Tubular vibration-damping device for motor mount

Abstract

To provide a tubular vibration-damping device for a motor mount of a novel structure which is able to prevent vibration state from deteriorating significantly at a specific frequency due to surging, while ensuring the durability of rubber legs.SOLUTION: A tubular vibration-damping device 10 for a motor mount in which an inner shaft member 12 and an outer tube member 14 are connected by a plurality of rubber legs 40 extending between radial facing surfaces of the inner shaft member 12 and the outer tube member 14, wherein the plurality of rubber legs 40 include four rubber legs 40a to 40d which, in an up-down direction and a left-right direction, mutually separate wider apart in a circumferential direction toward the outer periphery, and for the four rubber legs 40a to 40d, a difference in cross-sectional areas in a leg transverse cross section orthogonal to a length direction, which is a connection direction of the inner shaft member 12 and the outer tube member 14, is 20% or less, and the four rubber legs 40a to 40d are formed into mutually different shapes and have mutually different resonant states against a vibration input in the up-down direction.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a cylindrical vibration isolator for a motor mount used as a motor mount that vibrationally connects an electric motor to a vehicle body in an electrified vehicle such as a battery electric vehicle (BEV) or a hybrid car.

Background Art

[0002] Recently, with the electrification of vehicles, the development of motor mounts that vibrationally connect an electric motor to a vehicle body has been underway. As a motor mount, for example, as disclosed in FIG. 5 of German Patent Application Publication No. 102018221375 (Patent Document 1), a cylindrical vibration isolator in which an inner shaft member and an outer cylinder member are interconnected by a plurality of rubber legs extending in the radial direction is adopted.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in a motor mount that vibrationally supports an electric motor, which has less vibration than an internal combustion engine, deterioration of the vibration state in the high frequency range due to surging of the rubber legs tends to be a problem. In particular, as in FIG. 5 of Patent Document 1, when there are a plurality of rubber legs having substantially the same shape and size, the resonance frequencies of the plurality of rubber legs become substantially the same as each other, so there is a risk of significant deterioration of the vibration state at a specific frequency.

[0005] In Patent Document 1, mass projections are formed to protrude from rubber legs, and the adverse effects on the vibration state due to surging of the rubber legs are prevented by the mass damper action of the mass projections. However, if mass projections are provided on the rubber legs, when the rubber legs are deformed during vibration input, strain concentrates on the base end portion of the mass projections, making it easy for the mass projections and the rubber legs to be damaged.

[0006] The problem to be solved by the present invention is to provide a cylindrical vibration isolator for a motor mount with a novel structure that can prevent the vibration state from significantly deteriorating at a specific frequency due to surging while ensuring the durability of the rubber legs.

Means for Solving the Problem

[0007] Hereinafter, preferred embodiments for understanding the present invention will be described. However, each of the embodiments described below is described by way of example, and not only can they be adopted in appropriate combinations with each other, but also for the plurality of components described in each embodiment, they can be recognized and adopted independently as much as possible, and can also be adopted in combination with any of the components described in another embodiment as appropriate. Thereby, in the present invention, various other embodiments can be realized without being limited to the embodiments described below.

[0008] The first aspect is a cylindrical vibration isolator for a motor mount in which an inner shaft member and an outer cylinder member are connected by a plurality of rubber legs extending between the radially opposed surfaces of the inner shaft member and the outer cylinder member, wherein the plurality of rubber legs have four rubber legs that expand circumferentially toward the outer periphery in the vertical direction and the horizontal direction, respectively, and the difference in cross-sectional area in the leg cross-section perpendicular to the length direction, which is the connection direction between the inner shaft member and the outer cylinder member, of these four rubber legs is 20% or less, and these four rubber legs have different shapes from each other, and the resonance states with respect to vibration input in the vertical direction are different from each other.

[0009] According to the cylindrical vibration isolator for a motor mount having a structure according to this aspect, by making the difference in cross-sectional area at the leg cross-section of the four rubber legs 20% or less, the four rubber legs can have mutually similar volumes while having mutually different shapes. Thereby, for example, while ensuring the rubber volume of each rubber leg similarly to prevent deterioration of durability, etc., it is possible to shift the resonance frequencies of the four rubber legs, etc., to suppress deterioration of spring characteristics at a specific frequency.

[0010] A second aspect is the cylindrical vibration isolator for a motor mount described in the first aspect, wherein the upper two rubber legs have the same length dimension in the connecting direction between the inner shaft member and the outer cylinder member, and the lower two rubber legs have the same length dimension in the connecting direction between the inner shaft member and the outer cylinder member, and the upper two rubber legs and the lower two rubber legs have mutually different length dimensions in the connecting direction between the inner shaft member and the outer cylinder member.

[0011] According to the cylindrical vibration isolator for a motor mount having a structure according to this aspect, by making the lengths of the upper two rubber legs the same, the lengths of the lower two rubber legs the same, and making the lengths of the upper rubber legs and the lower rubber legs mutually different, for example, considering the shared support load of the motor unit, the load input during acceleration and deceleration, etc., the springs on the upper and lower sides can be appropriately set respectively. Also, due to the difference in the lengths of the upper and lower rubber legs, the shapes of the upper and lower rubber legs can be made mutually different.

[0012] A third aspect is the cylindrical vibration isolator for a motor mount described in the first or second aspect, wherein the upper two rubber legs include a first cross-sectional area common portion having the same cross-sectional area in a leg cross-section orthogonal to the length direction which is the connecting direction between the inner shaft member and the outer cylinder member, and the lower two rubber legs include a second cross-sectional area common portion having the same cross-sectional area in the leg cross-section.

[0013] According to the cylindrical vibration isolator for a motor mount having a structure according to this aspect, since the shape difference between the upper rubber legs can be suppressed and the shape difference between the lower rubber legs can be suppressed, the springs of the rubber legs on both the left and right sides with respect to the inner shaft member can be set in good balance. Therefore, for example, when vibration is input in the vertical direction, unintentional vibrations such as unbalance of the left and right springs are suppressed, and adverse effects on the vibration state are prevented.

[0014] The fourth aspect is the cylindrical vibration isolator for a motor mount according to any one of the first to third aspects, wherein the rubber leg located in the upper left and the rubber leg located in the lower right have the same shape as each other in the leg cross section, the rubber leg located in the upper right and the rubber leg located in the lower left have the same shape as each other in the leg cross section, and the rubber legs located in the upper left and lower right and the rubber legs located in the upper right and lower left have different shapes from each other in the leg cross section.

[0015] According to the cylindrical vibration isolator for a motor mount having a structure according to this aspect, by making the cross-sectional shapes of the rubber legs arranged in the diagonally opposite directions the same as each other, for example, unintentional relative displacements such as the vibration of the inner shaft member and the outer cylinder member during vibration input are less likely to occur, and the stabilization of the vibration state is easily achieved.

Effects of the Invention

[0016] According to the present invention, in the cylindrical vibration isolator for a motor mount, while ensuring the durability of the rubber legs, it is possible to prevent the vibration state from deteriorating significantly at a specific frequency due to surging.

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

Figure 3

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Figure 5

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Figure 11

Embodiments for Carrying Out the Invention

[0018] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0019] In FIGS. 1 and 2, a cylindrical vibration isolator 10 for a motor mount (hereinafter referred to as the cylindrical vibration isolator 10) as a first embodiment of the present invention is shown. The cylindrical vibration isolator 10 has a structure in which an inner shaft member 12 and an outer cylinder member 14 are radially connected by a main body rubber elastic body 16. In the following description, in principle, the vertical direction refers to the vertical direction in FIG. 1, the left-right direction refers to the left-right direction in FIG. 1, and the front-rear direction refers to the left-right direction in FIG. 2.

[0020] As can be seen from FIG. 1, the inner shaft member 12 has a substantially octagonal cross-sectional shape, and as shown in FIG. 2, it extends linearly in the front-rear direction with a substantially constant cross-sectional shape. The inner shaft member 12 has a width dimension in the vertical direction smaller than the width dimension in the left-right direction, and has a long and flat cross-sectional shape with the left-right direction being long. A circular bolt insertion hole 18 penetrating the central portion in the front-rear direction is provided in the inner shaft member 12. The inner shaft member 12 is formed of, for example, a metal such as iron or an aluminum alloy, a fiber-reinforced synthetic resin, or the like.

[0021] The outer peripheral surface of the octagonal columnar inner shaft member 12 includes an upper surface 20 and a lower surface 22 that extend in a direction substantially orthogonal to the vertical direction, a left surface 24 and a right surface 26 that extend in a direction substantially orthogonal to the horizontal direction, an upper left inclined surface 28 that connects between the upper surface 20 and the left surface 24, an upper right inclined surface 30 that connects between the upper surface 20 and the right surface 26, a lower left inclined surface 32 that connects between the lower surface 22 and the left surface 24, and a lower right inclined surface 34 that connects between the lower surface 22 and the right surface 26.

[0022] The outer cylinder member 14 has a thin-walled and large-diameter substantially cylindrical shape and linearly extends in the front-rear direction with a substantially constant circular cross-section. The outer cylinder member 14 is formed of metal, fiber-reinforced synthetic resin, or the like, similar to the inner shaft member 12.

[0023] The inner shaft member 12 is inserted into the inner circumference of the outer cylinder member 14, and a main body rubber elastic body 16 is formed between the radially opposed surfaces of the inner shaft member 12 and the outer cylinder member 14. The main body rubber elastic body 16 integrally includes a small-diameter cylindrical inner circumferential fixing portion 36 fixed to the outer peripheral surface of the inner shaft member 12, a large-diameter cylindrical outer circumferential fixing portion 38 fixed to the inner peripheral surface of the outer cylinder member 14, and a plurality of rubber legs 40 that connect the inner circumferential fixing portion 36 and the outer circumferential fixing portion 38 to each other.

[0024] The plurality of rubber legs 40 are constituted by four rubber legs 40a, 40b, 40c, and 40d. The four rubber legs 40a to 40d extend between the radially opposed surfaces of the outer peripheral surface of the inner shaft member 12 and the inner peripheral surface of the outer cylinder member 14, and extend in an oblique direction that expands circumferentially with respect to each other toward the outer periphery in the vertical direction and the horizontal direction. That is, the two rubber legs 40a and 40b extending upward from the inner shaft member 12 expand circumferentially with respect to each other toward the outer periphery, and the two rubber legs 40c and 40d extending downward expand circumferentially with respect to each other toward the outer periphery. As a result, the two rubber legs 40a and 40c extend leftward so as to expand circumferentially with respect to each other toward the outer periphery, and the two rubber legs 40b and 40d extend rightward so as to expand circumferentially with respect to each other toward the outer periphery. Further, the two rubber legs 40a and 40d are positioned in a substantially opposed direction so as to extend from the inner shaft member 12 toward the upper left and the lower right, and the two rubber legs 40b and 40c are positioned in a substantially opposed direction so as to extend from the inner shaft member 12 toward the upper right and the lower left.

[0025] Specifically, the rubber leg 40a extends obliquely upward to the left from the inner shaft member 12 so as to incline to the left as it goes upward, the rubber leg 40b extends obliquely upward to the right from the inner shaft member 12 so as to incline to the right as it goes upward, the rubber leg 40c extends obliquely downward to the left from the inner shaft member 12 so as to incline to the left as it goes downward, and the rubber leg 40d extends obliquely downward to the right from the inner shaft member 12 so as to incline to the right as it goes downward. Through holes 42 penetrating in the axial direction are respectively formed between the circumferential directions of the four rubber legs 40a to 40d. Further, the axial end surfaces of each rubber leg 40 are concave in the longitudinal section, the inner peripheral portion inclines axially inward toward the outer periphery (the outer cylinder member 14 side), and the outer peripheral portion inclines axially outward toward the outer periphery (see FIGS. 4, 6, 8, and 10).

[0026] The rubber leg 40a has an axial thickness dimension Ta that is larger than the circumferential width dimension Wa in the leg cross-section of FIG. 3, and is a substantially rectangular shape with a large flatness ratio in the leg cross-section of FIG. 3. The rubber leg 40b has an axial thickness dimension Tb that is substantially the same as the circumferential width dimension Wb in the leg cross-section of FIG. 5, and is a substantially square shape in the leg cross-section of FIG. 5. The rubber leg 40c has an axial thickness dimension Tc that is substantially the same as the circumferential width dimension Wc in the leg cross-section of FIG. 7, and is a substantially square shape in the leg cross-section of FIG. 7. The rubber leg 40d has an axial thickness dimension Td that is larger than the circumferential width dimension Wd in the leg cross-section of FIG. 9, and is a substantially rectangular shape with a large flatness ratio in the leg cross-section of FIG. 9. Note that the leg cross-section refers to a cross-section orthogonal to the stretching direction (length direction) of the rubber leg 40, and is a cross-section orthogonal to the elastic principal axis in the stretching direction. In this embodiment, it is a substantially orthogonal plane with respect to the radial line extending from the central axis of the inner shaft member 12. The leg cross-sections of each rubber leg 40 in FIGS. 3, 5, 7, and 9 are leg cross-sections at substantially the same distance from the central axis of the inner shaft member 12. Also, as shown in FIGS. 3, 5, 7, and 9, the axial end faces of the rubber legs 40 of the present embodiment are inclined inward in the axial direction as they go inward in the left and right directions in the circumferential direction. Therefore, the axial thickness dimension changes in the circumferential direction. For example, the thickness at a specific position in the circumferential direction or the average value of the thickness in the circumferential direction may be adopted as the thickness dimension.

[0027] As shown in FIGS. 3 and 9, the leg cross-sectional shapes of the upper left rubber leg 40a and the lower right rubber leg 40d are substantially the same as each other. Also, as shown in FIGS. 5 and 7, the leg cross-sectional shapes of the upper right rubber leg 40b and the lower left rubber leg 40c are substantially the same as each other. Also, the rubber legs 40a and 40d and the rubber legs 40b and 40c have different leg cross-sectional shapes from each other. In this embodiment, the upper left rubber leg 40a and the lower right rubber leg 40d have a larger ratio of the axial thickness dimension to the circumferential width dimension than the upper right rubber leg 40b and the lower left rubber leg 40c.

[0028] Note that the statement that the leg cross-sectional shapes of the rubber legs 40 are the same as each other does not necessarily mean that they are completely identical. It means that they have a high degree of shape similarity and are similar in shape. Since the rubber leg 40a has a high degree of shape similarity to the rubber leg 40d in the leg cross-section and a low degree of shape similarity to the rubber legs 40b and 40c, the rubber leg 40a has the same leg cross-sectional shape as the rubber leg 40d and a different leg cross-sectional shape from the rubber legs 40b and 40c. Similarly, since the rubber leg 40b has a high degree of shape similarity to the rubber leg 40c in the leg cross-section and a low degree of shape similarity to the rubber legs 40a and 40d, the rubber leg 40b has the same leg cross-sectional shape as the rubber leg 40c and a different leg cross-sectional shape from the rubber legs 40a and 40d.

[0029] The upper left rubber leg 40a and the lower right rubber leg 40d with a large axial thickness dimension have a larger inclination angle of the axial end face of the inner peripheral portion in the longitudinal section compared to the upper right rubber leg 40b and the lower left rubber leg 40c with a small axial thickness dimension. Therefore, the difference in the axial thickness dimensions between the upper left rubber leg 40a and the lower right rubber leg 40d and the upper right rubber leg 40b and the lower left rubber leg 40c becomes larger as going towards the outer periphery.

[0030] The length dimension La of the upper left rubber leg 40a and the length dimension Lb of the upper right rubber leg 40b are made to be approximately the same as each other. Also, the length dimension Lc of the lower left rubber leg 40c and the length dimension Ld of the lower right rubber leg 40d are made to be approximately the same as each other. Further, the length dimension La of the upper left rubber leg 40a and the length dimension Lb of the upper right rubber leg 40b and the length dimension Lc of the lower left rubber leg 40c and the length dimension Ld of the lower right rubber leg 40d are made to be different from each other. In this embodiment, the length dimension La of the upper left rubber leg 40a and the length dimension Lb of the upper right rubber leg 40b are made shorter than the length dimension Lc of the lower left rubber leg 40c and the length dimension Ld of the lower right rubber leg 40d. Thereby, the central axis of the inner shaft member 12 is shifted upward with respect to the central axis of the outer cylinder member 14. Note that the length of the rubber leg 40 refers to the length in the stretching direction of the rubber leg 40, which is the connecting direction of the inner shaft member 12 and the outer cylinder member 14 by the rubber leg 40.

[0031] As described above, at least one of the cross-sectional shape and the length of the four rubber legs 40a to 40d is different from each other, and they are shaped differently from each other. Therefore, the four rubber legs 40a to 40d can exhibit different spring characteristics associated with the shape differences, for example, in response to vertical vibration input.

[0032] Also, the difference in cross-sectional area in the leg cross-section of the four rubber legs 40a to 40d is set to 20% or less, for example, within the range of 10 to 20%. In the present embodiment, the difference in the minimum cross-sectional area in the leg cross-section of the four rubber legs 40a to 40d is set to 20% or less, for example, within the range of 10 to 20%. Thereby, the four rubber legs 40a to 40d are set such that their masses do not differ greatly from each other.

[0033] The rubber legs 40a and 40b extending upward from the inner shaft member 12 include a first cross-sectional area common portion where the cross-sectional areas in the leg cross-section are the same as each other. Also, the rubber legs 40c and 40d extending downward from the inner shaft member 12 include a second cross-sectional area common portion where the cross-sectional areas in the leg cross-section are the same as each other. The first cross-sectional area common portion and the second cross-sectional area common portion can be set at any position in the extending direction of each rubber leg 40. For example, it is desirable from the viewpoint of facilitating design, etc., to set them at the central position in the extending direction of each rubber leg 40, at a position at a certain distance from the inner shaft member 12 or the outer cylinder member 14 in each rubber leg 40, at a specific position in the extending direction of each rubber leg 40, etc.

[0034] In the present embodiment, the difference between the length dimension La of the upper left rubber leg 40a and the length dimension Lb of the upper right rubber leg 40b, and the length dimension Lc of the lower left rubber leg 40c and the length dimension Ld of the lower right rubber leg 40d is set to 20% or less, and more preferably 15% or less. Thereby, the mass difference between the four rubber legs 40a to 40d is made smaller.

[0035] The four rubber legs 40a to 40d have different shapes from each other, and the difference in the minimum cross-sectional area in the leg cross-section is 20% or less, so that the resonance states with respect to the vertical vibration input are different from each other. For example, the four rubber legs 40a to 40d are set to have different resonance frequencies with respect to the vertical vibration input. In other words, the resonance states of the four rubber legs 40a to 40d are made different from each other so that they do not resonate simultaneously at a specific frequency.

[0036] Particularly in this embodiment, the upper two rubber legs 40a and 40b have a first cross-sectional area common part with the same cross-sectional area, and the volume difference between these rubber legs 40a and 40b is made smaller. Similarly, the lower two rubber legs 40c and 40d have a second cross-sectional area common part with the same cross-sectional area, and the volume difference between these rubber legs 40c and 40d is made smaller. Thus, since the volume difference, in other words, the mass difference of the upper two rubber legs 40a and 40b is made smaller, it is easy to set the resonance frequencies of these rubber legs 40a and 40b to be different from each other depending on the cross-sectional shapes and lengths of these rubber legs 40a and 40b. Similarly, for the lower two rubber legs 40c and 40d, it is easy to set the resonance frequencies to be different from each other depending on the cross-sectional shapes and lengths.

[0037] Since the resonance frequencies of the four rubber legs 40a to 40d are made different in this way, in a vehicle-mounted state where the inner shaft member 12 is attached to an electric motor (not shown) and the outer cylinder member 14 is attached to a vehicle body (not shown), when vertical vibration is input between the inner shaft member 12 and the outer cylinder member 14, the deterioration of the vibration state due to the resonance of these rubber legs 40a to 40d is reduced.

[0038] The length dimensions La and Lb of the two upper rubber legs 40a and 40b are the same as each other, and the length dimensions Lc and Ld of the two lower rubber legs 40c and 40d are the same as each other. At the same time, the length dimensions La and Lb of the two upper rubber legs 40a and 40b are different from the length dimensions Lc and Ld of the two lower rubber legs 40c and 40d. As a result, it is not necessary to make the fixing parts of the rubber legs 40 on the inner shaft member 12 and the outer cylinder member 14 have a complicated shape, and the structure can be simplified. Also, for example, when vibration is input in the vertical direction, it is possible to prevent the load from concentrating on a specific rubber leg 40, and the durability of the rubber leg 40 can be improved. In particular, since the length dimensions Lc and Ld of the lower rubber legs 40c and 40d are longer than the length dimensions La and Lb of the upper rubber legs 40a and 40b, it is advantageous to ensure durability and reduce the spring rate with respect to the input load that displaces the inner shaft member 12 downward with respect to the outer cylinder member 14.

[0039] The rubber legs 40a and 40d have substantially the same leg cross-sectional shape as each other, and the rubber legs 40b and 40c have substantially the same leg cross-sectional shape as each other. The rubber legs 40a and 40d and the rubber legs 40b and 40c have different leg cross-sectional shapes from each other. In this way, since the rubber legs 40a and 40d arranged on both sides in one diagonal direction with respect to the inner shaft member 12 have substantially the same leg cross-sectional shape, and the rubber legs 40b and 40c arranged on both sides in the other diagonal direction with respect to the inner shaft member 12 have substantially the same leg cross-sectional shape, for example, it becomes difficult for unintended relative displacement such as the deflection of the inner shaft member 12 and the outer cylinder member 14 to occur during vertical input, and it becomes easier to stabilize the vibration state.

[0040] In the cylindrical vibration isolator 10 according to the present embodiment, it can be understood from the graph showing the simulation results of the vibration isolation characteristics shown in FIG. 11 that an excellent vibration isolation effect is realized due to the difference in the resonance frequencies of the rubber legs 40a to 40d. FIG. 11 is a graph showing the vibration isolation characteristics (Example) of the cylindrical vibration isolator 10 according to the present embodiment with respect to vertical vibration, and the vibration isolation characteristics (Base) of the cylindrical vibration isolator according to the conventional structure having four rubber legs of the same shape with respect to vertical vibration. The horizontal axis represents the frequency, and the vertical axis represents the dynamic spring constant.

[0041] According to FIG. 11, it can be seen that in the example, the peak of the dynamic spring is lower than that of the base, and the vibration isolation performance is excellent. That is, in the example, since the four rubber legs 40a to 40d are in a resonant state at mutually different frequencies, a decrease in vibration isolation performance due to simultaneously entering the resonant state is prevented, and excellent vibration isolation performance is maintained over a wide frequency range. On the other hand, in the base, a rapid and significant increase in the dynamic spring occurs at the frequency at which the four rubber legs having the same shape enter the resonant state simultaneously, and the vibration isolation performance is significantly reduced.

[0042] Thus, it is clear from the simulation results that the cylindrical vibration isolator 10 according to the present embodiment exhibits excellent vibration isolation performance compared to the cylindrical vibration isolator of the conventional structure.

[0043] As described above, the embodiments of the present invention have been described in detail, but the present invention is not limited by the specific description. For example, a stopper rubber that limits the relative displacement amount between the inner shaft member and the outer cylinder member can also be provided between the rubber legs adjacent in the circumferential direction. According to this, the durability of each rubber leg can be improved.

[0044] The resonance frequencies of the four rubber legs may be adjusted to be different from each other, for example, by either the leg cross-sectional shape or the length. In short, the four rubber legs may have the same one of the leg cross-sectional shape and the length, and the other one may be different from each other.

[0045] The four rubber legs have a cross-sectional area difference of 20% or less in the leg cross-section. However, the cross-sectional area in the leg cross-section referred to here is not necessarily limited to the minimum cross-sectional area exemplified in the first embodiment. For example, the cross-sectional area at a specific position (a position at a predetermined distance from the inner shaft member in the length direction, a position at a predetermined distance from the outer cylinder member in the length direction, the center in the length direction, etc.), the average value of the cross-sectional area in the length direction, etc. can also be adopted.

[0046] The inner shaft member is not limited to the octagonal cross-sectional shape as shown in the first embodiment. For example, various shapes such as circular shapes including elliptical and oval shapes, various polygons such as quadrilaterals, and irregular shapes can be adopted.

[0047] The four rubber legs may, for example, all have mutually different leg cross-sectional shapes, or all have mutually different lengths.

Explanation of Signs

[0048] 10 Cylindrical vibration isolator for motor mount (first embodiment) 12 Inner shaft member 14 Outer cylinder member 16 Main body rubber elastic body 18 Bolt insertion hole 20 Upper surface 22 Lower surface 24 Left surface 26 Right surface 28 Upper left inclined surface 30 Upper right inclined surface 32 Lower left inclined surface 34 Lower right inclined surface 36 Inner peripheral fixing portion 38 Outer peripheral fixing portion 40 Rubber leg 40a Rubber leg 40b Rubber leg 40c Rubber leg 40d Rubber leg 42 Drilled hole Ta Axial thickness dimension of rubber leg 40a Wa Circumferential width dimension of rubber leg 40a La Length dimension of rubber leg 40a Axial thickness dimension of the rubber leg 40b of Tb Circumferential width dimension of the rubber leg 40b of Wb Length dimension of the rubber leg 40b of Lb Axial thickness dimension of the rubber leg 40c of Tc Circumferential width dimension of the rubber leg 40c of Wc Length dimension of the rubber leg 40c of Lc Axial thickness dimension of the rubber leg 40d of Td Circumferential width dimension of the rubber leg 40d of Wd Length dimension of the rubber leg 40d of Ld

Claims

1. A cylindrical vibration isolator for a motor mount in which an inner shaft member and an outer cylinder member are connected by a plurality of rubber legs extending between radially opposed surfaces of the inner shaft member and the outer cylinder member, wherein the plurality of rubber legs each have four rubber legs that expand circumferentially with respect to each other toward the outer periphery in the vertical direction and the horizontal direction, and the difference in cross-sectional area in a leg cross-section orthogonal to the length direction, which is the connection direction between the inner shaft member and the outer cylinder member, of these four rubber legs is 20% or less, and the four rubber legs have different shapes from each other, and a cylindrical vibration isolator for a motor mount in which resonance states with respect to vertical vibration input are different from each other.

2. The upper two rubber legs have the same length dimension in the connection direction between the inner shaft member and the outer cylinder member, the lower two rubber legs have the same length dimension in the connection direction between the inner shaft member and the outer cylinder member, and the upper two rubber legs and the lower two rubber legs have different length dimensions in the connection direction between the inner shaft member and the outer cylinder member. The cylindrical vibration isolator for a motor mount according to Claim 1.

3. The upper two rubber legs include a first cross-sectional area common portion having the same cross-sectional area as each other in a leg cross-section orthogonal to the length direction, which is the connection direction between the inner shaft member and the outer cylinder member, and the lower two rubber legs include a second cross-sectional area common portion having the same cross-sectional area as each other in a leg cross-section. The cylindrical vibration isolator for a motor mount according to Claim 1 or 2.

4. The rubber leg located at the upper left and the rubber leg located at the lower right have the same shape as each other in a leg cross-section, the rubber leg located at the upper right and the rubber leg located at the lower left have the same shape as each other in a leg cross-section, and the rubber legs located at the upper left and the lower right and the rubber legs located at the upper right and the lower left have different shapes from each other in a leg cross-section. The cylindrical vibration isolator for a motor mount according to Claim 1 or 2.

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