JP6511365B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire that exhibits excellent cornering performance by making the rigidity and heat buildup of the tread portion compatible.

  For example, in Patent Document 1 below, a pneumatic tire that is used in both road driving and circuit driving is proposed. The pneumatic tire is provided with a plurality of grooves and recesses in the tread portion in order to ensure wet performance on a public road.

  In general, when the tread portion is provided with a recess, the rigidity of the tread portion tends to decrease, and in particular, the grip performance at cornering tends to decrease. On the other hand, when the tread portion is not provided with a recess, not only the wet performance is lowered but also the heat buildup of the tread portion during running is lowered. In particular, immediately after the start of traveling, the rubber of the tread portion does not generate heat sufficiently, so there is a problem that it is difficult to obtain excellent grip performance. For this reason, the pneumatic tire of Patent Document 1 has room for further improvement in achieving both the rigidity and heat generation of the tread portion.

JP 2004-338628 A

  The present invention has been made in view of the above problems, and based on improving the shape and the like of the recess provided in the tread portion, by making the rigidity and heat buildup of the tread portion compatible, The main object of the present invention is to provide a pneumatic tire capable of exhibiting excellent cornering performance.

  The present invention is a pneumatic tire having a tread portion in which an outer tread end and an inner tread end are defined by specifying the direction of mounting on a vehicle, and the tread surface of the tread portion is smooth. In the plan view of the tread portion, each recess has a length in the axial direction of the tire greater than a length in the circumferential direction of the tire in a plan view of the tread portion; The center is located on the inner tread end side with respect to the central position of the recess in the axial direction of the tire, and the outline shape is the tire circumferential direction from the maximum width position of the tire circumferential direction toward the outer tread end It is characterized in that it includes a portion where the width of.

  In the pneumatic tire according to the present invention, it is preferable that the respective recessed portions are disposed without overlapping the recessed portion projection regions obtained by projecting the recessed portions in the tire axial direction.

  In the pneumatic tire according to the present invention, the length of the recess in the tire axial direction is 4.0% to 7.5% of the tread contact width, and the length of the recess in the tire circumferential direction is on the tire equator It is desirable that it is 0.2% to 0.8% of the tire outer peripheral length.

  In the pneumatic tire according to the present invention, the tread portion includes an inner tread portion between the tire equator and the inner tread end, and an outer tread portion between the tire equator and the outer tread end, The inner tread portion is provided with one main groove continuously extending in the tire circumferential direction, and the recess is preferably provided only in the outer tread portion.

  In the pneumatic tire according to the present invention, it is desirable that a land portion between the inner tread end and the main groove be in a slick shape in which a groove and a sipe are not provided.

  The tread surface of the pneumatic tire according to the present invention is provided with a plurality of concave portions having a closed contour shape composed of smooth curves. Such a recess appropriately moderates the rigidity of the tread portion and promotes deformation of the tread portion at the time of road contact. Therefore, in the pneumatic tire according to the present invention, the rubber of the tread portion generates heat relatively early immediately after the disclosure of travel, and excellent grip performance can be obtained.

  Each recess has a length in the tire axial direction greater than a length in the tire circumferential direction. Such a recess is difficult to be deformed in the tire axial direction, and thus helps to maintain the axial rigidity of the tread portion. Furthermore, the center of the contour of the recess is located on the inner tread end side with respect to the central position of the length of the recess in the tire axial direction. Such a recess reduces the rubber volume on the inner tread end side with respect to the center position, and promotes deformation of the tread rubber. Therefore, the heat buildup of the tread portion is enhanced.

  Moreover, the contour shape of the recess includes a portion in which the width in the tire circumferential direction gradually decreases from the maximum width position in the tire circumferential direction toward the outer tread end side. As a result, the rubber volume on the outer tread end side of the recess is maintained, and the rigidity of the tread portion is maintained.

  As described above, in the pneumatic tire according to the present invention, the rigidity and heat buildup of the tread portion can be well balanced.

1 is a development view of a tread portion of a pneumatic tire according to an embodiment of the present invention. It is an enlarged view of the outer side tread part of FIG. It is an enlarged plan view of the recessed part of FIG. It is the sectional view on the AA line of the crevice of FIG. It is an expanded view of the tread part of other embodiment of this invention. It is an expanded view of the tread part of the pneumatic tire of a comparative example.

Hereinafter, an embodiment of the present invention will be described based on the drawings.
FIG. 1 is a development view of a tread portion 2 of a pneumatic tire (hereinafter sometimes simply referred to as “tire”) 1 of the present embodiment. The pneumatic tire 1 of the present embodiment is used, for example, for a passenger car, and is preferably used particularly as a high-performance tire on the premise of both road driving and circuit driving.

  The tread portion 2 has a tread pattern in which the direction of attachment to the vehicle is specified. The direction of attachment to the vehicle is displayed, for example, by characters or marks on a sidewall portion (not shown) or the like. In FIG. 1, when the tire 1 is mounted on a vehicle, the right side of FIG. 1 corresponds to the inside of the vehicle, and the left side of FIG. 1 corresponds to the outside of the vehicle.

  By designating the direction of attachment to the vehicle, the tread portion 2 has an outer tread end Te1 located on the outer side of the vehicle when attached to the vehicle and an inner tread end Te2 located on the inner side of the vehicle when attached to the vehicle. .

  Each tread end Te1 and Te2 is loaded with a normal load on a normal tire 1 that is rim-assembled on a normal rim (not shown) and filled with normal internal pressure, and is unloaded, and is flat at a camber angle of 0 °. It is the grounding position on the outermost side in the tire axial direction when the tire is in contact with the tire.

  The “regular rim” is a rim that defines the standard for each tire in the standard system including the standard on which the tire is based, for example, “standard rim” for JATMA, “Design Rim” for TRA, In the case of ETRTO, it is "Measuring Rim".

  The “normal internal pressure” is the air pressure specified by each standard in the standard system including the standard on which the tire is based, and in the case of JATMA, the “maximum air pressure”; in the case of TRA, the table “TIRE LOAD LIMITS AT The maximum value described in VARIOUS COLD INFlation PRESSURES, and in the case of ETRTO, it is “INFLATION PRESSURE”.

  "Normal load" is the load defined by each standard in the standard system including the standard on which the tire is based, and if it is JATMA, "maximum load capacity", if it is TRA, the table "TIRE LOAD LIMITS At the time of ETRTO, it is "LOAD CAPACITY".

  A plurality of recesses 10 are provided on the tread surface of the tread portion 2. The recess 10 of the present embodiment is provided, for example, only in the outer tread portion 5 between the tire equator C and the outer tread end Te1. However, the present invention is not limited to such an aspect, and the recess 10 may be provided in the inner tread portion 6 between the tire equator C and the inner tread end Te2.

  An enlarged view of the outer tread portion 5 of FIG. 1 is shown in FIG. As shown in FIG. 2, each recess 10 has a closed contour shape 15 consisting of a smooth curve. Such a recess 10 moderately reduces the rigidity of the tread portion 2 and promotes deformation of the tread portion 2 when the road surface is in contact with the ground. Therefore, in the tire 1 of the present invention, the rubber of the tread portion 2 generates heat relatively early immediately after traveling is disclosed, and excellent grip performance can be obtained. Note that “smooth curve” means a line that does not include a sharp apex that bends at one point, and can include a straight line as a part. The contour 15 of the recess 10 is preferably, for example, an outward bulge that does not include a portion that is concave toward the centroid 16 thereof. That is, as for the contour shape 15 of the recessed part 10, it is desirable that the code | symbol of the curvature seen from the centroid 16 is the same over the whole region.

  An enlarged plan view of the recess 10 is shown in FIG. In FIG. 3, the left side is the outer tread end Te1 side, and the right side is the inner tread end Te2 (respectively shown in FIG. 1 and hereinafter). As shown in FIG. 3, the recess 10 has a length L1 in the axial direction of the tire greater than a length L2 in the circumferential direction of the tire in a plan view of the tread. Such a recess 10 is less likely to be deformed in the tire axial direction, and thus helps to maintain the axial rigidity of the tread portion 2 (shown in FIG. 1 and the same hereinafter).

  In order to balance the rigidity and heat buildup of the tread portion 2 in a well-balanced manner, the ratio L2 / L1 of the axial length L1 of the recess 10 to the circumferential length L2 is preferably at least 0.55, More preferably, it is 0.60 or more, preferably 0.75 or less, more preferably 0.70 or less.

  The centroid 16 of the contour shape 15 of the recess 10 is located on the inner tread end Te2 side (right side in FIG. 3) than the center position 17 of the length of the recess 10 in the tire axial direction. Such a recess 10 reduces the rubber volume on the inner tread end Te2 side with respect to the center position 17 and promotes deformation of the rubber of the tread portion 2. Therefore, the heat buildup of the tread portion 2 is enhanced.

  The contour shape 15 is a portion 11 where the width in the tire circumferential direction gradually decreases from the maximum width position 18 in the tire circumferential direction toward the outer tread end Te1 side (left side in FIG. 3) (hereinafter referred to as "first portion 11" There is.). Thereby, the rubber volume by the side of outer tread end Te1 of crevice 10 is maintained, and the rigidity of tread part 2 is maintained by extension.

  In order to further exert the above-described effects, the first axial portion length L3 from the first outer end 21 on the outer tread end Te1 side to the maximum width position 18 is, for example, the axial direction of the recess 10 in the tire axial direction. The length L1 is preferably 0.65 to 0.75.

  The contour shape 15 of the present embodiment includes, for example, a second portion 12 in which the width in the tire circumferential direction gradually decreases from the maximum width position 18 in the tire circumferential direction toward the inner tread end Te2.

  The second part length L4 in the tire axial direction from the second outer end 22 on the inner tread end Te2 side to the maximum width position 18 is smaller than the first part length L3. The second portion length L4 is preferably, for example, 0.25 to 0.35 times the axial length L1 of the recess 10. If the second portion length L4 is smaller than 0.25 times the length L1 of the recess 10, the heat buildup of the rubber in the vicinity of the second portion 12 may be reduced. When the second portion length L4 is larger than 0.35 times the length L1 of the recess 10, the edge of the second portion 12 is suddenly bent in the vicinity of the second outer end 22, so the rubber in the vicinity of the second outer end 22 However, there is a possibility that heat is likely to be generated locally.

  The axial direction length L1 of the recess 10 is, for example, 4.0% to 7.5%, and more preferably 6.0% to 7.0% of the tread contact width TW (shown in FIG. 1). is there. The length L2 of the recess 10 in the tire circumferential direction is, for example, 0.20% to 0.80% of the tire peripheral length Lc (not shown) on the tire equator C, and more preferably 0.40% to It is 0.50%. Such a recess 10 makes the rigidity and heat buildup of the tread portion 2 compatible with each other in a well-balanced manner. The tread contact width TW is the axial distance between the outer tread end Te1 and the inner tread end Te2 of the tire 1 in the normal state.

  FIG. 4 is a cross-sectional view of the recess 10 of FIG. 2 taken along line A-A. As shown in FIG. 4, the wall surface 24 on the second outer end 22 side of the recess 10 is formed at an angle θ1 of 0 to 20 ° with respect to a normal extending inward in the tire radial direction from the edge of the recess 10 Is desirable. Thereby, uneven wear of the edge near the second outer end 22 is suppressed.

  As shown in FIG. 2, it is desirable that the respective recess portions 10 be disposed without overlapping the recess projection regions a obtained by projecting the recesses 10 in the tire axial direction. Such arrangement of the recesses 10 serves to uniformly heat the tread portion 2.

  The recess 10 of the present embodiment is provided only in the outer tread portion 5. In this embodiment, the sheet ratio SbSb / Sa, which is a ratio of the total ΣSb of the opening area of the recess 10 to the area Sa of the outer tread portion 5 measured in a state in which all the recesses 10 are filled, is preferably 6.5% or more More preferably, it is 7.0% or more, preferably 11.0% or less, more preferably 9.0% or less. Such arrangement of the recesses 10 helps to improve the rigidity and heat buildup of the tread portion 2 in a well-balanced manner.

  In the present embodiment, only the recess 10 having the above-described shape is provided in the outer tread portion 5, but the present invention is not limited to such an aspect. That is, in addition to the recess 10 described above, the outer tread portion 5 may be provided with a plurality of recesses each having a circular, elliptical, oval or rectangular outline shape.

  As shown in FIG. 1, the inner tread portion 6 is provided with at least one main groove 25 extending continuously in the tire circumferential direction. Such a main groove 25 helps to secure the wet performance necessary for traveling on a public road.

  As a desirable mode, in the present embodiment, the land portion 27 between the inner tread end Te2 and the main groove 25 is in the form of a slick in which a groove and a sipe are not provided. Such a land portion 27 has high rigidity and can exhibit excellent cornering performance.

  FIG. 5 shows a developed view of the tread portion 2 according to another embodiment of the present invention. In FIG. 5, the same reference numerals are given to configurations common to the above embodiment.

  As shown in FIG. 5, in this embodiment, an edge 26 on the inner tread end Te2 side extends in the tire circumferential direction at the maximum width position 18 of the recess 10 in the tire circumferential direction. In such a recess 10, deformation of the tire circumferential direction is suppressed by the edge 26. Therefore, deformation of the tread portion 2 in the tire circumferential direction is suppressed, and traction performance is enhanced.

  As mentioned above, although the pneumatic tire of one embodiment of the present invention was explained in detail, the present invention can be changed and carried out to various modes, without being limited to the above-mentioned specific embodiment.

A pneumatic tire of size 205 / 55R16 having the basic tread pattern of FIG. 1 was prototyped based on the specifications of Table 1. As a comparative example, as shown in FIG. 6, a pneumatic tire in which the outline of the recess has a circular shape was manufactured on a trial basis. The cornering performance of each test tire was tested. The common specification and test method of each test tire are as follows.
Rim: 16 × 7.0 JJ
Tire internal pressure: 200kPa

<Cornering performance>
The cornering performance at the beginning of traveling when traveling on a circuit course of asphalt in the following test vehicle equipped with the above test tire was evaluated by the driver's function. A result is a score which sets a comparative example to 100, and it shows that cornering performance is excellent, so that a numerical value is large.
Test vehicle: 2000 cc displacement, rear wheel drive vehicle Test tire mounting position: all wheels The results of the test are shown in Table 1.

  As a result of the test, it was confirmed that the pneumatic tire of the example exhibited excellent cornering performance by making the rigidity and heat buildup of the tread portion compatible with each other.

Reference Signs List 2 tread portion 10 recessed portion 15 contour shape 16 center 17 center position 18 maximum width position Te1 outer tread end Te2 inner tread end

Claims (5)

A pneumatic tire having a tread portion in which an outer tread end and an inner tread end are defined by specifying a direction of mounting on a vehicle.
The tread surface of the tread portion is provided with a plurality of concave portions having a closed contour shape formed of a smooth curve,
In a plan view of the tread portion,
In each of the recesses, the axial length of the tire is greater than the circumferential length of the tire,
The center of the contour shape is located on the inner tread end side with respect to the central position of the length of the recess in the tire axial direction,
The pneumatic tire is characterized in that the contour shape includes a portion in which the width in the circumferential direction of the tire gradually decreases from the maximum width position in the circumferential direction of the tire toward the end side of the outer tread.   The pneumatic tire according to claim 1, wherein each of the recesses is arranged such that the recess projection areas obtained by projecting the recesses in the tire axial direction do not overlap each other. The axial length of the recess is 4.0% to 7.5% of the tread contact width,
The pneumatic tire according to claim 1 or 2, wherein a length in a tire circumferential direction of the recess is 0.2% to 0.8% of a tire outer peripheral length on the tire equator. The tread portion includes an inner tread portion between the tire equator and the inner tread end, and an outer tread portion between the tire equator and the outer tread end.
The inner tread portion is provided with one main groove continuously extending in the tire circumferential direction,
The pneumatic tire according to any one of claims 1 to 3, wherein the recess is provided only in the outer tread portion.   The pneumatic tire according to claim 4, wherein a land portion between the inner tread end and the main groove is in a slick shape in which a groove and a sipe are not provided.

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