JP2012166719A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of improving maneuvering stability, without deteriorating partial abrasion resistance, by providing sufficient shearing rigidity, by securing belt durability.SOLUTION: This pneumatic tire includes at least a pair of circumferential directional grooves 17 by sandwiching the tire equator in a tread 13. A tread shoulder land 13a positioned on the tread outermost side partitioned by the circumferential directional grooves 17 is divided into the outside in the tire width direction and the inside in the tire width direction, and a rate B of the shoulder land inside groove volume in an inside area 18b in the tire width direction, is set larger than a rate of the shoulder land outside groove volume C in an outside area 18c in the tire width direction.

Description

  The present invention relates to a pneumatic tire, and more particularly, to a heavy-duty pneumatic tire suitable for use in trucks and buses, having a radial structure, employing a circumferential belt for maintaining the tire shape.

  Conventionally, a heavy duty radial tire that employs a circumferential belt mounted in layers in the tire circumferential direction on the outer side in the tire radial direction of the carcass, for example, an ultra flat truck / bus radial tire (Truck / Bus Radial Tire) : TBR) and the like are known.

  In recent years, in large trucks and buses, there are many examples of adopting a single tire mounting structure to reduce the fuel consumption and weight of the vehicle, and to reduce the flatness of the tire corresponding to this single mounting structure And the tread base is becoming wider. In general, a pneumatic tire with a low flatness ratio includes a belt composed of a pair of crossing belts and a circumferential belt for reinforcing the tire in the circumferential direction, so that the tire shape is maintained at a high internal pressure load, and The anti-centrifugal force and the heat resistance during running of the vehicle are improved, thereby improving the tire durability.

Thus, it is indispensable from the viewpoint of maintaining the shape of the tire to use a circumferential belt as the tire is reduced in flatness, and the load on the tire tends to increase year by year. There is also a need for improved tire durability.
Circumferential belts are highly effective in maintaining shape retention, that is, uniform growth in the tire radial direction of the tread, but since they rarely exhibit shear rigidity, In order to satisfy the demand for improved wearability, an angled belt in which a belt cord is inclined with respect to the tire equator is required. In order to determine the wear resistance of the tire, the angled belt needs to have a belt width that has a certain ratio to the tire width, and the upper and lower belt cords cross each other. Need to be.

In addition to having the function of efficiently maintaining the shape of the circumferential belt, the circumferential belt also has the function of making the ground pressure on the tread surface uniform when the tire is in contact with the load. When the width is narrow, the contact pressure on the tread surface is high in the circumferential belt arrangement region but extremely low on the outer side thereof, thereby causing uneven wear. Therefore, the belt in the circumferential direction requires a belt width that is a certain ratio or more with respect to the tread width, and the ratio (circumferential belt width / tire width) increases as the flattening of the tire proceeds.
As an example having such a circumferential belt and a crossing belt that reinforces the tire circumferential direction, for example, an “air” having a divided structure in which a tread is divided in the tire width direction and at least two kinds of rubber are arranged in the tire width direction. There is a “entered radial tire” (see Patent Document 1).

  By the way, in general, widening the belt width of each belt suppresses the occurrence of uneven wear and improves steering stability. However, when the belt width is widened in the dark clouds, the belt stretches when a load is applied to the tire. As a result, there is a risk that the cord may be cut at the end of the circumferential belt, so conventionally, the width of the crossing belt is narrowed or the width of the circumferential belt itself is narrowed, and the belt is distorted. By suppressing this, the occurrence of problems was prevented.

JP 2001-121919 A

  However, if the width of the crossing belt or the width of the circumferential belt itself is narrowed, there is a possibility that sufficient shearing rigidity may not be ensured with the crossing belt having a narrow belt width. The circumferential wear belt with a narrow belt width may lead to deterioration of uneven wear resistance, which may lead to insufficient rigidity of the entire belt. Will be worsened.

  An object of the present invention is to provide a pneumatic tire capable of ensuring belt durability and obtaining sufficient shear rigidity, without deteriorating uneven wear resistance, and improving steering stability. is there.

  In order to achieve the above object, a pneumatic tire according to the present invention is a pneumatic tire having at least a pair of circumferential grooves with the tire equator sandwiched between the treads and is located on the outermost side of the tread defined by the circumferential grooves. The shoulder land portion is divided into the tire width direction outer side and the tire width direction inner side, and the ratio of the shoulder land portion inner groove volume, which is the volume of the groove in the tire width direction inner region, is defined as the groove width in the tire width direction outer region. It is characterized by being larger than the ratio of the shoulder land outer groove volume which is the volume.

Further, in the pneumatic tire according to another aspect of the present invention, the tread is located on the outer side in the tire radial direction of the plurality of crossing belt layers, and the crossing belt layer is located on the outer side in the tire radial direction of the carcass. The shoulder land portion is located on the outer side in the tire radial direction of one circumferential belt layer, and the shoulder land portion is located on the outer side in the tire radial direction of the circumferential belt layer and the crossing belt layer.
A pneumatic tire according to another aspect of the present invention is characterized in that the outer region in the tire width direction of the shoulder land portion is 50% or less and 5% or more of the entire land portion volume.

  A pneumatic tire according to another aspect of the present invention divides an inner land portion adjacent to the shoulder land portion on the inner side in the tire width direction through the circumferential groove into a tire width direction outer side and a tire width direction inner side. The ratio of the inner land portion outer groove volume, which is the volume of the groove in the outer region in the tire width direction of the inner land portion, is smaller than the ratio of the shoulder land portion outer groove volume.

A pneumatic tire according to another aspect of the present invention divides an inner land portion adjacent to the shoulder land portion on the inner side in the tire width direction through the circumferential groove into a tire width direction outer side and a tire width direction inner side. A shoulder land portion inner groove in which the ratio of the inner land portion outer groove volume which is the volume of the groove in the tire width direction outer region of the inner land portion is the groove volume in the tire width direction inner region of the shoulder land portion. It is smaller than the volume ratio and larger than the shoulder land outer groove volume ratio.
Further, in the pneumatic tire according to another aspect of the present invention, an outer region in the tire width direction of the shoulder land portion and an outer region in the tire width direction of the inner land portion are 50% or less of the total volume of each land portion, It is characterized by being 5% or more.

According to the pneumatic tire according to the present invention, in the pneumatic tire having at least a pair of circumferential grooves with the tire equator sandwiched between the treads, a shoulder land portion located on the outermost side of the tread partitioned by the circumferential grooves is provided. Dividing into the tire width direction outer side and the tire width direction inner side, the ratio of the shoulder land portion inner groove volume that is the volume of the groove in the tire width direction inner region is the shoulder land that is the groove volume in the tire width direction outer region. Since it is larger than the ratio of the outer side groove volume, the belt durability can be ensured to obtain sufficient shear rigidity, the uneven wear resistance is not deteriorated, and the steering stability can be improved.
Further, according to the pneumatic tire according to another aspect of the present invention, the tread is positioned on the outer side in the tire radial direction of the plurality of crossing belt layers, and the crossing belt layer is positioned at least on the outer side in the tire radial direction of the carcass. The present invention can be applied to a pneumatic tire having a configuration in which one circumferential belt layer is positioned on the outer side in the tire radial direction and the shoulder land portion is positioned on the outer side in the tire radial direction of the circumferential belt layer and the crossing belt layer.

In the pneumatic tire according to another aspect of the present invention, the outer region in the tire width direction of the shoulder land portion is set to 50% or less and 5% or more of the entire volume of the shoulder land portion. When the ratio exceeds 1, the effect obtained by decreasing the groove volume ratio decreases, and when the ratio is less than 5%, the groove volume ratio increases, so that sufficient shear rigidity cannot be secured, and maneuvering is not possible. This is because it is insufficient for improving stability.
Moreover, according to the pneumatic tire according to another aspect of the present invention, the inner land portion adjacent to the shoulder land portion on the inner side in the tire width direction through the circumferential groove, the outer side in the tire width direction and the inner side in the tire width direction The ratio of the inner land portion outer groove volume, which is the volume of the groove in the tire width direction outer region of the inner land portion, is smaller than the ratio of the shoulder land portion outer groove volume, so that the lateral force is increased. And the steering stability can be further improved.

  Moreover, according to the pneumatic tire according to another aspect of the present invention, the inner land portion adjacent to the shoulder land portion on the inner side in the tire width direction through the circumferential groove, the outer side in the tire width direction and the inner side in the tire width direction The ratio of the inner land portion outer groove volume, which is the volume of the groove in the tire width direction outer region of the inner land portion, is the shoulder land, which is the groove volume in the tire width direction inner region of the shoulder land portion. Since it is smaller than the proportion of the inner groove volume and larger than the shoulder land outer groove volume, the lateral force can be reduced, and uneven shoulder wear can be further suppressed.

  Further, according to the pneumatic tire according to another aspect of the present invention, the outer width region of the shoulder land portion and the outer width direction region of the inner land portion are 50% of the total volume of each land portion. Below, 5% or more, if it exceeds 50%, the volume of the tread shoulder land part is too small, causing uneven wear on the part, but if it is less than 5%, This is because the force that promotes the tire lateral force by increasing the pattern rigidity is insufficient.

1 is a cross-sectional view along a tire width direction schematically showing a part of a configuration of a pneumatic tire according to an embodiment of the present invention. The generation | occurrence | production situation of the tire lateral force by a lateral input is shown, (a) is schematic explanatory drawing, (b) is the detailed explanatory drawing seen for every block.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view along the tire width direction schematically showing a part of the configuration of a pneumatic tire according to an embodiment of the present invention. As shown in FIG. 1, the pneumatic tire 10 is an ultra-flat radial heavy-duty tire such as a truck / bus radial tire (TBR), and the tire diameter of the carcass 11 and the carcass 11 constituting the tire skeleton. The belt 12 is located on the outer side in the tire direction, the tread 13 is located on the outer side in the tire radial direction of the belt 12, and the sidewall 14 is located on the outer side in the tire width direction of the carcass 11 following the tread 13.
The carcass 11 is bridged in a toroidal shape between a pair of left and right bead cores (not shown) having an annular structure.

  The belt 12 has a laminated structure in which at least one circumferential belt layer 15 and a plurality of intersecting belt layers 16 are arranged on the outer side in the tire radial direction of the carcass 11 in the order of description. Here, the case where the circumferential belt layer 15 is one layer and the cross belt layer 16 is two layers (16a, 16b) will be described as an example. These belt layers are formed by, for example, a strip formed by rubber coating a plurality of belt cords made of steel fiber material or organic fiber material. In particular, the circumferential belt is formed by spirally winding a narrow strip of rubber covered with several cords in the tire circumferential direction.

The circumferential belt layer 15 is disposed so that the belt cord arrangement direction is substantially parallel to the tire circumferential direction, that is, with an inclination angle of, for example, 1 ° to 2 ° with respect to the tire equator. It is desirable to form the cord with a straight cord such as a WAVY cord or a high elongation cord brazed in a wavy shape. The growth rate in the tire radial direction at the normal internal pressure at the belt end of the circumferential belt layer 15 is desirably 0.3% or less.
Here, the normal internal pressure is the air pressure defined by each tire size for each tire size. If JATMA (The Japan Automobile Tires Association, Inc.), the maximum air pressure, TRA (The Tire and Rim Association, Inc.) is the maximum value described in the table “TIRE LOAD LIMITS AT VARIOUS COLD INFRATION PRESURES”, and ETRTO (The European Tire and Rim Technical Organization) is “INFLATION PRESENCE”.

The crossing belt layer 16 includes a slant belt layer 16a having the widest belt width in the tire width direction and a belt width of the cross belt that is laminated on the outer side in the tire radial direction of the slant belt layer 16a. The layer 16 has the two-layer structure of the inclined belt layer 16b that is the second largest. The belt width (Wa) of the inclined belt layer 16a is not narrower than the belt width (L) of the circumferential belt layer 15, and the belt width (Wb) of the inclined belt layer 16b is not wider than the belt width of the circumferential belt layer 15. (See FIG. 1). That is, each belt width of the circumferential belt layer 15 and the inclined belt layers 16a and 16b is:
Inclined belt layer 16b ≦ circumferential belt layer 15 ≦ inclined belt layer 16a
Are in a relationship.

In the cross belt layer 16, the inclined belt layer 16a having the widest belt width is in contact with the normal internal pressure (the groove volume is measured under the condition of the maximum load and the maximum air pressure). The belt width is 80% to 95% with respect to the maximum distance in the tire width direction (hereinafter referred to as the maximum carcass width), the belt shape is flat, and the inclined belt layer 16a and the inclined belt 16b are The belt has a belt width difference d (see FIG. 1) of 10 to 50 mm on one side in the belt width direction.
The cross belt layers 16 are arranged such that the belt cord arrangement direction is inclined with respect to the tire circumferential direction (tire equator) at a predetermined angle, and each of the plurality of cross belt layers 16 has the belt cord arrangement direction in the tire circumferential direction. The layers are laminated so as to incline in the upper and lower layers by inclining in directions different from each other (upward or leftward).

  The tread 13 has circumferential grooves (main grooves) 17 extending along the tire circumferential direction, at least one on each side in the tire width direction across the tire equator. Here, as an example, a case will be described in which two circumferential grooves are provided on both sides in the tire width direction across the tire equator.

  As shown in FIG. 1, of the two circumferential grooves 17a and 17b, the outermost circumferential groove 17a on the outermost side in the tire width direction is the belt end portion of the inclined belt layer 16b whose belt width is narrower than the inclined belt layer 16a. The crossing belt layer 16 is positioned on the outer side in the tire radial direction so as to overlap the inclined belt layer 16b on the inner side in the tire width direction. The outermost circumferential groove 17a is disposed at the center of the opening width on the tread grounding end side from the position of 45% of the tread half width from the tread grounding end (groove volume is measured under the condition of maximum load and maximum air pressure). Preferably, the outermost circumferential groove 17a defines a tread shoulder land portion (shoulder land portion) 13a in a rib shape on the outermost side in the tire width direction of the tread 13.

Accordingly, the circumferential belt layer 15 and the inclined belt layers 16 a and 16 b reach the inner side in the tire radial direction of the tread shoulder land portion 13 a so as to be applied to the tread shoulder land portion 13 a of the tread 13.
The tread shoulder land portion 13a has a tread groove volume ratio provided across the entire tire circumferential direction on the inner and outer sides in the tire width direction divided into two in the tire width direction, that is, the groove on the entire apparent tread contact surface. Because of the formation, the proportion of the volume of the portion that is not actually grounded (groove volume proportion) is varied. The tread groove is a concave groove that forms a tread pattern, such as a sipe provided in a studless tire, and the volume is an tire having an opening area and an opening depth that are open on the tread installation surface of the tread groove. It is the volume of the entire groove over the entire circumferential direction.

The groove volume ratio, which is the ratio of the volume of the tread groove over the entire tire circumferential direction of the tread shoulder land portion 13a, is compared between the inner area and the outer area in the tire width direction, and is the groove volume ratio in the inner area in the tire width direction. The ratio of the shoulder land portion inner groove volume is made larger than the ratio of the shoulder land portion outer groove volume, which is the groove volume ratio in the outer region in the tire width direction.
Further, the tread land portion (inner land portion) 13b adjacent to the inner side in the tire width direction across the outermost circumferential groove 17a of the tread shoulder land portion 13a is also divided into two in the tire width direction, and in the outer region in the tire width direction. The shoulder land inner groove volume, which is the groove volume ratio in the inner region of the tread shoulder land portion 13a in the tire width direction, is larger than the inner land outer groove volume, which is the groove volume ratio. The land portion is divided by a perpendicular to the tire tread (the surface of the tread 11).

That is, the groove volume ratio of the outer region 18a in the tire width direction of the tread land portion 13b adjacent to the inner side in the tire width direction across the outermost circumferential groove 17a of the tread shoulder land portion 13a is A, and the tire width direction of the tread land portion 13a. When the groove volume ratio of the inner region 18b is B, and the groove volume ratio of the tire width direction outer region 18c of the tread shoulder land portion 13a is C (see FIG. 1),
B> A, B> C
And
Here, the groove volume serving as a reference for determining the groove volume ratio A and the groove volume ratio B does not include the outermost circumferential groove 17a, and the tire width direction outer region 18a (groove volume ratio A) and the tire width direction inner region 18b. The boundary of (groove volume ratio B) is the groove bottom center of the outermost circumferential groove 17a.
When the tread pattern formed on the tread 13 is a pattern composed of sipes, the number of sipes is adjusted so that B> A, and the number of sipes is further adjusted so that B> C. Is preferred.

The relationship between the groove volume ratios A, B, and C of these regions 18a, 18b, and 18c is different from the effect obtained by the relationship between the groove volume ratio A and the groove volume ratio C.
When the relationship between the groove volume ratios A, B, and C is B>A> C, the lateral input becomes the largest at the tread ground end (tread shoulder). Therefore, by increasing the groove volume ratio at the tread ground end, The driving force can be improved by increasing the force.
When the relationship between the groove volume ratios A, B, and C is B>C> A, the lateral force due to the lateral input at the tread ground contact end can be reduced to suppress the occurrence of uneven shoulder wear.

  The outer region in the tire width direction of the tread shoulder land portion 13a and the outer region in the tire width direction of the tread land portion 13b are 50% or less of the total volume of each tread shoulder land portion (block). This is because, when the outer region in the tire width direction exceeds 50%, the volume of the tread shoulder land portion is too small, causing uneven wear on the portion, but if it is 50% or less, the tread shoulder land portion This is because the volume can be secured and the occurrence of uneven wear at the portion can be suppressed.

  As described above, in the belt configuration of the pneumatic tire 10 according to the present invention, in order to improve the steering stability and suppress the occurrence of uneven wear, the wider belt width of the plurality of crossing belt layers 16 is set. The width of the carcass line is in the range of 80% to 95% and the belt width difference is 10 to 50 mm on one side in the belt width direction. The belt width of the layer 15 is also increased.

  However, if the belt width is increased as it is, the cord cut of the circumferential belt layer 15 occurs. Since the input for generating the cord break is due to the stretching of the belt of the circumferential belt layer 15 due to the stretching of the belt of the crossing belt layer 16, in order to suppress the stretching, the circumferential belt layer 15 Thus, it is effective to reduce the initial elongation generated when filling the tire with internal pressure. Therefore, if the growth in the tire radial direction at the normal inner pressure at the belt end portion of the circumferential belt layer 15 is 0.3% or less, the distortion of the belt end itself can be reduced.

The relationship between the belt widths of the circumferential belt layer 15 and the inclined belt layers 16a and 16b is as follows.
Inclined belt layer 16b ≦ circumferential belt layer 15 ≦ inclined belt layer 16a
This is because if the belt width of the circumferential belt layer 15 exceeds the belt width of the inclined belt layer 16a having the widest belt width, the failure core moves to the crossing belt layer 16 side and durability is deteriorated. If the belt width of the circumferential belt layer 15 is narrower than the belt width of the inclined belt layer 16b having the second largest belt width, the input from the cross belt layer 16 to the circumferential belt layer 15 increases, and the circumferential belt This is because the belt cord breakage of the layer 15 and the interlayer separation between the circumferential belt layer 15 and the crossing belt layer 16 occur.

At the same time, in order to ease the input from the circumferential belt layer 15, it is preferable to secure a belt end thickness (gauge: Ga.) Of 3 mm to 8 mm, particularly in the circumferential belt layer 15 where the input is concentrated. In order to secure the belt end thickness, the circumferential belt layer 15 is disposed along the carcass 11, and the crossing belt layer 16 is disposed substantially parallel to the tire width direction.
By having the configuration described above, the belt durability can be ensured and sufficient shear rigidity can be obtained. Therefore, it is not necessary to supplement the elastic modulus by arranging a rubber member around the belt 12.
In addition, by having the above-described configuration, sufficient belt rigidity can be obtained, and it is possible to achieve both improvement in steering stability and suppression of uneven wear. As described above, it was found that it is preferable to adjust the rigidity (pattern rigidity) of the tread pattern around the circumferential groove (main groove) 17 by adjusting the ratio of the groove volume in the tread shoulder land portion 13a and the tread land portion 13b. .

  FIGS. 2A and 2B show the state of occurrence of tire lateral force due to lateral input, where FIG. 2A is a schematic explanatory view, and FIG. 2B is a detailed explanatory view seen for each block. As shown in FIG. 2, when a steering angle is given to the wheels, the tire lateral force is generated by shear deformation of the tread rubber forming the tread 13 by lateral input to the tire (see (a)). Looking at the generation of tire lateral force in more detail for each block, it can be seen that deformation (see (b)) in which shear deformation due to lateral force and shear deformation due to crushing are combined has occurred. As a result, deformation in a direction that cancels the tire lateral force occurs in the tire width direction outer portion a (see (b)) of the circumferential groove (main groove) 17.

Since this deformation is unavoidable in a tire using rubber, the pattern rigidity of the outer region in the tire width direction of the circumferential groove 17 is set so as not to generate a force accompanying the deformation even if the deformation occurs. Lowering is desirable to improve steering stability.
On the other hand, the tire width direction inner portion b (see (b)) across the circumferential groove 17 opposite to the tire width direction outer portion a of the circumferential groove 17 is deformed to promote tire lateral force. Further, by increasing the pattern rigidity of the inner region in the tire width direction across the circumferential groove 17, it is possible to generate a force that further promotes the tire lateral force.

  Similarly, the outermost portion c in the tire width direction (see (b)) is also deformed to promote the tire lateral force. Therefore, by increasing the pattern rigidity of the outermost region in the tire width direction, the tire lateral force can be further increased. A conducive force is generated. However, increasing the pattern rigidity in the outermost region in the tire width direction also increases the reaction force that occurs when the tire tread 13 gets over the saddle on the road, so it is necessary to use it as necessary.

Two types of pneumatic tires 10 according to the present invention (Examples 1 and 2) were prototyped, and two types of conventional examples (conventional examples 1 and 2) were obtained with respect to the number of broken belt cords, feeling, and uneven wear amount (uneven wear vol.). A comparative test with 2) and one type of comparative example (Comparative Example 1) was performed.
Hereinafter, specifications of Examples 1 and 2, Conventional Examples 1 and 2, and Comparative Example 1 will be described with reference to Table 1. The pneumatic tires of Examples 1 and 2, Conventional Examples 1 and 2, and Comparative Example 1 are all ultra-flat radial tires for heavy loads having a tire size of 495 / 45R225.
Belt width of the inclined belt layer 16a having the widest belt width:
Example 1 is 440 mm, Example 2 is 440 mm, Conventional Example 1 is 420 mm, Conventional Example 2 is 430 mm, and Comparative Example 1 is 440 mm.

Belt width of the inclined belt layer 16b having the second largest belt width:
Examples 1 and 2 and Comparative Example 1 are all 400 mm, Conventional Example 1 is 220 mm, and Conventional Example 2 is 390 mm.
Belt width of circumferential belt layer 15:
Example 1 is 420 mm, Example 2 is 430 mm, Conventional Example 1 is 370 mm, Conventional Example 2 is 350 mm, and Comparative Example 1 is 420 mm.
Maximum width of carcass line:
Each of Examples 1 and 2, Conventional Examples 1 and 2, and Comparative Example 1 is 494 mm.

Groove volume ratio A:
Example 1 is 20%, Example 2 is 18%, Conventional Examples 1 and 2 and Comparative Example 1 are both 25%.
Groove volume ratio B:
Examples 1 and 2 are both 30%, and Conventional Examples 1 and 2 and Comparative Example 1 are both 25%.
Groove volume ratio C:
Example 1 is 20%, Example 2 is 15%, Conventional Examples 1 and 2 and Comparative Example 1 are both 25%.

The tire of the above-mentioned size (test tire) was assembled in an applicable rim having a rim size of 17.00 inches and evaluated for durability and handling stability at a regular internal pressure of 900 kPa.
Durability: The above-mentioned tire was run at 100,000 km in a drum-type running test machine at a specified load of 8500 kg and a speed of 80 km / h, and the number of belt cords in the circumferential belt layer 15 after running was examined.
Steering stability: The tire was mounted on the drive shaft of the tractor head, and a feeling evaluation was performed when the vehicle was slalomed with a trailer loaded with a constant load.
Also, for reference, the amount of uneven wear (uneven wear vol.) At the shoulder end (tread shoulder land) when the tire is mounted on the drive shaft of the tractor head and the trailer of the air load is pulled and the vehicle travels 50,000 km. The investigation confirmed the improvement in uneven wear resistance.

  Here, the applicable rim means “applied rim” defined in JATMA, “Design Rim” defined in TRA, or “Measuring Rim” defined in ETRTO. The specified load means “maximum load capacity” defined in JATMA, the maximum value of “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” defined in TRA, or “LOAD CAPACITY” defined in ETRTO.

In the pneumatic tires of Examples 1 and 2 according to the present invention, the following evaluation was made from the results of comparison with Conventional Examples 1 and 2 and Comparative Example 1 for durability (number of cords cut) and steering stability (feeling). Could be obtained (see Table 2).
Code cut number index (the smaller the number, the better):
The conventional example 1 is 100 (cont), the conventional example 2 is 131 and the comparative example 1 is 0, whereas both the examples 1 and 2 are 0 (that is, the belt cord is not cut).
Feeling index (higher is better):
The conventional example 1 is 100 (cont), the conventional example 2 is 110 and the comparative example 1 is 115, while the example 1 is 135 and the example 2 is 140.

Tread shoulder uneven wear index (the smaller the better):
The conventional example 1 is 100 (cont), the conventional example 2 is 93 and the comparative example 1 is 46, whereas the example 1 is 46 and the example 2 is 38.
As described above, the pneumatic tire 10 according to the present invention secures belt durability, obtains sufficient shear rigidity, does not deteriorate the uneven wear resistance in the land portion of the tread shoulder, and is stable in driving. Can be improved.

  According to the present invention, the durability of the belt is ensured to obtain sufficient shear rigidity, the uneven wear resistance is not deteriorated, and the steering stability can be improved, so that the tire shape is maintained. Therefore, it is suitable as a heavy duty pneumatic tire having a radial structure and suitable for use in trucks and buses.

DESCRIPTION OF SYMBOLS 10 Pneumatic tire 11 Carcass 12 Belt 13 Tread 13a Tread shoulder land part 13b Tread land part 14 Side wall 15 Circumferential belt layer 16 Crossing belt layer 16a, 16b Inclined belt layer 17 Circumferential groove 17a Outermost circumferential direction groove 18a, 18b, 18c Tire width direction region A, B, C Groove volume ratio a Tire width direction outer portion b Tire width direction inner portion c Tire width direction outermost portion d Belt width difference

Claims (6)

In a pneumatic tire having at least a pair of circumferential grooves sandwiching the tire equator with the tread,
A shoulder land portion located on the outermost side of the tread defined by the circumferential groove is divided into a tire width direction outer side and a tire width direction inner side, and a shoulder land portion inner groove volume which is a volume of the groove in the tire width direction inner region. Is greater than the ratio of the shoulder land outer groove volume, which is the volume of the groove in the outer region in the tire width direction. The tread is positioned on the outer side in the tire radial direction of a plurality of crossing belt layers, and the crossing belt layer is positioned on the outer side in the tire radial direction of at least one circumferential belt layer positioned on the outer side in the tire radial direction of the carcass.
2. The pneumatic tire according to claim 1, wherein the shoulder land portion is located on the outer side in the tire radial direction of the circumferential belt layer and the crossing belt layer.   3. The pneumatic tire according to claim 1, wherein an outer region in the tire width direction of the shoulder land portion is 50% or less and 5% or more of a total land portion volume.   An inner land portion adjacent to the shoulder land portion on the inner side in the tire width direction through the circumferential groove is divided into an outer side in the tire width direction and an inner side in the tire width direction, and a groove in a region on the outer side in the tire width direction of the inner land portion. 3. The pneumatic tire according to claim 1, wherein a ratio of the inner land portion outer groove volume, which is a volume of the inner land portion, is smaller than a ratio of the shoulder land portion outer groove volume.   An inner land portion adjacent to the shoulder land portion on the inner side in the tire width direction through the circumferential groove is divided into an outer side in the tire width direction and an inner side in the tire width direction, and a groove in a region on the outer side in the tire width direction of the inner land portion. The ratio of the inner land portion outer groove volume that is the volume of the shoulder land portion outer groove volume that is smaller than the ratio of the shoulder land portion inner groove volume that is the groove volume in the tire width direction inner region of the shoulder land portion. The pneumatic tire according to claim 1, wherein the pneumatic tire is larger.   6. The outer region in the tire width direction of the shoulder land portion and the outer region in the tire width direction of the inner land portion are 50% or less and 5% or more of the total volume of each land portion. Pneumatic tire described in 2.