CN117366077A - Non-equidistant threaded connection pair - Google Patents

Non-equidistant threaded connection pair Download PDF

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Publication number
CN117366077A
CN117366077A CN202311506120.4A CN202311506120A CN117366077A CN 117366077 A CN117366077 A CN 117366077A CN 202311506120 A CN202311506120 A CN 202311506120A CN 117366077 A CN117366077 A CN 117366077A
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China
Prior art keywords
thread
external thread
internal
external
pitch
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CN202311506120.4A
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Inventor
杨中桂
白洁
王自强
都军民
丁永春
王志敏
刘萍
刘振强
张永
李梦晗
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713rd Research Institute Of China Shipbuilding Corp ltd
China Shipbuilding Haiwei High Tech Co ltd
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713rd Research Institute Of China Shipbuilding Corp ltd
China Shipbuilding Haiwei High Tech Co ltd
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Priority to CN202311506120.4A priority Critical patent/CN117366077A/en
Publication of CN117366077A publication Critical patent/CN117366077A/en
Pending legal-status Critical Current

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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16B—DEVICES FOR FASTENING OR SECURING CONSTRUCTIONAL ELEMENTS OR MACHINE PARTS TOGETHER, e.g. NAILS, BOLTS, CIRCLIPS, CLAMPS, CLIPS OR WEDGES; JOINTS OR JOINTING
    • F16B33/00—Features common to bolt and nut
    • F16B33/02—Shape of thread; Special thread-forms
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16B—DEVICES FOR FASTENING OR SECURING CONSTRUCTIONAL ELEMENTS OR MACHINE PARTS TOGETHER, e.g. NAILS, BOLTS, CIRCLIPS, CLAMPS, CLIPS OR WEDGES; JOINTS OR JOINTING
    • F16B41/00—Measures against loss of bolts, nuts, or pins; Measures against unauthorised operation of bolts, nuts or pins
    • F16B41/002—Measures against loss of bolts, nuts or pins

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  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Transmission Devices (AREA)

Abstract

The invention provides a non-equidistant threaded connection pair, and belongs to the field of non-standard fasteners. The non-equidistant threaded connection pair comprises an internal thread and an external thread, the pitch of the internal thread and the external thread are constant, the pitch of the internal thread is larger than that of the external thread, and the pitch difference of the internal thread and the external threadCompared with the prior art, the invention reduces the pitch difference of the internal thread and the external thread, solves the pitch difference of the internal thread and the external thread on the basis of considering the material property and bearing load of the threaded connection pair, and can lead the stress borne by the thread to be more uniform by adopting the pitch difference in the range. At the same time, the clearance at the pitch diameter of the external thread is larger than the tooth width S of the internal thread n When the internal thread and the external thread are matched, the axial total fit clearance delta is larger than or equal to the length difference l of the internal thread and the external thread, so that the excessive tooth width of the internal thread and the excessive tooth width of the external thread are preventedThe interference fit of the inner screw teeth and the outer screw teeth is caused by overlarge screw pitch difference of the inner screw threads and the outer screw threads, so that the assembly resistance is reduced, and the assembly property is improved.

Description

Non-equidistant threaded connection pair
Technical Field
The invention relates to a non-equidistant threaded connection pair, and belongs to the field of non-standard fasteners.
Background
The bolt connection structure (comprising a bolt and a nut) is a common connection mode, is widely applied to the fields of machinery and construction, the pitch of internal threads and external threads of the traditional thread connection pair is equal and is a fixed value P, when the thread connection pair bears load, the external threads bear tensile force and stretch, the internal threads bear compressive force and are close to a supporting surface (taking the bolt and the nut as an example, the supporting surface is an end surface of the nut for compacting a connected piece, namely, the supporting surface is an end surface at the end position of an internal thread screwing region and an external thread screwing region, and the opposite end surface is an end surface at the initial position), the external thread stretch of the traditional thread connection pair is large, and the external thread stretch of the traditional thread connection pair is small, so that the axial load of the thread connection pair is mainly borne by the front three threads close to the supporting surface, and the front three threads are enabled to have obvious stress concentration phenomenon.
At present, two design ideas for improving the bearing uniformity of each circle of threads and the stress uniformity of each circle of threads exist to solve the problem of stress concentration of the front three threads close to the supporting surface. In the above two technical schemes, at least one of the internal thread and the external thread is a gradual change pitch thread, for example, the thread connection with variable gap disclosed in the chinese patent application published under CN101796312a adopts gradual change pitch thread to greatly increase the processing difficulty of the thread, which is not beneficial to the mass production of the thread and has low processing efficiency.
In order to solve the above problems, there is also an unequal pitch scheme in the prior art, that is, the pitches of the internal thread and the external thread are constant, but the pitches of the internal thread and the external thread are unequal. For example, the screw pitch interference fit screw thread, the screw thread connecting piece and the correction screw thread processing tool disclosed in the Chinese patent application with the application publication number of CN106438657A, wherein the screw pitches of the internal screw thread and the external screw thread are different, the screw pitch of one screw thread is 95% -99% of the screw pitch of the other screw thread, and the screw pitch difference delta P= (0.01-0.05) P of the internal screw thread and the external screw thread ensures that the screw thread generates axial interference within the screwing length range, and after all the screw threads are screwed, the screw thread interference at the two ends of the screwing length is maximum and gradually reduced to the middle. Because the internal thread and the external thread are in interference fit in the technical scheme, the assembly difficulty of the internal thread and the external thread is increased; in addition, the phenomenon that two ends are contacted and the middle is suspended after the internal thread and the external thread are assembled can occur, under the condition that the internal thread and the external thread are not loaded, larger interaction force exists between the internal thread and the external thread, when the internal thread and the external thread are loaded, the bearing capacity of the thread tooth at the supporting surface is reduced, the bearing capacity of the thread tooth at the position far away from the supporting surface is increased, and the stress is necessarily concentrated on a plurality of threads far away from the supporting surface.
In addition, the existing non-uniform pitch threads do not consider factors such as load and materials, but when the non-uniform pitch threads are used, the internal threads and the external threads can achieve higher bearing uniformity according to the load condition and the performance of the internal thread processing material and the external thread processing material.
Disclosure of Invention
The invention aims to provide a non-equidistant threaded connection pair, which solves the problems that in the existing threaded connection pair, the pitch difference of internal threads and external threads exceeds a certain value, and the internal threads and the external threads are in interference fit due to no consideration of factors such as load, materials and the like, so that stress concentration is caused.
In order to achieve the above purpose, the non-equidistant threaded connection pair in the invention adopts the following technical scheme:
a non-equidistant threaded connection pair comprises an internal thread and an external thread, wherein the pitches of the internal thread and the external thread are constant and are larger than those of the external thread, and the pitch difference of the internal thread and the external threadWherein: p is the pitch of the external thread; k is a comprehensive reference coefficient, and K is more than or equal to 0.8 and less than or equal to 4.5; k is the load coefficient, which is the axial load N born by the external thread, the yield strength sigma of the material and the external thread stress cross section area A 1 The ratio of the products, i.e.)>k c Is the material coefficient, which is the yield strength sigma of the material and the elastic modulus E of the material w The ratio of->
The beneficial effects of the technical scheme are that: the invention provides an improved non-equidistant threaded connection pair, which is mainly improved in that the pitch difference of internal threads and external threadsCompared with the prior art, the invention reduces the pitch difference of the internal thread and the external thread, solves the pitch difference of the internal thread and the external thread on the basis of considering the material property and bearing load of the threaded connection pair, and can lead the stress borne by the thread to be more uniform by adopting the pitch difference in the range.
Further, the pitch difference delta P of the internal thread and the external thread is less than 0.01P.
The beneficial effects of the technical scheme are that: the upper limit value of the pitch difference is given, and the design, the processing and the manufacturing of the screw thread are facilitated.
Further, the pitch difference DeltaP of the internal thread and the external thread is more than 0.003P.
The beneficial effects of the technical scheme are that: the lower limit value of the pitch difference is given, and the design, the processing and the manufacturing of the screw thread are facilitated.
Further, the pitch difference of the internal and external threadsWherein l is the length difference of the internal thread and the external thread, n 'is any number of turns taking the initial position of the screwing region of the internal thread and the external thread as a starting point, n' is more than or equal to 0 and less than or equal to n, and n is the total number of turns of the screwing region of the internal thread and the external thread;
the length difference l of the internal thread and the external thread is the total elongation l of the external thread w Total compression amount with internal thread l n The sum of the two values,wherein 0 < k 1 The external thread of the screwing area of the internal thread and the external thread is simplified into an equivalent stressed cylinder, f 1 (N ') is the resultant force of the loads at the positions of the tiny outer cylindrical surfaces of any N' turns of the equivalent stressed cylinder, and the resultant force of the loads at all the tiny outer cylindrical surfaces is equal to the axial load N;
wherein k is 2 ＞1，E n For the elastic modulus of the internal thread material, the internal thread of the screwing area of the internal thread and the external thread is simplified into an equivalent stressed hollow cylinder, A 2 Is the cross section area of the equivalent stressed hollow cylinder, f 2 (n ') is the resultant force of the loads at the positions of any n' turns of the equivalent stressed hollow cylinder and the resultant force of the loads at all the positions of the tiny inner cylindrical surfaces and the axial load F N Equal, F N Equal to N, opposite in direction;
thus (2)Let E w A 1 And E is connected with n A 2 Has a ratio of k 3 And let k 1 +k 2 k 3 =k, the equation for the length difference of internal and external threads/is simplified as: />
Further let theThen->Further deriveWhen n' =n, the length difference l between the internal and external threads is:further, the pitch difference of the internal and external threads is +.>
The beneficial effects of the technical scheme are that: the specific deducing process of the pitch difference delta P of the internal thread and the external thread is provided, and the design, the processing and the manufacturing of the threads are convenient.
Further, defining the tooth width of the external thread at the pitch diameter as S w The tooth width of the internal thread at the pitch diameter of the external thread is S n Axial total fit clearance delta=p-S when the internal and external threads are used in combination w -S n Delta is larger than or equal to the length difference l of the internal thread and the external thread, namely delta is larger than or equal to l.
The beneficial effects of the technical scheme are that: the problem that the fit clearance is too small due to too large pitch difference of the internal thread and the external thread, and interference fit is caused is avoided, so that the assembly resistance can be reduced, and the assembly property is improved.
Further, defining the tooth width of the external thread at the pitch diameter as S w External thread pitch diameter d 2 Notch C at n The width is larger than the pitch diameter d of the internal thread in the external thread 2 Tooth width S at n P-S w ＞S n 。
The beneficial effects of the technical scheme are that: the interference fit of the inner thread and the outer thread caused by the overlarge tooth width of the inner thread is prevented, so that the assembly resistance can be reduced, and the assembly property can be improved.
Drawings
FIG. 1 is a profile view of the external threads of a non-equidistant threaded connection set of the present invention;
FIG. 2 is a profile view of the internal threads of a non-equidistant threaded connection set of the present invention;
FIG. 3 is a schematic view of the start and end positions of a non-equidistant threaded connection pair of the present invention;
FIG. 4 is a diagram of the bite of the internal and external threads of a non-equidistant threaded connection pair of the present invention;
FIG. 5 is a schematic diagram of the principle of the present invention that the internal thread and the external thread do not bite;
FIG. 6 is a schematic illustration of an external thread according to the present invention simplified into an equivalent force cylinder;
FIG. 7 is a schematic illustration of the average elongation of the mini cylinder and the elongation at cylindrical surface of FIG. 6;
FIG. 8 is a schematic view of the internal thread of the present invention simplified into an equivalent stressed hollow cylinder;
FIG. 9 is a schematic diagram of the average compression of the tiny hollow cylinder and the compression at the inner cylindrical surface in FIG. 8;
FIG. 10 is a force-bearing schematic view of an external thread in the internal and external thread engagement region of the present invention;
FIG. 11 is a graph of three general cases of the trend of the axial force F (n') acting on the external thread;
FIG. 12 is a stress cloud of three trends of F (n') in FIG. 11;
FIG. 13 is a stress cloud for an internal and external thread when the threads of the present application and three comparative threads are unloaded;
FIG. 14 is a stress cloud for an internal and external thread of the present application when loaded with three comparative threads;
FIG. 15 is a schematic view of the numbering and average value position of the male thread;
fig. 16 is a graph of the mean stress of each thread ridge of the external thread of the present application and three comparative threads.
Detailed Description
The features and capabilities of the present invention are described in further detail below in connection with the examples.
The non-equidistant threaded connection pair of the invention comprises an internal thread and an external thread, the pitch of the internal thread and the external thread are constant, the pitch of the internal thread is larger than that of the external thread, and the pitch difference of the internal thread and the external threadCompared with the prior art, the invention reduces the pitch difference of the internal thread and the external thread, solves the pitch difference of the internal thread and the external thread on the basis of considering the material property and bearing load of the threaded connection pair, and can lead the stress borne by the thread to be more uniform by adopting the pitch difference in the range.
Example 1 of non-equidistant threaded connection pair in the invention:
the non-equidistant threaded connection pair comprises an internal thread and an external thread, the pitches of the internal thread and the external thread are constant, the pitch of the internal thread is larger than that of the external thread, the teeth of the internal thread and the external thread can be metric threads, MJ threads, trapezoidal threads, circular arc threads and the like, and a large axial gap is reserved when the circular arc threads are selected for processing and installation. For convenience of description, the present embodiment takes a metric thread form as an example.
As shown in FIG. 1, the pitch P of the external thread has a large diameter d and a small diameter d 1 Pitch diameter d of external thread 2 The tooth width at the position is S w The yield strength of the external thread material is sigma, and the elastic modulus E w 。
As shown in fig. 2 and 4, the pitch P' of the female screw has a large diameter D and a small diameter D 1 The internal thread has a pitch diameter d in the external thread 2 The tooth width at the position is S n The number of turns of the internal thread is n (namely the total number of turns of the screwing regions of the internal thread and the external thread), and the elastic modulus E of the internal thread material n . Wherein, the pitch diameter d of the external thread 2 Notch C at n The width is larger than the pitch diameter d of the internal thread in the external thread 2 Tooth width S at n The method comprises the following steps: P-S w ＞S n The interference fit of the inner screw teeth and the outer screw teeth caused by the overlarge tooth width of the inner screw threads is prevented, so that the assembly resistance can be reduced,improving assemblability.
For convenience of description, the invention sets a starting position and a terminating position, as shown in fig. 3 and 4, taking a bolt 1 and a nut 2 as an example, in the screwing region of the internal thread and the external thread, the invention takes one end surface of the internal thread perpendicular to the axis as a section Q of the starting position, the other end surface of the internal thread as a section Z of the terminating position (conventionally considered supporting surface, namely, the end surface of the nut 2 used for pressing a connected piece), and the direction of the starting position pointing to the terminating position is the same as the direction of the external thread bearing the rated axial load N.
Because the number of turns of the internal thread is n, when the internal thread and the external thread are matched, the n turns of the internal thread are matched with the n turns of the external thread, and under the condition that no load deformation occurs, the starting position is taken as the starting point, and the internal thread with any n 'turns (0 < n' < n) is longer than the external thread.
Specifically, the total length of the external thread with n' turns is L 1 The length of the internal thread with n' turns is L 2 The length difference of the internal thread and the external thread is as follows: l=l 2 -L 1 The method comprises the steps of carrying out a first treatment on the surface of the Axial total fit clearance delta=p-S when the internal and external threads are used in combination w -S n . As shown in fig. 5, in the upper drawing, the pitches of the internal thread and the external thread are equal, one side of the internal thread and one side of the external thread are attached, the other side of the internal thread and the external thread are not contacted, and the axial gap between the internal thread and the external thread is delta. In the lower diagram, the inner thread and the outer thread are attached at the leftmost side, and the inner thread pitch is larger than the outer thread pitch, so that the inner thread and the outer thread start to be separated from each other from the attaching position, and when the inner thread and the outer thread are at the rightmost side, the other sides of the inner thread and the outer thread are gradually close to each other, and the length difference of the inner thread and the outer thread is l. When delta=l, the rightmost side of the internal and external threads just contact; when delta is less than l, the internal thread and the external thread have interference fit, and the assembly is inconvenient. Therefore, delta is larger than or equal to l, so that the phenomenon of tooth biting caused by insufficient axial clearance can be prevented, the assembly resistance can be reduced, and the assembly property can be improved.
Further, the external thread length L 1 Length of internal thread L 2 N ' P ', the pitch difference Δp=p ' -P of the internal and external threads, l=l 2 -L 1 N ' (P ' -P) =n ' Δp, i.eTherefore, the length difference l between the internal and external threads must be calculated to solve the pitch difference Δp.
When the traditional equidistant threads are meshed under load, the external threads are pulled to be longer, the internal threads are compressed to be shorter, and the external threads and the internal threads at any position in the meshed area are stretched or compressed to different degrees. The invention leads the total elongation l of the external thread with n circles w Total compression amount with internal thread l n The sum is used as the length difference l of the internal thread and the external thread.
As shown in fig. 6, the external threads of the internal and external thread screwing regions are simplified to equivalent force cylinders for ease of analysis. The two circular sections of the equivalent stressed cylinder are respectively a starting position section Q and a terminating position section Z, and the sectional area A of the equivalent stressed cylinder 1 The axial load applied to the equivalent stressed cylinder at the end position section Z is N, and the direction of the axial load N points from the start position section Q to the end position section Z. The acting force between the internal thread and the external thread is simplified to be that the outer cylindrical surface of the equivalent stressed cylinder bears surface load, the surface load is opposite to the axial load N, and the resultant force of the surface load is the same as the axial load N. Taking the initial position as a starting point, and taking the resultant force of the load at the micro outer cylindrical surface at any n' turn number position as f 1 (N') the combined force of the loads at all the tiny outer cylindrical surfaces is equal to the axial load N, i.e
Intercepting a tiny cylinder at any height h=n 'P of the equivalent stressed cylinder, wherein the thickness of the tiny cylinder is dh=pdn', and the axial load applied to the lower section of the tiny cylinder is thatFrom Hooke's law it is possible to derive the average elongation of the tiny cylinders +.>Equivalent at arbitrary n' turnsThe total average elongation of the stressed cylinder is +.>
As can be seen from FIG. 7, since the direction of the surface load of the outer cylindrical surface of the micro cylinder and the load N of the lower section of the micro cylinder 1 The action directions are opposite, so that the elongation at the outer cylindrical surface of the tiny cylinder is small and the average elongation dl is small w1 The outer cylindrical surface of the equivalent stress cylinder is an external thread simplifying area, so that the elongation of the outer cylindrical surface is dl of the external thread w Dl is then w ＝k 1 ·dl w1 ，0＜k 1 < 1, for ease of analysis, assume k 1 For a fixed value, the starting position is taken as the starting point, and the total elongation of the external thread with arbitrary n' turns is obtained
As shown in fig. 8, for ease of analysis, the internal threads of the internal and external thread threading regions are reduced to equivalent stressed hollow cylinders. The two circular arc annular sections of the equivalent stressed hollow cylinder are respectively a starting position section Q and a terminating position section Z, and the sectional area A of the equivalent stressed hollow cylinder 2 The axial load borne by the equivalent stressed hollow cylinder at the section Z of the end position is F N (according to the balance of forces, F N Equal to N), the direction from the end position to the start position, the forces between the internal and external threads being reduced to equivalent force-bearing hollow cylinders with their inner cylindrical surfaces subjected to a surface load, the surface load and the axial force F N In opposite directions, the resultant force of the surface load is opposite to the axial force F N The sizes of the two are the same, the section of the initial position is taken as the starting point, and the resultant force of the load at the micro inner cylindrical surface at any n' turn positions is f 2 (n') the resultant of the loads at all the minor inner cylindrical surfaces and the axial load F N Equal, i.e.
Intercepting micro at any height h=n' P of equivalent stressed hollow cylinderA small hollow cylinder with thickness dh=pdn', and a lower section of the small hollow cylinder subjected to axial load ofAverage compression of tiny hollow cylinder with thickness dh +.>The total average compression of the equivalent hollow cylinder starting with the initial position section Q and at any n' turns can be found by integration
As can be seen from FIG. 9, since the surface load direction of the inner cylindrical surface of the minute hollow cylinder and the lower section load F of the minute hollow cylinder N The action directions are opposite, so that the compression quantity at the inner cylindrical surface of the tiny hollow cylinder is larger than the average compression quantity dl n1 . The inner cylindrical surface of the equivalent hollow cylinder is an internal thread simplifying region, so that the compression amount of the inner cylindrical surface is dl of the internal thread n Dl then n ＝k 2 ·dl n1 ，1＜k 2 For ease of analysis, assume k 2 For a fixed value, the starting position is taken as the starting point, and the total compression amount of the internal thread with any n' turns is given
As shown in fig. 10, the axial load of the internal thread on the external thread at any n ' turns from the start position is F (n '), and F (n ')=f is known from the mechanical relationship, which is a simplified manner of the equivalent force-receiving cylinder and the equivalent force-receiving hollow cylinder 1 (n′)＝f 2 (n'), therefore, there are: total elongation lw of the external thread and total compression l of the internal thread n The sum is the length difference l of the internal thread and the external thread, namely:
when internal and external thread materialI.e. after the external dimensions of the nut are selected, E n And A 2 Are all constant values, thus E w A 1 And E is connected with n A 2 Ratio k of (2) 3 Is constant, and the elastic modulus and the area in the formula are unified into E for the convenience of calculation w And A 1 ThenFor further simplification, let k=k 1 +k 2 k 3 K is a comprehensive reference coefficient, and the formula of the length difference l of the internal thread and the external thread is simplified into: />
Further, the length adjustment amount of the gradual change pitch threadIn the equation (a), only F (n ') and n ' are variables, but there are three common cases where the axial load F (n ') acting on the male thread follows the trend of n ', as shown in fig. 11, F (n ') increases with increasing n ', F (n ') is constant and constant in curve b, and F (n ') decreases with increasing n '. From the mechanical relationship, the accumulated value of the axial load F (N') on the external thread is the section axial load N, namely +.>
The three kinds of change trends of F (n') are respectively used for simulation calculation, the calculated stress cloud patterns are shown in fig. 12, fig. 12 (a) is a stress cloud pattern corresponding to a curve a, fig. 12 (b) is a stress cloud pattern corresponding to a curve b, and fig. 12 (c) is a stress cloud pattern corresponding to a curve c.
The high stress region of the pin thread root is typically created at the pin thread root, the magnitude of the stress value being influenced by a combination of the axial load F (N ') on the pin thread and the cross-sectional axial load N (N ') (i.e., the force of an N ' turn of the entire cross-section (excluding the threads)). When the internal and external threads deform under load, the section axial load N (N ') increases as the number of turns N' increases from the start position, and a maximum N is achieved at N turns. When the axial force F (N ') on the external thread is in accordance with the curve a as shown in fig. 11, F (N') at the start position is small and F (N ') at the end position is large, which has the same trend as that of N (N'), as shown in fig. 12 (a), the external thread is small in stress at the start position and large in stress at the end position, and a remarkable stress concentration phenomenon occurs.
As shown in fig. 11, when the axial force F (N ') on the external thread tooth is in accordance with the curve b, F (N') is constant and constant, but since the section axial load N (N ') gradually increases with N', the stress of the root on the external thread still occurs with a small stress value at the start position, a large stress value at the end position, and the stress concentration phenomenon is improved, as shown in fig. 12 (b). When the axial force F (n ') on the external thread tooth conforms to the curve c, F (n') is further increased at the start position and further reduced at the end position, so that the external thread root stress at the start position is further increased, the stress at the end position is further reduced, the stress value of the whole external thread root is more uniform, and the stress concentration phenomenon is smaller, as shown in fig. 12 (c).
Further, the F (n ') is preferably in accordance with the stress state of curve c, and the F (n') equation is selected to satisfy curve c. F (n') should satisfy two conditions: is a decreasing function in the interval of 0-n' to n,
for ease of calculation, it is assumed that the axial force on the external thread isLinearly decreasing and->Further deriveWhen n' =n, the length difference l between the internal and external threads is:let k be the load factor, the axial force N born by the external thread, the yield strength sigma of the material and the external thread stress sectional area A 1 The ratio of the products, i.e.)>Let k c Is the material coefficient, which is the yield strength sigma of the material and the elastic modulus E of the material w The ratio of->K and k after the main design parameters and materials of the bolts are determined c Is a fixed value. Further derive
Further, the pitch difference of the internal and external threads0.8≤K≤4.5。
Further, under the normal condition, the value range of the load coefficient k is more than 0.4 and less than 0.8, and the material coefficient k of common materials of the screw thread c =0.001 to 0.02, comprehensively considering k, k c And K defines a pitch difference of 0.003P < DeltaP < 0.01P between the internal and external threads.
The superiority of the range of the pitch difference delta P of the internal and external threads of the non-equidistant threaded connection pair is proved by combining specific parameters of the threads and a comparison test.
The first embodiment is as follows:
the external thread teeth are metric threads, the pitch P=4mm, the large diameter d=42mm and the small diameter d of the external thread teeth 1 =37.67 mm, pitch diameter d 2 =39.4mm, tooth width at pitch diameter of external thread S w =2mm. Elastic modulus E of external thread Material w =206 GPa, yield strength σ=930 Mpa, axial load n=0.7σa 1 。
Internal thread major diameter d=42.42 mm, minor diameter D 1 38.09mm internal thread diameter d in external thread 2 The tooth width at the position is S n The number of internal thread turns is n=7 turns =1.76 mm.
P-S in the present embodiment w ＝2mm＞1.76mm，δ＝P-S w -S n ＝0.24mm，l＝nΔP＝0.126mm，δ＞l。k＝0.7，ΔP＝0.00211×KP。
The comparative thread form provided in this embodiment is the same as the thread of this application, and the pitch differences between the internal and external threads of the various threads are shown in table 1. The pitch difference deltap=0.01p of the internal thread and the external thread of the comparison thread 1, the pitch difference deltap of the internal thread and the external thread of the comparison thread 2 is more than 0.01p (the comparison thread 2 is in the form disclosed in CN106438657A, the internal thread and the external thread are in interference fit, interaction is generated between the internal thread and the external thread before no load is applied, larger stress is generated at the starting position and the ending position, the threads of a few circles in the middle are in a suspended state), and the comparison thread 3 is a common equidistant thread.
TABLE 1 Pitch difference ΔP of internal and external threads
Type of thread Threads of the present application Contrast thread 1 Contrast thread 2 Contrast thread 3
K 2.133 4.739 9.479 0
ΔP/P 0.0045 0.01 0.02 0
ΔP 0.018mm 0.04mm 0.08mm 0mm
Fig. 13 and 14 are stress cloud diagrams under different axial loads, and it is to be noted that the simulation model is an elastic model, and the calculated average stress has a far-exceeding yield stress, which indicates that there is a significant stress concentration phenomenon. Fig. 13 is a stress cloud for four threads without axial loading, with the comparison thread 2 in an interference fit, with localized stresses at the initial and final positions. Fig. 14 is an axial load n=0.7σa 1 As can be seen from fig. 14, compared with the comparative threads 1 to 3, the high stress concentration phenomenon of the threads of the present application is significantly improved.
According to the numbers (1-7) of the external thread and the positions shown by the thickened vertical lines in fig. 15, the average stress of each thread of the external thread was extracted, the average stress change chart of each thread was drawn, and the stress concentration coefficient (stress concentration coefficient=maximum stress/total average stress) of each thread was calculated. The thread of the present application is better in stress uniformity as can be seen in fig. 16, and the minimum stress concentration coefficient as can be seen in table 2.
TABLE 2 stress concentration coefficient for each thread of external threads
Type of thread Threads of the present application Contrast thread 1 Contrast thread 2 Contrast thread 3
Stress concentration coefficient 1.30 1.69 1.90 2.57
In other embodiments: the total average elongation l of the equivalent stressed cylinder at any n' turns can also be directly used w1 To represent the total elongation l of the external thread with any n' turns w . Of course, the equivalent stressed hollow cylinder at any n' turns can be directly used, and the total average compression amount of the equivalent stressed hollow cylinder is l n1 Representing the total compression l of the internal thread of any n' turns n 。
In other embodiments: the simplified results of the equations for Δp and l may be different when the manner of simplification is different, depending on the requirements.
In other embodiments: the clearance at the pitch diameter of the external thread is equal to the tooth width S of the internal thread n The method comprises the following steps: P-S w ＝S n 。
The above description is only a preferred embodiment of the present invention, and the patent protection scope of the present invention is defined by the claims, and all equivalent structural changes made by the specification and the drawings of the present invention should be included in the protection scope of the present invention.

Claims (6)

1. A non-equidistant threaded connection pair comprises an internal thread and an external thread, wherein the pitches of the internal thread and the external thread are constant and are larger than those of the external thread, and the non-equidistant threaded connection pair is characterized in that the pitch difference of the internal thread and the external threadWherein: p is the pitch of the external thread; k is a comprehensive reference coefficient, and K is more than or equal to 0.8 and less than or equal to 4.5; k is the load coefficient, which is the axial load N born by the external thread, the yield strength sigma of the external thread material and the external thread stress cross section area A 1 The ratio of the products, i.e.)>k c Is the material coefficient, which is the yield strength sigma of the external thread material and the elastic modulus E of the external thread material w The ratio of->
2. The non-equidistant threaded connection as recited in claim 1, wherein the pitch difference Δp of the internal and external threads is less than 0.01P.
3. The non-equidistant threaded connection as defined in claim 1, wherein the pitch difference Δp of the internal and external threads is greater than 0.003P.
4. A non-equidistant threaded connection as defined in any one of claims 1-3, characterized in that the pitch difference of the internal and external threadsWherein l is the length difference of the internal thread and the external thread, n 'is any number of turns taking the starting position of the screwing region of the internal thread and the external thread as the starting point, n' is more than or equal to 0 and less than or equal to n, and n is the internal threadTotal number of turns of the external thread screwing region; the length difference l of the internal thread and the external thread is the total elongation l of the external thread w Total compression amount with internal thread l n Sum (S)/(S)>Wherein 0 < k 1 The external thread of the screwing area of the internal thread and the external thread is simplified into an equivalent stressed cylinder, f 1 (N ') is the resultant force of the loads at the positions of the tiny outer cylindrical surfaces of any N' turns of the equivalent stressed cylinder, and the resultant force of the loads at all the tiny outer cylindrical surfaces is equal to the axial load N;wherein k is 2 ＞1，E n For the elastic modulus of the internal thread material, the internal thread of the screwing area of the internal thread and the external thread is simplified into an equivalent stressed hollow cylinder, A 2 Is the cross section area of the equivalent stressed hollow cylinder, f 2 (n ') is the resultant force of the loads at the positions of any n' turns of the equivalent stressed hollow cylinder and the resultant force of the loads at all the positions of the tiny inner cylindrical surfaces and the axial load F N Equal, F N Equal to N, opposite in direction;
thus (2)Let E w A 1 And E is connected with n A 2 Has a ratio of k 3 And let k 1 +k 2 k 3 =k, the equation for the length difference of internal and external threads/is simplified as: />
Further let theThen
Further deriveWhen n' =n, the length difference l between the internal and external threads is:further, the pitch difference of the internal and external threads is +.>
5. A non-equidistant threaded connection as defined in any one of claims 1-3, wherein the pitch width of the external thread at pitch diameter is defined as S w The tooth width of the internal thread at the pitch diameter of the external thread is S n Axial total fit clearance delta=p-S when the internal and external threads are used in combination w -S n Delta is larger than or equal to the length difference l of the internal thread and the external thread, namely delta is larger than or equal to l.
6. A non-equidistant threaded connection as defined in any one of claims 1-3, wherein the pitch width of the external thread at pitch diameter is defined as S w External thread pitch diameter d 2 Notch C at n The width is larger than the pitch diameter d of the internal thread in the external thread 2 Tooth width S at n P-S w ＞S n 。
CN202311506120.4A 2023-11-13 2023-11-13 Non-equidistant threaded connection pair Pending CN117366077A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN202311506120.4A CN117366077A (en) 2023-11-13 2023-11-13 Non-equidistant threaded connection pair

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN202311506120.4A CN117366077A (en) 2023-11-13 2023-11-13 Non-equidistant threaded connection pair

Publications (1)

Publication Number Publication Date
CN117366077A true CN117366077A (en) 2024-01-09

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Family Applications (1)

Application Number Title Priority Date Filing Date
CN202311506120.4A Pending CN117366077A (en) 2023-11-13 2023-11-13 Non-equidistant threaded connection pair

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Country Link
CN (1) CN117366077A (en)

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