Bush and manufacturing method therefor

Abstract

The present invention provides: a bush with which it is possible to enhance a friction force with a member to be fastened, while suppressing intrusion of water into the inside; and a manufacturing method therefor.　A bush 1 includes: an outer cylinder 11; an inner cylinder 12 disposed in a hollow part of the outer cylinder 11; and an elastic body 13 interposed between the outer cylinder 11 and the inner cylinder 12 and connecting the outer cylinder 11 and the inner cylinder 12. End surface parts 12A, 12B of the inner cylinder 12 in the axial direction are each provided with an uneven part 21 in which a plurality of protrusions 211 and grooves 212 are alternately continuous and a flat part 22 in which a surface 220 is flat. The flat part 22 is positioned on an outer peripheral side of the uneven part 21, and the plurality of protrusions 211 protrude more than the position of the surface 220 of the flat part 22.

Description

Bush and manufacturing method thereof

[0001] The present invention relates to a bushing and a method for manufacturing the same.

[0002] Generally, when fastening a bushing to a fastened member such as a bracket, it is often tightened with a bolt. For example, when using a bushing in a vehicle suspension, the friction force between the end face of the bushing's inner tube and the fastening surface of the fastened member must be greater than the input load to prevent the bushing from slipping due to the input load to the suspension.

[0003] For example, Patent Document 1 discloses a bushing that includes a cylindrical mounting bracket (inner tube) for attachment to a mating member or other member that serves as a fastened member, and rubber that is vulcanized and bonded to the outer peripheral surface of the mounting bracket, with serrations formed on the surface of the mounting bracket that abuts against the mating member or other member, and a wall portion that rises up to cover the valleys of the serrations on the rubber bonding surface side adjacent to the serrations on the abutment surface.

[0004] In this bushing, the wall portion is formed to rise to the same height as the peaks of the serrations, and by tightly adhering the wall portion and serrations to the mating member, it is possible to prevent the mounting hardware from becoming loose due to vibrations, etc., and it is also possible to prevent water from entering the bushing, thereby preventing rust.

[0005] Japanese Patent Application Publication No. 11-22770

[0006] However, in the bushing described in Patent Document 1, the serration peaks are formed at the same height as the wall, and therefore cannot sufficiently bite into the mating member, etc. In particular, when this bushing is used in an electrically driven vehicle, which is heavier than conventional vehicles driven by internal combustion engines and which also has a greater input load to the suspension, there is a possibility that the frictional force between the contact surface of the mounting bracket and the mating member, etc. will be insufficient, resulting in slippage of the bushing.

[0007] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a bushing that is capable of increasing the frictional force with fastened members while suppressing the intrusion of water into the bushing, and a method for manufacturing the bushing.

[0008] In order to achieve the above object, the present invention provides a bushing comprising an outer tube, an inner tube disposed within the hollow portion of the outer tube, and an elastic body interposed between the outer tube and the inner tube to connect the outer tube and the inner tube, wherein the axial end face of the inner tube is provided with an uneven portion having a plurality of alternating successive protrusions and grooves, and a flat portion having a flat surface, the flat portion being located on the outer periphery of the uneven portion, and the plurality of protrusions protruding beyond the surface position of the flat portion.

[0009] According to the present invention, it is possible to increase the frictional force between the fastened members and the fastening members while suppressing the intrusion of water into the inside. Problems, configurations, and effects other than those described above will become clear from the following description of the embodiment.

[0010] 1 is a diagram showing an attached state of a bushing according to an embodiment of the present invention; FIG. 2 is an axial cross-sectional view showing one configuration example of a bushing; FIG. 3 is an enlarged view showing an X portion in FIG. 2; FIG. 4 is an enlarged view showing an inner cylinder as viewed from the Y arrow direction in FIG. 2; FIG. 5 is an enlarged view showing an Z portion in FIG. 1; FIG. 6 is a diagram showing a state in which the inner cylinder is set in a rubber molding die; FIG. 7 is a plan view of an inner cylinder according to a first modified example of the present invention as viewed from the Y arrow direction in FIG. 2; FIG. 8 is a plan view of an inner cylinder according to a second modified example of the present invention as viewed from the Y arrow direction in FIG. 2; FIG. 9 is a plan view of an inner cylinder according to a third modified example of the present invention as viewed from the Y arrow direction in FIG. 2;

[0011] Hereinafter, as one aspect of a bush according to an embodiment of the present invention, a bush for a vehicle used for connecting a vibrating member in a vehicle suspension or the like will be described as an example.

[0012] <Overall Configuration of Bush 1> First, the overall configuration of the bush 1 will be described with reference to FIGS. 1 and 2. FIG.

[0013] Fig. 1 is a view showing an attached state of a bushing 1 according to an embodiment of the present invention, and Fig. 2 is an axial cross-sectional view showing an example of the configuration of the bushing 1.

[0014] The bushing 1 includes an outer cylinder 11, an inner cylinder 12 disposed within the hollow portion of the outer cylinder 11, and an elastic body 13 interposed between the outer cylinder 11 and the inner cylinder 12 to connect the outer cylinder 11 and the inner cylinder 12. In this embodiment, the outer cylinder 11 and the inner cylinder 12 are each formed from a cylindrical metal member. Note that the outer cylinder 11 and the inner cylinder 12 do not necessarily have to be cylindrical and may be, for example, rectangular. In other words, the cross sections of the outer cylinder 11 and the inner cylinder 12 when cut in the axial direction or the radial direction do not necessarily have to be circular and may be polygonal, for example.

[0015] The hollow portion of the inner cylinder 12 forms a bolt hole 120 through which the bolt 2 is inserted. As shown in Fig. 1, the bolt 2 is inserted from one end side of the bolt hole 120 and fastened to a nut 3 arranged on the other end side.

[0016] Furthermore, the inner cylinder 12 has end face portions 12A, 12B on both axial ends that extend outward more than the outer cylinder 11. In the following description, the end face portion 12A on one end side of the bolt hole 120 will be referred to as the "one end face portion 12A," and the end face portion 12B on the other end side of the bolt hole 120 in which the nut 3 is disposed will be referred to as the "other end face portion 12B."

[0017] 1, when the bolt 2 is fastened to the nut 3, a fastened member 4 is sandwiched between one end surface 12A of the inner cylinder 12 and the bolt 2, and between the other end surface 12B of the inner cylinder 12 and the nut 3. At this time, the one end surface 12A and the other end surface 12B are each pressed firmly against the fastened member 4 (also referred to as an abutting state or a pressure-welded state) by the axial force of the bolt 2. The fastened member 4 is, for example, a bracket on the vehicle body side or a bracket on the tire side.

[0018] 1, the bushing 1 is attached, for example by press fitting, to the tip of a link member 5 of a vehicle suspension, connecting the fastened member 4 and the link member 5, and absorbing vibrations generated in the fastened member 4 and the link member 5 with an elastic body 13. In this embodiment, the elastic body 13 is made of a rubber material. Note that the elastic body 13 does not necessarily have to be a rubber material, and can be made of any material that can absorb vibrations.

[0019] <Configuration of End Surface Portions 12A, 12B> Next, the configuration of the end surface portions 12A, 12B of the inner cylinder 12 will be described with reference to Figures 3 to 6. Note that, since one end surface portion 12A and the other end surface portion 12B have the same configuration, the following description will be given using one end surface portion 12A as an example, and a description of the other end surface portion 12B will be omitted.

[0020] Fig. 3 is an enlarged view showing the X portion in Fig. 2. Fig. 4 is a plan view of the inner cylinder 12 as seen from the direction of the Y arrow in Fig. 2.

[0021] As shown in FIG. 3, one end surface 12A of the inner cylinder 12 is provided with an uneven portion 21 in which protrusions 211 and grooves 212 are alternately arranged in succession, and a flat portion 22 in which the surface 220 is flat.

[0022] The tip positions of the multiple protrusions 211 of the uneven portion 21 protrude higher than the surface 220 of the flat portion 22. In this embodiment, the multiple protrusions 211 have non-uniform heights H (shown in FIG. 3 ) from the surface 220 of the flat portion 22. The height H of the protrusions 211 is, for example, about 0.1 to 0.2 mm.

[0023] In this embodiment, the protrusions 211 and the grooves 212 are formed concentrically with the inner tube 12 and alternately arranged in the radial direction of the one end surface portion 12A, as shown in Fig. 4. In Fig. 4, the uneven portion 21 is shown as sand. Note that the protrusions 211 and the grooves 212 do not necessarily have to be formed concentrically with the inner tube 12, and may be formed in a spiral or vortex shape, for example. It is preferable that the protrusions 211 and the grooves 212 extend at least in the circumferential direction of the inner tube 12.

[0024] The uneven portion 21 is formed by, for example, laser processing. Specifically, a laser is scanned concentrically with the inner cylinder 12 at a pitch of, for example, about 0.05 mm on one end surface portion 12A of the inner cylinder 12, thereby forming a plurality of grooves 212 in the radial direction. At this time, metal melted by the heat of the laser rises on both sides of the grooves 212, forming protrusions 211.

[0025] Note that the raised portions are not formed uniformly (in the same shape), and as described above, the heights of the plurality of protrusions 211 are not uniform. In other words, by using laser processing to form the uneven portion 21, the plurality of protrusions 211 can be easily formed in random shapes.

[0026] Furthermore, unlike processes that use molds or shot blasting, for example, laser processing does not require large equipment, and there are no manufacturing process restrictions such as the need to perform the process within a predetermined process, making it highly convenient and allowing the uneven portion 21 to be formed easily.

[0027] 3 and 4 , the flat portion 22 is a region that has not been subjected to laser processing (laser unprocessed region) and is located on the outer circumferential side of the uneven portion 21. In this embodiment, the flat portion 22 is provided concentrically with the inner tube 12 on one end surface portion 12A, similar to the uneven portion 21. The radial width of the flat portion 22 is set smaller than the radial width of the uneven portion 21.

[0028] Fig. 5 is an enlarged view showing a portion Z in Fig. 1. Fig. 6 is a view showing a state in which the inner cylinder 12 is set in the rubber molding die α.

[0029] 5, when the bolt 2 is fastened to the nut 3, one end surface 12A of the inner tube 12 is pressed against the fastened member 4. At this time, the flat portion 22 located on the outer periphery of the uneven portion 21 has its surface 220 in close contact with the fastened member 4. This makes it possible to prevent water from entering from the outside to the inside of the inner tube 12, and prevents rust from forming on the inner tube 12.

[0030] Furthermore, because the multiple protrusions 211 of the uneven portion 21 protrude higher than the position of the surface 220 of the flat portion 22, when the one end surface portion 12A is pressed against the fastened member 4, the biting force of the multiple protrusions 211 into the fastened member 4 is greater than the biting force of the flat portion 22 into the fastened member 4. As a result, the frictional force between the one end surface portion 12A of the inner tube 12 and the fastened member 4 is higher than when the tip positions of the multiple protrusions 211 are the same as the position of the surface 220 of the flat portion 22, and slippage of the bushing 1 can be prevented even when the input load to the suspension is large.

[0031] In this embodiment, the extension direction of the protrusions 211 and grooves 212 is the circumferential direction of the inner tube 12, which is a direction that intersects the sliding direction of the bushing 1 (the extension direction of the suspension link member 5).Therefore, the friction force between one end surface portion 12A of the inner tube 12 and the fastened member 4 can be increased compared to when the extension direction of the multiple protrusions 211 and multiple grooves 212 is the radial direction of the inner tube 12.

[0032] Furthermore, in this embodiment, the protrusion 211 and the groove 212 are formed concentrically with the inner tube 12, so that the frictional force between the one end surface portion 12A of the inner tube 12 and the fastened member 4 can be maintained regardless of the mounting direction of the inner tube 12 relative to the suspension link member 5.

[0033] Furthermore, as shown in Figure 6, when rubber as the elastic body 13 is vulcanized and bonded to the outer peripheral surface of the inner tube 12, when the inner tube 12 is set in the rubber molding mold α, the surface 220 of the flat portion 22 of the inner tube 12 adheres closely to the inner surface of the rubber molding mold α, so that the rubber flowing in the direction of the arrow shown in Figure 6 can be prevented from spilling out inside the inner tube 12.

[0034] <Modification> Next, a bushing 1 according to a modification of the present invention will be described with reference to Figures 7 to 9. Note that components in the modification that are common to those described in the above embodiment will be assigned the same reference numerals and descriptions thereof will be omitted.

[0035] Fig. 7 is a plan view of the inner cylinder 12 according to the first modified example of the present invention, as seen from the direction of the arrow Y in Fig. 2. In Fig. 7, the uneven portion 21 is shown as sand, as in Fig. 4.

[0036] One end surface portion 12A of the inner cylinder 12 according to the first modification is further provided with a flat portion 22A on the inner peripheral side of the uneven portion 21. If the flat portion 22 located on the outer peripheral side of the uneven portion 21 is referred to as the "first flat portion 22" and the flat portion 22 located on the inner peripheral side of the uneven portion 21 is referred to as the "second flat portion 22A," the first flat portion 22 and the second flat portion 22A are positioned so as to sandwich the uneven portion 21 in the radial direction of the inner cylinder 12.

[0037] In this way, by providing the second flat portion 22A on the inner side of the uneven portion 21 on the one end surface portion 12A, when the one end surface portion 12A of the inner tube 12 is pressed against the fastened member 4, the surface 220 of the second flat portion 22A is in close contact with the fastened member 4, thereby also preventing water from entering from inside the inner tube 12.

[0038] Fig. 8 is a plan view of the inner cylinder 12 according to the second modified example of the present invention, as seen from the direction of the arrow Y in Fig. 2. In Fig. 8, the uneven portion 21 is shown as sand, as in Fig. 4.

[0039] A plurality of uneven portions 21 are provided at predetermined intervals along the circumferential direction of the inner cylinder 12 on one end surface portion 12A of the inner cylinder 12 according to the second modification. In Fig. 8, four uneven portions 21 (first to fourth uneven portions 21A to 21D) are arranged at regular intervals along the circumferential direction of the inner cylinder 12.

[0040] Therefore, the flat portion 22B is formed on the outer and inner sides of the four uneven portions 21, as well as between adjacent uneven portions 21, specifically, between the first uneven portion 21A and the second uneven portion 21B, between the second uneven portion 21B and the third uneven portion 21C, between the third uneven portion 21C and the fourth uneven portion 21D, and between the fourth uneven portion 21D and the first uneven portion 21A.

[0041] In this way, by arranging multiple uneven portions 21 at a predetermined interval along the circumferential direction of the inner tube 12, the total area of ​​the multiple uneven portions 21 becomes smaller than the area of ​​the uneven portions 21 in the embodiment and variant example 1, and the laser processing time can be shortened.

[0042] In Figure 8, the four uneven portions 21 are the same size and are arranged at regular intervals along the circumferential direction of the inner tube 12, but this is not limited to this, and the sizes of each uneven portion 21 may be different, and the distance between adjacent uneven portions 21 may not be constant.

[0043] Fig. 9 is a plan view of the inner cylinder 12 according to the third modified example of the present invention, as seen from the direction of the arrow Y in Fig. 2. In Fig. 9, the uneven portion 21 is shown as sand, as in Fig. 4.

[0044] One end surface portion 12A of the inner tube 12 according to the second modification has a plurality of uneven portions 21 formed concentrically with the inner tube 12 and spaced apart at predetermined intervals along the radial direction of the inner tube 12. In Fig. 9, two uneven portions 21 (a fifth uneven portion 21E and a sixth uneven portion 21F) are lined up along the radial direction of the inner tube 12. Of the two uneven portions 21, the uneven portion 21 located on the outer periphery side is referred to as the "fifth uneven portion 21E," and the uneven portion 21 located on the inner periphery side is referred to as the "sixth uneven portion 21F."

[0045] Therefore, on one end surface portion 12A of the inner cylinder 12 according to Modification 2, a first flat portion 22 is formed on the outer circumferential side of the fifth uneven portion 21E, a third flat portion 22C is formed between the fifth uneven portion 21E and the sixth uneven portion 21F, and a fourth flat portion 22D is formed on the inner circumferential side of the sixth uneven portion 21F. Note that the distance between the fifth uneven portion 21E and the sixth uneven portion 21F, i.e., the radial width dimension of the third flat portion 22C, is, for example, about 0.5 mm.

[0046] In this way, by providing multiple uneven portions 21 at a predetermined interval along the radial direction of the inner tube 12 and increasing the area of ​​the flat portion 22 (area not processed by the laser), the time required for laser processing can be shortened.

[0047] The above describes the embodiments and modifications of the present invention. Note that the present invention is not limited to the above-described embodiments and modifications, and various other modifications are also included. For example, the above-described embodiments and modifications have been described in detail to clearly explain the present invention, and are not necessarily limited to those including all of the described configurations. Furthermore, it is possible to replace part of the configuration of this embodiment and modifications with configurations of other embodiments, and it is also possible to add configurations of other embodiments to the configuration of this embodiment and modifications. Furthermore, it is possible to add, delete, or replace part of the configuration of this embodiment and modifications with other configurations.

[0048] For example, in the above embodiment and modified example, the protrusions 211 and grooves 212 extend circumferentially around the inner tube 12 and are aligned radially, but this is not limited to this, and there are no particular restrictions on the formation direction and arrangement direction of the protrusions 211 and grooves 212.

[0049] Furthermore, in the above embodiment and modified example, the protrusion heights of the plurality of protrusions 211 are not uniform, but this is not limitative and the protrusion heights may be uniform.

[0050] Furthermore, in the above embodiment and modified example, the uneven portion 21 is formed by laser processing, but this is not limitative and there is no particular limitation as long as the uneven portion 21 can be formed by any processing method.

[0051] Furthermore, the uneven portion 21 and the flat portion 22 may be provided on only one of the one end surface portion 12A and the other end surface portion 12B of the inner cylinder 12, or may be provided on both.

[0052] 1: Bush 11: Outer tube 12: Inner tube 12A: One end surface (end surface) 12B: Other end surface (end surface) 13: Elastic body 21, 21A to 21F: Uneven portion 22, 22A to 22D: Flat portion 211: Protrusion 212: Groove 220: Surface

Claims

1. A bushing comprising: an outer tube; an inner tube disposed within a hollow portion of the outer tube; and an elastic body interposed between the outer tube and the inner tube and connecting the outer tube and the inner tube, wherein an axial end face of the inner tube is provided with an uneven portion having a plurality of alternating successive projections and grooves, and a flat portion having a flat surface, wherein the flat portion is located on the outer periphery of the uneven portion, and the plurality of projections protrude beyond the surface position of the flat portion.

2. A bush as claimed in claim 1, characterized in that the heights of the plurality of protrusions from the position of the surface of the flat portion are non-uniform.

3. The bushing according to claim 1, wherein the plurality of protrusions and the plurality of grooves extend in the circumferential direction of the inner cylinder and are aligned in the radial direction.

4. The bushing according to claim 3, wherein the plurality of projections and the plurality of grooves are formed concentrically with the inner cylinder.

5. The bushing according to claim 3, characterized in that the uneven portion is provided in a plurality at intervals along the circumferential direction of the inner cylinder.

6. The bushing according to claim 3, characterized in that the uneven portion is provided in a plurality at intervals along the radial direction of the inner cylinder.

7. A bushing as claimed in claim 1, characterized in that the flat portion is further provided on the inner peripheral side of the uneven portion on the end face portion of the inner cylinder.

8. A method for manufacturing a bush as claimed in claim 1, characterized in that the uneven portion is formed by laser processing.

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