A method for preventing wavy edges from appearing on the lower guard plate of a vehicle body

Abstract

The present invention discloses a method for avoiding wavy edges on a vehicle body lower guard plate, comprising: S1, a buckle fixing seat for matching buckles is provided on the formed vehicle body lower guard plate, and the buckle fixing seat is arranged along the flange of one side of the vehicle body lower guard plate; S2, an auxiliary structure for avoiding wavy edges is arranged between the flange of the vehicle body lower guard plate and the buckle fixing seat, and the auxiliary structure for avoiding wavy edges can make the supporting forces of various parts of the flange consistent; S3, the flange on the vehicle body lower guard plate is inspected, and the vehicle body lower guard plate is sprayed after passing the inspection, and assembled after passing the inspection. The above method can not only effectively avoid the problem of wavy edges of the flange of the vehicle body lower guard plate during injection molding, but also the flange of the vehicle body lower guard plate after spraying will not have wavy edges, and no subsequent correction process is required, which reduces labor and manufacturing costs and shortens the manufacturing cycle. At the same time, there is no problem of unstable quality, and the molding quality of the vehicle body lower guard plate is ensured.

Description

Technical Field

[0001] The invention relates to the technical field of vehicle body structures, and in particular to a method for preventing wavy edges from appearing on a lower guard plate of a vehicle body. Background Art

[0002] At present, the length of the underbody guard plate can be more than 2 meters according to the requirements of the vehicle chassis, and the upper flange is longer, and the flange position is easy to deform. Most of them are injection molded and painted, and basically one or more decorative parts can be designed to embellish it; the traditional underbody guard plate generally has multiple clip fixing seats, and the clip fixing seats are used to cooperate with positioning columns and multiple clips, and are connected to the body sheet metal through clips; there are some problems in the traditional design method: through mold flow analysis and actual injection molding verification, it can be seen that the area of ​​the flange of the underbody guard plate with the clip fixing seat has better support and less shrinkage deformation, while the area between two adjacent clip fixing seats has no support and its shrinkage deformation is large. After painting, the deformation degree will be aggravated more obviously, resulting in serious wavy edges on the upper surface and the whole flange is deformed inward. Customers can easily see the defects and cannot accept them. For severe wavy edges, the traditional solution is to add post-process correction: correction after injection molding, correction with painting fixtures, and correction after assembly. This not only increases labor and manufacturing costs, but also extends the manufacturing cycle. At the same time, the correction is prone to rebound, resulting in unstable quality. Summary of the invention

[0003] The present invention provides a method for preventing wavy edges of a vehicle body lower guard plate, the main purpose of which is to make the flange of the vehicle body lower guard plate have consistent supporting force, and effectively prevent the wavy edges of the vehicle body lower guard plate after shrinkage and deformation.

[0004] According to the above technical problems, the technical solutions are as follows:

[0005] The present invention provides a method for preventing a wavy edge from appearing on a lower guard plate of a vehicle body, which is characterized by following the steps:

[0006] S1. The formed lower body guard plate has a buckle fixing seat that cooperates with the buckle, and the buckle fixing seat is arranged along the flange of one side of the lower body guard plate;

[0007] S2. An auxiliary structure for avoiding the wavy edge is provided between the flange of the lower guard plate of the vehicle body and the buckle fixing seat, and the auxiliary structure for avoiding the wavy edge can make the supporting force of each part of the flange consistent;

[0008] S3. Inspect the flange on the lower guard plate of the vehicle body, spray paint the lower guard plate if it passes the inspection, and assemble it after passing the inspection.

[0009] By adopting the above method, the supporting force of each part of the flange can be made consistent by avoiding the auxiliary structure of the wavy edge. Not only can the problem of wavy edges easily generated on the flange of the underbody guard plate during injection molding be effectively avoided, but also the wavy edges will not appear on the flange of the underbody guard plate after spraying, and subsequent shaping processes are no longer required, which not only reduces labor and manufacturing costs, but also shortens the manufacturing cycle. At the same time, there is no problem of unstable quality, thereby ensuring the molding quality of the underbody guard plate.

[0010] Furthermore, the auxiliary structure for avoiding the wave edge includes an inner bracket arranged on the inner side of the lower guard plate of the vehicle body, and the inner bracket is fixed on the inner side of the flange;

[0011] The inner bracket is formed with clearance notches corresponding to the buckle fixing seats one by one, and the clearance notches are adapted to the buckle fixing seats. When the inner bracket is fixed to the inner side of the lower guard plate of the vehicle body, the buckle fixing seats are respectively located in the corresponding clearance notches; an inner bracket side wall is formed between any two adjacent clearance notches, and the flanges are fixed on the side walls of the inner brackets, so that the supporting forces of various parts of the flanges are consistent;

[0012] By adopting the above method, the inner bracket is installed on the inner side of the lower guard plate of the vehicle body, and the clearance notch on the inner bracket is matched with the corresponding snap fixing seat, and the flange between the two snap fixing seats is fixed to the side wall of the inner bracket, so that the supporting force of each part of the flange is consistent, effectively avoiding the generation of wavy edges on the flange due to different supporting forces.

[0013] Furthermore, there are at least two inner brackets, and each inner bracket is evenly distributed on the flange;

[0014] The above method can reduce the difficulty of manufacturing the inner bracket, improve the qualified rate of the inner bracket during the manufacturing process, and avoid breakage.

[0015] Furthermore, the auxiliary structure for avoiding the wave edge includes an inner shell installed on the inner side of the lower guard plate of the vehicle body, the buckle fixing seat is integrally formed on the inner shell, and the inner shell is fixed on the inner side of the flange, so that the supporting force of each part of the flange is consistent;

[0016] By adopting the above method, through the inner shell with a plurality of snap-fit ​​fixing seats, the supporting forces of various parts of the flange can be made closer, avoiding the generation of gaps between the auxiliary structure and the snap-fit ​​fixing seats, thereby affecting the slight changes in the supporting force on the flange.

[0017] Using the above method, the inner shell is fixed to the lower guard plate of the vehicle body by ultrasonic welding; and the inner shell side of the inner shell is fixed to the flange by ultrasonic welding;

[0018] By adopting the above method and utilizing the ultrasonic welding connection method, the loss to the body of the underbody guard plate can be reduced, and when installing the auxiliary structure to avoid the wavy edge, the structural frame of the underbody guard plate can be more perfectly retained.

[0019] Furthermore, there are at least two inner shells, and each inner shell is evenly distributed on the flange;

[0020] The above method can reduce the difficulty of manufacturing the inner shell, improve the qualified rate of the inner shell during the manufacturing process, and avoid breakage.

[0021] Furthermore, the auxiliary structure for avoiding the wavy edge is a gap between the buckle fixing seat and the flange, and the gap enables each buckle fixing seat to be separated from the flange, so that the supporting force of each part of the flange is consistent;

[0022] By adopting the above method, by reserving a gap between the buckle fixing seat and the flange, not only can the supporting force of each part of the flange be completely consistent, effectively avoiding the generation of wavy edges, but also the cost is greatly reduced.

[0023] Furthermore, the buckle fixing seat is a trapezoidal structure, and a reinforcing rib fixed inside the buckle fixing seat is provided in the buckle fixing seat to separate the inside of the buckle fixing seat into an upper and lower layer structure, which is used to stabilize the main body structure of the buckle fixing seat;

[0024] By adopting the above method, the trapezoidal bayonet fixing seat can enhance its own stability, and reinforcing ribs for strengthening the internal structure are also arranged inside the bayonet fixing seat, so that it is divided into upper and lower layer structures, which can make the bayonet fixing seat more stable.

[0025] Further, the snap-fit ​​fixing seat comprises an integrally formed fixing seat top wall, fixing seat side walls and fixing seat inclined walls, the fixing seat side walls are perpendicular to the vehicle body lower guard plate and fixed to the inner side of the vehicle body lower guard plate, the fixing seat inclined walls are bent and formed on the side of the fixing seat side walls away from the flange, and are fixed to the vehicle body lower guard plate, the fixing seat top wall is bent and formed on the side of the fixing seat side wall away from the vehicle body lower guard plate, and one end of the fixing seat top wall away from the flange is connected to one end of the fixing seat inclined wall away from the vehicle body lower guard plate;

[0026] The reinforcing ribs include an integrally formed main rib, two auxiliary ribs and a side rib, one end of the side rib is connected to an end of the top wall of the fixing seat close to the flange, the other end of the side rib is connected to the bend between the lower guard plate of the vehicle body and the flange, the two ends of the main rib are respectively connected to the middle of the inclined wall of the fixing seat and the middle of the side rib, and the outer edge of one side of the main rib is connected to the side wall of the fixing seat, the two auxiliary ribs are respectively located on both sides of the main rib, and the auxiliary ribs are both connected to the side wall of the fixing seat;

[0027] By adopting the above method, the snap-fit ​​fixing seat is formed by an integrally formed fixing seat top wall, fixing seat side wall and fixing seat inclined wall which together form a trapezoidal structure snap-fit ​​fixing seat, and reinforcing ribs are arranged inside the snap-fit ​​fixing seat. The reinforcing ribs are divided into main ribs, auxiliary ribs and side ribs, which are respectively supported on the fixing seat top wall, fixing seat side wall and fixing seat inclined wall, thereby strengthening the overall structure of the snap-fit ​​fixing seat and effectively avoiding the occurrence of structural instability and fracture caused by the snap-fit ​​fixing seat detaching from the flange.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] A method for avoiding wavy edges on the underbody guard plate adopts the above technical solution. Through the auxiliary structure in the method for avoiding wavy edges on the underbody guard plate, the supporting force at the deformed part can be made consistent. Not only can the problem of wavy edges on the flange of the underbody guard plate during injection molding be effectively avoided, but also the wavy edges will not appear on the flange of the underbody guard plate after spraying, and subsequent shaping procedures are no longer required, which reduces labor and manufacturing costs and shortens the manufacturing cycle. At the same time, there is no problem of unstable quality, thereby ensuring the molding quality of the underbody guard plate. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of the three-dimensional structure of the first embodiment of the vehicle body underbody guard plate of the present invention;

[0031] Figure 2 This is a schematic diagram of the structure of the inner bracket in the first embodiment;

[0032] Figure 3 for Figure 2 A magnified view of part A;

[0033] Figure 4 It is a schematic diagram of the three-dimensional structure of the second embodiment of the vehicle body under guard plate of the present invention;

[0034] Figure 5 It is a schematic diagram of the structure of the inner shell in the second embodiment;

[0035] Figure 6 for Figure 5 A magnified view of part B;

[0036] Figure 7 It is a schematic diagram of the three-dimensional structure of the third embodiment of the vehicle body underbody guard plate of the present invention;

[0037] Figure 8 This is an installation diagram of the buckle fixing base fixed to the lower guard plate of the vehicle body in the third embodiment;

[0038] Fig. 9 for Figure 8 Enlarged view of part C;

[0039] Fig.10 It is a structural schematic diagram of a buckle fixing seat in the third embodiment;

[0040] Fig.11 for Fig.10 Enlarged view of part D. DETAILED DESCRIPTION

[0041] The present invention is further described below in conjunction with embodiments and drawings.

[0042] The present invention provides a method for preventing a wavy edge from appearing on a vehicle body lower guard plate 1, wherein the method is mainly performed in the following steps:

[0043] S1. A buckle fixing seat 2 cooperating with a buckle is provided on the formed lower body guard plate 1, and the buckle fixing seat 2 is arranged along the flange 11 on one side of the lower body guard plate 1;

[0044] S2, an auxiliary structure for avoiding the wavy edge is provided between the flange 11 of the lower guard plate 1 of the vehicle body and the buckle fixing seat 2, and the auxiliary structure for avoiding the wavy edge can make the supporting force of each part of the flange 11 consistent;

[0045] S3, inspecting the flange 11 on the vehicle body lower guard plate 1, spraying the vehicle body lower guard plate 1 after passing the inspection, and assembling after passing the inspection.

[0046] The present invention also provides the above-mentioned auxiliary structure for avoiding wave edges, and proposes the following embodiments:

[0047] First embodiment:

[0048] Reference Figures 1 to 3 As shown, the auxiliary structure for avoiding wavy edges is set as an inner bracket 3, which is fixed to the inner side of the lower guard plate 1 of the vehicle body, and a clearance gap 31 is opened on the side of the inner bracket 3 close to the snap fixing seat 2, and the clearance gap 31 corresponds to the snap fixing seat 2 one by one. When the inner bracket 3 is installed on the inner side of the lower guard plate 1 of the vehicle body, each snap fixing seat 2 is placed in the corresponding clearance gap 31, and an inner bracket side wall 32 is provided between two adjacent clearance gaps 31 on the inner bracket 3, and the inner bracket side wall 32 is fixed to the flange 11 of the lower guard plate 1 of the vehicle body; the inner bracket side wall 32 can be fixedly connected to the flange 11 of the lower guard plate 1 of the vehicle body by ultrasonic welding, and can also be fixed to the flange 11 of the lower guard plate 1 of the vehicle body by other methods, and it is only necessary to make the overall supporting force of the flange 11 of the lower guard plate 1 of the vehicle body consistent to avoid serious wavy edges after painting; at least two inner brackets 3 are provided, and they are evenly arranged on the flange 11 of the lower guard plate 1 of the vehicle body.

[0049] The design concept of this scheme is to design a reinforced inner bracket 3 inside the lower guard plate 1 of the vehicle body without changing the original design, and support the upper and lower areas that are easy to retract and deform between adjacent clip fixing seats 2, and design them to be a gradual interference state, and stretch the upper and lower deformed inward parts. The interference amount is determined according to the deformation amount after painting, and the interference amount is roughly between 0-2mm. The inner bracket 3 support is immediately installed during the injection molding of the lower guard plate 1 of the vehicle body, and the combined structure is used to design a spraying jig and spray products. Since there is a bracket for support during spraying, there is basically no serious deformation of the wavy edge.

[0050] Second embodiment:

[0051] Reference Figures 4 to 6 As shown, the auxiliary structure for avoiding wavy edges is configured as an inner shell 4 fixedly mounted on the inner side of the vehicle body lower guard plate 1, the snap-fit ​​fixing seat 2 is arranged on the inner shell 4, the inner shell side edge 41 of the inner shell 4 is fixed on the flange 11 of the vehicle body lower guard plate 1, and the connection method can also adopt ultrasonic welding, which can avoid damage to the vehicle body lower guard plate 1 itself as much as possible, and ensure the integrity of the vehicle body lower guard plate 1 itself during the welding process; other forms of fixed connection methods can also be adopted, and the inner shell side edge 41 of the inner shell 4 can be fixed on the flange 11 of the vehicle body lower guard plate 1, so that the flange 11 of the vehicle body lower guard plate 1 achieves the same supporting force, effectively avoiding the occurrence of serious wavy edges after painting; at least two inner shells 4 are provided, and are evenly arranged on the flange 11 of the vehicle body lower guard plate 1.

[0052] The design concept of this scheme is to change the original design and transform it into an inner and outer panel welding structure, set the clip fixing seat 2 on the inner shell 4, weld the inner shell 4 to the lower guard plate 1 of the vehicle body, and use the internal reinforcement to support the upper and lower areas that are prone to deformation. In this design, since the inner plate is no longer taken out, the clip fixing seats 2 can be designed to be in a zero-stick state. When the lower guard plate 1 of the vehicle body is injection molded, the inner shell 4 is welded to the lower guard plate 1 of the vehicle body for support. The combined structure is used to design a spraying jig and spray products. Since the inner shell 4 is supported during spraying, there is basically no serious deformation of the wavy edge.

[0053] Third embodiment:

[0054] Reference Figures 7 to 11As shown, the auxiliary structure for avoiding wavy edges reserves a gap 5 between the flange 11 of the lower body guard plate 1 and the snap-on fixing seat 2 fixed on the inner side of the lower body guard plate 1, so that the flange 11 of the lower body guard plate 1 is completely separated from the snap-on fixing seat 2, so that the flange 11 of the lower body guard plate 1 achieves a consistent supporting force effect and avoids the serious deformation of the wavy edge; the snap-on fixing seat 2 is configured as a trapezoidal structure, and a reinforcing rib 21 for stabilizing the structure of the snap-on fixing seat 2 itself is fixed in the snap-on fixing seat 2, and the trapezoidal structure of the snap-on fixing seat 2 is divided into upper and lower layers, which is used to compensate for the problem of stability of the snap-on fixing seat body structure caused by one side of the snap-on fixing seat 2 being separated from the flange 11 of the lower body guard plate 1, so that the snap-on fixing seat 2 has good stability and is not easy to break or fall off.

[0055] The design concept of this scheme is to renew the design concept of the structure design of the snap-on fixing seat 2. Since the deformation of the connection of the snap-on fixing seat 2 is very small, while the deformation of the part of the flange 11 between two adjacent snap-on fixing seats 2 is large, the deformation contrast difference between them leads to the existence of obvious wavy edges on the flange 11; that is, the support of the snap-on fixing seat 2 for the flange 11 is disconnected, the curvature of the wave is reduced, and the wavy edge is optimized. Preferably, the disconnection distance between the snap-on fixing seat 2 and the flange 11 is 1 to 1.5mm, so that the connection of the snap-on fixing seat 2 can also be slightly deformed inward by 1 to 1.5mm, relying on the part of the flange 11 separated by the snap-on fixing seat 2, thereby reducing the curvature of the entire wave and making the flange 11 relatively smooth;

[0056] The thickness of the connection between the snap-fit ​​fixing seat 2 and the flange 11 is 0.8 mm, which is relatively strong and not easy to deform. The snap-fit ​​fixing seat 2 is designed to have an upper and lower layer with a trapezoidal structure, and the upper and lower layers are disconnected by a reinforcing rib 21 arranged in the middle to strengthen the structural strength of the snap-fit ​​fixing seat 2. This snap-fit ​​fixing seat 2 can be fully realized on the mold through a slanted top. In order to ensure the strength of the slanted top, the connection between the snap-fit ​​fixing seat 2 and the flange 11 is allowed to have a thickness of 0.1 to 0.3 mm.

[0057] Preferably, the outer shell of the buckle fixing seat 2 mainly includes an integrally formed fixing seat top wall 2a, a fixing seat side wall 2b and a fixing seat inclined wall 2c, wherein the fixing seat side wall 2b is vertically fixed to the inner side of the vehicle body lower guard plate 1, and the fixing seat inclined wall 2c is bent and formed on the side of the fixing seat side wall 2b away from the flange 11, and is obliquely fixed to the inner side of the vehicle body lower guard plate 1, and the fixing seat top wall 2a is respectively connected to the fixing seat side wall 2b and the fixing seat inclined wall 2c, thereby enclosing and forming the buckle fixing seat 2, and a buckle insertion opening for inserting the buckle is opened on the fixing seat top wall 2a;

[0058] Preferably, the reinforcing rib 21 mainly includes an integrally formed main rib 21a, two auxiliary ribs 21b and a side rib 21c. The two adjacent sides of the main rib 21a are respectively fixed to the inner sides of the fixing seat side wall 2b and the fixing seat inclined wall 2c, thereby separating the buckle fixing seat 2 from top to bottom, so as to reduce the internal hollow volume of the buckle fixing seat 2 to achieve a structurally stable effect, and can serve as a basis for installing other ribs; the two auxiliary ribs 21b are divided into two ribs integrally formed with the top and bottom surfaces of the main rib 21a, and the two auxiliary ribs 21b are fixed to the fixing seat side wall 2b. Located on opposite sides of the main rib 21a, the side wall 2b of the fixing seat of the clip fixing seat 2 is strengthened; the side rib 21c is fixed on the side of the clip fixing seat 2 close to the flange 11, and one end of the side rib 21c is connected to one end of the fixing seat top wall 2a, and the other end of the side rib 21c is fixed to the bending part between the lower guard plate 1 of the vehicle body and the flange 11, and the middle part of the side rib 21 is connected to the end of the main rib 21a close to the flange 11, thereby avoiding the side of the clip fixing seat 2 close to the flange 11 being a cantilever, effectively enhancing the stability of the overall structure of the clip fixing seat 2.

[0059] Embodiments of the present invention are described in detail above, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described above with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0060] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "clockwise", "counterclockwise" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0061] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0062] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0063] Finally, it should be noted that the above description is only a preferred embodiment of the present invention. Under the guidance of the present invention, ordinary technicians in this field can make various similar expressions without violating the purpose and claims of the present invention, and such changes all fall within the scope of protection of the present invention.

Claims

1. A method for preventing wavy edges from appearing on a lower guard plate of a vehicle body, characterized in that: Follow these steps: S1. A buckle fixing seat (2) for matching with a buckle is provided on the molded lower body guard plate (1), and the buckle fixing seat (2) is arranged along a flange (11) on one side of the lower body guard plate (1); S2. An auxiliary structure for avoiding wavy edges is provided between the flange (11) of the lower guard plate (1) of the vehicle body and the buckle fixing seat (2), wherein the auxiliary structure for avoiding wavy edges can make the supporting force of each part of the flange (11) consistent; S3, inspecting the flange (11) on the lower guard plate (1) of the vehicle body, spraying the lower guard plate (1) after it passes the inspection, and assembling after it passes the inspection; The auxiliary structure for avoiding the wavy edge is a gap (5) between the buckle fixing seat (2) and the flange (11), and the gap (5) enables each buckle fixing seat (2) to be separated from the flange (11). The disconnection distance at the connection between the buckle fixing seat (2) and the flange (11) is 1 to 1.5 mm, so that the supporting force of each part of the flange (11) is consistent. The buckle fixing seat (2) is a trapezoidal structure, and a reinforcing rib (21) is provided in the buckle fixing seat (2) and is fixed inside the buckle fixing seat (2), so as to separate the inside of the buckle fixing seat (2) into an upper and lower layer structure, so as to stabilize the main body structure of the buckle fixing seat (2); The buckle fixing seat (2) comprises an integrally formed fixing seat top wall (2a), a fixing seat side wall (2b) and a fixing seat inclined wall (2c); the fixing seat side wall (2b) is perpendicular to the vehicle body lower guard plate (1) and is fixed to the inner side of the vehicle body lower guard plate (1); the fixing seat inclined wall (2c) is bent and formed on the side of the fixing seat side wall (2b) away from the flange (11) and is fixed to the vehicle body lower guard plate (1); the fixing seat top wall (2a) is bent and formed on the side of the fixing seat side wall (2b) away from the vehicle body lower guard plate (1); and one end of the fixing seat top wall (2a) away from the flange (11) is connected to one end of the fixing seat inclined wall (2c) away from the vehicle body lower guard plate (1); The reinforcing rib (21) comprises an integrally formed main rib (21a), two auxiliary ribs (21b) and a side rib (21c); one end of the side rib (21c) is connected to one end of the top wall (2a) of the fixing seat close to the flange (11); the other end of the side rib (21c) is connected to the bending portion between the lower guard plate (1) of the vehicle body and the flange (11); the two ends of the main rib (21a) are respectively connected to the middle of the inclined wall (2c) of the fixing seat and the middle of the side rib (21c); the outer edge of one side of the main rib (21a) is connected to the side wall (2b) of the fixing seat; the two auxiliary ribs (21b) are respectively located on both sides of the main rib (21a), and the auxiliary ribs (21b) are both connected to the side wall (2b) of the fixing seat.

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