JP2009073254A - Support member, support body, and pneumatic run-flat tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a support member with excellent formability and strength, capable of suitably preventing breaking of a weld part; and a pneumatic run-flat tire showing high strength to load and capable of obtaining excellent run-flat travelling performance. <P>SOLUTION: A stainless steel member with 600-1200 N/mm<SP>2</SP>tensile strength and 10% or more breaking elongation is used for the support member. The plate-like stainless steel member is formed in an annular shape, and the support member has at least the weld part where one end and the other end of the stainless steel member are bonded together by welding. In the support member, ratio of stiffness at the weld part to stiffness at a non-weld part is within +20%. The pneumatic run-flat tire is provided with the support member. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a run-flat tire that can travel a considerable distance as it is when the tire is punctured, and a support and a support member that are used in the run-flat tire.

Run-flat running with pneumatic tires is possible, that is, tires that can run with a certain distance even when punctured and the tire internal pressure becomes 0 kgf / cm ² (hereinafter referred to as “run-flat tires”). As such, a core type run-flat tire in which a core (support) is attached to a rim portion in the air chamber of the tire is known. The support body includes an annular support portion that protrudes outward in the tire radial direction and receives a load during run-flat travel, and leg portions that are attached to both sides in the axial direction of the support portion and are assembled to the rim.

A metal having high tension is preferably used for the support member used as the support portion of the run flat tire from the viewpoint of favorably supporting the load of the vehicle during the run flat running. For example, a support member using a high-tensile steel plate having a tensile strength of 590 N / mm ² or more and 1280 N / mm ² or less is shown (for example, see Patent Document 1). In view of rust prevention, stainless steel is particularly preferably used, and ferritic stainless steel is preferably used in terms of cost.
The supporting member made of high-strength stainless steel is formed by first forming a plate-shaped stainless steel member into an annular shape, and bonding one end portion and the other end portion on the opposite side by welding to form a welded portion. After that, in order to form a desired shape having a convex portion that actually contacts the back surface of the tread portion of the tire during run-flat running, a concave portion, a flange portion embedded in the leg portion, etc., further plastic processing such as roll forming processing is performed. It is given and a support member is produced.
JP 2004-314913 A

  However, high-tensile stainless steel has the property that the weld becomes coarser due to heating during welding, and ductility and toughness are deteriorated and intergranular corrosion is likely to occur. Therefore, when a strong pressure is applied in the plastic working, the welded portion may be destroyed due to stress concentration due to non-uniform hardness (strength), and a support member may not be formed.

  In consideration of the above facts, the present invention can suitably prevent fracture of the welded part, a support member excellent in formability and strength, high strength against load, and excellent run flat travelability. It is an object of the present invention to provide a pneumatic run-flat tire that exhibits high strength against load and excellent run-flat running performance.

Support member according to claim 1, the tensile strength is at 600N / mm ² or more 1200 N / mm ² or less, and a stainless steel member breaking elongation is 10% or more, at least the plate of the stainless steel member It has a welded part that is formed into an annular shape and one end and the other end of the stainless steel member are bonded together by welding, and the ratio of the hardness of the welded part to the hardness of the non-welded part is within ± 20%. Features.

The operation of the support member according to claim 1 will be described.
A metal having high tension is preferably used for the support member used for the support of the pneumatic run-flat tire, and stainless steel is particularly preferably used. The supporting member made of high-strength stainless steel is formed by first forming a plate-shaped stainless steel member into an annular shape, and bonding one end portion and the other end portion on the opposite side by welding to form a welded portion. After that, in order to form a desired shape having a convex portion that actually contacts the back surface of the tread portion of the tire during run-flat running, a concave portion, a flange portion embedded in the leg portion, etc., further plastic processing such as roll forming processing is performed. It is given and a support member is produced. However, high-tensile stainless steel has the property that the weld becomes coarser due to heating during welding, and ductility and toughness are deteriorated and intergranular corrosion is likely to occur. Therefore, when a strong pressure is applied in the plastic working, the welded portion may be destroyed due to stress concentration due to non-uniform hardness (strength), and a support member may not be formed.

  In the support member according to claim 1, since the ratio of the hardness in the welded portion to the hardness in the non-welded portion is controlled within ± 20%, ductility, toughness deterioration and intergranular corrosion are suitably prevented. Therefore, it is possible to prevent the welded portion from being broken during the plastic working, and to obtain a support member that is excellent in formability and strength.

  The support body according to claim 2 is disposed inside the pneumatic tire, and is attached to the annular support portion that receives a load during run-flat traveling, the support portion, and is assembled to the rim together with the pneumatic tire. And a support member according to claim 1, wherein the support member according to claim 1 is used as the support portion.

The operation of the support according to claim 2 will be described.
Since the support member according to claim 1 having excellent formability and strength is used, even when it is mounted on a pneumatic tire and the air pressure of the tire is reduced to run flat, On the other hand, it is possible to provide a support that exhibits high strength and provides excellent run-flat running properties.

  The pneumatic run-flat tire according to claim 3 is a carcass formed in a toroid shape between a pair of bead cores, a side rubber layer that is disposed on the outer side in the tire axial direction of the carcass and forms a tire side portion, and the carcass A tire comprising a tread rubber layer disposed outside the tire in the radial direction of the tire and constituting a tread portion, a rim on which the tire is mounted, an inner side of the tire, and assembled to the rim. And a support described above.

The operation of the pneumatic run-flat tire according to claim 3 will be described.
Since the support body according to claim 2 having a high strength against a load is provided, even when the tire has a low air pressure and run-flat running, a high strength against the load is exhibited. Excellent run-flat running performance can be obtained.

  As described above, according to the support member, the support body, and the pneumatic run flat tire of the present invention, it is possible to suitably prevent the welded portion from being destroyed, and it has excellent formability and strength, and good run flat running performance. The excellent effect that can be obtained can be obtained.

  The support member of this invention is a support member used as a support part of the support body in a pneumatic run flat tire. Here, FIG. 1 shows a first embodiment which is a preferred embodiment of the present invention. The run flat tire 10 in FIG. 1 is a tire in which a pneumatic tire 14, a support member 26, and a leg portion 28 are assembled to a general wheel rim 12.

  The rim 12 to which the support member 26 and the leg portion 28 are assembled is a standard rim corresponding to the size of the pneumatic tire 14. The pneumatic tire 14 includes a pair of bead portions 18, a toroid-like carcass 20 extending over both bead portions 18, and a plurality of (in the pneumatic tire 14 shown in FIG. 1, the crown portion of the carcass 20. Two belt layers 22, a tread portion 24 formed on the upper portion of the belt layer 22, and a tire side portion 25 configured by covering the outer side in the tire axial direction of the carcass 20 with a rubber layer. The run flat tire 10 shown in FIG. 1 has a general tire shape, but the present invention can be applied to various tire shapes. In the figure, “O” indicates the tire rotation axis, and “CL” indicates the tire equatorial plane perpendicular to the rotation axis O at the center in the tire width direction.

  The support member 26 in the first embodiment is disposed inside the pneumatic tire 14 via leg portions 28 made of vulcanized rubber as elastic bodies bonded to both ends, and is an annular support body as a whole. It is formed as. The leg portion 28 is annular in the longitudinal direction.

As shown in FIG. 1, the leg portion 28 is assembled by press-fitting or the like using rubber elasticity on the outer periphery of the rim 12 inside the pneumatic tire 14 when the rim is assembled. Examples of rubber materials used for the legs 28 include natural rubber (NR), isoprene rubber (IR), styrene-butadiene rubber (SBR), butadiene rubber (BR), butyl rubber (IIR), urethane rubber (U), and the like. These may be used alone or in a blended manner. These rubber materials contain a filler, and the hardness (Hd) of the rubber is adjusted by the amount of the filler. Examples of the filler that can be blended with these rubber materials include carbon black, CaCO ₃ , cucumber powder, and silica.

  A support member 26 is bonded to the leg portion 28. As shown in FIG. 1, the support member 26 includes a convex portion 26 </ b> A as a contact portion that is convex outward in the radial direction, a concave portion 26 </ b> B that is convex inward in the radial direction, and a width direction of the convex portion 26 </ b> A. A side portion 26C for supporting a load is integrally formed on the outer side (the side opposite to the concave portion 26B). A radially inner portion (rim side portion) of the side portion 26C is formed with an attachment portion that extends substantially in the tire rotation axis O direction and is embedded in the leg portion. A flange portion 26D as a base portion formed in a planar shape is formed. Both ends of the support member 26 are loaded into the mold as insert cores, and a pair of leg portions 28 are vulcanized with rubber, and at the same time, the pair of leg portions 28 are vulcanized and bonded to both end portions of the support member 26, respectively. Thus, it is integrated with the leg portion 28.

Support member 26, the tensile strength is at 600N / mm ² or more 1200 N / mm ² or less, and is formed of stainless steel member of high tension and elongation at break is 10% or more. Also, it has a welded part bonded by welding, and the ratio of the hardness of the welded part to the hardness of the non-welded part (hereinafter sometimes simply referred to as “the hardness change rate of the welded part”) is controlled within ± 20%. Has been.

Here, the manufacturing method of the said supporting member 26 is demonstrated using FIG.
First, as shown in FIG. 2A, a plate-like stainless steel member 260A cut to a predetermined size is prepared. Next, after forming the stainless steel member 260A into an annular shape, as shown in FIG. 2 (B), one end portion and the other end portion on the opposite side are bonded together to form a welded portion 262. The stainless steel member 260B is obtained. Thereafter, as shown in FIG. 3, plastic forming (roll forming) is performed by a roll forming apparatus including rolls 30 </ b> A, 30 </ b> B, and 30 </ b> C, and includes convex portions 26 </ b> A, concave portions 26 </ b> B, side portions 26 </ b> C, flange portions 26 </ b> D, and the like. The support member 26 shown in FIG. 2C is manufactured by molding into a desired shape. In addition to the roll forming process shown in FIG. 3, the plastic working process includes a spatula drawing process, a hydroforming process, and the like.

  However, conventionally, the annular stainless steel member 260B having a high tension has a property that the welded portion 262 is coarsened by heating during welding, and ductility and toughness are deteriorated and intergranular corrosion is likely to occur. Therefore, when a strong pressure is applied in the plastic working, the welded portion 262 is broken due to stress concentration due to uneven hardness (strength), and as a result, the support member 26 may not be formed. It was.

On the other hand, in the support member 26 according to the first embodiment, the ratio of the hardness in the welded portion 262 to the hardness in the non-welded portion (the hardness change rate of the welded portion 262) is within ± 20% as described above. Because it is controlled, ductility and toughness deterioration and intergranular corrosion can be suitably prevented, and welded parts can be prevented from breaking during plastic working, and it has excellent formability and strength. A support member can be obtained.
The hardness change rate of the welded portion 262 is preferably within ± 15%, and more preferably within ± 10%.

  Here, the hardness of the welded part 262 and the non-welded part refers to Vickers hardness and can be measured by the Vickers hardness test-test method defined in JIS Z2244 (2003).

  In addition, it is preferable that the hardness (namely, hardness of the stainless steel member to be used) of a non-welded part is 200 Hv or more.

  In order to control the hardness change rate of the welded portion 262 in the support member 26 to the above-described range, it can be performed by adjusting the components of the stainless steel member to be used. Specific examples include a method for reducing the content of C and N in the component and a method for increasing the content of Ti and Nb. More preferably, it is preferable to adjust the components in consideration of the formation conditions (welding conditions) of the welded portion 262.

Further, stainless steel member used in the support member 26, as described above tensile strength is 600N / mm ² or more 1200 N / mm ² or less. When the tensile strength is lower than the lower limit value, the support member 26 changes shape due to run-flat running. Further, when the tensile strength is higher than the above upper limit value, the toughness of the stainless steel member itself is lowered, and the support member 26 is damaged due to an impact during the run flat running.
The tensile strength can be measured by a metal material tensile test method specified in JIS Z2241 (1998).

Further, as described above, the stainless steel member used for the support member 26 has a breaking elongation of 10% or more, but the above range is further preferably 20% or more, particularly preferably 30% or more. . When the elongation at break is lower than the lower limit, a processing defect such as a crack occurs due to distortion or stress generated during the production of the support member 26. The processing defect grows due to load, vibration, impact, etc. during run-flat running and causes the support 26 to be damaged.
The elongation at break can be measured by a metal material tensile test method specified in JIS Z2241 (1998).

  Here, in the first embodiment, the support member 26 having two convex portions 26A that are equal in cross-sectional view is used. However, for example, a support member having one convex portion 26A may be used, and The shape of the member is not limited to this.

  Further, the overall shape of the leg portion 28 is not limited to the shape shown in the first embodiment, and may be other shapes such as a rectangular shape or a circular shape in a cross-sectional view.

In ferritic stainless steel members having a tensile strength of 700 N / mm ² and a breaking elongation of 25% or more and 30% or less, by adjusting the components (contents of C, N, Ti, Nb), the rate of change in hardness of the weld zone Plate-shaped stainless steel members (1) to (11) having a ratio of the hardness of the welded portion to the hardness of the non-welded portion shown in Table 1 below were prepared. The hardness of the non-welded part (that is, the hardness of the stainless steel member used) was 210 Hv.

The plate-like stainless steel members (1) to (11) were formed into an annular shape, and one end portion and the other end portion on the opposite side were bonded together to form a welded portion.
Subsequently, the supporting member was manufactured by performing a roll forming process.

[Evaluation]
-Cost-
By using a ferritic stainless steel member, it was possible to achieve a 15% cost reduction compared to the case of using other stainless steel members.

-Mechanical performance-
A 300 km run-flat run was performed and the stability of the run-flat run was evaluated. The results are shown in Table 1 below. (Good: ○, unstable: ×)

-Rust prevention performance-
SST (Salt spray (salt spray) test) shown in JIS-Z2371 was carried out for 1500 hours to evaluate the occurrence of rust. In addition, rust generate | occur | produces in 1200 hours when the material which gave rust prevention coating to iron is used as evaluation criteria. The results are shown in Table 1. (Not generated: ○, generated: ×)

-Formability-
Whether or not cracking occurred during the roll forming process was evaluated. The results are shown in Table 1. (Not generated: ○, generated: ×)

  In Table 1, the mechanical performance evaluation (marked with *) in the comparative example could not be tested due to the occurrence of cracks during molding.

It is sectional drawing cut | disconnected along the tire rotating shaft at the time of rim mounting | wearing of the pneumatic run-flat tire provided with the supporting member of this invention. (Only the upper part of the cross section along the tire rotation axis O is shown.) (A) is a plate-like stainless steel member used for manufacturing the support member of the present invention, (B) is an annular stainless steel member formed into an annular shape and a welded portion, and (C) is an embodiment of the present invention. It is a perspective view which shows a supporting member. It is a schematic block diagram which shows the roll forming apparatus which performs a plastic working to the cyclic | annular stainless steel member shown to FIG. 2 (B).

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Pneumatic run-flat tire 12 Rim 14 Pneumatic tire 18 Bead part 20 Carcass 24 Tread part 25 Tire side part 26 Support member 26A Convex part 26B Concave part 26C Side part 26D Flange part 28 Leg part 30 Roll forming apparatus 30A, 30B, 30C Roll 260A Plated stainless steel member 260B Annular stainless steel member 262 Welded part

Claims (3)

Tensile strength is at 600N / mm ² or more 1200 N / mm ² or less, and a stainless steel member breaking elongation is 10% or more,
At least a plate-like stainless steel member is formed into an annular shape, and has a welded portion in which one end and the other end of the stainless steel member are bonded by welding,
A ratio of the hardness of the welded portion to the hardness of the non-welded portion is within ± 20%. An annular support portion that is disposed inside the pneumatic tire and receives a load during run-flat travel, and is attached to the support portion and assembled to the rim together with the pneumatic tire to load the load during the run-flat travel And an elastic leg to be supported by
The support body of Claim 1 is used as the said support part, The support body characterized by the above-mentioned. A carcass formed in a toroid shape between a pair of bead cores, a side rubber layer that is disposed on the outer side in the tire axial direction of the carcass to form a tire side portion, and a tread portion that is disposed on the outer side in the tire radial direction of the carcass A tire having a tread rubber layer,
A rim for mounting the tire;
The support according to claim 2, which is disposed inside the tire and is assembled to the rim.
A pneumatic run-flat tire comprising:

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