JPS61157406A - Pneumatic tire having lug pattern - Google Patents

Abstract

PURPOSE:To prevent the one-sided abrasion of a lug part without deteriorating performances by forming, on the lug parts, the cut-in parts which are extended in the axial direction and opened onto the tread side surface so that the length is gradually reduced towards the center part from the edge in the circumferential direction of the lug, in the captioned tire for heavy car such as bus. CONSTITUTION:A lug part 6 is formed by lug grooves 4 and 4, and a plurality of cut-in parts 8 having a narrow width, e.g., 0.3-1.5mm extending in the axial direction of a tire 1 are formed in the lug part 6. In this case, the length a1-a6 in the axial direction of the cutting-in part 8 is gradually reduced towards the center part in the peripheral direction from the both edge pats in the peripheral direction of the lug, and the following relation is fulfilled: a1=a6>a2=a5> a3=a4. Further, each of a1 and a6 is set to at least 10% of the length (a) in the axial direction of the lug groove 4, and the line segment L1 connecting the top edges of the cutting-in parts 8 is varied into straight-line form or curved- line form in the part between the edge part in the peripheral direction and the center part. Further, the pitch b1-b7 between the cutting-in pats 8 is set as follows: b1=b7<b2=b6<b3=b5<b4. With such constitution, the one-sided abrasaon of the lug can be prevented without deteriorating performances.

Description

Detailed Description of the Invention (Industrial Field of Application) 11 This invention provides a method for controlling the side area of the tread by a plurality of lug grooves extending substantially in the axial direction of the tire and opening at the side surface of the tread. The present invention relates to a pneumatic tie V having a lug pattern formed by dividing a plurality of lugs in the circumferential direction, and is particularly applicable to heavy vehicles such as trucks and buses to effectively prevent uneven wear of treads.

(Prior Art) As a tire of this kind that has been widely used in the past, for example, there is one whose main parts are shown in a front view in FIG.

This tire divides the side region 5 of the tread 2 in the circumferential direction of the tire 1 with a plurality of lugs tR4 extending in the axis XX direction of the tire 1 and opening at the side surface 3 of the tread 2. A plurality of lugs 6 are formed, and the lugs 6 here
acts to enhance the traction performance of the tire 1 in the longitudinal direction and to exhibit excellent wear resistance.

(Problem to be Solved by the Invention) However, in such a conventional pneumatic tire, in the lug pattern portion of the tread 2, the depression of the lug 6 is determined by the rotation direction of the tire 1 (indicated by arrow A in the figure). The wear rate is different between the side and the kick side, and early wear occurs especially on the kick side as shown by diagonal lines in the figure.As a result, the side end surface shape of the lug 6 on the dread side has a sawtooth shape. There was a problem of uneven wear as shown in the figure.

Note that such uneven wear of the lugs 6 will occur at both ends of the lugs 6 in the circumferential direction when the rotation direction is changed by the 0-tension of the tire 1.

Therefore, proposals have been made to prevent uneven wear of the lugs 6 by shortening the length of the lug groove in the axial direction of the tire, increasing the circumferential distance between adjacent lug grooves, etc. According to the technology, there was a separate problem in that the inherent traction performance of pneumatic tires with lug patterns would be impaired.

The present invention advantageously solves the problems of the prior art, and provides a pneumatic tire that can sufficiently prevent uneven lug wear, in other words, heel-and-toe wear, without deteriorating traction or other performance. It is something.

<Means for Solving the Problems> The 9-favorite tire having a lug pattern of the present invention has the following features:
In a tire in which a plurality of lugs are formed by dividing the side region of the tread in the circumferential direction of the tire by a plurality of lug grooves extending substantially in the axial direction of the tire and opening on the side surface of the tread, The lug has a narrow notch extending substantially in the axial direction of the tire and opening on the side surface of the tread, and the width of the notch gradually decreases from the circumferential end of the lug toward the circumferential center.

Here, "extending substantially in the axial direction of the tire" means extending in a direction that intersects the tire axis at an angle of about 30 degrees or less; In addition to those in which only both ends of the tire are defined by lug grooves, the term also includes those in which the tire is defined by those lug grooves and a groove located on the axially inner side of the tire to form an independent abutment part.

In addition to gradually reducing the length or depth of the cut, it also means gradually reducing the inclination angle of the cut relative to the center plane of the lug groove on the tread surface, and the reduction of the cut relative to the radius surface of the tire. The inclination angle of the tread is 11! This includes gradually decreasing the number of cuts on the IWJ, and further includes gradually decreasing the number of cuts per unit length in the circumferential direction of the lug.

(Function) In the pneumatic tire of this invention, the narrow notch is
This reduces the stiffness of the lug at the widthwise end of the tread, and also reduces the stiffness at the circumferential end of the lug, reducing the difference in stiffness between the lug and the surrounding area. Therefore, in response to mechanical inputs such as lateral forces and circumferential slips during kick-off, the load burden on the portions of the lug where the rigidity is reduced is reduced, resulting in an effective reduction of heel and toe wear. It turns out.

In addition, the narrow □ notches are provided not only at the circumferential ends of the lugs, but also near the circumferential center while gradually reducing the damage, thereby preventing sudden changes in rigidity within the lugs. Therefore, other 11I wear caused by sudden changes in rigidity does not occur on the lugs.

Here, if the incisions are made uniform in the circumferential direction of the lug, the difference in the ratio of 11 dj burden to the lateral force and mechanical input between the circumferential end portion and the circumferential center portion of the lug is equal to the incision. As in the case where there is no provision at all, the size is not so large, so the desired effect of the present invention cannot be achieved. In other words, the desired effect of the present invention is to sufficiently lower the rigidity of the circumferential end portions of the lug than that of the circumferential center portion, thereby reducing the load bearing ratio of the circumferential center portion to the end portions. This can be achieved by raising the value sufficiently higher than that.

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

FIG. 1 is a front view of main parts showing an embodiment of the present invention.
In the figures, parts similar to those in the prior art are designated by the same numbers.

That is, 1 indicates the tire, 2 indicates the tread, 3 indicates the tread side surface, 4 indicates the lug groove cut in the radial direction of the tire 1, 5 indicates the side area of the tread 2, and 6 indicates the lug. .

Further, 7 indicates a tread groove cut into the tread surface so that the ridge line forms a zigzag shape along the circumferential direction of the tire 1. Due to the rotation, the tire 1 in this example is not only in the direction of the arrow but also in the opposite direction. It is assumed that the direction is also rotated.

Here, "" means that the lug grooves 4 extend in the axial direction of the tire 1, and the lugs 6 are divided by the adjacent lug grooves 4.4.
Also, a plurality of narrow cuts 8, in this case six narrow cuts 8, extending in the axial direction of the tire 1 are provided at intervals in the circumferential direction of the lug 6, for example, 0.3 to 5 mm. The lengths a1 to a6 of these cuts 8 in the axial direction of the tire 1 on the tread surface are gradually decreased from both circumferential ends of the lug 6 toward the circumferential center. That is, in the illustrated example, a 1 = a 6 > a 2-a
5>a 3=a. Note that the maximum length al, a of the notch 8 in the axial direction of the tire 1 is the lug groove 4.
It is preferable to set the length a in the same direction to 10% or more in order to effectively reduce the rigidity of the circumferential end portion of the lug 6, and the length of each notch 8 is preferably 10% or more of the length a in the same direction of the tread surface. The rigidity within the lug can be improved by changing the line segment L1 connecting the leading edge of the lug 6 into a substantially straight line or a curved line approximating it between the circumferential end and the circumferential center of the lug 6. This is preferable in order to prevent sudden changes.

Furthermore, in this example, in addition to changing the width of the notches 8 in the circumferential direction of the lug 6, the arrangement pitch b, -b of each notch 8 is directed from the circumferential end of the lug 6 to the circumferential center. and gradually increase b1=b y <b 2
By setting = b 6 < b s - b 5 < b 4, the number of cuts per unit length in the circumferential direction of the lug 6 is gradually decreased toward the circumferential center of the lug 6. This results in more effective stiffness reduction at the end portions. Note that if the maximum arrangement pitch b4 of the notches 8 is set to 5 to 60% of the circumferential length b of the lug 6, a sudden change in rigidity at the circumferential center of the lug 6 can be effectively prevented. can do.

Further, in this example, the depths d and -d6 of each notch 8 in the radial direction of the tire on the tread side surface 3 are made equal, and the depth is made smaller than the depth d of the lug groove 4 in the same direction.

In the embodiment described above, it is preferable that the circumferential length b of the lug 6 is equal to or greater than the length a of the lug groove 4 in the tire 1σ axial direction, and in this embodiment,
Although the case is shown in which the shape of the shoulder portion adjacent to the tread 2 is a square shoulder, the present invention can be similarly applied to either a round shoulder or a tabular shoulder. In the illustrated example, both the length and the arrangement pitch of the notches 8 are changed, but the desired effects of the present invention can be achieved even if only one of them is selected. .

! 1 In addition, in the illustrated example, the lug grooves 4 and the notches 8 extending in the axial and radial directions of the tire 1 are
It is also possible to extend in a direction intersecting the axis and radial surface of the tire 1 at an angle of about 30 degrees or less.

FIG. 2 is a side view of a main part showing another embodiment of the present invention. Here, the depth d in the radial direction of the tire on the tread side surface 3 of each notch 8 provided at an equal pitch on the lug 6, %d
, is gradually decreased from the circumferential end to the circumferential center of the lug 6, so that d1=d 6 >d 2 =d 5 >d
By setting s-d to 4, the stiffness is effectively reduced at the circumferential end portion of the lug 6, and a sudden change in stiffness within the lug is prevented. Here, preferably, the maximum depth d, d6 of the notch 8 in the tire radial direction on the tread side surface 3 is set to 30% of the depth d of the lug groove 4 in the same direction.
% or more, and/or a line segment L2 that connects the bottom edge of each cut 8 on the tread side surface is approximately straight or a curved line that approximates it between the circumferential end and the circumferential center of the lug 6 shall be as follows.

FIG. 3 is a front view of main parts showing still another embodiment of the present invention. In this example, a plurality of openings are formed at equal pitches in the tread side surface 3 and have equal lengths in the axial direction of the tire 1. Among the notches 8, the notches 8 near the lug groove 4, since the number of cuts here is relatively small, all the notches 8 are placed on the tread surface with respect to the lug groove center plane Y-Y, and the leading edges of the notches 8 are is closer to the lug groove center plane Y-Y than the rear edge
The inclination angle α1 to α6 of each recess 8 with respect to the lug groove center plane Y-Y is gradually decreased from the circumferential end ml of the lug 6 toward the circumferential center. Let α1-α6>α2=α5>α3-α4. Here, it is preferable that the maximum inclination angles α and α6 of the notches 8 with respect to the lug groove center plane Y-Y are 30 degrees or less.

FIG. 4 is a side view of a main part showing still another embodiment of the present invention, in which the depth of the notch 8 on the tread side surface in the radial direction of the tire is made uniform, while on the tread side surface, The notches 8 in the portion close to the lug groove 4, again in this example, all the notches 8, with respect to the radial surface R1-R+ to R6-R6 of the tire 1 passing through the upper edge thereof,
The bottom edges of the notches are provided so as to be inclined in a direction closer to the lug groove than the upper edges, and the radial surface R+ -R+~R of each cut 8,
- Gradually reduce the inclination angles β1 to β6 with respect to R6 from the circumferential ends of the lugs 6 toward the circumferential center to obtain β1-R6>
Let β2=β5>β3=β4.

In this example as well, the rigidity of the circumferential end portion of the lug 6 can be effectively reduced, and a sudden change in the rigidity within the lug can be effectively prevented, as in the case of the example shown in FIG. It is. Further, in this example, it is preferable that the maximum inclination angle β, R6, of the notch with respect to the radial surface is 30 degrees or less.

This invention has been explained above based on illustrated examples, but @2-4
In the embodiment shown in the figure, the length of the notch 8 on the tread surface in the axial direction of the tire 1 is 5% or more of the groove a of the lug groove 4 in the same direction. In the embodiment shown in Figs. 1 to 4, the depth of the notch 8 in the radial direction of the tire on the tread side surface is 15% or more of the depth d of the lug groove 4 in the same direction, and further, as shown in Figs. In the embodiments, the arrangement pitch of the notches 8 is set to 3 to 30% of the circumferential length of the lug 6, except when the pitch is changed in the embodiment shown in FIG. This is preferable in order to achieve the desired effect more effectively.

In the illustrated example, the notches 8 are provided symmetrically with respect to the circumferential center position of the lug 6, but it goes without saying that the present invention is not limited to this.

Furthermore, in the embodiment described above, the amount of the cut 8 is gradually reduced from both ends of the lug 6 in the circumferential direction, but when the direction of rotation of the tire is specified, the amount of the cut 8 is gradually reduced from both ends of the lug 6 in the circumferential direction. can also be gradually reduced.

Furthermore, the embodiments shown in FIGS. 2 to 4 can be modified as appropriate within the range described with respect to FIG. They can also be combined.

(Comparative Example) Comparison results regarding lug S wear between a tire according to the present invention and a comparative tire will be described below.

(1) Common specifications Tire size: 10.00 R2014PR Tire axial length of lug groove a = 40 mm Circumferential length of lug b =
70+u Depth of lug groove in tire radial direction d = 16+n Opening width of cut: 0.5 mm Number of cuts, / 20 lugs (2) Tire type A, B - Comparison tie 1, C to H - This Tire of the invention A: No notch, B: With notch, the most of the notch is uniform in the circumferential direction of the lug a1=a2=a3=a+=a5=a6=151111
d 1=d 2=d 3=d ＜=d 5=66=10
+11α1=α6;α2=α5−α3;α,=0β1−
β6=β2=β5=β3=β, =Ob + =b 2
= b 3 = b 4 = b 5 = b b = b y
= 1011111C: Gradual decrease in the length of the cut in the axial direction of the tire a + = 86 = 20 mm, a 2 = a
s = 1 sun.

a 3 = a , = 10 mm, other points are the same as B D:
Gradual decrease in tire radial depth of cut d H-d
6 = 131, d 2 = 6 5
=1011111°d3=d, =7g+(The ratio is the same as B. E: Gradual decrease in inclination angle of the notch on the □tread surface α1; α6 = 15 degrees, α2 = α5 = 10 degrees.

α3=α4=5 degrees, other things are the same as B F: Gradual decrease in inclination angle of the cut on the tread side surface β1-β6=15 degrees, β2=β5=10 degrees.

β3 = β4 = 5 degrees, other conditions are the same as B G: Gradual increase in pitch of notches b 1 ”b 7 = 61, b 2 = b 6 = 9
11111゜b3''b s = 121, b
4 = 16 + l111, the rest is the same as B H: combination of C and G (3) Test method Continuously run without tire rotation under JIS normal internal pressure and positive NA load, at 30,000 and 50,000 Kn + running As shown in FIG. 5, the difference in the wear opening between the kick-out side edge and the push-in side edge of the arm was measured, and the measurement results for Tire A were set as 100 and expressed as an index.

(4) Test Results In terms of traction performance, all of the Tief C-H of the present invention had better results than Comparative Tire A.

(Effects) As is clear from the comparative example, according to the present invention, by gradually reducing the depth of the cut from the circumferential end of the lug to the circumferential center of the lug by using any one of the means,
This effectively prevents wear of the circumferential end portions of the lugs by 1 m without deteriorating traction performance, resulting in a significant improvement in tire durability.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing one embodiment of the present invention; Figs. 2 to 4 are diagrams showing other embodiments of the invention; Fig. 5 is a side view showing measurement positions of uneven wear in a comparative example; FIG. 6 is a front view of main parts showing a conventional example. 1... Tire 2... Tread 3... Tread side 4... Lug groove 5... Side area
6...Lug 7...Tread groove 8...Notch A...Rotation direction a...Lug groove axial length of the tire 8, ~a6.17) Q. , I don't like it. 581b...
Circumferential length of lugs β1 to β7...Lug circumferential arrangement pitch of notches d.
... Depth of the lug groove in the radial direction of the tie V d, ~d, ...
Depth of the cut in the radial direction of the tire α1 to α6...Inclination angle of the cut on the tread surface to the center plane of the lug groove β1 to β6...The cut on the side surface of the tread,
Inclination angle with respect to the radial plane of the tire Patent applicant: Bridgestone Corporation - "- Beak" Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] 1. A plurality of lug grooves extending substantially in the axial direction of the tire and opening on the side surface of the tread divide the side region of the tread in the circumferential direction of the tire to form a plurality of lugs. In the tire, the lug is provided with a narrow cut extending substantially in the axial direction of the tire and opening on the side surface of the tread, and the amount of the cut is directed from the circumferential end of the lug toward the circumferential center. A pneumatic tire having a lug pattern characterized by a lug pattern that gradually decreases. 2. The tire according to item 1, wherein the length of the cut in the axial direction of the tire on the tread surface gradually decreases from the circumferential end of the lug toward the circumferential center. 3. The tire according to item 2, wherein the maximum length of the cut in the axial direction of the tire on the tread surface is 10% or more of the circumferential length of the lug groove. 4. The tire according to item 2 or 3, in which the portion connecting the leading edge of each cut on the tread surface is approximately straight or a curved line approximating it between the circumferential end and the circumferential center of the lug. . 5. The tire according to item 1, wherein the depth of the cut in the radial direction of the tire on the tread side surface gradually decreases from the circumferential end of the lug toward the circumferential center. 6. The tire according to item 5, wherein the maximum depth of the notch in the radial direction of the tire on the tread side surface is 20% or more of the circumferential depth of the lug groove. 7. Draw a line segment connecting the bottom edge of each notch on the side of the tread,
Item 5 or 6, which is a substantially straight line or a curved line approximating it between the circumferential end and the circumferential center of the lug.
Tires listed in section. 8. On the tread surface, each cut in a portion close to the lug groove is provided so that the leading edge thereof is inclined in a direction closer to the lug groove center plane than the rear end edge with respect to the lug groove center plane. 2. The tire according to claim 1, wherein the inclination angle of the lug with respect to the center plane of the lug gradually decreases from the circumferential end of the lug toward the circumferential center of the lug. 9. The tire according to item 8, wherein the maximum angle of inclination of the cut with respect to the center plane of the lug groove is 30 degrees or less. 10. On the side surface of the tread, each notch is provided in a portion close to the lug groove, with the bottom edge being inclined in a direction closer to the lug groove than the upper edge with respect to the radial surface of the tire passing through the upper edge, and each notch is 2. The tire according to claim 1, wherein the inclination angle of the lug with respect to the radial surface gradually decreases from the circumferential end of the lug toward the circumferential center. 11. The tire according to item 10, wherein the maximum angle of inclination of the cut with respect to the radial surface is 30 degrees or less. 12. The tire according to any one of Items 1, 8, and 10, wherein the pitch of the cuts is gradually increased from the circumferential ends of the lugs toward the circumferential center. 13. The tire according to item 12, wherein the maximum pitch of the cuts is 5 to 60% of the circumferential length of the lug. 14. The tire according to any one of Items 1 and 5 to 13, wherein the length of the notch in the axial direction of the tire on the tread surface is 5% or more of the length of the lug groove in the same direction. 15. The tire according to any one of items 1 to 4, 8 to 13, or 14, wherein the depth of the notch in the tire radial direction on the tread side surface is 15% or more of the depth of the lug groove in the same direction. . 16. Adjust the pitch of the notches to 3 of the circumferential length of the lug.
-30%.