Commercial vehicle rear protection device, method of designing the same and commercial vehicle

Abstract

The application belongs to the technical field of commercial vehicle chassis and protection, and discloses a commercial vehicle rear protection device, a design method thereof and a commercial vehicle. The design method of the commercial vehicle rear protection device, under the premise that the length of the cross beam and the width of the commercial vehicle rear protection device are determined, designs the cross beam to be of non-metal material according to the three-point loading test standard, determines the cross-sectional size of the cross beam by adopting the topological optimization method in combination with the bending resistance section coefficient according to the safety factor, and then the cross beam with the determined length and cross-sectional size can be obtained. The commercial vehicle rear protection device is designed to be lightweight by designing the cross beam of non-metal material, the topological optimization is beneficial to ensuring the structural strength of the cross beam, and is beneficial to improving the overall reliability and lightweight of the commercial vehicle.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of commercial vehicle chassis and protection, in particular to a commercial vehicle rear protection device, a design method thereof and a commercial vehicle. BACKGROUND

[0002] At present, the commercial vehicle rear protection device, including a rear protection beam and a connecting bracket, in order to have better protection strength, all adopt metal parts, so the overall weight is heavy and the cost is high; there are also a few rear protection beams and connecting brackets of the commercial vehicle in order to reduce the weight, the beam is usually a channel steel or a pipe beam, the rear protection beam with a hollow structure has good weight reduction effect, but the weight is large by using steel material, and the pipe beam has good buffering effect but low structural strength.

[0003] There is also a lightweight design by using a non-metal rear protection beam in the prior art, and the main problem is that the reliability of the metal longitudinal beam or the metal connecting bracket is low when connecting the non-metal rear protection beam, the strength of the rear protection beam structure with a cavity structure is not enough, the strength of the rear protection beam can be improved by arranging a reinforcing rib in the rear protection beam, the connection is not firm when the rear protection beam is bonded with the metal connecting bracket, and there is a position interference between the reinforcing rib in the rear protection beam and the hole when the hole is directly connected with the metal connecting bracket by bolts, therefore, the design optimization among the connection stability, the structural strength and the weight reduction of the rear protection beam still needs to be improved and enhanced. SUMMARY

[0004] The present application aims to provide a commercial vehicle rear protection device, a design method thereof and a commercial vehicle, so as to further improve the structural strength and reduce the structural weight of the commercial vehicle rear protection device, and solve the connection strength problem of the rear protection beam.

[0005] The present application first provides a design method of a commercial vehicle rear protection device, including the following steps:

[0006] determining the length L of the beam adopted by the commercial vehicle rear protection device and the width of the commercial vehicle rear protection device;

[0007] determining P1 loading point, P2 loading point and P3 loading point on the beam according to the three-point loading test standard; the P3 loading point is located on the longitudinal center plane of the commercial vehicle, the P2 loading point is located on the connecting plane of the longitudinal beam and the beam, and the P1 loading point is determined according to the distance of the outermost end of the rear axle wheel of the vehicle;

[0008] determining the bending section modulus W of the beam according to the material of the beam:

[0009]

[0010] In the formula, P is the load of the P1 loading point, σ max is the maximum positive stress of the crossbeam, M is the maximum bending moment of the crossbeam, and l is the distance between the P1 loading point and the P2 loading point.

[0011] The safety factor n is defined as:

[0012]

[0013] [σ] is the yield strength of the material of the crossbeam, and the following is obtained:

[0014]

[0015] According to the safety factor n, the sectional size of the crossbeam is determined by using a topology optimization method in combination with the bending-resistant sectional coefficient W.

[0016] Optionally, the topology optimization method is a variable-density method, and specifically includes the following steps.

[0017] The crossbeam is set as a rectangular section, and the crossbeam is meshed to obtain a finite element model of the crossbeam.

[0018] The relative density x e of each mesh element in the finite element model is set as a design variable, and x e continuously varies between 0 and 1, and 0 and 1 respectively represent that the crossbeam is hollow or solid; and a target function is obtained by updating and optimizing the design variable.

[0019] The target function is as follows.

[0020]

[0021] In the formula, C(x) is the flexibility of the crossbeam, n is the number of mesh elements, p is a penalty factor, K i is the stiffness matrix of the i th mesh element, U i is the displacement vector of the i th mesh element, E min is the minimum value of the elastic modulus of the crossbeam, ΔE i is the difference between the elastic moduli of two adjacent mesh elements, x i is the i th design variable.

[0022] The constraint conditions of the target function include the following.

[0023] Fixed constraint: the degrees of freedom of the connection between the crossbeam and the longitudinal beam are constrained.

[0024] Load condition: the loading condition of the P1 loading point in the three-point loading test standard is the load condition.

[0025] Manufacturing process constraint: extrusion process

[0026] Volume ratio constraint: volume fraction constraint is set to 0.3.

[0027] Optionally, the penalty factor p is 2-4.

[0028] The application further provides a rear protection device for a commercial vehicle, comprising a cross beam and a connecting bracket, the cross beam being connected to a longitudinal beam of the commercial vehicle through the connecting bracket; the cross beam is designed according to the design method of the rear protection device for the commercial vehicle, the cross beam is a tubular structure with a cavity, the cross beam has a rectangular cross section with rounded corners, two inclined ribs are arranged in the cavity of the cross beam, the two ends of the two inclined ribs are connected to the front side wall and the rear side wall of the cross beam respectively, and the two inclined ribs divide the cavity of the cross beam into three sub-cavities.

[0029] Optionally, an isosceles trapezoidal cross section is formed between the two inclined ribs, the front side wall and the rear side wall, the spacing of the two inclined ribs on the front side wall is the length of the upper base A, the spacing of the two inclined ribs on the rear side wall is the length of the lower base B, and the length of the upper base A is greater than the length of the lower base B.

[0030] Optionally, the ratio of the volume of the sub-cavity of the cross beam to the volume of the material of the cross beam is 3:7.

[0031] Optionally, the cross beam is made of glass fiber nylon composite material and is formed by online weaving and pultrusion, and the mass content of glass fiber of the cross beam reaches 80%.

[0032] Optionally, the rear protection device for the commercial vehicle further comprises:

[0033] The fixing bracket is provided in two groups, each group of the fixing bracket comprises a first fixing bracket and a second fixing bracket, the first fixing bracket and the second fixing bracket are arranged in the long axis direction of the cross beam and are connected between the cross beam and the connecting bracket respectively, the first fixing bracket is located at the P2 loading point of the cross beam, and the second fixing bracket is located between the P2 loading point and the P1 loading point of the cross beam; the cross beam is a non-metallic integrated structure.

[0034] Optionally, the first fixing bracket is U-shaped, the first fixing bracket is buckled on the cross beam, one side of the first fixing bracket is provided with a first flange to connect the connecting bracket, and the other side of the first fixing bracket is connected to the connecting bracket.

[0035] Optionally, the second fixing bracket is U-shaped, the second fixing bracket is buckled on the cross beam, and both sides of the second fixing bracket are provided with a second flange respectively, and the second flanges are connected to the connecting bracket respectively.

[0036] Optionally, the connecting bracket comprises a body, a rear flange is arranged on the rear side of the body, a bottom end of the rear flange is provided with an extension section, the extension section can be arranged against the cross beam, the body is arranged against the outer side of the longitudinal beam, a web plate is arranged between the body and the extension section, and the cross-sectional width of the web plate gradually increases from the second fixed bracket to the first fixed bracket.

[0037] The application further provides a commercial vehicle comprising the commercial vehicle rear protection device.

[0038] The application has the following beneficial effects:

[0039] The design method of the commercial vehicle rear protection device of the application realizes the structural optimization design of the non-metal cross beam and the weight and cost reduction by using the topological optimization method to design the cross beam section size.

[0040] The commercial vehicle rear protection device of the application realizes the high-strength connection between the non-metal cross beam and the metal longitudinal beam by designing the topologically optimized cross beam connected to the longitudinal beam, and the weight reduction of the metal cross beam is large, so that the lightweight commercial vehicle rear protection device is realized.

[0041] The commercial vehicle of the application has the following advantages: the cross beam is an integral structure made of non-metal material, so the weight is light, which is beneficial to the weight reduction and lightweight design of the whole vehicle; the cross beam is designed by using the topological optimization method, so the structural strength of the cross beam itself is large, which is beneficial to the improvement of the overall reliability of the commercial vehicle and the structural lightweight. BRIEF DESCRIPTION OF DRAWINGS

[0042] Figure 1 is a design method flowchart of a commercial vehicle rear protection device according to an embodiment of the application;

[0043] Figure 2 is a structural schematic diagram of a commercial vehicle rear protection device according to an embodiment of the application;

[0044] Figure 3 is a sectional structural schematic diagram of a cross beam in a commercial vehicle rear protection device according to an embodiment of the application;

[0045] Figure 4 is a structural schematic diagram of a connecting bracket in a commercial vehicle rear protection device according to an embodiment of the application;

[0046] Figure 5 is a structural schematic diagram of a first fixed bracket in a commercial vehicle rear protection device according to an embodiment of the application;

[0047] Figure 6 is a structural schematic diagram of a second fixed bracket in a commercial vehicle rear protection device according to an embodiment of the application.

[0048] Fig.

[0049] 100, longitudinal beam;

[0050] 1, cross beam; 11, front side wall; 12, rear side wall; 13, inclined rib;

[0051] 2, connecting bracket; 20, body; 21, rear flange; 211, extension section; 22, bottom flange; 23, front flange;

[0052] 3, fixing bracket; 31, first fixing bracket; 311, first flange; 32, second fixing bracket; 321, second flange;

[0053] 4, rib plate. DETAILED DESCRIPTION

[0054] The application will be further described below in conjunction with the drawings and embodiments. It can be understood that the specific embodiments described herein are only used to explain the application, and not to limit the application. In addition, it should be noted that, for the convenience of description, only the parts related to the application are shown in the drawings, not all the structures.

[0055] In the description of the application, unless otherwise explicitly specified and limited, the terms "connected", "connected", "fixed" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or it can be integrated; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the internal communication of two elements or the interaction relationship between two elements. For those skilled in the art, the specific meaning of the above terms in the application can be understood according to the specific circumstances.

[0056] In the present application, unless otherwise explicitly specified and limited, the "upper" or "lower" of the first feature to the second feature can include that the first and second features are in direct contact, or that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, the "upper", "above" and "on" of the first feature to the second feature includes that the first feature is directly above and obliquely above the second feature, or only indicates that the horizontal height of the first feature is higher than that of the second feature. The "below", "under" and "under" of the first feature to the second feature includes that the first feature is directly below and obliquely below the second feature, or only indicates that the horizontal height of the first feature is less than that of the second feature.

[0057] In the description of the embodiments, the terms "upper", "lower", "left", "right", and the like, orientation or positional relationship are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of description and simplification of operation, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second" are only used to distinguish in description, and have no special meaning.

[0058] The embodiments of the present application first provide a design method of a commercial vehicle rear protection device, such as Figure 1 flowchart, combined with Figure 2 and Figure 3 , comprising the following steps:

[0059] Determine the length L of the cross beam 1 adopted by the commercial vehicle rear protection device; the length of the cross beam 1 determines the width of the commercial vehicle rear protection device, and the length of the cross beam 1 meets the relevant provisions of the regulation GB 26511-2017 on the outer dimensions and strength of the rear protection structure. In actual design, the embodiments select the cross beam length L to adapt to the requirements of the full series of trucks and dump trucks. According to the length L of the cross beam, the width of the commercial vehicle rear protection device can be determined.

[0060] According to the three-point loading test standard, determine the P1 loading point, the P2 loading point and the P3 loading point on the cross beam; the P3 loading point is located on the longitudinal center plane of the commercial vehicle, the P2 loading point is located on the connecting plane of the longitudinal beam and the cross beam; the P1 loading point is determined according to the outermost end distance of the rear axle wheels of the vehicle;

[0061] GB26511-2017 "Rear Lower Protection Device Static Loading Test Conditions and Procedures" makes specific provisions for the loading device, the position of the loading point and the loading load. The embodiments design the cross beam 1 under the working condition of three-point loading.

[0062] In order to reduce the overall weight of the rear protection device, the cross beam 1 is made of non-metallic material, and the bending section modulus W of the cross beam 1 is determined:

[0063]

[0064] In the formula, P is the loading force of the P1 loading point, σ max is the maximum normal stress of the cross beam 1, M is the maximum bending moment of the cross beam 1, and l is the distance between the P1 loading point and the P2 loading point;

[0065] Define the safety factor n:

[0066]

[0067] In the formula, [σ] is the yield strength of the material of the cross beam 1, then:

[0068]

[0069] The safety factor n is an empirical value, and the value thereof should not be less than the safety factor of a reference structure or a standard structure,

[0070] That is

[0071] Wherein, [σ]0 is the material yield strength of the reference beam structure; W0 is the bending resistance sectional modulus of the reference beam structure; P0 is the load size of the P1 loading point on the reference beam structure; and l0 is the distance from the P1 loading point to the longitudinal beam 100 on the reference beam structure (when the beam 1 is connected to the longitudinal beam 100 through the connecting bracket 2, l0 is the distance from the P1 loading point to the root of the connecting bracket 2 on the reference beam structure).

[0072] The above formulae can be derived together as follows:

[0073]

[0074] According to the above, when the material of the designed beam 1 and the position of the connecting bracket 2 relative to the beam 1 are determined, the value of the required bending resistance sectional modulus W can be determined, and then the sectional size of the beam 1 can be determined.

[0075] In this embodiment, the sectional size of the beam 1 is determined according to the safety factor n and by using the topological optimization method combined with the bending resistance sectional modulus W.

[0076] The design method of the commercial vehicle rear protection device provided by the application improves the strength and weight reduction of the connecting structure by using a non-metallic material for the beam 1. In addition, the beam is made of a non-metallic material, the sectional size of the beam is designed by using the topological optimization method, the structural optimization design of the non-metallic beam is realized, the structural strength is increased, the connecting strength is improved, the self-weight of the non-metallic material is greatly reduced relative to the metal material, and the weight and cost are reduced.

[0077] In some embodiments, the topological optimization method is a variable density method based on the CAE optimization method, and specifically includes the following steps.

[0078] The beam 1 is set as a rectangular section, the beam 1 is meshed to obtain a finite element model of the beam 1, and the relative density x e The variable x e is continuously changed between 0 and 1, and 0 and 1 respectively represent a hollow or solid beam 1; and the target function is obtained by updating the optimization design variable;

[0079] After the above grid division of the structure of the cross beam 1, the density of each grid unit is a design variable, and the topology optimization target is to minimize the total flexibility of the structure or maximize the first-order natural frequency of the structure as the optimization design target, and the total mass of the structure is controlled and the boundary balance condition is considered.

[0080] In this embodiment, the SIMP method is used for material interpolation, the maximum stiffness problem of the structure is converted into the minimum flexibility problem, the volume constraint of the whole structure is taken as a constraint condition, and the objective function based on the flexibility density form of SIMP is:

[0081]

[0082] In the formula, C(x) is the flexibility of the cross beam, n is the number of grid units, p is the penalty factor, the penalty factor p is 2-4, K i is the stiffness matrix of the i-th grid unit; U i is the displacement vector of the i-th grid unit; E min is the minimum value of the elastic modulus of the cross beam, ΔE i is the difference between the elastic moduli of the adjacent two grid units, x i is the i-th design variable;

[0083] In Optistruct, the Compliance (single linear static working condition) can be selected as the objective function in the response response, and it is set to the minimum of the objective function.

[0084] The constraint conditions of the objective function include:

[0085] Fixed constraint: constrain the freedom of the connection between the cross beam 1 and the longitudinal beam 100; that is, the six-direction freedom of the connection between the cross beam 1 and the connecting bracket 2.

[0086] Load condition: the load condition of the P1 loading point in the three-point loading test standard is the load condition; since the cross beam 1 mainly bears the force of the P1 loading point in the three-point loading of the rear lower protection device, the optimization is a single-condition single-target optimization problem, so the load condition of the P1 loading point is selected.

[0087] Manufacturing process constraint: extrusion process; since the cross section at each position of the non-metallic cross beam 1 remains unchanged, the extrusion process constraint needs to be introduced in the optimization process to improve the processability of the topology optimization result. In the Optistruct software, it can be set under the Extrusion panel under the Optimization menu.

[0088] Volume ratio constraint: the volume fraction constraint is set to 0.3. The embodiment carries out structural single objective optimization on the cross beam 1, and the purpose is to improve the comprehensive performance of the cross beam 1 without increasing the material, so the volume fraction constraint is set to 0.3, the response with the attribute of volumefrac is established in the Optistruct software, which is set to dconstraint, and the upper limit value is set to 0.3.

[0089] According to the design method of the commercial vehicle rear protection device, as shown in Figures 2-5 The commercial vehicle rear protection device includes a cross beam 1 and a connecting bracket 2, and the cross beam 1 is connected to the longitudinal beam 100 of the commercial vehicle through the connecting bracket 2; the cross beam 1 is an integral structure of non-metallic material, the cross section of the cross beam 1 is a rectangular structure with rounded corners and has a cavity, two inclined ribs 13 are arranged in the cavity, and the two ends of the two inclined ribs 13 are connected to the front side wall 11 and the rear side wall 12 of the cross beam 1 respectively, and the two inclined ribs 13 divide the cavity into three sub-cavities.

[0090] As shown in Figure 3 The overall appearance of the cross beam 1 is a rectangular cross section with rounded corners, and the rectangular cavity is divided into three trapezoidal sub-cavities by the two inclined ribs 13. It can be understood that the stress of the cross beam 1 comes from the front side wall 11, and the inclined ribs 13 are arranged at a certain angle with the front side wall 11 and the rear side wall 12, which can support the front side wall 11 and the rear side wall 12, and can buffer the front side stress of the cross beam 1, and has a good supporting effect to reduce the stress deformation of the cross beam 1. The three sub-cavities can respectively absorb the collision energy to avoid large deformation of the cross beam 1 in a short time.

[0091] Optionally, the two inclined ribs 13 and the front side wall 11 and the rear side wall 12 form an isosceles trapezoidal cross section, the spacing of the two inclined ribs 13 on the front side wall 11 is the upper base length A, and the spacing of the two inclined ribs 13 on the rear side wall 12 is the lower base length B, and the upper base length A is greater than the lower base length B.

[0092] As shown in Figure 3 The two inclined ribs 13 form an opening horn shape from back to front in the cavity of the cross beam 1, and when the cross beam 1 is stressed in front, the cross beam 1 will first deform greatly to buffer the collision energy, and then the deformation amount will be reduced under the supporting action of the two inclined ribs 13, thereby avoiding large deformation of the cross beam 1 in a short time, buffering the deformation of the cross beam 1, and facilitating the slowing down of the collision process and reducing the collision loss. It should be noted that the connection between the two ends of the two inclined ribs 13 and the front side wall 11 and the rear side wall 12 is an arc transition structure formed by integral molding.

[0093] Optionally, the volume of the sub-cavity of the cross beam 1 is 70% of the total volume of the cross beam 1.

[0094] The volume of the sub-cavity of the cross beam 1 is 70% of the total volume of the cross beam 1, that is, the material volume ratio of the cross beam 1 is 30%, and the remaining 70% is the cavity volume. By designing and controlling the structure of the inclined rib 13 of the cross beam 1 and the volume ratio of the inclined rib 13 and the cavity, the function of the inclined rib 13 can be maximized, thereby reducing the self-weight of the cross beam 1 while ensuring the structural strength of the cross beam 1. The cross beam 1 of the present application is obtained by using the structural topology optimization method. When the total volume of the four side walls of the cross beam 1 and the inclined rib 13 does not exceed 30%, the inclined rib 13 has the best structural strength and load bearing capacity, which is the best material distribution. It should be noted that the cross beam 1 is a box-shaped cavity structure, and the two ends of the cross beam 1 are plugged with plugs made of ABS injection molding, which are installed at the two ends of the cross beam 1 by interference fit to plug the cavity.

[0095] In some embodiments, the cross beam 1 is made of glass fiber nylon composite material and is formed by online weaving and pultrusion. The mass content of glass fiber in the cross beam 1 reaches 80%. The method of online weaving and pultrusion of the composite material has the advantages of high production efficiency and low waste rate, so that the whole vehicle cost can be controlled, the mass content of glass fiber reaches 80%, and the mechanical properties of continuous fibers can be fully utilized, so that the product strength is high. By setting the glass fiber content in the material of the cross beam 1 and the cavity volume, the cross beam 1 can realize a weight reduction of 50% and a cost reduction of 15% compared with a solid beam, which has great economic benefits.

[0096] In one embodiment, the commercial vehicle rear protection device further comprises a fixing support 3, the fixing support 3 is provided with two groups, each group of fixing support 3 comprises a first fixing support 31 and a second fixing support 32 which are arranged at intervals along the long axis direction of the cross beam 1, and are respectively connected between the cross beam 1 and the connecting support 2, the first fixing support 31 is located at the P2 loading point of the cross beam 1, and the second fixing support 32 is located between the P2 loading point and the P1 loading point of the cross beam 1.

[0097] The commercial vehicle rear protection support commonly used in the prior art adopts a hollow pipe beam to reduce weight, and the cross beam 1 and the connecting support 2 are both made of metal material, which has a large self-weight, and are detachably connected by being respectively holed and then being connected by bolts. Holes are formed in the cross beam 1, which not only affects the strength of the cross beam 1 itself, but also limits the connection strength of the cross beam 1 at the hole position, which may cause local reduction or unreliability of the connection strength. In order to solve the above technical problems, the commercial vehicle rear protection device of the present application, such as Figure 1As shown, the length direction of the cross beam 1 is connected to the longitudinal beam 100 of the commercial vehicle through two connecting supports 2, and the cross beam 1 is symmetrically arranged about the vehicle longitudinal center plane, and two groups of fixing supports 3 are arranged to connect the two connecting supports 2 respectively, so as to improve the connection strength between the cross beam 1 and the connecting support 2. Among the two fixing supports 3, the second fixing support 32 is arranged between the P2 loading point and the P1 loading point of the cross beam 1, which reduces the cantilever length between the P2 loading point and the P1 loading point and is beneficial to reduce the stress deformation amount of the cross beam 1 between the P2 loading point and the P1 loading point, thereby improving the overall structural strength of the cross beam 1. Compared with the prior art, the two groups of fixing supports 3 realize multi-point fixed installation of the cross beam 1 without the need to open holes in the cross beam 1, which is beneficial to ensure the structural strength of the cross beam 1 itself; the cross beam 1 is a non-metal material integrated structure, which has a large weight reduction compared with the cross beam 1 of metal material, and the two groups of fixing supports 3 realize reliable connection between the connecting support 2 of metal material and the cross beam 1 of non-metal material.

[0098] Optionally, the first fixing support 31 is U-shaped, the first fixing support 31 is arranged to buckle the cross beam 1, one side of the first fixing support 31 is provided with a first flange 311 to connect the rear flange 21 of the connecting support 2, and the other side of the first fixing support 31 is connected to the bottom flange 22 of the connecting support 2.

[0099] As Figure 4 As shown is a structural schematic view of the connecting support 2 in the embodiment, the rear side of the connecting support 2 is provided with a rear flange 21, the bottom end of the rear flange 21 extends to form an extension section 211 in a direction away from the body 20 of the connecting support 2, and the extension section 211 can be arranged to abut against the rear side wall 12 of the cross beam 1, the body 20 of the connecting support 2 is arranged to abut against the outer side of the longitudinal beam 100, and is detachably connected to the longitudinal beam 100 through nine sparsely distributed bolts. The front side of the connecting support 2 is provided with a front flange 23 to increase the strength of the plate-shaped body 20 of the connecting support 2, and the front flange 23 and the rear flange 21 are bent to the same side of the body 20. The bottom end of the connecting support 2 is provided with a horizontal bottom flange 22, which is used to connect the other side of the first fixing support 31. As Figure 2 and Figure 5 It can be seen that the size of the U-shaped groove of the first fixing support 31 is consistent with the external size of the cross beam 1, so that the cross beam 1 can be just limited in the U-shaped groove of the first fixing support 31 for fixing and connecting.

[0100] Optionally, the second fixing support 32 is U-shaped, the second fixing support 32 is arranged to buckle the cross beam 1, and the two sides of the second fixing support 32 are respectively provided with a second flange 321, and the second flange 321 is respectively connected to the upper side and the lower side of the rear flange 21 of the connecting support 2.

[0101] In combination Figure 6 and Figure 1The U-shaped groove of the second fixing support 32 is matched with the size of the cross beam 1, so that the cross beam 1 can be just limited in the U-shaped groove of the second fixing support 32. After the second fixing support 32 buckles the cross beam 1, the second flanges 321 on both sides can abut against the outer side of the extension section 211 of the rear folded edge 21, and are connected through bolts. It can be understood that the length of the extension section 211 of the rear folded edge 21 realizes the spaced arrangement and connection of the first fixing support 31 and the second fixing support 32, the extension length of the extension section 211 extends from the P2 loading point of the cross beam 1 to the P1 loading point direction and is connected with the second fixing support 32, which realizes the multi-point fixed installation of the cross beam 1 and improves the connection strength.

[0102] The two first fixing supports 31 and the second fixing support 32 are adopted to realize the connection between the cross beam 1 and the connecting support 2, compared with the prior art which is connected through a wide size plate or directly connected, the support points on the cross beam 1 are increased and dispersed, which is beneficial to save materials and reduce the total weight, and the connection is more convenient and flexible.

[0103] Optionally, a web plate 4 is arranged between the body 20 of the connecting support 2 and the extension section 211 of the rear folded edge 21, and the cross-sectional width of the web plate 4 gradually increases from the second fixing support 32 to the first fixing support 31.

[0104] As shown in Figure 2 The web plate 4 is perpendicular to the body 20 of the connecting support 2 and the extension section 211 of the rear folded edge 21, and the web plate 4 is a triangular plate, in some embodiments, the connecting support 2 is a steel structure integrally stamped and formed, and is connected with the cross beam 1 of the composite material through the fixed support 3 and the bolt connection, which is convenient to disassemble, replace and has high connection strength. The connecting support 2 and the fixed support 3 are metal materials, and the cross beam 1 is a non-metal material, and the fixed support 3 realizes the connection between the non-metal cross beam 1 and the metal connecting support 2, and the web plate 4 is beneficial to the stress of the cross beam 1 being transmitted to the connecting support 2 and increasing the structural strength between the body 20 and the rear folded edge 21 of the connecting support 2. The web plate 4 is a steel structure, which is welded between the body 20 of the connecting support 2 and the extension section 211 of the rear folded edge 21.

[0105] The application also provides a commercial vehicle, which comprises the commercial vehicle rear protection device provided above. Figure 2 As shown in

[0106] In the rear protection device of the commercial vehicle, the cross beam 1 is a non-metal material, has the advantages of light weight and high structural strength, realizes reliable connection between the non-metal and the metal through the fixed support 3, and has good impact resistance.

[0107] Obviously, the above embodiments of the present application are merely exemplary and are not intended to limit the embodiments of the present application. Various obvious changes and modifications can be made by those skilled in the art without departing from the scope of the present application. It is not necessary to enumerate all the embodiments. Any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the claims of the present application.

Claims

1. Method for designing a rear protection device for a commercial vehicle, characterized in that: Comprising the following steps: Determine the length L of the cross beam (1) and the width of the commercial vehicle rear protection device adopted by the commercial vehicle rear protection device; According to the three-point loading test standard, determine the P1 loading point, P2 loading point and P3 loading point on the cross beam (1); the P3 loading point is located on the longitudinal center plane of the commercial vehicle, the P2 loading point is located on the connecting plane of the longitudinal beam (100) and the cross beam (1); the P1 loading point is determined according to the outermost end distance of the vehicle rear axle wheel; The cross beam (1) is made of non-metallic material, and the bending section modulus W of the cross beam (1) is determined: In the formula, P is the load size of the P1 load point, is the maximum positive stress suffered by the crossbeam (1), M is the maximum bending moment suffered by the crossbeam (1), is the distance between the P1 load point and the P2 load point; Define the safety factor n: ， wherein is the material yield strength of the cross member (1), then: ， According to the safety factor n, the cross section size of the cross beam (1) is determined by using the topology optimization method combined with the bending section modulus W; The topology optimization method is the variable density method, specifically comprising: The cross beam (1) is set as a rectangular cross section, and the cross beam (1) is meshed to obtain a finite element model of the cross beam (1); relative density of each mesh element in the finite element model is determined Let x be the design variable varying continuously between 0 and 1, 0 and 1 representing respectively a hollow or solid crossbeam (1); the objective function is obtained by updating the design variable The objective function is: wherein is the flexibility of the beam (1), is the number of grid elements; is the penalty factor, is the stiffness matrix of the i-th grid element; is the displacement vector of the i-th grid element; is the minimum value of the modulus of elasticity of the beam (1), is the difference of the modulus of elasticity of two adjacent grid elements, is the i-th design variable.

2. The design method of the commercial vehicle rear protection device according to claim 1, wherein The constraint conditions of the objective function include: Fixed constraint: constrain the freedom degree of the connection between the cross beam (1) and the longitudinal beam (100); Load condition: the loading condition of the P1 loading point in the three-point loading test standard is the load condition; Manufacturing process constraint: extrusion process; Volume ratio constraint: the volume fraction constraint is set to 0.

3.

3. The method of designing a commercial vehicle rear guard device according to claim 2, characterized in that, the penalty factor is 2-4.

4. Rear protection device for commercial vehicles, comprising a crossbar (1) and a connecting bracket (2), the crossbar (1) being connected to the longitudinal beams (100) of the commercial vehicle by means of the connecting bracket (2); characterized in that, The cross beam is designed according to the design method of the commercial vehicle rear protection device according to any one of claims 1-3, the cross beam (1) is a tubular structure with a cavity, the cross section of the cross beam (1) is a rectangle with rounded corners, two inclined ribs (13) are arranged in the cavity of the cross beam (1), and the two ends of the two inclined ribs (13) are connected to the front side wall (11) and the rear side wall (12) of the cross beam (1), respectively. Two inclined ribs (13) divide the cavity of the cross beam (1) into three sub-cavities.

5. The commercial vehicle rear guard device of claim 4, characterized in that An isosceles trapezoidal cross section is formed between the two inclined ribs (13), the front side wall (11) and the rear side wall (12), the spacing of the two inclined ribs (13) on the front side wall (11) is the upper base length A, the spacing of the two inclined ribs (13) on the rear side wall (12) is the lower base length B, and the upper base length A is greater than the lower base length B.

6. The commercial vehicle rear guard device of claim 4, characterized by The ratio of the volume of the sub-cavity of the cross beam (1) to the material volume of the cross beam (1) is 3:

7.

7. The commercial vehicle rear guard device of claim 4, characterized by The cross beam (1) is made of glass fiber nylon composite material by online braiding and pultrusion, and the mass content of glass fiber of the cross beam (1) reaches 80%.

8. The commercial vehicle rear guard device of claim 4, characterized by, The commercial vehicle rear protection device further comprises The fixed support (3) is provided with two groups, each group of the fixed support (3) comprises a first fixed support (31) and a second fixed support (32), the first fixed support (31) and the second fixed support (32) are arranged in the long axis direction of the cross beam (1) and are connected between the cross beam (1) and the connecting support (2) respectively, the first fixed support (31) is located at the P2 loading point of the cross beam (1), and the second fixed support (32) is located between the P2 loading point and the P1 loading point of the cross beam (1); the cross beam (1) is a non-metal material integral structure.

9. The commercial vehicle rear guard device according to any one of claims 4-8, characterized in that, The first fixed support (31) is U-shaped, the first fixed support (31) is buckled on the cross beam (1), one side of the first fixed support (31) is provided with a first flange (311) to connect the connecting support (2), and the other side of the first fixed support (31) is connected to the connecting support (2).

10. The commercial vehicle rear guard device according to any one of claims 4-8, characterized in that, The second fixed support (32) is U-shaped, the second fixed support (32) is buckled on the cross beam (1), both sides of the second fixed support (32) are respectively provided with a second flange (321), and the second flanges (321) are respectively connected to the connecting support (2).

11. The commercial vehicle rear guard device of claim 8, characterized by The connecting support (2) comprises a body (20), the rear side of the body (20) is provided with a rear flange (21), the bottom end of the rear flange (21) is provided with an extension section (211), the extension section (211) can be arranged close to the cross beam (1), the body (20) is arranged close to the outer side of the longitudinal beam (100), a rib plate (4) is arranged between the body (20) and the extension section (211), and the cross-sectional width of the rib plate (4) gradually increases from the second fixed support (32) to the first fixed support (31).

12. Commercial vehicle, characterized in that The commercial vehicle rear protection device comprises the commercial vehicle rear protection device according to any one of claims 4-11, and the commercial vehicle rear protection device is connected to the longitudinal beam (100) of the commercial vehicle.

Images