Non-equal-pitch periodic alternating thread connection pair and design method thereof
By designing a non-equal pitch periodic alternating threaded connection pair, the alternating pitch structure is used to increase radial pressure in static and interfere with energy transmission dynamically, the problem of bolt loosening is solved, and more efficient anti-loosening effect and energy dispersion is achieved, suppressing micro-wear, optimizing load distribution, and forming mechanical interlocking.
Patent Information
- Application Number
- CN202510654436.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-21
- Publication Date
- 2025-08-15
AI Technical Summary
In the prior art, vibration and bolt fatigue lead to loosening or wear of the bolts, which in turn leads to relative displacement between the connectors and between the connectors and the bolt nuts, losing the connection effect.
A non-equal pitch periodic alternating thread connection pair is designed, consisting of a standard thread side and a non-equal pitch side. The alternating pitch structure increases radial pressure under static, interferes with the energy transfer path under dynamic load, realizes energy dispersion and cancellation, and blocks the loosening mechanism.
It improves the anti-loosening ability of threaded connections, suppresses micro-wear and energy accumulation, optimizes load distribution, broadens the natural frequency range, avoids a single formant peak, forms a mechanical interlocking effect, and blocks the loosening mechanism.
Smart Images
Figure CN120487748A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the field of non-standard fasteners, and particularly relates to a non-uniform pitch periodically alternating thread connection pair and a design method thereof. Background Art
[0002] Vibration and bolt fatigue can cause the bolts to loosen or wear, which in the long run will lead to the failure of the bolt preload, and then cause relative displacement between the connecting parts and between the connecting parts and the bolts and nuts, resulting in loss of the connection function. Summary of the Invention
[0003] Purpose of the invention: To solve the problems raised in the background technology, the present invention proposes a non-equal pitch periodically alternating threaded connection pair and a design method thereof, which can be used in all fields requiring the application of threaded pairs.
[0004] Technical solution: A non-uniform pitch periodic alternating thread connection substructure, consisting of several minimum period connection substructures;
[0005] The minimum period connection pair structure is composed of a standard thread side and a non-equidistant periodic alternating thread side; within the minimum period, the difference between the total pitch of the standard thread side and the total pitch of the non-equidistant periodic alternating thread side is constant;
[0006] The non-equidistant periodic alternating thread side adopts two sizes of pitch, including a first pitch and a second pitch, and the first pitch is greater than the second pitch; the first pitch and the second pitch appear alternately in a regular manner so that the difference between the total pitch of the standard thread side and the total pitch of the non-equidistant periodic alternating thread side within the minimum period or the effective working section is constant.
[0007] Furthermore, the difference between the total pitch of the standard thread side and the total pitch of the non-equidistant periodic alternating thread side is less than or equal to the maximum tolerance of the thread profile plus the maximum elastic deformation of the material properties of the thread profile, and is greater than or equal to zero.
[0008] Furthermore, the first pitch is less than or equal to the pitch of the standard thread side plus the maximum tolerance of the thread profile plus the maximum elastic deformation of the material properties of the thread profile, and is greater than the pitch of the standard thread side.
[0009] Furthermore, the second pitch is less than or equal to the pitch of the standard thread side and greater than the pitch of the standard thread side minus the maximum tolerance of the thread profile minus the maximum elastic deformation of the material properties of the thread profile.
[0010] The present invention proposes a design method for a non-uniform pitch periodically alternating thread connection pair, comprising the following steps:
[0011] Step 1: Determine the range of the first pitch of the non-equidistant periodic alternating thread side by calculation; the range of the first pitch is greater than the pitch of the mating standard thread side, and less than or equal to the pitch of the mating standard thread side plus the maximum tolerance of the thread profile plus the maximum elastic deformation of the material properties of the thread profile;
[0012] Step 2: Within the calculation range, the size of the first pitch of the non-equidistant periodic alternating thread side is determined by the idling torque. A small interference fit is formed between the first pitch of the non-equidistant periodic alternating thread side and its mating standard thread side. The interference fit is determined by the idling torque.
[0013] Step 3: Determine the size of the second pitch of the non-equidistant periodic alternating thread side, ensuring that the size of the second pitch is less than or equal to the pitch of the mating standard thread side and greater than the pitch of the mating standard thread side minus the maximum tolerance of the thread profile minus the maximum elastic deformation of the material properties of the thread profile;
[0014] Step 4: By adjusting the difference between the total pitch of the standard thread side and the total pitch of the non-equidistant periodic alternating thread side in the working area, the standard thread side and the non-equidistant periodic alternating thread side are overall interfered with each other in the working area, and the first pitch of the standard thread side and the non-equidistant periodic alternating thread side are interfered with each other, forming a double interference fit.
[0015] Furthermore, by changing the size of the second pitch of the non-equidistant periodic alternating thread side in the working area, the minimum period and the difference between the total pitch of the standard thread side and the total pitch of the non-equidistant periodic alternating thread side in the working area can be adjusted.
[0016] Beneficial effects: Compared with the prior art, the present invention has the following advantages:
[0017] (1) The present invention increases the radial pressure between threads statically through an alternating pitch structure, improving the anti-loosening capability of the thread pair. It also more efficiently disrupts the energy transfer path under dynamic loads, achieving energy dispersion and offset, thereby more thoroughly blocking the loosening mechanism. Alternating pitch exhibits higher anti-loosening performance in vibration testing because its complex pitch pattern effectively suppresses fretting wear and energy accumulation.
[0018] (2) The present invention actively dissipates energy through structural design, especially forming local energy dissipation nodes in the alternating contact area, which has a more significant anti-loosening effect. The variable pitch design will change the equivalent stiffness of the thread pair, thereby affecting the natural frequency. In the area where the pitch increases, the stiffness decreases, which can locally reduce the natural frequency. When tightening, the standard thread is stretched, the contact surface is reduced, but an "elastic bite" effect can be produced. In the area where the pitch decreases: the stiffness increases, which can suppress low-frequency vibrations. When tightening, the standard thread is compressed, forming a local interference fit, which increases the contact surface pressure.
[0019] (3) Overall effect: Broadens the natural frequency range and avoids a single resonance peak. When there is a slight difference in pitch, additional radial pressure is generated on the contact surface of the two threads after tightening. This pressure increases friction between the threads: deformation of the contact surface increases friction between the threads, resisting loosening caused by lateral vibration or impact. Local deformation forms mechanical interlocking: The pitch difference forces the top and bottom of the thread to deform locally, forming a "wedge-tightening" effect, which hinders the rotation of the nut.
[0020] (4) The alternating pitch design also optimizes load distribution: the load of a traditional nut is concentrated on the first thread, while the alternating pitch may force the second and third threads to share more load, reducing stress concentration. The large thread itself is squeezed between the upper and lower threads on the standard side. After being loaded, the force of the upper thread on the standard side can be directly transferred to the lower thread on the standard side through the large thread, and then to the small thread. This makes the paired loaded threads form three or four threads that are collectively loaded (three or four depends on the magnitude of the force and the size of the small thread).
[0021] (5) The present invention can also form a standardized thread pair by setting a non-uniform pitch periodic alternating thread that matches the existing thread manufacturing process, and can also appropriately increase or decrease the pitch value of the alternating thread pair to increase or decrease the idling torque of the thread pair to match complex working conditions and special requirements. BRIEF DESCRIPTION OF THE DRAWINGS
[0022] Figure 1 This is a schematic diagram of a non-uniform pitch periodically alternating thread connection structure proposed by the present invention;
[0023] Figure 2 This is a structural diagram of an M10 bolt and nut manufactured using a non-uniform pitch periodically alternating thread connection structure proposed by the present invention;
[0024] Figure 3 This is a structural diagram of an M22 bolt made using the non-uniform pitch periodically alternating threaded connection structure proposed by the present invention. DETAILED DESCRIPTION
[0025] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings. It should be understood that these descriptions are only exemplary and are not intended to limit the scope of the present invention.
[0026] Example 1:
[0027] like Figure 1 As shown, this embodiment proposes a non-equal-pitch periodically alternating thread connection pair, which primarily consists of a standard thread side 1 and a non-equal-pitch periodically alternating thread side 2. While there is no distinction between internal and external threads, they are required to appear in pairs. Within the minimum period, the difference between the total pitch of the standard thread side 1 and the total pitch of the non-equal-pitch periodically alternating thread side 2 is constant.
[0028] The non-equidistant periodically alternating thread side 2 proposed in this embodiment will now be further described.
[0029] The non-equidistant periodic alternating thread side 2 proposed in this embodiment is divided into two pitches distinguished by the size of the matching standard thread. The two pitches are periodically and regularly staggered, and the overall pitch does not increase or decrease.
[0030] Among them, the first pitch is the large pitch a, which is less than or equal to the pitch of the standard thread side 1 + the maximum tolerance of the thread manufacturing + the maximum elastic deformation of the thread, and is greater than the pitch of the standard thread side 1.
[0031] Among them, the second pitch is a small pitch b that is smaller than the pitch of the standard thread side 1. The small pitch b is less than or equal to the pitch of the standard thread side 1 and greater than the pitch of the standard thread side 1 - the maximum tolerance of the thread manufacturing - the maximum elastic deformation of the thread (if there is no special requirement, select the standard side pitch value or a value infinitely close to the standard side pitch value) to minimize the negative impact of thread size differences.
[0032] The regular alternation of large pitch a and small pitch b makes the difference between the total pitch of the standard thread side and the total pitch of the non-equidistant periodic alternating thread side constant within the minimum period, and the structure within the minimum period runs through the entire thread area.
[0033] This embodiment proposes a non-uniform pitch, periodically alternating threaded connection that bridges the gap between non-standard and standard applications, complementing traditional standard threaded connections. This alternating pitch structure increases radial pressure between threads statically, enhancing the threaded connection's anti-loosening capabilities. Under dynamic loads, it more efficiently disrupts energy transfer paths, dissipating and offsetting energy, thereby more thoroughly blocking loosening mechanisms.
[0034] Example 2:
[0035] Figure 2The figure shows a schematic diagram of the non-uniform pitch periodically alternating threaded connection structure proposed in Example 1, applied to an 8.8-grade M10 bolt and a 8-grade M10 nut. The bolt has a standard 1.5mm pitch, while the nut has a non-uniform pitch periodically alternating thread with alternating pitches of 1.518mm and 1.482mm. Under lubrication, this embodiment has a no-load torque of 3 Nm and a tightening torque of 28 Nm.
[0036] Example 3:
[0037] Figure 3 The figure shows a schematic diagram of the non-uniform pitch periodically alternating threaded connection structure proposed in Example 1 applied to a 10.9-grade M22 bolt structure. The threaded hole has a 2.5mm pitch, and the bolt has alternating 2.547mm and 2.453mm pitch threads, creating a non-uniform pitch periodically alternating thread. Under lubrication, this embodiment has a no-load torque of 100 Nm and a tightening torque of 600 Nm.
[0038] Example 4:
[0039] This embodiment proposes a design method for a non-equidistant alternating thread connection pair, including the following steps:
[0040] Step 1: Determine the size of the first pitch, which is larger than the pitch of the standard thread side and whose maximum value is less than or equal to the pitch of the standard thread side plus the manufacturing tolerance plus the maximum elastic deformation of the material properties of its basic thread tooth profile.
[0041] In this step, the maximum elastic deformation plus the manufacturing tolerance determines the maximum pitch difference of the first pitch, that is, the first pitch is equal to the standard thread on the mating side plus its maximum elastic deformation plus the manufacturing tolerance. The tolerance can be found in the table. Elastic deformation ΔP = (2kkcK / 3)P, where P is the pitch of the standard thread side, K is the comprehensive reference coefficient and 0.8≤K≤4.5, k is the elastic deformation load coefficient and is equal to the ratio of the maximum load N (maximum force of elastic deformation) borne by the standard thread to the yield strength σ of the standard thread side material and the stress cross-sectional area A of the standard thread side, that is, k = N / σA. kc is the material coefficient and is equal to the ratio of the yield strength σ of the standard thread side material to the elastic modulus Ew of the standard thread side material, that is, kc = σ / Ew. Under the premise that the first pitch is greater than the pitch of the standard thread side and less than or equal to ΔP + maximum manufacturing tolerance. The size of the first pitch can be determined by the size of the idling torque to meet on-site needs.
[0042] Step 2: The second pitch is smaller than the pitch on the standard thread side and matches the size of the first pitch. Its size is less than or equal to the pitch on the standard thread side and larger than the pitch on the standard thread side - the maximum tolerance for thread manufacturing - the maximum elastic deformation of the thread. The thread corresponding to the first pitch and the thread corresponding to the second pitch cooperate with each other to ensure that the overall thread screwing continuity with the standard thread side is met. At the same time, the gap generated by the small size satisfies the elastic deformation generated by the thread corresponding to the first pitch against the standard thread side to prevent the thread from seizing. Ensure that within the minimum period, the difference between the total pitch of the standard thread side and the total pitch of the non-equidistant periodic alternating thread side is constant or zero, or the difference between the total pitch of the quasi-thread side in the working area and the total pitch of the non-equidistant periodic alternating thread side is constant or zero.
[0043] Step 3: A small interference fit is created between the first pitch of the non-equidistant, periodically alternating thread and the standard thread to increase inter-thread friction and radial force. This ensures the thread pair's anti-loosening performance. The amount of interference fit and anti-loosening performance can be determined based on the idling torque.
[0044] Step 4: By adjusting the minimum period and the difference between the total pitch of the standard thread side in the working area and the total pitch of the non-equidistant periodic alternating thread side (primarily by adjusting the second pitch size of the non-equidistant periodic alternating thread side), the threads in the working area can form an overall interference fit plus the first pitch interference fit, forming a double interference fit. This can better meet special anti-loosening requirements, such as shrink fitting or areas with large temperature fluctuations.
[0045] This embodiment utilizes an alternating pitch structure to statically increase radial pressure between threads, enhancing the thread pair's anti-loosening capability. Under dynamic loads, it more effectively disrupts the energy transfer path, dissipating and offsetting energy, thereby more thoroughly blocking the loosening mechanism. Alternating pitch exhibits enhanced anti-loosening performance in vibration testing because its complex pitch pattern effectively suppresses fretting wear and energy accumulation.
[0046] And this embodiment actively dissipates energy through structural design, especially forming local energy dissipation nodes in the alternating contact area, and the anti-loosening effect is more significant. The variable pitch design will change the equivalent stiffness of the thread pair, thereby affecting the natural frequency. In the area where the pitch increases, the stiffness decreases, and the natural frequency can be locally reduced. When tightening, the standard thread is stretched and the contact surface is reduced, but an "elastic bite" effect can be produced. In the area where the pitch decreases: the stiffness increases, which can suppress low-frequency vibrations. When tightening, the standard thread is compressed, forming a local interference fit, which increases the contact surface pressure.
[0047] Overall, the connection pair designed in this embodiment broadens the natural frequency range and avoids a single resonance peak. When there are slight differences in thread pitch, additional radial pressure is generated on the contact surface of the two threads after tightening. This pressure increases friction between the threads: deformation of the contact surface increases friction between the threads, resisting loosening caused by lateral vibration or impact. Local deformation creates a mechanical interlock: Pitch differences force local deformation of the thread crest and root, creating a "wedge-like" effect that hinders the nut from rotating.
[0048] The alternating pitch designed in this embodiment also optimizes the load distribution: the load of a traditional nut is concentrated on the first thread, while the alternating pitch may force the second and third threads to share more load, reducing stress concentration. The large thread itself is squeezed between the upper and lower threads on the standard side. After being stressed, the force of the upper thread on the standard side can be directly transferred to the lower thread on the standard side through the large thread, and then to the small thread. This allows the paired stressed threads to form three or four threads that are collectively stressed (three or four depends on the magnitude of the force and the size of the small thread).
Claims
1. A non-uniform pitch periodically alternating thread connection structure, characterized in that: It is composed of several minimum period connected substructures; The minimum period connection pair structure is composed of a standard thread side and a non-equidistant periodic alternating thread side; within the minimum period, the difference between the total pitch of the standard thread side and the total pitch of the non-equidistant periodic alternating thread side is constant; The non-equidistant periodic alternating thread side adopts two sizes of pitch, including a first pitch and a second pitch, and the first pitch is greater than the second pitch; the first pitch and the second pitch appear alternately in a regular manner so that the difference between the total pitch of the standard thread side and the total pitch of the non-equidistant periodic alternating thread side within the minimum period or the effective working section is constant.
2. The non-uniform pitch periodically alternating threaded connection pair according to claim 1, characterized in that: The difference between the total pitch of the standard thread side and the total pitch of the non-equidistant periodic alternating thread side is less than or equal to the maximum tolerance of the thread profile plus the maximum elastic deformation of the material properties of the thread profile, and is greater than or equal to zero.
3. The non-uniform pitch periodically alternating threaded connection pair according to claim 1, characterized in that: The first pitch is less than or equal to the pitch of the standard thread side plus the maximum tolerance of the thread profile plus the maximum elastic deformation of the material properties of the thread profile, and is greater than the pitch of the standard thread side.
4. The non-uniform pitch periodically alternating threaded connection pair according to claim 1, characterized in that: The second pitch is less than or equal to the pitch of the standard thread side and greater than the pitch of the standard thread side minus the maximum tolerance of the thread profile minus the maximum elastic deformation of the material properties of the thread profile.
5. A design method for a non-uniform pitch periodically alternating threaded connection pair, characterized by: The following steps are involved: Step 1: Determine the range of the first pitch of the non-equidistant periodic alternating thread side by calculation; the range of the first pitch is greater than the pitch of the mating standard thread side, and less than or equal to the pitch of the mating standard thread side plus the maximum tolerance of the thread profile plus the maximum elastic deformation of the material properties of the thread profile; Step 2: Within the calculation range, the size of the first pitch of the non-equidistant periodic alternating thread side is determined by the idling torque. A small interference fit is formed between the first pitch of the non-equidistant periodic alternating thread side and its mating standard thread side. The interference fit is determined by the idling torque. Step 3: Determine the size of the second pitch of the non-equidistant periodic alternating thread side, ensuring that the size of the second pitch is less than or equal to the pitch of the mating standard thread side and greater than the pitch of the mating standard thread side minus the maximum tolerance of the thread profile minus the maximum elastic deformation of the material properties of the thread profile; Step 4: By adjusting the difference between the total pitch of the standard thread side and the total pitch of the non-equidistant periodic alternating thread side in the working area, the standard thread side and the non-equidistant periodic alternating thread side are overall interfered with each other in the working area, and the first pitch of the standard thread side and the non-equidistant periodic alternating thread side are interfered with each other, forming a double interference fit.
6. The method for designing a non-uniform pitch periodically alternating threaded connection according to claim 5, characterized in that: By changing the size of the second pitch of the non-equidistant periodic alternating thread side in the working area, the minimum period and the difference between the total pitch of the standard thread side and the total pitch of the non-equidistant periodic alternating thread side in the working area can be adjusted.