JP4111943B2 - Bumper stay - Google Patents

Description

The present invention relates to a connection structure for fixing other members to front and rear flanges, and more particularly to a bumper stay for an automobile .

  For example, bumper reinforcement is provided as a reinforcing member inside a bumper installed at the front end (front) and rear end (rear) of an automobile body such as a passenger car or a truck. The bumper reinforcement is a hollow member having a front wall and a rear wall that are generally perpendicular to the load direction, and a lateral wall that connects them, and is supported by a pair of bumper stays from the rear side. It is fixed to the tip of the side member (front or rear).

Aluminum bumper stays can be broadly divided into vertical and lateral collapse types. As illustrated in FIG. 15A, the vertical crushing type bumper stay has plate-like flanges 2 and 3 (bumper reinforcements 4 and side members 5 formed on the front and rear ends of a hollow extruded member constituting the shaft portion 1. The direction of the extrusion axis is directed in the longitudinal direction of the vehicle body (substantially perpendicular to the longitudinal direction of the bumper reinforcement 4). The vertical crush-type bumper stay illustrated in FIG. 15B is made of an aluminum alloy extruded material (pipe material), and both ends of the shaft portion 6 are expanded by electromagnetic forming to form flanges 7 and 8. It is described in Patent Document 1.
Electromagnetic forming means that, by applying electric energy, the electromagnetic forming coil 18 forms a strong magnetic field for a very short time, and the workpiece (workpiece) placed in this magnetic field repels the magnetic field (framing). This is a technology for forming a workpiece into a predetermined shape by using a high-speed plastic deformation by receiving a strong expansion force or contraction force by a Lorentz force according to the left-hand rule of the left hand. As described in Patent Documents 2 to 5 and Non-Patent Document 1 below, electromagnetic forming itself is a known technique.

JP 2004-189062 A Japanese Patent Laid-Open No. 58-4601 JP-A-6-31226 JP 9-166111 A JP 2002-160032 A Mechanical Technology Research Institute Report No. 150 “Research on Plastic Working Using Electromagnetic Force” (published by Mechanical Technology Research Institute in March 1990)

On the other hand, as shown in FIG. 15C, the lateral crush type bumper stay is composed of an extruded shape member 9 in which front and rear end mounting flanges 11 and 12 and a rib 13 for connecting them are integrally formed. Is directed in the vertical direction of the vehicle body (perpendicular to the longitudinal direction of the bumper reinforcement 4). Examples of the lateral crush type bumper stay include the following Patent Documents 6 to 8.
Furthermore, Patent Document 9 described below describes a bumper stay in which a hollow shaft member is disposed inside a hollow of a lateral crush type bumper stay main body.

JP-A-8-91154 JP 2000-318552 A JP 2001-294106 A JP 2002-12107 A

  In the vertical crushing type bumper stay shown in FIG. 15A, three parts are integrated by welding. Near the welded part of the bumper stay is the place where the stress is most concentrated, and the highest strength (joint strength) is required, but in the case of aluminum alloy, the welded part is softened due to the thermal effect of welding, and inevitably There is a problem that the joint strength decreases. To compensate for this decrease in joint strength, it is conceivable to increase the thickness of the tubular member and the flange member, or to recover the hardness and strength by heat treatment (artificial aging treatment) if heat treated aluminum alloy is used. In the former case, the effect of weight reduction using an aluminum alloy is halved. In the latter case, there is a limit to the recovery of strength by heat treatment after welding, and there is an increase in cost by adding a heat treatment step after welding. Inevitable.

In the case of the vertical crushing type bumper stay shown in FIG. 15B, such a problem is solved, but the closer to the outer periphery of the flange, the larger the amount of tensile deformation in the circumferential direction, resulting in a reduction in thickness ( In some cases, the closer to the outer periphery, the thinner), and the larger the amount of deformation, the more likely it will crack, and it may be extremely difficult to mold a flange large enough to connect to the bumper reinforcement and the side member.
Further, the lateral crushing type bumper stay shown in FIG. 15 (c) has an advantage that the manufacturing cost is low and the bumper reinforcement end mounting portion can be easily accommodated even if it is inclined or curved with respect to the vehicle width direction. . However, there is a problem that the rib is buckled and deformed with a small impact force, the weight specific energy absorption amount is smaller than that of the longitudinal crushing type, and an advantageous weight reduction effect cannot be obtained.

  On the other hand, in the case of a bumper stay in which a hollow shaft member is disposed inside the hollow of the laterally crushed bumper stay body, the rib member is less likely to buckle (fall down) due to the reinforcing effect of the shaft member, and the shaft An increase in energy absorption due to the bellows-like deformation of the member can be expected. However, in this bumper stay, the shaft member is positioned by deforming a pair of protrusions integrally formed in the hollow interior of the main body, or by caulking, or by screwing from the outside of the front and rear walls into the hollow portion of the shaft member. Since measures such as screwing in pins are taken, there is an extra weight increase, and at the same time, the fixing means has a problem in positioning reliability.

  In the case where the laterally crushed bumper stay main body is reinforced with a tubular shaft member, the shaft member is not misplaced without causing an extra weight increase and the shaft member is misaligned. The purpose is to prevent waking.

Patent Document 5 relates to a joining structure of a channel-shaped shape member and a tubular shaft member (reinforcing member). Both end portions of the shaft member are formed in holes formed in a pair of plate portions facing each other. The shaft member is expanded and the shaft member is expanded in diameter by electromagnetic forming so as to be in close contact with the inner peripheral surface of the hole. A technique for joining a shaft member between the pair of flanges is disclosed. The present invention is completed by applying this method to the fixing of the bumper stay and the shaft member. The present invention is not limited to the bumper stay, but can be applied to a general connection structure in which a load is applied in the direction of narrowing the interval between the first and second flanges (compressing the shaft member).

The bumper stay according to the present invention includes a pair of first and second flanges, each having an attachment portion that abuts against an attachment portion of another member, and spaced apart from each other, and connecting the first and second flanges. A hollow member composed of a rib and a shaft member made of a tubular aluminum alloy extruded material and fixed to the first and second flanges, and the pair of ribs of the first and second flanges. A hole is formed in the middle part, each end of the shaft member is inserted into the hole, and is expanded in the radial direction by electromagnetic forming and is in close contact with the inner peripheral surface of the hole.
In the bumper stay , the hollow member may be configured by combining a plurality of members having an open cross section. Here, the open cross-section member includes a simple flat plate material.
In the bumper stay , as the hollow member, for example, a metal shape member having the same cross-sectional shape in a plane perpendicular to the length direction, such as an extruded material, can be used. The metal shape material includes not only the extruded material but also a shape material produced by, for example, pressing a metal plate. The material is preferably an aluminum alloy in terms of weight reduction, but other metals such as steel materials can also be used. . This metal profile can also be configured by combining multiple profiles with open cross-sections. Here, the shape of the open section includes a simple flat plate.

From the viewpoint of certainty of fixing the shaft member to the hollow member, in the bumper stay , the tip of the shaft member protrudes forward from the hole of the flange and expands in the radial direction, and / or It is desirable that the portion sandwiched between the first and second flanges of the shaft member protrudes in the radial direction by pipe expansion by electromagnetic forming. The front refers to the direction in which the tip of the shaft member faces.
From the viewpoint of attachment of other members, it is desirable that the tip of the shaft member is located on the same plane as the attachment portion of the flange or on the inside thereof. As a specific structure, it is good that the tip of the shaft member does not protrude forward from the hole. For example, the flange is provided with a step so that the attachment portion is located on the front side, and the position where the hole is formed is attached. If it is set to a position retracted from the portion, even if the tip of the shaft member protrudes forward from the hole of the flange, the tip can be positioned on the same plane as the mounting portion of the flange or on the inner side thereof. .

  A desirable form of the hole formed in the flange is a hole formed by burring from the front side of the flange. Since the hole formed by burring has a depth compared to the original thickness of the flange and expands toward the front side, if the end of the shaft member is brought into close contact with the inner peripheral surface of this hole The contact area is large and the end of the shaft member expands radially along the inner peripheral surface of the hole. Therefore, even if the end of the shaft member does not protrude to the front side of the hole, The shaft member is securely fixed.

According to the present invention, the first and second flanges each having a mounting portion that contacts the mounted portion of the other member and spaced from each other, and the pair of ribs that connect the first and second flanges In a bumper stay comprising a hollow member made of a tubular member and a shaft member made of a tubular aluminum alloy extruded material, each end portion being fixed to the first and second flanges. Both can be fixed to prevent the shaft member from being displaced. Forming the shaft member fixing holes in the first and second flanges also contributes to weight reduction. Further , according to the present invention , the reinforcing effect of the shaft member is effective in that the ribs are not likely to buckle (fall down) at the time of collision, and the energy absorption amount due to the bellows-like deformation of the shaft member is increased.

Hereinafter, the bumper stay according to the present invention will be specifically described with reference to FIGS.
A bumper stay 20 shown in FIG. 1 is disposed at an inclined end attachment location (see FIG. 15) of bumper reinforcement, and includes a hollow member 21 and a shaft member 22 each made of an aluminum alloy extruded material.

  As clearly shown in FIG. 2, the hollow member 21 includes a plate-like first flange 23, a second flange 24, and a pair of ribs 25 and 26 that connect them. The first flange 23 has a step, the central portion 27 is in a position retracted from the mounting portion 28 that contacts the bumper reinforcement, and a hole 29 for mounting the shaft member 22 is formed in the central portion 27. Similarly, the second flange 24 has a step, the central portion 31 is in a position retracted from the mounting portion 32 that contacts the side member, and a hole 33 for mounting the shaft member 22 is formed in the central portion 31. Each of the holes 29 and 33 is circular when viewed in the direction perpendicular to the central portion 31 (the hole 29 is slightly elliptical when viewed in the direction perpendicular to the central portion 27), and the width of each central portion 27 and 31 It is fully formed. The ribs 25 and 26 connect the central portions 27 and 31 of the first and second flanges and the corners of the inclined portions 34 and 35 and are curved outward. Reference numeral 36 denotes a fixing bolt hole.

  As shown in FIGS. 4 and 5, each end of the shaft member 22 is fitted into the holes 29, 33, expanded by electromagnetic forming, closely attached to the inner peripheral surfaces of the holes 29, 33, and the holes 29. , 33 projecting forward from the flange expand radially in the form of a flange (expanded portions 37, 38), and the portion sandwiched between the first and second flanges 23, 24 is radiated by expansion by electromagnetic forming. Projecting in the direction (projecting part 39). The expanded portions 37 and 38 are partially in contact with the inclined portions 34 and 35 in the circumferential direction, and are in contact with the central portions 27 and 31 in the other portions. The second flanges 23 and 24 are located on the rear side of the attachment portions 28 and 32. A part of the projecting portion 39 in the circumferential direction near the ribs 25 and 26 is in close contact with the ribs 25 and 26 (see FIG. 4), and the other parts are freely deformed according to the processing force of electromagnetic forming (see FIG. 4). Overhang). As described above, the shaft member 22 has a hollow member in such a manner that both end portions are in close contact with the inner peripheral surfaces of the holes 29 and 33 and the expanded portions 37 and 38 and the projecting portion 39 sandwich the central portions 27 and 31 at the same time. 21 is fixed to the first and second flanges 23 and 24.

A method for manufacturing the bumper stay 20 is shown in FIG. The ends of the shaft material 41 having a circular cross section are inserted into the holes 29 and 33 formed in the first and second flanges 23 and 24 of the hollow member 21, and the tip is projected forward (see the imaginary line in FIG. 3). ). One end of the shaft material 41 is cut by a plane perpendicular to the axial direction, the other end is cut along a plane inclined from the plane, the cut surface of the one end is parallel to the second flange 24, and the cut surface of the other end Are arranged in the holes 29 and 33 so as to be parallel to the first flange 23 (the protruding length from each of the holes 29 and 33 is uniform in the circumferential direction).
In this state, the shaft material 41 is positioned with respect to the hollow member 21, the electromagnetic forming coil body 42 is inserted into the shaft material 41, electric energy is input, electromagnetic forming is performed, and the shaft material 41 is moved in the radial direction. Expand the diameter. Thereby, the bumper stay 20 demonstrated previously can be obtained.

  In the bumper stay 20, both end portions of the shaft member 22 are in close contact with the inner peripheral surfaces of the holes 29, 33, and a part of the overhang portion 39 is in close contact with the ribs 25, 26, and the overhang portion 39. The shape in the circumferential direction is different (the part that protrudes freely from the part that is in close contact with the part protrudes larger). Therefore, the shaft member 22 is prevented from rotating in the holes 29 and 33 even if a force for relatively rotating the shaft member 22 and the hollow member 21 is applied. Moreover, the point which the 1st flange 23 (especially center part 27 in which the hole 29 is formed) inclines from the surface perpendicular | vertical with respect to the axial direction of the shaft member 22 also has this rotation prevention effect.

FIG. 6 shows another type of bumper stay 44. In the bumper stay 44, the hollow member 45 is different from the hollow member 21 in that the ribs 48, 49 connecting the first and second flanges 46, 47 are planar, and is the same in other points. The projecting portion 52 of the shaft member 51 is in close contact with the ribs 48 and 49, with a part in the circumferential direction close to the ribs 48 and 49, and is flat there (other points are the same as the shaft member 22. The same). The other portions of the overhanging portion 52 are freely deformed (overhanging) according to the electromagnetic forming processing force.
In the case of this form, the overhanging portion 52 of the shaft member 51 is strongly pressed by the ribs 48 and 49, and the close contact therebetween is further reinforced.

7 and 8 show another type of bumper stay 53. In the bumper stay 53, the hollow member 54 is planar in that ribs 57 and 58 that connect the first and second flanges 55 and 56 are disposed at both ends of the first and second flanges 55 and 56. Unlike the hollow member 21, the other points are the same. Since the shaft member 59 is separated from the ribs 57 and 58, the projecting portion 60 is not in close contact with the ribs 57 and 58, and is freely deformed (projected) according to the electromagnetic forming processing force on the entire circumference (others). The point is the same as the shaft member 22).
In the case of this form, since the space | interval between ribs 57 and 58 is wide, the stability at the time of load addition increases. On the other hand, since the gap between the ribs 57 and 58 and the shaft member 59 is wide, the shaft member 59 instantaneously expands during electromagnetic forming and pushes the inner peripheral surface of the hole (see the holes 29 and 33 of the hollow member 21) in the radial direction. When a force for spreading is applied, the first and second flanges 55 and 56 are likely to be distorted. In the case of the hollow member 21, the mounting portions 28 and 32 of the first and second flanges 23 and 24 are located outside the ribs 25 and 26 (the ribs 25 and 26 are in the vicinity of the holes 29 and 33). The ribs 25 and 26 serve as a support, and distortion of the first and second flanges 23 and 24 during electromagnetic forming can be suppressed. In addition, since the mounting portions 28 and 32 are located outside the ribs 25 and 26, the bumper stay 20 is easily attached to the bumper reinforcement and the side member.

  9 and 10 show another type of bumper stay 61. In this bumper stay 61, the hollow member 62 has holes 67 and 68 formed in the central portions 65 and 66 of the first and second flanges 63 and 64 so that the width of the central portions 65 and 66 is not full, but smaller. The portions formed and the portions (expanded portions 71, 72) that protrude forward from the holes 67, 68 of the shaft member 69 and expand radially in the form of flanges are formed in the central portions 65, 66 over the entire circumference. Although it differs in that it is not in contact, it is almost the same in other points.

  In the case of this form, there is almost no disadvantage in terms of operation and effect due to the fact that the expanded portions 71 and 72 of the shaft member 69 are not in contact with the central portions 65 and 66 of the first and second flanges 63 and 64. From the viewpoint of manufacturing, there is an advantage that an electromagnetic forming force that is small enough not to contact the central portions 65 and 66 is sufficient. As a result, the shaft member 69 can be expanded during electromagnetic forming to reduce the force of expanding the inner peripheral surfaces of the holes 67 and 68 in the radial direction, thereby suppressing distortion of the first and second flanges 63 and 64. . Further, since it is not necessary to input excessive electric energy to the electromagnetic forming coil body, it is possible to extend the life of the electromagnetic forming coil body and the control device.

FIG. 11 shows another form of bumper stay 74. The bumper stay 74 is also arranged at the end attachment portion (see FIG. 15) where the bumper reinforcement is inclined, and includes a hollow member 75 and a shaft member 76.
The hollow member 75 is configured by combining two plate-like members 77 and 78 (see FIGS. 12 and 13) each made of an aluminum alloy extruded material, and includes a plate-like first flange 79, a second flange 80, and these. It comprises a pair of ribs 81 and 82 for connecting the two. The first flange 79 has a step, the central portion 83 is in a position retracted from the mounting portion 84 that contacts the bumper reinforcement via the inclined portion 85, and a hole 86 for mounting the shaft member 76 is formed in the central portion 83. Is formed. The second flange 80 does not have a step, and corresponds to a mounting portion that contacts the side member as a whole, and a burring hole 87 for mounting the shaft member 76 is formed at substantially the center thereof. Each of the holes 86 and 87 has a circular shape when viewed in the direction perpendicular to the second flange 80 (the hole 86 has a slightly elliptical shape when viewed in the direction perpendicular to the central portion 83).

As shown in FIG. 12, one member 77 constituting the hollow member 75 is a plate-like member having a step, and is formed from the outer portion 88 and the central portion 83 in a position retracted through the inclined portion 89. The hole 86 is formed in the central portion 83. In addition, a work hole 90 and a work notch 91 are formed in the central portion 83, and a bolt hole 92 (for bumper reinforcement attachment) is formed in the outer portion 88. The other member 78 constituting the hollow member 75 includes an outer portion 93, an inclined portion 94 and the second flange 80, and the burring hole 87 is formed in the second flange 80. A bolt hole 95 (for attaching a side member) is formed in the second flange 80, and a bolt hole 96 is formed in the outer portion 93.
When the hollow member 75 is configured by combining the members 77 and 78, the outer portion 88 and the outer portion 93 overlap to form the mounting portion 84, and the inclined portion 89 and the upper end portion of the inclined portion 94 overlap to form the inclined portion 85. The inclined portion 94 of the member 78 becomes the ribs 81 and 82. The work hole 90 and the work notch 91 are located at positions corresponding to the bolt holes 95 for attaching the side members, and can be tightened by inserting a tool. Moreover, the bolt hole 92 and the bolt hole 96 overlap, and as shown in FIG. 11, the stud bolt 97 is driven here or the pierce nut 98 is fixed.

  As shown in FIG. 11, each end of the shaft member 76 is inserted into the holes 86 and 87, expanded by electromagnetic forming, and is in close contact with the inner peripheral surfaces of the holes 86 and 87, and the first flange 79 side. Then, a portion protruding forward from the hole 86 is expanded in a flange shape in the radial direction (expanded portion 99), and is in contact with the central portion 83 on the entire circumference, and on the second flange 80 side, the shaft member 76 is provided. Is closely attached to the inner peripheral surface of the burring hole 87 and expands radially along the burring hole 87 (expanded portion 100), and is further sandwiched between the first and second flanges 79 and 80. The projecting portion is projected in the radial direction by expansion by electromagnetic forming (projecting portion 101). Thus, both ends of the shaft member 76 are in close contact with the inner peripheral surfaces of the holes 86 and 87, and at the same time, the expanded portions 99 and 100 and the overhang portion 101 are the central portion 83 of the first flange 79 and the second flange 80. Is fixed to the first and second flanges 79 and 80. Further, the first flange 79 has a step, and the expanded portion 100 does not protrude forward from the burring hole 87 on the second flange 80 side where there is no step. Accordingly, the distal end of the shaft member 76 is located on the rear side of the attachment portions (the attachment portion 84 and the second flange 80 itself) of the first and second flanges 79 and 80.

FIG. 14 shows a method of manufacturing the bumper stay 74 by fixing the shaft member 76 to the hollow member 75. The ends of the shaft blank 102 are inserted into the holes 86 and burring holes 87 formed in the first and second flanges 79 and 80 of the hollow member 75, and the front end protrudes forward on the first flange 79 side (see FIG. 14 virtual lines). The shaft material 102 is made of an aluminum alloy extruded material having a circular cross section, one end is cut by a surface perpendicular to the axial direction, the other end is cut along a surface inclined from the surface, and the cut surface of the one end is a second flange. It is arranged in the holes 86 and 87 so that the cut surface at the other end is parallel to the first flange 79 (the protruding length from the hole 79 is uniform in the circumferential direction).
In this state, the shaft material 102 is positioned with respect to the hollow member 75, the coil body 103 for electromagnetic forming is inserted into the shaft material 102, electric energy is input, electromagnetic forming is performed, and the shaft material 102 is moved in the radial direction. Expand the diameter. As a result, the bumper stay 74 described above can be obtained.

  In this bumper stay 74, the hollow member 75 is constituted by two plate-like members 77 and 78, but this has the advantage that it is easier to make a hole than the integrated hollow member (for example, the hollow member 21). is there. Drilling is performed so that the axis of the hole is perpendicular to each flange on both the first flange side and the second flange side, but in the case of a hollow member, it is necessary to position a jig inside the hollow, etc. Extra time is required. In particular, when the axial lines of the hole 29 of the first flange 23 and the hole 33 of the second flange 24 are different as in the hollow member 21, there is a problem that upper and lower holes cannot be formed at a time. On the other hand, in the case of the hollow member 75, since each of the members 77 and 78 has a plate-like open cross section, it is easy to make a hole. Moreover, if it is a member of an open cross section, extrusion molding is easy and there also exists an advantage that a board can be press-processed and shape | molded.

It is a perspective view of the bumper stay concerning the present invention. It is a perspective view of the hollow member which comprises the bumper stay. It is sectional drawing explaining the manufacturing method of the bumper stay. It is II sectional drawing of FIG. It is II-II sectional drawing of FIG. It is sectional drawing of another bumper stay which concerns on this invention. It is a perspective view of another bumper stay concerning the present invention. It is III-III sectional drawing of FIG. It is a perspective view of another bumper stay concerning the present invention. It is IV-IV sectional drawing of FIG. It is a perspective view of another bumper stay concerning the present invention. It is a top view of one member which comprises the hollow member of the bumper stay. It is a top view of the other member which comprises the hollow member of the bumper stay. It is sectional drawing explaining the manufacturing method of the manufacturing method of the bumper stay. It is a figure explaining the bumper stay of various types (form).

Explanation of symbols

20, 44, 53, 61, 74 Bumper stay 21, 45, 54, 62, 75 Hollow member 22, 51, 59, 69, 76 Shaft member 23, 46, 55, 63, 79 First flange 24, 47, 56 , 64, 80 Second flange 25, 26, 48, 49, 57, 58, 81, 82 Rib 29, 30, 67, 68, 86 Hole 37, 38, 71, 72, 99, 100 Expanded portion 39, 52 , 60,101 Overhang 77,78 Plate member 87 Burring hole

Claims (9)

A hollow member comprising a first and a second flange each having a mounting portion that abuts against a mounted portion of another member and spaced from each other, and a pair of ribs connecting the first and second flanges; Each end portion is formed of a shaft member made of a tubular aluminum alloy extruded material and fixed to the first and second flanges, and a hole is formed in a portion between the pair of ribs of the first and second flanges. Each end portion of the shaft member is inserted into the hole, expanded by electromagnetic forming, closely attached to the inner peripheral surface of the hole, and a portion sandwiched between the first and second flanges of the shaft member is electromagnetic. A bumper stay , wherein the bumper stay projects radially by tube expansion by molding, and the tip of the shaft member is located on the same plane as or inward of the mounting portion of the flange . The flange has a step, the position where the hole is formed is at a position retracted from the mounting portion , the tip of the shaft member protrudes forward from the hole of the flange, and expands radially. The bumper stay according to claim 1, wherein: The hole formed in the flange is burring processed from the front side, the end of the shaft member expands radially along the inner peripheral surface of the hole , and the tip thereof is forward from the hole. The bumper stay according to claim 1 , wherein the bumper stay is not protruded . The first flange has a step, the portion where the hole of the first flange is formed is in a position retracted from the mounting portion, and the tip of the shaft member protrudes forward from the hole of the first flange. And the hole formed in the second flange is subjected to burring from the front side, and the end of the shaft member extends radially along the inner peripheral surface of the hole. The bumper stay according to claim 1, wherein the bumper stay is widened and a tip thereof does not protrude forward from the hole . The bumper stay according to any one of claims 1 to 4 , wherein the hollow member is made of an aluminum alloy shape having the same cross-sectional shape in a plane perpendicular to the length direction. The bumper stay according to claim 5 , wherein the hollow member is made of an extruded material. The bumper stay according to any one of claims 1 to 6 , wherein the hollow member is a combination of members having a plurality of open cross sections. The bumper stay according to any one of claims 1 to 7 , wherein a mounting portion of the first flange or / and the second flange is located outside the pair of ribs. Location where the hole is formed in the first flange and / or the second flange, to one of the claims 1 to 8, characterized in that the axial direction of the shaft member is inclined from the vertical plane The listed bumper stay .

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