Vibration-proof bushing

Abstract

Provided is a vibration-proof bushing capable of suppressing any increase in an absolute spring constant caused by surging in an axial direction.　This vibration-proof bushing comprises an outer cylinder 3, an inner cylinder 2, and a rubber body 4 positioned between the outer cylinder and the inner cylinder. The rubber body has: a main body rubber part 41 that connects the outer cylinder and the inner cylinder to each other in a radial direction and extends over only a portion of the rubber body in a circumferential direction; a groove 42 that is positioned in a circumferential-direction region other than the circumferential-direction region in which the main body rubber part extends, the groove penetrating into the rubber body in the axial direction; and a stopper rubber part 43 that faces the groove in the radial direction. The stopper rubber part is connected to the main body rubber part so as to be capable of moving directly in conjunction with the main body rubber part. In the vibration-proof bushing, a secondary peak value or a tertiary peak value of an absolute spring constant in the axial direction is at least 20% lower than in a reference bushing B in which the main body rubber part in the vibration-proof bushing is extended over the entire circumference and the rubber body is configured from only the main body rubber part.

Description

Anti-vibration bushing

[0001] The present invention relates to a vibration-isolating bushing.

[0002] Conventional vibration-damping bushings include those in which a main rubber portion (main rubber elastic body) is provided with a circumferential rubber mass portion (elastic protrusion) that protrudes outward in the axial direction and extends circumferentially (for example, Patent Document 1).

[0003] WO2020 / 175640A1

[0004] Although the above-described technique can effectively suppress an increase in the absolute spring constant due to surging in the direction perpendicular to the axis, there is room for improvement in the effect of suppressing an increase in the absolute spring constant due to surging in the axial direction.

[0005] SUMMARY OF THE INVENTION An object of the present invention is to provide a vibration-isolating bushing that can suppress an increase in absolute spring constant due to surging in the axial direction.

[0006] [1] A vibration-isolating bushing comprising an outer tube, an inner tube, and a rubber body located between the outer tube and the inner tube, wherein the rubber body has a main rubber portion that radially connects the outer tube and the inner tube and extends only partially in the circumferential direction, a groove that is located in a circumferential region other than the circumferential region in which the main rubber portion extends and penetrates the rubber body in the axial direction, and a stopper rubber portion that faces the groove in the radial direction, wherein the stopper rubber portion is connected to the main rubber portion so as to move directly in conjunction with the main rubber portion, and the vibration-isolating bushing has a secondary peak value or tertiary peak value of the axial absolute spring constant that is 20% or more lower than a reference bushing in which the main rubber portion of the vibration-isolating bushing extends around the entire circumference and the rubber body is composed only of the main rubber portion, thereby suppressing an increase in the absolute spring constant due to surging in the axial direction.

[0007] [2] The vibration-damping bushing according to [1], wherein the stopper rubber portion is configured to be displaceable in the axial direction opposite to the main rubber portion while the inner tube vibrates in the axial direction relative to the outer tube, thereby suppressing an increase in the absolute spring constant due to surging in the axial direction.

[0008] [3] The vibration-damping bushing according to [1] or [2], wherein at least one of the stopper rubber portions is located radially inward of at least a portion of the rib. In this case, the stopper rubber portion that interlocks with the main rubber portion can be easily formed.

[0009] [4] The vibration-damping bushing according to [1] or [2], wherein at least one of the stopper rubber portions is located radially outward of at least a portion of the rib. In this case, the stopper rubber portion that interlocks with the main rubber portion can be easily formed.

[0010] [5] The vibration-damping bushing according to [1] or [2], wherein the two ribs are spaced apart from each other in the radial direction, and at least one stopper rubber portion is disposed between the two ribs. In this case, the stopper rubber portion that interlocks with the main rubber portion can be easily formed.

[0011] [6] The vibration-damping bushing according to any one of [1] to [5], wherein the rubber body has a plurality of the grooves, and at least one of the stopper rubber portions faces each of the grooves in the radial direction. In this case, the stopper rubber portion that interlocks with the main rubber portion can be easily formed.

[0012] [7] The vibration-damping bushing according to any one of [1] to [6], wherein the axial length of the stopper rubber portion is equal to or less than the axial length of the main rubber portion. This allows the stopper rubber portion to move more easily in the axial direction, further suppressing an increase in the absolute spring constant due to surging in the axial direction.

[0013] [8] The vibration-damping bushing according to any one of [1] to [7], wherein the rubber body is formed from a rubber obtained by crosslinking a rubber composition containing a rubber component whose main components are natural rubber and non-diene rubber. This makes it possible to further suppress an increase in the absolute spring constant due to surging.

[0014] [9] The vibration-damping bushing according to any one of [1] to [8], wherein the rubber body further has a circumferential rubber mass portion that protrudes axially outward from at least one axial end face of the main rubber portion and extends circumferentially, thereby further suppressing an increase in the absolute spring constant due to surging.

[0015] According to the present invention, it is possible to provide a vibration-isolating bushing that can suppress an increase in the absolute spring constant due to surging in the axial direction.

[0016] 6(a) to 6(d) are views showing a vibration-isolating bushing according to an embodiment of the present invention as viewed from one axial side. FIG. 6(a) is a perspective view showing the vibration-isolating bushing of FIG. 1. FIG. 6(c) is a perspective view showing the vibration-isolating bushing of FIG. 1 together with a cross section passing through the central axis. FIG. 6(d) is an axial cross section showing the vibration-isolating bushing of FIG. 1 as a cross section passing through the central axis. FIG. 6(a) to 6(d) are views showing a vibration-isolating bushing according to a modified example, where FIG. 6(a) is a front view showing the appearance as viewed from one axial side, and FIG. 6(b) is an axial cross section showing the cross section passing through the central axis. FIG. 6(c) is a perspective view showing the vibration-isolating bushing according to the example of FIG. 1 to 5 and a reference bushing corresponding to the vibration-isolating bushing according to the example of FIG. 6. FIG. 7(a) is a front view showing the appearance as viewed from one axial side, FIG. 7(b) is a perspective view, FIG. 7(c) is a perspective view showing the cross section passing through the central axis, and FIG. 7(d) is an axial cross section showing the cross section passing through the central axis. 9, 10(a) to 10(d), 11(a) to 11(c), 12(a) to 12(c), 13(a) to 13(c), and 15 are front views showing the rubber bodies of the reference bushings corresponding to the vibration-isolating bushings of each example, as viewed from one axial side. Also, front views showing the rubber bodies of the vibration-isolating bushing of the first example, as viewed from one axial side. FIGS. 10(a) to 10(d) are axial cross-sectional views of the rubber bodies of the vibration-isolating bushings of the second to fifth examples, taken along a cross section passing through the central axis. FIGS. 11(a) to 11(c) are front views showing the rubber bodies of the vibration-isolating bushings of the sixth to eighth examples, as viewed from one axial side. FIGS. 12(a) to 12(c) are front views showing the rubber bodies of the vibration-isolating bushings of the first to second comparative examples and the ninth example, as viewed from one axial side. Figures 13(a) to 13(c) are front views showing the rubber body of the vibration-isolating bushings of Examples 10 to 12, respectively, as viewed from one side in the axial direction. Figure 13(a) to 13(c) are graphs showing the analysis results of the absolute spring constants in the axial direction of the vibration-isolating bushing of Example 1 and the corresponding reference bush. Figure 13(a) to 13(c) are front views showing part of the rubber body of the vibration-isolating bushing of Example 13, as viewed from one side in the axial direction.16 is a graph showing the analysis results of the absolute spring constant in the axial direction of the vibration-isolating bushing according to Example 13 and the corresponding reference bushing. FIG. 17 is a front view showing the state of a vibration-isolating bushing according to another modified example when viewed from one side in the axial direction. FIG. 18 is a front view showing the state of a vibration-isolating bushing according to yet another modified example when viewed from one side in the axial direction.

[0017] The vibration-damping bushing according to the present invention is suitable for use in, for example, vehicle vibration-damping devices (e.g., engine mounts, motor mounts), and is particularly suitable for use in vibration-damping devices (e.g., motor mounts) for electric vehicles (EVs). Hereinafter, an embodiment of the vibration-damping bushing according to the present invention will be described by way of example with reference to the drawings.

[0018] 1 to 5 show an anti-vibration bushing 1 according to one embodiment of the present invention. The anti-vibration bushing 1 is suitable for use in, for example, vehicle anti-vibration devices (e.g., engine mounts, motor mounts), and is particularly suitable for use in anti-vibration devices (e.g., motor mounts) for electric vehicles (EVs).

[0019] In this specification, when describing the structure of the vibration-damping bushing 1, unless otherwise specified, we will be describing the structure when no input is applied to the vibration-damping bushing 1 and the vibration-damping bushing 1 is in a stationary, normal state.

[0020] 1 to 4 show the vibration-isolating bushing 1 in its normal, stationary state. As shown in Figures 1 to 4, the vibration-isolating bushing 1 comprises an outer cylinder 2, an inner cylinder 3, and a rubber body 4.

[0021] The inner cylinder 3 is coaxial with the outer cylinder 2 and is located on the inner peripheral side of the outer cylinder 2. The outer cylinder 2 and the inner cylinder 3 are made of, for example, metal and / or resin. The outer cylinder 2 is configured to be attached to either a vibration generating unit (e.g., an engine or motor) or a vibration receiving unit (e.g., a vehicle body) during use. The inner cylinder 3 is configured to be attached to the other of the vibration generating unit and the vibration receiving unit during use. In this embodiment, the outer cylinder 2 and the inner cylinder 3 each have a cylindrical shape, but may have any other cylindrical shape.

[0022] In this specification, the central axis O of the outer cylinder 2 is regarded as the central axis O of the vibration-isolating bushing 1. In this specification, the direction parallel to the central axis O of the vibration-isolating bushing 1 is referred to as the "axial direction." The axial direction may be oriented in any direction. In this specification, the side farther from the center of the vibration-isolating bushing 1 in the axial direction is referred to as the "axial outer side," the side closer to the center of the vibration-isolating bushing 1 in the axial direction is referred to as the "axial inner side," and the direction perpendicular to the central axis O of the vibration-isolating bushing 1 is referred to as the "direction perpendicular to the axis." Unless otherwise specified, in this specification, the side closer to the central axis O of the vibration-isolating bushing 1 is referred to as the "inner peripheral side," the side farther from the central axis O of the vibration-isolating bushing 1 is referred to as the "outer peripheral side," the circumferential direction centered on the central axis O of the vibration-isolating bushing 1 is referred to as the "circumferential direction," and the radial direction centered on the central axis O of the vibration-isolating bushing 1 is referred to as the "radial direction."

[0023] The rubber body 4 is made of rubber, is located between the outer tube 2 and the inner tube 3 in the radial direction, and has a generally tubular shape (in this embodiment, a generally cylindrical shape). In this embodiment, the rubber body 4 is integrally formed (i.e., made of a single member). The outer peripheral surface of the rubber body 4 is in contact with the inner peripheral surface of the outer tube 2 and is joined thereto by, for example, vulcanization bonding. The inner peripheral surface of the rubber body 4 is in contact with the outer peripheral surface of the inner tube 3 and is joined thereto by, for example, vulcanization bonding.

[0024] 1 to 4, the rubber body 4 has one or more (one in this embodiment) main rubber portions 41, one or more (one in this embodiment) grooves 42, and one or more (one in this embodiment) stopper rubber portions 43. In Fig. 1, the boundary lines of the various portions of the rubber body 4 are indicated by dashed lines.

[0025] The main body rubber portion 41 radially connects the outer tube 2 and the inner tube 3. That is, the main body rubber portion 41 extends continuously in the radial direction from the inner circumferential surface of the outer tube 2 to the outer circumferential surface of the inner tube 3. Moreover, the main body rubber portion 41 extends only partially in the circumferential direction.

[0026] The groove 42 is a through-hole that penetrates the rubber body 4 in the axial direction. Here, "penetrating the rubber body 4 in the axial direction" is not limited to the case where the groove 42 is surrounded by the rubber that constitutes the rubber body 4 over the entire circumference of the groove 42 in a plan view, as in the example of Figure 1, but also includes the case where the groove 42 directly faces the outer tube 2 or the inner tube 3 without an outer peripheral covering rubber portion 46 or an inner peripheral covering rubber portion 45 (described later) in between, thereby forming a groove (recess) that extends over the entire axial direction of the rubber body 4 and opens into the outer tube 2 or the inner tube 3. The groove 42 is located only in a circumferential region other than the circumferential region in which the main rubber portion 41 extends.

[0027] The stopper rubber portion 43 faces the grooving portion 42 in the radial direction. That is, the stopper rubber portion 43 faces the grooving portion 42 in the radial direction, and the outer peripheral surface or inner peripheral surface (in this embodiment, the outer peripheral surface) of the stopper rubber portion 43 faces the grooving portion 42 and defines a portion of the grooving portion 42. The stopper rubber portion 43 is located only in a circumferential region other than the circumferential region in which the main rubber portion 41 extends. In this embodiment, the stopper rubber portion 43 is connected to the main rubber portion 41 at at least one end (in this embodiment, both ends) of the stopper rubber portion 43 in the circumferential direction. The stopper rubber portion 43 is connected to the main rubber portion 41 so as to be able to move directly in conjunction with the main rubber portion 41. Therefore, for example, if the stopper rubber portion 43 is connected to the main rubber portion 41 only via a thin-film rubber portion or the like provided on the inner circumferential surface of the outer tube 2 or the outer circumferential surface of the inner tube 3, the stopper rubber portion 43 cannot move in conjunction with the main rubber portion 41, and therefore cannot be said to be "connected so as to be able to move directly in conjunction with the main rubber portion 41." The stopper rubber portion 43 functions as a stopper that restricts excessive relative displacement between the inner tube 3 and the outer tube 2 in the axial direction. More specifically, the stopper rubber portion 43 is configured so that, while the inner tube 3 moves relative to the outer tube 2 in the axial direction in a direction narrowing the width of the groove 42, the stopper rubber portion 43 is compressed between the inner tube 3 and the outer tube 2 after the groove 42 is crushed, thereby preventing the inner tube 3 from further approaching the outer tube 2, thereby restricting the inner tube 3 from excessively approaching the outer tube 2 in the axial direction. This improves the durability of the vibration-damping bushing 1.

[0028] As described above, the stopper rubber portion 43 faces the rib 42 in the radial direction and is connected to the main rubber portion 41 so as to move in direct conjunction with the main rubber portion 41. Therefore, as shown schematically by the dashed lines in Fig. 5 , while the inner tube 3 vibrates in the axial direction relative to the outer tube 2, the stopper rubber portion 43 can be displaced in the axial direction to the opposite side from the main rubber portion 41. (Note that the dashed lines in Fig. 5 represent the state in which, when the inner tube 3 is displaced in the axial direction to one side (the right side in Fig. 5 ), the main rubber portion 41 is displaced in the axial direction to the other side (the left side in Fig. 5 ), and the stopper rubber portion 43 is displaced to one side (the right side in Fig. 5 ).) During this time, the phase of the stopper rubber portion 43 is not necessarily completely opposite to the phase of the main rubber portion 41, but the stopper rubber portion 43 can be at least partially displaced in the axial direction to the opposite side from the main rubber portion 41. As a result, part of the force generated by the main rubber portion 41 in either axial direction is offset by the force generated by the stopper rubber portion 43 in the other axial direction. In this way, the stopper rubber portion 43 can function as a dynamic damper. As a result, the vibration-isolating bushing 1 is able to suppress an increase in the absolute spring constant (dynamic spring constant) due to axial surging compared to the standard bushing B (FIG. 7). In other words, it is possible to reduce the spring constant in the axial direction. As shown in FIG. 7, the standard bushing B does not have the flange 42 and stopper rubber portion 43 of the vibration-isolating bushing 1, and instead has the main rubber portion 41 of the vibration-isolating bushing 1 extend all around (i.e., the main rubber portion 41 is extended so that it extends all around), and the rubber body 4 is composed only of the main rubber portion 41 that extends all around. The vibration-damping bushing 1 and the standard bushing B differ only in the above-mentioned points of the rubber body 4, and are the same in all other respects (outer diameter and material of the rubber body 4, structure, dimensions, material, etc. of the outer tube 2 and inner tube 3).

[0029] The mass of the stopper rubber portion 43 plays a particularly large role in determining how much the vibration-isolating bushing 1 can suppress the increase in absolute spring constant due to axial surging compared to the standard bushing B (i.e., how much the spring constant can be reduced in the axial direction), but the physical properties and material of the stopper rubber portion 43 also play a significant role. The shapes of the stopper rubber portion 43 and the ribs 42 are also thought to contribute to this to some extent. Furthermore, the smaller the difference between the surging frequency of the main rubber portion 41 and the surging frequency of the stopper rubber portion 43, the more effectively the stopper rubber portion 43 can function as a dynamic damper.

[0030] More specifically, the vibration-damping bushings 1 of each example within the scope of the present invention have a secondary peak value or tertiary peak value of the axial absolute spring constant that is 20% or more lower than that of the respective reference bushings B. This will be explained below with reference to the analysis results shown in Figures 8 to 14 and Tables 1 and 2. Figures 8 to 13 show models of the rubber body 4 of each example used in the FEM analysis. Figure 8 shows the rubber body 4 of the reference bushing B corresponding to the vibration-damping bushing 1 of each example shown in Figures 9 to 13. Figures 9, 10(a) to 10(d), 11(a) to 11(c), 12(a) to 12(c), and 13(a) to 13(c) each show the rubber body 4 of a different example of the vibration-damping bushing 1. Details of the rubber body 4 of each example shown in Figures 8 to 13 are shown in Tables 1 and 2 below. The rubber body 4 in each example shown in Figures 8 to 13 had the same outer diameter, inner diameter, and axial length, and the physical properties of the rubber body 4 were also the same. The rubber body 4 in each example shown in Figures 9 to 13 had a groove 42 and a stopper rubber portion 43 that faced the groove 42 in the radial direction and was connected to the main rubber portion 41 so as to move directly in conjunction with the main rubber portion 41. The rubber body 4 of Example 1 shown in Figure 9 basically had the same configuration as the embodiment shown in Figures 1 to 4, but differed from the embodiment shown in Figures 1 to 4 in that the axial length L43 (Figure 4) of the stopper rubber portion 43 was the same as the axial length L41 (Figure 4) of the main rubber portion 41. The examples shown in Figures 10 to 13 differed from Example 1 shown in Figure 9 only by the "Differences in configuration from Example 1" listed in Tables 1 and 2. In each example shown in Figures 11(a) to 11(c), the groove 42 has a circumferential groove portion 42a extending along the circumferential direction and a radial groove portion 42b extending radially inward from the circumferential center of the circumferential groove portion 42a. The circumferential groove portion 42a has the same configuration as the groove 42 in Example 1 (Figure 9). In each example shown in Figures 11(a) to 11(c), a stopper rubber portion 43 was provided, one on each side of the radial groove portion 42b in the circumferential direction (two in total). In Tables 1 and 2, "angle range" refers to the angle range centered on the central axis O. The angle range of the groove 42 in Example 1 (Figure 9) was 90°.In the FEM analysis, assuming a situation in which the inner cylinder 3 vibrates in the axial direction relative to the outer cylinder 2, the inner peripheral surface of the rubber body 4 was moved back and forth in the axial direction relative to the outer peripheral surface of the rubber body 4 at each frequency in a state without preload in each example of the rubber body 4 model, and the absolute spring constant (axial absolute spring constant K) at each frequency was measured. The results are shown in Fig. 14 and Tables 1 and 2.

[0031] In the graph of Fig. 14, the horizontal axis is frequency (Hz) and the vertical axis is the absolute spring constant K (N / mm) in the axial direction. In Fig. 14, waveform W1 is the waveform resulting from the FEM analysis performed on the rubber body 4 of the standard bushing B shown in Fig. 8, and waveform W2 is the waveform resulting from the FEM analysis performed on the rubber body 4 of the vibration-damping bushing 1 of Example 1 shown in Fig. 9. As can be seen from Fig. 14, waveforms W1 and W2 of the absolute spring constant K in the axial direction of the standard bushing B and the vibration-damping bushing 1 of Example 1 each have three peaks due to surging: a primary peak, a secondary peak, and a tertiary peak. The peak value of the absolute spring constant K of the vibration-damping bushing 1 of Example 1 was lower than that of the standard bushing B at each of these three peaks. Table 1 shows, in percentages, how much the peak value of the absolute spring constant K of the vibration-damping bushing 1 of Example 1 was able to reduce compared to the standard bushing B at each of the secondary and tertiary peaks. In calculating this percentage, the value of the absolute spring constant K at 1000 Hz was used as the peak value of the secondary peak of the absolute spring constant K in the axial direction, and the value of the absolute spring constant K at 1600 Hz was used as the peak value of the tertiary peak of the absolute spring constant K in the axial direction. As with the vibration-isolating bushing 1 of Example 1, the waveform of the absolute spring constant K in the axial direction for the vibration-isolating bushings 1 of each example shown in Figures 10 to 13 also had three peaks. As with Example 1, Tables 1 and 2 show, as a percentage (%), how much the vibration-isolating bushings 1 of each example shown in Figures 10 to 13 were able to reduce the peak values ​​of the absolute spring constant K at the secondary and tertiary peaks, compared to the standard bushing B shown in Figure 8.

[0032]

[0033]

[0034] As shown in Tables 1 and 2, the vibration-damping bushings 1 equipped with the rubber bodies 4 of the examples in Figures 9, 10(a) to 10(d), 11(a) to 11(c), 12(c), and 13(a) to 13(c), in which the secondary peak value (peak value at the secondary peak) or tertiary peak value (peak value at the tertiary peak) of the axial absolute spring constant K (in this example, the secondary peak value and tertiary peak value) is 20% or more lower than that of the reference bushing B, correspond to examples (Examples 1 to 12) that fall within the scope of the present invention, and the vibration-damping bushings 1 equipped with the rubber bodies 4 of the examples in Figures 12(a) to 12(b), in which the reduction rate of the secondary peak value or tertiary peak value (in this example, the secondary peak value and tertiary peak value) of the axial absolute spring constant K compared to the reference bushing B is less than 20%, correspond to comparative examples (Comparative Examples 1 and 2) that are outside the scope of the present invention. As can be seen from the examples in Figures 9, 10(a) to 10(d), 11(a) to 11(c), 12(c), and 13(a) to 13(c), the scope of the present invention can include vibration-damping bushings 1 having various shapes of stopper rubber portions 43 and recesses 42. Furthermore, as can be seen from the comparative examples in Figures 12(a) to 12(b), even in cases where the rubber body 4 has a recess 42 and a stopper rubber portion 43 that faces the recess 42 in the radial direction and is connected to the main rubber portion 41 so as to be able to move in direct conjunction with the main rubber portion 41, it is not necessarily possible to reduce the secondary peak value or tertiary peak value of the axial absolute spring constant K by 20% or more compared to the standard bushing B, depending on the mass, physical properties, material, etc. of the stopper rubber portion 43. As described above, adjusting the mass of the stopper rubber portion 43 is particularly important in reducing the peak value of the axial absolute spring constant K, but other adjustments can also be made to the physical properties and material of the stopper rubber portion 43. It is also believed that adjusting the shapes of the stopper rubber portion 43 and the rim 42 can contribute to this to some extent.

[0035] As described above, the vibration-damping bushing 1 of each example of the present invention has a secondary or tertiary peak value of the axial absolute spring constant that is 20% or more lower than that of the standard bushing B. Consequently, the increase in the absolute spring constant due to axial surging can be suppressed (i.e., axial springiness can be reduced). Therefore, when the vibration-damping bushing 1 is used, for example, as a vehicle vibration-damping device (e.g., an engine mount, a motor mount, and particularly as a vibration-damping device for an electric vehicle (EV) (e.g., a motor mount)), more desirable vibration-damping characteristics can be provided. In particular, vibration-damping devices for electric vehicles (EVs) (e.g., motor mounts) are required to suppress the increase in the absolute spring constant due to surging (i.e., lower springiness), particularly for vibrations in the high-frequency range, in all vibration directions. In the present invention, the reduction rate of the secondary or tertiary peak value of the axial absolute spring constant is 20% or more, so the increase in the absolute spring constant due to axial surging can be reliably suppressed. In each example of the vibration-damping bushing 1 of the present invention, the secondary peak value or tertiary peak value of the axial absolute spring constant is 20% or more lower than that of the standard bushing B. To achieve this, the rubber body 4 includes a groove 42 and a stopper rubber portion 43 that faces the groove 42 in the radial direction and is connected to the main rubber portion 41 so as to move in direct conjunction with the main rubber portion 41. With this configuration of the rubber body 4, as described above, the stopper rubber portion 43 can at least partially displace in the axial direction toward the opposite side from the main rubber portion 41 while the inner tube 3 vibrates axially relative to the outer tube 2. This allows a portion of the axial force generated by the main rubber portion 41 toward either side to be offset by a force generated by the stopper rubber portion 43 toward the other side. In this way, the stopper rubber portion 43 can function as a dynamic damper during axial vibration, thereby suppressing an increase in the absolute spring constant due to axial surging. In other words, the spring force in the axial direction can be reduced.If the stopper rubber portion 43 is not connected to the main rubber portion 41, or if it is connected to the main rubber portion 41 (via a thin-film rubber portion or the like) but is not designed to move in conjunction with the main rubber portion 41, the stopper rubber portion 43 will not be able to displace axially toward the opposite side from the main rubber portion 41 during axial vibration, making it difficult for the stopper rubber portion 43 to function as a dynamic damper and preventing an increase in the absolute spring constant due to axial surging. Furthermore, in the vibration-damping bushing 1 of each example of the present invention, the stopper rubber portion 43 also functions as a stopper that restricts excessive relative displacement between the inner tube 3 and the outer tube 2 in the direction perpendicular to the axis, as described above. Therefore, the two requirements for a vehicle vibration-damping device, namely, low spring force in the axial direction and restriction of excessive displacement between the inner tube 3 and the outer tube 2 in the direction perpendicular to the axis, can be achieved by the same stopper rubber portion 43.

[0036] In each example of the vibration-damping bushing 1 of the present invention, only one of the secondary peak value and the tertiary peak value of the axial absolute spring constant may be 20% or more lower than that of the standard bushing B, but it is preferable that both the secondary peak value and the tertiary peak value are 20% or more lower.

[0037] The following method, for example, can be used to determine the rate of reduction in the secondary or tertiary peak value of the absolute spring constant in the axial direction of an actual product vibration-isolating bushing 1 when compared with a reference bushing B. With regard to the vibration-isolating bushing 1, first the secondary or tertiary peak value of the absolute spring constant in the axial direction of the actual product vibration-isolating bushing 1 is determined by experiment, and the physical properties of the rubber body 4 of the vibration-isolating bushing 1 of the actual product are determined by measurement or analysis.The rubber body 4 of the vibration-isolating bushing 1 of the actual product is then modeled for FEM analysis (i.e., has the same shape and size as the actual vibration-isolating bushing 1), and the physical properties of the rubber body 4 of the vibration-isolating bushing 1 of the actual product thus determined are input into a model vibration-isolating bushing 1, into which the rubber body 4 of the vibration-isolating bushing 1 has been modeled for FEM analysis (i.e., has the same shape and size as the actual vibration-isolating bushing 1), and the secondary or tertiary peak value of the model vibration-isolating bushing 1 is determined by FEM analysis, and the relationship in secondary or tertiary peak value between the vibration-isolating bushing 1 of the actual product and the model vibration-isolating bushing 1 is confirmed. On the other hand, for the standard bushing B, the physical properties of the rubber body 4 of the vibration-isolating bushing 1 in the actual product determined above are input into a model (model standard bushing B) of the rubber body 4 of the standard bushing B created for FEM analysis and corresponding to that vibration-isolating bushing 1, and the secondary or tertiary peak value of the absolute spring constant in the axial direction of the rubber body 4 of the model standard bushing B is determined by FEM analysis, and the secondary or tertiary peak value of the standard bushing B in the hypothetical actual product is determined based on the secondary or tertiary peak value of the absolute spring constant in the axial direction of the rubber body 4 of the model standard bushing B and the relationship between the secondary or tertiary peak values ​​of the vibration-isolating bushing 1 in the actual product and the model vibration-isolating bushing 1. The reduction rate is then calculated using the secondary or tertiary peak values ​​of the vibration-isolating bushing 1 in the actual product determined as described above and the standard bushing B in the hypothetical actual product.

[0038] From a similar perspective, it is preferable that the vibration-isolating bushing 1 has a secondary peak value of the axial absolute spring constant that is 24% or more lower than that of the standard bushing B. From a similar perspective, it is preferable that the vibration-isolating bushing 1 has a tertiary peak value of the axial absolute spring constant that is 24% or more lower than that of the standard bushing B. Furthermore, it is also acceptable that the vibration-isolating bushing 1 has a secondary peak value of the axial absolute spring constant that is 40% or less lower than that of the standard bushing B, or 37% or less lower. Furthermore, it is also acceptable that the vibration-isolating bushing 1 has a tertiary peak value of the axial absolute spring constant that is 40% or less lower than that of the standard bushing B, or 37% or less lower.

[0039] As described above, the groove 42 and the stopper rubber portion 43 can have various configurations. For example, as shown in each of the examples shown in FIGS. 1, 9 to 13, and 15, at least one stopper rubber portion 43 (one in each of the examples shown in FIGS. 1, 9, 10, 12, 13, and 15; two in each of the examples shown in FIG. 11) may be located radially inward of at least a portion of the groove 42 (the entire groove 42 in each of the examples shown in FIGS. 1, 9, 10, 12, 13, and 15; only the circumferential groove portion 42a of the groove 42 in each of the examples shown in FIG. 11). In this case, the at least one stopper rubber portion 43 faces the at least a portion of the groove 42 in the radial direction. In this case, the stopper rubber portion 43 that interfaces with the main rubber portion 41 can be easily formed. In this case, the rubber body 4 may have an outer peripheral covering rubber portion 46 between the groove 42 and the outer tube 2. The outer peripheral surface of the outer peripheral covering rubber portion 46 contacts (and is joined to) the inner peripheral surface of the outer tube 2. Both circumferential ends of the outer peripheral covering rubber portion 46 are connected to the main body rubber portion 41, but are not configured to move in conjunction with the main body rubber portion 41. Alternatively, the outer peripheral covering rubber portion 46 may not be provided between the ridge 42 and the outer tube 2, and a portion of the ridge 42 may be defined by a portion of the inner peripheral surface of the outer tube 2. In this case, the rubber body 4 may also have an inner peripheral covering rubber portion 45 between the stopper rubber portion 43 and the inner tube 3. The inner peripheral surface of the inner peripheral covering rubber portion 45 contacts (and is joined to) the outer peripheral surface of the inner tube 3. Both circumferential ends of the inner peripheral covering rubber portion 45 are connected to the main body rubber portion 41, but are not configured to move in conjunction with the main body rubber portion 41. Alternatively, the inner peripheral surface of the stopper rubber portion 43 may be directly in contact with (and joined to) the outer peripheral surface of the inner tube 3 without providing the inner peripheral covering rubber portion 45 between the stopper rubber portion 43 and the inner tube 3. In this case, the grooves 42 may extend along the circumferential direction, as in the examples shown in Figs. 1, 9 to 13, and 15. Alternatively, the grooves 42 may have a circumferential groove portion 42a extending along the circumferential direction and a radial groove portion 42b extending radially inward from an arbitrary position (for example, the circumferential center) of the circumferential groove portion 42a, as in the example shown in Fig. 11.11(a) to 11(c), the stopper rubber portion 43 may be provided on each side of the radial groove portion 42b in the circumferential direction (two in total). Alternatively, the groove portion 42 may have any other shape.

[0040] Alternatively, as in a modified example shown in FIG. 17 , at least one stopper rubber portion 43 (one in the example shown in FIG. 17 ) may be located radially outward of at least a portion of the ridge 42 (the entire ridge 42 in the example shown in FIG. 17 ). In this case, the at least one stopper rubber portion 43 faces the at least a portion of the ridge 42 in the radial direction. In this case, the stopper rubber portion 43 that interfaces with the main rubber portion 41 can be easily formed. In this case, the rubber body 4 may or may not have an outer peripheral covering rubber portion 46 between the stopper rubber portion 43 and the outer tube 2. Furthermore, the rubber body 4 may or may not have an inner peripheral covering rubber portion 45 between the ridge 42 and the inner tube 3. Furthermore, in this case, the ridge 42 may extend along the circumferential direction. Alternatively, the groove 42 may have a circumferential groove portion 42a extending along the circumferential direction and a radial groove portion 42b extending radially outward from any point (for example, the circumferential center) of the circumferential groove portion 42a. In this case, the stopper rubber portion 43 may be provided on each side of the radial groove portion 42b in the circumferential direction (two in total). Alternatively, the groove 42 may have any other shape.

[0041] Alternatively, as in another modified example shown in FIG. 18 , two grooves 42 may be disposed at a distance from each other in the radial direction, and at least one stopper rubber portion 43 (one in the example shown in FIG. 18 ) may be disposed between the two grooves 42. In this case, the at least one stopper rubber portion 43 faces each of the two grooves 42 in the radial direction. In this case, the stopper rubber portion 43 interlocking with the main rubber portion 41 can be easily formed. In this case, the rubber body 4 may or may not have an outer peripheral covering rubber portion 46 between one groove 42 and the outer tube 2. Furthermore, the rubber body 4 may or may not have an inner peripheral covering rubber portion 45 between the other groove 42 and the inner tube 3.

[0042] Although not shown, the rubber body 4 may have multiple grooves 42. These multiple grooves 42 may be located at different positions in the circumferential direction and / or may be located at different positions in the radial direction. In this case, it is preferable that at least one stopper rubber portion 43 faces each groove 42 in the radial direction. In this case, the stopper rubber portion 43 that interlocks with the main rubber portion 41 can also be easily formed.

[0043] In each example described herein, as shown in FIGS. 4, 9, and 10, it is preferable that the axial length L43 (FIG. 4) of the stopper rubber portion 43 be equal to or less than the axial length L41 (FIG. 4) of the main rubber portion 41. In the example of FIG. 9, L43 = L41, and in the examples shown in FIGS. 4 and 10, L43 < L41. This allows the stopper rubber portion 43 to move more easily in the axial direction, further suppressing an increase in the absolute spring constant due to axial surging. Note that the axial length L43 (FIG. 4) of the stopper rubber portion 43 refers to the minimum axial length when the axial length of the stopper rubber portion 43 is nonuniform along the radial and / or circumferential directions. Similarly, the axial length L41 (FIG. 4) of the main rubber portion 41 refers to the minimum axial length when the axial length of the main rubber portion 41 is nonuniform along the radial and / or circumferential directions.

[0044] In each example described herein, as in the examples shown in FIGS. 6 and 15 , the rubber body 4 may further include a circumferential rubber mass 44 that protrudes axially outward from at least one axial end face of the main rubber portion 41 and extends circumferentially. In this case, the increase in the absolute spring constant due to surging in the axial direction can be further suppressed, and the increase in the absolute spring constant due to surging in the direction perpendicular to the axis can also be suppressed. Note that FIG. 15 shows a model of another example of the rubber body 4 used in the above-mentioned FEM analysis. The rubber body 4 in the example of FIG. 15 corresponds to the rubber body 4 in the example of FIG. 9 , except that circumferential rubber masses 44 that protrude axially outward and extend circumferentially are provided on both axial end faces of the main rubber portion 41. The rubber body 4 of the reference bush B corresponding to the vibration-damping bushing 1 equipped with the rubber body 4 in the example of FIG. 15 is shown in FIG. 8 . The graph in Fig. 16 is similar to the graph in Fig. 14, with waveform W1 being the waveform resulting from the FEM analysis performed on the rubber body 4 of the standard bushing B shown in Fig. 8, and waveform W3 being the waveform resulting from the FEM analysis performed on the rubber body 4 of the vibration-damping bushing 1 of the example shown in Fig. 15. As can be seen from a comparison of Fig. 14 and Fig. 16, waveform W3 (Fig. 16) of the vibration-damping bushing 1 of the example shown in Fig. 15 was able to reduce the secondary peak value of the absolute spring constant K relative to waveform W1 of standard bushing B even more than waveform W2 (Fig. 14) of the vibration-damping bushing 1 of the example shown in Fig. 9.

[0045] It is preferable that the rubber body 4 be formed from a rubber obtained by crosslinking a rubber composition containing a rubber component primarily composed of natural rubber and non-diene rubber. This can further suppress an increase in the absolute spring constant due to surging. Here, "a rubber component primarily composed of natural rubber and non-diene rubber" refers to a rubber component containing natural rubber and non-diene rubber as rubber components, and in which the total amount of the natural rubber and non-diene rubber in the rubber component is 50 mass% or more relative to the total amount of the rubber component. It is more preferable that the total amount of the natural rubber and non-diene rubber in the rubber component is more than 50 mass% relative to the total amount of the rubber component. The rubber component may contain only natural rubber and non-diene rubber, or may contain rubber other than natural rubber and non-diene rubber. An example of the rubber other than natural rubber and non-diene rubber is diene rubber. In the above case, the blending ratio of natural rubber to non-diene rubber in the rubber composition (natural rubber:non-diene rubber) is preferably 95:5 to 50:50 by mass, more preferably 95:5 to 60:40, even more preferably 95:5 to 65:35, and even more preferably 80:20 to 70:30. The natural rubber (NR) is not particularly limited, and any known rubber may be appropriately selected and used, and examples thereof include RSS (ribbed smoked sheets) and TSR (technically specified rubber). The non-diene rubber is not particularly limited and may be any known rubber selected and used as appropriate. Examples include butyl rubber (IIR), chlorinated butyl rubber (CIIR), brominated butyl rubber (BIIR), ethylene-propylene-norbornene rubber (EPDM), ethylene-acrylic rubber (AEM), polyacrylic rubber (ACM), silicone rubber (VMQ), fluororubber (FKM), polyurethane rubber (AU), ester-based polyurethane rubber (EU), polyether ether ketone rubber (PEEK), and the like. In the above-described embodiments, butyl rubber (IIR), chlorinated butyl rubber (CIIR), or brominated butyl rubber (BIIR) is particularly preferred.However, the rubber forming the rubber body 4 does not have to be the rubber mentioned above, and may be a combination of two or more types of rubber.

[0046] The vibration-damping bushing according to the present invention is suitable for use in, for example, vehicle vibration-damping devices (e.g., engine mounts, motor mounts), and is particularly suitable for use in vibration-damping devices (e.g., motor mounts) for electric vehicles (EVs).

[0047] 1: Anti-vibration bushing, B: Reference bushing, 2: Outer cylinder, 3: Inner cylinder, 4: Rubber body, 41: Main rubber portion, 42: Groove, 42a: Circumferential groove portion, 42b: Radial groove portion, 43: Stopper rubber portion, 44: Circumferential rubber mass portion, 45: Inner peripheral covering rubber portion, 46: Outer peripheral covering rubber portion, O: Central axis

Claims

1. A vibration-isolating bushing comprising an outer tube, an inner tube, and a rubber body located between the outer tube and the inner tube, wherein the rubber body has: a main rubber portion that connects the outer tube and the inner tube together in the radial direction and extends over only a portion of the circumferential direction; a groove that is located in a circumferential region other than the circumferential region in which the main rubber portion extends and penetrates the rubber body in the axial direction; and a stopper rubber portion that faces the groove in the radial direction, wherein the stopper rubber portion is connected to the main rubber portion so as to move in direct conjunction with the main rubber portion, and wherein the vibration-isolating bushing has a secondary peak value or tertiary peak value of the absolute spring constant in the axial direction that is 20% or more lower than that of a standard bush in which the main rubber portion of the vibration-isolating bushing extends over the entire circumference and the rubber body is composed only of the main rubber portion.

2. An anti-vibration bush as described in claim 1, wherein the stopper rubber portion is configured so as to be displaceable in the axial direction in the opposite direction to the main rubber portion while the inner tube vibrates in the axial direction relative to the outer tube.

3. The vibration-isolating bush according to claim 1, wherein at least one of said stopper rubber portions is located radially inward of at least a portion of said ridge.

4. The vibration-isolating bush according to claim 1, wherein at least one of said stopper rubber portions is located radially outward of at least a portion of said ridge.

5. The vibration-isolating bushing according to claim 1, wherein the two grooves are arranged at a distance from each other in the radial direction, and at least one of the stopper rubber portions is arranged between the two grooves.

6. The vibration-isolating bush according to claim 1, wherein the rubber body has a plurality of the grooves, and at least one of the stopper rubber portions faces each of the grooves in the radial direction.

7. The vibration-isolating bushing according to claim 1, wherein the axial length of said stopper rubber portion is equal to or less than the axial length of said main rubber portion.

8. The vibration-isolating bushing according to claim 1, wherein the rubber body is formed from a rubber obtained by crosslinking a rubber composition containing a rubber component whose main components are natural rubber and non-diene rubber.

9. An anti-vibration bush as described in claim 1, wherein the rubber body further has a circumferential rubber mass portion that protrudes axially outward from at least one axial end face of the main rubber portion and extends circumferentially.

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