Flexible joint with sound attenuation function and hydraulic forming method thereof

Abstract

The application discloses a flexible joint with a sound attenuation function and a hydraulic forming method, which comprises a bellows, a flow guide pipe and an outer net. The bellows comprises a corrugated section and a resonant shell section; the flow guide pipe is installed in the bellows and forms a fluid channel inside, the flow guide pipe comprises a hose and an inner liner pipe, the inner liner pipe and the resonant shell section enclose a resonant cavity, and a through hole is formed in the inner liner pipe and communicates the channel and the resonant cavity; and the outer net is wrapped on the outer surface of the bellows. The structure can transmit sound waves to the resonant cavity through the through hole to excite resonance, prolong the sound wave path by using the corrugated structure, promote attenuation, and inhibit secondary noise by combining the outer net, so that excellent sound attenuation effects of multiple levels and wide frequency bands are achieved.

Description

Technical Field

[0001] This invention relates to the field of vehicle technology, specifically to a flexible joint with noise reduction function and a hydroforming method. Background Technology

[0002] In the past, due to ample space under the vehicle chassis, a front-mounted muffler, either reactive or primarily reactive, was typically placed in the exhaust system. This muffler primarily utilized the principle of resonance to eliminate or reduce mid-to-high frequency noise. However, with the widespread adoption of hybrid powertrains, battery packs occupy a significant amount of chassis space. Exhaust system placement must make room for the battery pack, leaving very limited space for the exhaust system. It is difficult to place a front-mounted muffler in the traditional location, so it is usually eliminated. All noise reduction is now handled by a rear-mounted muffler. However, rear-mounted mufflers are typically used to eliminate or reduce relatively low-frequency noise and are generally larger in size. Such mufflers are usually difficult to use for reducing mid-to-high frequency noise, which is currently a pain point in the industry. Summary of the Invention

[0003] Addressing the existing technical problems and industry pain points in hybrid exhaust system layout, this invention aims to provide a flexible joint with silencing function and a hydroforming method. While providing the original vibration damping and decoupling functions of the flexible exhaust system joint itself, it also eliminates or reduces mid-to-high frequency noise. It replaces the original front-mounted muffler with almost no increase in space occupation, solving industry pain points. This invention boasts advantages such as compact structure, good performance, and diverse silencing methods. Furthermore, combined with the hydroforming manufacturing method, this invention offers higher product reliability, better product consistency, and lower cost.

[0004] To achieve the above objectives, in a first aspect, the present invention provides a flexible joint with noise reduction function, employing the following technical solution: A flexible joint with noise reduction function includes: Bellows; it includes: a bellows section and a resonant shell section; A flow guide tube is installed inside the corrugated pipe, and a channel is formed inside the flow guide tube. The flow guide tube is provided with a through hole that communicates with the channel and the resonant shell section.

[0005] By adopting the above configuration, the inner liner tube is provided with through holes, which allow sound waves to propagate through the through holes to the inner liner tube and the resonant shell section to form a resonant cavity, thereby effectively allowing the sound waves to enter the resonant cavity for resonance and noise reduction.

[0006] When sound waves pass through the guide pipe, both the corrugated pipe and the guide pipe have corrugated sections on their surfaces. When the sound waves encounter the protrusions or depressions of the corrugated sections, the sound wave energy is consumed by air friction, transmission to the corrugated pipe wall, and mutual interference, and the noise intensity gradually decreases. The guide pipe is provided with a connecting channel and a through hole in the resonant shell section. The sound waves are guided into the resonant shell section of the corrugated pipe, and the sound waves will drive the air inside the corrugated pipe to vibrate, thereby exciting the resonance of the air inside the resonant shell section, achieving targeted noise reduction. The resonant shell section inside the corrugated pipe and the guide pipe work together to silence the sound, and split the sound waves and propagate them through multiple paths, solving the problems of short paths and poor silencing effect when the sound waves stay in the resonant shell section.

[0007] Furthermore, the guide tube includes a flexible tube and an inner liner tube, and a resonant cavity is formed between the inner liner tube and the resonant shell section, and the through hole is opened on the inner liner tube.

[0008] By adopting the above configuration, the inner liner tube is provided with through holes, allowing sound waves to flow through the through holes to the inner liner tube and the resonant shell section to form a resonant cavity, thereby effectively allowing the sound waves to resonate and silence within the resonant cavity. The through holes can typically be circular, groove-shaped, or other shapes, as long as they achieve the effect of connection.

[0009] Furthermore, a cavity is formed between the corrugated section and the flexible tube, and the cavity is connected to the resonant cavity.

[0010] By adopting the above configuration, the cavity and resonant cavity formed between the bellows and the guide pipe are connected as one unit. When the sound wave enters the cavity, the sound wave in the cavity quickly enters the resonant cavity through the connecting part, resulting in a larger overall resonant volume, better noise reduction effect, and faster resonant transmission efficiency.

[0011] Furthermore, a cavity is formed between the corrugated section and the flexible tube, and the cavity and the resonant cavity are set independently of each other.

[0012] By adopting the above configuration, the cavity and the resonant cavity are independent of each other, and sound waves can be silenced and transmitted in both the cavity and the resonant cavity.

[0013] Furthermore, the corrugated pipe includes at least one resonant shell section and two corrugated sections, with the two corrugated sections integrally formed at both ends of the resonant shell section.

[0014] By adopting the above configuration, the corrugated sections are located at both ends of the resonant shell section and are directly connected to the resonant shell section. After the sound wave passes through one side of the corrugated section, it can directly enter the resonant shell section. At the same time, after the resonant shell section silences the sound wave, it can also directly transmit it to the other side of the corrugated section, making the silence more continuous and further strengthening the connection between the corrugated section and the resonant shell section.

[0015] Furthermore, the bellows includes at least one resonant shell section and one corrugated section, wherein the resonant shell section is integrally formed at the end of the bellows.

[0016] By adopting the above configuration: the bellows includes at least a resonant shell section and a corrugated section. The resonant shell section and the corrugated section realize the sound absorption function of the flexible joint. The corrugated section is located at one end of the resonant shell section. The integral molding makes the connection between the corrugated section and the resonant shell section more stable and the connection between them is smoother when transmitting sound waves.

[0017] Furthermore, the outer wall surface of the hose is provided with external corrugations, and the external corrugations of the hose are interlocked with the corrugated section of the corrugated pipe.

[0018] By adopting the above configuration, the outer wall surface of the corrugated pipe is provided with external corrugations, which are larger than those of the hose, and both surfaces are corrugated. This allows the external corrugations of the hose and the corrugations on the surface of the corrugated pipe to interlock, thus better stabilizing the tightness between the corrugated pipe and the hose.

[0019] Furthermore, a sound-absorbing component is provided locally between the guide pipe and the corrugated pipe, and the sound-absorbing component can be sound-absorbing cotton.

[0020] By adopting the above configuration, the sound-absorbing component is placed in a localized area between the guide pipe and the corrugated pipe. The porous sound-absorbing properties of the sound-absorbing cotton can be used to absorb and attenuate the mid-to-high frequency sound waves generated when the airflow passes through the guide pipe, thereby reducing the outward propagation of sound wave energy. At the same time, the localized placement of the sound-absorbing component achieves targeted sound absorption treatment without affecting the unobstructed flow of fluid in the guide pipe, which helps to improve the overall sound absorption effect of the flexible joint within a limited space.

[0021] Furthermore, a shock-absorbing component is provided locally between the guide pipe and the corrugated pipe, and the shock-absorbing component can be a knitted mesh.

[0022] By adopting the above configuration, the damping component is placed in a localized area between the guide pipe and the bellows. The elasticity and damping characteristics of the knitted mesh can buffer and absorb the vibrations generated in the guide pipe under airflow pulsation or external vibrations, thereby reducing the transmission of vibrations to the bellows. Simultaneously, the localized placement of the damping component reduces the possibility of rigid contact between the guide pipe and the bellows without affecting the unobstructed flow of fluid within the guide pipe, avoiding any abnormal noises and improving the damping performance and reliability of the flexible joint.

[0023] Furthermore, a partition section is provided inside the resonant cavity, which divides the resonant cavity into a first resonant cavity and a second resonant cavity that are independent of each other.

[0024] By employing the above configuration, the flexible joint can effectively eliminate noise from multiple specific frequency bands or a wider frequency range simultaneously. Compared to a single resonant cavity, which is only optimal for noise in a specific frequency band, this multi-cavity design significantly broadens the effective noise reduction frequency range, further enhancing the noise reduction effect.

[0025] Secondly, the present invention provides a method for hydraulic forming of bellows, which adopts the following technical solution: A method for hydraulic forming of bellows, comprising the following steps: S1: Place the tube blank in the forming mold and close the forming mold to cover the outer wall of the tube blank; the inner cavity of the forming mold is divided along the axial direction into at least one corrugated section forming area and at least one resonant shell section forming area; S2: Using sealing devices located at both ends of the tube blank along the axial direction, clamp the openings at both ends of the tube blank to achieve end sealing; inject high-pressure fluid into the tube blank through the sealing devices and discharge the air inside the tube blank until a closed hydraulic cavity is formed; S3: Start the booster equipment to inject high-pressure fluid into the sealed hydraulic cavity through the sealing device, so that the pressure of the high-pressure fluid in the tube blank increases to the set pressure value P1; S4: Drive the sealing device to push the two ends of the tube blank to the middle axial feed, generating axial compression displacement L, and at the same time control the pressure of the high pressure fluid in the tube blank to rise from the set pressure value P1 to the forming pressure P2, forcing the tube blank to form a corrugated section and a resonant shell section. S5: When the axial displacement of the sealing device reaches the preset end position, the pressure of the high-pressure fluid in the tube blank is increased to the shaping pressure P3 and maintained for a predetermined time T. S6: Release the high-pressure fluid pressure inside the tube blank.

[0026] It has the following beneficial effects: 1. The combination of the cavity and resonant cavity inside the bellows with the through hole on the guide pipe for noise reduction, so that the sound wave can propagate in each cavity, which solves the problems of small resonant cavity volume, small resonant frequency range, short sound wave transmission path and poor noise reduction effect.

[0027] 2. By setting separate sections within the resonant cavity to form independent first and second resonant cavities, the bellows can simultaneously resonate and absorb noise at multiple specific frequencies, significantly broadening the effective noise reduction frequency range and overcoming the limitation of narrow noise reduction bandwidth of a single resonant cavity. 3. By employing a hydraulic bulging process to achieve integrated molding of the bellows section and the resonant shell section, the leakage risk associated with traditional welding is fundamentally eliminated. Simultaneously, by utilizing a graded pressurization strategy and coordinated control of axial feed, a pressure value P1 is set to increase the rigidity of the tube blank to prevent instability and wrinkling; forming pressure P2, combined with axial displacement L, guides the plasticity of the tube blank to prevent excessive wall thinning; and forming pressure P3, combined with holding time T, forces the tube wall to adhere to the mold to eliminate elastic rebound. This significantly improves the overall structural strength and sealing reliability of the bellows while ensuring high-precision molding of the resonant cavity dimensions, thereby guaranteeing the accuracy and stability of the noise reduction frequency during mass production. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the structure of a flexible joint with noise reduction function according to this application; Figure 2 This is a half-sectional schematic diagram of a flexible joint with noise reduction function according to this application; Figure 3 This is a schematic diagram showing that the cavity and resonant cavity of this application are independent of each other; Figure 4 This is a schematic diagram showing the resonant shell section of this application located on one side of the bellows channel inlet. Figure 5 This is a schematic diagram showing the resonant shell section of this application located on the outlet side of the bellows channel; Figure 6 This is a schematic diagram of the first resonant cavity, the second resonant cavity, and the partition segment structure of this application; Figure 7 A schematic diagram showing that a sound-absorbing or vibration-damping component is provided between the flow guide pipe and the bellows in this application; Figure 8 This is a schematic diagram of the steps of a bellows hydraulic forming method according to Embodiment 2 of this application; Among them, 1. Corrugated pipe; 11. Corrugated section; 12. Resonant shell section; 2. Guide pipe; 21. Flexible hose; 22. Inner liner pipe; 23. Through hole; 3. Resonant cavity; 31. First resonant cavity; 32. Second resonant cavity; 33. Separating section; 4. Outer mesh; 5. Cavity; 6. Silencing component; 7. Vibration damping component. Detailed Implementation

[0029] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Example 1

[0030] See appendix Figures 1 to 4 As shown, this embodiment provides a flexible joint with noise reduction function, which includes: a bellows 1 and a guide pipe 2. The guide pipe 2 is installed inside the bellows 1, and the guide pipe 2 has a channel for airflow. The bellows 1 includes a bellows section 11 and a resonant shell section 12, and the guide pipe 2 is provided with a through hole 23 connecting the channel and the resonant shell section 12.

[0031] See appendix Figures 2 to 4 As shown, the guide tube 2 includes a flexible tube 21 and an inner liner tube 22. The flexible tube 21 and the corrugated section 11 are correspondingly arranged, and the resonant shell section 12 and the inner liner tube 22 are correspondingly arranged. A cavity 5 is formed between the corrugated section 11 and the flexible tube 21. The inner liner tube 22 and the resonant shell section 12 form a resonant cavity 3. A through hole 23 is formed on the inner liner tube 22. In some embodiments, the guide tube 2 is manufactured using an integral molding process, and the inner liner tube 22 is provided with through holes 23. Sound waves can simultaneously enter the resonant cavity 3 or the cavity 5 through the areas of the flexible tube 21 and the inner liner tube 22, increasing the path of sound wave diversion and the noise reduction area. In another embodiment, the inner liner tube 22 is made of a rigid material, and the inner liner tube 22 and the flexible tube 21 are integrally molded. The integral molding better maintains the shape stability of the resonant cavity 3.

[0032] When sound waves encounter the protrusions or depressions of the corrugations, they will undergo multiple reflections, scattering, and diffractions instead of propagating in a straight line. In each reflection and scattering process, the sound wave energy will be consumed due to air friction and mutual interference of sound waves, and the noise intensity will gradually decrease. The sound waves are transmitted to the resonant cavity 3 through the through hole 23 on the inner liner tube 22. The sound waves will drive the air in the corrugated tube 1 to vibrate, thereby exciting the resonance of the air in the resonant cavity 3. The inherent vibration characteristics will "target and absorb" sound waves of specific frequencies, achieving targeted noise reduction. The inner liner tube 22 and the resonant shell section 12 form a resonant cavity 3 combination for sound attenuation.

[0033] It also includes an outer mesh 4, which wraps around the outer surface of the corrugated pipe 1. The outer mesh 4 is a mesh structure that can serve as an auxiliary sound-absorbing element. Although the corrugated pipe 1 itself can attenuate some sound waves, the vibration of the pipe wall may still radiate sound waves to the outside in the form of air transmission. At the same time, the mesh structure of the outer mesh 4 adopts a high-density or multi-layer design, which can further block the penetration of high-frequency sound waves, while low-frequency sound waves will be partially absorbed by the vibration damping effect of the mesh structure, further enhancing the vibration damping. This solves the problems of the resonant cavity 3 having a short duration of resonant frequency, poor sound absorption effect, and a single sound absorption method.

[0034] In some embodiments, the through holes 23 on the inner liner 22 can also be formed on the flexible tube 21; there are multiple through holes 23, and the multiple through holes 23 are arranged circumferentially along the inner wall of the inner liner 22, and the angle occupied by all the through holes 23 in the circumferential direction is between 120 and 240 degrees of the 360 ​​degrees of the circumference of the inner liner 22. Therefore, the multiple through holes 23 connect the inner liner 22 and the resonant shell section 12 to achieve acoustic resonance.

[0035] See appendix Figure 2 As shown, in this embodiment, the bellows 1 includes at least one resonant shell section 12 and two corrugated sections 11. The two corrugated sections 11 are located on both sides of the resonant shell section 12. The corrugated sections 11 and the resonant shell section 12 are integrally formed. A resonant cavity 3 is formed between the resonant shell section 12 and the inner liner 22. The two corrugated sections 11 are integrally formed at both ends of the resonant shell section 12. The integral forming makes the resonant shell section 12 and the corrugated sections 11 tightly connected. After the sound waves are initially processed by the corrugated sections 11, the sound waves can be directly allowed to enter the resonant shell section 12 for further noise reduction. The resonant cavity 3 in the resonant shell section 12 is not limited to a rectangle, but can also be an arc shape, a cone shape, or other shapes.

[0036] See appendix Figure 4 As shown, in one embodiment, the resonant cavity 3 can be set on one side of the channel inlet of the bellows 1 and the flexible tube 21 to directly silence the transmitted sound waves at the inlet of the bellows 1, and at the same time further cooperate with the bellows 1 to perform concentrated silencing during the expansion process of the bellows 1 from a small diameter to a large diameter.

[0037] See appendix Figure 5 As shown, in another embodiment, the resonant cavity 3 can also be set on one side of the channel outlet of the bellows 1 and the hose 21 to perform noise reduction at the outlet of the bellows 1. When the sound wave enters the bellows 1 and the hose 21, the internal corrugated section 11 can gradually weaken it, and then the resonant cavity 3 can gradually reduce the noise.

[0038] See appendix Figure 6As shown, in another embodiment, a partition section 33 is provided in the resonant cavity 3. The partition section 33 divides the resonant cavity 3 into a first resonant cavity 31 and a second resonant cavity 32 that are independent of each other. The division of the resonant cavity 3 into the first resonant cavity 31 and the second resonant cavity 32 enables a bellows 1 to effectively eliminate noise of multiple specific frequencies at the same time, which greatly improves the targeting and efficiency of noise reduction, thereby improving the overall noise reduction performance.

[0039] See appendix Figures 3 to 7 As shown, in this embodiment, the outer wall surface of the hose 21 is provided with external corrugations. The waveform structure of the external corrugations matches the corrugated section 11 of the corrugated pipe 1, so that the external corrugations of the hose 21 can form an interlocking connection with the corrugated section 11 of the corrugated pipe 1. Through this interlocking connection structure, the guide pipe 2 can be limited and supported in the radial direction, thereby improving the assembly stability of the guide pipe 2 in the corrugated pipe 1 and helping to maintain the stability of the sound wave transmission path in the guide pipe 2.

[0040] Based on the above structure, a sound-absorbing component 6 can be provided in a local area between the guide pipe 2 and the corrugated pipe 1. The corrugated pipe 1 includes a corrugated section 11 and a resonant shell section 12. Therefore, the sound-absorbing component 6 can be provided at any local position between the guide pipe 2 and the corrugated pipe 1, specifically between the guide pipe 2 and the corrugated section 11, and / or between the guide pipe 2 and the resonant shell section 12. The sound-absorbing component 6 can be made of sound-absorbing cotton, metal knitted mesh, or other high-temperature resistant sound-absorbing materials. It absorbs and dissipates sound waves through the porous structure of the material itself, further weakening the sound wave energy, thereby enhancing the overall sound-absorbing effect of the flexible joint.

[0041] In some embodiments, a damping element 7 may be provided in a local area between the guide pipe 2 and the corrugated pipe 1. The damping element 7 may also be provided between the guide pipe 2 and the corrugated section 11, and / or between the guide pipe 2 and the resonant shell section 12. The damping element 7 is preferably made of stainless steel wire knitted mesh pad or high-ratio fluororubber elastic pad with excellent heat resistance and resilience. It forms radial elastic support and pre-tightening effect between the guide pipe 2 and the corrugated pipe 1 to absorb the vibration energy generated when the high-speed airflow passes through, counteract the radial sway of the guide pipe 2, and avoid rigid contact between the hose 21 and the inner wall of the corrugated pipe 1, which would cause abnormal noise or structural fatigue.

[0042] See appendix Figure 2 As shown, in this embodiment, the guide pipe 2 includes a flexible tube 21 and an inner liner tube 22. The flexible tube 21 and the corrugated section 11 are correspondingly arranged. A cavity 5 is formed between the corrugated section 11 and the flexible tube 21. The inner liner tube 22 and the resonant shell section 12 form a resonant cavity 3. The cavity 5 and the resonant cavity 3 are connected.

[0043] See appendix Figure 3As shown, in some embodiments, cavity 5 and resonant cavity 3 are independent of each other. While cavity 5 and resonant cavity 3 can independently silencing each other, in another embodiment, cavity 5 and resonant cavity 3 can be further connected through through hole 23 to cooperate in drainage and silencing.

[0044] In summary, sound waves enter the guide pipe 2 with the airflow and initially propagate through the hose 21 region. When the airflow reaches the inner liner pipe 22 region, the through-hole 23 on the inner liner pipe 22 acts as a diversion point, diverting some of the sound waves to the resonant cavity 3 formed by the resonant shell section 12 of the corrugated pipe 1 and the inner liner pipe 22. The sound waves entering the resonant cavity 3 excite the air column to resonate, consuming the sound energy of a specific frequency through the principle of acoustic impedance matching. At the same time, the residual sound waves that do not enter the through-hole 23 continue to propagate along the channel or enter the cavity 5 formed between the corrugated section 11 and the hose 21 (in the embodiment where the cavity 5 is connected to the resonant cavity 3). The sound waves impact the corrugated wall surface of the corrugated pipe 1, causing multiple reflections and scatterings, changing the propagation path from a straight line to a broken line, thereby prolonging the residence time of the sound waves in the pipe and increasing air friction loss. Finally, the outer mesh 4 wrapped around the outer surface of the corrugated pipe 1 restrains the pipe wall, using its damping characteristics to suppress the secondary vibration radiation of the pipe wall. Through the multiple coupling effects of micro-perforated resonance, ripple scattering, and external mesh damping, a multi-layered, wide-band noise reduction effect is achieved, solving the technical problems of narrow noise reduction frequency range and single noise reduction method in the existing technology. Example 2

[0045] See Figure 8 As shown, this embodiment involves processing a tube blank, and the specific forming steps are as follows; S1: Place the tube blank in the forming mold and close the forming mold to cover the outer wall of the tube blank; the inner cavity of the forming mold is divided along the axial direction into at least one corrugated section forming area and at least one resonant shell section forming area.

[0046] Before placing the tube blank into the forming mold, the tube blank needs to be cleaned to remove surface oil and a special lubricant is applied. This operation is to reduce the frictional resistance when the tube wall material flows into the mold cavity in the subsequent S4 step. The inner cavity of the forming mold is divided into at least one corrugated section forming area and at least one resonant shell section forming area along the axial direction. Depending on the specific product requirements, the resonant shell section forming area can be flexibly set between the two corrugated section forming areas, or set at either end of the corrugated section along the axial direction.

[0047] S2: Using sealing devices located at both ends of the tube blank along the axial direction, clamp the openings at both ends of the tube blank to achieve end sealing; inject high-pressure fluid into the tube blank through the sealing devices and discharge the air inside the tube blank until a closed hydraulic cavity is formed.

[0048] The sealing devices (such as hydraulic sealing heads) located at both ends of the tube blank move axially towards the center under the drive of a motor or hydraulic cylinder. The front end of the sealing device has a conical sealing surface structure, which causes a slight plastic deformation at the tube blank end through a tightening action, achieving a hard seal between the metals. High-pressure fluid (such as emulsion or water-based hydraulic oil) is injected into the tube blank through an injection channel opened in the center of one of the sealing devices. In the initial stage of injection, the tube is kept connected to the outside environment through the sealing device at the other end or an exhaust valve on the pipeline. Because air is highly compressible, if it is not expelled, subsequent pressurization will cause pressure fluctuations and temperature increases, affecting the shape accuracy of the corrugated section.

[0049] The exhaust passage is closed when the sensor detects high-pressure fluid flowing out of the exhaust end until the tube blank is completely filled with high-pressure fluid, thus forming a closed hydraulic cavity that uniformly transmits pressure inside the tube blank.

[0050] S3: Start the booster device to inject high-pressure fluid into the sealed hydraulic cavity through the sealing device, so that the pressure of the high-pressure fluid in the tube blank increases to the set pressure value P1.

[0051] The pressurization equipment is activated by injecting high-pressure fluid into the sealed hydraulic chamber through a sealing device, raising the pressure inside the tube blank to the set pressure value P1. In practice, the set pressure value P1 is dynamically set according to the tube blank material and wall thickness, typically selected as 10% to 30% of the yield strength of the tube blank material. For example, if a stainless steel tube blank is used, the set pressure value P1 can be set between 2 MPa and 8 MPa; the pressurization equipment can be activated using a high-pressure booster cylinder or a hydraulic pump set.

[0052] S4: Drive the sealing device to push the two ends of the tube blank to the middle axial feed, generating axial compression displacement L, and at the same time control the pressure of the high pressure fluid in the tube blank to rise from the set pressure value P1 to the forming pressure P2, forcing the tube blank to form a corrugated section 11 and a resonant shell section 12.

[0053] The control system drives the sealing devices at both ends to feed synchronously towards the middle, generating a total displacement L. At the same time, the high-pressure fluid pressure inside the tube blank increases from the set pressure value P1 to the forming pressure P2. The forming pressure P2 should be set higher than the yield strength of the tube blank material. The forming pressure P2 is usually set between 25MPa and 55MPa. If the pressure is too low, the crests of the corrugated section cannot completely fill the mold cavity; if the pressure is too high and the feed speed is slow, it is easy to cause the tube wall to be too thin at the crests or even burst.

[0054] The forming pressure P2 expands the tube wall into the mold cavity, while axial displacement pushes the tube material at both ends toward the forming area. This synergistic effect of radial expansion and axial feeding ensures that the thinning rate of the corrugated section 11 after forming is controlled within a predetermined range, thereby obtaining a high-strength corrugated structure.

[0055] The tube blank corresponding to the resonant shell section forming area expands and fits into the large space cavity under the forming pressure P2. Since the diameter of the resonant shell section forming area is larger than that of the corrugated section 11, the tube wall undergoes severe plastic deformation, and is finally formed into a resonant shell section 12 with a predetermined expansion shape.

[0056] By using closed-loop feedback from displacement and pressure sensors, the pressure rise rate is ensured to correspond proportionally to the axial feed rate, thereby eliminating local cracking or wrinkling caused by uneven force.

[0057] S5: When the axial displacement of the sealing device reaches the preset end position, the pressure of the high-pressure fluid in the tube blank is increased to the shaping pressure P3 and maintained for a predetermined time T.

[0058] Once the axial compression displacement L reaches the predetermined endpoint, the control system locks the axial position of the sealing devices at both ends, keeping them stationary to provide stable end support. Subsequently, the pressurization equipment instantaneously or incrementally increases the high-pressure fluid pressure inside the tube blank from the forming pressure P2 to the shaping pressure P3, which should be greater than the forming pressure P2. In practice, the shaping pressure P3 is typically set between 60 MPa and 90 MPa. The ultra-high pressure shaping pressure P3 forces the tube wall metal to completely adhere to the inner wall of the mold cavity, causing secondary plastic flow within the material and thus redistributing internal stress.

[0059] This step ensures the forming requirements of the resonant shell section 12 and the corrugated section 11 by offsetting the elastic rebound after unloading; the pressure needs to be maintained at the forming pressure P3 for a predetermined time T (usually 3s to 8s) to make the bellows 1 fully stable and prevent deformation caused by stress release at the micro level.

[0060] S6: Release the liquid pressure inside the tube blank.

[0061] The pressurization equipment is stopped, and the pressure of the liquid inside the pipe is slowly reduced from the forming pressure P3 to atmospheric pressure through the pressure relief valve. The controlled depressurization rate helps to release the internal stress of the material smoothly and prevents micro-deformation of the pipe wall caused by instantaneous pressure loss. The sealing devices at both ends move in the opposite direction along the axial direction under the drive of the actuator, disengaging from the openings at both ends of the bellows 1 and recovering the high-pressure fluid remaining in the pipe blank. The mold closing mechanism drives the forming mold to open radially, releasing the covering constraint on the outer wall of the pipe blank.

[0062] The formed flexible section with noise reduction function is removed from the mold cavity. At this time, the bellows 1 has an integrally formed corrugated section 11 and resonant shell section 12. The finished product after removal needs to undergo subsequent drying or cleaning to remove the fluid medium remaining on the inner and outer walls of the pipe.

[0063] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A flexible joint having a sound dampening function, characterized by, include: Bellows (1); It includes: a corrugated section (11) and a resonant shell section (12); The guide pipe (2) is installed inside the corrugated pipe (1) and has a channel inside it. The guide pipe (2) is provided with a through hole (23) that communicates with the channel and the resonant shell section (12).

2. The flexible joint with noise reduction function as described in claim 1, characterized in that: The guide tube (2) includes a flexible tube (21) and an inner liner tube (22). A resonant cavity (3) is formed between the inner liner tube (22) and the resonant shell section (12). The through hole (23) is opened on the inner liner tube (22).

3. A flexible joint with noise reduction function as described in claim 2, characterized in that: A cavity (5) is formed between the corrugated section (11) and the flexible tube (21), and the cavity (5) is connected to the resonant cavity (3).

4. A flexible joint with noise reduction function as described in claim 2, characterized in that: A cavity (5) is formed between the corrugated section (11) and the flexible tube (21), and the cavity (5) and the resonant cavity (3) are set independently of each other.

5. A flexible joint with noise reduction function as described in claim 1, characterized in that: The corrugated pipe (1) includes at least one resonant shell section (12) and two corrugated sections (11), with the two corrugated sections (11) being integrally formed at both ends of the resonant shell section (12).

6. A flexible joint with noise reduction function as described in claim 1, characterized in that: The bellows (1) includes at least one resonant shell section (12) and one corrugated section (11), wherein the resonant shell section (12) is integrally formed at the end of the bellows (1).

7. A flexible joint with noise reduction function as described in claim 2, characterized in that: A sound-absorbing component (6) is provided between the guide pipe (2) and the corrugated pipe (1).

8. A flexible joint with noise reduction function as described in claim 2, characterized in that: A shock absorber (7) is provided between the guide pipe (2) and the corrugated pipe (1).

9. A flexible joint with noise reduction function as described in claim 2, characterized in that: The resonant cavity (3) is provided with a partition section (33), which divides the resonant cavity (3) into a first resonant cavity (31) and a second resonant cavity (32) that are independent of each other.

10. A method for hydroforming a bellows, used to produce the bellows in a flexible joint with a noise-reducing function as described in any one of claims 1 to 9, characterized in that, Includes the following steps: S1: Place the tube blank in the forming mold and close the forming mold to cover the outer wall of the tube blank; the inner cavity of the forming mold is divided along the axial direction into at least one corrugated section forming area and at least one resonant shell section forming area; S2: Using sealing devices located at both ends of the tube blank along the axial direction, clamp the openings at both ends of the tube blank to achieve end sealing; inject high-pressure fluid into the tube blank through the sealing devices and discharge the air inside the tube blank until a closed hydraulic cavity is formed; S3: Start the booster equipment to inject high-pressure fluid into the sealed hydraulic cavity through the sealing device, so that the pressure of the high-pressure fluid in the tube blank increases to the set pressure value P1; S4: Drive the sealing device to push the two ends of the tube blank to the middle axial feed, generate axial compression displacement L, and at the same time control the pressure of the high pressure fluid in the tube blank to rise from the set pressure value P1 to the forming pressure P2, forcing the tube blank to form a corrugated section (11) and a resonant shell section (12). S5: When the axial displacement of the sealing device reaches the preset end position, the pressure of the high-pressure fluid in the tube blank is increased to the shaping pressure P3 and maintained for a predetermined time T. S6: Release the high-pressure fluid pressure inside the tube blank.

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