JP2003306012A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve traveling performance on a dirt road. <P>SOLUTION: Block rows Ri and Ro are formed on a tread surface 2a wherein blocks 11 are arranged to form a plurality of vertical grooves 9a and 9b continuously extending to the tire peripheral direction and a plurality of horizontal grooves 12 and 13 extending between the vertical grooves and between the vertical groove and a grounding end and inclined by an angle θ of 80 to 90° with respect to the tire peripheral direction. The block 11 is constituted by a lateral block having a ratio between the tire axial direction length A and the tire peripheral direction length B (B/A) of 0.30 to 0.70. A tread grounding width which is a tire axial direction distance between the grounding ends E is 80% or more with respect to a total tire width. <P>COPYRIGHT: (C)2004,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 suitable for rough terrain, especially for rally vehicles traveling on a dry and hard dirt road.

[0002]

2. Description of the Related Art In a pneumatic tire mounted on a rally vehicle running on rough terrain, especially on a hard dirt road, the tread surface is
A block pattern in which a large number of blocks divided by vertical grooves and horizontal grooves are provided is adopted. In addition, the block usually tends to have a square shape so as to be versatile with respect to inputs in the front-rear direction and the lateral direction.

The inventors of the present invention have conducted extensive studies on this type of tire in order to improve grip and turning ability on a hard dirt road. As a result, the angle of the lateral groove is regulated so that the block is located in the tire circumferential direction. The present invention has been completed by finding that it is effective to secure a wider tread grounding width in addition to a horizontally long shape having a large axial length.

As described above, it is an object of the present invention to provide a pneumatic tire capable of exhibiting high gripping force and turning performance when traveling on a hard dirt road.

[0005]

According to a first aspect of the present invention, a plurality of vertical grooves continuously extending in the tire circumferential direction are provided on the tread surface, between the vertical grooves, and between the vertical grooves and the ground contact. By providing a plurality of lateral grooves extending between the ends and tilting at an angle of 80 to 90 ° with respect to the tire circumferential direction, a block row is formed in which the blocks are arranged in the tire circumferential direction,
The block is a horizontally long block having a ratio (B / A) of the length A in the tire axial direction to the length B in the tire circumferential direction of 0.30 to 0.70, and the tire shaft between the tread ground contact ends. The tread contact width, which is the directional distance, is 80% of the total tire width.
It is characterized by doing the above.

Here, the "tread ground contact width" means the tire axial direction between the tread ground contact ends when the tire is assembled on a regular rim, filled with a regular internal pressure, and a regular load is applied to bring it into contact with a flat surface. Distance. The "tire total width" is the outermost position M of the sidewall portion (including patterns, projections, etc.) in the tire axial direction when the tire is assembled on a regular rim and filled with regular internal pressure, and when there is no load.
(Shown in FIG. 1) is the distance in the tire axial direction.

The "regular rim" is a rim that is defined for each tire in the standard system including the standard on which the tire is based. For example, JATMA is a standard rim, and TRA is "Design Rim". , Or ETRTO
If so, use "Measuring Rim". Also, "regular internal pressure"
Is the air pressure that each standard defines for each tire in the standard system including the standard on which the tire is based.
Maximum air pressure for TMA, and table "TIRE L for TRA.
Maximum value described in OAD LIMITS AT VARIOUS COLD INFLATION PRESSURES, or "INFLATION PRESSU for ETRTO
RE ", but 180 if the tire is for passenger cars
KPa. Furthermore, "regular load" is the load that each standard defines for each tire in the standard system including the standard on which the tire is based. For JATMA, the maximum load capacity, and for TRA, the table "TIRELOAD LIMITS AT VARIO
Maximum value stated in "US COLD INFLATION PRESSURES", ET
In case of RTO, the load will be "LOAD CAPACITY" multiplied by 0.88. Unless otherwise specified, the dimensions and the like of each part of the tire shall be specified in an unloaded state in which the tire is assembled into a regular rim and the regular internal pressure is filled.

According to a second aspect of the present invention, the vertical groove is
The total width of the groove width, which is made up of three grooves and each groove width is added, is 5 to 15% of the ground contact width of the tread, and the laterally elongated block has a ground contact area of the smallest block and a ground contact area of the largest block. It is-95%, The pneumatic tire of Claim 1 characterized by the above-mentioned.

According to a third aspect of the invention, the lateral groove is
A first lateral groove having a narrow portion with a small groove width on one end side and a wide portion with a large groove width on the other end side; and the wide portion on one end side and the other end. The pneumatic tire according to claim 1 or 2, further comprising a second lateral groove provided with the narrow portion on the side of the portion, wherein the first and second lateral grooves are alternately arranged in the tire circumferential direction. is there.

According to a fourth aspect of the present invention, the first and second lateral grooves have a narrow groove width GW1 and a wide groove width GW.
The pneumatic tire according to claim 3, wherein the ratio (GW2 / GW1) to 2 is 1.3 to 4.0.

According to a fifth aspect of the present invention, the first and second lateral grooves include at least one stepped portion having a stepwise change in groove width between the wide portion and the narrow portion. The pneumatic tire according to claim 3 or 4, characterized in that.

According to a sixth aspect of the present invention, the wide portion of the first lateral groove and the wide portion of the second lateral groove are opposed to each other on the tread surface via a vertical groove to form a substantially rectangular shape. The pneumatic tire according to any one of claims 3 to 5, characterized in that a gravel reservoir having a concave shape is provided.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view of a tire meridian including a tire shaft in an unloaded normal state in which the pneumatic tire 1 of the present embodiment is assembled to a regular rim J and filled with a regular internal pressure, and FIG. The developed view and FIG. 3 are partial perspective views of the tread portion, respectively. In the figure, a pneumatic tire 1 according to the present embodiment has a bead core 5 of a bead portion 4 from a tread portion 2 through a sidewall portion 3.
1 illustrates a radial tire for a competition rally vehicle, which includes a carcass 6 up to and a belt layer 7 arranged outside the carcass 6 in the tire radial direction and inside the tread portion 2.

The carcass 6 is composed of at least one carcass ply 6A, 6B having a radial structure in which carcass cords are arranged at an angle of, for example, 75 ° to 90 ° with respect to the tire equator C, and in this example, two carcass plies 6A, 6B. There is. As the carcass cord, a polyester cord is used in this example, but other than this, an organic fiber cord such as nylon, rayon, or aramid, or a steel cord if necessary can be used.
Further, each of the carcass plies 6A and 6B of the present embodiment is folded and locked from the tread portion 2 to the sidewall portion 3 and around the bead core 5 of the bead portion 4 from the inner side to the outer side in the tire axial direction. Further, a bead apex 8 extending from the bead core 5 to the outer side in the tire radial direction and made of hard rubber is arranged in the bead portion 4 to reinforce the bending rigidity of the bead portion 4.

The belt layer 7 has at least two belt cords arranged at a small angle of, for example, 10 to 45 ° with respect to the tire equator.
The belt plies 7A and 7B are superposed in a direction in which the cords cross each other. As the belt cord, a steel cord is used in this example, but a highly elastic organic fiber cord such as aramid or rayon can also be used if necessary.

In the pneumatic tire 1 of the present invention, the tread ground contact width TW, which is the axial distance between the tread ground contact ends E, E is 80% or more of the total tire width W, and more preferably 85.
% Or more. As described above, it is effective to secure a larger ground contact area in order to enhance the grip force on the hard dirt road. Particularly preferably, the tread ground contact width TW is 85 to 95% of the total tire width W. In this type of conventional tire, the tread ground contact width TW is 80% of the total tire width W.
Is set to less than.

The tread surface 2a is provided with a plurality of vertical grooves 9 and lateral grooves 10 extending continuously in the tire circumferential direction. The vertical groove 9 of this embodiment extends on the tire equator 1
The central vertical groove 9a of the book and the outer vertical grooves 9b, 9b arranged on both sides of the central vertical groove 9a are made up of a total of three. The total length of the groove widths g1, g2, g3 of the vertical groove 9 is 5 to 15% of the tread ground contact width TW, more preferably 8 to 13%. Thereby, the vertical groove 9
It helps prevent a decrease in the ground contact area due to, and helps prevent a decrease in grip on dirt roads. In this example, each groove width g1,
It shows an embodiment in which g2 and g3 are substantially the same. This helps prevent uneven wear. When the groove widths are different, the minimum groove width is preferably 70% or more of the maximum groove width. The vertical groove 9 of the present embodiment shows a straight line extending in the tire circumferential direction, but it may be formed in a zigzag shape or a wavy shape. Although the depth of the vertical groove 9 is not particularly limited, it is preferably 5 to 11 mm, more preferably 8 to 11 mm.

The lateral groove 10 extends between the central vertical groove 9a and the outer vertical groove 9b, and the inner lateral groove 12 extends between the outer vertical groove 9b and the tread grounding end E. And an outer lateral groove 13. Each lateral groove 10 is inclined at an angle θ of 80 to 90 ° with respect to the tire circumferential direction, and is 90 ° in the present embodiment.

By providing the vertical grooves 9 and the horizontal grooves 10 as described above, the inner block rows Ri and Ri formed on both sides of the tire equator C and the outer block rows Ro and Ro are formed on the tread surface 2a. It is formed. In addition, each block row Ri, R
o is composed of laterally long blocks 14 arranged in the tire circumferential direction such that the ratio (B / A) of the length A in the tire axial direction to the length B in the tire circumferential direction is 0.30 to 0.70.

As a result of various experiments by the inventors, the ratio (B /
It has been found that the horizontally long block 14 defined in A) as described above can generate a large traction force on a dirt road that is slippery compared to an asphalt road, and can improve the driving performance or the grip force. That is, the ratio (B / A)
However, if it is less than 0.30, the block becomes excessively long and oblong, and when the driving force or the braking force is applied, the block falls down like a hip and it is not possible to obtain sufficient traction ability. The rigidity of the block in the front-rear direction is rather too high on a slippery dirt road, and it is not possible to obtain satisfactory traction performance such as increasing slippage. Further, since the laterally elongated block 14 has increased rigidity against an input from the lateral direction, it is possible to prevent a decrease in grip force during cornering. In order to further enhance these effects, the ratio (B / A) is particularly preferably set to 0.
It is desirable to set it to 4 to 0.6.

Further, in this embodiment, the horizontally long blocks 14 arranged in the inner block row Ri are the outer block rows R.
The ground contact area is larger than that of the horizontally long block 14 arranged at o. A higher ground pressure tends to act on the inner block row Ri than on the outer block row Ro. Therefore, by varying the ground area of the blocks as described above, the forces acting on the blocks are made uniform. And helps improve wear resistance. However, in each horizontally long block 14, when the difference in the ground contact area becomes excessively large, the wear resistance may be deteriorated. Therefore, when the ground contact area of each block is different, the ground contact area of the smallest block is the ground contact area of the largest block. It is desirable to set it to be 75 to 95%.

The lateral groove 12 in the present embodiment has a narrow portion 12n having a small groove width at one end and a wide portion having a large groove width at the other end, as shown in FIG. 3, for example. The first lateral groove 12A provided with 12w, and the second lateral groove 12B provided with the wide portion 12w on one end side and the narrow portion 12n provided on the other end side, First and second lateral grooves 1 therein
2A and 12B are arranged alternately in the tire circumferential direction.

Further, in the present embodiment, the first and second lateral grooves 12A and 12B in the inside are the wide portion 12w and the narrow portion 1 respectively.
Two step portions 12 in which the groove width changes in a step shape between 2n
d1 and 12d2 are included. For example, in FIG. 2, the narrow portion 12n extends from the one end side with the groove width GW1 and has the groove width GW through the step-like first step portion 12d1.
Expand to 3. Then, the groove width is further expanded to GW2 through the second step portion 12d2 to widen the wide portion 1 having the largest groove width.
2w is formed.

In the inner block row Ri, the first and second lateral grooves 12A and 12B having the above-mentioned step portion 12d are alternately provided in the tire circumferential direction, so that the laterally long block 1 is formed.
1 is stepwise as shown in FIG. As shown in FIG. 4 (A), such a horizontally long block 11 has improved rigidity against the traction direction force F as compared with the block b in which the ground contact surface simply has a horizontally long rectangular shape. Therefore, so-called stability such as shape stability or shape restoration of the horizontally long block 11 can be improved and durability can be improved.

Further, in the first and second lateral grooves 12A, 12B, the wide portion 12w having a wide groove width can enhance the gripping force by increasing the biting force into the dirt road, but its reflective effect is wear performance. Is easy to get worse. However, the wide part 12
Narrow portion 1 with a small groove width on the opposite side of w to improve wear resistance
By providing 2n, the grip force and the wear resistance on the dirt road can be improved in a better balance. Furthermore, at the time of tire skidding such as drifting,
Since the edge e (shown in FIG. 4B) of the step portion 12d is oriented substantially at right angles to the sliding direction, a high frictional force can be exerted with the dirt road, and the turning ability is further improved. To help.

In order to more surely exhibit the above-mentioned action, it is preferable that the first and second lateral grooves 12A, 12 be formed.
In B, the groove width GW1 of the narrow portion 12n and the wide portion 12n
The ratio of w to the groove width GW2 (GW2 / GW1) is 1.3-
It is desirable to set it to 4.0, particularly preferably to about 1.8 to 4.0. In order to secure the minimum groove width, it is preferable to set the groove width GW1 of the narrow portion 12n to, for example, 3 to 10 mm, more preferably 5 to 8 mm. The depth of the lateral groove 12 is not particularly limited, but is preferably 5 to 11 mm, more preferably 7 to 11 mm.

Like the inner lateral groove 12, the outer lateral groove 13 of this embodiment has a narrow portion 13n having a small groove width at one end and a wide groove having a large groove width at the other end. While including an outer first lateral groove 13A provided with a portion 13w and an outer second lateral groove 13B having the wide portion 13w on one end side and the narrow portion 13n on the other end side , The outer first and second lateral grooves 1
3A and 13B are arranged alternately in the tire circumferential direction. Further, each of the first and second lateral grooves 13A, 13B includes one step portion 13d. Therefore, the same effect as the inner block row Ri can be obtained for the outer block row Ro.

Further, in the pneumatic tire 1 of this embodiment,
By enlarging the wide portion 13w of the outer first lateral groove 13A and the wide portion 12w of the inner second lateral groove 12B through the outer vertical groove 9b, as shown enlarged in FIG. A gravel reservoir 16 is provided which has a substantially rectangular shape and is recessed. The dirt road contains many so-called floating gravel portions where gravel is accumulated on the surface. Therefore, when traveling on such a floating gravel portion, the floating gravel is taken into the groove of the tire, and the tire is in a floating state. This makes it difficult to generate a traction force between the hard road surface under the gravel and the tread surface 2a. In the present embodiment, by providing the gravel reservoir 16 as described above, a large amount of floating gravel is taken into the gravel reservoir 16 to reduce the amount of floating of the tire. This is effective for ensuring frictional contact between the hard road surface under the gravel and the tire and improving traction performance.

From this point of view, the gravel reservoir 16 is
As shown in FIG. 5, a wide portion 13w, 1 facing the vertical groove 9,
The area Sa formed by 2w 1.5~5.0cm ^2, more preferably it is desirable to about ² 2.0～3.0Cm. Further, at least two such gravel reservoirs 16, more preferably 3 or more, still more preferably 3 to 3 are formed in the ground contact surface where the tire 1 is assembled on a regular rim and a regular internal pressure is filled to apply a regular load. It is desirable to determine the arrangement pitch of the lateral grooves and the like so as to include six. This is because if it is too small, the floating gravel intake effect is small, and if it is too large, the ground contact area is reduced. Further, since the gravel reservoir 16 is a concave portion, it is desirable to provide it along the outer vertical groove 9b as in this example rather than the tire equator side where the driving force is more effectively exerted.

[0030]

[Example] A pneumatic tire for rally having a tire size of 205 / 65R15 was prototyped based on the pattern shown in Table 1 and FIG. 2 and tested for traction performance, turning performance, grip feeling, durability and the like.

For the traction performance, turning performance, and grip feeling, the test tire was mounted on a 7J × 15 rim and the internal pressure was 210
Filled with kPa and mounted on all wheels of a four-wheel drive vehicle for rally competition with a displacement of 2000 cm ³ , run 5 laps on a dry, hard dirt test course (1 lap, about 2.5 km),
The test driver's sensory evaluation was performed by a 10-point method. As for the durability, the wear when traveling on a dirt course for 300 km was visually examined and indexed to a 10-point method.
In all cases, the larger the value, the better. The test results are shown in Table 1.

[0032]

[Table 1]

[0033]

As described above, in the pneumatic tire of the present invention, the tread ground contact width is increased as compared with the conventional tire, and the angle of the lateral groove is defined so that the tire circumferential length and the tire axial length can be increased. Since it has a horizontal block with a limited ratio of, it produces a large traction force on the dirt road,
Driving performance or grip power can be improved. Further, since the laterally elongated block has increased rigidity against lateral input, it is possible to prevent a decrease in grip force during cornering.

According to the second aspect of the present invention, the number of vertical grooves is limited, and the total width of the vertical grooves is set to 5 to 15% of the tread ground width. To prevent the above-mentioned effects from becoming more reliable. Further, in the horizontally long blocks, the ground contact area of the smallest block is set to 75 to 95% of the ground contact area of the largest block, and the size of the entire block can be made uniform. Therefore,
This helps to equalize the forces acting on each block, and thus prevent uneven wear.

Further, as in the invention described in claims 3 to 4, the lateral groove has a narrow portion having a small groove width on one end side and a wide portion having a large groove width on the other end side. A first lateral groove and a second lateral groove having the wide portion on one end side and the narrow portion provided on the other end side; and the first and second lateral grooves in the tire circumferential direction. When arranged alternately, the stability of the oblong block,
In addition, so-called stability such as shape restoration is improved, and durability can be increased. The wide part of the lateral groove is
The gripping force can be improved by increasing the biting force on the road surface, and a narrow portion with high wear resistance can be provided at the opposite end to improve both performances in a well-balanced manner.

According to the invention of claim 5, the first,
When the second lateral groove includes at least one step portion in which the groove width changes stepwise between the wide portion and the narrow portion, when the tire laterally slides, such as drifting, the second lateral groove is formed by the edge of the step portion. It is possible to exert a high frictional force with the dirt road, which helps to further improve the turning ability.

According to a sixth aspect of the present invention, the wide portion of the first lateral groove and the wide portion of the second lateral groove are opposed to each other on the tread surface through the vertical groove, thereby substantially reducing When a rectangular gravel reservoir is provided, it is useful for taking up gravel in the ground contact surface into this portion in a dirt road with a large amount of floating gravel to prevent the tire from rising and to improve traction performance.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a tire showing an embodiment of the present invention.

FIG. 2 is a development view showing a development of the tread surface.

FIG. 3 is a perspective view of a block.

4 (A) and (B) are more preferably plan views of a horizontally long block.

FIG. 5 is an enlarged view of a gravel reservoir.

[Explanation of symbols]

1 pneumatic tire 2 tread section 3 Side wall part 4 bead part 5 bead core 6 carcass 6A carcass ply 6a Carcass ply body 6b Carcass ply turns 7 Belt layer 9 flutes 9a Central vertical groove 9b Outer vertical groove 10 lateral grooves 11 Horizontal blocks Lateral groove in 12 First lateral groove within 12A Second lateral groove in 12B 13 lateral groove First lateral groove outside 13A Second lateral groove outside 13B 14 Horizontal blocks 16 Gravel Reservoir

Claims (6)

[Claims] 1. A plurality of vertical grooves extending continuously on the tread surface in the tire circumferential direction, and extending between the vertical grooves and between the vertical groove and the ground contact end, and 80 to 90 in the tire circumferential direction. By providing a plurality of lateral grooves inclined at an angle of °, the blocks form a row of blocks arranged in the tire circumferential direction, and the blocks have a length A in the tire axial direction and a length B in the tire circumferential direction. It is composed of a horizontally long block having a ratio (B / A) of 0.30 to 0.70, and a tread contact width, which is a tire axial distance between the tread contact ends, is 80% or more of the total tire width. Pneumatic tires. 2. The vertical groove is composed of three grooves, and the total groove width obtained by adding the groove widths together is 5 to 15% of the tread ground contact width.
2. The pneumatic tire according to claim 1, wherein the horizontal block has a ground contact area of the smallest block being 75 to 95% of a ground contact area of the largest block. 3. A first lateral groove having a narrow portion having a small groove width at one end side and a wide portion having a large groove width at the other end side, and the lateral groove at one end side thereof. A second lateral groove having a wide portion and having the narrow portion on the other end side is included, and the first and second lateral grooves are alternately arranged in the tire circumferential direction. Or the pneumatic tire according to 2. 4. The first and second lateral grooves have a groove width G of a narrow portion.
Ratio of W1 and wide groove width GW2 (GW2 / GW1)
Is 1.3 to 4.0, The pneumatic tire according to claim 3, wherein. 5. The first and second lateral grooves include at least one stepped portion having a stepwise change in groove width between the wide portion and the narrow portion. The pneumatic tire according to 3 or 4. 6. A gravel collecting portion which is recessed in a substantially rectangular shape by making the wide portion of the first lateral groove and the wide portion of the second lateral groove face each other on the tread surface via a vertical groove. The pneumatic tire according to any one of claims 3 to 5, further comprising: