder bore is mechanically roughened using a roughening tool. In the roughening step, the honing entrance forms a tool outlet, into which the roughening tool can be inserted up to a reversal point, is moved there in a radial direction and is then guided out of the cylinder bore without stress and out of engagement with the roughening structure. An APS coating can then be carried out, in which a melted APS coating material is spun onto the inner wall of the cylinder bore by means of a burner. The burner also uses the honing access as a tool outlet into which the burner can be inserted and reversed at a reversal point in the reversing direction. After the spin-coated APS layer has hardened, the APS layer is honed to form the cylinder raceway in the cylinder bore.

From a process engineering point of view, the following requirements apply to the geometry of the honing entrance: First, the honing entrance is to be designed as an annular circumferential groove in an inner wall of the cylinder bore, with an approximately semicircular or elliptical round profile in cross section. A radially outer groove bottom of the annular circumferential groove lies on a diameter that is larger than that of the cylinder bore diameter. Secondly, the honing passage is not smooth, but rather with a certain surface roughness (for example Rz100). In the case of a smooth-surface honing passage, there is a process risk during APS coating that particles of the APS coating material bounce off the smooth surface of the honing passage and - with the formation of defects - are thrown back into the cylinder bore. By providing the surface roughness, the particles of the APS coating material no longer bounce off the honey passage, but rather stick to it.

In the case of a generic generation of such a honey entrance in the cylinder bore, a preparatory process-related boring step is first carried out by means of a boring tool which bores the pilot hole down to the larger-diameter cylinder bore. The circular milling step then takes place using a milling tool. For this purpose, the milling tool is first lowered to the bottom of the cylinder bore without stress and then radially controlled (rotating around the axis of rotation of the tool) and guided in a circular path around the axis of the cylinder bore, thereby forming the honing passage.

To generate the honing access defined above, a conventional milling tool has a plurality of cutting elements spaced apart in the circumferential direction of the tool. Each cutting element is designed with a radially outwardly curved, approximately semicircular (or elliptical) round profile cutting edge, which defines the honing access round profile.

To create the surface roughness in the honing passage, serrated cutting corners are formed on the round profile cutting edge, which protrude radially outwards. In the circular milling step, the cutting edges are used to create unevenness in the honing passage that forms the surface roughness.

The provision of both a boring tool and a milling tool leads to a high tool expenditure and the associated long process time.

From the DE 10 23 687 A1 a tool for machining workpieces is known. From the WO 2009/026932 A1 a boring tool is known. From the DE 693 14 227 T2 a method for processing composite materials is known.

The object of the invention is to provide a rotary tool and a method for generating a honing access in a workpiece cylinder bore, which allow a reduced tool effort in comparison to the prior art with the associated reduced process time.

The object is solved by the features of claim 1, 8 or 9. Preferred developments of the invention are disclosed in the subclaims.

The invention is based on the knowledge that the circular milling step alone designed, conventional milling tool can not be used reliably for the boring step in which the rotating tool is lowered coaxially to the bore axis to the bottom of the cylinder bore. Because of the round-profile cutting of the milling tool, inclined force components are inevitably introduced into the milling tool during the boring step. These inclined force components lead to a tool swinging, in which the tool is deflected radially from its axis of rotation. This can result in chatter marks on the cylinder bore inner wall and / or a tool breakage.

Against this background, according to the characterizing part of claim 1, the rotary tool is designed both for the boring step and for the circular milling step. The rotary tool is driven in the boring step under rotation and machining until the target drilling depth (the bottom of the hole) is reached, with the tool rotation direction coaxial to the hole axis.

In order to ensure reliable drilling, the round profile cutting edge of the cutting element (designed primarily for circular milling) is implemented geometrically as follows: Thus, at least one cutting corner (creates the surface roughness in the honing passage) of the round profile cutting edge is a tool Axis of rotation exactly parallel to the longitudinal cutting edge and an end cross-cutting edge which runs approximately or essentially at right angles to the tool axis of rotation.

This cutting edge geometry ensures during the boring process (i.e. when the rotary tool is lowered to the bottom of the cylinder bore) that the axially parallel longitudinal cutting edge is in line contact with the inner wall of the cylinder bore. This enables the rotary tool to be supported radially on the inner wall of the cylinder bore. On the other hand, material removal is carried out on the front transverse cutting edge during the boring process. In the subsequent circular milling step, on the other hand, the cross-cutting edge is essentially inoperative, while metal cutting is carried out on the longitudinal cutting edge.

In the above cutting edge geometry, the longitudinal cutting edge and the front transverse cutting edge on the cutting corner span a cutting angle of essentially 90 °.

In order for the supporting function of the longitudinal cutting edge to be strengthened during the boring step, it is advantageous if the longitudinal cutting edge, in contrast to the transverse cutting edge, is not realized with sharp edges, but rather with a minimal circular chamfer. The cylindrical chamfer acts as a radial stop during the boring process, which prevents the rotary tool from deflecting excessively radially into the workpiece material. It is important that the round chamfer on the longitudinal cutting edge has a sufficiently small rounding radius so that sufficient material removal is possible on the longitudinal cutting edge during the circular milling step.

In a technical implementation, the cutting corner can be spaced axially from the tool tip and lie on a cutting corner diameter. Both the axial distances and the cutting edge diameters of the cutting edges lying axially one behind the other are successively smaller in the direction of the tool tip. The cutting corners arranged axially one behind the other therefore form a step profile consisting of axially parallel longitudinal cutting edges and cross cutting edges running approximately at right angles to the tool axis of rotation.

In the above step profile, the cross-cutting edge of a first cutting corner in the course of the cutting contour in the direction of the tool tip at an inner corner area can merge directly into a longitudinal cutting edge of a following cutting corner. As an alternative to this, the cross-cutting edge of a first cutting corner in the course of the cutting contour in the direction of the tool tip cannot pass directly, but indirectly with the interposition of an inclined cutting base into the longitudinal cutting edge of the following cutting corner. It should be emphasized that in the boring step and in the circular milling step, only the cutting edge corners are in chip engagement, while a cutting edge base is out of clamping engagement. This avoids that inclined force components act on the rotary tool in the boring step.

With regard to reliable generation of the honing access, the rotary tool can have at least two, in particular seven, cutting elements, with the aid of which the honing access is milled in the circular milling step. The cutting elements are evenly distributed around the circumference in the tool circumferential direction. It is of particular importance that the cutting corners formed on the respective cutting elements are not formed one behind the other in the circumferential direction, but rather are offset from one another by an axial offset. The axial offset between the cutting corners of different cutting elements can be dimensioned such that the cutting corners of all cutting elements lie on a common, imaginary circular line that corresponds to the inner contour of the round profile of the honing entrance.

An exemplary embodiment of the invention is described below with reference to the attached figures.

• 1 einen Ausschnitt aus einem Zylinderkurbelgehäuse mit einer Zylinderbohrung, an deren Bohrungsgrund ein Honfreigang ausgebildet ist;
• 2 in vergrößerter Teilansicht ein halbkreisförmiges Rundprofil des Honfreigangs mit mechanisch eingearbeiteten Oberflächenunebenheiten, die die Oberflächenrauigkeit bilden;
• 3 und 4 unterschiedliche Ansichten auf ein Rotations-Werkzeug;
• 5 in vergrößerter Darstellung den Konturverlauf einer Rundprofil-Schneide eines Schneidelements des Rotations-Werkzeugs;
• 6 ein Ersatzbild, in dem die Konturverläufe der Rundprofil-Schneiden sämtlicher sieben Schneidelemente des Rotations-Werkzeugs jeweils linienförmig dargestellt sind; und
• 7 bis 9 jeweils Ansichten, die den Aufbohr-Schritt und den Zirkularfräs-Schritt veranschaulichen.

Show it:

• 1 a section of a cylinder crankcase with a cylinder bore, at the bottom of the bore an honing passage is formed;
• 2nd an enlarged partial view of a semicircular round profile of the honing entrance with mechanically incorporated surface irregularities that form the surface roughness;
• 3rd and 4th different views of a rotary tool;
• 5 in an enlarged representation the contour of a round profile cutting edge of a cutting element of the rotary tool;
• 6 a replacement image in which the contour profiles of the round profile cutting edges of all seven cutting elements of the rotary tool are each shown in a line; and
• 7 to 9 views each illustrating the boring step and the circular milling step.

In the 1 is a section of a cylinder crankcase 1 with a cylinder bore 3rd shown. The cylinder bore 3rd has one around the bore axis B rotationally symmetrical honey entrance 5 on that at a hole depth t _B at a bottom of the hole 7 the cylinder bore 3rd is trained. The honey entrance 5 is as an annular circumferential groove with a radially outer groove bottom in an inner wall of the cylinder bore 3rd educated. The groove bottom diameter d _N of the honey entrance 5 is larger than the diameter dz the cylinder bore 3rd . As from the 2nd further emerges, the honey entrance points 5 in cross section an approximately semicircular or elliptical round profile with a predefined surface roughness Margin on in a circular milling step described later ( 7 ) in the honey entrance 5 is introduced mechanically.

In the 2nd is at the bottom of the hole 7 facing honey entrance side 6 the surface roughness Margin realized by means of a step profile. At every level 8th the step profile runs a circumferential to the bore axis B axially parallel step surface 10th with a circumferential, essentially perpendicular to the bore axis B aligned step surface 12th together. The step surfaces 10th , 12th span an essentially rectangular step angle.

The honey entrance 5 is carried out in the 3rd shown rotary tool (countersinking / milling tool) generated. The tool has a machine spindle, indicated by a dashed line 9 attachable tool shank 11 on that at the tool tip 13 a total of seven evenly distributed cutting elements S1 to S7 wearing. Each of the cutting elements S1 to S7 has a semicircular round profile cutting edge which is curved radially outwards 15 on. Their cutting contours are later based on the 5 and 6 described. On every round profile cutting edge 15 run in the 4th a rake face leading in the direction of rotation 17th that have a chip space 19th limited, and a lagging open space 21 together.

The round profile cutting edge 15 is in the 5 with a in a lowering direction I ( 7 ) trailing cutting edge 23 formed on a radially outer, large-diameter cutting apex 24th in a cutting edge leading in the lowering direction I. 25th transforms. In the leading edge of the cutting edge 25th are in the 5 exemplary the cutting corners E1 to E5 trained by a cutting edge 27 protrude radially outwards. By means of the cutting corners E1 to E5 circular milling step ( 9 ) the surface roughness Margin in the honey entrance 5 generated.

As from the 5 further emerges form the cutting corners E1 to E5 the round profile cutting edge shown S1 together a step profile in which each cutting corner E1 to E5 each with a longitudinal cutting edge 29 and a cross cutting edge 31 is trained. The longitudinal cutting edge 29 runs (continuously constant and uninterrupted) parallel to the axis of rotation of the tool R . The cross cutting edge 31 runs essentially at right angles to the tool axis of rotation R . The cutting corners E1 to E5 are at different axial distances a ₁ to a ₅ from the tool tip 13 spaced. In addition, the cutting corners E1 to E5 with different cutting edge diameters d ₁ to ds from the tool rotation axis R spaced. The distances a ₁ to a ₅ and the diameters d ₁ to ds are in that order E1 to E5 successively smaller, which results in the above step profile.

In the same way as the above round profile cutting edge S1 are also the other round profile cutting edges S2 to S7 educated. As from the replacement image of the 5 shows that are on all cutting elements S1 to S7 trained cutting corners E1 to E5 not aligned one behind the other in the tool circumferential direction, but rather by axial offsets Δa staggered. The cutting corners E1 to E5 all cutting elements S1 to S7 lie on a common, imaginary circular line 37 whose diameter is identical to the diameter of the round honing entrance profile. In the 5 is also a cutting angle α drawn in on a cutting corner between the longitudinal cutting edge 29 and the cross cutting edge 31 is spanned. The cutting angle α lies in the 5 at almost exactly 90 °. In addition, in the 5 the cross cutting edge 31 a cutting corner on an inner corner area 35 not directly into the longitudinal cutting edge 31 a following cutting edge above, but indirectly with the inclusion of an inclined cutting base 27 . The slanted cutting edge 27 is in the drilling step ( 8th ) not in chip engagement with the workpiece material in order to avoid that inclined force components are introduced into the tool.

As mentioned above are in the 5 the cutting corners E1 to E5 all cutting elements S1 to S7 along the tool axis of rotation R about axial offsets Δa offset from each other. As a result, the edge lengths of all longitudinal cutting edges add up 29 in the axial direction, which results in a stable radial tool support in the boring step.

The following is based on the 7 to 9 a process sequence for the production of the honey entrance 5 in the cylinder bore 3rd described: Accordingly, the cylinder crankcase is first 1 with a partially conical pilot hole 33 provided ( 7 ). This is followed by the boring step, in which the rotary tool in the lowering direction I until the target drilling depth is reached t _B in the pilot hole 33 is retracted, with one to the bore axis B coaxial tool rotation axis R . In the boring step, they are perpendicular to the tool rotation axis R running cross cutting edges 31 the cutting corners E1 to E5 all round profile cutting 15 in chip engagement with the inner wall of the pilot hole 33 . The longitudinal cutting edges 29 all cutting edges E1 to E5 are in line contact with the drilled inner wall of the cylinder bore 3rd , whereby a radial support of the rotary tool is guaranteed during the boring step. The longitudinal cutting edges are used to further strengthen the radial support 29 all cutting edges E1 to E5 compared to the cross cutting edges 31 not realized with sharp edges, but rather as a circular bevel that further reduces radial deflection of the rotary drilling tool into the workpiece material.

After the boring step, the circular milling step ( 9 ), where the rotary tool is offset radially Δr is controlled radially and in a circular path around the bore axis B is carried out, namely with the formation of the honey entrance 5 .

Reference list

1

Cylinder crankcase

3rd

Cylinder bore

5

Honey entrance

6

the bottom of the hole 7 facing honey entrance side

7

Bottom of the hole

8th

Honing entrance level

9

Machine spindle

10th

circumferential step surface

11

Tool shank

12th

circumferential step surface

13

Tool tip

15

Round profile cutting edge

17th

Rake face

19th

Chip space

21

Open space

23

Tool shank round flank

24th

radially outer cutting vertex

25th

Tool tip round flank

27

Cutting edge

29

Longitudinal cutting edge

31

Cross cutting edge

33

Pilot hole

35

Inside corner area

37

Circular line

E1 to

E5 Cutting corners

S1 to

S7 Cutting elements

Δa

Axial misalignment

a ₁ to a ₅

Axial distances

d ₁ to d ₅

Cutting edge diameter

dz

Cylinder bore diameter

d _N

Groove bottom diameter of the honey entrance 5

t _B

Drilling depth

B

Cylinder bore axis

R

Tool rotation axis

α

Cutting edge angle

Δr

Radial offset

QUOTES INCLUDE IN THE DESCRIPTION

This list of documents listed by the applicant has been generated automatically and is only included for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• DE 1023687 A1 [0008]
• WO 2009/026932 A1 [0008]
• DE 69314227 T2 [0008]

Claims (9)

Rotary tool for generating a honing entrance (5) in a cylinder bore (3) of a workpiece (1), which is larger in diameter compared to the cylinder bore (3), the honing entrance (5) having a round profile in cross section with a predefined surface roughness, whereby to produce the honing access (5), the rotary tool is lowered into the cylinder bore (3) in a lowering direction (I) until the target drilling depth (t _B ) is reached, and in a circular milling step the rotating tool is driven radially and in a circular path is guided around the bore axis (B), the tool having at least one cutting element (S1 to S7) with a radially outwardly curved round profile cutting edge (15) which has a cutting edge (25) leading in the lowering direction (I), in the at least one radially protruding cutting corner (E1 to E5) is formed, which generates the surface roughness (Rz) in the honing passage (5) during the circular milling step, and wherein the Z Irkularfräspping a drilling step is upstream in terms of process technology, in which a smaller-diameter workpiece pre-drilling (33) is drilled up to the larger-diameter cylinder bore (3), characterized in that the tool carries out both the drilling step and the circular milling step, and that in particular in the boring step, the rotating tool is driven under machining load until the desired drilling depth (t _B ) is reached, specifically with a tool axis of rotation (R) coaxial with the bore axis (B), and in particular for a reliable boring process Round profile cutting edge (15) is formed with at least one cutting corner (E1 to E5), at which a longitudinal cutting edge (29) parallel to the tool rotation axis (R) and an end cross-cutting edge (31) converge, which are essentially at right angles to the tool -Rotational axis (R) extends. Rotation tool after Claim 1 , characterized in that the longitudinal cutting edge (29) compared to the sharp-edged cross-cutting edge (31) of the cutting corner (E1 to E5) is realized as a circular bevel. Rotation tool after Claim 1 or 2nd , characterized in that the longitudinal cutting edge (29) and the transverse cutting edge (31) on the cutting edge (E1 to E5) span a cutting angle (α) of less than or equal to 90 °. Rotation tool after Claim 1 , 2nd or 3rd , characterized in that the cutting corner (E1 to E5) is at an axial distance (a ₁ to a ₅ ) from the tool tip (13) and lies on a cutting corner diameter (d ₁ to ds), and in particular that both the axial distances (a ₁ to a ₅ ) as well as the diameters (d ₁ to ds) of the axially successive cutting corners (E1 to E5) to the tool tip (13) gradually become smaller, namely with the formation of a step profile consisting of axially parallel longitudinal cutting edges (29) and transverse cutting edges (31) which run essentially at right angles to the tool axis of rotation (R) and which converge at the cutting corners (1 to E5). Rotary tool according to one of the preceding claims, characterized in that the cutting corner (E1 to E5) projects radially outward from an inclined cutting base (27) of the round profile cutting edge (15), and that both in the boring step and in the circular milling - Step only the cutting corner (E1 to E5) is in chip engagement, while the inclined cutting edge base (27) is out of clamping engagement. Rotary tool according to one of the preceding claims, characterized in that the cross-cutting edge (31) of a first cutting corner in the course of the cutting contour extends up to the tool tip (13) at an inner corner region (35) directly into a longitudinal cutting edge (29) of a following cutting corner, or that the transverse cutting edge (31) of a first cutting corner in the cutting contour course up to the tool tip (13) on the inner corner region (35) passes indirectly with the interposition of an inclined cutting edge base (27) into the longitudinal cutting edge (29) of the following cutting corner. Rotary tool according to one of the preceding claims, characterized in that the rotary tool has at least two, in particular seven cutting elements (S1 to S7) which are arranged circumferentially distributed in the circumferential direction of the tool, and that on the cutting elements (S1 to S7 ) formed cutting corners (E1 to E5) in the tool circumferential direction not in alignment, but rather offset by axial offsets (Δa), and that in particular the cutting corners (E1 to E5) of all cutting elements (S1 to S7) on a common, imaginary circular line (37), which corresponds to the inner contour of the round profile of the honing entrance (5). Method for generating a honey entrance (5) in a cylinder bore (3) of a workpiece (1) by means of a rotary tool according to one of the preceding claims. Workpiece with a cylinder bore (3), the honing passage (5) by means of a rotary tool after one of the Claims 1 to 7 as well as in a procedure according to Claim 8 is made.

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