Non-equidistant Anti-loosening threaded connection pair

Abstract

The present invention relates to the field of non-standard fasteners, and provides a non-equidistant anti-loosening threaded connection pair. The non-equidistant anti-loosening threaded connection pair comprises an inner thread and an outer thread. The pitch of the inner thread is greater than that of the outer thread. A length difference between the inner thread and the outer thread over n turns is as shown in formula (1). A screwing area of the inner thread and the outer thread comprises a primary load area close to a start position and a secondary load area close to an end position. The inner thread in the secondary load area has a load much smaller than that in the primary load area, or even unloaded, so that the effective action length of a bolt is increased. Load concentration areas are separated from main slip areas of the inner thread and the outer thread, the load concentration areas are located near the start position, the slip areas extend from the end position to the start position, and when a bolt rod bends, the secondary load area begins to make gradual contact and the interaction force between the inner thread and the outer thread is increased, helping to distribute the force generated by the bending of the bolt rod and reduce the possibility of relative slip between the inner thread and the outer thread, thereby achieving a better anti-loosening effect.

Description

A non-equidistant anti-loosening threaded connection pair Technical Field

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

[0002] Threaded connections, characterized by strong connection performance, easy disassembly, and simplified manufacturing, are widely used in fields such as wind power generation, shipbuilding, automotive manufacturing, aerospace, and mechanical products. However, when threaded connections are subject to external disturbances, bolts often loosen and fail, leading to serious safety incidents. Existing anti-loosening theories indicate that the primary cause of thread loosening is insufficient friction between the internal and external threads, resulting in relative slip.

[0003] The specific process is: when the thread is subjected to a lateral load in a 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 direction of the lateral load, and the bolt rod will produce a certain degree of 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 relative slip will occur 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 slip 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 cannot prevent the expansion of the slip area. Therefore, the threaded connection pair is prone to loosening.

[0005] Summary of the Invention

[0006] The purpose 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 support surface, resulting in that when the thread near the support surface completely slips, the friction between the internal and external threads away from the support surface is small, and the expansion of the sliding area cannot be prevented, which in turn causes the threaded connection pair to easily loosen.

[0007] To achieve the above-mentioned purpose, the non-equidistant anti-loosening threaded connection pair in the present invention adopts the following technical solutions:

[0008] A non-equidistant anti-loosening threaded connection pair includes an internal thread and an external thread, 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 ending position, where: b1 is the comprehensive reference boundary 1; P is the pitch of the external thread; n is the total number of turns of the internal and external thread screwing area; 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.

[0009] 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 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 slippage between the internal and external threads, thereby achieving a better anti-loosening effect.

[0010] Furthermore, considering k, k c , the value of K is limited to b1=0.0023Pn, so l>b1=0.0023Pn.

[0011] The beneficial effect of the above technical solution is that: a specific lower limit value of l is given to ensure the anti-loosening effect.

[0012] 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' turns is F(n'), then 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 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 nThe 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 deformation of the internal and external threads, so we get

[0013] The beneficial effect of the above technical solution is that: given the load conditions such as F(n'), the The overall process takes into account multiple factors and simplifies the formula to facilitate subsequent verification and comparison.

[0014] Furthermore, the length difference between n turns of internal thread and external thread Among them: b2 is the comprehensive reference boundary 2.

[0015] The beneficial effect of the above technical solution is that it further reduces the lower limit of the length difference l between n turns of internal thread and external thread, thereby ensuring a better anti-loosening effect.

[0016] Furthermore, considering k, k c , the value of K is limited to b2=0.0036Pn, so l>b2=0.0036Pn.

[0017] The beneficial effect of the above technical solution is that it provides a new specific value of the lower limit, which facilitates the design, manufacture and processing of the threaded connection pair.

[0018] 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' turns is F(n'), then N is the axial load borne by the external thread; That is, F(n') decreases with the number of thread turns in the range of 0 to n turns, 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. 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 nThe ratio of A2 is k3, and let k1 + k2k3 = K. Then, according to N = kσA1, and when n' = n, the formula for l'2 can be simplified when When the length difference l between the internal and external threads in n turns is greater than l'2(n), l is sufficient to provide the length l'2(n) required for the deformation of the internal and external threads. Therefore,

[0019] The beneficial effect of the above technical solution is that it gives the overall process of calculating F(n') within the range of 0 to n turns as the number of thread turns gradually decreases. Multiple factors are considered in the process, and the formula is simplified for later verification and comparison.

[0020] Furthermore, the length difference l1 between the internal and external threads of the first turn of the thread is less than b3 = 0.05P, where b3 is the comprehensive reference boundary three.

[0021] The beneficial effect of the above technical solution is that it gives the upper limit of the length difference l1 between the internal and external threads of the first turn of the thread, preventing the axial load of the external thread from being borne by one turn of the thread and protecting the first turn of the thread.

[0022] Furthermore, the length difference l1 between the internal and external threads of the first turn of the thread is less than b4 = 0.02P, where b4 is the comprehensive reference boundary four.

[0023] The beneficial effect of the above technical solution is that it further reduces the upper limit of the length difference l1 between the internal and external threads of the first turn of the thread, ensuring that the load borne by the first turn of the thread is less than 70% of the total load.

[0024] Furthermore, the pitch difference ΔP(n1) between the internal and external threads near the starting position is not greater than the pitch difference ΔP(n2) between the internal and external threads far from the starting position, that is, n1 < n2, ΔP(n1) ≤ ΔP(n2).

[0025] 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 of the number of thread turns, the bearing capacity of the first turn of the thread can be reduced, and the stress concentration phenomenon of the first turn of the thread can be reduced. Through comparative verification, it is found that the load ratio of the first turn of the thread is greater when ΔP is a fixed value.

[0026]

[0027] ​

[0028] Furthermore, when the internal and external threads are used together, the total axial clearance 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.

[0029] The beneficial effect of the above technical solution is to prevent the tooth biting phenomenon caused by insufficient axial clearance.

[0030] 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.

[0031] 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, which may cause tooth biting. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] FIG1 is a basic external thread profile diagram of the present invention;

[0033] FIG2 is a basic internal thread profile diagram of the present invention;

[0034] FIG3 is a tooth profile diagram of the internal thread of the non-equidistant anti-loosening threaded connection pair of the present invention;

[0035] FIG4 is a schematic diagram showing the principle of preventing tooth biting of the internal and external threads involved in the present invention;

[0036] FIG5 is a diagram showing the relationship between the lengths of the internal and external threads when the internal and external threads are not loaded;

[0037] FIG6 is a schematic diagram of the starting position and the ending position of the non-equidistant anti-loosening threaded connection pair during loading according to the present invention;

[0038] FIG7 is a schematic diagram of the force applied to the external thread in the screwing area between the internal and external threads of the present invention;

[0039] FIG8 is a common trend diagram of the F(n') curve in the present invention;

[0040] FIG9 is a schematic diagram of the effective length from the equivalent action point to the support point of a traditional equidistant thread;

[0041] FIG10 is a schematic diagram of the effective length from the equivalent action point to the support point of a non-equal pitch thread;

[0042] FIG11 is a schematic diagram of the external thread involved in the present invention simplified into an equivalent load-bearing cylinder;

[0043] FIG12 is a schematic diagram showing the average elongation of the tiny cylinder and the elongation at the cylindrical surface in FIG11 ;

[0044] FIG13 is a schematic diagram of the internal thread involved in the present invention simplified into an equivalent force-bearing hollow cylinder;

[0045] FIG14 is a schematic diagram showing the average compression amount and the compression amount at the inner cylindrical surface of the tiny hollow cylinder in FIG13;

[0046] Figure 15 shows the numbering and load value locations of the external thread teeth;

[0047] Figure 16 shows the load ratio on each thread tooth of threads 1 to 6 under the same boundary conditions;

[0048] FIG17 is a graph showing the variation of the preload percentage of threads 1 to 6 with the vibration period under the same axial load and lateral displacement load;

[0049] FIG18 is a graph showing the change in loosening angle of threads 1 to 6 with the vibration period under the same axial load and lateral displacement load;

[0050] Figure 19 shows the load ratio on each thread tooth of threads 7 to 12 under the same boundary conditions;

[0051] FIG20 is a graph showing the change in preload percentage of threads 7 to 12 with the vibration period under the same axial load and lateral displacement load;

[0052] FIG21 is a graph showing the change in the loosening angle of threads 7 to 12 with the vibration period under the same axial load and lateral displacement load. DETAILED DESCRIPTION

[0053] The features and performance of the present invention are further described in detail below with reference to the embodiments.

[0054] By setting a lower limit for the length difference, l, between the n turns of internal and external threads, the present invention ensures that the screwed-in area of ​​the internal and external threads includes a primary load zone near the starting position and a secondary load zone near the ending position. This helps increase the effective length of the bolt, distributes the forces generated by the bending of the bolt shank, and reduces the possibility of relative slippage between the internal and external threads, achieving a better anti-loosening effect. The present invention also sets an upper limit for the length difference, l1, between the internal and external threads of the first thread turn to prevent the first thread from bearing the axial load of the external thread.

[0055] Example 1 of the non-equidistant anti-loosening threaded connection pair of the present invention:

[0056] A 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. The pitch of both threads can be constant, or one can be a constant-pitch thread and the other a gradual-pitch thread. Gradual-pitch threads are obtained by adjusting the pitch based on the basic thread profile. The adjustment is based on the basic thread profile and is achieved by cutting or increasing the thread tooth width or adding a transition structure at the root of the thread. 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 with a width of one standard pitch along the axial direction.

[0057] As a specific embodiment, the external thread is a constant pitch thread, and the external thread tooth profile is a basic external thread tooth profile, as shown in Figure 1, 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 pitch diameter d2 is S w , the yield strength of the external thread material is σ, the elastic modulus of the external thread material is E w .

[0058] The basic internal thread profile is shown in Figure 2. The basic internal thread profile has a pitch P, a major diameter D, a minor diameter D1, the number of internal thread turns n, and an elastic modulus E of the internal thread material. n .

[0059] As a specific embodiment, the internal thread is a gradual pitch thread, and is based on the basic internal thread profile. The basic thread profile remains unchanged, and the internal thread pitch is increased by adding a transition structure. As shown in Figure 3, the internal thread profile on the plane through the axis is composed of multiple basic internal thread profiles and transition structures G spliced ​​end to end, and the longitudinal section of the transition structure G is a straight line segment. The internal thread pitch gradually increases along the axis direction. The internal thread pitch 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 external thread engagement area. Therefore, the internal thread pitch P2 is a non-constant value, and the internal thread pitch is greater than the external thread basic thread profile pitch, that is, P2>P. The pitch adjustment amount △P of the internal thread (i.e., gradual pitch thread) is P2-P. Since the external thread pitch P1=P, the pitch adjustment amount △P of the gradual pitch thread is the pitch difference between the internal and external threads.

[0060] As shown in Figures 3 and 5, the tooth width of the internal thread at the middle diameter d2 of the external thread is S n The total axial fit 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 tooth biting.

[0061] Furthermore, as shown in Figure 4, when the pitch of the internal and external threads is equal (see the graph where P2 = P1, upper figure in Figure 4), the length of both threads is L1. When the pitch of the internal thread is greater than the pitch of the external thread (see the graph where P2 > P1, lower figure in Figure 4), the length of the internal thread is L2, and the straight segment of the internal thread gradually contacts the straight segment of the external thread. As can be easily seen from Figure 4, in the upper figure, the pitch of the internal and external threads is equal, one side of the internal and external threads is in contact, while the other side is not in contact, and the axial gap between the internal and external threads is δ. In the lower figure, the internal and external threads are in contact at the far left. Because the pitch of the internal thread is greater than the pitch of the external thread, the internal and external threads begin to separate from the contact position. At the far right, the other sides of the internal and external threads gradually approach each other, and 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 have an interference fit, making assembly difficult. Therefore, l≤δ, which can prevent the tooth biting caused by insufficient axial clearance.

[0062] In addition, combined with what is shown in FIG5 , with the starting position section Q as the starting point, the length of the external thread of any n' number of turns is L1=n'P1=n'P, 0≤n'≤n, and the length of the internal thread of any n' number of 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' number of turns with the starting position as the starting point, that is, the length adjustment amount of the gradual pitch thread.

[0063] For the convenience of description, the present invention sets a starting position and an ending position, as shown in Figures 5 and 6. Taking the bolt 1 and the 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 (traditionally considered as the support surface, that is, the end face of the nut 2 used to press the connected parts). 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.

[0064] The number of turns of an internal thread is n. When an internal and external thread are used together, n turns of internal thread must be used in conjunction with n turns of external thread. In the absence of load deformation, starting from the starting position, any n' turns of internal thread (0 < n' ≤ n) will be longer than the external thread. The pitch difference ΔP(n1) between the internal and external threads near the starting position is less than or equal to the pitch difference ΔP(n2) between the internal and external threads away from the starting position, that is, n1 < n2, ΔP(n1) ≤ ΔP(n2).

[0065] As shown in Figure 7, 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 borne by the n turns of thread teeth is equal to the axial load N borne by the external thread, that is,

[0066] When a traditional equidistant thread is loaded, the internal and external threads of each circle contact simultaneously. Due to the cumulative effect of the load, the axial load on the external thread of the traditional equidistant thread is F(n'), which conforms to curve 1 in Figure 8 (that is, curve 1 is a common thread with equal distances between the internal and external threads). The axial load F(n') on the external thread near the end position is larger, while the axial load F(n') on the external thread 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, as shown in Figure 9.

[0067] 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 start 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 ending position decreases. The equivalent action point B of the internal thread on the external thread approaches the section Q at the starting position, as shown in Figure 10.

[0068] 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 thread is l B , l A Less than l B , under the action of 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, the matching method in Figure 9 is more likely to produce relative slip.

[0069] Therefore, in this embodiment, the length difference between n turns of internal thread and external thread is limited to l>b1=0.0023Pn, where 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. 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 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 bends, 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 slippage between the internal and external threads, thereby achieving a better anti-loosening effect.

[0070] The specific calculation process is given below. For the convenience of calculation, the present invention assumes that all n circles are engaged, and simplifies the n-circle external thread into an equivalent force-bearing cylinder. As shown in Figure 11, 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, respectively. 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 opposite to the axial load N in direction, 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 small external cylindrical surface at any n' number of circles is f1(n'), and the resultant force of the load on all small external 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

[0071] A small cylinder is cut off at any n' turn position 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 deduce the average elongation of a small 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

[0072] As shown in Figure 12, the direction of the surface load on 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, which makes the elongation at the outer cylindrical surface of the micro-cylinder smaller than the average elongation dl. w1, the outer cylindrical surface of the equivalent load-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 taking the starting position as the starting point, the total elongation of the external thread with any n' turns is

[0073] As shown in Figure 13, 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 borne by the equivalent force-bearing hollow cylinder at the ending position section Z is F. N , the direction is from the end position to the starting position, the force between the internal and external threads is simplified to the inner cylindrical surface of the equivalent hollow cylinder under load, the surface load and the axial force F N The 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' turns 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 thread are completely evenly loaded, that is, when the load of each circle of thread is equal,

[0074] A small hollow cylinder is cut off 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 loaded hollow cylinder at any n' number of turns starting from the starting section:

[0075] As shown in Figure 14, 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·dln1 , 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 n' turns is

[0076] Furthermore, starting from the starting position, 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:

[0077] When the internal and external thread materials, i.e. the nut dimensions, are selected, E n and A2 are both constant, so E w A1 and E n The ratio k3 of A2 is a constant. In order to facilitate the 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 to the elastic modulus of the thread 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 uses an equal load design, which assumes that each thread thread bears an equal load. When the length difference l between the n-turn internal and external threads is less than the length change l'1(n) between the n'-turn internal and external threads, i.e., l < l'1(n), the length difference l between the internal and external threads is insufficient to provide the length l'1(n) required for deformation. The threads at the end position need to bear more load. The load at the end position is greater than the load at the start position, and the main load zone is close to the end position. In this case, the variation trend of F(n') is similar to that shown in curve 2 in Figure 8. When l = l'1(n), the length difference l between the internal and external threads just provides the length l'1(n) required for deformation, and the variation trend of F(n') is similar to that shown in curve 3 in Figure 8. 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 deformation, and 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 variation trend of F(n') is similar to that shown in curve 4 in Figure 8.

[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 end 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 n turns of internal thread and 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 l>b2=0.0036Pn, 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, and That is, in the above calculation process Change to The total elongation of the external thread l can be calculated by taking the starting position as the starting point and calculating the length change of the internal and external threads l'2 for any n' turns. w Total compression with internal thread l n The sum of , then: According to the same simplified method (let E w A1 and E nThe ratio of A2 is k3, and let K = k1 + k2k3, where K is the comprehensive reference coefficient. Then, according to N = kσA1, where σ is the yield strength of the external thread material, k is the load coefficient and 0 < k < 1. At the same time, when n' = n, (at this time), we can obtain

[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 at the nth turn of the internal and external threads is 0, and the change trend of F(n') is similar to that shown in Curve 5 of Figure 8. 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 at less than n turns of the internal and external threads is 0. In this case, the change trend of F(n') is similar to that shown in Curve 6 of Figure 8.

[0084] Furthermore, when l ≥ l'2(n), there is a situation where the internal and external threads in the secondary load area do not mesh. Considering the load coefficient k, the ratio k of the yield strength to the elastic modulus of the material c and the comprehensive reference coefficient K, the range of the length difference l between the internal and external threads within n turns is: Further considering the values of k, k c and K, it is specified that b2 = 0.0036Pn. Therefore, l > b2 = 0.0036Pn.

[0085] In addition, when n = 1, the length change amount of the internal and external threads in the first turn is To prevent the axial load of the external thread from being borne by one turn of the thread (starting from the starting position), the length difference l1 between the internal and external threads of the first turn of the thread should be less than the length change amount l1′(1) of the internal and external threads in the first turn, that is Considering the load coefficient k, the ratio k of the yield strength to the elastic modulus of the material c and the comprehensive reference coefficient K, the range of the length difference l1 between the internal and external threads of the first turn of the thread is: l1 < b3 = 0.05P, where b3 is the comprehensive reference boundary three.

[0086] Furthermore, to ensure that the load borne by the first turn of the thread is less than 70% of the total load, the range of the length difference l1 between the internal and external threads of the first turn of the thread is: l1 < b4 = 0.02P, where b4 is the comprehensive reference boundary four. [[ID=二十九]]

[0087] Furthermore, to ensure that the load borne by the first turn of the thread is less than 50% of the total load, the range of the length difference l1 between the internal and external threads of the first turn of the thread is: l1 < b5 = 0.01P, where b5 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.

[0089] Specific implementation method one:

[0090] The external thread is an external arc thread with a constant pitch of P1 = 6.35 mm, a major diameter d = 41.5 mm, a minor diameter d1 = 36.5 mm, and a tooth width S at the mid-diameter of the external thread. 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 is n = 2.3 mm, and the number of internal thread turns is n = 10. Since the pitch of both the internal and external threads is constant, in this embodiment, the pitch difference ΔP(n1) between the internal and external threads near the starting position is equal to the pitch difference ΔP(n2) between the internal and external threads away 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] Furthermore, b1=0.0023Pn=0.14605mm;

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

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

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

[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 Thread 6 and gives the determination conditions between them and the boundaries. And the length difference l between the inner and outer threads of 10 turns of Threads 1 to Thread 6 is less than δ. A finite element model is established according to the thread parameters, and according to the bold short horizontal line position shown in Figure 15, the load ratios on each thread tooth of Threads 1 to Thread 6 under the action of the same boundary conditions are calculated, as shown in Figure 16.

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

[0101] Three-dimensional models of Threads 1 to Thread 6 are established, and the curves of the pre-tightening force and the loosening rotation angle changing with the vibration period under the action of the same axial load and transverse displacement load are calculated, as shown in Figures 17 and 18. It should be noted that the "-" of the loosening rotation angle in Figure 18 represents the rotation direction, and the counterclockwise rotation is negative.

[0102] As can be seen from Table 1 and Figures 16 - 18, for Threads 1 and 2, l < b1, the load ratio at the termination position of the thread is relatively large, and the main load area is close to the termination position. Under the action of the same vibration period, the pre-tightening force loss and the nut loosening rotation angle are relatively large; for Thread 3, l > b1 and l < b2, the load ratio at the termination position of the thread decreases, and the load ratio at the starting position increases and exceeds that at the termination position. Compared with Threads 1 and 2, under the action of the same vibration period, the pre-tightening force loss and the nut loosening rotation angle are reduced; for Threads 4 and 5, l > b1 and l > b2, the load ratio at the termination position of the thread further decreases, and there is even no load on some thread teeth. The main load area is close to the starting position. Compared with Thread 3, under the action of the same vibration period, the pre-tightening force loss and the nut loosening rotation angle are further reduced; for Thread 6 compared with Threads 4 and 5, under the action of the same vibration period, the pre-tightening force loss and the nut loosening rotation angle are further reduced, but for Thread 6, l1 > b5, and the load borne by the first turn of Thread 6 exceeds 50% of the total load, and the thread bearing performance begins to decrease.

[0103] Specific Embodiment 2:

[0104] The external thread is an external arc thread. The pitch of the external arc thread is constant, the pitch P1 = 6.35 mm, the major diameter d = 48.3 mm, the minor diameter d1 = 41.7 mm, and the tooth width S of the external thread at the pitch diameter w = 3.175 mm. The elastic modulus E of the external thread material is 206 Gpa, and the yield strength σ is 930 Mpa. The axial load N = (0.7σA1).

[0105] 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 is n =2.2mm, the number of internal thread turns is n=10 turns.

[0106] Furthermore, the length of 10 turns of external thread L1 = 63.5 mm.

[0107] Furthermore, b1=0.0023Pn=0.14605mm;

[0108] Further, b2 = 0.0038Pn = 0.2413 mm;

[0109] Further, b3 = 0.05P = 0.3175 mm;

[0110] Further, b4=0.02P=0.127mm;

[0111] Further, b5 = 0.01P = 0.0635 mm;

[0112] Furthermore, P1=6.35>S w +S n =5.475mm,δ=P1-S w -S n =0.875mm.

[0113] In this embodiment, all threads are based on the starting position, wherein the length difference l' between the inner and outer threads of threads 7 to 12 with any number of n' turns satisfies the equation Table 2 shows the specific parameters of threads 7 to 12.

[0114] Table 2 Specific thread parameters of thread 7 to thread 12

[0115] Referring to the locations of the bold dashed lines in Figure 15, the load ratios on each thread tooth for threads 7 through 12 under the same boundary conditions were calculated, as shown in Figure 19. A three-dimensional model of threads 7 through 12 was established, and the preload and loosening angle of each thread under the same axial load and lateral displacement load were calculated as a function of the vibration period, as shown in Figures 20 and 21. It should be noted that the "-" in the loosening angle in Figure 21 indicates the direction of rotation, with counterclockwise rotation being a negative value.

[0116] In addition, the difference between the second embodiment and the first embodiment is that: with the starting position as the starting point, the pitch difference ΔP between the internal and external threads in the second embodiment increases with the increase of the number of thread turns n'. Starting from the starting position, the total load on 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 and second circles of threads is prevented from being too large. This can also be seen by comparing Figures 16 and 19. Therefore, while achieving a larger difference in length between the internal and external threads or while achieving the same difference in length between the internal and external threads, 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.

[0117] 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 .

[0118] 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.

[0119] 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.

[0120] 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 , namely: PS w =S n .

[0121] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. The scope of patent protection of the present invention shall be based on the claims. Any equivalent structural changes made using the description and drawings of the present invention shall be included in the scope of protection 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.

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 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 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 l1 between the internal thread and the external thread of the first turn of the thread < b3 = 0.05P, where b3 is the comprehensive reference boundary three.

8. The non-equidistant anti-loosening threaded connection pair according to claim 7, characterized in that: The length difference l1 between the internal thread and the external thread of the first turn of the thread < b4 = 0.02P, where b4 is the comprehensive reference boundary four.

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

10. 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).

11. 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 , 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.

12. 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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