Cylindrical vibration isolation device for motor mount

Abstract

The present invention provides a cylindrical vibration isolation device for a motor mount with a novel structure capable of securing durability and further offering greater freedom in characteristics tuning while reducing deterioration of vibration isolation performance due to surging of a rubber leg.　In a cylindrical vibration isolation device 10 for a motor mount, an inner shaft member 12 and an outer cylinder member 14 are connected by two rubber legs 16, 16 extending between opposed surfaces of the inner shaft member 12 and outer cylinder member 14. The two rubber legs 16, 16 are both disposed on the lower side of the inner shaft member 12, which is the compression side when a main load is input, and extend in an up-down direction at positions separated from each other in a left-right direction. The two rubber legs 16, 16 have connection rubber parts 26, 26 for directly connecting the opposed surfaces of the inner shaft member 12 and outer cylinder member 14 continuously in the up-down direction. The two rubber legs 16, 16 are each provided with a rubber projection 28 projecting in an axial direction. The rubber projection 28 is disposed so as to be within the inside of the connection rubber part 26 in the left-right direction relative to left and right outer edges of the connection rubber part 26.

Description

Cylindrical vibration isolation device for motor mount

[0001] The present invention relates to a cylindrical vibration isolation device for a motor mount used as a motor mount that connects an electric motor to a vehicle body in an electrically powered vehicle such as an electric vehicle (BEV) or a hybrid car in a vibration-damping manner.

[0002] Recently, with the trend toward electric vehicles, development of motor mounts that connect electric motors to vehicle bodies in a vibration-damping manner has been progressing. For example, a cylindrical vibration-damping device in which an inner shaft member and an outer cylindrical member are interconnected by radially extending rubber legs is used as a motor mount. A four-legged structure with two rubber legs on each side of the inner shaft member has been adopted as a cylindrical vibration-damping device for motor mounts. However, a structure with two elastic legs (rubber legs) provided below the inner cylinder (inner shaft member), as disclosed in Japanese Patent Laid-Open Publication No. 2008-267443 (Patent Document 1), has also been considered for application to motor mounts.

[0003] JP 2008-267443 A

[0004] However, motor mounts that provide vibration isolation for electric motors, which vibrate less than internal combustion engines, are prone to problems with deterioration of vibration in the high frequency range due to surging of the rubber legs. Patent Document 1 therefore discloses that mass protrusions are provided that protrude axially from the elastic legs, and that surging of the elastic legs is suppressed by the resonance of the mass protrusions.

[0005] However, in the cylindrical vibration-damping device of Patent Document 1, the surface where the elastic legs are fixed to the inner cylinder and the surface where they are fixed to the outer cylinder (outer cylindrical member) are separated from each other when projected in the vertical direction, which is the main vibration input direction, and the elastic legs undergo shear deformation over a wide range when vibration is input, which could limit the degree of freedom in tuning the spring characteristics of the elastic legs, etc. Furthermore, in addition to the fact that shear deformation becomes dominant and the amount of deformation of the elastic legs tends to increase, strain tends to concentrate around the mass protrusions when the elastic legs deform, and so when trying to ensure durability, the positions where the mass protrusions can be formed are significantly limited, as specified in Patent Document 1.

[0006] The problem to be solved by the present invention is to provide a cylindrical vibration isolation device for motor mounts with a novel structure that ensures durability while suppressing a decrease in vibration isolation performance due to surging of the rubber legs, and also allows for greater freedom in tuning characteristics.

[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 in which an inner shaft member and an outer cylindrical member are connected by two rubber legs extending between the opposing surfaces of the inner shaft member and the outer cylindrical member, and the two rubber legs are both positioned below the inner shaft member, which is the compression side when the main load is input, and extend in the vertical direction at positions spaced apart from each other in the left-right direction, and the two rubber legs are continuous in the vertical direction and have connecting rubber parts that directly connect the opposing surfaces of the inner shaft member and the outer cylindrical member, and the two rubber legs are each provided with rubber protrusions that protrude in the axial direction, and the rubber protrusions are arranged in a state where they are located further inward on the left and right than the left and right outer ends of the connecting rubber parts.

[0009] In a cylindrical vibration-damping device for a motor mount constructed according to this aspect, the two rubber legs are located only on the underside of the inner shaft member, which makes it easier to ensure the free length and volume of the two rubber legs compared to when rubber legs are located on both the top and bottom of the inner shaft member, thereby improving durability, for example. Furthermore, the two rubber legs are provided with connecting rubber sections that are continuous in the vertical direction and directly connect the opposing surfaces of the inner shaft member and the outer cylindrical member, which advantageously ensures a compression spring component when the main load is input, allowing for greater tuning freedom in the spring characteristics and further improving durability by suppressing the deformation of the connecting rubber sections.

[0010] By providing rubber protrusions on each rubber leg, the mass damping action of the rubber protrusions can prevent deterioration of vibration conditions due to bending resonance (surging) of the rubber legs. Because the rubber protrusions each protrude in the axial direction, for example, when the rubber legs deform due to vibration input, the rubber protrusions are less likely to interfere with other members such as the outer cylindrical member.

[0011] Furthermore, the rubber protrusions are arranged inwardly of the left and right outer ends of the connecting rubber parts, which are compression regions of the rubber legs arranged below the inner shaft member (regions on which a compressive load is directly or predominantly exerted when a vertical load is applied by directly connecting the opposing vertical surfaces of the inner shaft member and the outer cylindrical member), so that strain around the rubber protrusions is reduced when the rubber legs are elastically deformed by vibration input, improving durability, compared to when the rubber protrusions are arranged in shear deformation regions on the left and right outer sides of the outer left and right ends of the connecting rubber parts (regions on which shear deformation is large when a vertical load is applied by not directly connecting the opposing vertical surfaces of the inner shaft member and the outer cylindrical member).

[0012] The second aspect is a cylindrical vibration isolation device for a motor mount described in the first aspect, in which 90% or more of the rubber protrusions are arranged on the connecting rubber portion, so that the rubber protrusions are essentially located only on the connecting rubber portion.

[0013] With a cylindrical vibration-damping device for a motor mount constructed in accordance with this embodiment, the rubber protrusions are essentially provided only on the connecting rubber portion, which is the compression area of ​​the rubber leg, so that distortion around the rubber protrusions is more effectively reduced when the rubber leg deforms.

[0014] In a third aspect, in a cylindrical vibration-damping device for a motor mount described in the first or second aspect, the inner shaft member has a pair of rubber fixing portions protruding on both the left and right sides, the two rubber legs are fixed to the pair of rubber fixing portions, and a stopper protrusion is provided between the pair of rubber fixing portions on the inner shaft member, protruding downward between the two rubber legs.

[0015] According to the cylindrical vibration-damping device for motor mounts constructed in accordance with this embodiment, the inner shaft member has a pair of rubber fixing portions that protrude on both the left and right sides, making it easier to position the two rubber legs below the inner shaft member and ensuring the cross-sectional area of ​​the connecting rubber portion to obtain a large compression spring component.

[0016] Furthermore, by fastening one of the two rubber legs to a pair of rubber fastening portions that protrude on both the left and right sides, a space is secured between the two rubber legs, and a stopper protrusion that protrudes downward is provided on the inner shaft member to utilize this space. This allows for the construction of a stopper mechanism that limits the amount of relative displacement between the inner shaft member and the outer cylindrical member in the up-down direction by the abutment of the stopper protrusion against the outer cylindrical member.

[0017] The fourth aspect is a cylindrical vibration-damping device for a motor mount described in any one of the first to third aspects, in which a stopper rubber is provided between the two rubber legs and protrudes in the vertical direction between the inner shaft member and the outer cylindrical member.

[0018] According to a cylindrical vibration-damping device for a motor mount constructed in accordance with this embodiment, a stopper mechanism can be provided by utilizing the space between the two rubber legs, which limits the amount of downward relative displacement of the inner shaft member with respect to the outer cylindrical member by indirect abutment between the inner shaft member and the outer cylindrical member via the stopper rubber.

[0019] In a fifth aspect, in a cylindrical vibration-damping device for a motor mount described in any one of the first to fourth aspects, the width dimension of the connecting rubber portion is set to 20% or more of the width dimension of the rubber foot, so that the compression spring component of the rubber foot against a downward input is made larger than the shear spring component.

[0020] With a cylindrical vibration-damping device for a motor mount constructed in accordance with this embodiment, the compression spring component is dominant in the rubber leg on which the rubber protrusion is provided, and therefore distortion around the rubber protrusion is reduced compared to when the rubber protrusion is provided on the rubber leg on which the shear spring component is dominant.

[0021] Furthermore, by setting the width dimension of the connecting rubber portion at a sufficiently large ratio to the width dimension of the rubber leg, the arrangement of the rubber protrusions on the axial end faces of the rubber legs can be set with a large degree of freedom.

[0022] According to the present invention, in a cylindrical vibration isolation device for a motor mount, it is possible to ensure durability while suppressing a decrease in vibration isolation performance due to surging of the rubber legs, and further to obtain a great degree of freedom in tuning the characteristics.

[0023] 1 is a perspective view showing a motor mount according to a first embodiment of the present invention; FIG. 2 is a cross-sectional view taken along the line III-III in FIG. 1; and FIG. 3 is a graph showing the spring characteristics of the motor mount shown in FIG. 1.

[0024] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0025] 1 and 2 show a motor mount 10 for a vehicle as a first embodiment of a cylindrical vibration-damping device for a motor mount according to the present invention. The motor mount 10 has a structure in which an inner axial member 12 and an outer tubular member 14 are interconnected by two rubber legs 16. In the following description, the vertical direction generally refers to the vertical direction in FIG. 2, the left-right direction generally refers to the left-right direction in FIG. 2, and the front-rear direction generally refers to the axial direction in FIG. 2, which is perpendicular to the plane of the page. Note that the vertical direction in the following description refers to the direction in which a main load is input to the motor mount 10 and does not necessarily correspond to the vertical direction of the vehicle when the motor mount 10 is mounted on the vehicle, as described below. Similarly, the left-right direction and front-rear direction in the following description do not necessarily correspond to the left-right direction and front-rear direction of the vehicle.

[0026] The inner shaft member 12 is a highly rigid member made of, for example, a metal such as iron or aluminum alloy, or a fiber-reinforced synthetic resin. The inner shaft member 12 is generally columnar and extends linearly with a substantially uniform cross-sectional shape, allowing it to be easily manufactured by, for example, extrusion. An attachment hole 18 is formed in the center of the inner shaft member 12, penetrating it in the axial direction.

[0027] The inner shaft member 12 of this embodiment has rubber fixing portions 20, 20 protruding to both the left and right sides. The upper surface of each rubber fixing portion 20 widens substantially perpendicular to the vertical direction, and the lower surface slopes upward outward to the left and right, narrowing in the vertical direction toward the protruding tip. The protruding tip surface of each rubber fixing portion 20 has a curved shape when viewed in the axial direction, and is smoothly continuous with both the upper and lower surfaces. The rubber fixing portions 20, 20 on both the left and right sides are shaped in plane symmetry with respect to a plane orthogonal to the left and right. The rubber fixing portion 20 of this embodiment is provided continuously over the entire axial length of the inner shaft member 12, but may, for example, have a shorter axial length than other portions of the inner shaft member 12.

[0028] The inner shaft member 12 is provided with a stopper protrusion 22 that protrudes downward. The stopper protrusion 22 protrudes downward with a substantially constant left-right width dimension in the left-right central portion of the inner shaft member 12. The protruding tip surface of the stopper protrusion 22 may be flat or the like, but in this embodiment, it has a curved shape that is convex downward when viewed in the axial direction. In this embodiment, the stopper protrusion 22 is provided continuously over the entire axial length of the inner shaft member 12, but may also have a shorter axial length than other portions of the inner shaft member 12, for example.

[0029] The outer tubular member 14 has a thin-walled, large-diameter, generally cylindrical shape, and is integrally formed at one axial end thereof with a flange-like portion 24 that protrudes outward. Note that the flange-like portion 24 of the outer tubular member 14 can be omitted, for example, when a stopper mechanism using a front buffer rubber 44 (described later) is not required.

[0030] The inner shaft member 12 is inserted into the inner periphery of the outer cylindrical member 14, and two rubber legs 16, 16 are provided between the inner shaft member 12 and the outer cylindrical member 14. The two rubber legs 16, 16 extend substantially in the vertical direction between the radially opposing surfaces of the inner shaft member 12 and the outer cylindrical member 14, with their upper end faces vulcanization bonded to the lower surfaces of the rubber fastening portions 20, 20 of the inner shaft member 12 and their lower end faces vulcanization bonded to the inner periphery surface of the outer cylindrical member 14. In this embodiment, the rubber legs 16 are vulcanization bonded not only to the lower surface of the rubber fastening portion 20 but also to the left and right side surfaces of the upper part of the stopper protrusion 22.

[0031] The two rubber legs 16, 16 are both positioned below the inner shaft member 12 and are compressed when the inner shaft member 12 is displaced downward relative to the outer cylindrical member 14 due to the input of a main load when mounted on a vehicle, as described below. The two rubber legs 16, 16 are positioned apart from each other in the left-right direction and extend in the up-down direction at positions apart from each other in the left-right direction. A stopper protrusion 22 of the inner shaft member 12 protrudes between the two rubber legs 16, 16. The upper ends of the two rubber legs 16, 16 are positioned above the vertical center of the outer cylindrical member 14, giving them a large free length.

[0032] The rubber legs 16 have a main elastic axis E in the vertical extension direction, indicated by a dashed line in Fig. 2, that slopes downward and outward to the left and right, and the two rubber legs 16, 16 form a V-shape when viewed in the axial direction. In particular, in this embodiment, on both the left and right inner and outer surfaces of each rubber leg 16, the end on the outer cylindrical member 14 side is positioned further outward in the left and right direction from the mount center line extending in the vertical direction than the end on the inner shaft member 12 side. As shown in Figs. 1 and 3, the rubber legs 16 have a smaller axial width than the inner shaft member 12 and outer cylindrical member 14, and are provided in the axial middle of the inner shaft member 12 and outer cylindrical member 14.

[0033] Each rubber leg 16 has a connecting rubber part 26 that directly connects the opposing surfaces of the inner shaft member 12 and the outer cylindrical member 14. The connecting rubber part 26 is located between the opposing surfaces of the rubber fixing part 20 of the inner shaft member 12 and the outer cylindrical member 14 in the vertical direction, and is continuous between the rubber fixing part 20 of the inner shaft member 12 and the outer cylindrical member 14 in the vertical direction.

[0034] The lateral width w1 of the connecting rubber portion 26 is preferably 20% or more, and more preferably 40% or more, of the lateral width W1 of the rubber leg 16. Furthermore, the lateral width w1 of the connecting rubber portion 26 is preferably 25% or more of the lateral width W1' of the intermediate portion of the rubber leg 16. Furthermore, the width w2 of the connecting rubber portion 26 in the direction perpendicular to the principal elastic axis E of the rubber leg 16 is preferably 20% or more, and more preferably 40% or more. By ensuring a sufficiently large proportion of the connecting rubber portion 26 in the rubber leg 16, the compression spring component of the rubber leg 16 is greater than the shear spring component when a main downward load is applied, causing the inner shaft member 12 to displace downward relative to the outer cylindrical member 14. The connecting rubber portion 26 is illustrated in FIG. 2 as surrounded by a two-dot chain line. The left-right width W1 of the rubber leg 16 refers to the left-right width of the portion of the rubber leg 16 outside the fillet surface (fillet radius) at the end of the inner shaft member 12 where the rubber leg 16 is fixed to the outer cylindrical member 14 .

[0035] 1 to 3, a rubber protrusion 28 that protrudes in the axial direction is integrally formed with each rubber leg 16. The rubber protrusion 28 is generally cylindrical in shape and protrudes from the center of the axial end face of the rubber leg 16. The rubber protrusion 28 is disposed on the main elastic axis E that extends in the extension direction of the rubber leg 16.

[0036] The rubber protrusions 28 are positioned on the rubber legs 16 so as to fit laterally inward relative to the left and right outer ends of the connecting rubber portions 26. In other words, the left and right outer ends of the rubber protrusions 28 are positioned at the same left and right positions or further inward relative to the left and right outer ends of the connecting rubber portions 26 without protruding outward relative to the left and right outer ends. It is desirable that 60% or more of the axial projected area of ​​the rubber protrusions 28 be located on the connecting rubber portions 26. More preferably, 90% or more of the axial projected area of ​​the rubber protrusions 28 be located on the connecting rubber portions 26, so that the rubber protrusions 28 are substantially located exclusively on the connecting rubber portions 26. In this embodiment, the rubber protrusions 28 are located between the left and right ends of the connecting rubber portions 26, and the entirety of the rubber protrusions 28 is located on the connecting rubber portions 26. In this embodiment, the left and right width dimension (diameter r) of the rubber protrusions 28 is approximately the same as or slightly smaller than the left and right width dimension w1 of the connecting rubber portions 26. As shown in FIG. 3 , the rubber protrusions 28 are provided to protrude from both axial sides of the rubber legs 16.

[0037] As shown in Figures 1 to 3, the outer peripheral surface of the inner shaft member 12 is covered with an inner rubber layer 30 that is integrally formed with the rubber legs 16, 16. The inner rubber layer 30 has a substantially constant thickness covering the lower surface and both left and right side surfaces of the inner shaft member 12, and the portion covering the upper surface is made of a thick inner buffer rubber 32. However, the inner rubber layer 30 may have a substantially constant thickness overall, or the thickness may vary in multiple locations. The inner rubber layer 30 has a shorter axial length than the inner shaft member 12, and both ends of the inner shaft member 12 protrude axially outward beyond the inner rubber layer 30 and are exposed to the outside.

[0038] The inner peripheral surface of the outer cylindrical member 14 is covered with an outer rubber layer 34 formed integrally with the rubber legs 16, 16. The outer rubber layer 34 has upper cushioning rubbers 36 that protrude toward the inner peripheral surface. The upper cushioning rubbers 36 are provided above and on both the left and right sides of the inner shaft member 12, and are provided continuously in the circumferential direction over more than half the circumference of the upper part of the outer cylindrical member 14. The upper cushioning rubbers 36 are spaced above and on both the left and right sides from the inner shaft member 12, and both circumferential ends of the upper cushioning rubbers 36 are spaced circumferentially from the two rubber legs 16, 16. First recess holes 38 that penetrate in the axial direction are formed between the upper cushioning rubbers 36 and the inner shaft member 12 (inner rubber layer 30) and the two rubber legs 16, 16. When the inner shaft member 12 is displaced significantly upward or to the left or right relative to the outer cylindrical member 14, the inner shaft member 12 and the outer cylindrical member 14 abut against each other via the upper cushioning rubber 36, thereby forming a stopper mechanism that limits the amount of relative displacement of the inner shaft member 12 upward or to the left or right relative to the outer cylindrical member 14.

[0039] The outer rubber layer 34 also includes a lower cushion rubber 40 serving as a stopper rubber. The lower cushion rubber 40 is provided below the stopper protrusion 22 of the inner shaft member 12 and protrudes upward from the outer cylindrical member 14 toward the inner shaft member 12. The lower cushion rubber 40 has a tapered shape that contracts in the front-to-rear and left-to-right directions toward the protruding tip. The lower cushion rubber 40 is located between the two rubber legs 16, 16 on the left and right, and is spaced downward from the stopper protrusion 22 of the inner shaft member 12 by a predetermined stopper clearance. A second recessed hole 42 penetrating in the axial direction is formed between the lower cushion rubber 40 and the inner shaft member 12 (inner rubber layer 30) and the two rubber legs 16, 16. When the inner shaft member 12 is displaced significantly downward relative to the outer tubular member 14, the inner shaft member 12 and the outer tubular member 14 abut against each other via the lower cushioning rubber 40, thereby forming a stopper mechanism that limits the amount of relative displacement of the inner shaft member 12 upward or to the left or right relative to the outer tubular member 14.

[0040] The stopper rubber may be formed integrally with the inner rubber layer 30 so as to protrude downward from the protruding tip end surface of the stopper projection 22 of the inner shaft member 12, in which case it is disposed spaced apart above the inner circumferential surface of the outer tubular member 14 (outer rubber layer 34). In this case, the stopper rubber is preferably tapered downward.

[0041] The outer rubber layer 34 is also provided with a front cushioning rubber 44 that is fixed to the flange-shaped portion 24. The front cushioning rubber 44 is formed continuously around the entire circumference, fixed to the front surface, which is the axial outer surface of the flange-shaped portion 24, and protrudes forward from the flange-shaped portion 24. The inner peripheral end of the front cushioning rubber 44 protrudes more inward than the outer tubular member 14, and is integrally continuous with the outer rubber layer 34 at the inner peripheral end. The outer peripheral end of the front cushioning rubber 44 is located more inward than the outer peripheral end of the flange-shaped portion 24.

[0042] The motor mount 10 configured as described above provides a vibration-damping connection between an electric motor (not shown) and a vehicle body (not shown). Specifically, the motor mount 10 is attached to the electric motor by, for example, inserting bolts or the like through the mounting holes 18 of the inner axial member 12 and press-fitting the outer tubular member 14 into mounting holes (not shown) provided in the vehicle body. Thus, the motor mount 10 is mounted to the vehicle, and the electric motor is supported in a vibration-damping manner relative to the vehicle body via the motor mount 10. The inner axial member 12 may be attached directly to the electric motor or indirectly via a bracket or the like. Similarly, the outer tubular member 14 may be attached directly to the vehicle body or indirectly via a bracket or the like. Alternatively, the inner axial member 12 may be attached to the vehicle body, and the outer tubular member 14 may be attached to the electric motor.

[0043] When the motor mount 10 is installed on a vehicle, vibrations are primarily input between the inner axial member 12 and the outer tubular member 14 in the vertical direction. When this vibration input causes the inner axial member 12 to displace downward relative to the outer tubular member 14, the two rubber legs 16, 16 arranged on the underside of the inner axial member 12 are compressed in the vertical direction, with the compression spring component dominating over the shear spring component. In particular, the connecting rubber portion 26, which is continuously provided in the vertical direction between the opposing vertical surfaces of the inner axial member 12 and the outer tubular member 14, has a smaller shear spring component in response to the input of a vertical compressive load, resulting in a region that is essentially purely compressed. When the inner axial member 12 is displaced downward relative to the outer tubular member 14 due to this primary load input, the two rubber legs 16, 16 function primarily as compression springs, making it easier to achieve higher dynamic spring characteristics and providing greater freedom in adjusting the spring characteristics.

[0044] The motor mount 10 has two rubber legs 16, 16 provided only on the lower side of the inner shaft member 12, and none on the upper side of the inner shaft member 12. This allows for a large degree of freedom in setting the free length of the two rubber legs 16, 16 without increasing the diameter of the outer cylindrical member 14, and also makes it possible to ensure a large rubber volume, thereby realizing a high degree of freedom in setting the spring characteristics of the rubber legs 16, 16 and ensuring durability, etc.

[0045] However, when vibration loads are applied, if bending elastic deformation or the like occurs in the two rubber feet 16, 16 in a resonant state, vibration-damping performance may deteriorate due to the high dynamic spring. To prevent this degradation of vibration-damping performance due to rubber surging, the motor mount 10 is provided with rubber protrusions 28, 28 protruding from both the front and rear of each rubber foot 16. That is, by providing the rubber protrusions 28, 28 on each rubber foot 16, the impact on the spring characteristics of the rubber feet 16, 16 is minimized. As shown in the graph in FIG. 4 , the mass damping action of the rubber protrusions 28 reduces the spring peak due to the resonance of the rubber feet 16, 16, thereby suppressing the degradation of vibration-damping performance due to the high dynamic spring. In particular, electric motors are quieter than engines, and high-frequency vibrations are more likely to be a problem with the motor mount 10 than with engine mounts. Therefore, by suppressing the degradation of vibration-damping performance due to rubber surging of the rubber feet 16, 16 in the high-frequency range of around 1000 Hz, improved quietness and ride comfort can be provided. In the graph shown in Figure 4, the spring characteristics of the motor mount 10 of this embodiment, which is equipped with the rubber protrusions 28, are shown by a solid line, and the spring characteristics of the motor mount which does not have the rubber protrusions 28 are shown by a dashed line.

[0046] Here, the rubber protrusions 28 are arranged so as to fit laterally inward of the left and right outer ends of the connecting rubber parts 26 of the rubber feet 16. As a result, the rubber protrusions 28 are not provided in the shear deformation region on the left and right outer sides of the connecting rubber parts 26 where shear deformation occurs when the main load is input, and the entire rubber protrusions 28 are located in the compressive deformation region of the rubber feet 16. As a result, strain is less likely to concentrate at the base ends of the rubber protrusions 28 due to large shear deformation of the rubber feet 16, preventing a decrease in durability such as cracks at the connection parts between the rubber protrusions 28 and the rubber feet 16.

[0047] It is desirable that 60% or more of the rubber projections 28 be located on the connecting rubber portions 26 when projected in the axial direction. More preferably, 90% or more of the rubber projections 28 be located on the connecting rubber portions 26 when projected in the axial direction, with substantially the entirety being disposed on the connecting rubber portions 26. In this way, by positioning almost the entire rubber projections 28 on the connecting rubber portions 26 where compressive deformation is more dominant, strain at the base ends of the rubber projections 28 is alleviated, further improving the durability of the rubber legs 16 and the rubber projections 28. In particular, in this embodiment, the width dimension of the rubber projections 28 is equal to or less than the width dimension of the connecting rubber portions 26, and the entire rubber projections 28 are contained between the left and right ends of the connecting rubber portions 26, so that strain at the base ends of the rubber projections 28 is more effectively reduced.

[0048] The left-right width dimension w1 of the connecting rubber portion 26 is set to be 20% or more of the left-right width dimension W1 of the rubber foot 16, so that the proportion of the connecting rubber portion 26, which is the compression region of the rubber foot 16, is set to be sufficiently large. This makes it easier to provide the rubber protrusions 28 in the region of the rubber foot 16 where the compression spring component is larger than the shear spring component. In particular, the large left-right width dimension w1 of the connecting rubber portion 26 increases the degree of freedom in the placement of the rubber protrusions 28 located on the left and right inner sides of the left and right outer ends of the connecting rubber portion 26, and also makes it easy to arrange substantially the entire rubber protrusions 28 on the connecting rubber portion 26 by setting the size of the rubber protrusions 28 to be sufficiently large.

[0049] The motor mount 10 is provided with upper and lower cushioning rubbers 36, 40 at portions circumferentially offset from the two rubber legs 16, 16, and has upper, lower, left, and right stopper mechanisms that limit the amount of relative displacement between the inner shaft member 12 and the outer cylindrical member 14. This prevents damage to the rubber legs 16 due to excessive relative displacement between the inner shaft member 12 and the outer cylindrical member 14, without restricting the degree of freedom in the shape and placement of the two rubber legs 16, 16.

[0050] Furthermore, a front cushion rubber 44 is provided on the flange-like portion 24 provided at the axial end of the outer cylindrical member 14, and a rear stopper mechanism is established that limits the amount of relative rearward displacement of the inner shaft member 12 with respect to the outer cylindrical member 14 by abutting the flange-like portion 24 and a member on the electric motor side via the front cushion rubber 44. This also makes it possible to prevent damage to the rubber legs 16 due to excessive relative axial displacement between the inner shaft member 12 and the outer cylindrical member 14.

[0051] Although the embodiments of the present invention have been described in detail above, the present invention is not limited by these specific descriptions. For example, it is sufficient that at least one rubber protrusion 28 is provided on each rubber foot 16. Specifically, for example, the rubber protrusion 28 may be provided so as to protrude from only one axial side of the rubber foot 16. Furthermore, the number and positions of the rubber protrusions 28 on the two rubber feet 16, 16 may be different from each other. However, considering the balance of the two rubber feet 16, 16 including the rubber protrusions 28, it is preferable that the same number of rubber protrusions 28 are provided on the two rubber feet 16, 16 in corresponding positions, as shown in the above embodiment. It is also possible to provide three or more rubber protrusions 28 on one rubber foot 16, in which case two or more rubber protrusions 28 are provided so as to protrude from one axial surface of the rubber foot 16.

[0052] The shape of the rubber protrusions 28 is not limited to a cylindrical shape, and various shapes may be adopted, including, for example, a polygonal pillar shape, a cylindrical shape, a plate shape, etc. Furthermore, the protruding height and outer diameter of the rubber protrusions 28 are not particularly limited.

[0053] Furthermore, the rubber protrusions 28 are not limited to being formed from rubber alone, but may also have a composite structure in which a mass member such as metal is provided on the rubber protrusions 28 and rubber feet 16 for the purpose of, for example, tuning the mass. Furthermore, when tuning the characteristics of the rubber protrusions 28, it is sufficient to achieve suppression of surging of the rubber feet 16, and it is also possible to take into account, for example, a dynamic damper effect in addition to or instead of a mass damper effect, or a tuning effect on the spring characteristics of the rubber feet 16.

[0054] In the above embodiment, the entire rubber protrusion 28 is located on the connecting rubber portion 26, but the rubber protrusion 28 may include, for example, a portion that protrudes laterally inward beyond the inner left and right ends of the connecting rubber portion 26. The amount by which the rubber protrusion 28 protrudes laterally inward beyond the connecting rubber portion 26 is not particularly limited, but it is desirable to set it as follows, for example, in consideration of preventing strain concentration at the base end of the rubber protrusion 28. That is, because the two rubber legs 16, 16 are formed in a V-shape that slopes downward and outward to the left and right, when they are compressed vertically due to the main load input and bulge horizontally, the contact area between the lower end of the rubber leg 16 and the outer tubular member 14 expands horizontally inward, and the inner end of the connecting rubber portion 26 may move horizontally inward. By positioning the rubber protrusions 28 so that their left and right inner ends are located outwardly of the left and right inner end positions of the connecting rubber portions 26 when the rubber legs 16 are compressed, it is possible to effectively prevent strain concentration at the base ends of the rubber protrusions 28, even if the rubber protrusions 28 are located left and right more inwardly of the connecting rubber portions 26 of the rubber legs 16 to which no load is applied. In other words, when the inner shaft member 12 moves downward relative to the outer tubular member 14 due to the input of a main load such as a static shared support load, the pair of connecting rubber portions 26, 26 elastically deform so as to bulge in the left and right direction. Due to this elastic deformation, the left and right outer surfaces of each connecting rubber portion 26 tend to move outwardly from the opposing upper and lower surfaces of the inner shaft member 12 and the outer tubular member 14, increasing the shear area, while the left and right inner surfaces of each connecting rubber portion 26 tend to increase the compression area that directly connects the opposing upper and lower surfaces of the inner shaft member 12 and the outer tubular member 14. Therefore, even if the rubber protrusions 28 are positioned further inward on the left and right than the connecting rubber portions 26 of the rubber legs 16, this is unlikely to cause any major problems.

[0055] In the initial state where no load is applied to the rubber legs 16, the rubber protrusions 28 are preferably located laterally inward from the left and right outer ends of the connecting rubber portions 26, but they need only be located on the connecting rubber portions 26 of the rubber legs 16 in a compressed state. That is, when the motor mount 10 is mounted on a vehicle or the like, the rubber legs 16 are compressed by the static shared support load (static primary load) of the motor or the like. As a result, the rubber protrusions 28 are located in the compressed regions of the rubber legs 16 when the primary load is applied, thereby preventing strain concentration around the rubber protrusions 28 and ensuring durability. The left and right outer ends of the rubber protrusions 28 may be located laterally inward from the left and right outer ends of the inner shaft member 12 and laterally outward from the left and right outer ends of the connecting rubber portions 26 of the rubber legs 16 in the initial state.

[0056] The inner shaft member may be configured, for example, by a cylindrical fixing tubular portion fixed to the rubber legs 16, 16, and an inner bracket inserted into and fitted to the inner periphery of the fixing tubular portion. The cross-sectional shape of the inner shaft member may also vary in the axial direction. The inner shaft member may also not have the rubber fixing portions 20, 20 or the stopper protrusion 22.

[0057] The stopper mechanisms for the up / down, front / rear, and left / right directions are not essential, and only one or two-way stopper mechanisms may be provided, or no stopper mechanisms may be provided.

[0058] REFERENCE SIGNS LIST 10 Motor mount (cylindrical vibration-damping device for motor mount, first embodiment) 12 Inner shaft member 14 Outer cylindrical member 16 Rubber leg 18 Mounting hole 20 Rubber fastening portion 22 Stopper protrusion 24 Flange-shaped portion 26 Connecting rubber portion 28 Rubber protrusion 30 Inner rubber layer 32 Inner buffer rubber 34 Outer rubber layer 36 Upper buffer rubber 38 First recess hole 40 Lower buffer rubber (stopper rubber) 42 Second recess hole 44 Front buffer rubber

Claims

1. A cylindrical vibration-damping device for a motor mount in which an inner shaft member and an outer cylindrical member are connected by two rubber legs extending between the opposing surfaces of the inner shaft member and the outer cylindrical member, wherein the two rubber legs are both positioned below the inner shaft member which is compressed when the main load is input, and extend in the vertical direction at positions spaced apart from each other in the left-right direction, the two rubber legs are connected in the vertical direction and have a connecting rubber part that directly connects the opposing surfaces of the inner shaft member and the outer cylindrical member, the two rubber legs are each provided with a rubber protrusion that protrudes in the axial direction, and the rubber protrusions are arranged so that they are located left and right inward from the left and right outer ends of the connecting rubber part.

2. A cylindrical vibration-isolating device for a motor mount as described in claim 1, wherein 90% or more of said rubber projections are disposed on said connecting rubber portion, so that said rubber projections are provided substantially only on said connecting rubber portion.

3. A cylindrical vibration isolation device for a motor mount as described in claim 1 or 2, wherein the inner shaft member has a pair of rubber fixing portions protruding on both the left and right sides, the two rubber feet are fixed to the pair of rubber fixing portions, and a stopper protrusion is provided between the pair of rubber fixing portions on the inner shaft member and protruding downward between the two rubber feet.

4. A cylindrical vibration-damping device for a motor mount as described in any one of claims 1 to 3, wherein a stopper rubber is provided between the two rubber legs and protrudes in the vertical direction between the inner shaft member and the outer cylindrical member.

5. A cylindrical vibration isolation device for a motor mount as described in any one of claims 1 to 4, wherein the width dimension of the connecting rubber portion is at least 20% of the width dimension of the rubber foot, thereby making the compression spring component of the rubber foot against a downward input greater than the shear spring component.

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