JP2001180227A - Tire for heavy load - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the abrasion resistance of a shoulder part. SOLUTION: This tire for heavy load has a shoulder block 6. Groove bottom raised parts 9 respectively connecting shoulder blocks 6, 6 raised from a groove bottom and adjacent to each other in the circumferential direction, are formed on lateral grooves 4. The groove bottom raised parts 9 respectively include a main part 9a continued from a longitudinal main groove 3 side in the longitudinal direction of the lateral groove 4 at an approximately uniform height, and an inclined part 9b connected to an terminal end X of the main part 9a and gradually lowered toward a tread edge E side. The shoulder block 6 has a chamfered part 14 formed by a slant face obtained by cutting an area including a reference ridge line em where a ground surface 10 and a groove wall face 11 of the lateral groove 4 are intersected, and surrounded by a first ridge line e1 extended on the ground surface 10, a second ridge line e2 extended on the groove wall face 11, and a third ridge line e3 extended on a buttress face 13. An axial inner end of the chamfered part 14 is located on the axial inside with respect to the terminal end X of the main part 9a. A circumferential length W of the chamfered part 13 is widened toward the buttress face 13.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a heavy duty tire capable of improving abrasion resistance.

[0002]

2. Description of the Related Art Heavy-duty tires used for trucks, buses, and the like have high load,
Because it is used under high internal pressure, the tread is easy to wear,
In particular, in a tire having a pattern in which shoulder blocks are arranged on the tread edge, there is a problem of uneven wear that the shoulder blocks are worn earlier than the crown portion. Conventionally, in order to solve this kind of problem, for example, by increasing the radius of curvature of the tread surface, flattening the tread surface to reduce the radius difference between the crown portion side and the shoulder portion side, or causing a large slip when braking. In particular, increasing the rigidity of the shoulder block, which is easily worn, on the rear surface side of the road surface is performed.

[0003] However, these proposals have not yet exerted a sufficient effect, and there is currently room for further improvement. In view of such a situation, the inventors have analyzed the contact shape of the shoulder block during vehicle braking. FIG. 8 (A) shows the grounding shape of the tire in a free rolling state, and FIG. 8 (B) shows a schematic view of the grounding shape at the time of braking. Symbol C is the tire equator position, and vector is the tread surface. The force acting on each is shown. At the time of braking, a large load and slip act on the shoulder portion, and the tread portion increases the contact length in the tire circumferential direction on the shoulder side. Such a change in the grounding shape is one of the main causes of uneven wear of the shoulder portion.

The present invention has been devised in view of the above-described problems. By improving the shape of the shoulder block, the contact shape of the tread surface changes between the free rolling state and the braking state of the tire. It is an object of the present invention to provide a heavy duty tire that can reduce uneven wear of the shoulder portion.

[0005]

According to the first aspect of the present invention, there is provided a vertical main groove extending continuously in the tire circumferential direction near a tread edge, and a vertical main groove and the tread edge are formed between the vertical main groove and the tread edge. A heavy groove tire in which a shoulder block defined by a lateral groove continuous between the tread edges forms a block row arranged in the tire circumferential direction, wherein the lateral groove protrudes from the groove bottom and extends in the tire circumferential direction. A groove bottom protruding portion that connects between the adjacent shoulder blocks is provided, and the groove bottom protruding portion is a main portion that is continuous at substantially the same height in the length direction of the horizontal groove from the vertical main groove side; Notch including a reference ridge line where the contact surface of the shoulder block and the groove wall surface of the lateral groove intersect with each other, and an inclined portion whose height is gradually reduced toward the tread edge side.
Forming a chamfer comprising a slope surrounded by a first ridge line extending on the ground contact surface, a second ridge line extending on the groove wall surface, and a third ridge line extending on a buttress surface of the tire connected to the tread edge; In the chamfered portion, the inner end in the tire axial direction is located at least inward in the tire axial direction from the terminal end of the main portion, and the length of the chamfered portion in the tire circumferential direction becomes wider toward the buttress surface. It is characterized by:

In the invention described in claim 2, the first ridge line has a length L of the shoulder block in the circumferential direction of the tire of 1.
The heavy load tire according to claim 1, wherein the tire has an arc shape having a radius of curvature of 5 times or more and protruding outward from the block.

According to a third aspect of the present invention, the chamfered portion includes a first surface parallel to a tire equator plane passing through a virtual vertex where the reference ridge line intersects the buttress surface, and the first chamfered portion extends from the virtual vertex to the first vertex. Tire circumferential length S to ridgeline
a is 15 to 30% of the length L of the shoulder block, the height ha in the tire radial direction from the virtual vertex to the second ridge is 0.5 to 1 mm, and the tire passes the terminal end of the main portion. On a second surface parallel to the equatorial plane, the length Sb in the tire circumferential direction from the reference ridge line to the first ridge line is defined as:
The heavy load tire according to claim 1, wherein the length L of the shoulder block is 3 to 10%.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, an embodiment of the present invention will be described with reference to the drawings, taking a heavy-load radial tire (hereinafter sometimes simply referred to as "tire") having a tire size of 11R22.5 as an example. It is explained based on. FIG. 1 is a development view of the tread surface 2. The tread surface 2 is provided with a vertical main groove 3 extending continuously in the tire circumferential direction and a horizontal groove 4 intersecting the vertical main groove 3.

In this embodiment, a plurality of vertical main grooves 3 are arranged. That is, the vertical main grooves 3 are, for example, a pair of vertical main grooves 3a, 3a arranged on both sides of the tire equator C, and a pair of outer vertical grooves arranged on each outer side in the tire axial direction and near the tread edge E. The tread surface 2 is composed of main grooves 3b and 3b.
Are formed in total. Each of the vertical main grooves 3 has a zigzag shape in the tire circumferential direction and is formed continuously in the tire circumferential direction, but can be changed in various shapes such as a linear shape or a sine wave shape.

In the present embodiment, the horizontal groove 4 is a first horizontal groove 4a which connects between the inner vertical main grooves 3a, 3a, and extends outward from the inner vertical main groove 3a in the tire axial direction and extends to the outer vertical main groove 3a. Groove 3
b, the second lateral groove 4 that terminates without communication with b
b, a third lateral groove 4c extending inward in the tire axial direction from the outer vertical main groove 3b and terminating without communication with the inner vertical main groove 3a, and a tire shaft extending from the outer vertical main groove 3b. 4th extending outward in the direction and opening at the tread edge E
That includes the lateral groove 4d. Note that the second and third
The horizontal grooves 4b and 4c are connected by the narrow groove 16 in this example.

The width and depth of each of the vertical main grooves 3 and each of the horizontal grooves 4 can be variously set as required. For example, the groove width of the vertical main groove 3 is 2.0% of the tread contact width TW.
As described above, the content is more preferably 2.5% or more. In the case of a heavy load tire as in this example, it is preferable that the tire is formed continuously with a width of at least 5 mm or more. It is desirable that the width of each lateral groove 4 is, for example, 1.5% or more of the tread contact width TW. The groove depth of the vertical main groove 3 is, for example, 5 to 12% of the tread contact width TW, and the groove depth of the horizontal groove 4 is
For example, it is desirable to set it to 2 to 12% of the tread contact width TW.

The tread contact width TW is a distance between the outermost tread edges E and E in the tire axial direction when the tire is rim-assembled on a regular rim, and a regular internal pressure and a regular load are applied and the tire is grounded on a plane. Determined as At this time, "Regular rim"
A rim is a rim defined for each tire in the standard system including the standard on which the tire is based.
Standard rim for TMA, "Design Rim" for TRA,
Or "Easy Rim" for ETRTO. Also,
"Normal internal pressure" is the air pressure specified for each tire in the standard system including the standard on which the tire is based. For JATMA, the maximum air pressure is used.
IRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURE
Maximum value described in "S", "INFLATION PRESS" for ETRTO
URE ". Further," regular load "is the load specified by each standard in the standard system including the standard on which the tire is based. For JATMA, the maximum load capacity, TRA BA table "TIRE LOAD LIMITS AT VARIOUS
The maximum value described in "COLD INFLATION PRESSURES" or "LOAD CAPACITY" for ETRTO.

The tire of this embodiment has a tread surface 2
A shoulder block 6 defined by the outer vertical main groove 3b, a fourth horizontal groove 4d continuous between the outer vertical main groove 3b and the tread edge E, and the tread edge E. Are provided with a row of blocks arranged in the tire circumferential direction. In the present invention, other portions of the tread surface 2 can be arbitrarily formed as long as the shoulder block 6 is provided. In this example, the central block 5 is provided between the inner vertical main grooves 3a and 3a, and the inner block 5 is provided. An example in which a rib-like portion 7 is formed between the vertical main groove 3a and the outer vertical main groove 3b is exemplified.

As shown in FIG. 2, the fourth lateral groove 4d is provided with a groove bottom raised portion 9 which protrudes from the groove bottom and connects between the shoulder blocks 6 adjacent in the tire circumferential direction. ing. The groove bottom ridge 9 is provided with the outer vertical main groove 3.
a main portion 9a continuous from the b side in the longitudinal direction of the fourth lateral groove 4d at substantially the same height, and an inclined portion connected to the end X of the main portion 9a and gradually decreasing in height toward the tread edge E side. 9b. Such groove bottom raised portions 9 help to increase the rigidity of the shoulder block 6 in the tire circumferential direction, for example, by suppressing a large fall of the shoulder block 6 in the tire circumferential direction. Can be suppressed. In addition, the groove bottom raised portion 9 is formed by the inclined portion 9b.
As a result, the tire circumferential rigidity on the tread edge E side of the shoulder block 6 can be relatively softened,
For example, it is also useful for improving wandering performance.

The height 9h of the main portion 9a is, for example, 40 to 80%, more preferably 50 to 80% of the depth of the lateral groove 4 (fourth lateral groove 4d). Preferably, the terminal end X of the main portion 9a is set at a position separated from the tread edge E by a distance Xa of 20 to 50% of the width W of the shoulder block in the tire axial direction, for example, as shown in FIG. The inclined portion 9b has a slope obtained by dividing the height 9h of the main portion 9a by a length along the lateral groove, for example, by 0.4.
It is desirable to set it to 1.2.

Further, the shoulder block 6 of the present embodiment is notched including a reference ridge line em where the ground surface 10 of the shoulder block 6 and the groove wall surface 11 of the fourth lateral groove 4d intersect,
A first ridge e1 extending on the ground surface 10, a second ridge e2 extending on the groove wall surface 11, and the tread edge E
A chamfered portion 14 formed of a slope surrounded by a third ridge line e3 extending on a buttress surface 13 of the tire connected to the tire is illustrated on both sides in the tire circumferential direction. In the chamfered portion 14, the inner end 14i in the tire axial direction is located at least inside the terminal end X of the main portion 9a in the tire axial direction, and the length S in the tire circumferential direction of the chamfered portion 14 is It is configured wide toward the buttress surface 13.

The buttress surface 13 of the tire is a side wall surface of the tire which is continuous with the tread edge E and extends to a side wall portion (not shown) and does not contact the road surface during normal running. Depending on the load conditions and the time of turning, there is a case where the ground is touched.

As a result of various experiments conducted by the inventors, the provision of the chamfered portion 14 on the shoulder block 6 together with the above-mentioned groove bottom raised portion 9 allows the tire to be in contact with the ground in the free rolling state and the braking state. It has been found that the change in the contact shape, particularly the change in the contact shape at the shoulder portion, is small, and that the uneven wear of the shoulder block 6 can be effectively suppressed. The reason is that, in addition to the improvement in the tire circumferential rigidity of the shoulder block 6 due to the groove bottom ridge 9, the chamfered portion 14 provided at least in the region where the slope 9 b of the groove bottom ridge 9 exists. It is considered that the ground pressure at the outer side in the tire axial direction of the shoulder block 6 and both ends in the tire circumferential direction is optimally controlled even during braking.

Here, as shown in FIG. 3, the first ridge line e1 is, for example, 1.5 times or more, more preferably 1.7 to 2.5 times, the length L of the shoulder block 6 in the tire circumferential direction. It is desirable to form a circular arc shape having a radius of curvature R1 and convex toward the outside of the block. As a result, under the slippage and the contact pressure acting on the shoulder block 6 in the braking state of the tire, the contact pressure of the shoulder block 6 is made uniform, the change in the contact shape is reduced, and the uneven wear of the shoulder block 6 is further reduced. The effect of prevention can be improved.

In this specification, a point at which the reference ridge line em intersects the buttress surface 13 (a virtual buttress surface extended from the buttress surface 13) is referred to as a virtual vertex VP, and a tire equatorial plane passing through the virtual vertex VP is shown in FIG. FIG. 4A shows an end view of the shoulder block on the first plane P1 parallel to FIG. In the present example, the chamfered portion 14 has a virtual vertex V
The length Sa in the tire circumferential direction from P to the first ridge line e1 is 15 to 30% of the length L of the shoulder block 6, and the height in the tire radial direction from the virtual vertex VP to the second ridge line e2. ha is set to 0.5 to 1 mm. If the length Sa of the chamfered portion 14 is less than 15% of the length L of the shoulder block 6 in the circumferential direction of the tire, the effect of reducing the change in the ground contact shape tends to be relatively reduced.
%, The circumferential length of the chamfered portion 14 tends to be large, which is not preferable because the contact pressure of the shoulder block 6 tends to be non-uniform during normal running. If the height ha is less than 0.5 mm, the effect of the chamfered portion 14 tends to be relatively reduced. Conversely, if the height ha is more than 1 mm, the ground pressure of the shoulder block 6 during normal running becomes uneven. Tends to be easy.

As shown in FIG. 4 (B), on a second plane P2 passing through the terminal end X of the main part 9a parallel to the tire equatorial plane, the shoulder block 6 moves from the reference ridge line em to the first plane. The length Sb in the tire circumferential direction up to the ridge line e1 is
It is desirable to set the length to about 3 to 10% of the length L of the shoulder block, and the reference ridge line em to the second ridge line e2
The height hb in the tire radial direction up to the first plane P1
Is preferably smaller than the height ha. In this example, such a chamfered portion 14 is formed as a flat surface, but it is needless to say that the chamfered portion 14 can be formed not only with a flat surface but also with various curved surfaces.

FIGS. 5 and 6 show another embodiment of the present invention. The shoulder block 6 of the present embodiment has a narrow groove 1 extending across the chamfers 14 on both sides in the tire circumferential direction.
7 is formed and the buttress surface 13 is formed by an outer buttress portion 13a and an inner buttress portion 13b, and the same reference numerals are given to the same portions as those in the embodiment. . The narrow groove 17 has a groove width GW of, for example, 1.5 to 3.0 mm, about 2.0 mm in this example, and has an arcuate curved portion 1 that protrudes outward in the tire axial direction.
7A and end portions 17B, 17B extending substantially linearly in the tire circumferential direction from the both ends in the circumferential direction of the curved portion 17A to the lateral groove (fourth lateral groove 4d) and opening.

The outer buttress portion 13a of this embodiment is inclined at a larger angle θ1 with respect to the tire radial direction line than the inner buttress portion 13b. This angle θ1 is, for example, 3
It is desirable that the angle be 0 to 70 °, more preferably 45 to 60 °.

[0024]

Embodiments of the present invention will be described below. A prototype tire having a tire size of 11R22.5 and a heavy load radial tire having the pattern shown in FIG. 1 and the specifications shown in Table 1 was prototyped, assembled into a regular rim, filled with an internal pressure of 700 (kPa), and free-rolled. Change of contact shape between state and braking state, wear energy at the time of braking,
The actual vehicle evaluation was performed. The change in the contact shape can be measured by using a contact surface measuring device and applying a vertical load of 2 per tire.
7620 (N) was applied and the ground contact shape in a braking state with a longitudinal acceleration of 0.2 G was examined. As shown in FIG. 7, the tire circumferential length Cr at the tire equator and the tire circumferential direction at the tread edge were measured. The ratio to the length Sh (Cr / Sh) was calculated. The closer this ratio value is to 1.0, the more excellent the wear characteristics of the shoulder portion against braking are.

Further, regarding the wear energy at the time of braking,
Using a wear energy measuring device consisting of a ground contact stress measuring sensor capable of measuring stresses in three axial directions provided with a large number of strain gauges and a slip amount measuring sensor, the first side of the shoulder block and the shoulder block during braking are used. The wear energy of each of the underwear side was calculated from the contact pressure and the slip amount. The wear energy is generally determined by the product of the contact pressure P and the slip amount S (P.
S) can be used instead, and this was determined by integrating the time from when the tire surface entered the contact surface to when it exited. Then, the wear energy Ea on the rear arrival side was evaluated by the ratio (Ea / Eb) to the wear energy Eb on the first arrival side.
When the value of this ratio is 1.5 or more, so-called heel & toe wear is likely to occur.

In the actual vehicle evaluation, the tire was mounted on a 2-D / 4 type truck, and after traveling 20,000 km, the difference between the amount of wear on the first arrival side and the amount of wear on the rear arrival side of the shoulder block was measured. The smaller the numerical value, the better the heel & toe wear and the better. Table 1 shows the test results.

[0027]

[Table 1]

As a result of the test, it was confirmed that the example of the present invention had less change in the contact shape and the ratio of the wear energy of the first-arrival portion and the rear-wear portion was smaller than the comparative example. As a result, it is possible to suppress a difference in wear between the crown portion and the shoulder portion. In a wear test using an actual vehicle, it was confirmed that heel and toe wear hardly occurred.

[0029]

As described above, the heavy duty tire of the present invention has a groove bottom protruding portion between shoulder blocks and a chamfered portion provided in connection with this groove bottom protruding portion, so that the tire can freely rotate. The change in the contact shape between the moving state and the braking state can be reduced, and uneven wear of the shoulder portion can be suitably suppressed.

[Brief description of the drawings]

FIG. 1 is a development view showing a tread surface of the present embodiment.

FIG. 2 is an enlarged partial perspective view of a shoulder block.

FIG. 3 is a plan view thereof.

4A is a sectional view of a first surface of the shoulder block, and FIG. 4B is a sectional view of a second surface of the shoulder block.

FIG. 5 is a partial perspective view of a shoulder block showing another embodiment of the present invention.

FIG. 6 is a plan view thereof.

FIG. 7 is a schematic view showing a ground contact shape of a tire.

FIG. 8 (A) is a schematic view of a grounding shape in a free rolling state,
(B) is a schematic diagram showing a grounding shape in a braking state.

[Explanation of symbols]

 2 Tread surface 3 Vertical main groove 4 Horizontal groove 6 Shoulder block 9 Groove bottom raised portion 9a Main portion 9b Inclined portion 10 Ground surface 11 Groove wall surface 14 Chamfered portion em Reference ridge line e1 First ridge line e2 Second ridge line e3 Third Ridgeline

Claims (3)

[Claims] 1. A tire is defined by a vertical main groove extending continuously in the tire circumferential direction near a tread edge, a horizontal groove continuous between the vertical main groove and the tread edge, and the tread edge. A heavy load tire in which a shoulder block forms a block row arranged in the tire circumferential direction, and the lateral groove is provided with a groove bottom protruding portion that protrudes from the groove bottom and connects between the shoulder blocks adjacent in the tire circumferential direction. The groove bottom protruding portion is connected to a main portion which is continuous at substantially the same height in the longitudinal direction of the horizontal groove from the vertical main groove side, and is connected to the end of the main portion, and the height gradually decreases toward the tread edge side. And a notch including a reference ridgeline at which the ground surface of the shoulder block and the groove wall surface of the lateral groove intersect, and a first ridge line extending over the ground surface, a third surface extending over the groove wall surface. 2 ridges, and A chamfered portion formed by a slope surrounded by a third ridgeline extending a buttress surface of the tire connected to the tread edge is formed, and the chamfered portion has an inner end in the tire axial direction at least from an end of the main portion. A tire for heavy loads, wherein the tire is located on the inner side in the tire axial direction, and the circumferential length of the chamfered portion becomes wider toward the buttress surface. 2. The method according to claim 1, wherein the first ridge has a radius of curvature equal to or more than 1.5 times a length L of the shoulder block in the circumferential direction of the tire and is formed in an arc shape convex toward the outside of the block. The heavy duty tire according to claim 1, wherein 3. The tire according to claim 1, wherein the chamfered portion is formed on a first surface parallel to a tire equator plane passing through a virtual vertex where the reference ridge line intersects the buttress surface, in a tire circumferential direction from the virtual vertex to the first ridge line. The length Sa is 15 to 30% of the length L of the shoulder block, the height ha in the tire radial direction from the virtual vertex to the second ridge line is 0.5 to 1 mm, and the end of the main portion is The second parallel to the passing tire equatorial plane
, The length Sb in the tire circumferential direction from the reference ridge line to the first ridge line is defined by the length L of the shoulder block.
The heavy duty tire according to claim 1 or 2, wherein the content of the tire is 3 to 10%.