Component nut thread

Abstract

Screw connection with a component nut thread (3) and a screw bolt (1), wherein the screw bolt (1) passes through a joining partner (7) clamped to the component (5) and extends over a screw-in length (I E ) is screwed into the component nut thread (3), wherein in the screwing process the screw bolt (1) is initially screwed in without load with axial flank play (s1, s2) from a nut thread start (9) over the screwing length (I E ) can be screwed in up to a nut thread end (11), and wherein the screwing-in process is completed with a tightening process in which the screw bolt (1) is turned by a tightening rotation angle (α) soll ) in the screw-in direction until a tightening torque (M) is reached soll) is further rotated, whereby during the tightening process the screw bolt tensile flanks (23) can be brought into pressure with corresponding nut thread tensile flanks (25) by utilizing the axial flank clearance (s1, s2), and during further screwing in a screw bolt stretching section (27) formed between the screw bolt tensile flanks (23) in pressure and a bolt head (15) is elastically stretched, whereby the screw bolt (1) is stretched over the entire screwing in length (I E) has a uniform external thread, and wherein the flank diameter (d2) in the screw bolt thread is constant in the axial direction, characterized in that, for the axial enlargement of the screw bolt stretching section (27), the component nut thread (3) is divided into a screw-in thread (17) located at the beginning (9) of the nut thread and into a tensile force build-up thread (19) located at the end (11) of the nut thread, and that in the still unloaded, screwed-in state (Z), the axial flank clearance (s2) in the screw-in thread (17) is greater by a flank clearance excess (Δa) than the axial flank clearance (s1) in the tensile force build-up thread (19).

Description

[0001] The invention relates to a component nut thread according to the preamble of claim 1, a screw connection with such a component nut thread and a tool for producing a component nut thread according to claim 9.

[0002] A screw connection of this type comprises a screw stud and a nut thread formed in a component. The screw stud passes through a joining partner clamped to the component and is screwed into the component's nut thread over a specified insertion length. During the insertion process, the screw stud is initially screwed in without load, with axial clearance, over the insertion length until it reaches the end of the nut thread. The insertion process concludes with a tightening operation, in which the screwed-in screw stud is rotated further by a specified angle until a predefined tightening torque is reached. During the tightening operation, the tensile flanks of the screw stud are brought into contact with the corresponding tensile flanks of the nut thread, thereby eliminating the axial clearance.During the tightening process, a section of the bolt is elastically stretched longitudinally in the axial direction between the tensile flanks of the bolt located in the pressure system and a bolt head. This creates a tensile force in the bolt, which the bolt head uses to preload the joining partner against the component.

[0003] In the standard screw connection known from the prior art, during the tightening process the tensile flanks of the nut thread located at the beginning come into early contact with the tensile flanks of the bolt. Therefore, only the bolt protruding from the nut thread and not engaged in the thread remains as the bolt extension section, which can elastically stretch to build up axial stress.

[0004] Especially when the joining partner is axially short, the bolt's extended section has a correspondingly short axial length. This results in a steep tightening torque / tightening angle characteristic curve, where a predefined tightening torque is achieved even with a small tightening angle (e.g., 60°). With such a steep tightening torque / tightening angle characteristic curve, an unintentional, slight deviation (e.g., 5%) from the required tightening angle (e.g., 60°) results in a considerable change in the effective tightening torque, which can compromise the safety of the bolted joint. The same applies to mechanical, dynamic, or thermal stresses acting on the bolted joint.

[0005] A screw and a screw system are known from DE 10 2017 126 685 A1. A screw-nut unit for hydraulic actuation is known from DE 199 40 976 A1.

[0006] The object of the invention is to provide a component nut thread for a screw connection in which the safety of the screw connection can be increased in a simple manner compared to the prior art.

[0007] The problem is solved by the features of claim 1 or 9. Preferred embodiments of the invention are disclosed in the dependent claims.

[0008] The invention relates to a screw connection in which, during the insertion process, the screw bolt is initially screwed in without load and with axial clearance over a certain insertion length until it reaches the end of the nut thread. The insertion process concludes with a tightening operation in which the screw bolt is rotated further in the insertion direction by a tightening angle until a predefined tightening torque is reached. During the tightening operation, the tensile flanks of the screw bolt come into compression with corresponding tensile flanks of the nut thread, thereby eliminating the axial clearance. Subsequently, a tensile section of the screw bolt between the tensile flanks of the screw bolt in compression and a bolt head is elastically stretched longitudinally in the axial direction. In this way, a tensile force builds up in the screw bolt, by means of which the bolt head preloads the joining partner against the component.

[0009] According to the characterizing part of claim 1, the following measure is implemented to axially increase the extension section of the screw bolt: The nut thread is divided into a screw-in thread located at the beginning of the nut thread and a tensile force build-up thread located at the end of the nut thread. The screw-in thread and the tensile force build-up thread are designed such that, in the unloaded, screwed-in state, the axial flank clearance in the screw-in thread is dimensioned larger by a flank clearance allowance than the axial flank clearance in the tensile force build-up thread. In a preferred embodiment, the axial flank clearance in the tensile force build-up thread can be reduced to zero clearance.

[0010] The following screw-in process results from the nut thread according to the invention: Towards the end of the screw-in process, i.e., during the tightening process, the tensile flanks of the screw bolt at the bolt tip come into contact with the tensile flanks of the nut thread located in the tensile force build-up thread very early on (due to the reduced axial flank clearance or zero clearance). This results in a free, axially long stretching section of the screw bolt between the bolt tip and the bolt head.

[0011] During the tightening process, the free, axially long section of the bolt is elastically stretched in the axial direction, thereby utilizing the excess backlash in the threaded section of the nut. This elastic stretching of the bolt's section can continue until essentially all of the bolt's tensile flanks are in contact with the tensile flanks of the nut thread in the threaded section. The remaining, axially short section can correspond to the bolt's projection protruding from the nut thread, which terminates at the bolt head.

[0012] According to the invention, a significantly larger bolt extension section can therefore be provided during the tightening process compared to the prior art. This results in a comparatively flat tightening torque / tightening angle characteristic curve, where a significantly larger tightening angle is required to achieve the predefined tightening torque compared to the prior art. With such a flat tightening torque / tightening angle characteristic curve, an unintentional, minor deviation (for example, 5%) from the required tightening angle (for example, 120°) leads only to a minor change in the effective tightening torque, so that the safety of the bolted joint is not compromised.

[0013] The axial backlash is directly proportional to the diameter difference between the flank diameter in the nut thread and the flank diameter in the bolt thread. According to the invention, the flank diameter in the tensile force-generating thread can be smaller than the flank diameter in the screw-in thread. The flank diameter is a common parameter for describing thread geometry and lies midway between the thread's outer diameter and its inner diameter.

[0014] According to one design variant, the flank diameter in the axial direction of the tensile force-building thread can be constant. In this case, the threads running in the tensile force-building thread have constant flank diameters. In contrast, the flank diameter in the axial direction of the screw-in thread can vary. In this case, the threads running in the screw-in thread can have different flank diameters.

[0015] In one specific embodiment, the tensile force-building thread and the screw-in thread of the nut thread can transition directly into each other in the axial direction. The tensile force-building thread preferably has a significantly smaller number of thread turns than the screw-in thread.

[0016] The invention makes it possible to increase the security of the screw connection simply by changing the shape of the nut thread. The screw bolt, on the other hand, can have a standard thread in which the external thread remains uniform over the entire screw-in length.

[0017] An embodiment of the invention is explained in more detail below with reference to the drawings.

[0018] They show: Fig. 1 a completed screw connection in half section; Fig. 2 in a view according to the Fig. 1 a nut thread of the screw connection with loosened screw bolt; Fig. 3 and Fig. 4 views illustrating a screw-in process; Fig. 5, Fig. 6 to Fig. 7 views of a comparative form not encompassed by the invention; and Fig. 8 A schematic half-section view of a tool for producing the component nut thread.

[0019] In the Fig. Figure 1 shows a screw connection with a screw bolt 1 and a nut thread 3 formed in a component 5. The screw bolt 1 passes through a joining partner 7 clamped to the component 5 and extends over a screw-in length l. E screwed into the component nut thread 3, starting from a nut thread start 9 facing the joining partner 7 over the screw length l Eup to a nut thread end 11. A screw bolt projection 13 protrudes from the nut thread 3 and terminates at a bolt head 15. A tensile force F is present in the screw bolt 1. Z constructed by means of which the bolt head 15 clamps the joining partner 7 against the component 5.

[0020] From the Fig. Figure 2 shows the geometry of the nut thread 3 and the screw bolt 1. Accordingly, the nut thread 3 is divided into a screw-in thread 17 located at the beginning 9 of the nut thread and a tensile force build-up thread 19 located at the end 11 of the nut thread, which transition directly into one another. The tensile force build-up thread 19 has a significantly smaller number of thread turns 21 than the screw-in thread 17. An example is shown in the Fig. 2. The tensile force build-up thread 19 is realized with three threads 21, while the screw-in thread 17 is realized with a total of six threads 21. The screw bolt 1 has a standard external thread that extends over the entire screw-in length l. E It proceeds uniformly.

[0021] As from the Fig. As can be seen further in section 2, the flank diameter D is 2a The tensile force build-up thread 19 is dimensioned smaller than the flank diameter D. 2b in the screw-in thread 17. Each thread 21 located in the tensile force build-up thread 19 has the same flank diameter D. 2a in contrast, the threads 21 in the screw-in thread 17 can have different flank diameters D. 2b exhibit.

[0022] With the nut thread 3 according to the invention, the Fig. 3 and Fig. 4 illustrated screw-in process feasible, leading to a secure screw connection.

[0023] For the sake of a simpler understanding of the invention, we will first refer to the Fig. 5, Fig. 6 to Fig. Figure 7 is taken, which describes a screwing-in process for a conventional standard screw connection that is not included in the invention: In the screwing-in process, the screw bolt 1 is first screwed in without load with axial flank play s over the screwing-in length l E screwed in up to the end of the nut thread 11 (compare screwed-in, unloaded state Z in the Fig. 5) The screwing-in process concludes with a tightening operation in which the screw bolt 1 is turned by a tightening angle α soll is turned further in the screw-in direction until a predefined tightening torque M is reached. soll is achieved. During the tightening process, the bolt tensile flanks 23 are brought into compression with corresponding nut thread tensile flanks 25, thereby eliminating the axial flank clearance s. As can be seen from the Fig. As can be seen from Figure 6, during the tightening process the tensile flanks 25 of the nut thread located at the beginning 9 of the nut thread come into early contact with the tensile flanks 23 of the bolt. Therefore, only the bolt projection 13 protruding from the nut thread 3 and not engaged with the thread remains as the bolt extension section 27 ( Fig. 6), which can deform elastically to create axial stress.

[0024] Especially in the case of the one in the Fig. 5 or Fig. In the axially short joining partner 7 shown in Figure 6, the bolt extension section 27 is dimensioned with a correspondingly short axial length. This results in a steep tightening torque / tightening angle characteristic curve ( Fig. 7), where the predefined tightening torque M soll even with a small tightening angle α soll(for example, 60°). With such a steep characteristic curve, an unintentional, slight deviation (for example, 5%) from the required tightening angle α leads to... soll (for example, 60°) leads to a considerable change in the effective tightening torque M soll , so that the safety of the screw connection may be compromised.

[0025] In contrast, the following screw-in process can be carried out using the nut thread geometry according to the invention, in which a significantly flatter tightening torque / tightening angle characteristic curve is achieved ( Fig. 4) results in: In the still unloaded, screwed-in state ( Fig. 3) The axial flank clearance s2 in the screw-in thread 17 is greater by a flank clearance interference Δa than the axial flank clearance s1 in the tensile force build-up thread 19. In the Fig. Figure 3 shows the unloaded, screwed-in state Z, in which the axial flank play s1 in the tensile force build-up thread 19 is reduced to approximately zero play.

[0026] As a result, immediately upon commencement of the tightening process, the bolt tensile flanks 23 located at the bolt tip 29 come into contact with the nut thread tensile flanks 25 in the tensile force build-up thread 19. In this way, a free, axially long bolt extension section 27 is obtained ( Fig. 3) between the bolt tip 29 and the bolt head 15. During the further course of the tightening process, the free, axially long bolt extension section expands elastically in the axial direction, thereby at least partially consuming the flank clearance Δa in the screw-in thread 17. The tightening process can be continued until essentially all bolt tensile flanks 23 of the screw-in thread 17 are in compression with the nut thread tensile flanks 25 located in the screw-in thread 17, as is the case in the Fig. 1 is shown. In the Fig. 1 are (starting from the beginning of the mother thread 9 in a direction to the left) the first screw bolt thread and the second screw bolt thread are not pressure system with the screw-in thread 17. The remaining, axially short residual stretching section 27' therefore extends from the third screw bolt thread to the bolt head 15.

[0027] The core of the invention consists in the fact that by changing the shape of the nut thread 3, a [missing information] is achieved compared to the prior art ( Fig. 5, Fig. 6 to Fig. 7) a significantly larger bolt extension section 27 can be provided. This results in a comparatively flat tightening torque / tightening angle characteristic curve ( Fig. 4) With such a flat characteristic curve, an unintentional, slight deviation (for example, 5%) from the required tightening angle α leads to soll (for example, 120°) only results in a slight change in the acting tightening torque M soll , so that the safety of the screw connection is not compromised.

[0028] In the Fig. Figure 8 shows a schematic half-section view of a tool for producing a component nut thread 3. The tool has a clamping shank 30 which can be clamped in a machine spindle.

[0029] The clamping shank 30 transitions into a tool body which is axially divided into a thread-forming section 31 located at the tool tip 32 and a second thread-forming section 33 on the clamping shank side. The first thread-forming section 31 is used to produce the tensile force-building thread 19, while the second thread-forming section 33 is used to produce the screw-in thread 17. The two thread-forming sections 31, 33 have axially arranged profile teeth 35, 36. During thread formation, these teeth engage with the inner circumference of a pre-drilled hole in the component in a forming and / or cutting manner. Therefore, the tool can function as a thread former and / or as a thread cutter. In a process sequence for producing the component's nut thread 3, the tool is inserted into the pre-drilled hole in a stroke movement with a superimposed rotational movement, coaxially with the axis of the pre-drilled hole.

[0030] The following is based on the Fig. 8. The geometry of the tool is described: Accordingly, the tool has a total of two incomplete threads at its tool tip 32, which transition further along the clamping shank 30 into a total of three profile teeth 35 arranged one behind the other of the first thread-forming section 31. The three profile teeth 35 of the first thread-forming section 31 have identical tooth geometry. Further along the clamping shank 30, the second thread-forming section 33 follows, which has a plurality of profile teeth 36.

[0031] In the first thread production section 31, the flank diameter d 2a The profile teeth 35 are essentially constant. Accordingly, the threads 21 produced in the tensile force build-up thread 19 also have essentially constant flank diameters d. 2a on.

[0032] The geometry of the profile teeth 35, 36 is designed such that in the component nut thread 3 to be manufactured, the axial flank clearance s2 in the screw-in thread 17 is greater by the flank clearance interference Δa than the axial flank clearance s1 in the tensile force build-up thread 19. For this purpose, the flank diameter d 2b In the second thread production section 33, the diameter difference Δd is larger than the flank diameter d. 2a in the first thread production section 31. In addition, the profile tooth width a measured at the flank diameter line is 1b In the second thread production section 33, a material allowance m1, m2 is dimensioned larger than the profile tooth width a. 1a in the first thread production section 31. In the Fig. 8 shows, for example, the material allowance m1, m2 on both the profile tooth flanks facing the tool tip 32 and on the profile tooth flanks of the profile teeth 36 facing away from it.

[0033] To illustrate the size difference between profile teeth 35 and profile teeth 36, the following are shown in the Fig. In the second thread production section 33, the contours of the profile teeth 35 of the first thread production section 31 are shown as dashed lines. These are dimensioned smaller than the profile teeth 36 by the material allowance m1, m2.

[0034] The material dimensions m1, m2 are located in the Fig. 8. This is exemplified by the material allowance on both the profile tooth flanks facing the tool tip 32 and the profile tooth flanks of the profile teeth 36 facing away from it. Alternatively, the material allowance m1, m2 can be present either only on the profile tooth flank facing the tool tip 32 or only on the profile tooth flank facing away from it. Furthermore, the flank diameter d can be 2b The profile teeth 36 in the second thread generation section 33 are essentially constant or vary via a mathematical function along the tool axial direction x. REFERENCE MARK LIST: 1 screw bolt 3 nut threads 5 components 7 joining partners 9 Nut thread start 11 Nut thread end 13 Screw bolt protrusion 15 bolt head 17 screw-in threads 19 Tensile force build-up threads 21 threads 23 Screw bolt tension flank 25 Nut thread tensile flank 27 long screw bolt stretch section 27' Remaining section 29 bolt tip I E Screw-in length S1, S2 flank play D 2a , D 2b Flank diameter in the nut thread d2 Flank diameter in the screw bolt thread M soll Tightening torque α soll Tightening angle Δa Excessive flank play Z screwed-in, axially unloaded state 30 clamping shaft 31 First thread production section 32 Tool tip 33 Second thread production section 35, 36 profile teeth a 1a , a 1b Profile tooth width Material measurement d 2a , d 2b Flank diameter x Tool axial direction Δd diameter difference

Claims

Screw connection with a component nut thread (3) and a screw bolt (1), wherein the screw bolt (1) passes through a joining partner (7) clamped to the component (5) and is screwed into the component nut thread (3) over a screw-in length (IE), wherein in the screw-in process the screw bolt (1) can initially be screwed in without load with axial flank clearance (s1, s2) from a nut thread start (9) over the screw-in length (IE) to a nut thread end (11), and wherein the screw-in process concludes with a tightening operation in which the screw bolt (1) is further rotated by a tightening rotation angle (αtarget) in the screw-in direction until a tightening torque (Mtarget) is reached, wherein in the tightening operation the screw bolt tensile flanks (23) are subjected to pressure with corresponding The nut thread tensile flanks (25) can be brought into contact with the,and, during further screwing in, a screw bolt stretching section (27) formed between the screw bolt tension flanks (23) located in the pressure system and a bolt head (15) is elastically stretched, wherein the screw bolt (1) has a uniform external thread over the entire screwing length (IE), and wherein the flank diameter (d2) in the screw bolt thread is constant in the axial direction, characterized in that, for axial enlargement of the screw bolt stretching section (27), the component nut thread (3) is divided into a screwing thread (17) located at the nut thread start (9) and into a tensile force build-up thread (19) located at the nut thread end (11), and that, in the still unloaded, screwed-in state (Z), the axial flank clearance (s2) in the screwing thread (17) is greater by a flank clearance interference (Δa) than the axial Flank play (s1) in the tensile force build-up thread (19)., Screw connection according to claim 1, characterized in that in the unloaded, screwed-in state (Z) the axial flank clearance (s1) in the tensile force build-up thread (19) is zero clearance. A screw connection according to claim 1 or 2, characterized in that, during the tightening process, the nut thread tensile flanks (25) located in the tensile force build-up thread (19) – compared to the nut thread tensile flanks (25) located in the screw-in thread (19) – come into compression with the screw bolt tensile flanks (23) at the bolt tip (29) at an early stage, so that a free, axially long screw bolt stretching section (27) results between the bolt tip (29) and the bolt head (15), and that, in particular, during the further course of the tightening process, the free, axially long screw bolt stretching section (27) expands elastically in the axial direction, thereby at least partially utilizing the flank clearance (Δa) in the screw-in thread (17), until substantially all screw bolt tensile flanks (23) are in compression with the screw bolts located in the screw-in thread (19). (17) located nut thread tensile flanks (25). Screw connection according to claim 3, characterized in that the axially short residual stretching section (27') remaining after the tightening process corresponds to a screw bolt projection (13) extending from the component nut thread (3) and terminating at the bolt head (15), or that the axially short residual stretching section (27') extends to the first screw bolt tensile flank (23) which is in pressure contact with a nut thread tensile flank (25) located in the screw-in thread (17). Screw connection according to one of the preceding claims, characterized in that in the tensile force build-up thread (19) the flank diameter (D2a) is constant in the axial direction, so that each thread (21) in the tensile force build-up thread (19) has the same flank diameter (D2a), and that in particular in the screw-in thread (17) the flank diameter (D2b) is constant or variable in the axial direction, so that the threads (21) in the screw-in thread (17) have constant or varying flank diameters (D2b). Screw connection according to one of the preceding claims, characterized in that the tensile force build-up thread (19) located at the end (11) of the nut thread has a smaller number of thread turns (21) than the screw-in thread (17) located at the beginning (9) of the nut thread. Screw connection according to one of the preceding claims, characterized in that the component nut thread (3) has an outer diameter that is only slightly larger than the outer diameter of the screw bolt thread, so that only a small radial play results during the screwing process and the coaxiality of screw bolt (1) and component nut thread (3) is ensured. A tool for producing a component nut thread (3) of a screw connection according to one of the preceding claims, wherein, for thread generation, the tool enters a component pre-bore in a reciprocating motion with a superimposed rotational motion, characterized in that the tool has a first thread generation section (31) at a tool tip (32) for generating the tensile force build-up thread (19), which transitions in the direction of a clamping shank (30) into a second thread generation section (33) for generating the screw-in thread (17), and in particular that the two thread generation sections (31, 33) have axially arranged profile teeth (35, 36) which are in form and / or cutting engagement with the inner circumference of the component pre-bore during thread generation, so that the tool acts as a thread former and / or as a thread cutter.and / or that, in particular, the first thread-forming section (31) has a metric thread, and that in the first thread-forming section (31) the flank diameter (d2a) of the profile teeth (35) remains substantially unchanged along the tool axial direction (x), so that, accordingly, the threads (21) in the tensile force build-up thread (19) have substantially constant flank diameters (D2a), and that, in particular, the flank diameter (d2b) of the profile teeth (36) in the second thread-forming section (33) is larger by a diameter difference (Δd) than the flank diameter (d2a) in the first thread-forming section (31), whereby the axial flank clearance (s2) in the screw-in thread (17) is larger by the flank clearance interference (Δa) than the axial flank clearance (s1) in the tensile force build-up thread (19). Tool according to claim 8, characterized in that the flank diameter (d2b) of the profile teeth (36) in the second thread-forming section (33) varies along the tool axial direction (x) via a mathematical function d2b(x), and / or that the profile tooth width (a1b) measured on the flank diameter line in the second thread-forming section (33) is dimensioned larger by a material allowance (m1, m2) than the profile tooth width (a1a) in the first thread-forming section (31), and / or that the material allowance (m1, m2) is present both on the profile tooth flanks facing the tool tip (32) and on the profile tooth flanks of the profile teeth (36) facing away from it, or that the material allowance (m1, m2) is present either only on the profile tooth flanks facing the tool tip or only on the profile tooth flanks facing away from it, and / or that the thread pitch in the first thread-forming section (31) remains essentially unchanged along the tool axial direction (x),and that the thread pitch in the second thread-forming section (33) varies along the tool axial direction (x).

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