Adjustable pre-tightening force spring mechanism based on integrated punch forming and assembling method

Abstract

The invention relates to the technical field of pre-tightening force springs, in particular to an adjustable pre-tightening force spring mechanism based on integrated punch forming and an assembling method.The assembling method comprises the steps that based on the maximum working load of a to-be-assembled spring, a first detection step length is determined so as to determine a plurality of different detection external forces, performing force control stress detection on the to-be-assembled spring for a plurality of times to obtain a size change trend, determining a second detection step length according to the size change trend and the first detection step length to determine a plurality of different detection sizes, performing size control stress detection on the to-be-assembled spring for a plurality of times to obtain a change trend of pre-tightening force, a loading path and an unloading path; based on each loading path and each unloading path, correcting the change trend of the pre-tightening force; and scale calibration is conducted on the pretightening force value of the pretightening force adjusting ruler, initial pretightening is conducted, and assembling of the spring with the adjustable pretightening force is completed. According to the spring pretightening force adjusting device, the pretightening force adjusting accuracy of the integrally punched and formed spring is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of preload springs, and in particular to an adjustable preload spring mechanism based on integral stamping and an assembly method. Background Art

[0002] The design and control of pre-compression of die springs used for integrated stamping (especially high-speed continuous stamping) are the key to ensuring stable operation of the die, extending the life of the spring, preventing product defects and even damage to the die. Pre-compression can ensure the initial pressing / ejection force. The moment the punch contacts the sheet, the pre-compression force already exists, which can immediately provide sufficient pressing force (to prevent the sheet from moving and wrinkling) or ejection force (to ensure smooth demolding of the workpiece). At the same time, pre-compression puts the spring in a "tight" state before starting to work, which can respond to impact loads more quickly and stably, reduce vibration and noise, prevent the spring from instantaneous overload or instability, resist impact, maintain stability, and extend the service life of the spring. When the pre-compression is insufficient, the noise and vibration will be aggravated, and the initial pressing force will be insufficient. The movement of the sheet metal during punching or forming will cause the sheet metal to deflect and wrinkle. When the sheet metal deflects seriously, it will cause die gnawing and edge breakage. At the same time, the spring will be suddenly subjected to a huge impact from a relaxed state, and the stress peak may exceed the material limit, leading to impact fracture of the spring. When the pre-compression is too large, it will cause crushing of the sheet metal or workpiece, and accelerate the wear of the guide components (guide pins, guide sleeves). At the same time, if the initial stress is too high, the effective fatigue life of the spring will be greatly shortened.

[0003] At present, the pre-tightening force of springs used for integral stamping is often completely dependent on the operator's experience during assembly, and the adjustment of the pre-tightening force is often repeated by adding or removing hardened gaskets. It is impossible to accurately control the pre-compression degree of the spring during the assembly process. Therefore, it is of great practical significance to develop a mechanism and assembly method that can accurately control the pre-compression degree of the spring.

[0004] Chinese Patent Publication No.: CN110763384B discloses a spring preload force detection device and method. The detection device includes a base, a column, a cross bar, a pressure assembly and a clamping assembly. A positive pressure equal to the preload force is applied to the clamping assembly in the detection device. At the same time, the pressure assembly applies a force opposite to the positive pressure to the cross bar. After the spring to be measured is compressed to a preloaded state, the length of the two force arms on the cross bar is measured. The magnitude of the preload force applied to the spring to be measured can be calculated based on the lever principle. It can be seen that the spring preload force detection device and method have the following problems: it is impossible to measure the deformation of the spring to be measured in real time while applying pressure to the spring to be measured, and it is impossible to obtain the relationship between the deformation of the spring to be measured and the corresponding preload force. Summary of the invention

[0005] To this end, the present invention provides an adjustable pre-tightening force spring mechanism based on integral stamping, so as to overcome the problem in the prior art that the corresponding relationship between the pre-tightening force of the adjustable pre-tightening force spring and the spring deformation cannot be accurately identified, resulting in the inability to precisely adjust the pre-tightening force of the adjustable pre-tightening force spring.

[0006] To achieve the above object, on the one hand, the present invention provides an assembly method for an adjustable pre-tightening force spring mechanism based on integral stamping, including: Step S1, obtaining the maximum working load of the spring to be assembled, and determining the first detection step length of the spring to be assembled based on the maximum working load; Step S2, determining a number of different detection external forces with the first detection step length, performing a number of force-controlled stress detections on the spring to be assembled, and obtaining the corresponding dimensional change trend of the spring to be assembled under each detection external force state, so as to determine the second detection step length of the spring to be assembled according to the dimensional change trend and the first detection step length; Step S3, determining a number of different detection dimensions with the second detection step length, performing a number of dimension-controlled stress detections on the spring to be assembled, and obtaining the corresponding pre-tightening force change trend, pre-tightening force loading path, and pre-tightening force unloading path of the spring to be assembled under each corresponding detection dimension state; Step S4, determining the corresponding hysteresis characteristic data based on the pre-tightening force loading path and pre-tightening force unloading path in each dimension-controlled stress detection, and correcting the pre-tightening force change trend with the hysteresis characteristic data to obtain a corrected pre-tightening force change trend; Step S5, determining the linear pre-tightening force change range and non-linear pre-tightening force change range of the spring to be assembled based on the analysis of the corrected pre-tightening force change trend, so as to determine the calibration range corresponding to the pre-tightening force adjustment scale; Step S6, calibrating the pre-tightening force value of the pre-tightening force adjustment scale according to the calibration range, and performing initial pre-tightening on the adjustable pre-tightening force spring according to the use requirement, to complete the assembly of the adjustable pre-tightening force spring.

[0007] Further, the step S1 includes: Step S11, determining the maximum allowable pre-tightening force of the spring to be assembled according to the maximum working load; Step S12, performing a reference stress detection on the spring to be assembled with the maximum allowable pre-tightening force, and obtaining the maximum pre-tightening dimension corresponding to the spring to be assembled under the maximum allowable pre-tightening force; Step S13, determining the first detection frequency of the spring to be assembled based on the maximum pre-tightening dimension; Step S14, determining the first detection step length of the spring to be assembled based on the maximum allowable pre-tightening force and the first detection frequency; Wherein, the first detection frequency is the total number of different detection external forces used in the force-variable force detection.

[0008] Further, the first detection step size is the change amount of the detection external force received by the to-be-assembled spring in adjacent times during the force-controlled force detection; The second detection step size is the change amount of the detection size of the to-be-assembled spring in adjacent times during the dimension-controlled force detection.

[0009] Further, the step S2 includes: Step S21, performing force-controlled force detection on the to-be-assembled spring with a plurality of different detection external forces determined by the first detection step size at the first detection frequency, and obtaining the corresponding dimension data of the to-be-assembled spring in each force-controlled force detection; Step S22, recording the mapping data points of the force-dimension data - detection external force formed by each detection external force and the corresponding dimension data to obtain the dimension change trend of the to-be-assembled spring; Step S23, determining the second detection step size of the to-be-assembled spring according to the dimension change trend and the first detection step size.

[0010] Further, the step S23 includes: Step S231, identifying the dimension linear change range and the dimension non-linear change range of the to-be-assembled spring according to the slope change characteristics of the dimension change trend; Step S232, calculating a reference second detection step size according to the maximum pre-tightening dimension and the first detection frequency; Step S233, narrowing the detection interval within the dimension non-linear change range, and calculating a first sub-step size and a second sub-step size based on the reference second detection step size; Step S234, obtaining the second detection step size according to the first sub-step size and the second sub-step size.

[0011] Further, the step S231 includes: Step S2311, performing a first derivative operation on the dimension change trend to obtain a first slope change sequence; Step S2312, detecting the mutation points in the first slope change sequence, wherein the mutation points satisfy that the slope change value in adjacent sections exceeds a preset mutation threshold; Step S2313, determining the pre-tightening force interval where the mutation points are located as the dimension non-linear change range, and the pre-tightening force intervals where the remaining points are located as the dimension linear change range.

[0012] Further, the step S3 includes: Step S31: Perform a dimensional controlled force detection on the spring to be assembled with a second detection frequency at several different detection sizes determined by the second detection step length, and simultaneously collect the pre-tightening force loading path and the pre-tightening force unloading path in each dimensional controlled force detection. Step S32: Record the mapping data points of the pre-tightening force data - detection size for each detection size and the corresponding pre-tightening force data to obtain the pre-tightening force change trend of the spring to be assembled.

[0013] Further, the step S4 includes: Step S41: Determine the hysteresis characteristic data corresponding to several compression amounts according to the absolute value of the difference between the pre-tightening forces corresponding to the pre-tightening force loading path and the pre-tightening force unloading path in the same compression amount during a single dimensional controlled force detection. Step S42: Determine the hysteresis difference in a single dimensional controlled force detection according to the maximum value among the hysteresis characteristic data in a single dimensional controlled force detection. Step S43: Determine the maximum hysteresis difference according to the maximum value among the hysteresis differences in each dimensional controlled force detection. Step S44: Calculate the correction factor in a single dimensional controlled force detection according to the hysteresis difference and the maximum hysteresis difference in a single dimensional controlled force detection. Step S45: Correct the numerical value of the pre-tightening force corresponding to the pre-tightening force change trend through the correction factor corresponding to each dimensional controlled force detection to obtain the corrected pre-tightening force change trend.

[0014] Further, the step S5 includes: Step S51: Obtain the linear pre-tightening force change range and the non-linear pre-tightening force change range of the spring to be assembled based on the dimensional linear change range and the dimensional non-linear change range of the spring to be assembled. Step S52: Obtain the calibration scale of the pre-tightening force adjustment ruler with the second detection step length and the corresponding pre-tightening force in the corrected pre-tightening force change trend. Wherein, the pre-tightening force adjustment ruler is calibrated with a linear working section and a non-linear working section identifier divided based on the linear pre-tightening force change range and the non-linear pre-tightening force change range.

[0015] On the other hand, the present invention also provides an integrally stamped adjustable pre-tightening force spring mechanism, which is assembled by the above-mentioned assembly method of the integrally stamped adjustable pre-tightening force spring, and includes: An adjustable pre-tightening force spring; An adjustment bolt, which is in contact connection with one end of the adjustable pre-tightening force spring, and is used to adjust the compression amount of the adjustable pre-tightening force spring by tightening / loosening the bolt to adjust the pre-tightening force of the adjustable pre-tightening force spring. A fastening nut, which is matched with the adjusting bolt to fix the position of the adjusting bolt so as to fix the compression amount of the adjustable pre-tightening force spring; A pre-tightening force adjusting scale, which is provided with dimensional graduations and corresponding pre-tightening force values to represent the pre-tightening force value corresponding to the relative position of the current adjusting bolt.

[0016] Compared with the prior art, the beneficial effect of the present invention is that by constructing a dual-mode collaborative detection mechanism of force control - dimension control and a dynamic correction model for hysteresis effect, a pre-tightening force adjustment scale with a non-linear warning mark is generated, realizing high-precision pre-tightening assembly of the integral stamping die spring under extreme working conditions, and significantly improving the dynamic stability and service life of the stamping die.

[0017] Furthermore, the present invention designs an adaptive step size based on the maximum working load to accurately match the actual force-bearing range of the die spring during the stamping process, avoiding the risk of pre-tightening force failure of the traditional empirical pre-tightening method under impact loads.

[0018] Furthermore, the present invention detects the slope mutation point, clearly marks the non-linear danger zone on the pre-tightening force adjustment scale and accurately defines the linear working area of the pre-tightening force, ensuring that the die spring is always in the optimal stiffness range and reducing the dimensional deviation of the stamped parts caused by the spring stiffness fluctuation.

[0019] Furthermore, the present invention establishes a correction factor for dimension hysteresis compensation to effectively compensate for the force value backlash generated by internal friction of the die spring during high-speed stamping cycles, ensuring the consistency between the static pre-tightening setting value and the dynamic working holding force.

[0020] Furthermore, the present invention converts the complex spring characteristics into a visual pre-tightening force adjustment scale, enabling operators to complete high-precision pre-tightening without professional instruments, and significantly shortening the maintenance downtime of the stamping die. Description of the Drawings

[0021] Figure 1 It is a schematic diagram of an adjustable pre-tightening force spring based on integral stamping forming according to an embodiment of the present invention; Figure 2 It is a flowchart of an assembly method of an adjustable pre-tightening force spring based on integral stamping forming according to an embodiment of the present invention; Figure 3 It is a flowchart of step S1 of an assembly method of an adjustable pre-tightening force spring based on integral stamping forming according to an embodiment of the present invention; Figure 4 It is a flowchart of step S2 of an assembly method of an adjustable pre-tightening force spring based on integral stamping forming according to an embodiment of the present invention; Figure 5 It is a flowchart of step S23 of an assembly method of an adjustable pre-tightening force spring based on integral stamping forming according to an embodiment of the present invention; In the figure, 1 - pre - tightening force adjusting ruler; 11 - pre - tightening force scale; 12 - dimension scale; 2 - adjusting bolt; 3 - fastening nut; 4 - adjustable pre - tightening force spring; 5 - upper clamping plate; 6 - limiting plate. Specific embodiments

[0022] In order to make the objectives and advantages of the present invention more clearly understood, the present invention will be further described below in conjunction with embodiments; it should be understood that the specific embodiments described herein are only for explaining the present invention and are not used to limit the present invention.

[0023] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are only for explaining the technical principles of the present invention and do not limit the protection scope of the present invention.

[0024] It should be noted that in the description of the present invention, the terms indicating directions or positional relationships such as "upper", "lower", "left", "right", "inner", "outer", etc. are based on the directions or positional relationships shown in the drawings. This is only for convenience of description and does not indicate or imply that the device or element must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation of the present invention.

[0025] In addition, it should also be noted that in the description of the present invention, unless otherwise clearly specified and limited, the terms "installation", "connection", and "coupling" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0026] As an illustration, in this embodiment, the adjustable pre - tightening force spring based on integral stamping is a stamping die spring.

[0027] Please refer to Figure 1 As shown, it is a schematic diagram of the adjustable pre - tightening force spring based on integral stamping in the embodiment of the present invention. This embodiment provides an adjustable pre - tightening force spring based on integral stamping, including: Adjustable pre - tightening force spring 4; Adjusting bolt 2, which is in contact connection with one end of the adjustable pre - tightening force spring and is used to adjust the pre - tightening force of the adjustable pre - tightening force spring according to its elongation; Fastening nut 3, which is connected to the adjusting bolt and is used to fix the position of the adjusting bolt; Pre - tightening force adjusting ruler 1, which is provided with dimension scales and corresponding pre - tightening force values and is used to represent the pre - tightening force value corresponding to the current adjusting bolt.

[0028] In this embodiment, the adjustable pre-tension spring 4, the adjusting bolt 2, and the fastening nut 3 are installed in the upper clamping plate 5 of the movable die of the stamping die. When adjusting the pre-tension of the adjustable pre-tension spring 4, by tightening or loosening the adjusting bolt 2, the compression amount of the adjustable pre-tension spring 4 relative to the limit plate 6 of the movable die is adjusted. The position of the adjustable pre-tension spring 4 corresponding to the current position of the adjusting bolt 2 is obtained through the dimension scale 12 on the pre-tension adjusting ruler 1. The reading of the pre-tension scale 11 of the pre-tension adjusting ruler 1 can directly read the pre-tension corresponding to the current compression amount of the adjustable pre-tension spring 4, so as to achieve the effect of accurately adjusting the pre-tension of the adjustable pre-tension spring 4 by adjusting the position of the adjusting bolt 2 on the pre-tension adjusting ruler 1.

[0029] Please refer to Figure 2 shown in the figure. It is a flowchart of the assembly method of the adjustable pre-tension spring based on integral stamping forming according to an embodiment of the present invention, including: Step S1, obtaining the maximum working load of the spring to be assembled, and determining the first detection step length of the spring to be assembled based on the maximum working load; It can be understood that the maximum working load of the spring to be assembled is the maximum value of the working load calibrated for the spring to be assembled in the stamping die.

[0030] Please refer to Figure 3 shown in the figure. It is a flowchart of step S1 of the assembly method of the adjustable pre-tension spring based on integral stamping forming according to an embodiment of the present invention. Specifically, the step S1 includes: Step S11, determining the maximum allowable pre-tension of the spring to be assembled according to the maximum working load; In a specific embodiment, according to the maximum working load F max of the spring of the stamping die, the maximum allowable pre-tension F a is calculated through the pre-tension safety factor q. The calculation formula of the maximum allowable pre-tension F a is specifically as follows: , wherein, F a is the maximum allowable pre-tension, with the unit of Newton (N); F max is the maximum working load, with the unit of Newton (N); q is the pre-tension safety factor, and the value range is 0.1 - 0.3. Preferably, q takes 0.2.

[0031] It can be understood that the pre-tension safety factor q is determined according to the safety margin requirement of the dynamic load condition of the spring during stamping work to ensure that the pre-tension does not exceed the yield limit of the spring and avoid plastic deformation; the maximum working load F max is provided by the stamping equipment parameter manual of the spring to be assembled.

[0032] Step S12: Detect the reference force of the spring to be assembled with the maximum allowable pre-tightening force, and obtain the maximum pre-tightening dimension corresponding to the spring to be assembled under the maximum allowable pre-tightening force. In a specific embodiment, the reference force detection is to apply the maximum allowable pre-tightening force F to the spring to be assembled on a universal material testing machine. a After maintaining the pressure for 30 seconds, measure the compression dimension of the spring and record it as L. max The unit is millimeter (mm); the detection conditions are: loading rate 60 N / min (in line with the quasi-static test specification of "GB / T 23934-2015"), ambient temperature: 23°C (to eliminate the influence of thermal expansion).

[0033] Step S13: Determine the first detection frequency of the spring to be assembled based on the maximum pre-tightening dimension, where the first detection frequency is the total number of different detection external forces used in the force-variable force detection.

[0034] In a specific embodiment, the calculation formula for the first detection frequency is specifically: where N is the first detection frequency, which is the calculation result of rounding up to ensure full range coverage; d is the dimension resolution, with the unit of millimeter (mm). Preferably, d is taken as 1 mm.

[0035] Step S14: Determine the first detection step size of the spring to be assembled based on the maximum allowable pre-tightening force and the first detection frequency. In a specific embodiment, the calculation formula for the first detection step size is specifically: where ΔF1 is the first detection step size, with the unit of Newton (N).

[0036] It can be understood that the equal step size ΔF1 makes the detection points evenly distributed in the working interval of the spring to be assembled, which is used as the premise of the linear hypothesis conforming to Hooke's law.

[0037] Based on the maximum preload force and maximum preload stroke of the spring to be detected, and through the spring precision grade, the present invention obtains the first detection step size, ensures that the sampling density of the force-dimension data matches the spring specification, eliminates the detection blind area caused by artificial experience, establishes a reusable detection parameter system, and standardizes the test process for different specification springs.

[0038] Step S2: Determine a number of different detection external forces at the first detection step length, perform a number of force-controlled stress detections on the spring to be assembled, obtain the corresponding dimensional change trends of the spring to be assembled under each detection external force state, and determine the second detection step length of the spring to be assembled according to the dimensional change trends and the first detection step length. Please refer to Figure 4 As shown in the figure, it is a flowchart of step S2 of the assembly method of the adjustable pre-tightening force spring based on integral stamping molding according to an embodiment of the present invention. Specifically, the step S2 includes: Step S21: Determine a number of different detection external forces determined at the first detection step length, perform force-controlled stress detections on the spring to be assembled at the first detection frequency, and obtain the corresponding dimensional data of the spring to be assembled in each force-controlled stress detection. In a specific embodiment, a servo press is used to apply a detection external force to the spring to be assembled, and the external force value increases in increments of the first detection step length ΔF1.

[0039] Step S22: Record the mapping data points of each detection external force and the corresponding dimensional data to form the stress-dimensional data - detection external force, so as to obtain the dimensional change trend of the spring to be assembled.

[0040] In a specific embodiment, the spring compression dimension L corresponding to the detection external force in each force-controlled stress detection is recorded by a laser displacement sensor i , generate a data point set, generate a data point set {(F0, L0), (F1, L1), (F2, L2),..., (F i , L i )}, draw a force-dimension line graph according to the data point set, that is, the dimensional change trend, the horizontal axis of which is the detection external force F i , and the vertical axis is the spring compression dimension L i ; it can be understood that, where i = 0, 1, 2, 3, 4... N, where F i+1 = F i + ΔF1, F N = F a , F0 = 0.

[0041] In a single force-controlled stress detection, after applying the external force each time and stabilizing the pressure for 3 seconds, then read the corresponding spring compression dimension L i to ensure the stability of the spring deformation.

[0042] Step S23: Determine the second detection step length of the spring to be assembled according to the dimensional change trend and the first detection step length. Please refer to Figure 5As shown, it is a flowchart of step S23 of the assembly method of the adjustable pre-tightening force spring based on integral stamping forming according to an embodiment of the present invention. Specifically, the step S23 includes: Step S231, identify the linear dimension change range and non-linear dimension change range of the spring to be assembled according to the slope change characteristics of the dimension change trend; Specifically, the step S231 includes: Step S2311, perform a first derivative operation on the dimension change trend to obtain a first slope change sequence; In a specific embodiment, calculating the first derivative of the dimension change trend is specifically: , The slope sequence is {k0, k1, k2, k3,..., k i-1}.

[0043] Step S2312, detect the mutation points in the first slope change sequence, where the mutation points satisfy that the slope change value in the adjacent section exceeds a preset mutation threshold; In a specific embodiment, the determination of the mutation point is specifically: When k i satisfies , determine k i as a mutation point, where p is a preset mutation threshold, preferably taken as 0.2.

[0044] It can be understood that the non-linear deformation of the spring will cause a change in the slope of the force-dimension curve. In this embodiment, the change is quantified through derivative operation to accurately judge the non-linear deformation region of the spring.

[0045] Step S2313, determine the pre-tightening force interval where the mutation point is located as the non-linear dimension change range, and the pre-tightening force intervals where the other points are located as the linear dimension change range.

[0046] In a specific embodiment, if there is a mutation point k i , then [F i , F i+2 is the non-linear dimension change range, and the pre-tightening force intervals where the other points are located are defined as the linear dimension change range.

[0047] It can be understood that since the detected data are discrete points, the mutation point k i indicates that the slope within [F i , F i+1 differs from the previous adjacent slope by more than the preset mutation threshold. Therefore, taking [F i , F i+2 as the non-linear dimension change range can ensure Fi+1 Located in the range of non - linear dimensional variation.

[0048] Step S232, calculate the reference second detection step size according to the maximum pre - tightening dimension and the first detection frequency. In a specific embodiment, the calculation formula of the reference second detection step size is specifically: , where, △L1 is the reference second detection step size, and the unit is millimeter (mm).

[0049] Step S233, narrow the detection interval within the range of non - linear dimensional variation, and calculate the first sub - step size and the second sub - step size based on the reference second detection step size. In a specific embodiment, the first sub - step size △L within the range of non - linear dimensional variation 11 =a×△L1, where a is the density coefficient, preferably, a takes values from 0.3 to 0.5.

[0050] The second sub - step size △L within the range of non - linear dimensional variation 12 =△L1.

[0051] Step S234, obtain the second detection step size according to the first sub - step size and the second sub - step size.

[0052] In a specific embodiment, integrate the first sub - step size and the second sub - step size to obtain the second detection step size. It can be understood that the second detection step size is a non - uniformly increasing detection size sequence. For example, the range demarcation point between a range of non - linear dimensional variation and an adjacent range of linear dimensional variation is L b , and it is necessary to set the dimensional control force detection corresponding to L b , and within the two adjacent range demarcation points, at least a dimensional detection sequence increasing according to the corresponding sub - step size is set according to the corresponding sub - step size.

[0053] It can be understood that capturing data within the range of non - linear dimensional variation with high density can avoid the risk of missed detection of failure points.

[0054] Step S3, determine several different detection sizes with the second detection step size, perform several dimensional control force detections on the spring to be assembled, and obtain the corresponding pre - tightening force change trend, pre - tightening force loading path, and pre - tightening force unloading path of the spring to be assembled in the corresponding states of each detection size. It can be understood that in the single - time dimensional control force detection, the detection dimension corresponding to the detection dimension sequence is used as the compression amount of the spring to be assembled, and the pre - tightening force value corresponding to the spring to be assembled in each corresponding detection dimension state is obtained. Preferably, after maintaining the corresponding compression amount for 3 seconds each time, the corresponding spring elastic force value is read as the pre - tightening force value to ensure the stability of the spring deformation.

[0055] Specifically, the step S3 includes: Step S31: Using several different detection dimensions determined by the second detection step, performing dimensional control force detection on the spring to be assembled with the second detection frequency, and synchronously collecting the pre - tightening force loading path and pre - tightening force unloading path in each dimensional control force detection. Step S32: Recording the mapping data points of each detection dimension and the corresponding pre - tightening force data to obtain the pre - tightening force change trend of the spring to be assembled.

[0056] Specifically, the second detection step is the change amount of the detection dimensions of the spring to be assembled in adjacent times during the dimensional control force detection. In a specific embodiment, a servo - press is used to apply a detection external force to the spring to be assembled, the test mode is set to the displacement control mode, and according to the second detection step sequence △L (including the first sub - step sequence △L of the non - linear section 11 and the second sub - step sequence △L of the linear section 12 and the demarcation point sequence) for stepped compression, according to the detection dimension and the corresponding pre - tightening force of each compressed spring, a data point set {(L0, F0), (L1, F1), (L2, F2),..., (L j , F j )} is generated, and a dimension - force broken - line graph is drawn according to the data point set, that is, the pre - tightening force change trend, with the horizontal axis being the detection dimension L j , and the vertical axis being the pre - tightening force F j .

[0057] Among them, when the servo - press compresses the spring to be assembled to the current detection dimension, it maintains a stable state for 2 seconds (eliminating creep interference), and records the loading force F load displayed by the real - time value of the sensor, obtaining the loading path curve at this detection dimension, releasing the spring to the zero - load state, recompressing it to the same detection dimension, and releasing the spring to the zero - load state again, and recording the unloading force F unload displayed by the real - time value of the sensor, obtaining the unloading path curve at this detection dimension, where the loading force F load and the unloading force F unload are recorded with the dimension resolution d as the step.

[0058] Step S4: Based on the pre-tightening force loading path and pre-tightening force unloading path in each dimensional control force detection, determine the corresponding hysteresis characteristic data, and correct the pre-tightening force change trend with the hysteresis characteristic data to obtain the corrected pre-tightening force change trend; Specifically, the step S4 includes: Step S41: Determine the hysteresis characteristic data corresponding to several compression amounts according to the absolute value of the difference between the pre-tightening forces corresponding to the pre-tightening force loading path and the pre-tightening force unloading path in the same compression amount during a single dimensional control force detection; In a specific embodiment, for any L j , its hysteresis characteristic data is {Δf1, Δf2, Δf3,..., Δf s}}, where, since the loading force F load and the unloading force F unload are recorded in steps of the dimensional resolution d, so the total amount s of the hysteresis characteristic data is s = L j / d. It can be understood that Δf s = |F load - F unload |.

[0059] Step S42: Determine the hysteresis difference in a single dimensional control force detection according to the maximum value among the hysteresis characteristic data in a single dimensional control force detection; In a specific embodiment, take the maximum value among the hysteresis characteristic data corresponding to each detection dimension L j and record it as the hysteresis difference Δf j of the detection dimension L j .

[0060] Step S43: Determine the maximum hysteresis difference according to the maximum value among the hysteresis differences in each dimensional control force detection; In a specific embodiment, take the maximum value among the hysteresis differences Δf j corresponding to all detection dimensions L j and record it as the maximum hysteresis difference Δf max .

[0061] Step S44: Calculate the correction factor in a single dimensional control force detection according to the hysteresis difference and the maximum hysteresis difference in a single dimensional control force detection; In a specific embodiment, the calculation formula of the correction factor t j is specifically: , where b is the hysteresis attenuation coefficient, and its value range is 0.2 to 0.3. Preferably, take 0.2.

[0062] Step S45: Modify the values of the pre-tightening forces corresponding to the pre-tightening force change trend by the corresponding correction factors in each dimensional control force detection to obtain a modified pre-tightening force change trend.

[0063] In a specific embodiment, for each pre-tightening force F j , there is a modified pre-tightening force F j ’ = F j × t j ; According to the detected dimensions and the corresponding modified pre-tightening forces of each compressed spring in each dimensional control force detection, generate a data point set {(L0, F0’), (L1, F1’), (L2, F2’),..., (L j , F j ’)}; draw a dimension-force line graph according to the data point set, which is the modified pre-tightening force change trend, with the horizontal axis being the detected dimension L j , and the vertical axis being the pre-tightening force F j ’.

[0064] It can be understood that during the working process of the die spring, due to the internal friction of the material and the structural deformation, a hysteresis effect is generated, resulting in the separation of its loading path and unloading path, and the set value of the pre-tightening force deviates from the true stiffness. By using the correction factor t j to quantify the hysteresis strength at each dimension point, reflecting the local non-linearity degree of the spring, dynamically attenuating the pre-tightening force weight in the high hysteresis area. The larger the hysteresis value (the more serious the energy loss), the smaller the corresponding correction factor t j , and the stronger the reduction force on the corresponding pre-tightening force, realizing the targeted suppression of non-linear errors, making the measured value approach the ideal linear response, and suppressing the influence of unreliable data.

[0065] Step S5: Based on the analysis of the modified pre-tightening force change trend, obtain the linear change range and non-linear change range of the pre-tightening force of the spring to be assembled, so as to determine the calibration range corresponding to the pre-tightening force adjustment scale; Specifically, the step S5 includes: Step S51: Based on the linear change range and non-linear change range of the dimensions of the spring to be assembled, obtain the linear change range and non-linear change range of the pre-tightening force of the spring to be assembled; In a specific embodiment, directly map the linear change range and non-linear change range of the dimensions obtained in step S23 to the curve of the modified pre-tightening force change trend, and mark the pre-tightening force interval corresponding to the linear change range of the dimensions on the curve of the modified pre-tightening force change trend as the linear change range of the pre-tightening force, and the pre-tightening force interval corresponding to the non-linear change range of the dimensions as the non-linear change range of the pre-tightening force.

[0066] Step S52: Obtain the calibration scale of the pre-tightening force adjustment ruler based on the second detection step length and the corresponding pre-tightening force in the corrected pre-tightening force change trend. Among them, the pre-tightening force adjustment ruler is calibrated with linear working section and non-linear working section identifiers divided based on the linear change range and non-linear change range of the pre-tightening force.

[0067] In a specific embodiment, with the second detection step length sequence ΔL as the scale interval, dimension scales are marked on the ruler body, and the corresponding corrected pre-tightening force values (read from the corrected pre-tightening force change trend curve) are marked beside each dimension scale. According to the division result of step S51, the working sections are marked on the ruler body with colors: Preferably, the linear working section is marked in green, and the non-linear working section is marked in red for obvious distinction.

[0068] The present invention converts the complex mechanical properties (linear / non-linear regions) of the spring into a scale tool that can be directly read by the assembly personnel, and forcibly distinguishes the safe area (linear region) and the dangerous area (non-linear region) through color marking, avoiding relying on empirical judgment.

[0069] Step S6: Calibrate the pre-tightening force value of the pre-tightening force adjustment ruler according to the calibration range, and perform initial pre-tightening on the adjustable pre-tightening force spring as required, completing the assembly of the adjustable pre-tightening force spring.

[0070] In this embodiment, select the required pre-tightening force on the pre-tightening force adjustment ruler, and turn the adjustment bolt 2 to the position of the pre-tightening force scale 11 corresponding to the required pre-tightening force to complete the initial pre-tightening. In subsequent use, the pre-tightening force of the spring is adjusted by turning the adjustment bolt 2 to the corresponding pre-tightening force scale value.

[0071] So far, the technical solution of the present invention has been described in conjunction with the preferred embodiments shown in the drawings. However, it is easy for those skilled in the art to understand that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principle of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will fall within the protection scope of the present invention.

Claims

1. An assembly method of an adjustable pre-tightening force spring based on integral stamping forming, characterized in that, Including: Step S1: Obtain the maximum working load of the spring to be assembled, and based on the maximum working load, determine the first detection step length of the spring to be assembled; Step S2: Determine several different detection external forces with the first detection step length, perform several force-controlled stress detections on the spring to be assembled, obtain the corresponding dimensional change trends of the spring to be assembled under the states of each detection external force, and determine the second detection step length of the spring to be assembled according to the dimensional change trends and the first detection step length; Step S3: Determine several different detection dimensions with the second detection step length, perform several dimension-controlled stress detections on the spring to be assembled, and obtain the corresponding pre-tightening force change trends, pre-tightening force loading paths, and pre-tightening force unloading paths of the spring to be assembled under the states of each corresponding detection dimension; Step S4: Based on the pre-tightening force loading paths and pre-tightening force unloading paths in each dimension-controlled stress detection, determine the corresponding hysteresis characteristic data, and correct the pre-tightening force change trends with the hysteresis characteristic data to obtain corrected pre-tightening force change trends; Step S5: Based on the analysis of the corrected pre-tightening force change trends, obtain the linear change range and non-linear change range of the pre-tightening force of the spring to be assembled, and determine the calibration range corresponding to the pre-tightening force adjustment scale; Step S6: Calibrate the pre-tightening force values of the pre-tightening force adjustment scale according to the calibration range, perform initial pre-tightening on the adjustable pre-tightening force spring according to the usage requirements, and complete the assembly of the adjustable pre-tightening force spring.

2. The assembling method of the adjustable pre-tightening force spring based on integral stamping as claimed in claim 1, wherein The said Step S1 includes: Step S11: According to the maximum working load, determine the maximum allowable pre-tightening force of the spring to be assembled; Step S12: Perform a reference stress detection on the spring to be assembled with the maximum allowable pre-tightening force, and obtain the maximum pre-tightening dimension corresponding to the spring to be assembled under the action of the maximum allowable pre-tightening force; Step S13: Based on the maximum pre-tightening dimension, determine the first detection frequency of the spring to be assembled; Step S14: Based on the maximum allowable pre-tightening force and the first detection frequency, determine the first detection step length of the spring to be assembled; Wherein, the first detection frequency is the total number of different detection external forces used in the force-variable stress detection.

3. The assembly method of the adjustable pre-tightening force spring based on integral stamping according to claim 2, characterized in that, The first detection step length is the change amount of the detection external forces received by the spring to be assembled in adjacent times during the force-controlled stress detection; The second detection step length is the change amount of the detection dimensions of the spring to be assembled in adjacent times during the dimension-controlled stress detection.

4. The assembling method of the adjustable pre-tightening force spring based on integral stamping as claimed in claim 3, wherein The said Step S2 includes: Step S21: Use several different detection external forces determined with the first detection step length to perform force-controlled stress detections on the spring to be assembled with the first detection frequency, and obtain the corresponding dimension data of the spring to be assembled in each force-controlled stress detection; Step S22: Record the mapping data points of each detection external force and the corresponding dimension data to form stress-dimension data - detection external force, so as to obtain the dimensional change trends of the spring to be assembled; Step S23: According to the dimensional change trends and the first detection step length, determine the second detection step length of the spring to be assembled.

5. The assembly method of the adjustable pre-tightening force spring based on integral stamping according to claim 4, characterized in that, The said Step S23 includes: Step S231: Identify the linear dimension change range and non-linear dimension change range of the spring to be assembled according to the slope change characteristics of the dimension change trend. Step S232: Calculate the reference second detection step size based on the maximum pre-tightening dimension and the first detection frequency. Step S233: Narrow the detection interval within the non-linear dimension change range and calculate the first sub-step size and the second sub-step size based on the reference second detection step size. Step S234: Obtain the second detection step size according to the first sub-step size and the second sub-step size.

6. The assembly method of the adjustable pre-tightening force spring based on integral stamping according to claim 5, characterized in that, The step S231 includes: Step S2311: Perform a first derivative operation on the dimension change trend to obtain a first slope change sequence. Step S2312: Detect the mutation points in the first slope change sequence, where the mutation points satisfy that the slope change value of adjacent sections exceeds a preset mutation threshold. Step S2313: Determine the pre-tightening force interval where the mutation points are located as the non-linear dimension change range, and the pre-tightening force intervals where the other points are located as the linear dimension change range.

7. The assembly method of the adjustable pre-tightening force spring based on integral stamping according to claim 6, characterized in that, The step S3 includes: Step S31: Perform dimension-controlled force detection on the spring to be assembled with the second detection step size at several different detection dimensions, and synchronously collect the pre-tightening force loading path and pre-tightening force unloading path in each dimension-controlled force detection. Step S32: Record the mapping data points of each detection dimension and the corresponding pre-tightening force data to form the pre-tightening force data - detection dimension mapping data points, so as to obtain the pre-tightening force change trend of the spring to be assembled.

8. The assembly method of the adjustable pre-tightening force spring based on integral stamping as claimed in claim 7, wherein, The step S4 includes: Step S41: Determine the hysteresis characteristic data corresponding to several compression amounts according to the absolute value of the difference between the pre-tightening forces corresponding to the pre-tightening force loading path and the pre-tightening force unloading path in the same compression amount during a single dimension-controlled force detection. Step S42: Determine the hysteresis difference in a single dimension-controlled force detection according to the maximum value among the hysteresis characteristic data in a single dimension-controlled force detection. Step S43: Determine the maximum hysteresis difference according to the maximum value among the hysteresis differences in each dimension-controlled force detection. Step S44: Calculate the correction factor in a single dimension-controlled force detection according to the hysteresis difference in a single dimension-controlled force detection and the maximum hysteresis difference. Step S45: Correct the numerical value of the pre-tightening force corresponding to the pre-tightening force change trend through the correction factor corresponding to each dimension-controlled force detection to obtain the corrected pre-tightening force change trend.

9. The assembly method of the adjustable pre-tightening force spring based on integral stamping according to claim 8, characterized in that, The step S5 includes: Step S51: Obtain the linear pre-tightening force change range and non-linear pre-tightening force change range of the spring to be assembled based on the linear dimension change range and non-linear dimension change range of the spring to be assembled. Step S52: Obtain the calibration scale of the pre-tightening force adjustment ruler with the second detection step size and the corresponding pre-tightening force in the corrected pre-tightening force change trend. Among them, the pre-tightening force adjustment ruler is calibrated with linear working section and non-linear working section identifiers divided based on the linear pre-tightening force change range and the non-linear pre-tightening force change range.

10. An integrally stamped adjustable pre-tightening force spring mechanism, which is assembled by using the assembly method of the integrally stamped adjustable pre-tightening force spring described in any one of claims 1-9, and is characterized in that, Includes: Adjustable pre-tightening force spring; Adjusting bolt, which is in contact connection with one end of the adjustable pre-tightening force spring, and is used to adjust the compression amount of the adjustable pre-tightening force spring by tightening / loosening the bolt so as to adjust the pre-tightening force of the adjustable pre-tightening force spring; Fastening nut, which is matched with the adjusting bolt and is used to fix the position of the adjusting bolt to fix the compression amount of the adjustable pre-tightening force spring; Pre-tightening force adjusting scale, which is provided with dimension scales and corresponding pre-tightening force values, and is used to represent the pre-tightening force value corresponding to the relative position of the adjusting bolt at present.

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