Cylindrical vibration isolation device for motor mount

Abstract

To provide a cylindrical vibration isolation device for motor mount of a new structure, by which performance demanded of a motor mount can be realized at a high level.SOLUTION: A cylindrical vibration isolation device comprises: a first molded article 12 in which an inner shaft member 16 is inserted into an intermediate sleeve 18, the inner shaft member 16 and the intermediate sleeve 18 being elastically connected in a radial direction by an inner circumferential rubber elastic body 20; and a second molded article 14 in which an outer circumferential rubber elastic body 36 is bonded to an inner circumferential surface of an outer cylindrical member 34. The intermediate sleeve 18 of the first molded article 12 is fitted to the inner circumference of the outer circumferential rubber elastic body 36 of the second molded article 14, such that the first molded article 12 and the second molded article 14 are assembled in a non-adhered state.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a cylindrical vibration isolation device for a motor mount used to support an electric motor in an electrically powered vehicle, for example, by isolating vibrations. [Background technology]

[0002] Conventionally, as one type of vibration-damping device used in vehicles, a cylindrical vibration-damping device such as the cylindrical rubber bushing disclosed in Japanese Patent Laid-Open Publication No. 58-097508 (Patent Document 1) has been known. The cylindrical vibration-damping device has a structure in which an inner shaft fitting and an outer cylindrical member are elastically connected by a main rubber elastic body. Patent Document 1 also discloses a structure in which an intermediate sleeve is disposed between the inner shaft member and the outer cylindrical member, and the inner shaft member and the intermediate sleeve are connected by an inner peripheral rubber elastic body, and the intermediate sleeve and the outer cylindrical member are connected by an outer peripheral rubber elastic body. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 58-097508 Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, in recent years, automobiles have become increasingly electric, and in electric vehicles, cylindrical vibration isolation devices are sometimes used as motor mounts for connecting electric motors to the vehicle body in a vibration-damping manner.

[0005] However, the performance required of a cylindrical vibration-damping device for a motor mount is different from the performance required of a conventional cylindrical vibration-damping device such as that described in Patent Document 1, and so if an attempt was made to use a conventional cylindrical vibration-damping device for a motor mount, there was a risk that it would not be able to fully meet the required vibration-damping characteristics, durability, etc.

[0006] An object of the present invention is to provide a cylindrical vibration isolator for a motor mount having a novel structure that is capable of achieving the high level of performance required of a motor mount. [Means for solving the problem]

[0007] The following describes preferred embodiments for understanding the present invention, but the embodiments described below are merely examples and may be appropriately combined with one another. Multiple components described in each embodiment may be recognized and employed independently to the greatest extent possible, and may also be appropriately combined with any of the components described in other embodiments. Accordingly, the present invention is not limited to the embodiments described below, and various other embodiments may be realized.

[0008] The first aspect is a cylindrical vibration-damping device for a motor mount, comprising a first molded product in which an inner shaft member is inserted into an intermediate sleeve, and the inner shaft member and intermediate sleeve are elastically connected in the radial direction by an inner rubber elastic body, and a second molded product in which an outer rubber elastic body is fixed to the inner surface of an outer cylindrical member, and the intermediate sleeve of the first molded product is fitted into the inner circumference of the outer rubber elastic body of the second molded product, thereby combining the first molded product and the second molded product without adhesive.

[0009] In a cylindrical vibration-damping device for a motor mount constructed according to this aspect, a mass-spring system (secondary vibration system) is formed between the inner shaft member and the outer cylindrical member, with the intermediate sleeve of the first molded product as the mass and the inner rubber elastic body of the first molded product and the outer rubber elastic body of the second molded product as springs, and the transmissibility of vibrations at frequencies higher than the resonance frequency of the mass-spring system is reduced. Therefore, high-frequency, small-amplitude vibrations that are particularly problematic in motor mounts are less likely to be transmitted between the inner shaft member and the outer cylindrical member, achieving excellent vibration-damping performance as a motor mount.

[0010] Because the first molded product and the second molded product are combined without bonding, it is easy to set the spring characteristics of the inner rubber elastic body in the first molded product and the outer rubber elastic body in the second molded product separately, providing a high degree of freedom in tuning the resonant frequency of the mass-spring system. In particular, because the spring characteristics of the inner rubber elastic body and the outer rubber elastic body are highly flexible, the resonant frequency of the mass-spring system can be tuned to a sufficiently low frequency even if the mass of the intermediate sleeve is relatively small. As a result, the vibration-damping effect exerted against vibrations higher than the resonant frequency of the mass-spring system can be obtained over a wider frequency range.

[0011] Furthermore, compared to when the outer circumferential rubber elastic body is bonded to the outer circumferential surface of the intermediate sleeve, there is no need to press the outer circumferential rubber elastic body firmly against the outer circumferential surface of the intermediate sleeve, making it easier to achieve low spring characteristics for the outer circumferential rubber elastic body. Moreover, because the protruding tip surface of the outer circumferential rubber elastic body is not fixed to the outer circumferential surface of the intermediate sleeve, for example, when the outer tubular member is reduced in diameter to pre-compress the outer circumferential rubber elastic body in the radial direction, pre-compression can be applied to an extent that prevents the first molded product from slipping out of the outer circumferential rubber elastic body, while preventing the spring of the outer circumferential rubber elastic body from becoming excessively hard.

[0012] In a second aspect, in the cylindrical vibration-damping device for a motor mount described in the first aspect, the outer rubber elastic body has a tapered cross-sectional shape in which the axial length dimension decreases toward the inner circumference.

[0013] In a cylindrical vibration-damping device for a motor mount constructed in accordance with this embodiment, the outer rubber elastic body has a cross-sectional shape that tapers toward the intermediate sleeve. Therefore, for example, when the intermediate sleeve is fitted onto the inner periphery of the outer rubber elastic body and the outer rubber elastic body is compressed radially, even if a relatively large compression allowance is set for the outer rubber elastic body, the spring of the outer rubber elastic body can be prevented from becoming excessively hard.

[0014] Furthermore, because the outer circumferential rubber elastic body is not bonded to the intermediate sleeve, there is no need to press the outer circumferential rubber elastic body against the intermediate sleeve as would be the case if the outer circumferential rubber elastic body and the intermediate sleeve were bonded. Therefore, even if the outer circumferential rubber elastic body has a tapered cross-sectional shape and its spring characteristics are softened, an effective holding force for assembling the first molded product and the second molded product can be obtained.

[0015] The third aspect is a cylindrical vibration-damping device for a motor mount described in the first or second aspect, wherein the axial length dimension at the inner end of the outer rubber elastic body is within the range of 30 to 200% of the protruding height dimension from the outer cylindrical member toward the inner circumference of the outer rubber elastic body.

[0016] In a cylindrical vibration-damping device for a motor mount constructed according to this aspect, the axial length of the inner peripheral end of the outer rubber elastic body is 30% or more of the protruding height of the outer rubber elastic body, thereby ensuring a sufficient contact area between the protruding tip surface of the outer rubber elastic body and the outer peripheral surface of the intermediate sleeve, preventing the intermediate sleeve from slipping off the outer rubber elastic body. Furthermore, the axial length of the inner peripheral end of the outer rubber elastic body is 200% or less of the protruding height of the outer rubber elastic body, ensuring a sufficiently large radial rubber thickness of the outer rubber elastic body, making it easier to achieve low spring characteristics of the outer rubber elastic body through its cross-sectional shape.

[0017] A fourth aspect is a cylindrical vibration-damping device for a motor mount described in any one of the first to third aspects, wherein the outer rubber elastic body is annular and continuous around the entire circumference.

[0018] With a cylindrical vibration-damping device for a motor mount constructed in accordance with this embodiment, when the intermediate sleeve is fitted and the outer peripheral rubber elastic body is compressed radially, the deformation of the outer peripheral rubber elastic body is restricted in the circumferential direction, thereby effectively retaining the intermediate sleeve in the outer peripheral rubber elastic body and preventing the intermediate sleeve from slipping out of the outer peripheral rubber elastic body.

[0019] A fifth aspect is a cylindrical vibration-damping device for a motor mount described in any one of the first to fourth aspects, wherein the outer rubber elastic body is partially provided in the circumferential direction with a spring reduction portion that reduces radial spring.

[0020] In a cylindrical vibration-damping device for a motor mount constructed according to this aspect, the spring-reducing portion is provided on the outer circumferential rubber elastic body, thereby reducing the springiness of the outer circumferential rubber elastic body that constitutes the spring of the secondary vibration system. This makes it easier to tune the resonance frequency of the secondary vibration system, which has the intermediate sleeve as its mass, to a lower frequency, and enables the vibration-damping effect of the secondary vibration system to be effectively obtained from a lower frequency range.

[0021] The spring reducing portion, which reduces the pull-out resistance of the intermediate sleeve, is partially provided in the circumferential direction, so that the pull-out resistance of the intermediate sleeve can be ensured by the portion of the outer rubber elastic body that is circumferentially outside the spring reducing portion.

[0022] A sixth aspect is a cylindrical vibration-damping device for a motor mount described in any one of the first to fifth aspects, wherein the inner rubber elastic body has a plurality of recessed holes that penetrate in the axial direction.

[0023] In a cylindrical vibration-damping device for a motor mount constructed according to this aspect, the formation of a recessed hole in the inner rubber elastic body reduces the springiness of the inner rubber elastic body. Moreover, by providing a recessed hole in the inner rubber elastic body, it is possible to tune the spring characteristics while ensuring the function of retaining the intermediate sleeve of the outer rubber elastic body. [Effects of the Invention]

[0024] According to the present invention, it is possible to achieve high performance required for a cylindrical vibration isolator for a motor mount. [Brief explanation of the drawings]

[0025] [Figure 1]FIG. 1 is a perspective view showing a cylindrical vibration isolation device for a motor mount according to a first embodiment of the present invention; [Figure 2] A front view of the cylindrical vibration isolation device for the motor mount shown in Figure 1. [Figure 3] III-III cross section of Figure 2 [Figure 4] IV-IV cross section of Figure 2 [Figure 5] VV cross section of Figure 2 [Figure 6] FIG. 2 is an exploded perspective view of the cylindrical vibration isolation device for the motor mount shown in FIG. 1. [Figure 7] FIG. 2 is a front view of a first molded product constituting the cylindrical vibration-damping device for a motor mount shown in FIG. [Figure 8] FIG. 2 is a front view of a second molded product constituting the cylindrical vibration-damping device for a motor mount shown in FIG. [Figure 9] Graph showing the vibration isolation characteristics of the cylindrical vibration isolation device for motor mounts in Figure 1 [Figure 10] FIG. 10 is a perspective view showing a cylindrical vibration isolation device for a motor mount according to a second embodiment of the present invention; [Figure 11] FIG. 11 is a front view of the cylindrical vibration isolation device for the motor mount shown in FIG. 10. [Figure 12] XII-XII cross section of Figure 11 [Figure 13] FIG. 11 is a perspective view of a second molded product constituting the cylindrical vibration-damping device for a motor mount shown in FIG. 10 . [Figure 14] 14 is a front view of the second molded product shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0026] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0027] 1 to 5 show a cylindrical vibration-damping device 10 for a motor mount (hereinafter referred to as cylindrical vibration-damping device 10) as a first embodiment of the present invention. Cylindrical vibration-damping device 10 is composed of a first molded product 12 and a second molded product 14. In the following description, as a general rule, the up-down direction refers to the up-down direction in FIG. 2, the left-right direction refers to the left-right direction in FIG. 2, and the front-rear direction refers to the left-right direction in FIG. 3.

[0028] As shown in Figures 6 and 7, the first molded product 12 has a structure in which an inner shaft member 16 is inserted into an intermediate sleeve 18, and the inner shaft member 16 and the intermediate sleeve 18 are elastically connected to each other by an inner rubber elastic body 20.

[0029] The inner shaft member 16 has a thick-walled, small-diameter, generally cylindrical shape and is provided with a bolt hole 22 that penetrates through in the axial direction. The inner shaft member 16 is made of, for example, metal or fiber-reinforced synthetic resin, and is a highly rigid member.

[0030] The intermediate sleeve 18 has a thin-walled, large-diameter, generally cylindrical shape, with an inner diameter dimension larger than the outer diameter dimension of the inner shaft member 16. The intermediate sleeve 18 is formed, for example, from metal or fiber-reinforced synthetic resin, etc., and is a highly rigid member. More preferably, the intermediate sleeve 18 is made of metal such as iron or aluminum alloy, which facilitates diameter reduction processing such as eight-way drawing. The axial end of the intermediate sleeve 18 has a tapered shape where the outer peripheral surface has a smaller diameter toward the axial outward, and the outer diameter dimension decreases toward the axial outward.

[0031] The inner circumferential rubber elastic body 20 has a generally cylindrical shape overall, and its inner circumferential surface is vulcanization bonded to the outer circumferential surface of the inner shaft member 16, and its outer circumferential surface is vulcanization bonded to the inner circumferential surface of the intermediate sleeve 18. The inner circumferential rubber elastic body 20 is formed as an integrally vulcanization molded product comprising the inner shaft member 16 and the intermediate sleeve 18. The inner circumferential end of the inner circumferential rubber elastic body 20 forms a generally cylindrical inner circumferential fixing portion 24 that is fixed to the inner shaft member 16, and its outer circumferential end forms a thin-walled, generally cylindrical outer circumferential fixing portion 26 that is fixed to the outer tubular member 34.

[0032] Four recessed holes 28, 28, 28, 28 are formed in the inner rubber elastic body 20. The recessed holes 28 penetrate in the axial direction, i.e., the front-rear direction. The four recessed holes 28, 28, 28, 28 are provided on both the up-down and left-right sides of the inner shaft member 16. The recessed holes 28 are provided with stopper rubbers 30 that protrude from the intermediate sleeve 18 toward the inner shaft member 16. The stopper rubbers 30 have a tapered shape that narrows circumferentially toward the inner circumferential side, which is the protruding tip side. The stopper rubbers 30 abut against the inner shaft member 16, limiting the amount of relative displacement between the inner shaft member 16 and the intermediate sleeve 18, thereby forming a stopper mechanism that prevents excessive deformation of the inner rubber elastic body 20.

[0033] The inner rubber elastic body 20 is provided with rubber legs 32 extending between adjacent recessed holes 28, 28 in the circumferential direction. Each rubber leg 32 is provided between each of the four recessed holes 28, 28, 28 in the circumferential direction. The inner shaft member 16 and the intermediate sleeve 18 are interconnected by four rubber legs 32a, 32b, 32c, and 32d. The upper left rubber leg 32a extends upward and inclines leftward from the inner shaft member 16 toward the intermediate sleeve 18. The upper right rubber leg 32b extends upward and inclines rightward from the inner shaft member 16 toward the intermediate sleeve 18. The lower right rubber leg 32c extends downward and inclines rightward from the inner shaft member 16 toward the intermediate sleeve 18. The lower left rubber leg 32d extends downward and inclines leftward from the inner shaft member 16 toward the intermediate sleeve 18. 5, the axial dimension of each rubber leg 32 decreases from the inner periphery toward the outer periphery. The inner end of each rubber leg 32 is continuous with the inner periphery fixing portion 24, and the outer periphery end is continuous with the outer periphery fixing portion 26.

[0034] Furthermore, by reducing the diameter of the intermediate sleeve 18 after vulcanization molding of the inner rubber elastic body 20, the tensile stress caused by thermal shrinkage of each rubber leg 32 in the inner rubber elastic body 20 after molding is reduced, thereby improving the durability of the inner rubber elastic body 20 including the rubber legs 32.

[0035] As shown in FIGS. 6 and 8, the second molded product 14 has a structure in which an outer peripheral rubber elastic body 36 is fixed to the inner peripheral surface of an outer cylindrical member 34.

[0036] The outer cylindrical member 34 has a thin-walled, large-diameter, and generally cylindrical shape. The inner diameter of the outer cylindrical member 34 is larger than the outer diameter of the intermediate sleeve 18. The outer cylindrical member 34 is a highly rigid member formed of metal, fiber-reinforced synthetic resin, or the like. More preferably, the outer cylindrical member 34 is made of metal such as iron or aluminum alloy. The axial length of the outer cylindrical member 34 is smaller than the axial length of the inner shaft member 16 and larger than the axial length of the intermediate sleeve 18.

[0037] The outer rubber elastic body 36 is annular as a whole, and is continuous over the entire circumference with a substantially constant longitudinal cross-sectional shape. The outer peripheral surface of the outer rubber elastic body 36 is vulcanization bonded to the inner peripheral surface of the outer cylindrical member 34. The outer rubber elastic body 36 is formed as an integrally vulcanization molded product with the outer cylindrical member 34. The outer peripheral end of the outer rubber elastic body 36 is a thin-walled, tubular fixed cylindrical portion 38, and the outer peripheral surface of the fixed cylindrical portion 38 is fixed to the inner peripheral surface of the outer cylindrical member 34. The outer rubber elastic body 36 may be formed from the same rubber material as the inner rubber elastic body 20, but it is preferable that the outer rubber elastic body 36 be formed from a different rubber material, which allows the required performance of the inner rubber elastic body 20 and the required performance of the outer rubber elastic body 36 to be respectively achieved to a high degree.

[0038] As shown in Figures 3 to 5, the outer circumferential rubber elastic body 36 has a tapered cross-sectional shape in which the axial length decreases toward the inner periphery from the fixing tubular portion 38. The inner circumferential end face, which is the protruding tip face of the outer circumferential rubber elastic body 36, is a cylindrical fitting surface 40 that extends linearly in the axial direction in a vertical cross section. The axial length L1 of the fitting surface 40 of the outer circumferential rubber elastic body 36 is preferably in the range of 30 to 200%, and more preferably in the range of 40 to 180%, of the radial thickness T, which is the radial protrusion height of the outer circumferential rubber elastic body 36 from the fixing tubular portion 38.

[0039] The axial length dimension L1 of the fitting surface 40 is preferably smaller than the axial minimum length dimension L2 of the inner rubber elastic body 20. The axial length dimension of the fitting surface 40 is preferably ⅔ or less, and more preferably ½ or less, of the axial length dimension of the intermediate sleeve 18. The axial length dimension of the fitting surface 40 is preferably ¼ or more, and more preferably ⅓ or more, of the axial length dimension of the intermediate sleeve 18. The axial maximum length dimension L3 of the outer rubber elastic body 36 excluding the fixing tubular portion 38 is greater than the axial minimum length dimension L1 of the inner rubber elastic body 20 and smaller than the axial maximum length dimension L4 of the inner rubber elastic body 20. Preferably, L3 > L2.

[0040] In the state of the second molded product 14 alone without the first molded product 12 attached, the diameter of the fitting surface 40, which is the inner diameter dimension of the outer peripheral rubber elastic body 36, is desirably made smaller than the outer diameter dimension of the intermediate sleeve 18. The radial thickness dimension T of the outer peripheral rubber elastic body 36 is made smaller than the radial thickness dimension of the inner peripheral rubber elastic body 20.

[0041] The first molded product 12 is inserted into the inner periphery of the second molded product 14. That is, the intermediate sleeve 18 of the first molded product 12 is inserted into the inner periphery of the outer peripheral rubber elastic body 36 of the second molded product 14, and the outer peripheral surface of the intermediate sleeve 18 and the inner peripheral surface of the outer peripheral rubber elastic body 36, which is the mating surface 40, are superposed in a direct abutting state. The mating surface 40 of the outer peripheral rubber elastic body 36 is elastically pressed against the outer peripheral surface of the intermediate sleeve 18, and is positioned axially relative to the intermediate sleeve 18. As a result, the first molded product 12 is elastically held by the outer peripheral rubber elastic body 36 of the second molded product 14, and the first molded product 12 and the second molded product 14 are combined together without adhesive. The cylindrical vibration damping device 10 is constructed by combining the first molded product 12 and the second molded product 14 together.

[0042] Because the fitting surface 40 of the outer peripheral rubber elastic body 36 has a smaller diameter than the outer peripheral surface of the intermediate sleeve 18, the outer peripheral rubber elastic body 36 is compressed radially when the intermediate sleeve 18 is inserted into the inner periphery of the outer peripheral rubber elastic body 36. As a result, the fitting surface 40 is pressed against the outer peripheral surface of the intermediate sleeve 18, and the intermediate sleeve 18 is elastically supported by the outer peripheral rubber elastic body 36. Furthermore, relative axial displacement of the intermediate sleeve 18 with respect to the fitting surface 40 is limited by frictional resistance acting between the fitting surface 40 and the outer peripheral surface of the intermediate sleeve 18.

[0043] Preferably, with the first molded product 12 inserted into the inner periphery of the second molded product 14, the outer tubular member 34 of the second molded product 14 is subjected to a diameter reduction process, whereby the outer circumferential rubber elastic body 36 is further compressed in the radial direction between the intermediate sleeve 18 and the outer tubular member 34. This more effectively prevents the intermediate sleeve 18 from coming off in the axial direction. Because the mating surface 40 of the outer circumferential rubber elastic body 36 and the outer circumferential surface of the intermediate sleeve 18 are not bonded, the mating surface 40 is not excessively constrained by the intermediate sleeve 18, and the mating surface 40 of the outer circumferential rubber elastic body 36 is allowed to slide against the outer circumferential surface of the intermediate sleeve 18 when the outer tubular member 34 is reduced in diameter, it is possible to prevent the outer circumferential rubber elastic body 36 from becoming excessively stiff when the outer tubular member 34 is reduced in diameter. Furthermore, since the outer rubber elastic body 36 is not bonded to the intermediate sleeve 18, it is possible to easily and effectively apply effective radial pre-compression to both the inner rubber elastic body 20 of the first molded product 12 and the outer rubber elastic body 36 of the second molded product 14, thereby improving durability, etc.

[0044] Because the fitting surface 40 of the outer circumferential rubber elastic body 36 is not bonded to the outer circumferential surface of the intermediate sleeve 18, it is possible to set a relatively small pressing force against the outer circumferential surface of the intermediate sleeve 18. Therefore, excessive compression of the outer circumferential rubber elastic body 36 is not necessary, and excessive constraint of the outer circumferential rubber elastic body 36 is also not necessary, allowing the soft spring characteristics of the outer circumferential rubber elastic body 36 to be maintained.

[0045] Because the outer rubber elastic body 36 has a longitudinal cross-sectional shape that tapers toward the inner circumference, the contact area between the fitting surface 40, which is the inner peripheral end surface of the outer rubber elastic body 36, and the outer peripheral surface of the intermediate sleeve 18 is relatively small, preventing the spring of the outer rubber elastic body 36 from becoming hard due to constraint by the intermediate sleeve 18 at the fitting surface 40. Furthermore, the tapered cross-sectional shape of the outer rubber elastic body 36 reduces the springiness of the outer rubber elastic body 36. In this embodiment, the axial length dimension L1 of the fitting surface 40, which is the protruding tip surface of the outer rubber elastic body 36, is smaller than the minimum axial length dimension L2 of the inner rubber elastic body 20, thereby achieving low spring characteristics of the outer rubber elastic body 36. In this embodiment, the axial length dimension L1 of the fitting surface 40 of the outer rubber elastic body 36 is set to 2 / 3 or less, and more preferably 1 / 2 or less, of the maximum axial length dimension L3 of the outer rubber elastic body 36, which is advantageous for further reducing the springiness. In addition, by making the axial length dimension L1 of the mating surface 40 at least 1 / 3 of the maximum axial length dimension L3 of the outer rubber elastic body 36, it is also advantageous in ensuring axial removal efficiency.

[0046] In particular, the axial length dimension L1 of the mating surface 40 of the outer circumferential rubber elastic body 36 is set to 200% or less of the radial thickness dimension T of the outer circumferential rubber elastic body 36, and since the radial thickness dimension T of the outer circumferential rubber elastic body 36 is sufficiently large, it is relatively easy to achieve low spring characteristics for the outer circumferential rubber elastic body 36. Furthermore, the axial length dimension L1 of the mating surface 40, which is the protruding tip surface of the outer circumferential rubber elastic body 36, is set to 30% or more of the radial thickness dimension T of the outer circumferential rubber elastic body 36, which prevents the outer circumferential rubber elastic body 36 from becoming excessively soft, and effectively achieves elastic support of the intermediate sleeve 18 by the outer circumferential rubber elastic body 36.

[0047] The outer peripheral rubber elastic body 36 of this embodiment is annular and has a substantially constant cross-sectional shape all around, and the fitting surface 40 that abuts against the outer peripheral surface of the intermediate sleeve 18 is a cylindrical surface that is continuous all around. Therefore, compared to when an outer peripheral rubber elastic body that is provided partially in the circumferential direction is used, the pull-out resistance acting on the intermediate sleeve 18 is greater, and the assembled state of the first molded product 12 and the second molded product 14 is maintained stably.

[0048] The inner circumferential rubber elastic body 20, which is vulcanization-bonded to both the inner shaft member 16 and the intermediate sleeve 18, does not need to hold other members by elasticity, so the portion connecting the inner shank 16 and the intermediate sleeve 18 is made into four rubber legs 32a, 32b, 32c, 32d that are spaced apart in the circumferential direction by recessed holes 28, thereby adjusting the spring characteristics. This allows the spring characteristics of the inner circumferential rubber elastic body 20 to be tuned while effectively realizing elastic support for the intermediate sleeve 18 by the annular outer circumferential rubber elastic body 36.

[0049] The cylindrical vibration isolator 10 for motor mounting has an inner shaft member 16 attached to the electric motor (not shown) and an outer cylindrical member 34 attached to the vehicle body (not shown), thereby connecting the electric motor and the vehicle body in a vibration-damping manner. When such a cylindrical vibration isolator 10 is mounted on a vehicle, if vibration in the vertical direction, for example, is input between the inner shaft member 16 and the outer cylindrical member 34, the vibration-damping action based on internal friction between the inner rubber elastic body 20 and the outer rubber elastic body 36 interposed between the inner shaft member 16 and the outer cylindrical member 34 can provide a vibration-damping effect that reduces vibration transmission between the inner shaft member 16 and the outer cylindrical member 34.

[0050] Additionally, a mass-spring system (secondary vibration system) is configured on the vibration transmission path from the inner shaft member 16 to the outer cylindrical member 34, with the intermediate sleeve 18 as the mass and the inner circumferential rubber elastic body 20 and the outer circumferential rubber elastic body 36 as springs. The resonant frequency of this mass-spring system is tuned to a lower frequency than the frequency of the vibration to be damped; for example, when vibration damping performance for vibrations of approximately 800 to 1500 Hz is required, it is tuned to approximately 500 Hz. As a result, when vibration to be damped that is higher in frequency than the resonant frequency of the mass-spring system is input, the vibration transmissibility from the inner shaft member 16 to the outer cylindrical member 34 decreases, and excellent vibration damping performance is demonstrated. In this embodiment, the entire cylindrical vibration-damping device 10 is approximately symmetrical on both axial sides, and the main elastic axes of the inner rubber elastic body 20 and the outer rubber elastic body 36 extend in the axis-perpendicular direction in common at the axial center.In addition, the inner surface of the outer rubber elastic body 36, which is superimposed on the intermediate sleeve 18, is not bonded and has a sufficiently small axial length, which suppresses the transmission of vibrations and displacements in the twisting and torsional directions, allowing the damping action of the secondary vibration system against vibrations in the axis-perpendicular direction to be more effectively exerted.

[0051] 9, it is clear that by utilizing the vibration-damping action of the secondary vibration system formed by the intermediate sleeve 18, inner rubber elastic body 20, and outer rubber elastic body 36, higher vibration-damping performance can be achieved than in a conventional cylindrical vibration-damping device formed only of a portion corresponding to the first molded product 12. In FIG. 9, the solid line shows the frequency characteristic of the spring constant in the cylindrical vibration-damping device 10 according to this embodiment, and the dashed line shows the frequency characteristic of the spring constant in a cylindrical vibration-damping device of the conventional structure. FIG. 9 shows that the cylindrical vibration-damping device 10 exhibits vibration-damping performance due to the vibration isolation action of the secondary vibration system in a frequency range higher than the resonant frequency f of the secondary vibration system, and exhibits vibration-damping performance due to the vibration isolation action that is superior to that of a cylindrical vibration-damping device of the conventional structure in a frequency range higher than frequency f'.

[0052] In the above mass-spring system, because the mass is formed by the intermediate sleeve 18, it is difficult to set the mass large, and therefore difficult to set the resonant frequency low. Therefore, in the cylindrical vibration damping device 10, the outer peripheral rubber elastic body 36 is not bonded to the intermediate sleeve 18, thereby reducing the springiness of the outer peripheral rubber elastic body 36. This makes it possible to tune the resonant frequency of the mass-spring system to a lower frequency without increasing the mass of the intermediate sleeve 18, and it is possible to set the vibration damping region higher than the resonant frequency over a wider frequency range.

[0053] In this embodiment, the outer peripheral rubber elastic body 36 has a tapered cross-sectional shape in which the axial length dimension decreases toward the inner circumference, and the axial length dimension L1 of the mating surface 40 of the outer peripheral rubber elastic body 36 is set to 200% or less of the radial protruding height dimension T of the outer peripheral rubber elastic body 36. This also reduces the spring constant of the outer peripheral rubber elastic body 36, making it easier to set the resonance frequency of the mass-spring system to a lower frequency.

[0054] Furthermore, the inner circumferential rubber elastic body 20 has four recessed holes 28, 28, 28, 28 formed therein, thereby reducing the spring force of the mass-spring system that includes the inner circumferential rubber elastic body 20, and it is possible to tune the resonant frequency of the mass-spring system to a lower frequency.

[0055] Furthermore, if the inner circumferential rubber elastic body 20 and the outer circumferential rubber elastic body 36 are formed from different rubber materials, it becomes easy to set different performances for each, for example, by realizing low spring characteristics with the inner circumferential rubber elastic body 20 while ensuring the retention force (pull-out resistance) of the first molded article 12 with the outer circumferential rubber elastic body 36. In particular, since the inner circumferential rubber elastic body 20 and the outer circumferential rubber elastic body 36 are independent and separate pieces of rubber, they can be easily formed from different rubber materials, making it easier to set differences in the properties of the inner circumferential rubber elastic body 20 and the outer circumferential rubber elastic body 36.

[0056] 10 to 12 show a cylindrical vibration damping device 50 for a motor mount as a second embodiment of the present invention. The cylindrical vibration damping device 50 is composed of a first molded product 12 and a second molded product 52. In the following explanation, components and parts that are substantially the same as those in the first embodiment are given the same reference numerals in the figures, and explanations thereof will be omitted.

[0057] As shown in Figures 13 and 14, the second molded product 52 has a structure in which an outer rubber elastic body 54 is vulcanization-bonded to the inner circumferential surface of the outer tubular member 34. A recessed portion 56 is formed in the outer rubber elastic body 54 as a spring reducing portion. The recessed portion 56 is a groove-shaped portion that opens onto the inner circumferential surface of the outer rubber elastic body 54 and extends in the axial direction with a substantially constant cross section, and penetrates the outer rubber elastic body 54 in the axial direction to open onto both axial surfaces of the outer rubber elastic body 54. The recessed portion 56 has a groove cross-sectional shape that widens circumferentially toward the inner periphery. It is desirable to provide a plurality of recessed portions 56 at equal intervals in the circumferential direction, and in this embodiment, four recessed portions 56 are provided at equal intervals in the circumferential direction.

[0058] The four recesses 56 are spaced apart from one another in the circumferential direction, and a circumferentially curved mating surface 58 is provided between adjacent recesses 56. In this embodiment, four mating surfaces 58 are provided, and these mating surfaces 58 are arc-shaped curved surfaces that form a cylindrical surface corresponding to the outer circumferential surface of the intermediate sleeve 18. The outer circumferential rubber elastic body 54 has a reduced radial protrusion height at the portion where the recesses 56 are formed, and a increased radial protrusion height at the portion where the mating surfaces 58 are formed circumferentially away from the recesses 56. In short, the outer circumferential rubber elastic body 54 in this embodiment is continuous around the entire circumference, and the formation of the recesses 56 causes the radial protrusion height to vary circumferentially. As can be seen from Figure 12, the axial length dimension at the inner peripheral end (fitting surface 58) of the outer peripheral rubber elastic body 54 is preferably within the range of 30 to 70% of the protruding height dimension of the outer peripheral rubber elastic body 54 from the outer tubular member 34, and more preferably within the range of 40 to 60%.

[0059] 10 to 12, the first molded product 12 is inserted and disposed on the inner peripheral side of the second molded product 52. The inner peripheral surface of the outer peripheral rubber elastic body 54 of the second molded product 52 is elastically pressed against the outer peripheral surface of the intermediate sleeve 18 of the first molded product 12, thereby elastically supporting the intermediate sleeve 18 by the outer peripheral rubber elastic body 56. In this embodiment, the outer peripheral rubber elastic body 54 abuts against the outer peripheral surface of the intermediate sleeve 18 at the fitting surface 58, and is separated from the intermediate sleeve 18 at the portion where the recessed portion 56 is formed. Therefore, even if the outer peripheral rubber elastic body 54 is compressed in the radial direction by assembling the first molded product 12 and the second molded product 52, the recessed portion 56 is not completely crushed but remains open.

[0060] In the cylindrical vibration damping device 50 constructed according to this embodiment, the outer circumferential rubber elastic body 54 is provided with recesses 56, and as a result, the radial spring of the outer circumferential rubber elastic body 56 when supporting the intermediate sleeve 18 is lower than that of the outer circumferential rubber elastic body 36 of the first embodiment, which has a uniform cross-sectional shape and is continuous around the entire circumference. This makes it possible to set the resonance frequency of the secondary vibration system formed by the intermediate sleeve 18, inner circumferential rubber elastic body 20, and outer circumferential rubber elastic body 56 lower, and the vibration isolation effect of the secondary vibration system can be effectively obtained over a wider frequency range.

[0061] The spring characteristics of the outer rubber elastic body 54 can be easily tuned with a great degree of freedom by changing the circumferential width, radial depth, axial shape, and number of recesses 56, thereby achieving the required vibration-damping performance to a higher degree.

[0062] The spring reducing portion is not limited to the groove-shaped recess 56 that penetrates in the axial direction shown in this embodiment. For example, in a peripheral rubber elastic body whose maximum radial protrusion height is substantially constant around the entire circumference, the spring reducing portion can be formed by a thin-walled portion with a small axial dimension that is provided partially in the circumferential direction. Furthermore, by two-color molding the peripheral rubber elastic body using a rubber material with a low spring constant in a portion in the circumferential direction, the portion formed by the rubber material with the low spring constant can be used as the spring reducing portion.

[0063] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to those specific descriptions. For example, the inner rubber elastic body 20 may not have any recess holes 28, and may have a continuous annular shape around the entire circumference. Furthermore, when recess holes 28 are formed in the inner rubber elastic body 20, the number of recess holes 28 is not limited to four. For example, three recess holes 28, 28, 28 may be formed in the inner rubber elastic body 20, resulting in a structure having three rubber legs 32, 32, 32.

[0064] From the viewpoint of ease of manufacturing, it is desirable that the outer rubber elastic body 36 be continuous over the entire circumference as shown in the above embodiment, but it may also be provided partially at multiple locations spaced apart in the circumferential direction. In this case, the spring reduction portion is formed by the circumferentially divided portion of the outer rubber elastic body. Furthermore, the outer rubber elastic body 36 is not necessarily limited to a tapered cross-sectional shape in which the axial dimension decreases toward the inner circumference.

[0065] In the state of the second molded product 14 alone, the inner diameter dimension of the outer peripheral rubber elastic body 36 may be larger than the outer diameter dimension of the intermediate sleeve 18. In this case, for example, when the outer cylindrical member 34 is reduced in diameter, the fitting surface 40 of the outer peripheral rubber elastic body 36 is pressed against the outer peripheral surface of the intermediate sleeve 18. [Explanation of symbols]

[0066] 10 Cylindrical vibration isolation device for motor mount (first embodiment) 12 First article 14 Secondary articles 16 Inner shaft member 18 Intermediate sleeve 20 Inner rubber elastic body 22 bolt holes 24 Inner circumference fixing part 26 Periphery fixing part 28 Currant Hole 30 Stopper rubber 32(32a~32d) Rubber feet 34 outer cylindrical member 36 Peripheral rubber elastic body 38 Fixed tube part 40 Mating surface 50 Cylindrical vibration isolation device for motor mount (second embodiment) 52 Secondary molded products 54 Peripheral rubber elastic body 56 Suguri recess (spring reduction part) 58 Mating surface L1 Axial length of the mating surface L2 Minimum axial length of the inner rubber elastic body L3: Maximum axial length of the outer rubber elastic body L4: Maximum axial length of inner rubber elastic body T Radial thickness of the outer rubber elastic body (radial protrusion height of the outer rubber elastic body)

Claims

1. a first molded product in which an inner shaft member is inserted into an intermediate sleeve, and the inner shaft member and the intermediate sleeve are elastically connected in the radial direction by an inner circumferential rubber elastic body; a second molded product in which an outer peripheral rubber elastic body is fixed to the inner peripheral surface of the outer cylindrical member; It is equipped with A cylindrical vibration-damping device for a motor mount in which the first molded product and the second molded product are combined without adhesive by fitting the intermediate sleeve of the first molded product into the inner circumference of the outer rubber elastic body of the second molded product.

2. 2. The cylindrical vibration-damping device for a motor mount according to claim 1, wherein the outer circumferential rubber elastic body has a tapered cross-sectional shape in which the axial length dimension decreases toward the inner periphery.

3. 3. A cylindrical vibration-damping device for a motor mount as described in claim 2, wherein the axial length dimension at the inner peripheral end of the outer rubber elastic body is within the range of 30 to 200% of the protruding height dimension of the outer rubber elastic body from the outer cylindrical member toward the inner circumference.

4. 4. The cylindrical vibration-damping device for a motor mount according to claim 1, wherein the outer peripheral rubber elastic body is formed in a continuous annular shape over the entire circumference.

5. 4. The cylindrical vibration-damping device for a motor mount according to claim 1, wherein the outer circumferential rubber elastic body is partially provided with a spring reducing portion in the circumferential direction to reduce radial spring.

6. 4. The cylindrical vibration-damping device for a motor mount according to claim 1, wherein the inner circumferential rubber elastic body has a plurality of recessed holes passing through in the axial direction.

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