JP2013212840A - Pneumatic tire for irregular ground running - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve turning performance, while maintaining traction performance at the time of straight running.SOLUTION: A pneumatic tire 1 for irregular ground running includes a plurality of blocks 4 in a tread part 2, wherein a rotational direction R is specified. The block 4 includes a center block 6, a middle block 7, and a shoulder block 8. The center block 6, the middle block 7, and the shoulder block 8 form a horizontally long shape in which a length L1 of a tire axial direction is larger than a width W1 of a tire circumferential direction, and angles Crθ, Miθ, and Shθ of respective blocks 6, 7, and 8 to the tire axial direction of a leading edge 4a of a tread 4S are limited to a predetermined range.

Description

  The present invention relates to a pneumatic tire for running on rough terrain that can improve turning performance while maintaining traction performance when traveling straight ahead.

  For example, ATV (ALL TERRAIN VEHICLE) for the purpose of traveling on rough terrain such as sand and muddy land is known. Since this ATV is not provided with a differential device mounted on a passenger car, the left and right tires rotate at the same rotational speed. Accordingly, such an ATV needs to turn while sliding while slipping at least one of the tires against the road surface.

  The pneumatic tire for running on uneven terrain mounted on the ATV is provided with a block pattern in which horizontally long blocks are formed in the tread portion. Such a block can exhibit traction performance when traveling straight. Related technologies include the following.

JP-A-1-148606

  However, since the block as described above generates a large traction with respect to rough terrain even at the time of turning, it is difficult to slide the tire while smoothly slipping the tire, and the turning performance cannot be sufficiently maintained. There was a problem.

  The present invention has been devised in view of the actual situation as described above. The center block, the middle block, and the shoulder block are formed in a horizontally long shape in which the length in the tire axial direction is larger than the width in the tire circumferential direction. Based on the fact that the length of the shoulder block is larger than the length of the center block and the middle block, a pneumatic tire for running on rough terrain that can improve turning performance while maintaining traction performance during straight traveling is provided. The main purpose is to provide.

  The present invention is a pneumatic tire for traveling on rough terrain having a plurality of blocks in the tread portion and whose rotation direction is specified, and the tread portion is 1/6 of a tread deployment width centered on the tire equator. A center area that is an area of the tread, a shoulder area that is a quarter of the tread width from the tread edge, and a middle area that is an area between the center area and the shoulder area, and the block includes the center area A center block having a centroid in the middle region, a shoulder block having a centroid in the shoulder region, and the center block, the middle block, and the shoulder block are tires. The length in the axial direction is longer than the width in the circumferential direction of the tire, and The length of the phrase, and greater than the length of the center block and the middle block.

  In the pneumatic tire for traveling on rough terrain according to the present invention, a ratio L1c / L1a between the length L1c of the shoulder block and the length L1a of the center block is 1.1 to 1.3. It is desirable.

In the pneumatic tire for traveling on rough terrain according to the present invention, it is desirable that the angle of the front edge of the tread surface of each block facing the first arrival side in the rotation direction with respect to the tire axial direction satisfies the following formula (1).
Crθ <Miθ <Shθ (1)
Here, the symbols are as follows.
Crθ: Angle of the front edge of the center block with respect to the tire axial direction Miθ: Angle of the front edge of the middle block with respect to the tire axial direction Shθ: Angle of the front edge of the shoulder block with respect to the tire axial direction

  In the pneumatic tire for traveling on rough terrain according to the present invention, the front edges of the middle block and the shoulder block may be inclined toward the rear arrival side in the rotational direction from the tire equator side toward the tread end side. desirable.

  In the pneumatic tire for running on rough terrain according to the present invention, the tread portion includes a center block row in which the center blocks are spaced in the tire circumferential direction, and a middle in which the middle blocks are spaced in the tire circumferential direction. It is desirable to provide a block row and a shoulder block row in which the shoulder blocks are spaced in the tire circumferential direction.

  In the pneumatic tire for traveling on rough terrain according to the present invention, it is preferable that the block is formed with a concave portion in which the tread surface is recessed.

In the pneumatic tire for running on rough terrain according to the present invention, the angle Crθ of the center block, the angle Miθ of the middle block, and the angle Shθ of the shoulder block are represented by the following formula (2) and the following formula: It is desirable to satisfy (3).
1.1 ≦ Miθ / Crθ ≦ 1.6 (2)
1.1 ≦ Shθ / Miθ ≦ 1.6 (3)

  In the present specification, unless otherwise specified, the dimensions of each part of the tire are shown in a no-load natural state in which a rim (not shown) is assembled and filled with an internal pressure of 30 kPa. The dimensions of each part are determined as values in this natural state.

  The pneumatic tire for running on rough terrain according to the present invention has a plurality of blocks in the tread portion, and the rotation direction is designated. The tread portion includes a center region that is 1/6 of the tread deployment width centered on the tire equator, a shoulder region that is a quarter of the tread deployment width from the tread edge, and a space between the center region and the shoulder region. It consists of the middle area which is the area.

  The block includes a center block having a centroid in the center region, a middle block having a centroid in the middle region, and a shoulder block having a centroid in the shoulder region, and the length in the tire axial direction is in the tire circumferential direction. It has a horizontally long shape larger than the width.

  Furthermore, the length of the shoulder block is larger than the length of the center block and the middle block.

  Thereby, the shoulder block can increase the edge component in the tire axial direction, and can reduce the rigidity in the tire circumferential direction. Therefore, the shoulder block can reduce the traction by increasing the deformation amount of the block at the time of turning, and can cause the tire to slip more smoothly and thus improve the turning performance.

It is an expanded view of the tread part which shows the pneumatic tire for rough terrain travel of this embodiment. It is AA sectional drawing of FIG. It is an enlarged view of FIG. (A) is an enlarged view of the center block, (b) is an enlarged view of the middle block, and (c) is an enlarged view of the shoulder block.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
In FIGS. 1 and 2, the pneumatic tire for rough terrain travel (hereinafter sometimes simply referred to as “tire”) 1 according to the present embodiment is intended to travel on rough terrain such as sand or muddy ground. A tire for ATV (ALL TERRAIN VEHICLE) is exemplified.

  The tread portion 2 of the tire 1 has a block pattern in which a plurality of blocks 4 defined by tread grooves 3 are arranged sparsely at intervals in the tire circumferential direction and the tire axial direction, and the rotation direction R is designated. It is formed.

  Such a block pattern can increase, for example, the amount of biting into the rough terrain of the block 4 and can exhibit traction performance. Further, since the tread groove 3 separating the blocks 4 is formed wide, clogging of mud and the like can be prevented.

  The sparse arrangement of the blocks 4 is such that the area of the tread surface 11v of all the blocks 4 with respect to the total area S of the outer surface of the tread portion 2 (the total area of the outer surface of the tread portion 2 when it is assumed that all of the tread grooves 3 are filled). Is obtained from the land ratio SL / S, which is the total SL of

  If the land ratio SL / S is excessively small, the traction performance on a hard hard road or medium road may not be sufficiently maintained. Conversely, even if the land ratio SL / S is too large, the traction performance on a soft road may not be sufficiently maintained. From such a viewpoint, the land ratio SL / S is preferably in the range of 20 to 30%.

  Further, the tread portion 2 of the present embodiment is a center region Cr that is a region of 1/6 of the tread deployment width TWe centered on the tire equator C, and a region that is 1/4 of the tread deployment width TWe from the tread end 2t. The shoulder region Sh includes a middle region Mi that is a region between the center region Cr and the shoulder region Sh.

  The block 4 includes a center block 6 having a centroid 6c in the center region Cr, a middle block 7 having a centroid 7c in the middle region Mi, and a shoulder block 8 having a centroid 8c in the shoulder region Sh. Thereby, in the tread portion 2, the center block row 11 in which the center block 6 is spaced in the tire circumferential direction, the middle block row 12 in which the middle block 7 is spaced in the tire circumferential direction, and the shoulder block 8 are in the tire circumferential direction. A shoulder block row 13 spaced apart from each other is provided.

  As shown in FIG. 2, the center block 6, the middle block 7, and the shoulder block 8 define a block contour extending inward in the tire radial direction from the tread surface 4 </ b> S to the groove bottom 3 </ b> B of the tread groove 3. And the block wall surface 4W to be formed. The block height H1 from the tread surface 4S of each block 6, 7 and 8 to the groove bottom 3B is set to about 12 to 16 mm, for example.

  Further, as shown in an enlarged view in FIG. 3, the tread surface 4S of each of the blocks 6, 7 and 8 includes a front edge 4a facing the first arrival side in the rotation direction R, a rear edge 4b facing the rear arrival side, and the front A pair of side edges 4c and 4c extending between the edge 4a and the rear edge 4b are included, and the length L1 in the tire axial direction is a horizontally long shape larger than the width W1 in the tire circumferential direction.

  The length L1 is measured by the maximum length in the tire axial direction of each of the blocks 6, 7, and 8. The width W1 is the maximum length in the tire circumferential direction between the front edge 4a and the rear edge 4b. Shall be measured in

  The center block 6 has a pair of center inclined portions 6A, 6A extending from the tire equator C toward the rear landing side in the rotational direction R toward the tread ends 2t, 2t on both sides.

  The center inclined portions 6A and 6A have their front edges 4a and rear edges 4b inclined in a straight line from the tire equator C toward the tread end 2t so as to incline toward the rear side in the rotational direction R, and have side edges. 4c extends in the tire circumferential direction between the front edge 4a and the rear edge 4b. Thereby, the center block 6 is formed in a substantially inverted V shape in plan view.

  The middle block 7 has a front edge 4a and a rear edge 4b that are inclined straight toward the rear side of the rotation direction R from the tire equator C toward the tread end 2t, and the side edge 4c is a front edge. 4a and the rear edge 4b extend in the tire circumferential direction. As a result, the middle block 7 is inclined from the tire equator C side to the tread end 2t side toward the rear arrival side in the rotational direction R, and is formed in a substantially parallelogram shape in plan view.

  Further, the middle block 7 of the present embodiment is cut in a substantially horizontally long shape on the outer side in the tire axial direction of the front edge 4a and the inner side in the tire axial direction of the rear edge 4b as shown in an enlarged view in FIG. A notched portion 7n is provided.

  Such a notch 7n can bend the front edge 4a and the rear edge 4b in a stepped manner to increase the length of the edge, and is useful for exerting a grip during straight travel and turning. Preferably, the length L4b of the notch 7n in the tire axial direction is, for example, 50 to 70% of the length L1b of the middle block 7, and the width W4b of the tire circumferential direction is, for example, 5 to 15 of the width W1b of the middle block 7. % Is desirable.

  Further, the corner 7ni of the notch 7n is preferably chamfered with an arc. As a result, it is possible to prevent strain from concentrating at the corner 7ni and prevent damage such as cracks.

  As shown in FIG. 3, the shoulder block 8 has a front edge 4 a and a rear edge 4 b that incline toward the rear arrival side in the rotational direction R from the tire equator C toward the tread end 2 t and linearly extend. The side edge 4c extends in the tire circumferential direction between the front edge 4a and the rear edge 4b. Thereby, like the middle block 7, the shoulder block 8 inclines from the tire equator C side to the tread end 2t side toward the rear arrival side in the rotational direction R, and is formed in a substantially parallelogram shape in plan view. .

And in this embodiment, the angle with respect to the tire axial direction of the said front edge 4a of each block 6, 7, and 8 satisfies following formula (1).
Crθ <Miθ <Shθ (1)
Here, the symbols are as follows.
Crθ: Angle of the front edge of the center block with respect to the tire axial direction Miθ: Angle of the front edge of the middle block with respect to the tire axial direction Shθ: Angle of the front edge of the shoulder block with respect to the tire axial direction

  Note that the angles Crθ, Miθ, and Shθ are respectively measured at the tread portions 2 on the left and right sides of the tire equator C. Therefore, in the case of the center block 6 straddling the tire equator C, the measurement is performed at the front edges 6a and 6a of the center inclined portions 6A and 6A respectively disposed on the left and right tread portions 2. When the front edge 4a is not formed in a straight line, the weighted average angle is weighted by the length of the front edge 4a in the tire axial direction.

  In such a block pattern, the center block 6 having a small angle Crθ can exhibit a large traction during straight traveling when the ground contact pressure of the center block 6 is relatively large, thereby improving traveling performance.

  Further, when the ATV is turning, the ground pressure of the middle block 7 and the shoulder block 8 is increased. However, since the angles Miθ and Shθ of the front edges 4a of these blocks 7 and 8 are gradually increased, these blocks are used during the turning. The traction at 7, 8 is reduced, and the slip of the tire 1 can be promoted. Therefore, the tire 1 can be smoothly slid, and as a result, turning performance can be improved.

In order to effectively exhibit the above-described action, the angle Crθ of the center block 6, the angle Miθ of the middle block 7, and the angle Shθ of the shoulder block 8 satisfy the following expressions (2) and (3). Is desirable.
1.1 ≦ Miθ / Crθ ≦ 1.6 (2)
1.1 ≦ Shθ / Miθ ≦ 1.6 (3)

  Accordingly, the angles Crθ, Miθ, and Shθ can be gradually increased gradually from the center block 6 to the shoulder block 8, and the traction performance and the turning performance at the time of straight traveling can be achieved at a high level.

  When the ratio Miθ / Crθ is less than 1.1, the inclination of the front edge 4a of the middle block 7 is not sufficient, and the tire 1 may not be able to slide smoothly. Conversely, if the ratio Miθ / Crθ exceeds 1.6, the traction in the middle block 7 may be excessively reduced. From such a viewpoint, the ratio Miθ / Crθ is more preferably 1.2 or more, and more preferably 1.5 or less.

  From the same viewpoint, the ratio Shθ / Miθ is more preferably 1.2 or more, and more preferably 1.5 or less.

  Further, the angle Crθ of the center block 6 is desirably 5 to 12 degrees. If the angle Crθ exceeds 12 degrees, the traction may not be sufficiently exhibited. On the other hand, if the angle Crθ is less than 5 degrees, there is a possibility that the traction cannot be sufficiently reduced at the initial turning.

  Moreover, in order to exhibit the traction and turning performance in a straight line with good balance, the ratio L1 / W1 between the length L1 and the width W1 of each of the blocks 6, 7, and 8 is preferably 180 to 340%.

  If the ratio L1 / W1 is less than 180%, the block rigidity becomes excessively large, traction is exhibited even during turning, and the turning performance may not be sufficiently improved. On the other hand, if the ratio L1 / W1 exceeds 340%, the block rigidity in the tire circumferential direction is excessively lowered, and there is a possibility that sufficient traction cannot be obtained. From such a viewpoint, the ratio L1 / W1 is more preferably 200% or more, and more preferably 300% or less.

  Further, as shown in FIG. 1, the ratio L1a / Wc between the length L1a of the center block 6 in the tire axial direction and the width Wc of the center region Cr in the tire axial direction is preferably 60 to 80%. If the ratio L1a / Wc is less than 60%, traction may not be obtained sufficiently. On the other hand, if the ratio L1a / Wc exceeds 80%, large traction is exhibited even during turning, and there is a possibility that sufficient turning performance cannot be obtained. From such a viewpoint, the ratio L1a / Wc is more preferably 65% or more, and more preferably 75% or less.

  Similarly, the ratio L1b / Wm between the length L1b of the middle block 7 in the tire axial direction and the width Wm of the middle region Mi in the tire axial direction is preferably 60% or more, more preferably 65% or more, Preferably, it is 80% or less, more preferably 75% or less.

  The ratio L1c / Ws between the length L1c of the shoulder block 8 in the tire axial direction and the width Ws of the shoulder region Sh in the tire axial direction (shown in FIG. 1) is preferably 50% or more, more preferably 55% or more. Desirably, it is preferably 70% or less, more preferably 65% or less.

  Further, it is desirable that the length L1c of the shoulder block 8 is formed larger than the lengths L1a and L1b of the center block 6 and the middle block 7. Thereby, the shoulder block 8 can increase the edge component of a tire axial direction, and can reduce the rigidity of a tire circumferential direction. Therefore, the shoulder block 8 can reduce the traction by increasing the deformation amount of the block at the time of turning, and can slip the tire 1 more smoothly. Preferably, the ratio (L1c / L1a) between the length L1c of the shoulder block 8 and the length L1a of the center block 6 is preferably 110 to 130%.

  If the ratio (L1c / L1a) is less than 110%, the above-described effects may not be sufficiently improved. On the contrary, even if the ratio (L1c / L1a) exceeds 130%, the deformation amount of the shoulder block 8 becomes excessively large at the time of turning, and the traction performance may not be sufficiently maintained. From such a viewpoint, the ratio (L1c / L1a) is more preferably 115% or more, and more preferably 125% or less.

  The blocks 6, 7 and 8 are preferably formed with a recess 4h in which the tread surface 4S is recessed. Such a recess 4h can relieve the rigidity of each of the blocks 6, 7, and 8 to improve road surface followability with respect to uneven terrain, and can further improve the traction performance and turning performance when traveling straight.

  Furthermore, the recess 4h of the present embodiment extends along the width center lines 6L, 7L, and 8L of the blocks 6, 7, and 8 while keeping the width W2 (shown in FIG. 4) in the tire circumferential direction constant. For this reason, the recessed part 4h can make the block rigidity of each block 6, 7, and 8 substantially uniform over a tire axial direction, and can further improve the traction performance and the turning performance at the time of going straight. Preferably, the width W2 of the recess 4h is about 15 to 35% of the width W1 of the block 4, the length L2 in the tire axial direction (shown in FIG. 4) is about 55 to 75% of the length L1 of the block 4, and the depth The length D2 (shown in FIG. 2) is preferably about 70 to 85% of the block height H1.

  Further, as shown in FIG. 2, each of the blocks 6, 7 and 8 includes a side wall surface 4Ws extending from the both sides in the tire axial direction of the tread surface 4S and the corner of the tread surface 4S by a sloped surface. It is desirable to form the catch 4t. Such a chamfered portion 4t can reduce traction during turning and can cause the tire 1 to slip smoothly. Preferably, the angle θ3 of the chamfered portion 4t with respect to the tread surface 4S is about 30 to 60 degrees, and the ratio W3 / L1 between the width W3 (shown in FIG. 3) and the block length L1 is about 5 to 10%.

  Further, as shown in FIG. 3, each block 6, 7 and 8 has a chamfer in which the corners of the front edge 4a and the side edge 4c and the corners of the rear edge 4b and the side edge 4c are cut out by slopes. The part 4u is preferably formed. Such a chamfered portion 4t can also reduce traction during turning.

  As mentioned above, although especially preferable embodiment of this invention was explained in full detail, this invention is not limited to embodiment of illustration, It can deform | transform and implement in a various aspect.

Pneumatic tires for running on rough terrain having the basic structure shown in FIGS. 1 and 2 and having the blocks specified in Table 1 were manufactured, and their performance was tested. The common specifications are as follows.
tire size:
Front wheel: AT21 × 7R10
Rear wheel: AT20 × 10R9
Rim size:
Front wheel: 10 × 5.5AT
Rear wheel: 9 × 8.0AT
Land ratio SL / S: 20-30%
Center region width Wc: 57.1 mm
Middle area width Wm: 57.1 mm
Shoulder width Ws: 83.3 mm
block:
Block height H1: 10-15mm
Recess:
Width W2: 3-5 mm, length L2: 20-30 mm, depth D2: 5-7 mm
Chamfer:
Width W3a: 2 to 5 mm, angle θ3a: 50 degrees Notch:
Length L4b: 20-25mm, Width W4b: 1-3mm
The test method is as follows.

<Traction performance and turning performance when going straight>
Each sample tire is assembled to the rim and filled with internal pressure (front wheel: 27.5 kPa, rear wheel: 30 kPa), and is mounted on the rear wheel of a 450 cc ATV (rear-wheel drive sports type four-wheel vehicle). The traction performance during straight running and the turning performance when installed and circulated in the ATV competition course were evaluated by a five-point method based on the driver's sensory evaluation. The larger the value, the better.
The test results are shown in Table 1.

  As a result of the test, it was confirmed that the pneumatic tire for running on rough terrain of the example can improve the turning performance while maintaining the traction performance when traveling straight.

1 Pneumatic tire for running on rough terrain 2 Tread 4 block 6 Center block 7 Middle block 8 Shoulder block

Claims (7)

A pneumatic tire for running on rough terrain having a plurality of blocks in the tread portion and having a designated rotation direction,
The tread portion includes a center region that is 1/6 of the tread deployment width centered on the tire equator, a shoulder region that is a quarter of the tread deployment width from the tread edge, and a center region and a shoulder region. The middle area is the area between
The block includes a center block having a centroid in the center region, a middle block having a centroid in the middle region, and a shoulder block having a centroid in the shoulder region,
The center block, the middle block, and the shoulder block have a horizontally long shape in which the length in the tire axial direction is larger than the width in the tire circumferential direction,
The pneumatic tire for running on rough terrain, wherein the length of the shoulder block is larger than the lengths of the center block and the middle block.   The pneumatic tire for rough terrain travel according to claim 1, wherein a ratio L1c / L1a between the length L1c of the shoulder block and the length L1a of the center block is 1.1 to 1.3. The pneumatic tire for running on uneven terrain according to claim 1 or 2, wherein an angle of a leading edge of the tread surface of each block facing the first arrival side in a rotation direction with respect to a tire axial direction satisfies the following formula (1).
Crθ <Miθ <Shθ (1)
Here, the symbols are as follows.
Crθ: Angle of the front edge of the center block with respect to the tire axial direction Miθ: Angle of the front edge of the middle block with respect to the tire axial direction Shθ: Angle of the front edge of the shoulder block with respect to the tire axial direction   The pneumatic tire for running on uneven terrain according to claim 1 or 2, wherein the front edges of the middle block and the shoulder block are inclined toward the rear landing side in the rotational direction from the tire equator side toward the tread end side.   The tread portion includes a center block row in which the center blocks are spaced in the tire circumferential direction, a middle block row in which the middle blocks are spaced in the tire circumferential direction, and a shoulder block in the tire circumferential direction. The pneumatic tire for rough terrain travel according to claim 1 or 2, wherein a shoulder block row is provided.   The pneumatic tire for running on uneven terrain according to claim 1 or 2, wherein the block is formed with a recess in which the tread surface is recessed. The rough terrain vehicle according to claim 3, wherein the angle Crθ of the center block, the angle Miθ of the middle block, and the angle Shθ of the shoulder block satisfy the following expressions (2) and (3). Pneumatic tires.
1.1 ≦ Miθ / Crθ ≦ 1.6 (2)
1.1 ≦ Shθ / Miθ ≦ 1.6 (3)

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