JP5046555B2 - Safety tire - Google Patents

Description

  The present invention has a toroidal shape over each part of a pair of bead portions in which a bead core and a bead filler are embedded, a pair of sidewall portions extending outward in the tire radial direction from the bead portion, and a tread portion extending between both sidewall portions. A carcass made of at least one ply that extends, and at least one belt layer that is positioned on the outer peripheral side of the crown portion of the carcass and that is made of rubber-coated cords, and extend along the tire circumferential direction in the tread portion The present invention relates to a safety tire provided with at least two main grooves.

  In a pneumatic tire, for example, a passenger car tire, gas is contained in the tire under a pressure of about 150 kPa to 250 kPa as a gauge pressure, and a tension is generated in a tire skeleton such as a carcass and a belt of the tire. The tire can be deformed and restored in response to the input to the tire. That is, by maintaining the tire's internal pressure within a predetermined range, a constant tension is generated in the tire skeleton, and a load supporting function is imparted and rigidity is increased, such as driving, braking and turning performance, The basic performance necessary for running the vehicle is given.

  By the way, when a tire held at a predetermined internal pressure is damaged, a tire frame portion is formed because a high-pressure gas leaks to the outside through the injury and the internal pressure of the tire decreases to atmospheric pressure. Most of the tension generated at the time is lost, the sidewall portion bulges and the bead portion collapses and deforms. As a result of the loss of the load support function and the driving, braking and turning performance obtained by applying a predetermined internal pressure to the tire, the vehicle equipped with the tire will be unable to travel.

  Therefore, many proposals have been made on tires that can run even in a puncture state, so-called safety tires. For example, one having a double wall structure, one having a load support device such as an air bladder in the tire, a tire air chamber partitioned by the tire and the rim, and a continuous phase made of a resin capable of thermal expansion Known are those in which a large number of hollow particles composed of closed cells are arranged to recover the internal pressure of the tire chamber by increasing the volume of the hollow particles during puncture. As a safety tire for passenger cars with relatively light weight, a reinforcing rubber layer with a crescent cross section is provided on the sidewall to support the tire load with the internal pressure when the internal pressure is normal. There is a known safety tire that supports a tire load with a reinforcing rubber layer instead of a shoulder, a so-called side-reinforced safety tire (see, for example, Patent Document 1). The side-reinforced safety tire has a relatively simple structure as compared to the safety tire described above, and does not require the collection of a load support device or hollow particles disposed in the tire when repairing a puncture or discarding the tire. This is advantageous.

  Also, in the side-reinforced safety tie during run-flat running, in addition to the bulging deformation of the sidewall portion and the falling deformation of the bead portion, so-called buckling occurs, which is the phenomenon that the center of the tread surface rises from the road surface. There is a case. In particular, when a main groove extending in the tire circumferential direction is provided in the tread portion, the main groove becomes a starting point of bending, and a large buckling is likely to occur. In tires with buckling, the relatively thin buttress area of the rubber is grounded, and the carcass and belt layer cords are exposed due to rubber wear, which can eventually break and cause tire destruction. is there.

  In order to suppress such buckling, for example, in Patent Document 2, at least one layer of tie elements is arranged on the outer periphery of the crown portion of the belt layer to form a large number of cord arrays substantially orthogonal to the tire equatorial plane. Tires are described. Patent Documents 3 and 4 describe tires in which an annular bead core is arranged on the inner side in the tire radial direction of the belt layer to improve run-flat running performance. Further, in Patent Document 5, a reinforcing cord layer for increasing circumferential rigidity and a reinforcing rubber layer for increasing width rigidity are disposed between the carcass and the belt layer to enhance run-flat durability. Tires are described.

Japanese Patent Laid-Open No. 2005-161964 JP-A-6-191243 JP-A-8-244422 European Patent Application No. 1022162 WO99 / 48710 pamphlet

  However, in the conventional side-reinforced safety tires as described in Patent Documents 1 to 5, since the load is supported when the internal pressure is reduced only by the compression rigidity of the rubber, the reinforced rubber layer necessary for it is provided. There is a problem that the size of the tire is inevitably increased, and the mass of the tire is greatly increased. Further, the tire described in Patent Document 2 may not be able to sufficiently suppress buckling depending on the cord material, and the tires described in Patent Documents 3 and 4 are manufactured using conventional manufacturing equipment. In addition, since the rigidity of the annular bead core is too high, vibration ride comfort may be deteriorated when there is projection input from the road surface. In the tire described in Patent Document 5, the tire width is Regarding reinforcement in the direction, only a reinforcing layer made of rubber was provided, and the effect of suppressing buckling was not sufficient.

  An object of the present invention is to solve such problems of the prior art, and an object of the present invention is to achieve run-flat running while achieving weight reduction by optimizing the load support structure. An object of the present invention is to provide a safety tire in which the buckling at the time is effectively suppressed and the durability is remarkably improved.

  In order to achieve the above-described object, the present invention extends across a pair of bead portions in which a bead core and a bead filler are embedded, a pair of sidewall portions extending outward in the tire radial direction from the bead portions, and both sidewall portions. The tread portion includes a carcass formed of at least one ply extending in a toroidal shape over each portion of the tread portion, and at least one belt layer formed on the outer periphery of the crown portion of the carcass and covered with a rubber cord. In the safety tire provided with at least two main grooves extending along the tire circumferential direction, a metal cord is covered with rubber on the outer surface of the carcass in a cross section in the tire width direction, and at least the width of the belt layer A pair of left and right reinforcement layers that extend beyond the buttress area from the end, and the cords constituting them extend in the tire circumferential direction And at least one auxiliary belt layer formed by rubber coating a metal cord on the outer side in the tire radial direction of the belt layer so that the cord constituting the belt extends across the tire circumferential direction. It is a safety tire characterized by doing. By adopting such a configuration, it is possible to effectively prevent the bulging deformation of the sidewall portion, the falling-down deformation of the bead portion, and the occurrence of buckling during the run-flat running without providing a reinforcing rubber layer having a crescent-shaped cross section. .

  The “width end portion of the belt layer” here refers to the outermost end of the belt layer when the belt layer is one layer, and the widest belt layer when the belt layer is a plurality of layers. Part.

  Moreover, it is preferable that the both ends of the auxiliary belt layer are positioned outside a pair of outermost main grooves which are main grooves positioned on the outermost side in the tire width direction.

  Furthermore, it is preferable that the cords constituting the auxiliary belt layer each have an angle formed by the tire circumferential direction in a range of 40 ° to 90 ° and a filament having a diameter of 0.6 mm or more.

  Furthermore, it is preferable that the angle formed between the metal cord constituting each reinforcing layer and the tire circumferential direction is in the range of 80 ° or more and less than 90 °.

  In addition, the tire radial direction distance between the tire radial outer end of the bead filler and the rim diameter line is 200% of the flange height of the standard rim when mounted on the standard rim and filled with the specified internal pressure. Or less, more preferably 150% or less, and even more preferably less than 100. Here, “standard rim” and “regulated pressure” are industrial tires that are effective in areas where tires are manufactured, sold, or used, such as JATMA, TRA, ETRTO, etc., for safety tires that store pneumatic bladders. This means the standard rim (or “Approved Rim”, “Recommended Rim”) at the applicable size specified in the standards, standards, etc., and the internal pressure according to the maximum load capacity of the tire. "Means the position where the rim diameter is measured.

  The bead filler is preferably composed of rubber having a Young's modulus of less than 14.7 kPa.

  Furthermore, it is preferable to further provide an auxiliary rubber layer between the carcass and the reinforcing layer.

  According to the present invention, the reinforcing layer prevents bulging deformation of the sidewall portion and the falling-down deformation of the bead portion during the run-flat running without using a crescent-shaped reinforcing rubber layer, and the auxiliary belt layer prevents buckling. Since generation | occurrence | production is prevented, the significant weight reduction and durability improvement of a safety tire can be achieved simultaneously.

  Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view in the width direction of a typical safety tire (hereinafter simply referred to as “tire”) according to the present invention, and shows a state where it is mounted on a standard rim R.

  A tire 1 shown in FIG. 1 includes a pair of bead portions 4 (only one bead portion is shown in the figure) in which a bead core 2 and a bead filler 3 are embedded, and a pair of bead portions 4 extending outward in the tire radial direction. A side wall portion 5 (only one side wall portion is shown in the figure) and a tread portion 6 extending between both side wall portions are formed. Further, the tire 1 includes a carcass 7 including at least one ply (one ply in FIG. 1) extending in a toroid shape over each part of the bead part 4, the sidewall part 5, and the tread part 6. 7 is provided with at least one belt layer 8 (two layers in FIG. 1), which is located on the outer peripheral side of the crown portion and is made of rubber-coated cords. Further, the tread portion 6 is provided with at least two main grooves 9a, 9b, 9c (three in each of the left and right half regions in FIG. 1, total 6) extending along the tire circumferential direction.

  The main feature of the present invention is that the metal cord is covered with rubber on the outer surface of the carcass 7 in the cross section in the tire width direction, and the buttress region 11 is at least from the width end portion 10 of the belt layer 8. The pair of left and right reinforcing layers 12 extending beyond the cords constituting them, as shown in FIG. 2, are arranged so as to cross each other across the tire circumferential direction C, on the outer side in the tire radial direction of the belt layer 8, At least one layer (one layer in FIG. 1) of the auxiliary belt layer 13 formed by rubber-coating a metal cord is arranged so that the cord constituting the cord extends across the tire circumferential direction C as shown in FIG. There is.

Hereinafter, how the present invention has adopted the above configuration will be described together with the operation.
The inventors examined how the destruction of the tire proceeds when a normal radial tire is punctured, and found that the progress of cracks from the width end of the belt layer and the buttress area were large. It was found that the case destruction due to bending deformation and the wear and heat generation in the buttress area due to buckling are the major factors. Cracks from the width end of the belt layer are caused by a large difference in rigidity between the portion where the belt layer is disposed and the portion where the belt layer is not disposed. Particularly, the cord constituting the belt layer is a steel cord. Yes, it occurs remarkably when the cut end of the cord is exposed. Further, the buttress region is not provided with a reinforcing member such as a belt layer or a bead filler, and the thickness of the covering rubber is thin, so that the structural rigidity is significantly smaller than other portions and is easily bent. Therefore, the inventors arrange the reinforcing layer at least in a range beyond the buttress area from the width end portion of the belt layer, preferably in a state of being overlapped with the width end portion of the belt layer as shown in FIG. Thus, the idea that the tire breakage as described above can be prevented if the rigidity step at the width end of the belt layer is eliminated and the structural rigidity of the buttress area is improved is obtained.

  However, simply disposing the reinforcing layer in the above range could not effectively prevent tire destruction even though the occurrence of cracks from the width end portion of the belt layer could be suppressed. The inventors have further studied the tire destruction, and have found that the tire destruction occurs when the cords constituting the left and right reinforcing layers are inclined in the same direction with respect to the tire circumferential direction. This reason will be further described with reference to FIG. In FIG. 11, the cords constituting both the left and right reinforcing layers are inclined in the same direction with respect to the tire circumferential direction, that is, the second coordinate plane having the tire circumferential direction as the y axis and the tire width direction as the x axis. A cord extends into the quadrant and the fourth quadrant. When a tire having such a cord configuration is grounded in order from the lower side of FIG. 11, in the left half region, the cord of the reinforcing layer receives a load first from the end located on the tread portion side and bears this load. Since it acts as a beam, the deformation of the tire is small, on the contrary, in the right half area, the cord of the reinforcement layer receives the load from the end located on the bead part side first, so it does not bear the load, Compared to the left half, tire deformation is large. For this reason, as a result of the generation of a lateral force from the left half region to the right half region, the deformation of the buttress region in the right half region becomes increasingly larger, and the destruction of the tire is promoted. Therefore, the inventors, as shown in FIG. 2, lay the left and right reinforcing layers so that the cords constituting them are opposite to each other in the tire circumferential direction, that is, cross each other across the tire circumferential direction. By arranging and maintaining the deformations of the left and right halves of the tire to the same extent, the inventors have conceived of preventing the occurrence of such lateral force in addition to eliminating the rigidity step in the buttress area and improving the structural rigidity. As a result, it has been found that the structure can be simplified and greatly reduced in weight while maintaining the run-flat durability at the same level as compared with the case of using a conventional reinforcing rubber having a crescent cross section.

  Further, in the tire in which the main groove extending along the tire circumferential direction is arranged in the tread portion, the rigidity of the tread portion is reduced due to the main groove, and as shown in FIG. If the auxiliary belt layer 13 including a metal cord extending across the tire circumferential direction C is arranged to raise the buckling that deforms into a concave shape, the rigidity of the tread portion 6 is increased, and as shown in FIG. It was found that it can be effectively suppressed. The present invention has been completed based on these findings, and can significantly reduce weight and improve durability at the same time as compared with conventional safety tires.

  Here, the cords constituting the reinforcing layer 12 and the auxiliary belt layer 13 are made of metal cords, because these layers act as a beam when the tire internal pressure is reduced, and act to suppress deformation of the tire. This is because compressibility is required. A preferred metal cord is a steel cord from the viewpoint of cost and resistance to fretting.

  Further, in a tire in which a plurality of main grooves are arranged in each of the left and right half regions, among these main grooves, the outermost main groove 9c, which is the main groove located on the outermost side in the tire width direction, is particularly localized. It is known that deformation occurs and the entire tread portion 6 buckles greatly. In order to suppress local deformation centered on the outermost main groove 9c, the width end portion 14 of the auxiliary belt layer 13 is disposed on the outer side in the tire width direction of the outermost main groove 9c, that is, the auxiliary belt layer. 13 is preferably disposed extending from the tire equatorial plane E directly below the outermost main groove 9c and further to the outside in the tire width direction. As a result, the rigidity of the portion where the outermost main groove 9c is disposed can be reinforced, and the local deformation of the tread portion 6 around the outermost main groove 9c, and hence the buckling can be effectively suppressed. it can.

  When buckling occurs, a compressive force acts on the auxiliary belt layer 13 in the tire width direction. Therefore, in order to more effectively suppress buckling, it is preferable to increase the compressive force in the tire width direction of the auxiliary belt layer 13. Specifically, the angle α formed by the cord constituting the auxiliary belt layer 13 and the tire circumferential direction is preferably relatively large, more preferably 40 ° or more and 90 ° or less, and 60 ° or more and 90 ° or less. More preferably, it is 90 °. Alternatively, if the cord constituting the auxiliary belt layer 13 is a filament having a relatively large diameter, preferably a filament having a diameter of 0.6 mm or more, even if the same amount of material is used, it is compared with a filament having a relatively large diameter. Therefore, the buckling can be effectively suppressed while suppressing an increase in mass. Of course, if the cord using the filament having a relatively large diameter is arranged so that the angle formed with the tire circumferential direction is relatively large, the compression rigidity of the auxiliary belt layer in the tire width direction is further improved.

  From the viewpoint of reducing the rigidity step at the width end of the belt layer 8, the belt layer 8 and the reinforcing layer 12 are preferably disposed so as to overlap each other by 3 mm or more, and disposed so as to overlap each other by 5 mm or more. More preferably. However, when the overlap amount exceeds 20 mm, there is almost no change in the effect of reducing the rigidity step, but since the mass of the tire 1 increases as the reinforcing layer 12 increases, the overlap amount is set to 20 mm or less. It is preferable to do.

  Further, during run-flat running, the maximum width position 15 of the tire 1 (which refers to the position at which the cross-sectional width of the tire is measured) is followed by the buttress area 11 where the deformation is maximum. If there is a portion, etc., a failure is likely to occur at a position where the cross-sectional width of the tire excluding these is measured. The reason is as follows. A driving force transmitted to the bead portion 4 via the rim R and a resistance force acting in a direction opposite to the driving force of the tire wheel is generated on the traveling tire wheel due to friction between the tread portion 6 and the road surface. . As a result, a difference in rotational angular velocity occurs between the bead portion 4 fixed to the rim R and the tread portion 6 that contacts the road surface, and torsional deformation occurs in the sidewall portion 5. In side-reinforced run-flat tires, when running flat, the ply cord does not have sufficient tension, and the tire load is supported only by the inherent rigidity of the reinforced sidewall portion 5. The torsional deformation of the sidewall portion 5 is large, and this torsional deformation becomes maximum at the tire maximum width position 15. Therefore, the reinforcing layer 12 is disposed in a range beyond the tire maximum width position 15 from the width end portion 10 of the belt layer 8, thereby further increasing the rigidity of the sidewall portion 5 and torsional deformation at the tire maximum width position 15. It is preferable from the viewpoint of improving run flat durability. In this case, since sufficient tension is not applied to the ply cord, the inner end 16 in the tire radial direction of the reinforcing layer 12 becomes a free end, which may be a core of failure occurrence. Therefore, the inner end portion 16 is connected to a rim line with little bending deformation (a tire is assembled to a standard rim and an inner pressure is applied in accordance with the maximum load capacity, and the tire rim direction from the outermost end in the tire radial direction of the rim flange is applied. It is preferable to dispose the inner end portion 16 in the tire radial direction and substantially fix the inner end portion 16 in the tire radial direction from the portion separated by 30 mm outward).

  Moreover, you may provide the rim guard part 17 which protrudes on the outer surface of the tire 1 and the tire width direction outer side rather than the flange RF of the standard rim R to which the tire is mounted. When such a rim guard part 17 is provided, the bending rigidity of the bead part 4 is remarkably increased, and the deflection and deformation amount of the sidewall part 5 during the run-flat running are effectively suppressed, so that a tire failure is less likely to occur. In this case, since there is little bending deformation in the range where the rim guard portion 17 is provided, the inner end portion 16 in the tire radial direction of the reinforcing layer 12 passes through the outer end portion 18 in the tire radial direction of the rim guard portion 17 and is orthogonal to the tire inner surface. If it is on the inner side in the tire radial direction than the straight line N, the inner end portion 16 in the tire radial direction of the reinforcing layer 12 can be substantially fixed, and the occurrence of failure from here can be suppressed.

  In particular, when the load applied to the tire is large, the cords constituting the left and right reinforcing layers 12 are subjected to the load from the ends located on the tread portion 6 side when the tire rolls. That is, it is preferable to arrange each reinforcing layer 12 so that the cords constituting both the reinforcing layers have a square shape when viewed from the tire rotation direction. With such an arrangement, as described above, the reinforcing layer 12 acts as a beam, so that the deformation of the tire can be further suppressed, and it contributes further to the improvement of the run-flat durability.

  Further, when the metal cords constituting the reinforcing layer 12 are arranged close to the tire circumferential direction C, that is, when the angle β formed by the metal cords constituting the reinforcing layer 12 and the tire circumferential direction C is reduced, the reinforcing layer 12 is arranged. As a result, the occurrence of flexural deformation in the buttress area 11 can be suppressed, and the load applied to the cord can be reduced. However, the smaller the angle β is, the more the cord is cut because the reinforcing layer 12 is deformed in a twisting direction when the buttress region 11 is bent. And if the former is compared with the latter, the influence of the latter is very large. Based on these findings, the inventors have intensively studied the appropriate range of the angle β formed by the metal cord constituting the reinforcing layer 12 and the tire circumferential direction C, and found that it is advantageous to increase the angle β. Specifically, if the angle β is in the range of 80 ° or more and less than 90 °, the occurrence of bending deformation of the buttress region 11 can be suppressed without worrying about the cord being cut, and the run-flat durability can be improved. It was found that it is advantageous for improvement. A more preferable range of the angle β is 85 ° or more and less than 90 °. The configuration of the metal cord is not particularly limited, but a filament with a relatively small diameter is used from the viewpoint of reducing deformation strain and improving run-flat durability even when a large bending input occurs during run-flat running. In particular, it is preferable to use fine filaments having a diameter of 0.3 mm or less.

In general tires, by increasing the bead filler or by using hard rubber, the rigidity of the bead portion and the sidewall portion is increased, and deformation of the tire is suppressed. However, when such a configuration is adopted for a side-reinforced run-flat tire, the area that can be deformed when the internal pressure of the tire decreases is reduced, and the deformation concentrates locally, particularly in the buttress area. It can be a factor that reduces flat durability. Therefore, it is preferable to lower the bead filler 3 from the viewpoint of maintaining run-flat durability. Specifically, in a state where the tire 1 is mounted on the standard rim R and a prescribed internal pressure is filled, the bead filler 3 The tire radial direction distance h ₁ between the tire radial direction outer end 19 and the rim diameter line RL is preferably 200% or less of the height h ₂ of the rim flange RF. The height h ₁ can be reduced within a range that does not impair the effect of reinforcing the bead portion 4 during traveling at normal internal pressure, and a more preferable range is 150% or less of h ₂ , and a more preferable range is as shown in FIG. 4, it is less than 100% of _{h 2.} For the same reason, the rubber constituting the bead filler 3 is preferably soft, and specifically, the rubber having a Young's modulus of less than 14.7 kPa is preferable.

  Furthermore, as shown in FIG. 5, an auxiliary rubber layer 20 may be provided between the carcass 7 and the reinforcing layer 12. When such a configuration is adopted, since rubber is generally resistant to compression, the auxiliary rubber layer 20 also bears a load, and the load applied to the reinforcing layer 12 is reduced. Therefore, the life of the metal cord of the reinforcing layer 12 is extended, the number of cords of the reinforcing layer 12 driven in can be reduced, and the weight of the reinforcing layer 12 can be reduced. When the auxiliary rubber layer 20 is disposed in this manner, the reinforcing layer 12 can be disposed on the outer surface side of the tire more than when the auxiliary rubber layer 20 is not disposed. When the tire is bent and deformed, a tensile force acts on the outer surface side of the tire. However, since the metal cord is excellent in tensile resistance, the buttress of the tire 1 can be more effectively disposed by arranging it on the outer surface side. The deformation of the region 11 can be suppressed. In particular, when at least a part of the reinforcing layer 12 is positioned on the outer surface side of the thickness center line TC of the tire 1 in the region where the auxiliary rubber layer 20 is disposed, the effect of suppressing deformation becomes large.

  Note that the above description shows only a part of the embodiment of the present invention, and these configurations can be combined with each other or various modifications can be made without departing from the gist of the present invention. . For example, FIG. 1 shows a mode in which the end of the reinforcement layer 12 on the bead side is sandwiched between the main body portion and the folded portion of the carcass 7, but as shown in FIG. It is good also as arrangement | positioning which covers an outer surface. Further, as shown in FIGS. 7 to 9, an auxiliary reinforcing layer 21 can be disposed on the inner surface or the outer surface of the reinforcing layer 12 in a portion where the tire 1 is particularly likely to bend and deform. This is because the auxiliary reinforcing layer 21 can more effectively suppress the bending deformation of the tire 1. The auxiliary reinforcing layer 21 is preferably configured in the same manner as the reinforcing layer 12. In addition, the angle β formed by the metal cord constituting the reinforcing layer 12 and the tire circumferential direction C may be the same in the left and right half regions as shown in FIG. 2, but as shown in FIG. May be different.

  Next, tires according to the present invention were prototyped and performance evaluations were performed, which will be described below.

The tire of Example 1 is a radial tire for passenger cars having a tire size of 205 / 55R16, a reinforcing layer formed by rubber coating a steel cord, and an auxiliary belt layer formed by rubber coating a steel cord having a diameter of 0.3 mm. And the specifications shown in Table 1. The tire of Example 1 has an angle between the cord constituting the auxiliary belt layer and the tire circumferential direction of 90 °, and the tire of Example 1 has a structure as shown in FIG. The angle formed by the cord constituting the layer and the tire circumferential direction is the same in each of the left and right half regions, and is 85 °.

For comparison, the tire size is the same as the tire of Example 1 , the tire of Conventional Example 1 having a crescent-shaped reinforcing rubber layer, the tire size is the same as the tire of Example 1 , and has a reinforcing structure. The tire of the conventional example 2 and the tire size are the same as the tire of the example 1, the cord constituting the reinforcing layer is a steel cord, and the angle formed by this cord and the tire circumferential direction is 85 °. The tire of Comparative Example 1 that does not have a belt layer, the tire size is the same as the tire of Example 1 , has the structure shown in FIG. 1, and the angle formed with the tire circumferential direction is 90 °. Although the steel cord has an auxiliary belt layer formed by rubber coating, the cord constituting the reinforcing layer is an organic fiber cord, and the tire of Comparative Example 2 in which the angle formed between the cord and the tire circumferential direction is 85 ° is also shown. The prototype Te.

  The mass of each test tire was measured. The measurement results are shown in Table 1. Further, each test tire is mounted on a rim of size 7J × 16 to be a tire wheel, is attached to a test vehicle, is applied with a tire load of 3.92 kN, and has an internal pressure of 0 kPa (relative pressure) and 80 km. The test course was run at a speed of / h, the running time until the tire was destroyed was measured, and the run-flat durability was evaluated based on the running time. The evaluation results are shown in Table 1.

  Each of the test tires was mounted on a rim of size 7J × 16 to form a tire wheel, and the internal pressure was 0 kPa (relative pressure). And the change of the tire axial height from the road surface in the state which applied the load load of 3.92 kN with the no-load state was measured, and this was evaluated as a deflection amount. Further, the maximum lifting amount from the road surface of the tread portion immediately under the load with the load applied was measured, and this was evaluated as the buckling amount. Table 1 shows the evaluation results of the deflection amount and the buckling amount.

  The height of the bead filler in Table 1 is an index ratio when the rim flange height of the standard rim is 100%. Moreover, the evaluation result of mass is shown by the index ratio when the mass of the tire of Conventional Example 1 is set to 100, and the smaller the value, the lighter the weight. Furthermore, the run-flat durability evaluation results are as follows: A for running time of 60 minutes or more, B for 45 minutes to less than 60 minutes, C for 30 minutes to less than 45 minutes, 15 minutes to less than 30 minutes. Is shown as D and less than 15 minutes as E, with A being the best and E being the worst.

From the results shown in Table 1, Example 1 tire, as compared with the conventional example 1 tire, it can be seen that encourages significant weight while maintaining good run-flat durability. Moreover, although the tire of the prior art example 2 is lightweight, it turns out that run flat running is impossible. Furthermore, the tires of Example 1, as compared with the tires of Comparative Examples 1 and 2, the mass although slightly larger, flexure and buckling are greatly reduced, it is seen that the best overall performance.

  According to the present invention, by providing an appropriate load support structure, it is possible to effectively reduce the buckling during run-flat running while achieving weight reduction, and to provide a safety tire with greatly improved durability. Became possible.

FIG. 2 is a left half sectional view in the width direction of a typical safety tire according to the present invention, schematically showing a state where the tire is mounted on a standard rim. 1 is a schematic development view showing a cord arrangement of a belt layer, a reinforcing layer, and a carcass of a typical safety tire according to the present invention. FIG. 3 is a cross-sectional view in the width direction schematically showing a state in which the internal pressure of a typical safety tire according to the present invention is reduced. FIG. 6 is a left half sectional view in the width direction of another safety tire according to the present invention, schematically showing a state in which the safety tire is mounted on a standard rim. FIG. 6 is a left half sectional view in the width direction of another safety tire according to the present invention, schematically showing a state in which the safety tire is mounted on a standard rim. FIG. 6 is a left half sectional view in the width direction of another safety tire according to the present invention, schematically showing a state in which the safety tire is mounted on a standard rim. FIG. 6 is a left half sectional view in the width direction of another safety tire according to the present invention, schematically showing a state in which the safety tire is mounted on a standard rim. FIG. 6 is a left half sectional view in the width direction of another safety tire according to the present invention, schematically showing a state in which the safety tire is mounted on a standard rim. FIG. 6 is a left half sectional view in the width direction of another safety tire according to the present invention, schematically showing a state in which the safety tire is mounted on a standard rim. It is an expanded view which shows the cord arrangement | sequence of the belt layer of another safety tire according to this invention, a reinforcement layer, and a carcass. It is an expanded view which shows the cord arrangement | sequence of the belt layer of a conventional safety tire, a reinforcement layer, and a carcass. FIG. 5 is a cross-sectional view in the width direction schematically showing a state in which the internal pressure of a safety tire not having an auxiliary belt layer is reduced.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tire 2 Bead core 3 Bead filler 4 Bead part 5 Side wall part 6 Tread part 7 Carcass 8 Belt layer 9, 9a, 9b, 9c Main groove 10 Width end part of belt layer 11 Buttress area 12 Reinforcement layer 13 Auxiliary belt layer 14 Auxiliary Belt layer width end portion 15 Tire maximum width position 16 Reinforcement layer inner end portion in tire radial direction 17 Rim guard portion 18 Rim guard portion outer end portion in tire radial direction 19 Bead radial end portion in tire radial direction 20 Auxiliary rubber layer 21 Reinforcing layer R rim RF rim flange RL rim diameter line C tire circumferential direction

Claims (3)

At least one sheet extending in a toroidal shape over each part of a pair of bead portions in which a bead core and a bead filler are embedded, a pair of sidewall portions extending outward in the tire radial direction from the bead portion, and a tread portion extending between both sidewall portions. A carcass made of a ply and a crown portion of the carcass, and at least one belt layer formed by rubber covering the cord, and at least two of the tread portion extending along the tire circumferential direction. In safety tires with main grooves,
In the tire width direction cross-section, a metal cord is covered with rubber on the outer surface of the carcass, and at least a pair of left and right reinforcing layers extending beyond the buttress area from the width end portion of the belt layer are cords constituting them. Arranged to cross each other across the tire circumferential direction,
A safety tire characterized in that at least one auxiliary belt layer formed by rubber-coating a metal cord is disposed outside the belt layer in the tire radial direction so that the cord constituting the belt extends across the tire circumferential direction. .   2. The safety tire according to claim 1, wherein both end portions of the auxiliary belt layer are positioned outside a pair of outermost main grooves that are main grooves positioned on the outermost side in the tire width direction.   The safety tire according to claim 1 or 2, further comprising an auxiliary rubber layer between the carcass and the reinforcing layer.

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