Manufacturing method for vehicle tubular beam with non-circular cross section, and tubular beam structure

Abstract

The present invention provides a manufacturing method for a vehicle tubular beam with a non-circular cross section and a tubular beam structure. At least one of two tubular blanks connected to each other is formed by using a hot-gas bulging process, and the two tubular blanks are then fastened and connected in a proper manner according to requirements in terms of actual strength, cost, production efficiency, etc. Resultant tubular beams can realize a comprehensive balance between a plurality of aspects, e.g., structural strength, light weight, manufacturing cost, production efficiency, and product reliability, conform to an advanced trend of multi-material blend and integral forming for the current vehicle bodies, and can be widely applicable to large-scale batch production of various vehicle-body structural parts.

Description

Manufacturing method and structure of automotive tubular beam with non-circular cross section Technical Field

[0001] The present invention belongs to the technical field of processing and manufacturing vehicle body structural parts, and specifically relates to a manufacturing method and a tubular beam structure for an automobile that uses a hot air expansion process during the manufacturing process to form a tubular beam structure with a non-circular cross-section. Background Art

[0002] Currently, the mainstream trend in automotive design and manufacturing is to utilize tubular beam combinations with varying diameters, wall thicknesses, and materials to achieve both high strength and lightweighting, tailored to the specific structural strength requirements of different locations within the vehicle body frame structure. Currently, the assembly of automotive tubular beams is still largely accomplished through welding, a process often associated with weld defects and leaks. Some prior art, such as CN115151476B, improves the crystalline microstructure of welded cylindrical tubular beams by preheating, which can improve connection reliability to a certain extent. However, since a subsequent thermal expansion process is required to achieve a specific tubular beam cross-section, or even to form a non-uniform tube with a variable cross-section, the differing wall thicknesses of the mating joints at the ends of the tubes can lead to differences in tube deformation rates due to temperature fluctuations during heating. This creates the potential for further weld expansion, potentially reducing structural strength rather than improving it. This approach also limits its applicability to other processes besides thermal expansion, and the two tubes must be made of the same material, making it unsuitable for vehicle body frame reliability.

[0003] Summary of the Invention

[0004] In view of this, and in response to the technical problems existing in the art, the present invention provides a method for manufacturing a tubular beam for a vehicle with a non-circular cross-section and a tubular beam structure, wherein the tubular beam structure includes at least a first tube blank and a second tube blank connected to each other. The method specifically comprises the following steps:

[0005] Step 1: processing a first tube blank and a second tube blank respectively according to the designed tube wall and non-circular tube cross-section shape; at least one of the two tube blanks is formed by performing a hot air expansion process;

[0006] Step 2: Connecting the process notch end of the first tube blank to the end of the second tube blank so that the end of the first tube blank and the end of the second tube blank are at least partially in contact with each other;

[0007] Step 3: At the position where the end of the first tube blank and the end of the second tube blank are in contact with each other, a suitable fixing method is used to fasten the first tube blank and the second tube blank to obtain the final finished tube beam structure.

[0008] Furthermore, in step one, one of the first tube blank and the second tube blank is formed by performing a hot air expansion process, and the other tube blank is formed by a water expansion process, a rolling process, or a stamping process.

[0009] Furthermore, different materials are specifically selected to manufacture the first tube blank and the second tube blank respectively.

[0010] Furthermore, one of MAG welding, laser welding, bonding, riveting, bolt connection, and mortise and tenon jointing is specifically selected for the position where the first tube blank end portion and the second tube blank end portion are bonded to each other to achieve a fastened connection between the two tube blanks.

[0011] Furthermore, a process notch is provided on the peripheral surface of the end portion of the first tube blank for connection with the second tube blank, so as to facilitate insertion thereof when connecting with the second tube blank.

[0012] Furthermore, at least one of the first tube blank and the second tube blank is formed into an end portion that shrinks into a thinner shape relative to the rear portion away from the connection between the two tube blanks; the end portion and the rear portion have a smooth transition or a stepped transition; and the two tube blanks are plug-connected.

[0013] Furthermore, at least one of the first tube blank and the second tube blank is formed into an end portion that expands into a thicker shape relative to the rear portion away from the connection between the two tube blanks; a smooth transition or a stepped transition is formed between the end portion and the rear portion; and the two tube blanks are plug-connected.

[0014] Accordingly, the present invention also provides a vehicle tubular beam structure with a non-circular cross-section, which is manufactured by executing the aforementioned method.

[0015] The above-mentioned manufacturing method and tubular beam structure for automobiles with non-circular cross-sections provided by the present invention first utilize a hot air expansion process to form at least one of the two interconnected tube blanks, and then select an appropriate method to fasten the two tube blanks together based on actual strength, cost, production efficiency, and other requirements. The resulting tubular beam product can achieve a comprehensive balance in multiple aspects such as structural strength, lightweight, manufacturing cost, production efficiency, and product reliability. It conforms to the current advanced trend of integrated multi-material hybrid molding of vehicle bodies and is widely applicable to the large-scale mass production of various vehicle body structural parts. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] FIG1 is a side view of a tubular beam with a variable cross-section curved axis and a rounded rectangular cross-section according to the present invention;

[0017] FIG2 is a cross-sectional view of a tubular beam having a variable cross-section curved axis and a rounded rectangular cross-section according to the present invention;

[0018] FIG3 is a cross-sectional view of a tubular beam having a variable cross-section curved axis and a rounded rectangular cross-section according to the present invention;

[0019] FIG4 is a side view of a tubular beam with a variable cross-section curved axis and a trapezoidal cross-section according to the present invention;

[0020] FIG5 is a riveted structure of a tubular beam with a variable cross-section curved axis and a trapezoidal cross-section according to the present invention;

[0021] FIG6 is a bolt connection structure of a tubular beam with a variable cross-section curved axis and a trapezoidal cross-section according to the present invention;

[0022] FIG7 is an optional structure of the ends of two tube blanks that cooperate with each other according to the present invention;

[0023] FIG8 is an optional structure of the ends of two tube blanks that cooperate with each other according to the present invention;

[0024] FIG9 is an optional structure of the ends of two tube blanks that cooperate with each other according to the present invention;

[0025] FIG. 10 shows an optional structure of the ends of two tube blanks that cooperate with each other according to the present invention. DETAILED DESCRIPTION

[0026] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0027] In the description of the present invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate and simplify the description of the present invention. They are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation, and therefore should not be construed as limitations on the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0028] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0029] The present invention provides a method for manufacturing a tubular beam for a vehicle with a non-circular cross-section and a tubular beam structure. The tubular beam structure includes at least a first tube blank and a second tube blank connected to each other. The method specifically includes the following steps:

[0030] Step 1: Process a first tube blank and a second tube blank separately according to the designed tube wall and non-circular cross-sectional shape; at least one of the two tube blanks is formed by performing a hot air expansion process. In the current design of structural components such as vehicle body frames, circular cross-sectional tube beams are rarely used due to strength and rigidity considerations. Tube beams with trapezoidal, rectangular, or other irregular cross-sectional shapes are more common. Therefore, the present invention uses a hot air expansion process to obtain the predetermined non-circular cross-sectional shape during the tube blank processing stage. The entire tube blank shape is not limited to a regular, uniform straight tube; it can also be an irregular curved tube with a variable cross-section and a curved axis, such as the optional tube beam structure with a variable cross-sectional curved axis and a rounded rectangular cross-section shown in Figures 1-3. This process is completely different from the prior art method of welding a circular tube blank followed by expansion or other forming methods. If the expansion process is performed after welding, the weld seam cannot be expanded, and even the tube beam may break during the process. Furthermore, expansion cannot be performed after two tube blanks of different materials are connected. Compared with the traditional forging-type tube blank processing method, the hot air expansion process of the present invention has obvious advantages in forming accuracy, surface roughness, mold tooling cost and other aspects, and is also conducive to thinning the tube blank without reducing the strength.

[0031] Step 2: Connect the process-notched end of the first tube blank to the end of the second tube blank, so that the first and second tube blanks are at least partially aligned. Whether the alignment between the first and second tube blanks is a small area of ​​alignment or a complete alignment can be flexibly selected based on the specific application location and strength requirements of the tubular beam product in the vehicle body. For example, a more secure, complete alignment should be selected for key load-bearing locations such as the A, B, and C pillars. At the connection between the vehicle body frame and chassis, where strength and rigidity vary, a small, incomplete alignment can be used to reduce process complexity and, consequently, vehicle manufacturing costs.

[0032] Step 3: At the position where the end of the first tube blank and the end of the second tube blank are in contact with each other, a suitable fixing method is used to fasten the first tube blank and the second tube blank to obtain the final finished tube beam structure.

[0033] In a preferred embodiment of the present invention, in step 1, one of the first and second tube blanks is formed by performing a hot air expansion process, and the other tube blank is formed by performing a water expansion process, a roll bending process, or a stamping process. Because the hot air expansion process and the water expansion process differ in terms of pressure indicators, forming, product strength, process complexity, and labor and material costs, the present invention provides a method of forming two tube blanks using different expansion methods to meet different strength requirements. This method ensures that each tube blank meets its respective strength requirements while reducing process complexity and costs.

[0034] Based on the same general concept of balancing strength performance indicators and cost as described above, the present invention can also specifically select different materials for manufacturing the first and second tube blanks. For example, for tube blanks in key load-bearing locations such as the A, B, and C pillars, high-strength but low-machinability steel can be selected, while for locations such as the chassis, more expensive lightweight aluminum or composite materials can be selected.

[0035] In a preferred embodiment of the present invention, one of MAG welding, laser welding, bonding, bolting, or mortise and tenon joints is specifically selected for the location where the inner surface of the first tube end and the outer surface of the second tube end meet to achieve a secure connection between the two tubes. The selection of a specific fastening method can also be based on strength, performance, and cost considerations. For example, at the A, B, and C pillars, where rigidity is extremely high, welding or a superimposed mortise and tenon joint is suitable for a more secure connection. However, at the chassis, where rigidity should be appropriately reduced to ensure comfort, bonding or bolting can be used at the connection between the body frame and chassis.

[0036] FIG4 shows a tubular beam having a variable-section curved axis and a trapezoidal cross-section that can be obtained based on the present invention, wherein a process notch is formed at the end of one tube blank, and another tube blank connected thereto is inserted through the process notch and can be fixed by riveting or bolting as shown in FIG5 or 6 .

[0037] Figures 7-10 illustrate several optional tube end configurations that can be manufactured based on the present invention. For example, at least one of the first and second tube blanks can be formed so that the end tapers to a narrower shape relative to the rear of the connection between the two tube blanks, with a smooth or stepped transition between the end and the rear. Alternatively, at least one of the first and second tube blanks can be formed so that the end expands to a wider shape relative to the rear of the connection between the two tube blanks, with a smooth or stepped transition between the end and the rear. The two tube blanks can be plugged into each other, with the inner surface of one tube blank partially or completely abutting against the outer surface of the other. The specific end configurations of various tube blanks can be manufactured using the method provided by the present invention based on actual performance or production needs. The available fixing methods for connection are also very flexible. For example, the welding method shown in the figure can be used as needed, including large-area welding, spot welding, and laser butt welding with or without patches. When butt welding is used, only the edges of the tube blank ends can be abutted.

[0038] Correspondingly, the present invention also provides a hot-air-bulged tubular beam structure for vehicles, which is manufactured by executing the aforementioned method.

[0039] It should be understood that the size of the serial numbers of the steps in the embodiment of the present invention does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiment of the present invention.

[0040] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for manufacturing a tubular beam for a vehicle with a non-circular cross section, wherein the tubular beam structure comprises at least a first tube blank and a second tube blank connected to each other, characterized in that: The method specifically comprises the following steps: Step 1: processing the first tube blank and the second tube blank respectively according to the designed tube wall and the non-circular tube cross-section shape; at least one of the two tube blanks is formed by performing a hot air expansion process; Step 2: Connecting the process notch end of the first tube blank to the end of the second tube blank so that the end of the first tube blank and the end of the second tube blank at least partially fit each other; Step three: At the position where the end of the first tube blank and the end of the second tube blank are in contact with each other, a suitable fixing method is used to fasten the first tube blank and the second tube blank to obtain a final finished tube beam structure.

2. The method according to claim 1, characterized in that: In step one, one of the first tube blank and the second tube blank is obtained by performing a hot air expansion process, and the other tube blank is obtained by a water expansion process, a rolling process or a stamping process.

3. The method according to claim 1, characterized in that: Specifically, different materials are selected to manufacture the first tube blank and the second tube blank respectively.

4. The method according to claim 1, characterized in that: According to the position where the end of the first tube blank and the end of the second tube blank are bonded to each other, one of MAG welding, laser welding, bonding, riveting, bolt connection, and mortise and tenon joint fitting is specifically selected to achieve a fastening connection between the two tube blanks.

5. The method according to claim 1, characterized in that: A process notch is provided on the peripheral surface of the end of the first tube blank for connecting with the second tube blank, so as to facilitate the insertion of the first tube blank when connecting with the second tube blank.

6. The method according to claim 1, characterized in that: At least one of the first tube blank and the second tube blank is formed into an end portion that shrinks to a thinner shape relative to the rear portion away from the connection between the two tube blanks; there is a smooth transition or a step transition between the end portion and the rear portion; and the two tube blanks are plug-connected.

7. The method according to claim 1, characterized in that: At least one of the first tube blank and the second tube blank is formed so that the end portion expands to a thicker shape relative to the rear portion away from the connection between the two tube blanks; there is a smooth transition or a step transition between the end portion and the rear portion; and the two tube blanks are plug-connected.

8. A tubular beam structure for a vehicle with a non-circular cross section, characterized in that: The method is carried out by performing any one of the methods described in claims 1 to 7.

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