Underrun protector mounting structure

Abstract

To suppress increase of shear input to a bolt while suppressing a large-scale change of a constitution and cost increase.SOLUTION: In an attachment structure 10 of an underrun protector, being the attachment structure of the underrun protector 13 attached to a side rail 11 via a stay 12 which is fastened to the side rail 11 of a truck 1, the stay 12 has a plurality of attachment holes 120 at a portion which is fastened to the side rail 11, and is fastened to the side rail 11 by the insertion of bolts into the plurality of attachment holes 120, and hole diameters of the plurality of attachment holes 120 are set on the basis of shear input to the corresponding bolt at the generation of input for moving the underrun protector 13.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] One aspect of the present invention relates to a mounting structure for an underrun protector. [Background technology]

[0002] Patent Document 1 describes a vehicle body frame structure equipped with an underrun protector. Specifically, it discloses a structure in which an underrun protector is attached to a side rail formed with a U-shaped cross section by a web, an upper flange, and a lower flange via a stay extending downward. In this structure, the stay is bolted to the side rail. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-152128 A Summary of the Invention [Problem to be solved by the invention]

[0004] When an input force that moves the underrun protector occurs, the stay attempts to rotate, increasing the shear input force to the bolts that fasten the stay. To deal with this increased shear input force to the bolts, it is possible to take measures such as increasing the bolt diameter, increasing the strength of the bolts, or increasing the number of bolts.

[0005] However, when the bolt diameter is increased, the diameter of the grid holes in the side rail must be changed, which results in a large-scale change in the configuration. When the bolt strength is increased, the cost of parts increases, which is a problem. When the number of bolts is increased, the layout of the peripheral components of the underrun protector must be changed, which results in a large-scale change in the configuration.

[0006] One aspect of the present invention has been made in consideration of the above-mentioned situation, and aims to suppress an increase in shear input to a bolt while suppressing large-scale changes to the configuration and cost increases. [Means for solving the problem]

[0007] One aspect of the present invention relates to an underrun protector mounting structure, which is mounted to a side rail of a vehicle via a stay fastened to the side rail, and the stay has a plurality of mounting holes in a portion fastened to the side rail and is fastened to the side rail by inserting bolts into the plurality of mounting holes, and the hole diameter of each of the plurality of mounting holes is set based on the shear input to the corresponding bolt when an input occurs that moves the underrun protector.

[0008] In the mounting structure for an underrun protector according to one aspect of the present invention, the diameter of the mounting hole in the stay into which the fastening bolt is inserted is set based on the shear input applied to the bolt when the underrun protector moves. Usually, the smaller the hole diameter, the earlier the timing of contact between the stay and the bolt, and the larger the shear input applied to the corresponding bolt. In view of this, for example, by making the hole diameter larger for the mounting hole that receives a larger shear input applied to the corresponding bolt, the timing of contact with the stay is delayed for the bolt with a relatively large shear input, and the timing of contact with the stay is earlier for the bolt with a relatively small shear input, thereby suppressing the variation in the shear input of each bolt and suppressing the occurrence of a bolt with an excessively large shear input. And, by adopting a configuration that simply adjusts the hole diameter of the mounting hole of the stay in this way, it is possible to suppress the large-scale change in the configuration and the increase in cost as described as the conventional technology. As described above, according to the mounting structure for an underrun protector according to one aspect of the present invention, it is possible to suppress the increase in the shear input to the bolt while suppressing the large-scale change in the configuration and the increase in cost.

[0009] The hole diameter of each of the multiple mounting holes is set according to the distance from the rotation center of the stay that rotates based on the input that moves the underrun protector, and may be set larger as the distance from the rotation center increases. Considering the rotation moment, the bolt corresponding to the mounting hole that is farther away from the rotation center of the stay will have a larger shear input. Therefore, by making the hole diameter of the multiple mounting holes larger as the distance from the rotation center increases, the timing of contact with the stay will be delayed for bolts with a relatively large shear input, and the timing of contact with the stay will be advanced for bolts with a relatively small shear input, thereby suppressing the variation in shear input among the bolts and preventing the occurrence of bolts with an excessively large shear input. Effect of the Invention

[0010] According to one aspect of the present invention, it is possible to suppress an increase in shear input to a bolt while suppressing large-scale changes to the configuration and an increase in cost. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram showing a schematic diagram of a truck including an underrun protector mounting structure according to the present embodiment. [Diagram 2] FIG. 2 is a diagram illustrating a mounting structure of the underrun protector of FIG. [Diagram 3] FIG. 3 is a diagram for explaining moment balance. [Figure 4] FIG. 4 is a diagram illustrating the relationship between the distance from the center of rotation and the shear input to the bolt. [Diagram 5] FIG. 5 is a graph showing the shear input to each bolt. [Figure 6] FIG. 6 is a diagram showing a schematic diagram of setting the hole diameter of the fastening hole taking into consideration the result of FIG. [Figure 7] FIG. 7 is a graph comparing the comparative example and this embodiment with respect to the shear input to each bolt. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, an underrun protector mounting structure according to an embodiment will be described with reference to the drawings. In the following description, the same or corresponding elements are designated by the same reference numerals, and duplicated description will be omitted.

[0013] 1 is a schematic diagram of a truck 1 including an underrun protector mounting structure 10 according to this embodiment. The underrun protector mounting structure 10 is, for example, a rear underrun protector mounting structure provided in the rear portion of the truck 1. In the following, the underrun protector mounting structure 10 will be described as a rear underrun protector mounting structure provided in the rear portion of the truck 1, but the underrun protector mounting structure 10 may also be a front underrun protector mounting structure provided in the front portion of the truck 1.

[0014] The underrun protector mounting structure 10 includes a pair of side rails 11 extending along the fore-and-aft direction of the truck 1 and spaced apart in the vehicle width direction, a pair of stays 12 attached to each side rail 11, and an underrun protector 13 extending in the vehicle width direction and attached to the pair of stays 12.

[0015] The underrun protector 13 is an intrusion prevention device for preventing a vehicle (e.g., a passenger car) from going under the truck 1 when the vehicle collides. In the example shown in FIG. 1, the underrun protector 13 prevents a vehicle 100 colliding from behind from going under the truck 1. The underrun protector 13 is formed in a hollow rectangular shape, and is attached so as to span a pair of stays 12. The underrun protector 13 is attached to the side rail 11 via the stays 12 which are fastened to the side rail 11. The underrun protector 13 is fixed to the stays 12 by, for example, bolts and nuts.

[0016] The side rail 11 has, for example, a web extending along the fore-and-aft direction of the truck 1, an upper flange extending inward in the vehicle width direction from the upper end of the web, and a lower flange extending inward in the vehicle width direction from the lower end of the web, and is formed into a U-shaped cross section by this configuration.

[0017] The stay 12 will be described in detail below with reference to Figs. 2 and 3. Fig. 2 is a schematic diagram of the mounting structure 10 of the underrun protector of Fig. 1. Fig. 3 is a diagram for explaining moment balance. For ease of explanation, the shapes of the components of the mounting structure 10 shown in Figs. 2 and 3 differ in some places from the shapes of the components of the mounting structure 10 shown in Fig. 1. Also, in Figs. 2 and 3, an arrow Fr indicates the forward direction of the truck 1.

[0018] As shown in FIG. 2, the stay 12 has a plurality of mounting holes 120 in a portion fastened to the side rail 11. In the example shown in FIG. 2, the plurality of mounting holes 120 are configured to include four mounting holes 121, 122, 123, 124 on the front side and four mounting holes 125, 126, 127, 128 on the rear side, sandwiching the center in the front-rear direction. The mounting hole 121 is formed in the front upper part on the front side. The mounting hole 122 is formed below the mounting hole 121. The mounting hole 123 is formed rearward of the mounting hole 121. The mounting hole 124 is formed below the mounting hole 123 and rearward of the mounting hole 122. The mounting hole 125 is formed in the front upper part on the rear side. The mounting hole 126 is formed below the mounting hole 125. The mounting hole 127 is formed rearward of the mounting hole 125. The mounting hole 128 is formed below the mounting hole 127 and behind the mounting hole 126 .

[0019] The stay 12 is fastened to the side rail 11 by inserting bolts 151-158 into a plurality of mounting holes 120. The bolt 151 is inserted into the mounting hole 121. The bolt 152 is inserted into the mounting hole 122. The bolt 153 is inserted into the mounting hole 123. The bolt 154 is inserted into the mounting hole 124. The bolt 155 is inserted into the mounting hole 125. The bolt 156 is inserted into the mounting hole 126. The bolt 157 is inserted into the mounting hole 127. The bolt 158 ​​is inserted into the mounting hole 128.

[0020] Here, as shown in Fig. 2, it is assumed that the front part 101 of the vehicle 100 collides with the underrun protector 13 and an input F is applied to the underrun protector 13. In this case, a force (stay rotation moment) that tends to rotate clockwise in Fig. 2 is applied to the stay 12 in response to the input F. As a resistance to such a rotation moment of the stay 12, a resistance (shear input) is applied counterclockwise to the bolts 151-158. Then, from the balance between the above-mentioned stay rotation moment and the bolt resistance moment related to the shear input of each of the bolts 151-158, the rotation center r of the stay 12 (see Fig. 3) is derived.

[0021] As shown in Fig. 3, the stay rotation moment M s is expressed by the following equation (1) based on the moment arm length l from the center of rotation r and the input load F to the stay 12. M s = l × F (1)

[0022] In addition, the bolt reaction moment M B are the distances r1, r2, ..., r8 of each bolt from the center of rotation r, and the shear input F B1 ,F B2 ,…F B8 Based on this, it is shown in the following equation (2). M B =r1×F B1 +r2×F B2 +…+r8×F B8 (2)

[0023] As mentioned above, the stay rotation moment M s and bolt reaction moment M B Since these equations balance each other (equation (1) = equation (2)), the center of rotation r can be found from equations (1) and (2) above.

[0024] FIG. 4 is a diagram for explaining the relationship between the distance from the rotation center r and the shear input to the bolt. As shown in FIG. 4, when the stay 12 rotates by θ at a point whose distance from the rotation center r is R1, the displacement amount is R1θ. When the stay 12 rotates by θ at a point whose distance from the rotation center r is R2, which is longer than R1, the displacement amount is R2θ. In this case, the point whose distance from the rotation center r is R2 is longer than the point whose distance from the rotation center r is R1, so the displacement amount R2θ is larger than the displacement amount R1θ, and the shear input applied to the bolt at the point whose distance from the rotation center r is R2 is larger. In this way, the longer (farther) the bolt is from the rotation center r, the larger the shear input applied (the larger the load it bears).

[0025] FIG. 5 is a graph showing the shear input to each bolt. In FIG. 5, the horizontal axis indicates each bolt, and the vertical axis indicates the bolt input shear force. In FIG. 5, BOLT1 indicates the above-mentioned bolt 151, BOLT2 indicates the above-mentioned bolt 152, BOLT3 indicates the above-mentioned bolt 153, BOLT4 indicates the above-mentioned bolt 154, BOLT5 indicates the above-mentioned bolt 155, BOLT6 indicates the above-mentioned bolt 156, BOLT7 indicates the above-mentioned bolt 157, and BOLT8 indicates the above-mentioned bolt 158. The graph shown in FIG. 5 shows the results when the hole diameters of the mounting holes 120 are the same. As is clear from Figures 3 and 5, the shear input to bolt 153 (BOLT 3) and bolt 155 (BOLT 5), which are located at a relatively short distance from the center of rotation r, is relatively small, the shear input to bolt 151 (BOLT 1), bolt 154 (BOLT 4), bolt 156 (BOLT 6), and bolt 157 (BOLT 7), which are located at a medium distance from the center of rotation r, is medium, and the shear input to bolt 152 (BOLT 2) and bolt 158 ​​(BOLT 8), which are located at a relatively long distance from the center of rotation r, is relatively large.

[0026] In this way, if there is variation in the load borne by each bolt, there is a risk that a large load will be applied to some bolts. In the underrun protector mounting structure 10 according to this embodiment, the hole diameter of each mounting hole 120 is adjusted to suppress the variation in the load borne by each bolt. Specifically, the hole diameter of each of the multiple mounting holes 120 is set based on the shear input to the corresponding bolt when an input F that moves the underrun protector 13 occurs.

[0027] More specifically, the hole diameter of each of the multiple mounting holes 120 is set (adjusted) to be larger for the mounting hole 120 that will receive a larger shear input to the corresponding bolt when an input F that moves the underrun protector 13 occurs. That is, the hole diameter of each of the multiple mounting holes 120 is set according to the distance from the rotation center r of the stay 12 that rotates based on the input F that moves the underrun protector 13, and the hole diameter of the mounting hole 120 that is farther from the rotation center r and receives a larger shear input to the bolt is set to be larger.

[0028] That is, instead of making the size of each mounting hole 120 constant as shown in the left diagram of Fig. 6, the hole diameter is made larger for mounting holes 122, 128 which are far from the rotation center r (see Fig. 3) and have a relatively large shear input to the bolt, and the hole diameter is made smaller for mounting holes 123, 125 which are far from the rotation center r (see Fig. 3) and have a relatively small shear input to the bolt, as shown in the right diagram of Fig. 6. By adjusting the hole diameter of mounting holes 120 in this way, the load burden of the corresponding bolt is reduced for mounting holes 122, 128 which have a large hole diameter and a delayed timing of contact with the bolt compared to when the hole diameter is constant (as shown in the left diagram of Fig. 6), and the load burden of the corresponding bolt is increased for mounting holes 123, 125 which have a small hole diameter and have an earlier timing of contact with the bolt compared to when the hole diameter is constant (as shown in the left diagram of Fig. 6). In this way, by having the excessive load of the bolt that is likely to bear a high load depending on the distance from the center of rotation r be borne by the bolt that is less likely to bear a high load, the variation in shear input in each bolt is reduced, and the occurrence of bolts with excessively large shear input is prevented.

[0029] FIG. 7 is a graph comparing the comparative example and this embodiment with respect to the shear input to each bolt. The comparative example here is an example in which the hole diameter of the mounting hole 120 is constant. As shown in FIG. 7, as in this embodiment, the hole diameter is adjusted so that the hole diameter is larger for the mounting hole 120 that is farther from the rotation center r and has a larger shear input to the bolt. In this way, the shear input to bolt 152 (BOLT2) and bolt 158 ​​(BOLT8) that have a large shear input in the comparative example is reduced, and the shear input to bolt 153 (BOLT3) and bolt 155 (BOLT5) that have a small shear input in the comparative example is increased, thereby suppressing the variation in the shear input to each bolt.

[0030] Finally, the effects of the underrun protector mounting structure 10 according to this embodiment will be described.

[0031] The underrun protector mounting structure 10 in this embodiment is a mounting structure for an underrun protector 13 that is attached to a side rail 11 of a truck 1 via a stay 12 that is fastened to the side rail 11, the stay 12 having a plurality of mounting holes 120 in the portion that is fastened to the side rail 11, and the stay 12 is fastened to the side rail 11 by inserting bolts into the plurality of mounting holes 120, and the hole diameter of each of the plurality of mounting holes 120 is set based on the shear input to the corresponding bolt when an input occurs that moves the underrun protector 13.

[0032] In the mounting structure 10 for the underrun protector according to the present embodiment, the hole diameter of the mounting hole 120 in the stay 12 into which the fastening bolt is inserted is set based on the shear input applied to the bolt when the underrun protector 13 moves. Usually, the smaller the hole diameter, the earlier the timing of contact between the stay 12 and the bolt, and the larger the shear input applied to the corresponding bolt. In view of this point, for example, by making the hole diameter larger for the mounting hole 120 to which the corresponding bolt is subjected to a larger shear input, the timing of contact with the stay 12 is delayed for the bolt subjected to a relatively large shear input, and the timing of contact with the stay 12 is earlier for the bolt subjected to a relatively small shear input, thereby suppressing the variation in the shear input of each bolt and preventing the occurrence of a bolt with an excessively large shear input. In addition, by adopting a configuration in which the hole diameter of the mounting hole 120 of the stay 12 is simply adjusted in this way, it is possible to suppress large-scale changes to the configuration and cost increases as described as the prior art. As described above, according to the underrun protector mounting structure 10 of this embodiment, it is possible to suppress an increase in shear input to the bolt while suppressing large-scale changes to the configuration and increases in cost.

[0033] The hole diameter of each of the multiple mounting holes 120 is set according to the distance from the rotation center r of the stay 12, which rotates based on the input that moves the underrun protector 13, and may be set larger as the distance from the rotation center r increases. Considering the rotation moment of the stay 12, the bolt corresponding to the mounting hole 120 that is farther from the rotation center r of the stay 12 will have a larger shear input. For this reason, by making the hole diameter of the multiple mounting holes 120 larger as the distance from the rotation center r increases, the timing of contact with the stay 12 will be delayed for bolts with a relatively large shear input, and the timing of contact with the stay 12 will be earlier for bolts with a relatively small shear input, thereby suppressing the variation in the shear input among the bolts and preventing the occurrence of bolts with an excessively large shear input. [Explanation of symbols]

[0034] 1...truck (vehicle), 10...mounting structure, 11...side rail, 12...stay, 13...underrun protector, 120...mounting hole, 151 to 158...bolts, r...rotation center.

Claims

1. An underrun protector mounting structure that is attached to a side rail of a vehicle via a stay that is fastened to the side rail, comprising: the stay has a plurality of mounting holes in a portion that is fastened to the side rail, and is fastened to the side rail by inserting bolts into the plurality of mounting holes, a hole diameter of each of the plurality of mounting holes is set based on a shear input to a corresponding bolt when an input that moves the underrun protector occurs, The bolts inserted into the mounting holes have a common size, This underrun protector mounting structure has a larger hole diameter for the mounting hole to which the corresponding bolt is subjected, so that the timing of contact with the stay is delayed for bolts subjected to a relatively large shear input, and the timing of contact with the stay is advanced for bolts subjected to a relatively small shear input.

2. 2. The underrun protector mounting structure as described in claim 1, wherein the hole diameter of each of the plurality of mounting holes is set according to the distance from the center of rotation of the stay, which rotates based on an input that moves the underrun protector, and the hole diameter is set larger as the distance from the center of rotation is longer.

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