JP2003205706A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress heat generation in a center area of a tread without impairing any wear resistance. <P>SOLUTION: A pair of sub grooves 20A and 20B extending substantially along the circumferential direction Y of the tread 14 are provided on a part of a center area A of a land part 16 so as to be provided one by one across a center line CL of the tread 14. The inequalities of 0.2W≤L≤0.4W, 0.15D≤H≤0.5D, and 0.2W≤Σ(K+H)≤0.4W are satisfied, where L is the interval between the sub grooves 20A and 20B, H is the depth of the sub grooves 20A and 20B, and Σ(K+H) is the total of the width K and the depth H of the sub grooves 20A and 20B. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire that suppresses heat generation in the center region of a tread without impairing wear resistance, and is particularly suitable for heavy load radial tires.

[0002]

2. Description of the Related Art Conventionally, as a heavy-duty radial tire, which is a pneumatic tire used in a vehicle such as a dump truck, as shown in FIG. 4, a tire tread 114, which is a tread portion in contact with a road surface, is mainly used. It is known that a plurality of grooves 118 are formed at equal intervals and have a tread pattern that serves as a lug pattern. And
In heavy-duty radial tires that have this lug pattern on the tread, in order to improve the wear resistance of the tread and extend the life, use rubber material with excellent wear resistance or increase the volume of the tread. Alternatively, techniques such as reducing the negative ratio have been used.

On the other hand, the tire performance required for the above heavy load radial tire is how long the life can be achieved without failure, but in recent years, the size and speed of the vehicle have become extremely large and large. Therefore, it is becoming difficult to achieve long life without failure.

In other words, an increase in the size of the vehicle leads to an increase in the size of the tire, and it is necessary to increase the volume of the tread in order to secure a proper tire life. As a result of increasing the amount of energy lost due to bending deformation and shearing deformation during movement, the tire temperature rises. Here, the tire temperature means the temperature at the upper part of the belt of the radial tire in particular, but the increase in the temperature at the upper part of the belt is
It may cause separation between the belt and the rubber material forming the tread.

[0005]

As described above, since the wear resistance is emphasized as described above in the heavy load radial tire, as a result, the heat generation from the tread portion tends to increase during rolling of the tire. There is. In addition, a lug pattern generally used as a tread pattern for heavy-duty radial tires has a rib in the center region that is the center region of the tread, and therefore, there is also a tendency that the heat dissipation effect is particularly reduced in this center region. ing.

As a result, it is difficult to achieve both wear resistance and suppression of heat generation in the conventional heavy duty radial tire having a lug pattern, and failure such as heat separation and cut separation is caused in the center region of the tread. I was afraid. The present invention takes the above facts into consideration,
An object of the present invention is to provide a pneumatic tire capable of suppressing heat generation in the center region of the tread without impairing wear resistance.

[0007]

A pneumatic tire according to a first aspect of the present invention has at least main grooves on both sides of the tread, and at least ribs in the central area of the tread which is half the total width of the tread. In the pneumatic tire, a plurality of sub-grooves each extending along the circumferential direction of the tread are provided in this central region, the depth of the main groove is D, the width of the central region is W, and the width of the sub-groove is K. And the depth is H and the sum of the width K and the depth H of each sub-groove is Σ (K + H): 0.15D ≦ H ≦ 0.5D 0.2W ≦ Σ (K + H) ≦ 0. It is characterized by being set to 4W.

The operation of the pneumatic tire according to claim 1 will be described below. According to the present invention, the pneumatic tire has a structure in which at least main grooves are provided in both side areas of the tread, and at least a rib is provided in a central area of the tread which is half the total width of the tread. A plurality of sub-grooves extending in the circumferential direction of the tread are provided in this central region, the depth of the main groove is D, the width of the central region is W, the width of the sub-groove is K, and the depth is Suppose that H is H and the sum of width K and depth H of each sub-groove is Σ (K + H), depth H of the sub-groove and sum Σ (K + H) of width K and depth H of each sub-groove.
, 0.15D ≦ H ≦ 0.5D 0.2W ≦ Σ (K + H) ≦ 0.4W, respectively.

That is, if the depth H of the sub-groove is made shallower than 0.15D, the temperature reducing effect by heat dissipation is impaired, and
When the depth H of the auxiliary groove is deeper than 0.5D, the wear resistance is significantly reduced. Therefore, the depth H of the sub-groove is set to 0.1 above.
The size was in the range of 5D ≦ H ≦ 0.5D.

Further, in order to secure the total surface area of heat radiation by the sub-grooves and reduce the temperature, the total sum Σ (K + H) of the widths K and depths H of the sub-grooves is 0.2 W. It is preferable that the size is in the range of 0.4 W or less. That is, if this total is less than 0.2 W,
The heat dissipation area cannot be secured enough, and this sum is 0.4
When it is larger than W, the rigidity of the tread is lowered and the wear resistance is impaired.

As described above, according to the pneumatic tire of the present invention, a plurality of sub-grooves are provided in the circumferential direction of the tread even if the tread pattern has a lug system having main grooves on both sides of the tread. By arranging in a form that extends along the, it is possible to suppress the heat generation in the center region, which is the portion corresponding to the central region of the tread, while minimizing the deterioration of wear resistance.

The operation of the pneumatic tire according to claim 2 will be described below. The present invention has the same structure as in claim 1 and operates in the same manner, but further, when the distance between the plurality of sub-grooves is L, 0.2W ≦ L ≦ 0.4W have.

That is, if a plurality of sub-grooves are provided in this central region and the distance L between the sub-grooves is narrowed to be smaller than 0.2 W, the rigidity of the tread is lowered, and as a result, the durability of the tire at the initial stage of tire mounting is reduced. Abrasion property decreases. On the other hand, if the distance L between the sub-grooves is made wider than 0.4 W, the effect of reducing heat generation cannot be sufficiently obtained. Therefore, it is preferable that the size of the interval L between the sub-grooves be within the above range. As described above, when applied to the radial tire in which the size of the distance L between the sub-grooves is within the above range, the function and effect of claim 1 can be more exerted.

The operation of the pneumatic tire according to claim 3 will be described below. The present claim has the same structure as in claims 1 and 2 and operates in the same manner, but further has a structure in which the depth D of the main groove is set to 60 mm or more. That is, when the invention is applied to a radial tire having a main groove depth D of 60 mm or more, which is a large-sized tire in which it is difficult to both improve wear resistance and suppress heat generation, the action and effect of claim 1 can be more exerted.

The operation of the pneumatic tire according to claim 4 will be described below. The present invention has the same structure as the first to third embodiments and operates in the same manner, but the negative ratio of the portion excluding the auxiliary groove in the central region is set to 10% to 30%. have. That is, when the value of the negative ratio of the portion excluding the auxiliary groove in the central region is applied to the radial tire within the above range, the action and effect of claim 1 is further exhibited.

The operation of the pneumatic tire according to claim 5 will be described below. This claim has the same structure as in claims 1 to 4 and operates in the same manner, but further has a structure in which both sides of the tread have a lug pattern of a combination of a main groove and a land portion. is doing. That is, when applied to a heavy duty radial tire having a lug pattern in which it is difficult to both improve wear resistance and suppress heat generation, the action and effect of claim 1 will be more exerted.

The operation of the pneumatic tire according to claim 6 will be described below. The present invention has the same structure as that of claims 1 to 5 and operates in the same manner, but the sub-groove further comprises:
The structure is such that one is provided with the center line of the tread sandwiched therebetween. That is, in addition to the same operation as in claim 1, as a result of providing one sub-groove on each side of the center line of the tread, heat generation can be suppressed evenly in the width direction in the center region of the tread. Become.

The operation of the pneumatic tire according to claim 7 will be described below. The present invention has the same structure as that of claims 1 to 5 and operates in the same manner, but the sub-groove further comprises:
The tread has a configuration in which one is provided on each side of the center line and one is provided along the center line. In other words, not only does it operate in the same manner as in claim 1, but one sub-groove is provided so as to sandwich the center line,
As a result of the sub-grooves being provided along the center line, it is possible to suppress heat generation more evenly in the width direction in the center region of the tread.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION A pneumatic tire according to a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a typical example of a tread pattern of a pneumatic tire 10 according to this embodiment. Here, regarding the internal structure of the pneumatic tire 10, a carcass 12 which is a radial carcass, a highly rigid belt (not shown) arranged so as to cover the crown portion of the carcass 12, and an outer peripheral surface of the belt Since it is a very common pneumatic tire of this type in which the tread 14 configured and arranged of tread rubber is combined, the description thereof will be omitted in the following description.

Further, as shown in FIG. 1, the outer surface of the pneumatic tire 10 in contact with the road surface constitutes the above-mentioned tread 14 having an arcuate crown-shaped outer surface. A pattern in which a land portion 16 that is a rib extending along the circumferential direction Y of the tread 14 is formed in a central area A around the center line CL of the tread 14 and the tread 14
The central area A of is. Although the central area A of the tread 14 is centered on the center line CL,
Has a width W that is half (that is, 1/2) the total width W0 of

The main groove 18 and the land portion 16 are arranged at equal intervals along the circumferential direction Y of the tread 14 in both side regions B near the shoulder portion 14A forming the end portion of the tread 14. A lug pattern formed by a combination of the main groove 18 and the land portion 16 is formed in the both side areas B. The depth D of these main grooves 18 is 60 mm or more 8
The size of 0 mm is set in this embodiment.

On the other hand, in the central area A of the land portion 16, the tread 14 extends substantially along the circumferential direction Y of the tread 14 such that the tread 14 and the tread 14 are provided one by one. A pair of sub-grooves 20A and 20B are provided. Here, specifically, the distance L between the sub-grooves 20A and 20B is set to 0.28 W, the depth H of the first sub-groove 20A on the left side in the figure and the depth H of the second sub-groove 20B on the right side in the figure. The size H is 0.30D. In addition, the width K and depth H of each sub-groove 20A, 20B
Since K + H, which is the sum of the two, is 0.11 W, the sum Σ (K + H) of the width K and the depth H of each sub-groove 20A, 20B is 0.22 W.

In the present embodiment, the sub groove 20A,
Interval L between 20B, depth H of each sub-groove 20A, 20B, and sum Σ of width K and depth H of each sub-groove 20A, 20B.
(K + H) has a relationship of 0.2W ≦ L ≦ 0.4W 0.15D ≦ H ≦ 0.5D 0.2W ≦ Σ (K + H) ≦ 0.4W. However, in the tread 14 of the pneumatic tire 10 according to the present embodiment,
The negative ratio of the portion of the central region A excluding the sub-grooves 20A and 20B is 25%, which is within 10% to 30%.

Next, the operation of the pneumatic tire 10 according to this embodiment will be described below. In the pneumatic tire 10 according to the present embodiment, the main groove 18 is formed in the both side regions B of the tread 14.
And has a rib in the central area A of the tread 14 which is half the total width W0 of the tread 14. Then, the sub-grooves 20A and 20B extending substantially along the circumferential direction Y of the tread 14 are provided one by one with the center line CL of the tread 14 interposed therebetween, so that two sub-grooves are provided in the central area A. And sub groove 2
Distance L between 0A and 20B, depth H of the sub-grooves 20A and 20B
And the sum Σ of width K and depth H of each sub-groove 20A, 20B.
(K + H) is within the above range.

That is, when the two sub-grooves 20A and 20B are provided in the central area A, the interval L between the sub-grooves 20A and 20B is narrowed to be smaller than 0.2 W, so that the rigidity of the tread 14 is lowered. As a result, the wear resistance at the initial stage of tire mounting is reduced. On the other hand, if the distance L between the sub-grooves 20A and 20B is made wider than 0.4 W, the effect of reducing heat generation cannot be sufficiently obtained. Therefore, the sub-grooves 20A, 20B
It is preferable that the size of the interval L between them is within the above range.

On the other hand, the depth H of the sub-grooves 20A and 20B is set to 0.
If the depth is less than 15D, the temperature reduction effect due to heat radiation is impaired, and if the depth H of the sub-grooves 20A, 20B is deeper than 0.5D, the wear resistance is significantly reduced. Therefore,
The depth H of the sub-grooves 20A and 20B is set to 0.15D ≦ H ≦
The size was in the range of 0.5D.

Further, in order to secure the total surface area of heat radiation by the sub-grooves 20A and 20B and reduce the temperature, the sum Σ (K + H) of the sub-grooves 20A and 20B added with the width K and the depth H as described above. ) Is preferably in the range of 0.2W ≦ Σ (K + H) ≦ 0.4W. That is, if the total sum is less than 0.2 W, the heat dissipation area cannot be sufficiently secured, and if the total sum is greater than 0.4 W, the rigidity of the tread 14 is lowered and the wear resistance is impaired. become.

As described above, according to the pneumatic tire 10 of the present embodiment, the main groove 18 is formed in the both side regions B of the tread 14.
Even if it has a lug type tread pattern such as that having a plurality of sub-grooves 20A, 20B extending in the circumferential direction Y of the tread 14, a decrease in wear resistance is minimized. It is possible to suppress heat generation in the center region of the tread 14 while keeping the above. Then, at this time, as a result of providing one sub-groove 20A and one sub-groove 20B with the center line CL of the tread 14 interposed therebetween, it is possible to uniformly suppress heat generation in the width direction in the central region A of the tread 14. .

On the other hand, in the present embodiment, the depth D of the main groove 18 is set to 60 mm or more, and the sub groove 2 in the central area A is formed.
The negative ratio of the portion excluding 0A and 20B is 10% to 3
The pneumatic tire is 0%, and both side regions B of the tread 14 have a lug pattern of a combination of the main groove 18 and the land portion. That is, the secondary groove 20A, 20B of the central groove A having a depth D of 60 mm or more and a radial groove for heavy load having a lug pattern in which it is difficult to both improve wear resistance and suppress heat generation is provided. When the present embodiment is applied to the radial tire in which the value of the negative ratio of the excluded portion is within the above range, the above-mentioned action and effect are further exhibited.

Next, a pneumatic tire according to a second embodiment of the present invention will be described with reference to FIG. The members described in the first embodiment are designated by the same reference numerals, and duplicate description will be omitted. As shown in FIG. 2, one tread 14 is provided in the central region A of the land portion 16 of the pneumatic tire 10 according to the present embodiment with the center line CL of the tread 14 interposed therebetween. The first sub-groove 20A on the left side in the drawing and the third sub-groove 20C on the right side in the drawing, which are two sub-grooves extending substantially along the circumferential direction Y of
However, in addition to being formed, the second sub groove 20B is provided along the center line CL. In other words, this embodiment is
The structure has a total of three sub-grooves 20A, 20B, 20C.

The distance L between the two sub-grooves 20A and 20B is 0.26W to 0.36W, and the distance L between the two sub-grooves 20B and 20C is also 0.26W to.
The size is 0.36W. That is, the central line CL
Two sub-grooves 20A and 20C, which are respectively provided with the two in between.
Are inclined with respect to the circumferential direction Y of the tread 14, but the second sub-groove 20B is provided so as to extend along the circumferential direction Y of the tread 14 on the center line CL. The size of L will change.

Furthermore, in this embodiment, the first sub groove 20 is used.
The depth H of A and the depth H of the third sub-groove 20C are 0.
The size is 36D, and the depth H of the second sub-groove 20B located between them is 0.48D. On the other hand, the width K and the depth H of the first sub-groove 20A and the third sub-groove 20C
And the sum K + H is 0.11 W, and the sum K of the width K and the depth H of the second sub-groove 20B is K.
Since + H has a size of 0.16 W, each sub groove 2
Sum Σ (K + of width K and depth H of 0A, 20B, 20C
H) becomes 0.38 W.

That is, in the present embodiment, the sub groove 20A,
The distance L between the sub-grooves 20B, the distance L between the sub-grooves 20B and 20C, the depth H of each of the sub-grooves 20A, 20B and 20C, and the sum Σ (K of the width K and the depth H of each sub-groove 20A, 20B, 20C.
Since + H) is within the range described in the first embodiment, it is possible to suppress the heat generation in the center region of the tread 14 while minimizing the deterioration of wear resistance. Further, in the present embodiment, the sub-grooves 20A and 20C are provided one by one with the center line CL sandwiched therebetween, and the second sub-groove 20B is provided along the center line CL, and as a result, the central region of the tread 14 is formed. In A, it becomes possible to suppress heat generation more evenly in the width direction.

Next, the pneumatic tire 10 described in the first embodiment will be referred to as Example 1, and the pneumatic tire 10 described in the second embodiment will be referred to as Example 2.
Results of comparing these two types of examples with the tire according to the comparative example and the tire according to the conventional example will be described based on Table 1 below.

That is, a comparative example has a structure shown in FIG. This comparative example is similar to Example 1 in that the land portion 1
6, a pair of sub-grooves 20A, 20B extending substantially along the circumferential direction Y of the tread 14,
Although provided, the space L between the sub-grooves 20A and 20B has a size of 0.16 W, and the depth H of the first sub-groove 20A and the depth H of the second sub-groove 20B are 0.72 D, respectively. It is said that. In addition, K + H of each sub-groove 20A, 20B
Is 0.22 W, the sum Σ (K + H) of the width K and the depth H of each sub-groove 20A, 20B is 0.44 W. On the other hand, the conventional example is shown in FIG.
The tire has the rug pattern shown in FIG.

[0036]

[Table 1]

Here, the conditions for the test are as follows, and each tire as described above was mounted on a drum tester, and a running test using a drum was conducted. Tire size: 40.00R57 Rim used: 29.00 / 6.0 * 57 Air pressure: 700KPa Regular load: 60ton

From the results of Table 1, regarding the heat generation property, the tire of the conventional example has a temperature of 95 ° C., and the tire of the comparative example has a temperature of 89 ° C.
The tire of Example 1 had a temperature of 93 ° C, while the tire of Example 1 had a temperature of 93
C. and the tire of Example 2 had a temperature of 92.degree. Further, regarding the wear resistance, the tire of the conventional example is 100
The tire of Comparative Example was 88, whereas the tire of Example 1 was 97 and the tire of Example 2 was 96.
Met.

In other words, although Examples 1 and 2 have a slightly low evaluation of wear resistance, they are improved in heat generation property as compared with the conventional example, and heat generation in the center region of the tread is maintained without impairing wear resistance as compared with Comparative Example. I can understand that I was able to suppress it. Here, the heat generation property is the average temperature on the belt in the central area A in the result of the drum test, and the wear property is shown by an index when the conventional example is 100, and the smaller the value, the better the evaluation. .

Although the above embodiment is applied to a heavy load radial tire, it goes without saying that it may be applied to other types of tires. Further, the width and depth dimensions of the sub-groove are not limited to those in the above embodiment.

[0041]

Since the pneumatic tire of the present invention has the above structure, it has an excellent effect that heat generation in the center region of the tread can be suppressed without impairing wear resistance.

[Brief description of drawings]

FIG. 1 is a diagram showing a pneumatic tire according to a first embodiment of the present invention, (A) is a plan view, and (B) is a cross-sectional view taken along line 1B-1B of (A). It is a figure.

FIG. 2 is a diagram showing a pneumatic tire according to a second embodiment of the present invention, (A) is a plan view, and (B) is a cross-sectional view taken along line 2B-2B of (A). It is a figure.

FIG. 3 is a diagram showing a pneumatic tire according to a comparative example, (A) is a plan view, and (B) is 3B-3 of (A).
It is a cross-sectional view taken along the arrow B.

FIG. 4 is a diagram showing a pneumatic tire according to a conventional example, (A) is a plan view, and (B) is 4B-4 of (A).
It is a cross-sectional view taken along the arrow B.

[Explanation of symbols]

10 pneumatic tires 14 tread 14A shoulder part 16 Land (rib) 18 main groove 20A secondary groove 20B Sub groove 20C Sub groove

Claims (7)

[Claims] 1. A pneumatic tire having at least main grooves in both sides of the tread, and at least ribs in the central region of the tread, which is half the total width of the tread, in a circumferential direction of the tread. A plurality of extending sub-grooves are provided in the central area, the depth of the main groove is D, the width of the central area is W, the width of the sub-groove is K, and the depth is H, and the width of each sub-groove. A pneumatic tire characterized in that when the total sum of K and depth H is Σ (K + H), 0.15D ≦ H ≦ 0.5D 0.2W ≦ Σ (K + H) ≦ 0.4W. 2. The pneumatic tire according to claim 1, wherein when the distance between the plurality of sub-grooves is L, 0.2W ≦ L ≦ 0.4W. 3. The pneumatic tire according to claim 1 or 2, wherein the depth D of the main groove is 60 mm or more. 4. The negative ratio of the portion excluding the sub groove in the central region is set to 10% to 30%.
4. The pneumatic tire according to claim 3. 5. The pneumatic tire according to claim 1, wherein both sides of the tread have a lug pattern of a combination of a main groove and a land portion. 6. The pneumatic tire according to claim 1, wherein one sub-groove is provided so as to sandwich the center line of the tread. 7. The sub groove according to claim 1, wherein one sub groove is provided on each side of the center line of the tread, and one sub groove is provided along the center line. Pneumatic tire described.