JP5533212B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire used on icy and snowy road surfaces.

In general, in a statless tire, a plurality of blocks defined by a circumferential groove and a width direction groove are formed on a tread surface to ensure traveling performance on an icy and snowy road surface. In order for the statless tire to maintain the performance on ice and the performance on snow, the depth of the groove forming the block needs to be sufficiently secured. Therefore, it is prohibited by law to use a statless tire with a block worn by 50% or more of the depth of the circumferential groove on an icy and snowy road surface.
In order to indicate the limit of using a statless tire on an icy and snowy road surface (snow wear limit), platforms with a height of 50% or more of the circumferential groove depth should be provided in at least four locations along the tire circumferential direction. Is required.

JP 2005-53257 A

  In general, when the platform is formed in the circumferential groove, the cross-sectional area of the groove is reduced, so that the drainage is reduced. Further, in the conventional pneumatic tire, the user cannot always find the platform easily.

  Then, an object of this invention is to provide the pneumatic tire which can improve drainage property and can improve the visibility of a snow wear limit compared with the conventional pneumatic tire.

  The pneumatic tire of the present invention is defined by a plurality of circumferential grooves extending in the tire circumferential direction, a plurality of width grooves extending in the tire width direction, the plurality of circumferential grooves, and the plurality of width grooves. And the cross-sectional shape of the block on the outer side in the tire radial direction from the first position is the inner side in the tire radial direction from the first position. Different from the cross-sectional shape of the block, the wall surface of the block is formed with a discrimination groove extending in the tire radial direction.

  Further, when the position indicating the tire wear limit in the tire radial direction is the second position, the cross-sectional shape of the block that is on the inner side in the tire radial direction from the first position and on the outer side in the tire radial direction from the second position However, it is preferable that the discrimination groove is formed on the wall surface of the block so as to be different from the cross-sectional shape of the block on the inner side in the tire radial direction from the second position.

  Moreover, it is preferable that the height from the bottom of the said circumferential groove | channel of a 1st position is 50% or more of the height of the said block.

  Further, the circumferential groove is provided with a platform protruding from the bottom of the circumferential groove, and the height from the bottom of the circumferential groove at the first position is 100% or more of the height of the platform. It is preferably 115% or less.

  Moreover, it is preferable that the height from the bottom of the said circumferential groove | channel of a 2nd position is 1.6 mm.

Further, the cross-sectional area of the determination groove at the outer side in the tire radial direction from the first position is A ₁ , the determination groove at the inner side in the tire radial direction from the first position, and at the outer side in the tire radial direction from the second position. When the cross sectional area of A ₂ is A ₂ , the discrimination groove preferably satisfies the relationship of A ₁ / A ₂ ≦ 0.80.

Moreover, it is preferable that the discrimination groove satisfies a relationship of 0.40 ≦ A ₁ / A ₂ ≦ 0.60.

  Further, assuming that the cross-sectional area of the block is S inside in the tire radial direction from the first position and outside the second position in the tire radial direction, and the cross-sectional area of the discrimination groove is A, the discrimination groove is , 0.03 ≦ A / S ≦ 0.07 is preferably satisfied.

  Moreover, it is preferable that the said discrimination groove is formed in the wall surface by the side of the said circumferential direction groove among the wall surfaces of the said block.

  According to the pneumatic tire of the present invention, drainage can be improved and visibility at the snow wear limit can be enhanced.

It is an expanded view showing an example of the tread pattern of the pneumatic tire of an embodiment. It is a figure which shows an example of the block of embodiment. (A) is sectional drawing of the block of embodiment of the tire radial direction outer side from the position which shows a snow wear limit, (b) is a tire radial inside and tire wear from the position which shows a snow wear limit. It is sectional drawing of the block of embodiment in the tire radial direction outer side from the position which shows a limit, (c) is sectional drawing of the block of embodiment in the tire radial direction inner side from the position which shows a tire wear limit. It is a figure which shows the block of the modification 1. FIG. (A) is sectional drawing of the block of the modification 1 in the tire radial direction outer side from the position which shows a snow wear limit, (b) is a tire radial direction inner side from the position which shows a snow wear limit, and a tire It is sectional drawing of the block of the modification 1 in the tire radial direction outer side from the position which shows a wear limit, (c) is sectional drawing of the block of the modification 1 in a tire radial direction inner side from the position which shows a tire wear limit. is there. It is a figure which shows the block of the modification 2. It is a figure which shows the block of the modification 3. It is a figure which shows the block of a prior art example.

<Embodiment>
Hereinafter, the pneumatic tire of this embodiment will be described in detail.
In the following description, the tire width direction is a direction parallel to the rotation axis of the pneumatic tire. Further, the outward in the tire width direction is a direction away from the tire equator line CL in the tire width direction. Further, the tire circumferential direction is a direction in which the rotation axis of the pneumatic tire rotates around the rotation center. The tire radial direction is a direction orthogonal to the rotation axis of the pneumatic tire.

  First, the tread pattern of the pneumatic tire of this embodiment will be described with reference to FIG. FIG. 1 is a development view showing an example of a tread pattern of a pneumatic tire according to the present embodiment. The vertical direction in FIG. 1 indicates the tire circumferential direction. Moreover, the horizontal direction of FIG. 1 shows a tire width direction. CL indicates a tire equator line. As shown in FIG. 1, the pneumatic tire according to the present embodiment includes a plurality of blocks defined by a plurality of circumferential grooves 10 extending in the tire circumferential direction and a plurality of width grooves 12 extending in the tire width direction. 20 in the tread portion. A platform 14 is formed in the circumferential groove 10. A discrimination groove 30 is formed in the block 20. The shape of the determination groove 30 will be described later.

Here, the circumferential groove 10 is not limited to a groove parallel to the tire equator line CL as shown in FIG. The circumferential groove 10 includes, for example, a groove that is inclined at an angle of 35 degrees or less with respect to the tire equator line CL. Moreover, the width of the circumferential groove 10 is 5 mm or more. Moreover, the depth of the circumferential groove | channel 10 is 15.5 mm or more and 25.5 mm or less.
Moreover, the width direction groove | channel 12 is not limited to a groove | channel parallel to a tire width direction as FIG. 1 shows. The width direction groove 12 includes, for example, a groove inclined at an angle of 35 degrees or less with respect to the tire width direction. Moreover, the width of the width direction groove | channel 12 is 2 mm or more, for example. Moreover, the depth of the width direction groove | channel 12 is 15.5 mm or more and 25.5 mm or less, for example.
Moreover, in this embodiment, although the depth of the circumferential groove | channel 10 and the width direction groove | channel 12 shall be the same, you may make the depth of a groove | channel different.

Next, the shape of the block 20 will be described with reference to FIG. FIG. 2 is a diagram showing the block 20 in which the discrimination groove 30 is formed. Two discrimination grooves 30 are formed on the wall surface of the block 20 shown in FIG. As shown in FIG. 2, the determination groove 30 extends in the tire radial direction. Further, the determination groove 30 is formed in the block 20 so that the cross-sectional shape of the block 20 is different between the outer side and the inner side in the tire radial direction with the position (first position) indicating the snow wear limit in the tire radial direction as a boundary. In the present embodiment, the height from the bottom of the circumferential groove 10 at the position indicating the snow wear limit is the same as the height of the platform 14.
In the example shown in FIG. 2, the cross-sectional shape of the determination groove 30 is a triangle on the outer side in the tire radial direction from the position indicating the snow wear limit. On the other hand, the cross-sectional shape of the determination groove 30 is a quadrangle on the inner side in the tire radial direction from the position indicating the snow wear limit.

Further, the determination groove 30 is formed in the block 20 so that the cross-sectional shape of the block 20 is different between the outer side and the inner side in the tire radial direction with the position (second position) indicating the tire wear limit in the tire radial direction as a boundary. The height from the bottom of the circumferential groove 10 at the position indicating the tire wear limit is, for example, 1.6 mm.
In the example shown in FIG. 2, the cross-sectional shape of the determination groove 30 is a quadrangular shape on the outer side in the tire radial direction from the position indicating the tire wear limit. Further, the lower end of the discrimination groove 30 is terminated at a position indicating the tire wear limit. Therefore, the determination groove 30 is not formed on the inner side in the tire radial direction from the position indicating the tire wear limit.

  Here, with reference to FIG. 3, when the block 20 of this embodiment wears, a mode that the cross-sectional shape of the block 20 changes is demonstrated. FIG. 3A is a cross-sectional view of the block 20 on the outer side in the tire radial direction from the position indicating the snow wear limit. FIG. 3B is a cross-sectional view of the block 20 on the inner side in the tire radial direction from the position showing the snow wear limit and on the outer side in the tire radial direction from the position showing the tire wear limit. FIG. 3C is a cross-sectional view of the block 20 on the inner side in the tire radial direction from the position indicating the tire wear limit.

  The new contact surface of the block 20 has a shape shown in FIG. Thereafter, the wear of the block 20 proceeds, and when the wear of the block 20 exceeds the snow wear limit, the contact surface of the block 20 changes to the shape shown in FIG. Therefore, the user can easily determine whether or not the wear of the block 20 has reached the snow wear limit by checking the shape of the block 20.

  Further, when the wear of the block 20 further progresses and the wear of the block 20 exceeds the tire wear limit, the contact surface of the block 20 changes to the shape shown in FIG. Therefore, the user can easily determine whether or not the wear of the block 20 has reached the tire wear limit by checking the shape of the block 20.

  As described above, in the pneumatic tire of the present embodiment, the cross-sectional shape of the block 20 on the outer side in the tire radial direction from the position showing the snow wear limit is larger than the position on the inner side in the tire radial direction than the position showing the snow wear limit. A discrimination groove 30 is formed on the wall surface of the block 20 so as to be different from the cross-sectional shape of the block 20. Therefore, according to the pneumatic tire of this embodiment, the visibility of the snow wear limit can be enhanced.

  Further, in the pneumatic tire of the present embodiment, the cross-sectional shape of the block 20 on the tire radial direction inner side than the position indicating the snow wear limit and on the tire radial direction outer side than the position indicating the tire wear limit is the tire. A determination groove 30 is formed on the wall surface of the block 20 so as to be different from the cross-sectional shape of the block 20 on the inner side in the tire radial direction from the position indicating the wear limit. Therefore, according to the pneumatic tire of this embodiment, the visibility of the tire wear limit can be enhanced.

Here, as shown in FIG. 3 (a), the cross-sectional area of one determination groove 30 in the tire radial direction outer side than the position shown snow wear limit is defined as A _1. Further, as shown in FIG. 3B, one discrimination groove 30 is located on the inner side in the tire radial direction from the position indicating the snow wear limit and on the outer side in the tire radial direction from the position indicating the tire wear limit. the cross-sectional area is defined as _{a 2.} The discrimination groove 30 of this embodiment satisfies the relationship of A ₁ / A ₂ ≦ 0.80.

In general, when the wear of the block 20 progresses, the volume of the circumferential groove 10 and the width groove 12 decreases, and the drainage of the pneumatic tire decreases. On the other hand, in the pneumatic tire of this embodiment, the discrimination groove 30 is formed in the block 20, so that the drainage of the pneumatic tire can be improved. Particularly, when the discrimination groove 30 satisfies the relationship of A ₁ / A ₂ ≦ 0.80, the drainage of the pneumatic tire can be maintained even when the wear of the block 20 exceeds the snow wear limit. .

In order to increase the visibility of the snow wear limit, it is preferable to reduce A ₁ / A _2. However, even before the wear of the block 20 reaches the snow wear limit, the discrimination groove 30 drains the pneumatic tire. It is preferable to improve the property. To also enhance the drainage of a pneumatic tire before the wear of the block 20 reaches the snow wear limit, it is preferable to increase the A ₁ to some extent. For example, it is more preferable that the determination groove 30 satisfies a relationship of 0.40 ≦ A ₁ / A ₂ ≦ 0.60.

Further, the cross-sectional area of the block 20 is defined as S on the inner side in the tire radial direction from the position indicating the snow wear limit and on the outer side in the tire radial direction from the position indicating the tire wear limit. In addition, the cross-sectional area of the discrimination groove 30 formed in the block 20 is defined as A. In the example shown in FIG. 3 (b), since the two discrimination groove 30 in the block 20 is formed, the total cross-sectional area A ₂ of the discrimination groove 30 and A. At this time, the block 20 of this embodiment satisfies the relationship of 0.03 ≦ A / S ≦ 0.07. By setting 0.03 ≦ A / S, the drainage of the pneumatic tire can be maintained even when the wear of the block 20 exceeds the snow wear limit. Further, by setting A / S ≦ 0.07, it is possible to suppress the occurrence of uneven wear due to a decrease in block rigidity. Note that the number of discrimination grooves 30 formed in one block 20 is preferably within three.

  Moreover, although this embodiment demonstrated the case where the position (1st position) which shows a snow wear limit was the same as the height of the platform 14, this invention is not limited to this. For example, if the height from the bottom of the circumferential groove 10 at the position indicating the snow wear limit (first position) is 50% or more of the height of the block 20, it is necessarily required to be the same position as the height of the platform 14. There is no. For example, a position where the height from the bottom of the circumferential groove 10 is not less than 100% and not more than 115% of the height of the platform 14 can be a position indicating the snow wear limit (first position).

  Moreover, the discrimination groove 30 of this embodiment should just be formed in the at least 1 block 20 of a pneumatic tire. In order to improve the drainage performance of the pneumatic tire by the discrimination groove 30, it is more preferable that the discrimination groove 30 is formed on the wall surface of the block 20 on the circumferential groove side.

  In order to further improve the visibility of the snow wear limit and the tire wear limit, it is preferable that the determination groove 30 is formed in a place where the user can easily check. Therefore, as shown in FIG. 1, the wall surface of the block 20 along the circumferential groove 10 located most outward in the tire width direction among the plurality of circumferential grooves 10, and the plurality of widthwise grooves 12. Of these, it is preferable that the determination groove 30 is formed at a position where the width direction groove 12 located most outward in the tire width direction is extended.

  As described above, according to the pneumatic tire of the present embodiment, the drainage can be improved and the visibility of the snow wear limit can be increased.

<Modification 1>
Next, a pneumatic tire according to Modification 1 will be described. The basic configuration of the tread pattern of the pneumatic tire according to this modification is the same as that shown in FIG. Hereinafter, the shape of the block 20 of this modification will be described with reference to FIG. FIG. 4 is a diagram showing the block 20 in which the discrimination groove 30 is formed. Two discrimination grooves 30 are formed on the wall surface of the block 20 in the example shown in FIG. As shown in FIG. 4, the determination groove 30 extends in the tire radial direction. In addition, the determination groove 30 is formed in the block 20 so that the cross-sectional shape of the block 20 is different between the outer side and the inner side in the tire radial direction with the position indicating the snow wear limit (first position) as a boundary.
In the example shown in FIG. 4, the upper end of the determination groove 30 is terminated at a position indicating the snow wear limit. Therefore, the determination groove 30 is not formed on the outer side in the tire radial direction from the position indicating the snow wear limit. Moreover, the cross-sectional shape of the discrimination groove 30 is a quadrangle on the inner side in the tire radial direction from the position indicating the snow wear limit.

In addition, the determination groove 30 is formed in the block 20 so that the cross-sectional shape of the block 20 is different between the outer side and the inner side in the tire radial direction with the position indicating the tire wear limit (second position) as a boundary.
In the example shown in FIG. 4, the cross-sectional shape of the determination groove 30 is a quadrangular shape on the outer side in the tire radial direction from the position indicating the tire wear limit. Further, the lower end of the discrimination groove 30 is terminated at a position indicating the tire wear limit. Therefore, the determination groove 30 is not formed on the inner side in the tire radial direction from the position indicating the tire wear limit.

  Here, with reference to FIG. 5, how the cross-sectional shape of the block 20 changes when the block 20 of this modification is worn will be described. FIG. 5A is a cross-sectional view of the block 20 on the outer side in the tire radial direction from the position indicating the snow wear limit. FIG. 5B is a cross-sectional view of the block 20 on the inner side in the tire radial direction from the position showing the snow wear limit and on the outer side in the tire radial direction from the position showing the tire wear limit. FIG.5 (c) is sectional drawing of the block 20 in a tire radial inside rather than the position which shows a tire wear limit.

  The contact surface of the block 20 at the time of a new article has a shape shown in FIG. Thereafter, the wear of the block 20 proceeds, and when the wear of the block 20 exceeds the snow wear limit, the contact surface of the block 20 changes to the shape shown in FIG. Therefore, the user can easily determine whether or not the wear of the block 20 has reached the snow wear limit by checking the shape of the block 20.

  Further, when the wear of the block 20 further progresses and the wear of the block 20 exceeds the tire wear limit, the contact surface of the block 20 changes to the shape shown in FIG. Therefore, the user can easily determine whether or not the wear of the block 20 has reached the tire wear limit by checking the shape of the block 20.

  Even in the case where the upper end of the determination groove 30 is terminated at the position indicating the snow wear limit as in the present modification, the drainage is improved and the visibility of the snow wear limit is increased as in the above-described embodiment. be able to.

<Modification 2>
Next, a pneumatic tire according to Modification 2 will be described. The pneumatic tire of this modification is different from Modification 1 described with reference to FIG. 4 in the shape of the block 20. Other configurations are the same as those of the first modification. Hereinafter, the shape of the block 20 of this modification will be described with reference to FIG. FIG. 6 is a diagram showing the block 20 in which the discrimination groove 30 is formed.
Unlike the first modification, the cross-sectional shape of the block 20 of this modification is the same on the outer side and the inner side in the tire radial direction, with the position indicating the tire wear limit (second position) as a boundary.

  The user can determine whether or not the wear of the block 20 has reached the tire wear limit by the slip sign. Therefore, if the discrimination groove 30 is formed in order to easily discriminate whether or not the wear of the block 20 has reached the snow wear limit, the tire diameter with the position (second position) indicating the tire wear limit as a boundary. It is not necessary to make the cross-sectional shape of the block 20 different between the outer side and the inner side.

  Even in the case where the cross-sectional shape of the block 20 is the same on the outer side and the inner side in the tire radial direction with the position indicating the tire wear limit (second position) as a boundary as in this modification, the drainage is the same as in the above-described embodiment. This improves the visibility of the snow wear limit.

<Modification 3>
Next, a pneumatic tire according to Modification 3 will be described. The pneumatic tire of this modification is different from the embodiment described with reference to FIG. 2 in the shape of the block 20. Other configurations are the same as in the embodiment. Hereinafter, the shape of the block 20 of the present modification will be described with reference to FIG. FIG. 7 is a diagram showing the block 20 in which the discrimination groove 30 is formed.

In the example shown in FIG. 7, the cross-sectional shape of the determination groove 30 is a quadrangular shape on the outer side in the tire radial direction from the position indicating the snow wear limit. On the other hand, the cross-sectional shape of the discrimination groove 30 is a triangle on the inner side in the tire radial direction from the position indicating the snow wear limit.
In the example shown in FIG. 7, the cross-sectional shape of the determination groove 30 is a triangle on the outer side in the tire radial direction from the position indicating the tire wear limit. Further, the lower end of the discrimination groove 30 is terminated at a position indicating the tire wear limit. Therefore, the determination groove 30 is not formed on the inner side in the tire radial direction from the position indicating the tire wear limit.

The discrimination groove 30 of this modification satisfies the relationship of A ₁ > A ₂ . Therefore, compared with the case where the determination groove 30 satisfies the relationship of A ₁ <A ₂ , the determination groove 30 can be easily formed when the pneumatic tire is molded.
Even in the case where the determination groove 30 satisfies the relationship of A ₁ > A ₂ as in the present modification, the drainage performance can be improved and the visibility of the snow wear limit can be increased as in the above-described embodiment.

  The test which confirms the effect of this invention was done using the various pneumatic tires. The tire size was 11R22.5, and the normal air pressure conditions specified in JATMA YEAR BOOK 2009 (Japan Automobile Tire Association Standard) were used. Each test tire was mounted on a test vehicle, and the following tests were performed.

(Wear limit visibility)
Each test tire whose block wear exceeded the snow wear limit was visually observed, and the visibility of the snow wear limit was evaluated by a five-point method using the conventional tire as a reference (three points). In addition, each test tire whose block wear exceeded the tire wear limit was visually observed, and the visibility of the tire wear limit was evaluated by a five-point method using the conventional tire as a reference (three points). An evaluation result shows that visibility is so high that a score is high.

(Drainage)
For each test tire when it is new and for each test tire with 70% worn blocks, the tire slip rate is obtained from the vehicle speed and the rotational speed of the test tire by gradually increasing the traveling speed on a straight path with a water depth of 10 mm. The lowest speed at which 10% was reached was measured. The evaluation results are indicated by an index with the measurement result of the conventional example as 100. The larger the index value, the better the drainage performance when traveling straight ahead.

(Conventional example, Examples 1 to 5)
Using the conventional example and the pneumatic tires of Examples 1 to 5, the effect of changing A ₁ / A ₂ was examined.

  First, a conventional pneumatic tire will be described. A discrimination groove is not formed in the block 20 of the conventional pneumatic tire. The tread pattern of the conventional pneumatic tire is the same as that of FIG. 1 described above except that the discrimination groove is not formed. Hereinafter, the shape of the block 20 of the conventional example will be described with reference to FIG. FIG. 8 is a diagram showing a conventional block 20. As shown in FIG. 8, no discrimination groove is formed in any block 20 of the conventional pneumatic tire. The block 20 of the conventional example has a width (length in the tire width direction) of 26.3 mm, a length (length in the tire circumferential direction) of 32.8 mm, and a height of 20.6 mm.

  Moreover, the basic structure of the pneumatic tire of each Example is the same as that of embodiment described with reference to FIG. 1, FIG. Further, the width, length, and height of the block 20 of each embodiment are the same as those of the block 20 of the conventional example. The discrimination groove 30 formed in the block 20 of Examples 1 to 5 satisfies the relationship of A / S = 0.05.

The discrimination grooves 30 formed in the blocks 20 of Examples 1 to 5 have different A ₁ / A ₂ from each other.
The discrimination groove 30 of Example 1 satisfies the relationship of A ₁ / A ₂ = 0.30.
The determination groove 30 of Example 2 satisfies the relationship of A ₁ / A ₂ = 0.40.
The discriminating groove 30 of Example 3 satisfies the relationship A ₁ / A ₂ = 0.60.
The discrimination groove 30 of the fourth embodiment satisfies the relationship A ₁ / A ₂ = 0.80.
The discrimination groove 30 of Example 5 satisfies the relationship of A ₁ / A ₂ = 0.90.

Table 1 shows the test results of snow wear limit visibility, tire wear limit visibility, drainage at the time of new article, and drainage at 70% wear in the conventional examples and Examples 1 to 5.

From the results shown in Table 1, it was found that the pneumatic tires of Examples 1 to 5 were improved in drainage compared to the conventional pneumatic tire by forming the discrimination groove 30 in the block 20. Further, it is understood that the pneumatic tires of Examples 1 to 5 have increased visibility of the snow wear limit and the tire wear limit compared to the conventional pneumatic tire by forming the discrimination groove 30 in the block 20. It was.
Further, it has been found that the visibility of the snow wear limit is further increased when the determination groove 30 satisfies the relationship of A ₁ / A ₂ ≦ 0.80. Furthermore, it was found that the drainage performance before the wear of the block 20 reaches the snow wear limit is further improved by the determination groove 30 satisfying the relationship of 0.40 ≦ A ₁ / A ₂ .

(Conventional example, Examples 3, 6-9)
Using the conventional example, the pneumatic tires of Examples 3 and 6 to 9, the effect of changing A / S was examined.
The discrimination width 30 formed in the blocks 20 of the third and sixth to ninth embodiments satisfies the relationship of A ₁ / A ₂ = 0.60.
The discrimination grooves 30 formed in the blocks 20 of the third and sixth to ninth embodiments have different A / S.
The discrimination groove 30 of Example 6 satisfies the relationship of A / S = 0.02.
The discrimination groove 30 of Example 7 satisfies the relationship of A / S = 0.03.
The discrimination groove 30 of Example 3 satisfies the relationship of A / S = 0.05.
The discrimination groove 30 of Example 8 satisfies the relationship of A / S = 0.07.
The discrimination groove 30 of Example 9 satisfies the relationship of A / S = 0.08.

Table 2 shows the test results of snow wear limit visibility, tire wear limit visibility, drainage at the time of new article, and drainage at 70% wear in the conventional example, Examples 3 and 6-9.

  From the results of Table 2, it was found that by setting 0.03 ≦ A / S, the drainage property at the time of 70% wear is further improved. Note that if 0.07 <A / S, uneven wear is likely to occur due to a decrease in the block rigidity of the block 20, and therefore it is preferable to satisfy A / S ≦ 0.07.

  As mentioned above, although the pneumatic tire of this invention was demonstrated in detail, this invention is not limited to the said embodiment. It goes without saying that various improvements and modifications may be made without departing from the spirit of the present invention.

10 circumferential groove 12 width groove 14 platform 20 block 30 discrimination groove

Claims (9)

A plurality of circumferential grooves extending in the tire circumferential direction;
A plurality of widthwise grooves extending in the tire width direction;
A block defined by the plurality of circumferential grooves and the plurality of widthwise grooves,
A discrimination groove extending in the tire radial direction is formed on the wall surface of the block,
When the position indicating the snow wear limit in the tire radial direction is the first position, the cross-sectional shape of the determination groove on the outer side in the tire radial direction from the first position is the cross-sectional shape of the determination groove on the inner side in the tire radial direction from the first position. a pneumatic tire characterized by that different from the cross-sectional shape.   When the position indicating the tire wear limit in the tire radial direction is the second position, the cross-sectional shape of the block on the inner side in the tire radial direction from the first position and on the outer side in the tire radial direction from the second position, 2. The pneumatic tire according to claim 1, wherein the discrimination groove is formed on a wall surface of the block so as to be different from a cross-sectional shape of the block on the inner side in the tire radial direction from the second position.   The pneumatic tire according to claim 1 or 2, wherein a height of the first position from the bottom of the circumferential groove is 50% or more of a height of the block. The circumferential groove is provided with a platform protruding from the bottom of the circumferential groove,
The pneumatic tire according to any one of claims 1 to 3, wherein a height of the first position from the bottom of the circumferential groove is not less than 100% and not more than 115% of the height of the platform.   The pneumatic tire according to any one of claims 2 to 4, wherein a height of the second position from the bottom of the circumferential groove is 1.6 mm. The cross-sectional area of the discrimination groove on the outer side in the tire radial direction from the first position is A ₁ , and the cut-off of the discrimination groove on the inner side in the tire radial direction from the first position and on the outer side in the tire radial direction from the second position. When the area and _{a 2,} the discrimination groove _satisfies a relation of _a 1 / a ₂ ≦ 0.80, pneumatic tire according to any one of claims 2 to 5. The pneumatic tire according to claim 6, wherein the determination groove satisfies a relationship of 0.40 ≦ A ₁ / A ₂ ≦ 0.60.   If the cross-sectional area of the block is S inside and the cross-sectional area of the discriminating groove is A inside the tire radial direction from the first position and outside the second position, the discriminating groove is 0. The pneumatic tire according to claim 2, satisfying a relationship of 0.03 ≦ A / S ≦ 0.07.   The pneumatic tire according to claim 1, wherein the discrimination groove is formed on a wall surface on the circumferential groove side among the wall surfaces of the block.