JPH08282213A - Tire for heavy load - Google Patents

Abstract

PURPOSE: To provide a tire for a heavy load, which can be suitably used as an all weather tire, and by which wear resistance and biased wear resistance can be heightened while keeping the on-ice and snow performance. CONSTITUTION: A tread grounding surface S is divided into a central grounding surface area S1 and a shoulder grounding surface area S2 on the side of the above by main longitudinal grooves G, G on both sides of a tire equator C, and the distance L from the tire equator C of the groove center of the main longitudinal groove G is 0.25-0.40 times as large as the tread grounding surface width SW. The central grounding area S1 is divided into blocks by a longitudinal fine groove (g) and a lateral fine groove (y) which have a width 0.10 to 0.60 times as large as the groove width WG of the main longitudinal groove G.

Description

Detailed Description of the Invention

[0001]

INDUSTRIAL APPLICABILITY The present invention can be suitably used as an all-weather tire and has wear resistance while maintaining performance on ice and snow.
The present invention relates to a heavy-duty tire that can improve uneven wear resistance.

[0002]

2. Description of the Related Art In recent years, all-weather tires have been developed to enable heavy-duty loading on trucks, buses, etc., while still maintaining running performance on dry, good roads, and allowing the vehicle to properly run on ice-covered roads with snow and icing. It is often used in vehicles. As a typical tread pattern of this type of tire, for example, as described in JP-A-3-128705, an area between two circumferential main grooves provided on both sides of the tire equator is defined as a circumferential direction. It is known that the block is divided into a large number of blocks by grooves and lateral grooves. In addition, in order to obtain good performance on ice and snow, this block reduces the shape and size of the block itself and increases the number of blocks. The edge component is increased by providing siping on the.

[0003]

However, such segmentation of blocks and formation of siping impair the wear resistance due to the movement of the blocks during running under a high load such as a heavy-duty tire, and the heels are damaged. There is a problem that it is easy to induce uneven wear such as and-toe wear.

The present invention is based on the fact that the positions of the vertical main grooves provided on both sides of the tire equator are specified and the blocks formed between the vertical main grooves are divided by fine grooves having specified groove widths. It is an object of the present invention to provide a heavy-duty tire capable of improving the wear resistance and the uneven wear resistance even when it is turned into a solution, and solving the above problems.

[0005]

In order to achieve the above object, the heavy-duty tire of the present invention is provided with vertical main grooves extending in the tire circumferential direction on both sides of the tire equator so that the tread contact surface has the vertical main grooves. Between the central ground contact surface area and the shoulder ground contact surface area on the outer side in the tire axial direction, and the distance L from the tire equator C at the groove center of this vertical main groove is 0.25 to 0. 40 times, and the central ground contact area is set to 0.10 of the groove width WG of the vertical main groove.
The central ground contact area is formed as an area composed of blocks having a groove width of 0.60 times and extending in the tire circumferential direction and lateral fine grooves extending in a direction intersecting with the longitudinal fine grooves. There is.

The groove depth Dy of the horizontal narrow groove is preferably 0.10 to 0.33 times the groove depth DG of the vertical main groove, and siping is applied to the groove bottom of the horizontal narrow groove. Provided and sum Dy of the depth Ds of this siping and the groove depth Dy of the lateral narrow groove
+ Ds is 0.80 to 1.2 of the groove depth DG of the vertical main groove.
It is good to double.

[0007]

According to the tread pattern of the present application, the block is formed in the central ground contact surface area where the ground contact pressure is high and which is divided by the vertical main groove. This block has a groove width WG of the vertical main groove of 0.6.
Since it is divided by vertical fine grooves and horizontal fine grooves of 0 times or less, even if the blocks are made smaller and the number of blocks is increased, the reduction of land ratio is mitigated and the pattern rigidity is maintained relatively high. Since the position of the groove is specified within a distance range of 0.25 to 0.40 times the ground contact surface width SW,
The progress of wear in the central contact area and the shoulder contact area can be made uniform, and wear resistance and uneven wear resistance can be improved by these synergistic effects.

Further, since the vertical fine grooves and the horizontal fine grooves are used, when forming a block pattern with the same land ratio, the number of blocks is improved along with the edge length thereof, and the drainage performance and the on-ice performance due to road surface scratching are enhanced. . In addition, since the block is formed in the central ground contact surface area where the ground contact pressure is high, there is a large amount of bite into the snow of the block, the adhesive friction with the ice surface is increased, and moreover, it is compared to those that form siping in the block. Since the block rigidity is maintained, the performance on ice and snow is ensured even in a heavy-duty tire. Further, since the groove volume is reduced, the sound pressure of the pumping sound is reduced, which can contribute to noise reduction.

Further, the depth of the lateral narrow groove is 0.3 of the vertical main groove depth DG.
When it is 3 times or less, the effect of maintaining rigidity in the circumferential direction of the block is further enhanced, and wear resistance and uneven wear resistance can be further improved. At this time, in order to prevent loss of wettability and iceability due to early abrasion of the lateral narrow groove, it is preferable to form a siping of a predetermined depth at the groove bottom of the lateral narrow groove. Due to the edge effect of siping that appears after abrasion, good wettability and iceability are secured until the end of life.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, the heavy load tire 1 includes a tread portion 2
A sidewall portion 3 extending inward in the tire radial direction from both ends thereof, and a bead portion 4 arranged at the tire radial inner end of each sidewall portion 3, and in this example, for example, a tire size 11R22.5. Formed as a radial tire.

The tire 1 also comprises a toroidal carcass 6 extending between the bead portions 4 and 4, and a belt layer 7 arranged outside the carcass 6 in the radial direction.

The carcass 6 is composed of one or more carcass plies, for example, two carcass plies which are folded around the bead core 5 of the bead part 4 from the tread part 2 to the side wall part 3, and the carcass ply is composed of: The carcass cords are arranged at an angle of 75 to 90 degrees with respect to the tire equator C. In this example, a steel cord is used as the carcass cord. The carcass may be composed of a plurality of plies using an organic fiber cord such as aromatic polyamide, nylon, rayon, polyester in addition to the steel cord. Further, the folded-back portion 6a of the carcass 6 is interrupted above the bead core 5 and below the maximum width position of the tire, and between the folded-back portion 6a and the main body portion 6b, a triangular cross-section that rises radially outward from the bead core 5 is formed. The bead apex rubber 8 is filled to reinforce the bead portion 4 and enhance the tire lateral rigidity.

The belt layer 7 comprises a plurality of belt cords arranged at an angle of 15 to 80 degrees with respect to the tire equator C,
In this example, it is composed of, for example, four belt plies, and as the belt cord, a metal fiber cord of low extensibility such as steel is preferably used. As the belt cord, high-strength organic fiber cords such as aromatic polyamide are also available.
It can be selected according to the required tire performance.

As shown in FIG. 2, the tread portion 2 is provided with two vertical main grooves G extending in the tire circumferential direction on both sides of the tire equator C, and the tread contact surface S is provided with the vertical main groove S. The grooves G, G are divided into a central ground contact surface area S1 of G and a shoulder ground contact surface area S2 on the outer side in the tire axial direction, and the central ground contact surface area S1 includes a vertical fine groove g extending in the tire circumferential direction and the vertical groove g thereof. It is formed as an area consisting of a block B which is defined by a lateral narrow groove y that faces the narrow groove.

The tread contact surface S is a region where the tread surface TS, which is the outer surface of the tread, comes into contact with the road surface when the tire is mounted on the standard rim, is filled with the standard internal pressure, and is loaded with the standard load. Also, the standard rim and standard internal pressure are JATMA, TRA, ETR.
The maximum air pressure of the standard rim and each tire defined by standards such as TO, and the standard load are defined as the maximum load. Further, the tread surface TS is centered on the tire equatorial plane and has a radius of curvature R1 of, for example, a tread width TW of 1. of the tread width TW in the meridional section of the tire filled with the standard internal pressure.
Curved in a convex shape along an arc with a range of 5 to 5.0 times,
As a result, a profile is obtained in which the ground contact pressure in the central ground contact area S1 is larger than the ground contact pressure in the shoulder ground contact area S2. Both ends of the tread surface TS intersect with the buttress surface BS at edges via, for example, an inclined surface, and thus the tread surface TS coincides with the tread contact surface S in this example.

As shown in an enlarged view in FIG. 3, the vertical main groove G is formed into a linear or zigzag groove having a groove width WG of 5 mm or more, and in this example, is a zigzag groove. The zigzag swing angle α is 6 with respect to the tire circumferential direction.
The range is set to -25 degrees. The distance L between the center of the vertical main groove G and the tire equator C is equal to the tread contact surface S.
Width SW is 0.25 to 0.4 times, and this distance L
Is measured as the distance from the center of the zigzag swing at the groove center when the vertical main groove G has a zigzag shape.

Further, the vertical narrow groove g and the horizontal narrow groove y formed in the central ground contact surface area S1 have groove widths Wg and Wy, respectively, of 0.10 to 0..0 of the groove width WG of the vertical main groove. In the present example, as shown in FIG. 2, the vertical narrow groove g is a central vertical narrow groove ga extending on the tire equator C and both outer narrow vertical grooves gb. And extend linearly in the tire circumferential direction. Further, the horizontal narrow groove y is the vertical narrow groove ga, g
A lateral narrow groove ya that divides into a block row in which the blocks Ba are arranged by crossing b, and a block row in which blocks Bb are arranged by crossing between the vertical narrow groove ga and the vertical main groove G The inner lateral narrow groove ya and the outer lateral narrow groove yb are inclined at an angle of 25 degrees or less, for example, 20 degrees with respect to the tire axial direction. The number of lateral fine grooves ya, yb formed in each block row is 120 to 1.
Eighty pieces are preferable, so that each block Ba, Bb
Is formed into a horizontally long and small parallelogram that can exhibit high cornering power. In this example, the lateral narrow grooves ya and yb are inclined in mutually opposite directions, and are located between the lateral narrow grooves ya and yb adjacent to each other in the tire axial direction and the lateral narrow grooves ya and ya.
The phase in the circumferential direction is approximately 1/2 of the pitch length of the lateral narrow groove.
The length is doubled to improve uniformity.

In this way, the formation position of the vertical main groove G is specified, and the central ground contact surface area S1 is divided into blocks by the vertical narrow grooves g and the horizontal narrow grooves y whose groove widths are restricted. Even when the size is reduced and the number of blocks is increased, the reduction in land ratio is mitigated and a relatively high pattern rigidity is maintained, and the wear resistance is combined with the uniform wear between the central contact surface area and the shoulder contact surface area. And the uneven wear resistance can be improved.

Table 1 shows a tire having a tread pattern as shown in FIG. 6, which schematically shows the vertical main groove G, the vertical narrow groove g, and the horizontal narrow groove y.
The tires were prototyped based on the specifications, and the tires were compared for wear resistance, uneven wear resistance, and passage noise resistance. Abrasion resistance is as follows: The tire is mounted on the rear wheel drive shaft and traveled on a general road for a distance of 50,000 km, and the amount of wear at each position of the marks M1 and M2 is measured to determine the amount of wear at M1 and M2. The wear amount at M1 and M2 of the example product B is used as a reference (10
It was shown as an index 0). The larger the index, the better. Uneven wear resistance: The tire was attached to the front wheels and the tire was run on a general road for a distance of 5000 km, and the uneven wear amount (uneven wear depth) at the uneven wear occurrence point was measured. In the table, ○ indicates an uneven wear amount of 5 m
Less than m, Δ is an uneven wear amount of 0.5 to 1.0 mm, and X is an uneven wear amount of 1.0 mm or more. Passing noise is 50km / H when engine is off with test tires mounted on all wheels.
The microphone is set at a position 7.5 mm laterally away from the vehicle traveling in the direction, noise is measured according to JASO standard C606, and the measured value (dB value) is used as an example product B.
Was displayed as an index with the reference value (100). The road surface is a dense-grained asphalt concrete road surface, and the larger the index, the better.

[0020]

[Table 1]

As a result, as the distance L of the longitudinal main groove G from the tire equator C increases, the wear on the shoulder contact surface area S2 increases, while on the contrary, as the distance L decreases, the central contact surface area S1 decreases. Wear increases, and the distance L is the ground contact surface width S
It can be confirmed that in the range of W from 0.25 to 0.40, the progress of wear in both the ground contact surface areas S1 and S2 is made uniform, and the wear resistance and the uneven wear resistance are improved. The above 0.25 to 0.
Even in the range of 40, the groove width W of the vertical narrow groove g and the horizontal narrow groove y
If g and Wy exceed 0.60 times the groove width WG of the vertical main groove, it is confirmed that the wear in the central ground contact surface area S1 deteriorates and the wear resistance and uneven wear resistance cannot be improved. it can. That is, when the distance L is less than 0.25 SW, when it exceeds 0.4 SW, and when the groove widths Wg and Wy exceed 0.60 WG, the intended effect of improving wear resistance cannot be expected. Further, when the distance L is less than 0.25 SW, air column resonance in the vertical main groove G is excited by tire vibration, and noise characteristics are deteriorated.
In addition, the amount of heat stored in the shoulder ground contact surface area S2 increases, leading to belt edge separation and the like, which impairs durability. When the distance L exceeds 0.4 SW, the shoulder ground contact surface area S2 becomes too small and shoulder wear is induced. Groove width Wg, Wy
Is less than 0.10 WG, the drainage function cannot be sufficiently exhibited.

Further, the vertical main groove G is preferably zigzag-shaped as in the present example, whereby a drainage function is provided over the entire width of the zigzag swing, and the groove edge exerts a road surface scratching effect, and wets. Helps improve performance and performance on ice. However, when the zigzag swing angle α is less than 6 degrees, the improvement effect is not expected. On the contrary, when the zigzag swing angle α is more than 25 degrees, it causes pitch noise and the rigidity of the top of the zigzag is reduced to cause the point of orbital wear (core). It induces new uneven wear.

Further, when the number of lateral fine grooves ya, yb formed in each block row is less than 120, sufficient wet performance,
On the other hand, the performance on ice cannot be exhibited. On the contrary, when the number of blocks exceeds 180, the size of the block becomes too small and there is a risk of uneven wear. Therefore, the number of formed lines is preferably in the range of 130 to 160.

Further, as shown in FIGS. 2 and 4, the lateral narrow groove y has a groove depth Dy of 0.10 of the groove depth DG of the vertical main groove.
It has a shallow bottom of 0.33 times, and the width of the lateral narrow groove is 0.5 times or more, more preferably 0.7 times or more, the length K of the lateral narrow groove y. A siping 9 extending on the center line is formed. The siping 9 is a notched member having a siping width in the range of 0.5 to 1.5 mm, and maintains the pattern rigidity in the circumferential direction by closing its opening by the compressive force when the tire touches the ground. If the siping width is less than 0.5 mm, it is difficult to form the siping by the molding die, and if it exceeds 1.5 mm, the opening cannot be closed at the time of grounding, and the rigidity is significantly reduced.

By making the lateral narrow groove y shallow as described above, the effect of maintaining rigidity in the circumferential direction of the block is further enhanced, and it becomes possible to further improve wear resistance and uneven wear resistance. When the groove depth Dy of the lateral narrow groove exceeds 0.33DG, the block rigidity may be insufficient and the uneven wear may be deteriorated to a level where it cannot be completely corrected even by the first tire rotation.

The siping 9 appears on the tread surface TS when the shallow lateral groove y is worn away, and its edge effect ensures good wettability and iceability until the end of the wear life of the tire. Therefore, if the siping length is less than 0.5 times the lateral narrow groove length K, a sufficient edge effect cannot be generated. In addition, the siping 9 has a siping depth D in order to exert the edge effect until the end of the wear life.
It is necessary that the sum Dy + Ds of s and the groove depth Dy of the lateral narrow groove y is 0.80 times or more the vertical main groove depth DG, and the sum Dy + Ds exceeds 1.20DG. And, the thickness of the rubber gauge of the entire tread rubber becomes excessive, which causes unnecessary weight increase. Therefore, the sum D
More preferably, y + Ds is 0.90 DG or more, and the upper limit is 1.00 DG or less.

The vertical narrow groove g has a deeper bottom than the horizontal narrow groove y. For example, the groove depth Dg is 0.
By setting the ratio to 8 to 1.2 times, the drainage property is exhibited throughout the end of the wear life. The groove depth Dg is more preferably 1.0 times or less the depth DG of the vertical main groove G. If it exceeds 1.0 times, cracks are likely to occur at the groove bottom of the vertical fine groove g, and if the rubber gauge below the groove bottom is increased to prevent the crack, the tire weight increases.

In the shoulder contact area S2, in this example,
A lug groove 1 extending from the vertical main groove G to the buttress surface BS
0 is formed, and the lug groove 10 has a shallow bottom portion 10A having a groove depth on the inner side in the tire axial direction that approximates the groove depth Dy of the lateral narrow groove, and a groove depth on the outer side of the lag groove 10 in the longitudinal main direction. A deep bottom portion 10B that is similar to the groove depth DG of the groove G is formed, and further, a siping 11 having the same depth as the siping 9 is formed in the shallow bottom portion 10A. The lug groove 10 is more effective in increasing the block rigidity than a flat-bottom groove having the same groove volume as the lug groove, and the air column resonance in the groove is caused by the height change of the groove bottom. It can suppress and improve noise performance.

Further, since the siping 11 of the shallow bottom portion 10A does not restrain the movement of the rubber in the direction along the siping like the siping 9, the pattern rigidity in the axial direction of the tire can be relaxed, and as a result, especially during turning. It is possible to suppress the reduction of the contact area and make the distribution of the contact pressure uniform, which is useful for improving the contact property and maintaining the wet performance.

(Specific Example) A tire having a tire size of 11R22.5 having the structure shown in FIGS. 1 and 2 was trial-produced based on the specifications of Table 2, and the wear resistance, uneven wear resistance, and wettability of the trial tire were tested. Was measured and the results are shown in the table.

The test for wear resistance and uneven wear resistance was conducted according to the test specifications in Table 1 above, and the wear resistance was measured at the position of mark M3 in FIG. Wetness is an index of braking distance when test tires are mounted on all wheels and the wheels are rock-braked at a speed of 50 km / H on an asphalt road surface with a water film thickness of 2 mm. The larger the index, the better. The results of wear resistance and wettability (numerical values) are obtained by indexing Example Product 2 as 100. The larger the index value, the better the performance.

[0032]

[Table 2]

[0033]

Since the heavy duty tire of the present invention is constructed as described above, wear resistance while maintaining performance on ice and snow,
The uneven wear resistance can be enhanced, and it can be suitably used as an all-weather tire.

[Brief description of drawings]

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

FIG. 2 is a pattern development view showing an example of the tread pattern.

FIG. 3 is a cross-sectional view showing a vertical main groove.

FIG. 4 is a cross-sectional view showing lateral narrow grooves together with siping.

FIG. 5 is a cross-sectional view showing a vertical fine groove.

FIG. 6 is a development view of the tread pattern of the tire used in Table 1.

[Explanation of symbols]

 9 Siping C Tire equator G Vertical main groove g, ga, gb Vertical fine groove y, ya, yb Horizontal fine groove S Tread contact surface S1 Central contact surface area S2 Shoulder contact surface area

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[Procedure amendment]

[Submission date] August 16, 1995

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be amended] Title of invention

[Correction method] Change

[Correction content]

[ Title of Invention] Heavy duty tire

Claims (3)

[Claims] 1. A tread contact surface is formed by providing longitudinal main grooves extending in the tire circumferential direction on both sides of the tire equator C so that a central contact surface area between the vertical main grooves and a shoulder contact surface area outside the tire axial direction are provided. And the distance L from the tire equator C of the center of the vertical main groove to the tread contact surface width SW of 0.
A vertical narrow groove having a groove width of 0.10 to 0.60 times the groove width WG of the vertical main groove and extending in the tire circumferential direction while having a width of 25 to 0.40 times. And a heavy-duty tire formed as a region consisting of a block in which this central ground contact surface region is defined by lateral fine grooves extending in a direction intersecting with the vertical fine grooves. 2. The heavy-duty tire according to claim 1, wherein the lateral fine groove has a groove depth Dy of 0.10 to 0.33 times the groove depth DG of the vertical main groove. 3. The lateral narrow groove is provided with a siping extending along the lateral narrow groove at the groove bottom, and the sum Dy + Ds of the depth Ds of the siping and the groove depth Dy of the lateral narrow groove.
Is 0.80 to 1.2 times the groove depth DG of the vertical main groove, The heavy duty tire according to claim 1, wherein