JP2892154B2 - Radial tires for heavy loads - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a heavy duty radial tire capable of suppressing the occurrence of track wear and improving the wet resistance and the grip performance in the middle and final stages of tread surface wear. .

[Conventional technology]

2. Description of the Related Art There is known a tire in which a main groove which is arranged on a tread surface and extends in a circumferential direction is formed in a zigzag shape so as to enhance traction and braking. Also, by making the runout width of the zigzag groove larger at the groove bottom than the runout width of the tread surface, the track wear was reduced, and the wet performance was improved and the steering stability was measured from the middle to the end of the tread surface wear. Tires have also been proposed.

Furthermore, as a purpose of preventing uneven wear without causing a decrease in wet grip performance of heavy duty tires,
JP-B-51-15282, JP-A-46-4553, JP-A-61-92902, JP-A-61-178205, JP-A-6
No. 1-1115703, U.S. Pat. No. 4,423,760, etc., but none of them have taken drastic measures. For example,
As seen in No. 15282, the cross-sectional shape of the circumferential groove adjacent to the central rib is set such that the width of the central rib decreases inward in the radial direction of the tire, and as a countermeasure against stone debris, Separated protrusions are provided so that the cross-sectional shape of the groove is substantially inverted V-shaped so as to reduce track wear that generates ribs in the circumferential groove, but the shape of the groove is complicated. Therefore, there is a manufacturing problem, and a stone may be cut into both side cuts of the groove to break the rib side edge. The track wear is shown in FIGS. 9 (a) and 9 (b).
Wear becomes severe at the corners of the ribs of the zigzag groove. The rigidity of the protruding corner portion is lower than that of the other portions, so that abrasion easily proceeds at the protruding corner portion of the rib, so that local wear at this portion becomes severe. As shown in FIG. 9 (c), as a method of increasing the rigidity of the protruding corner portion and reducing uneven wear, the protruding corner portion is removed, and the longitudinal grooves G3 and G4 are replaced with circumferential groove components Ga parallel to the tire circumferential direction. , Gc and oblique groove components Gb and Gd formed at an angle α with respect to the tire circumferential direction.

[Problems to be solved by the invention]

Although reduction of track wear can be achieved by this method, it is necessary to increase the angle α of the oblique groove components Gb and Gd with respect to the circumferential direction from the viewpoint of the grip of the tire, and as a result, the heel and Toe wear occurs near the ridgeline of the oblique groove component.

The present invention provides a zigzag groove in which the runout has a groove bottom larger than the tread surface, and furthermore, at the peak of the side wall of the groove,
Based on the provision of a slot and a siping extending from the slot, the occurrence of track wear is suppressed, and the wet grip system and braking performance are improved even at the middle and end of tread surface wear, and tire durability is improved. It is intended to provide a radial tire for heavy loads that can improve the tire performance.

[Means for solving the problem]

The present invention relates to a groove having a groove bottom extending in a tire axial direction extending in a tire axial direction with a groove bottom having a runout width (h1) in a tire circumferential direction and forming a groove on a tread surface. 8) is an outer groove upper edge (M1) extending in the tire circumferential direction at a position on the tread surface away from the protruding corner (M) of the zigzag, and a tire circumferential position at a position on the tread surface away from the inward corner (V) of the zigzag. Formed in such a way that the distance (hu) in the tire axial direction between the outer groove upper edge (M1) and the outer groove upper edge (M1) is smaller than the runout width (h1). As a result, a main groove (4) having a mountain-shaped protrusion (6) having an inclined groove wall inclined outward from the protruding corner (M) of the groove bottom toward the tread surface and extending to the tread surface is formed. On the other hand, a mountain-shaped protrusion (6) is A slot (9) having an inner wall (10) having a height (HS) of 3 to 6 mm and a depth (DS) in the tire axial direction from the inclined groove wall gradually increasing downward in the radial direction, and a depth of the slot (9). A back wall (12) provided on the wall (10) and having the same or gradually increasing depth (DC) in the tire axial direction downward from the back wall (10), and the groove width is greater than the slot width (HS); This is a heavy duty radial tire including a notched mountain-like projection (6) formed with a small siping (11).

[Action]

The groove bottom of the main groove has a zigzag shape, and the distance hu in the tire axial direction between the outer groove upper edge M1 and the inner groove upper edge V1 on the tread surface is made smaller than the runout width h1 of the groove bottom. Further, in conjunction with the outer groove upper edge M1 and the inner groove upper edge V1 extending in the tire circumferential direction,
As described above with reference to FIG. 9 (a), the abrasion of the track is reduced by reducing the protrusion distance of the protruding corner portion of the rib in the early stage of wear to prevent the deformation of the protrusion. In addition, track wear is usually reduced with the increase in rigidity of the protruding corners due to the wear signal, thereby reducing track wear throughout the entire period from the early to middle and late stages, improving tire durability, and improving track wear. Can increase braking performance on wet road surfaces.

Further, in the case where the rib height is reduced due to tread surface wear and the tread stiffness is increased, the mountain-shaped protrusion is provided with a slot having an inner wall that gradually increases downward, so that the tread, particularly at the mountain-shaped protrusion, is provided. As a result, the rigidity is reduced and the rubber at the mountain-shaped protrusions is easily moved during traveling, so that the braking performance is prevented from lowering.

Moreover, by setting the slot width HS to 3 mm or more,
While the wet grip performance is greatly improved, the thickness is set to 6 mm or less, so that there is no possibility of stone biting.

In addition, since the depth DC includes a notched mountain-shaped protrusion having the same or gradually increasing siping downward, the movement of the rubber of the mountain-shaped protrusion 6 during running is reduced. It becomes easier and the braking performance can be further improved.

As described above, the heavy-load radial tire according to the present invention was able to significantly improve the braking performance and the wet grip performance while suppressing the track wear and increasing the durability by organically and integrally forming the above-described configuration. is there.

〔Example〕

 An embodiment of the present invention will be described below with reference to the drawings.

1 to 5, the heavy load radial tire 1 has a plurality of main grooves 4 in which a tread surface 2 is depressed and is continuous in a tire circumferential direction, and a groove bottom 3 repeats a corner M and a corner V in a zigzag manner. It has.

In this embodiment, four main grooves 4 are provided,
A central rib RC is provided between the main grooves 4 and 4 and a lug groove 21 is provided therebetween. A shoulder rib RS is provided between the main groove 4 and the tread edge E.

The main groove 4 has a groove bottom 3 which is bent in a zigzag as described above, and an outgoing corner M is formed, while a groove upper edge 8 defining the main groove 4 on the tread surface 2 is formed in the zigzag outgoing corner M. The outer groove upper edge M1 extending linearly in the circumferential direction of the tire at the position of the tread surface 2 away from the tire, and the inner groove upper edge V1 extending linearly in the tire circumferential direction at the position of the tread surface 2 away from the zigzag entry corner V. And are alternately connected.

Also, the pitch of the zigzag of the groove bottom 3 and the pitch of the upper and lower grooves M1 and V1 outside and inside the groove upper edge 8 are made substantially equal pitch, and the distance hu between the outer groove upper edge M1 and the inner groove upper edge V1 is hu. Are formed smaller than the runout width hl of the groove bottom 3.

Therefore, the main groove 4 is formed with a mountain-shaped protrusion 6 having an inclined groove wall 5 extending outward from the corner M of the groove bottom 3 toward the upper edge M1 of the groove outside the tread surface 2.

The main groove 4 is formed with a concave groove wall 22 of a concave portion that extends outward from the corner V of the groove bottom 3 toward the upper edge V1 of the groove in the tread surface 2 in the same manner as the inclined groove wall 5. The side walls of the main groove 4 are formed by alternately connecting the inclined groove walls 5 and the inclined groove walls 22 of the concave portions.

The inclined groove wall 5 of the mountain-shaped projection 6 is composed of three surfaces F1, F2, F3 divided by a ridge line J connecting the corner of the groove bottom 3 and the corner of the tread surface 2.

A slot 9 is provided in the mountain-shaped protrusion 6 facing the main groove 4 of the shoulder rib RS. In the present embodiment, the slots 9 are respectively provided in the inclined groove walls 5 at a substantially intermediate position in the circumferential direction of the mountain-shaped projection 6, and extend from the intermediate position in the height direction of the inclined groove walls 5 to the groove bottom edge 3a. And the slot width HS is 3-6m
Set to the range of m. In the present embodiment, the back wall 10 of the slot 9 hangs in a direction substantially perpendicular to the tread surface 2, so that the back wall 10 gradually increases in the tire axial depth DS from the inclined groove wall 5 downward. .

If the slot width HS is less than 3 mm, the wet grip performance is greatly reduced, while if it exceeds 6 mm, the tread surface 2 is greatly worn and stones are likely to bite.

The back wall 10 of the slot 9 is provided with a siping 11 that opens at the back wall 10, extends in the tire axial direction, and opens at the tread surface 2.

In this embodiment, the sipes 11 are spaced apart from every other one of the slots 9 arranged in the circumferential direction.
11 has a back wall 12 substantially parallel to the back wall 10 of the slot 9.

Therefore, in this embodiment, the siping 11 has the same back wall 12 in which the depth CD from the back wall 10 of the slot 9 is downward.

Note that the groove width of the siping 11 is desirably 2.0 mm or less. If it exceeds 2.0 mm, when the tread surface 2 comes into contact with the ground, the pressing force at which both ends of the siping are pressed against each other is reduced, so that the rigidity of the shoulder rib RS is reduced and the wear resistance is reduced.

Further, as shown in FIG. 6, the slot 9 and the siping 11 can be formed over the entire height of the inclined groove wall 5 from the groove bottom 3 to the tread surface 2 as shown in FIG. As shown in FIG. 7, the siping 11 may be formed in a range from the intermediate height of the inclined groove wall 5 to the groove bottom 3, and the depth DC of the siping 11 may be gradually increased downward.

Further, the sipes may be provided over the entire number of the slots, or the slots and the sipes having the above-mentioned configuration may be provided on the mountain-shaped projections of the central rib. The present invention can be modified in various forms.

〔Concrete example〕

A tire (Example) having a tire size of 10.00 R20 and having the configuration shown in Table 1 was prototyped, and the wet braking performance and the amount of track wear were tested. For comparison, a tire having a conventional specification (Comparative Example 1) and a tire other than the configuration of the present invention (Comparative Examples 2 and 3 shown in Table 1) were also prototyped and compared.

 The test was performed under the following conditions.

1) Wet brake performance The prototype tire is mounted on a 2.2TON product truck, the specified maximum load is loaded on the truck, and the vehicle is accelerated on a wet road surface from a speed of 60km / Hr to a speed of 80km / Hr. And the distance until the vehicle stopped was measured.

The test results are shown in FIG. 8 where the distance until the vehicle stops is measured. The reciprocal of the measured value was calculated as 1 in Comparative Example 1. The index was set to 00. The larger the value, the better.

2) Amount of track wear The tires of the example manufactured experimentally with the same specifications as in the above item 1) and the tires manufactured experimentally with the respective specifications of Comparative Examples 1 to 3 were mounted on the rear wheels of a truck having two front wheels and four rear wheels. The amount of track wear was measured every 10,000 km.

The amount of wear was calculated by measuring the volume (shown by oblique lines in the figure) that disappeared due to wear as shown in FIGS. 9 (a) and 9 (b).

3) Wet gripping property A prototype tire with a tire size of 10.00 R20 and the configuration shown in Fig. 1 to 4 with slot groove widths varying from 1mm to 9mm in steps of 1mm was installed on these actual vehicles. The vehicle was run on a wet road surface and judged by the driver's feeling.

The graph in the figure is indicated by an index with 50 for a groove width of 3 mm, and the larger the numerical value, the better. As a result of the test, it was found that the configuration of the present invention having a groove width of 3 mm or more was excellent. If the groove width exceeds 6 mm, the wet grip property is flat, but there is a risk of stone biting. Further, the wear on the tread surface increases, so that it is necessary to regulate the groove width to 6 mm or less.

〔The invention's effect〕

As described above, the heavy-duty radial tire of the present invention is characterized in that the groove bottom of the main groove is formed in a zigzag shape to form an outer corner and an inner corner, and a slot and a siping are provided in the inclined groove wall of the mountain-shaped protrusion. Therefore, even if the tread surface wear is late, the slot and siping remain, so that the track wear can be significantly reduced and the braking performance on a wet road surface is improved,
The wet grip property can be improved.

[Brief description of the drawings]

FIG. 1 is a plan view showing a tread surface of the tire of the present invention in an unfolded state, FIG. 2 is a partial cross-sectional view of the tire, FIG. 3 is a plan view showing an enlarged main part of the tread surface, FIG. FIG. 5 is a perspective view showing a mountain-shaped protrusion, FIG.
The figure is a sectional view showing another example of the slot and siping, and FIG.
FIG. 8 is a sectional view showing still another example of the slot and siping, FIG. 8 is a graph showing the results of the wet brake test, FIGS. 9 (a) and 9 (b) are drawings schematically showing the state of track wear, and FIG. Fig. (C) is a pattern diagram showing one example of conventional measures against track wear, Fig. 10 is a graph showing the relationship between running distance and track wear, and Fig. 11 is the relationship between slot groove width and wet grip. FIG. 2 ... tread surface, 3 ... groove bottom, 4 ... main groove, 5 ... inclined groove wall, 6 ... mountain-shaped projection, 8 ... groove upper edge, 9 ... slot, 10 ... back wall, 11 ... Siping, 12 ... Back wall, M ... Out corner, V ... In corner, M1 ... Outer groove upper edge, V1 ... Inner groove upper edge, HS ... Slot width, DS ... Throttle Depth, DC ... The depth of siping.

Continuation of the front page (56) References JP-A-61-178205 (JP, A) JP-A-58-61008 (JP, A) JP-A-58-167207 (JP, A) JP-A-63-102507 (JP) , U) JP-B 63-55443 (JP, B2) (58) Fields surveyed (Int. Cl. ⁶ , DB name) B60C 11/06

Claims (1)

(57) [Claims] An upper edge of a groove that extends in the tire circumferential direction by recessing a tread surface, has a runout width (h1) in the tire axial direction, extends in a zigzag manner in the tire circumferential direction, and defines a groove on the tread surface. (8) A tire at an outer groove upper edge (M1) extending in the circumferential direction of the tire at a position on the tread surface away from the protruding corner (M) of the zigzag, and a tire at a position on the tread surface away from the entering corner (V) of the zigzag. It extends in the circumferential direction and alternately connects with the inner upper edge groove (V1) in which the axial distance (hu) between the outer groove upper edge (M1) and the outer groove upper edge (M1) is smaller than the swing width (1). A main groove (4) having a mountain-shaped protrusion (6) having an inclined groove wall which is formed so as to incline outward from the protruding corner (M) of the groove bottom toward the tread surface in the radial direction and extend to the tread surface. ), While the mountain-shaped protrusion (6) is provided on the inclined groove wall. A slot (9) having a slot width (HS) of 3 to 6 mm and a depth (DS) in the tire axial direction (DS) from the inclined groove wall gradually increasing radially downward, and an outer slot (9). ) Has a back wall (12) provided in the back wall (10) and having the same or gradually increasing depth (DC) in the tire axial direction downward from the back wall (10), and the groove width is equal to the slot width ( A heavy duty radial tire comprising a notched mountain-like projection (6) formed with a siping (11) smaller than HS).