Vibration damper, vibration damping device, installation method of vibration damper, and vibration damping method

Abstract

It does not require a large space and can reduce airborne sound with a simple structure. Find two or more target points (P) with different amplitudes in the natural mode of the object (O) to be reduced, such as the casing of an engine, gear box, motor, etc., fix the arm (11) to a position (target point Pf) with a relatively small amplitude among these target points (P), and press the vibration absorber (31) set on the free end (12) side of the arm (11) to a position (target point Pp) with a relatively large amplitude. When the object (O) vibrates, the vibration absorber (31) presses the target point (Pp) with a relatively large amplitude while the arm (11) follows the vibration of the object (O).

Description

Technical Field

[0001] The present invention relates to a vibration damper, a vibration damping device, a method for mounting the vibration damper, and a vibration damping method. Background Art

[0002] Various machines generate vibrations through their movements. For example, a car has many vibration sources such as engines, motors, compressors, gear boxes, etc. These parts vibrate during operation and generate radiated sound. Recently, the electrification of cars has been increasingly developed, and there is a trend towards quieter driving than before, so some countermeasures are also required.

[0003] Noise caused by the vibration of each component can be roughly divided into two types. One is the noise caused by the vibration of the component being transmitted to its supporting side. The other is the airborne sound caused by the vibration of the component being transmitted in the air.

[0004] Patent Documents 1 and 2 disclose vibration isolators provided on engine mounts. These vibration isolators suppress the transmission of vibration of a component to the support side thereof, thereby reducing the noise excited by the transmission of vibration to the support side.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Publication No. 2009-270587;

[0008] Patent document 2: Japanese Patent Application Publication No. 2019-060454. Summary of the invention

[0009] Problems to be solved by the invention

[0010] The noise generated by the vibration of a component being transmitted to its supporting side can be dealt with by, for example, the vibration isolation devices disclosed in Patent Documents 1 and 2. On the other hand, such vibration isolation devices do not reduce airborne sound.

[0011] Regarding airborne sound, noise countermeasures are generally taken in the form of shielding the vibration source. For example, the vibration source is covered with a shielding plate, sound insulation material, etc. However, the structure that covers the vibration source in a certain way requires a large installation space, and the structural parts themselves will cost a lot of money. Considering such space constraints, costs, etc., it cannot be said to be a countermeasure that can be used conveniently.

[0012] Therefore, it is desired to reduce airborne sound with a simple structure without requiring a large space.

[0013] Means used to solve problems

[0014] One form of a vibration-damping damper comprises: an arm fixed to a position where the amplitude is relatively small among two or more target points with different amplitudes in an inherent mode at a specific inherent vibration frequency; and a vibration absorber arranged on the arm in a manner to press a position where the amplitude is relatively large among the target points.

[0015] One embodiment of a vibration reduction device comprises: an arm, which is fixed to a position where the amplitude is relatively small among two or more target points with different amplitudes in an inherent mode at a specific inherent vibration frequency; and a vibration absorber, which is arranged on the arm in a manner to press a position where the amplitude is relatively large among the target points.

[0016] In one method of installing a vibration damper, two or more target points having different amplitudes in a natural mode in a specific natural vibration frequency are found, an arm is fixed at a position of the target point where the amplitude is relatively small, and a vibration absorber provided on the arm is pressed at a position of the target point where the amplitude is relatively large.

[0017] In one embodiment of the vibration reduction method, when an object vibrates, an arm follows the vibration of the object, the arm is fixed at a position with a relatively small amplitude among two or more target points with different amplitudes in an inherent mode at a specific inherent vibration frequency, and while the arm follows the vibration of the object, a vibration absorber provided on the arm presses a position with a relatively large amplitude among the target points.

[0018] Effects of the Invention

[0019] It does not require a large space and can reduce airborne sound with a simple structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a perspective view showing one embodiment of a vibration reduction damper to be attached to an object.

[0021] Figure 2 This is a graph comparing the vibration levels of the object in three situations: without a vibration damper, with a vibration damper (massless body), and with a vibration damper (mass body).

[0022] Figure 3 It is a perspective view showing another embodiment of a vibration reduction damper to be attached to an object.

[0023] Figure 4 This is a perspective view showing still another embodiment of a vibration reduction damper attached to an object in accordance with a vibration mode of the object.

[0024] Figure 5 Schematic diagram showing an experimental device for collecting the amplitude of vibration generated by an object.

[0025] Figure 6 (A) is a graph showing a frequency response function of vibration generated by an object, Figure 6 (B) is a graph showing the frequency response function of the radiated sound at this time.

[0026] Figure 7 This is a graph showing a frequency response function of vibration generated by an object.

[0027] Figure 8 The diagrams are schematic diagrams showing vibration modes of an object at (A) 105 Hz, (B) 139 Hz, (C) 280 Hz, (D) 291 Hz, (E) 361 Hz, and (F) 675 Hz.

[0028] Fig. 9 This is a schematic diagram showing an example of a prototype (massless body) for verifying the effect of a vibration damper.

[0029] Fig.10 The graphs are graphs showing frequency response functions of vibrations generated in an object in the case where (A) there is no vibration damper and (B) there is a vibration damper (without a mass body).

[0030] Fig.11 (A) is a schematic diagram showing the vibration mode of the object at 291 Hz and (B) is 675 Hz.

[0031] Fig.12 This is a schematic diagram showing another example of a prototype (a body with mass) for verifying the effect of the vibration damper.

[0032] Fig.13 The graphs are graphs showing frequency response functions of vibrations generated in an object in the case where (A) there is no vibration damper and (B) there is a vibration damper (mass body). DETAILED DESCRIPTION

[0033] Embodiments of a vibration damper, a vibration damping device, a vibration damping method, and a method for mounting a vibration damper will be described with reference to the drawings.

[0034] Figure 4 , Figure 8 (A)~(F) and Fig.11(A) and (B) schematically show the vibration mode generated in the object O as the vibration reduction object, that is, the form and state of the vibration. In these figures, the light and dark colors of the achromatic colors indicate the magnitude of the vibration amplitude. In the figures, the amplitude is expressed by only three achromatic colors, light gray, dark gray and black, or two achromatic colors, light gray and dark gray, but this is just for the sake of convenience. In fact, the area between the light and dark colors should be a gradual change in light and dark. That is, the amplitude of the vibration does not change in stages as expressed by the light and dark colors of the achromatic colors in the above figures, but represents a smooth change regardless of whether the degree of change is steep or gentle.

[0035] Follow the instructions for the following items.

[0036] [One embodiment]

[0037] (1) Overall structure

[0038] (2) Target point

[0039] (3) Installation method of vibration damper

[0040] (4) Vibration reduction method

[0041] [Another embodiment]

[0042] [Another embodiment]

[0043] [One embodiment]

[0044] The object O to be subjected to vibration reduction is, for example, an engine, a motor, a compressor, a gear box, etc. of an automobile. The vibration reduction damper 1 is mounted on the object O. When the vibration reduction damper 1 is mounted on the object O, a vibration reduction device 2 is formed. The vibration reduction damper 1 and the vibration reduction device 2 reduce airborne sound generated by the vibration generated by the object O propagating in the air.

[0045] (1) Overall structure

[0046] like Figure 1 As shown, the arm 11 is fixed to the object O, and a portion of the object O is pressed by the vibration absorber 31 provided on the free end 12 side of the arm 11 .

[0047] The arm 11 is a long and narrow rectangular member, and has a fixed end 13 on the opposite side of the free end 12, and a curved portion 14 between the free end 12 and the fixed end 13. As an example, the arm 11 is made of metal, resin, etc., and is given elasticity.

[0048] The arm 11 is fixed to the object O by, for example, screwing with a fixing screw 21. The fixing screw 21 passes through a through hole (not shown) provided at the fixed end 13 of the arm 11 and is screwed into a threaded hole (not shown) provided at the object O. The arm 11 is fastened to the object O by screwing the fixing screw 21.

[0049] The vibration absorber 31 is a cylindrical member having elasticity made of rubber, for example, and is fixed to the free end 12 of the arm 11 by, for example, bonding, welding, or the like.

[0050] (2) Target point

[0051] In the object O, the position where the arm 11 is fixed and the position where the vibration absorber 31 is pressed are target points P. These target points P are positions where the amplitudes of the eigenmodes existing in the object O are different.

[0052] The position where the arm 11 is fixed is a position where the vibration amplitude is smaller than the position where the vibration absorbing member 31 is pressed. That is, the fixed end 13 of the arm 11 is fixed to the target point P where the vibration amplitude is relatively small, and the vibration absorbing member 31 is positioned to press the target point P where the vibration amplitude is large. For the sake of convenience, the target point P where the arm 11 is fixed is referred to as the target point Pf, and the target point P where the vibration absorbing member 31 is pressed is referred to as the target point Pp.

[0053] As described above, the two target points Pf and Pp are two target points P with different amplitudes in the natural mode existing on the object O. The natural mode in this case is a natural mode at a specific natural vibration frequency. For this point, see Figure 7 Provide explanation.

[0054] like Figure 7 The graph shown shows a frequency response function (ratio of the exciting force to the response acceleration) when the object O vibrates.

[0055] More specifically, each of the intersection points of the cells generated by a plurality of virtual lines arranged in parallel vertically and horizontally at a plurality of positions of the object O, for example, at equal intervals, is used as a measurement point, and the vibration generated at these measurement points is measured by the acceleration sensor 101 (see Figure 5 ). The vibration is generated by hitting the object O with the pulse hammer 102, for example. Figure 7 2 is a graph showing a frequency response function calculated based on the output of the acceleration sensor 101 at this time. The horizontal axis represents the frequency, and the vertical axis represents the frequency response function of the vibration.

[0056] As another embodiment, Figure 7The graph shown can also be obtained as a Fourier spectrum. To this end, the output of the acceleration sensor 101 is collected for a predetermined amount of time, for example, 10 seconds. Thus, the time axis waveform of the output of the acceleration sensor 101 is obtained. Therefore, the time axis waveform is transformed into a spectrum by FFT (Fast Fourier Transform). If the spectrum at each measurement point obtained in this way is superimposed, the following is obtained: Figure 7 The chart shown.

[0057] See also Figure 7 , it can be seen that peak waveforms appear near 105Hz, 139Hz, 280Hz, 291Hz, 361Hz and 675Hz. Peak waveforms are also generated in other frequencies, such as the area between 500Hz and 600Hz, the area between 700Hz and 800Hz, etc., but they are omitted in this description.

[0058] Figure 8 (A)~ Figure 8 (F) of FIG. 1 shows the vibration mode of the object O at the above frequency where the peak waveform appears. For example, if we focus on Figure 8 As shown in (A), the large amplitude that appears in the upper and lower regions of the object O decreases toward the central region, and the reduced amplitude increases in the central region. The amplitude of the vibration generated in the central region is smaller than the amplitude of the vibration generated in the upper and lower regions.

[0059] Figure 8 (A)~ Figure 8 The +-marks in (F) represent vibration modes generated in the object O by the impact of the hammer 102. In this figure, + represents the amplitude generated on the front side, and - represents the amplitude generated on the rear side.

[0060] from Figure 8 (A)~ Figure 8 As can be seen from (F), the white area becomes the vibration node (node) and the dark gray area becomes the vibration antinode (anti-node).

[0061] As an example, the target point Pf of the fixed end 13 of the fixed arm 11 is determined as the position of the vibration node, and the target point Pp of the pressing vibration absorber 31 is determined as the position of the vibration antinode. Of course, the positions of the two target points Pf and Pp are not necessarily limited to the vibration nodes and antinodes, as long as the position with relatively small vibration amplitude is determined as the target point Pf, and the position with large vibration amplitude is determined as the target point Pp.

[0062] (3) Installation method of vibration damper

[0063] The method of attaching the vibration damper 1 to the object O is performed through three steps: a target point search step, a fixing step, and a positioning step.

[0064] The target point search step is a step of finding two or more target points P having different amplitudes in a natural mode at a specific natural vibration frequency existing on the object O.

[0065] At this time, the specific natural vibration frequency appears, for example, Figure 7 The frequency of such a peak waveform is shown as an example. Figure 7 It can also be known that the natural vibration frequency is not limited to one but exists in multiples. Which natural vibration frequency is selected as the specific natural vibration frequency can be determined based on the correspondence with the airborne sound to be reduced. That is, the natural vibration frequency that causes the airborne sound to be reduced is determined, and the natural vibration frequency is selected as the specific natural vibration frequency.

[0066] Once a specific natural vibration frequency is determined, the vibration mode of the object O at the natural vibration frequency is analyzed to determine two or more target points P with different vibration amplitudes. Figure 7 In the example, it is assumed that 291 Hz is selected as the specific natural vibration frequency. The vibration mode of the object O at this frequency is as follows Figure 8 See (D). Figure 8 (D) can find two or more target points P with different vibration amplitudes anywhere.

[0067] For example, in Figure 8 In (D), vibration antinodes (antinodes) appear at the upper left corner and lower right corner and slightly above the lower right corner of the object O. Therefore, the positions of these vibration antinodes and positions other than the antinodes can be selected as two or more target points P with different vibration amplitudes.

[0068] The fixing step is a step of determining a position with a relatively small amplitude among the found target points P, for example, a vibration node (node ​​point), as a target point Pf and fixing the arm 11 to the target point Pf.

[0069] For example, in Figure 8 In (D), the white area is a vibration node. In addition, the amplitude of the light gray area is smaller than that of the dark gray area which is a vibration antinode. Therefore, it is sufficient to determine one of the white area or the light gray area as the target point Pf and fix the arm 11 to the target point Pf.

[0070] The positioning step is a step of determining a position with a relatively large amplitude among the found target points P, such as a vibration antinode (anti-node), as a target point Pp and pressing the vibration absorber 31 provided on the arm 11 to the target point Pp.

[0071] For example, in Figure 8In (D), the dark gray area is the vibration antinode. Therefore, it is sufficient to determine the dark gray area as the target point Pp and press the vibration absorber 31 provided on the arm 11 to the target point Pp. Under the premise that the fixed position of the vibration absorber 31 relative to the arm 11 is appropriately determined, the pressing of the vibration absorber 31 relative to the target point Pp can be easily achieved by appropriately setting the installation angle of the arm 11.

[0072] (4) Vibration reduction method

[0073] The vibration reduction method of the object O is performed through two steps of a following step and a pressing step.

[0074] The following process is a process in which the arm 11 is fixed to a position (target point Pf) with a relatively small amplitude among two or more target points P having different amplitudes in an eigenmode existing in the object O to follow the vibration of the object O when the object O vibrates.

[0075] The arm 11 follows the vibration of the object O in the entire arm 11 including the fixed position of the fixing screw 21. When the arm 11 is fixed to a vibration node, since no amplitude is generated at this position, the following of this part means that the object O without displacement is integrated with the arm 11. In contrast, the arm 11 follows the vibration of the object O via the vibration absorber 31 in the portion other than the vibration node.

[0076] The pressing step is a step of causing the vibration absorber 31 provided on the arm 11 to press a position (target point Pp) having a relatively large amplitude among the target points P while the arm 11 follows the vibration of the object O.

[0077] exist Figure 2 In FIG. 1 , the amplitude of the vibration generated in the object O to which the vibration damper 1 is not attached is indicated by a solid line, and the amplitude of the vibration generated in the object O to which the vibration damper 1 is attached is indicated by a dotted line. When the pressing step is performed, the amplitude of the vibration generated in the object O becomes smaller. Figures 7 to 11 (A) Fig.11 (B) is described in detail.

[0078] In the method for installing the vibration damper, for example, it is assumed that 280 Hz is determined as the specific natural vibration frequency (see Figure 7 ). In the target point search process, two or more target points P having different amplitudes in the 280 Hz natural mode are found.

[0079] like Figure 8 As shown in (C), in the 280 Hz vibration mode, a vibration node (white area) appears slightly above the lower right corner of the object O, and an amplitude area (light gray area) appears in the lower right corner. Fig. 9As shown in FIG. 1 , the vibration damper 1 is attached to the object O with the slightly upper side of the lower right corner of the object O being determined as the target point Pf and the lower right corner being determined as the target point Pp.

[0080] Fig.10 (A) Fig.10 (B) is a graph showing a frequency response function of a ratio of an exciting force of vibration generated in the object O to a response acceleration. Fig.10 (A) shows the frequency response function of the object O to which the vibration damper 1 is not installed. Fig.10 (B) shows the frequency response function of the object O to which the vibration damper 1 is mounted. Fig.10 (A) and Fig.10 As can be seen from (B), the peak waveforms at 280 Hz and 291 Hz appear when there is no vibration damper 1 (see Fig.10 (A)) is provided with a vibration damper 1 to become Fig.10 The waveform shown in (B) is shown in Fig.10 (A) and Fig.10 When compared with (B), not only the waveform has changed, but also the amplitude has decreased.

[0081] From the above results, it can be seen that the amplitude of the vibration generated in the object O becomes smaller.

[0082] Moreover, if Fig.10 As shown in (B), the amplitude of the vibration generated by the object O at 675 Hz is also reduced. This is caused by the following reason: in the above-mentioned target point search process, the target point Pf where the arm 11 is fixed and the target point Pp where the vibration absorber 31 is pressed are determined to be positions with opposite phases between two other frequencies different from 280 Hz as the specific natural vibration frequency. The other two frequencies are 291 Hz and 675 Hz.

[0083] See also Fig.11 (A) Fig.11 (B). Fig.11 (A) is the vibration mode generated in the object O at 291 Hz. In contrast, Fig.11 (B) is a vibration mode generated in the object O at 675 Hz. If attention is paid to the position of the target point Pp pressed by the vibration absorber 31 of the vibration damper 1, in the vibration mode of 291 Hz, the target point Pf is - and the target point Pp is + (see Fig.11 (A)). In the 675Hz vibration mode, the target point Pf is + and the target point Pp is - (see Fig.11 That is, when the vibration modes of 291 Hz and 675 Hz are compared, it can be seen that the two target points Pf and Pp are determined as positions with opposite phases to each other.

[0084] It is estimated that the decrease in the amplitude of the vibration generated by the object O at the frequency of 675 Hz is due to the above-mentioned opposite phase relationship.

[0085] According to this embodiment, the amplitude of the vibration generated by the object O is reduced by executing the pressing step. Therefore, the airborne sound generated by the vibration of the object O propagating in the air is also reduced. Figure 1 It can be seen that the vibration damper 1 is small and has a simple structure, so it does not need to occupy a large space and can easily reduce airborne sound.

[0086] [Another embodiment]

[0087] based on Figure 3 Another embodiment will be described. Figure 1 The same parts in the illustrated embodiments are denoted by the same reference numerals, and description thereof is omitted.

[0088] In the vibration damper 1 of the present embodiment, a mass body 41 is fixed to the surface on the free end 12 side of the arm 11. The mass body 41 is fixed to the surface on the opposite side to the vibration absorber 31.

[0089] The mass body 41 absorbs the vibration of the natural frequency and reduces the vibration of the object O.

[0090] exist Figure 2 In FIG. 1 , the single-dot chain line indicates the amplitude of the vibration generated by the object O when the mass body 41 is fixed to the vibration damper 1. It can be seen that the amplitude of the vibration generated by the object O is further reduced compared to when the vibration damper 1 without the mass body 41 is attached to the object O (see the dotted line). Therefore, the airborne sound generated by the vibration of the object O propagating in the air is further reduced.

[0091] [Another embodiment]

[0092] based on Figure 4 Another embodiment is described below. Figure 3 The same parts as those in other embodiments shown are denoted by the same reference numerals, and the description thereof is also omitted.

[0093] The vibration reduction device 2 of this embodiment is suitable for Figure 4 Two target points Pf and three target points Pp are determined in accordance with the vibration mode of the object O shown below in the example, and one vibration damper 1 is installed at these target points P.

[0094] The vibration damper 1 has an arm 11 bent 90 degrees to form an L shape, and the two ends of the arm 11 are fixed to the object O. These fixed positions are target points Pf. At this time, a spacer 51 is placed between the target point Pf to ensure a gap between the arm 11 and the object O. The gap is a space for arranging a vibration absorber 31, and the vibration absorber 31 is fixed to the lower surface of the arm 11 opposite to the object O. The vibration absorber 31 is fixed at three locations: the bending position of the arm 11 and the center position of both sides. These positions are target points Pp. A mass body 41 is fixed to the surface side of the arm 11 corresponding to the back side of the vibration absorber 31.

[0095] As shown in the present embodiment, there may be two or more target points Pf, and there may be three or more target points Pp. The vibration damper 1 of the present embodiment is fixed to these target points Pf, and the target points Pp can be pressed by the vibration absorber 31 .

[0096] Example

[0097] The inventors who created the embodiments of the vibration damper, the vibration damping device, the mounting method of the vibration damper, and the vibration damping method conducted experiments to confirm the effects thereof.

[0098] (1) Experimental setup

[0099] like Figure 5 As shown, the experimental device is configured to treat a flat SPHC steel plate as an object O, and to use each of the intersection points of units generated by multiple virtual lines arranged in parallel at equal intervals as a measurement point, so that vibrations generated at these measurement points can be measured by the acceleration sensor 101.

[0100] At this time, instead of arranging the acceleration sensor 101 at each measurement point, a plan is made to be able to measure the vibration generated at all measurement points by arranging one acceleration sensor 101 at the center of the object O. As a structure for this purpose, a dot-shaped mark M is applied to all measurement points. By collecting the vibration generated in the object O when the position of the mark M is hit by the pulse hammer 102 using the acceleration sensor 101, an attempt is made to obtain vibration data equivalent to the vibration generated at all measurement points.

[0101] The experimental device also has a microphone 103 installed just above the acceleration sensor 101 , which can collect the sound when the pulse hammer 102 hits the object O.

[0102] (2) Vibration and sound

[0103] like Figure 6 The graph shown in (A) shows the frequency response function when the object O vibrates. Figure 6In the graph of (A), the position of the mark M assigned to the object O as the measurement point is struck with the impulse hammer 102. The frequency response function is calculated based on the output of the acceleration sensor 101 at this time. By superimposing the frequency response functions when all the positions of the mark M are struck, the frequency response function is obtained. Figure 6 The graph shown in (A).

[0104] like Figure 6 The graph shown in (B) shows the frequency response function when the object O vibrates. Figure 6 In the graph (B), the position of the mark M assigned to the object O as the measurement point is struck with the impulse hammer 102. At this time, the frequency response function is calculated based on the sound signal acquired from the microphone 103. By superimposing the frequency response functions when all the positions of the mark M are struck, Figure 6 The graph shown in (B).

[0105] Compare Figure 6 (A) and Figure 6 As can be seen from (B), the peak frequencies of the acceleration obtained from the output of the acceleration sensor 101 and the sound obtained from the output of the microphone 103 match. This means that when the object O vibrates, the vibration propagates in the air and generates airborne sound. Figure 6 (A) Figure 6 The graph (B) of exemplifies the correspondence between the vibration generated by the object O and the airborne sound caused by it. Figure 6 (A) Figure 6 The experimental results shown in (B) are evidence that airborne sound can be reduced by attenuating vibration.

[0106] (3) Confirmation of vibration reduction effect

[0107] Figure 7 To express in words Figure 6 The graph shown in (A) shows graphs of 105 Hz, 139 Hz, 280 Hz, 291 Hz, 361 Hz, and 675 Hz where peak waveforms appear. Figure 8 (A)~ Figure 8 (F) is a schematic diagram showing the vibration mode of the object O at the above frequency at which the peak waveform appears, that is, the natural vibration frequency. Figure 8 (A)~ Figure 8 In the schematic diagram shown in (F), the amplitude shape and size of the vibration are clearly visible for each natural vibration frequency where the peak waveform appears.

[0108] Therefore, the inventors determined two or more target points P on the object O having different amplitudes in the natural mode at a specific natural vibration frequency, such as Fig. 9The vibration damper 1 is mounted by fixing the arm 11 at a position (target point Pf) with relatively small amplitude and positioning the vibration absorber 31 to press a position with relatively large amplitude.

[0109] In this way, the object O to which the vibration damper 1 is mounted is struck again with the pulse hammer 102 at the position of the mark M to produce the same Figure 6 The result is as follows Fig.10 The diagram shown in (B) is shown in Fig.10 The diagram shown in (A) is for Fig.10 The comparison of (B) shows that Figure 6 The same diagram as (A).

[0110] As a result, the inventors also confirmed that: when there is no vibration damper 1, the peak waveforms appearing at 280 Hz and 291 Hz (see Fig.10 The amplitude of (A)) is reduced by providing the vibration damper 1.

[0111] The above experimental results have proven that the amplitude of vibration generated in the object O is reduced by attaching the vibration damper 1 to the object O. This also enables reduction of airborne sound.

[0112] In addition, the inventors confirmed that: Fig.11 (A) Fig.11 As shown in (B), by determining the target point Pf where the arm 11 is fixed and the target point Pp where the vibration absorber 31 is pressed to be positions with opposite phases between the two frequencies (291 Hz and 675 Hz), the amplitude of the vibration generated on the object O is also reduced. Fig.10 As shown in (B), the amplitude of vibration decreases at a frequency of 675 Hz.

[0113] And, if Fig.12 As shown, the inventors made a prototype with a mass body 41 on the vibration damper 1, and repeated the same Fig. 9 The same experiment was conducted on the prototype (massless body) shown in the figure. The results are as follows Fig.13 (A) Fig.13 As shown in (B), a further vibration reduction effect was confirmed.

[0114] Fig.13 The graph shown in (A) shows the experimental results in a structure without the vibration damper 1. Fig.13 The diagram shown in (B) shows the use of Fig.12 The experimental results of the prototype shown in the figure all show the frequency response function of each measurement point (marked M) near 139 Hz.

[0115] In such Fig.13 In the structure without the vibration damper 1 shown in (A), two peak waveforms appear at 105 Hz and 139 Hz. Fig.13 In the trial product (B) in which both the vibration damper 1 and the mass body 41 are present, the peak waveform of 139 Hz is divided into two (120 Hz and 150 Hz), and the amplitude thereof becomes smaller.

[0116] The above experimental results prove that the amplitude of vibration generated in the object O in a specific frequency range is further reduced by attaching the vibration damper 1 with the mass body 41 to the object O. This proves that the airborne sound can be further reduced.

[0117] Explanation of symbols

[0118] 1 Vibration damper

[0119] 2 Vibration reduction device

[0120] 11 Arm

[0121] 12 Free end

[0122] 13 Fixed end

[0123] 14 Bend

[0124] 21 Fixing screw

[0125] 31. Vibration absorber

[0126] 41 Mass

[0127] 51 Spacer

[0128] P Target point

[0129] Pf Target Point

[0130] Pp Target point

[0131] O Object

[0132] M Mark

[0133] 101 Accelerometer

[0134] 102 Pulse Hammer

[0135] 103 Microphone

Claims

1. A vibration reduction device comprising: an arm having a free end and a fixed end, wherein the fixed end is fixed to a position where the amplitude is relatively small among two or more target points having different amplitudes in a natural mode at a specific natural vibration frequency; and a vibration absorber, the vibration absorber being arranged on the arm in such a manner that the free end presses a position of the target point where the amplitude is relatively large, The arm is elastic. The vibration absorber is fixed to the free end of the arm, and is pressed to a position of the target point where the amplitude is relatively large due to the elasticity of the arm.

2. The vibration reduction device according to claim 1, wherein: The target point of the fixed arm is the position of the node of the amplitude.

3. The vibration reduction device according to claim 1 or 2, wherein: The target point pressed by the vibration absorber is the position of the antinode of the amplitude.

4. The vibration reduction device according to claim 1, wherein: The two target points where the arm is fixed and the vibration absorber is pressed are determined as positions where the amplitudes of natural modes in two natural vibration frequencies other than the specific natural vibration frequency are in opposite phases to each other.

5. The vibration reduction device according to claim 1 or 2, wherein: A mass body for reducing vibration is provided at the position of the vibration absorber.

6. A method for installing a vibration damper, comprising: Find two or more target points with different amplitudes in a natural mode at a specific natural vibration frequency; Fixing the fixed end of an arm having a free end and a fixed end at a position of the target point where the amplitude is relatively small, the arm having elasticity; and The vibration absorber provided at the free end of the arm is pressed to a position of the target point where the amplitude is relatively large due to the elasticity of the arm.

7. A vibration reduction method, comprising: When the object vibrates, the arm follows the vibration of the object, the arm includes a free end and a fixed end, the fixed end is fixed to a position where the amplitude is relatively small among two or more target points having different amplitudes in an eigenmode at a specific eigenfrequency, and the arm has elasticity; While the arm follows the vibration of the object, the vibration absorber provided at the free end of the arm presses a position of the target point where the amplitude is relatively large due to the elasticity of the arm.

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