JP4869089B2 - Pneumatic tire - Google Patents

Description

The present invention relates to a pneumatic tire, and more particularly to a balance-oriented pneumatic tire that is excellent in drainage, handling stability, and uneven wear resistance, and that also reduces noise.

In order to achieve both drainage and steering stability in a pneumatic tire , a tread portion is provided with a circumferential groove extending along the tire circumferential direction and an inclined groove extending obliquely with respect to the tire circumferential direction. In this type of tire, drainage in the front-rear direction of the tire can be performed by the circumferential groove, and drainage to the tire side can be performed by the inclined groove.

In such a tire, when the inclined grooves are arranged at a large angle with respect to the tire circumferential direction, steering stability is improved by ensuring uneven wear resistance and land rigidity, but pattern noise and drainage are deteriorated. There was a problem to do.
On the other hand, as a means for improving the drainage, or extend at a small angle inclined grooves to the tire circumferential direction, expanding the groove width, it increases the proportion of the (negative ratio) of the grooves occupying the tire ground contact surface it is effective, but in this case, reduction worsening of steering stability by the land portion rigidity, uneven wear is disadvantageously likely to occur.

For this reason, there is a limit to satisfy both the handling stability and drainage performance at a high level.

For example, in Patent Document 1, the surface contour shape of the block is tapered at both ends of the convex lens cross-section, and the tapered end portion is provided with an inclined surface that gradually decreases the block height toward the tip edge side. By projecting from the groove bottom of the groove that defines the tapered end of the block and interconnecting with a smoothly continuous rib to the inclined surface that gradually reduces the block height, performance such as noise and uneven wear resistance is sacrificed Without doing so, it is disclosed that drainage and steering stability on a dry road surface can be advantageously improved.
According to the tire described in Patent Document 1, it becomes that good drainage and the steering stability can be obtained, the present inventors have carried out then further examined, in this tire, near the most tire equatorial plane Since the groove wall on the tread end side of the circumferential groove located at is completely divided by the opening of the inclined groove, even if water existing in the ground contact central area is once taken into the circumferential groove, it is diverted to the inclined groove. Therefore, it was found that the drainage efficiency in the tire longitudinal direction through the circumferential groove is not sufficient.
In addition, it is advantageous in terms of drainage efficiency to drain the water taken into the circumferential groove and moved to the inclined groove by the diversion to drain the tire sideward through the circumferential groove. .

Therefore, an object of the present invention is to adopt a tread pattern in which a central main groove and an inclined groove are arranged in the tread part, and in such a tread pattern, by optimizing the shape of the block in the central land part, An object of the present invention is to provide a pneumatic tire that improves drainage and noise while maintaining performance such as uneven wear resistance and ride comfort.

In order to achieve the above object, the gist of the present invention is as follows.
(1) One central main groove located in the pattern center or in the vicinity thereof and extending along the tire circumferential direction in a half area where the tread portion is divided into two at the pattern center, and the central main groove and the tread end At least one side main groove located between and extending along the tire circumferential direction, and a plurality of steep slopes extending at a relatively small angle with respect to the tire circumferential direction between the central main groove and the side main grooves A central land portion is defined by a central main groove and a first side main groove that is a side main groove adjacent to the central main groove, and the central main groove, the first side main groove, and the tire circumferential direction In the pneumatic tire formed by dividing the central land portion into a plurality of blocks substantially by two steeply inclined grooves adjacent to each other to form a block row, the central main groove side wall portion of the block in the central land portion is The pattern center with a predetermined radius of curvature along the tire circumferential direction in plan view The central main groove side wall of the central land portion has a substantially continuous wavy shape, and the steeply inclined groove has a groove depth of the first side main groove. An inclined groove bottom portion gradually increasing toward the center is provided, and the intersection position of the arc portion constituting the central main groove side wall of the block and the virtual arc extension line of the adjacent arc portion is adjacent to the inclined groove bottom portion. Pneumatic tire characterized by being made.
(2) The pneumatic tire according to (1), wherein the block further includes a gently inclined groove extending at a relatively large angle with respect to the tire circumferential direction.
(3) A first chamfered portion whose land portion height gradually decreases toward the tip of the first acute angle portion defined by the central main groove and the steeply inclined groove is provided, and the tip of the first acute angle portion is located at the intersection position. The pneumatic tire according to the above (1), which substantially matches.
(4) The pneumatic tire according to any one of (1) to (3), wherein the radius of curvature of the arc portion is 40 to 400 mm.
(5) The pneumatic tire according to any one of (1) to (4), wherein the steeply inclined groove has an angle with respect to the tire circumferential direction of 42 ° or less.
(6) The gently inclined groove is the pneumatic tire according to (2), wherein the angle with respect to the tire circumferential direction is 45 to 90 °.
(7) The pneumatic tire according to (2) or (6), wherein the block is provided with a sipe extending in parallel with the gently inclined groove.
(8) The central main groove is a pair of central main grooves sandwiching the pattern center, and a rib-like land portion extending continuously along the tire circumferential direction is provided between the central main grooves. The pneumatic tire according to any one of (7) to (7).
(9) The above (1) to (1), wherein the second chamfered portion in which the land height gradually decreases toward the tip of the second acute angle portion of the block defined by the steeply inclined groove and the first side main groove. The pneumatic tire according to any one of 8).

Here, “the vicinity of the pattern center” specifically refers to a region in a range of 33% of the tread width TW with the pattern center CL as the center. Further, “one central main groove in a half area” means a rib shape continuously extending in the tire circumferential direction C on the pattern center CL in addition to the case where one central main groove is formed on the pattern center CL. In order to form the land portion, the case where a pair of central main grooves are disposed with the pattern center CL interposed therebetween is also included.
Furthermore, “substantially block” means that the opening position of the steeply inclined groove to the central main groove is higher than the groove bottom position of the central main groove and is not completely divided into blocks.

According to the present invention, a tread pattern in which a central main groove and an inclined groove are arranged in the tread portion is adopted, and in such a tread pattern, by optimizing the shape of the block in the central land portion, maneuvering stability, It has become possible to provide a pneumatic tire with improved drainage and noise while maintaining performance such as uneven wear and ride comfort.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a tread pattern showing one basic form of the present invention, FIG. 2 (a) is a cross-sectional view taken along line AA in FIG. 1, FIG. 2 (b) is a cross-sectional view taken along line BB in FIG. (C) is CC sectional drawing of FIG. 1, and FIG.2 (d) is DD sectional drawing of FIG. In the figure, 1 is a tread portion, 2 is a tread end, 3 is a central main groove, 4 is a rib-like land portion, 5 is a first side main groove, 6 is a central land portion, 7 is a block, and 8 is a steep slope. A groove, 9 is a gently inclined groove, 10 is a bottom of the inclined groove, 11 is a first chamfered portion, and 20 is an arc portion.

The tire having the tread pattern shown in FIG. 1 is located in the half area S ₁ , S _{2 in} which the tread portion 1 is divided into _two by the pattern center CL, or in the vicinity of the pattern center CL, in FIG. Each central main groove 3 extending along the tire circumferential direction C, and at least one side main groove extending between the central main groove 3 and the tread end 2 and extending along the tire circumferential direction C. In FIG. 1, one first side main groove 5 and a steeply inclined groove 8 extending between the central main groove 3 and the first side main groove 5 at a relatively small angle with respect to the tire circumferential direction C. The central land portion 6 is defined by the central main groove 3 and the first lateral main groove 5.
In FIG. 1, a rib-like land portion 4 that extends continuously in the tire circumferential direction C is formed between the central main groove 3 and the central main groove 3 in the other half section in order to emphasize steering stability. In the present invention, it can be provided as necessary.

In the tire of the present invention, a tire ground contact surface that is the minimum necessary for a high-performance tire is provided in the tread portion 1 by disposing a central main groove 3 and a first side main groove 5 extending along the tire circumferential direction C. A steeply inclined groove extending between the central main groove 3 and the first lateral main groove 5 at a relatively small angle with respect to the tire circumferential direction C, preferably 42 ° or less. 8 can mainly control the drainage of water existing in the tire ground contact surface to the side, and the first side main groove which is the central main groove 3 and the side main groove adjacent thereto. The central land portion 6 is partitioned by the groove 5, and the central land portion 6 is divided into a plurality of substantial portions by the central main groove 3, the first side main groove 5, and the two steeply inclined grooves 8 adjacent to the tire circumferential direction C. By dividing the upper block 7 and forming the block row 15, the basic performance of the tire can be ensured.

The main structural feature of the present invention is that the central main groove side wall 7a of each block 7 constituting the central land portion 6 has a pattern center with a predetermined radius of curvature R along the tire circumferential direction C in plan view. as well as have the arcuate portion 20 pushed out toward the CL, the center main groove side wall 6a of the center land portion 6 is to have a substantially continuous wavy shape as a whole.

In the present invention, not only the steeply inclined groove 8 is appropriately disposed in the tread portion 1 of the tire, but the shape of the block 7 constituting the central land portion 6 is optimized so that the central main groove 3 is substantially divided. By having a shape that continuously extends along the tire circumferential direction C without being improved, drainage performance in the tire front-rear direction is significantly improved and the central main groove side sidewall 6a of the central land portion 6 is wave-shaped. As a result, the diversion to the steeply inclined groove 8 becomes smooth, the drainage is improved, and the groove width continuously changes, so that air column resonance can be reduced.

The details of this configuration will be described below.
The present invention relates to a central main groove of a block 7 of a central land portion 6 defined by a central main groove 3 of the tread portion 1, a first side main groove 5 and two steeply inclined grooves 8 adjacent to the tire circumferential direction C. The side wall 7a has an arcuate portion 20 that protrudes toward the pattern center CL with a predetermined radius of curvature R, preferably 40 to 400 mm, along the tire circumferential direction C in plan view.
Here, the shape of the arcuate portion 20 is assumed to also include a single well arcuate shape having a radius of curvature R, a substantially arc shape gently made continuous two or more arcs having different radii of curvature R.

Since the central main groove side wall 7a portion of the block 7 has the arc portion 20, water can be smoothly introduced from the central main groove 3 to the steeply inclined groove 8 along the arc portion 20 of the central main groove side wall 7a. Improve drainage.
Further, by having this arc portion 20, the first acute angle portion of the block 7 partitioned by the central main groove 3 and the steeply inclined groove 8 and the rigidity of the land portion in the vicinity thereof are enhanced, and the steering stability is improved. You can also.

Further, in the present invention, the central main groove side wall 6a of the central land portion 6 has a substantially continuous wave shape as a whole.
Here, “substantially continuous” means that at least a part of the central main groove side wall 6a of the central land portion 6, preferably the lower side wall portion 6aa is a steeply inclined groove as shown in FIG. 8 means that it is not completely divided. Specifically, the case where the groove depth of the central main groove 3 is deeper than the groove depth of the steeply inclined groove 8 at the opening position of the steeply inclined groove 8 to the central main groove 3 is exemplified.

Since the central main groove side sidewall 6a of the central land portion 6 has a substantially continuous wave shape as a whole, the water in the central main groove 3 located in the tire contact area can be drained with high pressure in the tire front-rear direction. In addition, as a result of the smooth diversion from the central main groove 3 to the steeply inclined groove 8, the drainage can be remarkably improved. Furthermore, since the groove width of the central main groove 3 changes continuously, air column resonance can also be reduced.

In the present invention, it is preferable that the block 7 further includes a gently inclined groove 9 extending at a relatively large angle with respect to the tire circumferential direction C.
By providing a gently slant groove 9 extending at a relatively large angle with respect to the tire circumferential direction C, and under sufficient land portion rigidity, to improve the steering stability, it is Rukoto improve the uneven wear resistance.

In the present invention, the steeply inclined groove 8 is provided with the inclined groove bottom portion 10 whose groove depth gradually increases toward the first side main groove 5, and the arc portion 20 constituting the central main groove side wall 7 a of the block 7, The intersection position 20a of the arc portion 20 adjacent to the arc virtual extension line is adjacent to the inclined groove bottom portion 10 .

That is, the groove volume of the steeply inclined groove 8 toward the first side main groove 5 is provided in the steeply inclined groove 8 by providing the inclined groove bottom 10 whose groove depth gradually increases toward the first side main groove 5. Therefore, there is an effect of accelerating the flow of water taken into the steeply inclined groove 8 in the central region of the tread, and drainage is improved.
For example, the extending length of the inclined groove bottom 10 is set in a range of 10 to 70 mm, and in a range shown by hatching in FIG.

The inclined groove bottom portion 10 can have a flat inclined surface, for example, a concave curved surface shown in FIG. 3 (a), a convex curved surface shown in (b), and a groove depth of the inclined surface shown in (c). Various shapes such as a three-dimensional structure different in the width direction can be used.

In FIG. 1, the intersection position 20 a between the arc portion 20 and the arc portion 20 adjacent to the arc portion 20 is disposed adjacent to the inclined groove bottom portion 10.
Since the intersection position 20a and the inclined groove bottom 10 are disposed adjacent to each other, the space (volume) as a groove can be maintained on the tire surface side, so that drainage can be ensured, and the groove bottom side can be supported to support and land. Steering stability can be ensured as a result of obtaining part rigidity.

A first chamfered portion 11 whose land portion height gradually decreases toward the tip end 11a is provided at the first acute angle portion defined by the central main groove 3 and the steeply inclined groove 8, and the tip end 11a of the first acute angle portion is illustrated in FIG. As shown in FIG. 1, it is preferable to substantially coincide with the intersection position 20a.

The first acute angle portion of the block 7 which is defined by the center main groove 3 and the steep slant groove 8, Ri by the providing the first chamfered portion 11 gradually decreases the land portion height toward its tip end 11a, the distal end Reduces noise by increasing the rigidity of the 11a portion, preventing crushing when the first acute angle portion is grounded, and thus preventing escape deformation into the groove, improving drainage, and ensuring smoother grounding. Can also be planned.
Further, the first chamfered portion 11 has an effect of increasing the tire ground contact surface pressure at the tip 11a portion, and the steering stability and uneven wear resistance are improved. For example, the chamfer length of the first chamfered portion 11 is preferably in the range of 2 to 15 mm, and in the range shown by hatching in FIG.

The first chamfered portion 11 can have a chamfered surface as a flat surface, for example, a concave curved surface shown in FIG. 4 (a), a convex curved surface shown in FIG. 4 (b), or a chamfered surface shown in FIG. 4 (c). Various shapes such as a three-dimensional structure with different land heights in the width direction can be used.

The radius of curvature R of the arc portion 20 is preferably 40 to 400 mm.
If the radius of curvature R is less than 40 mm, the groove volume of the central main groove 3 tends to be too small and the drainage tends to deteriorate. If the radius of curvature R exceeds 400 mm, the circular arc part 20 becomes a substantially straight groove wall surface and the drainage is improved. This is because they tend not to be recognized.

The steeply inclined groove 8 preferably has an angle with respect to the tire circumferential direction C of 42 ° or less. By appropriately setting the angle of the steeply inclined groove 8 with respect to the tire circumferential direction C, the drainage can be more effectively improved.
Further, the steeply inclined groove 8 is particularly preferably an angle close to 0 ° such that the angle with respect to the tire circumferential direction C is in contact with the arc portion 20.

The gently inclined groove 9 preferably has an angle with respect to the tire circumferential direction C of 45 to 90 °. By appropriately setting the angle of the gently inclined groove 9 with respect to the tire circumferential direction C, it has sufficient land portion rigidity with respect to the tire circumferential direction C of the block 7 and can improve steering stability, and is resistant to uneven wear. Can also be improved.
In FIG. 1, a gently inclined groove 9 that terminates in the block 7 is provided. This is because the block 7 that is long in the tire circumferential direction C is substantially divided so that the rigidity of the land portion is optimized and the steering stability is improved. It is for improving a property, and can be provided as needed.

Here, it is preferable that the angle difference in the tire circumferential direction C between the steeply inclined groove 8 and the gently inclined groove 9 is 10 ° or more in that the effect of the steeply inclined groove 8 and the gently inclined groove 9 is exhibited in a balanced manner.

FIG. 5 is a tread pattern showing an embodiment of the present invention, FIG. 6 (a) is a cross-sectional view taken along line EE of FIG. 5, FIG. 6 (b) is a cross-sectional view taken along line FF of FIG. FIG. 6C is a GG cross-sectional view of FIG.

The embodiment shown in Figure 5, the distal end 11a of the first acute angle portion, an arc portion 20, a Rukoto this match on intersections 20a substantially on the arc imaginary extension of the arcuate portion 20 adjacent the first side square in which the groove depth toward the main groove 5 was adjacent to the inclined groove bottom portion 10 for increasing the first chamfered portion 11.
With this configuration, since the inclined groove bottom portion 10 and the first chamfered portion 11 are adjacent to each other in the tread central region, drainage performance is improved as a result of being able to form a large volume space as a groove on the tire surface side. Steering stability can be ensured as a result of supporting and supporting the land portion by overlapping on the groove bottom side.

The block 7 is preferably provided with a sipe 12 extending in parallel with the gently inclined groove 9. By cutting the block 7 with a sipe 12 having substantially the same angle as that of the gently inclined groove 9 and reducing the difference in shape and area of the block 7, the rigidity of the land portion can be optimized and uneven wear resistance can be improved. Edge components can also be increased, improving wet brake performance and optimizing land rigidity to improve riding comfort.

In the case of the pair of central main grooves 3 sandwiching the pattern center CL, it is preferable to provide a rib-like land portion 4 extending continuously along the tire circumferential direction C between the central main grooves 3. By disposing the rib-like land portion 4 on the pattern center CL, it is possible to increase the feeling of grip of the steering wheel at the time of steering and the straight running stability, and to further improve the steering stability.
Further, in FIG. 5, the circumferential narrow groove 18 extending along the tire circumferential direction C on the pattern center CL of the rib-like land portion 4 in terms of suppressing straight running performance during traveling and particularly uneven wear of the tire center portion. The case where is provided is shown.

It is preferable to provide a second chamfered portion 13 whose land portion height gradually decreases toward the tip of the second acute angle portion of the block 7 defined by the steeply inclined groove 8 and the first side main groove 5. By having such a second chamfered portion 13, the land portion rigidity of the central land portion 6 is reinforced without deteriorating the drainage property of the first side main groove 5, is Rukoto more to further improve the steering stability it can.

The central main groove side wall 7a portion of the block 7 is substantially continuous not only by the arc portion 20 having a single curvature radius R but also by the arc portion 20 having a different curvature radius R along the tire circumferential direction C in plan view. Can have a wavy shape.

Further, in FIG. 1 and FIG. 5, the steeply inclined grooves 8 and the gently inclined grooves 9 are alternately arranged. However, by alternately arranging inclined grooves having different inclination angles, the rigidity of the land portion can be ensured and drainage can be performed. it is possible to achieve both an improvement and. It can also contribute to noise reduction due to the frequency dispersion effect of pattern noise.

Further, since the rigidity of the land portion of the block 7 of the central land portion 6 in the vicinity of the opening position of the steeply inclined groove 8 and the first side main groove 5 is increased and the steering stability is improved, the steeply inclined state as shown in FIG. The wall surface of the block 7 of the central land portion 6 adjacent to the opening position of the groove 8 and the first side main groove 5 projects into the first side main groove 5, and the land portion height is the groove bottom of the side main groove 5. It is also possible to provide a third chamfer 19 that gradually decreases toward the front.

In FIG. 1 and FIG. 5, a short sipe 16 that opens in each of the lateral side main groove 5 and the circumferential sipe in the shoulder land portion on the tread end side from the first side main groove 5 , Although it shows a case where a gentle slope portion 17 is formed on the extension line and extending to the tread end 2 at an angle in a range of 70 to 90 ° while being curved with respect to the tire circumferential direction C , the short sipe is shown. Instead of 16, the gently inclined portion 17 may be opened in the first side main groove 5.

The tread pattern configured as described above is a point-symmetric pattern with respect to the pattern center CL in FIGS. 1 and 5, but may be a directional pattern in the present invention.

FIG. 5 shows only a typical embodiment of the present invention, and various modifications can be made within the scope of the claims. For example, FIG. 5 shows a case where only one side main groove (first side main groove 5) is provided as the side main groove, but two or more side main grooves are provided. May be.

Next, a tire according to the present invention was prototyped and performance evaluation was performed, which will be described below.

The tire of Example 1 has the tread pattern shown in FIG. 5, the tire size is 195 / 65R15 (tread width TW 145 mm), the central main groove, the side main groove, the steeply inclined groove, the gently inclined groove, and the rib shape. Tables 1 to 5 summarize the dimensions and other dimensions of the land and blocks. In the present invention, since the tire structure other than the tread portion does not require modification, the tire structure is almost the same as that of a conventional pneumatic tire for passenger cars.

The tire of Comparative Example 1 had the tread pattern shown in FIG. 7 and was substantially the same as the tire of Example 1 except that the tread tire structure and the extended length of the inclined groove bottom 10 were 7 mm. The tire of Comparative Example 2 employs a configuration in which the central main groove side wall 6a of the central land portion 6 is completely divided by the steeply inclined groove 8, and the extending length of the inclined groove bottom 10 is 7 mm. It was almost the same as the tire of Example 1.

(Test method)
Each of the above test tires was mounted on a test vehicle, and the following tests were performed under the conditions of tire pressure: 230 kPa (relative pressure) and tire load load: equivalent to two passengers.

1. The vehicle travels straight on a wet road surface having a water depth of 5 mm when straight running, and the critical speed at which hydroplaning occurs is measured and evaluated based on this measured value.

2. Steering stability when dry The circuit course in the dry state was driven by sports in various driving modes and evaluated by the feeling of the test driver.

3. Steering stability when wet We drove sports on various circuit modes in various driving modes, and evaluated them based on the feeling of test drivers.

4). The vehicle was run in various driving modes on a smooth road surface with a pattern noise dry condition and evaluated by feeling by a test driver.

5. Riding comfort test We ran on a general road in a dry state in various driving modes and evaluated it by feeling by a test driver.

6). A general road in an uneven wear-resistant dry state was run in various running modes, and evaluation was performed based on the amount of step wear between adjacent blocks when running at 5000 km.

These evaluation results are shown in Table 6.
In addition, the numerical value of the evaluation result in Table 6 is shown as an index ratio when the evaluation result of Comparative Example 1 is 100, and the larger the numerical value, the better.

From the results of Table 6, Example 1 is superior to Comparative Example 1 in all the performances of drainage when traveling straight, driving stability when dry, driving stability when wet, pattern noise, riding comfort, and uneven wear resistance. It was. The comparative example 2 is superior in ride comfort by providing a sipe, but is inferior in drainage during straight traveling and has reduced rigidity, so that it is less stable than that in the first embodiment in terms of dry and wet handling stability. It was inferior.

According to the present invention, a tread pattern in which a central main groove and an inclined groove are disposed in the tread portion is adopted, and in such a tread pattern, by optimizing the shape of the block in the central land portion, steering stability and uneven wear resistance are achieved. It has become possible to provide a pneumatic tire with improved drainage and noise while maintaining performance such as performance and ride comfort.

It is the figure which expanded and showed a part of tread part the form used as the foundation of this invention. (A), (b), (c), (d) is sectional drawing on the AA, BB, CC, and DD line | wire of FIG. 1, respectively. (A), (b), (c) is a perspective view which shows the various forms of the inclination groove bottom part 10. FIG. (A), (b), (c) is a perspective view which shows the various form of the 1st chamfering part 11. FIG. An embodiment of a pneumatic tire according to the present invention, a diagram shows by expanding a part of the tread portion. (A), (b), (c) is sectional drawing on the EE, FF, and GG line | wire of FIG. 5, respectively. It is the figure which expanded a part of tread part of a comparison tire (comparative example 1).

DESCRIPTION OF SYMBOLS 1 Tread part 2 Tread end 3 Central main groove 4 Rib-shaped land part 5 1st side main groove 6 Central land part 6a Central main groove side side wall 6aa Lower side wall part 7 Block 7a Central main groove side side wall 8 Steeply inclined groove 9 Slowly inclined groove 10 Inclined groove bottom part 11 First chamfered part 11a Tip 12 Sipe 13 Second chamfered part 15 Block row 16 Short sipe 17 Slowly inclined part 18 Circumferential narrow groove 19 Third chamfered part 20 Arc part TW Tread width CL Pattern center C Tire circumferential direction W Tire width direction R Curvature radius

Claims (9)

One central main groove located in the pattern center or in the vicinity thereof and extending along the tire circumferential direction, between the central main groove and the tread end, in a half area where the tread portion is divided into two by the pattern center At least one side main groove located and extending along the tire circumferential direction, and a plurality of steeply inclined grooves extending at a relatively small angle with respect to the tire circumferential direction between the central main groove and the side main grooves. A central land portion is defined by the central main groove and the first side main groove which is a side main groove adjacent to the central main groove, and is adjacent to the central main groove, the first side main groove and the tire circumferential direction. In a pneumatic tire formed by dividing a central land portion into a number of blocks substantially by two steeply inclined grooves to form a block row,
Central main groove side wall portion of the block of the central land portion, as well as have the arcuate portion pushed out toward the pattern center along the tire circumferential direction at a predetermined radius of curvature in a plan view, the center main groove side of the center land portion sidewalls have a substantially continuous wavy shape as a whole,
The steeply inclined groove is provided with an inclined groove bottom portion where the groove depth gradually increases toward the first side main groove, and an arc portion constituting the central main groove side wall of the block and an arc portion of the arc portion adjacent thereto The pneumatic tire is characterized in that an intersection position with a virtual extension line is arranged adjacent to the bottom of the inclined groove . Wherein the block, the pneumatic tire according to claim 1 ing further disposed gently slant groove extending at a relatively large angle with respect to the tire circumferential direction. A first chamfered portion whose land portion height gradually decreases toward the tip thereof is provided at the first acute angle portion defined by the central main groove and the steeply inclined groove, and the tip of the first acute angle portion substantially coincides with the position of the intersection. The pneumatic tire according to claim 1, which matches. The pneumatic tire according to any one of claims 1 to 3, wherein a radius of curvature of the arc portion is 40 to 400 mm. The pneumatic tire according to any one of claims 1 to 4, wherein the steeply inclined groove has an angle with respect to the tire circumferential direction of 42 ° or less. The pneumatic tire according to claim 2, wherein the gently inclined groove has an angle of 45 to 90 ° with respect to the tire circumferential direction. The pneumatic tire according to claim 2, wherein the block is provided with a sipe extending in parallel with the gently inclined groove. The central main groove is a pair of central main grooves sandwiching the pattern center, and a rib-like land portion extending continuously along the tire circumferential direction is provided between the central main grooves . The pneumatic tire according to any one of the above. Second acute angle portion of the block which is defined by the steeply slant groove and a first side main groove, to one of the claims 1 to 8 to provide a second chamfer gradually decreases the land portion height toward its tip The described pneumatic tire.