Unequal pitch screw connection pair

Abstract

A non-equal pitch screw connection pair, comprising a female thread and a male thread, where the pitches of both the female and male threads are constant, and the pitch of the female thread is greater than the pitch of the male thread, and the pitch difference between the female and male threads (I): ΔP = (2kk c K / 3)P. Here, P is the pitch of the male screw, K is the overall reference coefficient, k is the load coefficient, and k c This is the material coefficient. The pitch difference of this connection pair can make the stress on the threads more uniform.

Description

[Technical Field]

[0001] The present invention relates to non-equal pitch screw connection pairs and belongs to the field of non-standard fastening members. [Background technology]

[0002] Bolt connection structures (including bolts and nuts) are a relatively common connection method and are widely applied in the fields of machinery and construction. Currently, in traditional screw connection pairs, the pitch of the female and male threads is equal and constant P. When a load is applied to the screw connection pair, the male thread is subjected to tensile force and elongates, and the female thread is subjected to pressure and compressed. The amount of elongation of the male thread closer to the support surface (taking a bolt and nut as an example, the support surface is the end face of the nut that crimps the connected member, that is, the support surface is the end face at the end position of the threaded area of ​​the female and male threads, and the other end face is the end face at the starting position) is greater, and the amount of elongation of the male thread further from the support surface is smaller. As a result, the axial load of the screw connection pair is mainly applied to the first three threads close to the support surface, and a significant stress concentration phenomenon occurs in the first three turns of the thread.

[0003] Currently, there are two design concepts that improve the uniformity of load on the threads in each turn and the uniformity of stress on the threads in each turn, thereby solving the problem of stress concentration in the first three threads near the support surface. In the two technical embodiments described above, at least one of the female and male threads is a gradually changing pitch thread. For example, the screw connection with a variable gap disclosed in Patent Document 1 employs a gradually changing pitch thread, which significantly increases the difficulty of machining the threads, making it unsuitable for mass production of screws and reducing machining efficiency.

[0004] In response to the above problem, the prior art includes a form of technology where the pitch of the female and male threads is constant, but the pitch of the female and male threads is not equal. For example, in the pitch-tightening fitted screw, screw connecting member, and screw correction tool disclosed in Patent Document 2, the pitch of the female and male threads is not equal, and the pitch of one screw is 95% to 99% of the pitch of the other screws. By setting the pitch difference between the female and male threads ΔP = (0.01 to 0.05)P, the screw tightens axially within the threaded length range, and when the screw is fully threaded, the tightening is greatest at both ends of the threaded length and gradually decreases towards the middle. In this form of technology, since the female and male threads are tightly fitted, the difficulty of assembling the female and male threads increases. Furthermore, once the female and male threads are assembled, a phenomenon occurs where both ends are in contact and the middle is suspended in mid-air. Even when no load is applied to the female and male threads, a large interaction force already exists between them. When a load is applied to the female and male threads, the support force of the threads on the support surface decreases, and the support force of the threads away from the support surface increases, inevitably leading to stress concentration in some threads away from the support surface.

[0005] Furthermore, conventional non-uniform pitch screws do not take into account factors such as load and material. However, when using non-uniform pitch screws, it is necessary to consider the load conditions and the performance of the materials used for processing the female and male threads in order to achieve relatively high load uniformity between the male and female threads. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Chinese Patent Application Publication No. 101796312 Specification [Patent Document 2] Chinese Patent Application Publication No. 106438657 Specification [Overview of the project] [Problems that the invention aims to solve]

[0007] The object of the present invention is to provide a non-equal pitch screw connection pair that solves the problem in conventional screw connection pairs where the pitch difference between the female and male threads exceeds a certain value, causing the female and male threads to tighten and fit together without considering load, material, etc., and further leading to stress concentration. [Means for solving the problem]

[0008] To achieve the above objective, the non-equal pitch screw connection pair in the present invention employs the following technical aspects.

[0009] A non-equal pitch screw connection pair, comprising a female thread and a male thread, wherein the pitches of both the female and male threads are constant, and the pitch of the female thread is greater than the pitch of the male thread, and the pitch difference between the female and male threads ΔP = (2kk c K / 3)P (where P is the pitch of the male screw, K is the overall reference coefficient, and 0.8 ≤ K ≤ 4.5, k is the load coefficient, which is the ratio of the axial load N applied to the male screw to the product of the yield strength σ of the material and the stress cross-sectional area A1 of the male screw, i.e., k = N / σA1, k c These are material coefficients, where σ is the yield strength of the material and E is the elastic modulus of the material. w It is the ratio of k, that is, k c =σ / E w It is.

[0010] The beneficial effects of the above technical embodiment are as follows: The present invention proposes an improved non-equal pitch screw connection pair, the main improvement being the pitch difference between the female and male threads ΔP=(2kk c It is located at K / 3)P. Compared to the conventional technology, the present invention reduces the pitch difference between the female and male threads, and also takes into account the material attributes and load of the screw connection pair when determining the solution for the pitch difference between the female and male threads. Verification shows that by adopting a pitch difference within the above range, the stress on the screw threads can be made more uniform.

[0011] Furthermore, the pitch difference between the female and male threads is ΔP < 0.01P.

[0012] The beneficial effects of the above technical solution are as follows. By providing the upper limit value of the pitch difference, the design and processing and manufacturing of the screw are facilitated.

[0013] Furthermore, the pitch difference ΔP between the female screw and the male screw is ΔP > 0.003P.

[0014] The beneficial effects of the above technical solution are as follows. By providing the lower limit value of the pitch difference, the design and processing and manufacturing of the screw are facilitated.

[0015] Furthermore, the pitch difference ΔP between the female screw and the male screw is ΔP = l / n′ (where l is the difference in length between the female screw and the male screw, n′ is an arbitrary number of turns starting from the starting position of the screwing region of the female screw and the male screw, 0 ≤ n′ ≤ n, and n is the total number of turns of the screwing region of the female screw and the male screw).

[0016] The difference in length l between the female screw and the male screw is the sum of the total elongation amount l w of the male screw and the total compression amount l n of the female screw.

Number

[0017]

Number

[0018] Therefore,

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[0019] Furthermore

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[0020] The beneficial effects of the above-described technical embodiment are as follows: It provides a specific method for deriving the pitch difference ΔP between the female and male threads, thereby facilitating the design and manufacturing of screws.

[0021] Furthermore, the tooth width in the middle diameter of the male screw is S w The tooth width of the female thread in the middle diameter of the male thread is S n Defined as follows, the total axial fitting gap δ = PS when a female thread and a male thread are used in mating. w -S n Therefore, δ is greater than or equal to the difference l between the lengths of the female thread and the male thread, i.e., δ≧l.

[0022] The beneficial effects of the above-described technology are as follows: By avoiding a situation where the fitting gap is too small due to an excessively large pitch difference between the female and male threads, which can lead to overtight fitting, assembly resistance can be reduced and assembly efficiency can be improved.

[0023] Furthermore, the tooth width in the middle diameter of the male screw is S w Defined as follows, the notch C in the middle diameter d2 of the male screw n Width S of the female thread at the male thread's mid-diameter d2 n If it is greater than, PS w >S n That is the case.

[0024] The beneficial effects of the above-described technical embodiment are as follows: By preventing tightening and engagement between the female and male threads due to the excessively large tooth width of the female thread, assembly resistance can be reduced and assembly efficiency can be improved. [Brief explanation of the drawing]

[0025] [Figure 1] Figure 1 is a tooth profile diagram of the male screw of the non-equal pitch screw connection pair in the present invention. [Figure 2] Figure 2 is a tooth profile diagram of the female thread of the non-equal pitch screw connection pair in the present invention. [Figure 3] Figure 3 is a schematic diagram showing the start and end positions of the non-equal pitch screw connection pair under load in the present invention. [Figure 4] Figure 4 is a diagram showing the meshing state of the female and male threads of the non-equal pitch screw connection pair in the present invention. [Figure 5] Figure 5 is a schematic diagram illustrating the principle by which the tooth-meshing phenomenon between the female and male threads of the present invention does not occur. [Figure 6] Figure 6 is a schematic diagram showing how the male screw according to the present invention is simplified into an equivalent force-receiving cylindrical body. [Figure 7] Figure 7 is a schematic diagram showing the average elongation and elongation on the cylindrical surface of the small cylindrical body in Figure 6. [Figure 8] Figure 8 is a schematic diagram illustrating the simplification of the female screw according to the present invention into an equivalent force-receiving hollow cylindrical body. [Figure 9] Figure 9 is a schematic diagram showing the average compression amount and the compression amount on the inner cylindrical surface of the minute hollow cylinder in Figure 8. [Figure 10] Figure 10 is a schematic diagram showing the force received by the male screw in the threaded region of the female and male screws of the present invention. [Figure 11] Figure 11 shows three typical scenarios illustrating the changing trends of the axial force F(n′) acting on the male screw threads. [Figure 12(a)] Figure 12(a) is a stress cloud map corresponding to curve a in Figure 11. [Figure 12(b)] Figure 12(b) is a stress cloud map corresponding to curve b in Figure 11. [Figure 12(c)] Figure 12(c) is a stress cloud map corresponding to curve c in Figure 11. [Figure 13(a)] Figure 13(a) shows the stress cloud maps of the female and male threads of the screw of this application when there is no load. [Figure 13(b)] Figure 13(b) shows the stress cloud maps of the female and male threads of comparison screw 1 when there is no load. [Figure 13(c)] Figure 13(c) shows the stress cloud maps of the female and male threads of comparison screw 2 when there is no load. [Figure 13(d)] Figure 13(d) shows the stress cloud maps of the female and male threads of comparison screw 3 when there is no load. [Figure 14(a)] Figure 14(a) shows the stress cloud maps of the female and male threads of the screw of this application under load. [Figure 14(b)] Figure 14(b) shows the stress cloud maps of the female and male threads of comparison screw 1 under load. [Figure 14(c)] Figure 14(c) shows the stress cloud maps of the female and male threads of comparison screw 2 under load. [Figure 14(d)] Figure 14(d) shows the stress cloud maps of the female and male threads of comparison screw 3 under load. [Figure 15] Figure 15 is a schematic diagram showing the thread numbers and average position of the male screw threads. [Figure 16]Figure 16 shows the average stress diagram for each thread of the male screws of the present invention and three types of comparative screws. [Modes for carrying out the invention]

[0026] The features and performance of the present invention will be described in more detail below in relation to the examples.

[0027] The unequal pitch screw connection pair of the present invention includes a female thread and a male thread, wherein the pitches of both the female and male threads are constant, and the pitch of the female thread is greater than the pitch of the male thread, and the pitch difference between the female and male threads is ΔP = (2kk c The formula is K / 3)P, where P is the pitch of the male thread. Compared to the prior art, the present invention reduces the pitch difference between the female and male threads, and also considers the material attributes and load of the screw connection pair when determining the solution for the pitch difference between the female and male threads. Verification shows that by adopting a pitch difference within the above range, the stress on the screw threads can be made more uniform.

[0028] Example 1 of the non-equal pitch screw connection pair in the present invention:

[0029] An unequal-pitch screw connection pair includes a female thread and a male thread, where the pitches of both the female and male threads are constant, and the pitch of the female thread is greater than the pitch of the male thread. Here, the tooth profiles of the female and male threads can be metric threads, MJ threads, trapezoidal threads, and arc threads, and when an arc thread is selected, there is a large axial clearance, making machining and installation easier. For the sake of explanation, this embodiment uses a metric thread profile as an example.

[0030] As shown in Figure 1, the pitch of the male screw is P, the large diameter is d, the small diameter is d1, and the tooth width at the middle diameter d2 of the male screw is S w The yield strength of the male screw material is σ, and the modulus of elasticity is E. w That is the case.

[0031] As shown in FIGS. 2 and 4, the pitch of the female thread is P′, the major diameter is D, the minor diameter is D1, and the tooth width of the female thread at the pitch diameter d2 of the male thread is S n The number of turns of the female thread is n (i.e., the total number of turns in the screwing region of the female and male threads), and the modulus of elasticity of the female thread material is E n Here, the notch C n width at the pitch diameter d2 of the male thread is larger than the tooth width S of the female thread at the pitch diameter d2 of the male thread, i.e., P - S n > S w That is, by preventing the interference fit between the female and male threads due to the tooth width of the female thread being too large, the assembly resistance can be reduced and the assembly property can be improved n For convenience of explanation, the present invention provides a start position and an end position. As shown in FIGS. 3 and 4, taking the bolt 1 and the nut 2 as an example, within the screwing region of the female and male threads, the present invention uses one end face perpendicular to the axis of the female thread as the start position section Q, and the other end face of the female thread as the end position section Z (the conventionally considered support surface, i.e., the end face for pressing the connected member of the nut 2), and the direction from the start position to the end position is the same as the direction of the rated axial load N applied to the male thread

[0032] Since the number of turns of the female thread is n, when the female and male threads are used in combination, the n - turn female thread must be used in combination with the n - turn male thread. When no load deformation occurs, starting from the start position, any female thread with n′ turns (0 < n′ ≤ n) is longer than the length of the male thread

[0033] Specifically, the total length of the male thread with n′ turns is L1, the length of the female thread with n′ turns is L2, the difference in length between the female and male threads is l = L2 - L1, and the total axial fitting gap δ during the combined use of the female and male threads is P - S

[0034] - S w That is, by preventing the interference fit between the female and male threads due to the tooth width of the female thread being too large, the assembly resistance can be reduced and the assembly property can be improved nIt is as follows. As shown in Fig. 5, in the upper figure, the pitches of the female thread and the male thread are equal. One side of the female thread and the male thread is bonded together, and the other side does not contact. The axial gap between the female thread and the male thread is δ. In the lower figure, the female thread and the male thread are bonded together at the leftmost side. Since the pitch of the female thread is larger than the pitch of the male thread, the female thread and the male thread start to separate from the bonding position, and the other side of the female thread and the male thread gradually approaches at the rightmost side. At this time, the length difference between the female thread and the male thread is l. When δ = l, the rightmost sides of the female thread and the male thread just contact. When δ < l, interference fit appears between the female thread and the male thread, which is inconvenient for assembly. Therefore, δ ≥ l. This can prevent the tooth meshing phenomenon caused by insufficient axial gap, reduce the assembly resistance, and improve the assembly performance.

[0035] Furthermore, if the length of the male thread L1 = n′P, the length of the female thread L2 = n′P′, and the pitch difference between the female thread and the male thread ΔP = P′ - P, then l = L2 - L1 = n′(P′ - P) = n′ΔP, that is, ΔP = l / n′. Therefore, to solve the pitch difference ΔP, the length difference l between the female thread and the male thread must be obtained.

[0036] For the conventional equal-pitch screw, when under load meshing, the male thread is pulled and becomes longer, and the female thread is compressed and becomes shorter. The male thread and the female thread at any position within the meshing region are stretched or compressed to different degrees. In the present invention, the sum of the total elongation amount l w of the male thread for n turns and the total compression amount l n of the female thread is taken as the length difference l between the female thread and the male thread.

[0037] As shown in Figure 6, for the sake of analysis, the male thread in the threaded region of the female and male threads is simplified to an equivalent load-bearing cylinder. The two circular cross-sections of the equivalent load-bearing cylinder are the starting position cross-section Q and the ending position cross-section Z, respectively. The cross-sectional area A1 of the equivalent load-bearing cylinder is the stress cross-sectional area of ​​the thread. The magnitude of the axial load received by the equivalent load-bearing cylinder at the ending position cross-section Z is N, and the direction of the axial load N is directed from the starting position cross-section Q to the ending position cross-section Z. The forces acting between the female and male threads are simplified to surface loads applied to the outer cylindrical surface of the equivalent load-bearing cylinder. The surface loads are in the opposite direction to the axial load N, and the resultant force of the surface loads is the same as the magnitude of the axial load N. Starting from the starting position, the resultant force of the loads on the minute outer cylindrical surface at any n' turn position is f1(n'), and the resultant force of the loads on all minute outer cylindrical surfaces is equal to the axial load N, i.e.

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[0038] A small cylindrical section is cut from an equivalent-forced cylinder at an arbitrary height h=n′P, with thickness dh=Pdn′, and the axial load acting on the lower cross-section of the small cylindrical section is:

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[0039] As is clear from Figure 7, the direction of the surface load on the outer cylindrical surface of the minute cylinder is opposite to the direction of the load N1 on the lower cross-section of the minute cylinder. Therefore, the amount of elongation on the outer cylindrical surface of the minute cylinder is the average elongation dl. w1 For smaller, equivalent force-bearing cylindrical bodies, the outer cylindrical surface is a simplified male thread region, and therefore the elongation of the outer cylindrical surface is equal to the elongation of the male thread dl.w should be, that is, dl w =k1·dl w1 , 0 < k1 < 1. For convenience of analysis, assuming k1 is a constant value, starting from the starting position, the total elongation of the male thread for any number of n' turns [Number] .

[0040] As shown in Fig. 8, for convenience of analysis, the female thread in the threaded engagement region of the female and male threads is simplified to an equivalent force-bearing hollow cylinder. The two circular arc-shaped cross-sections of the equivalent force-bearing hollow cylinder are the starting position cross-section Q and the ending position cross-section Z respectively. The cross-sectional area of the equivalent force-bearing hollow cylinder is A2, and the axial load at the ending position cross-section Z of the equivalent force-bearing hollow cylinder is F N (F and N are equal due to the balance of forces) N ), and the direction is from the ending position to the starting position. The acting force between the female and male threads is simplified to a surface load being applied to the inner cylindrical surface of the equivalent force-bearing hollow cylinder. The surface load is opposite to the direction of the axial force F N , and the resultant force of the surface load is the same as the magnitude of the axial force F N . Starting from the starting position cross-section, the resultant force of the load on the small inner cylindrical surface at any number of n' turns position is f2(n'), and the resultant force of the load on all the small inner cylindrical surfaces is equal to the axial load F N , that is [Number] .

[0041] Cut out a small hollow cylinder at an arbitrary height h = n'P position of the equivalent force-bearing hollow cylinder. The thickness of the small hollow cylinder is dh = Pdn', and the axial load applied to the lower cross-section of the small hollow cylinder is [Number] , and the average compression amount of the small hollow cylinder with a thickness of dh is [Number] and the total average compression amount of the equivalent hollow cylinder at an arbitrary number of n' turns is obtained by integration from the starting position cross-section Q.

Equation

[0042] As can be seen from FIG. 9, since the surface load direction of the inner cylindrical surface of the micro hollow cylinder is opposite to the acting direction of the lower cross-section load F N of the micro hollow cylinder, the compression amount on the inner cylindrical surface of the micro hollow cylinder is larger than the average compression amount dl n1 . Since the inner cylindrical surface of the equivalent hollow cylinder is a simplified region of the female thread, the compression amount of the inner cylindrical surface is the compression amount dl n of the female thread. Therefore, dl n = k2·dl n1 , where 1 < k2. For the convenience of analysis, assuming k2 is a constant value, starting from the starting position, the total compression amount of the female thread at an arbitrary number of n' turns is

Equation

[0043] As shown in FIG. 10, the axial load acting from the female thread to the male thread crest at an arbitrary number of n' turns starting from the starting position is F(n'), and from the simplified method of the equivalent force-bearing cylinder and the equivalent force-bearing hollow cylinder, that is, the mechanical relationship, F(n') = f1(n') = f2(n'). Therefore, the sum of the total elongation amount l w of the male thread and the total compression amount l n of the female thread is the difference l in the lengths of the female thread and the male thread, that is

Equation

[0044] When the materials of the female thread and the male thread, that is, the external dimensions of the nut are determined, since both E n and A2 are constant values, the ratio k3 of E w A1 and E n A2 is a constant. For the convenience of calculation, when the elastic modulus and area in the formula are unified to E w and A1,

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[0045] Furthermore, the length adjustment amount of the gradually changing pitch screw

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[0046] Three different trends in the change of F(n') were simulated, and the resulting stress cloud maps are as follows: Figure 12(a) is the stress cloud map corresponding to curve a, Figure 12(b) is the stress cloud map corresponding to curve b, and Figure 12(c) is the stress cloud map corresponding to curve c.

[0047] The high-stress region at the base of the male thread typically occurs there, and the magnitude of the stress value is influenced by the combined effect of the axial load F(n') at the male thread and the axial load N(n') at the cross-section (i.e., the force on the entire cross-section (excluding the thread) for n' turns). When a load is applied to the female and male threads and they deform, the axial load N(n') at the cross-section increases from the starting position as the number of turns n' of the screw increases, reaching a maximum value N at n turns. As shown in Figure 11, when the axial force F(n') at the male thread matches curve a, F(n') is small at the starting position and large at the ending position, which is the same as the trend of change of N(n'). As shown in Figure 12(a), Y in the figure represents the area with the largest stress value. As can be seen from the figure, the stress is small at the starting position of the male thread, while the stress is large at the ending position, resulting in a clear stress concentration phenomenon. That is, Y is concentrated at the ending position, and the area of ​​Y increases as it approaches the ending position.

[0048] As shown in Figure 11, when the axial force F(n') in the male thread matches curve b, although F(n') remains constant, the axial load N(n') in the cross-section gradually increases with n'. Therefore, the stress at the base of the male thread is still small at the starting position and large at the ending position, but the stress concentration phenomenon is improved. As shown in Figure 12(b), the area of ​​Y at the ending position becomes smaller. When the axial force F(n') in the male thread matches curve c, F(n') further increases at the starting position and further decreases at the ending position. This further increases the stress at the base of the male thread at the starting position and further decreases the stress at the ending position, making the stress value across the entire base of the male thread more uniform and reducing the stress concentration phenomenon. As shown in Figure 12(c), Y is uniformly distributed from the starting position to the ending position.

[0049] Furthermore, if F(n') matches curve c, the stress state is good, and the selected F(n') equation should satisfy curve c. F(n') should satisfy two conditions: namely, it is a decreasing function within the interval 0 ≤ n' ≤ n.

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[0050] For the convenience of calculation, the axial force in the male thread is [Number] (0 < n ≤ n'), decreases linearly, and further [Number] , [Number] is obtained. When n' = n, the difference l in the lengths of the female and male threads is [Number] . Let k be the load coefficient, which is the ratio of the axial force N applied to the male thread to the product of the yield strength σ of the material and the stress cross-sectional area A1 of the male thread, that is, k = N / σA1. k c is taken as the material coefficient, which is the ratio of the yield strength σ of the material to the elastic modulus E w of the material, that is, kc = σ / E w . When the main design parameters and material of the bolt are determined, k and k c become constant values. Further, l = (2kk c KP / 3)n is derived.

[0051] Furthermore, the pitch difference ΔP between the female and male threads is ΔP = l / n = (2kk c K / 3)P (0.8 ≤ K ≤ 4.5).

[0052] Furthermore, generally, the value of the load coefficient k is in the range of 0.4 < k < 0.8, and the material coefficient k c of the commonly used material of the thread is 0. = 0.001 - 0.02. Considering k, k c and K comprehensively, the pitch difference between the female and male threads is limited to 0.003P < ΔP < 0.01P.

[0053] The following combines specific screw parameters and comparative tests to demonstrate the superiority of the range of pitch difference ΔP values ​​between the female and male threads of the unequal pitch screw connection pair of the present invention.

[0054] Specific Embodiment 1:

[0055] The male thread type is a metric thread, and in the male thread type, the pitch P=4mm, the large diameter d=42mm, the small diameter d1=37.67mm, the medium diameter d2=39.4mm, and the tooth width at the medium diameter of the male thread is S w = 2 mm. The elastic modulus E of the male screw material. w =206GPa, yield strength σ=930Mpa, axial load N=0.7σA1.

[0056] The tooth width of the female thread at the large diameter D=42.42mm, small diameter D1=38.09mm, and medium diameter d2 of the male thread is S n = 1.76 mm, and the number of turns of the female thread is n = 7 turns.

[0057] In this embodiment, PS w =2mm>1.76mm, δ=PS w -S n =0.24mm, l=nΔP=0.126mm, δ>l. k=0.7,k c =σ / E w = 0.00451, ΔP = 0.00211 × KP.

[0058] The comparative thread type according to this embodiment is the same as the screw of the present application, and the pitch difference between the female and male threads of the various screws is as shown in Table 1. The pitch difference between the female and male threads of comparative screw 1 is ΔP = 0.01P, and the pitch difference between the female and male threads of comparative screw 2 is ΔP > 0.01P (comparative screw 2 is the form disclosed in Patent Document 2, in which the female and male threads are tightly fitted, interaction occurs between the female and male threads before loading, large stress is generated at the start and end positions, and the intermediate turns of the screw are suspended in mid-air), and comparative screw 3 is a normal equal-pitch screw.

[0059] [Table 1]

[0060] Figures 13(a) to 13(d) and 14(a) to 14(d) are stress cloud maps under different axial loads. Note that the simulation model is an elastic model, and the calculated mean stress may far exceed the yield stress. In this case, it means that there is a clear stress concentration phenomenon. Figure 13(a) is the stress cloud map of the present screw without axial load, Figure 13(b) is the stress cloud map of comparison screw 1 without axial load, Figure 13(c) is the stress cloud map of comparison screw 2 without axial load, and Figure 13(d) is the stress cloud map of comparison screw 3 without axial load. In the stress cloud maps of the four types of screws without axial load, comparison screw 2 is in a tight fit, and local stresses exist at the initial and end positions of the screw. Figure 14(a) shows the stress cloud map of the present invention's screw under an axial load N=0.7σA1, Figure 14(b) shows the stress cloud map of comparison screw 1 under an axial load N=0.7σA1, Figure 14(c) shows the stress cloud map of comparison screw 2 under an axial load N=0.7σA1, and Figure 14(d) shows the stress cloud map of comparison screw 3 under an axial load N=0.7σA1. As can be seen from Figures 14(a) to 14(d), the high stress concentration phenomenon of the present invention's screw is clearly improved compared to comparison screws 1 to 3.

[0061] According to the thread numbers (1-7) and positions indicated by the thickened short vertical lines in Figure 15, the average stress of each thread of the male screw was extracted, an average stress change diagram was drawn for each thread, and the stress concentration factor (stress concentration factor = maximum stress / total mean stress) for each thread was calculated. From Figure 16, it can be seen that the stress uniformity of the screw of this invention is good, and from Table 2, it can be seen that the stress concentration factor of the screw of this invention is minimal.

[0062] [Table 2]

[0063] In another embodiment, the total average elongation amount l of the equivalent force-bearing cylinder at any n' turn count. w1 Using this directly, the total elongation of the male screw at any n' turns l w It can also represent the total average compressibility l of an equivalent stressed hollow cylinder at any n' turn count. n1 Using this directly, the total compression amount of the female thread at any n' turns l n It can also represent this.

[0064] In other embodiments, the simplified results of the equations for ΔP and l may differ depending on the simplification method used to meet different needs.

[0065] In another embodiment, the gap in the middle diameter of the male screw is the tooth width S of the female screw. n Equivalent to, i.e., PS w =S n .

[0066] The above are merely preferred embodiments of the present invention and are not intended to limit the invention. The scope of patent protection of the present invention shall be in accordance with the claims, and all equivalent structural modifications made using the description and drawings of the present invention shall be included within the scope of protection of the present invention.

[0067] (Note) (Note 1) A non-equal pitch screw connection pair, comprising a female thread and a male thread, wherein the pitch of both the female and male threads is constant, and the pitch of the female thread is greater than the pitch of the male thread, The pitch difference between the female and male threads ΔP = (2kk c K / 3)P (However, P is the pitch of the male screw, K is a general reference coefficient, and 0.8 ≤ K ≤ 4.5. k is the load factor, which is the ratio of the axial load N applied to the male screw to the product of the yield strength σ of the male screw material and the stress cross-sectional area A1 of the male screw; that is, k = N / σA1. k c These are material coefficients, where σ is the yield strength of the male screw material and E is the elastic modulus of the male screw material.w This is the ratio, i.e., kc = σ / E w A non-equal pitch screw connection pair characterized by being ( ).

[0068] (Note 2) The unequal-pitch screw connection pair described in Appendix 1, characterized in that the pitch difference between the female and male threads is ΔP < 0.01P.

[0069] (Note 3) The unequal-pitch screw connection pair described in Appendix 1, characterized in that the pitch difference between the female and male threads is ΔP > 0.003P.

[0070] (Note 4) The pitch difference between the female and male threads is ΔP = l / n′ (where l is the difference in length between the female and male threads, n′ is an arbitrary number of turns starting from the starting position of the threaded region of the female and male threads, 0 ≤ n′ ≤ n, and n is the total number of turns in the threaded region of the female and male threads). The difference in length l between the female and male threads is equal to the total elongation of the male thread l. w and the total compression amount of the female thread l n It is the sum of,

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[0071] ]](Appendix 5) Define the tooth width at the pitch diameter of the male screw as S w , and the tooth width of the female screw at the pitch diameter of the male screw as S n and define the total axial fitting clearance δ = P - S w ]] - S n ​Then, δ is greater than or equal to the difference l in length between the female thread and the male thread, that is, δ ≥ l, and it is a non-uniform pitch screw connection pair according to any one of Appendices 1 to 3.

[0072] (Appendix 6) Define the tooth width at the pitch diameter of the male thread as S w and the notch C at the pitch diameter d2 of the male thread n with a width greater than the tooth width S of the female thread at the pitch diameter d2 of the male thread n Then, P - S w > S n and it is a non-uniform pitch screw connection pair according to any one of Appendices 1 to 3.

Claims

1. A non-equal pitch screw connection pair, comprising a female thread and a male thread, wherein the pitch of both the female and male threads is constant, and the pitch of the female thread is greater than the pitch of the male thread, The pitch difference between the female and male threads ΔP = (2kk ｃ K / 3)P (However, P is the pitch of the male screw, K is a general reference coefficient, and 0.8 ≤ K ≤ 4.

5. k is a load coefficient, where N is the axial load applied to the male screw, σ is the yield strength of the male screw material, and A is the stress cross-sectional area of ​​the male screw. １ It is the ratio of the product of, i.e., k = N / σA １ And, k ｃ These are material coefficients, where σ is the yield strength of the male screw material and E is the elastic modulus of the male screw material. ｗ This is the ratio, i.e., kc = σ / E ｗ A non-equal pitch screw connection pair characterized by being ( ).

2. The unequal pitch screw connection pair according to claim 1, characterized in that the pitch difference between the female thread and the male thread is ΔP < 0.01P.

3. The unequal pitch screw connection pair according to claim 1, characterized in that the pitch difference between the female thread and the male thread is ΔP > 0.003P.

4. The pitch difference between the female and male threads is ΔP = l / n' (where l is the difference in length between the female and male threads, n' is an arbitrary number of turns starting from the starting position of the threaded region of the female and male threads, 0 ≤ n' ≤ n, and n is the total number of turns in the threaded region of the female and male threads). The difference l between the lengths of the female and male threads is the total elongation of the male thread. ｗ and the total compression amount of the female thread l ｎ It is the sum of, [Math 1] (However, 0 < k １ < 1, The male thread in the threaded region of the female and male threads is simplified to an equivalent force-receiving cylindrical body, f １ (n') is the resultant force of the loads on the infinitesimal outer cylindrical surface at any n' turn position of the equivalent load-bearing cylinder, and the resultant force of the loads on all infinitesimal outer cylindrical surfaces is equal to the axial load N. [Math 2] (However, k ２ >1, E ｎ This is the elastic modulus of the female screw material, The female thread in the threaded region of the female and male threads is simplified to an equivalent force-receiving hollow cylindrical body. A ２ This is the cross-sectional area of ​​the hollow cylindrical body subjected to the equivalent force, f ２ (n') is the resultant force of the loads on the infinitesimal inner cylindrical surface at any n' turn number position of the equivalent load-bearing hollow cylinder, and the resultant force of the loads on all infinitesimal inner cylindrical surfaces is the axial load F Ｎ Equivalent to F Ｎ (This is equal to N, but in the opposite direction.) Therefore, [Math 3] E ｗ A １ and E ｎ A ２ The ratio of k ３ Toshi, Katsuk １ +k ２ k ３ Let K be the formula for the difference l in length between the female and male threads. [Math 4] Simplified to, Furthermore [Math 5] So, [Math 6] 、 Furthermore, [Number 7] Obtained, When n' = n, the difference l between the lengths of the female and male threads is, [Number 8] And, Furthermore, the pitch difference between the female and male threads ΔP = l / n = (2kk ｃ A non-equal pitch screw connection pair according to any one of claims 1 to 3, characterized in that it is K / 3)P.

5. The tooth width in the middle diameter of the male screw is S ｗ The tooth width of the female thread in the middle diameter of the male thread is S ｎ Defined as follows, the total axial fitting gap δ = P - S when a female thread and a male thread are used in mating. ｗ -S ｎ The non-equal pitch screw connection pair according to any one of claims 1 to 3, characterized in that δ is greater than or equal to the difference l in length between the female thread and the male thread, i.e., δ ≥ l.

6. The tooth width in the middle diameter of the male screw is S ｗ Defined as the middle diameter d of the male screw. ２ Notch C ｎ The width is the diameter d of the male thread. ２ The tooth width S of the female screw in ｎ If it is greater than, then P - S ｗ > S ｎ A non-equal pitch screw connection pair according to any one of claims 1 to 3, characterized in that it is the same as the one described above.

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