JP4963459B2 - How to install a pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire mounting method that can be suitably used for racing carts, sports cars, and the like and can improve durability while ensuring excellent steering stability by increasing carcass rigidity.

  For example, in pneumatic tires used in high-speed four-wheeled vehicles such as sports cars and racing carts, the carcass that forms the skeleton of the tire is made up of multiple carcass plies in order to increase tire rigidity and improve steering stability. While being formed, a highly elastic organic fiber cord such as an aramid fiber cord or a PEN fiber cord (polyethylene 2, 6 naphthalate fiber cord) is adopted as the carcass cord (see, for example, Patent Document 1).

JP 2003-54215 A

  However, the high-elasticity organic fiber cord has a problem that the elastic modulus is inferior in fatigue resistance due to the high elastic modulus, and the strength of the cord is reduced by running and the durability of the tire is thereby lowered. For this reason, when such a highly elastic cord is used, means such as increasing the number of twists of the cord to enhance the elongation characteristic and increasing the inclination angle of the cord with respect to the tire circumferential direction are employed. However, all of these means bring about a reduction in the carcass rigidity, so that the characteristics of the highly elastic cord cannot be fully exhibited, and the improvement in steering stability has been limited.

In view of such a situation, as a result of research conducted by the inventor, when the carcass cord is deteriorated in strength due to fatigue and causes cord damage, the carcass cord is concentrated on the tires of the left front wheel and the right rear wheel, and the radius of the carcass ply It has been found that there is a specific tendency to occur, such as being noticeable at the carcass ply on the innermost side in the direction, particularly at the position of the side wall portion inside the vehicle. As a result of further research on the cause of this trend, the following facts could be found. That is,
(A) In a four-wheeled vehicle for high-speed traveling, each tire is mounted with a so-called negative camber angle in order to improve turning performance, so that a larger load is applied to the inside of the vehicle than to the outside of the vehicle. Is done. That is, since a larger stress repeatedly acts on the side wall portion inside the vehicle, the strength of the carcass cord is likely to decrease due to fatigue.
(B) The fatigue resistance of the highly elastic cord is lower in the compression direction. However, when a plurality of carcass plies are used, the innermost carcass ply is more susceptible to compressive stress and tends to get fatigued. Become.
(C) In a four-wheel vehicle for high-speed traveling, a large stress acts on the front wheels during braking, and a large stress acts on the rear wheels, which are driving wheels, during driving. On the other hand, in the pneumatic tire, conventionally, the innermost carcass ply has been manufactured by attaching a ply material to the uppermost carcass ply, that is, the inclination direction of the carcass cord is raised to the right. The inclination direction of the cord is applied. Due to the direction of the inclination of the cord, during braking, the innermost carcass ply of the left front wheel is subjected to compressive stress on the inner side wall of the vehicle, resulting in a significant decrease in strength due to fatigue and driving. Sometimes, in the innermost carcass ply in the right rear wheel, a compressive stress acts on the side wall portion inside the vehicle, and the strength reduction due to fatigue becomes remarkable.

  In order to suppress such strength reduction due to fatigue of the carcass cord, tensile stress, not compressive stress, acts on the inner side carcass ply in the innermost carcass ply at the left and right front wheels during braking. The direction of the carcass cord inclination is set as described above, and the right and left rear wheels are driven so that the carcass cord inclination direction is applied to the vehicle inner side wall portion of the innermost carcass ply when driving. I found that it should be set. Further, at this time, restrictions on the number of twists of the cord and the inclination angle of the cord are alleviated, so that it is possible to further improve the handling stability such as increasing the carcass rigidity.

  Therefore, the present invention is based on identifying the inclination direction of the carcass cord of the innermost carcass ply in the left front wheel, the right front wheel, the left rear wheel, and the right rear wheel, and suppresses the strength reduction of the carcass cord due to fatigue. An object of the present invention is to provide a method for mounting a pneumatic tire that can increase the durability of the tire and increase the carcass rigidity to further improve the steering stability.

In order to achieve the above object, the invention of claim 1 of the present application is directed to a pneumatic tire having a carcass extending from a tread portion to a side wall portion to a bead core of a bead portion. A method for mounting pneumatic tires to be mounted on the rear wheel and the right rear wheel,
The carcass is composed of at least two carcass plies in which carcass cords are inclined and arranged at an angle of 25 to 80 ° with respect to the tire circumferential direction, and each carcass ply has the direction of inclination of the carcass cord between the plies. It is placed inside and outside in the radial direction with different,
The pneumatic tire mounted on the left front wheel and the right rear wheel is when the direction of inclination of the carcass cord of the innermost carcass ply disposed on the radially innermost side is viewed from above the vehicle toward the front of the vehicle. , Rise to the left,
In addition, the pneumatic tire mounted on the right front wheel and the left rear wheel is seen from the upper side of the vehicle toward the front of the vehicle in the direction of inclination of the carcass cord of the innermost carcass ply disposed on the innermost side in the radial direction. Sometimes, it is characterized by a rising shoulder.

  According to a second aspect of the present invention, the pneumatic tire has a negative camber angle and is mounted on a left front wheel, a right front wheel, a left rear wheel, and a right rear wheel, respectively.

  According to a third aspect of the present invention, the pneumatic tire includes at least two pieces of belt cords inclined at an angle of 15 to 30 degrees with respect to the tire circumferential direction on the radially outer side of the carcass and inside the tread portion. A belt layer comprising a belt ply is provided, and the inclination direction of the belt cord of the innermost belt ply arranged at the innermost radial direction is set to the direction of the carcass cord of the outermost carcass ply arranged at the outermost radial direction. It is characterized by having a different inclination direction.

  As described above, in a four-wheel vehicle for high-speed traveling, a large load is applied to the inside of the vehicle due to the negative camber angle, a large stress is applied to the front wheels during braking, and a large stress is applied to the rear wheels during driving. Works. In addition, the high elastic cord is inferior in fatigue resistance against compressive stress.

  At this time, in the present invention, in the pneumatic tire mounted on the four-wheeled vehicle, the left front wheel and the right rear wheel have a left-side upward inclination of the carcass cord of the innermost carcass ply, and the right front wheel and the left rear wheel. The circle is raised to the right. Therefore, as will be described in the section of the “Embodiment of the Invention” described later, the carcass cord is resistant to the carcass ply in the side wall portion and the innermost carcass ply, which is the portion most susceptible to fatigue damage in each wheel. The stress in the tensile direction, which is advantageous for fatigue, will act. As a result, the strength reduction due to the fatigue of the carcass cord can be suppressed, the cord damage resulting therefrom can be suppressed, and the durability of the tire can be improved.

  Moreover, since the strength reduction due to fatigue is suppressed, the restrictions on the number of twists of the cord and the inclination angle of the cord are eased. Therefore, it is possible to increase the carcass rigidity by means such as using a high elastic cord with a lower number of twists or reducing the inclination angle of the cord, and further improvement in steering stability can be achieved.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing an example of a pneumatic tire used in a pneumatic tire mounting method (hereinafter referred to as a tire mounting method) according to the present invention, and FIGS. 2A and 2B illustrate a carcass cord arrangement. FIG. 3 is a conceptual diagram showing the tire mounting method together with the inclination direction of the carcass cord of the innermost carcass ply.

  In FIG. 1, a pneumatic tire 1 used in the tire mounting method of the present invention includes at least a carcass 6 that extends from a tread portion 2 through a sidewall portion 3 to a bead core 5 of a bead portion 4. In this example, the case where the pneumatic tire 1 is a cart tire 1A mounted on a racing cart is illustrated.

  This cart tire 1A is a small flat tire having an outer diameter DT of 300 mm or less and an aspect ratio H / W of 0.5 or less, which is a ratio of a tire cross-sectional height H to a tire width W. In this example, the tread rubber 2G forming the tread surface 2S is directly overlapped on the outer side in the radial direction of the carcass 6 without using a belt layer. A rubber composition having a 300% modulus of 1.5 to 5.0 MPa is suitable for the tread rubber 2G. Such a rubber composition has a gripping force and wear resistance on a road surface during extreme racing. Can be balanced in a high dimension with a good balance. In other words, when the 300% modulus of the tread rubber 2G is less than 1.5 MPa, the tread rubber 2G tends to be too soft and the wear resistance tends to be excessively decreased. There is a tendency that the road surface cannot be gripped sufficiently. The 300% modulus is a value measured in accordance with JIS K6251 “Method of tensile test for vulcanized rubber”.

  Next, the carcass 6 includes a winding portion 6b that winds around the bead core 5 from the inner side to the outer side in the tire axial direction at both ends of the toroidal main body portion 6a straddling the bead cores 5 and 5. A bead apex rubber 8 having a triangular cross section extending radially outward from the bead core 5 is provided between the main body 6 a and the winding portion 6 b, and is reinforced from the bead 4 to the sidewall 3. As the bead apex rubber 8, one having a rubber hardness (durometer A hardness) of 65 to 95 ° is used.

  2A and 2B, the carcass 6 has an angle θ of 25 to 80 ° (25 to 45 ° in the case of the cart tire 1A) with respect to the tire circumferential direction. It is formed of at least two carcass plies 6A and 6B in which an array of inclined carcass cords 10 is covered with a topping rubber, in this example. In this example, the carcass ply 6A constitutes the innermost carcass ply arranged on the innermost side in the radial direction, and the carcass ply 6B constitutes the outermost carcass ply arranged on the outermost side in the radial direction. Each of the carcass plies 6A and 6B is overlapped with the direction of the inclination of the carcass cord 10 being different between the plies. In the tire mounting method of the present invention, the inclination of the carcass cord 10 in the innermost carcass ply 6A is arranged. When the direction is viewed from the top of the vehicle toward the front of the vehicle, both a case where the shoulder rises right (FIG. 2A) and a case where the orientation rises left (FIG. 2B) are used.

  As the carcass cord 10, a highly elastic organic fiber cord such as an aramid fiber cord or a PEN fiber cord is adopted, and by improving the carcass rigidity and tire rigidity, steering stability including turning performance at high speed driving is improved. Yes. From the viewpoint of improving the handling stability, the carcass topping rubber has a rubber hardness (durometer A hardness) in the range of 50 to 80 °, further in the range of 60 to 80 °, which is harder than before. Can be suitably employed. As a result, the carcass rigidity can be further improved and the steering stability can be further improved. In addition, since the hard topping rubber can reduce the burden of stress on the carcass cord 10, the problem of fatigue resistance in the carcass cord 10, which is a highly elastic fiber cord, can be compensated, and the durability of the carcass 6 can be improved. Will also be advantageous,

  In the present invention, as conceptually shown in FIG. 3, in the pneumatic tire 1 attached to the left front wheel FL and the right rear wheel RR, the inclination direction of the carcass cord 10 of the innermost carcass ply 6 </ b> A is In the pneumatic tire 1 that rises to the left and is attached to the right front wheel FR and the left rear wheel RL when viewed from the top of the vehicle toward the front of the vehicle, the inclination direction of the carcass cord 10 of the innermost carcass ply 6A Is going up.

  Next, the function and effect of the present invention will be described. First, in a four-wheel vehicle for high-speed traveling, a negative camber angle of −0.5 to −10 ° is given to each tire 1 for the purpose of improving turning performance. A large load is applied. Further, a large force acts on the left and right front wheels FL, FR during braking, and as shown in FIG. 4, the rim 20 is relative to the tire 1 in a direction K1 opposite to the tire rotation direction. Rotate. Therefore, as in the present invention, when the direction of inclination of the carcass cord 10 of the innermost carcass ply 6A is the left front wheel FL rising left and the right front wheel FR rising right shoulder, both the left and right front wheels FL, FR In the side wall portion 3 inside the vehicle, the stress Pa in the pulling direction acts on the carcass cord 10.

  On the other hand, in the tires 1 of the left and right rear wheels RL and RR, a large force acts during driving. At that time, the rim 20 rotates relative to the tire 1 in the tire rotation direction K2. Therefore, as in the present invention, when the direction of the inclination of the carcass cord 10 of the innermost carcass ply 6A is a right shoulder rising at the left rear wheel RL and a left shoulder rising at the right rear wheel RR, the left and right rear wheels RL , RR, the stress Pa in the tensile direction acts on the carcass cord 10 in the side wall portion 3 inside the vehicle.

  As described above, the carcass cord 10 is advantageous in terms of fatigue resistance in the side wall portion 3 and the innermost carcass ply 6A, which are the parts most susceptible to fatigue damage in each of the wheels FL, FR, RL, and RR. The stress Pa in the tensile direction can be applied. As a result, the strength reduction due to the fatigue of the carcass cord can be suppressed, the cord damage resulting therefrom can be suppressed, and the durability of the tire can be improved.

  On the other hand, as shown in FIG. 5, in the case of the conventional mounting method in which the inclination direction of the carcass cord of the innermost carcass ply is raised to the right as shown in FIG. Since the stress Pb in the compression direction acts on the front wheel FL and the right rear wheel RR, the strength decrease due to fatigue becomes severe and the durability of the tire is reduced.

  In addition to the racing cart as in this example, such a tire mounting method can also be applied to a high-speed four-wheel vehicle such as a sports car traveling on a public road or a racing car traveling on a circuit course. FIG. 6 shows a high-performance tire 1B that is suitably used for such a vehicle.

  As shown in FIG. 6, the high-performance tire 1 </ b> B includes a belt layer 7 on the outer side in the radial direction of the carcass 6 and inside the tread portion 2. The carcass 6 is composed of two or more carcass plies 6A and 6B in which carcass cords are arranged at an inclination angle of 45 ° to 80 °, preferably 65 ° to 80 ° with respect to the tire circumferential direction. Each of the carcass plies 6A and 6B is placed so that the inclination directions of the carcass cords are different between the plies.

  In this example, the innermost carcass ply 6A is provided with a series of ply winding portions that wind up around the bead core 5 from the inner side to the outer side in the tire axial direction on both sides of the ply main body portion 6Aa straddling between the bead cores 5 and 5. The outermost carcass ply 6B is formed by a so-called winding ply, and is formed by a lowering ply that passes the outside of the ply main body portion 6Aa and covers the ply winding portion 6Ab and is wound radially inward. A so-called 1-1 structure is illustrated. As in the case of the cart tire 1A, a 2-0 structure in which the carcass plies 6A and 6B are wound up plies can be used. As the carcass cord, highly elastic organic fiber cords such as aramid fiber cords and PEN fiber cords are adopted, and the steering stability including turning performance at high speed is improved by increasing the carcass rigidity and tire rigidity. .

  The belt layer 7 is composed of at least two belt plies 7A and 7B, in this example two belt plies 7A and 7B, in which belt cords are inclined and arranged at an angle of 15 to 30 ° with respect to the tire circumferential direction. Are placed with different directions of inclination of the cords so that the belt cords cross each other between the plies. Steel cords are preferably employed as the belt cords, but highly elastic organic fiber cords such as aramid fiber cords and PEN fiber cords can also be used. In the belt layer 7, it is preferable that the inclination direction of the belt cord of the innermost belt ply 7A is different from the inclination direction of the carcass cord of the outermost carcass ply 6B, thereby further increasing the belt rigidity and the tread. The part 2 can be reinforced more firmly. In the high-performance tire 1B, it is preferable to form a band layer 12 that suppresses the belt layer 7 from rising due to centrifugal force on the outer side of the belt layer 7 for the purpose of further improving the high-speed running performance. The band layer 12 is composed of a jointless ply in which a band cord made of an organic fiber cord is spirally wound at an angle of 5 degrees or less with respect to the tire circumferential direction, and in this example, the outer end is the innermost side on the wide side. The belt ply 7A terminates substantially in line with the outer end of the belt ply 7A.

  Also in such a high performance tire 1B, as shown in FIG. 3, in the pneumatic tire 1 attached to the left front wheel FL and the right rear wheel RR, the carcass cord 10 of the innermost carcass ply 6A has an inclination. When viewed from the top of the vehicle toward the front of the vehicle, the pneumatic tire 1 that rises to the left and is attached to the right front wheel FR and the left rear wheel RL has the carcass cord 10 of the innermost carcass ply 6A. By increasing the direction of inclination to the right, it is possible to suppress a decrease in the strength of the carcass cord due to fatigue and the cord damage associated therewith, and to improve durability.

  As mentioned above, although especially preferable embodiment of this invention was explained in full detail, this invention is not limited to embodiment of illustration, It can deform | transform and implement in a various aspect.

(A)
A cart tire (tire size: 11 × 7.10-5) having the basic structure shown in FIG. 1 was prototyped and mounted on the four wheels of the vehicle according to the specifications shown in Table 1, and a cart course (course length 734 m) was installed. Steering stability and lap time (average time of 10 laps) at the time of limit driving were measured. The tire was disassembled, and the cord strength of the carcass cord in the new tire was measured and compared with the cord strength of the carcass cord of the tire after 30 turns. All tires have the same specifications except that the direction of the inclination of the carcass cord is different, and the following are used as the carcass.
Carcass cord: Aramid fiber cord (1670 dtex / 2),
-Number of cord twists (under twist / up twist): 35/35 times / 10 cm
・ Cord angle θ: 30 °
・ Number of driven: 50 / 5cm

<Lap time and handling stability>
Each sample tire was mounted on a racing cart with a displacement of 100 cc, and the cart course was run 10 laps, and the average lap times at that time were compared. Further, the steering stability (including gripping property, traction property, braking property, etc.) at that time is shown as an index with Comparative Example A1 as 100 by sensory evaluation of the driver. The larger the number, the better.

<Strong code>
In accordance with “tensile strength and elongation” described in Section 8.5 of JIS L1017 (chemical fiber tire cord test method), the load at break of the carcass cord taken out from the tire was measured. Comparison was made using an index with a code strength of 100. The larger the number, the higher the code strength.

(B)
When a prototype of a high-performance tire (tire size: 265 / 35R18) having the basic structure shown in FIG. 6 is mounted on the four wheels of the vehicle according to the specifications shown in Table 1, and the circuit course (course length: 3703 m) is run to the limit. The steering stability and lap time (average time of 10 laps) were measured. The tire was disassembled, and the cord strength of the carcass cord in the new tire was measured and compared with the cord strength of the carcass cord of the tire after 50 laps. All tires have the same specifications except that the direction of the inclination of the carcass cord is different, and the following are used as the carcass.
Carcass cord: Aramid fiber cord (1670 dtex / 2),
-Number of cord twists (under twist / up twist): 40/40 times / 10 cm
・ Cord angle θ: 65 °
・ Number of drives: 49 / 5cm

<Lap time and handling stability>
Each sample tire was mounted on all wheels of a race car with a displacement of 2600cc, and the circuit course was run 10 laps, and the average lap times at that time were compared. Further, the steering stability (including grip performance, traction performance, braking performance, etc.) at that time is shown as an index with Comparative Example B1 as 100 by sensory evaluation of the driver. The larger the number, the better.

  As shown in the table, in each of the wheels FL, FR, RL, and RR, it can be confirmed that there is little decrease in strength due to fatigue of the carcass cord, and the durability of the tire is improved.

It is sectional drawing which shows an example of the pneumatic tire used for the mounting method of the pneumatic tire of this invention. (A) and (B) are conceptual diagrams illustrating a carcass code arrangement. It is a conceptual diagram which shows the mounting method of a pneumatic tire with the direction of inclination of the carcass cord of the innermost carcass ply. It is drawing explaining the effect of the mounting method of this invention. It is drawing explaining the problem of the conventional mounting method. It is sectional drawing which shows the other example of the pneumatic tire used for the mounting method of the pneumatic tire of this invention.

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 Inner carcass ply 7 Belt layer 7A, 7B Belt ply 10 Carcass cord FL Left front wheel FR Right front wheel RL Left rear wheel RR Right rear wheel

Claims (3)

A pneumatic tire mounting method in which a pneumatic tire having a carcass extending from a tread portion to a sidewall portion to a bead core of a bead portion is mounted on a left front wheel, a right front wheel, a left rear wheel, and a right rear wheel of a four-wheel vehicle. Because
The carcass is composed of at least two carcass plies in which carcass cords are inclined and arranged at an angle of 25 to 80 ° with respect to the tire circumferential direction, and each carcass ply has the direction of inclination of the carcass cord between the plies. It is placed inside and outside in the radial direction with different,
The pneumatic tire mounted on the left front wheel and the right rear wheel is when the direction of inclination of the carcass cord of the innermost carcass ply disposed on the radially innermost side is viewed from above the vehicle toward the front of the vehicle. , Rise to the left,
In addition, the pneumatic tire mounted on the right front wheel and the left rear wheel is seen from the upper side of the vehicle toward the front of the vehicle in the direction of inclination of the carcass cord of the innermost carcass ply disposed on the innermost side in the radial direction. A method of wearing a pneumatic tire, characterized in that it is raised to the right.   The method for mounting a pneumatic tire according to claim 1, wherein the pneumatic tire has a negative camber angle and is mounted on each of a left front wheel, a right front wheel, a left rear wheel, and a right rear wheel.   The pneumatic tire includes a belt layer including at least two belt plies in which a belt cord is inclined and arranged at an angle of 15 to 30 ° with respect to the tire circumferential direction on the radially outer side of the carcass and inside the tread portion. In addition, the inclination direction of the belt cord of the innermost belt ply arranged at the innermost radial direction is different from the inclination direction of the carcass cord of the outermost carcass ply arranged at the outermost radial direction. The method for mounting a pneumatic tire according to claim 1 or 2, characterized in that:

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