JP2022098190A - tire - Google Patents

Abstract

To provide a tire improved in center wear resistance.SOLUTION: A tire 1 is provided with a plurality of lateral grooves 3 joining tread ends Te at both sides to each other. The lateral groove 3 includes a pair of outer groove parts 8 extending to inside in a tire axial direction, from the tread ends Te toward a tire equator C side and an inner groove part 9 joining the pair of outer groove parts 8 to each other. The pair of outer groove parts 8 are inclined in the same direction with respect to the tire axial direction. The inner groove part 9 is inclined in a direction opposite to the direction of the outer groove parts 8 with respect to the tire axial direction. A groove depth d2 of the inner groove part 9 is smaller than groove depths d1 of the outer groove parts 8.SELECTED DRAWING: Figure 1

Description

The present invention relates to a tire.

In Patent Document 1 below, a plurality of lug main grooves extending in the tire width direction and opening at the tread end on both sides of the tire equator and the lug main grooves located on both sides of the tire equator are connected to each other in the tread portion. Pneumatic tires with center tread grooves are described.

Japanese Unexamined Patent Publication No. 2018-16772

For tires that have many opportunities to run on rough roads, for example, pneumatic tires for trucks, the contact shape of the tread portion changes greatly depending on the load capacity. In particular, in the pneumatic tire mounted on the drive wheel, there is a problem that a large contact pressure acts on the tread crown portion when the tire is empty, and center wear is likely to occur.

The present invention has been devised in view of the above circumstances, and an object of the present invention is to provide a tire capable of effectively suppressing center wear, particularly an OR (off-the-road) tire.

The present invention is a tire having a tread portion, and the tread portion is provided with a plurality of lateral grooves connecting the tread ends on both sides, and each of the lateral grooves extends inward in the tire axial direction from the tread ends on both sides. The pair of outer grooves and the inner groove connecting the pair of outer grooves are included, and the pair of outer grooves are inclined in the same direction with respect to the tire axial direction, and the inner groove is inclined with respect to the tire axial direction. The inner groove portion is inclined in the opposite direction to the outer groove portion, and the groove depth of the inner groove portion is smaller than the groove depth of each of the pair of outer groove portions.

In the tire according to the present invention, it is desirable that the groove depth of the inner groove portion is 65% to 85% of the groove depth of the outer groove portion.

In the tire according to the present invention, it is desirable that the angle of the inner groove portion with respect to the tire axial direction is 20 to 50 degrees.

In the tire according to the present invention, the outer groove portion is connected to the first portion extending from the tread end toward the tire equator side to the first portion and is inclined at a larger angle with respect to the tire axial direction than the first portion. It is desirable to include the second part.

In the tire according to the present invention, it is desirable that the groove width of the inner groove portion is smaller than the groove width of the first portion.

In the tire according to the present invention, it is desirable that the groove width of the inner groove portion is 60% to 80% of the groove width of the first portion.

In the tire according to the present invention, it is desirable that the length of the first portion in the tire axial direction is 5% to 20% of the tread width.

It is desirable that the tire according to the present invention has an angle of the first portion with respect to the tire axial direction of 10 degrees or less.

It is desirable that the tire according to the present invention has an angle of the second portion with respect to the tire axial direction of 10 to 30 degrees or less.

In the tire according to the present invention, the tread portion includes a crown region having a width in the tire axial direction of 40% of the tread width from the equator of the tire to both sides in the tire axial direction, and the inner groove portion is provided in the crown region. , Is desirable.

In the tire according to the present invention, it is desirable that the tread portion is provided with a first joint groove connecting the inner groove portions of the lateral grooves adjacent to each other in the tire circumferential direction.

In the tire according to the present invention, it is desirable that the groove depth of the first joint groove is smaller than the groove depth of the inner groove portion.

In the tire according to the present invention, it is desirable that the first joint groove includes a widening portion in which the groove width increases toward the inner groove portion.

In the tire according to the present invention, it is desirable that the widened portion is connected to the inner groove portion.

In the tire according to the present invention, it is desirable that the length of the widened portion is 10% to 40% of the length of the first joint groove.

In the tire according to the present invention, it is desirable that the tread portion is provided with a second joint groove connecting the outer groove portions of the lateral grooves adjacent to each other in the tire circumferential direction.

In the tire according to the present invention, it is desirable that the outer groove portion is provided with a protrusion for preventing stone biting at the groove bottom where the second joint groove is connected.

It is desirable that the tire according to the present invention is for a heavy load.

By adopting the above configuration, the tire of the present invention can suppress center wear.

It is a top view of the tread part which shows one Embodiment of this invention. FIG. 3 is a cross-sectional view taken along the line AA of FIG. It is a top view of the tread part. It is a top view of the tread part.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a plan view of a tread portion 2 of a tire 1 showing an embodiment of the present invention. The present invention is applied to, for example, OR tires for heavy loads, which often travel on rough roads such as dirt roads. However, the present invention can be applied to pneumatic tires for passenger cars and light trucks, or non-pneumatic tires that are not filled with compressed air.

As shown in FIG. 1, in the tire 1 of the present embodiment, the tread portion 2 is provided with a plurality of lateral grooves 3 connecting the tread end Tes on both sides. As a result, the tread portion 2 is provided with a plurality of land portions 4 arranged between the lateral grooves 3 adjacent to each other in the tire circumferential direction.

In the present specification, the "tread end Te" means the most outer contact position in the tire axial direction when a normal load is applied to the tire 1 in a normal state and the tire 1 is grounded on a flat surface at a camber angle of 0 degrees. .. The distance in the tire axial direction between the tread end Tes on both sides is the tread width TW.

The "normal state" is a state in which, in the case of a pneumatic tire for which various standards are defined, the tire is rim-assembled on a normal rim (not shown), the normal internal pressure is filled, and there is no load. In the present specification, unless otherwise specified, the dimensions and the like of each part of the tire are values measured in the normal state.

A "regular rim" is a rim defined for each tire in the standard system including the standard on which the tire is based. For example, "standard rim" for JATMA and "Design Rim" for TRA. If it is ETRTO, it is "Measuring Rim".

"Regular internal pressure" is the air pressure defined for each tire in the standard system including the standard on which the tire is based. For JATMA, "maximum air pressure", for TRA, the table "TIRE LOAD LIMITS AT" The maximum value described in "VARIOUS COLD INFLATION PRESSURES", or "INFLATION PRESSURE" for ETRTO.

"Regular load" is the load defined for each tire in the standard system including the standard on which the tire is based, in the case of pneumatic tires with various standards, and in the case of JATMA, "maximum" Load capacity ", TRA is the maximum value listed in the table" TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES ", ETRTO is" LOAD CAPACITY ".

Each of the lateral grooves 3 includes a pair of outer groove portions 8 extending inward in the tire axial direction from the tread ends Te on both sides, and an inner groove portion 9 connecting the pair of outer groove portions 8. The pair of outer groove portions 8 are inclined in the same direction (upward to the right in the figure) with respect to the tire axial direction. The inner groove portion 9 is inclined in the direction opposite to the outer groove portion 8 (downward to the right in the figure) with respect to the tire axial direction. Such a lateral groove 3 disperses the load during traveling in a plurality of directions, suppresses slip deformation of the tread portion 2, and suppresses wear of the land portion 4.

FIG. 2 is a cross-sectional view taken along the line AA of FIG. As shown in FIG. 2, the groove depth d2 of the inner groove portion 9 is smaller than the groove depth d1 of each of the pair of outer groove portions 8. As a result, when traveling straight, the rigidity of the land portion 4 on the tire equator C side on which a relatively larger contact pressure acts than the land portion 4 on the tread end Te side is maintained high, so that center wear is particularly suppressed. Can be done. In the present specification, such tire performance is referred to as "center wear resistance". Further, the land portion 4 on the tire equator C side is in contact with the road surface even in a low load load state as compared with the land portion 4 on the tread end Te side. In this respect, in the present embodiment, since the groove depth d2 of the inner groove portion 9 is small, the stone biting into the inner groove portion 9 is suppressed, so that excellent stone biting resistance performance is exhibited especially in a low load load state. Will be done. The "low load load state" is a state in which a load of 30% or less of the normal load is applied to the tire 1 in the normal state.

In order to exert the above-mentioned action, the groove depth d2 of the inner groove portion 9 is preferably 85% or less of the groove depth d1 of the outer groove portion 8, and more preferably 80% or less. If the groove depth d2 of the inner groove portion 9 is excessively small, the running performance (traction) on a rough road may deteriorate. Therefore, the groove depth d2 of the inner groove portion 9 is preferably 65% or more, and more preferably 70% or more of the groove depth d1 of the outer groove portion 8. Although not particularly limited, the groove depth d2 of the inner groove portion 9 is preferably, for example, 17 mm or more, more preferably 19 mm or more, more preferably 25 mm or less, and further preferably 23 mm or less.

As shown in FIG. 1, the tread portion 2 includes a crown region Cr having a width in the tire axial direction of 40% of the tread width TW from the tire equatorial line C to both sides in the tire axial direction, a crown region Cr, and a tread end Te. Includes a pair of shoulder treads Sh arranged between. The crown region Cr is a region on which a ground pressure relatively larger than the shoulder region Sh acts when traveling straight.

The tread portion 2 of the present embodiment further includes a first joint groove 6 that connects the inner groove portions 9 adjacent to each other in the tire circumferential direction, and a second joint groove 7 that connects the outer groove portions 8 adjacent to each other in the tire peripheral direction. It has been. The second joint groove 7 is arranged on both sides of the tire equator C in this embodiment. As a result, the land portion 4 of the present embodiment has a pair of inner blocks 4A sandwiched between the first joint groove 6 and the second joint groove 7, and a pair of outer sides sandwiched between the second joint groove 7 and the tread end Te. It is divided into block 4B.

The pitch P1 in the tire circumferential direction of the lateral groove 3 is preferably 20% or more, more preferably 25% or more, preferably 40% or less, and further preferably 35% or less of the tread width TW. Since the pitch P1 of the lateral groove 3 is 20% or more of the tread width TW, the rigidity of the tread portion 2 is maintained high and the wear is suppressed, so that the center wear resistance performance and the life performance are enhanced. Since the pitch P1 of the lateral groove 3 is 40% or less of the tread width TW, a large traction can be exhibited and the running performance on a rough road is enhanced.

FIG. 3 is a plan view of the tread portion 2 of the present embodiment. As shown in FIG. 3, the outer groove portion 8 is connected to the first portion 10 extending from the tread end Te toward the tire equator C side and the first portion 10, and has a larger angle with respect to the tire axial direction than the first portion 10. It includes a second portion 11 that is inclined at θ1b. In the present specification, the groove angle is measured at the groove width center line.

The groove width W1 of the outer groove portion 8 of the present embodiment becomes smaller from the tread end Te toward the tire equator C side. The groove width W1 of the outer groove portion 8 is continuously reduced, for example, from the outer end 8e in the tire axial direction to the inner end 8i in the tire axial direction. Such an outer groove portion 8 maintains high rigidity of the tread portion 2 on the tire equator C side, and enhances center wear resistance. Further, even when stone biting occurs, the outer groove portion 8 can discharge stones from the tread end Te having a large groove width W1 by utilizing the rolling of the tire 1, so that the stone biting resistance is improved.

In the present embodiment, the first portion 10 and the second portion 11 are connected to each other via a bent portion 8k. Such a bent portion 8k disperses the load during traveling to improve the uneven wear resistance performance, and also suppresses block chipping that tends to occur at the tread end Te. The first portion 10 and the second portion 11 extend, for example, in a straight line. In the present embodiment, the bent portion 8k is arranged in the shoulder region Sh (shown in FIG. 1). As a result, the above-mentioned action is effectively exerted. In the outer groove portion 8, the first portion 10 and the second portion 11 may be connected in an arc shape (not shown).

The length La of the first portion 10 in the tire axial direction is preferably 5% or more, more preferably 10% or more, preferably 20% or less, and further preferably 15% or less of the tread width TW. Since the length La of the first portion 10 is 5% or more of the tread width TW, the effect of ejecting stones from the tread end Te is high. The stone bitten in the outer groove portion 8 is smoothly discharged by using the first portion 10. Since the length La of the first portion 10 is 20% or less of the tread width TW, an excessive decrease in the rigidity of the crown region Cr is suppressed.

In the present embodiment, the first portion 10 is inclined with respect to the tire axial direction. Since such a first portion 10 disperses the load in the tire circumferential direction during straight-ahead traveling, the life performance is improved. If the angle θ1a of the first portion 10 with respect to the tire axial direction is excessively large, the rigidity of the land portion 4 in the vicinity of the first portion 10 in the tire axial direction becomes small, and block chipping is likely to occur, so that the life performance is rather deteriorated. There is a risk. From such a viewpoint, the angle θ1a of the first portion 10 is preferably larger than 0 degrees, preferably 10 degrees or less, and more preferably 5 degrees or less.

The groove width W1b of the second portion 11 is preferably 70% or more, more preferably 75% or more, more preferably 90% or less, still more preferably 85% or less of the groove width W1a of the first portion 10. As a result, the rigidity of the tread portion 2 on the tire equator C side and the rigidity of the tread portion 2 on the tread end Te side are maintained in a well-balanced manner, and the life performance is improved. The groove width W1a of the first portion 10 and the groove width W1b of the second portion 11 are average values of the maximum groove width and the minimum groove width, respectively.

The angle θ1b of the second portion 11 with respect to the tire axial direction is preferably 10 degrees or more, and more preferably 15 degrees or more. As a result, the load in the tire circumferential direction during straight running can be more dispersed. The angle θ1b of the second portion 11 is preferably 30 degrees or less, and more preferably 25 degrees or less. As a result, the tire axial rigidity of the land portion 4 in the vicinity of the second portion 11 is maintained, and chipping and chipping of the tread portion 2 due to turning running are suppressed. Although not particularly limited, the difference (θ1b−θ1a) between the angle θ1b of the second portion 11 and the angle θ1a of the first portion 10 is preferably 5 degrees or more, more preferably 10 degrees or more, and 25 degrees or less. Is desirable, and 20 degrees or less is even more desirable.

The outer groove portion 8 is provided with a protrusion 12 for preventing stone biting at the groove bottom 8s in which the second joint groove 7 is connected. The protrusion 12 extends outward in the radial direction of the tire, for example, apart from the groove wall of the outer groove portion 8.

In the present embodiment, the protrusion 12 is provided on the groove bottom 11s of the second portion 11. As a result, stone biting in the second portion 11 where stones are less likely to be discharged than in the first portion 10 is suppressed. The protrusion 12 is not provided on, for example, the first portion 10 extending from the tread end Te. Further, in the present embodiment, the protrusion 12 is not provided in the inner groove portion 9 having a small groove depth.

The protrusion 12 includes a pair of outer protrusions 13 arranged on both sides in the longitudinal direction, and an inner protrusion 14 connecting the pair of outer protrusions 13. The inner protrusion 14 of the present embodiment is formed with a width smaller than that of the outer protrusion 13. Such protrusions 12 are useful for the inner protrusions 14 to increase the rigidity of the outer protrusions 13 to suppress deterioration of stone biting resistance and to improve traction on rough roads.

The outer protrusion 13 of the present embodiment is arranged on a virtual straight line 7k in which the groove center line 7c of the second joint groove 7 is smoothly extended in the longitudinal direction thereof. As a result, the decrease in the rigidity of the land portion 4 near the second joint groove 7 (the rigidity in the groove width direction of the second joint groove 7) is suppressed, and the deformation of the second joint groove 7 is suppressed, so that the second joint is suppressed. The biting of stones into the groove 7 is reduced. In the present embodiment, the outer protrusions 13 are arranged on both sides of the second joint groove 7 in the longitudinal direction.

Although not particularly limited, the width Wb of the inner protrusion 14 is preferably 20% or more, more preferably 30% or more, more preferably 50% or less, and further 40% or less of the width Wa of the outer protrusion 13. desirable. Further, the width Wa of the outer protrusion 13 is preferably 10% or more, more preferably 15% or more, more preferably 30% or less, and further preferably 25% or less of the maximum groove width W1 m of the second portion 11.

In order to improve the stone biting resistance performance, the length L2 of the protrusion 12 in the tire axial direction is preferably 35% or more, and more preferably 40% or more of the length Lb in the tire axial direction of the second portion 11. In order to maintain the traction performance on rough roads, the length L2 of the protrusion 12 is preferably 55% or less, and more preferably 50% or less of the length Lb of the second portion 11.

In order to effectively exert the above-mentioned action, the protrusion height h of the protrusion 12 is preferably 10% or more, more preferably 12% or more, and more preferably 20% or more of the groove depth d1 (shown in FIG. 2) of the outer groove portion 8. % Or less is desirable, and 18% or less is even more desirable.

The inner groove portion 9 of the present embodiment is provided in the crown region Cr (shown in FIG. 1). The inner groove portion 9 is arranged so as to straddle the tire equator C, for example. As a result, the stone biting resistance and the center wear resistance are further enhanced. The length Lc of the inner groove portion 9 in the tire axial direction is preferably 10% or more, more preferably 15% or more, more preferably 35% or less, and further preferably 30% or less of the tread width TW.

It is desirable that the angle θ2 of the inner groove portion 9 with respect to the tire axial direction is larger than the angle θ1b of the second portion 11. Since such an inner groove portion 9 can further disperse the load during traveling in the crown region Cr on which a relatively large contact pressure acts, the center wear resistance performance can be further improved. If the angle θ2 of the inner groove portion 9 is large, the traction becomes small, and the running performance on a rough road may deteriorate. Therefore, the angle θ2 of the inner groove portion 9 is preferably 20 degrees or more, more preferably 30 degrees or more, more preferably 50 degrees or less, and even more preferably 40 degrees or less.

The groove width W2 of the inner groove portion 9 is formed to be smaller than the groove width W1a of the first portion 10, for example. Such an inner groove portion 9 further maintains the rigidity of the land portion 4 (inner block 4A) of the crown region Cr to be higher, and improves the center wear resistance performance. In the present embodiment, the inner groove portion 9 extends in the longitudinal direction with the same groove width W2.

In order to effectively exert the above-mentioned action, the groove width W2 of the inner groove portion 9 is preferably 80% or less of the groove width W1a of the first portion 10, and more preferably 75% or less. If the groove width W2 of the inner groove portion 9 is excessively small, the running performance on a rough road may deteriorate. Therefore, the groove width W2 of the inner groove portion 9 is preferably 60% or more, and more preferably 65% or more of the groove width W1a of the first portion 10.

FIG. 4 is a plan view of the tread portion 2 of the present embodiment. As shown in FIG. 4, the first joint groove 6 is arranged so as to straddle the tire equator C, for example.

The first joint groove 6 is arranged on both sides of the equal width portion 15 extending in the longitudinal direction with the same groove width W3a and toward the inner groove portion 9 (toward a direction away from the equal width portion 15). It is formed to include a pair of widening portions 16 in which the groove width W3b is increased. In the widening portion 16 of the present embodiment, the groove width W3b is continuously increased toward the inner groove portion 9.

The widening portion 16 is connected to, for example, the inner groove portion 9. As a result, the chance of stones being pinched between the widening portion 16 and the inner groove portion 9 is reduced.

The length Le of the widening portion 16 is preferably 10% or more, more preferably 20% or more, more preferably 40% or less, and further preferably 30% or less of the length Ld of the first joint groove 6. Since the length Le of the widening portion 16 is 10% or more of the length Ld of the first joint groove 6, the rigidity step of the portion where the widening portion 16 and the equal width portion 15 are connected is suppressed. Since the length Le of the widening portion 16 is 40% or less of the length Ld of the first joint groove 6, the length of the equal width portion 15 is secured and the center wear resistance performance is maintained. The length Le of the widening portion 16 and the length Ld of the first joint groove 6 are lengths along the groove center line 15c of the equal width portion 15.

The first joint groove 6 is continuously inclined to one side with respect to the tire circumferential direction. Such a first joint groove 6 suppresses a decrease in rigidity of the crown region Cr (shown in FIG. 1) and improves center wear resistance.

The angle θ3 of the first joint groove 6 with respect to the tire circumferential direction is preferably 45 degrees or less, more preferably 40 degrees or less, and even more preferably 35 degrees or less. Such a first joint groove 6 is useful for reducing the biting of stone bites and improving the stone biting resistance performance. The angle θ3 of the first joint groove 6 is preferably 15 degrees or more, and more preferably 20 degrees or more. As a result, the traction by the first joint groove 6 is enhanced, and the running performance on a rough road is improved. The angle θ3 of the first joint groove 6 is measured at the groove center line 15c of the equal width portion 15 having a length in the longitudinal direction larger than that of the widening portion 16.

The groove width W3a of the monospaced portion 15 of the first joint groove 6 is smaller than, for example, the groove width W2 of the inner groove portion 9. Such a first joint groove 6 has high stone biting resistance. If the groove width W3a of the equal width portion 15 of the first joint groove 6 is excessively smaller than the groove width W2 of the inner groove portion 9, the running performance due to traction on rough roads may deteriorate. Therefore, the groove width W3a of the monospaced portion 15 of the first joint groove 6 is preferably 55% or more, more preferably 60% or more, preferably 75% or less, and 70% or less of the groove width W2 of the inner groove portion 9. More desirable.

The groove depth d3 (shown in FIG. 2) of the first joint groove 6 is smaller than the groove depth d2 of the inner groove portion 9 in the present embodiment. Such a first joint groove 6 enhances center wear resistance and stone bite resistance.

In order to effectively exert the above-mentioned action, the groove depth d3 of the first joint groove 6 is preferably 60% or less of the groove depth d1 of the outer groove portion 8, and more preferably 55% or less. If the groove depth d3 of the first joint groove 6 is excessively small, the running performance on a rough road may deteriorate. Therefore, the groove depth d3 of the first joint groove 6 is preferably 40% or more, and more preferably 45% or more of the groove depth d1 of the outer groove portion 8.

In the present embodiment, the second joint groove 7 is formed as a monospaced groove extending in the longitudinal direction with the same groove width W4. For example, the second joint groove 7 is continuously inclined in the direction opposite to that of the first joint groove 6 with respect to the tire circumferential direction.

In the present embodiment, the second joint groove 7 is arranged so as to straddle the shoulder region Sh and the crown region Cr (shown in FIG. 1). As a result, the rigidity of the shoulder region Sh and the crown region Cr is maintained in a well-balanced manner, so that the running performance on rough roads is improved. The second joint groove 7 is arranged in the shoulder region Sh larger than the crown region Cr, for example. As a result, the rigidity of the land portion 4 of the crown region Cr is maintained high, so that the center wear resistance performance is enhanced. The second joint groove 7 may be provided only in the shoulder region Sh, for example, in order to secure the rigidity of the land portion 4 of the crown region Cr (not shown).

The groove width W4 of the second joint groove 7 is smaller than the groove width W2 of the inner groove portion 9 in this embodiment. Such a second joint groove 7 enhances the running performance on a rough road and maintains high center wear resistance performance and life performance. Although not particularly limited, the groove width W4 of the second joint groove 7 is preferably 55% or more, more preferably 60% or more, more preferably 75% or less, and 70% or less of the groove width W2 of the inner groove portion 9. Is even more desirable.

It is desirable that the angle θ4 of the second joint groove 7 with respect to the tire circumferential direction is smaller than the angle θ3 of the first joint groove 6. Such a second joint groove 7 has excellent stone biting resistance because even when a stone is caught in the groove, the stone can be smoothly discharged by utilizing the rolling of the tire 1. From such a viewpoint, the angle θ4 of the second joint groove 7 is preferably 45 degrees or less, more preferably 35 degrees or less, and even more preferably 30 degrees or less. Further, in order to improve the running performance on a rough road, the angle θ4 of the second joint groove 7 is preferably 5 degrees or more, and more preferably 10 degrees or more.

The groove depth d4 (shown in FIG. 2) of the second joint groove 7 is smaller than, for example, the groove depth d1 of the outer groove portion 8. Such a second joint groove 7 maintains high center wear resistance, life performance, and stone biting resistance. In order to effectively exert such an action and improve running performance on rough roads, it is desirable that the groove depth d4 of the second joint groove 7 is 40% or more of the groove depth d1 of the outer groove portion 8. 45% or more is more desirable, 60% or less is more desirable, and 55% or less is even more desirable. It is desirable that the groove depth d4 of the second joint groove 7 is, for example, the same as the groove depth d3 of the first joint groove 6.

Although the particularly preferred embodiment of the present invention has been described in detail above, the present invention is not limited to the illustrated embodiment and can be modified into various embodiments.

A pneumatic tire having the basic pattern shown in FIG. 1 was prototyped based on the specifications shown in Table 1, and was tested for center wear resistance and stone biting resistance. The test method is as follows.

<Center wear resistance / stone bite resistance>
The test tires were mounted on each of the eight wheels (driving wheels and driven wheels) of the two-axle trailer towed by the 2DD vehicle under the following conditions, and ran on a dirt road surface. After that, the groove depth of each groove and the number of stones bitten in the groove were measured. The center wear resistance performance was expressed as an exponent in which the average value of the groove depths of each groove in the crown region was calculated and the value of Example 1 was set to 100. Further, the stone biting resistance was expressed as an index with the reciprocal of the number of stones in Example 1 as 100. In each test, the larger the number, the better, and 90 or more pass.
Tire size: 295 / 75R22.5
Rim: 22.5 x 8.25
Internal pressure: 850kPa
Load: 10.44kN (mileage: 5000km)
Load: 34.81kN (mileage: 5000km)
Traveling speed: 40-80km / h
Total mileage: 10000km
"A" in Table 1 means that the inner groove portion is inclined in the opposite direction to the outer groove portion, and "B" means that the inner groove portion is inclined in the same direction as the outer groove portion.
The test results are shown in Table 1.

As shown in the table, the tires of the examples have high center wear resistance. Further, the tire of the embodiment is excellent in stone biting resistance. Furthermore, due to the sensuality of the test driver, the tires of the examples were highly evaluated for their running performance on rough roads.

1 Tire 3 Horizontal groove 8 Outer groove 9 Inner groove C Tire equatorial Te tread end

Claims (18)

A tire with a tread
The tread portion is provided with a plurality of lateral grooves connecting the tread ends on both sides.
Each of the lateral grooves includes a pair of outer groove portions extending inward in the tire axial direction from the tread ends on both sides thereof, and an inner groove portion connecting the pair of outer groove portions.
The pair of outer grooves are inclined in the same direction with respect to the tire axial direction.
The inner groove portion is inclined in the direction opposite to the outer groove portion with respect to the tire axial direction.
The groove depth of the inner groove portion is smaller than the groove depth of each of the pair of outer groove portions.
tire. The tire according to claim 1, wherein the groove depth of the inner groove portion is 65% to 85% of the groove depth of the outer groove portion. The tire according to claim 1 or 2, wherein the angle of the inner groove portion with respect to the tire axial direction is 20 to 50 degrees. The outer groove portion includes a first portion extending from the tread end toward the tire equator, and a second portion connected to the first portion and inclined at a larger angle with respect to the tire axial direction than the first portion. The tire according to any one of claims 1 to 3. The tire according to claim 4, wherein the groove width of the inner groove portion is smaller than the groove width of the first portion. The tire according to claim 4 or 5, wherein the groove width of the inner groove portion is 60% to 80% of the groove width of the first portion. The tire according to any one of claims 4 to 6, wherein the length of the first portion in the tire axial direction is 5% to 20% of the tread width. The tire according to any one of claims 4 to 7, wherein the angle of the first portion with respect to the tire axial direction is 10 degrees or less. The tire according to any one of claims 4 to 8, wherein the angle of the second portion with respect to the tire axial direction is 10 to 30 degrees or less. The tread portion includes a crown region having a width in the tire axial direction of 40% of the tread width from the equator of the tire to both sides in the axial direction of the tire.
The tire according to any one of claims 1 to 9, wherein the inner groove portion is provided in the crown region. The tire according to any one of claims 1 to 10, wherein the tread portion is provided with a first joint groove that connects the inner groove portions of the lateral grooves adjacent to each other in the tire circumferential direction. The tire according to claim 11, wherein the groove depth of the first joint groove is smaller than the groove depth of the inner groove portion. The tire according to claim 11 or 12, wherein the first joint groove includes a widening portion in which the groove width increases toward the inner groove portion. The tire according to claim 13, wherein the widening portion is connected to the inner groove portion. The tire according to claim 13, wherein the length of the widened portion is 10% to 40% of the length of the first joint groove. The tire according to any one of claims 1 to 15, wherein the tread portion is provided with a second joint groove connecting the outer groove portions of the lateral grooves adjacent to each other in the tire circumferential direction. The tire according to claim 16, wherein the outer groove portion is provided with a protrusion for preventing stone biting at the groove bottom where the second joint groove is connected. The tire according to any one of claims 1 to 17, wherein the tire is for a heavy load.

Images