JP2000264022A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the durability of a crown without impairing abrasion resistance of a tread of a pneumatic tire having a lug groove pattern. SOLUTION: A tread 12 generates heat when the tread 12 is repeatedly deformed by rolling of a pneumatic tire 10. An ancillary lug groove 22 formed in a center section 24 reduces heat generation around a tire equator surface CL through a reduced volume thereof, and improves heat radiation effect through an increased groove area, resulting in a suppressed temperature rise around the tire equator surface CL on rolling. In addition, a depth of the ancillary groove 22 reduced gradually toward the tire equator surface CL secures an abrasion resistance without degrading a stiffness of a tread 12.

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 pneumatic tire having a lug pattern capable of improving the durability of a crown portion used for a heavy-duty vehicle mounted on a construction vehicle or the like. The purpose is to provide.

[0002]

2. Description of the Related Art In a pneumatic tire used for a construction vehicle, a lug groove pattern having a land portion substantially continuous in a tire circumferential direction at a tire center portion is mainly used.

In such a lug groove pattern, the heat radiation effect at the tire center is small, the temperature distribution at the tire center is high, and the temperature at the shoulder is low.

[0004]

In order to improve the durability of the crown portion, it is necessary to reduce the temperature of the crown portion, that is, to improve the durability of the crown portion.
It is effective to suppress the rise in temperature due to running. Conventionally, a tread compound with low heat generation has been used, and the volume of the tread has been reduced (reduced groove depth, reduced negative ratio). Have been.

[0005] However, in the prior art, the durability (heat separation resistance and cut separation resistance) of the crown portion is improved in any case, but the wear resistance of the tread is reduced. .

The present invention has been made in consideration of the above-described circumstances, and has as its object to provide a pneumatic tire having a lug groove pattern capable of improving the durability of a tread crown portion without impairing the wear resistance of the tread. is there.

[0007]

The invention according to claim 1 has a plurality of main lug grooves extending from the shoulder side to the tire equatorial plane in the tire circumferential direction, and substantially in the tire circumferential direction in the tread central region. Pneumatic tire having a lug pattern having a land portion extending continuously to the tire, an auxiliary lug groove having a groove depth gradually decreasing toward a tire equatorial plane in a center region corresponding to within 30% of a tire contact maximum width. Is provided to extend to the main lug groove, and the negative rate of the center region is set to 10 to 35%.

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

[0009] The temperature of the tread portion is determined by the heat generated by repeated deformation (compression and bending) during rolling of the tire and the amount of heat radiation on the tire pattern surface.

In the pneumatic tire according to the first aspect, since the auxiliary lug groove is disposed in the center region of the tread, the volume of the land portion in the center region is reduced, the calorific value is reduced, and the groove area is increased ( Since the amount of heat radiation increases due to the increase in the groove peripheral), it is possible to suppress a rise in the temperature of the center region during rolling of the tire.

If the groove area in the center region is simply increased, the lug rigidity in the center region is reduced and the wear resistance is reduced. However, the groove depth of the auxiliary lug groove is gradually reduced toward the tire equatorial plane. By doing so, a decrease in rigidity can be suppressed, and wear resistance is ensured.

The pneumatic tires are used by being mounted on standard rims specified by standards issued by JATMA (Japan), TRA (US), ETRTO (Europe), etc., according to their sizes. Standard rims are usually referred to as regular rims.

[0013] In the present specification, the "regular rim" refers to a standard rim in an application size specified in the 1998 edition of YEAR BOOK issued by the American Tire and Rim Association TRA, in accordance with the conventional name.

Similarly, "regular load" and "regular internal pressure" are defined as 199 issued by the American Tire and Rim Association TRA.
Applicable size specified in the 8 year version of YEAR BOOK
Refers to the maximum load in the ply rating and the air pressure corresponding to the maximum load.

In the present specification, the "maximum tire contact width" is defined as a value obtained when a tire is assembled to a "regular rim" and filled with "regular internal pressure" and "regular load" is statically applied. Refers to the maximum width of the tread in the tire axial direction.

Here, the load is the maximum load (maximum load capacity) of a single wheel in the applicable size described in the following standard.
The internal pressure is the air pressure corresponding to the maximum load (maximum load capacity) of a single wheel in the applicable size described in the following standard, and the rim is the air pressure in the applicable size described in the following standard. Standard rim (or “Approved”
Rim "," Recommended Rim ').

The standard is determined by an industrial standard effective in a region where the tire is manufactured or used. For example, in the United States "The Tire and Rim Associa
tion Inc.'s Year Book and in Europe, "The Europea
n Standards Ma of Tire and Rim Technical Organization
nual ”and in Japan, the Japan Automobile Tire Association's“ JATM
A Year Book ".

The invention according to claim 2 has a plurality of main lug grooves extending from the shoulder side to the tire equatorial plane in the tire circumferential direction, and extends substantially continuously in the tire circumferential direction in the central region of the tread. In the pneumatic tire having a lug pattern having a land portion, the auxiliary lug groove having a groove depth gradually decreasing toward the tire equatorial plane is provided in a center region corresponding to within 30% of the maximum tire contact width. And the negative rate of the center area is set to 10 to 35%.

The temperature of the tread portion is determined by heat generated by repeated deformation (compression and bending) during rolling of the tire and the amount of heat radiation on the tire pattern surface.

In the pneumatic tire according to the second aspect, since the auxiliary lug groove is arranged in the center region of the tread, the volume of the land portion in the center region is reduced, the calorific value is reduced, and the groove area is increased ( Since the amount of heat radiation increases due to the increase in the groove peripheral), it is possible to suppress a rise in the temperature of the center region during rolling of the tire.

When the groove area in the center region is simply increased, the lug rigidity in the center region is reduced and the wear resistance is reduced. However, the groove depth of the auxiliary lug groove is gradually reduced toward the tire equatorial plane. By doing so, a decrease in rigidity can be suppressed, and wear resistance is ensured.

The auxiliary lug grooves provided independently of the main lug grooves are preferably arranged between the main lug grooves arranged at intervals in the circumferential direction.

According to a third aspect of the present invention, in the pneumatic tire according to the first or second aspect, the groove depth of the auxiliary lug groove is 45 to 70 times the maximum depth of the main lug groove.
%.

Next, the operation of the pneumatic tire according to claim 3 will be described.

Since the depth of the auxiliary lug groove is set to 45 to 70% of the maximum depth of the main lug groove, it is possible to secure the rigidity of the center region while obtaining the effect of suppressing the temperature rise in the center region.

When the depth of the auxiliary lug groove is less than 45% of the maximum depth of the main lug groove, the effect of suppressing the temperature rise is insufficient, and the groove depth of the auxiliary lug groove is less than the maximum depth of the main lug groove. 70% of
Is exceeded, the rigidity of the center region is insufficient.

According to a fourth aspect of the present invention, in the pneumatic tire according to any one of the first to third aspects,
The angle formed by the groove width center line from the width direction end of the center region of the auxiliary lug groove toward the tire equatorial plane to the tire equatorial plane is 40 to 55 °.

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

The angle formed by the groove width center line from the end of the center region of the auxiliary lug groove toward the tire equatorial plane and the tire equatorial plane is 40 to 55 °, so that the effect of suppressing the temperature rise in the center region is ensured. , Circumferential traction can be secured.

If the angle formed by the center line of the auxiliary lug groove and the tire equatorial plane exceeds 55 °, the effect of suppressing the temperature rise is insufficient, and the angle formed by the center line of the auxiliary lug groove and the equatorial plane of the tire is insufficient. If the angle is less than 40 °, traction in the circumferential direction will be insufficient.

[0031]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [First Embodiment] A first embodiment of a pneumatic tire according to the present invention will be described with reference to FIGS. 1 (A) and 1 (B).

As shown in FIGS. 1A and 1B, the tread 12 of the pneumatic tire 10 of the present embodiment has a main lug groove 20 extending from a shoulder portion 18 toward the tire equatorial plane CL. Auxiliary lug grooves 22 continuously provided at the end of the main lug groove 20 on the tire equatorial plane CL side are formed at intervals in the tire circumferential direction (arrow B direction), and in the tread central region, land portions 16 extend substantially continuously in the tire circumferential direction.

Here, in the tread 12, a region corresponding to within 30% of the maximum tire contact width W is defined as a center region 24, and regions on both sides thereof are defined as both side regions 25. Most of the auxiliary lug groove 22 is provided in the center region 24.

The negative rate of the center area 24 is set within a range of 10 to 35%.

The auxiliary lug groove 22 has a groove depth set within a range of 45 to 70% of the maximum depth D of the main lug groove 20, and has a groove depth d toward the tire equatorial plane CL. It is gradually decreasing.

The main lug groove 20 of this embodiment is inclined (the angle β with respect to the tire circumferential direction) with respect to the tire width direction (the direction of arrow A).

The auxiliary lug groove 22 extending from the end of the center region 24 toward the tire equatorial plane CL is also inclined in the same direction as the main lug groove 20, and the auxiliary lug groove extending from the end of the center region 24 toward the tire equatorial plane CL. 22 between the groove width center line GL and the tire circumferential direction (tire equatorial plane CL) is 40 to
It is set within the range of 55 °.

Since the internal structure of the pneumatic tire 10 of the present embodiment is the same as that of a normal radial tire, the description of the internal structure is omitted.

Next, the operation of the pneumatic tire 10 of the present embodiment will be described.

The pneumatic tire 10 rolls and the tread 1
When tread 2 repeatedly deforms, tread 12 generates heat,
In the pneumatic tire 10 of the present embodiment, since the auxiliary lug groove 22 is formed in the center region 24 of the tread 12, the volume near the center region 24, that is, the tire equatorial plane CL is reduced, and the volume near the tire equatorial plane CL is reduced. The heat generation amount is reduced, and the groove area (the side surface of the groove, the surface area of the bottom surface) is increased, so that the heat radiation effect is improved, and the temperature rise near the tire equatorial plane CL during rolling can be suppressed.

In the present embodiment, since the groove depth d of the auxiliary lug groove 22 is gradually reduced toward the tire equatorial plane CL, the rigidity of the tread 12 near the tire equatorial plane CL is not reduced, and the wear resistance is reduced. Nature can be secured.

Further, since the groove depth d of the auxiliary lug groove 22 is set to 45 to 70% of the maximum depth D of the main lug groove 20, the effect of suppressing the temperature rise near the tire equatorial plane CL is obtained while the tire equatorial plane is obtained. Rigidity near CL can be secured.

If the groove depth d of the auxiliary lug groove 22 is less than 45% of the maximum depth D of the main lug groove 20, the effect of suppressing the temperature rise is insufficient, and the groove depth d of the auxiliary lug groove 22 is smaller than the main lug groove depth d. Groove 2
If it exceeds 70% of the maximum depth D of 0, the tire equatorial plane CL
Insufficient rigidity in the vicinity.

The angle α between the groove width center line GL of the auxiliary lug groove 22 and the tire circumferential direction (tire equatorial plane CL) is 4
Since the angle is 0 to 55 °, traction in the circumferential direction can be obtained while obtaining an effect of suppressing a temperature rise near the tire equatorial plane CL.

If the angle α exceeds 55 °, the length of the auxiliary lug groove 34 in the center region 24 becomes short, so that the effect of suppressing the temperature rise is insufficient. If the angle α is less than 40 °, the auxiliary lug groove 34 becomes less. Since the direction (shape) of 34 approaches the circumferential groove, circumferential traction is insufficient. Second Embodiment A pneumatic tire according to a second embodiment of the present invention will be described with reference to FIGS. Note that the same components as those of the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

As shown in FIGS. 2A and 2B, the tread 12 of the pneumatic tire 30 of the present embodiment has a main lug groove 32 extending from the shoulder 18 toward the tire equatorial plane CL. The auxiliary lug grooves 34 provided independently of the main lug grooves 32 are respectively provided in the tire circumferential direction (arrow B direction).
The land portion 16 extends substantially continuously in the tire circumferential direction in the tread central region.

The auxiliary lug grooves 34 are arranged between the main lug grooves 32 arranged at intervals in the circumferential direction.

The main lug grooves 32 are provided in both side regions 25, and the auxiliary lug grooves 34 are provided in the center region 24 for the most part.

The negative rate of the center area 24 is set within a range of 10 to 35%.

The auxiliary lug groove 34 has a groove depth d set within a range of 45 to 70% of the maximum depth D of the main lug groove 32, and the groove depth d faces the tire equatorial plane CL. It is gradually decreasing.

The main lug groove 32 of this embodiment is inclined with respect to the tire width direction.

The auxiliary lug groove 34 extending from the end of the center region 24 toward the tire equatorial plane CL is also inclined in the same direction as the main lug groove 32, and the auxiliary lug groove extending from the end of the center region 24 toward the tire equatorial plane CL. The angle α between the 32 groove width center line GL and the tire circumferential direction (tire equatorial plane CL) is 40 to
It is set within the range of 55 °.

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

When the pneumatic tire 30 rolls, the tread 1
When tread 2 repeatedly deforms, tread 12 generates heat,
In the pneumatic tire 30 according to the present embodiment, since the auxiliary lug groove 34 is formed in the center region 24 of the tread 12, the volume near the center region 24, that is, the tire equatorial plane CL is reduced, and the vicinity of the tire equatorial plane CL is reduced. The heat generation amount of the groove decreases and the groove area (surface area of the groove side and bottom)
Increases, the heat radiation effect is improved, and the temperature rise near the tire equatorial plane CL during rolling can be suppressed.

In this embodiment, since the groove depth d of the auxiliary lug groove 34 is gradually reduced toward the tire equatorial plane CL, the rigidity of the tread 12 is not reduced and the wear resistance can be secured. it can.

Further, since the groove depth d of the auxiliary lug groove 34 is set to 45 to 70% of the maximum depth D of the main lug groove 32, the effect of suppressing the temperature rise near the tire equatorial plane CL is obtained, and the tire equatorial plane is obtained. Rigidity near CL can be secured.

When the groove depth d of the auxiliary lug groove 34 is less than 45% of the maximum depth D of the main lug groove 32, the effect of suppressing the temperature rise is insufficient, and the groove depth d of the auxiliary lug groove 34 is Groove 3
2 exceeds 70% of the maximum depth D, the tire equatorial plane CL
Insufficient rigidity in the vicinity.

The angle α between the groove centerline GL of the auxiliary lug groove 34 and the tire circumferential direction (tire equatorial plane CL) is 4
Since the angle is 0 to 55 °, traction in the circumferential direction can be obtained while obtaining an effect of suppressing a temperature rise near the tire equatorial plane CL.

If the angle α exceeds 55 °, the length of the auxiliary lug groove 34 in the center region 24 becomes short, so that the effect of suppressing the temperature rise is insufficient, and if the angle α is less than 40 °, the auxiliary lug groove 34 becomes less. Since the direction (shape) of 34 approaches the circumferential groove, circumferential traction is insufficient.

In this embodiment, the auxiliary lug grooves 34
Are arranged between the main lug grooves 32 which are arranged at intervals in the circumferential direction.
May be arranged on an extension of the main lug groove 32 on the tire equatorial plane CL side. (Test Example) In order to confirm the effect of the present invention, two kinds of tires of the embodiment to which the present invention was applied and one kind of conventional tire (both having a tire size of ORR18.00R25) were prepared, and an indoor drum test was performed. A heat test and an abrasion test were carried out with a machine.

Example 1 A pneumatic tire having a lug pattern shown in FIG.

Example 2 A pneumatic tire having a lug pattern shown in FIG.

Conventional Example: As shown in FIGS. 3A and 3B, a pneumatic tire having a lug pattern formed by main lug grooves 100 extending into the center region 24.

The other specifications of the test tire are as described in Table 1 below.

Heat generation test: A test tire was mounted on a regular rim (13.
00 / 2.5) with a regular internal pressure (700 kPa) and a regular load (14000 kg) and a speed of 10 km
At / h, the temperature in the center region of the tread after running for a certain period of time was measured by an indoor drum tester.

The test result of the heat generation test is represented by an index with the reciprocal of the temperature of the conventional tire being 100. The larger the numerical value, the smaller the temperature rise and the tread durability (heat generation durability). Indicates that it is excellent.

Abrasion test: A test tire was mounted on a regular rim (13.
00 / 2.5) with a regular internal pressure (700 kPa) and a regular load (14000 kg) and a speed of 10 km
At / h, the wear amount of the tread after running for a certain period of time was measured by an indoor drum tester.

The test result of the wear test is represented by an index with the reciprocal of the amount of wear of the conventional tire being 100,
The larger the numerical value, the smaller the abrasion and the higher the abrasion resistance performance.

[0069]

[Table 1]

As a result of the test, Example 1 to which the present invention was applied
In addition, the tire of Example 2 has a smaller temperature rise in the center region during rolling than the tire of the conventional example, and it is apparent from this that the tire has excellent heat generation durability.

The tires of Examples 1 and 2 to which the present invention was applied had the same abrasion resistance as the conventional tire.

[0072]

As described above, since the pneumatic tire of the present invention has the above-described structure, the durability of the crown portion of the tread can be improved without impairing the wear resistance of the tread. Has excellent effects.

[Brief description of the drawings]

FIG. 1A is a plan view of a tread of a pneumatic tire according to a first embodiment of the present invention, and FIG.
It is 1 (B) -1 (B) line sectional drawing of the tread shown in (A).

FIG. 2A is a plan view of a tread of a pneumatic tire according to a second embodiment of the present invention, and FIG.
FIG. 3 is a cross-sectional view of the tread shown in FIG.

3A is a plan view of a tread of a pneumatic tire according to a conventional example, and FIG. 3B is a cross-sectional view of the tread shown in FIG. 3A taken along line 3 (B) -3 (B). .

[Description of Signs] 10 Pneumatic tire 12 Main lug groove 16 Land portion 20 Main lug groove 22 Auxiliary lug groove 24 Center area 30 Tire equatorial plane 32 Main lug groove 34 Auxiliary lug groove

Claims (4)

[Claims] 1. A tire having a plurality of main lug grooves extending from a shoulder side to a tire equatorial plane in a tire circumferential direction,
In a pneumatic tire having a lug pattern having a land portion extending substantially continuously in a tire circumferential direction in a tread central region, a groove depth is set in a center region corresponding to within 30% of a maximum tire contact width. A pneumatic tire, wherein an auxiliary lug groove gradually decreasing toward an equatorial plane is provided to extend to the main lug groove, and a negative rate of the center region is set to 10 to 35%. 2. A tire having a plurality of main lug grooves extending from the shoulder side to the tire equatorial plane in the tire circumferential direction,
In a pneumatic tire having a lug pattern having a land portion extending substantially continuously in a tire circumferential direction in a tread central region, a groove depth is set in a center region corresponding to within 30% of a maximum tire contact width. A pneumatic tire, wherein an auxiliary lug groove gradually decreasing toward an equatorial plane is provided independently of the main lug groove, and a negative rate of the center region is set to 10 to 35%. 3. The pneumatic tire according to claim 1, wherein a groove depth of the auxiliary lug groove is 45 to 70% of a maximum depth of the main lug groove. 4. An angle between a groove width center line extending from a width direction end of the center region of the auxiliary lug groove to a tire equatorial plane and the tire equatorial plane is 40 to 55 °. The pneumatic tire according to any one of claims 1 to 3.