EP3341618A1

EP3341618A1 - Component, provided with a thread

Info

Publication number: EP3341618A1
Application number: EP16745446.1A
Authority: EP
Inventors: Peter Kury; Dirk Hänsel; Marc Lange
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 2015-09-30
Filing date: 2016-07-26
Publication date: 2018-07-04
Also published as: WO2017054955A1; US20180266468A1; JP2018536807A; CN108138828A; EP3150869A1

Abstract

The invention aims to provide a component (1, 2), provided with a thread (4, 6) that has increased play (δ) in the axial direction in comparison with a standard thread, which allows nuts to be screwed on, even in the case of highly preloaded bolts, and also enables a highly loadable threaded connection. For this purpose, the play (δ) is monotonically increasing in the axial direction.

Description

description

The invention relates to a component, provided with a thread, which has a relation to a standard thread increased clearance in the axial direction. It further relates to a method for reworking a standard thread of a component, in which an increased clearance is introduced in the axial direction.

In various technical areas, particularly highly stressed bolts are often stretched externally (eg hydraulically) in the axial direction, the nuts are positively screwed in the stretched state and the external prestressing force is then released, so that the nuts take over the load in the axial direction. This method avoids torsional forces in Bol ^¬ zen and fretting in the threaded connection, which until the desired preload be the case with an actively rotated mother. In some applications, such as tie rods for stationary power plant gas turbines, an active rotation of the mother for the reasons mentioned would even be impossible.

Typical elongations in such stretching in the axial direction are in the range of a few parts per thousand (relative elongation). Since common standard threads (this is understood in particular metric ISO standard thread [DIN 13 and DIN 14], thread according to Unified Thread Standard [ANS I / ASME Bl.1-2003] or Whitworth thread) have no explicit axial play, but this only results in the tolerances of the pitch diameter, this low axial clearance is often completely consumed at a Belas ^¬ tion and subsequent expansion of the bolt. This may make it impossible to install standard threaded nuts on highly preloaded bolts.

As a solution to this problem, it is proposed in EP 1 527 283 B1 to modify the thread form and decouple axial and radial clearance from the standard thread form or that Expand nut thread and in particular to introduce an additional ^¬ Royal axial play. However, this can entail cost and compatibility issues as special cutting tools must be used; Furthermore, the thread overlap and thus the load capacity (stripping ^¬ strength) is reduced.

It is therefore an object of the invention to provide a component and a method of the type mentioned above, which on the one hand a turning nuts, even on heavily prestressed bolts, on the other hand, but also a high load capacity

Screw connection allows.

This object is achieved according to the invention with respect to the component in that the play is monotonically increasing in the axial direction.

With regard to the method, the object is achieved by the game is introduced monotonically increasing in the axial direction. The invention is based on the consideration that a lighter twisting the nut on a prestressed bolt is then possible when the axial play increases in the axial direction according to the elongation of the bolt. However, as this also leaves areas with a slight increase in the axial play, a high stability of the screw connection nevertheless remains.

For this purpose, the axial play is linearly increasing or linearly increasing introduced in procedural ^¬ ren. This is advantageous since the deformation of the bolt during stretching is distributed uniformly over its length.

According to the invention it is provided that the axially li ^¬ near rising clearance over the entire axial length of the thread, ie the axial displacement increases over the entire axial length of the thread linear. Basically, each of the two threaded partners, ie internal or external thread can be provided with the described axially increasing axial play, both threaded partners can be reworked accordingly. In a particularly advantageous embodiment, however, the reworked, reworked with an axially increasing axial play Bau ^¬ part is designed as a nut, while the bolting to be stretched during turning is designed as a normal thread normal. In an advantageous embodiment of the method, the game is introduced with a standard cutting tool. This ver ^¬ simplifies the post-processing considerably.

Furthermore, a play in the radial direction proportional to the play in the axial direction is advantageously additionally introduced. This too can be easily achieved with a standard cutting tool and increases the ^size

Smooth running when turning the nut. Advantageously, a nut described above verwen ^¬ det in a method for screwing the nut on a bolt, wherein the bolt is mechanically stretched by a predetermined relative elongation before screwing the nut, and wherein the maximum introduced axial play the product of relative elongation and axial Height of the thread corresponds. This ensures that the introduced Axial ^¬ game is sufficient to perform a twisting the nut on the bolt without eating can. Advantageously, the bolt is part of a tie rod of a gas turbine. In particular, in gas turbines Namely, the tie rods, the fi xed ^¬ the shaft of the rotor of the gas turbine, stretched in the manner described, before it is fixed with a nut.

The advantages achieved by the invention are, in particular, that by a reworking of a standard thread with an axially increasing axial clearance on the one hand a simple Turning on a stretched bolt is made possible, and on the other hand a particularly good load capacity of the ent ^¬ standing screw connection is ensured.

Embodiments of the invention will be explained in more detail with reference to drawings. Show:

1 shows a schematic cross section of a screw connection of two standard threads according to the prior art,

2 shows the maximum possible elongation of the bolt of the screw ^¬ compound according to the prior art,

3 shows the maximum possible elongation of the bolt one

Screw with increasing in the axial direction

Axial play in the thread of the nut,

4 shows an illustration of the linearly increasing axial

Post-processing of the example of FIG. 3,

5 shows an illustration of the linearly increasing axial

Post-processing of both thread partner in a schematic longitudinal section of a screw connection, FIG 6 is a schematic longitudinal section through a screw ^¬ connection with a proportional axial and radial post-processing of the mother,

FIG 7 is a schematic longitudinal section through a screw ^¬ connection with a proportional axial and radial threaded post-processing of both partners,

8 shows a schematic longitudinal section through a thread illustrating the variables used in the graphs shown in the following figures,

9 shows graphs of the axial linearly rising play plotted against the axial position, FIG 10-13 graphs of possible further embodiments applied for an axial play against the Axialposi ^¬ tion, and FIG 14 is a graph of the load / load capacity of the threaded ^¬ against the axial position.

Identical parts are provided in all figures with the same Bezugszei ^¬ chen.

1 shows a schematic partial longitudinal section through the upper part of a screw connection. Shown are the profiles of both threaded partners, namely a nut 1 and a bolt 2. The thread 4 of the nut 1 and the thread 6 are designed according to the standard, i. as metric ISO standard thread

(DIN 13 and DIN 14), as thread according to Unified Thread Standard (ANS I / ASME Bl.1-2003) or as Whitworth thread. In any case, no explicit Axial ^¬ play Axmin is provided with such threads 4, 6. Rather, the Axialspiel Axmin is given only by the production-related tolerance fields of the flank diameter. The arrows 8, 10 show the loading directions of nut 1 or bolt 2.

The nuts 1 and 2 described here are intended for a particularly high load. In exemplary embodiments, the pin may be disposed 2, for example coaxial to the shaft of a gas turbine not shown in detail at the end, and the shaft and the turbine wheels fixie ^¬ ren. In the form of a tie rod To this end, 2 is the bolt, first externally, eg hydraulically stretched, the nut 1 then added positively in the stretched state, and then the biasing force ge ^¬ triggers, so that the mother 1 takes over the load.

2 shows the screw connection of FIG. 1, but additionally a lattice representation 12 of the bolt 2 in the stretched state. The mesh representation 12 illustrates the maximum possible elongation of the bolt 2 so that the nut 1 with the vorhande ^¬ NEN Axmin axial play remains rotatable. Stronger strains would cause the mother 1 would no longer actively turn or it would come to eat.

FIG 3 now shows the screw of FIG 1 and 2, which has been reworked. With a standard thread cutting tool in this case an additional axial clearance was introduced into the thread 4 of the nut 1. The axial play increases in the 3 from left to right, ie the cutting tool was moved continuously in the post-processing in the axial direction to the right from the standard position. Thereby, the axial play is increased monotonically increasing in the thread 4 of the nut 1. Since the flank angle is not changed on ^¬ due to the use of the standard thread-cutting tool, this also leads to a radially increasing offset, ie, the height of the profile of the thread 4 is reduced continuously left to right.

Also shown in FIG 3 is a grid representation 12 of the bolt 2, which shows the maximum possible elongation of the bolt 2, so that the nut 1 with the existing axial play Axmin still remains rotatable. FIG. 3 clearly shows that a considerably greater elongation of the bolt 2 is made possible by the post-processing. FIG. 4 shows the screw connection from FIG. 3, but in this case the tips of the profile of the thread 4 of the nut 1 are connected to one another by a dashed line 14. FIG. 4 shows that the first two threads (in the illustration on the left) have not been modified, only then does the finishing work commence. This takes place with a linearly increasing axial play, which is shown by the formation of the line 14 as a straight line.

5 shows a further variant in which both threads 4, 6 of the nut 1 and bolt 2 are reworked in the same way. The thread 4 of the nut 1 is reworked exactly as shown in Figures 3 and 4, while the bolt 2 is also reworked with the standard thread cutting tool. Here- at the respective right flanks of the thread 6 nachbear ^¬ processed in the same way reworked, ie after the first two threads with linearly increasing axial play, represented by the line 14th

6 and FIG 7 show variants of the embodiments of FIG 4 or FIG 5. In contrast to the latter from ^¬ exemplary embodiments, the cutting tool is in this case not only axially but also axially into the profile of the thread 4 of the nut 1 (FIG 6) or In the profiles of both threads 4, 6 ver ^¬ pushed. As a result, a radial clearance in the respective thread 4, 6 is introduced to the same extent, ie proportional to the introduced axial clearance. Based on the following FIGS 8 and 9, the course of the ^{¬ introduced} additional game will be explained.

FIG. 8 explains the variables used in the graphs of FIG. 9. FIG 8 shows in the upper part of the thread 4, 6 of nut 1 or bolt 2, depending on the embodiment, and in the lower part of an abscissa of a graph indicating the Axialpo ^¬ position x. The origin lies in the axial beginning of the thread 4, 6, the axial height of the thread 4, 6 is denoted by L0. The abscissa denotes the periodic axial positions of the incisions between thread flanks with x1, x2, x3.

The axial offset, ie, the additional axial play (explained in ande ^¬ ren embodiments how to Figures 6 and 7 and the additional radial play) depending on the axial position of x is denoted by δ (x). FIG. 8 shows this by way of example for an approximately linear course of the game δ (x); Here an additional axial play is solely δ (x) introduced ^¬. The regions 18 of the thread flanks removed thereby are shown hatched. In all ^exemplary embodiments of progressions of the play δ (x), the following is a condition for L0: δ (L0) -δ (0) + Axmin> LOxs, where ε is the relative elongation of the bolt 2 during assembly of the nut 1, which is usually in the range of a few per thousand. As a result, a slight rotation of the nut 1 is ensured on the stretched bolt. The FIG 9 show this the course of the game δ (x). This is shown in the graph, in which the introduced zusätzli ^¬ che, deviating from the standard game is δ (x) versus Axialposi ^¬ tion x. In this case, δ (0) = 0, 5 (L0) = L0><s (or alternatively δ (LO) = L0 ^χ s-Axmin). The additional clearance LO introduced over the entire length LO is therefore sufficient to compensate for the elongation of the bolt 2.

The course of the game δ (x) in the embodiment of FIG 9 is linear between the already mentioned extreme values over the entire axial length, i. it has a slope of ε. This is the simplest case of post processing.

It is also possible, in the front region of the thread 4, 6, to provide no axial offset over a certain initial length LN. This can advantageously be a length, on which ^¬ even by the Axial ^¬ game Axmin ^¬ even with the standard thread even with stretched bolt 2 still no seizure can occur, ie it applies LN <Axmin / s. Such embodiments are shown in FIGS. 10-12. In all exemplary embodiments shown in FIGS 10-12 is in the range x <LN therefore δ (χ) = 0, ie, the thread 4, 6 here corresponds to the standard threaded ^¬ de.

Depending on whether the highest possible load capacity or maximum ease of movement or low risk of seizing is concerned, after the initial length LN either the axial offset can be directly adjusted to the value necessary for a linear increase (shown in FIG. 10, for LN <x <L0 If δ (χ) = ε ^χ χ), or linearly continuously to the desired final value (shown in FIG. 11, for LN <x <L0, then δ (x) = L0 ^χ ε ^χ (x-LN)) / (L0-LN)). Since consideration of the initial axial play is also optional for the final value 5 (L0) (see above, 5 (L0) = L0x £ or alternatively δ (LO) = L0 ^χ ε-Δχιηίη), this results in four possible thread reworks for the combination of a linearly increasing correction δ (x) and a neutral initial length LN. The extreme cases are the abrupt change of δ (x) for x> LN to the slope ε up to the length LO, where

ö (L0) = L0x £, and the continuous transition from δ (x) for x> LN to the slope ε to the length LO, where δ (LO) = L0 ^χ ε-Δχιηίη. Both courses of the game δ (x) are shown in FIG. All Verläu ^¬ fe therebetween (shown in phantom) are possible, clotting ^¬ Gere values for the additional axial play δ (x) than the un ^¬ tere limit lead to a sticking of the nut and larger values than by the upper limit given weaken the thread structurally more than necessary.

13 shows a further possible course of the additional axial play δ (x), which may be useful in elastically load-optimized nuts. Such nuts are, for example, the Thumsche mother form, the skilled worker from Illgner, K.H., flower D .: screws Vademecum; Publication of Bauer & Schaurte Karcher GmbH, 5th edition 1983 is known Flexmuttern the Fa. Nord-Lock. In such nuts 1, in addition to the previously described exclusive post-processing of the non-load-bearing flank of nut 1 and / or pin 2, a reworking of the supporting flank can be useful.

Since only a modification of the supporting flank or a modification of the non-supporting flank takes place at a given axial position x, in the graph according to FIG. 13 the modification of the supporting flank is designated by negative values of δ (x). In the embodiment, for post-processing for increasing the axial clearance (x) δ to FIG 13 for elastically strainoptimised nuts 1 is carried out in the initial region of the length of 0 to the length LR of the nut 1, first a post ^¬ machining of the supporting edge (negative value of δ (x)) with the slope ε. In a subsequent area is done with Continuous transition no postprocessing for LR <x <LX + LR, ie δ (χ) = 0. The be ^¬ already takes place only subsequently, for x> LX + LR to FIG explained 11 linear increase with steady over ^¬ transition to the desired final value.

FIG 14 shows, finally, that the herein described ^¬ After machining of the threads whose load does not verrin ^¬ device. FIG. 14 shows a graph showing the typical load σ (χ) of a thread 4, 6 along its axis (that is, as a function of the threads n or the axial position x), cf. Definition in Ch. J. Mech. Eng. 22 (6), 869ff. (2009). The yield strength Y of the mother material must be selected so that a durability even at the beginning of threading (x = 0), if necessary under light plasticization still exists. A

Radial expansion of the nut 1 reduces the effective belast ^¬ bility Y 'ST (the peel strength is a good approximation proportional to the overlap) so that it can be exceeded in the front loading area of the nut 1 ^¬. The post-processing described above shows this effect on the effective load capacity Y'EG only in the slightly loaded rear area of the nut 1. Also for load-optimized elastic nuts 1 (see above) with milder stress gradients σ '(x) the above-described monotonically increasing post-processing is always better than a gross expansion of the mother 1.

Claims

claims

1st component (1, 2),

provided with a thread (4, 6) having a relative to a standard thread increased monotonically increasing clearance (δ) in Axi ^¬ alrichtung,

characterized in that

the play (δ) is linearly increasing over the entire axial length of the thread (4, 6).

2. component (1, 2) according to claim 1,

trained as a mother (1).

3. A method for finishing a standard thread of a component (1, 2), in which an increased monotonically increasing game

(δ) is introduced in the axial direction,

characterized in that

the play (δ) over the entire axial length of the thread (4, 6) is introduced linearly rising.

4. The method according to claim 3,

in which the component (1, 2) is designed as a nut (1).

5. The method according to claim 3 or 4,

in which the game (δ) is introduced with a standard cutting tool.

6. The method according to claim 5,

in which additionally a play (δ) is introduced in the radial direction proportionally to the clearance (δ) in the axial direction.

7. A method for screwing a nut (1) according to claim 2 or a nut (1) whose thread (4) has been processed by a method according to one of the preceding claims, on a bolt (2),

wherein the bolt (2) is mechanically stretched by a predetermined relative elongation (ε) before screwing the nut (1), and

wherein the maximum introduced axial play (5 (L0)) the Pro ^¬ domestic product of relative elongation equal to (ε) and the axial height (LO) of the Ge ^¬ wind (4).

8. The method according to claim 7,

in which the bolt (2) is part of a tie rod of a gas turbine.