Obstacle-avoiding fender support and design method

Abstract

The application discloses a kind of barrier type mudguard support and design method, mainly related to commercial vehicle chassis support design technical field.Main body structure includes pedestal, mudguard mounting support, pivot mechanism, reset spring and fastening kingpin, the mudguard mounting support is rotatably connected on pedestal by pivot mechanism and fastening kingpin, one end of the reset spring is fixed on mudguard mounting support and the other end is detachably connected with pedestal.The beneficial effects of the application are that it can realize contact barrier swing arm, automatic reset support while the reliability of mudguard support, vibration response performance has significant improvement.

Description

Technical Field

[0001] This invention relates to the field of commercial vehicle chassis support design technology, specifically an obstacle avoidance mudguard support and its design method. Background Technology

[0002] Due to the complex operating environment of commercial vehicles, especially in dense obstacle scenarios such as mines, forestry, oil fields, and logistics stations, the rear mudguard bracket often comes into contact with and collides with obstacles in the surrounding environment during the reversing process, causing deformation, breakage, and other failures. How to achieve a contact obstacle swing arm and automatic reset support while taking into account good reliability and vibration response has become a key research and development focus.

[0003] Traditional solutions focus only on simple arm swing and reset, typically designing the mudguard bracket as a two-part system consisting of a base plate and a mudguard mounting bracket. The mudguard mounting bracket is simply held in place and fixed to the base plate by a coil spring. This approach fails to adequately constrain the system's degrees of freedom, leading to frequent collisions with surrounding obstacles during reversing, resulting in deformation, breakage, and other failures. This solution has significant drawbacks. The design requirement for the coil spring to bear the stiffness in the main excitation directions (Z, RX) places stringent demands on the consistency of coil spring stiffness and fatigue durability. Furthermore, the system's reliability and vibration response are two crucial aspects that cannot be ideally controlled. These problems severely restrict the widespread adoption of traditional solutions.

[0004] Therefore, a new mudguard bracket and a new design method are urgently needed to solve the above problems. Summary of the Invention

[0005] The purpose of this invention is to provide an obstacle avoidance mudguard bracket and its design method, which can realize obstacle contact swing arm and automatic reset support, while significantly improving the reliability and vibration response performance of the mudguard bracket.

[0006] To achieve the above objectives, the present invention employs the following technical solution:

[0007] The main structure includes a base, a mudguard mounting bracket, a rotating shaft mechanism, a return spring, and a fastening main pin. The mudguard mounting bracket is rotatably connected to the base through the rotating shaft mechanism and the fastening main pin. One end of the return spring is fixed to the mudguard mounting bracket, and the other end is detachably connected to the base.

[0008] Preferably, the base includes a rectangular plate, with screw holes at the four ends of the top surface of the rectangular plate. An upper cantilever, a lower cantilever, and a semi-circular groove are fixed on the top surface of the rectangular plate. The semi-circular groove is located between the upper and lower cantilever. Coaxial circular holes of the same diameter are provided through the ends of the upper and lower cantilever. A triangular plate is integrally fixed on the side of the rectangular plate away from the upper and lower cantilever. A hanging hole structure is provided at the top vertex of the triangular plate.

[0009] Preferably, the mudguard mounting bracket is a cylindrical tubular structure with one end in contact with a semi-circular groove on the top surface of the base. The outer wall of the mudguard mounting bracket is in clearance fit with the inner sidewalls of the upper and lower cantilever arms. A first through hole is provided through the peripheral wall of the mudguard mounting bracket, and the first through hole is coaxial with the circular hole. A second through hole is provided through the side wall of the mudguard mounting bracket near the hanging hole device.

[0010] Preferably, the rotating shaft mechanism includes an inner sleeve and an outer sleeve, the inner sleeve and the outer sleeve are coaxial and clearance-fitted, the length of the inner sleeve is greater than and the diameter is smaller than that of the outer sleeve, the two ends of the outer sleeve are respectively fixed to the first through hole of the mudguard mounting bracket by welding, and the two ends of the outer sleeve are respectively tightly fitted to the inner sidewall of the upper cantilever and the lower cantilever.

[0011] Preferably, the fastening kingpin includes a bolt for applying preload and two nuts. The bolt is disposed in a circular hole of the same diameter and coaxiality of the upper and lower cantilever arms and is sleeved in the inner sleeve of the rotating shaft mechanism. The bolt and the inner sleeve are clearance-fitted, and the two nuts are respectively bolted to both ends of the bolt.

[0012] A method for designing an obstacle avoidance mudguard bracket includes the following steps:

[0013] S1: Calculate the stiffness of the reset spring;

[0014] S2: Calculate the longitudinal width of the upper and lower cantilever arms.

[0015] Preferably, the calculation of the return spring stiffness specifically includes:

[0016] The preset maximum impact acceleration in the X direction is a, the maximum allowable angular displacement is θ, the weight of the mudguard mounting bracket is m, the length is s, the stiffness of the return spring is K, the length of the return spring in the free state is l, the pre-deformation is x0, and in normal driving conditions, the structural triangle is ABC, the rotation angle of the mudguard mounting bracket is 0, at this time:

[0017] The tension of the reset spring is:

[0018] F = Kx0

[0019] The length of the reset spring is:

[0020] L = l + x0

[0021] The longitudinal projection component of the return spring tension is:

[0022] F x =Fsinθ=Kx0sinθ

[0023] The torque acting at point 0 is:

[0024] T = F X L2=Kx0sinθL2

[0025] When the contact obstacle causes the mudguard mounting bracket 2 to rotate at an angle of θ0, the structural triangle is ABE.

[0026] The stroke CE of the reset spring mounting point is calculated, and the length of CE is:

[0027] CE=L2θ0

[0028] Since line segment CE lies within both triangles OCE and ACE, the travel angle of the return spring at the contact barrier is θ1. θ1 is calculated as follows:

[0029] θ1=CE / AC

[0030] At the same time, we can obtain:

[0031] BE=L0+L2θ0

[0032] AB = L1 + L2

[0033] At this point, the total length AE of the return spring can be calculated as follows:

[0034] AE = sqrt(BE) 2 +AB 2 )

[0035] AE = sqrt(L0 2 +2L0L2θ0+L2 2 θ0 2 +L1 2 +2L1L2+L2 2 )

[0036] The elongation X1 of the return spring is:

[0037] X1 = AE-1

[0038] X1 = sqrt(L0) 2 +2L0L2θ0+L2 2 θ0 2 +L1 2 +2L1L2+L2 2 )-1

[0039] The tension of the reset spring is:

[0040] F(X1) = KX1

[0041] F(X1)=K(sqrt(L0 2 +2L0L2θ0+L2 2 θ02 +L1 2 +2L1L2+L2 2 )-1)

[0042] The longitudinal projection component of the return spring tension is:

[0043] F(X1) X =F(X1)sin(θ+θ1)

[0044] F(X1) X =sin(θ+θ1)K(sqrt(L0) 2 +2L0L2θ0+L2 2 θ0 2 +L1 2 +2L1L2+L2 2 )-1)

[0045] The torque acting at point O is:

[0046] T1 = F(X1) x L2

[0047] T1=sin(θ+θ1)K(sqrt(L0 2 +2L0L2θ0+L2 2 θ0 2 +L1 2 +2L1L2+L2 2 )-1)L2

[0048] Due to the relationship between force and reaction force, we know that:

[0049] T1 = mas / 2

[0050] sin(θ+θ1)K(sqrt(L0 2 +2L0L2θ2+L2 2 θ0 2 +L1 2 +2L1L2+L2 2 )-1)L2=mas / 2

[0051] The first minimum value Kmin1 of the return spring stiffness K can be obtained as follows:

[0052] Kmin1=mas / 2L2(sqrt(L0 2 +2L0L2θ0+L2 2 θ0 2 +L1 2 +2L1L2+L2 2 )-1)sin(θ+θ1)

[0053] Controlling the vibration response of the mudguard mounting bracket, the vibration equilibrium equation of the torsional vibration system is established:

[0054] KA S -ω 2 IA S =0

[0055] Where ω is the angular frequency, I is the system's moment of inertia, and A... S It is a motion vector, and both sides are simultaneously connected to A. S Multiplying the inverse vectors yields:

[0056] K-ω 2 I = 0

[0057] ω = sqrt(K / I)

[0058] Dividing both sides by 2π simultaneously yields the frequency form:

[0059] f = sqrt(K / I) / 2π

[0060] The first modal frequency of the mudguard mounting bracket system is set to 1.414 times the excitation frequency. When f is 25Hz, the following is obtained:

[0061]

[0062] The second minimum value of the return spring stiffness, Kmin2, can be obtained as follows:

[0063] Kmin2=5000Iπ 2

[0064] The stiffness K of the return spring should be chosen from the two minimum values, with the corresponding formula being:

[0065] K = min(Kmin1, Kmin2)

[0066]

[0067] Preferably, the calculation of the longitudinal width of the upper and lower cantilever specifically includes:

[0068] The longitudinal width of the upper and lower cantilever rear sides is H2. Based on the fact that during the reversing process, when the mudguard mounting bracket rotates to an angle θ0 after contacting an obstacle, the tail end OD1 of the mudguard mounting bracket rotates to position OD2, forming a bracket triangle OD1D2.

[0069]

[0070] D1D2=OD1tanθ0

[0071] L1 = OD1

[0072] D1D2=L1tanθ0

[0073] Considering a safety margin factor of 10%, we can obtain:

[0074] H2=L1tanθ0(1+10%).

[0075] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0076] This invention starts by ensuring the stiffness of the main excitation direction of the system. Considering that the load generated by the contact collision with the obstacle is concentrated in the X direction, which is the normal direction of the main excitation direction of the system, the invention adopts a technical solution that combines the base and the rotating shaft mechanism, and the high pair and the low pair work together to improve the stiffness of the main excitation direction. While realizing the contact obstacle swing arm and automatic reset support, the reliability and vibration response performance are significantly improved. Attached Figure Description

[0077] Figure 1 This is a perspective view of the mudguard bracket of the present invention.

[0078] Figure 2 This is a side view of the mudguard bracket of the present invention.

[0079] Figure 3 This is a bottom view of the mudguard bracket of the present invention.

[0080] Figure 4 This is a rear view of the mudguard bracket of the present invention.

[0081] Figure 5 This is a front view of the mudguard mounting bracket and rotating shaft mechanism of the present invention.

[0082] Figure 6 This is a front view of the rotating shaft mechanism of the present invention.

[0083] Figure 7 This is a kinematic teaching model of the mudguard mounting bracket of the present invention.

[0084] The labels shown in the attached diagram:

[0085] 1. Base; 2. Mudguard mounting bracket; 3. Return spring; 4. Fastening kingpin; 5. Second through hole; 6. Rotating shaft mechanism; 11. Base plate; 12. Upper cantilever; 13. Lower cantilever; 14. Semi-circular groove; 15. Hanging hole structure; 61. Inner sleeve; 62. Outer sleeve. Detailed Implementation

[0086] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined in this application.

[0087] Example 1: An obstacle avoidance mudguard bracket

[0088] like Figure 1 , Figure 2 As shown, the main structure includes a base, a mudguard mounting bracket, a rotating shaft mechanism, a return spring, and a fastening kingpin. The mudguard mounting bracket is connected to the base through the rotating shaft mechanism, and the tail end of the mudguard mounting bracket contacts the inner wall of the semi-circular groove of the base.

[0089] Because of the need to support the mudguards, the fully constrained mudguard mounting bracket at the very rear of the vehicle frame is highly susceptible to failure from impacts by obstacles during reversing in harsh and complex environments, causing the mudguard support to malfunction. The purpose of this invention is to solve this problem. Simultaneously, the solution needs to possess good support stiffness characteristics in the primary excitation directions (Z, RX) to ensure system reliability and vibration response performance.

[0090] like Figure 2 , Figure 3 , Figure 4 As shown, the base supports the mudguard mounting bracket and also has limiting, rotating, and returning functions. The base has a base plate, upper cantilever, lower cantilever, semi-circular groove, and mounting holes. These structures are integrally formed by casting or welding, and are symmetrically distributed around the bisecting plane of the semi-circular groove. The base plate is used for mounting and fixing to the side wing of the vehicle frame. The base plate also has the upper and lower cantilever, semi-circular groove, and mounting holes. The upper and lower cantilever of the base are vertically aligned with the bisecting plane of the semi-circular groove. The upper and lower cantilever arms are symmetrically distributed, with coaxial, same-diameter through holes at their ends for mounting and fixing the rotating shaft mechanism and securing the kingpin. All three components have a clearance fit in the radial direction (to achieve rotation). The semi-circular grooves on the base are used to contact and limit the mudguard mounting bracket, and to enhance the support stiffness in the main excitation direction of the system. These semi-circular grooves are symmetrically distributed along the horizontal plane. The mounting holes on the rear side of the base are used to install and fix the passive end of the return spring (to achieve return function). The return spring is actively fixed to the mudguard mounting bracket. The chamfer radius corresponding to the inner side of the outer ends of the upper and lower cantilever arms is not less than R5 to reduce stress concentration damage to the mudguard mounting bracket caused by the inner side of the outer ends of the upper and lower cantilever arms.

[0091] like Figure 2 , Figure 5 , Figure 6As shown, the rotating shaft mechanism consists of two coaxial, variable-diameter sleeves strung together. The inner and outer sleeves are respectively the inner sleeve and the outer sleeve, with a clearance fit. The inner sleeve is longer than the outer sleeve but smaller in diameter, and their fit is a clearance fit. The length of the inner sleeve is less than the axial distance between the outer surfaces of the cantilever and lower cantilever on the base plate under the condition of preload applied by the fastening pin, but greater than the axial distance between the inner surfaces of the upper and lower cantilever under the condition of preload applied by the fastening pin. That is, the two ends of the inner sleeve of the rotating shaft mechanism can only move linearly within the limited space formed by the outer and inner surfaces of the upper and lower cantilever. The outer sleeve is fixed by welding to the coaxial through hole at the tail end of the mudguard mounting bracket, and under the condition of preload applied by the fastening pin, the two ends of the outer sleeve are tightly fitted with the upper and lower cantilever of the base.

[0092] like Figure 1 , Figure 2 , Figure 5 As shown, the fastening kingpin is a bolt and nut mechanism that applies preload. It is used to assemble in the coaxial through hole of the upper and lower cantilever of the base and is sleeved in the inner sleeve of the rotating shaft mechanism. The two are fitted with clearance.

[0093] The mudguard mounting bracket is used to install mudguards and other functional accessories, and has a circular cross-section. The mudguard mounting bracket has a coaxial through hole at both its tail and outer ends. The through holes are used for welding and fixing to the outer sleeve of the rotating shaft mechanism, and under the tension of the return spring, the tail end fits against the two inclined surfaces of the semi-circular groove of the base. The through holes are used to install the return spring.

[0094] like Figure 1 , Figure 2 As shown, the return spring is a helical spring or a leaf spring, with a linear curve stiffness of K. The return spring has hook structures or bolt mounting structures at both ends for fixing the return spring.

[0095] like Figure 2As shown, the connection between the base and the mudguard mounting bracket is mainly achieved through the cooperation of the fastening kingpin and the rotating shaft mechanism 7. The fastening kingpin and the rotating shaft mechanism are combined in a coaxial, variable-diameter manner, primarily in a coaxial arrangement with the inner sleeve of the rotating shaft mechanism. The contact is set as a clearance fit, retaining two degrees of freedom: mutual rotation (RZ rotational degree of freedom) and mutual movement along the axis. Since the inner sleeve of the rotating shaft mechanism is located within the effective range of the fastening kingpin, i.e., the flange of the nut and bolt of the fastening kingpin, the range of movement along the axis is limited. Simultaneously, because the two ends of the fastening kingpin form a closed cylindrical space of height H1 with the upper and lower cantilever arms of the base, the inner sleeve of the rotating shaft mechanism (inner sleeve length H3) is confined within this closed cylindrical space, i.e., H3 is less than H1. The mudguard bracket achieves the function of contacting the obstacle swing arm through mutual rotation (RZ rotational degree of freedom). During the reversing process, contact with the obstacle generates a thrust load. The thrust load acts on the mudguard mounting bracket to generate an RZ rotational torque around the rotating shaft mechanism. After the RZ rotational torque overcomes the tension of the return spring, it generates an RZ rotational action that moves away from the obstacle.

[0096] Under the preload, the fastening kingpin presses against the outer sides of the upper and lower cantilever arms of the base. The upper and lower cantilever arms of the base are further subjected to the preload, and the inner sides of the upper and lower cantilever arms press against the outer side of the mudguard mounting bracket. This is the first method to improve the support stiffness in the main excitation directions (Z, RX) of the system. Simultaneously, since the mudguard mounting bracket structure is a tubular structure, in order to reasonably withstand the preload, the design requires arranging an outer sleeve of the rotating shaft mechanism inside the opening of the mudguard mounting bracket.

[0097] Because it is necessary to control the vibration displacement response of the mudguard mounting bracket under normal road surface excitation, it is necessary to further improve the support stiffness in the main excitation directions (Z, RX). The semi-circular groove of the base solves this problem. Since the rotating shaft mechanism has a rotational degree of freedom (RZ), when the mudguard mounting bracket is subjected to tension and contacts the semi-circular groove, the combined action of the symmetrical and reverse semi-circular inclined surfaces ensures that the tail end of the mudguard mounting bracket fits against the surface of the semi-circular groove, restricting the degrees of freedom in the main excitation directions (Z, RX). This is the second method to improve the support stiffness in the main excitation directions. Simultaneously, the combined action of the symmetrical and reverse semi-circular inclined surfaces of the semi-circular groove ensures the centering constraint of the tail end of the mudguard mounting bracket within the semi-circular groove. This significantly improves the problem of insufficient system constraint caused by the clearance fit involved in the rotating shaft mechanism and the fastening kingpin assembly, further improving system reliability and vibration response performance.

[0098] To ensure that the tail end of the mudguard mounting bracket fits snugly against the surface of the semi-circular groove 14 under normal driving conditions, and to simultaneously provide automatic reset support after the vehicle has cleared obstacles during a reversing maneuver in harsh and complex environments, a reset spring is provided. The two ends of the reset spring are respectively constrained to the hanging hole structure of the base plate and the mounting hole on the outer side of the mudguard mounting bracket. During the process of clearing obstacles, the thrust load generated by contact with the obstacle gradually decreases, i.e., the RZ rotational torque around the rotating shaft mechanism gradually decreases. Under the tension of the reset spring, the mudguard mounting bracket generates an RZ reverse rotational torque around the rotating shaft mechanism, resulting in an RZ reverse rotation action. This gradually leads to contact between the mudguard mounting bracket and the semi-circular groove, restoring normal driving conditions. It also possesses sufficient and reasonable support stiffness in the main excitation directions (Z, RX), achieving both good reliability and vibration response performance.

[0099] Example 2: A design method for an obstacle avoidance mudguard bracket

[0100] The design method mainly involves the design of the reset spring stiffness K, the upper cantilever of the base, and the longitudinal width H2 of the lower cantilever.

[0101] Since the system has only the RX degree of freedom, and the RX degree of freedom affects the impact angular displacement and vibration response of the mudguard mounting bracket in the X direction, a design method for the stiffness K of the reset spring is required.

[0102] like Figure 7 As shown, the first step is to control the impact angular displacement of the mudguard mounting bracket in the X direction. The preset maximum impact acceleration in the X direction is a, the maximum allowable angular displacement is θ, the weight of the mudguard mounting bracket is m, the length is s, and the center of gravity is located at the center position. The stiffness of the return spring is K, the length of the return spring in the free state is l, and the pre-deformation is x0.

[0103] Under normal driving conditions, the structural triangle is ABC, and the mudguard mounting bracket has a rotation angle of 0°.

[0104] The tension of the reset spring is:

[0105] F = Kx0

[0106] The length of the reset spring is:

[0107] L = l + x0

[0108] The longitudinal projection component of the return spring tension is:

[0109] F X =Fsinθ=Kx0sinθ

[0110] The torque acting at point 0 is:

[0111] T = F XL2=Kx0sinθL2

[0112] When the vehicle reverses and comes into contact with an obstacle, causing the mudguard mounting bracket 2 to turn at an angle of θ0 (OF1 turns to OF2), the structural triangle is ABE. By using the equation of triangle ABC, the working length variable of the return spring 3 can be obtained.

[0113] First, the stroke CE of the return spring mounting point needs to be calculated. Since the mudguard mounting bracket rotates around point O, the stroke CE is an arc segment. However, because θ0 is relatively small, the stroke CE can be considered a straight segment. Based on this, the length of CE is calculated as follows:

[0114] CE=L2θ0

[0115] Since line segment CE lies within both triangles OCE and ACE, the travel angle of the return spring 3 when it contacts the obstacle during the reversing process is θ1. θ1 is calculated as follows:

[0116] θ1=CE / AC

[0117] At the same time, we can obtain:

[0118] BE=L0+L2θ0

[0119] AB = L1 + L2

[0120] At this point, the total length AE of the return spring can be calculated as follows:

[0121] AE = sqrt(BE) 2 +AB 2 )

[0122] AE = sqrt(L0 2 +2L0L2θ0+L2 2 θ0 2 +L1 2 +2L1L2+L2 2 )

[0123] The elongation X1 of the return spring is:

[0124] X1 = AE-1

[0125] X1 = sqrt(L0) 2 +2L0L2θ0+L2 2 θ0 2 +L1 2 +2L1L2+L2 2 )-1

[0126] The tension of the reset spring is:

[0127] F(X1) = KX1

[0128] F(X1)=K(sqrt(L0 2 +2L0L2θ0+L2 2 θ0 2 +L1 2 +2L1L2+L2 2 )-1)

[0129] The longitudinal (X-direction) projection component of the return spring tension is:

[0130] F(X1) X =F(X1)sin(θ+θ1)

[0131] F(X1) X =sin(θ+θ1)K(sqrt(L0) 2 +2L0L2θ0+L2 2 θ0 2 +L1 2 +2L1L2+L2 2 )-1)

[0132] The torque acting at point O is:

[0133] T1 = F(X1) X L2

[0134] T1=sin(θ+θ1)K(sqrt(L0 2 +2L0L2θ0+L2 2 θ0 2 +L1 2 +2L1L2+L2 2 )-1)L2

[0135] Due to the relationship between force and reaction force, we know that:

[0136] T1 = mas / 2

[0137] sin(θ+θ1)K(sqrt(L0 2 +2L0L2θ0+L2 2 θ0 2 +L1 2 +2L1L2+L2 2 )-1)L2=mas / 2

[0138] The first minimum value Kmin1 of the return spring stiffness K can be obtained as follows:

[0139] Kmin1=mas / 2L2(sqrt(L0 2 +2L0L2θ0+L2 2 θ0 2 +L1 2 +2L1L2+L22 )-1)sin(θ+θ1)

[0140] Next is controlling the vibration response of the mudguard mounting bracket in the X direction. Here, the main focus is on controlling the first-order modal frequency of the system to exceed the common road surface excitation frequency (0-25Hz), that is, the first-order modal frequency is not less than 25Hz.

[0141] Establish the vibration equilibrium equations for the torsional vibration system:

[0142] KA S -ω 2 IA S =0

[0143] Where ω is the angular frequency, I is the system's moment of inertia, and A... S It is a motion vector, multiplied by A on both sides. S The inverse vector can be obtained

[0144] K-ω 2 I = 0

[0145] ω = sqrt(K / I)

[0146] To obtain the frequency form, divide both sides by 2π:

[0147] f = sqrt(K / I) / 2π

[0148] Due to vibration isolation requirements, the first modal frequency of the system is required to reasonably exceed the excitation frequency. Therefore, the first modal frequency of the mudguard mounting bracket system is set to be 1.414 times the excitation frequency.

[0149] When f equals 25Hz, we get:

[0150]

[0151] The second minimum value of the return spring stiffness, Kmin2, can be obtained as follows:

[0152] Kmin2=5000Iπ 2

[0153] The above-mentioned calculation method for the two minimum values ​​of the stiffness K of the return spring 3 is as follows: Since an excessively large stiffness K will cause an excessive thrust load on the mudguard mounting bracket 2 and its accessories after contacting the obstacle during the reversing process, thereby causing failure and damage to the mudguard mounting bracket 2 and its accessories, the stiffness K value of the return spring 3 should be controlled as small as possible.

[0154] Based on the above calculation methods, the stiffness K value of the return spring 3 should be the smaller of the two minimum values, and the corresponding specific formula is as follows:

[0155] K = min(Kmin1, Kmin2)

[0156]

[0157] At the same time, such as Figure 2 As shown, the longitudinal width H2 of the upper and lower cantilever rear sides of the base needs to cover the rotation range of the mudguard mounting bracket tail end OD1 when the mudguard mounting bracket rotates to an angle θ0 (OF1 to OF2) due to contact with an obstacle during reversing, in order to provide effective support stiffness and set a safety range factor of 10%.

[0158] When the mudguard mounting bracket rotates to an angle θ0 (OF1 rotates to OF2) due to contact with an obstacle during the reversing process, it can be seen that the tail end OD1 of the mudguard mounting bracket rotates to the OD2 position, forming a bracket triangle OD1D2.

[0159]

[0160] D1D2=OD1tanθ0

[0161] L1 = OD1

[0162] D1D2=L1tanθ0

[0163] Considering a safety margin factor of 10%, we can obtain:

[0164] H2=L1tanθ0(1+10%).

Claims

1. A design method for an obstacle-avoidance mudguard bracket, comprising an obstacle-avoidance mudguard bracket, characterized in that, The obstacle avoidance mudguard bracket includes a base, a mudguard mounting bracket, a rotating shaft mechanism, a return spring, and a fastening main pin. The mudguard mounting bracket is rotatably connected to the base through the rotating shaft mechanism and the fastening main pin. One end of the return spring is fixed to the mudguard mounting bracket and the other end is detachably connected to the base. The base includes a rectangular plate with screw holes at the four ends of its top surface. An upper cantilever, a lower cantilever, and a semi-circular groove are fixed on the top surface of the rectangular plate. The semi-circular groove is located between the upper and lower cantilever. Coaxial circular holes of the same diameter are provided through the ends of the upper and lower cantilever. A triangular plate is integrally fixed on the side of the rectangular plate away from the upper and lower cantilever. A hanging hole structure is provided at the top vertex of the triangular plate. The mudguard mounting bracket is a cylindrical tubular structure with one end in contact with a semi-circular groove on the top surface of the base. The outer wall of the mudguard mounting bracket is in clearance fit with the inner sidewalls of the upper and lower cantilever arms. A first through hole is provided through the peripheral wall of the mudguard mounting bracket. The first through hole is coaxial with the circular hole. A second through hole is provided through the side wall of the mudguard mounting bracket near the hanging hole device. The rotating shaft mechanism includes an inner sleeve and an outer sleeve, which are coaxial and clearance-fitted. The inner sleeve has a longer length and a smaller diameter than the outer sleeve. The two ends of the outer sleeve are respectively fixed to the first through hole of the mudguard mounting bracket by welding. The two ends of the outer sleeve are respectively in close contact with the inner sidewalls of the upper and lower cantilever. The fastening kingpin includes a bolt for applying preload and two nuts. The bolt is disposed in a circular hole of the same diameter and coaxiality of the upper and lower cantilever arms and is sleeved in the inner sleeve of the rotating shaft mechanism. The bolt and the inner sleeve are clearance-fitted, and the two nuts are respectively bolted to both ends of the bolt. The design method of the obstacle avoidance mudguard bracket includes the following steps: S1: Calculate the stiffness of the reset spring; S2: Calculate the longitudinal width of the upper and lower cantilever arms; The calculation of the return spring stiffness specifically includes: The preset maximum impact acceleration in the X direction is a, the weight of the mudguard mounting bracket is m and the length is s, the stiffness of the return spring is K, the length of the return spring in the free state is l, and the pre-deformation is... The Y-axis is the direction perpendicular to the X-axis; The return spring has a first end and a second end. The connection point between the first end and the base is designated as point A. When the mudguard mounting bracket is not in contact with an external obstacle, the connection point between the second end of the return spring and the mudguard mounting bracket is designated as point C. The axis of the rotating shaft mechanism is designated as point O. When the mudguard mounting bracket comes into contact with an external obstacle, it rotates around point O. At this time, the other end of the return spring moves from point C to point E when it connects with the mudguard mounting bracket. Since the mudguard mounting bracket rotates around point O within a small range, point E mainly shifts along the X-direction relative to point C, while the shift along the Y-direction is negligible. The intersection of the extensions of points C and E with the straight line passing through point A and parallel to the Y-axis is point B. Therefore, when the mudguard mounting bracket is not in contact with an external obstacle, the connection points A, C, and B of the return spring form a right triangle ABC. When the mudguard mounting bracket contacts an external obstacle and rotates around point O, the connection points A, E, and B of the return spring form a right triangle ABE. Simultaneously, when the mudguard mounting bracket contacts an external obstacle and rotates around point O... At that time, the tail end point D1 of the mudguard mounting bracket rotates to D2; In normal driving conditions, the structural triangle is ABC, and the angle between side AB and side AC is . The mudguard mounting bracket has the following rotation angle: ,at this time: The tension of the reset spring is: ； The length of the reset spring is: ； The longitudinal projection component of the return spring tension is: ； The torque acting at point 0 is: ； The contact obstacle causes the mudguard mounting bracket to rotate at an angle of 100 degrees. At this angle, the structural triangle is ABE. The stroke CE of the reset spring mounting point is calculated, and the length of CE is: ； Since line segment CE lies within both triangles OCE and ACE, the travel angle of the return spring at the contact barrier is... ,calculate for: ； At the same time, we can obtain: ； ； in, From point A to The distance of the point along the X-axis; Let line segment A be The distance from point O along the Y-axis; This represents the distance from point O to point C along the Y-axis. At this point, the total length AE of the return spring can be calculated as follows: ； ； Elongation of the return spring for: ； ； The tension of the reset spring is: ； ； The longitudinal projection component of the return spring tension is: ； ； The torque acting at point O is: ； ； Due to the relationship between force and reaction force, we know that: ； ； The first minimum value of the return spring stiffness K can be obtained. for: ； Controlling the vibration response of the mudguard mounting bracket, the vibration equilibrium equation of the torsional vibration system is established: ； in, It is the angular frequency. It is the system's rotational inertia. It is a motion vector, simultaneously interacting with both sides. Multiplying the inverse vectors yields: ； ； Divide both sides simultaneously The frequency form is obtained as follows: ； The first modal frequency of the mudguard mounting bracket system is set to 1.414 times the excitation frequency. At 25Hz, the following was obtained: ； The second minimum value of the return spring stiffness can be obtained. for: ； The stiffness K of the return spring should be chosen from the two minimum values, with the corresponding formula being: ； 。 2. The design method of the obstacle avoidance mudguard bracket according to claim 1, characterized in that, The calculation of the longitudinal width of the upper and lower cantilever specifically includes: The longitudinal width of the upper and lower cantilever rear sides is The mudguard mounting bracket rotates to a certain angle due to contact with an obstacle during the reversing process. From the angle, it can be seen that the tail end of the mudguard mounting bracket Rotate to Position, forming a support triangle : ； ； ； ； Considering a safety margin factor of 10%, we can obtain: 。

Images