JPH04243605A - Pneumatic radial tire - Google Patents

Abstract

PURPOSE:To suppress decrease in the drainage performance, increase in the pattern noises, and gripping performance at the time of cornering, by constituting a shoulder block by a first tread portion defined using a lateral groove at a forward end portion thereof as viewed in the rotational direction of the tire, an L-shaped second portion, and a third rectangular tread portion. CONSTITUTION:A shoulder block 28 disposed at a tire widthwise end portion of a tread portion 12 is increased in the circumferential and in the widthwise direction. The end portion of the shoulder block 28 as viewed in the rotational direction of the tire is named as an elongate first tread portion 28A prepared by being sectioned using a lateral groove 30 extending in the widthwise direction of the tire. A second tread portion 28B provided after the lateral groove 30 and rearwardly from the first tread portion 28A in the rotational direction of the tire is in the form of an L shape constituted by an equator plane 22 side portion and a portion located on the rear side as viewed in the rotational direction of the tire. The portion sectioned by an L shaped groove 34 and a lateral groove 30 is named as a rectangular 'third tread portion 28C'.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic radial tire mounted on a vehicle such as an automobile.

0002

[Prior Art] Conventionally, a tread portion 61 of a pneumatic radial tire 60 mounted on a vehicle such as an automobile shown in FIG.
is divided into a plurality of tread land portions 68 by main grooves 64 along the circumferential direction of the tire surface and lug grooves 66 along the tire width direction.

As shown in FIG. 5, the ground pressure P of the contact surface of each tread land portion 68 of this pneumatic radial tire 60 is
are substantially equal to each other when no force in the lateral direction of the tire, so-called side force, is applied.

However, in this pneumatic radial tire 60, as shown in FIG. 6, when cornering, a side force (
When arrow F) in FIG. 6 acts, each tread land portion 6
The end 6 on the exit side of the side force of 8 (right side in Figure 6)
8A stands out. Further, even when the side force does not rise, the ground pressure at the end 68A on the exit side of the side force decreases. On the other hand, the ground pressure at the end 68B of each tread land portion 68 on the side where the side force enters (the left side in FIG. 6) is high, and the end 68B is rolled up between it and the road surface. Also, the end 6
When 8B is rolled up, the ground contact area of the end 68B on the side where the side force enters becomes smaller, and the ground contact pressure decreases.

Therefore, as shown in FIG. 7, the relationship between the slip angle SA and the side force SF is such that as the slip angle SA increases, the side force SF also increases, but the side force SF of each tread land portion 68 increases.
The exit side end 68A and the side force SF input side end 68B do not bear the burden of side force SF, and the upper limit value SF1 of side force SF is lower than the value SF0 determined by the friction coefficient μ of the tread rubber, and when cornering. There was a problem in that the grip performance of the grip was reduced, and uneven wear was likely to occur on the tread land portion 68.

On the other hand, as shown in FIG. 8, the tread land portions provided at the ends of the pneumatic radial tire 70 in the tire width direction are arranged in the tire circumferential direction (vertical direction in FIG. 8) and in the tire width direction (left and right directions in FIG. 8). The shoulder block 72 increases the rigidity of the tire's contact surface and reduces the floating and curling of the edge of the tire's contact surface on the toe land, thereby improving the grip performance of the tire. It is possible to improve this.

However, in this case, since there are no grooves along the circumferential direction of the tire and the negative ratio is low, water between the road surface and the tire cannot be sufficiently drained when driving on a wet road surface. , drainage performance deteriorates. Furthermore, since the contact surface of the shoulder block 72 becomes larger and the rigidity increases, the outer end 72A in the tire width direction (the right side in FIG. 8), which is the side force input side of the shoulder block 72, becomes more rigid.
and a front end 72B in the tire rotation direction which is the driving force input side.
(lower side of FIG. 8), there is a problem in that the ground pressure is concentrated on the lower side of the tire, and the uneven wear characteristics are deteriorated. On the other hand, if the width of the lug groove 74 is widened in order to prevent deterioration of drainage performance, the impact force when stepping on the front end 72B of the shoulder block 72 in the tire rotational direction increases, resulting in an increase in putter noise. A problem will occur.

[0008]

SUMMARY OF THE INVENTION In consideration of the above facts, the present invention is capable of suppressing the deterioration of drainage performance and increase of putter noise, as well as improving grip performance during cornering, and suppressing uneven wear. The purpose is to obtain a pneumatic radial tire that can.

[0009]

Means for Solving the Problems In order to achieve the above object, the present invention as set forth in claim 1 provides a main groove formed on the tire surface of the tread portion along the tire circumferential direction, and a main groove formed along the tire width direction. A pneumatic radial tire comprising lug grooves formed therein, and a tread land portion defined by the main groove and the lug groove, the tread portion being larger in the tire width direction and in the tire circumferential direction than the tread land portion. a first land portion having a shoulder block provided at an end in the tire width direction of the tire ground contact area, the shoulder block being partitioned by a lateral groove provided at the front end in the tire rotation direction and extending in the tire width direction; An L-shaped second land portion provided on the rear side in the tire rotation direction of the first land portion and consisting of a tire equatorial plane side portion and a rear side portion in the tire rotation direction, and an L-shaped second land portion along the second land portion. and a rectangular third land portion defined by the lateral groove and provided on the rear side of the first land portion in the tire rotation direction.

[0010] Further, the invention according to claim 2 is characterized in that the length of the shoulder block in the tire circumferential direction is equal to or less than 3 of the tire outer circumferential length.
% to 7%.

[0011] Further, the invention according to claim 3 is characterized in that the length of the shoulder block in the tire width direction is equal to 3 of the tire ground contact width.
It is characterized by being set at 0% to 50%.

[0012] The invention according to claim 4 is characterized in that the width of the lug groove is set to 10% to 20% of the length of the shoulder block in the tire circumferential direction.

Further, the invention according to claim 5 is characterized in that at least one of holes and sipes extending from the tire surface toward the inner side of the tread land portion are provided intermittently along the width direction of the tire in the first land portion. It is said that

[0014]

[Function] In the pneumatic radial tire of the present invention, the shoulder block, which is larger in the tire width direction and the tire circumferential direction than the tread land portion and is provided at the end of the tire width direction of the tire ground contact area of the tread portion, controls the rotation of the tire. A first land section provided at the front end of the tire and partitioned by a lateral groove extending in the width direction of the tire, and a tire equatorial plane side section and a rear side section of the tire rotation direction provided at the rear side of the first land section in the tire rotation direction. an L-shaped second land portion, and a rectangular third land portion partitioned by the second land portion, an L-shaped groove, and a lateral groove and provided on the rear side of the first land portion in the tire rotation direction. It is composed of and.

[0015] Therefore, by enlarging the shoulder block in the tire circumferential direction and tire width direction, the rigidity of the tire contact patch can be improved. Therefore, when the side force acts on the tire's contact surface during cornering, the deformation of the tread land and shoulder block is reduced, and the floating and curling of the tread land and the edge of the shoulder block's contact surface is suppressed. be done. As a result, the ground pressure distribution of the tread land portion and the shoulder block is more uniformly distributed over the entire ground contact surface than in the past.

Furthermore, when the pneumatic radial tire of the present invention runs on a wet road surface, water between the tire and the road surface is drained along the main grooves and lug grooves, reducing drainage performance. Without this, grip performance during cornering can be improved and uneven wear can be suppressed.

On the other hand, the first land portion, which is partitioned by the lateral groove and has low rigidity in the tire rotational direction, reduces the impact force when stepping on the front end of the shoulder block in the tire rotational direction. As a result, putter noise can be reduced. Further, when at least one of holes and sipes extending from the tire surface toward the inner side of the tread land portion is provided intermittently along the width direction of the tire in the first land portion,
Putter noise can be further reduced.

Furthermore, since the outer end in the tire width direction, which is the side force input side of the shoulder block, and the front end in the tire rotational direction, which is the driving force input side, are divided into the second land part and the third land part, It is possible to prevent ground pressure from concentrating on the outer end in the tire width direction and the front end in the tire rotational direction, thereby improving uneven wear characteristics.

The length of the shoulder block in the tire circumferential direction is preferably set to 3% to 7% of the tire outer circumference, and the length of the shoulder block in the tire circumferential direction is 3% of the tire outer circumference. If it is less than that, sufficient rigidity will not be obtained and the grip characteristics will not be improved. On the other hand, if the length of the shoulder block in the tire circumferential direction exceeds 7% of the tire outer circumferential length, the rigidity becomes too high and uneven wear characteristics deteriorate.

Further, the length of the shoulder block in the tire width direction is preferably set to 30% to 50% of the tire ground contact width, and the length of the shoulder block in the tire width direction is less than 30% of the tire ground contact width. In this case, sufficient rigidity cannot be obtained and grip characteristics cannot be improved. On the other hand, the length of the shoulder block in the tire width direction is 50% of the tire contact width.
If it exceeds this, the rigidity will become too high and the uneven wear characteristics will deteriorate.

Further, the width of the lug groove is preferably set to 10% to 20% of the length of the shoulder block in the tire circumferential direction, and the width of the lug groove is set to 10% to 20% of the length of the shoulder block in the tire circumferential direction. If it is less than %, wet performance will deteriorate. On the other hand, if the width of the lug groove exceeds 20% of the length of the shoulder block in the tire circumferential direction, pattern noise increases.

[0022]

[Embodiment] A first embodiment of the present invention will be described with reference to FIGS. 1 and 2.

As shown in FIG. 1, the pneumatic radial tire 10 of this embodiment (tire size 225/50R/1
6) is a pneumatic radial tire designed to be mounted on a vehicle body so that the lower side in FIG. 1 is the side in the direction of tire rotation of the tread land portion when the vehicle moves forward (the side that first steps onto the road surface). Tread portion 1 of this pneumatic radial tire 10
Three main grooves 14, 16, and 18 along the tire circumferential direction are formed at approximately equal intervals from the vicinity of the right side in FIG. 1 to the left side in FIG. 1 of the tire equatorial plane 22 of No. 2.

In addition, in the tread portion 12 of the pneumatic radial tire 10, from near the left side of the tire equatorial plane 22 in FIG.
Lug grooves 24 that are slightly inclined toward the rear side in the tire rotational direction (upper side in FIG. 1) toward A are formed at predetermined intervals in the tire circumferential direction. Therefore, the tread portion 12 has main grooves 14, 1
A plurality of tread land portions 26 are formed which are defined by the tread grooves 6 and 18 and the lug grooves 24.

A shoulder block 28 is disposed at the end of the tread portion 12 of the pneumatic radial tire 10 in the width direction of the tire (the right end in FIG. 1). These shoulder blocks 28 are arranged in the tire circumferential direction (vertical direction in FIG. 1).
The shoulder block 28 is enlarged in the tire width direction (horizontal direction in FIG. 1) and has a rectangular shape larger than the tread land portion 26, and the front end of the shoulder block 28 in the tire rotation direction (lower end in FIG. 1) The first land portion 28A is elongated and defined by a horizontal groove 30 extending in the width direction.

As shown in FIG. 2, this first land portion 28A
On the contact surface of the tire, circular holes 32 are provided intermittently along the width direction of the tire, extending from the tire surface toward the inside of the tread land portion.

As shown in FIG. 1, a second land portion 28B is provided on the rear side (upper side in FIG. 1) of the first land portion 28A in the tire rotational direction, with a lateral groove 30 in between. This second land section 28
B has an L-shape consisting of a portion on the equatorial plane 22 side (left side in FIG. 1) and a portion on the rear side in the tire rotation direction (upper side in FIG. 2). Further, a portion divided by the L-shaped groove 34 and the lateral groove 30 is a third land portion 28C, and the third land portion 28C has a rectangular shape.

The length L of the shoulder block 28 in the tire circumferential direction is 3% to 3% of the tire outer circumferential length S (not shown).
It is set at 7%. Also, shoulder block 28
The length N in the tire width direction is set to 30% to 50% of the tire ground contact width W (not shown). Also, lug groove 2
The width N of the shoulder block 28 is set to 10% to 20% of the length L of the shoulder block 28 in the tire circumferential direction.

Next, the operation of this embodiment will be explained. In the pneumatic radial tire 10 of this embodiment, the shoulder block 28 is larger in the tire width direction and the tire circumferential direction than the tread land portion 26 and is partitioned by the lateral grooves 30. A hole 32 extends from the tire surface toward the inside of the tread land portion.
A first land portion 28A is provided with a first land portion 28A, and an L-shaped second land portion 28B is provided on the rear side of the first land portion 28A in the tire rotation direction and consists of a tire equatorial plane side and a rear side portion in the tire rotation direction. ,
It is composed of this second land portion 28B and a rectangular third land portion 28C partitioned by an L-shaped groove 34.

Therefore, by enlarging the shoulder block 28 in the tire circumferential direction and tire width direction, the rigidity of the tire contact patch can be improved. Therefore, when a side force acts on the tire's contact surface during cornering, the deformation of the tread land portion 26 and shoulder block 28 is reduced, and the edges of the contact surface of the tread land portion 26 and shoulder block 28 are lifted. and entrainment is suppressed. As a result, the ground pressure distribution of the tread land portion 26 and the shoulder block 28 is more uniformly distributed over the entire ground contact surface than in the past.

Furthermore, when the pneumatic radial tire 10 of this embodiment runs on a wet road surface, water between the tire and the road surface is drained along the lug grooves 24 and the main grooves 14, 16, and 18. Therefore, grip performance during cornering can be improved without deteriorating drainage performance, and uneven wear can be suppressed.

On the other hand, since the first land portion 28A has a low rigidity in the tire rotation direction due to the lateral grooves 30 and holes 32, the impact force when stepping on the front end of the shoulder block 28 in the tire rotation direction is reduced. As a result, putter noise can be reduced.

Furthermore, the outer end in the tire width direction (the right side in FIG. 1), which is the side force input side of the shoulder block 28, and the front end in the tire rotation direction, which is the drive force input side (the lower side in FIG. 1), are By dividing the second land portion 28B and the third land portion 28C, it is possible to prevent ground pressure from concentrating on the outer end in the tire width direction and the front end in the tire rotation direction, and improve uneven wear characteristics. can.

In the above embodiment, the circular hole 3 is provided in the first land portion.
2, however, as shown in FIG. 3, a sipe 40 may be provided instead of the circular hole 32. (Experimental example) The pneumatic radial tire of this example (tire size 225/50R16) and the conventional pneumatic tire 60 (Fig. 4) were prototyped with the specifications shown in Table 1, and each tire was fitted with a wheel 8J-16. installed, internal pressure 2.8Kg/c
m2, a load of 400 kg, and a speed of 50 km/h, the maximum side force SF was measured with the slip angle SA between 0° and 15°, and the results are shown in Table 1 as an index with the maximum side force SF of a conventional pneumatic tire as 100. displayed.

Furthermore, the pattern noise of each tire was measured under the above conditions, and the results are shown in Table 1 as an index, with the pattern noise of a conventional pneumatic tire set as 100.

Furthermore, each tire was attached to an actual Porsche 928 vehicle, and while driving at a speed of 100 km/h on a road surface with a water depth of 5 mm, the brakes were suddenly applied and the distance taken to stop was measured.
The results are shown in Table 1, where the distance until stopping of a conventional pneumatic tire is set as 100, and the wet braking performance is expressed as an index.

[0037]

[Table 1]

From the above results, it is clear that the pneumatic radial tire of this example is superior to the conventional pneumatic radial tire.

[0039]

[Effects of the Invention] Since the present invention has the above structure, it is possible to suppress the deterioration of water drainage performance and increase of putter noise, improve the grip performance during cornering, and suppress uneven wear. Has excellent effects.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing a tread pattern of a pneumatic radial tire according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a first land portion of a shoulder block of a pneumatic radial tire according to an embodiment of the present invention.

FIG. 3 is a perspective view showing another example of the first land portion of the shoulder block of the pneumatic radial tire according to the embodiment of the present invention.

FIG. 4 is a plan view showing a tread pattern of a conventional pneumatic radial tire.

FIG. 5 is a schematic meridian cross-sectional view showing the ground pressure distribution of a conventional pneumatic radial tire.

FIG. 6 is a meridian cross-sectional view showing a tread land portion of a conventional pneumatic radial tire.

FIG. 7 is a graph showing the relationship between slip angle and side force.

FIG. 8 is a plan view showing a tread pattern of another conventional pneumatic radial tire.

[Explanation of symbols]

10 Pneumatic radial tires 12　　　Tread section 14, 16, 18 Main groove 24 Lug groove 26 Toredo Rikubu 28 Shoulder block 28A 1st Land Department 28B 2nd Land Department 28C 3rd Land Department 30 Horizontal groove 32 holes 34 L-shaped groove 40 Sipe

Claims (5)

[Claims] 1. A main groove formed on the tire surface of the tread portion along the tire circumferential direction, a lug groove formed along the tire width direction, and a tread land portion partitioned by the main groove and the lug groove. A pneumatic radial tire comprising: a shoulder block provided at an end in the tire width direction of the tire ground contact area of the tread portion, which is larger in the tire width direction and the tire circumferential direction than the tread land portion;
This shoulder block is provided at the front end in the tire rotation direction and is divided by a lateral groove extending in the tire width direction, and the tire equatorial plane side part is provided at the rear side of the first land part in the tire rotation direction. an L-shaped second land portion consisting of a rear side in the tire rotation direction; an L-shaped groove along the second land portion and the lateral groove, and a rear side of the first land portion in the tire rotation direction; A pneumatic radial tire comprising: a rectangular third land portion provided therein; 2. The pneumatic radial tire according to claim 1, wherein the length of the shoulder block in the tire circumferential direction is set to 3% to 7% of the tire outer circumferential length. 3. The pneumatic radial tire according to claim 1, wherein the length of the shoulder block in the tire width direction is set to 30% to 50% of the tire ground contact width. 4. The pneumatic radial tire according to claim 1, wherein the width of the lug groove is set to 10% to 20% of the length of the shoulder block in the tire circumferential direction. 5. The air compressor according to claim 1, wherein at least one of holes and sipes extending from the tire surface toward the inner side of the tread land portion are provided intermittently along the width direction of the tire in the first land portion. Includes radial tires.