JP2011007257A - Vibration absorbing bush - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve both low dynamic spring characteristics with respect to high frequency vibration in a twisting direction and high attenuation characteristics with respect to low frequency vibration in an axially orthogonal direction, while preventing slipping off of polyurethane foam.SOLUTION: A pair of first elastic connection parts 20 opposed to a first axially orthogonal direction Y1 is disposed to a rubber elastic body 16 interposed between an inner tube 12 and an outer tube 14. A pair of hollow parts 22 formed by penetrating in an axial direction at circumferential positions excluding the first elastic connection parts 20, and a pair of second elastic connection parts 30 made from polyurethane foam are disposed in a second axially orthogonal direction Y2 perpendicular to the first axially orthogonal direction Y1. The second elastic connection parts 30 are subjected to foam molding in a state where they are adhered to inner peripheral faces and outer peripheral faces of the hollow parts 22, after vulcanizing molding of the elastic body 16.

Description

  The present invention relates to an anti-vibration bush that is suitably used for a connection portion between a vibration source and a vehicle body in a vehicle such as an automobile.

  In general, the anti-vibration bush is used for the purpose of vibration damping, buffering, etc. at a connection part between a vibration source such as a wheel or an engine and the vehicle body, and the inner cylinder and the outer cylinder are made of a rubber elastic body. Combined with In such an anti-vibration bushing, for example, as used in an automobile suspension arm, it is required to have both a low dynamic spring characteristic for high frequency vibration in the torsional direction and a high damping characteristic for low frequency vibration in the direction perpendicular to the axis. There is. In order to satisfy such a requirement, a vibration isolating bush having a liquid enclosure is sometimes used. However, a liquid seal type vibration isolating bush is expensive to manufacture and is difficult to reduce in weight. Therefore, it is required to exhibit the above characteristics, particularly high attenuation characteristics, while reducing the cost and weight.

  By the way, in order to obtain a high damping characteristic that cannot be obtained with a rubber elastic body, a technique has been proposed in which a polyurethane foam having an open cell structure is incorporated in a part of a vibration-proof base made of a rubber elastic body. That is, the polyurethane foam can increase the damping performance while suppressing the dynamic magnification as compared with the rubber elastic body due to its material characteristics. Therefore, the polyurethane foam intends to use this characteristic. For example, in Patent Document 1 below, a housing portion is provided inside a vibration-isolating base made of a rubber elastic body, between a vibration-isolating base and an outer cylinder, or between a vibration-isolating base and an inner cylinder. It has been proposed to be filled with polyurethane foam. Further, in Patent Document 2 below, a rubber elastic portion is provided on the inner cylinder side, a stopper rubber portion is provided in the rubber elastic portion with a space portion facing the inner peripheral surface of the outer cylinder, and is made of polyurethane foam. It has been proposed that the elastic portion is provided so as to support the inner cylinder with respect to the outer cylinder on both sides in the circumferential direction of the stopper rubber portion. Although these structures can be reduced in cost and weight, it is highly possible to achieve both a low dynamic spring characteristic for high frequency vibration in the torsional direction and a high damping characteristic for low frequency vibration in the direction perpendicular to the axis. difficult.

  Further, in Patent Document 3 below, by inserting a polyurethane foam member into a straight portion formed in a rubber elastic body between the inner and outer cylinders, spring characteristics that cannot be obtained with rubber alone are exhibited and durability is improved. It is disclosed. However, in this configuration, the inserted polyurethane foam member may fall off, and in the insertion type, the polyurethane foam member may be displaced from the rubber member when the polyurethane foam member is compressed and deformed. May not be evenly crushed, and thus high attenuation characteristics may not be sufficiently exhibited.

Japanese Patent Laid-Open No. 06-017864 JP 2008-196611 A JP 2001-193776 A

  In view of the above points, the present invention can achieve both a low dynamic spring characteristic for high-frequency vibration in the torsional direction and a high damping characteristic for low-frequency vibration in the direction perpendicular to the axis while preventing the polyurethane foam from falling off. The object is to provide an anti-vibration bush.

  An anti-vibration bush according to the present invention includes a shaft member, an outer cylinder that surrounds the shaft member in an axis-parallel manner, and a rubber elastic body interposed between the shaft member and the outer cylinder, and the rubber elasticity The body includes a pair of first elastic connection portions that connect the shaft member and the outer cylinder at positions opposed to each other in a direction perpendicular to the first axis across the shaft member, and the pair of elastic connection portions A pair of straight portions penetrating in the axial direction is formed at circumferential positions except for the shaft member, and the pair of straight portions include the shaft member and the outer portion in a second axis perpendicular direction perpendicular to the first axis perpendicular direction. A pair of second elastic connecting portions made of polyurethane foam are provided so as to connect between the cylinders and to secure a space portion penetrating in the axial direction between the first elastic connecting portions on both sides in the circumferential direction. The second elastic connecting portion is formed by vulcanizing the rubber elastic body. It is obtained foamed molded in a state of being adhered to the inner and outer circumferential surfaces of the hollow portion after.

  According to the present invention, the shaft member and the outer cylinder are connected by the pair of first elastic connection portions of the rubber elastic body having the above-described configuration and the pair of second elastic connection portions made of polyurethane foam. It is possible to achieve both a low dynamic spring characteristic for high frequency vibration in the direction and a high damping characteristic for low frequency vibration in the direction perpendicular to the axis. Moreover, since the 2nd elastic connection part which consists of polyurethane foams is adhesively integrated with the rubber elastic body by foam molding, dropping of the polyurethane foam can be prevented.

The front view of the vibration proof bush concerning one embodiment of the present invention II-II sectional view of FIG. Partially enlarged sectional view of the anti-vibration bush Top view of the lower arm link of the front suspension Sectional view in the manufacturing process of the anti-vibration bush

  Hereinafter, an anti-vibration bush 10 according to an embodiment of the present invention will be described with reference to the drawings.

  This anti-vibration bush 10 is a bush used as the rear bush 10 in the lower arm link 1 of the front suspension shown in FIG.

  In the lower arm link 1 shown in FIG. 4, the front and rear vibration isolating bushes 4 and 10 are used for vibration isolating the ball joint 3 on the wheel 2 side and the cross member on the vehicle body side. The arm link 1 includes a ball joint 3 attached to one end of an arm portion 5 extending in the vehicle width direction, and a front bush mounting portion 6 to which a front bush 4 is mounted on the other end, and is branched from the arm portion 5. A rear bush mounting portion 8 to which the rear bush 10 is mounted is provided at the tip of the branch arm 7 extending rearward of the vehicle. The front and rear anti-vibration bushes 4 and 10 are both arranged with the axial direction facing the vehicle front-rear direction.

  As shown in FIGS. 1 and 2, the anti-vibration bush 10 includes an inner cylinder 12 as a shaft member, an outer cylinder 14 that surrounds the inner cylinder 12 in an axially parallel manner, and an inner cylinder 12 and an outer cylinder 14. And a rubber elastic body 16 made of vulcanized rubber such as natural rubber.

  The inner cylinder 12 is a cylindrical metal fitting having an outward flange portion 18 at one end portion in the axial direction X. The outer cylinder 14 is a cylindrical metal fitting that is coaxial with the inner cylinder 12, that is, has a common axis O, and has a smaller dimension in the axial direction X than the inner cylinder 14.

  The rubber elastic body 16 has a pair of upper and lower first connecting the inner cylinder 12 and the outer cylinder 14 at a position facing the first axis perpendicular direction Y1 (vertical direction in FIG. 1) across the inner cylinder 12. The elastic connection parts 20 and 20 are provided. Here, the axis-perpendicular direction is a direction perpendicular to the axis direction X (that is, the same as the radial direction), and one of the directions (vertical direction in FIG. 1) is defined as a first axis-perpendicular direction Y1. The first elastic connecting portion 20 is vulcanized and connected to the outer peripheral surface of the inner cylinder 12 and the inner peripheral surface of the outer cylinder 14 to connect the two.

  The rubber elastic body 16 is provided with a pair of left and right straight portions 22, 22 penetrating in the axial direction X at circumferential positions excluding the pair of first elastic coupling portions 20, 20. Specifically, the rubber elastic body 16 includes a cylindrical inner rubber layer 24 that covers the entire outer circumference of the inner cylinder 12 and substantially the entire axial direction X, and an inner circumference of the outer cylinder 14 over the entire circumference. And a cylindrical outer rubber layer 26 covering the entire axial direction X, and a pair of upper and lower first elastic connecting portions 20 between the inner rubber layer 24 and the outer rubber layer 26 in the first axially perpendicular direction Y1. 20 and a pair of right and left straight portions 22 extending in an arc shape in the circumferential direction C are formed between the inner rubber layer 24 and the outer rubber layer 26 in the other circumferential portion. The thickness of the inner rubber layer 24 is set to be equal to the protruding height of the flange portion 18. On the other hand, the outer rubber layer 26 is formed as a thin film.

  The outer rubber layer 26 corresponding to the outer peripheral surface of the straight portion 22 is provided with a stopper protrusion 28 that protrudes toward the inner cylinder 12 side. The stopper protrusions 28 are provided at a pair of left and right circumferential positions facing each other across the inner cylinder 12 in a second axis perpendicular direction Y2 (left and right direction in FIG. 1) perpendicular to the first axis perpendicular direction Y1. Yes. The distal end surface (that is, the inner peripheral surface) of the stopper convex portion 28 is formed in a curved surface shape in which a cross-sectional shape orthogonal to the axis O is curved in an arc shape, and between the outer peripheral surfaces of the opposed inner rubber layers 24. A constant stopper clearance is secured in the circumferential direction C and the axial direction X.

  The pair of left and right corners 22 and 22 have an open cell structure so as to connect the inner cylinder 12 and the outer cylinder 14 at a position facing the second axis-perpendicular direction Y2 with the inner cylinder 12 interposed therebetween. A pair of left and right second elastic connecting portions 30, 30 made of a polyurethane foam is provided. Specifically, the second elastic connecting portion 30 is between the outer peripheral surface of the inner rubber layer 24 corresponding to the inner peripheral surface of the straight portion 22 and the inner peripheral surface of the outer rubber layer 26 corresponding to the outer peripheral surface of the straight portion 22. Therefore, both the inner cylinder 12 and the outer cylinder 14 are connected via these rubber layers 24 and 26.

  On both sides of the second elastic connecting portion 30 in the circumferential direction C, spaces 22A and 22A penetrating in the axial direction X with the first elastic connecting portion 20 are provided. The space portion 22A constitutes both end portions in the circumferential direction C of the straight portion 22, that is, the second elastic connecting portion 30 secures the space portion 22A at both ends in the circumferential direction C of the straight portion 22. , And is formed so as to fill the straight portion 22 with a circumferential portion therebetween.

  The formation width in the circumferential direction C of the second elastic coupling portion 30 is set to be larger than the formation width in the circumferential direction C of the first elastic coupling portion 20. In this example, the second elastic coupling portion 30 is arranged in the circumferential direction C. The first elastic connecting portion 20 is formed in the range of about 40 ° in the circumferential direction C, and the former is set to be about twice as wide as the latter. Yes.

  As shown in FIG. 2, the second elastic connecting portion 30 is formed so that the stopper convex portion 28 of the outer rubber layer 26 is embedded, and thus the stopper convex portion 28 is not exposed to the outside.

  The second elastic connecting portion 30 is foam-molded in a state where it is bonded to the inner peripheral surface and the outer peripheral surface of the straight portion 22 after the rubber elastic body 16 is vulcanized. A polyurethane foam raw material is foam-filled between the outer peripheral surface.

  Specifically, in this example, after the rubber elastic body 16 is vulcanized and molded between the inner cylinder 12 and the outer cylinder 14, the vulcanized molded body is set in a foam mold 50 as shown in FIG. The second elastic connecting portion 30 is foam-molded, and then the outer cylinder 14 is drawn in the diameter-reducing direction so that the rubber elastic body 16 (specifically, the first elastic connecting portion 20) and the second elastic connecting portion 30 are reserved. Give compression. The foaming mold 50 includes a first mold 52 and a second mold 54 that can be divided in the axial direction X, and a cavity 56 for molding the second elastic connecting portion 30 is formed by matching the molds. Is done. By injecting the polyurethane foam material into the cavity 56 and filling it with foam, the second elastic connecting portion 30 made of polyurethane foam having an open-cell structure is integrally foam-molded with the vulcanized molded body. Thereby, the second elastic connecting portion 30 is bonded to the outer peripheral surface of the inner rubber layer 24 on the inner peripheral side thereof, and is bonded to the inner peripheral surface of the outer rubber layer 26 on the outer peripheral side thereof.

  As shown in FIG. 3, the outer peripheral surface of the inner rubber layer 24 that is the inner peripheral surface of the straight portion 22 and the inner peripheral surface of the outer rubber layer 26 that is the outer peripheral surface of the straight portion 22 (in this example, the stopper convex portion 28 In order to improve the adhesiveness of the second elastic connecting portion 30 to the rubber elastic body 16, a plurality of minute protrusions 32 and 34 are provided on the tip end surface of the rubber elastic body 16. In order to prevent the second elastic coupling part 30 from coming off in the axial direction X, the microprotrusions 32 and 34 form a protrusion extending in the circumferential direction C, and a plurality of the microprotrusions 32 and 34 are provided in the axial direction X at regular intervals. The heights of the minute protrusions 32 and 34 are set to such a minute protrusion height that a mold part (not shown) for forming the straight part 22 can be removed in the axial direction X when the rubber elastic body 16 is vulcanized. Yes.

  The anti-vibration bush 10 having the above structure is attached to the lower arm link 1 of the front suspension shown in FIG. 4 by pressing the outer cylinder 14 into the cylindrical holder of the rear bush mounting portion 8, and is not attached to the inner cylinder 12. The mounting shaft of the cross member on the vehicle body side shown in the figure is inserted and fixed so that the axial direction X is assembled in the vehicle front-rear direction.

  The assembled anti-vibration bush 10 receives an input in the torsional direction (rotation direction) when the wheel 2 is displaced in the vertical direction, and receives an input in the vehicle width direction when the wheel 2 is displaced in the front-rear direction. Input direction. Therefore, the anti-vibration bush 10 has the rear bush mounting portion so that the second elastic coupling portions 30 are opposed to each other in the vehicle width direction, that is, the vehicle width direction is the second axis perpendicular direction Y2. 8 is attached.

  The vibration isolating bush 10 exhibits low dynamic spring characteristics with respect to vibration input in a high frequency range in the torsional direction by the first elastic connecting portion 20 made of rubber having a lower dynamic spring constant than polyurethane foam. can do. On the other hand, for a vibration input in a low frequency range with a relatively large amplitude in the second axis-perpendicular direction Y2, the pair of left and right second elastic coupling portions 30, 30 made of polyurethane foam having a large loss factor are alternately compressed and deformed. By doing so, high damping performance can be exhibited. Therefore, the low elastic spring characteristic can be exhibited by the first elastic connecting portion 20 with respect to the vibration in the high frequency range with a small amplitude in the vertical direction of the wheel 2 and a relatively small amplitude in the longitudinal direction of the wheel 2. With respect to large vibrations in a low frequency range, the second elastic coupling portion 30 can exhibit high damping performance, and both can be highly compatible.

  In particular, the second elastic connecting part 30 made of polyurethane foam is integrally formed by post-foaming with respect to the rubber elastic body 16 and is not assembled by inserting a polyurethane foam member. It does not move, and therefore, each foam cell of the polyurethane foam is uniformly crushed during compression deformation, so that the high damping performance can be further enhanced. Also, the polyurethane foam member can be prevented from falling off.

  In addition, since the space 22A is secured between the first elastic coupling part 20 on both sides of the second elastic coupling part 30 and both are provided independently, the second axis in the second axis-perpendicular direction Y2 is provided. When the elastic connecting portion 30 is deformed, air is discharged and supplied also from both side surfaces in the circumferential direction C of the second elastic connecting portion 30, and the deformation can be performed smoothly. In this example, the space portion 22A is provided to reduce the width of the first elastic connecting portion 20, and more specifically, the first elastic connecting portion 20 is formed to be narrower than the diameter of the inner cylinder 12. When the vibration is input in the direction perpendicular to the axis Y2, the first elastic connecting part 20 is only subjected to shear deformation, and the spring constant becomes small. Therefore, the characteristics of the second elastic connecting part 30 become more dominant, and the high damping performance can be further improved. it can. Further, since the space 22A is secured on both sides of the second elastic connecting portion 30, there is also an advantage that the second elastic connecting portion 30 is easily foam-molded.

  In addition, since the plurality of minute protrusions 32 and 34 are provided on the inner peripheral surface and the outer peripheral surface of the straight portion 22A, the adhesion of the second elastic connecting portion 30 made of polyurethane foam to the rubber elastic body 16 can be improved. Dropout can be prevented more reliably. In addition, although it is preferable to provide such a microprotrusion on both the inner peripheral surface and the outer peripheral surface of the straight portion 22A, it may be provided on only one of them.

  Moreover, since the stopper convex part 28 which protrudes toward the inner cylinder 12 side in the outer peripheral surface of the straight part 22 is provided in the state embed | buried under the 2nd elastic connection part 30, it is very difficult in the 2nd axis orthogonal direction Y2. When the stopper convex portion 28 comes into contact with the inner peripheral surface of the straight portion 22, the further bending deformation can be restricted.

  In the present embodiment, since the outer cylinder 14 is drawn after the rubber elastic body 16 is vulcanized and the second elastic connecting portion 30 is foam-molded, Both the rubber of the first elastic connecting portion 20 and the polyurethane worm of the second elastic connecting portion 30 can be pre-compressed, and the durability of the rubber and the polyurethane foam can be improved.

  In addition, the anti-vibration bush 10 of the present embodiment does not provide a liquid sealing chamber in order to obtain the above characteristics, and thus can be reduced in cost and weight. In addition, the liquid-sealed type anti-vibration bush exhibits a damping performance only in a specific frequency range set by the orifice, while a polyurethane foam is used as in this embodiment, a wide frequency range. Can exhibit high damping performance, which is also advantageous in this respect.

  In addition, the said embodiment is only what showed the preferable 1 aspect of this invention, and this invention is not limited by this. For example, in the above embodiment, the stopper convex portion is provided on the outer rubber layer, but it may be provided on the inner rubber layer, or the stopper convex portion itself may be omitted. Moreover, although the said embodiment demonstrated the anti-vibration bush used for the suspension arm of a motor vehicle, this invention is not limited to this, The connection part of the vibration source and vehicle body of various vehicles including a motor vehicle etc. It can be applied to various anti-vibration bushes used in In addition, various modifications can be made without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 10 ... Anti-vibration bush, 12 ... Inner cylinder, 14 ... Outer cylinder, 16 ... Rubber elastic body 20 ... 1st elastic connection part, 22 ... Straight part, 22A ... Space part 28 ... Stopper convex part, 30 ... 2nd elastic connection Portions 32, 34 ... minute projection C ... circumferential direction, X ... axial direction, Y1 ... first axis perpendicular direction, Y2 ... second axis perpendicular direction

Claims (3)

A shaft member;
An outer cylinder surrounding the shaft member in parallel to the axis;
A rubber elastic body interposed between the shaft member and the outer cylinder,
The rubber elastic body includes a pair of first elastic connection portions that connect the shaft member and the outer cylinder at positions facing each other in a direction perpendicular to the first axis across the shaft member. A pair of straight portions penetrating in the axial direction at a circumferential position excluding the elastic connecting portion is formed,
The pair of straight portions connect the shaft member and the outer cylinder in a second axis perpendicular direction perpendicular to the first axis orthogonal direction, and the first elastic connection on both sides in the circumferential direction. A pair of second elastic connecting portions made of polyurethane foam is provided so as to ensure a space portion penetrating in the axial direction between the two portions, and the second elastic connecting portions are formed after the rubber elastic body is vulcanized and molded. An anti-vibration bush characterized by being foam-molded in a state of being bonded to the inner peripheral surface and the outer peripheral surface of the straight part.   2. The prevention according to claim 1, wherein at least one of an inner peripheral surface and an outer peripheral surface of the straight portion is provided with a plurality of minute protrusions that enhance adhesion of the second elastic connecting portion to the rubber elastic body. Swing bush.   The anti-vibration device according to claim 1 or 2, wherein a stopper convex portion projecting toward the shaft member side is provided on the outer peripheral surface of the straight portion so as to be embedded in the second elastic coupling portion. bush.

Images