Cylindrical vibration isolation device for motor mounts

Abstract

This invention provides a novel cylindrical vibration isolation device for motor mounts that can prevent deterioration of vibration conditions due to surging and improve vibration isolation performance when a preload load is applied. [Solution] A cylindrical vibration damping device 10 for motor mounting is provided, in which an inner shaft member 12 and an outer cylindrical member 14 are connected by a main rubber elastic body 16, wherein the main rubber elastic body 16 has a first connecting leg portion 20 and a second connecting leg portion 22 that are arranged on either side of the inner shaft member 12 in one direction perpendicular to the axis, which is the direction in which the preload load is input, the first connecting leg portion 20 located on the compression side due to the input of the preload load has a longer leg length perpendicular to the axis than the second connecting leg portion 22 located on the tension side, the resonant frequencies of the first connecting leg portion 20 and the resonant frequencies of the second connecting leg portion 22 are different from each other, and at least one of the first connecting leg portion 20 and the second connecting leg portion 22 is provided with a vibration damping protrusion 30 (38) that protrudes from the surface in the middle portion in the leg length direction.

Description

Technical Field

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

Background Art

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

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

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

[0005] Furthermore, in motor mounts, for example, the support load of the electric motor and the load based on the inertial force during acceleration may act as preload loads in approximately the same radial direction. In this case, the inner shaft member and the outer cylindrical member undergo a large relative displacement in the direction of the input preload load. In Patent Document 1, the inner shaft member and the outer cylindrical member come into contact via a stopper rubber, thereby limiting the relative displacement between the inner shaft member and the outer cylindrical member and ensuring the durability of the rubber foot. However, it has recently been discovered that the abrupt change in the dynamic spring characteristics caused by the contact between the inner shaft member and the outer cylindrical member via the stopper rubber can be one of the factors that worsen the ride comfort of the vehicle.

[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 can prevent the vibration state from being significantly worsened at a specific frequency due to rubber surging, and can further improve vibration isolation performance when a preload load is applied. [Means for solving the problem]

[0007] The following describes preferred embodiments for understanding the present invention. However, each embodiment described below is illustrative and can be combined with others as appropriate. Furthermore, the multiple components described in each embodiment can be recognized and adopted as independently as possible, and can be combined with any component described in another embodiment as appropriate. Thus, the present invention is not limited to the embodiments described below, and various other embodiments can be realized.

[0008] The first embodiment is a cylindrical vibration damping device for a motor mount in which an inner shaft member and an outer cylindrical member are connected by a main rubber elastic body, wherein the main rubber elastic body has a first connecting leg and a second connecting leg that are positioned on either side of the inner shaft member in one direction perpendicular to the axis, which is the direction in which the preload load is input, the first connecting leg located on the compression side due to the input of the preload load has a longer leg length perpendicular to the axis than the second connecting leg located on the tension side, the resonance frequencies of the first connecting leg and the second connecting leg are different from each other with respect to the input of a vibration load in the same direction as the preload load, and at least one of the first connecting leg and the second connecting leg is provided with a vibration damping protrusion that protrudes from the surface in the middle portion in the leg length direction.

[0009] According to the cylindrical vibration isolation device for motor mounts with a structure conforming to this embodiment, the first connecting leg and the second connecting leg constituting the main body rubber elastic body are set to different resonant frequencies, and the rubber surging of the first connecting leg and the rubber surging of the second connecting leg occur at different frequencies. Therefore, compared to the case where the rubber surging of the first connecting leg and the rubber surging of the second connecting leg occur at the same frequency, the deterioration of vibration isolation characteristics caused by rubber surging can be suppressed.

[0010] Furthermore, at least one of the first connecting leg and the second connecting leg is provided with a vibration-damping protrusion in the middle portion in the leg length direction, and the vibration-damping effect due to the deformation of the vibration-damping protrusion can reduce at least one of the rubber surging of the first connecting leg and the rubber surging of the second connecting leg.

[0011] Since the first and second connecting legs are positioned on both sides of the inner shaft member in one direction perpendicular to the axis, which is the direction in which the preload load is applied, even when the relative displacement between the first and second connecting legs becomes large due to the application of the preload load, the linear spring characteristics due to the elastic deformation of the first and second connecting legs are exhibited, preventing deterioration of ride comfort due to abrupt changes in spring characteristics.

[0012] Furthermore, since the free length of the first connecting leg, which is compressed by the input of a preload load, is longer than that of the second connecting leg, the distortion of the first connecting leg during compression is reduced, and a wide linear region can be secured in the deflection-load characteristics of the main rubber elastic body. Therefore, shock sensations due to nonlinear changes in the spring characteristics of the main rubber elastic body are prevented, and a good ride comfort is provided. On the other hand, the second connecting leg, which has a shorter leg length than the first connecting leg, is located on the tension side when a preload load is applied, and its influence on the spring characteristics of the main rubber elastic body when a preload load is applied is relatively small, so it is less likely to cause nonlinear spring characteristics of the main rubber elastic body, and a wide linear region can be secured in the deflection-load characteristics. In addition, since the leg length of the first connecting leg is longer than that of the second connecting leg, the leg length of the first connecting leg can be increased within the range of the diameter dimensions of the outer cylindrical member specified by the target to which the cylindrical vibration damping device is installed.

[0013] The second embodiment is a cylindrical vibration damping device for a motor mount as described in the first embodiment, wherein the outer dimension of the inner shaft member in the direction of input of the preload load is smaller than the outer dimension in the direction perpendicular to the axis and perpendicular to the direction of input of the preload load.

[0014] According to the cylindrical vibration damping device for motor mounts with a structure conforming to this embodiment, the outer dimensions of the inner shaft member are reduced in the direction of input of the preload load, and the distance between the opposing surfaces of the inner shaft member and the outer cylindrical member is increased. As a result, the sum of the leg lengths of the first connecting legs and the second connecting legs, which are arranged on both sides of the inner shaft member in the direction of input of the preload load, can be increased. Furthermore, because the outer dimensions of the inner shaft member are increased in the direction perpendicular to the direction of input of the preload load, it becomes easier to obtain a larger fixing area between the first and second connecting legs and the inner shaft member.

[0015] A third embodiment is a cylindrical vibration damping device for a motor mount described in the first or second embodiment, wherein grooves are provided on both sides of the inner shaft member in a direction perpendicular to the axis and perpendicular to the input direction of the preload load, and the grooves are provided with a gentle impact portion that protrudes from one side to the other between the inner shaft member and the outer cylindrical member.

[0016] In the cylindrical vibration damping device for motor mounts constructed according to this embodiment, in the direction perpendicular to the preload input direction, where large loads are less likely to be input compared to the preload input direction, the presence of recessed holes allows for soft spring characteristics (low spring characteristics) due to the shear spring components of the first and second connecting legs. Furthermore, during sharp turns or other situations where large loads are input in the direction perpendicular to the preload input direction, the inner shaft member and the outer cylindrical member come into contact via a gentle collision portion, limiting relative displacement and improving driving stability.

[0017] The fourth embodiment is a cylindrical vibration damping device for a motor mount as described in any one of the first to third embodiments, wherein at least one of the first connecting leg and the second connecting leg has a vibration damping projection that extends in the circumferential direction.

[0018] According to the cylindrical vibration damping device for motor mounts with a structure conforming to this embodiment, the circumferential length of the vibration damping protrusion can be increased, making it easier to increase the mass of the vibration damping protrusion, thus advantageously obtaining a vibration damping effect. Furthermore, for example, because the vibration damping protrusion extends in the circumferential direction, it is positioned away from the inner and outer cylindrical members without partially approaching them. As a result, the vibration damping protrusion is less likely to be excessively constrained by the inner shaft member or the outer cylindrical member, and the vibration damping effect due to the elastic deformation of the vibration damping protrusion is efficiently exerted.

[0019] The fifth embodiment is a cylindrical vibration damping device for a motor mount described in any one of the first to fourth embodiments, wherein the first connecting leg and the second connecting leg, including the vibration damping protrusion, are symmetrical on both sides in the circumferential direction.

[0020] According to the cylindrical vibration isolator for a motor mount having a structure according to this aspect, when the first connecting leg portion and the second connecting leg portion are elastically deformed, the difference in the deformation modes on both circumferential sides in the first connecting leg portion and the second connecting leg portion can be suppressed, and stress concentration due to uneven deformation can be prevented.

[0021] A sixth aspect is the cylindrical vibration isolator for a motor mount according to any one of the first to fifth aspects, in which the ratio of the static spring constant in the input direction of the preload load to the static spring constant in the direction perpendicular to the input direction is within a range of 1.5 to 3.5.

[0022] According to the cylindrical vibration isolator for a motor mount having a structure according to this aspect, by setting the ratio of the static spring constant in the direction perpendicular to the input direction of the preload load to the static spring constant in the input direction of the preload load within a range of 1.5 to 3.5, a support spring for an electric motor can be appropriately obtained.

[0023] A seventh aspect is the cylindrical vibration isolator for a motor mount according to any one of the first to sixth aspects, in which the first connecting leg portion extends on both circumferential sides from the inner shaft member side toward the outer cylinder member side, and the maximum circumferential width dimension on the outer cylinder member side is within a range of 1.3 to 2 times the minimum circumferential width dimension on the inner shaft member side in the first connecting leg portion.

[0024] According to the cylindrical vibration isolator for a motor mount having a structure according to this aspect, it becomes easy to realize a linear spring characteristic of the main body rubber elastic body with respect to the input of the preload load. Further, since the circumferential side surface of the first connecting leg portion becomes an inclined surface that extends while being inclined with respect to the connecting direction of the inner shaft member and the outer cylinder member by the first connecting leg portion, the free surface of the first connecting leg portion becomes large, and an improvement in the durability of the first connecting leg portion can be expected.

[0025] The eighth aspect is the cylindrical vibration isolator for a motor mount according to any one of the first to seventh aspects, wherein the vibration damping protrusion has a tapered cross-sectional shape that gradually becomes thinner in the radial direction from the protruding base end to the protruding tip end, and the inclination angle of the inner peripheral side surface with respect to the axial direction is made larger than the inclination angle of the outer peripheral side surface with respect to the axial direction.

[0026] According to the cylindrical vibration isolator for a motor mount having a structure according to this aspect, when the axial surface on the inner shaft member side of the first connecting leg portion and / or the second connecting leg portion provided with the vibration damping protrusion has an inclined shape that inclines axially outward toward the inner circumference, both the inner peripheral side surface and the outer peripheral side surface of the vibration damping protrusion can be made at an angle closer to a right angle with respect to the axial surface of the first connecting leg portion or the second connecting leg portion. As a result, deformation of the vibration damping protrusion is likely to occur when a vibration load is input, and reduction of rubber surging by the vibration damping protrusion is effectively realized. In addition, irregular deformation including harmonic components in the vibration damping protrusion itself can be suppressed, and while suppressing an increase in the mass of the vibration damping protrusion itself, it is also possible to improve the transmission efficiency of the vibration damping action by the vibration damping protrusion to the first connecting leg portion and the second connecting leg portion.

[0027] The ninth aspect is a cylindrical vibration isolator for a motor mount in which an inner shaft member and an outer cylinder member are connected by a main body rubber elastic body, the main body rubber elastic body includes a plurality of connecting leg portions that extend in a direction perpendicular to the axis and connect the inner shaft member and the outer cylinder member, and at least one of the connecting leg portions is provided with a vibration damping protrusion that protrudes from its surface at an intermediate portion in the leg length direction, the vibration damping protrusion has a tapered cross-sectional shape that gradually becomes thinner in the radial direction from the protruding base end to the protruding tip end, and the inclination angle of the inner peripheral side surface with respect to the axial direction is made larger than the inclination angle of the outer peripheral side surface with respect to the axial direction.

[0028] According to the cylindrical vibration damping device for motor mounts constructed in accordance with this embodiment, both the inner and outer circumferential sides of the vibration damping protrusion can be set at an angle closer to a right angle with respect to the axial surface of the first or second connecting leg. This makes deformation of the vibration damping protrusion more likely to occur when a vibration load is input, effectively reducing rubber surging caused by the vibration damping protrusion. Furthermore, it is possible to suppress irregular deformation including harmonic components in the vibration damping protrusion itself, and to improve the transmission efficiency of the vibration damping effect from the vibration damping protrusion to the first and second connecting legs while suppressing the mass increase of the vibration damping protrusion itself. [Effects of the Invention]

[0029] According to the present invention, in a cylindrical vibration isolation device for motor mounts, it is possible to prevent the vibration state from being significantly worsened at a specific frequency due to rubber surging of the connecting legs, and to improve vibration isolation performance when a preload load is applied. [Brief explanation of the drawing]

[0030] [Figure 1] Perspective view showing a motor mount as the first embodiment of the present invention. [Figure 2] Front view of the motor mount shown in Figure 1 [Figure 3] Section III-III in Figure 2 [Figure 4] Figure 2, section IV-IV [Figure 5] Graph showing the measured spring characteristics of the motor mount. [Modes for carrying out the invention]

[0031] Embodiments of the present invention will be described below with reference to the drawings.

[0032] Figures 1 to 4 show a motor mount 10 for an automobile as a first embodiment of a cylindrical vibration damping device for a motor mount having a structure according to the present invention. The motor mount 10 has a structure in which an inner shaft member 12 and an outer cylindrical member 14 are connected by a main rubber elastic body 16. In the following description, as a general rule, the vertical direction refers to the vertical direction in Figure 2, the left-right direction refers to the left-right direction in Figure 2, and the front-rear direction refers to the left-right direction in Figure 3. In the following description, the input load (preload load) due to the support load of the electric motor and the inertial force of the electric motor during acceleration acting on the motor mount 10 when it is mounted on a vehicle acts downward on the inner shaft member 12, so the direction of action of the preload load is downward in Figure 2.

[0033] The inner shaft member 12 is shaped like a small-diameter cylinder overall, for example, with an outer surface that is approximately octagonal. The inner shaft member 12 has a roughly circular cross-section and a bolt insertion hole 18 that penetrates through it in the axial direction (front-to-back direction). The vertical outer dimension Li of the inner shaft member 12 is smaller than the horizontal outer dimension Wi, preferably 0.3 to 0.9 times the horizontal outer dimension Wi, and more preferably 0.5 to 0.8 times. The vertical outer dimension Li of the inner shaft member 12 is desirable to be smaller in order to ensure a longer free length for the first and second connecting legs 20, 22 and to reduce the outer diameter of the mount, but it is set considering, for example, the outer diameter of the bolt head inserted into the bolt insertion hole 18 and the outer diameter of the washer fitted onto the bolt. The inner shaft member 12 is a highly rigid member made of, for example, an aluminum alloy, iron (stainless steel), or a fiber-reinforced synthetic resin.

[0034] The outer cylindrical member 14 has a generally thin-walled, large-diameter, substantially cylindrical shape. The inner diameter of the outer cylindrical member 14 is larger than the maximum outer diameter of the inner shaft member 12, and its length in the front-to-back direction is shorter than the length of the inner shaft member 12 in the front-to-back direction. The outer cylindrical member 14 is made of a highly rigid material such as an aluminum alloy, iron (stainless steel), or fiber-reinforced synthetic resin. The outer cylindrical member 14 is not limited to a perfect cylinder shape, and may be an elliptical cylinder with an elliptical cross-section where the vertical direction is the major axis.

[0035] The inner shaft member 12 is inserted into the inner circumference of the outer cylindrical member 14, and the main rubber elastic body 16 is positioned radially between the outer circumferential surface of the inner shaft member 12 and the inner circumferential surface of the outer cylindrical member 14. The inner shaft member 12 is positioned such that its front-to-back center is approximately coincident with that of the outer cylindrical member 14, and it protrudes from both sides in the axial direction.

[0036] The main rubber elastic body 16 is equipped with a first connecting leg portion 20 and a second connecting leg portion 22 that connect the inner shaft member 12 and the outer cylindrical member 14 to each other. The first connecting leg portion 20 and the second connecting leg portion 22 each extend in the vertical direction and are arranged on one side of the inner shaft member 12, with the first connecting leg portion 20 being located below the inner shaft member 12 and the second connecting leg portion 22 being located above the inner shaft member 12. The first connecting leg portion 20 and the second connecting leg portion 22 are integrally formed in a continuous manner by a cylindrical inner fixing portion 24 fixed to the outer circumferential surface of the inner shaft member 12 and a cylindrical outer fixing portion 26 fixed to the inner circumferential surface of the outer cylindrical member 14. The first connecting leg portion 20 and the second connecting leg portion 22 are arranged on the same straight line, and the leg length direction of both is vertical.

[0037] The first connecting leg portion 20 has its upper end fixed to the outer circumferential surface (lower surface) of the inner shaft member 12, and its lower end fixed to the inner circumferential surface of the outer cylindrical member 14. The first connecting leg portion 20 is shaped to expand circumferentially from the end on the inner shaft member 12 side (upper end) to the end on the outer cylindrical member 14 side (lower end), with the left-right width dimension increasing toward the outer cylindrical member 14 side. The maximum circumferential width dimension W1 on the outer cylindrical member 14 side of the first connecting leg portion 20 is preferably within the range of 1.3 to 2 times the minimum circumferential width dimension w1 on the inner shaft member 12 side of the first connecting leg portion 20. The left-right width dimension W1 of the lower end of the first connecting leg portion 20 is larger than the left-right outer dimension Wi of the inner shaft member 12.

[0038] The first connecting leg portion 20 is symmetrical on both sides in the circumferential direction with respect to the circumferential center. In this embodiment, the first connecting leg portion 20 is symmetrical on both sides in the circumferential direction with respect to the left-right center of the motor mount 10, which is shown by the dashed line in Figure 2, and the elastic center in the vertical direction substantially coincides with the left-right center of the motor mount 10.

[0039] The first surface 28 of the first connecting leg portion 20 is a concave curved surface, and in particular the inner circumference is inclined inward and outward. The portion of the first surface 28 of the first connecting leg portion 20 where the tangential direction in the longitudinal cross-section shown in Figure 3 is perpendicular to the axis is located at the connection point with the first outer peripheral side surface 34 of the first vibration damping protrusion portion 30, which will be described later.

[0040] The first connecting leg portion 20 is provided with a first vibration damping projection portion 30. The first vibration damping projection portion 30 protrudes outward and forward from the first surface 28 of the first connecting leg portion 20 and is integrally formed with the first connecting leg portion 20. A pair of first vibration damping projection portions 30 are provided, protruding from the first surfaces 28, 28 on both the front and rear sides of the first connecting leg portion 20, and these pairs of first vibration damping projection portions 30, 30 are substantially symmetrical in the axial direction. The first vibration damping projection portion 30 is located midway along the leg length direction (the direction of connection between the inner shaft member 12 and the outer cylindrical member 14) of the first connecting leg portion 20 and is provided away from the inner shaft member 12 and the outer cylindrical member 14. The first vibration damping projection portion 30 is provided continuously along substantially the entire circumferential length of the first connecting leg portion 20. The first vibration damping projection 30 is formed as a curved projection that extends circumferentially with approximately the same curvature as the outer cylindrical member 14. The first inner circumferential surface 32 and the first outer circumferential surface 34 of the first vibration damping projection 30 are smoothly continuous with the first surface 28 of the first connecting leg 20 by a fillet radius. Preferably, the entire first connecting leg 20, including the pair of first vibration damping projections 30, 30, is approximately symmetrical on both the left and right sides.

[0041] The first vibration damping projection 30 is thinned radially toward the protruding tip, and has a tapered cross-sectional shape as shown in Figure 3. The inclination angle α of the first inner circumferential surface 32 with respect to the axial direction is greater than the inclination angle of the first outer circumferential surface 34 with respect to the axial direction. In this embodiment, the first outer circumferential surface 34 is approximately parallel to the axial direction, and the inclination angle of the first outer circumferential surface 34 with respect to the axial direction is approximately 0 degrees. As a result, the elastic center C1 of the first vibration damping projection 30 in the protruding direction, shown by the dashed line in Figure 3, is inclined toward the outer circumference toward the protruding tip. The elastic center C1 of the first vibration damping projection 30 can be understood, for example, as the straight line formed by the central position of the first inner circumferential surface 32 and the first outer circumferential surface 34 in the direction perpendicular to the axis in a longitudinal cross-section of the first vibration damping projection 30 as shown in Figure 3.

[0042] In the first vibration damping projection 30, the inclination angle α of the first inner circumferential surface 32 with respect to the axial direction is greater than the inclination angle of the first outer circumferential surface 34 with respect to the axial direction. Furthermore, the first surface 28 of the first connecting leg portion 20 in the forming portion of the first vibration damping projection 30 is a curved surface whose inclination angle changes such that the inclination angle with respect to the axial direction decreases toward the inner shaft member 12. As a result, the angle θ1 between the first inner circumferential surface 32 of the first vibration damping projection 30 and the first surface 28 of the first connecting leg portion 20 on the inner circumferential side of the first vibration damping projection 30 is set to be greater than when the inner circumferential surface of the first vibration damping projection 30 widens in the axial direction. In addition, the base end position of the first vibration damping projection 30 is located axially outward on the inner circumferential side than on the outer circumferential side, and the axial distance H1 between the base ends of the first inner circumferential surfaces 32, 32 in the first vibration damping projections 30, 30 on both axial sides is greater than the axial distance h1 between the base ends of the first outer circumferential surfaces 34, 34.

[0043] The second connecting leg portion 22 has its lower end fixed to the outer circumferential surface (upper surface) of the inner shaft member 12, and its upper end fixed to the inner circumferential surface of the outer cylindrical member 14. The second connecting leg portion 22 is shaped to expand circumferentially from the end on the inner shaft member 12 side (lower end) to the end on the outer cylindrical member 14 side (upper end), with the left-right width dimension increasing toward the outer cylindrical member 14 side. The maximum circumferential width dimension W2 on the outer cylindrical member 14 side of the second connecting leg portion 22 is preferably within the range of 1.3 to 2 times the minimum circumferential width dimension w2 on the inner shaft member 12 side of the second connecting leg portion 22. The left-right width dimension W2 of the upper end of the second connecting leg portion 22 is larger than the left-right outer dimension Wi of the inner shaft member 12. The minimum circumferential width dimension w1 of the first connecting leg portion 20 and the minimum circumferential width dimension w2 of the second connecting leg portion 22 are approximately the same. Furthermore, the maximum circumferential width dimension W1 of the first connecting leg 20 is larger than the maximum circumferential width dimension W2 of the second connecting leg 22.

[0044] The second connecting leg portion 22 is symmetrical on both sides in the circumferential direction with respect to the circumferential center. In this embodiment, the second connecting leg portion 22 is symmetrical on both sides in the circumferential direction with respect to the left-right center of the motor mount 10, which is shown by the dashed line in Figure 2, and the elastic center in the vertical direction substantially coincides with the left-right center of the motor mount 10.

[0045] The second surface 36 of the second connecting leg portion 22 is a concave curved surface, and in particular the inner circumference is inclined inward and outward. The portion of the second surface 36 of the second connecting leg portion 22 where the tangential direction in the longitudinal cross-section shown in Figure 3 is perpendicular to the axis is located at the connection point with the second outer peripheral side surface 42 of the second vibration damping protrusion portion 38, which will be described later.

[0046] The second connecting leg portion 22 is provided with a second vibration damping projection portion 38. The second vibration damping projection portion 38 protrudes outward and forward from the second surface 36 of the second connecting leg portion 22 and is integrally formed with the second connecting leg portion 22. A pair of second vibration damping projection portions 38 are provided, protruding from the second surfaces 36, 36 on both the front and rear sides of the second connecting leg portion 22, and these pairs of second vibration damping projection portions 38, 38 are substantially symmetrical in the axial direction. The second vibration damping projection portion 38 is located midway along the leg length of the second connecting leg portion 22 and is provided away from the inner shaft member 12 and the outer cylindrical member 14. The second vibration damping projection portion 38 is provided continuously along substantially the entire circumferential length of the second connecting leg portion 22. The second vibration damping projection portion 38 is formed in a curved projection shape that curves with substantially the same curvature as the outer cylindrical member 14 and extends in the circumferential direction. The second inner circumferential surface 40 and the second outer circumferential surface 42 of the second vibration damping projection 38 are smoothly continuous with the second surface 36 of the second connecting leg 22 by a fillet radius. Preferably, the second connecting leg 22, including the pair of second vibration damping projections 38, 38, has a substantially symmetrical shape on both the left and right sides.

[0047] The second vibration damping projection 38 is thinned radially toward the protruding tip, and has a tapered cross-sectional shape as shown in Figure 3. The inclination angle β of the second inner circumferential surface 40 of the second vibration damping projection 38 with respect to the axial direction is greater than the inclination angle of the second outer circumferential surface 42 with respect to the axial direction. In this embodiment, the second outer circumferential surface 42 is substantially parallel to the axial direction, and the inclination angle of the second outer circumferential surface 42 with respect to the axial direction is substantially 0 degrees. As a result, the elastic center C2 of the second vibration damping projection 38 in the protruding direction, shown by the dashed line in Figure 3, is inclined toward the outer circumference toward the protruding tip. The elastic center C2 of the second vibration damping projection 38 can be understood, for example, as the straight line formed by the central position of the second inner circumferential surface 40 and the second outer circumferential surface 42 in the direction perpendicular to the axis in the longitudinal cross-section of the second vibration damping projection 38 as shown in Figure 3.

[0048] In the second vibration damping projection 38, the inclination angle β of the second inner circumferential surface 40 with respect to the axial direction is greater than the inclination angle of the second outer circumferential surface 42 with respect to the axial direction. Furthermore, the second surface 36 of the second connecting leg 22 in the portion where the second vibration damping projection 38 is formed is a curved surface whose inclination angle changes such that the inclination angle with respect to the axial direction decreases toward the inner shaft member 12. As a result, the angle θ2 between the second inner circumferential surface 40 of the second vibration damping projection 38 and the second surface 36 of the second connecting leg 22 on the inner circumferential side of the second vibration damping projection 38 is set to be greater than when the inner circumferential surface of the second vibration damping projection 38 widens in the axial direction. In addition, the base end position of the second vibration damping projection 38 is located axially outward on the inner circumferential side than on the outer circumferential side, and the axial distance H2 between the base ends of the second inner circumferential surfaces 40, 40 of the second vibration damping projections 38, 38 on both axial sides is greater than the axial distance h2 between the base ends of the second outer circumferential surfaces 42, 42.

[0049] The first connecting leg 20 and the second connecting leg 22 have different leg lengths in the direction of connecting the inner shaft member 12 and the outer cylindrical member 14. Specifically, the leg length L1 of the first connecting leg 20, which is on the compressive deformation side when a preload load is applied, is longer than the leg length L2 of the second connecting leg 22, which is on the tensile deformation side when a preload load is applied. As a result, the vertical spring constant of the first connecting leg 20 is smaller than that of the second connecting leg 22, making the first connecting leg 20 softer in the vertical direction than the second connecting leg 22. The central axis of the inner shaft member 12 is offset upward with respect to the central axis of the outer cylindrical member 14.

[0050] For vibration loads applied in the same direction (vertical direction) as the preload load, the resonant frequencies of the first connecting leg 20 and the second connecting leg 22 are made to be different from each other. This prevents the vibration state from deteriorating due to both the first and second connecting leg 20 and the second connecting leg 22 simultaneously resonating at a specific frequency. It is desirable that the resonant frequencies of the first and second connecting leg 22 differ by 1.1 times or more. Either the resonant frequency of the first or second connecting leg 22 may be at a higher frequency, but for example, the resonant frequency of the first connecting leg 20, which has a longer leg length, is tuned to a lower frequency than the resonant frequency of the second connecting leg 22, which has a shorter leg length. The preload load is set considering the maintenance of the required characteristics and durability of the first and second connecting legs 20 and 22. Since the preload load applies a corresponding compressive or tensile load to the first and second connecting legs 20 and 22, the difference in the resonant frequencies of the first connecting leg 20 and the second connecting leg 22 is maintained even when the preload load is applied. The resonant frequencies of the first and second connecting legs 20 and 22 can be adjusted based on factors such as the rubber volume (mass) of the first and second connecting legs 20 and 22, the cross-sectional shape of the first and second connecting legs 20 and 22, and the restraint state of the first and second connecting legs 20 and 22, even if both legs 20 and 22 are made of the same material.

[0051] A pair of slit holes 44, 44 are formed in the circumferential direction between the first connecting leg portion 20 and the second connecting leg portion 22. The slit holes 44, 44 are provided on both the left and right sides of the inner shaft member 12. Because the slit holes 44, 44 penetrate the main rubber elastic body 16 in the axial direction, the main rubber elastic body 16 is not continuous between the left and right sides of the inner shaft member 12 and the left and right opposing surfaces of the outer cylindrical member 14. Therefore, when vibration input is applied in the left and right direction, the low spring characteristics due to the shear spring component of the first and second connecting leg portions 20, 22 are exhibited.

[0052] As shown in Figures 2 and 4, a soft impact portion 46 protrudes from each of the slit holes 44. The soft impact portion 46 is integrally formed with the main rubber elastic body 16 and protrudes in the left-right direction toward the inner shaft member 12 from the outer fixing portion 26 fixed to the inner circumferential surface of the outer cylindrical member 14. The soft impact portion 46 has a tapered shape, with its outer dimensions in the vertical and front-back directions decreasing toward the protruding tip. The soft impact portion 46 does not reach the inner fixing portion 24 that covers the outer circumferential surface of the inner shaft member 12, and the protruding tip surface is separated from the inner surface of the left and right inner holes of the slit hole 44.

[0053] The motor mount 10 is attached to an electric motor (not shown) by an inner shaft member 12 inserted through a bolt insertion hole 18, and an outer cylindrical member 14 is attached to the vehicle body, thereby vibration-damping the electric motor to the vehicle body. When mounted on the vehicle, the motor mount 10 receives a static support load from the electric motor in a direction that displaces the inner shaft member 12 downward relative to the outer cylindrical member 14. The motor mount 10 has a first connecting leg 20 that is compressed vertically by the input of the support load, and its free length in the vertical direction is longer than that of the second connecting leg 22, which prevents the dynamic spring constant from becoming high when the support load is applied.

[0054] The motor mount 10 is mounted on the vehicle with the first and second connecting legs 20 and 22 extending in the direction of input of preload and vibration loads. For example, cylindrical engine mounts that provide vibration isolation support to internal combustion engines are used in the high-temperature environment generated by the internal combustion engine, making it difficult to ensure durability when the first and second connecting legs are mounted on the vehicle with the first and second connecting legs extending in the direction of input of preload and vibration loads. In contrast, it has been found that motor mounts are not subject to the same severe temperature conditions as engine mounts, and the extension direction of the first and second connecting legs can be set with a greater degree of freedom than that of engine mounts. Therefore, the motor mount 10 adopts the arrangement of the first and second connecting legs 20 and 22 as described above, which could not be adopted in engine mounts, thereby achieving excellent spring characteristics under heavy load input, as described later.

[0055] In this embodiment, when the motor mount 10 is mounted on a vehicle, the axial direction of the motor mount 10 is the front-rear direction of the vehicle. However, the axial direction of the motor mount 10 may also be the left-right direction of the vehicle, and the relative orientation of the motor mount 10 to the vehicle is not particularly limited. The outer cylindrical member 14 is fixed to the vehicle body by means of, for example, press-fitting into a mounting cylinder provided on the vehicle body side or bolting via a bracket.

[0056] The motor mount 10 has a ratio of the static spring constant in the left-right direction, which is perpendicular to the input direction of the preload load, to the static spring constant in the vertical direction, which is the input direction of the preload load, within the range of 1.5 to 3.5. This ensures that the electric motor is properly supported by the motor mount 10.

[0057] When a vibration load is applied between the inner shaft member 12 and the outer cylindrical member 14, vibration isolation effects are exerted based on the vibration isolation and vibration damping effects of the first and second connecting legs 20 and 22. For example, when vibration is applied in the vertical direction, vibration damping effects are exerted by the compression / tensile deformation of the first and second connecting legs 20 and 22, while when vibration is applied in the longitudinal (axial) and lateral directions, vibration isolation effects are exerted based on the soft spring characteristics due to the shear spring component of the first and second connecting legs 20 and 22. The main vibration input direction for vibration isolation to the motor mount 10 is the vertical direction, which is approximately the same direction as the input direction of the preload load when mounted on a vehicle. However, the input direction of vibration to be isolated is not limited, and for example, it is conceivable that vibrations including a vertical vibration component, which is the input direction of the preload load, may be input, and vibration isolation characteristics can be exerted against vibrations input in various directions.

[0058] The first and second connecting legs 20 and 22 are symmetrical on both sides of the circumferential direction with respect to the circumferential center. This stabilizes the deformation of the first and second connecting legs 20 and 22, especially with respect to vibration input in the longitudinal direction (axial direction) and vibration input in the vertical direction (preload load input direction), thereby preventing stress concentration in the first and second connecting legs 20 and 22 and preventing unintended vibration of the inner shaft member 12 and outer cylindrical member 14. More preferably, the first and second connecting legs 20 and 22, including the first and second vibration damping protrusions 30 and 38, are symmetrical on both sides of the circumferential direction, so that the magnitude and distribution of mass are the same on both sides of the circumferential direction, thereby more advantageously achieving stable deformation of the first and second connecting legs 20 and 22.

[0059] When vibration is input, the deterioration of the vibration state due to resonance (rubber surging) of the first and second connecting legs 20 and 22 becomes a problem. However, in the motor mount 10, rubber surging is reduced by the first and second vibration damping protrusions 30 and 38 provided on the first and second connecting legs 20 and 22. The first and second vibration damping protrusions 30 and 38 suppress rubber surging of the first and second connecting legs 20 and 22 by, for example, deforming in opposite phase to the first and second connecting legs 20 and 22, thereby reducing the vibration energy of the first and second connecting legs 20 and 22.

[0060] The first vibration damping protrusion 30 has a tapered shape, and the first inner circumferential surface 32 is an inclined surface. As a result, the angle θ1 formed between the first inner circumferential surface 32 and the front and rear surfaces of the first connecting leg 20 is made relatively large, closer to 90 degrees. This makes the first vibration damping protrusion 30 more susceptible to deformation such as bending and tilting in the inner and outer circumference, allowing the vibration damping effect due to the elastic deformation of the first vibration damping protrusion 30 to be effectively exerted and suppressing rubber surging of the first connecting leg 20. The second vibration damping protrusion 38 is also more susceptible to deformation such as bending and tilting in the inner and outer circumference, similar to the first vibration damping protrusion 30, thus effectively suppressing rubber surging of the second connecting leg 22.

[0061] The first and second vibration-damping protrusions 30 and 38 are curved plates extending in the circumferential direction, and a large mass is ensured. Therefore, the vibration-damping effect due to the deformation of the first and second vibration-damping protrusions 30 and 38 is more advantageously exerted, preventing deterioration of the vibration state due to rubber surging of the first and second connecting legs 20 and 22.

[0062] In this embodiment, the motor mount 10 has perforations 44, 44 in the main rubber elastic body 16, and the mass of the connection portion between the inner shaft member 12 and the outer cylindrical member 14 in the main rubber elastic body 16 is reduced. By suppressing the mass of the part of the main rubber elastic body 16 that causes rubber surging in this way, the deterioration of the vibration state caused by rubber surging can be suppressed.

[0063] For example, if a large load in the lateral direction is applied to the motor mount 10 due to a sharp turn of the vehicle, causing a large relative displacement between the inner shaft member 12 and the outer cylindrical member 14 in the lateral direction, the relative displacement between the inner shaft member 12 and the outer cylindrical member 14 is limited by the indirect contact between them via the gentle collision portion 46. This prevents excessive deformation of the first and second connecting legs 20 and 22, and avoids damage to the first and second connecting legs 20 and 22.

[0064] For example, when a large load is input due to the rapid acceleration of a vehicle, causing the inner shaft member 12 to be displaced significantly downward relative to the outer cylindrical member 14, the first connecting leg 20 is compressed between the upper and lower opposing surfaces of the inner shaft member 12 and the outer cylindrical member 14. Since the amount of compression deformation of the first connecting leg 20 in the motor mount 10 increases continuously, abrupt changes in spring characteristics are prevented compared to the case where a stopper is provided to limit the relative displacement between the inner shaft member 12 and the outer cylindrical member 14 by contact from a separated state. Therefore, shocks caused by abrupt changes in spring characteristics, such as when a stopper contacts, are avoided, and a good ride comfort is achieved. The motor mount 10 receives the support load of the electric motor when it is mounted on the vehicle, and for example, during rapid acceleration of the vehicle, the load due to the inertia of the electric motor and the support load of the electric motor are input to the motor mount 10 as a preload load.

[0065] The leg length L1 of the first connecting leg 20 is longer than the leg length L2 of the second connecting leg 22. This longer leg length of the first connecting leg 20 suppresses distortion in response to compression input in the leg length direction, and maintains linear dynamic spring characteristics in response to compression input up to a larger load range. Therefore, abrupt changes in the spring characteristics of the first connecting leg 20 due to preload input are less likely to occur, and good ride comfort is achieved through linear spring characteristics even with larger preload inputs.

[0066] The second connecting leg 22 undergoes tensile deformation when a preload load is applied, but the tension spring of the second connecting leg 22 has less impact on vibration damping performance compared to the compression spring of the first connecting leg 20. Therefore, by making the leg length L2 of the second connecting leg 22 shorter than the leg length L1 of the first connecting leg 20, the leg length L1 of the first connecting leg 20 can be increased while maintaining the outer diameter dimension of the outer cylindrical member 14 as defined by the mounting structure on the vehicle body side.

[0067] The inner shaft member 12 has an outer dimension Li in the vertical direction, which is the direction in which the preload load is applied, which is smaller than the outer dimension Wi in the horizontal direction, which is perpendicular to the direction in which the preload load is applied. This allows the distance between the opposing surfaces of the inner shaft member 12 and the outer cylindrical member 14 in the vertical direction to be increased without increasing the diameter of the outer cylindrical member 14, making it easier to set longer leg lengths for the first and second connecting legs 20 and 22. In addition, the larger outer dimension Wi in the horizontal direction of the inner shaft member 12 allows for a larger fixing area between the first and second connecting legs 20 and 22 and the inner shaft member 12.

[0068] The first connecting leg portion 20 extends circumferentially on both sides from the inner shaft member 12 side toward the outer cylindrical member 14 side, and the maximum circumferential width dimension W1 of the first connecting leg portion 20 is set to be within the range of 1.3 to 2 times the minimum circumferential width dimension w1. This makes it less likely for buckling-like deformation of the first connecting leg portion 20 to occur when a preload load is applied, and the linear spring characteristics can be maintained over a wider load range. In addition, by ensuring a large free surface area of ​​the first connecting leg portion 20 that is compressed when a preload load is applied, improvements in the durability of the first connecting leg portion 20 can be expected.

[0069] The first connecting leg portion 20 has a symmetrical shape on both sides in the circumferential direction (left-right direction) with respect to the center in the circumferential direction. As a result, when a preload load is applied, the first connecting leg portion 20 is less likely to tilt to one side in the circumferential direction, and the first connecting leg portion 20 is compressed stably.

[0070] Furthermore, when a large load is applied in the lateral direction, the gentle collision section 46 may come into contact from a separated state, potentially affecting vibration damping performance due to a sudden change in spring characteristics. However, since large loads in the lateral direction are applied under unusual driving conditions, such as when the vehicle makes a sharp turn, the impact on required performance such as ride comfort is unlikely to be a problem.

[0071] The excellent vibration damping performance of the motor mount 10 according to this embodiment can also be confirmed by the graph shown in Figure 5. Figure 5 is a graph showing the relationship between frequency and spring constant with respect to vertical input, and shows the measured results when a small load and a large load are input to the motor mount 10 according to this embodiment and when a small load and a large load are input to the motor mount as a comparative structure. The motor mount as a comparative structure has a structure in which four connecting legs are provided so as to extend in four diagonal directions that are inclined with respect to the vertical and left-right directions, and stopper rubber is provided between adjacent connecting legs in the circumferential direction. In addition, the motor mount as a comparative structure does not have vibration damping protrusions on the connecting legs. The motor mount 10 according to this embodiment and the motor mount as a comparative structure have the same static spring constant in the vertical direction.

[0072] According to the graph in Figure 5, the dashed and double-dotted lines in Figure 5, which show the spring characteristics of a motor mount as a comparative structure, show a sharp increase in the dynamic spring constant around 650 Hz. However, the solid and dashed lines in Figure 5, which show the spring characteristics of the motor mount 10 according to this embodiment, show that the increase in the dynamic spring constant around 650 Hz is suppressed. Thus, the damping action of the first and second vibration damping protrusions 30 and 38 effectively suppresses rubber surging, as confirmed by the measured results.

[0073] Furthermore, according to the dashed-dotted line graph in Figure 5, which shows the case where a large load is applied to the motor mount as a comparative structure, a sharp increase in the dynamic spring constant occurs around 850 Hz. However, according to the solid line graph in Figure 5, which shows the case where a large load is applied to the motor mount 10 according to this embodiment, the increase in the dynamic spring constant around 850 Hz is suppressed.

[0074] As can be seen from the measurement results in Figure 5, the motor mount 10 according to this embodiment suppresses changes in the dynamic spring constant compared to the motor mount of the comparative structure, and excellent vibration damping performance can be expected.

[0075] Furthermore, as can be seen from the graph in Figure 5, the difference in spring constants between low and high load input in the motor mount 10 according to this embodiment is smaller than the difference in spring constants between low and high load input in the motor mount as a comparative structure. This is because, in the motor mount as a comparative structure, a rapid increase in spring constant occurs due to the contact of the stopper rubber when a high load is applied, whereas in the motor mount 10 according to this embodiment, even when a high load is applied, the change in spring constant is due to the elastic deformation of the first and second connecting legs 20 and 22. Therefore, it is considered that the difference in spring constants between low and high load input in the motor mount 10 is relatively small. In this way, since the change in spring characteristics in response to changes in input load is suppressed in the motor mount 10 according to this embodiment, stable performance of the desired vibration damping performance can be expected.

[0076] This can be understood from the fact that the ratio of the spring constant k2 under heavy load input to the spring constant k1 under light load input in the motor mount 10 according to this embodiment (k2 / k1) is smaller than the ratio of the spring constant k2' under heavy load input to the spring constant k1' under light load input in the motor mount as a comparative structure (k2' / k1'). More specifically, in the measured results in Figure 5, the ratio of the average values ​​of the above spring constants in the frequency range of 100 to 1500 Hz was 1.17 for the motor mount 10 according to this embodiment and 1.96 for the motor mount as a comparative structure. Thus, the ratio of the average values ​​of the above spring constants in the frequency range of 100 to 1500 Hz is approximately 0.60 times for the motor mount 10 according to this embodiment compared to the motor mount as a comparative structure, and it has been confirmed by measurement that the change in the spring constant between light load input and heavy load input in the motor mount 10 according to this embodiment is smaller than that of the motor mount as a comparative structure.

[0077] Furthermore, in the initial spring region of 100-300 Hz, the spring characteristics can be understood by comparing the ratio of the spring constant under heavy load input to the spring constant under light load input. In this case, as shown in the measurement results in Figure 5, the ratio of the average values ​​of the spring constants in the frequency range of 100-300 Hz was 1.28 for the motor mount 10 according to this embodiment and 3.00 for the motor mount as a comparative structure. Thus, the initial spring characteristics of the motor mount 10 according to this embodiment, with the influence of resonance eliminated, are approximately 0.43 times that of the motor mount as a comparative structure. This confirms through measurements that the change in spring characteristics in response to differences in the magnitude of the input load in the motor mount 10 according to this embodiment is significantly suppressed compared to the motor mount as a comparative structure.

[0078] Furthermore, the ratio of the spring constant k2 under heavy load input to the spring constant k1 under light load input in the motor mount 10 (k2 / k1) is preferably 1.8 or less, and more preferably 1.5 or less, on average over the frequency range of 100 to 1500 Hz.

[0079] Although embodiments of the present invention have been described in detail above, the present invention is described in detail below. It is not limited to this. For example, in the first embodiment, an inner shaft member 12 with a substantially octagonal cross-section was exemplified, but the inner shaft member can have various cross-sectional shapes, such as a circular cross-section, an oval cross-section, a polygonal cross-section other than an octagon, or an irregularly shaped cross-section. However, it is desirable that the outer dimensions of the inner shaft member in the direction of input of the preload load are smaller than the outer dimensions in the direction perpendicular to the axis, which is perpendicular to the direction of input of the preload load.

[0080] The first and second connecting legs are preferably shaped to expand circumferentially toward the outer circumference (outer cylindrical member side), but for example, they may extend with a substantially constant circumferential width, or the circumferential width dimension may decrease toward the outer circumference.

[0081] The vibration-damping protrusions may be provided on at least one of the first and second connecting legs 20 and 22. Furthermore, the vibration-damping protrusions may be provided on only one of the axial surfaces of the connecting legs. In addition, multiple vibration-damping protrusions may be provided on one axial surface of a connecting leg, and different numbers of vibration-damping protrusions may be provided on the axial surfaces of one connecting leg, or five or more vibration-damping protrusions may be provided on the first and second connecting legs.

[0082] Furthermore, when vibration-damping protrusions are provided on both the first and second connecting legs 20 and 22, the first vibration-damping protrusion 30 provided on the first connecting leg 20 and the second vibration-damping protrusion 38 provided on the second connecting leg 22 may differ from each other in shape, size, number, arrangement, etc.

[0083] Furthermore, the specific shape of the vibration-damping protrusion is not particularly limited. For example, it may be a plate-like shape that extends in a straight shape in the left-right direction without curving in the circumferential direction, or it may be a spot-like protrusion such as a columnar or weight-like shape.

[0084] In the first embodiment, first and second vibration-damping protrusions 30 and 38 were shown as having an overall tapered shape. However, the vibration-damping protrusions may be partially tapered. For example, the base portion may have a tapered shape as shown in the first embodiment, while the tip portion may have a substantially constant radial thickness. To effectively obtain the effects of setting a tapered shape for the vibration-damping protrusion as in the first embodiment, it is desirable to set a tapered shape at least for the base portion, which is the connection side with the connecting leg. The vibration-damping protrusion may also have a tapered shape in which the outer peripheral surface inclins inward toward the protruding tip. In this case, it is desirable that the angle of inclination of the outer peripheral surface with respect to the axial direction is smaller than the angle of inclination of the inner peripheral surface with respect to the axial direction. The vibration-damping protrusion is not limited to a tapered shape, and may have a substantially constant radial thickness throughout.

[0085] In the first embodiment, the left-right width dimensions of the ends of the first connecting leg 20 and the second connecting leg 22 are approximately the same, and the left-right width dimensions of the ends of the ends of the outer cylindrical member 14 are set by the difference in length. However, for example, the left-right width dimensions of the first connecting leg 20 and the second connecting leg 22 can be actively made different. Specifically, for example, the left-right width dimension of the second connecting leg, on which the preload load acts in tension, may be sufficiently smaller over the entire length direction of the leg compared to the left-right width dimension of the first connecting leg, on which the preload load acts in compression. [Explanation of Symbols]

[0086] 10. Motor Mount (Cylindrical Vibration Isolator for Motor Mount - First Embodiment) 12 Inner shaft member 14 Outer cylindrical member 16 Main body rubber elastic body 18 bolt insertion holes 20 First connecting leg 22 Second connecting leg 24 Inner fixation part 26 Outside fixation part 28 First surface (surface of the first connecting leg) 30 First vibration damping protrusion (vibration damping protrusion) 32 First inner surface (inner surface) 34 First outer circumferential side (outer circumferential side) 36. Second surface (surface of the second connecting leg) 38 Second vibration damping protrusion (vibration damping protrusion) 40 Second inner surface (inner surface) 42 Second outer peripheral side (outer peripheral side) 44 slit holes 46 Slow collision part Li Inner shaft member's vertical outer dimensions Wi Inner shaft member outer dimensions in the left-right direction W1 Maximum circumferential width dimension on the inner shaft member side of the first connecting leg portion w1 Minimum circumferential width dimension on the inner shaft member side of the first connecting leg portion α is the inclination angle of the first inner surface relative to the axial direction. C1 Elastic principal axis in the protruding direction of the first vibration damping projection θ1 Inclination angle of the first inner surface relative to the first surface H1 Axial distance between the first inner surface surfaces h1 Axial distance between the first outer perimeter sides W2 Maximum circumferential width dimension on the inner shaft member side of the second connecting leg w2 Minimum circumferential width dimension on the inner shaft member side of the second connecting leg β The inclination angle of the second inner surface relative to the axial direction. C2 Elastic principal axis in the protruding direction of the second vibration damping projection θ2: Inclination angle of the second inner surface relative to the second surface. H2 Axial distance between the second inner surface surfaces h2 Axial distance between the second outer perimeter sides L1 Leg length of the first connecting leg L2 Leg length of the second connecting leg

Claims

1. A cylindrical vibration damping device for motor mounting, in which an inner shaft member and an outer cylindrical member are connected by a main body rubber elastic material, The main body rubber elastic body has a first connecting leg and a second connecting leg that are arranged on either side of the inner shaft member in one direction perpendicular to the axis, which is the direction in which the preload load is input. The first connecting leg, located on the compression side due to the input of the preload load, has a longer leg length perpendicular to the axis than the second connecting leg, which is located on the tension side. The resonant frequencies of the first connecting leg and the second connecting leg are made different from each other in response to the input of a vibration load in the same direction as the preload load. A cylindrical vibration isolation device for a motor mount, wherein at least one of the first connecting leg and the second connecting leg is provided with a vibration-damping projection that protrudes from the surface in the intermediate portion in the leg length direction.

2. The cylindrical vibration damping device for a motor mount according to claim 1, wherein the outer dimension of the inner shaft member in the direction of input of the preload load is smaller than the outer dimension in the direction perpendicular to the axis and perpendicular to the direction of input of the preload load.

3. On both sides of the inner shaft member, perpendicular to the direction perpendicular to the input direction of the preload load, are provided with slit holes. The cylindrical vibration damping device for motor mounting according to claim 1 or 2, wherein the groove is provided with a gentle impact portion that protrudes from one side of the inner shaft member and the outer cylindrical member toward the other side.

4. The cylindrical vibration damping device for motor mounting according to claim 1 or 2, wherein at least one of the first connecting leg and the second connecting leg has a vibration damping projection that is curved and extends in the circumferential direction.

5. The cylindrical vibration damping device for motor mounting according to claim 1 or 2, wherein the first connecting leg and the second connecting leg, including the vibration damping protrusion, are symmetrically shaped on both sides in the circumferential direction.

6. The cylindrical vibration damping device for a motor mount according to claim 1 or 2, wherein the ratio of the static spring constant in the input direction of the preload load and in the direction perpendicular to the axis perpendicular thereto is within the range of 1.5 to 3.

5.

7. The first connecting leg portion extends circumferentially on both sides from the inner shaft member side toward the outer cylindrical member side. A cylindrical vibration damping device for motor mounting according to claim 1 or 2, wherein the maximum circumferential width dimension on the outer cylindrical member side of the first connecting leg is within the range of 1.3 to 2 times the minimum circumferential width dimension on the inner shaft member side.

8. The vibration damping projection has a tapered cross-sectional shape that gradually thins radially from the base end to the tip of the projection, and the inclination angle of the inner circumferential surface with respect to the axial direction is greater than the inclination angle of the outer circumferential surface with respect to the axial direction, as described in claim 1 or 2.

9. A cylindrical vibration damping device for motor mounting, in which an inner shaft member and an outer cylindrical member are connected by a main body rubber elastic material, The main body rubber elastic body is provided with a plurality of connecting legs that extend in a direction perpendicular to the axis and connect the inner shaft member and the outer cylindrical member. At least one of the connecting legs is provided with a vibration-damping projection that protrudes from the surface in the middle portion in the leg length direction. The vibration damping projection has a tapered cross-sectional shape, gradually becoming thinner radially from the base end to the tip of the projection, and the inclination angle of the inner circumferential surface with respect to the axial direction is greater than the inclination angle of the outer circumferential surface with respect to the axial direction, in a cylindrical vibration damping device for motor mounting.

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