A non-equidistant anti-loosening threaded connection pair

Abstract

The present invention provides a non-equidistant anti-loosening threaded connection pair, which belongs to the field of non-standard fasteners. The non-equidistant anti-loosening threaded connection pair includes an internal thread and an external thread, the internal thread pitch is greater than the external thread pitch, and the length difference between the internal thread and the external thread in n turns is that the screwing area of ​​the internal and external threads includes a main load area near the starting position and a secondary load area near the end position. The load between the internal threads in the secondary load area is much smaller than the main load area, and is even not subject to load, which helps to increase the effective action length of the bolt; the load concentration area is separated from the main sliding area of ​​the internal and external threads, and the load concentration area is located near the starting position. The sliding area extends from the end position to the starting position. When the bolt rod is bent, the secondary load area begins to gradually contact, and the force between the internal and external threads increases, which helps to share the force generated by the bending of the bolt rod, reduce the possibility of relative slippage between the internal and external threads, and achieve a better anti-loosening effect.

Description

Technical Field

[0001] The invention relates to a non-equidistant anti-loosening threaded connection pair, belonging to the field of non-standard fasteners. Background Art

[0002] Threaded connections have the characteristics of strong connection performance, easy disassembly, and easy manufacturing. They are widely used in wind power generation, shipbuilding, automobile manufacturing, aerospace, mechanical products and other fields. When threaded connections are disturbed by external factors, bolts often loosen and fail, causing major safety accidents. Existing anti-loosening theories show that the main reason for thread loosening is the relative slip caused by insufficient friction between the internal and external threads.

[0003] The specific process is: when the thread is subjected to lateral load in the pre-tightened state, the friction generated between the nut and the supporting surface (the end face where the connected part and the nut are pressed tightly together) will drive the nut to move along the lateral load direction, and the bolt rod will produce a certain bending. When the lateral load is small, the static friction between the internal and external thread teeth is sufficient to overcome the force generated by the bending of the bolt rod, and there will be no relative slip between the internal and external threads. However, as the lateral load increases, the static friction between the internal and external thread teeth is insufficient to overcome the force generated by the bending of the bolt rod, and there will be relative slip between the internal and external threads, that is, looseness will occur.

[0004] The main reason is that the load concentration area of ​​traditional equidistant threads and the main sliding areas of internal and external threads are all near the supporting surface (taking the nut as an example, the supporting surface is the end face of the nut used to press the connected parts, that is, the supporting surface is the end face at the end position of the internal and external thread screwing area, and the other end face is the end face at the starting position). When the thread near the supporting surface slips completely, the friction between the internal and external threads away from the supporting surface is small, and the expansion of the sliding area cannot be prevented. Therefore, the threaded connection pair is prone to loosening. Summary of the invention

[0005] The object of the present invention is to provide a non-equidistant anti-loosening threaded connection pair to solve the problem that the load concentration area and the main sliding area of ​​the internal and external threads of the existing threaded connection pair are all near the supporting surface, resulting in that when the thread near the supporting surface completely slips, the friction force between the internal and external threads away from the supporting surface is small, and the expansion of the sliding area cannot be prevented, which further causes the threaded connection pair to easily loosen.

[0006] To achieve the above purpose, the non-equidistant anti-loosening threaded connection pair in the present invention adopts the following technical solution:

[0007] A non-equidistant anti-loosening threaded connection pair includes an internal thread and an external thread, wherein the pitch of the internal thread is greater than the pitch of the external thread, and the length difference between the internal thread and the external thread is n turns. So that the screwing area of ​​the internal and external threads includes a main load area near the starting position and a secondary load area near the end position, wherein: b1 is the comprehensive reference boundary 1; P is the pitch of the external thread; n is the total number of turns of the screwing area of ​​the internal and external threads; k is the load coefficient and 0<k<1; σ is the yield strength of the external thread material, E w is the elastic modulus of the external thread material; K is the comprehensive reference coefficient and 0.8≤K≤10.

[0008] The beneficial effect of the above technical solution is that: the present invention proposes an improved non-equidistant anti-loosening threaded connection pair, the main improvement of which is the length difference between the n-turn internal thread and the external thread. The screwing area of ​​the internal and external threads includes a main load area near the starting position and a secondary load area near the ending position. The load between the internal threads in the secondary load area is much smaller than that in the main load area, or even unloaded, which helps to increase the effective action length of the bolt and reduce the force caused by thread bending. In addition, since the load concentration area of ​​the internal and external threads is changed, the load concentration area is separated from the main sliding area of ​​the internal and external threads. The load concentration area is located near the starting position, and the sliding area extends from the ending position to the starting position. When the bolt rod is bent, the secondary load area begins to gradually contact, and the force between the internal and external threads increases, which helps to share the force caused by the bending of the bolt rod and reduce the possibility of relative sliding of the internal and external threads, thereby achieving a better anti-loosening effect.

[0009] Furthermore, considering k and k c , the value of K is limited to b1=0.0023Pn, so l>b1=0.0023Pn.

[0010] The beneficial effect of the above technical solution is: a specific lower limit value of l is given to ensure the anti-loosening effect.

[0011] Furthermore, if the internal and external thread engagement area is taken as the starting point, and the axial load on the external thread teeth at any n' number of turns is F(n'), then 0≤n'≤n, N is the axial load borne by the external thread; if the load borne by each circle of thread teeth is equal, that is At this time, the length change l'1 of the internal and external threads for any number of n' turns is equal to the total elongation l of the external thread w Total compression with internal thread l n The sum of Where: k1 and k2 are constants; A1 is the stress cross-sectional area of ​​the external thread, E n is the elastic modulus of the internal thread material, A2 is the stress cross-sectional area of ​​the internal thread; let E w A1 and E n The ratio of A2 is k3, and let k1+k2k3=K, simplifying the formula of l'1 to: Then according to N=kσA1, we can get When n'=n, use Available When the length difference between the n-turn internal and external threads is l>l'1(n), l is sufficient to provide the length l'1(n) required for the deformation of the internal and external threads, so we get

[0012] The beneficial effect of the above technical solution is that: given the load conditions such as F(n'), the In this process, many factors are taken into consideration and the formula is simplified to facilitate subsequent verification and comparison.

[0013] Furthermore, the length difference between the n turns of internal thread and external thread is Among them: b2 is the comprehensive reference boundary 2.

[0014] The beneficial effect of the above technical solution is that it further reduces the lower limit of the length difference l between the n turns of internal thread and external thread, thereby ensuring a better anti-loosening effect.

[0015] Furthermore, considering k and k c , the value of K is limited to b2=0.0036Pn, so l>b2=0.0036Pn.

[0016] The beneficial effect of the above technical solution is that a new specific value of the lower limit is given, which facilitates the design, manufacture and processing of the threaded connection pair.

[0017] Furthermore, if the internal and external thread engagement area is taken as the starting point, and the axial load on the external thread teeth at any n' number of turns is F(n'), then 0≤n'≤n, N is the axial load borne by the external thread; That is, as the number of threads decreases in the range of 0 to n turns, the main load area is closer to the starting position, and at n'=n, F(n')=0, and there is no force between the internal and external threads. At this time, the length change l'2 of the internal and external threads for any n' number of turns is equal to the total elongation l of the external thread. w Total compression with internal thread l n The sum of Where: k1 and k2 are constants; A1 is the stress cross-sectional area of ​​the external thread, E n is the elastic modulus of the internal thread material, A2 is the stress cross-sectional area of ​​the internal thread; let E w A1 and E n The ratio of A2 is k3, and let k1+k2k3=K, then according to N=kσA1, when n'=n, When , the formula of l'2 can be simplified to When the length difference between the n-turn internal thread and the external thread is l>l'2(n), l is sufficient to provide the length l'2(n) required for the deformation of the internal and external threads, so we get

[0018] The beneficial effect of the above technical solution is that: it gives the value of F(n') in the range of 0 to n turns as the number of thread turns gradually decreases. In this process, many factors are taken into consideration and the formula is simplified to facilitate subsequent verification and comparison.

[0019] Furthermore, the length difference between the internal thread and the external thread of the first thread circle is l1<b3=0.05P, and b3 is the comprehensive reference boundary three.

[0020] The beneficial effect of the above technical solution is that it provides an upper limit of the length difference l1 between the internal thread and the external thread of the first thread circle, preventing the axial load of the external thread from being borne by one thread circle, thereby protecting the first thread circle.

[0021] Furthermore, the length difference between the internal thread and the external thread of the first thread circle is l1<b4=0.02P, and b4 is the comprehensive reference boundary four.

[0022] The beneficial effect of the above technical solution is that it further reduces the upper limit of the length difference l1 between the internal thread and the external thread of the first thread circle, ensuring that the load of the first thread circle is less than 70% of the total load.

[0023] Furthermore, the length difference between the internal thread and the external thread of the first thread circle is l1<b5=0.01P, and b5 is the comprehensive reference boundary five.

[0024] The beneficial effect of the above technical solution is that it further reduces the upper limit of the length difference l1 between the internal thread and the external thread of the first thread circle, ensuring that the load of the first thread circle is less than 50% of the total load.

[0025] Furthermore, the pitch difference ΔP(n1) between the internal thread and the external thread near the starting position is not greater than the pitch difference ΔP(n2) between the internal thread and the external thread far from the starting position, that is, n1<n2, ΔP(n1)≤ΔP(n2).

[0026] The beneficial effect of the above technical solution is that it unifies the cases where ΔP is a fixed value and a non-fixed value. When ΔP is a fixed value, the thread is easy to process and manufacture; when ΔP gradually increases with the increase in the number of thread turns, the bearing capacity of the first thread can be reduced, and the stress concentration phenomenon of the first thread can be reduced. Comparative verification shows that the load of the first thread is greater than when ΔP is a fixed value.

[0027] Furthermore, when the internal and external threads are used together, the total axial clearance δ = PS w -Sn , where S w S is the tooth width of the external thread at the mid-diameter. n is the tooth width of the internal thread at the middle diameter of the external thread, then l≤δ.

[0028] The beneficial effect of the above technical solution is to prevent the tooth biting phenomenon caused by insufficient axial clearance.

[0029] Furthermore, when the internal and external threads are used together, the total axial clearance δ = PS w -S n >0, that is, P>S w +S n , where S w S is the tooth width of the external thread at the mid-diameter. n It is the tooth width of the internal thread at the middle diameter of the external thread.

[0030] The beneficial effect of the above technical solution is to prevent the internal thread from having too large a tooth width and the external thread from having insufficient clearance and causing tooth biting. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is the basic external thread profile diagram involved in the present invention;

[0032] Figure 2 It is the basic internal thread profile diagram involved in the present invention;

[0033] Figure 3 A tooth profile diagram of the internal thread of the non-equidistant anti-loosening threaded connection pair of the present invention;

[0034] Figure 4 It is a schematic diagram of the principle of preventing the internal and external threads from biting according to the present invention;

[0035] Figure 5 A length relationship diagram of the internal and external threads when the internal and external threads involved in the present invention are not loaded;

[0036] Figure 6 It is a schematic diagram of the starting position and the ending position of the non-equidistant anti-loosening threaded connection pair during loading of the present invention;

[0037] Figure 7 It is a schematic diagram of the force of the external thread in the screwing area of ​​the internal and external threads of the present invention;

[0038] Figure 8 It is a common trend diagram of the F(n') curve in the present invention;

[0039] Fig. 9 It is a schematic diagram of the effective length from the equivalent action point to the support point of the traditional equidistant thread;

[0040] Fig.10It is a schematic diagram of the effective length from the equivalent action point to the support point of a non-equal pitch thread;

[0041] Fig.11 It is a schematic diagram of the external thread involved in the present invention being simplified into an equivalent force-bearing cylinder;

[0042] Fig.12 for Fig.11 Schematic diagram of the average elongation of the micro-cylinder and the elongation at the cylindrical surface;

[0043] Fig.13 It is a schematic diagram of the internal thread involved in the present invention simplified into an equivalent force-bearing hollow cylinder;

[0044] Fig.14 for Fig.13 Schematic diagram of the average compression of a tiny hollow cylinder and the compression at the inner cylindrical surface;

[0045] Fig.15 It is the number of external thread teeth and the position of load value;

[0046] Fig.16 is the load ratio on each thread tooth of thread 1 to thread 6 under the same boundary conditions;

[0047] Fig.17 It is a curve diagram showing the change of the preload percentage of threads 1 to 6 with the vibration period under the same axial load and lateral displacement load;

[0048] Fig.18 It is a curve diagram showing the change of loosening angle of thread 1 to thread 6 with vibration period under the same axial load and lateral displacement load;

[0049] Fig.19 is the load ratio on each thread tooth of thread 7 to thread 12 under the same boundary conditions;

[0050] Fig. 20 It is a curve diagram showing the change of the preload percentage of threads 7 to 12 under the same axial load and lateral displacement load as a function of the vibration period;

[0051] Fig.21 This is a curve diagram of the loosening angle of threads 7 to 12 under the same axial load and lateral displacement load as a function of the vibration period. DETAILED DESCRIPTION

[0052] The features and performance of the present invention are further described in detail below in conjunction with the embodiments.

[0053] The present invention sets a lower limit value of the length difference l between n turns of internal and external threads, so that the screwing area of ​​the internal and external threads includes a main load area near the starting position and a secondary load area near the ending position, which helps to increase the effective action length of the bolt, share the force generated by the bending of the bolt rod, reduce the possibility of relative slippage between the internal and external threads, and achieve a better anti-loosening effect. At the same time, the present invention also sets an upper limit value of the length difference l1 between the internal and external threads of the first turn of threads, to prevent the axial load of the external thread from being borne by the first turn of threads.

[0054] Embodiment 1 of the non-equidistant anti-loosening threaded connection pair of the present invention:

[0055] The non-equidistant anti-loosening threaded connection pair includes an internal thread and an external thread. The pitch of the internal thread is greater than that of the external thread. The pitch of the internal thread and the external thread can be constant, or one of them can be a constant pitch thread and the other can be a gradual pitch thread. For the gradual pitch thread, it is obtained by adjusting the pitch based on the basic thread profile. The adjustment is based on the basic thread profile, and is obtained by cutting or increasing the thread tooth width or adding a transition structure at the bottom of the tooth. Among them, the basic thread profile is a standard thread such as metric thread, MJ thread, trapezoidal thread and arc thread. Non-standard threads can also be used. The basic external thread profile is a profile along the axial direction with a width of a standard pitch.

[0056] As a specific implementation, the external thread is a constant pitch thread, and the external thread profile is a basic external thread profile, such as Figure 1 As shown, the external thread pitch P1 is equal to the basic external thread pitch P, the major diameter d, the minor diameter d1, and the tooth width at the external thread middle diameter d2 is S w , the yield strength of the external thread material is σ, and the elastic modulus of the external thread material is E w .

[0057] Basic internal thread profile Figure 2 As shown, the pitch P, major diameter D, minor diameter D1 of the basic internal thread profile, the number of internal thread turns n, and the elastic modulus E of the internal thread material n .

[0058] As a specific implementation method, the internal thread is a gradual pitch thread, and based on the basic internal thread profile, the basic thread profile is kept unchanged, and the internal thread pitch is increased by adding a transition structure, such as Figure 3As shown, the tooth profile of the internal thread on the plane through the axis is composed of multiple basic internal thread profiles and transition structure G spliced ​​end to end, and the longitudinal section of the transition structure G is a straight line segment. The pitch of the internal thread gradually increases along the axial direction. The pitch of the internal thread P2 is the distance between two adjacent basic internal thread profiles on the internal thread profile and any set of corresponding points MM' on the screwing area of ​​the external thread. Therefore, the pitch of the internal thread P2 is a non-constant value, and the pitch of the internal thread is greater than the pitch of the basic thread profile of the external thread, that is, P2>P. The pitch adjustment amount ΔP of the internal thread (i.e., the gradual pitch thread) is P2-P. Since the pitch of the external thread P1 is P, the pitch adjustment amount ΔP of the gradual pitch thread is the pitch difference between the internal and external threads.

[0059] like Figure 3 and Figure 5 As shown, the tooth width of the internal thread at the middle diameter d2 of the external thread is S n The total axial clearance between the internal and external threads at the external thread diameter d2 is δ = P1-S w -S n ,>0, that is, P>S w +S n This can prevent the internal thread from being too wide and the external thread from having insufficient clearance, which can cause biting.

[0060] Furthermore, if Figure 4 As shown, when the pitch of the internal and external threads are equal (refer to the graph of P2=P1, Figure 4 In the middle and upper figure), the length of the internal and external threads are both L1. When the internal thread pitch is greater than the external thread pitch (refer to the line P2>P1, Figure 4 (Figure 2-3) When the internal thread length is L2, the internal thread straight line segment gradually contacts the external thread straight line segment. Figure 4 It is easy to see that in the figure above, the pitch of the internal and external threads is equal, one side of the internal and external threads fits together, and the other side does not touch, and the axial clearance between the internal and external threads is δ. In the figure below, the internal and external threads fit together on the far left. Since the pitch of the internal thread is greater than the pitch of the external thread, the internal and external threads start to separate from the fitting position. When they are on the far right, the other side of the internal and external threads gradually approach each other. At this time, the length difference between the internal and external threads is l. When l=δ, the rightmost sides of the internal and external threads just touch; when l>δ, the internal and external threads will have an interference fit, which is not convenient for assembly. Therefore, l≤δ, which can prevent the phenomenon of biting caused by insufficient axial clearance.

[0061] In addition, combined Figure 5As shown, taking the starting position section Q as the starting point, the length of the external thread of any n' turns is L1=n'P1=n'P, 0≤n'≤n, and the length of the internal thread of any n' turns is L2=n'P1+l=n'P+l, then: L2-L1=l, where l is the length difference between the internal and external threads of any n' turns starting from the starting position, that is, the length adjustment amount of the gradual pitch thread.

[0062] For the convenience of description, the present invention sets a starting position and an ending position, such as Figure 5 and Figure 6 As shown, taking bolt 1 and nut 2 as an example, in the screwing area of ​​the internal and external threads, the present invention uses one end face of the internal thread perpendicular to the axis as the starting position section Q, and the other end face of the internal thread as the ending position section Z (the traditionally considered support surface, that is, the end face of the nut 2 used to press the connected parts), and the direction from the starting position to the ending position is the same as the direction in which the external thread bears the rated axial load N.

[0063] The number of threads of the internal thread is n. When the internal and external threads are used together, n turns of internal thread must be used together with n turns of external thread. In the case of no load deformation, starting from the starting position, any n' turns of internal thread (0<n'≤n) are longer than the length of external thread. The pitch difference ΔP(n1) between the internal thread and the external thread near the starting position is less than or equal to the pitch difference ΔP(n2) between the internal thread and the external thread far from the starting position, that is, n1<n2, ΔP(n1)≤ΔP(n2).

[0064] like Figure 7 As shown in the figure, the axial load of the internal thread on the external thread teeth at any n' number of turns in the screwing area of ​​the internal and external threads is F(n'). Regardless of whether it is a traditional equidistant thread or a non-equidistant pitch thread, when the axial load of the external thread is N, there are n turns of thread used together, then the resultant force of the n turns of thread teeth is equal to the axial load N on the external thread, that is,

[0065] When the traditional equidistant thread is loaded, the inner and outer threads of each circle are in contact at the same time. Due to the cumulative effect of the load, the axial load on the outer thread of the traditional equidistant thread is F(n') which meets the requirements. Figure 8 In the middle curve 1 (i.e., curve 1 is a common thread with equal distance between internal and external threads), the axial load F(n') on the external thread teeth near the end position is larger, while the axial load F(n') on the external thread teeth at the starting position is smaller. The equivalent action point A of the internal thread on the external thread is closer to the end position section Z and the support surface position, such as Fig. 9 shown.

[0066] When the pitch of the internal thread is greater than the pitch of the external thread, during the loading process of the internal thread, the internal and external threads begin to contact from the starting position. As the load increases, the subsequent threads contact one by one, which increases the axial load F(n') on the external thread teeth at the starting position, while the axial load F(n') on the external thread teeth at the end position decreases. The equivalent action point B of the internal thread on the external thread approaches the section Q at the starting position, such as Fig.10 shown.

[0067] The effective length from the equivalent action point A to the support point O of the traditional equidistant thread is l A , the effective length from the equivalent action point B of the non-equal pitch thread to the support point O is l B , then l A Less than l B At this time, the bolt can be regarded as a cantilever beam, the bolt head position is a support position, and the cantilever of the equidistant thread is l A , the cantilever of non-equidistant threads is l B , l A Less than l B , under the same displacement load (the two cantilever beams produce the same deflection), the bending degree of the rod with a shorter cantilever is greater, that is, the force generated by the bending of the rod is also greater. Therefore, under the same axial load and friction coefficient, the effect of the bending of the equidistant thread is greater, and relative slip is more likely to occur between the internal and external threads, that is, Fig. 9 The matching method is more likely to produce relative slip.

[0068] Therefore, in the present embodiment, the length difference between n turns of internal thread and external thread is limited to l>b1=0.0023Pn, wherein b1 is the comprehensive reference boundary one, so that the screwing area of ​​the internal and external threads includes a main load area near the starting position and a secondary load area near the ending position, and the load between the internal threads in the secondary load area is much smaller than that in the main load area, or even unloaded, which helps to increase the effective action length of the bolt and reduce the force generated by the bending of the thread; in addition, since the load concentration area of ​​the internal and external threads is changed, the load concentration area is separated from the main sliding area of ​​the internal and external threads, and the load concentration area is located near the starting position, and the sliding area extends from the ending position to the starting position. When the bolt rod is bent, the secondary load area begins to gradually contact, and the force between the internal and external threads increases, which helps to share the force generated by the bending of the bolt rod and reduce the possibility of relative sliding of the internal and external threads, thereby achieving a better anti-loosening effect.

[0069] The specific calculation process is given below. For the convenience of calculation, the present invention assumes that all n circles are meshed and simplifies the n circles of external threads into an equivalent force-bearing cylinder. Fig.11As shown, the two circular cross-sections of the equivalent force-bearing cylinder are the starting position cross-section Q and the ending position cross-section Z. The cross-sectional area A1 of the equivalent force-bearing cylinder is the stress cross-sectional area of ​​the thread. The axial load borne by the equivalent force-bearing cylinder at the ending position cross-section Z is N axial load, and the direction of the axial load N is from the starting position cross-section Q to the ending position cross-section Z. The acting force between the internal and external threads is simplified to the outer cylindrical surface of the equivalent force-bearing cylinder bearing a surface load. The surface load is in the opposite direction to the axial load N, and the resultant force of the surface load is the same as the magnitude of the axial load N. Taking the starting position as the starting point, the resultant force of the load on the tiny outer cylindrical surface at any n' number of turns is f1(n'), and the resultant force of the load on all tiny outer cylindrical surfaces is equal to the axial load N, that is, For the convenience of calculation, it is assumed that all n threads are stressed and the stress is uniform, then

[0070] A small cylinder is cut off at any position of n' turns of the equivalent force-bearing cylinder. The thickness of the small cylinder is dh = Pdn'. The axial load on the lower section of the small cylinder is From Hooke's law, we can get the average elongation of a tiny cylinder with a thickness of dh Starting from the starting section, the total average elongation of the equivalent loaded cylinder at any n' turns is

[0071] Depend on Fig.12 It can be seen that since the surface load direction of the outer cylindrical surface of the micro-cylinder is opposite to the direction of the load N1 on the lower section of the micro-cylinder, the elongation at the outer cylindrical surface of the micro-cylinder is less than the average elongation dl w1 , the outer cylindrical surface of the equivalent force-bearing cylinder is the simplified area of ​​the external thread, so the elongation of the outer cylindrical surface should be the elongation of the external thread dl w , then dl w =k1·dl w1 , 0<k1<1, for the convenience of analysis, assuming k1 is a constant value, then starting from the starting position, the total elongation of any n' turns of external thread

[0072] like Fig.13 As shown in the figure, for the convenience of analysis, the internal thread in the screwing area of ​​the internal and external threads is simplified into an equivalent force-bearing hollow cylinder. The two annular sections of the equivalent force-bearing hollow cylinder are the starting position section Q and the ending position section Z. The cross-sectional area of ​​the equivalent force-bearing hollow cylinder is A2. The axial load of the equivalent force-bearing hollow cylinder at the ending position section Z is F. N , the direction is from the end position to the start position, the force between the internal and external threads is simplified to the inner cylindrical surface of the equivalent force-bearing hollow cylinder subjected to surface load, the surface load and the axial force F NThe direction is opposite, the resultant force of the surface load and the axial force F N The size is the same. Taking the starting section as the starting point, the resultant force of the load on the small inner cylindrical surface at any n' turn position is f2(n'). The resultant force of the load on all small inner cylindrical surfaces is equal to the axial load F N Equal, that is Furthermore, according to the force balance relationship between the internal and external threads, it can be known that F N = N, and when the thread teeth of each circle of threads are completely evenly loaded, that is, when the load of each circle of threads is equal,

[0073] A small hollow cylinder is cut at any height h = n'P of the equivalent force-bearing hollow cylinder. The thickness of the small hollow cylinder is dh = Pdn'. The axial load on the lower section of the small hollow cylinder is Average compression of a tiny hollow cylinder with a thickness of dh By integration, we can find the total average compression of the equivalent hollow cylinder at any n' number of circles starting from the starting section:

[0074] Depend on Fig.14 It can be seen that due to the surface load direction of the cylindrical surface inside the tiny hollow cylinder and the load F on the lower section of the tiny hollow cylinder N The direction of action is opposite, making the compression on the cylindrical surface of the tiny hollow cylinder greater than the average compression dl n1 The inner cylindrical surface of the equivalent hollow cylinder is the simplified area of ​​the internal thread, so the compression of the inner cylindrical surface is the compression of the internal thread dl n , then dl n =k2·dl n1 , 1<k2, for the convenience of analysis, assuming k2 is a constant value, then starting from the starting position, the total compression of the internal thread with any number of n' turns

[0075] Furthermore, taking the starting position as the starting point, the length change l'1 of the internal and external threads for any n' turns is equal to the total elongation l of the external thread. w Total compression with internal thread l n The sum of , then:

[0076]

[0077] When the internal and external thread materials, i.e. the nut dimensions, are selected, E n and A2 are both constants, so E w A1 and E n The ratio k3 of A2 is a constant. In order to facilitate calculation, the elastic modulus and area in the formula are unified into E w and A1, then In order to facilitate subsequent calculations, let the comprehensive reference coefficient K = k1 + k2k3, and simplify the formula for the length change l'1 of the internal and external threads to:

[0078] Normally, the cross-sectional stress of the axial load borne by the external thread on the equivalent load-bearing cylinder is less than the yield strength σ of the material, that is, N = kσA1 < σA1, where k is the load factor and 0 < k < 1, then

[0079] Furthermore, when n'=n, use Available Among them, the ratio of the yield strength and elastic modulus of the threaded material is usually k c The range is 0.001~0.2, that is: The value range of the comprehensive reference coefficient K is 0.8≤K≤10.

[0080] The above calculation and analysis process adopts equal load design, that is, based on the fact that each circle of thread teeth bears equal load. When the length difference l between the n-circle internal thread and the external thread is less than the length change l'1(n) of the n'-circle internal and external thread, that is, l<l'1(n), it means that the length difference l between the internal and external threads is not enough to provide the length l'1(n) required for the deformation of the internal and external threads. The thread at the end position needs to bear more load. The load at the end position is greater than the load at the starting position. The main load area is close to the end position. In this case, the change trend of F(n') is similar to Figure 8 As shown in curve 2. When l = l'1(n), the length difference l between the internal and external threads just provides the length l'1(n) required for the deformation of the internal and external threads, and the change trend of F(n') is similar to Figure 8 Curve 3 shows that when l>l'1(n), the length difference l between the internal and external threads is sufficient to provide the length l'1(n) required for the deformation of the internal and external threads. The load between the internal and external threads at the end position is less than the load at the start position. In this case, the change trend of F(n') is similar to Figure 8 As shown in curve 4.

[0081] When l>l'1(n), the main load area is close to the starting position, and the secondary load area is close to the ending position. Further, considering the load coefficient k, the ratio of the yield strength to the elastic modulus of the material k c And the comprehensive reference coefficient K, the range of the length difference l between the n-turn internal thread and the external thread is obtained as follows: Further comprehensive consideration of k, k c , the value of K is limited to b1=0.0023Pn, so l>b1=0.0023Pn.

[0082] Furthermore, the length difference between the n-turn internal thread and the external thread is l>b2=0.0036Pn, where b2 is the second comprehensive reference boundary. The specific calculation process is: when F(n') decreases with the number of thread turns in the range of 0 to n turns, and is 0 at n turns, for the convenience of analysis, assume Then F(n') decreases linearly when 0<n'≤n, the main load area is closer to the starting position, and F(n')=0 at n'=n, and there is no force between the internal and external threads at this point, and That is, Change to The change in length of the internal and external threads for any n' turns with the starting position as the starting point can be calculated as l'2, which is the total elongation of the external thread. w Total compression with internal thread l n The sum of , then: According to the same simplified method (let E w A1 and E n The ratio of A2 is k3, and let K = k1 + k2k3, K is the comprehensive reference coefficient, and then according to N = kσA1, where σ is the yield strength of the external thread material, k is the load factor and 0 < k < 1, and when n' = n, ), we can get

[0083] Furthermore, when l = l'2(n), the length difference l between the internal and external threads just provides the length l'2(n) required for the deformation of the internal and external threads. The load of the internal and external threads at the nth turn is 0, and the variation trend of F(n') is similar to Figure 8 As shown in curve 5. When l>l'2(n), the length difference l between the internal and external threads is sufficient to provide the length l'(n) required for the deformation of the internal and external threads. The load of the internal and external threads at less than n turns is 0. In this case, the change trend of F(n') is similar to Figure 8 As shown in curve 6.

[0084] Furthermore, when l≥l'2(n), the internal and external threads in the secondary load zone are not meshed. Comprehensively consider the load coefficient k, the ratio of the yield strength to the elastic modulus k of the material c And the comprehensive reference coefficient K, the range of the length difference l between the n-turn internal thread and the external thread is obtained as follows: Further comprehensive consideration of k, k c , the value of K is limited to b2=0.0036Pn, so l>b2=0.0036Pn.

[0085] In addition, when n = 1, the change in length of the first inner and outer threads is In order to prevent the axial load of the external thread from being borne by one circle of thread (starting from the initial position), the length difference l1 between the internal thread and the external thread of the first circle of thread should be smaller than the length change l′1(1) of the internal and external threads of the first circle, that is, Consider the load factor k, the ratio of the material's yield strength to its elastic modulus k c And the comprehensive reference coefficient K, the range of the length difference l1 between the internal thread and the external thread of the first thread circle is: l1<b3=0.05P, b3 is the comprehensive reference boundary three.

[0086] Furthermore, in order to ensure that the load of the first thread circle is less than 70% of the total load, the length difference l1 between the internal thread and the external thread of the first thread circle is in the range of: l1<b4=0.02P, b4 is the comprehensive reference boundary four.

[0087] Furthermore, in order to ensure that the load of the first thread circle is less than 50% of the total load, the length difference l1 between the internal thread and the external thread of the first thread circle is within the range of: l1<b5=0.01P, b4 is the comprehensive reference boundary five.

[0088] The performance of the non-equidistant anti-loosening threaded connection pair of the present invention is analyzed and verified in combination with specific thread parameters and comparative tests. Specific implementation method one:

[0090] The external thread is an external arc thread, the pitch of the external arc thread is constant and the pitch P1 = 6.35mm, the major diameter d = 41.5mm, the minor diameter d1 = 36.5mm, and the tooth width S of the external thread at the mid-diameter w =3.175mm, elastic modulus of external thread material E=206Gpa, yield strength σ=930Mpa, axial load N=0.7σA1.

[0091] The internal thread is a matching internal arc thread with a constant pitch. The internal thread major diameter D = 42.36 mm, the minor diameter D1 = 37.56 mm, and the tooth width S of the internal thread at the middle diameter of the external thread n = 2.3 mm, and the number of internal thread turns is n = 10 turns. Since the pitches of the internal and external threads are constant, the pitch difference ΔP(n1) between the internal thread and the external thread near the starting position in this embodiment is equal to the pitch difference ΔP(n2) between the internal thread and the external thread far from the starting position, that is, n1 < n2, ΔP(n1) = ΔP(n2).

[0092] Furthermore, the length of 10 turns of external thread L1 = 63.5 mm.

[0093] Further, b1 = 0.0023Pn = 0.14605 mm;

[0094] Further, b2 = 0.0038Pn = 0.2413 mm;

[0095] Further, b3 = 0.05P = 0.3175 mm;

[0096] Further, b4 = 0.02P = 0.127 mm;

[0097] Further, b5 = 0.01P = 0.0635 mm;

[0098] Furthermore, P1=6.35>S w +S n =5.475mm,δ=P1-S w -S n =0.875mm.

[0099] Table 1 shows the specific parameters of threads 1 to 6, and gives the judgment conditions of them and the boundary. And the length difference l of the inner and outer threads of 10 turns of threads 1 to 6 is less than δ. The finite element model is established according to the thread parameters. Fig.15 The load ratio on each thread tooth of thread 1 to thread 6 under the same boundary conditions is calculated at the position of the bold short horizontal line shown in the figure. Fig.16 shown.

[0100] Table 1 Specific thread parameters of the present application thread and the comparative thread

[0101]

[0102] The three-dimensional models of threads 1 to 6 are established, and the variation curves of the preload and loose rotation angle of each thread with the vibration period under the same axial load and lateral displacement load are calculated, such as Fig.17 and Fig.18 It should be noted that Fig.18 The “-” in the loose angle indicates the direction of rotation, and counterclockwise rotation is a negative value.

[0103] From Table 1, Figure 16-18It can be seen that in thread 1 and thread 2, l<b1, the load proportion of the thread at the end position is large, the main load area is close to the end position, and under the same vibration cycle, the preload loss and the nut loosening angle are large; in thread 3, l>b1 and l<b2, the load proportion of the thread at the end position is reduced, and the load ratio at the starting position increases and exceeds the end position. Compared with threads 1 and 2, under the same vibration cycle, the preload loss and the nut loosening angle are reduced; in thread 4 and thread 5, l>b1 and l>b2, the load proportion of the thread at the end position is further reduced, and even some thread teeth are unloaded. The main load area is close to the starting position. Compared with thread 3, under the same vibration cycle, the preload loss and the nut loosening angle are further reduced; compared with thread 4 and thread 5, under the same vibration cycle, the preload loss and the nut loosening angle of thread 6 are further reduced, but l1>b5 of thread 6, the load borne by the first circle of thread 6 exceeds 50% of the total load, and the thread bearing performance begins to decrease. Specific implementation method 2:

[0105] The external thread is an external arc thread, the pitch of the external arc thread is constant and the pitch P1 = 6.35mm, the major diameter d = 48.3mm, the minor diameter d1 = 41.7mm, and the tooth width S of the external thread at the mid-diameter w =3.175mm, elastic modulus of external thread material E = 206Gpa, yield strength σ = 930Mpa. Axial load N = 0.7σA1.

[0106] The internal thread is a matching internal arc thread. The pitch of the internal arc thread is a gradual pitch and the pitch difference ΔP increases with the number of thread turns n'. The internal thread major diameter D = 49.6mm, minor diameter D1 = 44mm, tooth height H = 2.8, and the tooth width S of the internal thread at the middle diameter of the external thread n =2.2mm, the number of internal thread turns is n=10 turns.

[0107] Furthermore, the length of 10 turns of external thread L1 = 63.5 mm.

[0108] Further, b1 = 0.0023Pn = 0.14605 mm;

[0109] Further, b2 = 0.0038Pn = 0.2413 mm;

[0110] Further, b3 = 0.05P = 0.3175 mm;

[0111] Further, b4 = 0.02P = 0.127 mm;

[0112] Further, b5 = 0.01P = 0.0635 mm;

[0113] Furthermore, P1=6.35>S w +S n =5.475mm,δ=P1-S w -S n =0.875mm.

[0114] In this embodiment, all threads are based on the starting position, and the length difference l' between the inner and outer threads of any n' turns of threads 7 to 12 satisfies the equation Table 2 shows the specific parameters of threads 7 to 12.

[0115] Table 2 Specific thread parameters of thread 7 to thread 12

[0116]

[0117] refer to Fig.15 The load ratio on each thread tooth of threads 7 to 12 under the same boundary conditions is calculated at the position of the bold short horizontal line shown in the figure. Fig.19 The three-dimensional model of threads 7 to 12 is established, and the variation curves of the preload and loosening angle of each thread with the vibration period under the same axial load and lateral displacement load are calculated, as shown in Fig. 20 and Fig.21 It should be noted that Fig.21 The “-” in the loose angle indicates the direction of rotation, and counterclockwise rotation is a negative value.

[0118] In addition, the difference between the specific implementation mode 2 and the specific implementation mode 1 is that: taking the starting position as the starting point, the pitch difference ΔP between the internal and external threads in the specific implementation mode 2 increases with the increase of the number of thread turns n'. Starting from the starting position, the total load of the axial section of the external thread increases with the increase of the number of thread turns n'. Taking the first two circles of threads as an example, when the pitch difference between the internal and external threads is constant, the total deformation of the first circle of threads is equal to the pitch difference between the internal and external threads. Since the slight deformation of the first circle of internal and external threads will accumulate in the second circle of threads, the effective gap of the second circle of threads is smaller than the pitch difference between the internal and external threads. Then, the total deformation of the second circle of threads is less than one pitch difference, that is, the total load of the first circle of threads is greater than the load of the second circle. When the pitch of the internal and external threads increases with the number of thread turns, the total load of the second circle of threads can be increased, that is, the load ratio between the first circle and the second circle of threads is prevented from being too large. This is achieved by comparison. Fig.16 and Fig.19 Therefore, when a larger difference in length between the internal and external threads is obtained or when the same difference in length between the internal and external threads is obtained, the gradual pitch thread in the second embodiment can reduce the total load of the first turn of the thread and improve the load-bearing safety of the thread.

[0119] In other embodiments, the total average elongation l of the equivalent force-bearing cylinder at any n' number of turns can also be directly used. w1 To represent the total elongation l of any n' number of turns of external thread w Of course, we can also directly use the total average compression of the equivalent hollow cylinder at any n' number of circles as l n1 To represent the total compression of any n' number of internal threads l n .

[0120] In other implementations: according to different requirements, when the simplification methods are different, the simplified results of the equations of the length changes l'1 and l'2 of the internal and external threads may be different.

[0121] In other embodiments: according to k, k c The specific values ​​of b1 and b2 will be different if the specific values ​​of K are different.

[0122] In other embodiments: the gap at the middle diameter of the external thread is equal to the tooth width S of the internal thread n , that is: PS w =S n .

[0123] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. The patent protection scope of the present invention shall be based on the claims. All equivalent structural changes made using the contents of the description and drawings of the present invention should also be included in the protection scope of the present invention.

Claims

1. A non-equidistant anti-loosening threaded connection pair, comprising an internal thread and an external thread, wherein the pitch of the internal thread is greater than the pitch of the external thread, and characterized in that: n turns of the length difference between the internal thread and the external thread So that the screwing area of ​​the internal and external threads includes a main load area near the starting position and a secondary load area near the end position, wherein: b1 is the comprehensive reference boundary 1; P is the pitch of the external thread; n is the total number of turns of the screwing area of ​​the internal and external threads; k is the load coefficient and 0<k<1; σ is the yield strength of the external thread material, E w is the elastic modulus of the external thread material; K is the comprehensive reference coefficient and 0.8≤K≤10; the length difference between the internal thread and the external thread of the first thread is l1<b3=0.05P, b3 is the comprehensive reference boundary three; the total axial clearance when the internal and external threads are used together is δ=PS w -S n , where S w S is the tooth width of the external thread at the mid-diameter. n is the tooth width of the internal thread at the middle diameter of the external thread, then l≤δ.

2. The non-equidistant anti-loosening threaded connection pair according to claim 1, characterized in that: Considering k and k c , the value of K is limited to b1=0.0023Pn, so l>b1=0.0023Pn.

3. The non-equidistant anti-loosening threaded connection pair according to claim 1 or 2, characterized in that: If the internal and external thread engagement area is taken as the starting point, and the axial load on the external thread teeth at any n' turns is F(n'), then 0≤n'≤n, N is the axial load borne by the external thread; if the load borne by each circle of thread teeth is equal, that is At this time, the length change l'1 of the internal and external threads for any number of n' turns is equal to the total elongation l of the external thread w Total compression with internal thread l n The sum of Where: k1 and k2 are constants; A1 is the stress cross-sectional area of ​​the external thread, E n is the elastic modulus of the internal thread material, A2 is the stress cross-sectional area of ​​the internal thread; let E w A1 and E n The ratio of A2 is k3, and let k1+k2k3=K, simplifying the formula of l'1 to: Then according to N=kσA1, we can get When n'=n, use Available When the length difference between the n-turn internal thread and the external thread is l>l'1(n), l is sufficient to provide the length l'1(n) required for the deformation of the internal and external threads, so we get 4. The non-equidistant anti-loosening threaded connection pair according to claim 1 or 2, characterized in that: n turns of the length difference between the internal thread and the external thread Among them: b2 is the comprehensive reference boundary 2.

5. The non-equidistant anti-loosening threaded connection pair according to claim 4, characterized in that: Considering k and k c , the value of K is limited to b2=0.0036Pn, so l>b2=0.0036Pn.

6. The non-equidistant anti-loosening threaded connection pair according to claim 4, characterized in that: If the internal and external thread engagement area is taken as the starting point, and the axial load on the external thread teeth at any n' turns is F(n'), then 0≤n'≤n, N is the axial load borne by the external thread; That is, as the number of threads decreases in the range of 0 to n turns, the main load area is closer to the starting position, and at n'=n, F(n')=0, and there is no force between the internal and external threads. At this time, the length change l'2 of the internal and external threads for any n' number of turns is equal to the total elongation l of the external thread. w Total compression with internal thread l n The sum of Where: k1 and k2 are constants; A1 is the stress cross-sectional area of ​​the external thread, E n is the elastic modulus of the internal thread material, A2 is the stress cross-sectional area of ​​the internal thread; let E w A1 and E n The ratio of A2 is k3, and let k1+k2k3=K, then according to N=kσA1, when n'=n, When , the formula of l'2 can be simplified to When the length difference between the n-turn internal and external threads is l>l'2(n), l is sufficient to provide the length l'2(n) required for the deformation of the internal and external threads, so we get 7. The non-equidistant anti-loosening threaded connection pair according to claim 1 or 2, characterized in that: The length difference between the internal thread and the external thread of the first thread circle is l1<b4=0.02P, and b4 is the comprehensive reference boundary four.

8. The non-equidistant anti-loosening threaded connection pair according to claim 7, characterized in that: The length difference between the internal thread and the external thread of the first thread circle is l1<b5=0.01P, and b5 is the comprehensive reference boundary five.

9. The non-equidistant anti-loosening threaded connection pair according to claim 1 or 2, characterized in that: The pitch difference ΔP(n1) between the internal thread and the external thread near the starting position is not greater than the pitch difference ΔP(n2) between the internal thread and the external thread far from the starting position, that is, n1<n2, ΔP(n1)≤ΔP(n2).

10. The non-equidistant anti-loosening threaded connection pair according to claim 1 or 2, characterized in that: When the internal and external threads are used together, the total axial clearance δ=PS w -S n >0, that is, P>S w +S n , where S w S is the tooth width of the external thread at the mid-diameter. n It is the tooth width of the internal thread at the middle diameter of the external thread.

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