JP4928065B2 - Pneumatic tires for passenger cars - Google Patents

Description

The present invention relates to a pneumatic tire for excellent passenger cars to uniformity while improving the high-speed durability.

  In order to cope with the recent expansion of the expressway network and higher output of the vehicle system, it is an urgent task to improve the high-speed durability of the tire. Conventionally, in order to improve high-speed durability, various pneumatic radial tires in which a band layer is provided inside a tread portion have been proposed. For example, in the case of a radial tire for a passenger car, the band layer is formed by one or a plurality of band plies in which organic fiber cords are arranged substantially parallel to the tire circumferential direction. Such a band layer can suppress the protruding deformation of the carcass or the belt layer due to the centrifugal force during high-speed traveling, and can suppress damage such as tread separation.

  Further, although the band layer is generally generally disposed outside the belt layer in the tire radial direction, the following Patent Document 1 proposes a technique for providing a belt layer between the carcass and the belt layer. .

JP-A-8-216618

  Patent Document 1 does not describe a specific manufacturing method for the tire. However, in this type of pneumatic tire prototyped based on the general technical level at the time of filing, the difference between the intermediate elongation at the crown portion and the intermediate elongation at the shoulder portion in the band cord is very large. I found it big. In particular, since the intermediate elongation at the shoulder portion is large, the binding force on the end of the belt layer that is most likely to protrude during high-speed running is insufficient, and there is room for further improvement in high-speed durability.

  Further, in the finished tire, the so-called meandering of the carcass cord around the shoulder portion is likely to occur. This defect appears as a deterioration of uniformity and causes vibration and noise during driving.

  Here, a conventional method for manufacturing a pneumatic tire will be briefly described. As shown in phantom lines in FIG. 8, first, a cylindrical cover base a including bead cores b and b and carcass plies c each having both sides locked by the bead cores b and b is prepared. Then, as indicated by the solid line, the cover base a has the carcass ply c bulged in a toroidal shape while the bead cores b and b are close to each other in the axial direction. The bulging of the cover base a is performed by filling the lumen side with high-pressure air.

  A tread member d is waited in advance on the outer side in the tire radial direction of the cover base a. The tread member d is an unvulcanized tread rubber e, a belt layer f, and a band layer g arranged on the inside thereof in a ring shape that is previously laminated and integrated on a flat deck with a cylindrical surface. Is formed. And the outer peripheral surface of the bulged cover base | substrate a is affixed on the inner peripheral surface of the tread member d (shaping process).

  When the tread member d and the cover base a are attached to each other, the tread member d is bent in accordance with the expansion and deformation of the cover base a and is curved into an arc shape having a smooth cross section. In particular, the carcass ply has a larger bulge amount in the crown portion. For this reason, the band cord of the band layer g greatly expands by receiving a larger tension at the crown portion, but receives a relatively small tension at the shoulder portion, and the elongation amount is also small. As described above, the band cord of the shoulder portion is considered to have increased intermediate elongation in the finished tire because of insufficient pretension during shaping.

  In addition, the carcass ply c tends to bulge out in an arc shape as shown by phantom lines in the figure, but since it is constrained in a more linear shape by the flat band layer g, only the difference is the carcass cord. It is considered that the meandering was caused by being compressed in the length direction.

The present invention has been devised in view of the above-described problems. In the band layer, the difference in the intermediate elongation of the band cord between the shoulder portion and the crown portion is regulated within a certain range. It is an object of the present invention to provide a passenger car pneumatic tire that while improving the durability can improve the uniformity.

The invention according to claim 1 is a tire radius comprising a carcass extending from a tread portion through a sidewall portion to a bead core of the bead portion, and inside the tread portion and radially outward of the carcass and made of a steel cord. A pneumatic tire for passenger cars comprising a belt layer composed of two belt plies in the direction and outside,
Between the carcass and the belt layer, a band cord is inclined with respect to the tire equator at an angle of more than 0 ° and not more than 5 °, and the direction of the inclination is a steel cord of the belt ply in the tire radial direction. A band layer composed of at least one band ply opposite to the inclination direction of
The band ply is formed by spirally winding a band-like ply in which one or more band cords are covered with a topping rubber around the carcass ply,
Moreover, the band cord is characterized in that the difference obtained by the following formula (1) between the intermediate elongation Ct (%) at the crown portion and the intermediate elongation St (%) at the shoulder portion is 10% or less. Yes.
Difference in intermediate elongation (%) = | (St / Ct) −1 | × 100 (1)

  The invention according to claim 2 is the pneumatic tire according to claim 1, wherein the band cord has an intermediate elongation of 10% or less over the entire region.

  According to a third aspect of the present invention, in the belt layer, the difference | θc−θs | between the cord angle θc at the crown portion and the cord angle θs at the shoulder portion is 5 ° or less. Item 3. The pneumatic tire according to Item 1 or 2.

According to a fourth aspect of the present invention, the width of the band ply in the tire axial direction is 70 to 130% of the width of the belt layer in the tire axial direction and 60 to 90% of the maximum tire width. Oh Ru pneumatic tire according to any one of claim 1 to 3.

  In the pneumatic tire of the present invention, in the band layer disposed between the carcass and the belt layer, the difference in the intermediate elongation of the band cord is regulated within a certain range between the shoulder portion and the crown portion. For this reason, the restraining force by the band ply is made uniform, and the durability during high-speed traveling can be improved. Further, since the intermediate elongation of the band cord is made uniform, the tension on the carcass ply and the belt layer is easily optimized. This prevents the carcass cord from meandering and helps stabilize the cord angle in the belt layer.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view of a tire meridian in a normal state including the tire shaft of the pneumatic tire 1 of the present embodiment, and FIG. 2 is a developed view of the internal structure thereof. In this specification, “normal state” means that the tire 1 is assembled in the normal rim J with the rim assembled and filled with the normal internal pressure, and when there is no particular notice, the dimensions of each part of the tire are measured in this normal state. Value.

  The “regular rim” is a rim determined for each tire in the standard system including the standard on which the tire is based. For example, a standard rim for JATMA, “Design Rim” for TRA, and ETRTO If there is, “Measuring Rim”. In addition, “regular internal pressure” is the air pressure that each standard defines for each tire in the standard system including the standard on which the tire is based. It is the maximum air pressure for JATMA and the table “TIRE LOAD LIMITS” for TRA. The maximum value described in “AT VARIOUS COLD INFLATION PRESSURES”, “INFLATION PRESSURE” for ETRTO, but 180 kPa for tires for passenger cars.

  The pneumatic tire 1 includes a carcass 6 extending from the tread portion 2 through the sidewall portion 3 to the bead core 5 of the bead portion 4, and a belt layer 7 disposed on the outer side in the tire radial direction of the carcass 6 and inside the tread portion 2. A radial tire for a passenger car provided with a band layer 9 disposed between the carcass 6 and the belt layer 7 is exemplified.

  The carcass 6 is composed of one or more carcass plies 6A in this example. As shown in FIG. 2, the carcass ply 6A is formed of a radial ply in which carcass cords 6C are arranged at an angle of, for example, 75 ° to 90 ° with respect to the tire equator C. As the carcass cord, a polyester cord is used in this example. However, for example, an organic fiber cord such as nylon, rayon, or aramid, or a steel cord if necessary may be used.

  The carcass ply 6A of the present embodiment includes a main body portion 6a extending from the tread portion 2 through the sidewall portion 3 to the bead core 5 of the bead portion 4, and extending around the bead core 5 from the main body portion 6a to the outer side in the tire axial direction. And a folded portion 6b folded back. A bead apex 8 made of hard rubber extending from the bead core 5 to the outer side in the tire radial direction is disposed between the main body portion 6a and the folded portion 6b, and the bead portion 4 is appropriately reinforced. The rubber hardness of the bead apex rubber 8 is not particularly limited, but for example, a JIS durometer A hardness of 75 to 98 degrees, more preferably about 80 to 96 degrees is suitable.

The belt layer 7 is composed of at least two belt plies 7A and 7B, in this example, the inner and outer two belt plies. Each belt ply 7A, 7B is composed of a ply in which the belt cord 7C is inclined with respect to the tire equator at a small angle of, for example, 10 to 45 °, and the belt cords 7C are overlapped in a direction intersecting each other. A steel cord is adopted as the belt cord 7C. The inner belt ply 7A is formed wider than the outer belt ply 7B, and the width W1 (shown in FIG. 1) of the belt layer 7 is determined as the width of the inner belt ply 7A.

The band layer 9 is provided between the carcass 6 and the belt layer 7, and at least one band ply 9A that inclines the band cord 9C with respect to the tire equator C at an angle greater than 0 ° and less than 5 °. Consists of

As shown in FIG. 2, the band ply 9A has a narrow belt-like ply 10 in which one or a plurality of (in this example, a plurality of) band cords 9C are covered with a topping rubber and spirally formed outside the carcass ply 6A. Ru is formed by winding a. Further, the band cord 9C is inclined with respect to the tire equator C at an angle greater than 0 ° and not more than 5 °, and the inclination direction is opposite to the inclination direction of the belt cord 7C of the belt ply 7A. Thereby, a new tagging effect arises and the restraining force to the carcass 6 can be increased. The band cord 9C is preferably, for example, an organic fiber cord, particularly nylon, rayon, polyethylene-2,6-naphthalate, or aramid. The belt-like ply 10 is not particularly limited, but when covering a plurality of band cords 10C, a narrow tape shape having an upper limit of about ten is preferable.

  The width BW (shown in FIG. 1) of the band ply 9A in the tire axial direction is preferably 70 to 130% of the width W1 of the belt layer 7. If the width BW of the band ply 9A is less than 70% of the width W1 of the belt layer 7, the tread region cannot be sufficiently covered and the effect of improving the high-speed durability tends to be reduced, and conversely 130% If it exceeds the limit, the end portion 9e of the band ply 9A approaches the buttress portion having a large distortion during traveling, and damage such as looseness is easily induced. Particularly preferably, the width BW of the band ply 9A is 80 to 110% of the width W1 of the belt layer. From the same viewpoint, the width BW of the band ply 9A is desirably 60 to 90% of the maximum tire width SW. In the present embodiment, an example in which the width BW of the band ply 9A is substantially equal to the width W1 of the belt layer 7 and is 74% of the tire maximum width SW is exemplified.

In the pneumatic tire 1 of the present invention, in the band cord 9C, the difference between the intermediate elongation Ct (%) at the crown portion Cr and the intermediate elongation St (%) at the shoulder portion is limited to 10% or less. Yes. That is, the difference in intermediate elongation between the crown portion Cr and the shoulder portion Sh is very small.
Difference in intermediate elongation (%) = | (St / Ct) −1 | × 100 (1)

As described above, in the band cord 9C, the difference between the intermediate elongation Ct (%) and St (%) is set to 10% or less, so that the binding force of the band layer 9 is made uniform in the tire axial direction. As described above, it is possible to effectively prevent the reduction of the restraining force in the shoulder portion Sh. In addition, the ground contact shape and contact pressure distribution during high-speed traveling can be made uniform, and the driving stability such as straight-line stability and linearity during lane change can be improved. Particularly preferably, the difference is 8% or less, more preferably 0 to 5% . Further, the value of {(St / Ct) -1} may be a negative value. In this case, in the band cord 9C, it means that the intermediate elongation St (%) of the shoulder portion Sh is smaller than the intermediate elongation Ct (%) of the crown portion Cr. Therefore, the restraining force of the shoulder portion Sh is relatively Can improve.

Further, when the intermediate elongation of the band cord in the middle portion Md between the crown portion Cr and the shoulder portion Sh is Mt (%), the difference in the intermediate elongation calculated by the following formula (2) is also 10% or less. It is desirable to be.
Difference in intermediate elongation (%) = | (Mt / Ct) −1 | × 100 (2)
Thereby, since the intermediate elongation of the band cord can be made more uniform in the tire axial direction, the high-speed durability can be further improved.

  In this specification, the crown portion Cr is a region of 30% of the width W1 of the belt layer 7 around the tire equator C as shown in FIG. Similarly, the shoulder portion Sh is a region 15% of the width W1 from the outer end 7e of the belt layer 7. The middle part Md is an area between them. Further, the intermediate elongation Ct (%) of the band cord of the crown portion Cr is obtained by disassembling the finished tire, randomly extracting eight band cord samples from the crown portion Cr, and averaging the intermediate elongation measured from them. Value. The band cord of the shoulder portion Sh is dismantled from the finished tire, and eight band cord samples are randomly extracted from the shoulder portions Sh on both sides, respectively, and the intermediate elongation measured from them is measured and a total of sixteen cord cords are measured. Average value. The band code of the middle part Md also conforms to that of the shoulder part. The intermediate elongation of each band cord is the elongation at constant load measured according to “Standard Test” in Section 8.7 of JIS L1017. The rubber adhered around the band cord is carefully removed.

  The band layer 9 desirably has a band cord intermediate elongation of 10% or less in the entire region. Thereby, not only the restraining force by the band ply 9A is made uniform in the tire axial direction, but the elongation amount is further reduced, so that the durability during high-speed running can be further improved.

  In order to obtain a pneumatic tire having the band layer 9 as described above, it is important to uniformize and control the tension acting on the band cord 9C in the tire axial direction in the tire manufacturing process.

  3 to 5 show an example of a method for manufacturing such a pneumatic tire, which will be described below in order. First, as shown in FIG. 3A, the carcass ply 6 </ b> A is wound around the base portion 11 a of the cylindrical former 11. In this example, the carcass ply 6A protrudes from the base part 11a on both sides, and is wound around the sub-parts 11b provided on both sides of the base part 11a.

  Next, as shown in FIG. 3B, the diameter of the sub part 11b of the former 11 is reduced, and the bead core 5 and the bead apex 8 are attached to both outer sides of the carcass ply 6A. Thereafter, both ends of the carcass ply 6A are folded around the bead cores 5 and 5 as shown in FIG. Thereby, a substantially cylindrical cover base 14 including the carcass ply 6A and the bead core 5 is formed. The cover base 14 can contain an inner liner rubber, a sidewall rubber, a clinch rubber, or the like at this stage, if necessary.

  Next, as shown in FIG. 4A, the cover base 14 is transferred from the former 11 to the molding apparatus 15, for example. The molding device 15 is arranged between a pair of clamp rings 16, 16 that can clamp the bead cores 5, 5 of the cover base 14 and can move in an axial direction, and the cover base 14. And a profile deck 17 that bulges between the bead cores 5 and 5.

  FIG. 5 shows a schematic side view of the profile deck 17. The profile deck 17 is configured by combining first segments 18 and second segments 19 that are alternately arranged in the tire circumferential direction. Each segment 18 and 19 is made of a hard material that is not easily deformed, such as metal or resin in this example, and both can move in and out in the tire radial direction by using a drive mechanism (not shown). By changing the movement amounts of the segments 18 and 19, the outer diameter of the profile deck 17 can be expanded or reduced between a small diameter state S1 indicated by a virtual line in FIG. 5 and a large diameter state S2 indicated by a solid line. .

  In the large-diameter state S1, the profile deck 17 can substantially continue the outer peripheral surface of each segment 18 to 19 in the tire circumferential direction. The profile deck 17 is arranged such that its axial center line is aligned with the axial center line of the cover base 14. In the initial state, the outer peripheral surface 20 of the profile deck 17 is positioned on the inner side without contacting the transferred cover base 14. Further, as shown in FIG. 4, each of the segments 18 and 19 of the profile deck 17 has a substantially arc-shaped outer peripheral surface 20 that protrudes outward in the tire radial direction in a cross-sectional shape including the tire rotation axis. Various cross-sectional shapes of the outer peripheral surface 20 can be determined according to the intended tire shape. This will be described later.

  As shown in FIG. 4B, the forming device 15 moves the clamp rings 16 and 16 in the axial direction in the direction of approaching each other and gradually increases the diameter of the profile deck 17. As a result, the cover base 14 bulges by being pushed outward in the tire radial direction in a shape along the profile deck 17. In particular, by linking the movement of the profile deck 17 in the tire radial direction and the approaching movement of the clamp ring 16 in a timely manner, the carcass cord of the cover base 14 can bulge out in a toroidal form while always receiving an appropriate tension. .

  As shown in FIG. 4C, the tread region 14t of the cover base 14 is shaped into a cross-sectional shape along the outer periphery 20 of the profile deck 17 by contacting with it. As one embodiment, the shape of the outer peripheral surface 20 of the profile deck 17 can be adapted to the cross-sectional contour shape of the target band layer 9. Specifically, the outer peripheral surface 20 of the profile deck 17 is formed as an arc surface having a radius of curvature obtained by subtracting the thickness of the cover base 14 from the radius of curvature RB (shown in FIG. 1) of the inner peripheral surface of the band ply 9A. Can do. However, in practice, this arc surface can be corrected more in consideration of various parameters. Thus, the cross-sectional shape of the outer peripheral surface 20 of the profile deck 17 can be variously changed.

  Then, as shown in FIG. 6, a step of spirally winding the belt-like ply 10 around the outer peripheral surface of the tread region 14t of the cover base 14 bulged by the profile deck 17 is performed. At this time, the belt-like ply 10 is wound spirally in a direction in which the band cord is substantially parallel to the tire equator C. Since the tread region 14t of the cover base 14 is supported from the inside by the profile deck 17 having the hard outer peripheral surface 20, the shape can be maintained even when the belt-like ply 10 is spirally wound. Therefore, the carcass cord is not disturbed when the belt-like ply 10 is wound. On the other hand, in the manufacturing method shown in FIG. 8, since the carcass ply is bulged and held by air, if the belt-like ply 10 is spirally wound around the tread region in this state, the shape of the carcass ply is distorted. As a result, the carcass cord is disturbed.

  The method for winding the belt-like ply 10 in a spiral shape is not particularly limited. That is, any of a mode in which the side edges of the belt-like plies 10 are in contact with each other, a mode in which they overlap each other (this is shown in FIG. 6), and a mode in which they are separated from each other may be used. The belt-like ply 10 is preferably wound while receiving an appropriate tension. Thereby, pretension can be given to the band cord 9C. Of course, the tension is desirably adjusted so as to be uniform over the tire axial direction, and to give an elongation such that the intermediate elongation of the band cord 9C of the finished tire is 10% or less.

  Further, after winding the belt-like ply 10, the profile deck 17 may be further expanded in diameter. The outer peripheral surface of the profile deck 17 has an arc shape. For this reason, when the diameter of the profile deck 17 is expanded, each band cord of the crown portion and the shoulder portion is stretched according to the amount of diameter expansion and the outer diameter of the profile deck 17 at each position. Are slightly different. However, it is possible to substantially uniform the intermediate elongation of the band cord in the tire axial direction by regulating the difference in elongation.

  As shown in FIG. 6, belt plies 7 </ b> A and 7 </ b> B and tread rubber 21 are sequentially wound around the outside of the band layer 9 to form a raw cover 22. At this time, if a difference in curvature occurs between the band ply 9A of the cover base 14 and the belt ply 7A, cushion rubber or the like can be appropriately interposed. The raw cover 22 is vulcanized and molded with a tire vulcanization mold, and the pneumatic tire 1 as shown in FIG. 1 can be obtained.

  In addition, by forming the band ply through the above-described process, a stable tension acts on the carcass 6 and the belt layer 7 even during vulcanization and the like. Therefore, in the finished tire, The difference | θc−θs | between the cord angle θc and the cord angle θs at the shoulder portion can be 5 ° or less. Thereby, even in the belt layer 7, the code angle can be made uniform, and the uniformity is improved. For the cord angle θc at the crown portion Cr, eight cord angles at the crown portion Cr are measured, and the average value thereof is adopted. For the cord angle θs at the crown portion Cr, eight cord angles are measured in each shoulder portion Sh, and the average value thereof is adopted.

  When the band layer 9 is disposed on the outer side in the tire radial direction of the belt layer 7, the belt layer 9 restricts the elongation of the belt layer 7 during shaping or vulcanization molding, and the angle of the belt cord is varied. The angle difference is larger than 5 °. In this embodiment, since the band layer 9 has a small intermediate elongation difference between the crown portion Cr and the shoulder portion Sh and is disposed inside the belt layer 7, it is possible to suppress such variations in belt cord angle.

  In the above, a particularly preferred embodiment of the present invention has been described in detail. For example, according to a single stage molding method, the cover base 14 may be molded without being transferred from the former 11 to the molding apparatus 15, and FIG. As shown in the drawing, the band ply 9A is divided into a crown band ply 9a covering the crown portion Cr and a pair of shoulder band plies 9b and 9b covering the shoulder portion Sh. Absent. As described above, the present invention is not limited to the illustrated embodiment, and can be implemented with various modifications.

  With respect to the pneumatic radial tire for a passenger car shown in FIG. 1 and Table 1 (tire size: 225 / 60R16 98H), high-speed durability, uniformity, and the finished state of the tire were measured. The evaluation method is as follows.

<High speed durability>
In accordance with JIS D4230, based on the conditions of rim (16 x 6.5 JJ), internal pressure (200 kPa), load load 4.61 KN, the speed is stepped up by 10 km / h every 10 minutes from the initial speed of 200 km / h. The speed and time (min) when the tire was damaged was recorded.

<Uniformity>
The radial force variation (RFV), lateral force variation (LFV) and conicity (CON) of each test tire were measured using a uniformity testing machine. Each of them is shown as an average value of 20 pieces, and the smaller the numerical value, the better. Conicity is expressed in standard deviation.

<Tire finish>
Before and after vulcanization, the tire was disassembled, and the presence or absence of meandering of the carcass cord and the cord angle of the belt ply on the inner side in the tire radial direction were measured at the shoulder portion and the crown portion.
Table 1 shows the test results.

  As a result of the test, it can be confirmed that the tires of the examples are excellent in uniformity while improving high-speed durability. As a result, the finishing accuracy of the carcass cord and the belt cord is improved.

It is a right half sectional view of a pneumatic tire showing an embodiment of the present invention. It is an expanded view which expands and shows the internal structure. (A)-(C) are the cross-sectional schematic diagrams which show the formation process of a cover base | substrate. (A)-(C) are the cross-sectional schematic diagrams which show the swelling process of a cover base | substrate. It is a side view of a profile deck. It is sectional drawing of a raw cover. It is a fragmentary sectional view of the tread part which shows other embodiments of the present invention. It is a section schematic diagram explaining the manufacturing method of the conventional tire.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Tread part 3 Side wall part 4 Bead part 5 Bead core 6 Carcass 6A Carcass ply 7 Belt layer 7A, 7B Belt ply 9 Band layer 9A Band ply

Claims (4)

A carcass extending from the tread portion through the sidewall portion to the bead core of the bead portion, and a belt comprising two belt plies arranged inside the tread portion and outside the carcass in the radial direction of the carcass, and in the tire radial direction and made of steel cord. A pneumatic tire for a passenger car comprising a layer,
Between the carcass and the belt layer, a band cord is inclined with respect to the tire equator at an angle of more than 0 ° and not more than 5 °, and the direction of the inclination is a steel cord of the belt ply in the tire radial direction. A band layer composed of at least one band ply opposite to the inclination direction of
The band ply is formed by spirally winding a band-like ply in which one or more band cords are covered with a topping rubber around the carcass ply,
Moreover, the band cord is characterized in that the difference obtained by the following formula (1) between the intermediate elongation Ct (%) at the crown portion and the intermediate elongation St (%) at the shoulder portion is 10% or less. Pneumatic tires for passenger cars.
Difference in intermediate elongation (%) = | (St / Ct) −1 | × 100 (1)   The pneumatic tire for a passenger car according to claim 1, wherein the band cord has an intermediate elongation of 10% or less over the entire area.   3. The passenger car according to claim 1, wherein the belt layer has a difference | θc−θs | between the cord angle θc at the crown portion and the cord angle θs at the shoulder portion of 5 ° or less. Pneumatic tire.   The width in the tire axial direction of the band ply is 70 to 130% of the width in the tire axial direction of the belt layer, and is 60 to 90% of the maximum tire width. Pneumatic tires for passenger cars.

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