JP6511384B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire.

  Conventionally, in a pneumatic tire having land portions partitioned by a plurality of circumferential grooves, various tires defining the outer contour of the land portions in cross-sectional view in the tread width direction, for example, in order to improve braking performance It is proposed (for example, patent document 1).

JP, 2009-161001, A

  Here, with the conventional tire as described above, although the braking performance can be improved, there is room for further improvement of the braking performance. Further, in recent years, environmental consideration has been required at a high level, and it has also been required to simultaneously improve the low rolling resistance performance that leads to low fuel consumption as well as the braking performance.

  Then, an object of this invention is to provide the pneumatic tire which can make braking performance and low rolling resistance performance make compatible.

The pneumatic tire according to the present invention comprises at least two circumferential grooves continuously extending in the circumferential direction of the tire, and at least one land portion defined by the two circumferential grooves on the tread surface. The at least one land portion continuously extends in the circumferential direction of the tire, and at least a portion on the tread tread side of the outer contour in a cross-sectional view in the tire width direction The arc width obtained by measuring the arc of the arc-shaped land portion along the tire width direction in a cross-sectional view including the arc-shaped land portion, which is an arc having a central angle of 90 ° or more, is the tread contact width In the range of 10 to 30%.
According to the present invention, both braking performance and low rolling resistance performance can be achieved.

In the present invention, unless otherwise specified, the dimensions of the tire refer to the dimensions measured in a no-load state where the tire assembled to the application rim is filled with a prescribed air pressure. In addition, “application rim” is an industrial standard effective for the area where tires are produced and used, and in Japan, JATMA (Japan Automobile Tire Association) JATMA YEAR BOOK, and in Europe ETRTO (The European Tire and Rim Standard rims in application size (Measuring Rim for ETRTO, STDARDARD MANUAL for ETRTO, Design for YEAR BOOK for TRA, Design for STANDARDS MANUAL in Technical Organization) Refers to the Rim). In addition, in the state where "a specified air pressure is filled" in the tire assembled to the application rim, the tire is attached to the application rim described above, and the maximum size of single wheels in application size and ply rating described in JATMA etc. It refers to the state of air pressure (maximum air pressure) corresponding to the load capacity. In addition, it is also possible to substitute air here called inert gas other than nitrogen gas etc., and others.
Further, in the present invention, “tread contact width” is a length obtained by measuring the tread contact ends on both sides of the tread along the tire width direction, and “tread contact end” refers to the tread width direction of the tread surface. The “tread tread” refers to the road surface when the tire is assembled with the applicable rim and filled with the specified air pressure, with the load applied corresponding to the maximum load capacity. “Maximum load capacity” refers to the maximum load capacity of a single wheel in application size and ply rating as described in the above JATMA etc.
In the present invention, the "arc-like land portion" extends continuously in the circumferential direction of the tire, and at least a portion on the tread surface side of the outer contour line has a central angle in the cross-sectional view in the tire width direction. In the case where the central angle is less than 90 °, even if the entire tread tread surface side of the outer contour line of one land portion is a circular arc, this refers to a land portion that is an arc that is 90 ° or more. It is not included in "Arc shaped land".

Here, in the pneumatic tire according to the present invention, a plurality of the arcuate land portions are provided on the tread surface, and a total of the arc widths of the plurality of arcuate land portions is 20 to 50% of the tread contact width. It is preferable to be within the range.
According to this configuration, both braking performance and low rolling resistance performance can be sufficiently achieved.

Further, in the pneumatic tire according to the present invention, it is preferable that the tire is a tire in which the mounting direction to the vehicle is specified, and all the circular land portions are located in a tire half inside the vehicle mounting direction.
According to this configuration, it is possible to improve motion performance such as steering stability performance, braking performance, and drive performance.
In addition, a "tire half part" points out the part located in the tire width direction one side with respect to a tire equator line among tread treads.

Further, in the pneumatic tire according to the present invention, it is preferable that a portion where the tire equator line is located in the tread surface is flat.
According to this configuration, it is possible to improve motion performance such as steering stability performance, braking performance, and drive performance.
In the present invention, “a portion of the tread surface on which the tire equator line is located” refers to a region of the tread surface with a width of 15% of the tread contact width centered on the tire equator line. . In addition, “flat” may be a substantially flat shape, and it is acceptable that a groove not continuous in the tire circumferential direction be located in the portion where the tire equator is located in the tread surface. Be done.

Further, in the pneumatic tire according to the present invention, in a cross-sectional view in the tire width direction, the contour line of the connecting portion connecting the groove bottom of the circumferential groove defining the arcuate land portion and the arcuate land portion is a curve. Is preferred.
According to this configuration, the durability of the tire can be sufficiently maintained.

  According to the present invention, it is possible to provide a pneumatic tire capable of achieving both braking performance and low rolling resistance performance.

1 is a development view showing a tread pattern of a pneumatic tire according to an embodiment of the present invention. It is a tire width direction sectional view which meets the AA of the pneumatic tire of FIG. It is a perspective view of the pneumatic tire of FIG.

Embodiments of the present invention will be illustrated and described below with reference to the drawings.
FIG. 1 is a development view showing a tread pattern of a pneumatic tire (hereinafter also referred to as a tire) 1 according to an embodiment of the present invention. 2 is a cross-sectional view in the tire width direction taken along the line AA of the tire 1 of FIG. 1, and FIG. 3 is a perspective view of the tire 1.
The tire 1 can be used, for example, as a pneumatic tire for a passenger car, in which a mounting direction to a vehicle is designated. Hereinafter, in the present specification, the present invention will be described as a pneumatic tire in which the mounting direction to the vehicle is specified, but the present invention can be applied to a tire in which the mounting direction is not specified.

  Although this tire 1 is partially omitted in the figure, a carcass having a radial structure extending in a toroidal shape between bead portions, a belt disposed on the tire radial direction outer side of the carcass of the tread portion, and a tire radial direction of the belt And a tread rubber disposed on the outer side to form a tread surface T. In addition, the internal reinforcing structure of the tire 1 can be the same as that of a general radial tire.

As shown in FIGS. 1 and 3, the tire 1 has at least two circumferential grooves 2 continuously extending in the tire circumferential direction on the tread surface T. As shown in FIG. In the illustrated example, the tire 1 is one of the tire halves located on both sides in the tire width direction with respect to the tire equator line CL in the tread tread surface T in the tire half in the vehicle mounting direction (left side in FIG. 1) Although three circumferential grooves 21, 22 and 23 are provided, circumferential grooves extending continuously in the tire circumferential direction are provided in the tire half portion on the outer side (right side in FIG. 1) of the vehicle mounting direction It is not done.
Although the circumferential grooves 2 shown in the drawings extend linearly in the circumferential direction of the tire, they may be in the form of zigzags, waves or the like. In the illustrated example, the circumferential grooves 21 and 22 on the outer side in the tire width direction have the same groove width and are narrower than the circumferential groove 23 on the inner side in the tire width direction, but the groove width is arbitrary. can do. Furthermore, the number and arrangement of the circumferential grooves 2 can be different from the illustrated example.

  The tire 1 includes at least one land portion 3 divided by two adjacent circumferential grooves 2 of at least two circumferential grooves 2. Specifically, in the illustrated example, two land portions 3 are provided by the three circumferential grooves 21, 22 and 23 provided in the tire half portion on the inner side in the vehicle mounting direction, and the tire width direction outer side (this In the example, one circumferential land 21 on the inner side of the vehicle mounting direction and the innermost tire in the tire width direction (in this example, the outer side in the vehicle mounting direction) by the circumferential groove 21 and the tread ground contact end TE. The circumferential land 23 and the tread ground contact end TE define an outer land portion 5 which is located on the outer side in the vehicle mounting direction across the tire equator line CL.

In the tire 1, at least one land portion (FIGS. 1 and 3) divided by the above-described at least two circumferential grooves 2 (circumferential grooves 21 22 and 23 in the examples of FIGS. 1 and 3) In this case, the two lands 3) extend continuously in the circumferential direction of the tire (that is, no crossing groove is provided to cross the lands 3), and as shown in FIG. In a cross-sectional view in the tire width direction, at least a portion C of the outer contour line on the tread surface T side includes an arc-shaped land portion 31 which is one arc whose center angle θ is 90 ° or more. In the illustrated example, each of the two land portions 3 is an arc-shaped land portion 31. Further, as shown in FIG. 2, the entire outer contour of the arcuate land portion 31 may be an arc, and although not shown, a portion C of the outer contour on the tread tread surface T side The remaining portion can be a straight line or a curve extending from the end of the arc.
The “outer contour line” of the arcuate land portion 31 includes the contour line of the groove wall of the circumferential groove 2 that divides the arcuate land portion 31 in the tire width direction sectional view, in other words, The outer contour line of the arcuate land portion 31 from the groove wall of one circumferential groove 2 to the groove wall of the other circumferential groove 2 is meant.

  Moreover, in this tire 1, although the groove bottom of the circumferential direction groove 2 which divides the arc-like land part 31 and the said arc-like land part 31 form a corner and are connected, although illustration is omitted, it is tire width direction In a sectional view, it is preferable to provide a connecting portion for connecting the groove bottom of the circumferential groove 2 that divides the arcuate land portion 31 and the arcuate land portion 31 and make the outline of the connecting portion curved. Specifically, it is more preferable that the contour of the connection portion be convexly curved inward in the tire radial direction, and in particular, be a circular arc.

  In the tire 1, the circumferential groove 2 partitioning the arcuate land portion 31 has a flat groove bottom having a predetermined width of the circumferential groove 2, and the arcuate land portion 31 in cross section in the tire width direction. The portion where the outer contour line is a circular arc forms a concave shape recessed from the tread surface T, and for example, drainage performance is exhibited in the concave shape. However, the circumferential groove 2 can also be made concave by a groove bottom having no width and a portion where the outer contour of the arcuate land portion 31 is an arc. That is, for example, two arcuate land portions 31 can be positioned adjacent to each other. In such a case, the groove bottom of the circumferential groove 2 is the most circumferential groove of the circumferential grooves in the tire width direction cross sectional view It becomes a point located inside.

  In the tire 1, when the virtual contour O of the tread surface T formed by the land portions other than the arcuate land portion 31 is drawn in a cross-sectional view in the tire width direction, The top (apex) 31 t of the arc that is a point can be substantially positioned on the virtual contour O. More specifically, the arc is preferably positioned so as to contact the virtual contour O at the top 31t, but the length measured along the tire radial direction from the top 31t to the contour is the top 31t The apex 31t can be substantially positioned on the virtual contour O such that the distance from the tire axis to the tire axis is 1.6% or less of the length measured along the tire radial direction. The top 31t of the arc is preferably located at the center in the width direction of the arc-shaped land 31 in a cross-sectional view in the tire width direction as illustrated.

Further, in the tire 1, in a cross-sectional view in the tire width direction, an arc width CW obtained by measuring the arc of the arc land portion 31 along the tire width direction is in a range of 10 to 30% of the tread contact width. It is inside. Specifically, as in the illustrated example, when all the outer contours of the arc-shaped land portion 31 are formed by arcs, the arc width CW extends in the tire width direction along the arc-shaped land portion 31. Although it is a measured length, although illustration is omitted, when a part of the outer contour is formed by a circular arc, a length obtained by measuring a part of the circular arc land 31 along the tire width direction It is.
In the case where a plurality of arcuate lands 31 are provided on the tread surface T as in the illustrated example, the total of the arc widths CW of the plurality of arcuate lands 31 is 20 to 50% of the tread contact width. It is preferable to be within the range of

Subsequently, land portions other than the land portions 3 (in this example, the land portions 31 are all arc-shaped in the present embodiment) provided on the tread surface T and divided by the two circumferential grooves in the present embodiment will be described.
As shown in FIGS. 1 and 3, the shoulder land portion 4 on the inner side in the vehicle mounting direction is a land portion divided by the circumferential groove 21 and the tread ground contact end TE, and the portion on the tread tread surface T side is a figure. As shown in 2, the outer contour thereof is a curve which is slightly curved convexly outward in the tire radial direction. Further, the portion on the circumferential groove 21 other than the portion on the tread tread surface T is a groove wall of the circumferential groove 21 and the outer contour thereof is a straight line inclined with respect to the tire radial direction. Further, the shoulder land portion 4 on the inner side in the vehicle mounting direction extends continuously in the tire circumferential direction, and no crossing groove that crosses the land portion 4 is provided.

  In addition, as shown in FIGS. 1 and 3, the outer land portion 5 located on the outer side in the vehicle mounting direction across the tire equator line CL is a circumferential groove 23 located on the outermost side in the vehicle mounting direction and the tread contact end TE. As shown in FIG. 2, a portion of the outer contour of the outer land portion 5 which is a divided land portion and which has a portion on the tread surface T side (excluding a groove provided in the land portion 5) is a tire diameter. It is a curve which is slightly curved convexly outward in the direction. Further, among the outer contours of the outer land portion 5, a portion other than the tread surface T side on the inner side in the vehicle mounting direction (a portion from the tread surface T side to the circumferential groove 23 side) is an arc.

  As shown in FIGS. 1 and 3, the outer land portion 5 includes a plurality of first width direction grooves 51 extending from the inner portion in the vehicle mounting direction of the land portion 5 to the tread contact end TE, and the first land direction groove 51. A plurality of second width direction grooves 52 adjacent to the width direction groove 51 and the tire circumferential direction one side and extending from the inner portion of the land portion 5 in the vehicle mounting direction to the land portion 5 of the outer portion in the vehicle mounting direction And a first connecting groove 53 provided at a portion on the inner side in the vehicle mounting direction of the land portion 5 for connecting an end portion of the first width direction groove 51 and an end portion of the second width direction groove 52; A first width direction groove 51 provided in a portion on the outer side in the vehicle mounting direction, and a second bending portion connecting the end portion of the first width direction groove 51 and the second width direction groove 52 adjacent to the other side in the tire circumferential direction And a connecting groove 54. Furthermore, the outer land portion 5 is located in the tire circumferential direction from the tire circumferential direction end on the other side in the tire circumferential direction where the end of the first width direction groove 51 is located among the tire circumferential direction ends of the first connection groove 53 A circumferential narrow groove 55 which extends to the other side in the tire circumferential direction and terminates is provided up to the front of the first connection groove 53 adjacent to the second connection groove 53.

  More specifically, the first width direction groove 51 and the second width direction groove 52 respectively extend while inclining in the tire circumferential direction with respect to the tire width direction, and are substantially parallel to each other. ing. The first connection groove 53 extends substantially in the circumferential direction of the tire, and has a notch 56 in the vehicle mounting direction on the inner side of which the groove depth gradually increases in the tire width direction from the tread surface T to the groove bottom. doing. The second connection groove 54 has one convex bending portion on the inner side in the tire width direction at the middle in the extending direction. The first width direction groove 51 and the second connection groove 54 have a step portion 57, and the step portion 57 is sandwiched between the first width direction groove 51 and the second connection groove 54 to form a sharp corner portion. It is located adjacent to the land portion 5 and has a depth shallower than the groove depth of the first width direction groove 51 and the second connection groove 54.

Here, the operation and effects of the pneumatic tire 1 of the present invention provided with the above-described arcuate land portion 31 will be described below.
In the tire 1 according to the present invention, at least one arcuate land portion 31 is provided as at least one land portion 3 partitioned by the circumferential groove 2, and in the tire width direction cross section, the arcuate land portion 31 The braking performance and low rolling are achieved by setting the central angle θ of the arc of the outer contour line to 90 ° or more and setting the arc width CW of the arc land 31 within the range of 10 to 30% of the tread contact width. Resistance performance can be made compatible. Specifically, during traveling, a portion C of the arc-shaped land portion 31 where the outer contour line is an arc comes into contact with the road surface, but during steady traveling (the speed is constant), the land Since only the vicinity of the top 31t of the portion 31 is in contact with the road surface, the ground contact area can be reduced, and hence the low rolling resistance performance can be improved (rolling resistance can be reduced). On the other hand, when a large load is applied to the tire 1 at the time of braking or the like, a load is applied to the arcuate land portion 31 and the vicinity of the top 31t of the land portion 31 collapses in the tire radial direction. The ground area can be increased in accordance with the applied load. Therefore, the grip strength can be improved and the braking performance can be improved.

In cross-sectional view in the tire width direction, when the central angle θ of the arcs of the outer contours is less than 90 °, or when the arc width CW of one arc land portion 31 is less than 10% of the tread contact width In this case, almost all of the arc portion C of the arcuate land portion 31 may contact the ground during steady running or when only a small load is applied to the tire 1, and the contact area may be changed by the load applied to the tire 1. become unable. When the arc width CW of one arc-like land portion 31 is more than 30% of the tread contact width, the contact area of the tire 1 tends to be insufficient at the time of braking or the like.
In addition, since the arcuate land portion 31 extends continuously in the tire circumferential direction, the land portion 3 does not have a rigid step, and the silence can be improved.
In a normal tire, even if a portion on the tread side of the outer contour line of one land portion is temporarily formed in one arc shape, the radius of curvature is smaller than the arc width of the arc shape. Because it is extremely large, the central angle θ is extremely small.

  In addition, the contact area is changed by the load applied to the tire 1 to improve the braking performance, and at the same time, the arc land portion 31 can be sufficiently opposed to, for example, a lateral force at cornering. In a cross sectional view, the central angle θ of the arc among the outer contours of the arcuate land portion 31 is preferably 90 to 180 °, and more preferably 100 to 140 °. Moreover, it is preferable to make circular-arc width CW of one circular-arc-like land part 31 into the range of 15 to 20% of a tread contact width from the same viewpoint.

  Furthermore, in the tire 1, as shown in FIGS. 1 and 3, a plurality of arcuate land portions 31 are provided on the tread surface T, and the total arc width CW of the plurality of arcuate land portions 31 is the tread contact It is preferable to be in the range of 20 to 50% of the width. According to this configuration, since the ground contact area can be sufficiently reduced during steady traveling, the low rolling resistance performance can be sufficiently improved, and the total of the arc width CW of the arc land 31 is too large. As a result, the width in the tire width direction of the land portion other than the arcuate land portion 31 becomes too small, and the contact area becomes insufficient, which can sufficiently suppress the possibility that the braking performance is deteriorated. Moreover, it is more preferable that the sum total of circular-arc width CW of several circular-arc-like land part 31 exists in the range of 25 to 35% of a tread contact width from the same viewpoint.

  Further, in the tire 1, the portion of the arc-shaped land portion 31 which is the arc is from a position at the outermost side in the tire radial direction of the land portion 31 to a position at 80% of the groove depth of the circumferential groove 2 It is preferable that the groove extends to the bottom of the groove. According to this configuration, the ground contact area can be sufficiently changed in accordance with the load applied to the tire 1, and the low rolling resistance performance and the braking performance can be sufficiently achieved. The length from the outermost position in the tire radial direction of the arcuate land portion 31 is the length measured along the tire radial direction, and the groove depth of the circumferential groove 2 is from the tread surface T, The length measured along the tire radial direction.

  Moreover, it is preferable that the curvature radius of the circular arc of the circular arc land part 31 is 10-30 mm. According to this configuration, since the ground contact area can be reduced during steady traveling, the low rolling resistance performance can be sufficiently improved. Further, the ground contact area due to the large arced portion of the arcuate land portion 31 It is possible to prevent the possibility that the braking performance is reduced due to the lack of

  The groove depth of the circumferential groove 2 can be 4 to 8 mm. Further, in a cross-sectional view in the tire width direction, it is preferable that the width of the groove bottom of one circumferential groove 2 that divides the arcuate land portion 31 be 1 to 3% of the tread contact width. The width of the groove bottom of the circumferential groove 2 is a width obtained by measuring the groove bottom of the circumferential groove 2 along the direction orthogonal to the extending direction of the circumferential groove 2.

  When the tire 1 is a tire whose mounting direction to the vehicle is specified as in this example, a large load is applied to the tire half portion on the outer side in the vehicle mounting direction during cornering traveling. Therefore, the ground contact area of the tread surface T is made sufficiently large, and the rigidity of the land portion on the outer side in the vehicle mounting direction is secured, and the movement stability such as steering stability, braking performance, and driving performance, particularly steering stability at cornering From the viewpoint of improvement, it is preferable that all the arcuate land portions 31 be located in the tire half portion on the inside in the vehicle mounting direction.

  Further, in the tread surface T, in the portion where the tire equator line CL is located, it is preferable that the arcuate land portion 31 and the circumferential groove 2 not be located, and that the portion be particularly flat. During traveling, the contact length of the portion where the tire equator line CL is located is the longest in the tread surface T. Therefore, the corresponding portion affects the handling response when turning the vehicle, but the tire equator line CL A ground area can be secured by flattening the positioned portion. Therefore, it is possible to improve motion performance such as steering stability performance, braking performance, and driving performance, in particular, steering stability performance when turning the vehicle from straight running. When the circular land portion 31 is positioned on the tire equator line CL, the ground contact area can be secured when traveling while the circular land portion 31 is sufficiently loaded with a load, but straight traveling is possible. When turning the vehicle from time (when steady traveling), the load is not sufficiently applied to the arcuate land portion 31 and there is a risk that the ground contact area can not be sufficiently secured, and the response of handling decreases. There is a risk of

  Further, if there is no connecting portion which is a curve at the boundary between the arcuate land portion 31 and the groove bottom of the circumferential groove 2 which divides the arcuate land portion 31, a crack is generated from the boundary and it is If it progresses, there is a possibility that the durability of the tire 1 may be reduced, or the water existing between the tread surface and the road surface may not be efficiently guided into the circumferential groove 2 and drainage may be reduced. . Therefore, in the tire width direction cross sectional view, it is preferable that the outline of the connecting portion connecting the groove bottom of the circumferential groove 2 that divides the arcuate land portion 31 and the arcuate land portion 31 is a curved line. From the viewpoint of further improving the durability of the tire 1 and sufficiently securing the drainage property, the connecting portion is preferably a circular arc in a cross-sectional view in the tire width direction, and the circular arc is 0.5 to 0.5. More preferably, it has a radius of curvature of 2 mm.

  As mentioned above, although the embodiment of the present invention was described with reference to drawings, the pneumatic tire of the present invention is not limited to the above-mentioned example, and a modification is suitably added to the pneumatic tire of the present invention Can.

  Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to the following examples.

The tire of Example 1 has a tire size of 195 / 65R15 91H and has a tread pattern as shown in FIGS. Specifically, the tire according to the first embodiment is provided with three circumferential grooves while defining the mounting direction to vehicle attachment, and two circles divided by the three circumferential grooves. It has an arcuate land. Further, this tire has the central angle θ of the arc of the arc-like land portion, the sum of the arc widths, and the negative ratio (groove area ratio) described in Table 1.
The tires of Examples 2 to 5 and the tire of Comparative Example 3 are the same as the tires of Example 1 except that they are changed as shown in Table 1.
In the tires of Comparative Examples 1 and 2, the arcs of the land portions in which the arcs are included in the outer contours of the tire according to Example 1 are made flat (in other words, the outer contours of the lands have a substantially angular shape) And the same as the tire of Example 1 except that the groove width of the groove was adjusted to be the negative ratio in Table 1).
Braking performance
In the braking performance test, a vehicle equipped with each test tire filled with a prescribed air pressure is allowed to travel on a dry road surface at a speed of 100 Km / h and then fully braked, the distance at which the vehicle stops (M) was measured. The results are shown in Table 1 as index values with the tire of Comparative Example 1 being 100, with the result being the reciprocal. The index value indicates that the larger the numerical value, the better the braking performance.
[Low rolling resistance performance]
In the low rolling resistance performance test, each test tire with an internal pressure of 196 kPa was mounted on a steam drum tester with a smooth surface with a diameter of 1707 mm, and rolling when running under a load condition of 4.0 kN and a speed of 80 km / h The resistance was measured by the ellipticity method defined in JIS D4234. The index value with the tire of Comparative Example 1 being 100 is shown in Table 1. The index value indicates that the lower the rolling resistance performance, the better the larger the value.

  From the results of Table 1, since the tires of Examples 1 to 5 have arcuate land portions, the low rolling resistance performance can be improved as compared to the case of having the land portions of the tire of Comparative Example 1. Moreover, Examples 1-5 can improve damping | braking performance compared with the bibliographic documents 2 and 3 which have the same negative rate. Therefore, it is understood that the invention according to Examples 1 to 5 of the present invention can achieve both braking performance and low rolling resistance performance.

  According to the present invention, it is possible to provide a pneumatic tire capable of achieving both braking performance and low rolling resistance performance.

1: Tire 2, 21, 22, 23: circumferential groove 3: land portion 31: arcuate land portion 31t: top (apex)
4: Shoulder land portion 5: outer land portion 51: first width direction groove 52: second width direction groove 53: first connection groove 54: second connection groove 55: circumferential narrow groove 56: notch 57: step Part C: A portion on the tread tread side among the outer contours of the arcuate land portion CL: tire equator line CW: arc width O: virtual contour line of tread tread T: tread tread TE: tread contact edge θ: central angle

Claims (5)

A pneumatic tire comprising at least two circumferential grooves continuously extending in the circumferential direction of the tire and at least one land portion partitioned by the two circumferential grooves on a tread surface. ,
The at least one land portion extends continuously in the circumferential direction of the tire, and in a cross-sectional view in the tire width direction, an arc of which at least a portion on the tread surface side in the outer contour line has a central angle of 90 ° or more , Including arc-shaped lands,
In a tire width direction sectional view, a circular arc width obtained by measuring the circular arc of the circular arc land portion along the tire width direction is within a range of 10 to 30% of a tread contact width. . The plurality of arcuate land portions are provided on the tread surface,
The pneumatic tire according to claim 1, wherein a total of the arc widths of the plurality of arc-shaped land portions is within a range of 20 to 50% of the tread contact width. The tire is a tire whose mounting direction to a vehicle is specified,
The pneumatic tire according to claim 1, wherein all the arcuate land portions are located in a tire half inside in a vehicle mounting direction.   The pneumatic tire according to any one of claims 1 to 3, wherein a portion where the tire equator line is located in the tread surface is flat. In the tire width direction sectional view,
The pneumatic tire according to any one of claims 1 to 4, wherein a contour of a connecting portion connecting the groove bottom of the circumferential groove defining the arcuate land portion and the arcuate land portion is a curve.