Cold header crankshaft capable of reducing deflection

Abstract

The utility model discloses a cold header crankshaft capable of reducing deflection, and aims to effectively reduce the deflection of the crankshaft and improve the working precision and stability of a cold header by optimizing the section shape of a connecting rod journal under the condition of not changing the structure of an original stressed part. The cold header crankshaft comprises a main journal, a connecting rod journal and a crank, the connecting rod journal comprises bearing sections at the two ends and a non-bearing section in the middle, and the cold header crankshaft is characterized in that the section inertia moment of the non-bearing section is larger than that of the bearing sections. The utility model further provides a design method of the cold header crankshaft. The design method comprises the following steps: determining a load distribution coefficient alpha; setting a target deflection reduction proportion beta; calculating a conversion coefficient lambda; the diameter d1 of the non-bearing section or the offset of the center axis of the non-bearing section relative to the center axis of the bearing section is calculated and determined; and manufacturing the variable cross-section crankshaft. The crankshaft is simple in structure, deflection can be accurately controlled through the design method, the forming precision and the product quality of the cold header are improved, and the crankshaft is also suitable for other similar shaft parts.

Description

Technical Field

[0001] This utility model belongs to the field of mechanical manufacturing technology, specifically relating to a crankshaft structure for a cold heading machine, which is particularly suitable for the optimized design of large-span crankshafts. Background Technology

[0002] Cold heading machines are key equipment in the field of metal plastic forming. Their crankshafts are subjected to large cyclic loads during operation, making them prone to deflection and directly affecting the dimensional accuracy and surface quality of the forged parts. Traditional crankshaft designs typically employ a constant-section connecting rod journal structure, concentrating the load on the two sides near the crank (i.e., the load-bearing section) to reduce deformation. However, due to the large span and concentrated load of cold heading machine crankshafts, existing designs still struggle to effectively suppress the deflection of the non-load-bearing section in the middle of the journal, resulting in insufficient overall stiffness.

[0003] In existing technologies, the main methods for improving crankshaft stiffness include two aspects: one is to add support constraints in the middle region of the journal to change the stress state of the shaft and reduce deformation, but this method requires adjustment of the shaft system structure, significantly increasing assembly precision requirements and manufacturing costs; the other is to optimize load distribution, such as transferring the load from the middle region to the load-bearing sections at both ends. However, while such methods can reduce local deformation, they do not fully utilize the structural potential of non-load-bearing sections, making it difficult to achieve a synergistic improvement in overall stiffness.

[0004] Furthermore, the non-load-bearing section of a traditional constant-section connecting rod journal has a fixed moment of inertia, making it impossible to further resist bending deformation through structural optimization. Therefore, how to improve crankshaft stiffness through innovative design of the non-load-bearing section while maintaining the original load distribution and stress state has become an urgent technical problem to be solved. Summary of the Invention

[0005] To address the aforementioned problems, the purpose of this invention is to provide a cold heading machine crankshaft with reduced deflection. This crankshaft can effectively reduce deflection and improve the working accuracy and stability of the cold heading machine by optimizing the cross-sectional shape of the connecting rod journal without altering the original stress-bearing structure.

[0006] To achieve the above objectives, the following technical solution is adopted:

[0007] A cold heading machine crankshaft with reduced deflection includes a main journal, a connecting rod journal, and a crank connecting the main journal and the connecting rod journal; the connecting rod journal includes a load-bearing section at both ends and a non-load-bearing section in the middle of the two load-bearing sections; the moment of inertia of the non-load-bearing section is greater than that of the load-bearing section.

[0008] Through the above design, without changing the overall stress state and load distribution of the crankshaft, the moment of inertia of the non-load-bearing section of the connecting rod journal is increased, thereby improving the bending stiffness of the connecting rod journal and reducing the deflection under the same load.

[0009] Furthermore, the non-load-bearing section is cylindrical, and its diameter is larger than that of the load-bearing section. This design is simple, easy to implement, and convenient to manufacture.

[0010] Furthermore, the non-load-bearing section is coaxially arranged with the load-bearing section. This design ensures the dynamic balance performance of the crankshaft.

[0011] Furthermore, the non-load-bearing section is eccentrically positioned relative to the load-bearing section. This design can further increase the moment of inertia of the non-load-bearing section while reducing material consumption.

[0012] Furthermore, the outer circle of the non-load-bearing section is tangent to the outer circle of the load-bearing section. This design, based on the eccentric setting, can maximize the moment of inertia of the non-load-bearing section.

[0013] Furthermore, the length of the load-bearing section is 'a', where the total load-bearing length is 2a, the total length of the connecting rod journal is 'L', and the load distribution coefficient α = a / L, α ≤ 1 / 2. These constraints ensure that the variable cross-section design can effectively reduce deflection.

[0014] The present invention provides a design method for reducing the deflection of a cold heading machine crankshaft, comprising the following steps:

[0015] (a) Determine the load distribution coefficient α: Measure or determine the length a of the load-bearing section on the connecting rod journal according to the design requirements, and calculate the load distribution coefficient as the ratio of the length a of the bearing section to the total length L of the connecting rod journal;

[0016] (b) Set the target deflection reduction ratio β λ / α Select the target deflection reduction ratio based on design requirements;

[0017] (c) Calculate the reduction factor λ: Based on the target deflection reduction ratio and the load distribution coefficient, using the formula:

[0018]

[0019] Solve for the conversion factor λ;

[0020] (d) Calculate and determine the diameter d1 of the non-load-bearing section: Based on the reduction factor λ and the moment of inertia of the section, using the formula:

[0021]

[0022] Calculate the diameter d1 of the non-load-bearing section, where d is the diameter of the load-bearing section;

[0023] (e) Manufacturing variable cross-section crankshaft: Based on the adjusted non-load-bearing section structure, the crankshaft is machined to obtain a crankshaft with low deflection.

[0024] Using the above design method, the dimensions of the non-load-bearing section can be accurately calculated according to the actual working conditions and design requirements, thereby achieving precise control of crankshaft deflection.

[0025] Furthermore, in step (d), the center axis of the non-load-bearing section is offset relative to the center of the load-bearing section by an offset amount of c.

[0026]

[0027] Let c = kd1

[0028] Then the conversion factor λ c The formula between d1 and c:

[0029]

[0030] This eccentric design method can further reduce deflection while optimizing material distribution and reducing crankshaft weight.

[0031] The cold heading machine crankshaft with reduced deflection and its design method proposed in this utility model have significant advantages compared with the prior art. By increasing the moment of inertia of the non-load-bearing section of the connecting rod journal, the deflection of the crankshaft under working conditions is effectively reduced, thereby improving the forming accuracy and product quality of the cold heading machine. Due to the reduction in crankshaft deflection, the deformation error generated during the cold heading process is reduced, resulting in a significant improvement in the dimensional and shape accuracy of the cold-headed parts.

[0032] The variable cross-section design of this invention mainly focuses on the non-load-bearing section of the connecting rod journal, without requiring changes to other parts of the crankshaft, or the original stress state and load distribution. The structure is simple and easy to manufacture. This design reduces manufacturing difficulty and cost while ensuring structural strength.

[0033] The design method of this invention is applicable not only to crankshafts of cold heading machines, but also to other similar shaft parts that require control of deflection deformation, demonstrating its wide applicability. For other types of shafts, similar deflection reduction effects can be achieved simply by adjusting the design parameters according to their specific working conditions and stress characteristics.

[0034] Furthermore, the design method of this invention is calculable and designable. Through precise mathematical models and calculation formulas, the crankshaft deflection can be accurately controlled according to actual needs, avoiding the drawbacks of relying on experience and repeated trials in traditional designs, thus improving design efficiency and reliability. Using this design method can reduce the number of design iterations and shorten the product development cycle. Finally, for the eccentric circle design, not only is deflection reduced and stiffness increased, but due to its structural characteristics, it can also reduce material usage and lower manufacturing costs while maintaining the same performance. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of a crankshaft structure with a medium cross-section connecting rod journal in the prior art;

[0036] Figure 2 This is a schematic diagram of the crankshaft structure of the variable cross-section connecting rod journal in Example 1;

[0037] Figure 3 This is a schematic diagram of the force distribution on the connecting rod journal in Example 1;

[0038] Figure 4 This is a schematic diagram of the shear force on the connecting rod journal in Example 1;

[0039] Figure 5 This is a schematic diagram of the bending moment of the connecting rod journal in Example 1;

[0040] Figure 6 This is a schematic diagram of the structure and force of the variable cross-section connecting rod journal in Example 1;

[0041] Figure 7 This is a schematic diagram of the bending moment of the variable cross-section connecting rod journal in Example 1;

[0042] Figure 8 In Example 1, based on the calculation of β λ / α Formula, schematic diagram of the relationship between α and β under different conversion factors;

[0043] Figure 9 In Example 1, based on the calculation of β λ / α Formula, schematic diagram of the relationship between λ and β under different distribution coefficients;

[0044] Figure 10 This is a schematic diagram of the structure and stress of the eccentric variable cross-section connecting rod journal in Example 2;

[0045] Figure 11 This is a schematic diagram of the bending moment of the journal of the eccentric variable cross-section connecting rod in Example 2. Detailed Implementation

[0046] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0047] Example 1.

[0048] This embodiment provides a cold heading machine crankshaft with reduced deflection, such as... Figure 2 , Figure 7 As shown, the crankshaft includes a main journal 1, a connecting rod journal 2, and a crank 3 connecting the main journal 1 and the connecting rod journal 2. The connecting rod journal 2 is a key improvement of this invention.

[0049] Without altering the force and load distribution of the connecting rod journal 2, the force states of the crank 3 and main journal 1 also remain unchanged. Furthermore, without altering the structure and dimensions of the crank 3 and main journal 1, the deformation of these parts under the same load on the connecting rod journal 2 will not be affected.

[0050] Under the aforementioned circumstances, the change in deflection caused by altering the structural components of the connecting rod journal 2 directly reflects the change in the stiffness of the entire crankshaft. Therefore, studying the deflection problem caused by the bending deformation of the entire crankshaft can be simplified to studying the deflection problem of the connecting rod journal 2.

[0051] Analyzing the flexural deformation of connecting rod journal 2 allows us to further simplify it into a simply supported beam.

[0052] If the original load-bearing structure of the connecting rod journal 2 remains unchanged, then the response capability of that part to external loads remains unchanged.

[0053] Typically, the load on the connecting rod journal 2 is distributed near the crank 3, such as Figure 1 As shown, in the prior art, the load of the connecting rod journal 2 is applied to the load-bearing sections on the left and right sides with a length of a, while the non-load-bearing section in the middle with a length of b is not subjected to force.

[0054] Under the same external load, the uniform distribution of the load along the entire length of the connecting rod journal 2 is transferred to the left and right bearing sections, which can greatly reduce the bending deformation of the connecting rod journal 2.

[0055] The connecting rod journal 2 is supported by cranks 3 at both ends, and its model can be applied as a simply supported beam. From mechanics of materials, it can be directly obtained that the maximum bending deflection of the connecting rod journal 2, uniformly distributed over the entire length L, is located at the midpoint of the beam, and its value is:

[0056] y Lmax =5q L L 4 / 384EI (1)

[0057] In the formula: q L For load distribution density;

[0058] L is the total length of connecting rod journal 2;

[0059] E is the elastic modulus of the crankshaft material;

[0060] I is the moment of inertia of the cross section under the linkage load;

[0061] The deflection value when the distributed load is expressed as a total load of T is:

[0062] y Lmax =5TL 3 / 384EI (2)

[0063] When the load is transferred to the two load-bearing sections a near crank 3 of the connecting rod, the maximum deflection remains at the midpoint, and the maximum deflection value is determined by the load distribution density q. a The total load T is expressed as follows:

[0064]

[0065] In the formula: α is the load distribution coefficient.

[0066] The bending of the connecting rod journal, and the resulting rotation angle at both cranks, have the following angle values ​​for the two scenarios described above:

[0067]

[0068] and

[0069]

[0070] The ratio of their maximum deflections is:

[0071]

[0072] It is evident that the deflection of the two-segment distribution, relative to the uniformly distributed deflection along the entire length, decreases as α decreases, achieving a significant effect. When α is 3... 1 At that time, the ratio was 0.74, which means that the bending deformation of the crankshaft on the connecting rod journal was reduced by 26%.

[0073] This embodiment utilizes the non-load-bearing section left after the load is transferred to both sides of crank 3. This section does not bear any load and does not directly contact the connecting rod. Without affecting the movement of the crankshaft slider mechanism, the stiffness and moment of inertia of this non-load-bearing section are increased by redesigning its structure, thereby improving the ability of the connecting rod journal 2 to resist bending deformation.

[0074] Figure 2 The structure shown is a modified version of the original constant cross-section beam within the non-load-bearing section b, while the rest of the crankshaft retains its original form and dimensions. A simply supported beam mechanical model of this beam is also constructed. Figure 2 Structure and Figure 1 The mechanical models of simply supported beams are the same, with the same load distribution, and the same shear force and bending moment distribution, such as... Figure 3-5 As shown.

[0075] Support reaction force at the support end:

[0076]

[0077] like Figure 7 As shown.

[0078] Shear force Q and bending moment M of the left segment (AC segment):

[0079] Q = R A ―q a x = q a (a―x)

[0080]

[0081] Shear force Q and bending moment M in the middle section (section CD):

[0082] Q = 0

[0083]

[0084] Shear force Q and bending moment M of the right segment (DB segment):

[0085] Q = q a (x―a―b)

[0086]

[0087] Where x is the position of the fulcrum on the connecting rod journal 2 from left to right.

[0088] Constructing the deflection equation of a variable cross-section beam under load and determining the maximum deformation under the same load is the main technical solution to prove that variable cross-section beams are beneficial to reducing deformation and improving stiffness, and it is also the theoretical basis for the main technical problem to be solved by this utility model.

[0089] At the junction of the load-bearing and non-load-bearing sections, the abrupt change in the structural cross-section causes a discontinuity in the internal forces. In the absence of a deflection calculation method for variable cross-section beams, appropriate concentrated forces and moments are introduced at the junction of the two sections with different cross-sections. These forces are made equal to the discontinuity of the internal forces, transforming the deflection problem of the variable cross-section beam into a comparable problem for a beam with a constant cross-section, thus establishing the deflection curve equation for the variable cross-section beam.

[0090] like Figure 6 , Figure 7 As shown, the additional bending moment at the connection between the left load-bearing section and the middle non-load-bearing section:

[0091]

[0092] Additional bending moment at the connection between the right load-bearing segment and the middle non-load-bearing segment:

[0093]

[0094] The deflection curve equation expressed in terms of initial parameters is used to solve the deformation problem of beams with variable cross-sections. We have:

[0095]

[0096] In the formula:

[0097] y0 represents the initial deflection of the beam at the origin x = 0;

[0098] θ0 represents the initial rotation angle of the beam at the origin x = 0;

[0099] P0 represents the concentrated load P acting at x = 0;

[0100] M0 represents the bending moment M acting at x = 0;

[0101] M i and a i Let a represent the coordinates of the i-th bending moment M and the point of application of this bending moment M, respectively, from x=0 to the right.

[0102] P i and b i Let b represent the coordinates of the i-th concentrated load P and the point of application of this load P, respectively, from x = 0 to the right.

[0103] q i and c i Let c represent the load with uniform distribution density q to the right from x=0, and c be the starting coordinate of the load with uniform distribution density q.

[0104] Initial boundary conditions at the fulcrum:

[0105] When x = 0, y A =0

[0106] When x = L, y B =0

[0107] Obtain the initial parameter θ0:

[0108]

[0109] The above formula represents the initial angle θ of a beam with a uniform cross-section. A Compared to formula (6), there is one more term. (1―2α), where the range of values ​​for the conversion factor λ and the load distribution factor α during use is:

[0110] λ≤1

[0111]

[0112] When the first formula is equal, i.e., λ = 1, this term is 0, which means it transforms into a beam with a uniform cross-section, where the load is evenly distributed on the left and right sides and there is no load in the middle; when the second formula is equal, i.e., α = 1 / 2, it is the case where the load is evenly distributed throughout the beam. The above formula (12) transforms into formula (6) and formula (5) respectively, which are the initial conditions for a beam with a uniform cross-section in special cases.

[0113] For a beam with a variable cross-section, the deflection at each point can be calculated using the following formula:

[0114]

[0115] Because of the symmetrical structure and symmetrical load distribution, the maximum deflection of the variable cross-section beam is located at the midpoint of the beam, that is:

[0116]

[0117] The maximum deflection is:

[0118]

[0119] Compared with the formula for the maximum deflection of a beam with a constant cross-section, the first term of this formula represents the deformation under the same distribution coefficient, while the second term represents the value of the reduction in deflection caused by the change in cross-section. This value depends on the reduction factor λ and the load distribution coefficient α generated by the change in cross-section, and decreases as the reduction factor λ and the load distribution coefficient α decrease.

[0120] The ratio of a variable cross-section beam to a constant cross-section beam is:

[0121]

[0122] The last term of the above relation (16) indicates that the moment of inertia is increased in the middle part, making it a reduction in the maximum deformation of the variable cross-section structure relative to the constant cross-section structure.

[0123] Similarly, taking the load distribution coefficient α as 0.3, when the conversion factor λ is 0.3, the deformation can be further reduced by 42% on top of the original reduction; when the conversion factor λ is 0.5, the deformation can also be reduced by 30%. Increasing the moment of inertia in the middle part can achieve significantly higher stiffness and reduce bending deformation, thereby improving the processing accuracy of the equipment.

[0124] Compared to the case where the load is uniformly distributed across the entire connecting rod journal 2, the effect is as follows:

[0125]

[0126] When the conversion factor λ is taken as 0.3 or 0.5 respectively, the deflection values ​​are 0.518 and 0.429 for the whole-segment distributed structure.

[0127] By using different conversion factors and load distribution factors in the second term of the above formula, and then converting them into a table as shown below. Figure 8-9 As shown, this provides convenience for setting parameters when controlling deformation in the design.

[0128] like Figure 7As shown, in this embodiment, the bearing section and non-bearing section of the connecting rod journal 2 are coaxially arranged. The diameter of the bearing section a is d, and the diameter of the intermediate non-bearing section b is d1. Then, the moment of inertia of the cross sections at these two locations is as follows in the bearing section:

[0129]

[0130] Intermediate non-load-bearing section:

[0131]

[0132] Based on the journal moment of inertia of the original connecting rod structure, the ratio of the two moments of inertia is calculated and used as a conversion factor for converting cross-sectional changes into load changes:

[0133]

[0134] The conversion factor varies according to the fourth power of the ratio of the diameters of two adjacent segments, and the effect is significant. Furthermore, d1 is greater than d, and the ratio λ is less than 1.

[0135] When the diameter d1 of the non-load-bearing section b is selected to be 1.1, 1.2, and 1.3 times the diameter of the two load-bearing sections a, the conversion factor quickly drops to 0.68, 0.48, and 0.35 of the original deformation.

[0136] Example 2.

[0137] like Figure 10-11 As shown, the design method of the cold heading machine crankshaft with reduced deflection described in this embodiment is basically the same as that in Embodiment 1, but the central axes of the load-bearing section and the non-load-bearing section are parallel and not on the same axis, and the outer circle of the non-load-bearing section is tangent to the outer circle of the load-bearing section.

[0138] When the center axis of the non-load-bearing section is offset by a distance c from the center axes of the left and right load-bearing sections, according to the theorem of moment of inertia translation, the relationship between the moment of inertia of the large circle of the non-load-bearing section and the center of the small circle of the load-bearing section is as follows:

[0139]

[0140] When the large circle of the non-load-bearing section is tangent to the small circle of the load-bearing section, the offset c is at its maximum, and its value is:

[0141]

[0142] set up

[0143] c = kd1

[0144] but:

[0145]

[0146] The conversion factor in this case is:

[0147]

[0148] In the formula: k≥0, then λ c If ≤λ, the deflection of connecting rod journal 2 will further decrease.

[0149] By rationally selecting the diameter and offset of the intermediate section, the requirement of minimizing the deformation of the connecting rod journal 2 is optimized and matched.

[0150] In the description of this utility model, it should be noted that the terms "vertical", "up", "down", "horizontal", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0151] In the description of this utility model, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0152] Finally, it should be noted that the above description is merely a preferred embodiment of this utility model and is not intended to limit the utility model. Although the utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this utility model should be included within the protection scope of this utility model.

Claims

1. A cold heading machine crankshaft with reduced deflection, characterized in that, The crankshaft includes a main journal, a connecting rod journal, and a crank connecting the main journal and the connecting rod journal; the connecting rod journal includes a load-bearing section at both ends and a non-load-bearing section in the middle of the two load-bearing sections; the moment of inertia of the non-load-bearing section is greater than that of the load-bearing section.

2. The cold heading machine crankshaft according to claim 1, characterized in that, The non-load-bearing section is cylindrical, and its diameter is larger than that of the load-bearing section.

3. The cold heading machine crankshaft according to claim 2, characterized in that, The non-load-bearing section is coaxially arranged with the load-bearing section.

4. The cold heading machine crankshaft according to claim 2, characterized in that, The non-load-bearing section is eccentrically positioned relative to the load-bearing section.

5. The cold heading machine crankshaft according to claim 4, characterized in that, The outer circle of the non-load-bearing section is tangent to the outer circle of the load-bearing section.

6. The cold heading machine crankshaft according to any one of claims 1-5, characterized in that, The length of the bearing section is a, the total length of the connecting rod journal is L, and the load distribution coefficient α = a / L, α ≤ 1 / 2.

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