JP4363927B2 - Radial tires for passenger cars - Google Patents

Description

The present invention relates to a radial tire for a passenger car with reduced road noise.

  As the quality and quality of vehicles increase, it is desired to reduce the noise generated in the vehicle. As one of such noises, the running tire spreads the unevenness of the road surface, and the vibration is transmitted to remove the air in the vehicle. The demand for improvement of so-called road noise generated based on vibration is becoming extremely high.

  In recent years, it has been proposed to form a band layer formed by spirally winding a band cord on the outer side in the radial direction of the belt layer as one of means for reducing the road noise. This band layer increases the restraint force on the belt layer, suppresses the radial resonance of the tire, changes the vibration transmission characteristics, and shifts the peak of the vibration transmission rate to a higher frequency side. Road noise is reduced by causing a deviation from the peak. It is also known that this road noise reduction effect is more effective if the band layer is provided at both ends of the belt layer rather than the entire width of the belt layer.

  However, such a band layer needs to be formed between the groove bottom of the tread groove and the belt layer so as not to be exposed to the ground contact surface even at the end of wear. Therefore, there is a problem that when the band layer is thickened in order to be restricted by the thickness of the band layer or to obtain stronger restraining force, the gauge thickness under the groove increases, leading to an increase in tire weight. . In addition, the band layer causes an increase in costs such as an increase in the types of tire constituent members, an increase in the number of manufacturing steps, and an increase in material costs.

In view of such a situation, the present inventor conducted research while paying attention to tread rubber. As a result, when a circumferential rib having a predetermined size extending continuously in the tire circumferential direction is provided at a position to be the outer end portion of the belt layer, and the circumferential rib is formed of rubber having a large modulus in the tire circumferential direction, It has been found that this circumferential rib can have the same function as a conventional band layer, and it is possible to increase the restraining force on the belt layer and reduce road noise.
JP-A-8-238910 JP-A-11-99806

According to the present invention, a circumferential rib having a predetermined size extending continuously in the tire circumferential direction is provided at a position to be the outer end portion of the belt layer, and the circumferential rib is formed of rubber having a large modulus in the tire circumferential direction. The objective is to provide a radial tire for a passenger car that can increase the restraining force on the belt layer and reduce road noise without causing an increase in weight or cost.

In order to achieve the above object, the invention of claim 1 of the present application is continuous in the tire circumferential direction within a range region Y that is separated from the tread portion and the tire equator by a distance of 55% to 120% of the tread ground half width TW. And a plurality of circumferential ribs having a tire axial width W of 2.0 to 7.0 mm,
And the sum total ΣS of the cross-sectional areas S in the tire meridional section of each circumferential rib is set to 100 mm ² or more,
The tread rubber forming the tread portion is characterized in that at least the 5% modulus Ea in the tire circumferential direction of the rib rubber portion forming the circumferential rib is 10 to 50 Mpa.

In the invention of claim 2, the at least rib rubber portion is made of a short fiber-blended rubber in which short fibers are blended in the rubber, and the short fibers are oriented in the tire circumferential direction, so that 5% of the tire circumferential direction is obtained. The modulus Ea is in the range of 10 to 50 Mpa, and the 5% modulus Eb in the tire radial direction is reduced to 0.5 times or less of the 5% modulus Ea in the tire circumferential direction. The invention according to claim 3 is characterized in that 5 to 7 circumferential ribs are provided in the range region Y. The invention of claim 4 is characterized in that the sum ΣS of the cross-sectional areas S of the circumferential ribs in the tire meridian section is 200 mm ² or less.

  In this specification, “tread grounding half width TW” means a tread grounding surface that is grounded when 80% of the normal load is applied to a tire in a normal internal pressure state in which a rim is assembled on a normal rim and filled with a normal internal pressure. It means the distance between the tire axial direction outer end (tread ground contact end) and the tire equator.

  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, or ETRTO means “Measuring Rim”. The “regular internal pressure” is the air pressure specified by the tire for each tire. The maximum air pressure in the case of JATMA, the maximum value described in the table “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” in the case of TRA, If it is ETRTO, it is “INFLATION PRESSURE”, but if the tire is for a passenger car, it is 180 kPa. The “regular load” is the load specified by the standard for each tire. The maximum load capacity shown in the table “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” is the maximum load capacity for JATMA and TRA for TRA. In the case of ETRTO, it is “LOAD CAPACITY”, and in the case of passenger car tires, it means a load corresponding to 88% of the load.

  Since the present invention is configured as described above, it is possible to perform the same function as the conventional band layer without increasing the weight or increasing the cost, increasing the binding force on the belt layer and increasing the road noise. Can be reduced.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

Figure 1 is a sectional view illustrating a case where the vehicle radial tire for a multiplication of the present invention, FIG. 2 is a development view showing the tread pattern.

  In FIG. 1, a pneumatic tire 1 includes a carcass 6 extending from a tread portion 2 through a sidewall portion 3 to a bead core 5 of a bead portion 4, and a belt disposed inside the tread portion 2 and outside the carcass 6. With layer 7.

  The carcass 6 is formed of one or more, in this example, one carcass ply 6A in which carcass cords are arranged at an angle of, for example, 75 to 90 ° with respect to the tire circumferential direction. The carcass ply 6A is integrally provided with ply turn-back portions 6b that are folded back from the inside around the bead core 5 at both ends of the ply main body portion 6a straddling the bead cores 5 and 5, and the ply main body portion 6a A bead apex 8 made of hard rubber extending in a radially outward direction from the bead core 5 is arranged between the ply folded portion 6b and the bead portion 4 is reinforced.

  As the carcass cord, in this example, an organic fiber cord such as nylon, rayon, or polyester is employed.

  The belt layer 7 is composed of two or more belt plies 7A and 7B in this example, in which belt cords are arranged at an angle of, for example, 10 to 35 ° with respect to the tire circumferential direction. The belt plies 7A and 7B are stacked with different inclination directions so that the belt cords cross each other between the plies, thereby increasing the belt rigidity, and having a substantially full width of the tread portion 2 with a tagging effect. Strongly reinforced.

  In addition, in this example, the tread rubber 2G forming the tread portion 2 is superposed on the outside of the belt layer 7 without providing the conventional band layer. Can be formed. In such a case, the binding force on the belt layer 7 is further increased, and the high-speed durability performance and the road noise performance can be further improved.

  Next, as shown in FIG. 2, the tread portion 2 continues linearly in the tire circumferential direction in a range region Y that is separated from the tire equator C by a distance of 55% or more and 120% or less of the tread grounding half width TW. A plurality of circumferential ribs 11 having a tire axial width W of 2.0 to 7.0 mm are provided.

  Specifically, in this example, the tire includes an inner longitudinal main groove 12A extending in the circumferential direction on both sides of the tire equator C, and an outer longitudinal main groove 12B arranged on the outer side thereof. It is divided into a land portion R1 between the longitudinal main grooves 12A and 12A, an intermediate land portion R2 between the longitudinal main grooves 12A and 12B, and an outer land portion R3 between the longitudinal main groove 12B and the tread edge Te. Yes.

  Of these, the inner land portion R1 is formed as a wide circumferential rib 13 extending continuously in the tire circumferential direction, and in this example, incisions 14 extending toward the tire equator C are alternately formed on both side edges thereof. By arranging it, drainage is improved. Further, the intermediate land portion R2 is formed as a block row Br in which the blocks B are arranged in the circumferential direction by the transverse main groove 15 crossing the land portion R2.

  In addition, the outer land portion R3 includes, in this example, a vertical rib body group 17 in which a plurality of narrow vertical rib bodies 17A divided by vertical narrow grooves 16 extending in the tire circumferential direction are arranged in the tire axial direction, and a tire shaft. A lateral rib body 18A extending from the outermost longitudinal rib body 17A to the tread edge Te is formed by the lateral rib body group 18 arranged in the tire circumferential direction. Further, the vertical rib group 17 is disposed to the outside in the tire axial direction beyond the ground contact end Te.

  Here, the inner and outer vertical main grooves 12A and 12B are wide grooves having a groove width WG of 3 mm or more, preferably 5 to 15 mm, and the groove depth HG (shown in FIG. 3) is 6 to 10 mm. Is common. The vertical narrow groove 16 is a narrow groove having a groove width WG of 2 mm or less, and the groove depth Hg is generally 0.6 to 1.0 times the groove depth HG.

In this example, by arranging the vertical rib group 17 in the range region Y, a plurality (five in this example) of the vertical rib bodies 17A constituting the vertical rib group 17 are arranged in the circumferential direction. A rib 11 is formed. The range region Y is a position corresponding to the outer end portion of the belt layer 7 and is the most preferable position for increasing the binding force on the belt layer 7 and reducing road noise. From such a point of view, the range region Y is preferably 60 to 110%, more preferably 60 to 95% of the tread ground half width TW. In addition, as described in Examples below, it is preferable that 5 to 7 circumferential ribs 11 are provided in the range region Y.

  Next, the tread rubber G that forms the tread portion 2 is formed by at least a rib rubber portion G1 that forms the circumferential rib 11 and a tread main rubber portion G2 that is the remaining portion.

  Among these, as the tread main rubber portion G2, in this example, as in the conventional tire, a two-layer structure of a cap rubber layer G2A forming a tread surface and a base rubber layer G2B inside thereof is illustrated. . A single layer structure may also be used. For the tread main rubber portion G2, a conventional well-known tread rubber material set with an emphasis on rolling resistance, grip properties, wear resistance and the like is preferably used.

  However, as the rib rubber portion G1, it is important to use a highly elastic rubber having a 5% modulus Ea in the tire circumferential direction of 10 to 50 Mpa in order to exert a tagging effect on the belt layer 7.

  Therefore, in this example, the rib rubber part G1 is made of a short fiber-blended rubber in which short fibers are blended in a rubber base material, and the short fibers are oriented in the tire circumferential direction, so that 5 in the tire circumferential direction is obtained. % Modulus Ea is in the range of 10 to 50 Mpa, and 5% modulus Eb in the tire radial direction is kept low to 0.5 times or less of 5% modulus Ea in the tire circumferential direction.

Thus, by using rubber with a high circumferential modulus Ea for the rib rubber part G1, each circumferential rib 11 functions as a strong annular elastic ring. As a result, it is possible to exert a tagging effect on the belt layer 7, and like the conventional band layer, it is possible to increase the binding force on the belt layer 7 and improve the high-speed durability performance and road noise performance. On the other hand, the short fiber blended rubber is flexible in the radial direction because the modulus Eb in the radial direction is suppressed to a low level close to the modulus of the rubber of the tread main rubber portion G2 by the orientation of the short fibers. Therefore, while maintaining riding comfort, it becomes difficult to pick up vibration from the road surface, which is more advantageous for road noise performance.

At this time, in order to exert the above effect, as shown in FIG. 3, it is necessary to set the width W in the tire axial direction of the circumferential rib 11 to 2.0 to 7.0 mm, and each range region Y It is also important that the total sum ΣS of the cross-sectional areas S at the tire meridian cross-sections of the circumferential ribs 11 disposed on the rim is 100 mm ² or more.

This is because if the width W is less than 2.0 mm, the circumferential rib 11 does not function sufficiently as an elastic ring, and the tagging effect on the belt layer 7 is not effectively exhibited. On the other hand, if the width W exceeds 7.0 mm, vibrations from the road surface are easily picked up, and the effect of improving road noise performance is impaired. If the total sum ΣS of the cross-sectional areas S is less than 100 mm ^{2, the} hoop effect of the circumferential rib 11 as a whole is insufficient and the effect of improving road noise performance is not exhibited. The sum ΣS of the cross-sectional areas S of the circumferential ribs in the tire meridional section is preferably 200 mm ² or less.

  Here, the cross-sectional area S means a cross-sectional area between the groove bottom line passing through the groove bottom of the groove constituting the circumferential rib 11 and the radial outer surface (tread surface) of the circumferential rib 11. In addition, when the groove depth of the groove | channel adjacent to the circumferential direction rib 11 differs in right and left, the groove bottom line which passes through the groove bottom of a deep groove is employ | adopted. The width W of the circumferential rib 11 is the width on the tread surface, and the circumferential rib 11 needs to be a straight rib in order to function as an elastic ring.

  Further, in this example, the outer vertical main groove 12B is formed adjacent to the vertical rib body group 17, but the position of the vertical rib body group 17 is a node in the resonance mode of the tire. Even when the vertical main groove 12B is wide to suppress a decrease in drainage due to the formation of the vertical rib group 17, the deterioration of the road noise performance is prevented.

  Next, as the short fiber blended rubber, a mixture of 6 to 30 parts by weight of short fibers with respect to 100 parts by weight of the rubber base material is suitable. If it is less than 6 parts by weight, the reinforcing effect is inferior, and conversely 30 If it exceeds the parts by weight, the viscosity of the unvulcanized rubber increases and the processability decreases. As the rubber base material, for example, one or a combination of diene rubbers such as natural rubber (NR), styrene / butadiene rubber (SBR), butadiene rubber (BR), and isoprene rubber (IR) is used. it can.

  Here, the short fibers tend to be oriented in the extrusion direction when the short fiber compounded rubber is extruded into a sheet shape by an extruder or a calender roll, and this can be used to orient the short fibers in the tire circumferential direction. it can. “Short fibers are oriented in the tire circumferential direction” means that 90% or more of the short fibers are oriented in an angle range of ± 30 degrees or less centering on the tire circumferential direction.

  Due to the orientation of the short fibers, as shown in FIG. 4, the short fiber compounded rubber can significantly increase the modulus Ea in the tire circumferential direction while suppressing the increase in the modulus Eb in the radial direction. If the ratio Ea / Eb is 2 or more, it can be increased to 10 or more. FIG. 4 shows an example of changes in the 5% modulus Ea and Eb in the circumferential direction and the radial direction based on the blending amount of the short fibers.

  Examples of the short fibers include organic fibers such as nylon, polyester, aramid, rayon, vinylon, cotton, cellulose resin, crystalline polybutadiene, and inorganic fibers such as metal fibers, whiskers, boron, and glass fibers. These can be used alone or in combination of two or more. More preferably, the short fiber may be subjected to an appropriate surface treatment in order to improve the adhesion to the rubber substrate.

  The average fiber length L of the short fibers is preferably 20 μm or more, particularly preferably 50 to 5000 μm. The aspect ratio L / D between the average fiber length L and the fiber diameter D is preferably 10 or more, particularly preferably 20 to 500. When the average fiber length L is less than 20 μm and the aspect ratio L / D is less than 10, even when the short fibers are oriented with high accuracy, the reinforcing effect on the orientation direction becomes insufficient, and conversely, the average fiber length L Is greater than 5000 μm and the aspect ratio L / D is greater than 500, the orientation of the short fiber itself is lowered, and in any case, the effect of the present application tends to be impaired.

  In addition to the above short fibers, conventional additives for tire rubber such as carbon black, oil, anti-aging agent, wax, vulcanization accelerator and the like can be appropriately blended with the short fiber blended rubber.

  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 tire with a tire size of 195 / 65R15 having the structure shown in FIG. 1 was prototyped based on the specifications shown in Table 1, and road noise performance, steering stability, and riding comfort of each sample tire were tested and compared. The specifications other than those shown in Table 1 were the same.
(1) Road noise performance:
Mounted on all wheels of the vehicle (FF car, 2000cc) under the conditions of rim (6JJ × 15), internal pressure (200kPa), run smoothly on the road surface at a speed of 50km / h, The noise level dB (A) was measured.
(2) Steering stability and ride comfort:
Using the vehicle, run on a dry asphalt tire test course, and display the steering stability and riding comfort at that time in three stages: ○ (good), △ (normal), × (bad) is doing.

It is sectional drawing of the tire of one Example of this invention. It is an expanded view which shows the tread pattern. It is sectional drawing which shows a circumferential direction rib. It is a diagram which shows an example of the change of the modulus of the circumferential direction and radial direction based on the compounding quantity of a short fiber.

Explanation of symbols

2 Tread part 11 Circumferential rib G Tread rubber GA Rib rubber part

Claims (4)

Within the range region Y that is 55% or more and 120% or less of the tread ground half width TW from the tread portion and the tire equator, it is continuous in the tire circumferential direction and the tire axial width W is 2.0 to 7.0 mm. Provided with a plurality of circumferential ribs,
And the sum total ΣS of the cross-sectional areas S in the tire meridional section of each circumferential rib is set to 100 mm ² or more,
A radial tire for a passenger car , wherein the tread rubber forming the tread portion has at least a 5% modulus Ea in the tire circumferential direction of the rib rubber portion forming the circumferential rib of 10 to 50 Mpa. The at least rib rubber part is made of a short fiber blended rubber in which short fibers are blended in rubber, and the short fibers are oriented in the tire circumferential direction so that a 5% modulus Ea in the tire circumferential direction is 10 to 50 Mpa. 2. The radial tire for a passenger car according to claim 1, wherein the range is 5% modulus Eb in the tire radial direction and is reduced to 0.5 times or less of 5% modulus Ea in the tire circumferential direction. The radial tire for passenger cars according to claim 1, wherein 5 to 7 circumferential ribs are provided in the range area Y. The sum ΣS of the cross-sectional areas S of the circumferential ribs at the tire meridian section is 200 mm. ² The radial tire for a passenger car according to claim 3, wherein:

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