Annular thread nut connecting structure with gradually-changed spacing and design method thereof

Abstract

The invention relates to the field of threaded connection structures, and discloses an annular tooth nut connection structure with gradually-changed spacing and a design method thereof.The annular tooth nut connection structure comprises a connection structure body, the connection structure body comprises a nut and a pull rod, and when the nut and the pull rod are connected and bear an axial load, corresponding annular teeth make contact in sequence, and the load is evenly distributed; the annular teeth on the nut are consistent in size, the tooth spacing is gradually changed, and the annular teeth on the pull rod are consistent in size and equal in tooth spacing; the nut is of a split structure and is composed of two or more fan-shaped petals, and the petals can move in the radial direction of the nut. At least eight pairs of annular teeth are arranged at the joint of the nut and the pull rod; according to the invention, the annular teeth in the nut can uniformly distribute loads when bearing axial loads, so that the maximum load and stress borne by a single annular tooth are reduced, and the fatigue life of the nut structure is prolonged.

Description

Technical Field

[0001] The invention relates to the field of threaded connection structures, and in particular to a ring-shaped nut connection structure with a gradient pitch and a design method thereof. Background Art

[0002] Prestressed frames are widely used in plastic forming equipment such as presses, rolling mills, straightening machines and extruders, and machine tool equipment such as die-casting machines and injection molding machines. The tie rod is the main load-bearing part in the frame, and both ends are connected to the nut through threads / equidistant annular teeth. In actual engineering applications, it is found that at the connection, the thread / annular tooth closest to the external load always bears the largest load. The load borne by the first thread / annular tooth accounts for about 28% of the total, and the load borne by each subsequent circle of threads / annular teeth gradually decreases. The first few circles of threads / annular teeth bear most of the load, resulting in the stress of the first few circles of threads / annular teeth being much greater than that of the subsequent threads. Excessive stress will lead to failure of the connection, thereby reducing the fatigue life of the connection structure.

[0003] The concept of non-equidistant nuts is mentioned in the article "Application of non-equidistant nuts in injection molding machines". The forces on the designed nut ring teeth decrease in sequence. The force on tooth 8 is P, and the force on tooth 7 is Tooth 6 is Tooth 1 is The stress state is improved compared with the equidistant annular tooth structure, but it still cannot achieve uniform stress distribution.

[0004] The disclosure discloses a non-equidistant thread connection pair with the publication number CN117366078A, which includes an internal thread and an external thread, wherein one of the internal thread and the external thread is a constant pitch thread, and the other is a gradual pitch thread, wherein the pitch of the internal thread is greater than the pitch of the external thread, and starting from the starting position of the internal and external thread engagement area, the pitch difference between the internal and external threads gradually increases with the increase in the number of thread turns, and the trend of the increasing pitch difference gradually decreases.

[0005] Based on the above technical features, the defects are: three common situations in which the axial force F(n') acting on the external thread follows the trend of n' change are analyzed, which are not all situations and are not necessarily the real situation. In addition, verifying the correctness of the trend only through simulation analysis is not necessarily the optimal solution. The solution of gradually reducing the pitch difference between the internal and external threads of this structure can improve the uneven stress distribution, but cannot achieve uniform stress distribution.

[0006] Therefore, the above problems are solved by a ring-shaped nut connection structure with a gradually varying pitch that can evenly distribute the load and a design method thereof. Summary of the invention

[0007] The object of the present invention is to provide a ring-shaped thread nut connection structure with a gradient pitch and a design method thereof, so as to solve the problems raised in the above-mentioned background technology.

[0008] To achieve the above object, the present invention provides the following technical solution: comprising a connection structure, the connection structure comprising a nut and a pull rod, S1, when the nut and the pull rod are connected and bear an axial load, the corresponding annular teeth contact in sequence and evenly distribute the load;

[0009] S2. The annular teeth on the nut are of the same size, and the tooth spacing changes gradually. The annular teeth on the pull rod are of the same size and the tooth spacing is equal;

[0010] S3. The nut is a petal structure, consisting of two or more fan-shaped petals, which can move radially along the nut;

[0011] S4, there are at least 8 pairs of annular teeth at the connection between the nut and the tie rod;

[0012] S5. The distance between the two teeth on the nut that are farthest from the axial force surface is greater than the tooth distance of the pull rod. Along the axial direction, as the distance to the axial force surface becomes closer, the tooth distance of the nut gradually increases, and the distance between adjacent teeth is arranged in an arithmetic progression.

[0013] A design method for a ring-shaped tooth nut with a gradient pitch, 1. When subjected to an axial load, multiple pairs of ring-shaped teeth on the nut and the pull rod contact each other, and the load is evenly distributed;

[0014] S2. Perform force analysis on the nut and the tie rod under axial load, and calculate the internal force of each annular tooth segment;

[0015] S3. Calculate the deformation of each annular tooth segment of the nut and the tie rod after unloading;

[0016] S4. According to the deformation, the design length of any annular tooth segment of the nut is obtained;

[0017] S5. As the distance to the axial force-bearing surface gets closer, the tooth spacing of the nut gradually increases, and the distance between adjacent teeth is arranged in an arithmetic progression.

[0018] Preferably, in the step S1, in the step S1, the lengths of the annular tooth segments of the nut and the pull rod under the axial load are equal, both being L0.

[0019] Preferably, in step S1, the axial forces borne by the annular teeth on the nut are equal in magnitude and in the same direction.

[0020] Preferably, in step S1, the axial forces borne by the annular teeth on the pull rod are equal in magnitude and in the same direction.

[0021] Preferably, the axial forces borne by any pair of annular teeth on the nut and the pull rod that are in contact with each other are equal in magnitude and opposite in direction.

[0022] Preferably, the internal force on any annular tooth segment s of the nut is pressure, and its magnitude is:

[0023]

[0024] Preferably, the internal force on any annular tooth segment s on the pull rod is a tensile force, the magnitude of which is:

[0025]

[0026] Preferably, the length of any annular tooth segment s on the nut is shortened after being stressed, and the deformation amount is:

[0027]

[0028] Wherein L0 is the length of the annular tooth segment s under the axial load state, E1 is the elastic modulus of the nut 1 material, and A1 is the cross-sectional area of ​​the nut 1 on the s segment.

[0029] Preferably, in step S3, the length of any annular tooth segment s on the pull rod increases after being stressed, and the deformation amount is:

[0030]

[0031] Wherein L0 is the length of the annular tooth segment s under the axial load state, E2 is the elastic modulus of the tie rod 2 material, and A2 is the cross-sectional area of ​​the tie rod 2 on the s segment.

[0032] Preferably, in step S4, after unloading, the length of any s segment on the nut is:

[0033]

[0034] After unloading, the length of any s segment on the tie rod is:

[0035]

[0036] After unloading, the difference in tooth spacing between the nut and the tie rod at any s segment is:

[0037]

[0038] Due to the deformation and The value is much smaller than L0. In order to make the nut and the tie rod connected at different positions, the spacing of the annular teeth on the tie rod is simplified and designed to be a fixed value L0. Then the spacing of any annular tooth s segment on the nut is:

[0039]

[0040] The tooth spacing increment is:

[0041] Preferably, in step S4, the design length L of each annular tooth segment on the nut is s It increases with the increase of the value s, that is, L1<…… <L s <…… <L n .

[0042] Preferably, the distances between adjacent teeth are arranged in an arithmetic progression.

[0043] That is: L1-L=L2-L1=……=L s -L s-1 =......=L n -L n-1 ;

[0044] The tooth spacing increment value is within the range of 0-0.1, that is: 0 <L n -L n-1 <0.1mm.

[0045] Technical effects and advantages of the present invention:

[0046] 1. The present invention breaks through the limitation that the pitch of the thread must be consistent during the screwing process by changing the ordinary thread connection into an annular tooth structure, and sets the tooth spacing to a gradual size, thereby achieving sequential contact of the annular teeth during loading, and ultimately achieving the purpose of changing the load sharing ratio of the annular teeth. The nut adopts a petal structure, and the petals achieve connection or separation between the nut and the pull rod by moving in the radial direction. The annular tooth spacing of the nut is arranged in an arithmetic progression, and the value is within the range of 0-0.1mm.

[0047] 2. In the design method of the present invention, when the connection structure of the nut and the pull rod is subjected to an axial load, the final state is that the annular teeth evenly distribute the load and the spacing is equal. The internal forces of the annular tooth segments on the nut and the pull rod under the axial load are calculated respectively, and further, the deformation of each annular tooth segment is calculated. Finally, the deformation and the spacing of each annular tooth segment are accumulated and superimposed to obtain the spacing size of each annular tooth on the nut in the free state before the axial load is subjected to. The present invention can achieve that when the axial load is subjected to, the annular teeth in the nut evenly distribute the load, thereby reducing the maximum load and stress borne by a single annular tooth, which is beneficial to improving the fatigue life of the nut structure.

[0048] 3. The present invention takes into account the deformation of parts under load, reduces the stress concentration of the loaded parts as much as possible, makes the stress distribution uniform, reduces the material usage requirements, and improves the reliability of the entire mechanism. The variable spacing design can be extended to other parts with multiple contact surfaces, large contact deformation, and stress concentration. The design dimensions are changed to make the stress distribution uniform, so as to reduce the maximum stress value, which has important reference significance for mechanical design. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 A flow chart of a design method for uniformly distributing nut load provided by the present invention;

[0050] Figure 2 This is a schematic diagram of the loading state provided by the present invention.

[0051] Figure 3 This is a schematic diagram of the internal force at any position under the loading state provided by the present invention.

[0052] Figure 4 This is a schematic diagram of the deformation of the annular tooth segment s in the unloading state provided by the present invention.

[0053] Figure 5 A schematic diagram of the design lengths of the annular tooth segments provided by the present invention.

[0054] Figure 6 A schematic diagram of the annular tooth width of the nut provided by the present invention.

[0055] Figure 7 A schematic diagram of a stress cloud diagram of a nut force analysis in the prior art provided by the present invention.

[0056] Figure 8 A schematic diagram of a stress cloud diagram for nut force analysis provided by the present invention.

[0057] Fig. 9 A schematic diagram for comparing the force analysis change curves provided by the present invention.

[0058] Fig.10 This is a schematic diagram of the nut structure provided by the present invention.

[0059] In the figure: 1. nut; 2. pull rod. DETAILED DESCRIPTION

[0060] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0061] The present invention provides Figures 1 to 8 A ring-shaped tooth nut connection structure with a gradient pitch is shown, comprising a connection structure, wherein the connection structure comprises a nut 1 and a tie rod 2, S1, when the nut 1 and the tie rod 2 are connected and subjected to an axial load, the corresponding ring-shaped teeth contact in sequence and evenly distribute the load;

[0062] S2, the annular teeth on nut 1 are of the same size, and the tooth spacing changes gradually, while the annular teeth on tie rod 2 are of the same size and the tooth spacing is equal;

[0063] S3, the nut 1 is a petal structure, consisting of two or more fan-shaped petals, and the petals can move radially along the nut 1;

[0064] S4, there are at least 8 pairs of annular teeth at the connection between nut 1 and tie rod 2;

[0065] S5. The spacing between the two teeth on the nut 1 that are farthest from the axial force-bearing surface is greater than the tooth spacing of the pull rod 2. Along the axial direction, as the distance to the axial force-bearing surface becomes closer, the tooth spacing of the nut 1 gradually increases and is arranged in an arithmetic progression.

[0066] When in use, the nut 1 (composed of an upper and a lower halves) is simultaneously engaged toward the center of the nut 1 and fixed thereafter. The nut 1 is subjected to a pressure F and transmits the force to the rod 2 through the deformation of the annular teeth, causing the rod 2 to stretch and deform.

[0067] The annular tooth spacing of the tie rod 2 is the same, and the annular tooth spacing of the nut 1 is greater than the annular tooth spacing of the tie rod 2, so that the nut 1 is meshed with the tie rod 2.

[0068] The nut 1 is divided into two halves, which are encircled on the pull rod 2. The annular teeth of the nut 1 are in clamping contact with the annular teeth of the pull rod 2 to complete the connection between the nut 1 and the pull rod 2.

[0069] A design method for a ring-shaped tooth nut with a gradually varying pitch, S1, when subjected to an axial load, multiple pairs of ring-shaped teeth on a nut 1 and a pull rod 2 contact each other, and the load is evenly distributed.

[0070] In step S1, in step S1, the lengths of the annular tooth segments under the axial load are equal, both L0, and the axial forces borne by the annular teeth on the nut 1 are equal in magnitude and in the same direction;

[0071] In step S1, the axial forces borne by the annular teeth on the tie rod 2 are equal in magnitude and in the same direction, and the axial forces borne by any pair of annular teeth on the tie rod 2 and the nut 1 that are in contact with each other are equal in magnitude and in opposite directions.

[0072] S2, the annular teeth on the nut 1 are of the same size, and the tooth spacing gradually changes. The annular teeth on the pull rod 2 are of the same size and the tooth spacing is equal. In this embodiment, Figure 3As shown, the closer to the force point of the axial load F, the greater the internal force of the annular tooth segment, which increases in a step-by-step manner from left to right, and the increase amplitude is equal.

[0073] The internal force on any annular tooth segment s of the nut 1 is pressure, and its magnitude is:

[0074]

[0075] In step S2, the internal force on any annular tooth segment s on the pull rod 2 is a tensile force, and its magnitude is:

[0076]

[0077] S3, calculate the deformation of each annular tooth segment of the nut 1 and the pull rod 2 after unloading. Figure 4 As shown, in step S3, the length of any annular tooth segment s on the nut 1 is shortened after being stressed, and the deformation amount is:

[0078]

[0079] Wherein L0 is the length of the annular tooth segment s under the axial load state, E1 is the elastic modulus of the nut 1 material, and A1 is the cross-sectional area of ​​the nut 1 on the S segment.

[0080] In step S3, the length of any annular tooth segment s on the pull rod 2 increases after being stressed, and the deformation amount is:

[0081]

[0082] Wherein L0 is the length of the annular tooth segment s under the axial load state, E2 is the elastic modulus of the tie rod 2 material, and A2 is the cross-sectional area of ​​the tie rod 2 on the S segment.

[0083] S4. According to the deformation, the design length of any annular tooth segment of the nut 1 is obtained, and the deformation is superimposed on the initial length to obtain the design length of any annular tooth segment of the nut 1 and the pull rod 2. Figure 5 As shown, taking the die-casting machine as an example, in order to facilitate the use of molds of different thicknesses, the nut 1 needs to be tightly clamped with the annular teeth at different positions on the tie rod 2, so the design lengths of the annular tooth segments of the tie rod 2 are equal; the deformation amount needs to be accumulated on the nut 1.

[0084] In step S4, after unloading, the length of any segment s on the nut 1 is:

[0085]

[0086] After unloading, the length of any s segment on the tie rod 2 is:

[0087]

[0088] After unloading, the difference in tooth spacing between the nut 1 and the tie rod 2 at any segment s is:

[0089]

[0090] Due to the deformation and The value is much smaller than L0. In order to enable the nut 1 to be connected to different positions on the tie rod 2, the spacing of the annular teeth on the tie rod 2 is simplified and designed to be a fixed value L0. Then the spacing of any annular tooth s segment on the nut 1 is:

[0091]

[0092] The tooth spacing increment is: In the specific case it is a fixed value.

[0093] In step S4, the design length L of each annular tooth segment on the nut 1 is s It increases with the increase of the value s, that is, L1<…… <L s <…… <L n .

[0094] S5. As the distance to the axial force-bearing surface gets closer, the tooth spacing gradually increases, and the distances between adjacent teeth are arranged in an arithmetic progression;

[0095] The tooth spacing is an arithmetic progression.

[0096] That is: L1-L=L2-L1=……=L s -L s-1 =......=L n -L n-1

[0097] The tooth spacing increment value is within the range of 0-0.1, that is: 0 <L n -L n-1 <0.1mm.

[0098] The annular tooth farthest from the axial load F is tooth No. 1, and the tooth No. 10 is arranged from left to right. By calculating this example, the deformation of the annular tooth segments No. 1-10 can be obtained, as shown in Table 1;

[0099] Table 1

[0100]

[0101] According to the data in Table 1, the structure is designed and the steps of the design method in the present invention are reversed. It can be known that the 10 annular teeth evenly distribute the axial load, thereby achieving the purpose of reducing the maximum stress value and increasing the fatigue life of the nut 1 connection structure.

[0102] In Table 1, the annular pitch of the tie rod 2 is the same, and the annular pitch of the nut 1 is variable, which is different from the traditional nut 1. When loading, the annular teeth with a smaller load in the original structure first contact the tie rod 2 and bear the load, and the annular teeth with a larger load in the original structure contact the tie rod 2 later, finally making the stress evenly distributed.

[0103] The designed variable pitch parameters are relatively small data, and the pitch change of adjacent teeth may be only 0.0052mm. Since the part size has a tolerance range, the actual parts will have a certain deviation. Compressing the tolerance range of the pitch will increase the processing cost or scrap it due to over-tolerance, while relaxing it may not achieve the purpose of variable pitch. It is feasible to ensure a reasonable pitch tolerance in combination with the processing conditions, so the design needs to ensure a reasonable pitch tolerance to achieve the design goal.

[0104] In actual use, the number of annular teeth of nut 1 is 10, and the tooth spacing gradually increases in an arithmetic progression. The number of annular teeth of pull rod 2 is 30, and the tooth spacing is the same. Nut 1 can be connected to different positions on pull rod 2. The cumulative sum of the tooth spacing increments from annular tooth segment 1 to annular tooth segment 10 is less than the difference between the annular tooth groove width on pull rod 2 and the annular tooth width of nut 1.

[0105] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A ring-shaped nut connection structure with a gradient pitch, characterized in that: The invention comprises a connection structure, wherein the connection structure comprises a nut (1) and a pull rod (2), wherein when the nut (1) and the pull rod (2) are connected and subjected to an axial load, corresponding annular teeth contact in sequence and evenly distribute the load; S2, the annular teeth on the nut (1) are of uniform size, the tooth spacing changes gradually, and the annular teeth on the pull rod (2) are of uniform size, the tooth spacing is equal; S3, the nut (1) is a petal structure, consisting of two or more fan-shaped petals, and the petals can move radially along the nut (1); S4, there are at least 8 pairs of annular teeth at the connection between the nut (1) and the pull rod (2); S5. The spacing between the two teeth on the nut (1) that are farthest from the axial force-bearing surface is greater than the spacing between the teeth of the pull rod (2). Along the axial direction, as the distance to the axial force-bearing surface becomes closer, the spacing between the teeth of the nut (1) gradually increases and is arranged in an arithmetic progression.

2. A method for designing a ring-shaped nut with a gradient pitch, characterized in that: S1. When subjected to axial load, multiple pairs of annular teeth on the nut (1) and the pull rod (2) are in contact with each other, and the load is evenly distributed; S2, performing a force analysis on the nut (1) and the tie rod (2) under an axial load, and calculating the internal force of each annular tooth segment; S3, calculating the deformation of each annular tooth segment of the nut (1) and the tie rod (2) after unloading; S4. According to the deformation amount, the design length of any annular tooth segment of the nut (1) is obtained; S5. As the distance to the axial force-bearing surface becomes closer, the tooth spacing of the nut (1) gradually increases, and the distances between adjacent teeth are arranged in an arithmetic progression.

3. The design method of a ring-shaped nut with a gradient pitch according to claim 2, characterized in that: In the step S1, the lengths of the annular tooth segments of the nut (1) and the pull rod (2) are equal and both are L0 when subjected to an axial load.

4. The design method of a ring-shaped nut with a gradient pitch according to claim 3 is characterized in that: In step S1, the axial forces borne by the annular teeth on the nut (1) are equal in magnitude and in the same direction; In step S1, the axial forces borne by the annular teeth on the pull rod (2) are equal in magnitude and in the same direction.

5. The method for designing a ring-shaped nut with a gradient pitch according to claim 4, characterized in that: The axial forces borne by any pair of annular teeth on the nut (1) and the pull rod (2) that are in contact with each other are equal in magnitude and opposite in direction.

6. The method for designing a ring-shaped nut with a gradient pitch according to claim 5, characterized in that: The internal force on any annular tooth segment s of the nut (1) is pressure, and its magnitude is: In step S2, the internal force on any annular tooth segment s on the pull rod (2) is a tensile force, the magnitude of which is:

7. The method for designing a ring-shaped nut with a gradient pitch according to claim 6, characterized in that: In step S3, the length of any annular tooth segment s on the nut (1) is shortened after being subjected to force, and the deformation amount is: Wherein L0 is the length of the annular tooth segment s under the axial load state, E1 is the elastic modulus of the material of the nut (1), and A1 is the cross-sectional area of ​​the nut (1) on the segment s; In the step S3, the length of any annular tooth segment s on the pull rod (2) increases after being stressed, and the deformation amount is: Wherein L0 is the length of the annular tooth segment s under the axial load state, E2 is the elastic modulus of the material of the tie rod (2), and A2 is the cross-sectional area of ​​the tie rod (2) on the s segment.

8. The method for designing a ring-shaped nut with a gradient pitch according to claim 7, characterized in that: In step S4, after unloading, the length of any segment s on the nut (1) is: After unloading, the length of any s segment on the pull rod (2) is: After unloading, the difference in tooth spacing between the nut (1) and the pull rod (2) at any segment s is: Due to the deformation and The value is much smaller than L0. In order to enable the nut (1) to be connected to different positions on the pull rod (2), the spacing of the annular teeth on the pull rod (2) is simplified and designed to be a fixed value L0. Then, the spacing of any annular tooth s segment on the nut (1) is: The tooth spacing increment is:

9. The method for designing a ring-shaped nut with a gradient pitch according to claim 8, characterized in that: In step S4, the design length L of each annular tooth segment on the nut (1) is s It increases with the increase of the value s, that is, L1<…… <L s <…… <L n .

10. The method for designing a ring-shaped nut with a gradient pitch according to claim 9, characterized in that: The distances between adjacent teeth are arranged in an arithmetic progression. Number: L1-L, L2-L1,……, L s -L s-1 =......=L n -L n-1 ; The tooth spacing increment value is within the range of 0-0.1, that is: 0 <L n -L n-1 <0.1mm.

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