JP2000142030A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain uneven abrasion of a driving wheel, and to restrain an increase in noise caused by abrasion by forming a plurality of land parts of a plurality of circumferential directional grooves and lateral directional grooves, and setting the inside end lower by a specific value than a crown part outer contour line of a tread in the outermost side first land part among these. SOLUTION: In a tread 12, four circumferential directional grooves 14 in total are formed on the tire width directional both sides by sandwiching the tire equatorial surface CL. By these circumferential directional grooves 14, in the tread 12, a center rib 16 is partitioned in a tire width directional center part, a second rib 18 is partitioned outside, and a shoulder rib 20 is partitioned on the outermost side. In a tread of this shoulder rib 20, the tire width directional inside end 20A is set lower by 0.3 mm than an outer contour line OL of the tread 12. The tire width directional inside end 18A of the second rib 18 and a tire width directional central part of the center rib 16 are set lower by about 0.3 mm than the outer contour line OL. Thus, abrasion quantity becomes uniform in the tire width direction to prevent the deterioration of pitch noise.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire and, more particularly, to a plurality of circumferential grooves extending parallel to or substantially parallel to a circumferential direction, and a plurality of transverse grooves intersecting the circumferential grooves. The present invention relates to a pneumatic tire capable of suppressing uneven wear of a pneumatic tire having a tread pattern formed with a plurality of land portions and reducing noise (pitch noise) at the time of wear.

[0002]

2. Description of the Related Art In general, when a pneumatic tire is used for a driving wheel, a protruding portion (usually a center portion) of a tread surface tends to be worn more than other portions.

[0003] This is because, when the tire is rolled, a region having a large outer diameter has a large driving force due to a difference in the outer diameter of the tire when the tire is not in contact with the ground (usually, a diameter of the center portion> a diameter of the shoulder portion). And the portion having the largest outer diameter (usually the inner portion in the tire width direction) in the land portion tends to wear more than the outer portion.

[0004] As a result, a phenomenon occurs in which the amount of wear becomes uneven in the tread surface, and the grounding shape at the time of wear gradually changes, so that the order of grounding is disturbed. Direction) is shifted or a lot of worn parts cannot bear the load, and the load burden on surrounding parts increases,
Since the impact at the time of stepping in increases, the noise (pitch noise) worsens, and it becomes impossible to maintain the performance when new, so that it is strongly desired to improve this.

[0005] On the other hand, in order to suppress the deterioration of performance due to such abrasion, for example, the tread has a two-layer structure,
By arranging a soft rubber on the lower side, a method of reducing the impact at the time of abrasion or changing the pattern design to lower the noise level in advance has been adopted.

[0006]

However, when the tread is 2
The use of a layered structure has disadvantages such as difficulty in manufacturing and a decrease in rigidity of a land portion to deteriorate steering stability.

[0007] Further, changing the pattern design is problematic from the viewpoint of securing the merchantability and the degree of freedom of design, and may have a large effect on other performances.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and suppresses uneven wear of driving wheels and reduces noise (pitch noise) caused by the wear. It is an object to provide a pneumatic tire that can suppress an increase.

[0009]

According to the first aspect of the present invention, there are provided a plurality of circumferential grooves extending parallel or substantially parallel to a circumferential direction, and a plurality of transverse grooves intersecting the circumferential grooves. A pneumatic tire having a tread pattern in which a plurality of land portions are formed by grooves, wherein, among the plurality of land portions, a first land portion disposed on the outermost side in a tire width direction is in a tire width direction. Is characterized in that the inside edge of the tread is .delta.1 lower than the outer contour line of the crown portion of the tread.

Next, the operation of the pneumatic tire according to the first aspect will be described.

In the pneumatic tire according to the first aspect, the first land portion has an inner end in the tire width direction lower by δ1 than the outer contour line of the crown portion of the tread. Thereby, the difference in the outer diameter in the first land portion (the difference between the outer diameter of the inner end in the tire width direction and the outer diameter of the outer end) tends to be eliminated, and the driving force distribution at the time of driving changes in the tire width direction. It becomes uniform, and the wear amount of the first land portion becomes uniform in the tire width direction.

In a pneumatic tire, when a plurality of land portions are continuous in the tire circumferential direction, the pitch noise can be reduced by variously changing the circumferential length of the land portions, the pitch of the land portions, and the like by various methods. It is common to try.

Therefore, in the case of such a pneumatic tire, if the wear of the land portion is not uniform, the contact position with the road surface may be different from that at the time of the new product, and the pitch noise is deteriorated.

However, in the pneumatic tire according to the first aspect, since the first land portion can be uniformly worn in the tire width direction, it is possible to prevent deterioration of pitch noise due to wear.

Here, in the first land portion (shoulder block), when the amount of wear inside increases, the load that cannot be borne by that portion is separated not only by the other portions in the same land portion but also by the circumferential groove. Since it is necessary to bear the burden on the adjacent land, the impact is increased in those areas and the noise is deteriorated, which is effective in suppressing the noise.

It is preferable that the tread of the first land portion gradually approaches the outer contour of the crown portion from the inner end in the tire width direction to the outer side.

According to a second aspect of the present invention, in the pneumatic tire according to the first aspect, the second land portion adjacent to the first land portion inward in the tire width direction is an inner end in the tire width direction. However, it is characterized by δ2 lower than the outer contour line of the crown portion of the tread.

Next, the operation of the pneumatic tire according to claim 2 will be described.

In the pneumatic tire according to the second aspect, the inner end of the second land portion in the tire width direction is lower than the outer contour line of the crown portion of the tread by δ2. Thereby, the difference in the outer diameter in the second land portion (the difference between the outer diameter of the inner end in the tire width direction and the outer diameter of the outer end) tends to be eliminated, and the driving force distribution at the time of driving changes in the tire width direction. The wear amount of the second land portion becomes uniform in the tire width direction.

Since the second land portion can be worn uniformly in the tire width direction, it is possible to prevent the pitch noise from being deteriorated due to the wear.

It is preferable that the tread surface of the second land portion gradually approaches the outer contour of the crown portion from the inner end in the tire width direction to the outer side.

According to a third aspect of the present invention, in the pneumatic tire according to the first or second aspect, an even number of the circumferential grooves are formed, and a central land disposed at a central portion in the tire width direction. The portion is characterized in that the central portion in the tire width direction is δ3 lower than the outer contour line of the crown portion of the tread.

Next, the operation of the pneumatic tire according to the third aspect will be described.

In the pneumatic tire according to the third aspect, the central land portion disposed at the central portion in the tire width direction is such that the central portion in the tire width direction (that is, the portion on the tire equatorial plane) has a crown outer contour line. Lower than that by δ3.

Thus, the difference between the outer diameters in the central land portion (the difference between the outer diameter of the central portion in the tire width direction and the outer diameters of both outer ends thereof).
, The driving force distribution during driving becomes uniform in the tire width direction, and the wear amount of the central land portion becomes uniform in the tire width direction.

Since the central land portion can be worn uniformly in the tire width direction, it is possible to prevent deterioration of pitch noise due to wear.

It is preferable that the tread of the central land portion gradually approach the outer contour of the crown portion from the central portion in the tire width direction to both sides in the tire width direction.

According to a fourth aspect of the present invention, in the pneumatic tire according to any one of the first to third aspects,
In one land area, the angle between the inner side wall in the tire width direction and the normal formed on the outer contour of the crown of the tread is θ1, and the angle formed by the outer side wall on the outer side of the tire and the outer contour of the tread crown is formed. When an angle between the line and the line is θ2, θ1 <θ2.

Next, the operation of the pneumatic tire according to claim 4 will be described.

In the land portion, the angle formed between the inner side wall in the tire width direction and the normal set on the outer contour line of the crown of the tread is small (or the normal set on the outer contour line of the side wall and the crown of the tread is smaller). Comparing the (parallel) portion with the large angle portion, the compression rigidity of the small angle portion is relatively smaller than that of the large angle portion.

Therefore, if θ1 <θ2, the compression stiffness of the inner side wall in the tire width direction in one land portion is lower than that of the outer side wall in the tire width direction. Near the inner side wall in the tire width direction> near the outer side wall in the tire width direction, and there is a tendency to substantially cancel the difference in outer diameter between the originally inner portion and the outer portion in the tire width direction. For this reason, the driving force distribution at the time of driving tends to be uniform in the tire width direction, the amount of wear also tends to be uniform in the tire width direction, the driving force distribution is more uniform in the tire width direction, and the amount of wear is also reduced. It can be made more uniform in the tire width direction.

This makes it possible to further prevent the pitch noise from deteriorating due to wear.

In a land portion located on the outermost side in the tire width direction, the side wall on the outer side in the tire width direction becomes a shoulder portion, and this is not always the case when giving priority to the shape of the shoulder portion. At the outermost land portion in the tire width direction, the inner wall in the tire width direction is formed by making the angle between the inner wall in the tire width direction and the normal formed on the outer contour line of the tread crown close to 0 °. Can be reduced, and the amount of wear becomes more uniform in the tire width direction.

In the central land portion, there is no inner side wall in the tire width direction and only the outer side wall in the tire width direction. In this case, the outer side wall in the tire width direction and the outer contour line of the crown of the tread are provided. By increasing the angle between the normal and the vertical line, the compression rigidity of the outer side wall in the tire width direction can be increased, and the wear amount becomes more uniform in the tire width direction.

According to a fifth aspect of the present invention, in the pneumatic tire according to any one of the first to fourth aspects,
In the case of a passenger car, δ1, δ2, and δ3 are characterized by being 1 mm or less.

Next, the operation of the pneumatic tire according to claim 5 will be described.

In the case of a tire for a general passenger car, δ1, δ2 is determined from the ground pressure and the compression rigidity of the tread rubber.
It is appropriate that δ3 is at most about 1 mm.

When δ1, δ2, and δ3 exceed 1 mm, the end of the land does not contact the ground, and the contact area of the land decreases, and the impact on the road surface in other areas (land) increases. The noise at the time of brand-new operation is adversely affected, and the amount of wear on the land is extremely increased at the outer end in the tire width direction.

Accordingly, in the case of a general passenger car tire, it is preferable that δ1, δ2 and δ3 be suppressed to a maximum of about 1 mm.

Here, "tires for passenger cars" are tires described in the following standards.

The standard is determined by an industrial standard effective in an area where the tire is manufactured or used. For example, in the United States "The Tire and Rim
Association Inc. Year Book, and in Europe, "Th
e St. of European Tire and Rim Technical Organization
andards Manual ", which is specified in Japan in the Japan Automobile Tire Association's" JATMA Year Book ".

[0042]

[First Embodiment] A first embodiment of a pneumatic tire according to the present invention will be described with reference to FIGS.

FIG. 2 shows a tread pattern of a pneumatic tire (tire size: 225 / 45ZR17) 10 for a passenger car.

The tread 12 of the pneumatic tire 10 has a total of four circumferential grooves 14, two on each side of the tire equatorial plane CL on both sides in the tire width direction (the direction of arrow W).

The tread 1 is formed by these circumferential grooves 14.
2, a center rib 16 is provided at the center in the tire width direction, and a second rib 18 is provided outside the center rib 16 in the tire width direction.
A shoulder rib 20 is defined outside the second rib 18 in the tire width direction.

The second rib 18 is divided into a plurality of land portions 19 in the tire circumferential direction (the direction of arrow S) by a plurality of inclined grooves 22 inclined with respect to the tire width direction.
The shoulder rib 20 is divided into a plurality of land portions 21 in the tire circumferential direction by a plurality of inclined grooves 24.

Here, the land portion 19 of the second rib 18 and the land portion 21 of the shoulder rib 20 are formed by using a generally known method for reducing pitch noise in the tire circumferential direction. The pod arrangement pitch is determined.

As shown in the sectional view of FIG.
The outer contour line OL (shown by a two-dot chain line) is a tire equatorial plane C.
The vicinity of L is set to an arc curve having a radius of curvature R1, the outer portion in the tire width direction is set to an arc curve having a radius of curvature R2, and the outer portion in the tire width direction is set to an arc curve having a radius of curvature R3. The center of curvature of each of the arc curve having the radius of curvature R1, the arc curve having the radius of curvature R2, and the arc curve having the radius of curvature R3 is located inside the tire.

In this embodiment, the radius of curvature R1 is 1200
mm, radius of curvature R2 is 940 mm, radius of curvature R3 is 150 mm
It is.

Here, the shoulder rib 20 (land portion 21)
The tread surface of the tire width direction inner end 20A is δ1 lower than the outer contour line OL, and the tire width direction inner end 20A and the width w of the shoulder rib 20 from the tire width direction inner end 20A are 1/1.
In a region between the tire 20 and the point 20C which is separated outward in the tire width direction by the dimension of 3, the point 20C passes through the tire width direction inner end 20A.
In the region between the point 20C and the outer end 20B in the tire width direction, the outer contour line OL is set in an arc-shaped surface shape defined by a curvature radius R4 inscribed in the outer contour line OL.
The surface shape is set so as to match. Note that the center of curvature of the arc-shaped surface shape having the curvature radius R4 is located inside the tire.

In the pneumatic tire 10 of the present embodiment, δ
1 is 0.3 mm and the radius of curvature R4 is 87 mm.

The inner surface 20a of the shoulder rib 20 in the tire width direction is parallel to a normal line h formed on the outer contour line of the crown of the tread (the angle of the inner surface 20a in the tire width direction with respect to the normal line h). In the present invention, θ1) is 0 °).

Next, the tread surface of the second rib 18 (land portion 19) is such that the inner end 18A in the tire width direction is δ2 lower than the outer contour line OL, and the tread between the inner end 18A in the tire width direction and the outer end 18B in the tire width direction. In the region (ie, the entire tread surface), the tire passes in the tire width direction inner end 18A and the tire width direction outer end 18B
Is set to an arc-shaped surface shape defined by a curvature radius R5 inscribed in the outer contour line OL. Note that the center of curvature of the arc-shaped surface shape having the curvature radius R5 is located inside the tire.

In the pneumatic tire 10 of the present embodiment, δ
2 is 0.3 mm and the radius of curvature R5 is 572 mm.

The inner side surface 18a of the second rib 18 in the tire width direction is parallel to the normal line h (the angle of the inner side surface 18a in the tire width direction relative to the normal line h (θ1 in the present invention) is 0 °).
The outer surface 18b in the tire width direction is parallel to the normal h (the angle of the outer surface 18b in the tire width direction to the normal h (θ2 in the present invention) is 0 °).

Next, the center of the tread of the center rib 16 in the tire width direction (on the tire equatorial plane CL) is the outer contour line OL.
In the vicinity of the center in the tire width direction, it is set to an arc-shaped surface shape having a radius of curvature R6 having a center of curvature outside the tire. Furthermore, the tread of the center rib 16
At both sides in the tire width direction, the curvature has a center of curvature on the inner side of the tire, is smoothly connected to the arc-shaped surface having the radius of curvature R6 on the inner side in the tire width direction, and inscribes the outer contour line OL at the outer end 16A in the tire width direction. The arc-shaped surface shape is defined by the radius R7.

In the pneumatic tire 10 of the present embodiment, δ
3 is 0.3 mm, radius of curvature R6 is 448 mm, radius of curvature R7
Is 303 mm.

The outer surface 16a in the tire width direction of the center rib 16 is parallel to the normal h (the angle of the outer surface 16a in the tire width direction to the normal h is 0 °).

The structure other than the tread 12 of the pneumatic tire 10 according to the present embodiment is the same as the structure of a normal radial tire, and therefore the description is omitted. (Operation) Next, the operation of the pneumatic tire 10 of the present embodiment will be described.

In the pneumatic tire 10 of the present embodiment, the inner end 20A of the shoulder rib 20 in the tire width direction is lower than the outer contour line OL of the tread 12 by 0.3 mm, and the inner end 18A of the second rib 18 in the tire width direction is outer. Since the center width direction center portion of the center rib 16 is set to be 0.3 mm lower than the outer contour line OL, the center rib 16 is set 0.3 mm lower than the outer contour line OL.
In each rib, the difference between the outer diameter of the inner end in the tire width direction and the outer diameter of the outer end tends to be eliminated, and the driving force distribution during driving becomes uniform in the tire width direction.

Therefore, the amount of wear in each of the shoulder ribs 20, the second ribs 18, and the center ribs 16 becomes uniform in the tire width direction, and deterioration of pitch noise due to wear of the tread 12 can be prevented.

In the pneumatic tire 10 of this embodiment, δ1, δ2, and δ3 are each set to 0.3 mm. However, the present invention is not limited to this, and in the case of a general passenger car tire, the contact pressure and tread Judging from the compression stiffness of rubber No. 12,
It is appropriate that δ1, δ2 and δ3 have a maximum of about 1 mm.

In the case of the pneumatic tire 10 of this embodiment, which is a passenger car tire, when δ1, δ2, and δ3 exceed 1 mm, the outer end 16A of the center rib 16 in the tire width direction and the inner end of the second rib 18 in the tire width direction. The tire 18A and the inner end 20A of the shoulder rib 20 in the tire width direction do not contact the road surface, and the contact area is reduced, and the impact on the road surface in other areas (land portion) is increased. On the other hand, the amount of wear on the land is extremely increased at the outer end in the tire width direction, which is not preferable.

The values of δ1, δ2, and δ3 are appropriately changed depending on the load used by the tire and the like, and may be 1 mm or more for heavy load tires.

Further, δ1, δ2, and δ3 may be equal to each other, or may be different values. [Second Embodiment] Next, a second embodiment of the pneumatic tire of the present invention will be described with reference to FIG. The first
The same reference numerals are given to the same components as those of the embodiment, and the description thereof will be omitted.

As shown in FIG. 3, in the pneumatic tire 30 of the present embodiment, the outer surface 16a of the center rib 16 in the tire width direction is θa in the direction in which the groove opening opens with respect to the normal h.
(= 15 °), and the outer surface 18b in the tire width direction of the second rib 18 is inclined θb (= 15 °) in the direction in which the groove opening is opened with respect to the normal h. The other configuration is the same as that of the first embodiment.

Next, the operation of the pneumatic tire 30 of this embodiment will be described.

Outer side surface 1 of center rib 16 in tire width direction
6a in the direction in which the groove opening opens with respect to the normal h.
5 °), the compression stiffness near the outer end 16A in the tire width direction is higher than in the first embodiment, and the amount of longitudinal deflection is smaller than in the first embodiment. For this reason, the wear amount of the center rib 16 can be made more uniform in the tire width direction, and the deterioration of the pitch noise due to the wear can be further prevented.

Further, the outer side surface 18b of the second rib 18 in the tire width direction is set to θb in the direction in which the groove opening opens with respect to the normal h.
(= 15 °), the inner surface 18 in the tire width direction is inclined.
The compression stiffness near the tire width direction outer side surface 18b is higher than that near the tire width direction a, and the vertical deflection amount near the tire width direction outer side surface 18b is smaller than the vertical deflection amount near the tire width direction inner side surface 18a. For this reason, the wear amount of the second rib 18 can be made more uniform in the tire width direction, and the deterioration of the pitch noise due to the wear can be further prevented.

In one rib (land portion), the angle formed by the outer surface in the tire width direction with the normal h is different from the angle formed by the inner surface in the tire width direction with the normal h by 5 degrees or more. It is effective.

In the above embodiment, the number of the circumferential grooves 14 is four, but the number of the circumferential grooves 14 is not limited to this.
The number of the circumferential grooves 14 may be three or less or five or more.

In the above embodiment, the center rib 1
Although no inclined groove (lateral groove) is formed in 6, a lateral groove may be formed in the center rib 16. Even when the center rib 16 is divided into a plurality of land portions by the lateral grooves, similarly to the second rib 18 and the shoulder rib 20, deterioration of pitch noise can be prevented. (Test Example 1) In order to confirm the effect of the present invention, two kinds of tires of the example to which the present invention was applied, three kinds of tires of the comparative example, and one kind of tire of the conventional example having four circumferential grooves in the tread were used. They were prepared and subjected to a wear test and a noise test. Abrasion test The abrasion test was performed using a test tire (tire size: 225/45).
ZR17) was assembled on a 7.5J rim at an internal pressure of 220 kpa, and mounted on an actual vehicle. The test conditions are as follows.

Vehicle: FF passenger car Mounting position: front wheel Front wheel load: 500 kg (equivalent to 4 passengers) Speed: 0 to 200 km / h Traveling distance: 10000 km The comparative evaluation is based on the difference in the amount of wear between the inner end and the outer end of each rib. ,
The index is expressed as an index with the conventional tire set as 100.

For convenience, the smaller the value, the smaller the difference in the amount of wear in the rib and the better. The results are as described in Table 1 below. Noise Test The noise test was performed using a worn tire after the above wear test with a drum noise tester. The test conditions are as follows.

Road surface: safety walk Slip angle: 0 degrees Load braking force: free rolling Room temperature: 30 ° C. Load: 500 kg Speed: 40 km / h A sound level meter was installed at a distance of 50 cm from the tire tread side, and the worn tire was used. The noise level in the primary band of the pitch is indicated as an index with the conventional tire set as 100. The smaller the value, the lower the noise level and the better. The results are as shown in Table 1 below. Test Tire Tire of Example 1: Tire of First Embodiment (FIGS. 1 and 2)
See).

Example 2 Tire: The tire according to the second embodiment (see FIG. 3).

The tire of Comparative Example 1 is a pneumatic tire 32 having the cross-sectional shape shown in FIG. 4, and the same components as those of the tires of Examples 1 and 2 are denoted by the same reference numerals. In the pneumatic tire 32 of Comparative Example 1, the shape of the tread of the shoulder rib 20 is the same as that of the first example. The tread surface of the second rib 18 has an inner end portion 18A and an outer end portion 18B each having an outer contour line O.
0.3 mm lower than the inner end 18A and the outer end 1
It is set to an arc-shaped surface shape defined by a radius of curvature R8 that passes through 8B and inscribes the outer contour line OL at the center in the tire width direction. Also, the tread surface of the center rib 16 has a width direction end 16A lower than the outer contour line OL by 0.3 mm, and passes through the width direction end 16A at an outer contour line O at a central portion in the tire width direction.
An arc-shaped surface shape defined by a curvature radius R9 inscribed with L is set. The tire width direction inner surface 20a of the shoulder rib 20, the tire width direction inner surface 18a and the tire width direction outer surface 18b of the second rib 18, and the tire width direction outer surface 16a of the center rib 16 are respectively normal h.
Is parallel to

Tire of Comparative Example 2 This is a pneumatic tire 34 having the cross-sectional shape shown in FIG. 5, and the shape of the tread of the center rib 16 is the same as that of Comparative Example 1. Second rib 18
Has a radius of curvature R10 at which the outer end 18B in the tire width direction is 0.3 mm lower than the outer contour line OL, passes through the outer end 18B in the tire width direction, and inscribes the outer contour line OL at the inner end 18A in the tire width direction. It is set to a prescribed arcuate surface shape. In addition, the shape of the tread surface of the shoulder rib 20 entirely matches the outer contour line OL. In addition, the tire width direction inner surface 20a of the shoulder rib 20, the tire width direction inner surface 18a and the tire width direction outer surface 18b of the second rib 18, and the tire width direction outer surface 16a of the center rib 16 are each with respect to the normal h. Parallel.

Tire of Comparative Example 3 This is a pneumatic tire 36 having the cross-sectional shape shown in FIG. 6, and the tread surface of each rib has the same curved surface configuration as the pneumatic tire of Example 1 (see FIG. 1). However, this is a tire in which each of δ1, δ2 and δ3 is 1.0 mm. In addition, the tire width direction inner surface 20a of the shoulder rib 20, the tire width direction inner surface 18a and the tire width direction outer surface 18b of the second rib 18, and the tire width direction outer surface 16a of the center rib 16 are each with respect to the normal h. Parallel.

Conventional Example 1 Tire: A pneumatic tire 38 having a sectional shape shown in FIG.
The tread surface of each of the second rib 18 and the shoulder rib 20 coincides with the outer contour line OL. In addition, the tire width direction inner surface 20a of the shoulder rib 20, the tire width direction inner surface 18a and the tire width direction outer surface 18b of the second rib 18, and the tire width direction outer surface 16 of the center rib 16 are provided.
a are each parallel to the normal h.

[0081]

[Table 1] As a result of the test, Example 1 and Example 2 to which the present invention was applied
Tire has less uneven wear than the tires of Conventional Example 1 and Comparative Examples 1 to 3, and noise due to wear (pitch noise).
Is also small. (Test Example 2) In order to confirm the effect of the present invention, one kind of a tire having five circumferential grooves in a tread according to an embodiment of the present invention and one kind of a conventional tire were prepared. The same wear test and noise test were performed.

Conventional Example 2 Tire: A pneumatic tire 40 having a sectional shape shown in FIG.
A total of five circumferential grooves 14 are provided, two on each of the tire equatorial plane CL and on both sides in the tire width direction across the tire equatorial plane CL.
Are formed. A shoulder rib 42, a second rib 44, and a third rib 46 are defined on the tread 12 by these five circumferential grooves 14. The shape of the outer contour line OL of the tread 12 is the same as that of the test tire of Test Example 1. Further, the side surfaces of the ribs (the groove side walls of the circumferential groove 14) are all parallel to the normal h.

Example 3 Tire: A pneumatic tire 48 having the cross-sectional shape shown in FIG.
In the tread surface No. 2, the inner end 42A in the tire width direction is 0.3 mm lower than the outer contour line OL, the inner end 42A in the tire width direction and the width w of the shoulder rib 42 from the inner end 42A in the tire width direction.
42C which is 1/3 of the distance away from the tire in the width direction
Has an arc-shaped surface shape defined by a radius of curvature inscribed in the outer contour line OL at the point 42C, and the outer contour line O in a region outside the point 42C in the tire width direction.
The surface shape is set so as to match L.

The tread surface of the second rib 44 is such that the inner end 44A in the tire width direction is 0.3 mm lower than the outer contour line OL, and the outer end 44A in the tire width direction passes through the inner end 44A in the tire width direction.
B has an arc-shaped surface shape defined by a radius of curvature inscribed in the outer contour line OL.

The tread surface of the third rib 46 is such that the inner end 46A in the tire width direction is 0.3 mm lower than the outer contour line OL, and the outer end 4A passes through the inner end 46A in the tire width direction.
6B has an arc-shaped surface shape defined by a radius of curvature inscribed in the outer contour line OL.

[0086]

[Table 2] As a result of the test, the tire of Example 3 to which the present invention was applied,
It can be seen that there is less uneven wear and less noise (pitch noise) due to wear than the tire of Conventional Example 2.

[0087]

As described above, since the pneumatic tire of the present invention has the above-described structure, it has an excellent effect of preventing uneven wear and preventing pitch noise from being deteriorated due to wear. .

[Brief description of the drawings]

FIG. 1 is a sectional view taken along an axis of a pneumatic tire according to a first embodiment of the present invention.

FIG. 2 is a tread pattern of the pneumatic tire shown in FIG.

FIG. 3 is a sectional view taken along an axis of a pneumatic tire according to a second embodiment of the present invention.

FIG. 4 is a sectional view taken along an axis of the pneumatic tire according to Comparative Example 1.

FIG. 5 is a sectional view taken along an axis of a pneumatic tire according to Comparative Example 2.

FIG. 6 is a sectional view taken along an axis of a pneumatic tire according to Comparative Example 3.

FIG. 7 is a cross-sectional view of the pneumatic tire according to Conventional Example 1 taken along an axis.

FIG. 8 is a cross-sectional view along the axis of the pneumatic tire according to the third embodiment.

FIG. 9 is a sectional view taken along an axis of a pneumatic tire according to Conventional Example 2.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Pneumatic tire 12 Tread 14 Circumferential groove 16 Center rib (central land part) 16a Tire width direction outer surface (side wall) 18 Second rib (second land part) 18A Tire width direction inner end (inner end) 18a Tire width Inner surface (side wall) 18b Outer surface (side wall) in tire width direction 20 Shoulder rib (first land portion) 20a Inner surface (side wall) in tire width direction 20A Inner end (inner end) in tire width direction 22 Inclined groove (lateral direction) Groove) 24 Inclined groove (lateral groove) 30 Pneumatic tire 46 Third rib (land portion) 48 Pneumatic tire OL Crown outer contour h Normal line

Claims (5)

[Claims] 1. A tread pattern in which a plurality of land portions are formed by a plurality of circumferential grooves extending parallel to or substantially parallel to a circumferential direction, and a plurality of lateral grooves intersecting the circumferential grooves. A pneumatic tire having: a first land portion, which is arranged on the outermost side in the tire width direction among the plurality of land portions, has an inner end in the tire width direction having a tread crown outer contour line. A pneumatic tire characterized in that the tire also has a lower δ1. 2. A second land portion adjacent to the first land portion on the inner side in the tire width direction has an inner end in the tire width direction lower by δ2 than the outer contour line of the crown portion of the tread. The pneumatic tire according to claim 1. 3. An even number of the circumferential grooves are formed, and the central land portion disposed in the central portion in the tire width direction is such that the central portion in the tire width direction is δ3 lower than the outer contour line of the crown portion of the tread. The pneumatic tire according to claim 1 or 2, wherein: 4. In one land portion, the angle between the inner side wall in the tire width direction and the normal set to the outer contour line of the crown portion of the tread is θ1, and the outer side wall of the tire width direction and the outer contour portion of the tread crown are formed. Θ is the angle between the line and the normal
The pneumatic tire according to any one of claims 1 to 3, wherein θ1 <θ2 when 2. 5. In the case of a passenger car, the δ1, δ2 and δ
The pneumatic tire according to any one of claims 1 to 4, wherein 3 is 1 mm or less.