JPH05286311A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To improve the quality of anti-wear while heating durability and operation stability are being maintained, by making respectively the value of the ratio of an effective tread width and a center rib width, the value of the ratio of a shoulder rib width and a center rib width and the value of the ratio of a tire maximum width and the effective tread width, specific. CONSTITUTION:A plurality of peripheral main grooves 14 are provided at the tread 12 of a pneumatic tire 10, and are divided into center ribs 16 and shoulder ribs 18. When the average value (W1+W2)/2 of a tread width W1 and a width W2 between both intersection points 26 where a groove bottom supposition line 22 that passes the groove bottoms 14A of peripheral main grooves 14 in parallel with a tread sphere outer contour 20 crosses with a tire outer contour 24, is made to be an effective tread width We, the relation of the effective tread width We and the width Wc of a center rib 16 is made to be 0.3>=Wc/We>=0.225, and the relation of the width Ws of a shoulder rib 18 and the width Wc of a center rib 16 is made to be 2.0>=Wc/Ws>=1.15, and the relation of a tire maximum width WT and the effective tread width We is made to be 0.9>=We/WT>=0.8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire used for trucks, buses, etc., and is particularly suitable for running on a good road, and improves wear life while maintaining durability, especially heat resistance. Furthermore, the present invention relates to a pneumatic tire having improved steering stability, particularly wandering property.

[0002]

2. Description of the Related Art In order to improve the wear life of a pneumatic tire, there are a method of increasing the amount of rubber in a tread and a method of increasing the hardness of rubber to improve the wear resistance of rubber.

In order to increase the amount of rubber in the tread, there are a method of lengthening the tread width and a method of thickening the tread. However, if the tread width is lengthened, steering stability is lowered, and if the tread is thickened, heat generation durability is lowered. There is a problem that causes belt separation and blowout.

On the other hand, when the hardness of the rubber is increased, the rubber becomes brittle, so that the breaking strength is lowered and the tread is likely to be chipped or cracked.

As described above, the conventional techniques have a problem that they are contradictory, and there is a limit in improving wear life while maintaining heat generation durability.

[0006]

SUMMARY OF THE INVENTION In consideration of the above facts, an object of the present invention is to provide a pneumatic tire capable of improving wear resistance while maintaining heat generation durability and steering stability.

[0007]

The invention according to claim 1 is
A pneumatic tire having at least one center rib formed by a plurality of circumferential main grooves extending substantially circumferentially in a tread region and a pair of shoulder ribs,
An average value (W1 +) of the width W1 of the tread region and the width W2 between both intersections where a virtual groove bottom line that passes through the groove bottom of the circumferential main groove in parallel to the outer contour of the tread region intersects the tire outer contour.
When W2) / 2 is defined as the effective tread width We, the relationship between the effective tread width We and the width Wc of the center rib is set to 0.3 ≧ Wc / We ≧ 0.225.

According to a second aspect of the present invention, in the pneumatic tire according to the first aspect, the relationship between the width Ws of the shoulder rib and the width Wc of the center rib is 2.0 ≧ Wc / Ws ≧ 1.
The feature is that it is set to 15.

The invention according to claim 3 is the pneumatic tire according to claim 1 or 2, wherein the maximum tire width W is W.
The relationship between T and the effective tread width We is 0.9 ≧ We / WT
The feature is that ≧ 0.8.

The invention according to claim 4 is the pneumatic tire according to claim 1, claim 2 or claim 3, wherein the center rib is provided with a sipe extending in a direction transverse to the center rib. Is characterized by.

According to a fifth aspect of the present invention, in the pneumatic tire according to the first aspect, the second aspect, the third aspect, or the fourth aspect, the shoulder region on the outer side of the tread region in the tire axial direction is the tire rotation axis. On the other hand, it is characterized in that the inclined portion is inclined in the range of 15 to 75 °.

According to a sixth aspect of the present invention, in the pneumatic tire according to the first, second, third or fourth aspect, the shoulder region on the outer side in the tire axial direction of the tread region has a radius of curvature R. It is characterized by having an arc shape of 15 mm or more.

The invention according to claim 7 is the pneumatic tire according to claim 5 or 6, wherein a large number of sipes extending substantially in the tire axial direction are provided in the shoulder region in the shoulder region. I am trying.

[0014]

According to the invention of claim 1, the relationship between the effective tread width We and the center rib width Wc is 0.3 ≧ Wc / W.
Since e ≧ 0.225, the rubber amount of the center rib becomes appropriate, wear resistance can be improved without lowering heat generation durability, and proper drainage can be secured.

According to the second aspect of the invention, the relationship between the shoulder rib width Ws and the center rib width Wc is 2.0 ≧ W.
Since c / Ws ≧ 1.15, the balance between the shoulder rib and the center rib is improved, steering stability is improved, and shoulder wear and rib tear can be prevented from occurring. In addition, the wear resistance can be improved without causing a shortage of the amount of wear rubber of the center rib.

According to the third aspect of the invention, the relationship between the tire maximum width WT and the effective tread width We is 0.9 ≧ We /
Since WT ≧ 0.8, the amount of rubber in the tread becomes appropriate, and the balance between heat resistance and wear resistance is good.
It is possible to prevent the wandering phenomenon from occurring.

According to the fourth aspect of the present invention, since the center rib is formed with the sipe extending in the direction crossing the center rib, the bending stress generated in the ground contact portion of the center rib when the tire rotates. Distributed by sipes,
Since the behavior of the center rib is made uniform, uneven wear resistance is improved. Further, since the sipe is closed by the compressive stress that acts at the time of ground contact and the groove wall surfaces are pressed against each other, the center rib in the ground contact surface is substantially integrated and wear resistance is prevented. In addition, the draining action of the sipes improves the wet performance.

According to the fifth aspect of the present invention, the shoulder region outside the tread region in the axial direction of the tire is provided with the inclined portion that is inclined within the range of 15 ° to 75 ° with respect to the tire rotation axis. The occurrence of the phenomenon is prevented, and it is possible to smoothly overcome the ruts and projections of the road surface when the vehicle is over a shallow angle. If the inclination angle of the inclined portion is less than 15 °, the inclined portion may come into contact with the road surface during traveling, which may cause shoulder drop wear.
When it exceeds the range, the wandering phenomenon is likely to occur and the ability to overcome the rut is deteriorated.

According to the sixth aspect of the invention, since the shoulder region on the outer side in the tire axial direction of the tread region has an arc shape with a radius of curvature R of 15 mm or more, the occurrence of the wandering phenomenon is prevented and the rut of the road surface is prevented. It is possible to smoothly get over these projections and the like when getting over at a shallow angle.

According to the seventh aspect of the invention, the shoulder region is softened by the sipes extending substantially in the tire axial direction. This prevents the occurrence of wandering phenomenon and allows smooth passage over ruts and projections on the road surface at a shallow angle.In addition, the shoulder area can easily follow the road surface, which causes uneven wear on the shoulder ribs. Is prevented.

[0021]

【Example】

[First Embodiment] A pneumatic tire 10 according to a first embodiment of the present invention will be described with reference to Figs. Since the pneumatic tire 10 of this embodiment has a normal radial structure, description of the internal structure is omitted.

As shown in FIGS. 2 and 3, the tread 12 of the pneumatic tire 10 is provided with a plurality of circumferential main grooves 14 extending in the tire circumferential direction (direction of arrow S).
Here, it is preferable to provide three or four circumferential main grooves 14. If the circumferential main groove 14 is two, the wettability (drainability) is not sufficient, and if it is five or more, the wear rubber amount of the tread 12 is insufficient.

In this embodiment, the tread 12 has a circumferential main groove 1 formed therein.
3 are provided, one of which is provided on the tread center CL, and the other two are provided on the tread center C.
They are arranged at predetermined intervals on both sides of L in the tire width direction (direction of arrow A). Here, the land portions on both sides of the tread center CL are respectively formed as center ribs 16, and the land portions on the tire width direction outer side of the center ribs 16 are respectively formed as shoulder ribs 18.

As shown in FIG. 1, a groove bottom virtual line 22 passing through the tread width W1 and the groove bottom 14A of the circumferential main groove 14 in parallel to the tread area outer contour 20 intersects the tire outer contour 24 at both intersections. Average value with width W2 between 26 (W1 + W2)
When / 2 is defined as the effective tread width We, the relationship between the effective tread width We and the width Wc of the center rib 16 is 0.
It is preferable that 3 ≧ Wc / We ≧ 0.225. In this embodiment, the effective tread width We is 238 mm and the width Wc of the center rib 16 is 56.2 mm.
c / We is 0.236.

Here, when Wc / We exceeds 0.3,
The amount of rubber in the center rib 16 becomes excessively large, resulting in poor heat generation durability and poor drainage performance at the center of the ground. When Wc / We is less than 0.225, the amount of wear rubber of the center rib 16 that plays an important role in wear life is insufficient.

On the other hand, the groove width W3 of the circumferential main groove 14 is preferably in the range of 3 to 8% with respect to the effective tread width We. In the pneumatic tire 10 of the present embodiment, the groove width W3 of the circumferential main groove 14 is set to 10 mm, and the ratio of the groove width W3 of the circumferential main groove 14 to the effective tread width We is 4.2%. There is. In this embodiment, the groove depth D1 of the circumferential main groove 14 is set to 16.3 mm (see FIG. 1).

Further, in the tread 12, the relationship between the width Ws of the shoulder rib 18 and the width Wc of the center rib 16 is preferably 2.0 ≧ Wc / Ws ≧ 1.15, and 1.5 ≧ Wc / More preferably, Ws ≧ 1.15. In the present embodiment, the width Ws of the shoulder rib 18
Is 47.5 mm, and Wc / Ws is 1.183.

Here, when Wc / Ws exceeds 2.0, the shoulder ribs 18 become too small and the steering stability is deteriorated, and shoulder wear and rib tear are likely to occur. The amount of wear rubber of the center rib 16 that plays an important role in the above is insufficient.

The relationship between the tire maximum width WT and the effective tread width We is preferably 0.9 ≧ We / WT ≧ 0.8. In this embodiment, the maximum tire width WT is 280 mm
And We / WT is set to 0.85. Here, when We / WT exceeds 0.9, the tread width becomes excessive, the heat generation durability deteriorates, and the wandering phenomenon easily occurs. On the other hand, We / WT is 0.
If it is less than 8, the tread width is too small and the tread is 12
Wear resistance deteriorates.

As shown in FIG. 2, sipes 28 are formed on the center rib 16. Since the rib width is widened, the behavior of the tread portion becomes non-uniform and uneven wear is apt to occur. However, since the degree of freedom is given by the sipe 28, the behavior of the tread portion is made uniform and uneven wear can be prevented.

It is preferable that at least one end of the sipe 28 communicates with the circumferential main groove 14 in order to improve drainage, and in the tire width direction (arrow) to prevent opening, prevent cracks from being generated from the groove bottom, and prevent chipping. It is preferable to incline in a constant direction with respect to the (A direction). Further, it is preferable that a part of the sipe 28 in the longitudinal direction is bent in order to suppress the opening when the side force is input.

The sipe 28 of the present embodiment is entirely inclined with respect to the tire width direction, and a predetermined range in the longitudinal middle portion is a steep inclination portion 28A. The groove width of the sipe 28 is set to a size such that the groove is substantially closed within the ground contact surface, and is preferably 2 mm or less in order to secure the rigidity of the center rib 16. Also, the sipe depth D of the sipe 28
2 is preferably 60 to 120% of the groove depth D1 of the circumferential main groove 14 (see FIG. 1). The sipe depth D2 of the sipe 28 of this embodiment is 15.3 mm, which is 93.7% of the groove depth D1 (16.3 mm) of the circumferential main groove 14.

The pitch P of the sipe 28 in the tire circumferential direction is
The range of 15 to 70 mm is preferable, and the range of 25 to 50 mm is more preferable (see FIG. 2).

On the other hand, the shoulder rib 18 has a lug groove 30.
Are formed. It is preferable that the lug groove 30 does not communicate with the circumferential main groove 14 in order to secure the rigidity of the shoulder rib 18.

As shown in FIG. 1, inclined portions 32 are provided at both ends of the tread 12 in the tire width direction.

As shown in detail in FIG. 4, the inclination angle θ of the inclined portion 32 with respect to the tire rotation axis (direction of arrow A) is 15
The angle is preferably in the range of ° to 75 °, more preferably in the range of 40 to 70 °. In this embodiment, the inclined portion 32
The inclination angle θ with respect to the tire rotation axis is 55 °.

Here, if the inclination angle θ is less than 15 °, the inclined portion 32 may come into contact with the road surface during running and shoulder wear may occur, and if the inclination angle θ exceeds 75 °, the wander will occur. A ring phenomenon is likely to occur, and the ability to overcome a rut is reduced.

Further, the length L1 of the inclined portion 32 in the tire axial direction is
Is a combination of wandering prevention and wear resistance,
The range of 2 to 10% of the effective tread width We is preferable. In this embodiment, the tire axial length L1 of the inclined portion 32 is 10
mm, and the ratio to the effective tread width We is
It is set at 4.2%.

As shown in FIG. 2, end sipes 34 are provided at both ends of the tread 12 in the tire width direction.
The end sipes 34 are arranged at a substantially uniform small interval in the tire circumferential direction, and the sipes have dimensions such that they are substantially closed within the ground contact surface. In the end sipe 34 of the present embodiment, the tire circumferential pitch P is set to 9.8 mm, the sipe depth D3 is set to 4.5 mm, and the sipe width is set to 0.7 mm.

Next, the operation of this embodiment will be described. In the pneumatic tire 10 of the present embodiment, the relationship between the effective tread width We and the width Wc of the center rib 16 is 0.3 ≧ Wc / We.
Since .gtoreq.0.225, the amount of rubber in the center rib 16 becomes appropriate, and the balance of heat generation durability, drainage, and amount of worn rubber becomes optimum.

The relationship between the width Ws of the shoulder rib 18 and the width Wc of the center rib 16 is 2.0 ≧ Wc / Ws ≧.
Since it is set to 1.15, the balance between the shoulder rib 18 and the center rib 16 is improved, steering stability is improved, and shoulder wear and rib tear can be prevented from occurring. Further, the amount of worn rubber of the center rib 16 does not become insufficient.

Further, since the relationship between the tire maximum width WT and the effective tread width We is set to 0.9 ≧ We / WT ≧ 0.8, the rubber amount of the tread 12 becomes appropriate, and the heat generation durability and wear resistance are improved. The balance is good and the wandering phenomenon does not easily occur.

A sipe 28 is formed on the center rib 16, and the sipe 28 has a pitch P of 1 in the tire circumferential direction.
Since it is set in the range of 5 to 70 mm, the bending stress generated in the center rib 16 is dispersed by the sipe 28, the behavior of the center rib 16 is made uniform, and the uneven wear resistance is improved.

Since the sipe 28 is closed by the compressive stress acting at the time of ground contact and the groove wall surfaces are pressed against each other, the center rib 16 in the ground contact surface is substantially integrated and wear resistance is improved.

Furthermore, since both ends of the sipe 28 are connected to the circumferential main groove 14, the drainage of water in the sipe 28 is improved, and the draining action of the circumferential main groove 14 and the draining action of the sipe 28 are improved. Both effects improve the wet performance.

Further, since the sipe 28 is inclined with respect to the tire circumferential direction (arrow S direction), when the tread 12 is bent in the vicinity of the ground contact end, the entire lengthwise direction is not opened. Therefore, stress is not concentrated on the sipe bottom of the sipe 28, cracks are prevented from being generated from the groove bottom, and the center rib 16 is not chipped.

On the other hand, when the side force acts on the pneumatic tire 10, the side force SF acts on the steep slope portion 28A at a deep angle.
The inner wall surfaces of 8A strongly adhere to each other, and the opening of the sipe 28 is suppressed. Therefore, even when the side force SF is input, cracking from the sipe bottom of the sipe 28 is prevented.

Further, since the inclined portions 32 are provided at both ends in the tire width direction of the pneumatic tire 10, the occurrence of the wandering phenomenon is prevented, and when the rudder of the road surface, the projections, etc. are passed over at a shallow angle, these Can be overcome smoothly.

Furthermore, since the end sipes 34 are provided at both ends of the tread 12, the vicinity of the inclined portion 32 becomes flexible, the effect of preventing the wandering phenomenon is further improved, and both ends of the tread 12 are improved. Uneven wear of parts (so-called edge drop) is suppressed. .. [Second Embodiment] A pneumatic tire 10 according to a second embodiment of the present invention will be described with reference to FIG. The same components as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

As shown in FIG. 5, the pneumatic tire 10 of the present embodiment is different from the pneumatic tire 10 of the first embodiment in that instead of the inclined portion 32 at both ends of the tread 12 in the tire width direction. A circular arc portion 36 is provided in the. The radius R of the arc portion 36 is preferably 15 mm or more. In this embodiment, the radius R of the arc portion 36 is set to 30 mm. Further, the end sipe 34 is not provided in this embodiment. The rest of the configuration is the same as in the first embodiment.

In the pneumatic tire 10 of this embodiment, since the arc portions 36 are provided at both ends of the tread 12,
As with the pneumatic tire 10 of the first embodiment, the occurrence of the wandering phenomenon is prevented, and it is possible to smoothly ride over ruts and protrusions on the road surface at a shallow angle. When the radius R of the circular arc portion 36 is less than 15 mm, the effect of preventing the wandering phenomenon is reduced.

Also in this embodiment, the tread 12
By providing the end sipes 34 at both ends of the tread 12 to make both ends of the tread 12 flexible, the effect of preventing the occurrence of the wandering phenomenon can be further improved.

(Test Example) In Table 1 below, 5 types of pneumatic tires to which the present invention is applied, 1 type of conventional pneumatic tire and 3 types of tires as comparative examples are used, and wear life and heat generation durability are used. , The results of testing for steering stability are shown.

The example 1 in Table 1 is the pneumatic tire 10 of the first example without the sipe 28, the end sipe 34 and the inclined part 32, and the example 2 is the first example. Inclined portion 32 and end sipe 34 of example pneumatic tire 10.
There is no thing. Further, Example 3 is the pneumatic tire 10 of the first example without the end sipe 34, and Example 4 is the pneumatic tire 10 of the second example.
Example 5 is the pneumatic tire 10 of Example 1.

On the other hand, in Conventional Example 1, in the pneumatic tire 10 of the first embodiment, the dimensions of the effective tread width We, the main groove depth D, the center rib width Wc and the shoulder rib width Ws are different from each other. (See Table 1 for various dimensions). Further, in Comparative Examples 1 to 3, in the pneumatic tire 10 of Example 1, the effective tread width We, the main groove depth D,
The center rib width Wc and the shoulder rib width Ws have different dimensions (see Table 1 for the dimensions).

All the test tires had a size of 1000R.
It is set to 20. Abrasion life: 5 with test tires mounted on the drive wheels of the actual vehicle
From the amount of wear of the tread after running 10,000 km, the running distance per unit amount of wear was displayed as an index. The numerical value is 100 for the tire of Conventional Example 1, and the larger the value, the better.

Heat resistance: Drum test (15 at specified load)
The distance traveled until a tread failure was displayed as an index at 0% load and speed 65 km / h). In addition, the numerical value is 1 for the tire of Conventional Example 1
00, the larger the value, the better.

Maneuverability: Test tires were mounted on an actual vehicle and the feeling was evaluated by a test driver. The term "controllability" as used herein refers to the feeling of operation of the steering wheel when the tire runs out of the rut and the tire leaves the rut and when the tire returns to the inside of the rut. The tire of Conventional Example 1 was used as a control.

[0059]

[Table 1]

From the test results shown in Table 1 above, the pneumatic tire 10 to which the present invention is applied shows that the durability against heat generation and the steering stability are maintained at the same level as the conventional one, and the wear resistance is greatly improved. Became clear.

In this embodiment, the tread 12 is provided with the lug groove 30, but the present invention is not limited to this, and the lug groove 30 may not be provided.

[0062]

Since the pneumatic tire of the present invention has the above-mentioned structure, it has an excellent effect of improving wear resistance while maintaining heat generation durability and steering stability.

[Brief description of drawings]

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

FIG. 2 is a partial development view of the tread of the pneumatic tire according to the first embodiment of the present invention.

FIG. 3 is a perspective view of a pneumatic tire according to a first embodiment of the present invention.

FIG. 4 is a cross-sectional view in the vicinity of an inclined portion of the pneumatic tire according to the first embodiment of the present invention.

FIG. 5 is a sectional view taken along the axis of a pneumatic tire according to a second embodiment of the present invention.

[Explanation of symbols]

 10 Pneumatic Tire 12 Tread (Tread Area) 14 Circumferential Main Groove 14A Groove Bottom 16 Center Rib 18 Shoulder Rib 20 Tread Area Outer Contour 22 Groove Bottom Virtual Line 24 Tire Outer Contour 26 Intersection 28 Sipe 32 Slope 34 34 End Sipe

Claims (7)

[Claims] 1. A pneumatic tire having at least one center rib formed by a plurality of circumferential main grooves extending substantially circumferentially in a tread region and a pair of shoulder ribs, the tread region comprising: An average value (W1 +) of the width W1 and the width W2 between both intersections where a virtual groove bottom line passing through the groove bottom of the circumferential main groove in parallel to the outer contour of the tread region intersects the tire outer contour.
When W2) / 2 is defined as the effective tread width We, the pneumatic tire is characterized in that the relationship between the effective tread width We and the center rib width Wc is 0.3 ≧ Wc / We ≧ 0.225. .. 2. The pneumatic tire according to claim 1, wherein the relationship between the width Ws of the shoulder rib and the width Wc of the center rib is 2.0 ≧ Wc / Ws ≧ 1.15. 3. A tire maximum width WT and an effective tread width We
The pneumatic tire according to claim 1 or 2, wherein a relationship with the relation is 0.9 ≧ We / WT ≧ 0.8. 4. The pneumatic tire according to claim 1, wherein the center rib is provided with a sipe extending in a direction crossing the center rib. 5. The tire according to claim 1, wherein the shoulder region on the outer side in the tire axial direction of the tread region is an inclined portion that is inclined within a range of 15 to 75 ° with respect to the tire rotation axis. The pneumatic tire according to claim 3 or claim 4. 6. The shoulder region on the outer side in the tire axial direction of the tread region is formed into an arc shape having a radius of curvature R of 15 mm or more, claim 1, claim 2, claim 3 or claim 3. 4. The pneumatic tire according to 4. 7. The pneumatic tire according to claim 5, wherein the shoulder region is provided with a large number of sipes extending substantially in the tire axial direction in the tire circumferential direction.