Structural design method and structural design program for vehicle

Abstract

To place a reinforcement member having secured bending rigidity and torsional rigidity at an appropriate position in a vehicle.SOLUTION: A structural design method for a vehicle includes placing a beam element 62 at a temporary attachment position P0 so as to connect fastening portions Pc to each other in a vehicle body model 61, deforming the vehicle body model 61 so as to realize a first mode M1 that twists a vehicle body and acquiring a first indicator I1 that increases as an internal force or a moment acting on the beam element 62 increases, deforming the vehicle body model 61 so as to realize a second mode M2 that causes membrane vibration of a floor portion of the vehicle and acquiring a second indicator I2 that increases as an internal force or a moment acting on the beam element 62 increases, and determining the attachment position P0 of the beam element 62 and adopting the beam element 62 as a reinforcement member 101 when both the first indicator I1 and the second indicator I2 are equal to or greater than a predetermined value.SELECTED DRAWING: Figure 9

Description

[Technical Field]

[0001] The present disclosure relates to a vehicle structural design method and a structural design program. [Background technology]

[0002] For example, Patent Document 1 discloses a method for supporting wiring design of a wire-like structure. This method considers the wire-like structure as an elastic body to which multiple beam elements are connected, and applies the finite element method to it.

[0003] Meanwhile, Patent Document 2 discloses a first connecting member that connects a dash member and a suspension tower member of a vehicle. The first connecting member has a higher proportion of fibers extending in the longitudinal direction than in directions other than the longitudinal direction. Furthermore, a synthetic resin material is impregnated between the fibers.

[0004] According to Patent Document 2, the vertical displacement of the top of the suspension is reduced. By using the bending rigidity of the first connecting member, the so-called vehicle body torsion mode can be suppressed.

[0005] Furthermore, according to Patent Document 2, the torsional displacement between the upper part of the suspension tower member and the dash member can be converted into the torsional displacement of the first connecting member, thereby increasing the vibration damping capacity of the vehicle and suppressing the so-called membrane vibration mode. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-139568 [Patent Document 2] Japanese Patent Publication No. 2022-131228 Summary of the Invention [Problem to be solved by the invention]

[0007] Incidentally, a reinforcing member such as the first connecting member of Patent Document 2 can only maximize its effectiveness if it is installed in a location where both external forces that try to bend it and external forces that try to twist it are input in a balanced manner.

[0008] By providing a reinforcing member in such an area, it is possible to simultaneously achieve, with a single reinforcing member, improved vehicle handling performance due to suppression of the body torsion mode and improved vehicle ride comfort performance due to suppression of the membrane vibration mode.

[0009] However, identifying such sites is not easy.

[0010] The present disclosure has been made in consideration of these points, and its purpose is to arrange reinforcing members that ensure bending rigidity and torsional rigidity at appropriate locations in a vehicle. [Means for solving the problem]

[0011] A first aspect of the present disclosure relates to a vehicle structural design method that is executed by a computer having a processor to identify attachment locations of reinforcing members that ensure bending rigidity and torsional rigidity.

[0012] According to the first aspect, the structural design method includes the steps of: the processor placing beam elements at temporary attachment locations so as to connect fastening portions in a vehicle body model corresponding to the vehicle; the processor deforming the vehicle body model with an external force so as to realize a first mode in which the vehicle body is twisted around a central axis extending in the fore-and-aft direction of the vehicle body, and acquiring a first index that increases as the internal force or moment acting on the beam element increases with the deformation of the vehicle body model; the processor deforming the vehicle body model with an external force so as to realize a second mode in which a membrane vibrates a floor portion of the vehicle in the vehicle height direction, and acquiring a second index that increases as the internal force or moment acting on the beam element increases with the deformation of the vehicle body model; and the processor, when both the first index and the second index are equal to or greater than a predetermined value, determining the attachment location of the beam element and adopting the beam element as the reinforcing member.

[0013] In the first aspect, the first mode corresponds to a so-called vehicle body torsion mode. Meanwhile, the second mode corresponds to a so-called membrane vibration mode. Furthermore, "when both the first index and the second index are equal to or greater than a predetermined value" means "when the absolute values ​​of each index are equal to or greater than a predetermined value." When making this determination, different comparison targets may be used for the first index and the second index.

[0014] According to the first aspect, when the condition that the first index and the second index are each equal to or greater than a predetermined value is satisfied, the processor employs the beam element in that case as a reinforcing member. Here, satisfying the condition means that the external forces tending to bend and twist the beam element located at the temporary attachment portion are both relatively high.

[0015] In other words, an attachment location that satisfies the above conditions is one where reinforcement in terms of both bending rigidity and torsional rigidity is important, and it can be said that this is an attachment location where the above-mentioned reinforcing member can maximize its function and effect.

[0016] Therefore, by using a beam element that can be attached to such a mounting location as a reinforcing member, the reinforcing member can be placed in an appropriate location within the vehicle, which makes it possible to simultaneously achieve improved vehicle handling stability due to suppression of the body torsion mode and improved ride comfort due to suppression of the membrane vibration mode, even with just one reinforcing member.

[0017] Furthermore, according to the second aspect, the reinforcing member may be a member made of fiber-reinforced resin in which a plurality of reinforcing fibers are blended and a polymer resin is impregnated between the plurality of reinforcing fibers, and the proportion of the reinforcing fibers oriented in a predetermined first direction may be greater than the proportion of the reinforcing fibers oriented in other directions.

[0018] According to the second aspect, by relatively increasing the proportion of reinforcing fibers oriented in a first direction, the bending rigidity of the reinforcing member in this first direction (fiber direction) can be ensured. Furthermore, by impregnating the spaces between the reinforcing fibers with a polymer resin, when the reinforcing member is twisted in a second direction (the direction in which the reinforcing fibers are aligned and sheared) perpendicular to the first direction, the polymer resin located between the reinforcing fibers is effectively strained. This strain ensures the torsional rigidity of the reinforcing member.

[0019] Thus, according to the second aspect, bending rigidity is ensured in a first direction, while torsional rigidity is ensured in a second direction different from the first direction, thereby achieving physical properties suitable for the reinforcing member.

[0020] According to the third aspect, the internal force may be an internal force acting in the first direction, and the moment may be a torsional moment around the first direction.

[0021] According to the third aspect, when searching for an attachment site, the first and second indices can be set appropriately, which makes it possible to more appropriately identify the attachment site.

[0022] According to the fourth aspect, at least a portion of the reinforcing member may be configured to be elongated, and the first direction may be a longitudinal direction of the reinforcing member.

[0023] According to the fourth aspect, the reinforcing fibers are oriented along the longitudinal direction of the long portion of the reinforcing member, which makes it possible to obtain a reinforcing member with excellent bending rigidity.

[0024] According to the fifth aspect, the first direction is a direction extending parallel to a plane along the vehicle body longitudinal direction and vehicle width direction, and the longitudinal elastic modulus of the reinforcing member in the first direction is E [MPa], the transverse elastic modulus of the reinforcing member in a direction perpendicular to the first direction is G [MPa], and the cross-sectional area of ​​the reinforcing member in a cross-sectional view perpendicular to the first direction is A [mm 2 ], and the moment of inertia of the reinforcing member in the vehicle height direction is I1 [mm 4 ], and the second moment of area of ​​the reinforcing member in the direction perpendicular to the vehicle height direction and the first direction is I2 [mm 4 ], Poisson's ratio is ν, and the torsional constant is J [mm 4 ], the reinforcing member may be configured to satisfy all of the following conditions (A), (B), (C), and (D) so that the reinforcing member itself does not contribute to the deformation of each of the first and second modes.

[0025] E·A≦1000[N] …(A) E·I1≦1000 [N·mm 2 ] …(B) E·I2≦1000 [N·mm 2 ] …(C) G·J≦385 [N·mm 2 ] …(D) However, the transverse elastic modulus G in the condition (D) is calculated based on the following formula (E).

[0026] G=E / (2·(1+ν)) …(E) According to the findings of the present inventors as a result of extensive research, by configuring the reinforcing member to satisfy the above conditions, the reinforcing member itself will not contribute to the deformation of either the first or second mode.

[0027] This makes it possible to suppress the influence of deformation of the reinforcing member, and in turn, the beam element corresponding to the reinforcing member, on the search for the attachment location. In other words, the influence of the deformation of the reinforcing member itself would become noise when searching for the attachment location, but by setting it from the beginning so that it does not contribute to the deformation, it is possible to eliminate the influence of such noise as much as possible. This makes it possible to search for the attachment location with high accuracy.

[0028] Furthermore, according to the sixth aspect, the first index may be the proportion of energy borne by the beam element out of the total strain energy of the vehicle body model in the first mode, and the second index may be the proportion of energy borne by the beam element out of the total strain energy of the vehicle body model in the second mode.

[0029] Let us consider a case where the internal force and moment are used as the first and second indices, respectively. In this case, the comparison targets for the first and second indices may change depending on the magnitude of the external force that causes the first and second modes, the input position of the external force, etc.

[0030] Furthermore, since internal force and moment are physical quantities of different dimensions, it is inconvenient to compare the importance and contribution of the first and second modes at a specific mounting location.

[0031] In contrast, according to the sixth aspect, both the first and second indices are the ratios (share rates) of the energy that the beam elements bear to the total strain energy. By using the ratios instead of the absolute values ​​of the energy, it becomes possible to make accurate judgments regardless of the magnitude of the external force that causes the first and second modes, the input positions of the external forces, etc.

[0032] Furthermore, according to the sixth aspect, both the first index and the second index are dimensionless, so that it becomes possible to more appropriately compare and consider them.

[0033] The seventh aspect relates to a vehicle structural design program that, when executed by a computer having a processor, identifies attachment locations of reinforcing members that ensure both bending rigidity and torsional rigidity.

[0034] According to the seventh aspect, the structural design program causes the computer to execute the following steps: placing beam elements at temporary attachment locations so as to connect fastening portions in a vehicle body model corresponding to the vehicle; deforming the vehicle body model by an external force so as to realize a first mode in which the vehicle body is twisted around a central axis extending in the fore-and-aft direction of the vehicle body, and acquiring a first index that increases as the internal force or moment acting on the beam element increases with the deformation of the vehicle body model; deforming the vehicle body model by an external force so as to realize a second mode in which a membrane vibrates the floor portion of the vehicle in the vehicle height direction, and acquiring a second index that increases as the internal force or moment acting on the beam element increases with the deformation of the vehicle body model; and, when the first index and the second index are both equal to or greater than a predetermined value, the processor determines the attachment location of the beam element and adopts the beam element as the reinforcing member. [Effects of the Invention]

[0035] As described above, according to the present disclosure, reinforcing members that ensure both bending rigidity and torsional rigidity can be disposed in appropriate locations within a vehicle. [Brief explanation of the drawings]

[0036] [Figure 1] FIG. 1 is a diagram illustrating an example of a hardware configuration of a structural design apparatus. [Figure 2] FIG. 2 is a diagram illustrating an example of the software configuration of the structural design apparatus. [Figure 3]FIG. 3 is a diagram illustrating an example of the vehicle body model data. [Figure 4] FIG. 4 is a diagram illustrating the reinforcement model data. [Figure 5A] FIG. 5A is a diagram illustrating bending deformation of a reinforcing member. [Figure 5B] FIG. 5B is a diagram illustrating torsional deformation of the reinforcing member. [Figure 6] FIG. 6 is a flowchart illustrating the procedure of the structural design method. [Figure 7] FIG. 7 is a diagram illustrating provisional settings of attachment locations and beam elements. [Figure 8A] FIG. 8A is a diagram illustrating the first mode. [Figure 8B] FIG. 8B is a diagram for explaining the second mode. [Figure 9] FIG. 9 is a diagram illustrating a determination map of the first index and the second index. [Figure 10] FIG. 10 is a graph showing the frequency response characteristics of Examples 1 and 2 and Comparative Examples 1 and 2. In FIG. [Figure 11] FIG. 11 is a diagram showing a reinforcing member according to a first modified example. [Figure 12] FIG. 12 is a diagram showing a reinforcing member according to a second modified example. DETAILED DESCRIPTION OF THE INVENTION

[0037] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. Note that the following description is for illustrative purposes only.

[0038] <1.Device configuration> FIG. 1 is a diagram illustrating an example of the hardware configuration of a structural design device according to the present disclosure (specifically, a computer 1 constituting the device), and FIG. 2 is a diagram illustrating an example of the software configuration thereof.

[0039] 1, the computer 1 includes a central processing unit (CPU) 3 that controls the entire computer 1, a read only memory (ROM) 5 that stores a boot program and the like, a random access memory (RAM) 7 that functions as a main memory, and a solid state drive (SSD) 9 that serves as a secondary storage device. Note that a hard disk drive (HDD) or the like can also be used as the secondary storage device instead of the SSD 9.

[0040] Of these elements, the CPU 3 executes various programs. The CPU 3 is an example of a "processor" in this embodiment. The RAM 7 and SSD 9 temporarily or continuously store the programs executed by the CPU 3. The RAM 7 and SSD 9 each function as a storage unit in this embodiment.

[0041] The computer 1 also includes a display 11, a graphics memory (Video RAM: VRAM) 13 that stores image data to be displayed on the display 11, and a keyboard 15 and a mouse 17 as man-machine interfaces. The keyboard 15 and the mouse 17 function as a reception unit that receives input from an operator. The display 11 functions as a display unit that displays a screen based on the results of calculations by the CPU 3. The computer 1 according to this embodiment can also send and receive data to and from external devices via a communication interface 21.

[0042] As illustrated in Figure 2, the program memory of SSD9 stores an operating system (OS) 19, a beam element setting program 291, a first index acquisition program 292, a second index acquisition program 293, an index determination program 294, and various application programs 39, etc.

[0043] Of these programs, the beam element setting program 291, the first index acquisition program 292, the second index acquisition program 293, and the index determination program 294 constitute a structural design program 29 in this embodiment.

[0044] Here, the structural design program 29 is a program for executing the structural design method according to this embodiment, and is configured to cause the computer 1 to execute each step constituting the method. The structural design program 29 is pre-stored in a computer-readable storage medium 18. This storage medium 18 is a tangible storage medium constituted by a disk medium or the like.

[0045] In the program memory of the SSD 9, each program constituting the structural design program 29 is started in response to a command input from the keyboard 15, mouse 17, etc. At that time, each program is loaded from the SSD 9 into the RAM 7 and executed by the CPU 3.

[0046] Meanwhile, the data memory of SSD 9 stores vehicle body model data 49 and reinforcement model data 59. The vehicle body model data 49 is data that is read at the start of the structural design method. The reinforcement model data 59 is data that is generated and stored as needed during the structural design method.

[0047] The vehicle body model data 49 represents a vehicle body model 61 corresponding to the vehicle to be analyzed (see FIG. 3). The vehicle body model data 49 is object data in which each part constituting the vehicle is meshed to support, for example, the finite element method. Of the mesh structure of the vehicle body model data 49, portions 61a, 61b, and 61c related to the joint Pc described below are extracted and shown in FIG. 3.

[0048] The vehicle according to this embodiment is a four-wheeled automobile with two front wheels and two rear wheels. Furthermore, the vehicle analyzed in the specific examples described below is an ICE vehicle powered by an internal combustion engine (ICE). However, the present disclosure is not limited to application to ICE vehicles. The present disclosure can also be applied to electric vehicles powered by a motor alone, hybrid vehicles powered by both a motor and an engine, and the like.

[0049] As shown in Fig. 4, the reinforcement model data 59 is data that models a reinforcement member 101. The reinforcement member 101 is modeled as a beam element 62 in the finite element method to support the finite element method. The beam element 62 is, for example, a beam-shaped element connecting two nodes 62a. The reinforcement member 101 is a member at least a portion of which is configured to be elongated.

[0050] The reinforcing member 101 in this embodiment is configured as an elongated member whose longitudinal and lateral directions can be defined, similar to the beam element 62 that models it. The reinforcing member 101 is a member that ensures bending rigidity and torsional rigidity. In this embodiment, the reinforcing member 101 is a member made of a polymer material.

[0051] Specifically, the reinforcing member 101 is a fiber-reinforced resin member in which a plurality of reinforcing fibers 101a are blended and polymer resin 101b is impregnated between the reinforcing fibers 101a (see FIG. 4). Of the reinforcing fibers 101a, the proportion of the reinforcing fibers 101a oriented in a predetermined first direction A1 is greater than the proportion of the reinforcing fibers 101a oriented in other directions.

[0052] More specifically, the fiber reinforced resin constituting the reinforcing member 101 is a CFRP (Carbon Fiber Reinforced Plastics) that uses carbon fiber as the reinforcing fiber 101a and epoxy resin, for example, as the polymer resin 101b.

[0053] Furthermore, in relation to the bending rigidity of the reinforcing member 101 and, by extension, the suppression of torsional deformation of the vehicle obtained by the bending rigidity, the first direction A1 is set to extend parallel to a plane along the longitudinal direction and the width direction of the vehicle body. In particular, the first direction A1 according to this embodiment is set to coincide with the longitudinal direction of the reinforcing member 101. That is, the longitudinal direction of the reinforcing member 101 according to this embodiment extends parallel to a plane along the longitudinal direction and the width direction of the vehicle body. By orienting many reinforcing fibers 101a along the first direction A1, bending in a direction bending relative to the first direction A1, as illustrated in FIG. 5A, is suppressed.

[0054] The first direction A1 can be referred to as the "fiber direction." In the examples of FIGS. 4, 5A, and 5B, the first direction A1 can also be simply referred to as the "longitudinal direction." In this case, the short-side direction of the reinforcing member 101 corresponds to the direction in which the beam element 62 is sheared. Hereinafter, this direction will also be referred to as the second direction A2.

[0055] Furthermore, the parameters characterizing the material properties of the reinforcing member 101 are each set within a specific range. In detail, first, the longitudinal elastic modulus of the reinforcing member 101 in the first direction A1 is defined as E [MPa], the transverse elastic modulus of the reinforcing member 101 in the direction perpendicular to the first direction A1 (second direction A2) is defined as G [MPa], and the cross-sectional area of ​​the reinforcing member 101 in the cross-sectional view perpendicular to the first direction A1 is defined as A [mm 2 ], and the second moment of area of ​​the reinforcing member 101 in the vehicle height direction is I1 [mm 4 ], and the second moment of area of ​​the reinforcing member 101 in the direction perpendicular to the vehicle height direction and the first direction A1 is I2 [mm 4 ], Poisson's ratio is ν, and the torsional constant is J. Here, the torsional constant is the Saint-Venant torsional constant.

[0056] Regarding the above parameters, the reinforcing member 101 of this embodiment is configured to satisfy all of the following conditions (A), (B), (C), and (D) so that the reinforcing member 101 itself does not contribute to the deformation of the first and second modes.

[0057] E·A≦1000[N] …(A) E·I1≦1000 [N·mm 2 ] …(B) E·I2≦1000 [N·mm 2 ] …(C) G·J≦385 [N·mm 2 ] …(D) However, the transverse elastic modulus G in the condition (D) is calculated based on the following formula (E).

[0058] G=E / (2·(1+ν)) …(E) For example, the index (first index) shown on the left side of condition (A) indicates the resistance to deformation in the tensile direction (first direction A1). The index (second index) shown on the left side of condition (B) indicates the resistance to bending in the vehicle height direction. The index (third index) shown on the left side of condition (C) indicates the resistance to bending in a direction perpendicular to the vehicle height direction and the tensile direction. The index (fourth index) shown on the left side of condition (D) indicates the resistance to deformation in a torsional direction with the tensile direction as the axis.

[0059] For each of these first to fourth indices, the larger the value, the less likely the corresponding deformation will occur. By setting upper limits for these indices, when an external force is applied to the vehicle, the reinforcing member 101 itself can be prevented from affecting the deformation of the car body model 61 caused by the external force.

[0060] Furthermore, the torsional rigidity of the reinforcing member 101, and therefore the vibration damping performance of the vehicle obtained by the torsional rigidity, is ensured by the polymer resin 101b between the reinforcing fibers 101a.

[0061] For example, consider the case where the first direction A1 coincides with the longitudinal direction of the reinforcing member 101 as described above. In this case, when the reinforcing member 101 twists, the polymer resin 101b between the reinforcing fibers 101a is distorted. This distortion damps the twisting of the reinforcing member 101 and, ultimately, the vibration of the vehicle. This damping is particularly effective when the reinforcing member 101 twists in the arrangement direction of the reinforcing fibers 101a, i.e., in the second direction A2 as shown in FIG. 5B.

[0062] In relation to vibration damping performance, the reinforcing member 101 according to this embodiment is configured so that its loss factor (tan δ) is specifically 0.015 or more, and more specifically 0.02 or more.

[0063] <2. Outline of structural design method> FIG. 6 is a flowchart illustrating the steps of a structural design method. This structural design method is a method for identifying an attachment site P0 of a reinforcing member 101. Note that FIG. 6 is merely a simplified example. For example, the order of steps S2 and S3 may be reversed, or steps S2 and S3 may be performed in parallel. For details about the attachment site P0, see FIG. 7 described below.

[0064] As shown in Figure 3, the structural design method is implemented by sequentially executing a beam element setting process (step S1), a first index acquisition process (step S2), a second index acquisition process (step S3), and an index determination process (step S4).

[0065] The structural design program 29 is configured to cause the computer 1 to execute these processes. That is, of these processes, the beam element setting process is performed by the CPU 3 executing the beam element setting program 291 described above, and the first index acquisition process is performed by the CPU 3 executing the first index acquisition program 292 described above. Similarly, the second index acquisition process is performed by the CPU 3 executing the second index acquisition program 293, and the index determination process is performed by the CPU 3 executing the index determination program 294.

[0066] When the CPU 3 executes the beam element setting program 291 etc., a structural design device is configured by the computer 1. That is, the computer 1 functions as a structural design device including a beam element setting means that executes a beam element setting process, a first index acquisition means that executes a first index acquisition process, a second index acquisition means that executes a second index acquisition process, and an index determination means that executes an index determination process.

[0067] <3. Details of structural design method> (3-1. Beam element setting process) First, in step S1, the CPU 3 executes a beam element setting process. In the beam element setting process, the CPU 3 sets beam elements 62 at the temporary attachment sites P0 so as to connect the fastening portions Pc in the vehicle body model 61 to each other.

[0068] Specifically, the CPU 3 first reads the vehicle body model data 49 from the SSD 9 and displays the vehicle body model 61 on the display 11 as a display unit. The CPU 3 places a beam element 62 at the temporary attachment site P0 based on, for example, an input received by a receiving unit (at least one of the keyboard 15 and the mouse 17).

[0069] The fastening parts Pc connected by the beam elements 62 refer to parts that can be fastened with fasteners such as bolts among the constituent parts of the car body model 61. Each fastening part Pc may be a part that is bolted up.

[0070] For example, as shown in FIG. 3, the fastening portion Pc may be provided on a strut tower 61a that connects the upper ends of the left and right suspensions, or on a floor panel 61b, or on a dash panel 61c.

[0071] In addition, the beam element 62 may be arranged to connect the fastening portion Pc of one part to the fastening portion Pc of another part, or to connect the fastening portion Pc of one part to the fastening portion Pc of the same part.

[0072] The example in FIG. 7 corresponds to the latter arrangement. In FIG. 7, both of the two fastening parts Pc are provided on the underside of the floor panel 61b of the vehicle body model 61. Three or more fastening parts Pc may be set. As shown in a modified example described later, the shape of the beam element 62 may be changed depending on the number of fastening parts Pc.

[0073] Furthermore, the setting of the shape of the beam element 62 and the setting of the attachment site P0 corresponding to the beam element 62 may be specified by the user each time, or the CPU 3 may read a data set that has been set in advance.

[0074] When the placement of the beam elements 62 (setting of the attachment site P0) is completed, the CPU 3 stores in the storage unit (RAM 7 or SSD 9) the placement of the beam elements 62. The control process proceeds from step S1 to step S2 in FIG.

[0075] (3-2. First indicator acquisition process) In the following step S2, the CPU 3 executes a first index acquisition process. In the first index acquisition process, the CPU 3 deforms the vehicle body model 61 by an external force so as to realize a first mode M1 as a vehicle body deformation mode, and acquires a first index I1 that increases as the internal force or moment acting on the beam elements 62 increases with the deformation of the vehicle body model 61 in the first mode M1. The vehicle body model 61 to be deformed is the vehicle body model 61 in a state in which the beam elements 62 are arranged.

[0076] The first mode M1 is a vehicle body deformation mode in which the vehicle body is twisted around a central axis Ac extending in the vehicle body longitudinal direction, as illustrated in Fig. 8A. The vehicle body longitudinal direction here refers to the direction in which the vehicle body model 61 moves forward or backward, as shown in Fig. 8A. The first mode M1 affects the handling and stability performance of the vehicle.

[0077] In detail, the first mode M1 in this embodiment is realized by fixing the two damper apexes located on the rear wheel side (see the triangle marks on the rear wheel side in Figure 8A), fixing the center of the bumper reinforcement at the front of the vehicle body (see the triangle mark on the front wheel side in Figure 8A), and applying weights in opposite vertical directions (see arrows in Figure 8A) to one and the other of the two damper apexes located on the front wheel side.

[0078] The CPU 3 also acquires the first index I1. The first index I1 is, for example, the internal force of the beam element 62. As described above, when the first direction A1 is aligned with the longitudinal direction of the reinforcing member 101, the first index I1 is determined based on the internal force acting in the first direction A1 out of the internal force and the moment. In this case, the first index I1 increases as the internal force acting in the first direction increases.

[0079] Specifically, the first index I1 according to this embodiment is the energy contribution rate of the beam elements 62 to the total strain energy of the vehicle body model 61 in the first mode M1. This energy contribution rate is derived from the strain energy caused by the internal force of the beam elements 62.

[0080] Once the first index I1 is obtained, the control process proceeds to step S3 of FIG.

[0081] (3-3. Second indicator acquisition process) In the following step S3, the CPU 3 executes a second index acquisition process. In the second index acquisition process, the CPU 3 deforms the vehicle body model 61 by an external force so as to realize a second mode M2 ​​as a vehicle body deformation mode, and acquires a second index I2 that increases as the internal force or moment acting on the beam elements 62 increases with the deformation of the vehicle body model 61 in the second mode M2. The vehicle body model 61 to be deformed is the vehicle body model 61 in a state in which the beam elements 62 are arranged.

[0082] The second mode M2 ​​is a vehicle body deformation mode that causes membrane vibration of the floor portion (e.g., floor panel 61b) of the vehicle body model 61 in the vehicle height direction, as shown in Fig. 8B. Note that the vehicle body longitudinal direction here refers to the height direction (i.e., the up-down direction) of the vehicle body model 61, as shown in Fig. 8B. The second mode M2 ​​affects the ride comfort performance of the vehicle.

[0083] Specifically, the second mode M2 ​​according to this embodiment is a vehicle body deformation mode realized by so-called inertial relief analysis. The second mode M2 ​​is related to the vibration of the vehicle body model 61 relative to the road surface F on which the vehicle is placed. The second mode M2 ​​is realized by applying a load to the road surface F that causes the floor panel 61b to vibrate up and down.

[0084] The CPU 3 also acquires the second index I2. The second index I2 is, for example, a moment (particularly, a moment of force) acting on the beam element 62. As described above, when the first direction A1 is aligned with the longitudinal direction of the reinforcing member 101, the second index I2 is determined based on the torsional moment around the first direction A1. Here, the "torsional moment around the first direction A1" refers to a moment that twists the beam element 62 in the direction that shears the beam element 62 (the second direction A2). In this case, the second index I2 increases as the torsional moment around the first direction A1 increases.

[0085] More specifically, the second index I2 according to this embodiment is the energy contribution rate of the beam elements 62 to the total strain energy of the vehicle body model 61 in the second mode M2. This energy contribution rate is derived from the strain energy caused by the moment acting on the beam elements 62.

[0086] Once the second index I2 is obtained, the control process proceeds to step S4 of FIG.

[0087] (3-4. Indicator Judgment Process) In the next step S4, the CPU 3 executes an index determination process. In the index determination process, if the first index I1 and the second index I2 are both equal to or greater than a predetermined value, the CPU 3 determines the attachment position P0 of the beam element 62 and adopts the beam element 62 as the reinforcing member 101.

[0088] In step S4, when both the first index I1 is equal to or greater than the first threshold value T1 and the second index is equal to the second threshold value T2 are satisfied, the CPU 3 determines the mounting location P0 of the beam element 62. Hereinafter, the condition for determining the mounting location P0 is also referred to as the specific condition Cs (see the formula shown in the upper right corner of FIG. 9).

[0089] The determination in step S4 can be made using a model or map that uses the first index I1 and the second index I2 as input.

[0090] Fig. 9 shows an example of a configuration when a determination map 79 is used. The determination map 79 is stored in advance in the SSD 9 as shown in Fig. 2. The boundary line Lr in Fig. 9 indicates the boundary where the first index I1 is equal to or greater than the first threshold value T1 and the second index I2 is equal to or greater than the second threshold value T2, that is, the boundary where the specific condition Cs is satisfied. This boundary line Lr is a set of the first threshold value T1 and the second threshold value T2 that change continuously.

[0091] As shown in the determination map 79 of FIG. 9, the boundary line Lr may be defined so that the larger the first index I1, the smaller the second threshold T2, and so that the larger the second index I2, the smaller the first threshold T1.

[0092] The determination map 79 is divided by the boundary line Lr into a first region R1 where the specific condition Cs is not satisfied and a second region R2 where the specific condition Cs is satisfied. Each plot in the determination map 79 corresponds to the tentative attachment site P0 set in step S1.

[0093] For example, the circle plots on the determination map 79 indicate a set of configurations in which the first index I1 and the second index I2 corresponding to the tentative attachment site P0 do not satisfy the specific condition Cs and are determined to belong to the first region R1. In this case, the CPU 3 does not adopt the beam element 62 corresponding to the attachment site P0 as the reinforcing member 101.

[0094] On the other hand, the rectangular plots in the determination map 79 indicate a set of configurations determined to belong to the second region R2 because the first index I1 and the second index I2 corresponding to the tentative attachment site P0 satisfy the specific condition Cs. In this case, the CPU 3 adopts the beam element 62 corresponding to the attachment site P0 as the reinforcing member 101.

[0095] When the attachment position P0 of the beam element 62 is determined, the CPU 3 determines and outputs the beam element 62 located at the attachment position P0, and further the reinforcing member 101 corresponding to the beam element 62, as the identification result.

[0096] <4. Example of structural design method> Reinforcing members 101 were prepared in Examples 1 and 2 and Comparative Examples 1 and 2 shown below. The configuration of each example is also shown in Table 1. The inventors of the present application then examined the ease of deformation of the reinforcing member 101 itself in Examples 1 and 2 and Comparative Example 2, and verified the appropriateness of the above conditions (A) to (D).

[0097] In the following Examples 1 and 2 and Comparative Examples 1 and 2, the material properties and part shapes other than the parameters related to the first to fourth indices are all common. For example, the shapes of the vehicle model 61 and the reinforcing member 101 are fixed to a common shape in all of the following Examples 1 and 2 and Comparative Examples 1 and 2.

[0098] Example 1 In Example 1, the longitudinal elastic modulus (Young's modulus) E was 0.01 [MPa], the first index (=E·A) was 0.01 [N], and the second index (=E·I1) was 0.01 [N·mm 2 ] and the third index (=E·I2) is 0.01 [N·mm 2] and the fourth index (= G·J) is 0.00385 [N·mm 2 ].

[0099] Example 2 In Example 2, the longitudinal elastic modulus (Young's modulus) E is 1000 [MPa], the first index (= E·A) is 1000 [N], and the second index (= E·I1) is 1000 [N·mm 2 ] and the third index (=E·I2) is 1000 [N·mm 2 ] and the fourth index (= G·J) is 385 [N·mm 2 Example 2 corresponds to an example on the boundary between conditions (A) to (D).

[0100] -Comparative Example 1- In Comparative Example 1, the longitudinal elastic modulus (Young's modulus) E was 3000 [MPa], the first index (=E·A) was 3000 [N], and the second index (=E·I1) was 3000 [N·mm 2 ] and the third index (=E·I2) is 3000 [N·mm 2 ] and the fourth index (= G·J) is 1155 [N·mm 2 ].

[0101] -Comparative Example 2- In Comparative Example 2, the longitudinal elastic modulus (Young's modulus) E was 5000 [MPa], the first index (=E·A) was 5000 [N], and the second index (=E·I1) was 5000 [N·mm 2 ] and the third index (=E·I2) is 5000 [N·mm 2 ] and the fourth index (= G·J) is 1925 [N·mm 2 ].

[0102] [Table 1]

[0103] (Evaluation method) Beam elements 62 corresponding to each reinforcing member 101 prepared as described above were placed at the same mounting position P0 of the same vehicle body model 61. An external force was then applied to each vehicle body model 61 on which the beam elements 62 were placed, and the acceleration generated in the vehicle body model 61 was evaluated. The evaluation results are shown in FIG. 10.

[0104] Fig. 10 is a graph showing the frequency response characteristics of Examples 1 and 2 and Comparative Examples 1 and 2. In detail, Fig. 10 shows the frequency response characteristics of the acceleration occurring in each vehicle body model 61 for each of Examples 1 and 2 and Comparative Examples 1 and 2. Fig. 10 also shows an extracted portion Ra2 obtained by cutting out and enlarging the characteristic portion Ra1 of Fig. 10, superimposed thereon.

[0105] Here, in Example 1, the first to fourth indices are all set near the lower limits. The first to fourth indices of Example 1 are smaller than the first to fourth indices of Example 2, Comparative Example 1, and Comparative Example 2. The reinforcing member 101 corresponding to Example 1 is more easily deformed than the reinforcing members 101 corresponding to the other examples because the first to fourth indices are smaller. The reinforcing member 101 corresponding to Example 1 can be considered to make substantially no contribution to the deformation of each of the first and second modes M1 and M2 (deformation contribution: none).

[0106] On the other hand, as shown in Table 1, the first to fourth indexes of Example 2 are respectively smaller than the first to fourth indexes of Comparative Example 1. The first to fourth indexes of Comparative Example 1 are respectively smaller than the first to fourth indexes of Comparative Example 2.

[0107] As described above, the first to fourth indices indicate the resistance to deformation of the reinforcing member 101 in the corresponding direction. Therefore, the reinforcing member 101 itself becomes less likely to deform in the order of Example 1, Example 2, Comparative Example 1, and Comparative Example 2. If the reinforcing member 101 itself is less likely to deform, this may become a resistance to deformation in each of the first and second modes M1 and M2.

[0108] The reinforcing member 101 in Example 1 is relatively easy to deform itself, and does not provide resistance to the deformations of the first and second modes M1 and M2. Here, the acceleration waveform in Example 2 substantially matches the acceleration waveform in Example 1. In contrast, the acceleration waveforms in Modifications 1 and 2 are significantly separated in the frequency direction from the acceleration waveforms in Examples 1 and 2. Furthermore, the separation direction shifts the frequency characteristics toward the high frequency side.

[0109] In other words, it is considered that the rigidity of the vehicle body model 61 in Comparative Examples 1 and 2 is significantly increased compared to Examples 1 and 2, which has shifted the acceleration waveform to the higher frequency side. In the cases of Comparative Examples 1 and 2, it can be interpreted that the rigidity of the reinforcing member 101 itself contributes significantly to the deformation of each of the first and second modes M1 and M2 (large contribution to deformation).

[0110] On the other hand, in Example 2, the rigidity of the vehicle body model 61 is not as increased as in Comparative Examples 1 and 2, which is thought to be why the acceleration waveform did not shift significantly. In the case of Example 2, it can be interpreted that the rigidity of the reinforcing member 101 itself does not contribute to the deformation of each of the first and second modes M1 and M2 (deformation contribution: small), as in Example 1.

[0111] <5. Significance of structural design methods> As shown in Figure 8A, the first mode M1 corresponds to a so-called vehicle body torsion mode, while as shown in Figure 8B, the second mode M2 ​​corresponds to a so-called membrane vibration mode.

[0112] 6 and 9, when the condition (specific condition Cs) that the first index I1 and the second index I2 are each equal to or greater than a predetermined value is satisfied, the CPU 3 as a processor adopts the beam element 62 in that case as the reinforcing member 101. Here, satisfying the specific condition Cs means that the external forces that try to bend and twist the beam element 62 located at the temporary mounting site P0 are both relatively high.

[0113] In other words, the mounting location P0 that satisfies the specific condition Cs is a location where reinforcement in terms of both bending rigidity and torsional rigidity is important, and it can be said that this is the mounting location P0 where the aforementioned reinforcing member 101 can maximize its function and effect.

[0114] Therefore, by employing the beam element 62 attached to such an attachment position P0 as the reinforcing member 101, the reinforcing member 101 can be disposed at an appropriate position in the vehicle. This makes it possible to simultaneously achieve, with a single reinforcing member 101, improvement in vehicle handling stability due to suppression of the body torsion mode and improvement in vehicle ride comfort due to suppression of the membrane vibration mode.

[0115] 4, by relatively increasing the proportion of reinforcing fibers 101a oriented in the first direction A1, the bending rigidity of the reinforcing member 101 in this first direction A1 (fiber direction) can be ensured. Furthermore, by impregnating the spaces between the reinforcing fibers 101a with polymer resin 101b, when the reinforcing member 101 is twisted in a second direction A2 (the direction in which the reinforcing fibers 101a are aligned and in which the reinforcing fibers 101a are sheared) perpendicular to the first direction A1, the polymer resin 101b located between the reinforcing fibers 101a is effectively strained. This strain ensures the torsional rigidity of the reinforcing member 101.

[0116] Thus, while bending rigidity is ensured in the first direction A1, torsional rigidity is ensured in the second direction A2 different from the first direction A1, thereby realizing physical properties suitable for the reinforcing member 101.

[0117] 4, the reinforcing fibers 101a are oriented along the longitudinal direction of the long portion of the reinforcing member 101. This allows the reinforcing member 101 to have excellent bending rigidity.

[0118] Furthermore, according to the findings obtained as a result of extensive research by the inventors of the present application, when all of the above-mentioned conditions (A) to (D) are satisfied, the reinforcing member 101 itself does not contribute to the deformation of the first and second modes M1 and M2.

[0119] This makes it possible to suppress the influence of deformation of the reinforcing member 101, and in turn, the beam element 62 corresponding to the reinforcing member 101, on the search for the attachment site P0. In other words, the influence of deformation of the reinforcing member 101 itself would become noise when searching for the attachment site P0, but by setting it from the beginning so that it does not contribute to deformation, it is possible to eliminate the influence of such noise as much as possible. This makes it possible to search for the attachment site P0 with high accuracy.

[0120] Furthermore, let us consider a case where the internal force and moment are used as the first and second indices I1 and I2, respectively. In this case, the comparison targets (first threshold T1, second threshold T2) for the first and second indices I1 and I2 may change depending on the magnitude of the external force that causes the first mode M1 and the second mode M2, the input position of the external force, etc.

[0121] Furthermore, since internal force and moment are physical quantities of different dimensions, it is inconvenient to compare the importance and contribution of the first mode M1 and the second mode M2 ​​at a specific mounting location P0.

[0122] In contrast to this, according to the embodiment, both the first index I1 and the second index I2 are the ratio (share rate) of the energy shared by the beam element 62 with respect to the total strain energy. By using the ratio instead of the absolute value of the energy, it becomes possible to make an accurate determination regardless of the magnitude of the external force that causes the first mode M1 and the second mode M2, the input position of the external force, etc.

[0123] Furthermore, since both the first index I1 and the second index I2 are dimensionless, it becomes possible to more appropriately compare and consider them.

[0124] <6. Modified Examples of Reinforcing Members> In the above embodiment, as shown in FIG. 4, a configuration is exemplified in which the fiber direction of the reinforcing fibers 101a is aligned with the longitudinal direction (first direction A1) of the reinforcing member 101, but the present disclosure is not limited to such a configuration.

[0125] Fig. 11 shows a reinforcing member 101' according to a first modified example. As shown in Fig. 11, the fiber direction of the reinforcing fibers 101a may be inclined with respect to the longitudinal direction of the reinforcing member 101. In this case, the inclination angle may be, for example, 45°.

[0126] 11, the bending stiffness of the reinforcing member 101', and therefore the torsional resistance of the vehicle that is achieved by that bending stiffness, is primarily related to internal forces acting in the second direction A2, not the first direction A1. The reinforcing member 101' resists bending in a direction that bends relative to the second direction A2.

[0127] In this case, the damping of vehicle vibrations is particularly pronounced in the direction in which the reinforcing fibers 101a' in the modified example are arranged, i.e., when twisted in the first direction A1 (twisted around the second direction A2) as illustrated in Figure 11.

[0128] Furthermore, the shape of the reinforcing member 101 may be changed depending on the number of fastening portions Pc connected by one reinforcing member 101. FIG. 12 shows a reinforcing member 101" according to a second modified example. For example, if the number of connecting portions Pc is four instead of two as in the above embodiment, a reinforcing member 101" having a cross shape may be used as shown in FIG. 12.

[0129] In this case, the beam element 62" corresponding to the reinforcing member 101" according to the second modified example is a beam-shaped, cross-shaped element connecting four nodes 62a". By using the beam element 62" according to the second modified example instead of the beam element 62 in FIG. 7, symmetrical reinforcement in the vehicle width direction can be achieved. This allows various performances to be improved in a balanced manner.

[0130] The reinforcing member 101" according to the second modified example can be considered to have four long sections branched in a cross shape. Furthermore, a connection section 101c" for bolting up is provided at the tip of each long section. Each connection section 101c" can be fastened to the corresponding fastening section Pc by means of a fastening tool such as a bolt.

[0131] 5A and 5B, the reinforcing member 101 according to the embodiment also has a connecting portion 101c for bolting at the tip of its long portion. As in the second modification, each connecting portion 101c can be fastened to a corresponding fastening portion Pc by means of a fastener such as a bolt.

[0132] <7. Other embodiments> Furthermore, although the above embodiment illustrates a configuration implemented by one computer 1, the present disclosure is not limited to this example. The structural design method and structural design program 29 according to the present disclosure may be executed using multiple computers 1, such as by having a first computer execute some processes and a second computer execute other processes. Furthermore, the computer 1 in the present disclosure also includes parallel computers such as supercomputers and PC clusters.

[0133] Furthermore, the display unit used for various displays is not limited to the display 11 of the computer 1. Various information may be displayed on a screen prepared separately from the computer 1. [Explanation of symbols]

[0134] 1 Computer (structural design device) 3 CPU (processor) 7 RAM (memory section) 9 SSD (storage unit) 11 Display (display unit) 15 Keyboard (reception area) 17 Mouse (Reception) 18 Storage medium 29 Structural Design Program 291 Beam element setting program 292 First Index Acquisition Program 293 Second Index Acquisition Program 294 Index Judgment Program 61 Car Model 61a Floor panel (floor part) 62 Beam element 101 Reinforcement member 101a Reinforced Fiber 101b Polymer resin Ac central axis A1 1st direction I1 1st indicator I2 Second indicator M1 First mode M2 Second mode P0 Mounting location PC fastening part T1 First threshold T2 Second threshold S1 Beam element setting process S2 First indicator acquisition process S3 Second indicator acquisition process S4 Index Judgment Process

Claims

1. A vehicle structural design method that is executed by a computer having a processor to identify attachment locations of reinforcing members that ensure bending rigidity and torsional rigidity, the method comprising: The processor places beam elements at temporary attachment locations so as to connect fastening portions in a vehicle body model corresponding to the vehicle; the processor deforms the vehicle body model by an external force so as to realize a first mode in which the vehicle body is twisted around a central axis extending in a longitudinal direction of the vehicle body, and acquires a first index that increases as an internal force or a moment acting on the beam element increases with the deformation of the vehicle body model; the processor deforms the vehicle body model by an external force so as to realize a second mode in which a membrane vibrates a floor portion of the vehicle in a vehicle height direction, and acquires a second index that increases as an internal force or a moment acting on the beam element increases with the deformation of the vehicle body model; and when the first index and the second index are both equal to or greater than a predetermined value, the processor determines an attachment location of the beam element and employs the beam element as the reinforcing member. A vehicle structural design method comprising:

2. 2. The vehicle structural design method according to claim 1, the reinforcing member is a fiber-reinforced resin member in which a plurality of reinforcing fibers are blended and a polymer resin is impregnated between the plurality of reinforcing fibers, The ratio of the reinforcing fibers oriented in a predetermined first direction is greater than the ratio of the reinforcing fibers oriented in other directions. A vehicle structural design method comprising:

3. 3. The vehicle structural design method according to claim 2, the internal force is an internal force acting in the first direction, The moment is a torsional moment about the first direction. A vehicle structural design method comprising:

4. 4. The vehicle structural design method according to claim 3, At least a portion of the reinforcing member is configured to be elongated, The first direction is the longitudinal direction of the reinforcing member. A vehicle structural design method comprising:

5. 5. The vehicle structural design method according to claim 4, the first direction is a direction extending parallel to a plane along the vehicle body longitudinal direction and the vehicle width direction, The longitudinal elastic modulus of the reinforcing member in the first direction is E [MPa], the transverse elastic modulus of the reinforcing member in a direction perpendicular to the first direction is G [MPa], and the cross-sectional area of ​​the reinforcing member in a cross-sectional view perpendicular to the first direction is A [mm ２ ], and the moment of inertia of the reinforcing member in the vehicle height direction is I1 [mm ４ ], and the second moment of area of ​​the reinforcing member in the direction perpendicular to the vehicle height direction and the first direction is I2 [mm ４ ], Poisson's ratio is ν, and torsional constant is J, The reinforcing member is configured to satisfy all of the following conditions (A), (B), (C), and (D) so that the reinforcing member itself does not contribute to the deformation of the first and second modes. E・A≦1000[N]…(A) E・I1≦1000[N・mm ２ ] …(B) E・I2≦1000[N・mm] ２ ] …(C) G・J≦385[N・mm ２ ] …(D) A vehicle structural design method comprising: However, the transverse elastic modulus G in the condition (D) is calculated based on the following formula (E). G=E / (2・(1+ν))…(E)

6. 2. The vehicle structural design method according to claim 1, the first index is a share of energy borne by the beam element in the total strain energy of the vehicle body model in the first mode, The second index is a ratio of the energy shared by the beam element to the total strain energy of the vehicle body model in the second mode. A vehicle structural design method comprising:

7. A vehicle structural design program that, when executed by a computer having a processor, identifies attachment locations of reinforcing members that ensure bending rigidity and torsional rigidity, The computer, placing beam elements at temporary attachment locations so as to connect fastening portions in a vehicle body model corresponding to the vehicle; a step of deforming the vehicle body model by an external force so as to realize a first mode in which the vehicle body is twisted around a central axis extending in a longitudinal direction of the vehicle body, and acquiring a first index that increases as an internal force or moment acting on the beam element increases with the deformation of the vehicle body model; the processor deforms the vehicle body model by an external force so as to realize a second mode in which a membrane vibrates a floor portion of the vehicle in a vehicle height direction, and acquires a second index that increases as an internal force or a moment acting on the beam element increases with the deformation of the vehicle body model; the processor executes a step of determining an attachment portion of the beam element and adopting the beam element as the reinforcing member when both the first index and the second index are equal to or greater than a predetermined value. A vehicle structural design program characterized by:

Images