Vehicle body structure

Abstract

To provide a vehicle body structure that can reduce road noise across a wide range of vibration frequencies. [Solution] When the subframe 2 of the rear suspension is supported via a pin 3 having a central axis substantially aligned in the vertical direction, a spiral-shaped vibration damping member 5 is provided, which is positioned at the lower end of the subframe 2 along the axis of the pin 3 and has a fixed center.

Description

[Technical Field]

[0001] This invention relates to a vehicle body structure. [Background technology]

[0002] Patent Document 1 discloses a vehicle body structure in which a subframe is supported via a plurality of cylindrical bushings in a rear suspension. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Patent No. 5366723 [Overview of the project] [Problems that the invention aims to solve]

[0004] To suppress the transmission of vibrations and noise from the rear suspension to the vehicle body, elastic materials such as rubber bushings are often used on the vehicle body. However, since road noise vibrations span a wide range, rubber bushings are not sufficient to cover that wide range of vibrations. The present invention aims to provide a vehicle body structure capable of efficiently attenuating road noise over a wide area. [Means for solving the problem]

[0005] According to one aspect of the present invention, the present invention comprises a suspension or power source device and a vehicle body frame fastened to the suspension or power source device, and has a spiral-type vibration damping member positioned at the lower end of the suspension or power source device, with its center fastened to the suspension or power source device via a fastening member. Furthermore, according to another aspect of the present invention, a vehicle body structure supports a rear suspension subframe via a rear suspension member pin having a central axis substantially aligned in the vertical direction, and includes a spiral-shaped vibration damping member positioned at the lower end of the subframe along the axis of the rear suspension member pin and having a fixed center. [Effects of the Invention]

[0006] According to the present invention, a spiral-type vibration damping member makes it possible to attenuate road noise across a wide range of vibrations. [Brief explanation of the drawing]

[0007] [Figure 1] This is an assembled perspective view showing one embodiment of the vehicle body structure. [Figure 2] Figure 1 is a front view of the spiral-type vibration damping member used in the vehicle body structure. [Figure 3] Figure 2 is an explanatory diagram of the frequency response characteristics of the spiral-type vibration damping member. [Figure 4] Figure 2 is an explanatory diagram of the specifications of the spiral-type vibration damping member. [Figure 5] Figure 4 is an explanatory diagram of the frequency response characteristics of a spiral-type vibration damping member with parameter tuning applied to the specifications shown. [Figure 6] Figure 2 is a front view of a first modified example of the spiral-type vibration damping member. [Figure 7] Figure 2 is a front view of a second modified example of the spiral-type vibration damping member. [Figure 8] Figures 6 and 7 are explanatory diagrams illustrating the frequency response characteristics of 7 measured using the spiral-type vibration damping members shown in Figure 6 and 7 with the vehicle body structure shown in Figure 1. [Figure 9] This is a front view of a modified example in which a damping material is bonded to the spiral-shaped vibration damping member shown in Figure 6. [Figure 10] Figure 6 is a front view of a modified example in which damping material is filled into the spiral-shaped vibration damping member. [Figure 11] Figures 9 and 10 illustrate the frequency response characteristics of the spiral-type vibration damping member. [Figure 12] Figure 10 is an explanatory diagram of the frequency response characteristics when the physical properties of the filler material of the spiral-type vibration damping member are changed. [Figure 13] Figure 10 is an explanatory diagram of the frequency response characteristics when the physical properties of the filler material of the spiral-type vibration damping member are changed. [Modes for carrying out the invention]

[0008] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that each drawing is schematic and may be different from the actual one. Further, the embodiments of the present invention shown below exemplify devices and methods for embodying the technical idea of the present invention, and the technical idea of the present invention does not specify the structure, arrangement, etc. of the components as the following. The technical idea of the present invention can be variously modified within the technical scope defined by the claims described in the claims.

[0009] The vehicle body structure of the embodiment shown in FIG. 1 supports a sub-frame (suspension member) 2 of a rear suspension on a vehicle body frame 1 at the rear of the vehicle. In this example, a rear suspension member pin (hereinafter, also simply referred to as a pin) 3 having a central axis substantially along the vertical direction projects downward from the vehicle body frame 1, and this pin 3 is inserted into a hole portion 4 provided in the sub-frame 2 and having a central axis in the vertical direction, whereby the sub-frame 2 is attached to the vehicle body frame 1. Needless to say, a suspension arm (not shown) is attached to this sub-frame 2, and a rear suspension is constituted by these. In this embodiment, a spiral vibration damping member (hereinafter, also simply referred to as a vibration damping member) 5 is attached to the lower end portion of the pin 3 inserted into the sub-frame 2. That is, in other words, the vibration damping member 5 is disposed at the lower end of the sub-frame 2 along the axis of the pin 3.

[0010] The vibration damping member 5 shown in Fig. 2 is of the so-called scroll type and has a planar spread, but is thin in the direction perpendicular to the paper surface (different from a helix). As an example, the material constituting this vibration damping member 5 is steel, but any material can be applied as long as it can resonate with the excitation force. This vibration damping member 5 can be formed, for example, by punching a metal plate material by pressing or the like. However, when it is stretched so as to unwind the vortex, it becomes approximately a single rod shape. Therefore, the member constituting the scroll type vibration damping member 5 is defined as a rod-shaped member 6. Conversely, when the rod-shaped member 6 is wound into a scroll shape, a gap is formed between adjacent rod-shaped members 6. This scroll type vibration damping member 5 obtains a vibration damping (attenuation) effect by being displaced so that the gap between the rod-shaped members 6 expands or contracts. In addition, a hole 8 for inserting the screw portion of a fastening member such as a bolt is provided at the central portion of the vibration damping member 5, which is the center of the scroll. Further, the shape of the vibration damping member 5 is not limited to a scroll, and may be a substantially circle or a square.

[0011] Fig. 3 shows the frequency response characteristics obtained for analyzing the vibration damping mechanism of the vibration damping member 5 in Fig. 2. The two-dot chain line in the figure is the vibration point response characteristic at the vibration position (= the lower end position of the pin 3) of the vehicle body structure in Fig. 1 without the vibration damping member 5, and the solid line is the vibration point response characteristic in the state where the vibration damping member 5 in Fig. 2 is attached to the lower end portion of the pin 3 of the vehicle body structure in Fig. 1. The weight of the vibration damping member 5 was 156 g. As shown in the figure, a large damping effect can be seen around approximately 520 Hz and 640 Hz. As a result of the analysis, it was found that this damping effect is a reduction effect by a broadband dynamic damper due to two in-plane modes in the X direction and the Y direction shown in Fig. 2.

[0012] In order to make this vibration damping member 5 suitable for reducing road noise (low frequency), it was considered necessary to lower the frequency of the vibration reduction effect of the in-plane modes and to appropriately adjust the interval between the eigenvalues ​​of the two in-plane modes, and the parameters for this purpose were extracted. The parameters considered were the width and thickness of the rod-shaped member 6 shown in Figure 4a, the diameter (outer diameter) of the spiral and the total length when the rod-shaped member 6 is unraveled and extended or the number of turns of the spiral shown in Figure 4b, and the overall longitudinal and transverse stiffness ratio shown in Figure 4c. In the left side of Figure 4c, the longitudinal and transverse stiffness ratio (ratio of diameters) is 1, and as shown in the right side of Figure 4c, the longitudinal and transverse stiffness ratio can be changed by changing the aspect ratio of the spiral. The longitudinal and transverse stiffness ratio is also the frequency ratio of the two modes. Of these parameters, it was found that increasing the width of the rod-shaped member 6 increases the effective frequency and thus the effect range. It was also found that increasing the diameter of the spiral decreases the effective frequency and thus the effect range. Furthermore, it was found that the longitudinal and transverse stiffness ratio contributes greatly to the bandwidth of the effective frequency, but there is an optimal value. The analysis results are shown in Table 1.

[0013] [Table 1]

[0014] Figure 5 shows the frequency response characteristics of the vibration damping member 5 with tuned parameters. Figure 5a shows the excitation point response characteristics, and Figure 5b shows the outer ear response characteristics, where the outer ear response refers to the frequency response characteristics of sound transmitted to the ear. The dashed line in the figure shows the frequency response characteristics at the excitation position (= lower end position of pin 3) of the vehicle body structure in Figure 1 without the vibration damping member 5, and the solid line shows the frequency response characteristics with the tuned vibration damping member 5 attached to the lower end of pin 3 of the vehicle body structure in Figure 1. The weight of the tuned vibration damping member 5 used in the test was 110g. In both cases, a damping effect was observed in the frequency band of 230Hz to 310Hz, indicating that the damping frequency band has been lowered. Furthermore, the attenuation amount of the excitation point response in this attenuation frequency band was 3dB, and the attenuation amount of the outer ear response was 2.5dB.

[0015] To further improve the vibration damping member 5, which was parameter-tuned as described above, a fastening seat surface 7 for a fastening member was added to the center of the spiral as shown in Figure 6, and the number of turns of the rod-shaped member 6 was reduced for further rationalization. The vibration damping member 5 in Figure 6 was modified in shape as shown in Figure 7 in order to lower the frequency band in which the damping effect can be obtained. Specifically, the width was reduced and the thickness was doubled, as explained in Figure 4. The weight of the vibration damping member 5 in Figure 6 was 111g, and the weight of the vibration damping member 5 in Figure 7 was 171g. Figure 8 shows the frequency response characteristics when these vibration damping members 5 were attached to the subframe 2 of an actual vehicle and driven. In all figures, the upper figure shows the frequency response characteristics for sound, and the lower figure shows the frequency response characteristics for vibration, with the left figure showing the frequency response characteristics in the X direction and the right figure showing the frequency response characteristics in the Y direction. The dashed line in the figure represents the frequency response characteristics of the vehicle body structure in Figure 1 without the vibration damping member 5, while the solid line represents the frequency response characteristics of the vehicle body structure in Figure 1 with the vibration damping member 5 attached to the lower end of pin 3. The range indicated by the arrows in the figure is the frequency band in which the damping effect is sought. As is clear from the figure, a damping effect is obtained in the target frequency band in both cases.

[0016] To further enhance the damping effect of the vibration damping member 5, we considered providing a damping material 9 to the vibration damping member 5. When providing a damping material 9 to a spiral-shaped vibration damping member 5, for example, as shown in Figure 9, the damping material 9 can be attached (adhered) to the surface of the rod-shaped members 6 that constitute the vibration damping member 5, as shown in Figure 6, or the damping material 9 can be filled into the gaps between the rod-shaped members 6 that constitute the vibration damping member 5, as shown in Figure 10 (in both cases, the shaded areas indicate the damping material 9). The frequency response characteristics of the damping effect were analyzed for vibration damping members 5 with fillers provided using these two methods. The analysis conditions were set as follows: modal damping coefficient 0.0, structural damping coefficient 0.03, in-plane natural modes 280Hz and 301Hz, mode ratio 1.08, and damping coefficient of damping material 9 0.1. The analysis results are shown in Figure 11. Figure 11a shows the excitation point response characteristics in the Y direction, and Figure 11b shows the excitation point response characteristics in the X direction. In all cases, the excitation point response characteristics of the vibration damping member 5 in Figure 6 without the damping material 9 are shown by the dashed line, the excitation point response characteristics of the vibration damping member 5 in Figure 9 with the damping material 9 bonded to the rod-shaped member 6 are shown by the dashed line, and the excitation point response characteristics of the vibration damping member 5 in Figure 10 with the damping material 9 filled between the rod-shaped members 6 are shown by the solid line. In all cases, compared to the graph of the vibration damping member 5 without the damping material 9, a suppressed peak indicates a higher damping effect. As is clear from the figures, the peak tends to be suppressed in the vibration damping member 5 filled with the damping material 9. Furthermore, in the vibration damping member 5 with the filler bonded, even if the thickness and rigidity of the damping material 9 were increased, only the frequency at which the damping effect occurred shifted, and no change in the damping effect was observed.

[0017] Therefore, the frequency response characteristics (excitation point response characteristics) of a vibration-damping member 5 filled with damping material 9 were analyzed by changing the parameters of the damping material 9. Figure 12 shows the excitation point response characteristics and phase characteristics when the damping coefficient of the damping material 9 is set to 0.1, 0.5, and 0.8, and the Young's modulus (stiffness) of the damping material 9 is changed. In all cases, the dashed line in the figure represents the Young's modulus of the damping material 9 being 2.0 × 10⁻⁶ mmN / mm 2 The solid line represents Young's modulus 2.0 × 10⁻⁶. 2 mmN / mm 2 The dashed line indicates Young's modulus of 2.0 × 10⁻⁶. 3 mmN / mm 2shows the case. From the figure, it can be said that when the Young's modulus of the damping material 9 is relatively large, there is a damping effect (Young's modulus = 2.0×10 2 mmN / mm 2 ), but if it is too large (Young's modulus = 2.0×10 3 mmN / mm 2 ), resonance does not occur. Comparing the solid line graphs (Young's modulus = 2.OH×10 2 mmN / mm 2 ) with damping coefficients of 0.1 and 0.5, since the peak decreases by one in the solid line graph with a damping coefficient of 0.5, it can be seen that the damping effect is higher for a damping coefficient of 0.5. On the other hand, comparing the solid line graphs with damping coefficients of 0.5 and 0.8 shows little difference, so it can be said that a damping coefficient of 0.5 is sufficient.

[0018] Figure 13 is the evaluation of the graph in Figure 12 by the Young's modulus. In each case, the two-dot chain line in the figure shows the case where the damping coefficient of the damping material 9 is 0.1, the solid line shows the case where the damping coefficient of the damping material 9 is 0.5, and the broken line shows the case where the damping coefficient of the damping material 9 is 0.8. That is, with Young's moduli of 2.0×10mmN / mm 2 , 2.0×10 2 mmN / mm 2 , 2.0×10 3 mmN / mm 2 , the vibration point response characteristics and phase characteristics when the damping coefficient of the damping material 9 is changed are shown. In each case, the two-dot chain line in the figure shows the case where the damping coefficient of the damping material 9 is 0.1, the solid line shows the damping coefficient of 0.5, and the broken line shows the damping coefficient of 0.8. From the figure, it can be seen that a smaller Young's modulus has less effect, and if the Young's modulus is too large, the desired damping effect cannot be obtained.

[0019] Although the vehicle body structure according to the embodiment has been described above, the present invention is not limited to the configuration described in the above embodiment, and various modifications are possible within the scope of the gist of the present invention. For example, in the above embodiment, only a configuration in which a subframe 2 constituting part of the suspension is fastened to the vehicle body frame 1, and a spiral-type vibration damping member 5 is placed at the lower end of the subframe 2, with its center fastened to the subframe 2 via a fastening member has been described. However, even if a power source device is fastened to the vehicle body frame 1 instead of this suspension or the subframe 2 of the suspension, and the spiral-type vibration damping member 5 is placed at the lower end of this power source device with its center fastened to the power source device with a fastening member, road noise across a wide frequency range can be attenuated.

[0020] Thus, in the vehicle body structure of this embodiment, when the rear suspension subframe 2 is supported via a pin 3 having a central axis substantially aligned in the vertical direction, a spiral-shaped vibration damping member 5 is positioned at the lower end of the subframe 2 along the axis of the pin 3 and has a fixed center. Furthermore, when the suspension or power source is fastened to the vehicle body frame 1, a spiral-shaped vibration damping member 5, whose center is fastened to the suspension or power source via a fastening member, is positioned at the lower end of the suspension or power source. These vehicle body structures make it possible to reduce road noise across a wide range of vibrations.

[0021] Furthermore, by setting the ratio of the diameter of the spiral-shaped vibration damping member 5 in the vehicle's left-right direction to the diameter in the vehicle's front-rear direction to a value other than 1, attenuation effects in different frequency bands can be obtained. Furthermore, by bonding the damping material 9 to the rod-shaped members 6 that constitute the spiral-shaped vibration damping member 5, or by filling the space between the rod-shaped members 6 that constitute the spiral-shaped vibration damping member 5 with the damping material 9, it is possible to add a further damping effect to the vibration damping member 5. [Explanation of Symbols]

[0022] 1...Body frame, 2...Subframe, 3...Pin (suspension member pin), 4...Hole, 5...Vibration damping member (spiral-type vibration damping member), 6...Rod-shaped member, 7...Fastening seat, 8...Hole, 9...Damping material

Claims

1. Suspension or power source device, The vehicle comprises a body frame fastened to the suspension or power source device, The suspension or the power source device is positioned at the lower end, its center is fastened to the suspension or the power source device via a fastening member, and it has a vibration damping member formed by winding a rod-shaped member around it, A vehicle body structure characterized in that the rod-shaped members of the vibration damping member are wound on a plane with a predetermined distance between them and adjacent rod-shaped members.

2. A vehicle body structure that supports the rear suspension subframe via a rear suspension member pin having a central axis substantially aligned in the vertical direction, A vehicle body structure characterized by having a spiral-shaped vibration damping member positioned at the lower end of the subframe along the axis of the rear suspension member pin, with its center fixed.

3. The vehicle body structure according to claim 1 or 2, characterized in that the spiral-shaped vibration damping member has a ratio of less than 1 between the diameter in the left-right direction of the vehicle and the diameter in the front-rear direction of the vehicle.

4. The vehicle body structure according to claim 1 or 2, characterized in that a damping material is bonded to the rod-shaped member constituting the spiral vibration damping member.

5. The vehicle body structure according to claim 1 or 2, characterized in that a damping material is filled between the rod-shaped members constituting the spiral vibration damping member and the rod-shaped members.

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