JP2016130076A - Vehicle rear floor structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively suppress vibrations of a rear floor panel, while suppressing the increase of weight of a vehicle.SOLUTION: In a vehicle rear floor structure S, a storing box 30 is configured as a foamed resin molding, so that the weight-reduction of the storing box 30 can be attempted. The storing box 30 abuts on a front part of a bottom wall portion 12A on a floor pan 12 at a projecting portion 44. Namely, a front part of a bottom wall portion 12A which becomes an antinode in a primary natural frequency mode of the rear floor panel 10 is received by the projecting portion 44 of the storing box 30. Therefore, the storing box 30 is acted as a dynamic damper. Consequently, a resonance frequency of the rear floor panel 10 including the storing box 30 is scattered, and a vibration level of the rear floor panel 10 can be reduced.SELECTED DRAWING: Figure 1

Description

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

  Patent Document 1 listed below discloses a resonance vibration isolation structure for a rear floor panel of a vehicle. Briefly describing this resonance vibration isolation structure, a storage box as a resonance vibration isolation body is placed on a floor pan formed on the rear floor. The storage box presses against the bottom wall of the floor pan with the weight of the storage box and the tool stored in the storage box (load on the vehicle lower side), so that the portion pressed against the storage box in the floor pan is rigid. It is comprised so that it may act as a part. In other words, the portion of the floor pan that is not pressed against the storage box is configured to act as a spring portion. And the resonant frequency in a rear floor panel is changed by changing the area of the part pressed down by the storage box in a floor pan.

JP 2013-43464 A JP 2005-170270 A

  However, since the portion of the floor pan pressed against the storage box acts as a rigid body portion in the resonance vibration isolating structure of Patent Document 1, it is necessary to press the bottom wall of the floor pan with a relatively large load by the storage box. There is. For this reason, there is room for improvement in the point of effectively suppressing the vibration of the rear floor while suppressing the weight increase of the vehicle in the resonance vibration isolating structure of Patent Document 1.

  In view of the above facts, an object of the present invention is to provide a vehicle rear floor structure capable of effectively suppressing vibration of a rear floor panel while suppressing an increase in the weight of the vehicle.

  The vehicle rear floor structure according to claim 1 constitutes a floor at the rear of the vehicle, a rear floor panel formed with a concave floor pan opened to the vehicle upper side, and the rear floor panel so as to cover the floor pan from the vehicle upper side. Is disposed on the upper side of the vehicle, and stores a storage item such as a jack, and is also formed with a protruding portion that protrudes toward the lower side of the vehicle and contacts the front portion of the bottom wall portion of the floor pan. And a configured storage box.

  In the vehicle rear floor structure according to the first aspect, the floor pan is formed on the floor panel constituting the floor at the rear of the vehicle, and the floor pan is formed in a concave shape opened to the upper side of the vehicle. A storage box is disposed on the vehicle upper side of the rear floor panel so as to cover the floor pan from the vehicle upper side. And storage things, such as a jack, are stored in a storage box.

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

  Here, the storage box is configured as a foamed resin molded body. For this reason, it is possible to store storage items such as jacks while reducing the weight of the storage box. Further, the storage box is formed with a protruding portion protruding downward from the vehicle, and the protruding portion is in contact with the front portion of the bottom wall portion of the floor pan. That is, the front portion of the bottom wall portion that becomes an antinode in the primary natural vibration mode of the rear floor panel is received by the contact portion of the storage box. For this reason, it can comprise so that a storage box may act as a dynamic damper. Thereby, the resonance frequency of the rear floor panel including the storage box is dispersed, and the vibration level of the rear floor panel can be reduced. As described above, the storage box is applied to the front portion of the bottom wall portion of the floor pan where the vibration (amplitude) increases in the primary natural vibration mode of the rear floor panel, thereby effectively suppressing the vibration generated in the rear floor panel. Can do.

  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 an increase in the weight of the vehicle.

(A) is a schematic side sectional view (sectional view taken along line 1A-1A in FIG. 2) as 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. ) Is a schematic cross-sectional view (cross-sectional view taken along line 1B-1B in FIG. 2) of the rear portion of the vehicle shown in FIG. It is the typical top view which looked at the rear part of vehicles shown in Drawing 1 (A) from the vehicles upper part. It is the figure which modeled the rear part of the vehicle shown by FIG. 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 a vehicle interior and the vibration level of a rear floor panel with respect to the rotation speed of the engine of a vehicle, comparing with a comparative example.

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

  As shown in these drawings, the vehicle V includes a rear floor panel 10 that constitutes a rear floor of the vehicle V, and a storage box that is disposed on the vehicle upper side of the rear floor panel 10 and stores storage items such as a jack 50. 30. Hereafter, each said structure is demonstrated.

  The rear floor panel 10 is made of a steel plate and is arranged with the plate thickness direction being the vehicle vertical direction. A floor pan 12 is formed at an intermediate portion of the rear floor panel 10 in the vehicle width direction. The floor pan 12 is formed in a concave shape that bulges to the vehicle lower side, and is open to the vehicle upper side and the vehicle rear side. Specifically, the floor pan 12 includes a bottom wall portion 12A that constitutes a bottom wall of the floor pan 12, and a vertical wall 12B that extends from the outer periphery of the bottom wall portion 12A to the vehicle upper side. Further, the ridgeline 12C between the bottom wall portion 12A and the vertical wall 12B is curved in a substantially arc shape in a vertical 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, a pair of left and right rear side members 20 constituting a skeleton member of the vehicle V are provided at both ends of the rear floor panel 10 in the vehicle width direction on the vehicle lower side. The rear side member 20 extends in the vehicle front-rear direction and is formed in a cross-sectional inverted hat shape that is open to the vehicle upper side. The rear floor panel 10 (the floor portion 14) is joined to the opening of the rear side member 20 by welding or the like. As a result, the rear side member 20 and the rear floor panel 10 form a closed cross section.

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

  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. Further, a lower back panel 24 (not shown in FIG. 2) is provided on the rear side of the rear floor panel 10, and the lower back panel 24 is arranged with the vehicle front-rear direction being the plate thickness direction. The rear end of the rear floor panel 10 is joined to the lower back panel 24 by welding or the like. As a result, the floor pan 12 is closed from the vehicle rear side by the lower back panel 24.

  As shown in FIGS. 1 and 2, the storage box 30 is a box for storing a jack 50 or a puncture repair kit 52, 54 as “storage”, and is a foamed resin molded body (in the present embodiment). , A foamed resin molded body obtained by foaming PP beads). The storage box 30 includes a box body portion 32 formed in a substantially block shape, and the box body portion 32 is disposed inside the floor pan 12.

  A first flange portion 34 (see FIG. 2) is integrally formed at the front end portion of the storage box 30 so as to project from the box main body portion 32 toward the vehicle front side. The first flange portion 34 is a floor of the rear floor panel 10. It is arranged on the vehicle upper side of the part 14. In addition, a pair of left and right second flange portions 36 (see FIG. 2) projecting from the box body portion 32 to both sides in the vehicle width direction are integrally formed at the rear end portion of the storage box 30 at both sides 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 clips (not shown). Specifically, in a portion surrounded by a dotted line A in FIG. 2, the storage box 30 is supported by the rear floor panel 10 (the floor portion 14 thereof) and fixed to the rear floor panel 10 by a clip (not shown) or the like. ing.

  A first storage recess 38 (which is an element grasped as a “storage recess” in a broad sense) is formed at the front end of the box body 32. The 1st accommodation recessed part 38 is formed in the concave shape open | released by the vehicle upper side, and is extended in the vehicle width direction. The jack 50 is housed inside the first housing recess 38.

  Further, as shown in FIG. 2, in the vehicle front-rear direction intermediate portion of the box main body portion 32, a second storage recess 40 (which is an element grasped as “storage recess” in a broad sense) 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 is configured such that the puncture repair kit 52 is stored inside the second storage recess 40.

  Further, a third storage recess 42 (which is an element grasped as a “storage recess” in a broad sense) is provided at an intermediate portion of the box main body 32 in the vehicle longitudinal direction at a position on the vehicle left side of the second storage recess 40. Is formed. The third storage recess 42 is formed in a concave shape opened to the upper side of the vehicle, and is configured such that the puncture repair kit 54 is stored inside the third storage recess 42.

  Further, as shown in FIGS. 1A and 1B, a projecting portion 44 projecting downward from the vehicle is integrally formed on the lower surface of the box body portion 32 at the position of the front end portion of the box body portion 32. 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 (the portion on the front side of the vehicle in the vehicle front-rear direction of the floor pan 12). More specifically, it protrudes to the front end portion (the portion close to the vehicle rear side with respect to the ridge line 12C between the vertical wall 12B and the bottom wall portion 12A having an arc shape in plan view) in the bottom wall portion 12A of the floor pan 12. The part 44 is in contact. The protrusion 44 is disposed directly below the first storage recess 38, and the first storage recess 38 (jack 50) so that the first storage recess 38 (jack 50) and the protrusion 44 wrap in plan view. ) Position is set. In addition, although mentioned later for details, the storage box 30 is comprised with a foaming resin molding, and in this Embodiment, the spring constant which the storage box 30 has becomes lower than the spring constant which the floor pan 12 has. Is set to Further, the weight of the floor pan 12 is set to be heavier than the weight of the storage box 30.

  Next, the operation and effect 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. The 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 vehicle upper side, 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 a vehicle in which spare tires and jacks are housed in the floor pan 12. In the type of vehicle in which the spare tire is stored in the floor pan 12, the spare tire is relatively heavy, so that the spare tire and the jack act as a mass damper on the rear floor panel 10. Thereby, the vibration level of the rear floor panel 10 is reduced.

  On the other hand, in the present embodiment, as described above, the puncture repair kits 52 and 54 are stored in the storage box 30 instead of the spare tire, and the storage box 30 is disposed on the vehicle upper side of the rear floor panel 10. For this reason, for example, the storage box 30 is formed of a hard resin material, and the storage box 30 including the jack 50 and the puncture repair kits 52 and 54 is operated as a mass damper. Can be reduced. However, in this case, it is necessary to increase the weight of the storage box 30 including the jack 50 and the puncture repair kits 52 and 54, and the weight of the vehicle V increases. For this reason, in the present embodiment, the vibration level of the rear floor panel 10 is reduced while suppressing an increase in the weight of the vehicle V with respect to such a type of vehicle V. This will be specifically 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 become a stomach. 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 relative 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 where the lower back panel 24 and the rear floor cross member 22 are joined becomes a node, and the middle portion of the rear floor panel 10 in the longitudinal direction of the vehicle The rear floor panel 10 tends to vibrate so as to become a stomach. Further, the rear floor panel 10 is formed with a concave floor pan 12 that bulges downward from the vehicle. For this reason, when vibration in the vehicle vertical direction is input to the rear floor panel 10, the rear floor panel 10 tries to vibrate so that the ridgeline 12C between the bottom wall portion 12A of the floor pan 12 and the vertical wall 12B starts. Thereby, the rear floor panel 10 tends to vibrate so that the front portion (front end portion) of the bottom wall portion 12A of the floor pan 12 becomes a belly.

  Here, the storage box 30 is configured as a foamed resin molded body, and storage items such as a jack 50 are stored in the storage box 30. For this reason, the storage items such as the jack 50 can be stored 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 protruding portion 44 protruding downward from the vehicle, and the protruding portion 44 contacts the front portion (front end portion) of the bottom wall portion 12A of the floor pan 12. It is touched. That is, the front portion of the bottom wall portion 12 </ b> A that becomes an antinode in the primary natural vibration mode of the rear floor panel 10 is received by the protruding portion 44 of the storage box 30. As a result, the storage box 30 can be attached to a portion having the largest vibration (amplitude) in the primary natural vibration mode of the rear floor panel 10, and the storage box 30 configured as a foamed resin molded body acts as a dynamic damper. To come. 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 two-degree-of-freedom system model. 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 items such as the jack 50, K2 is the spring constant of the storage box 30, and C2 is the damping 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 storage box 30 as the foamed resin molded body is applied to the front portion of the bottom wall portion 12A that becomes an antinode in the primary natural vibration mode of the rear floor panel 10, thereby suppressing an increase in the weight of the vehicle V and the rear floor. Vibration generated in the panel 10 can be effectively suppressed.

  Hereinafter, this point will be described using the 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 from the present embodiment. The graph shown in FIG. 4 is a graph showing the vibration level at the front portion of the floor pan 12 when vibration in the vehicle vertical direction is input to the front end portion of the rear floor panel 10, and the horizontal axis indicates the vibration frequency (Hz). The vertical axis represents the vibration level (dB) at the front portion of the floor pan 12 with respect to the input vibration. 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 about 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 to be smaller than the spring constant of the rear floor panel 10, and the weight of the rear floor panel 10 is determined by the jack 50. It is set to be heavier than the same weight. For this reason, in the present embodiment, the primary resonance frequency of the rear floor panel 10 including the storage box 30 is distributed in the vicinity of about 26 Hz and about 50 Hz. Further, the vibration level in the vicinity of about 26 Hz in the rear floor panel 10 including the storage box 30 is about 47 dB, and the vibration level in the vicinity of 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 in the comparative example. In particular, the vibration level of the rear floor panel 10 can be reduced in a low frequency band (35 Hz to 50 Hz, see the region surrounded by a thick line in FIG. 4). As described above, even when the relatively light weight jack 50 and the puncture repair kits 52 and 54 are stored in the rear floor panel 10 by the storage box 30, the storage box 30 is caused to act as a dynamic damper, thereby suppressing an increase in the weight of the vehicle V. In addition, vibration of the rear floor panel 10 can be effectively suppressed.

  Furthermore, according to the present embodiment, the vibration level of the rear floor panel 10 in the low frequency band (35 Hz to 50 Hz) is reduced, so that the noise of the vehicle interior when the engine of the vehicle V is rotated at a low speed is generated. Can be reduced. Hereinafter, this point will be described with reference to a graph shown in FIG. The upper part of the graph shown in FIG. 5 shows the sound pressure level in the passenger compartment of the vehicle V with respect to the engine speed 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 portion of the floor pan 12 with respect to the engine speed of the vehicle V. The data indicated by the solid line is the data of the present embodiment, and the data indicated by the dotted line is the data in the comparative example. The frequency of vibration input to the rear floor panel 10 varies depending on the engine specifications (the number of cylinders), but in the present embodiment, the engine speed is 1050 to 1500 rpm (a band surrounded by a thick line in FIG. 5). In this case, 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 portion of the floor pan 12 exceeds 30 dB and the sound pressure level in the passenger compartment exceeds 80 dB in the range where the engine speed is 1050 to 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 reduced as compared with the comparative example in the range where the engine speed is 1050 to 1500 rpm. As a result, in the present embodiment, the sound pressure level in the passenger compartment can be made lower 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 speed (that is, the frequency of the vibration input to the rear floor panel 10 is 35 Hz to 50 Hz), the noise of the vehicle interior generated by the vibration of the rear floor panel 10 is reduced. be able to.

  In the present embodiment, the first storage recess 38 is formed on the vehicle upper side (directly above) the protrusion 44, and the jack 50 is stored inside the first storage recess 38. For this reason, the jack 50 as a storage thing is arrange | positioned in the vehicle upper side (directly above) of the front part of the floor pan 12 used as a belly in a primary natural vibration mode. Accordingly, since the jack 50 that functions as a weight when the storage box 30 is configured as a dynamic damper is disposed on the vehicle upper side (directly above) of the front portion of the floor pan 12, the storage box 30 functions efficiently as a dynamic damper. Can be made.

  Moreover, the storage box 30 is comprised with the foaming resin molding. For this reason, the rear floor panel 10 is damped according to the vibration characteristics of the rear floor panel 10 by appropriately changing (adjusting) the position and shape of the protruding portion 44 corresponding to the form of the rear floor panel 10 of various vehicles. Can do.

  In the present embodiment, the storage box 30 is supported by the rear floor panel 10 at predetermined positions (portions surrounded by a dotted line A shown in FIG. 2) in the first flange portion 34 and the second flange portion 36. However, the part where the storage box 30 is supported can be arbitrarily set. In other words, 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 storage items such as the jack 50. Moreover, you may change suitably the part supported by the rear floor panel 10 in the 1st flange part 34 and the 2nd flange part 36. FIG.

  Further, in the present embodiment, the protruding portion 44 of the storage box 30 is in contact with the front portion of the bottom wall portion 12A of the floor pan 12, but the weight balance of the storage box 30 including the storage items such as the jack 50 is improved. In consideration, the storage box 30 may be brought into contact with the bottom wall portion 12 </ b> A also in other parts. That is, at least the protruding portion 44 of the storage box 30 only needs to be in contact with the front portion of the bottom wall portion 12 </ b> A of the floor pan 12.

10 Rear floor panel 12 Floor pan 12A Bottom wall 30 Storage box 44 Projection 50 Jack (storage)
52 Punk repair kit (containment)
54 Punk repair kit (containment)

Claims (1)

A rear floor panel that forms a floor at the rear of the vehicle and has a concave floor pan that is open to the upper side of the vehicle;
The floor pan is disposed on the vehicle upper side of the rear floor panel so as to cover the vehicle from the upper side, and stores storage items such as jacks, protrudes to the vehicle lower side, and abuts against the front portion of the bottom wall portion of the floor pan. A storage box that is formed as a foamed resin molded body,
Vehicle rear floor structure with