Vibration isolation device

Abstract

To provide a vibration controller capable of improving a reduction effect of a surging phenomenon.SOLUTION: A resonant frequency of a first protrusion 18 is lower than a resonant frequency of elastic legs 13a to 13d, and a resonant frequency of a second protrusion 19 is higher than the resonant frequency of the elastic legs 13a to 13d. Consequently, a low frequency side of a surge peak due to the elastic legs 13a to 13d alone can be reduced by the first protrusion 18, and a high frequency side of the surge peak can be reduced by the second protrusion 19. With a vibration controller 10, the first protrusion 18 and the second protrusion 19 can improve a reduction effect of a surging phenomenon (surge peak).SELECTED DRAWING: Figure 1

Description

[[Technical Field]]

[0001] The present invention relates to a vibration damping device, and particularly to a vibration damping device capable of improving the reduction effect on surging phenomenon. [[Background Art]]

[0002] For example, as a vibration damping device for elastically supporting a vibration source such as an automobile engine or motor on a vehicle body, there is known a structure in which the outer peripheral surface of an inner cylinder attached to one of the vehicle body side and the vibration source side and the inner peripheral surface of an outer cylinder attached to the other of the vehicle body side and the vibration source side are connected by a vibration damping base body made of an elastic material. In this vibration damping device, the dynamic spring constant (absolute spring constant) of the vibration damping base body increases at the resonance frequency of the vibration damping base body, and a surging phenomenon in which the vibration damping base body vibrates violently at the resonance frequency may occur.

[0003] In the vibration damping device disclosed in Patent Document 1, a protrusion is projected from the axial end face of the vibration damping base body in order to reduce the surging phenomenon. By setting the resonance frequency of the protrusion near the resonance frequency of the vibration damping base body, the surge peak (the peak of the dynamic spring constant) in the frequency-specific graph of the dynamic spring constant is divided from one peak to two peaks, and the peak value is reduced. [[Prior Art Literature]] [[Patent Literature]]

[0004] [[Patent Document 1]] Japanese Unexamined Patent Publication No. 2008-267443 [[Summary of the Invention]] [[Problem to be Solved by the Invention]]

[0005] However, in Patent Document 1, even if one of the two divided surge peaks formed by the protrusion can be sufficiently suppressed, the other peak value cannot be sufficiently suppressed, so that a sufficient reduction effect on the surging phenomenon by the protrusion cannot be obtained.

[0006] This invention was made to solve the above-mentioned problems and aims to provide a vibration isolation device that can improve the effect of reducing surging phenomena. [Means for solving the problem]

[0007] To achieve this objective, the vibration isolation device of the present invention comprises a first member extending in the axial direction, a cylindrical second member surrounding the first member, an elastic vibration isolation base connecting the outer circumferential surface of the first member and the inner circumferential surface of the second member, and a plurality of types of protrusions each composed of an elastic body protruding from the axial end face of the vibration isolation base, the protrusions having different resonant frequencies, and at each resonant frequency, the vibration of the vibration isolation base and the vibration of the protrusions are in opposite phase, and the types of protrusions include a first protrusion having a resonant frequency lower than the resonant frequency of the vibration isolation base and a second protrusion having a resonant frequency higher than the resonant frequency of the vibration isolation base. [Effects of the Invention]

[0008] According to the vibration isolation device described in claim 1, at each resonant frequency, the vibration of the vibration isolation base and the vibration of the projection protruding from the axial end face of the vibration isolation base are in opposite phase. Therefore, a single surge peak caused by the vibration isolation base alone can be reduced near the resonant frequency of the projection. Furthermore, there are two types of projections: a first projection with a resonant frequency lower than that of the vibration isolation base, and a second projection with a resonant frequency higher than that of the vibration isolation base. This allows the first projection to reduce the low-frequency side of the surge peak caused by the vibration isolation base alone, while the second projection reduces the high-frequency side of that surge peak. In this way, the first and second projections can improve the effect of reducing the surging phenomenon (surge peak).

[0009] The vibration isolation device described in claim 2 provides the following effects in addition to those of the vibration isolation device described in claim 1. The vibration isolation base is formed by a plurality of elastic legs that are spaced apart from each other in the circumferential direction, connecting the first member and the second member in a direction perpendicular to the axis. If multiple types of protrusions are provided on one of these elastic legs, the vibration of the elastic leg may become more complex, potentially reducing the durability of the elastic leg. In contrast, by providing only one type of protrusion on one elastic leg, the vibration of the elastic leg can be simplified, and the durability of the elastic leg can be improved.

[0010] The vibration isolation device described in claim 3 provides the following effects in addition to those of the vibration isolation device described in claim 1. The projection has a shape that extends in a predetermined direction when viewed from the axial direction (in axial view). In this case, the adjustable parameters (length in the predetermined direction, width in a direction substantially perpendicular to the predetermined direction, and height in the axial direction) are greater than the adjustable parameters (diameter, height in the axial direction) when the projection is cylindrical, for example. Therefore, it is easier to set the resonant frequency of the projection according to the adjustment of the parameters.

[0011] The vibration isolation device described in claim 4 provides the following effects in addition to those of the vibration isolation device described in claim 1: The resonance frequency of the first projection is set within ±15 Hz of the frequency of the low-frequency peak (surge peak) in the frequency characteristics of the absolute spring constant when all projections of the vibration isolation device are designated as second projections. This allows the second projections to reduce surge peaks mainly on the high-frequency side, while the first projections effectively reduce surge peaks on the low-frequency side that could not be reduced by the second projections alone.

[0012] The vibration isolation device described in claim 5 provides the following effects in addition to those of the vibration isolation device described in claim 1: The difference between the resonant frequency of the first projection and the resonant frequency of the vibration isolation base, and the difference between the resonant frequency of the second projection and the resonant frequency of the vibration isolation base, are both 50 to 120 Hz. This effectively reduces both the low-frequency and high-frequency sides of surge peaks caused by the vibration isolation base alone.

[0013] The vibration isolation device described in claim 6 provides the following effect in addition to the effect of the vibration isolation device described in any one of claims 1 to 5: The difference between the resonant frequency of the first projection and the resonant frequency of the second projection is 200 Hz or less. By bringing these resonant frequencies closer together, it becomes easier to reduce surge peaks overall. [Brief explanation of the drawing]

[0014] [Figure 1] This is a front view of the vibration isolation device in the first embodiment. [Figure 2] This is a cross-sectional view of the vibration isolation device along line II-II in Figure 1. [Figure 3] This graph shows the frequency characteristics of the absolute spring constant in the examples and comparative examples. [Modes for carrying out the invention]

[0015] Preferred embodiments will be described below with reference to the attached drawings. Figure 1 is a front view of the vibration isolation device 10 in the first embodiment. Figure 2 is a cross-sectional view of the vibration isolation device 10 along the line II-II in Figure 1.

[0016] In Figure 1, arrows U, D, L, R, F, and B indicate the upward, downward, leftward, rightward, forward, and backward directions of the vibration isolation device 10, respectively. The vertical, leftward, and forward / backward directions are perpendicular to each other. Figures 1 and 2 also show the vibration isolation device 10 in an unloaded state where no vibration (load) is being input.

[0017] The vibration isolation device 10 is an engine mount for elastically supporting the engine of an automobile or the like on the vehicle body. The vibration isolation device 10 mainly comprises a axial first member 11 attached to the vehicle body side, a cylindrical second member 12 attached to the engine side which is the source of vibration, and four elastic legs (vibration isolation bases) 13a, 13b, 13c, and 13d that connect the first member 11 and the second member 12.

[0018] The first member 11 and the second member 12 share a common axis C, are arranged coaxially, and are formed to extend in the direction of the axis C (hereinafter simply referred to as the "axial direction"). This axial direction corresponds to the front-rear direction of the vibration isolation device 10. In addition, the direction orthogonal to the axis C (hereinafter referred to as the "axis-perpendicular direction") includes the up-down direction and the left-right direction of the vibration isolation device 10. In the present embodiment, the front-rear direction, up-down direction, and left-right direction of the vibration isolation device 10 respectively coincide with the front-rear direction, up-down direction, and left-right direction of a vehicle on which the vibration isolation device 10 is mounted.

[0019] The up-down direction of the vibration isolation device 10 is the main vibration direction of the vibration isolation device 10. The main vibration direction is the direction in which the first member 11 and the second member 11 mainly move relative to each other in response to the main vibration from an engine, which is the vibration source. Further, the vibration isolation device 10 is formed symmetrically in the left-right direction.

[0020] The first member 11 is a member made of metal, synthetic resin, or the like. The first member 11 is formed into a cylindrical shape surrounding the axis C, one axial end thereof is closed by a closing portion 11e, and the other end is open. Two through holes 11f are provided in the closing portion 11e so as to be spaced apart in the up-down direction. The first member 11 is attached to the vehicle body side by two bolts inserted into the through holes 11f. The attachment using two bolts can prevent rotation of the first member 11 around the axis C relative to the vehicle body.

[0021] The inner peripheral surface and the outer peripheral surface of the first member 11 are formed substantially parallel to the axis C in a cross section including the axis C. Further, when viewed in the axial direction, the inner peripheral surface of the first member 11 is formed into a rounded rectangular shape (oval shape) in which two parallel lines extending in the up-down direction are connected by circular arcs.

[0022] In an axial view, both vertically opposite sides of the outer circumferential surface of the first member 11 are each formed in an outwardly convex arc shape in the direction perpendicular to the axis, similarly to the arc of the inner circumferential surface of the first member 11. Further, in an axial view, both horizontally opposite sides of the outer circumferential surface of the first member 11 are each formed in a mountain shape by inclined surfaces 11a to 11d that incline outward in the left-right direction as they go toward the center in the up-down direction. The inclined surface 11a is provided at the upper left, the inclined surface 11b is provided at the upper right, the inclined surface 11c is provided at the lower left, and the inclined surface 11d is provided at the lower right, respectively.

[0023] The second member 12 is a cylindrical member surrounding the first member 11, and is formed of metal, synthetic resin, or the like. The inner circumferential surface and the outer circumferential surface of the second member 12 are formed substantially parallel to the axis C in a cross section including the axis C. In an axial view, the outer circumferential surface and the inner circumferential surface of the second member 12 are formed in a circular shape centered on the axis C.

[0024] The plurality of elastic legs 13a to 13d are members formed of rubber (elastic body), and respectively connect the first member 11 and the second member 12 in the direction perpendicular to the axis. The elastic leg 13a extends from the inclined surface 11a substantially perpendicularly toward the upper left. Similarly, the elastic leg 13b extends from the inclined surface 11b substantially perpendicularly toward the upper right, the elastic leg 13c extends from the inclined surface 11c substantially perpendicularly toward the lower left, and the elastic leg 13d extends from the inclined surface 11d substantially perpendicularly toward the lower right, respectively. The plurality of elastic legs 13a to 13d are respectively vulcanized and bonded to the inclined surfaces 11a to 11d and the inner circumferential surface of the second member 12, and are arranged spaced apart from each other in the circumferential direction of the first member 11 and the second member 12.

[0025] An elastic film 14 that connects the radially inner ends of the plurality of elastic legs 13a to 13d is vulcanized and bonded to the outer circumferential surface of the first member 11. Further, an elastic film 15 that connects the radially outer ends of the plurality of elastic legs 13a to 13d is vulcanized and bonded to the inner circumferential surface of the second member 12. The plurality of elastic legs 13a to 13d and the elastic films 14, 15 are integrally molded from rubber.

[0026] The elastic membrane 14 includes a stopper 14a that protrudes outward in a direction perpendicular to the axis from near the upper end of the first member 11, and a stopper 14b that protrudes outward in a direction perpendicular to the axis from near the lower end of the first member 11. The elastic membrane 15 includes a stopper 15a that protrudes inward in a direction perpendicular to the axis from near the upper end of the second member 12, and a stopper 15b that protrudes inward in a direction perpendicular to the axis from near the lower end of the second member 12.

[0027] Stoppers 14a and 15a face each other, and stoppers 14b and 15b face each other. As a result, when vibration input in the main vibration direction (vertical direction) occurs, these stoppers 14a, 14b, 15a, and 15b come into contact with each other, cushioning the collision between the first member 11 and the second member 12. The lower stoppers 14b and 15b have a greater circumferential length and thickness perpendicular to the axis than the upper stoppers 14a and 15a. This is to ensure the cushioning performance of the lower stoppers 14b and 15b, which are more susceptible to large loads due to gravity when input in the main vibration direction occurs.

[0028] When vibrations perpendicular to the axis are input to the vibration isolation device 10, a surging phenomenon may occur. Surging is a phenomenon in which, at the resonant frequency of the elastic legs 13a to 13d, the absolute spring constant (dynamic spring constant) of the elastic legs 13a to 13d increases, causing the elastic legs 13a to 13d to vibrate violently.

[0029] In this embodiment, in order to reduce this surging phenomenon (reduce the absolute spring constant at the resonant frequency), the first projection 18 and the second projection 19 are made to protrude from the elastic legs 13a to 13d. In order to reduce the surging phenomenon, it is necessary to make the vibrations of the elastic legs 13a to 13d and the vibrations of the first projection 18 and the second projection 19 out of phase at each resonant frequency.

[0030] The first projection 18 protrudes axially from each of the axial end faces of the multiple elastic legs 13a and 13b. The second projection 19 protrudes axially from each of the axial end faces of the multiple elastic legs 13c and 13d.

[0031] The first projection 18 and the second projection 19 are both formed in a plate shape and are arranged to extend in the tangential direction (approximately circumferential direction) of the second member 12 in an axial view. Since the tangential dimensions of the elastic legs 13a to 13d connecting the first member 11 and the second member 12 are larger than the dimensions in the direction perpendicular to the axis, extending the first projection 18 and the second projection 19 in the tangential direction makes it easier to enlarge the first projection 18 and the second projection 19.

[0032] In the first projection 18, the tangential dimension is defined as length L1, the dimension perpendicular to the axis and approximately perpendicular to the tangential dimension is defined as width W1, and the axial dimension is defined as height H1. Similarly, in the second projection 19, the tangential dimension is defined as length L2, the dimension perpendicular to the axis and approximately perpendicular to the tangential dimension is defined as width W2, and the axial dimension is defined as height H2. By adjusting these lengths L1, L2, widths W1, W2, and heights H1, H2, the volume and mass of the first projection 18 and the second projection 19 are determined, respectively. Furthermore, the resonant frequencies of the first projection 18 and the second projection 19 are set according to their respective masses. By setting the mass of the first projection 18 to be smaller than the mass of the second projection 19, the resonant frequency of the first projection 18 is lower than the resonant frequency of the second projection 19.

[0033] Next, the effects of the first projection 18 and the second projection 19 will be explained with reference to Figures 1 and 2, as well as Figure 3. Figure 3 is a graph showing the analysis results of the frequency characteristics of the absolute spring constant in Example E12 using the vibration isolation device 10 and in Comparative Examples E0, E1, and E2, which have some modifications from the vibration isolation device 10 (Example E12).

[0034] The results of this analysis show that for Example E12 and Comparative Examples E0, E1, and E2, the principal vibration direction was 9.8 m / s². 2 This shows the case when vibration is applied. The horizontal axis of the graph in Figure 3 is frequency [Hz]. The vertical axis of the graph in Figure 3 is the absolute spring constant [N / mm] in the principal vibration direction. Only equally spaced scales are shown on the vertical axis, and the numerical values ​​are omitted.

[0035] Comparative Example E0 is the vibration isolation device 10 with the first projection 18 and the second projection 19 removed, and the dimensions of the elastic legs 13a to 13d are set so that the resonant frequency is approximately 1500 Hz. Therefore, as shown by the dashed line in Figure 3, the surge peak (peak of absolute spring constant) in Comparative Example E0 appears as only one peak at approximately 1500 Hz.

[0036] Example E12 is provided with a first projection 18 and a second projection 19 compared to Comparative Example E0. Furthermore, in Example E12, the lengths L1, L2, widths W1, W2, and heights H1, H2 are set so that the resonant frequency of the first projection 18 is approximately 1400 Hz and the resonant frequency of the second projection 19 is approximately 1570 Hz. Figure 3 shows the frequency characteristics of the absolute spring constant in Example E12 as a solid line.

[0037] Comparative Example E1 is obtained by replacing all of the second protrusions 19 with first protrusions 18 compared to Example E12. Comparative Example E2 is obtained by replacing all of the first protrusions 18 with second protrusions 19 compared to Example E12. In Figure 3, the frequency characteristics of the absolute spring constant in Comparative Example E1 are shown by a dashed line, and the frequency characteristics of the absolute spring constant in Comparative Example E2 are shown by a double dashed line.

[0038] As shown in Figure 3, in Comparative Example E1, which has only the first projection 18 whose resonant frequency is lower than the resonant frequency of the elastic legs 13a to 13d, the surge peak of one peak in Comparative Example E0, which has neither the first projection 18 nor the second projection 19, is divided into two peaks, and the peak values ​​of those two peaks are reduced. Similarly, in Comparative Example E2, which has only the second projection 19 whose resonant frequency is higher than the resonant frequency of the elastic legs 13a to 13d, the surge peak of one peak in Comparative Example E0 is divided into two peaks, and the peak values ​​of those two peaks are reduced.

[0039] However, comparing Comparative Example E1 and Comparative Example E2, Comparative Example E1 failed to adequately suppress the high-frequency peak value of the two divided surge peaks, while Comparative Example E2 failed to adequately suppress the low-frequency peak value.

[0040] In contrast, in Example E12 (vibration isolation device 10), which has both the first projection 18 and the second projection 19, the first projection 18 can reduce the low-frequency side of the surge peak caused by the elastic legs 13a to 13d alone, while the second projection 19 can reduce the high-frequency side of the surge peak. The surge peak of Example E12 is divided into three peaks by the two types of first projections 18 and second projections 19, but all peak values ​​are sufficiently reduced compared to comparative examples E0, E1, and E2. As described above, in Example E12, the first projection 18 and the second projection 19 can improve the effect of reducing the surging phenomenon (surge peak).

[0041] The surge peak of Comparative Example E2, which is divided into two peaks by the second projection 19, has its low-frequency side at approximately 1400 Hz. This frequency is approximately the same as the resonant frequency of the first projection 18. Note that "approximately the same frequency" is defined as a frequency difference of within ±15 Hz. Because these frequencies are approximately the same, in Example E12, the second projection 19 primarily reduces the high-frequency surge peak, while the first projection 18 effectively reduces the low-frequency surge peak that the second projection 19 alone could not fully reduce. As a result, the surge peak of the vibration isolation device 10 can be reduced overall more easily.

[0042] The difference between the resonant frequency of the first projection 18 and the resonant frequencies of the elastic legs 13a to 13d is preferably 50 to 120 Hz. In Example E12 and Comparative Example E1, this difference is approximately 100 Hz. Therefore, the first projection 18 can effectively reduce the low-frequency side of the surge peak caused by the elastic legs 13a to 13d alone.

[0043] Preferably, the difference between the resonant frequency of the second projection 19 and the resonant frequencies of the elastic legs 13a to 13d is 50 to 120 Hz. In Example E12 and Comparative Example E2, this difference is approximately 70 Hz. Therefore, the high-frequency side of the surge peak caused by the elastic legs 13a to 13d alone can be effectively reduced by the second projection 19.

[0044] Furthermore, it is preferable that the difference between the resonant frequency of the first projection 18 and the resonant frequency of the second projection 19 is 200 Hz or less. In Example E12, this difference is 170 Hz or less. By bringing the resonant frequencies of the first projection 18 and the second projection 19 closer together in this way, it becomes easier to reduce the surge peak of the vibration isolation device 10 overall.

[0045] Although the present invention has been described above based on embodiments and examples, it can be easily inferred that the present invention is not limited in any way to the above embodiments and examples, and that various improvements and modifications are possible without departing from the spirit of the present invention. For example, the outer and inner surfaces of the first member 11 in the axial view may be elliptical, polygonal, or circular in shape. Also, the axis of the first member 11 and the axis of the second member 12 may be offset from each other in a direction perpendicular to their axes. The first member 11 may be formed in the shape of a rod or column.

[0046] In the above embodiment, the case where the longitudinal direction, vertical direction, and left-right direction of the vibration damping device 10 coincide with the longitudinal direction, vertical direction, and left-right direction of the vehicle, respectively, has been described, but the embodiment is not limited to this. For example, the longitudinal direction of the vibration damping device 10 may coincide with the left-right direction of the vehicle, and the vertical direction or left-right direction of the vibration damping device 10 may coincide with the longitudinal direction of the vehicle. Furthermore, the directions of the vibration damping device 10 and the directions of the vehicle may be diagonally offset.

[0047] In the above embodiment, an engine mount was given as an example of an application target for the vibration damping device 10, but the application target is arbitrary. Other examples of application targets include motor mounts, member mounts, and differential mounts. Furthermore, it is not limited to attaching the first member 11 to the vibration receiving side such as the vehicle body and attaching the second member 12 to the vibration source side such as the engine; the second member 12 may be attached to the vibration receiving side and the first member 11 may be attached to the vibration source side.

[0048] In the above embodiment, the vibration-damping base connecting the first member 11 and the second member 12 was described as being formed by four elastic legs 13a to 13d, but it is not limited to this. For example, the first member 11 and the second member 12 may be connected around their entire circumference by a cylindrical vibration-damping base. Also, the number of elastic legs 13a to 13d may be three or fewer, or five or more.

[0049] In the above embodiment, the case in which the elastic legs 13a to 13d, the first projection 18, and the second projection 19 are made of rubber has been described, but the embodiment is not limited to this. For example, the elastic legs 13a to 13d, the first projection 18, and the second projection 19 may be made of a thermoplastic elastomer, which is an elastic material other than rubber. Furthermore, the resonant frequencies of the first projection 18 and the second projection 19 may be adjusted by providing weights such as metal at the tips or inside the first projection 18 and the second projection 19.

[0050] In the above embodiment, a case was described in which one first projection 18 protrudes from each of the axial end faces of elastic legs 13a and 13b, and one second projection 19 protrudes from each of the axial end faces of elastic legs 13c and 13d, but the embodiment is not limited to this. For example, the first projection 18 and the second projection 19 may protrude from only one axial side of elastic legs 13a to 13d. Alternatively, two or more first projections 18 and second projections 19 may protrude from one axial side of elastic legs 13a to 13d. The first projection 18 may protrude from elastic legs 13c and 13d, and the second projection 19 may protrude from elastic legs 13a and 13b.

[0051] Protrusions of a different type (with different resonant frequencies) than the first protrusion 18 and the second protrusion 19 may be projected from the elastic legs 13a to 13d. Alternatively, multiple protrusions of different types, such as both the first protrusion 18 and the second protrusion 19, may be provided on a single elastic leg 13a to 13d. For example, the first protrusion 18 may be projected from one end face in the axial direction of the elastic leg 13a, and the second protrusion 19 may be projected from the other end face in the axial direction of the elastic leg 13a. However, in such a case, the vibration of the elastic legs 13a to 13d may become more complex, potentially reducing the durability of the elastic legs 13a to 13d.

[0052] In contrast, in the first embodiment, each of the elastic legs 13a to 13d is provided with only one of either the first projection 18 or the second projection 19, i.e., only one type of projection. This simplifies the vibration of the elastic legs 13a to 13d and improves the durability of the elastic legs 13a to 13d.

[0053] In the above embodiment, the case in which the first projection 18 and the second projection 19 are plate-shaped has been described, but the embodiment is not limited to this. For example, the first projection 18 and the second projection 19 may be cylindrical, elliptical, oblong, polygonal, frustoconical, or truncated pyramidal. When the first projection 18 and the second projection 19 are cylindrical, the parameters for adjusting their resonant frequencies are diameter and height.

[0054] In contrast, it is preferable that the first projection 18 and the second projection 19 have a shape that extends in a predetermined direction when viewed axially, such as a plate or an elliptical column. In this case, there are three adjustable parameters: the length in the predetermined direction (e.g., lengths L1, L2), the width in a direction substantially perpendicular to the predetermined direction (e.g., widths W1, W2), and the height in the axial direction (e.g., heights H1, H2), which is more than in the case of a cylindrical shape. Therefore, it is easier to set the resonant frequency of the first projection 18 and the second projection 19 according to the adjustment of the parameters.

[0055] In the above embodiment, the case in which the first projection 18 and the second projection 19 protrude in the axial direction was described, but the embodiment is not limited to this. For example, the first projection 18 and the second projection 19 may protrude in a direction inclined with respect to the axial direction. In this case, when axial vibration is input to the vibration isolation device 10, the first projection 18 and the second projection 19 become more susceptible to vibration, and the surge peak reduction effect of the first projection 18 and the second projection 19 may be exhibited.

[0056] In the above embodiment E12, the case where the low-frequency side of the surge peak of comparative example E2 is approximately the same as the resonant frequency of the first projection 18 was described, but the invention is not limited to this. For example, the vibration isolation device 10 may be configured such that the high-frequency side of the surge peak of comparative example E1, which is divided into two peaks by the first projection 18, is approximately the same as the resonant frequency of the second projection 19. This allows the first projection 18 to reduce the surge peak mainly on the low-frequency side, while the second projection 19 effectively reduces the surge peak on the high-frequency side that could not be reduced by the first projection 18 alone. As a result, the surge peak of the vibration isolation device 10 can be reduced overall more easily. [Explanation of Symbols]

[0057] 10 Vibration Isolator 11. First Member 12 Second Member 13a~13d Elastic legs (vibration isolation base) 18 1st protrusion (protrusion) 19 Second protrusion (protrusion)

Claims

1. A first member extending in the axial direction, A cylindrical second member surrounding the first member, An elastic vibration-damping base connecting the outer circumferential surface of the first member and the inner circumferential surface of the second member, The vibration-damping base comprises multiple types of protrusions, each composed of an elastic body protruding from the axial end face of the vibration-damping base, and having mutually different resonant frequencies. At each resonant frequency, the vibration of the vibration-isolating base and the vibration of the protrusion are in opposite phase. The vibration isolation device is characterized in that the type of protrusion includes a first protrusion whose resonant frequency is lower than the resonant frequency of the vibration isolation base, and a second protrusion whose resonant frequency is higher than the resonant frequency of the vibration isolation base.

2. The vibration-damping base is formed by a plurality of elastic legs that connect the first member and the second member in a direction perpendicular to the axis and are spaced apart from each other in the circumferential direction. The vibration isolation device according to claim 1, characterized in that one of the elastic legs is provided with one type of projection.

3. The vibration isolation device according to claim 1, characterized in that the projection has a shape that extends in a predetermined direction when viewed from the axial direction.

4. The vibration isolation device according to claim 1, characterized in that the resonant frequency of the first projection is set within ±15 Hz of the frequency of the low-frequency peak in the frequency characteristics of the absolute spring constant when all of the projections of the vibration isolation device are second projections.

5. The vibration isolation device according to claim 1, characterized in that the difference between the resonant frequency of the first projection and the resonant frequency of the vibration isolation base, and the difference between the resonant frequency of the second projection and the resonant frequency of the vibration isolation base, are each 50 to 120 Hz.

6. The vibration isolation device according to any one of claims 1 to 5, characterized in that the difference between the resonant frequency of the first projection and the resonant frequency of the second projection is 200 Hz or less.

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