Plastic air reservoir for automotive air brake system and its composite molding method

Abstract

The application relates to the technical field of automobile air brake devices, and discloses a plastic air cylinder for an automobile air brake device and a composite forming method thereof. The air cylinder comprises an upper cylinder body and a lower cylinder body. An annular tenon is integrally formed at one end of the upper cylinder body. An annular riveting structure is arranged on the inner wall of the connecting end of the lower cylinder body. The annular tenon is inserted into the annular riveting structure and is vibrationally friction-welded in the annular riveting structure. A friction-welded sealing area and a structural adhesive bonding area are formed between the annular tenon and the annular riveting structure. One or more joint parts of a metal insert joint are integrally formed at the ends of the upper cylinder body and the lower cylinder body, which are away from each other, and are used for the inlet and outlet of compressed air. Reinforcing ribs are arranged on the inner walls of the upper cylinder body and the lower cylinder body. Through the technical scheme, the problems that the connection strength is insufficient and the sealing reliability is poor due to the fact that the adhesive interface of the existing plastic air cylinder is more and the glue injection quality is difficult to guarantee, the interface separation leakage of the metal joint and the plastic cylinder body is prone to occur due to the difference in material performance, and the pressure resistance and deformation resistance of the cylinder body and the light weight are difficult to be considered are solved.

Description

Technical Field

[0001] This invention relates to the field of automotive air brake system technology, specifically to a plastic air reservoir for automotive air brake systems and its composite molding method. Background Technology

[0002] Automotive air brake systems typically utilize air reservoirs to store compressed air generated by an air compressor, providing a stable air supply to the brake actuators during vehicle braking. Therefore, the air reservoirs require high levels of sealing performance, pressure resistance, fatigue resistance, and environmental adaptability. Currently, air reservoirs for automotive air brake systems are mostly made of steel or aluminum alloy. While metal air reservoirs offer high pressure resistance, they also suffer from significant drawbacks, including increased weight, susceptibility to external corrosion, and numerous manufacturing processes. To achieve lightweight and non-metallic automotive components, existing technologies are beginning to employ composite structures combining a high-density polyethylene inner liner with an outer fiber-wound layer, or injection molding multiple cylindrical components from fiber-reinforced thermoplastics such as PA6GF50, which are then connected using structural adhesives to form the air reservoir. These non-metallic air reservoirs can reduce product weight and improve corrosion resistance to some extent, but their structural design and connection processes still have room for further improvement.

[0003] Existing plastic gas cylinders, typically formed by bonding multiple injection-molded cylindrical components, usually have multiple annular connection interfaces. Each interface must withstand not only the axial separation and shear loads generated by the internal pressure of the gas cylinder but also maintain long-term airtightness. Therefore, the structural adhesive must simultaneously perform the functions of connection and sealing. Influenced by the viscosity of the structural adhesive, the condition of the bonding surface, the uniformity of the adhesive application, and the injection process, phenomena such as insufficient adhesive, adhesive breaks, gas entrainment, or inadequate local filling can easily occur in the bonding gaps, thus affecting the connection strength and sealing reliability. Simultaneously, the metal joint and the plastic cylinder have different material shrinkage rates and thermal expansion properties. Under repeated pressurization, depressurization, and alternating high and low temperatures, the bonding interface between the two may partially separate, forming leakage channels. Furthermore, the plastic cylinder is prone to expansion and deformation under internal pressure; simply increasing the cylinder wall thickness would increase material consumption and product quality.

[0004] Therefore, there is a need for a plastic air reservoir for automotive air brake devices and its composite molding method, which has fewer connection interfaces, combines sealing and load-bearing functions, and can improve the deformation resistance of the cylinder and the reliability of metal joint connections. Summary of the Invention

[0005] To overcome the above-mentioned defects, the present invention provides a plastic air reservoir for automotive air brake devices and its composite molding method, which solves the problems of insufficient connection strength and poor sealing reliability caused by the large number of bonding interfaces and the difficulty in ensuring the quality of glue injection in existing plastic air reservoirs, as well as the easy interface separation and leakage between metal joints and plastic cylinders due to differences in material properties, and the difficulty in simultaneously achieving the cylinder's pressure resistance, deformation resistance and lightweight.

[0006] According to one aspect, at least one embodiment of the present invention provides a plastic air reservoir for an automotive air brake device, comprising an upper cylinder and a lower cylinder arranged axially opposite to each other. An annular tenon is integrally formed at one end of the upper cylinder facing the lower cylinder. An annular riveting structure is provided on the inner wall of the connecting end of the lower cylinder facing the upper cylinder. The connecting end of the annular tenon is inserted into the annular riveting structure and fixed to the annular riveting structure by vibration friction welding, so that the upper cylinder and the lower cylinder together form a sealed air reservoir. Between the annular tenon and the annular riveting structure, there is a friction welding sealing area a and a structural adhesive bonding area b. The friction welding sealing area a forms a continuous annular weld, and the structural adhesive bonding area b is filled with structural adhesive to form a continuous annular adhesive layer. One or more joints are integrally formed at the ends of the upper cylinder and the lower cylinder that are far apart from each other. Each joint is equipped with a metal insert connector, and the internal channel of the metal insert connector is connected to the sealed gas storage cavity. The inner walls of both the upper and lower cylinders are provided with reinforcing ribs integrally formed with the corresponding cylinders.

[0007] For example, in a plastic air reservoir for an automotive air brake device provided in at least one embodiment of the present invention, the reinforcing ribs protrude from the inner wall of the corresponding upper or lower cylinder toward the sealed air reservoir cavity and extend along the inner wall of the corresponding cylinder to improve the resistance of the upper and lower cylinders to internal pressure deformation.

[0008] For example, in a plastic air reservoir for an automotive air brake device provided in at least one embodiment of the present invention, the annular riveting structure covers the connecting end of the annular tenon along the axial direction of the plastic air reservoir.

[0009] For example, in a plastic air reservoir for an automotive air brake device provided in at least one embodiment of the present invention, the upper cylinder, the annular tenon, the lower cylinder, the joint, and the reinforcing rib are all made of fiber-reinforced thermoplastic, wherein the fiber-reinforced thermoplastic is PA6GF50 material with polyamide as the matrix and containing 50% glass fiber by mass.

[0010] For example, in a plastic air reservoir for an automotive air brake device provided in at least one embodiment of the present invention, at least a portion of the outer peripheral surface of the metal insert connector is embedded in a corresponding connector portion. The embedded portion of the metal insert connector is provided with a primer layer and is covered by fiber-reinforced thermoplastic forming the connector portion, so as to form a sealed interface between the metal insert connector and the connector portion.

[0011] For example, in a plastic air reservoir for an automotive air brake device provided in at least one embodiment of the present invention, the lower cylinder is further provided with an injection port and an exhaust overflow port that are respectively connected to the structural adhesive bonding area b.

[0012] For example, at least one embodiment of the present invention also provides a composite molding method for a plastic air reservoir for an automotive air brake system, comprising the following steps: S1. An upper cylinder is integrally injection molded from fiber-reinforced thermoplastic, including an annular tenon at the connecting end of the upper cylinder, a joint at the other end of the upper cylinder, and reinforcing ribs on the inner wall of the upper cylinder; a lower cylinder is integrally injection molded from fiber-reinforced thermoplastic, including an annular riveting structure on the inner wall of one end of the lower cylinder, a joint at the other end of the lower cylinder, and reinforcing ribs on the inner wall of the lower cylinder, with metal insert joints installed in the corresponding joints; S2. Cool and solidify the upper and lower cylinders after injection molding, and perform surface treatment on the surfaces to be bonded of the annular tenon and the annular riveting structure. S3. Insert the connecting end of the annular tenon into the annular riveting structure of the lower cylinder, and perform vibration friction welding on the annular tenon and the annular riveting structure to form an annular weld seam that is continuously distributed around the sealed gas storage cavity. S4. After forming the annular weld, structural adhesive is injected into the structural adhesive bonding area b between the annular tenon and the annular riveting structure, so that the structural adhesive fills the structural adhesive bonding area b and cures to form an annular adhesive layer, thereby obtaining the plastic gas cylinder.

[0013] For example, in a composite molding method for a plastic air reservoir for an automotive air brake device provided in at least one embodiment of the present invention, in step S1, the metal insert connector is pre-positioned in the corresponding injection mold, the outer peripheral surface of the metal insert connector to be covered is cleaned and primed, and the insert is injection molded using a precision injection molding machine with a clamping force of 450-500t, so that the fiber-reinforced thermoplastic plastic forming the connector portion covers at least a portion of the outer peripheral surface of the metal insert connector.

[0014] For example, in a composite molding method for a plastic air reservoir for an automotive air brake device provided by at least one embodiment of the present invention, in step S2, the surfaces to be bonded of the annular tenon and the annular riveting structure are sequentially ground, dusted, and cleaned; in step S4, structural adhesive is injected into the structural adhesive bonding area b through the injection port until the structural adhesive fills the structural adhesive bonding area b and reaches the exhaust overflow port.

[0015] For example, in a composite molding method for a plastic air reservoir for an automotive air brake device provided in at least one embodiment of the present invention, after the structural adhesive in step S4 is cured, the plastic air reservoir is subjected to underwater leak testing and pressure resistance testing, and the plastic air reservoir is subjected to burst limit testing according to a preset sampling cycle.

[0016] The beneficial effects of the embodiments of the present invention are as follows: 1. In this invention, the upper cylinder and the annular tenon are integrally injection molded, and the annular tenon is inserted into the annular riveting structure inside the lower cylinder. This reduces the number of independent injection-molded parts and annular connection interfaces, which helps to reduce assembly errors and potential leakage points. By setting a friction welding sealing area and a structural adhesive bonding area between the annular tenon and the annular riveting structure, a continuous annular weld is first formed by vibration friction welding, and then structural adhesive is injected into the structural adhesive bonding area to form a continuous annular adhesive layer. The annular weld mainly bears the gas sealing function, and the annular adhesive layer mainly bears the axial load and shear load, thereby improving the sealing reliability and structural strength of the connection. The annular riveting structure is set on the inner side of the lower cylinder connection end, which can avoid the formation of an outwardly protruding annular weld structure on the outer surface of the gas storage cylinder; the structural adhesive bonding area completes the filling and venting of structural adhesive through the injection port and the vent overflow port, which helps to improve the continuity and integrity of the annular adhesive layer.

[0017] 2. In this invention, reinforcing ribs are integrally formed on the inner walls of the upper and lower cylinders, which improves the overall rigidity of the cylinder walls, disperses the load of internal pressure acting on the cylinder walls, and reduces the expansion deformation of the gas storage cylinder during repeated inflation, pressure holding, and depressurization processes. The joint is integrally injection molded with the corresponding cylinder. The embedded part of the metal insert joint is covered with fiber-reinforced thermoplastic after cleaning and primer treatment, which helps to enhance the bonding performance and interface sealing performance between the metal insert joint and the joint, reducing the possibility of interface separation and leakage under high and low temperature changes and pressure cycling. Thus, the resulting plastic gas storage cylinder has the characteristics of being lightweight, corrosion-resistant, having strong pressure bearing capacity, stable sealing performance, and suitable for mass injection molding. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the drawings described below are merely some exemplary embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the content of the exemplary embodiments of the present invention and these drawings without any creative effort.

[0019] Figure 1 This is a perspective view of the external structure of the present invention; Figure 2 This is an exploded view of the overall structure of the present invention; Figure 3 This is a perspective view of the lower cylindrical structure in this invention; Figure 4 This is a schematic diagram of the composite molding of the plastic gas storage cylinder in this invention; In the diagram: 1. Upper cylinder; 2. Lower cylinder; 3. Joint; 4. Metal insert joint; 5. Ring tenon; 6. Ring riveting structure; 7. Reinforcing rib. Detailed Implementation

[0020] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of protection of the present invention.

[0021] To simplify the illustrations, each figure only schematically represents the structure related to the technical solution of this invention. The actual dimensions, wall thickness, and proportional relationships of each component can be determined based on the volume of the plastic air tank, the rated working pressure, the installation space, and the interface requirements of the vehicle's air braking system. Components with the same structure or function in the figures use the same reference numerals.

[0022] It should be noted that the terms "installation," "connection," "linking," and "fixing" should be interpreted broadly, referring to direct connections or indirect connections via intermediate components; they can be fixed connections or integral connections formed during the manufacturing process. The term "axial" refers to the direction in which the plastic air tank extends from the upper cylinder 1 to the lower cylinder 2, and the term "circumferential" refers to the direction surrounding the axial direction. The terms "upper" and "lower" are only used to describe the relative positional relationship between the components shown in the attached drawings and do not constitute a limitation on the actual installation direction of the plastic air tank.

[0023] Example 1

[0024] See Figures 1 to 3This embodiment provides a plastic air reservoir for an automotive air brake system, comprising an upper cylinder 1 and a lower cylinder 2 arranged axially opposite each other. Both the upper cylinder 1 and the lower cylinder 2 are cylindrical components with one end closed and the other end connected to each other. After the upper cylinder 1 and the lower cylinder 2 are connected, their internal spaces are interconnected and together form a sealed air reservoir, which is used to store compressed air required by the automotive air brake system.

[0025] like Figure 2 As shown, an annular tenon 5 is integrally formed at the end of the upper cylinder 1 facing the lower cylinder 2. The annular tenon 5 extends axially from the connecting end of the upper cylinder 1 towards the lower cylinder 2. An annular riveting structure 6 is provided on the inner wall of the connecting end of the lower cylinder 2 facing the upper cylinder 1. During assembly, the upper cylinder 1 and the lower cylinder 2 are arranged opposite each other along the same axis. The connecting end of the annular tenon 5 is inserted axially into the annular riveting structure 6, and the outer circumferential surface of the annular tenon 5 overlaps with the mating surface of the annular riveting structure 6. After the annular tenon 5 and the annular riveting structure 6 are connected, the upper cylinder 1 and the lower cylinder 2 form a complete gas storage cylinder body.

[0026] The annular tenon 5 and the upper cylinder 1 are integrally injection molded using the same injection mold, and there is no seam formed by subsequent assembly between the annular tenon 5 and the upper cylinder 1. The plastic gas storage cylinder only forms one annular connection part between the annular tenon 5 and the annular riveting structure 6 of the lower cylinder 2, thereby reducing the number of cylinder parts and the number of annular seams, which helps to reduce assembly errors and the number of potential leakage points.

[0027] One or more connector portions 3 are integrally formed at opposite ends of the upper cylinder 1 and lower cylinder 2 for the entry and exit of compressed air. Each connector portion 3 contains a metal insert connector 4 with a through-hole connecting to a sealed air storage chamber for connecting to automotive air brake lines, drainage devices, or testing lines. The connector portion 3 is integrally formed with the corresponding upper cylinder 1 or lower cylinder 2, eliminating any additional assembly seams between the connector installation position and the cylinder body.

[0028] Both the upper cylinder 1 and the lower cylinder 2 have reinforcing ribs 7 on their inner walls. The reinforcing ribs 7 protrude from the inner wall of the corresponding cylinder toward the sealed air storage cavity and extend along the inner wall of the corresponding cylinder. The reinforcing ribs 7 are integrally injection molded with the corresponding cylinder and are used to improve the local rigidity of the cylinder wall, disperse the load of compressed air acting on the cylinder wall, and reduce the expansion deformation of the cylinder during inflation, pressure holding, and pressure release.

[0029] Example 2

[0030] See Figures 2 to 4 Based on Example 1, this example further explains the composite connection structure between the annular tenon 5 and the annular riveting structure 6.

[0031] An annular riveting structure 6 is formed on the inner side of the connecting end of the lower cylinder 2 and extends continuously around the axis of the lower cylinder 2. The annular riveting structure 6 constitutes an annular receiving part for accommodating the connecting end of the annular tenon 5. After the annular tenon 5 is inserted into the annular riveting structure 6, the annular riveting structure 6 covers part of the outer peripheral surface of the annular tenon 5 along the axial direction, thereby forming an annular overlapping interface with a predetermined axial length. Since the overlapping structure is set on the inner side of the lower cylinder 2, the connecting part forms an in-between structure. The connecting structure generated by vibration friction welding is located inside the cylinder. The outer surface of the plastic gas storage cylinder does not need to be provided with a welding rib that protrudes outward around the circumference, which is beneficial to maintaining the continuity of the outer surface of the gas storage cylinder.

[0032] like Figure 4 As shown, the lap interface between the annular tenon 5 and the annular riveting structure 6 is divided into a friction welding sealing zone a and a structural adhesive bonding zone b. The friction welding sealing zone a is continuously arranged around the annular tenon 5. During vibration friction welding, the materials of the annular tenon 5 and the annular riveting structure 6 located in this area soften or melt under frictional heat and fuse together under welding pressure. After vibration stops and pressure is maintained for cooling, a continuous annular weld is formed in the friction welding sealing zone a. This annular weld extends circumferentially around the plastic air reservoir, blocking the leakage of compressed air from the sealed air reservoir cavity along the lap interface.

[0033] The structural adhesive bonding area b is also continuously arranged around the annular tenon 5, and is divided into sections with the friction welding sealing area a along the lap interface. After the structural adhesive fills the structural adhesive bonding area b and cures, a continuous annular adhesive layer is formed between the annular tenon 5 and the annular riveting structure 6, which is used to withstand the axial separation load caused by the internal pressure of the cylinder and the shear load of the connection part.

[0034] The lower cylinder 2 is equipped with an injection port and an vent / overflow port that communicate with the structural adhesive bonding area b. The injection port is used to connect the injection equipment and deliver the structural adhesive into the structural adhesive bonding area b. The vent / overflow port is used to expel the air originally present in the structural adhesive bonding area b during the injection process and to determine whether the structural adhesive has reached the predetermined position. The position and number of the injection port and the vent / overflow port are set according to the viscosity of the structural adhesive, the circumferential length of the structural adhesive bonding area b, and the injection pressure, so that the structural adhesive flows continuously along the annular bonding gap and covers the entire structural adhesive bonding area b.

[0035] This embodiment employs a composite connection method combining annular welds and annular adhesive layers. The annular welds primarily form an airtight seal, while the annular adhesive layers enhance the load-bearing capacity of the connection surfaces. This avoids the problem of uneven adhesive application when relying solely on structural adhesive to balance sealing and connection strength, and also avoids the issue of relying solely on friction welds to bear all axial and shear loads.

[0036] Example 3

[0037] See Figures 1 to 3 Based on Example 1 or Example 2, this example further explains the joint installation structure and the cylinder reinforcement structure.

[0038] Both the upper cylinder 1 and the lower cylinder 2 have a connector 3 at their respective ends, which are far apart from each other. The connector 3 is integrally injection molded with the end of the corresponding cylinder. The pipe hole of the connector 3 extends toward the sealed air storage cavity, and the internal channel of the metal insert connector 4 communicates with the sealed air storage cavity through the pipe hole. The exposed end of the metal insert connector 4 is used to connect with the pipe joint, valve, or drainage component in the automotive air brake line, and the embedded end of the metal insert connector 4 is located inside the connector 3.

[0039] During manufacturing, the metal insert connector 4 is pre-positioned in the injection mold, and at least a portion of the outer peripheral surface of the metal insert connector 4 is covered by fiber-reinforced thermoplastic forming the connector portion 3. To improve the interfacial bonding performance between the metal insert connector 4 and the connector portion 3, the outer peripheral surface to be covered is cleaned and primed before the metal insert connector 4 is placed into the injection mold. The cleaning treatment removes oil, dust, and other impurities that may affect the bonding from the metal surface, while the priming treatment forms a transition bonding layer between the metal surface and the fiber-reinforced thermoplastic. After the insert injection molding is completed, a sealed bonding interface is formed between the metal insert connector 4 and the connector portion 3 to reduce the possibility of leakage along the metal-plastic bonding interface during repeated pressurization and depressurization of the plastic gas reservoir.

[0040] The inner walls of the upper cylinder 1 and the lower cylinder 2 are respectively provided with a number of reinforcing ribs 7, each of which is injection molded synchronously with the corresponding cylinder. The protrusion height, extension length, cross-sectional dimensions, and distribution spacing of the reinforcing ribs 7 are determined according to the cylinder wall thickness, the working pressure of the gas storage chamber, and the cylinder shape. Under the condition of not obstructing the gas flow in the gas storage chamber, the reinforcing ribs 7 extend along the inner wall of the cylinder and form a continuous force transmission structure with the cylinder wall. When the cylinder is subjected to internal pressure, the reinforcing ribs 7 provide support to the cylinder wall, reducing stress concentration and radial expansion in local areas of the cylinder wall.

[0041] The upper cylinder 1, lower cylinder 2, joint 3, annular tenon 5, annular riveting structure 6, and reinforcing rib 7 are all made of fiber-reinforced thermoplastic. In this embodiment, the fiber-reinforced thermoplastic is PA6GF50 material, which is based on polyamide 6 and contains 50% glass fiber by mass. The glass fiber is used to improve the strength, stiffness, and dimensional stability of the material, while the polyamide 6 matrix is ​​used to achieve injection molding and subsequent vibration friction welding. Using the same fiber-reinforced thermoplastic to mold the upper cylinder 1 and lower cylinder 2 respectively is beneficial to ensure that the materials on both sides of the friction welding interface have matching thermal properties and melting characteristics.

[0042] Example 4

[0043] See Figures 2 to 4This embodiment provides an injection molding method for the above-mentioned plastic gas storage cylinder.

[0044] First, the PA6GF50 raw material is inspected for appearance, moisture content, and material properties, and then dried and prepared according to the process conditions specified by the material supplier. The outer peripheral surface of the metal insert connector 4 to be coated is cleaned to remove surface oil and particles. Then, a primer compatible with the metal material and PA6GF50 material is applied to the outer peripheral surface to be coated, and the primer is allowed to reach the predetermined surface dry state.

[0045] The processed metal insert joints 4 are placed in the insert positioning positions of the upper and lower cylinder injection molds, respectively. The axial and radial displacements of the metal insert joints 4 are restricted by the positioning structure inside the mold, while keeping the internal channels of the metal insert joints 4 unobstructed. After the insert positioning is completed, the mold is closed, and injection molding is performed using a precision injection molding machine with a clamping force of 450–500 t.

[0046] The upper cylinder injection mold is used for one-time molding of the upper cylinder 1, the annular tenon 5, the joint portion 3 located at the end of the upper cylinder 1, and the reinforcing rib 7 located on the inner wall of the upper cylinder 1. Molten PA6GF50 material enters the mold cavity, covers the embedded portion of the corresponding metal insert joint 4, and fills the cavity forming the joint portion 3, the annular tenon 5, and the reinforcing rib 7. After pressure holding and cooling, the upper cylinder 1, the annular tenon 5, the joint portion 3, and the reinforcing rib 7 form an inseparable one-piece injection molded part.

[0047] The lower cylinder injection mold is used to mold the lower cylinder 2, the annular riveting structure 6 located on the inner wall of the connecting end of the lower cylinder 2, the joint 3 located at the other end of the lower cylinder 2, and the reinforcing rib 7 located on the inner wall of the lower cylinder 2 in one step. Molten PA6GF50 material covers the embedded part of the corresponding metal insert joint 4 and fills the cavity forming the annular riveting structure 6 and the reinforcing rib 7. The injection port and the vent overflow port can be formed simultaneously through the molding structure in the mold, or they can be machined according to the predetermined position after the lower cylinder 2 has been injection molded, but the machining must not damage the annular riveting structure 6 and the pressure-bearing wall of the lower cylinder 2.

[0048] After injection molding, the upper cylinder 1 and lower cylinder 2 are cooled and shaped separately, and removed from their respective molds once the demolding conditions are met. After demolding, the gates and flash are cleaned, and the cylinder appearance, wall thickness, mating dimensions of the annular tenon 5 and the annular riveting structure 6, the connection status of the joint 3 and the metal insert joint 4, and the molding integrity of the reinforcing rib 7 are inspected. The annular tenon 5 and the annular riveting structure 6 must not have obvious warping, missing material, or surface contamination that would affect assembly, welding, or glue injection.

[0049] Example 5

[0050] See Figure 2 and Figure 4 Based on Example 4, this example further explains the composite connection process of the upper cylinder 1 and the lower cylinder 2.

[0051] After cooling and setting, the dimensions of the annular tenon 5 and the annular riveting structure 6 were checked to confirm that the annular tenon 5 could be inserted axially into the annular riveting structure 6, and that the relative positions of the friction welding sealing area a and the structural adhesive bonding area b met the design requirements. Subsequently, a surface treatment device with spot grinding, dust removal, and cleaning functions was used to treat the surface to be bonded corresponding to the structural adhesive bonding area b. Grinding was used to remove the weak interface layer of the surface to be bonded and to create a surface condition suitable for structural adhesive adhesion; dust removal was used to remove the powder generated during grinding; and cleaning was used to remove residual contaminants. After surface treatment, the surfaces to be bonded were kept clean and dry to prevent secondary contamination by oil or dust before assembly.

[0052] The upper cylinder 1 and lower cylinder 2 are placed into the positioning clamping fixture of the vibration friction welding equipment, ensuring their axes coincide, and the connecting end of the annular tenon 5 is inserted into the annular riveting structure 6. The positioning fixture clamps the upper cylinder 1 and lower cylinder 2 respectively, restricting displacement unrelated to the vibration direction during welding. After confirming that the insertion depth and circumferential position meet the requirements, welding pressure is applied to the annular tenon 5 and the annular riveting structure 6, and one cylinder is subjected to high-frequency reciprocating vibration relative to the other cylinder.

[0053] Under the combined action of welding pressure and relative vibration, frictional heat is generated at the contact interface of the friction-welded sealing zone a, causing the PA6GF50 material at the interface to gradually soften and melt. Vibration is stopped after reaching the set welding displacement, welding energy, or welding time, while axial pressure is maintained to allow the molten material to fuse and solidify under pressure, forming a continuous annular weld around the sealed gas storage cavity. Welding parameters are determined through process experiments based on the properties of PA6GF50 material, the size of the weld reinforcement, and the specifications of the gas storage cylinder, with the control conditions being continuous annular welds, no abnormal deformation of the cylinder, and overlap positions conforming to design dimensions.

[0054] After completing the vibration friction welding, check the relative positions of the upper cylinder 1 and the lower cylinder 2, as well as the forming condition of the circumferential weld. Once the welded connection meets the requirements, connect the adhesive injection equipment to the adhesive injection port on the lower cylinder 2. The structural adhesive used should be compatible with PA6GF50 material; as one implementation method, a structural adhesive with a tensile shear strength of 14–20 MPa when tested according to GB / T 7124 can be selected.

[0055] During adhesive injection, the injection flow rate and pressure are set according to the viscosity of the structural adhesive and the volume of the adhesive bonding area b. The structural adhesive enters the annular gap between the annular tenon 5 and the annular riveting structure 6 through the injection port and flows circumferentially along the adhesive bonding area b. The injection pressure is limited to the level sufficient to continuously fill the structural adhesive without causing significant deformation of the cylinder. When the structural adhesive is continuously discharged from the vent overflow port and there are no obvious air bubbles in the discharged adhesive, it indicates that the structural adhesive has reached the vent overflow port and completed the filling of the corresponding flow path. After stopping the injection, the injection port and vent overflow port are sealed or the adhesive is closed, and the mixture is allowed to stand according to the specified curing conditions to allow the structural adhesive to cure and form a continuous annular adhesive layer.

[0056] The above process is carried out in the order of vibration friction welding followed by the injection of structural adhesive. Vibration friction welding first forms an annular sealing boundary and completes the initial positioning of the upper cylinder 1 and the lower cylinder 2; subsequently, the injected structural adhesive cures within the structural adhesive bonding area b to improve the connection strength of the lap joint. This process sequence also avoids contamination of the friction welding interface by uncured structural adhesive.

[0057] Example 6

[0058] See Figures 1 to 4 This embodiment further explains the testing process and working status of the plastic gas cylinder.

[0059] After the structural adhesive reaches the specified curing state, the appearance and dimensions of the plastic gas cylinder are first inspected. The inspection includes the coaxiality of the upper cylinder 1 and the lower cylinder 2, the appearance of the connection parts, the sealing status of the glue injection port and the vent overflow port, the bonding status of the joint 3 and the metal insert joint 4, and whether there are cracks, missing materials or abnormal deformation on the surface of the cylinder.

[0060] After the appearance and dimensions have passed inspection, connect the metal insert connector 4 of the plastic air tank to the inflation pipeline and sealing components. Inflate the sealed air tank with test gas, and then place the pressurized plastic air tank underwater for leak testing. During the leak testing process, pay close attention to the connection between the annular tenon 5 and the annular riveting structure 6, the interface between the metal insert connector 4 and the connector part 3, and the positions of the glue injection port and the vent overflow port. If no continuous bubbles appear during the test and the pressure change meets the corresponding technical conditions, the sealing performance is deemed to meet the requirements.

[0061] After underwater leak testing, pressure resistance testing was conducted according to the items and conditions specified in QC / T 200—2015 and QDFACC047 Technical Conditions for Gas Storage Tank Assemblies. For the dissimilar material interface between the metal insert joint 4 and the joint portion 3, pressure holding and pressure cycling verification were performed under normal temperature, high temperature, and low temperature conditions to examine the impact of the different shrinkage rates and thermal expansion properties of plastic and metal materials on the sealing performance of the interface. During the pressure resistance test, the deformation of the cylinder, the condition of the annular connection, and the pressure leakage around the metal insert joint 4 were observed simultaneously.

[0062] According to the preset sampling cycle, samples are drawn from products that have completed sealing and pressure resistance tests, and burst limit tests are conducted in a burst limit test chamber. During the test, the pressure in the sealed gas storage chamber is gradually increased, and the deformation of the cylinder, the state of the connection parts, and the final failure location are recorded. This data is used to evaluate the comprehensive load-bearing capacity of the upper cylinder 1, lower cylinder 2, reinforcing rib 7, circumferential weld, circumferential adhesive layer, and the metal insert joint 4 covering interface. The test results are used to verify the stability of injection molding, vibration friction welding, and adhesive injection processes.

[0063] After the plastic air reservoir is installed in the automotive air braking system, compressed air enters the sealed air storage chamber through a metal insert connector 4, and is output through another metal insert connector 4 or drained through a corresponding connector according to the control requirements of the air braking system. During the air storage process, the internal pressure load is borne by the upper cylinder 1, the lower cylinder 2, and the reinforcing ribs 7 on their inner walls; the annular weld between the annular tenon 5 and the annular riveting structure 6 prevents compressed air from leaking along the lap joint interface, and the annular adhesive layer bears the axial load and shear load of the connection part; the covering interface between the metal insert connector 4 and the connector part 3 maintains the seal at the joint position. All structures work together to meet the requirements of the automotive air braking device for air storage, sealing, and pressure resistance.

[0064] After the product completes testing, the product model, production batch, traceability code, and certification mark can be formed on the outer surface of the cylinder by laser marking. The marking location should avoid the annular connection parts and major pressure-bearing weak areas, and the laser marking depth should not adversely affect the pressure-bearing performance of the cylinder.

[0065] 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 it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A plastic air reservoir for an automotive air brake system, characterized in that, The device includes an upper cylinder (1) and a lower cylinder (2) arranged opposite each other along the axial direction. The upper cylinder (1) has an integrally formed annular tenon (5) at one end facing the lower cylinder (2). The lower cylinder (2) has an annular riveting structure (6) on the inner wall of the connecting end facing the upper cylinder (1). The connecting end of the annular tenon (5) is inserted into the annular riveting structure (6) and fixed in the annular riveting structure (6) by vibration friction welding, so that the upper cylinder (1) and the lower cylinder (2) together form a sealed gas storage cavity. The annular tenon (5) and the annular riveting structure (6) are provided with a friction welding sealing area a and a structural adhesive bonding area b. The friction welding sealing area a forms a continuous annular weld, and the structural adhesive bonding area b is filled with structural adhesive and forms a continuous annular adhesive layer. One or more connectors (3) are integrally formed at the ends of the upper cylinder (1) and the lower cylinder (2) that are far apart from each other. Each connector (3) is equipped with a metal insert connector (4), and the internal channel of the metal insert connector (4) is connected to the sealed gas storage cavity. The inner walls of the upper cylinder (1) and the lower cylinder (2) are provided with reinforcing ribs (7) integrally formed with the corresponding cylinders.

2. The plastic air reservoir for an automotive air brake system according to claim 1, characterized in that, The reinforcing rib (7) protrudes from the inner wall of the corresponding upper cylinder (1) or lower cylinder (2) toward the sealed gas storage cavity and extends along the inner wall of the corresponding cylinder to improve the resistance of the upper cylinder (1) and the lower cylinder (2) to internal pressure deformation.

3. A plastic air reservoir for an automotive air brake system according to claim 1, characterized in that, The annular riveting structure (6) covers the connecting end of the annular tenon (5) along the axial direction of the plastic gas storage cylinder.

4. A plastic air reservoir for an automotive air brake system according to claim 1, characterized in that, The upper cylinder (1), the annular tenon (5), the lower cylinder (2), the joint (3), and the reinforcing rib (7) are all made of fiber-reinforced thermoplastic, which is PA6GF50 material with polyamide 6 as the matrix and containing 50% glass fiber by mass.

5. A plastic air reservoir for an automotive air brake system according to claim 1, characterized in that, At least a portion of the outer peripheral surface of the metal insert connector (4) is embedded in the corresponding connector portion (3). The embedded portion of the metal insert connector (4) is provided with a base coating layer and is covered by fiber-reinforced thermoplastic forming the connector portion (3) to form a sealed interface between the metal insert connector (4) and the connector portion (3).

6. A plastic air reservoir for an automotive air brake system according to claim 1, characterized in that, The lower cylinder (2) is also provided with an injection port and an exhaust port that are respectively connected to the structural adhesive bonding area b.

7. A composite molding method for a plastic air reservoir for an automotive air brake system, characterized in that, The process for molding a plastic air reservoir for an automotive air brake device according to any one of claims 1-6 comprises the following steps: S1. An upper cylinder (1) is integrally injection molded from fiber-reinforced thermoplastic, with an annular tenon (5) at the connecting end of the upper cylinder (1), a joint (3) at the other end of the upper cylinder (1), and a reinforcing rib (7) on the inner wall of the upper cylinder (1); a lower cylinder (2) is integrally injection molded from fiber-reinforced thermoplastic, with an annular riveting structure (6) on the inner wall of one end of the lower cylinder (2), a joint (3) at the other end of the lower cylinder (2), and a reinforcing rib (7) on the inner wall of the lower cylinder (2), and a metal insert joint (4) is installed in the corresponding joint (3); S2. Cool and shape the upper cylinder (1) and lower cylinder (2) after injection molding, and perform surface treatment on the surfaces to be bonded of the annular tenon (5) and the annular riveting structure (6). S3. Insert the connecting end of the annular tenon (5) into the annular riveting structure (6) of the lower cylinder (2), and perform vibration friction welding on the annular tenon (5) and the annular riveting structure (6) to form an annular weld seam that is continuously distributed around the sealed gas storage cavity. S4. After forming the annular weld, structural adhesive is injected into the structural adhesive bonding area b between the annular tenon (5) and the annular riveting structure (6) so that the structural adhesive fills the structural adhesive bonding area b and cures to form an annular adhesive layer, thereby obtaining the plastic gas cylinder.

8. A composite molding method for a plastic air reservoir for an automotive air brake device according to claim 7, characterized in that, In step S1, the metal insert connector (4) is pre-positioned in the corresponding injection mold, the outer peripheral surface of the metal insert connector (4) to be covered is cleaned and primed, and the insert is injection molded using a precision injection molding machine with a clamping force of 450-500 t, so that the fiber-reinforced thermoplastic forming the connector part (3) covers at least part of the outer peripheral surface of the metal insert connector (4).

9. A composite molding method for a plastic air reservoir for an automotive air brake device according to claim 7, characterized in that, In step S2, the surfaces to be bonded of the annular tenon (5) and the annular riveting structure (6) are sequentially ground, dusted, and cleaned. In step S4, structural adhesive is injected into the structural adhesive bonding area b through the injection port until the structural adhesive fills the structural adhesive bonding area b and reaches the venting and overflow port.

10. A composite molding method for a plastic air reservoir for an automotive air brake device according to claim 7, characterized in that, After the structural adhesive in step S4 has cured, the plastic gas cylinder is subjected to underwater leak testing and pressure resistance testing, and the plastic gas cylinder is subjected to burst limit testing according to a preset sampling cycle.

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