A novel valve system vibration damper piston rod with superior structure and stable performance and its manufacturing process

Abstract

This invention discloses a vibration damper technology, aiming to provide a new valve system vibration damper piston rod with superior structure and stable performance, as well as its manufacturing process. The key technical points include a piston rod body; the piston end of the piston rod body has an extended section for mounting a new 30K recovery valve assembly; a stepped structure is provided on the cylindrical section near the piston rod body on the piston end for mates with a concave-convex limiting plate; the piston end also has an extended threaded portion for accommodating various specifications of flow valve springs; the surface of the piston rod body is subjected to high-frequency quenching to form a hardened layer with a depth of 0.4-0.8 mm and a hardness of 42-45 HRC; the surface is also covered with a micro-cracked chromium plating layer with a thickness of 0.02±0.005 mm, a hardness of 800-1200 HV, and a micro-crack count of ≥500 cracks / cm; the chromium plating layer is also subjected to post-plating hydrogen removal treatment; applicable to the field of vibration damper technology.

Description

Technical Field

[0001] This invention relates to a vibration damper technology, and more specifically, to a novel valve-system vibration damper piston rod with superior structure and stable performance, and its manufacturing process. Background Technology

[0002] As a core component of the automotive chassis, the damping performance of the shock absorber directly affects the vehicle's ride comfort and handling stability. With the upgrading of automotive manufacturing technology, models such as the Honda HR-V adopt a new valve system design, whose damping curve trend differs significantly from that of the traditional valve system. Due to structural limitations, the traditional piston rod lacks an installation position suitable for the new valve system, and the flow valve spring has poor adaptability, failing to meet personalized damping adjustment needs. Therefore, there is an urgent need to develop a new valve system shock absorber piston rod with optimized structure, reliable performance, and compatibility with the new valve system, so as to install snap rings, positioning sleeves, guides, oil seals, internal buffer blocks, and the new structure valve system 30K recovery valve assembly. Summary of the Invention

[0003] To address the shortcomings of existing technologies, the present invention aims to provide a novel valve system vibration damper piston rod with superior structure and stable performance, as well as its manufacturing process.

[0004] To achieve the above objectives, the present invention provides the following technical solution: a piston rod for a new valve system vibration damper with superior structure and stable performance, comprising a piston rod body, wherein the piston end of the piston rod body is provided with an extended section for mounting a new valve system 30K restoration valve assembly; a stepped structure is provided on the cylindrical section of the piston end near the piston rod body for cooperating with a concave-convex limiting plate; the piston end is also provided with an extended threaded portion for adapting to various specifications of flow valve springs; the surface of the piston rod body is subjected to high-frequency quenching treatment. A hardened layer is formed with a depth of 0.4-0.8 mm and a hardness of 42-45 HRC. The surface is also covered with a micro-cracked chromium plating layer with a thickness of 0.02±0.005 mm, a hardness of 800-1200 HV, and a micro-crack count of ≥500 cracks / cm. The chromium plating layer is also subjected to post-plating hydrogen removal treatment. The straightness of the cylindrical section of the piston rod body is ≤0.01 mm, the roundness is ≤0.01 mm, the coaxiality of the piston end is ≤φ0.05 mm, and the end face runout is ≤0.04 mm.

[0005] The present invention is further configured such that the radius of the transition fillet at the connection between the stepped structure and the piston end is 0.2-0.3 mm.

[0006] The present invention is further configured such that the plating solution used for the chromium plating layer is formulated as follows: 220-250 g / L of chromium anhydride, 1.2-1.5 g / L of sulfuric acid, 0.5-1.0 g / L of rare earth additives, and 0.2-0.4 g / L of surfactant, wherein the mass ratio of chromium anhydride to sulfuric acid is 150-200:1.

[0007] The present invention is further configured such that: the heating temperature of the high-frequency quenching treatment is 820-860℃, the heating time is 30-45s, the quenching medium is a polymer aqueous solution, and the cooling rate is controlled at 80-120℃ / s.

[0008] The present invention is further configured such that the surface roughness Ra of the stepped structure is ≤0.4μm, and the fitting gap with the concave-convex limiting plate is 0.03-0.05mm.

[0009] A manufacturing process for a novel valve system vibration damper piston rod with superior structure and stable performance is characterized by the following steps: S1. Blank pretreatment: Select 40Cr or 20CrMnTi alloy steel bars that meet the design requirements. After rough machining to remove the excess, use an ultrasonic flaw detector to detect internal defects. If the flaw detection results show no cracks or inclusions, proceed to S2; otherwise, reject unqualified blanks. S2. Rough machining of the piston end: The extended section of the piston end is machined using a CNC lathe, and the stepped structure and extended threaded part are machined at the same time to obtain the piston rod blank. S3. Surface high-frequency quenching: Place the piston rod blank in an induction heating device, heat it to 820-860℃ and hold it for 30-45 seconds, then quickly immerse it in a polymer aqueous solution quenching medium to cool it. The cooling rate is controlled at 80-120℃ / s. After quenching, use a Rockwell hardness tester to test the hardness of the hardened layer. If the hardness value does not meet 42-45HRC, adjust the heating temperature or the concentration of the cooling medium and quench again. S4. Finishing: Complete the finishing machining of the piston rod body in sequence to ensure that the straightness of the cylindrical section of the piston rod body is ≤0.01mm and the roundness is ≤0.01mm. After finishing, use a roundness tester and a straightness measuring instrument to check respectively. If the straightness or roundness exceeds the target value, readjust the tool compensation parameters and rework. S5. Microcrack chrome plating: The precision-machined piston rod is placed in a chrome plating bath for microcrack chrome plating, wherein the current density is controlled at 30-40A / dm during chrome plating. 2 Ensure that the thickness of the chrome plating layer is controlled within 0.02±0.005mm and the hardness is controlled within 800-1200HV; S6. Post-plating hydrogen removal treatment: Place the chromium-plated piston rod in a constant temperature chamber at 180-200℃ for 2-3 hours to eliminate internal stress in the chromium plating layer and prevent hydrogen embrittlement. After hydrogen removal, use a tensile testing machine to check the adhesion of the chromium plating layer. If the chromium plating layer peels off, extend the hydrogen removal time or reduce the chromium plating current density and re-treat. S7. Final finishing: Perform final correction on the coaxiality and end face runout of the piston end to ensure that the coaxiality is ≤ φ0.05mm and the end face runout is ≤ 0.04mm. After correction, use a coaxiality measuring instrument and a runout detector to check. If the coaxiality or end face runout exceeds the target value, fine-tune it through grinding or lapping process until it is qualified. S8. Comprehensive performance testing: A composite testing module is used to conduct comprehensive performance testing on the finished piston rod, including: collecting the contact pressure curve of the piston end step structure and the concave-convex limiting plate during simulated assembly using a laser displacement sensor; if the peak contact pressure exceeds the preset threshold P0, the reliability of the step structure fit is determined to be insufficient; loading reciprocating motion at different frequencies using a damping force simulation testing machine, and collecting the fullness parameter of the indicator graphic; if the fullness of the indicator graphic is <90%, the valve system matching performance is determined to be substandard; based on the comprehensive test results, if any item fails to meet the requirements, it is marked as a non-conforming product and the corresponding process is traced back for adjustment; if all items pass, it is put into storage.

[0010] The present invention is further configured as follows: the hardness detection and control method after S3 high-frequency quenching is as follows: firstly, a Rockwell hardness tester is used to detect the hardness values ​​H1, H2, and H3 at three evenly distributed points on the piston rod end face, and the average value Hp is calculated as (H1+H2+H3) / 3; if Hp is within the range of 42-45HRC, it is directly judged as qualified; if Hp < 42HRC, the microstructure of the hardened layer is further observed through a metallographic microscope. If the martensite needle length is > 5μm, it is judged as insufficient heating temperature or too low cooling rate, and the heating temperature is increased by 10-20℃ or a high-concentration polymer quenching medium is replaced; if Hp > 45HRC, the temperature distribution curve of the quenching heating process is traced back through an infrared thermal imager. If the highest temperature on the piston rod surface is > 880℃, it is judged as overheating, and the power parameters of the induction coil are adjusted or the holding time is shortened; after adjustment, S3 is re-executed until the hardness is qualified.

[0011] The present invention is further configured such that, in step S5, the specific control method for microcrack chromium plating includes: real-time detection of the chromium anhydride concentration C1 and sulfuric acid concentration C2 of the chromium plating solution, with a sampling frequency of once every 30 seconds; if C1 < 220 g / L and C2 < 1.2 g / L, then according to the concentration difference ΔC1 = 230 - C1 and ΔC2 = 1.3 - C2, simultaneously replenishing the chromium anhydride mother liquor and sulfuric acid mother liquor according to the volume ratio V1:V2 = ΔC1:ΔC2; if 220 g / L ≤ C1 ≤ 250 g / L and 1.2 g / L ≤ C2 ≤ 1.5 g / L, then maintaining the composition of the chromium plating solution; if C1 > 250 g / L and C2 > 1.5 g / L, then calculating the required amount of deionized water to be added according to the dilution ratio, adding it to the chromium plating tank in three equal portions, with an interval of 5 minutes between each addition, until 220 g / L ≤ C1 ≤ 250 g / L. Furthermore, 1.2 g / L ≤ C2 ≤ 1.5 g / L, after dilution, let stand for 10 minutes before resuming chromium plating; during the chromium plating process, check the chromium plating layer thickness d. If d < 0.015, extend the chromium plating time Δt1; if d > 0.025, shorten the chromium plating time Δt2; after chromium plating, check the number of microcracks N. If N < 500 cracks / cm, perform a second microcrack treatment on the chromium plating layer and check the number of microcracks N again; if N ≥ 500 cracks / cm, check the plating hardness HV. If HV < 800, adjust the chromium plating current to 1.05-1.1 times the original current and re-plat the chromium plating until HV is in the range of 800-1200; if HV > 1200, reduce the chromium plating current to 0.9-0.95 times the original current and re-plat the chromium plating until HV is in the range of 800-1200.

[0012] The present invention is further configured such that: the method for judging the contact pressure curve in S8 includes: during the simulated assembly process, the pressure module presses down the piston end step structure at a constant speed of 5 mm / s until it contacts the concave-convex limiting plate. The pressure sensor collects the contact pressure P(t) in real time. After removing environmental vibration noise through a filtering algorithm, the pressure peak value Pmax is extracted. If Pmax≤P0 and the pressure rise time T≤0.1s, that is, the time elapsed from the start of contact to P reaching 90% of Pmax is ≤0.1s, then the step fit reliability is determined to be qualified. If Pmax>P0 or T>0.1s, then the pressure curve database of qualified products is further compared. If the similarity between the current curve and the historical qualified curve is less than 85%, then the fit reliability is determined to be insufficient and an alarm is triggered. If the similarity is ≥85%, the sensor is recalibrated and the test is repeated.

[0013] The beneficial effects of this invention are: 1. Compared to existing technologies, the extended piston end of the piston rod of the new valve system vibration damper in this invention provides a precise installation reference for the 30K recovery valve assembly, meeting various damping curve requirements of customers and improving customer satisfaction; the stepped structure and the concave-convex limiting plate design ensure the stability of assembly positioning, avoiding displacement deviation during operation, while enhancing the durability and reliability of the limiting plate and reducing impact and wear on valve system parts; the extended threaded part is compatible with various specifications of flow valve springs, improving product versatility and also improving the adjustability of the recovery valve system, ensuring the tightening torque of the recovery adjusting nut; the 0.4-0.8mm hardened layer formed by high-frequency quenching on the surface, combined with 42 A hardness index of -45HRC significantly enhances the piston rod's wear resistance; the microcracked chromium plating layer combines a precise thickness of 0.02±0.005mm, a high hardness of 800-1200HV, and a microcrack density of ≥500 cracks / cm. This ≥500 crack density means an average of ≥500 cracks per centimeter of length, improving surface finish and corrosion resistance while releasing stress through microcracks. Combined with post-plating hydrogen removal treatment, it effectively prevents hydrogen embrittlement. Strictly controlled straightness, roundness, coaxiality, and end-face runout accuracy ensure the smoothness of the piston rod's movement, reducing damping fluctuations during vibration damping operation, ultimately improving the overall vibration damping effect and service life of the vibration damping system.

[0014] 2. In the piston rod of the novel valve system vibration damper of this invention, which features superior structure and stable performance, the transition radius of the stepped structure at the connection with the piston end is 0.2-0.3mm. Firstly, this effectively disperses the contact stress when the stepped structure mates with the concave-convex limiting plate, preventing localized wear or cracks caused by stress concentration, thus solving the problem of fatigue damage easily caused by traditional right-angle transitions and extending the service life of the piston rod. Secondly, the reasonable radius ensures that the concave-convex limiting plate can smoothly conform to the stepped surface during assembly, avoiding abnormal fit clearance caused by excessively large transition radius, or... The small radius prevents assembly jamming, ensuring assembly efficiency and fitting accuracy. Simultaneously, this radius is compatible with the overall structural design of the piston rod, not affecting the assembly accuracy of the extended section and the restoring valve assembly, or the extended thread and the flow valve spring, balancing structural integrity and operational reliability. Furthermore, this radius design facilitates tool movement during machining, reducing finishing difficulty and burr generation, further improving the surface quality of the stepped structure. This lays the foundation for precise fitting with the limiting plate, ensuring stable damping performance of the shock absorber during high-frequency reciprocating motion.

[0015] 3. In this invention, the mass ratio of chromium anhydride to sulfuric acid is 150-200:1. Combined with 220-250 g / L of chromium anhydride and 1.2-1.5 g / L of sulfuric acid, the crystal morphology of the chromium plating layer can be precisely controlled, ensuring the density and uniformity of the plating layer and avoiding defects such as pinholes and pitting. The addition of rare earth additives refines the plating grains, improves the hardness and wear resistance of the chromium plating layer, and stabilizes the hardness of the plating layer at 800-1200 HV, meeting the wear resistance requirements of the piston rod's high-frequency reciprocating motion. Surfactants can improve the plating... The liquid wettability ensures a tight bond between the chromium plating layer and the substrate, reducing the risk of peeling. The plating solution formula is compatible with the micro-crack chromium plating process, and can precisely control the number of micro-cracks to 500 per centimeter. This micro-cracks release the internal stress of the plating layer, preventing cracking of the chromium plating layer, without affecting the anti-corrosion performance of the chromium plating layer, effectively resisting the corrosion of oil and water vapor in the working environment of the shock absorber. The chromium plating layer under this formula has high hardness, high adhesion and excellent corrosion resistance, significantly improving the durability and reliability of the piston rod and reducing the maintenance cost of the shock absorber.

[0016] 4. The present invention has a simple and reasonable structure, is easy to manufacture and operate, avoids the defects of the prior art, and is suitable for promotion and application. Attached Figure Description

[0017] Figure 1 The structural diagram shows the piston rod of a new valve system vibration damper with superior structure and stable performance.

[0018] Figure 2 A flowchart illustrating the manufacturing process of the piston rod for a new valve system vibration damper with superior structure and stable performance.

[0019] Figure 3 The first part of the flowchart is a specific method for controlling microcracks in chrome plating.

[0020] Figure 4 The second part of the flowchart is a specific method for controlling microcracks in chrome plating.

[0021] Figure 1-4 Reference numerals: 1. Piston end; 2. Extended section; 3. Stepped structure; 4. Extended threaded section. Detailed Implementation

[0022] Reference Figure 1-4 The piston rod of the novel valve system vibration damper of the present invention, which has superior structure and stable performance, and its manufacturing process are further described in the following embodiments.

[0023] For ease of explanation, spatial relative terms such as “up,” “down,” “left,” and “right” are used in the embodiments to describe the relationship of one element or feature shown in the figures relative to another element or feature. It should be understood that, in addition to the orientations shown in the figures, spatial terms are intended to include different orientations of the device in use or operation. For example, if the device in the figures is inverted, an element described as being “down” of other elements or features would be positioned “up” of those other elements or features. Therefore, the exemplary term “down” can encompass both up and down orientations. The device may be positioned in other ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0024] Moreover, relational terms such as “first” and “second” are used merely to distinguish one component from another that has the same name, without necessarily requiring or implying any such actual relationship or order between the components.

[0025] Figures 1 to 4 The piston rod of a new valve system vibration damper, as shown, features a superior structure and stable performance. It includes a piston rod body, with an extended section 2 at the piston end 1 for mounting a new 30K recovery valve assembly. A stepped structure 3, near the cylindrical section of the piston rod body, is provided at the piston end 1 for engaging with a concave-convex limiting plate. An extended threaded portion 4 is also provided at the piston end 1 for accommodating various sizes of flow valve springs. The surface of the piston rod body undergoes high-frequency quenching to form a hardened layer. The hard layer has a depth of 0.4-0.8 mm and a hardness of 42-45 HRC. The surface is also covered with a micro-cracked chromium plating layer with a thickness of 0.02±0.005 mm, a hardness of 800-1200 HV, and a micro-crack count of ≥500 lines / cm. The chromium plating layer is also subjected to post-plating hydrogen removal treatment. The straightness of the cylindrical section of the piston rod body is ≤0.01 mm, the roundness is ≤0.01 mm, the coaxiality of the piston end 1 is ≤φ0.05 mm, and the end face runout is ≤0.04 mm. The extended section 2 at piston end 1 provides a precise installation reference for the 30K recovery valve assembly, meeting various damping curve requirements and improving customer satisfaction. The stepped structure 3, in conjunction with the concave-convex limiting plate, ensures stable assembly positioning, preventing displacement deviations during operation. Simultaneously, it enhances the durability and reliability of the limiting plate, reducing impact and wear on valve components. The extended threaded section 4 is compatible with various specifications of flow valve springs, improving product versatility and enhancing the adjustability of the recovery valve system, ensuring the tightening torque of the recovery adjusting nut. The 0.4-0.8mm hardened layer formed by high-frequency quenching, combined with a hardness index of 42-45HRC, demonstrates… This significantly enhances the piston rod's wear resistance. The microcracked chromium plating layer boasts a precise thickness of 0.02±0.005mm, a high hardness of 800-1200HV, and a microcrack density of ≥500 cracks / cm. This density means that the average number of cracks per centimeter of length is ≥500. This improves surface finish and corrosion resistance, while also releasing stress through microcracks. Combined with post-plating hydrogen removal treatment, it effectively prevents hydrogen embrittlement. Strictly controlled straightness, roundness, coaxiality, and end-face runout accuracy ensure the smoothness of the piston rod's movement, reducing damping fluctuations during vibration damping operation, ultimately improving the overall vibration damping effect and service life of the vibration damping system.

[0026] The radius of the transition fillet at the connection between the stepped structure 3 and the piston end 1 is 0.2-0.3 mm; Firstly, it effectively disperses the contact stress when the stepped structure 3 mates with the concave-convex limiting plate, avoiding localized wear or cracks caused by stress concentration, solving the problem of fatigue damage easily caused by traditional right-angle transitions, and extending the service life of the piston rod. Secondly, the reasonable fillet radius ensures that the concave-convex limiting plate can smoothly fit the stepped surface during assembly, avoiding abnormal fit clearance caused by excessively large fillet radius or assembly jamming caused by excessively small fillet radius, ensuring assembly efficiency and fit accuracy. At the same time, the fillet radius is compatible with the overall structural design of the piston rod, and does not affect the assembly accuracy of the extended section 2 with the restoration valve assembly, the extended thread with the flow valve spring, taking into account both structural integrity and reliability. In addition, the fillet radius design facilitates tool movement during machining, reduces the difficulty of finishing, reduces the generation of machining burrs, further improves the surface quality of the stepped structure 3, lays the foundation for the subsequent precise fit with the limiting plate, and ensures that the shock absorber maintains stable damping performance in high-frequency reciprocating motion.

[0027] The plating solution used for the chromium plating layer is formulated as follows: 220-250 g / L chromium anhydride, 1.2-1.5 g / L sulfuric acid, 0.5-1.0 g / L rare earth additives, and 0.2-0.4 g / L surfactant, wherein the mass ratio of chromium anhydride to sulfuric acid is 150-200:1. A mass ratio of chromium anhydride to sulfuric acid of 150-200:1, combined with 220-250 g / L of chromium anhydride and 1.2-1.5 g / L of sulfuric acid, allows for precise control of the crystal morphology of the chromium plating layer, ensuring its density and uniformity and preventing defects such as pinholes and pitting. The addition of rare earth additives refines the plating grains, improving the hardness and wear resistance of the chromium plating layer, stabilizing its hardness at 800-1200 HV to meet the wear resistance requirements of high-frequency reciprocating piston rods. Surfactants improve the wettability of the plating solution. This ensures a tight bond between the chromium plating layer and the substrate, reducing the risk of peeling. The plating solution formula is compatible with the micro-crack chromium plating process, and can precisely control the number of micro-cracks to 500 per centimeter. This releases the internal stress of the plating layer through micro-cracks, preventing the chromium plating layer from cracking, without affecting the anti-corrosion performance of the chromium plating layer, effectively resisting the corrosion of oil and water vapor in the working environment of the shock absorber. The chromium plating layer under this formula has high hardness, high adhesion and excellent corrosion resistance, significantly improving the durability and reliability of the piston rod and reducing the maintenance cost of the shock absorber.

[0028] The heating temperature for the high-frequency quenching treatment is 820-860℃, the heating time is 30-45s, the quenching medium is a polymer aqueous solution, and the cooling rate is controlled at 80-120℃ / s. A heating temperature of 820-860℃ and a heating time of 30-45 seconds prevent excessive heat conduction into the matrix, ensuring the hardened layer depth is controlled at 0.4-0.8mm. This improves surface hardness and wear resistance while preserving the toughness of the matrix, preventing the piston rod from breaking due to excessive overall hardness. Using a polymer aqueous solution as the quenching medium, combined with a cooling rate of 80-120℃ / s, enables rapid and uniform cooling, stabilizing the hardened layer hardness at 42-45HRC. This ensures the piston rod is not easily worn or deformed under high-frequency impact and friction. The optimized design of these process parameters solves the problems of uneven hardened layer depth and large hardness fluctuations in traditional quenching processes, improving product performance consistency. Simultaneously, reasonable heating temperature and cooling rate reduce quenching deformation, laying the foundation for subsequent precision machining and avoiding rework due to excessive deformation. The piston rod after high-frequency quenching achieves a good balance between surface wear resistance and internal toughness, adapting to the long-term high-frequency reciprocating motion of the vibration damper and extending its service life.

[0029] The surface roughness Ra of the stepped structure 3 is ≤0.4μm, and the fitting clearance with the concave-convex limiting plate is 0.03-0.05mm; By limiting the surface roughness and fitting clearance of the stepped structure 3, assembly reliability and operational stability are ensured. A surface roughness of Ra≤0.4μm reduces the frictional resistance when the stepped structure 3 contacts the concave-convex limiting plate, lowers the wear rate, and improves the fit of the contact surface, avoiding stress concentration caused by surface roughness and extending the service life of the mating parts. The fitting clearance design of 0.03-0.05mm provides reasonable installation allowance for the assembly process, ensuring that the concave-convex limiting plate can be accurately positioned, avoiding damage to parts caused by excessive tightness or positioning deviation caused by excessive looseness. It can also absorb a certain amount of vibration and thermal expansion during the operation of the piston rod, avoiding impact noise caused by excessive clearance or jamming caused by insufficient clearance. At the same time, reasonable fitting clearance and surface roughness can reduce assembly difficulty, improve production efficiency, and reduce wear on the mating surfaces, thereby reducing the maintenance frequency and cost of the vibration damper.

[0030] A manufacturing process for a novel valve system vibration damper piston rod with superior structure and stable performance is characterized by the following steps: S1. Blank pretreatment: Select 40Cr or 20CrMnTi alloy steel bars that meet the design requirements. After rough machining to remove the excess, use an ultrasonic flaw detector to detect internal defects. If the flaw detection results show no cracks or inclusions, proceed to S2; otherwise, reject unqualified blanks. S2. Rough machining of piston end 1: The extended section 2 of piston end 1 is machined by CNC lathe, and the stepped structure 3 and the extended threaded part 4 are machined at the same time to obtain the piston rod blank. S3. Surface high-frequency quenching: Place the piston rod blank in an induction heating device, heat it to 820-860℃ and hold it for 30-45 seconds, then quickly immerse it in a polymer aqueous solution quenching medium to cool it. The cooling rate is controlled at 80-120℃ / s. After quenching, use a Rockwell hardness tester to test the hardness of the hardened layer. If the hardness value does not meet 42-45HRC, adjust the heating temperature or the concentration of the cooling medium and quench again. S4. Finishing: Complete the finishing machining of the piston rod body in sequence to ensure that the straightness of the cylindrical section of the piston rod body is ≤0.01mm and the roundness is ≤0.01mm. After finishing, use a roundness tester and a straightness measuring instrument to check respectively. If the straightness or roundness exceeds the target value, readjust the tool compensation parameters and rework. S5. Microcrack chrome plating: The precision-machined piston rod is placed in a chrome plating bath for microcrack chrome plating, wherein the current density is controlled at 30-40A / dm during chrome plating. 2 Ensure that the thickness of the chrome plating layer is controlled within 0.02±0.005mm and the hardness is controlled within 800-1200HV; S6. Post-plating hydrogen removal treatment: Place the chromium-plated piston rod in a constant temperature chamber at 180-200℃ for 2-3 hours to eliminate internal stress in the chromium plating layer and prevent hydrogen embrittlement. After hydrogen removal, use a tensile testing machine to check the adhesion of the chromium plating layer. If the chromium plating layer peels off, extend the hydrogen removal time or reduce the chromium plating current density and re-treat. S7. Final finishing: Perform final correction on the coaxiality and end face runout of piston end 1 to ensure that the coaxiality is ≤ φ0.05mm and the end face runout is ≤ 0.04mm. After correction, use a coaxiality measuring instrument and a runout detector to check. If the coaxiality or end face runout exceeds the target value, fine-tune it through grinding or lapping process until it is qualified. S8. Comprehensive performance testing: A composite testing module is used to conduct comprehensive performance testing on the finished piston rod, including: collecting the contact pressure curve of the piston end 1 step structure 3 and the concave-convex limiting plate during simulated assembly using a laser displacement sensor; if the peak contact pressure exceeds the preset threshold P0, the reliability of the step structure 3 is deemed insufficient; loading reciprocating motion at different frequencies using a damping force simulation testing machine, and collecting the fullness parameter of the indicator graphic; if the fullness of the indicator graphic is <90%, the valve system matching performance is deemed substandard; based on the comprehensive test results, if any item fails to meet the requirements, it is marked as a non-conforming product and the corresponding process is traced back for adjustment; if all items pass, it is put into storage. Through precise multi-process control and closed-loop testing, the high quality and high performance of the piston rod are ensured. S1, the pre-treatment of the blank uses ultrasonic testing to effectively remove unqualified blanks with internal cracks and inclusions, ensuring product quality from the source. S2, the rough machining of the piston end 1 is achieved through integrated machining on a CNC lathe, ensuring the relative positional accuracy of the extended section 2, the stepped structure 3, and the extended threaded part 4. S3, surface high-frequency quenching combined with hardness testing and parameter adjustment ensures the hardened layer meets performance standards. S4, the finishing process is monitored in real-time by precision testing instruments to ensure the straightness and roundness of the cylindrical section meet requirements. S5, the micro-crack chrome plating precisely controls the current density to ensure the plating thickness and hardness. S6, post-plating hydrogen removal treatment and adhesion testing effectively prevent hydrogen embrittlement and plating peeling. S7, the final finishing process corrects coaxiality and end face runout, improving assembly accuracy. S8, comprehensive performance testing, through simulated assembly and damping force testing, fully verifies product reliability. This process flow is logically rigorous, with each process having a testing and rework mechanism, forming a closed-loop quality control system that solves the problems of insufficient precision control and unstable performance in traditional processes.

[0031] The hardness detection and control method after S3 high-frequency quenching is as follows: First, use a Rockwell hardness tester to detect the hardness values ​​H1, H2, and H3 at three evenly distributed points on the piston rod end face, and calculate the average value Hp = (H1 + H2 + H3) / 3; if Hp is within the range of 42-45 HRC, it is directly judged as qualified; if Hp < 42 HRC, further observe the microstructure of the hardened layer through a metallographic microscope. If the martensite needle length is > 5 μm, it is judged that the heating temperature is insufficient or the cooling rate is too low. Increase the heating temperature by 10-20℃ or replace it with a high-concentration polymer quenching medium; if Hp > 45 HRC, trace back the temperature distribution curve of the quenching heating process through an infrared thermal imager. If the highest temperature on the piston rod surface is > 880℃, it is judged as overheating. Adjust the power parameters of the induction coil or shorten the holding time; after adjustment, repeat S3 until the hardness is qualified. First, hardness is measured at three evenly distributed points on the piston rod end face, and the average value is calculated to avoid the randomness of single-point testing and ensure the accuracy of hardness assessment. When the hardness is below 42 HRC, the length of martensite needles is observed using a metallographic microscope to accurately locate the root cause of insufficient heating temperature or excessively low cooling rate, and process parameters are adjusted accordingly to avoid blind rework. When the hardness is above 45 HRC, the temperature distribution curve is traced back using an infrared thermal imager to determine the problem of overheating, and the power of the induction coil or the holding time is adjusted in time to effectively control the hardness exceeding the standard. Compared with the traditional single hardness testing method, this method realizes a closed-loop control of "detection-judgment-adjustment". It can not only quickly identify the situation of unqualified hardness, but also accurately analyze the cause and provide targeted solutions, significantly reducing rework costs and time. At the same time, this method ensures that the hardened layer hardness is stable within the target range of 42-45 HRC, ensuring the balance between the wear resistance of the piston rod surface and the internal toughness, avoiding premature wear due to insufficient hardness or brittle fracture risk due to excessive hardness. This lays a solid foundation for the smooth progress of subsequent processes and the improvement of the overall product performance, and further ensures the reliability and service life of the vibration damper.

[0032] In step S5, the specific control method for microcrack chromium plating includes: real-time detection of the chromium anhydride concentration C1 and sulfuric acid concentration C2 in the chromium plating solution, with a sampling frequency of once every 30 seconds. If C1 < 220 g / L and C2 < 1.2 g / L, then based on the concentration difference ΔC1 = 230 - C1 and ΔC2 = 1.3 - C2, chromium anhydride mother liquor and sulfuric acid mother liquor are simultaneously replenished according to the volume ratio V1:V2 = ΔC1:ΔC2. If 220 g / L ≤ C1 ≤ 250 g / L and 1.2 g / L ≤ C2 ≤ 1.5 g / L, then the composition of the chromium plating solution is maintained. If C1 > 250 g / L and C2 > 1.5 g / L, then the required amount of deionized water is calculated according to the dilution ratio and added to the chromium plating tank in three equal portions, with each portion spaced 5 minutes apart, until 220 g / L ≤ C1 ≤ 250 g / L and 1.2 g / L < C2 < 1.5 g / L. / L≤C2≤1.5g / L, dilute and let stand for 10 minutes before resuming chrome plating; during chrome plating, check the chrome plating layer thickness d. If d<0.015, extend the chrome plating time Δt1; if d>0.025, shorten the chrome plating time Δt2; after chrome plating, check the number of microcracks N. If N<500 cracks / cm, perform a second microcrack treatment on the chrome plating layer and check the number of microcracks N again; if N≥500 cracks / cm, check the coating hardness HV. If HV<800, adjust the chrome plating current to 1.05-1.1 times the original current and re-chrome plating until HV is in the range of 800-1200; if HV>1200, reduce the chrome plating current to 0.9-0.95 times the original current and re-chrome plating until HV is in the range of 800-1200. Real-time monitoring and dynamic adjustments ensure stable and compliant chromium plating quality. High-frequency detection and precise control of the plating solution composition, including simultaneous replenishment of mother liquor, maintenance of composition, and dilution adjustments, ensure that the concentrations of chromium anhydride and sulfuric acid remain within the optimal range, preventing chromium plating defects caused by composition fluctuations. Real-time monitoring and time-based adjustments of the chromium plating thickness ensure precise control within 0.02±0.005mm. Grading detection and parameter adjustments of microcrack count and plating hardness ensure a microcrack count ≥500 cracks / cm and a hardness between 800-1200 HV. This method satisfies stress release requirements while ensuring wear resistance and adhesion. It achieves precise control over the entire chrome plating process, solving problems such as uneven plating thickness, large hardness fluctuations, and insufficient microcrack count in traditional chrome plating processes, significantly improving the consistency of chrome plating quality. At the same time, by specifically adjusting parameters such as current density and processing time, it effectively avoids problems such as chrome plating peeling, insufficient hardness, or excessive hardness, ensuring that the chrome plating layer has excellent corrosion resistance, wear resistance, and adhesion, extending the service life of the piston rod, and reducing the risk of vibration damper failure in harsh environments.

[0033] The method for judging the contact pressure curve in S8 includes: during the simulated assembly process, the pressure module presses down the piston end 1 step structure 3 at a constant speed of 5 mm / s until it contacts the concave-convex limiting plate. The pressure sensor collects the contact pressure P(t) in real time. After removing environmental vibration noise through a filtering algorithm, the pressure peak value Pmax is extracted. If Pmax≤P0 and the pressure rise time T≤0.1s, that is, the time elapsed from the start of contact to P reaching 90% of Pmax is ≤0.1s, then the step fit reliability is determined to be qualified. If Pmax>P0 or T>0.1s, then the pressure curve database of qualified products is further compared. If the similarity between the current curve and the historical qualified curve is less than 85%, then the fit reliability is determined to be insufficient and an alarm is triggered. If the similarity is ≥85%, the sensor is recalibrated and the test is repeated. The assembly process is simulated by uniformly pressing down the pressure module. Pressure curves are collected in real time by pressure sensors, and noise interference is removed to ensure data accuracy. Two key parameters, peak pressure and rise time, are extracted for dual assessment of the fit, avoiding the limitations of single-parameter evaluation. When parameters exceed limits, similarity is compared with a historical database of qualified product curves to further verify fit reliability and reduce the risk of misjudgment. Compared to traditional gap measurement or static pressure testing, this method better simulates the dynamic contact state of the piston rod during actual operation, accurately identifying problems such as excessively tight, loose, or poor contact, ensuring that the fit between the stepped structure 3 and the limiting plate is both stable and reliable, and meets the requirements of the high-frequency reciprocating motion of the vibration damper. This method effectively eliminates products with insufficient fit reliability, preventing displacement deviation, damping fluctuations, or accelerated component wear during vibration damper operation due to fit problems, ensuring the overall performance stability of the vibration damping system and improving product safety and durability. The above description is only a preferred embodiment of the present invention and is not intended to limit the invention. Ordinary changes and substitutions made by those skilled in the art within the scope of the present invention should be included within the protection scope of the present invention.

Claims

1. A novel valve-system vibration damper piston rod with superior structure and stable performance, comprising a piston rod body, characterized in that, The piston end (1) of the piston rod body is provided with an extended section (2) for installing the new valve system 30K restoration valve assembly; the piston end (1) near the cylindrical section of the piston rod body is provided with a stepped structure (3) for cooperating with the concave-convex limiting plate; the piston end (1) is also provided with an extended threaded portion (4) for adapting to various specifications of flow valve springs; the surface of the piston rod body is subjected to high-frequency quenching treatment to form a hardened layer with a hardened layer depth of 0.4-0. The surface is covered with a micro-cracked chromium plating layer with a thickness of 0.02±0.005mm, a hardness of 800-1200HV, and a micro-crack number of ≥500 lines / cm. The chromium plating layer is also treated with hydrogen removal after plating. The straightness of the cylindrical section of the piston rod body is ≤0.01mm, the roundness is ≤0.01mm, the coaxiality of the piston end (1) is ≤φ0.05mm, and the end face runout is ≤0.04mm.

2. The piston rod of a novel valve system vibration damper with superior structure and stable performance according to claim 1, characterized in that, The radius of the transition fillet at the connection between the stepped structure (3) and the piston end (1) is 0.2-0.3 mm.

3. The piston rod of a novel valve system vibration damper with superior structure and stable performance according to claim 1, characterized in that, The plating solution used for the chromium plating layer is formulated as follows: 220-250 g / L chromium anhydride, 1.2-1.5 g / L sulfuric acid, 0.5-1.0 g / L rare earth additives, and 0.2-0.4 g / L surfactant, wherein the mass ratio of chromium anhydride to sulfuric acid is 150-200:

1.

4. The piston rod of a novel valve system vibration damper with superior structure and stable performance according to claim 1, characterized in that, The high-frequency quenching process is carried out at a heating temperature of 820-860℃ for 30-45s, with the quenching medium being a polymer aqueous solution and the cooling rate controlled at 80-120℃ / s.

5. The piston rod of a novel valve system vibration damper with superior structure and stable performance according to claim 1, characterized in that, The surface roughness Ra of the stepped structure (3) is ≤0.4μm, and the fitting gap with the concave-convex limiting plate is 0.03-0.05mm.

6. A manufacturing process for the piston rod of a novel valve system vibration damper with superior structure and stable performance as described in any one of claims 1-5, characterized in that, Includes the following steps: S1. Blank pretreatment: Select 40Cr or 20CrMnTi alloy steel bars that meet the design requirements. After rough machining to remove the excess, use an ultrasonic flaw detector to detect internal defects. If the flaw detection results show no cracks or inclusions, proceed to S2; otherwise, reject unqualified blanks. S2. Rough machining of piston end (1): The extended section (2) of piston end (1) is machined by CNC lathe, and the stepped structure (3) and the extended threaded part (4) are machined at the same time to obtain the piston rod blank. S3. Surface high-frequency quenching: Place the piston rod blank in an induction heating device, heat it to 820-860℃ and hold it for 30-45 seconds, then quickly immerse it in a polymer aqueous solution quenching medium to cool it. The cooling rate is controlled at 80-120℃ / s. After quenching, use a Rockwell hardness tester to test the hardness of the hardened layer. If the hardness value does not meet 42-45HRC, adjust the heating temperature or the concentration of the cooling medium and quench again. S4. Finishing: Complete the finishing machining of the piston rod body in sequence to ensure that the straightness of the cylindrical section of the piston rod body is ≤0.01mm and the roundness is ≤0.01mm. After finishing, use a roundness tester and a straightness measuring instrument to check respectively. If the straightness or roundness exceeds the target value, readjust the tool compensation parameters and rework. S5. Microcrack chrome plating: The precision-machined piston rod is placed in a chrome plating bath for microcrack chrome plating, wherein the current density is controlled at 30-40A / dm during chrome plating. 2 Ensure that the thickness of the chrome plating layer is controlled within 0.02±0.005mm and the hardness is controlled within 800-1200HV; S6. Post-plating hydrogen removal treatment: Place the chromium-plated piston rod in a constant temperature chamber at 180-200℃ for 2-3 hours to eliminate internal stress in the chromium plating layer and prevent hydrogen embrittlement. After hydrogen removal, use a tensile testing machine to check the adhesion of the chromium plating layer. If the chromium plating layer peels off, extend the hydrogen removal time or reduce the chromium plating current density and re-treat. S7. Final finishing: make final corrections to the coaxiality and end face runout of the piston end (1) to ensure that the coaxiality is ≤ φ0.05mm and the end face runout is ≤ 0.04mm. After correction, use a coaxiality measuring instrument and a runout detector to check. If the coaxiality or end face runout exceeds the target value, fine-tune it through grinding or lapping process until it is qualified. S8. Comprehensive performance testing: A composite testing module is used to conduct comprehensive performance testing on the finished piston rod, including: collecting the contact pressure curve of the piston end (1) step structure (3) and the concave-convex limiting plate during simulated assembly by a laser displacement sensor. If the peak contact pressure exceeds the preset threshold P0, it is determined that the reliability of the step structure (3) is insufficient; loading reciprocating motion at different frequencies by a damping force simulation tester and collecting the fullness parameter of the indicator graphic. If the fullness of the indicator graphic is <90%, it is determined that the valve system matching performance is not up to standard; based on the comprehensive test results, if any item does not meet the requirements, it is marked as a non-conforming product and the corresponding process is traced for adjustment. If all items are qualified, they are put into storage.

7. The manufacturing process of the piston rod of the new valve system vibration damper with superior structure and stable performance according to claim 6, characterized in that, The hardness detection and control method after S3 high-frequency quenching is as follows: First, use a Rockwell hardness tester to detect the hardness values ​​H1, H2, and H3 at three evenly distributed points on the piston rod end face, and calculate the average value Hp = (H1 + H2 + H3) / 3; if Hp is within the range of 42-45 HRC, it is directly judged as qualified; if Hp < 42 HRC, the hardened layer microstructure is further observed through a metallographic microscope. If the martensite needle length is > 5 μm, it is judged that the heating temperature is insufficient or the cooling rate is too low. The heating temperature is increased by 10-20℃ or a high-concentration polymer quenching medium is replaced; if Hp > 45 HRC, the temperature distribution curve of the quenching heating process is traced back through an infrared thermal imager. If the highest temperature on the piston rod surface is > 880℃, it is judged as overheating. The power parameters of the induction coil are adjusted or the holding time is shortened. After adjustment, repeat S3 until the hardness meets the requirements.

8. The manufacturing process of the piston rod of the new valve system vibration damper with superior structure and stable performance according to claim 6, characterized in that, In step S5, the specific control method for microcrack chromium plating includes: real-time detection of the chromium anhydride concentration C1 and sulfuric acid concentration C2 in the chromium plating solution, with a sampling frequency of once every 30 seconds. If C1 < 220 g / L and C2 < 1.2 g / L, then based on the concentration difference ΔC1 = 230 - C1 and ΔC2 = 1.3 - C2, chromium anhydride mother liquor and sulfuric acid mother liquor are simultaneously replenished according to the volume ratio V1:V2 = ΔC1:ΔC2. If 220 g / L ≤ C1 ≤ 250 g / L and 1.2 g / L ≤ C2 ≤ 1.5 g / L, then the composition of the chromium plating solution is maintained. If C1 > 250 g / L and C2 > 1.5 g / L, then the required amount of deionized water is calculated according to the dilution ratio and added to the chromium plating tank in three equal portions, with each portion spaced 5 minutes apart, until 220 g / L ≤ C1 ≤ 250 g / L and 1.2 g / L < C2 < 1.5 g / L. For a concentration of C2 ≤ 1.5 g / L, dilute and let stand for 10 minutes before resuming chromium plating. During chromium plating, check the thickness d of the chromium layer. If d < 0.015, extend the plating time Δt1; if d > 0.025, shorten the plating time Δt2. After chromium plating, check the number of microcracks N. If N < 500 cracks / cm, perform a second microcrack treatment on the chromium layer and check the number of microcracks N again. If N ≥ 500 cracks / cm, check the hardness HV of the plating layer. If HV < 800, adjust the chromium plating current to 1.05-1.1 times the original current and re-plat the chromium layer until HV is in the range of 800-1200. If HV > 1200, reduce the chromium plating current to 0.9-0.95 times the original current and re-plat the chromium layer until HV is in the range of 800-1200.

9. The manufacturing process of the piston rod of the new valve system vibration damper with superior structure and stable performance according to claim 6, characterized in that, The method for judging the contact pressure curve in S8 includes: during the simulated assembly process, the pressure module presses down the piston end (1) step structure (3) at a speed of 5 mm / s until it contacts the concave-convex limiting plate. The pressure sensor collects the contact pressure P(t) in real time. After removing the environmental vibration noise through the filtering algorithm, the pressure peak value Pmax is extracted. If Pmax≤P0 and the pressure rise time T≤0.1s, that is, the time elapsed from the start of contact to P reaching 90% of Pmax ≤0.1s, the step fit reliability is determined to be qualified. If Pmax>P0 or T>0.1s, the pressure curve database of qualified products is further compared. If the similarity between the current curve and the historical qualified curve is less than 85%, the fit reliability is determined to be insufficient and an alarm is triggered. If the similarity is ≥85%, the sensor is recalibrated and the test is repeated.

Images