JP2012086756A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of reducing rolling resistance while maintaining steering stability.SOLUTION: This invention is characterized in that a plurality of groove parts 9 extended in the inclined direction against a tire circumferential direction TC are formed on a surface of a buttress part 3 arranged at both outside in a tire width direction TW of a tread part 4, each of the groove parts 9 is arranged along the tire circumferential direction TC, a plurality of reinforcement ribs extended toward a tire radial direction TR from groove walls 9a, 9b are arranged along the groove walls with intervals at the bottom of each of the groove parts 9, and the reinforcement ribs are configured with a first rib 11 which gradually reduces height on the opposite groove walls from one of the groove walls 9a toward the another of the groove walls 9b and a second rib 12 which gradually reduces height on the groove walls from the another of the groove walls 9b toward the one of the groove walls 9a.

Description

  The present invention relates to a pneumatic tire in which a plurality of groove portions are formed in a buttress portion positioned on both outer sides in the tire width direction of a tread portion.

  A pneumatic tire mounted on a vehicle generates rolling resistance and energy loss due to deformation of the tire during traveling. That is, if the rolling resistance of the pneumatic tire is large, the amount of fuel consumed when the vehicle is running increases. Therefore, it is desirable that the rolling resistance of the pneumatic tire is small.

  As one of the methods for reducing the rolling resistance of a pneumatic tire, as shown in Patent Documents 1 to 3, a method for reducing the weight of the pneumatic tire is known. Specifically, Patent Document 1 describes a configuration in which a hollow portion extending annularly in the tire circumferential direction is formed on the surface of a shoulder portion located inside the vehicle.

  Patent Document 2 describes a configuration in which a hollow portion extending in the tire width direction from the ground contact end position to the edge position on the side wall portion side is provided in the center portion of the shoulder block in the tire circumferential direction. Further, Patent Document 3 is provided with an arch-shaped recess facing the tire equatorial plane starting from the widthwise outer end of the block-shaped land portion on the block-shaped land portion of the shoulder portion, The structure which has the unevenness | corrugation of is described.

JP 2008-1114810 A JP-A-9-193614 JP 2006-27498 A

  However, in the above-mentioned Patent Document 1, since the hollow portion is formed in an annular shape in the tire circumferential direction, the rigidity of this portion is reduced, so that the lateral rigidity of the tire (rigidity in the tire width direction) is reduced. As a result, there was a problem that the steering stability performance was lowered.

  Moreover, in patent document 2, since the hollow part was formed in the center part of the tire circumferential direction of a shoulder block, the hollow part could not be formed so much, and the effect of weight reduction of the tire had become small. . In Patent Document 2, when the recessed portion is formed large, the block rigidity is lowered, and the steering stability performance is lowered similarly to Patent Document 1.

  Furthermore, in Patent Document 3, the area of the recess is narrow because it is arched, and the effect of reducing the weight of the tire is reduced because of the configuration in which a large number of recesses and protrusions are formed, rather than a large recess. It was.

  As described above, with the conventional method, it has been difficult to achieve both a reduction in rolling resistance due to weight reduction of the tire and a steering stability performance. Then, in view of the said problem, this invention aims at providing the pneumatic tire which reduced rolling resistance, maintaining steering stability performance.

  In order to solve the above-mentioned problems, the present inventor diligently studied, in order to achieve both reduction in rolling resistance of the pneumatic tire and maintenance of steering stability performance, not only reducing the weight of the pneumatic tire, In addition, the inventors have found that the rolling resistance can be effectively reduced by suppressing the groove bottom distortion of the main groove in the tread portion, and have completed the present invention.

  That is, in the pneumatic tire according to the present invention, a plurality of groove portions extending in a direction inclined with respect to the tire circumferential direction are formed on the surface of the buttress portion disposed on both outer sides in the tire width direction of the tread portion, A plurality of reinforcing ribs that are arranged along the tire circumferential direction and that extend from the groove wall toward the tire radial direction are provided at intervals along the groove wall at the bottom of each groove portion. It is characterized by comprising a first rib whose height gradually decreases from one side of the wall toward the other side and a second rib whose height gradually decreases from the other side of the groove wall toward the one side.

  According to the above configuration, since the plurality of groove portions are formed in the buttress portion, the effect of reducing the rolling resistance by reducing the weight of the pneumatic tire is obtained, and the formation of the groove portion increases the deflection of the entire buttress portion. While suppressing, it becomes possible to suppress the groove bottom distortion in a tread ground surface, and rolling resistance can be reduced effectively.

  In addition, since the groove portion is formed so as to extend in a direction inclined with respect to the tire circumferential direction, the change in rigidity in the tire radial direction can be reduced, and distortion can be prevented from concentrating on the bottom of the groove portion. It becomes possible to disperse the entire buttress portion. Further, coupled with the auxiliary rib formed in the groove, it is possible to maintain the steering stability by preventing the decrease in the lateral rigidity while realizing the weight reduction of the tire. In addition, by forming the reinforcing ribs (the first rib and the second rib) in a tapered shape so that the height is gradually reduced, it is possible to prevent a decrease in lateral rigidity without impairing the tire weight reduction effect.

  In the present invention, the buttress portion is an area formed on both outer sides in the tire width direction of the tread portion, and the edge of the tread rubber (on the side wall portion side) from the ground contact end that is the outermost end in the tire width direction of the tread portion. The area between the positions. That is, a buttress part means the area | region comprised with the same tread rubber as a tread part.

  Depending on the type of tire, the surface of the edge portion of the tread rubber may be covered with a reinforcing rubber layer. Even in such a case, the area between the ground contact edge and the edge position of the tread rubber is the buttress. Part. In this case, a groove portion may be formed in the reinforcing rubber layer in the buttress portion.

  In the present invention, the term “contacting end” means that the rim is assembled on a regular rim, the tire is placed vertically on a flat road surface in a state where normal internal pressure is filled, and the tire is axially grounded on the road surface when a normal load is applied. Refers to the outermost position. The “regular rim” is a rim determined by each tire in the standard system including the standard on which the tire is based. For example, JATMA is a standard rim, TRA is a design rim, or ETRTO is a standard rim. It becomes Measuring Rim.

  “Regular internal pressure” is the air pressure determined by each standard for each tire in the standard system including the standard on which the tire is based. The maximum air pressure is JATMA, and the table “TIRE LOAD LIMITS AT VARIOUS” is TRA. The maximum value described in “COLD INFRATION PRESURES”, “INFLATION PRESSURE” in the case of ETRTO, is 180 kPa when the tire is for a passenger car.

  “Regular load” is a load determined by each standard for each tire in the standard system including the standard on which the tire is based. If JATA is the maximum load capacity, if it is TRA, the table “TIRE LOAD LIMITS AT” The maximum value described in “VARIOUS COLD INFRATION PRESURES” is “LOAD CAPACITY” if it is ETRTO, but it is 88% of the corresponding load of the maximum load capacity when the tire is for passenger cars.

  In the groove portion, the reinforcing rib is preferably formed such that the first rib and the second rib are alternately formed one or more along the groove wall. Thereby, the rigidity of a buttress part can be equalized.

  The groove portion is formed on the surface of the buttress portion, that is, on a land portion such as a block or a rib. At this time, it is preferable that the groove portions are arranged so as not to overlap each other in the tire circumferential direction. With the above configuration, the rigidity of the buttress portion can be maintained uniformly.

  In addition, when the buttress part is divided into a plurality of land parts in the tire circumferential direction by a lateral groove extending in the tire radial direction, the groove part is formed so as to straddle the adjacent lateral grooves across the land part for each land part. do it. Thereby, the groove portions can be arranged so as not to overlap each other in the tire circumferential direction.

  In the present invention, a plurality of groove portions extending in a direction inclined with respect to the tire circumferential direction are formed on the surface of the buttress portion, each groove portion is disposed along the tire circumferential direction, and the bottom of each groove portion is formed from the groove wall. A plurality of reinforcing ribs extending in the radial direction of the tire are provided at intervals along the groove wall, and the reinforcing rib includes a first rib whose height gradually decreases from one side of the opposite groove wall to the other side. Since the second rib has a height that gradually decreases from the other side of the groove wall toward the one side, a pneumatic tire with reduced rolling resistance can be obtained while maintaining steering stability performance.

Schematic sectional view of the pneumatic tire of the first embodiment of the present invention Partial side view of the pneumatic tire in FIG. Development view showing the tread pattern (half part) in FIG. The enlarged view which shows the groove part of FIG. AA sectional view of FIG. Development view showing tread pattern (half part) of tire of second embodiment Partially enlarged side view of the tire of the second embodiment BB sectional view of FIG. Development view showing tread pattern (half part) of Comparative Example 1 Development view showing tread pattern (half part) of Comparative Example 2 Sectional drawing of the groove part of the comparative example 3

[First embodiment]
1 to 5 are views of a pneumatic tire showing a first embodiment of the present invention. FIG. 1 is a sectional view schematically showing a pneumatic tire, FIG. 2 is a partial side view of the pneumatic tire, and FIG. 3 is a development view showing a tread pattern of the tire. In FIG. 3, since the dread pattern is formed symmetrically about the tire equator C, only the half part is shown.

  The pneumatic tire of the present embodiment is a radial tire, and as shown in FIGS. 1 to 3, a pair of bead portions 1, 1 and a sidewall portion 2 extending outward in the tire radial direction TR from the bead portions 1, 1. And a buttress portion 3 formed outside the tire radial direction TR of the sidewall portion 2 and a tread portion 4 connecting the upper ends thereof. Other reinforcing structures are the same as those of a general radial tire.

  That is, a carcass layer (not shown) having both ends folded back and supported by a bead core 1a along the inner periphery of the pneumatic tire is provided, and a carcass cord extending in the radial direction is embedded in the carcass layer. . A belt layer (not shown) is provided between the tread portion 3 and the carcass layer. The belt layer is composed of at least two belt plies in which belt cords inclined in the opposite direction with respect to the tire equator C are embedded.

  The tread portion 4 and the buttress portion 3 are composed of a tread rubber 5. That is, the tread portion 4 and buttress portion 3 of the pneumatic tire are covered with the tread rubber 5 having a high rigidity on the tire surface. Four main grooves 6 formed annularly in the tire circumferential direction TC are formed on the outer peripheral surface of the tread portion 4, and lateral grooves 7 are formed so as to intersect the main grooves 6.

  The buttress portion 3 is formed on both outer sides in the tire width direction of the tread portion 4 where the pneumatic tire contacts the ground. More specifically, the buttress part 3 is formed between the ground contact E of the tread part 4 and the edge position 5a of the tread rubber 5 on the side wall part 2 side. In the present embodiment, the lateral groove 7 extends from the tread portion 4 to the buttress portion 3.

  That is, the lateral groove 7 is formed so as to extend in the tire width direction so as to intersect the main groove 6 in the tread portion 4, and as it goes around the side surface of the tire, toward the center side in the tire radial direction TR, The tread rubber 5 is formed up to the edge position on the side wall 2 side.

  Accordingly, the tread portion 4 and the buttress portion 3 are partitioned into a plurality of blocks by the four main grooves 6 and the plurality of lateral grooves 7. As described above, the buttress portion 3 is partitioned into a plurality of land portions (blocks) 8 having the same shape in the tire circumferential direction, and a groove portion 9 is formed for each land portion 8. The groove portion 9 is formed so as to straddle the adjacent lateral grooves 7 with the land portion 9 interposed therebetween.

  As shown in FIGS. 4 and 5, the groove 9 has a groove depth (GD) of 0.5 mm to 3.0 mm and a groove width (GW) of 5.0 mm to 20.0 mm. preferable. In the present embodiment, the groove 9 has a depth GD of 1.5 mm and a width GW of 8.0 mm.

  The groove 9 is formed to extend in a direction inclined with respect to the tire circumferential direction TC. As a result, the change in rigidity in the tire radial direction TR can be reduced, and the distortion can be prevented from concentrating on the bottom of the groove 9 and the distortion can be distributed throughout the buttress 3. The groove portion 9 of each land portion 8 is formed at a position that coincides with the other groove portions 9 when being rotated about the tire rotation axis.

  The inclination of the groove 9 is set so that the change in rigidity in the tire radial direction is small. Specifically, first, among the groove walls 9a and 9b facing each other in the groove portion 9, the portion closest to the tire rotation center in the groove wall 9a located on the outer side in the tire radial direction is located on the inner side in the tire radial direction. A portion of the groove wall 9b farthest from the tire rotation center is defined as 9b2. Then, when the distance from the tire rotation center to 9a1 is R1, and the distance from the tire rotation center to 9b2 is R2, the inclination of the groove 9 is set so that at least R1−R2 (= X) ≦ 0.1 mm. More preferably, the inclination of the groove 9 is set so that R1 ≦ R2.

  That is, by setting the inclination of the groove 9 so that R1 ≦ R2, the circle whose radius is set so as to pass through the area of the buttress 3 always passes through the land 8 regardless of the radius. Thus, the concentration of distortion can be prevented. When R1 is made larger than R2 in terms of design, the rigidity of the buttress portion 3 is substantially equivalent to the case of R1 ≦ R2 by setting R1−R2 (= X) ≦ 0.1 mm. Can be secured. In this embodiment, the groove 9 is formed so that R1−R2 = 0.1 mm.

  A plurality of reinforcing ribs extending from the groove walls 9a and 9b toward the tire radial direction TR are provided on the bottom of the groove portion 9 at intervals along the groove walls 9a and 9b. The reinforcing rib includes a first rib 11 whose height gradually decreases from the groove wall 9a toward the groove wall 9b, and a second rib 12 whose height gradually decreases from the groove wall 9b toward the groove wall 9a.

  The first rib 11 and the second rib 12 have substantially the same shape, and are arranged so as to face each other. In this embodiment, the 1st rib 11 and the 2nd rib 12 are alternately arrange | positioned for every one on a groove bottom, and the adjacent 1st rib 11 and the 2nd rib 12 are provided at fixed intervals. ing.

  Regarding how many first ribs 11 are formed in the groove portion 9, the length of the groove wall 9a (groove wall 9b) is GL, and the first rib width (second rib width) is RW. When the number of the first ribs 11 is n, the width (RW) and the number (n) of the first ribs are set so that 0.3GL ≧ n × first rib width (RW) ≧ 0.2GL. do it. The second rib 12 is set in the same manner.

  As the first rib 11 and the second rib 12, specifically, the rib width RW is set to 0.5 mm to 1.5 mm, and the intervals between the adjacent first rib 11 and second rib 12 are all the same. It is preferable to form them at equal intervals. In the present embodiment, both the first rib 11 and the second rib 12 have a rib width of 1.5 mm.

  The first rib 11 and the second rib 12 are tapered at the bottom of the groove so that the height is the highest at the base end side and the height gradually decreases toward the tip end in order to achieve both weight reduction and reinforcement. Formed. And the base end side of a rib is provided in a row by the groove wall. In particular, in order to enhance the effect of reducing the weight, the first rib 11 and the second rib 12 are preferably formed in a substantially triangular shape in a side view so that the rib height is just zero at the tip of the rib. Regarding the specific sizes of the first rib 11 and the second rib 12, the rib height on the base end side is 30% to 100% of the groove depth GD, and the rib length RL is 60% to the groove width GW. What is necessary is just to form so that it may become 100%.

  In the present embodiment, as shown in FIGS. 4 and 5, the first rib 11 and the second rib 12 have a base rib height of 80% of the groove depth GD and a rib length RL of the groove width GW. Is set to be exactly the same as the groove width G at 100%. Further, the first rib 11 and the second rib 12 are formed in a substantially triangular shape in a side view so that the rib height is exactly zero at the tip of the rib.

  With the above configuration, the effect of reducing the rolling resistance by reducing the weight of the pneumatic tire can be obtained, and the groove portion 9 can be used to suppress the groove bottom distortion of the main groove 6 in the tread portion 4. Can be effectively reduced.

  Further, since the groove portion 9 is formed so as to extend in a direction inclined with respect to the tire circumferential direction TC, a change in rigidity in the tire radial direction TR can be reduced, and distortion can be prevented from concentrating on the bottom of the groove portion 9. Thus, the strain can be distributed throughout the buttress portion. Further, coupled with the auxiliary rib formed in the groove portion 9, it is possible to maintain the steering stability by preventing the decrease in the lateral rigidity while realizing the weight reduction of the tire.

[Second Embodiment]
6 to 8 are views of a pneumatic tire showing a second embodiment of the present invention. 6 is a development view showing a half portion of the tread pattern of the tire, FIG. 7 is a partially enlarged side view of the tire showing the groove portion, and FIG. 8 is a cross-sectional view taken along line BB in FIG. The present embodiment is characterized in that the length RL of the first rib 11 and the second rib 12 is shorter than that of the first embodiment, and the other configurations are the same as those of the first embodiment. ing.

  In the present embodiment, the length RL of the first rib 11 and the second rib 12 is set to 80% of the groove width GW and smaller than 100% of the first embodiment. Therefore, the first rib 11 and the second rib 12 have a shape that is interrupted in the middle of the groove bottom of the groove portion 9 without reaching the opposite groove walls at the tips of the ribs. Reinforcing properties can be ensured.

  Although the said embodiment demonstrated the aspect in which the buttress part 3 was divided by the some block, it is not restricted to this, It can also be set as the aspect by which the rib extended in a tire circumferential direction was formed in the buttress part 3 as a land part. It is.

  In this case, the plurality of groove portions may be arranged so as not to overlap each other in the tire circumferential direction. Further, the groove portions may be arranged so as to be in contact with each other, or may be arranged at a slight interval. In addition, what is necessary is just to form each groove part in the position corresponded with another groove part, when rotating around a tire rotating shaft similarly to 1st embodiment.

[Production of tires]
In this example, the pneumatic radial tire shown in the first embodiment and the second embodiment was actually produced and its performance was evaluated. Specifically, the radial tire produced in the first embodiment was taken as Example 1, and the radial tire produced in the second embodiment was taken as Example 2. More specifically, the produced tire size was 195 / 65R15, and the length of each land portion 8 formed in the buttress portion 3 in the circumferential direction (the length of the groove forming position) was 30 mm.

  On the other hand, the basic configuration was the same as in Examples 1 and 2, and as shown in FIG. 9, a tire was manufactured without providing a groove portion in buttress portion 3 as Comparative Example 1. Moreover, as shown in FIG. 10, the groove part 29 was formed along the tire circumferential direction TC, and the first rib 11 and the second rib 12 were formed in a tapered shape as in the first embodiment (see FIG. 5). This was designated as Comparative Example 2.

  Further, as Comparative Example 3, the groove portion 9 is formed so as to extend in a direction inclined with respect to the tire circumferential direction TC, as in the first embodiment, and the reinforcing rib 30 has a groove wall 9a as shown in FIG. To the groove wall 9b at the same height (40% of the groove depth GD).

[Evaluation test]
An evaluation test was performed on the five types of tires produced in Examples 1-2 and Comparative Examples 1-3. Each test condition is as follows. The results are shown in Table 1.

(1) RRC
RRC (Rolling Resistance Coefficient) is a rolling resistance coefficient expressed as a coefficient obtained by dividing the rolling resistance by the load. The measurement was performed by setting the inner pressure to 200 kPa, setting the test tire with the rim assembled on a drum tester, measuring the rotational resistance by running the drum at a load of 505 kg and a speed of 80 km / h, and the rotational resistance of the tire of Comparative Example 1 Is represented as an index of 100 as the rotational resistance of Comparative Example 1 / the rotational resistance of the evaluation tire. The larger the value of RRC, the smaller the rolling resistance and the better the performance.

(2) Steering stability (dry handling stability)
Test tires are installed on all wheels of a real vehicle (domestic 4-door sedan) and the air pressure is 230 kPa, and the vehicle is driven on a dry road with a load of 1100 kg on the front wheels and 780 kg on the rear wheels. It was carried out and evaluated by a sensory test of the driver. The index evaluation is made with the result of Comparative Example 1 being 100, and the larger the value, the better the steering stability.

[Evaluation results]
From Table 1, Examples 1 and 2 are better than Comparative Examples 1 to 3 in terms of RRC while maintaining the same level of performance as Comparative Example 1 in which no groove is formed for steering stability performance. confirmed. This makes it possible to reduce the change in rigidity in the tire radial direction while suppressing an increase in the deflection of the entire buttress portion by forming the groove portion extending in a direction inclined with respect to the tire circumferential direction. In addition, by forming the first rib and the second rib in a tapered shape, the distortion in the width direction of the groove is dispersed between the high portion and the low portion due to the difference in taper, and the first rib and the second rib This is thought to be because it was possible to increase the number of strain distribution locations by maintaining the ribs alternately, and to maintain lateral stiffness.

  On the other hand, for Comparative Example 2, the RRC was formed by forming a groove and forming a tapered first rib and a second rib (triangular shape having a bottom length GW and a height of 0.8 GD in a side view). Is improving. However, the formation of the groove portion along the tire circumferential direction makes it easier for strain to concentrate on the bottom of the groove portion, resulting in a decrease in steering stability.

  Moreover, about the comparative example 3, after forming the groove part extended in the direction which inclines with respect to a tire circumferential direction, it is a rectangular-shaped reinforcement rib (base length GW, height 0.4GD in a side view, as an area, Since the same as the first rib and the second rib in Example 1 is formed, RRC is improved. However, the steering stability was lower than in Examples 1 and 2. This was thought to be because distortion was easily concentrated on the reinforcing rib portion because the reinforcing rib was formed with a constant height in the rib length direction.

DESCRIPTION OF SYMBOLS 1 Bead part 2 Side wall layer 3 Buttress part 4 Tread part 5 Tread rubber 6 Main groove 7 Lateral groove 8 Land part 9 Groove part 11 First rib 12 Second rib C Tire equatorial plane E Ground contact edge TC Tire circumferential direction TR Tire radial direction TW Tire width direction GD Groove depth GW Groove width GL Groove wall length RW Rib width RL Rib length

Claims (4)

A plurality of groove portions extending in a direction inclined with respect to the tire circumferential direction are formed on the surface of the buttress portion disposed on both outer sides in the tire width direction of the tread portion, and each groove portion is disposed along the tire circumferential direction, and each groove portion A plurality of reinforcing ribs extending from the groove wall toward the tire radial direction are provided at intervals along the groove wall, and the reinforcing ribs are formed so as to increase from one side of the opposite groove wall to the other side. A pneumatic tire comprising a first rib that gradually decreases and a second rib that gradually decreases in height from the other side of the groove wall toward one side. 2. The pneumatic tire according to claim 1, wherein the first rib and the second rib are alternately formed along the groove wall in the groove portion for every one or a plurality of the ribs. The pneumatic tire according to claim 1, wherein the groove portions are arranged so as not to overlap each other in the tire circumferential direction. 4. The buttress portion is partitioned into a plurality of land portions in the tire circumferential direction by lateral grooves, and the groove portions are formed so as to straddle adjacent lateral grooves across the land portions for each land portion. The described pneumatic tire.

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