CN113118564A

CN113118564A - Method for producing a threaded through-hole in a workpiece

Info

Publication number: CN113118564A
Application number: CN202110036720.3A
Authority: CN
Inventors: P·科普顿
Original assignee: Audi AG
Current assignee: Audi AG
Priority date: 2020-01-15
Filing date: 2021-01-12
Publication date: 2021-07-16
Also published as: DE102020100853B4; DE102020100853A1

Abstract

The invention relates to a method for producing a threaded through-hole (13) in a workpiece (9) by means of a thread producing tool (23), having a tapping stroke (G) in which the thread producing tool (23) is driven into a pre-drilled workpiece through-hole (24) in order to form an internal thread (28) in the workpiece through-hole (24), and having a reversing stroke (R) in which the thread producing tool (23) is guided out of the internal thread (28) formed in the through-hole (24) with a reversed direction of rotation. According to the invention, in order to avoid the formation of a cut (17) in the opening (25) of the through-hole (24) facing away from the tool, the method comprises a reaming stroke (A) in which a countersink (19) is produced in the opening (25) of the through-hole (24) facing away from the tool.

Description

Method for producing a threaded through-hole in a workpiece

Technical Field

The present invention relates to a method for producing a threaded through-hole in a workpiece according to the preamble of claim 1, a thread producing tool/cutter according to the preamble of claim 7 and a workpiece, in particular a connecting rod, according to the preamble of claim 10.

Background

DE 4433252 a1 discloses a connecting rod of a reciprocating piston internal combustion engine, which has a connecting rod bore with a small diameter and a connecting rod bore with a large diameter, which are connected to one another by a connecting rod web. The piston pin of the piston of a reciprocating piston internal combustion engine can be supported in a connecting rod bore of small diameter, while the crank pin of the crankshaft can be supported in a connecting rod bore of large diameter. The connecting rod shank with the reduced cross section transitions into the connecting rod bore with the larger diameter at the obliquely disposed, widened connecting rod side. The large-diameter connecting rod bore is designed to be separable and has a bearing cap which can be mounted on the connecting rod base body by means of a screw. A corresponding bolt passes through the bearing cap and is threadedly engaged with the threaded through-hole of the connecting rod base.

In document DE 4433252 a1, the opening of the corresponding threaded through-hole facing away from the bearing cap is located in the obliquely placed connecting rod side. Correspondingly, between two axially spaced-apart hole edge end positions (bohrungstrand-scheitelstellle), the hole edge facing away from the bearing cap extends elliptically in an inclined position, so that the internal thread of the threaded through-hole is partially exposed laterally outwards transversely to the hole axis. The thread path of the internal thread thus transitions directly into the obliquely arranged connecting rod flank at the edge of the bore facing away from the bearing cap, so that a cutout is formed.

A method for producing a threaded bore is known from DE 3939795 a 1. A method for producing a threaded bore is known from DE 2017007419 a 1.

Disclosure of Invention

The object of the present invention is to provide a method for producing a threaded through-hole in a workpiece, in particular in a connecting rod, in which method a reduction in the stability of the workpiece is prevented as compared with the prior art due to the notch effect.

This object is achieved by the features of claim 1, 7 or 10. Preferred developments of the invention are disclosed in the dependent claims.

The invention is based on a method for producing an internal thread in a through-hole of a workpiece by means of a thread production tool. The method has a tapping stroke in which a thread making tool is driven into the workpiece through-bore at a thread making feed and a thread making rotational speed synchronized with the thread making feed to form an internal thread in the workpiece through-bore. The method also has a reversing stroke in which the thread-making tool is guided out of the internal thread formed in the workpiece through-hole by a reversing stroke path of a reversing rotation with a reversing direction of rotation reversed, with a reversing feed and a reversing rotational speed synchronized with the reversing feed.

According to the characterizing part of claim 1, the formation of a cut in the aperture of the through-hole facing away from the tool is avoided in the following manner: that is, the method also has a reaming stroke in which the thread-producing tool produces a countersink/undercut with a thread-free, in particular smooth-surfaced, inner circumference at the opening facing away from the tool with a reaming feed and a reaming rotational speed.

In this way, it is ensured that the thread path of the internal thread no longer passes, in the case of the formation of the undercut, directly into the workpiece side facing away from the tool at the edge of the bore facing away from the tool.

In technical practice, the internal thread of the workpiece through-hole may have a radially outer thread root which is located on the thread outer diameter. The inner periphery of the countersink formed in the aperture facing away from the tool may be funnel-shaped or preferably cylindrical. In a cylindrical countersink, the countersink diameter may correspond to the thread outer diameter.

In terms of simple tool control, it is preferred that the thread-making tool not be operated in a circular motion about the bore axis during the reaming stroke, tapping stroke and/or reversing stroke, but rather that the thread-making tool be rotated coaxially about the bore axis.

In a preferred embodiment, the thread-making tool can be moved with its thread-making region beyond the opening facing away from the tool up to the reversal point in the tapping stroke. A reaming stroke may then be performed (with the direction of rotation reversed). During the reaming stroke, the thread making tool may be advanced into the bore facing away from the tool at the reaming feed and the reaming rotation speed until the countersink depth is reached.

Starting from the reaching of the undercut depth, a reverse stroke is initiated, in which the thread-making tool enters with its thread-making region (substantially unloaded) into the thread groove of the internal thread and is guided out of the internal thread formed in the through-bore.

The invention is particularly useful in connecting rods in which the connecting rod shank with a reduced cross section transitions into a large-diameter, separate connecting rod bore at an obliquely disposed, widened connecting rod flank. In this case, the substantially smooth-surfaced, thread-free inner circumference of the countersink transitions into the connecting rod flank at the hole edge facing away from the bearing cap, so that no notch effect is produced at the hole edge.

In order to carry out the reaming operation without problems, it is preferred that the thread-making tool has at least one reaming cutting edge, by means of which the reaming operation of the cutting process can be carried out. The reaming cutting edge may be free-cutting during the tapping stroke and the reversing stroke (spanbeararbeitung sfrei), and only during the reaming stroke is the reaming cutting edge brought into cutting engagement with the internal thread of the through-bore (Spaneingriff).

In the case of operationally reliable thread production, it is preferable for the reaming cutting edge to be embodied as a counter-cutting edge. The counter cutting edge is not brought into cutting engagement with the internal thread until after the reversal of the direction of rotation which takes place after the tapping stroke, as a result of which a countersink is produced in the opening facing away from the tool.

Drawings

Embodiments of the present invention are described below with reference to the drawings.

Shown here are:

FIG. 1 shows an enlarged partial perspective view of a connecting rod;

FIG. 2 shows a thread making tool with which an internal thread can be made in a pre-drilled workpiece through-hole;

fig. 3 to 8 show respective views illustrating process steps for producing a threaded through-hole; and

fig. 9 shows a view according to the prior art corresponding to fig. 1.

Detailed Description

For a simple understanding of the invention, reference is first made to fig. 9, which shows a connecting rod for a reciprocating piston internal combustion engine known from the prior art. The connecting rod has a small-diameter connecting rod bore, not shown, and a large-diameter, separate connecting rod bore 1, which are connected to one another by a connecting rod shank 3 of reduced cross-section. The connecting rod shank 3 with the reduced cross section merges into the large-diameter connecting rod bore 1 at the obliquely disposed, widened connecting rod flank 5. The large-diameter connecting rod bore 1 has a bearing cap 7, which is mounted on a connecting rod base body 9 by means of bolts, not shown. Each of the bolts is guided through an unthreaded bearing cap bore 11 and is in threaded engagement with a threaded bore 13 in the connecting rod base 9.

In fig. 9, the threaded bore 13 is realized as a through-bore, wherein the internal thread 28 of the threaded bore 13 merges into a connecting rod flank 5 facing away from the bearing cap 7, which is disposed at an angle to the bore axis B. Correspondingly, the bore edge 15 facing away from the bearing cap 7 extends elliptically in the obliquely placed connecting rod side 5, i.e. between bore edge end positions S1 and S2, which are spaced apart from one another by an axial distance Δ a. Between the two hole edge endpoint positions S1 and S2, the internal threads 28 of the threaded hole 13 are exposed laterally outward, transverse to the hole axis B. The course of the internal thread 28 is interrupted at the opening 25 facing away from the bearing cap 7 by the hole edge 15, so that the course transitions directly into the connecting rod flank 9 at the hole edge 15 with the formation of the cutout 17.

In fig. 9, the cut formation 17 results in a reduced component stability of the connecting rod in the case of a connecting rod load. Against this background, according to the invention, a depression 19 is formed in fig. 1 on an opening 25 of the threaded bore 13 facing away from the bearing cap 7, said depression having an unthreaded, smooth-surfaced inner circumferential portion 21.

The threaded bore 13 shown in fig. 1 can be produced by means of a thread production tool 23, which is shown separately in fig. 2. Thus, the thread making tool 23 has a tool shank 20 with a thread making area 27. The thread making zone is comprised of a series of thread cutting or forming teeth. The thread making region 27 transitions into the run-in profile 22 in the direction of the workpiece tip and into the reaming cutting edge 37 in the direction of the tool shank 20. A reaming stroke a (fig. 6) described later can be performed by means of the reaming cutting edge 37. The reaming edge 37 is realized as a counter-cutting edge which, after a reversal of the direction of rotation after the tapping stroke G (fig. 3 to 5), can perform a cutting action with the internal thread 28. The reaming cutting edge 37 therefore remains free of cutting work during the tapping stroke G and during the reversing stroke R and is only in cutting engagement with the internal thread 28 during the reaming stroke a.

A process for manufacturing the threaded through hole 13 is shown according to fig. 3 to 8. Thus in fig. 3, a workpiece 9 (i.e. a connecting rod base) is provided with a pre-drilled through hole 23. Subsequently, in fig. 3, a tapping stroke G is started, in which the thread-making tool 23 is advanced by the thread-making feed f_GAnd a thread making rotational speed n synchronized with the thread making feed_GIs driven into the workpiece through bore 24 to form the internal thread 28. The internal thread 28 has a radially outer thread root 29 (fig. 8) located at the thread outer diameter d_AThe above. At the beginning of the tapping stroke G (fig. 3), the cutting is first started by means of the cutting contour 22 on the tool side. During the further course of the tapping stroke G, the thread-making tool 23 is moved beyond the bore 25 facing away from the tool up to a reversal point (fig. 5), at which the thread-making region 27 of the thread-making tool 23 is disengaged from the through-bore 24.

After reaching reversal point U, reaming stroke a (fig. 6) begins. In the reaming stroke a, the thread making tool 23 is advanced by reaming f_AAnd reaming speed n_AInto the aperture 25 facing away from the tool until a depression depth s (fig. 7) is reached. The removal of material by means of the cutting operation of the internal thread 28 takes place in the reaming stroke a by means of the reaming cutting edge 37 of the thread-making tool 23, and until the undercut depth s (fig. 1) is reached.

As the set depth s is reached, a reverse stroke R (fig. 7) begins, in which the thread-making tool 23 penetrates into the thread groove of the internal thread via its thread-making region 27 and is guided out of the internal thread 28 formed in the through-opening 24 substantially without load, i.e. in the opposite direction of travel to the tapping stroke G and in the opposite direction of rotation, at a reverse rotational speed n_RAnd a reverse feed f synchronized with the reverse rotation speed_R。

List of reference numerals:

1 connecting rod hole with large diameter

3 connecting rod handle

Side surface of 5 connecting rod

7 bearing cap

9 connecting rod base body

11 unthreaded bearing cap bore

13 screw hole

15 hole edge

17 incision formation

19 sunk part

20 tool handle

21 inner peripheral part of depressed part

22 cutting-in profile

23 thread making tool

24 pre-drilled through-hole

25 opening facing away from the tool

27 thread making zone with thread cutting/forming teeth

28 internal screw thread

29 radially outer thread roots

37 reaming cutting edge

d_AOuter diameter

A hole enlarging stroke

Reverse stroke of R

G tapping stroke

Axis of B hole

n number of revolutions

f feed

Depth of s-sink

Point of U reversal

F plane of junction

Δ a axial spacing

Depth of s-sink

End point positions of S1 and S2 holes

Claims

1. A method for producing a threaded through-hole (13) in a workpiece (9) by means of a thread production tool (23) has a tapping stroke (G) in which the thread production tool (23) is fed with a thread production feed (f)_G) And a thread making rotational speed (n) synchronized with the thread making feed_G) Is driven into the pre-drilled workpiece through-hole (24) so as to form an internal thread (28) in the workpiece through-hole (24), and has a reverse stroke (R) in which the thread-making tool (23) is fed in a reverse direction (f) in a reverse rotation with the direction of rotation reversed_R) And a reverse rotation speed (n) synchronized with the reverse feeding_R) Is led out from an internal thread (28) formed in the through hole (24),

it is characterized in that the preparation method is characterized in that,

in particular, in order to avoid the formation of a cut (17) in an opening (25) of the through-hole (24) facing away from the tool, the method has a reaming stroke (A) in which the thread-making tool (23) is advanced (f) for reaming_A) And reaming rotational speed (n)_A) A recess (19) is produced in an opening (25) of the through-hole (24) facing away from the tool, in particular the recess (19) having an essentially thread-free, in particular smooth-surfaced, inner circumferential portion (21).

2. A method according to claim 1, characterized in that the internal thread (28) has a radially outer thread root (29) at the thread outer diameter (d)_A) And/or the inner circumference (21) of the recess (19) formed in the opening (25) facing away from the tool is cylindrical, in particular the diameter of the recess corresponds to the outer diameter (d) of the thread_A)。

3. Method according to claim 1 or 2, characterized in that the thread making tool (23) is rotated coaxially with the bore axis (a) in the reaming stroke (a), the tapping stroke (G) and/or the reversing stroke (R).

4. A method according to claim 1, 2 or 3, characterized in that in the tapping stroke (G) the thread making tool (23) is moved by its thread making area (27) beyond the orifice (25) facing away from the tool up to a reversal point (U), whereafter a reaming stroke (a) is started in which the thread making tool (23) is advanced (f) in reaming_A) And reaming rotational speed (n)_A) Into the opening (25) facing away from the tool until the depression depth(s) is reached, so that in the opening facing away from the tool(s)25) A countersink (19) is formed and/or the thread making area (27) is formed with thread cutting teeth and/or thread forming teeth.

5. Method according to claim 4, characterized in that a reverse stroke (R) is started as the countersinking depth(s) is reached, in which the thread-making tool (23) penetrates into the thread groove of the internal thread (28) via its thread-making region (27), in particular without load, and is guided out of the internal thread (28) formed in the through-hole (24).

6. Method according to one of the preceding claims, characterized in that the countersink inner peripheral portion (21) transitions at the hole edge (15) into the workpiece side (5) facing away from the tool, in particular the workpiece side (5) facing away from the tool is placed obliquely with respect to the hole axis (B), so that the hole edge (15) extends elliptically between axially spaced-apart hole edge end point positions (S1, S2), between which the countersink inner peripheral portion (21) is laterally exposed transversely to the hole axis (B).

7. Thread-making tool for making an internal thread (28) in a workpiece through-hole (24) by means of a method according to any one of the preceding claims,

it is characterized in that the preparation method is characterized in that,

the thread making tool (23) has at least one reaming cutting edge (37) by means of which a reaming stroke (A) can be carried out.

8. Thread making tool according to claim 7, characterized in that the reaming cutting edge (37) is non-functional, that is to say free of machining, in the tapping stroke (G) and the reversing stroke (R), the reaming cutting edge (37) being capable of cutting engagement with the internal thread (28) in the reaming stroke (A), so that the internal thread (28) can be at least partially cut off.

9. Thread making tool according to claim 7 or 8, characterized in that the reaming cutting edge (37) is realized as a counter cutting edge which, after the tapping stroke (G), can only be brought into cutting engagement with the internal thread (28) with a reversal of the direction of rotation.

10. A workpiece, in particular a connecting rod, having a threaded through-hole (13) which is produced by means of a method according to one of claims 1 to 6 and by means of a thread production tool (23) according to one of claims 7, 8 or 9, wherein the thread production tool (23) can be driven into the pre-drilled workpiece through-hole (24) in a tapping stroke (G) so that an internal thread (28) is formed in the workpiece through-hole (24), said thread production tool being able to be guided out of the internal thread (28) formed in the through-hole (24) in the reverse stroke (R) with a reversal of the direction of rotation,

it is characterized in that the preparation method is characterized in that,

in particular, in order to avoid the formation of a cutout (17) in the opening (25) of the through-bore (24) facing away from the tool, a depression (19) can be formed in the opening (25) of the through-bore (24) facing away from the tool during the reaming stroke (A) of the thread-making tool (23).