JP6426481B2 - Vehicle rear floor structure. - Google Patents

Description

  The present invention relates to a vehicle rear floor structure provided with a storage box.

  Patent Document 1 below discloses a resonant vibration isolation structure in a rear floor panel of a vehicle. To briefly explain this resonance vibration isolation structure, a storage box as a resonance vibration isolator is mounted on a floor pan formed on the rear floor. Then, the storage box presses the bottom wall portion of the floor pan by the weight of the storage box and the tools stored in the storage box (load to the lower side of the vehicle), and the portion pressed against the storage box in the floor pan becomes a rigid body It is configured to act as a part. In other words, the portion of the floor pan not pressed against the storage box is configured to act as a spring portion. The resonance frequency of the rear floor panel is changed by changing the area of the portion pressed down to the storage box in the floor pan.

JP, 2013-43464, A JP 2005-170270 A

  However, in the resonant vibration isolation structure of Patent Document 1, since the portion pressed against the storage box in the floor pan is made to act as a rigid body portion, the bottom wall portion of the floor pan needs to be pressed with a relatively large load by the storage box. There is. For this reason, in the resonant vibration isolation structure of the said patent document 1, there exists room for improvement in the point of suppressing the vibration of a rear floor effectively, suppressing the weight increase of a vehicle.

  An object of the present invention is to provide a vehicle rear floor structure capable of effectively suppressing the vibration of the rear floor panel while suppressing the weight increase of the vehicle in consideration of the above-mentioned fact.

The vehicle rear floor structure according to claim 1 constitutes a floor at the rear of the vehicle, is formed in a concave shape opened to the upper side of the vehicle, and a rear cross member extending in the vehicle width direction is disposed on the front side of the vehicle A rear floor panel formed with a floor pan to which a lower back panel extending in the vertical direction of the vehicle is joined is formed at an end portion, and is disposed on the vehicle upper side of the rear floor panel to cover the floor pan from the vehicle upper side while accommodating the projecting portion to be abutted against the front of the bottom wall portion in and the floor pan is projected to the vehicle lower side are formed, and a storage box which is configured as a foamed resin molded body, the housing The spring constant of the box is set to be lower than the spring constant of the floor pan, and the weight of the floor pan is the weight of the storage box The rear cross member is joined to the front side portion of the rear floor panel on the vehicle front side of the floor pan, and the flange portion projected from the outer peripheral portion of the storage box is the rear floor panel. It is supported by the floor part which is a part other than a floor pan, and the storage box acts as a dynamic damper .

In the vehicle rear floor structure according to the first aspect of the present invention, the floor panel forming the floor at the rear of the vehicle is formed with a recessed floor pan that opens to the upper side of the vehicle . The rear end of the floor pan is joined to a lower back panel extending in the vehicle vertical direction. Further, the vehicle front side of the floor pan, there is disposed a rear cross member that extends in the vehicle width direction, the vehicle front portion is joined to the rear cross member than the floor pan in the rear floor panel. And, on the vehicle upper side of the rear floor panel, a storage box supported by the floor portion which is a portion other than the rear floor pan in the rear floor panel is arranged to cover the floor pan from the vehicle upper side. ing. Then, a storage item such as a jack is stored in the storage box. Thereby, the storage box acts as a dynamic damper.

  By the way, in the primary natural vibration mode of the rear floor panel having a concave floor pan, the rear floor panel tends to vibrate so that the front of the bottom wall portion of the floor pan is an antinode.

Here, the storage box is configured as a foamed resin molded body. For this reason, storage objects, such as a jack, can be stored, achieving weight reduction of a storage box. Further, the storage box is formed with a projecting portion that protrudes to the lower side of the vehicle, and the projecting portion is in contact with the front portion of the bottom wall portion of the floor pan. That is, in the primary natural vibration mode of the rear floor panel, the front portion of the bottom wall which is an antinode is received by the contact portion of the storage box. Therefore, the storage box can be configured to act as a dynamic damper. Thereby, the resonance frequency of the rear floor panel including the storage box can be dispersed, and the vibration level of the rear floor panel can be reduced. As described above, by applying the storage box to the front portion of the bottom wall portion of the floor pan where the vibration (amplitude) is increased in the primary natural vibration mode of the rear floor panel, the vibration generated in the rear floor panel is effectively suppressed. Can.
According to a second aspect of the present invention, in the vehicle rear floor structure according to the first aspect of the present invention, the storage box is in a state where the projecting portion is in contact with a front portion of a bottom wall portion of the floor pan. By being fixed to the rear floor panel, the storage box is attached at the front of the bottom wall of the floor pan in relation to the bottom wall of the floor pan.
The vehicle rear floor structure according to the present invention according to claim 3 is the invention according to claim 1 or 2, wherein the storage item is a jack, and the storage box is formed in the storage box and the jack is stored. The recess is disposed so as to overlap with the protrusion in plan view.

  As described above, according to the vehicle rear floor structure of the present invention, it is possible to effectively suppress the vibration of the rear floor panel while suppressing the weight increase of the vehicle.

(A) is a schematic side sectional view (1A-1A sectional view taken on the line of FIG. 2) seen from the left side of the vehicle showing the rear part of the vehicle to which the vehicle rear floor structure according to the present embodiment is applied. 2 is a schematic cross-sectional view (a cross-sectional view taken along line 1B-1B of FIG. 2) of the rear portion of the vehicle shown in FIG. It is a schematic plan view which looked at the rear of the vehicles shown in Drawing 1 (A) from the vehicles upper part. FIG. 3 is a diagram modeling the rear of the vehicle shown in FIG. 2; It is a graph for demonstrating, comparing with the comparative example the vibration level of the rear floor panel shown by FIG. It is a graph for demonstrating the sound pressure in the vehicle interior with respect to the rotation speed of a vehicle engine, and the vibration level of a rear floor panel, comparing with a comparative example.

  FIG. 2 is a schematic plan view of the rear portion of the vehicle V to which the vehicle rear floor structure S according to the embodiment of the present invention is applied, viewed from the upper side of the vehicle. Further, FIG. 1 (A) shows the rear of the vehicle V in a side cross-sectional view (a cross-sectional view taken along line 1A-1A in FIG. 2) as viewed from the left side of the vehicle. The rear portion of V is shown in a cross-sectional view (a cross-sectional view along line 1B-1B in FIG. 2) as viewed from the rear side of the vehicle. The arrow FR appropriately shown in these drawings indicates the front side of the vehicle V, the arrow LH indicates the left side (one side in the vehicle width direction), and the arrow UP indicates the upper side of the vehicle.

  As shown in these figures, the vehicle V includes a rear floor panel 10 forming a floor of the rear of the vehicle V, and a storage box disposed on the vehicle upper side of the rear floor panel 10 for storing articles such as the jacks 50 and the like. And 30 are configured. Each of the above configurations will be described below.

  The rear floor panel 10 is made of steel plate and is disposed with its thickness direction in the vertical direction of the vehicle. A floor pan 12 is formed at an intermediate portion in the vehicle width direction of the rear floor panel 10. The floor pan 12 is formed in a concave shape bulging toward the lower side of the vehicle and is open to the upper side and the rear side of the vehicle. Specifically, the floor pan 12 is configured to include a bottom wall portion 12A constituting a bottom wall of the floor pan 12 and a vertical wall 12B extending from the outer peripheral portion of the bottom wall portion 12A to the upper side of the vehicle. Further, a ridgeline 12C between the bottom wall portion 12A and the vertical wall 12B is curved in a substantially arc shape in a longitudinal sectional view. Furthermore, the front end portion of the floor pan 12 is curved in a substantially semicircular shape that is convex toward the vehicle front side in a plan view. A portion other than the floor pan 12 in the rear floor panel 10 is a floor portion 14.

  As shown in FIG. 2, at both ends of the rear floor panel 10 in the vehicle width direction, a pair of left and right rear side members 20 that constitute a framework member of the vehicle V is provided on the vehicle lower side. The rear side member 20 extends in the front-rear direction of the vehicle, and is formed in an inverted hat shape in cross section opened to the upper side of the vehicle. The rear floor panel 10 (the floor portion 14 thereof) is joined to the opening of the rear side member 20 by welding or the like. Thus, a closed cross section is formed by the rear side member 20 and the rear floor panel 10.

  Further, a rear floor cross member 22 is provided on the upper side of the vehicle on a portion on the vehicle front side of the rear floor panel 10 (specifically, on the vehicle front side of the floor pan 12). The rear floor cross member 22 extends in the vehicle width direction and is formed in a hat shape in cross section opened to the lower side of the vehicle. The rear floor panel 10 is joined to the opening of the rear floor cross member 22 by welding or the like. Thus, a closed cross section is formed by the rear floor cross member 22 and the rear floor panel 10.

  Further, as shown in FIG. 1A, the rear end portion of the rear floor panel 10 (floor pan 12) is bent to the upper side of the vehicle. Furthermore, a lower back panel 24 (not shown in FIG. 2) is provided on the vehicle rear side of the rear floor panel 10, and the lower back panel 24 is disposed with the vehicle front-rear direction in the thickness direction. The rear end portion of the rear floor panel 10 is joined to the lower back panel 24 by welding or the like. Thus, the floor pan 12 is closed by the lower back panel 24 from the rear side of the vehicle.

  As shown in FIG. 1 and FIG. 2, the storage box 30 is a box for storing the jack 50 as a "stored item" and the puncture repair kits 52, 54, and is a foamed resin molded body (in the present embodiment) , PP beads are formed as a foamed resin molded body). The storage box 30 includes a box main body 32 formed in a substantially block shape, and the box main body 32 is disposed inside the floor pan 12.

  At the front end of the storage box 30, a first flange portion 34 (see FIG. 2) projected from the box body 32 to the front side of the vehicle is integrally formed. The first flange portion 34 is a floor of the rear floor panel 10. It is disposed on the upper side of the vehicle of the unit 14. Further, at the rear end portion of the storage box 30, a pair of left and right second flange portions 36 (see FIG. 2) projecting integrally from the box body 32 to both sides in the vehicle width direction are integrally formed at both side portions in the vehicle width direction. The second flange portion 36 is disposed on the vehicle upper side of the floor portion 14 in the rear floor panel 10. The storage box 30 is supported by the rear floor panel 10 at predetermined portions of the first flange portion 34 and the second flange portion 36 and is fixed to the rear floor panel 10 by a clip (not shown) or the like. Specifically, the storage box 30 is supported by (the floor portion 14 of) the rear floor panel 10 and is fixed to the rear floor panel 10 by a clip (not shown) or the like in a portion surrounded by a dotted line A in FIG. ing.

  At the front end of the box body 32, a first storage recess 38 (in a broad sense, an element regarded as a "storage recess") is formed. The first storage recess 38 is formed in a concave shape opened to the upper side of the vehicle and extends in the vehicle width direction. The jack 50 is configured to be stored inside the first storage recess 38.

  Further, as shown in FIG. 2, at the vehicle longitudinal direction intermediate portion of the box main body portion 32, a second storage recess 40 (in a broad sense, an element regarded as a “storage recess”) in the vehicle right side portion Is formed. The second storage recess 40 is formed in a concave shape opened to the upper side of the vehicle, and the puncture repair kit 52 is configured to be stored inside the second storage recess 40.

  Furthermore, a third storage recess 42 (in a broad sense, an element regarded as a “storage recess”) is provided at the vehicle left side of the second storage recess 40 in the vehicle longitudinal direction middle part of the box main body 32. It is formed. The third storage recess 42 is formed in a concave shape opened to the upper side of the vehicle, and the puncture repair kit 54 is configured to be stored inside the third storage recess 42.

  Further, as shown in FIGS. 1A and 1B, on the lower surface of the box main body 32, a projection 44 projecting downward is integrally formed at the position of the front end of the box main body 32. It is formed. The projecting portion 44 is formed in a substantially rectangular parallelepiped shape, and is in contact with the front portion of the bottom wall portion 12A of the floor pan 12 (a portion on the vehicle front side of the center portion in the vehicle longitudinal direction of the floor pan 12). More specifically, it projects from the front end of the bottom wall 12A of the floor pan 12 (a portion close to the vehicle rear side with respect to the ridgeline 12C between the vertical wall 12B and the bottom wall 12A forming an arc shape in plan view) The part 44 is in contact. Further, the protrusion 44 is disposed immediately below the first storage recess 38, and the first storage recess 38 (jack 50) is disposed such that the first storage recess 38 (jack 50) and the protrusion 44 overlap in a plan view. The position of) is set. In addition, although the details will be described later, the storage box 30 is formed of a foamed resin molded body, so that in the present embodiment, the spring constant of the storage box 30 is lower than the spring constant of the floor pan 12 Is set as. In addition, the weight of the floor pan 12 is set to be heavier than the weight of the storage box 30.

  Next, the operation and effects of the present embodiment will be described.

  In the vehicle rear floor structure S configured as described above, the floor pan 12 is formed on the rear floor panel 10, and the floor pan 12 is formed in a concave shape opened to the upper side of the vehicle. A storage box 30 is disposed on the vehicle upper side of the rear floor panel 10 so as to cover the floor pan 12 from the upper side of the vehicle, and storage items such as jacks 50 are stored in the storage box 30. That is, the vehicle V to which the vehicle rear floor structure S of the present embodiment is applied has a structure different from that of the type in which the spare tire and the jack are stored in the floor pan 12. Then, in a type of vehicle in which the spare tire is stored in the floor pan 12, the spare tire and the jack act as a mass damper on the rear floor panel 10 because the weight of the spare tire is relatively heavy. Thereby, the vibration level of the rear floor panel 10 is reduced.

  On the other hand, in the present embodiment, as described above, puncture repair kits 52 and 54 are stored in storage box 30 instead of spare tires, and storage box 30 is disposed on the vehicle upper side of rear floor panel 10. For this reason, for example, the storage box 30 is formed of a hard resin material or the like, and the storage box 30 including the jack 50 and the puncture repair kits 52 and 54 acts as a mass damper to similarly vibrate the rear floor panel 10 as described above. It can be reduced. However, in this case, the weight of the storage box 30 including the jack 50 and the puncture repair kits 52 and 54 needs to be increased, and the weight of the vehicle V is increased. Therefore, in the present embodiment, the vibration level of the rear floor panel 10 is reduced while suppressing the weight increase of the vehicle V with respect to the vehicle V of such type. The details will be described below.

  First, in the primary natural vibration mode in the vehicle vertical direction of the rear floor panel 10 having the concave floor pan 12, the front portion of the bottom wall portion 12A of the floor pan 12 (specifically, the front end portion of the bottom wall portion 12A) The rear floor panel 10 tends to vibrate so as to be an antinode. That is, the lower back panel 24 is joined to the rear end portion of the rear floor panel 10, and the rear floor cross member 22 is joined to the vehicle front side portion of the rear floor panel 10 with respect to the floor pan 12. Therefore, in the primary natural vibration mode of the rear floor panel 10 in the vertical direction of the vehicle, the portion of the rear floor panel 10 to which the lower back panel 24 and the rear floor cross member 22 are joined becomes a node, and the vehicle longitudinal direction intermediate portion of the rear floor panel 10 The rear floor panel 10 tends to vibrate so as to be an antinode. Further, a concave floor pan 12 bulging out toward the lower side of the vehicle is formed on the rear floor panel 10. For this reason, when vibration in the vertical direction of the vehicle is input to the rear floor panel 10, it tries to vibrate so that the ridgeline 12C between the bottom wall 12A of the floor pan 12 and the vertical wall 12B becomes the starting point. As a result, the rear floor panel 10 tends to vibrate such that the front (front end) of the bottom wall 12A of the floor pan 12 is an antinode.

  Here, the storage box 30 is configured as a foamed resin molded body, and in the storage box 30, storage objects such as the jacks 50 are stored. Therefore, it is possible to store the storage item such as the jack 50 in the storage box 30 while reducing the weight of the storage box 30. Further, the box main body 32 of the storage box 30 is formed with a protrusion 44 that protrudes to the lower side of the vehicle, and the protrusion 44 contacts the front (front end) of the bottom wall 12A of the floor pan 12 It is connected. That is, in the primary natural vibration mode of the rear floor panel 10, the projection 44 of the storage box 30 receives the front portion of the bottom wall 12A which is an antinode. As a result, the storage box 30 is attached to the portion with the largest vibration (amplitude) in the primary natural vibration mode of the rear floor panel 10, so the storage box 30 configured as a foamed resin molded body acts as a dynamic damper You will come to That is, as shown in FIG. 3, the rear portion of the vehicle V (the rear floor panel 10 including the storage box 30) can be configured as a model of a two degree of freedom system. Note that M1 shown in FIG. 3 is the weight of the rear floor panel 10, K1 is the spring constant of the rear floor panel 10, and C1 is the damping coefficient of the rear floor panel 10. On the other hand, M2 shown in FIG. 3 is the weight of the storage box 30 including the storage item such as the jack 50, K2 is the spring constant of the storage box 30, and C2 is the attenuation coefficient of the storage box 30.

  Thus, when vibration is input to the rear floor panel 10, the resonance frequency of the rear floor panel 10 including the storage box 30 is dispersed, and the vibration level of the rear floor panel 10 can be reduced. As described above, the rear floor panel 10 suppresses the weight increase of the vehicle V by applying the storage box 30 as the foamed resin molded body to the front portion of the bottom wall portion 12A which becomes an antinode in the primary natural vibration mode of the rear floor panel 10. Vibration generated in the panel 10 can be effectively suppressed.

  Hereinafter, this point will be described using a graph shown in FIG. 4 in comparison with a comparative example. In the comparative example, the storage items such as the storage box 30 and the jack 50 are omitted with respect to the present embodiment. The graph shown in FIG. 4 is a graph showing the vibration level at the front of the floor pan 12 when vibration in the vertical direction of the vehicle is input to the front end of the rear floor panel 10. The horizontal axis represents the vibration frequency (Hz) And the vertical axis is the vibration level (dB) at the front of the floor pan 12 with respect to the input vibration. Further, in FIG. 4, the data indicated by the dotted line is the data of the comparative example, and the data indicated by the solid line is the data of the present embodiment. As shown in this figure, in the comparative example, the primary resonance frequency of the rear floor panel 10 is around 45 Hz, and the vibration level of the rear floor panel 10 at this resonance frequency is about 58 dB.

  On the other hand, in the present embodiment, as described above, the spring constant of the storage box 30 is set smaller than the spring constant of the rear floor panel 10, and the weight of the rear floor panel 10 is the jack 50. It is set to be heavier than the weight of etc. For this reason, in the present embodiment, the primary resonance frequency of the rear floor panel 10 including the storage box 30 is dispersed around about 26 Hz and around 50 Hz. Further, the vibration level at about 26 Hz in the rear floor panel 10 including the storage box 30 is about 47 dB, and the vibration level at about 50 Hz is about 52 dB. That is, it can be seen that the vibration level of the rear floor panel 10 including the storage box 30 in the present embodiment is smaller than that of the comparative example. In particular, the vibration level of the rear floor panel 10 can be reduced in the low frequency band (35 Hz to 50 Hz, see the region surrounded by the thick line in FIG. 4). As described above, even in the case where the relatively light jack 50 and the flat repair kits 52 and 54 are stored by the storage box 30 on the rear floor panel 10, the weight increase of the vehicle V is suppressed by acting the storage box 30 as a dynamic damper. Thus, the vibration of the rear floor panel 10 can be effectively suppressed.

  Furthermore, according to the present embodiment, since the vibration level of the rear floor panel 10 in the low frequency band (35 Hz to 50 Hz) is reduced, the booming noise in the passenger compartment when the engine of the vehicle V is rotated at low speed It can be reduced. Hereinafter, this point will be described using the graph shown in FIG. The upper part of the graph shown in FIG. 5 shows the sound pressure level in the compartment of the vehicle V relative to the rotational speed of the engine when the engine of the vehicle V is started. The lower part of the graph shown in FIG. 5 shows the vibration level in the vehicle vertical direction at the front of the floor pan 12 with respect to the rotational speed of the engine of the vehicle V. Further, data indicated by a solid line is data of the present embodiment, and data indicated by a dotted line is data in the comparative example. Although the frequency of vibration input to the rear floor panel 10 differs depending on the engine specification (number of cylinders), in the present embodiment, the engine speed is 1050 to 1500 rpm (the band enclosed by the thick line in FIG. 5) The frequency of vibration input to the rear floor panel 10 is set to 35 to 50 Hz.

  As shown in FIG. 5, in the comparative example, the vibration level at the front of the floor pan 12 exceeds 30 dB and the sound pressure level in the passenger compartment is 80 dB in the range where the engine speed is 1050-1500 rpm. Over. On the other hand, according to the present embodiment, the vibration level at the front portion of the floor pan 12 can be made smaller than that in the above-described comparative example in the range where the engine speed is 1050-1500 rpm. As a result, in the present embodiment, the sound pressure level in the passenger compartment can be made smaller than 80 dB when the engine speed is in the range of 1050 to 1500 rpm. Thereby, when the engine of the vehicle V is rotated at a low rotation speed (i.e., the frequency of vibration input to the rear floor panel 10 is 35 Hz to 50 Hz), the booming noise generated in the vehicle interior by the vibration of the rear floor panel 10 is reduced. be able to.

  Further, in the present embodiment, the first accommodation recess 38 is formed on the vehicle upper side (directly above) of the projecting portion 44, and the jack 50 is accommodated inside the first accommodation recess 38. For this reason, the jack 50 as a stored item is disposed on the upper side (directly above) of the vehicle at the front of the floor pan 12 which is the belly in the first-order natural vibration mode. Thus, when the storage box 30 is configured as a dynamic damper, the jack 50 that functions as a weight is disposed on the vehicle upper side (directly above) of the front portion of the floor pan 12, so the storage box 30 functions efficiently as a dynamic damper. It can be done.

  Moreover, the storage box 30 is comprised by the foamed resin molding. Therefore, by appropriately changing (adjusting) the position and the shape of the projecting portion 44 corresponding to the form of the rear floor panel 10 of various vehicles, the rear floor panel 10 is damped according to the vibration characteristic of the rear floor panel 10 Can.

  In the present embodiment, storage box 30 is supported by rear floor panel 10 at a predetermined position (a portion surrounded by dotted line A shown in FIG. 2) in first flange portion 34 and second flange portion 36. However, the part where the storage box 30 is supported can be set arbitrarily. That is, the positions of the first flange portion 34 and the second flange portion 36 may be changed as appropriate in consideration of the weight balance of the storage box 30 including the items such as the jacks 50 and the like. Further, the portion of the first flange portion 34 and the second flange portion 36 supported by the rear floor panel 10 may be changed as appropriate.

  Further, in the present embodiment, although the protrusion 44 of the storage box 30 is in contact with the front of the bottom wall 12A of the floor pan 12, the weight balance of the storage box 30 including the contents such as jacks 50 is In consideration of this, the storage box 30 may be in contact with the bottom wall 12A at other parts. That is, at least the protrusion 44 of the storage box 30 may be in contact with the front of the bottom wall 12A of the floor pan 12.

10 rear floor panel 12 floor pan 12A bottom wall portion 30 storage box 44 projecting portion 50 jack (stored item)
52 puncture repair kit (stored item)
54 puncture repair kit (stored item)

Claims (3)

A rear cross member which forms a floor at the rear of the vehicle and is formed in a concave shape opened upward to the vehicle and extends in the vehicle width direction is disposed on the front side of the vehicle and extends in the vehicle vertical direction at the rear end. A rear floor panel having a floor pan formed by joining lower back panels;
The floor pan is disposed on the vehicle upper side of the rear floor panel so as to cover the floor from the upper side of the vehicle, stores the stored items, and projects to the lower side of the vehicle and contacts the front of the bottom wall portion of the floor pan. A storage box formed as a foam resin molded body,
Equipped with
The spring constant of the storage box is set to be lower than the spring constant of the floor pan, and the weight of the floor pan is set to be heavier than the weight of the storage box.
A floor in which the rear cross member is joined to a front side portion of the rear floor panel on the vehicle front side than the floor pan, and a flange portion projected from an outer peripheral portion of the storage box is a portion other than the floor pan in the rear floor panel Supported by the department,
The storage box acts as a dynamic damper,
Vehicle rear floor structure. The storage box is fixed to the rear floor panel in a state in which the projecting portion abuts on a front portion of a bottom wall portion of the floor pan.
The storage box is mounted at the front of the bottom wall of the floor pan in relation to the bottom wall of the floor pan
The vehicle rear floor structure according to claim 1. The stored item is a jack,
A storage recess formed in the storage box and in which the jack is stored is arranged to overlap with the protrusion in a plan view.
The vehicle rear floor structure according to claim 1 or 2.