A tube expansion mechanism for automotive parts
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-08-29
- Publication Date
- 2026-08-11
AI Technical Summary
目前，现有扩管模具在对汽车管件进行冲扩管加工时，普遍存在管件内侧R角过大的问题：由于扩管过程中缺乏对R角区域材料流动的有效控制，导致R角区域材料过度扩张，无法形成符合图纸要求的有效R角
[0027] The guide mounting seat has a groove that matches the guide block and the guide block fixing seat. The guide block fixing seat is fixed in the groove, and the guide block can move freely along the groove and along the axial direction of the spindle guide hole, providing movement space for the guide block during adjustment.
Smart Images
Figure CN224614870U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to a tube expansion mechanism for automotive parts. Background Technology
[0002] In the automotive parts manufacturing industry, tube expansion is a common process for tubular components, and the quality of tube expansion directly affects the subsequent assembly accuracy and product functionality. Currently, existing tube expansion dies commonly suffer from excessively large inner radius (R-angle) on the inner side of the tubes during the punching and expansion process: due to the lack of effective control over the material flow in the R-angle area during the expansion process, the material in the R-angle area expands excessively, failing to form an effective R-angle that meets the requirements of the drawings.
[0003] This problem can lead to serious hidden dangers in subsequent assembly and use: when assembling MMG (a key mating component in the automotive safety system), the excessive radius of curvature makes the tube lack sufficient internal plane support, and the MMG cannot be assembled stably; more importantly, when a vehicle is involved in a collision, the safety structure based on this tube cannot achieve normal lifting action, directly causing the finished product's safety function to fail, which has a great impact on vehicle safety. Utility Model Content
[0004] To address the aforementioned problems, this utility model provides a tube expansion mechanism for automotive parts, which effectively solves the problems mentioned in the background art.
[0005] The technical solution adopted in this utility model is:
[0006] A tube expansion mechanism for automotive parts includes a punch assembly, a forming area, a clamping area, and a mandrel guide area arranged sequentially from left to right. The clamping area includes an upper clamping die and a lower clamping die, forming a clamping cavity for clamping the tube between the upper and lower clamping dies. The forming area includes an upper forming die and a lower forming die, forming a forming cavity for forming the tube between the upper and lower forming dies. The mandrel guide area includes a guide block and a guide block fixing seat. The guide block has a mandrel guide hole in the axial direction of the clamping cavity. The clamping cavity, the forming cavity, and the mandrel guide hole are coaxially arranged. A mandrel is matched and installed in the mandrel guide hole. The guide block is fixed on the guide block fixing seat. The guide block fixing seat and the guide block are installed in a guide mounting seat. The forming area, the clamping area, and the mandrel guide area are all fixed on the top of the base, and the tops of the forming area, the clamping area, and the mandrel guide area are pressed together by a cover plate.
[0007] Preferably, an adjustment mechanism is provided between the guide block and the guide block fixing seat for adjusting the distance between the guide block and the guide block fixing seat in the axial direction of the mandrel guide hole.
[0008] Preferably, the guide mounting seat has a groove that matches the guide block and the guide block fixing seat. The guide block fixing seat is fixed in the groove, and the guide block can move axially along the mandrel guide hole in the groove.
[0009] Preferably, the guide mounting base has an auxiliary clamping through hole extending downward through the guide mounting base at the location of the guide block along the longitudinal direction.
[0010] Preferably, the mandrel can move axially along the mandrel guide hole and extend into the interior of the molding cavity. In the initial state, the left end of the mandrel extends beyond the left end of the molding cavity.
[0011] Preferably, the right end of the mandrel is provided with a mandrel cylinder for driving the mandrel to move. During the forming process, the mandrel cylinder is in a depressurized state. When the punch assembly moves toward the tube to form, it simultaneously pushes the mandrel backward in a direction away from the punch assembly, so that the punch assembly and the mandrel remain in a closed state at the R-angle forming point of the tube.
[0012] Preferably, the mandrel cylinder is equipped with a pressure relief control unit. The pressure relief control unit is used to switch the mandrel cylinder to the pressure relief state before the punch assembly contacts the tube, and to control the mandrel cylinder to reset after the tube expansion forming is completed so as to drive the mandrel out of the tube.
[0013] Preferably, in the initial state, the length of the end of the mandrel extending beyond the left end of the molding cavity is 0.2~1.5mm.
[0014] The innovative points of this utility model are as follows:
[0015] 1. Spindle synchronous follow-up mechanism:
[0016] The root cause of an excessively large radius (R-angle) is the lack of continuous support in the R-angle area during the forming process, resulting in unrestrained material expansion. This solution innovatively designs a follow-up mechanism that synchronizes the movement of the mandrel and punch assembly, achieving full-process closed constraint of the R-angle area, dynamically closing the R-angle forming area, and fundamentally solving the problem of excessive material expansion.
[0017] 2. Passive synchronous backward movement of the spindle:
[0018] During the forming process, the mandrel cylinder is in a depressurized state (does not actively drive the mandrel); when the punch assembly moves toward the tube and applies forming force, the punch synchronously pushes the mandrel backward along the mandrel guide hole in a direction away from the punch assembly. Through the "indirect driving force of the punch assembly to drive the mandrel backward", it is ensured that the punch assembly and the mandrel always maintain a "closed state" at the forming point of the tube's R-corner: the punch assembly extrudes the material forward, and the mandrel synchronously retreats backward but does not leave the R-corner area, forming a "pinch" constraint space, which completely prevents the material from flowing excessively into the R-corner and precisely controls the R-corner size;
[0019] 3. Intelligent control of pressure relief timing:
[0020] The accompanying "pressure relief control unit" is designed to achieve two key timing controls:
[0021] Pre-depressurization: Before the punch assembly contacts the pipe, switch the mandrel cylinder to the depressurization state in advance to ensure that the mandrel can be smoothly pushed by the punch and avoid the failure of synchronous action due to cylinder resistance;
[0022] Reset: After the tube expansion and forming is completed, control the mandrel cylinder to retract, then release the upper and lower clamping molds, the upper forming mold and the lower forming mold, and take out the tube. Then control the mandrel cylinder to reset.
[0023] Innovative Value: Through "time-sequential intelligent control", the "follow-up support" and "automatic withdrawal" of the mandrel are seamlessly connected, which not only ensures the forming accuracy of the R-angle, but also takes into account the convenience of processing;
[0024] 4. Adjustable structure of the guide block:
[0025] Traditional pipe expansion mechanisms typically use fixed guide blocks, which cannot accommodate pipes of different lengths. This necessitates replacing the entire mold set, resulting in high costs and low efficiency. This solution overcomes this limitation through design adjustments:
[0026] An "adjustment mechanism" (such as adjusting bolts, shims, etc.) is set between the guide block and the guide block fixing seat, which can precisely adjust the distance between the two in the axial direction of the mandrel guide hole. Therefore, the position of the guide block can be adjusted according to the length requirements of different pipe fittings.
[0027] The guide mounting seat has a groove that matches the guide block and the guide block fixing seat. The guide block fixing seat is fixed in the groove, and the guide block can move freely along the groove and along the axial direction of the spindle guide hole, providing movement space for the guide block during adjustment.
[0028] 5. Auxiliary clamping through hole design:
[0029] When the guide block is adjusted to the right for forming a longer pipe, the right end of the pipe is suspended. At this time, an external clamping component (such as a clamping mold) can be inserted through the auxiliary clamping through hole to clamp the right end of the pipe, thereby improving the clamping effect and further ensuring the R-angle forming accuracy. When performing auxiliary clamping, first insert the external clamping component into the auxiliary clamping through hole to clamp the right end of the pipe, and then use the base to seal the bottom of the auxiliary clamping through hole.
[0030] This utility model takes the synchronous follow-up of the mandrel as its core, and through the adjustable guide block to adapt to multiple specifications of pipe fittings, and through auxiliary clamping to strengthen fixation, it finally forms a technical solution with controllable material flow throughout the process, accurate R-angle dimensions, and effective safety function guarantee. It completely solves the fatal problems of "unstable MMG assembly and failure of safety structure during collision" in the background technology, and significantly improves the processing quality and safety performance of automotive pipe fittings. Attached Figure Description
[0031] Figure 1 This is a schematic diagram of the structure of this utility model;
[0032] Figure 2 This is a schematic diagram of the exploded structure of this utility model;
[0033] Figure 3 This is a schematic diagram of the molding area.
[0034] Figure 4 This is a schematic diagram of the clamping area.
[0035] Figure 5 This is a structural schematic diagram of the guide mounting base;
[0036] Figure 6 This is a structural diagram of the guide block and guide block mounting base. Detailed Implementation
[0037] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.
[0038] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.
[0039] Furthermore, in the description of this utility model, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.
[0040] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this utility model, unless otherwise stated, "a plurality of" means two or more, unless otherwise expressly defined.
[0041] In this utility model, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.
[0042] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.
[0043] The present invention will now be described in further detail with reference to specific embodiments and accompanying drawings.
[0044] like Figure 1-6As shown, a tube expansion mechanism for an automotive component includes a punch assembly 1, a forming area, a clamping area, and a mandrel guide area arranged sequentially from left to right. The clamping area includes an upper clamping die 31 and a lower clamping die 32, with a clamping cavity 33 formed between the upper and lower clamping dies 31 and 32 for clamping the tube component 5. The forming area includes an upper forming die 21 and a lower forming die 22, with a forming cavity 23 formed between the upper and lower forming dies 21 and 22 for forming the tube component 5. The mandrel guide area includes a guide block 41 and a guide block fixing seat 42. The guide block 41 has a spindle guide hole 43 in the axial direction of the clamping cavity 33. The clamping cavity 33, the forming cavity 23 and the spindle guide hole 43 are coaxially arranged. A spindle 44 is matched in the spindle guide hole 43. The guide block 41 is fixed on the guide block fixing seat 42. The guide block fixing seat 42 and the guide block 41 are installed in the guide mounting seat 45. The forming area, the clamping area and the spindle guide area are all fixed on the top of the base 6, and the tops of the forming area, the clamping area and the spindle guide area are pressed by the cover plate 7.
[0045] An adjustment mechanism is provided between the guide block 41 and the guide block fixing seat 42 for adjusting the distance between the guide block 41 and the guide block fixing seat 42 in the axial direction of the spindle guide hole 43.
[0046] The guide mounting base 45 has a sliding groove 46 that matches the guide block 41 and the guide block fixing base 42. The guide block fixing base 42 is fixed in the sliding groove 46. The guide mounting base 45 has a positioning groove 48 on the upper part of the guide block fixing base 42 that matches the guide block fixing base 42. The guide block fixing base 42 is fixed in the guide mounting base 45 through the positioning groove 48. The guide block 41 can move axially along the mandrel guide hole 43 in the sliding groove 46.
[0047] The guide mounting base 45 has an auxiliary clamping through hole 47 extending through the guide mounting base 45 along the longitudinal direction at the location of the guide block 41.
[0048] The mandrel 44 can move axially along the mandrel guide hole 43 and extend into the interior of the molding cavity 23. In the initial state, the left end of the mandrel 44 extends beyond the left end of the molding cavity 23.
[0049] The right end of the mandrel 44 is provided with a mandrel cylinder that drives the mandrel 44 to move. During the forming process, the mandrel cylinder is in a depressurized state. When the punch assembly 1 moves toward the tube 5 to form, it simultaneously pushes the mandrel 44 to move backward away from the punch assembly 1, so that the punch assembly 1 and the mandrel 44 remain in a closed state at the R-angle forming point of the tube 5.
[0050] The mandrel cylinder is equipped with a pressure relief control unit. The pressure relief control unit is used to switch the mandrel cylinder to the pressure relief state before the punch assembly 1 contacts the tube 5, and to control the mandrel cylinder to reset after the tube expansion is completed so as to drive the mandrel 44 out of the tube.
[0051] In the initial state, the length of the end of the mandrel 44 extending beyond the left end of the molding cavity 23 is 0.2~1.5mm.
[0052] The guide mounting base 45 consists of two parts, upper and lower. The positioning groove 48 is located in the upper part, and the sliding groove 46 and the auxiliary clamping through hole 47 are located in the lower part. The guide mounting base 45 adopts a structure consisting of two parts, which facilitates the installation of the guide block 41 and the guide block fixing base 42.
[0053] The working principle of this utility model is as follows:
[0054] This automotive component tube expansion mechanism is based on the core principle of "synchronous follow-up constraint of material flow by the mandrel," combined with a full-process design of "pre-adaptation and adjustment + mid-term precision forming + post-automatic reset" to achieve precise control of the R-angle dimension and adaptation of multiple tube specifications. The specific working principle is explained in four stages:
[0055] I. Preliminary Preparations: Fitting and Clamping of Pipe Fittings (Ensuring the Accuracy of the Molded Foundation):
[0056] Before the formal pipe expansion process, the mechanism needs to be adjusted and the pipe clamped according to the length specifications of the automotive pipe to be processed, to ensure the stability and axis accuracy of the pipe during the subsequent forming process.
[0057] 1. Guide block position adjustment (to adapt to different pipe fitting lengths):
[0058] An adjustment mechanism (such as adjusting bolts, shims, etc.) is provided between the guide block and the guide block fixing seat. An axial groove matching the guide block and the guide block fixing seat is opened in the guide mounting seat. According to the pipe length requirements, the distance between the guide block and the guide block fixing seat in the axial direction of the mandrel guide hole is adjusted by the adjustment mechanism, so that the guide block can move freely along the groove to the appropriate position. The distance is increased for short pipes and decreased for long pipes to ensure that the right end of the pipe can stably abut against the guide block and avoid axial displacement of the pipe after clamping.
[0059] 2. Pipe fitting clamping and auxiliary reinforcement:
[0060] The tube to be processed is placed between the upper and lower clamping dies in the clamping area. The upper and lower clamping dies are closed, so that the clamping cavity formed by the two clamps radially clamps the tube. At the same time, because the clamping cavity, the forming cavity of the forming area, and the mandrel guide hole of the mandrel guide area are coaxially set, the tube automatically keeps the axis aligned with the forming cavity and the mandrel guide hole after clamping, providing coaxial accuracy guarantee for the subsequent mandrel extension and punch assembly forming.
[0061] If the pipe is long (the right end of the pipe is suspended after the guide block is adjusted to the right), an external clamping component (such as a clamping mold) can be added through the auxiliary clamping through hole on the guide mounting seat (which extends vertically downward through the guide mounting seat) to perform secondary radial clamping on the right end of the pipe, further eliminating radial swaying during the pipe forming process and preventing irregular flow of material in the R-corner area due to pipe offset. When performing auxiliary clamping, first insert the external clamping component into the auxiliary clamping through hole to clamp the right end of the pipe, and then use the base to seal the bottom of the auxiliary clamping through hole.
[0062] 3. Pre-forming:
[0063] First, the forming end of the pipe fitting is pre-formed using a pre-formed punch assembly, which enlarges the opening at the end of the pipe fitting to achieve flaring, thus facilitating the smooth entry of the formed punch assembly into the pipe fitting (the formed punch assembly is stepped and cannot directly enter the pipe fitting; the pre-formed punch assembly adopts a smooth transition structure, which can enter the pipe fitting for flaring, and after flaring, it can be ensured that the formed punch assembly can smoothly enter the pipe fitting).
[0064] 4. Initial state confirmation:
[0065] Adjust the position of the mandrel so that the left end of the mandrel extends 0.2~1.5mm beyond the left end of the forming cavity in the initial state. This design ensures that the mandrel extends into the R-angle forming area from the beginning of processing, forming support in advance and avoiding excessive material expansion in the R-angle area due to lack of support when the punch assembly initially applies force.
[0066] II. Pre-depressurization control:
[0067] Before the punch assembly contacts the fitting, the pre-pressure relief operation of the mandrel cylinder must be completed through the pressure relief control unit:
[0068] The pressure relief control unit sends a signal to the mandrel cylinder to switch the cylinder to the pressure relief state (the cylinder has no active driving force). The core purpose of this step is to eliminate the resistance to the axial movement of the mandrel. If the cylinder is not depressurized, its internal pressure will hinder the movement of the mandrel, causing the subsequent punch assembly to be unable to push the mandrel backward synchronously, thereby destroying the "closed constraint" of the R-angle forming. Therefore, pre-pressure relief is a key prerequisite for achieving synchronous movement of the punch and the mandrel.
[0069] III. Molding:
[0070] After pre-depressurization is completed, the mechanism enters the tube expansion and forming stage. The punch assembly and mandrel form a fully enclosed constraint on the material in the R-corner area through "passive synchronous action". The specific process is as follows:
[0071] 1. The punch applies force and the mandrel retracts synchronously:
[0072] The punch assembly moves axially (from left to right), gradually contacting the left end of the tube and applying a tube-expanding forming force, pushing the tube material into the forming cavity. Since the mandrel cylinder has been depressurized, the mandrel can move freely axially along the mandrel guide hole. While pushing the tube, the punch assembly simultaneously pushes the left end of the mandrel, causing the mandrel to passively retreat along the mandrel guide hole in a direction away from the punch assembly (from left to right). During this process, the "forward thrust" of the punch assembly and the "reverse retreat" of the mandrel are always synchronized: the advancing speed of the punch assembly matches the retreating speed of the mandrel, ensuring that the mandrel will not leave the R-angle area due to retreating too quickly, nor will it hinder the punch forming due to retreating too slowly.
[0073] 2. Enclose and constrain the material to control the radius (R-angle) dimension:
[0074] The punch assembly continuously extrudes the tubular material to the right, gradually shaping it into the target form under the constraint of the forming cavity. Simultaneously, although the mandrel retracts in sync, it remains positioned at the rounded corner of the tubular part, creating a closed, "pinch" constraint space with the punch assembly.
[0075] The punch assembly extrudes material from the left-side forward in the R-angle region, restricting the material's flow to the left.
[0076] The mandrel "follows and supports" the material in the R-corner area from right to back, preventing the material from expanding excessively into the R-corner.
[0077] The closed constraints of both completely cut off the path of "unconstrained flow" of material in the R-corner area, avoiding excessive material expansion, and ultimately ensuring that the R-corner size accurately meets the drawing requirements, thus solving the problem of "excessive R-corner causing unstable MMG assembly and collision safety failure" in traditional mechanisms.
[0078] IV. Repositioning after molding:
[0079] Once the tube expansion forming reaches the preset requirements (such as the punch assembly moving to the set stroke), the mechanism enters the reset phase:
[0080] The pressure relief control unit sends a discharge signal to the mandrel cylinder, which retracts. Subsequently, the upper clamping mold in the clamping area opens upward, the upper forming mold in the forming area opens upward, and the auxiliary clamping assembly (if used) is released. The operator can then remove the formed pipe. After the pipe is manually removed, the pressure relief control unit sends a reset signal to the mandrel cylinder, which drives the mandrel to move to the left along the mandrel guide hole until it returns to the initial state, completing one pipe expansion cycle.
[0081] In summary, this mechanism, through its entire workflow logic of "pre-adaptation and adjustment to ensure clamping accuracy → pre-depressurization to eliminate synchronous resistance → synchronous follow-up to constrain material flow → automatic reset to improve efficiency," not only eradicates the problem of excessive R-angle in traditional pipe expansion, but also achieves flexible adaptation of multiple pipe specifications, ultimately ensuring the assembly accuracy and safety performance of automotive pipe components.
[0082] Finally, it should be noted that the above examples are merely specific embodiments of this utility model. Obviously, this utility model is not limited to the above embodiments and can have many variations. All variations that can be directly derived or conceived by those skilled in the art from the disclosure of this utility model should be considered within the protection scope of this utility model.
Claims
1. A tube expansion mechanism for an automotive component, characterized in that, The device includes, from left to right, a punch assembly (1), a forming area, a clamping area, and a mandrel guide area. The clamping area includes an upper clamping die (31) and a lower clamping die (32), with a clamping cavity (33) for clamping the pipe fitting (5) formed between the upper clamping die (31) and the lower clamping die (32). The forming area includes an upper forming die (21) and a lower forming die (22), with a forming cavity (23) for forming the pipe fitting (5) formed between the upper forming die (21) and the lower forming die (22). The mandrel guide area includes a guide block (41) and a guide block fixing seat (42). A mandrel guide hole (43) is provided in the axial direction of the clamping cavity (33). The clamping cavity (33), the forming cavity (23) and the mandrel guide hole (43) are coaxially arranged. A mandrel (44) is matched in the mandrel guide hole (43). The guide block (41) is fixed on the guide block fixing seat (42). The guide block fixing seat (42) and the guide block (41) are installed in the guide mounting seat (45). The forming area, the clamping area and the mandrel guide area are all fixed on the top of the base (6), and the top of the forming area, the clamping area and the mandrel guide area are pressed by the cover plate (7).
2. The tube expansion mechanism for an automotive component according to claim 1, characterized in that, An adjustment mechanism is provided between the guide block (41) and the guide block fixing seat (42) for adjusting the distance between the guide block (41) and the guide block fixing seat (42) in the axial direction of the spindle guide hole (43).
3. The tube expansion mechanism for an automotive component according to claim 2, characterized in that, The guide mounting base (45) has a groove (46) that matches the guide block (41) and the guide block fixing base (42). The guide block fixing base (42) is fixed in the groove (46). The guide block (41) can move axially along the spindle guide hole (43) in the groove (46).
4. The tube expansion mechanism for an automotive component according to claim 3, characterized in that, The guide mounting base (45) has an auxiliary clamping through hole (47) extending downward through the guide mounting base (45) at the location of the guide block (41).
5. The tube expansion mechanism for an automotive component according to claim 4, characterized in that, The mandrel (44) can move axially along the mandrel guide hole (43) and extend into the interior of the molding cavity (23). In the initial state, the left end of the mandrel (44) extends beyond the left end of the molding cavity (23).
6. The tube expansion mechanism for an automotive component according to claim 5, characterized in that, The right end of the mandrel (44) is provided with a mandrel cylinder that drives the mandrel (44) to move. During the molding process, the mandrel cylinder is in a depressurized state. When the punch assembly (1) moves toward the tube (5) to perform molding, it simultaneously pushes the mandrel (44) to move backward away from the punch assembly (1), so that the punch assembly (1) and the mandrel (44) remain in a closed state at the R-angle forming point of the tube (5).
7. The tube expansion mechanism for an automotive component according to claim 6, characterized in that, The mandrel cylinder is equipped with a pressure relief control unit. The pressure relief control unit is used to switch the mandrel cylinder to the pressure relief state before the punch assembly (1) contacts the pipe fitting (5), and to control the mandrel cylinder to reset after the expansion forming is completed so as to drive the mandrel (44) out of the pipe fitting.
8. The tube expansion mechanism for an automotive component according to claim 7, characterized in that, In the initial state, the length of the end of the mandrel (44) extending beyond the left end of the molding cavity (23) is 0.2~1.5mm.