Transmission shaft connecting method and transmission shaft

Abstract

The invention relates to a connecting method of a transmission shaft and the transmission shaft, and belongs to the technical field of pipe forming, the connecting method comprises the steps that according to the first design requirement, the target wall thickness of a reinforcing inner pipe is determined, and the first design requirement comprises the steps that after the reinforcing inner pipe is welded to the inner side of the end of a shaft pipe, the reinforcing inner pipe is welded; the total bearing capacity of the area, welded with the reinforcing inner pipe, of the shaft pipe is not lower than the bearing capacity of other areas of the shaft pipe. According to a second design requirement, design parameters of welding seams between the reinforcing inner pipe and the shaft pipe are determined, and the second design requirement includes that after the reinforcing inner pipe is welded to the inner side of the end of the shaft pipe, the bearing capacity of the area, welded to the shaft pipe, of the reinforcing inner pipe is not larger than that of all the welding seams; and according to the design parameters of the weld joints, reinforcing inner pipes with target wall thicknesses are welded to the inner sides of the two ends of the shaft pipe correspondingly. By reinforcing the local area and reasonably determining the target wall thickness and the welding seam design parameters of the reinforced inner pipe, the bearing capacity of the transmission shaft is guaranteed, material waste is effectively avoided, and the material utilization rate is increased.

Description

Technical Field

[0001] This application relates to the field of pipe forming technology, and in particular to a method for connecting a drive shaft and a drive shaft. Background Technology

[0002] The driveshaft is a core component of the transmission system, responsible for efficiently transmitting engine power to the drive wheels. Its performance directly affects the vehicle's power, economy, and reliability. The connection between the driveshaft tube and the universal joint forks at both ends is usually achieved through welding. During operation, it must withstand complex alternating torque loads, placing stringent requirements on the strength, toughness, and fatigue life of the welded joint.

[0003] Currently, high-strength steel of 800MPa grade and above, or heat-treatable aluminum alloys, are preferred materials for lightweight drive shafts due to their high specific strength and lightweight potential. However, when using conventional welding processes such as friction welding and MIG / MAG welding, microstructural degradation phenomena such as grain coarsening, over-aging, or microstructural transformation inevitably occur in the weld heat-affected zone, leading to a joint strength reduction of up to 20%, with the higher the material strength grade, the more significant the performance degradation. This defect necessitates that drive shaft designs consider the weld heat-affected zone of the shaft tube as a weak point, and perform strength checks based on the weakened technical specifications, resulting in an increase in the overall wall thickness of the shaft tube to compensate for local strength losses.

[0004] After increasing the overall wall thickness of the shaft tube to compensate for local strength loss, the connection between the shaft tube and the universal joint forks at both ends will increase the weight of the drive shaft. Therefore, without changing the cross-sectional dimensions of the shaft tube, thickening the entire shaft tube only for the extremely short welded joint area not only wastes materials, but also seriously weakens the weight reduction and cost reduction effect of the lightweight design. Summary of the Invention

[0005] This application provides a method for connecting a drive shaft and a drive shaft to solve the problem of material waste caused by increasing the overall wall thickness of the shaft tube to compensate for local strength loss in related technologies, thereby improving the weight reduction and cost reduction effect of lightweight design.

[0006] In a first aspect, a method for connecting a drive shaft is provided, comprising: determining the target wall thickness of a reinforcing inner tube according to a first design requirement, the first design requirement including: after the reinforcing inner tube is welded to the inner side of the end of the shaft tube, the total load-bearing capacity of the area of ​​the shaft tube where the reinforcing inner tube is welded is not less than the load-bearing capacity of the remaining areas of the shaft tube; determining the design parameters of the weld between the reinforcing inner tube and the shaft tube according to a second design requirement, the second design requirement including: after the reinforcing inner tube is welded to the inner side of the end of the shaft tube, the load-bearing capacity of the area where the reinforcing inner tube is welded to the shaft tube is not greater than the load-bearing capacity of all welds; welding reinforcing inner tubes with the target wall thickness to the inner sides of both ends of the shaft tube according to the weld design parameters; and simultaneously connecting the welded shaft tube and the reinforcing inner tube to a universal joint fork and a spline sleeve to realize the installation of the drive shaft.

[0007] By adopting the above technical solution, the traditional drive shaft structure is changed by reinforcing the inner tube. The original method of compensating for strength by increasing the overall wall thickness of the shaft tube is transformed into local structural reinforcement. This optimization method no longer thickens the entire shaft tube due to the extremely short welding joint area, reducing unnecessary material usage and lowering material costs. Furthermore, by optimizing the weld design of each part, the performance degradation points are dispersed, ensuring the load-bearing capacity of the drive shaft.

[0008] In some embodiments, determining the target wall thickness of the reinforcing inner tube according to the first design requirement specifically includes: selecting a reinforcing inner tube whose material properties match those of the shaft tube; establishing an inequality based on the material mechanical property data of the shaft tube and the reinforcing inner tube and the dimensional parameters of the shaft tube, with the first design requirement as a constraint, and calculating the range of wall thickness of the reinforcing inner tube; and selecting the target wall thickness of the reinforcing inner tube from the calculated range of wall thicknesses of the reinforcing inner tube according to the design standards and usage requirements of the drive shaft.

[0009] By adopting the above technical solution: based on the material mechanical property data of the shaft tube and the reinforcing inner tube and the dimensional parameters of the shaft tube, the target wall thickness of the reinforcing inner tube is calculated by establishing an inequality. This ensures the performance of the reinforcing inner tube and the design strength and stability of the weld between the inner walls of the reinforcing inner tube and the shaft tube ends, thereby improving the overall quality and reliability of the drive shaft. The reinforcing inner tube can precisely reinforce the area that may experience strength loss in the weld heat-affected zone. This precise reinforcement method only treats the parts that need reinforcement, avoiding unnecessary overall thickening of the shaft tube and improving the targeted use of materials.

[0010] In some embodiments, determining the design parameters of the weld between the reinforcing inner tube and the shaft tube specifically includes: selecting a reinforcing inner tube whose material properties match those of the shaft tube; establishing an inequality based on the material mechanical properties data of the reinforcing inner tube and the dimensional parameters of the shaft tube, using the second design requirement as a constraint, and calculating the range of values ​​for the design parameters of the weld; and selecting weld design parameters regarding weld length, width, and quantity from the calculated range of values ​​for the design parameters of the weld, according to the design standards and usage requirements of the drive shaft.

[0011] By adopting the above technical solution: based on the material mechanical properties data of the reinforcing inner tube and the dimensional parameters of the shaft tube, and using the second design requirement as a constraint, an inequality is established to calculate the range of design parameters for the weld, which can ensure the design strength and stability of the weld and improve the overall quality and reliability of the drive shaft.

[0012] In some embodiments, before welding reinforcing inner tubes with the target wall thickness to the inner sides of both ends of the shaft tube according to the weld design parameters, the connection method further includes: obtaining a weld arrangement scheme according to the weld design parameters; establishing a control scheme for the welding heat-affected zone of the arrangement scheme; and completing the welding of the reinforcing inner tube and the shaft tube based on the control scheme to ensure the strength performance of the drive shaft.

[0013] By adopting the above technical solutions—namely, by obtaining a weld layout scheme, establishing a welding heat-affected zone control scheme, and completing the welding—the welding quality can be effectively improved, ensuring the strength performance of the drive shaft.

[0014] In some embodiments, the arrangement includes: arranging multiple welds along the circumferential direction of the tube around the shaft, each weld extending along the axial direction of the reinforcing inner tube, and forming a welding heat-affected zone between the multiple welds.

[0015] By adopting the above technical solution, multiple welds are arranged along the circumference of the shaft tube, and each weld extends along the axis of the reinforcing inner tube. This arrangement increases the connection area between the reinforcing inner tube and the shaft tube. More connection points mean that when bearing load, the stress can be more evenly distributed on multiple welds, thus avoiding structural damage caused by local stress concentration.

[0016] In some embodiments, the control scheme further includes controlling the length difference between adjacent welds after reduction to be no less than the width of the weld itself.

[0017] By adopting the above technical solution, the length difference between adjacent welds after reduction is guaranteed to be no less than the width of the weld itself. The shape and size of the end of the heat-affected zone of the shaft tube at the welded area of ​​the longitudinally reinforced weld are different. This increases the length and area of ​​the end of the heat-affected zone of the shaft tube at the welded area of ​​the longitudinally reinforced weld, making the heat distribution more non-linear. It avoids the local flatness of the heat-affected zone of the shaft tube at the welded area of ​​the longitudinally reinforced weld, allowing the softened area of ​​the shaft tube to be evenly distributed circumferentially on the inner wall of the shaft tube. This enables the shaft tube to better bear the load and avoids the reduction in load-bearing capacity caused by the concentrated and linearly distributed heat-affected zone of the shaft tube.

[0018] In some embodiments, the control scheme further includes: controlling the total width of the welding heat-affected zone on the inner wall of the shaft tube to be no less than the reduced circumference of the inner wall of the shaft tube.

[0019] By adopting the above technical solution, when the total width of the heat-affected zone is not less than the circumference of the inner wall of the shaft tube after reduction, this strengthening effect can be evenly distributed in the circumferential direction of the inner wall of the shaft tube, so that the shaft tube can better disperse stress when bearing load and avoid structural damage caused by local stress concentration.

[0020] In some embodiments, the control scheme includes controlling the weld heat-affected zone on the inner wall of the shaft tube to not extend beyond the end of the reinforcing inner tube.

[0021] By adopting the above technical solution, the heat-affected zone of the weld is controlled to not extend beyond the end of the reinforcing inner tube, thus preventing welding to areas outside the reinforcing inner tube and avoiding unpredictable degradation of the material properties of the reinforcing inner tube due to the shape distortion of the end of the weld heat-affected zone.

[0022] In some embodiments, the welded shaft tube and the reinforcing inner tube are simultaneously connected to the universal joint fork, specifically including: at one end of the shaft tube, welding and fixing the shaft tube to the outer wall of the universal joint fork and welding and fixing the reinforcing inner tube to the inner wall of the universal joint fork; at the other end of the shaft tube, welding and fixing the shaft tube to the outer wall of the spline sleeve and welding and fixing the reinforcing inner tube to the inner wall of the spline sleeve.

[0023] By adopting the above technical solution, the shaft tube and reinforcing inner tube are effectively welded to the universal joint fork, ensuring the performance of the drive shaft.

[0024] In a second aspect, a drive shaft is provided, comprising: a shaft tube; a reinforcing inner tube; a universal joint fork; and connecting the reinforcing inner tube to the inner side of the end of the shaft tube using a connection method as described in any of the preceding claims, and having one end of the shaft tube connected to the universal joint fork and the other end connected to the reinforcing inner tube at both ends.

[0025] By adopting the above technical solution—connecting the shaft tube, reinforcing inner tube, and universal joint fork—the connection of the drive shaft is effectively achieved. This results in a drive shaft with good load-bearing capacity, light weight, convenient manufacturing, and low cost.

[0026] The beneficial effects of the technical solution provided in this application include: This application provides a method for connecting a drive shaft and a drive shaft itself. Because the reinforcing inner tube changes the traditional structure of the drive shaft, the original method of compensating for strength by increasing the overall wall thickness of the shaft tube is transformed into local structural reinforcement. This optimization method no longer thickens the entire shaft tube due to the extremely short welding joint area, reducing unnecessary material usage and lowering material costs. Furthermore, by designing the reinforcing inner tube and welding process, the shape and distribution of the weld heat-affected zone are optimized, transforming the linearly distributed softening zone of conventional welding or upsetting heat-affected zones into a non-linearly distributed heat-affected zone. This disperses the performance degradation areas when the shaft tube is subjected to torsional deformation, improving the load-bearing capacity of the joint, reducing weld stress, and avoiding accidental damage caused by strength degradation in the heat-affected zone of the shaft tube, thereby improving the reliability and safety of the welded structure of the drive shaft. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a schematic diagram of the overall structure provided for an embodiment of this application; Figure 2 This is a schematic diagram illustrating the weld seam, provided as an embodiment of this application.

[0029] In the diagram: 1. Shaft tube; 2. Reinforcing inner tube; 3. Weld seam; 4. Weld heat-affected zone. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0031] This application provides a method for connecting a drive shaft, which solves the problem in related technologies where the overall wall thickness of the shaft tube is increased to compensate for local strength loss, resulting not only in material waste but also severely weakening the weight reduction and cost reduction effect of lightweight design.

[0032] Example 1 Reference Figure 1-2 This application discloses a method for connecting a drive shaft, which includes: Step 1: Determine the target wall thickness of the reinforcing inner tube 2 according to the first design requirements. The first design requirements include: after the reinforcing inner tube 2 is welded to the inner end of the shaft tube 1, the total load-bearing capacity of the area of ​​the shaft tube 1 where the reinforcing inner tube 2 is welded is not less than the load-bearing capacity of the remaining areas of the shaft tube 1. Determining the target wall thickness of the reinforcing inner tube 2 according to the first design requirements includes: firstly, selecting a reinforcing inner tube 2 with material properties matching those of the shaft tube 1, including but not limited to steel or aluminum; then, based on the material mechanical property data of the shaft tube 1 and the reinforcing inner tube 2 and the dimensional parameters of the shaft tube 1, establishing inequalities under the constraints of the first design requirements, and calculating the range of wall thickness of the reinforcing inner tube 2; finally, selecting the target wall thickness of the reinforcing inner tube 2 from the calculated range of wall thicknesses according to the design standards and usage requirements of the drive shaft.

[0033] The inequality is: , In the formula: D represents the outer diameter of shaft tube 1; t0 represents the wall thickness of shaft tube 1; σ0 represents the tensile strength of shaft tube 1 material; ψ0 represents the welding joint coefficient of shaft tube 1 material; t represents the wall thickness of reinforcing inner tube 2; σ represents the tensile strength of reinforcing inner tube 2 material; and ψ represents the welding joint coefficient of reinforcing inner tube 2 material. The mechanical properties of shaft tube 1 and reinforcing inner tube 2 are σ0, σ, ψ0, and ψ, respectively.

[0034] In this application, increasing the overall wall thickness of the axle tube 1 to compensate for the strength loss due to softening caused by local circumferential welds leads to an increase in the overall weight of the vehicle. The applicant has discovered that adding reinforcing inner tubes 2 at both ends of the axle tube 1 can achieve a precise match between material strength and stiffness, significantly reducing the mass of the axle tube 1 while ensuring structural strength, making it an ideal solution for lightweighting the drive shaft.

[0035] The design standards and usage requirements for drive shafts are formulated based on extensive engineering practice and theoretical research. Therefore, to ensure a precise match between the reinforcing inner tube 2 and the drive shaft, the dimensions of the shaft tube 1 and the mechanical properties of its materials are directly determined based on the drive shaft's performance requirements. Furthermore, the welding joint coefficient between the shaft tube 1 and the reinforcing inner tube 2 is confirmed according to experimental standards used in the work. Selecting a reinforcing inner tube 2 with material properties compatible with the shaft tube 1 avoids differences in thermal expansion coefficients, stress concentration, or brittle cracks caused by welding dissimilar materials, thus effectively ensuring the drive shaft's performance.

[0036] Therefore, firstly, a reinforcing inner tube 2 is selected based on its material properties matching those of shaft tube 1. Then, inequalities are established based on the material mechanical property data of shaft tube 1 and reinforcing inner tube 2, and the dimensional parameters of shaft tube 1, to calculate the wall thickness range. Finally, the target wall thickness is determined according to the design standards and usage requirements of the drive shaft, ensuring that the target wall thickness meets the first design requirement: the total load-bearing capacity of the area of ​​shaft tube 1 welded with reinforcing inner tube 2 is not less than the load-bearing capacity of the remaining areas of shaft tube 1. The design standards and usage requirements of the drive shaft include, but are not limited to, selecting the minimum value from the target wall thickness range as the target wall thickness according to the requirements of lightweight design.

[0037] Therefore, when the reinforcing inner tube 2 is connected to the shaft tube 1, the reinforcing inner tube 2 can precisely reinforce the potential strength reduction problem in the weld heat-affected zone 4, unlike the traditional method of compensating for local strength loss by increasing the overall wall thickness of the shaft tube 1. This precise reinforcement method only treats the parts that need reinforcement, avoiding unnecessary material accumulation and improving the targeted use of materials. The target wall thickness also ensures that each area of ​​the drive shaft has sufficient load-bearing capacity, preventing the welded area from becoming a weak point in the entire drive shaft. This ensures that the drive shaft can withstand the corresponding load during operation and will not fail as a whole due to local strength problems.

[0038] Step Two: After confirming the target wall thickness according to the first design requirement, a welding scheme for the shaft tube 1 and the reinforcing inner tube 2 must be formulated. Therefore, this application determines the design parameters of the weld 3 between the reinforcing inner tube 2 and the shaft tube 1 according to the second design requirement. The second design requirement includes: after the reinforcing inner tube 2 is welded to the inner end of the shaft tube 1, the load-bearing capacity of the area where the reinforcing inner tube 2 is welded to the shaft tube 1 is not greater than the load-bearing capacity of all welds 3. Determining the design parameters of the weld 3 between the reinforcing inner tube 2 and the shaft tube 1 specifically includes: selecting a reinforcing inner tube 2 with material properties matching those of the shaft tube 1; then, based on the material mechanical properties data of the reinforcing inner tube 2 and the dimensional parameters of the shaft tube 1, establishing inequalities with the second design requirement as a constraint, and calculating the range of design parameters for the weld 3; finally, according to the design standards and usage requirements of the drive shaft, selecting the weld 3 design parameters regarding the length, width, and number of welds from the calculated range of design parameters for the weld 3.

[0039] The inequality is: In the formula, D represents the outer diameter of the shaft tube 1; t0 represents the wall thickness of the shaft tube 1; t represents the wall thickness of the reinforcing inner tube 2; σ represents the tensile strength of the reinforcing inner tube 2 material; ψ represents the welding joint coefficient of the reinforcing inner tube 2 material; τ represents the shear strength of the reinforcing inner tube; n represents the number of welds 3; W represents the width of weld 3; and L represents the length of weld 3. The mechanical properties of the reinforcing inner tube 2 material are σ, τ, and ψ, respectively.

[0040] Different materials differ in their physical and chemical properties, such as coefficient of thermal expansion, elastic modulus, and yield strength. Therefore, when the reinforcing inner tube 2 and the shaft tube 1 have the same material properties, they can better coordinate deformation and load-bearing during welding and subsequent use. The mechanical properties of the reinforcing inner tube 2 reflect its resistance to stress. The actual strength of the welded joint is usually lower than that of the base material. This coefficient is used to correct the load-bearing capacity calculation of weld 3, making the calculation results more consistent with reality. Since the reinforcing inner tube 2 is connected to the inner end of the shaft tube 1, the dimensional parameters of the reinforcing inner tube 2 can be calculated and confirmed using the dimensional parameters of the shaft tube 1. Combining the dimensions of the reinforcing inner tube 2 with the aforementioned material property data and the weld joint coefficient, inequalities are established based on mechanical principles. A reasonable range of values ​​for the design parameters of weld 3 can be obtained. Then, within this range, according to the design standards and usage requirements of the drive shaft, through precise calculation and reasonable selection of the design parameters of weld 3, the load-bearing capacity of weld 3 can meet the design requirement that the load-bearing capacity of the area where the reinforcing inner tube 2 is welded to the shaft tube 1 is not greater than the load-bearing capacity of all welds 3. This means that when the transmission bearing is under load, weld 3 can reliably transmit stress and will not become a weak link in the structure, thus ensuring the overall load-bearing capacity and safety of the transmission shaft.

[0041] Step 3: After determining the specific design parameters of weld 3, weld reinforcing inner tubes 2 with the target wall thickness to the inner sides of both ends of the shaft tube 1 according to the design parameters of weld 3. During welding, the appropriate welding method should be selected according to the materials of shaft tube 1 and reinforcing inner tube 2. Specifically, the reinforcing inner tube 2 is first fitted onto both ends of shaft tube 1 by cold shrinking and then pressing in, that is, the reinforcing inner tube 2 is located inside the shaft part of shaft tube 1. During nesting, shaft tube 1 and reinforcing inner tube 2 are fitted with a clearance or interference fit to ensure that shaft tube 1 and reinforcing inner tube 2 are tightly fitted without gaps. To avoid defects at the root of weld 3 caused by the gap between shaft tube 1 and reinforcing inner tube 2 during welding of the circumferential weld of shaft tube 1 and the longitudinal reinforcing weld 3 of reinforcing inner tube 2, and to ensure that the circumferential weld 3 of shaft tube 1 and the longitudinal reinforcing weld 3 of reinforcing inner tube 2 are evenly distributed on the circumferential inner wall of shaft tube 1, reducing the local stress concentration of weld 3 between shaft tube 1 and reinforcing inner tube 2 under load, the welding quality can be effectively improved to ensure the strength performance of the drive shaft.

[0042] When the shaft tube 1 and the reinforcing inner tube 2 are made of steel, the reinforcing inner tube 2 should be slotted or drilled and then connected to both ends of the drive shaft tube 1 by CMT or MAG welding. Alternatively, for aluminum shaft tube 1 and the reinforcing inner tube 2, the reinforcing inner tube 2 should be slotted or drilled and then connected to both ends of the shaft tube 1 by CMT welding or direct friction stir welding.

[0043] Step 4: After the shaft tube 1 and the reinforcing inner tube 2 are assembled, finally connect the welded shaft tube 1 and the reinforcing inner tube 2 simultaneously to the universal joint fork and spline sleeve (not shown in the figure) to complete the installation of the drive shaft. Connecting the welded shaft tube 1 and the reinforcing inner tube 2 to the universal joint fork and spline sleeve simultaneously includes: at one end of the shaft tube 1, welding the shaft tube 1 to the outer wall of the universal joint fork and welding the reinforcing inner tube 2 to the inner wall of the universal joint fork; at the other end of the shaft tube 1, welding the shaft tube 1 to the outer wall of the spline sleeve and welding the reinforcing inner tube 2 to the inner wall of the spline sleeve. This effectively ensures that the shaft tube 1 and the reinforcing inner tube 2 are fully welded to the universal joint fork and spline sleeve, ensuring connection strength and guaranteeing the performance of the drive shaft.

[0044] In this application, because the softened zone affected by welding or upsetting heat is linearly distributed, the performance degradation of the shaft tube 1 under torsional deformation is concentrated on a single plane. That is, if the heat-affected zone is linearly distributed, the heat-affected zones of adjacent welds 3 may overlap significantly, leading to excessive heat concentration in localized areas, causing overheating, coarse grains, and reduced mechanical properties of the welded joint. To avoid this, before welding reinforcing inner tubes 2 with target wall thicknesses to the inner sides of both ends of the shaft tube 1 according to the design parameters of welds 3, the connection method designed in this application further includes: obtaining the arrangement scheme of welds 3 based on the design parameters of welds 3, then establishing a control scheme for the welding heat-affected zone 4 based on the arrangement scheme, and finally completing the welding of the reinforcing inner tube 2 and the shaft tube 1 based on the control scheme to ensure the strength performance of the transmission shaft. Specifically, the arrangement scheme includes: arranging multiple welds 3 along the circumference of the shaft tube 1, each weld 3 extending along the axial direction of the reinforcing inner tube 2, with multiple welds 3 forming a welding heat-affected zone 4. This application includes, but is not limited to, six welds 3. This arrangement increases the connection area between the reinforcing inner tube 2 and the shaft tube 1. More connection points mean that when bearing loads, stress can be more evenly distributed on multiple welds 3, avoiding structural damage caused by local stress concentration.

[0045] Further control measures include ensuring that the length difference between adjacent welds 3 after reduction is not less than the width of weld 3 itself. Specifically, an inequality is established based on the width of weld 3 itself, the material welding joint coefficient of the reinforcing inner tube 2, and the absolute length difference between two adjacent welds 3: L i +1 and L iHere, W represents the length of two adjacent welds 3, W represents the width of weld 3, and ψ represents the welding joint coefficient of the reinforcing inner tube 2 material. When selecting the reduced length of adjacent welds 3, it should be based on a reasonable range of weld 3 design parameters to ensure that the difference in length between adjacent welds 3 after reduction is not less than the width of weld 3 itself. Controlling the difference in length between adjacent longitudinal welds 3 after reduction to be not less than the width of weld 3 itself confirms the length of the reinforcing inner tube 2, ensuring that the shape and size of the end of the heat-affected zone of the shaft tube 1 at the weld area of ​​weld 3 in the longitudinal direction differ. This increases the length and area of ​​the end of the heat-affected zone of the shaft tube at the weld area of ​​weld 3, making the heat distribution more non-linear. This avoids local flushing of the heat-affected zone of the shaft tube 1 at the weld area of ​​weld 3, allowing the softened area of ​​the shaft tube 1 to be evenly distributed circumferentially on the inner wall of the shaft tube 1. This enables the shaft tube 1 to better bear the load and avoids a decrease in load-bearing capacity due to a concentrated and linearly distributed heat-affected zone.

[0046] In this application, the control scheme further includes: ensuring that the total width of the weld heat-affected zone 4 on the inner wall of the shaft tube 1 is not less than the reduced circumference of the inner wall of the shaft tube 1. Specifically, an inequality is established based on the width of the weld 3, the width of the weld heat-affected zones 4 on both sides, the dimensional parameters of the shaft tube 1, and the welding joint coefficient of the shaft tube 1 material: In the formula, W i1 W i2 This represents the width of the heat-affected zones 4 on both sides of the weld. Furthermore, the control scheme also includes: controlling the heat-affected zones 4 on the inner wall of the shaft tube 1 to not extend beyond the end of the reinforcing inner tube 2. Specifically, an inequality is established based on the width of the heat-affected zones 4 on both sides and the length of the adjacent weld 3: .

[0047] In this application, when the total width of the heat-affected zone is not less than the reduced circumference of the inner wall of the shaft tube 1, it ensures that heat is fully applied to the circumferential area of ​​the inner wall of the shaft tube 1, thereby obtaining a uniform width of the heat-affected zone. This avoids excessive changes in the microstructure in local areas, thus ensuring the uniformity of the mechanical properties of the welded joint and improving the welding quality. Furthermore, when the welded heat-affected zone 4 on the inner wall of the shaft tube 1 is controlled not to extend beyond the end of the reinforcing inner tube 2, it prevents excessive heat transfer to areas outside the reinforcing inner tube 2, avoiding material performance degradation due to local overheating. For example, if the heat-affected zone extends beyond the end of the reinforcing inner tube 2, it may cause problems such as coarse grains and reduced hardness in the surrounding non-reinforcing areas, affecting the overall performance of the shaft tube 1. Therefore, it is evident that the design of the control scheme can optimize structural performance and improve the feasibility of the manufacturing process.

[0048] Therefore, while minimizing the length of the reinforcing inner tube 2, the connection area between the reinforcing inner tube 2 and the shaft tube 1 is increased, and the stress can be more evenly distributed on multiple welds when bearing loads, avoiding structural damage caused by local stress concentration. Controlling the heat-affected zone of the weld 3 to not extend beyond the end of the reinforcing inner tube 2 can prevent welding to areas outside the reinforcing inner tube 2, and can avoid unpredictable degradation of the material properties of the reinforcing inner tube 2 due to the shape distortion of the end of the heat-affected zone of the weld 3.

[0049] Example 2 Reference Figure 1-2 This application provides a drive shaft, including: a shaft tube 1, a reinforcing inner tube 2, a universal joint fork, and a spline sleeve (not shown in the figure); and connecting the shaft tube 1, the reinforcing inner tube 2, the universal joint fork, and the spline sleeve using the connection method disclosed in Embodiment 1. Specifically: the reinforcing inner tube 2 is pressed into the shaft tube 1 after cold shrinkage and nested at both ends of the shaft tube 1. During nesting, the shaft tube 1 and the reinforcing inner tube 2 are interference-fitted to ensure a tight fit between the shaft tube 1 and the reinforcing inner tube 2 without gaps. This avoids gaps between the shaft tube 1 and the reinforcing inner tube 2 during welding of the circumferential weld 3 on the shaft tube 1 and the longitudinal reinforcing weld 3 of the reinforcing inner tube 1, which could lead to defects at the root of the weld 3. Furthermore, it enables the circumferential weld 3 of the shaft tube 1 and the longitudinal reinforcing weld 3 of the reinforcing inner tube 2 to be evenly distributed circumferentially on the inner wall of the shaft tube 1, reducing local stress concentration of the weld 3 between the shaft tube 1 and the reinforcing inner tube 2 under load, effectively improving the welding quality, and ensuring the strength performance of the drive shaft. Then, the reinforcing inner tube 2 is connected to the inner side of the end of the shaft tube 1, and to both ends of the shaft tube 1. One end is connected to the universal joint fork, and the other end is connected to the reinforcing inner tube 2. During connection, the shaft tube 1 is welded and fixed to the outer wall of the universal joint fork, and the reinforcing inner tube 2 is welded and fixed to the inner wall of the universal joint fork. At the other end of the shaft tube 1, the shaft tube 1 is welded and fixed to the outer wall of the spline sleeve, and the reinforcing inner tube 2 is welded and fixed to the inner wall of the spline sleeve. That is, after welding the area of ​​the shaft tube 1 with the reinforcing inner tube 2, the reinforcing inner tube 2 and the shaft tube 1 should be completely fused together. This ensures that the shaft tube 1 and the reinforcing inner tube 2 are completely welded to the universal joint fork and the spline sleeve to ensure the performance of the drive shaft, effectively realize the manufacturing of the drive shaft, and achieve good load-bearing performance, light weight, convenient manufacturing and processing, and low cost.

[0050] The existing manufacturing process suffers from the following technical bottlenecks: Firstly, the differential thickness plate welding process involves: variable thickness rolling or unequal thickness plate welding, annealing heat treatment, continuous pipe rolling, welding into pipes, and weld seam treatment. The drawbacks include: complex procedures, high heat treatment energy consumption, and unstable weld joint quality, resulting in high overall manufacturing costs and hindering large-scale application.

[0051] Secondly, mechanical pipe expansion or upsetting processes involve using seamless or welded pipes as blanks and locally expanding or upsetting them under the constraint of an external mold. The drawbacks include the tendency to generate surface defects such as indentations and wrinkles during deformation, and the formation of new heat-affected zones or work-hardened layers in the expanded or upsetting areas, requiring additional heat treatment to eliminate these defects, further increasing costs. This application addresses this by welding reinforcing inner tubes 2 to the inner sides of both ends of the shaft tube 1. The shaft tube 1 and reinforcing inner tubes 2 are then welded and fixed to the universal joint fork and spline sleeve, effectively forming a drive shaft. The welding process is simple, and welding quality can be guaranteed through weld control. The reinforcing inner tubes 2 can precisely reinforce the potential strength reduction in the weld heat-affected zone 4, and also ensure sufficient load-bearing capacity in all areas of the drive shaft, achieving a lightweight design.

[0052] Example 3 This application discloses a method for connecting a drive shaft, comprising welding stacked welds 3 on the inner walls of both ends of the shaft tube 1 according to the design standards and usage requirements of the drive shaft, and using the welds 3 to connect the shaft tube 1 to the universal joint fork and spline sleeve. The welds 3 disperse the performance degradation areas of the shaft tube 1 under torsional deformation, improve the load-bearing capacity of the joint, reduce weld stress, and avoid accidental damage caused by strength degradation in the heat-affected zone of the shaft tube 1, thereby improving the reliability and safety of the welded structure of the drive shaft.

[0053] In the description of this application, it should be noted that the terms "upper," "lower," etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application 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, and therefore should not be construed as a limitation of this application. Unless otherwise expressly specified and limited, the terms "installed," "connected," and "linked" 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; they can refer to the internal communication between two elements. For those skilled in the art, the specific meaning of the above terms in this application can be understood according to the specific circumstances.

[0054] It should be noted that in this application, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0055] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for connecting a drive shaft, characterized in that, It includes: According to the first design requirements, the target wall thickness of the reinforcing inner tube (2) is determined. The first design requirements include: after the reinforcing inner tube (2) is welded to the inner side of the end of the shaft tube (1), the total bearing capacity of the area of ​​the shaft tube (1) where the reinforcing inner tube (2) is welded is not lower than the bearing capacity of the other areas of the shaft tube (1). According to the second design requirements, the design parameters of the weld (3) between the reinforcing inner tube (2) and the shaft tube (1) are determined. The second design requirements include: after the reinforcing inner tube (2) is welded to the inner side of the end of the shaft tube (1), the bearing capacity of the area where the reinforcing inner tube (2) is welded to the shaft tube (1) is not greater than the bearing capacity of all welds (3). According to the design parameters of the weld (3), a reinforcing inner tube (2) with the target wall thickness is welded to the inner side of both ends of the shaft tube (1). The welded shaft tube (1) and reinforcing inner tube (2) are simultaneously connected to the universal joint fork and spline sleeve to realize the installation of the drive shaft.

2. The method for connecting a transmission shaft as described in claim 1, characterized in that: According to the first design requirements, the target wall thickness of the reinforcing inner tube (2) is determined, specifically including: Select a reinforcing inner tube (2) that matches the material properties of the shaft tube (1); Based on the material mechanical properties data of the shaft tube (1) and the reinforcing inner tube (2) and the size parameters of the shaft tube (1), inequalities are established with the first design requirement as a constraint to calculate the wall thickness range of the reinforcing inner tube (2); According to the design standards and usage requirements of the drive shaft, the target wall thickness of the reinforcing inner tube (2) is selected from the calculated range of wall thicknesses.

3. The method for connecting a transmission shaft as described in claim 1, characterized in that: The design parameters of the weld (3) between the reinforcing inner tube (2) and the shaft tube (1) are determined, specifically including: Select a reinforcing inner tube (2) that matches the material properties of the shaft tube (1); Based on the material mechanical properties data of the reinforcing inner tube (2) and the size parameters of the shaft tube (1), an inequality is established with the second design requirement as a constraint, and the range of design parameters of the weld (3) is calculated. According to the design standards and usage requirements of the drive shaft, the design parameters of weld (3) regarding the length, width and number of welds (3) are selected from the range of design parameters of weld (3) obtained by calculation.

4. The method for connecting a transmission shaft as described in claim 1, characterized in that: According to the design parameters of the weld (3), before welding the reinforcing inner tubes (2) with the target wall thickness to the inner sides of both ends of the shaft tube (1), the connection method further includes: Based on the design parameters of the weld (3), the arrangement scheme of the weld (3) is obtained; Establish a control scheme for the welding heat-affected zone (4) of the aforementioned arrangement; The welding of the reinforcing inner tube (2) and the shaft tube (1) is completed based on the control scheme to ensure the strength performance of the transmission shaft.

5. The method for connecting a transmission shaft as described in claim 4, characterized in that: The arrangement scheme includes: arranging multiple welds (3) along the circumferential direction of the axial tube (1), each weld (3) extending along the axial direction of the reinforcing inner tube (2), and forming a welding heat-affected zone (4) between the multiple welds (3).

6. The method for connecting a transmission shaft as described in claim 4, characterized in that: The control scheme includes: controlling the length difference between adjacent welds (3) after reduction to be no less than the width of the weld (3) itself.

7. The method for connecting a transmission shaft as described in claim 6, characterized in that: The control scheme further includes: controlling the total width of the welding heat-affected zone (4) on the inner wall of the shaft tube (1) to be no less than the reduced circumference of the inner wall of the shaft tube (1).

8. The method for connecting a transmission shaft as described in claim 7, characterized in that: The control scheme further includes: controlling the welding heat-affected zone (4) on the inner wall of the shaft tube (1) to not extend beyond the end of the reinforcing inner tube (2).

9. The method for connecting a transmission shaft as described in claim 1, characterized in that: The welded shaft tube (1) and reinforcing inner tube (2) are simultaneously connected to the universal joint fork and spline sleeve, specifically including: At one end of the shaft tube (1), the shaft tube (1) is welded and fixed to the outer wall of the universal joint fork, and the reinforcing inner tube (2) is welded and fixed to the inner wall of the universal joint fork; At the other end of the shaft tube (1), the shaft tube (1) is welded and fixed to the outer wall of the spline sleeve, and the reinforcing inner tube (2) is welded and fixed to the inner wall of the spline sleeve.

10. A drive shaft, characterized in that, include: Shaft tube (1); Reinforce the inner tube (2); Universal joint fork; Spline sleeve; And the reinforcing inner tube (2) is connected to the inner side of the end of the shaft tube (1) using the connection method described in any one of claims 1-9 above, and at both ends of the shaft tube (1), one end is connected to the universal joint fork and the other end is connected to the reinforcing inner tube (2).

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