JPS61193903A - Heavy loading radial tire - Google Patents

Abstract

PURPOSE:To ensure sufficient rigidity of shoulder rib while to maintain balance between the central section and the grounding pressure by positioning the outer face of shoulder rib to the inside in radial direction of the extended line of the outer face of central section. CONSTITUTION:The tread 3 made on the outercircumference of a belt 2 is partitioned through a circumferential groove 5 into the shoulder rib 6 and the central section 7 at the position separated by the distance W1 which is 7.5-20% of the tread width W from the side end line. In the radial cross-section of tire the outer face of arched or linear shoulder rib 6 is positioned at the inside in radial direction of the outer face of the central section 7 having the curvature R 2-4 times of the maximum width of tire. The extended lines of said outer faces are crossed or contacted within the range of opening width W2 of the groove 5 to reduce the riding resistance of rut considerably.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) This invention relates to an air pump 9 used in trucks, buses, etc.
This relates to tires, especially heavy-duty radial tires that improve steering stability by suppressing wandering phenomena without causing uneven tire wear.〇 (Conventional Technique #) Known general method Type A tires have a so-called square shoulder shape that connects to the sidewall with an angular edge at the tread side end, so they tend to wander when rolling in ruts. There was a problem.

Here, the wandering phenomenon is defined as a phenomenon in which a vehicle travels in ruts caused by subsidence or wear due to the weight of a paved road surface with high traffic frequency, and the vehicle is forced to move in order to change lanes or avoid obstacles. This refers to the phenomenon of the steering wheel being taken off, which is often experienced when trying to get out of a rut.

As a countermeasure to this problem, it is known that one end of the shoulder of the tire is made into a rounded shoulder, or a so-called tapered shoulder, which is sloped in a conical shape, in order to reduce the resistance when riding over ruts. On the other hand, Japanese Unexamined Patent Publication No. 58-19
As shown in Publication No. 4606, lateral ribs are divided into narrow linear circumferential groups at the side edges of the tread, and the outer surfaces of these lateral ribs are connected to the central part of the tread F. It has been proposed to extend parallel to and be located radially inward from the outer surface, and furthermore to have a top width of the lateral lip approximately equal to the maximum depth of the circumferential group.

(Problem to be Solved by the Invention) However, in the former technique, when there is an imbalance in the alignment of the wheel, the wheel is divided by a main groove substantially extending in the circumferential direction. The ground pressure of each rib, especially the shoulder rib located at the widthwise end of the tread, and the second rib adjacent to the inner side of the shoulder rib are not balanced, and the ground pressure of the shoulder rib is considerably higher than that of the second rib. At the same time, the rigidity difference within the shoulder rib also plays a role, causing so-called wavy wear in which the shoulder rib wears unevenly around the circumference, and railway wear that occurs along the edge of the second rib. There is a problem of premature wear originating from this, or second lip drop wear caused by a drop in the ground contact pressure of the ribs.
In addition, in the latter case, the circumferential group is narrow and extends linearly in the circumferential direction, so when the vehicle turns, the side walls of the group contact each other at the top, causing the circumferential group to Wear along the edge of the rib adjacent to the inside is accelerated, resulting in uneven wear similar to the former prior art.Moreover, since the width of the side lip is narrow, its rigidity is low, and therefore the vehicle There was a risk that the lateral lip could become partially missing while the vehicle was being driven.

The present invention advantageously solves the problems of the prior art, and provides a heavy-duty radial tire that can effectively suppress the wandering phenomenon without causing problems such as uneven wear.

(Means for Solving the Problems) The heavy-duty radial tire of the present invention is particularly characterized in that the radial tire for heavy loads of the present invention has a tread width of 7.5" from the side edge of the tread of a pneumatic tire.
A groove extending generally in the circumferential direction of the tire separates the shoulder rib from the center part at a distance of ~20%, and within the radial cross section of the tire, the outer surface of the shoulder rib is separated from the outer surface of the center part. The extension lines of these external surfaces intersect or contact each other within the opening width of the groove.

(Function) In this heavy-duty radial tire, by specifying the shape of the outer surface of the shoulder ribs as described above, the resistance that acts on the tire when going over ruts is reduced, suppressing the wandering phenomenon, and also suppressing the wandering phenomenon. By associating the positions of the shoulder ribs and the outer surfaces of the center section as described above, sufficient rigidity of the shoulder ribs is ensured, and a balance between the ground pressure on the shoulder ribs and the center section is maintained. As,
Not only missing shoulder ribs but also uneven wear of each rib can be effectively prevented.

(Example) The present invention will be explained below based on illustrated examples.

FIG. 1 is a radial cross-sectional view showing an embodiment of the present invention for half of the tread, and the first Fl:i (a),
(b) shows a tire in which the outer surface of the shoulder ribs has an arcuate shape and a linear shape, respectively.

In the figure, 1 indicates a substantially radial carcass extending in a toroidal shape between a pair of left and right bead cores (not shown), and 2 indicates a belt that rigidly reinforces the crown portion of this carcass 1. The belt layer 2a is composed of at least a nibry, a four-ply wire or cable in the figure. Here, among these belt layers 2a, the cords of at least one pair of mutually adjacent plies, in this example, the second cord from the innermost side in the radial direction.
The cords of the belt layer 2a located in the 8th layer and the 8th layer and the 4th layer are at a small angle with respect to the equatorial plane C-C of the tire, for example 10-ffi Is.

and extend in directions intersecting each other across the equatorial plane.

Further, 8 indicates a tread provided on the outer periphery of the belt 2, and 4
is a sidewall continuous to this tread 8.

In this invention, the tread 8 is located at a distance W□ of 7.5 to 80% of the tread mw from the side edge of the tread 8.
The tire is divided into a shoulder rib 6 and a center portion 7 by a groove 5 extending generally in the circumferential direction of the tire. Here, the distance W0
7. of tread width W. ! 1-20% is 7.5
If it is less than %, the rigidity of the shoulder rib 6 will be too low and there is a risk of the same chipping as described in the prior art, and 2.
If it is larger than 0%, the grounding range of the center part becomes narrower,
It causes accelerated wear.

Here, the tread width W is the maximum width of the tire from O to
It is preferable that the groove 6 extends in a zigzag shape in the circumferential direction, and that the zigzag pitch and swing width of the ridge line formed by the groove 6 and the shoulder rib 6 are set to be 90%. The zigzag pitch and swing width of the ridge line formed by the groove 6 and the center part 7 are made smaller than those of the center groove 8 disposed within the center part γ. This is preferable in order to more effectively prevent uneven wear of the tread.

Note that the side edge of the tread 8 here refers to the side edge of the sidewall 4, especially when the outer surface of the shoulder rib 6 has an arc shape as shown in the first IN (a) in the radial cross section of the tire. It refers to the point where it touches the outer surface line.

In addition, in the radial cross section of the tire, the outer surface of the shoulder rib 6, which is arcuate or linear, is preferably arranged so that the outer surface of the center portion 7 has a radius of curvature R that is 2 to 4 times the maximum width of the tire. position inside the direction,
And the extension line of these both outer surfaces is the opening mw of the groove 5,
intersect or touch within the range of Here, when the outer surface of the shoulder rib is formed into an arc shape, it is preferable that the radius of curvature r thereof is equal to or larger than SSW. This means that if the radius of curvature is less than 25 -, it will closely approximate a square shoulder and therefore will not be able to return even a sufficient reduction in the crossing resistance of -1 ruts.

Furthermore, when the groove 5 has a zigzag shape, the opening width W of the groove 5 means the interval in the tread width direction between the centers of the zigzags mp of both ridgelines.

By specifying the outer surface shape of the shoulder rib 6 in relation to that of the center portion 7 in this manner, the resistance to overcome the ruts is sufficiently reduced, and the wandering phenomenon is effectively suppressed. In addition to this, by specifying the position of the groove 6 as described above, it is possible to optimize the relationship between the ground pressure between the shoulder rib 6 and the center portion. To explain this relationship of ground pressure based on Fig. 2, in conventional tires, the 8th
As shown in Figure (5L), due to the stiffness, the second lip suffers from early wear due to dragging, and the shoulder rib suffers from excessive ground contact pressure and uneven wear due to the difference in rigidity. However, in the above-mentioned tire, as shown in Fig. 2 (-b), the ground contact pressure of the tread 8 gradually decreases from the center in the width direction toward the outside. Therefore, neither lip suffers from the disadvantageous premature wear or uneven wear that occurs in the prior art.

In order to make the ground pressure relationship more appropriate here, the vertical distance between the ridgeline position B formed by the groove 5 and the center part 7 and the side edge position of the tread 8 in the radial cross section of the tire is ■, R-5Σ (W/2)”
It is preferable that <■<o, ggsw. That is, when the vertical pressure 1IIH is 0.225W or more, the ground pressure of the shoulder rib 6 becomes too low, which may cause premature wear of the lip, and conversely,
(W/g)"- or less, the ground pressure of the second lip becomes lower than that of the shoulder rib, and second lip drop wear tends to occur.

As shown in the enlarged cross-sectional view in No. 81iU (5L), the groove 6 has an outer portion Sa whose width tapers out toward the tread surface, and an outer portion Sa whose width is substantially uniform. an inner portion 5b, preferably an outer portion 5b;
It is preferable that the opening end W of a is set to 1.5 to 7% of the tread width W, and the width of the inner portion 5b is set to 1 to 3 mm. Here, the reason why the opening width W is specified in this way is that when the width exceeds 7%, the shoulder rib and the second lip deform independently when a lateral force is applied, and the movement of the shoulder rib in particular increases, so the width of 5b is The purpose of setting it to 1 to 8 ml is to prevent stones from getting into the groove and to suppress the movement of the shoulder rib by bringing the shoulder rib into contact with the second lip. As shown in FIG. 8(b), the lateral force causes the wall surfaces to come into contact with each other at least at the outer end of the inner portion lsb, thereby increasing the rigidity of the shoulder rib 6 with the help of the center portion 7. bring up. On the one hand, the outer part 5a of the groove 5 maintains the open state shown in the figure even under the action of lateral forces of the tire, thereby always providing reliable drainage.

Furthermore, this groove 5 has a maximum depth Ho of 70% to 100% of the depth H' of the center groove 8, and a depth Hl of the inner portion 5b of 40% to 100% of the maximum depth H. 60% is preferable in the sense that both drainage performance and uneven wear prevention effect due to groove contact are improved.In addition, the inclination angle α0. It is preferable to set α and 10 to 80°, respectively, from the standpoint of ensuring more reliable drainage.

Furthermore, in the belt 2, which acts as a paddle reinforcement for the tread 8 and has a large effect on the rigidity, uneven wear, and driving stability of the tread 8, the cord is connected to the equatorial plane of the tire.
- The one having the largest width among the intersecting portions of a pair of adjacent intersecting belt layers that extend in mutually intersecting directions across the equatorial plane at a small angle with respect to C, and thus contribute to ensuring circumferential rigidity. It is preferable to specify the end position in the tread width direction, in this example, the six end positions of the eighth belt layer ga from the innermost layer as follows. That is, the end position M is preferably located at a perpendicular position passing through position B of the ridgeline formed by the groove S and the center portion 7, or closer to the shoulder rib than that, to ensure that at least the rigidity of the second lip is ensured. However, if the end position M is separated by more than 7.6% of the tread width W from the perpendicular line passing through position B, the rigidity of the shoulder rib 6 becomes too high and uneven wear cannot be sufficiently suppressed. Therefore, in the end, the distance W from the perpendicular position of the terminal position M is preferably set to W8=0 to o, o5W.

This invention has been explained above based on the illustrated examples, but the dimensions, angles, etc. specified above are based on the unloaded condition when the tire is assembled on a regular rim and filled with the regular internal pressure. be.

[Comparative example]

Comparative test results for confirming the effects brought about by this invention are shown below.

A total of four types of tires were tested: two types of tires according to the present invention, B, and two types of tires 0 and D according to the prior art.
In 4PR, the tread has four grooves extending generally in the layer direction of the tire.

Taim and B according to this invention are each the first FgJ(a
) # Same as that shown in (1)), where the distance W1 between the tread side edge and the groove 6 is 18% of the tread width W, and the end of the maximum width intersection of the crossed belt layers. The distance W between the position M and the ridgeline position B formed by the groove 5 and the center part γ is unified to Is% of W, and the relationship between the outer surface of the shoulder rib 6 and the outer surface of the center part 7 is In addition to being as specified in the invention, the cross-sectional shape of the groove 5 was as shown in FIG. 8(a).

On the other hand, in both tires O and D according to the prior art, the outer surface of the tread exhibits an arc shape with one radius of curvature over the entire area, that is, from the center part f to beyond the groove S to the shoulder rib 6. Tire 0 is a square-shaped rounded type with one end of the shield having a square shape and a zigzag that connects to the sidewall 14. Tire D is a round-shaped rounded type where one end of the shield has a very small radius of curvature and is connected to the sidewall 4. It was made into a thing. In addition, the distance mw is 28 rumored to be the tread width W, and similarly Wa is 9% of W (the belt width itself is Tiam, B
), and the shape of the groove 6 is the conventional general V
It has a glyph shape.

These tires were subjected to actual vehicle tests under JIS standard internal pressure and standard load, and the results shown in Table 1 were obtained. Regarding uneven wear, it is estimated that uneven wear occurs on the shoulder rib and second lip when a vehicle equipped with these tires is driven for 60,000 miles on a test track that includes highways and ordinary roads at a ratio of 7:8. The magnitude of uneven wear was visually compared and checked between each tire.

Table 1 (Effects of the Invention) As is clear from the above description, according to the present invention, the wandering phenomenon can be sufficiently effectively suppressed without causing any inconvenience such as uneven lip wear.

[Brief explanation of drawings]

FIG. 1 is a radial cross section Wi1 showing an embodiment of the present invention in half of the tread. FIG. 8 is a graph showing ground pressure, and No. 8 wI is an enlarged sectional view showing grooves. 1-・φ carcass 3...Belt sa...
Belt layer 8...Tread 4...Side wall 5...Groove 6...Shoulder rib 7...
・Center Department Patent Applicant: Kinsha Bridgestone Co., Ltd. Figure 2 (a) (b) Figure 3 (a) b (b) -

Claims (1)

[Claims] 1. The cord runs over the crown of a substantially radial carcass extending in a toroidal manner between a pair of bead cores, making a small angle to the equatorial plane of the tire. A pneumatic tire which is rigidly reinforced by a belt having at least one pair of mutually adjacent belt layers extending in a direction intersecting with each other, and which has a tread continuous to the sidewall on the outer periphery of the belt. The tread is divided into a shoulder rib and a center portion by a groove extending generally in the circumferential direction of the tire at a distance of 7.5 to 20% of the tread width from the side edge of the tread. In addition, within the radial cross section of the tire, the outer surface of the shoulder rib is located radially inward than the extension line of the outer surface of the center part, and the extension lines of both outer surfaces intersect within the opening width of the groove. A radial tire for heavy loads that is characterized by being in contact with each other. 2. In the tread width direction of the tire, the end of the widest intersection of the belt layers is at a perpendicular position passing through the ridge line formed by the groove and the center portion, or 7.5% or less of the tread width. The tire according to item 1, which is located closer to the shoulder rib than the above range. 3. The tire according to item 1 or 2, wherein the groove comprises an outer portion whose width gradually increases toward the tread surface and an inner portion whose width is substantially uniform.