JP3112428B2 - Pneumatic tire - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire capable of facilitating visual inspection of a tire uniformity.

[0002]

2. Description of the Related Art In a pneumatic tire, a tread pattern is formed by providing various grooves on a tread surface. These grooves are usually provided with unvulcanized tread rubber and expanded in a toroidal shape. It is formed by vulcanizing and pressing the green tire cover in a mold.

[0003] A projection for forming a groove is formed in a mold, and the vulcanization is performed by accurately aligning the equatorial position of the raw tire cover with the equatorial position of the mold and vulcanizing the tire. A tread pattern can be obtained.

[0004] Therefore, when the equatorial position of the tire green cover and the equatorial position of the mold are set to be displaced during tire molding, the vulcanized tire is inferior in uniformity and is also a target. I can't get a tread pattern.

Conventionally, such a uniformity check is
This is performed as follows according to the tread pattern.

In the tread pattern shown in FIG. 7A, a center rib a extending linearly continuously on the tire equator C is formed by providing vertical grooves b extending on both sides of the tire equator C. You. When a tire having such a pattern is manufactured, an equatorial mark m for tire uniformity inspection is usually provided on the tread rubber of the raw tire cover d along the position of the equator CL of the raw tire cover as shown in FIG. Keep it. For the equator mark m, a paint or the like that does not disappear even by vulcanization is used.

The equator mark m written on the tread rubber e of the raw tire cover d is accurately applied on an automated production line.

After vulcanization, a tread pattern is formed as shown in FIG. 9, but the equator mark m remains visible on the straight center rib a. While rotating the tire t, the center rib a and the equatorial mark m remaining on the center rib a
Based on the relative positional relationship with the above, it is visually inspected whether or not the tread pattern is swaying in the tire axial direction, or whether or not the sway amount is within an allowable range.

As shown in FIG. 7B, the tire equator C
In the case where the drainage groove g extending continuously and linearly on the top is formed, as shown in FIG. 10A, after vulcanization, a visual inspection is performed while rotating the tire t around the tire axis. be able to.

If the straight groove g is not accurately formed in the tire equator C, as shown in FIG. 1B, a runout h occurs in the tire axial direction, thereby causing poor uniformity. Tires can be sorted.

[0011]

By the way, in recent years, tread patterns have become more and more complicated, and particularly in tread patterns and the like in which sport performance is emphasized, not only left and right asymmetric patterns but also straight grooves and straight rib-like rows are used. There are various proposals that do not exist at all.

However, the tire having such a tread pattern cannot be visually inspected for the uniformity as described above, and must be separately inspected by an expensive uniformity measuring device or the like.

In particular, as shown in FIG. 1, a central longitudinal groove 3 extending continuously in a zigzag manner on the tire equator C on the tread surface 2.
In the case where A is formed and a plurality of blocks 5C are provided along which the tire equator passes through the ground contact surface along the tire equator C, even if the equator mark is attached to the tire raw cover,
The formation of a number of grooves across the tire equator greatly increases the rubber flow at this point.

Therefore, the equatorial mark hardly remains after vulcanization, and even if the mark remains, the mark is greatly deformed.
It is almost impossible to perform a uniformity check based on this.

An object of the present invention is to provide a pneumatic tire that can facilitate visual inspection of a tire uniformity even when having such a tread pattern.

[0016]

Means for Solving the Problems In the present invention, claim 1 is provided.
The described invention uses a lateral groove crossing the tire equator on the tread surface.
The rubber flow at the tire equator position is large due to having
Yes Uniformity inspection using the equator mark is difficult
While disposing the blocks along the tire equator,
On the tread surface, without providing an equatorial mark, the block is vulcanized and molded with a linear pattern portion for tire uniformity visual inspection having a protrusion extending substantially on the tire equator , and the linear pattern portion is formed by one. Protrusions or tires
Protrusions that extend in a straight line parallel to the tire equator on both sides of the equator
A pneumatic tire characterized by a gap between raised portions.
You.

Further, the invention according to claim 2 is characterized in that the linear pattern portion is formed of one projection , and the length L in the tire circumferential direction is larger than 10 mm and less than 10 times this length L. The height d of the projections is larger than 0.2 mm and smaller than 1.0 mm, and the width W in the tire axial direction is larger than 0.3 mm and 2 mm. It is characterized by being smaller than 0.0 mm.

Further, in the invention according to claim 3, the linear pattern portion is formed on both sides of the tire equator and between the protrusions extending in a straight line parallel to the tire equator and protruding from the tread surface, Moreover, the distance W1 between the boundaries is 0.3 mm
And smaller than 2.0 mm.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. The pneumatic tire of the present invention is premised on a pneumatic tire having no groove extending straight on the tire equator or rib-like row extending straight on the tire equator on the tread surface. This is because a pneumatic tire having such grooves or rib-like rows can be visually inspected as described above. That is, a lateral groove 4 that crosses the tire equator is provided on the tread surface.
Rubber flow at the tire equator position
Makes uniformity inspection using the equator mark difficult
Block 5C is arranged along the tire equator. Therefore, for example, the tread pattern as shown in FIGS. 7A and 7B is out of the scope of the present invention.

The "rib-shaped rows extending straight on the tire equator" include those in which a center rib extending straight on the tire equator is divided in the tire circumferential direction by a lateral groove, lateral siping, or the like. Therefore, tires having these are also outside the scope of the present invention.

Further, as shown in FIG. 6, for example, the zigzag rib 15 extending on the tire equator between the two zigzag grooves 14, 14 has a larger rubber flow during vulcanization than a straight rib, Since there is no formation of a groove crossing the equator C, the ratio at which the equatorial mark remains is relatively high. Therefore, such a pneumatic tire is also outside the scope of the present invention.

In the present embodiment, as shown in FIG. 1, the central longitudinal groove 3A crossing the tire equator C by extending in a zigzag manner on the tread surface 2 with the tire equator C as the center of amplitude.
A vertical groove 3 including outer vertical grooves 3B and 3B arranged on both sides of the central vertical groove 3A and extending in a zigzag is formed. The tread surface 2 is provided with a large number of substantially V-shaped lateral grooves 4 which connect between the tread edges E and E and which are gently bent at the central vertical groove 3A, thereby providing a large number of blocks 5 on the tread surface 2. Sections are formed.

In such a pneumatic tire, since the central longitudinal groove 3A and the lateral groove 4 both cross the tire equator C, the rubber flow at the tire equator position during vulcanization increases, and the equatorial mark is removed. The uniformity test used becomes difficult.

The vertical groove 3 has a groove width at a cross-sectional position orthogonal to the groove center measured on the tread surface of about 5 to 20 mm, in this example, 12 mm, and a groove depth of about 6 to 15 mm. In this example, it is about 8 mm. The lateral groove 4 has a groove width of about 2 to 8 mm, and in this example, a small width of about 2 mm and a groove depth of about 7 mm.

In the present embodiment, the protrusions 6 extending substantially on the tire equator C are arranged along the tire equator C and on the plurality of blocks 5C passing through the ground contact surface. The linear pattern portion 7 for visual inspection of the tire uniformity is characterized by being vulcanized and formed. In this example, the linear pattern portion 7 is provided on all of the blocks 5C.
Illustrates an example in which the protrusion 6 is formed by intermittently appearing on the tire circumference.

The phrase "extending substantially on the tire equator C" means that
In addition to being present in line with the tire equator C, as shown in FIG. This small range CW is usually the tread width T
Although it may be 5% of W, it is preferably 3% of the tread width TW, more preferably 1% of the tread width TW, in order to increase the uniformity inspection accuracy.

Normally, in a pneumatic tire, the contour of the tread surface is bilaterally symmetric about the tire equator C.
It is easy and accurate to inspect the uniformity at such a position. In this example, the straight pattern portion 7 is provided so as to coincide with the tire equator C.

The linear pattern portion 7 has a projection 6 extending substantially on the equator C of the tire, so that the block 5
It has the effect of reducing the impact sound of C.

That is, when the central longitudinal groove 3A crosses the tire equator C in a zigzag manner as in the present embodiment, the block 5C is arranged along the tire equator C, and is particularly arranged along the tire equator C and passes through the ground contact surface. The tip 5T hits the road surface and tends to increase the impact sound.

However, if the protrusion 6 is provided substantially on the tire equator C of the block 5C as in the present embodiment, the protrusion 6 is first moved during running of the tire before the tip 5T of the block 5C comes into contact with the ground. Contact the road surface, then block 5C
Will hit the road surface. This allows
The impact energy of the entire block 5C is dispersed.
Therefore, the impact energy of the tip 5T of the block 5C can be reduced, and the impact sound can be reduced.

FIG. 2 shows an AA section of the linear pattern portion 7 for visual inspection of the tire uniformity. In this example, as shown in FIG. 1A, a single protruding portion 6 protruding from the tread surface is employed as the linear pattern portion 7. In addition, the protrusion 6 may adopt various shapes such as a polygonal shape or a V-shape that is easily formed, in addition to the illustrated circular cross section.

Preferably, the linear pattern portion 7 facilitates uniformity visual inspection without substantially affecting basic tire running performance such as cornering force, ride comfort, and drainage performance.

In the present embodiment, the straight pattern portions 7 are intermittently arranged at an arrangement pitch P having a length L in the tire circumferential direction larger than 10 mm and less than 10 times the length L. .

The length L of the straight pattern portion 7 in the tire circumferential direction.
Is less than 10 mm, or the arrangement pitch P is equal to the length L
In the case of 10 times or more, although there is no effect on the running performance, it is difficult to visually discriminate them, and visual inspection becomes difficult.

Further, as shown in FIG. 2A, for example, the height d of the projection 6 is preferably larger than 0.2 mm and smaller than 1.0 mm. 6 has a height d of 0.3 mm by being formed of a circular projection having a curvature radius of 0.3 mm.

When the height d is 0.2 mm or less,
There is a tendency that it is difficult to visually discriminate the protrusions 6. Conversely, if the protrusions 6 are more than 1.0 mm, the appearance of the tire is liable to be impaired. Grip force tends to decrease.

Further, the width W of the protrusion 6 in the tire axial direction is preferably, for example, larger than 0.3 mm and smaller than 2.0 mm. In this example, the width W of the protrusion 6 is 0 mm. .
Make 6mm.

The width W of the protrusion 6 in the tire axial direction is
If it is less than 0.3 mm, it tends to be invisible. or,
Unlike the continuous linear groove passing on the tire equator C, the linear pattern portion 7 is intermittently arranged in the tire circumferential direction in this example. Therefore, if the width is too large, the accuracy at the time of the visual inspection of the tire uniformity is increased. Tends to decrease. For these reasons, it is preferable that the width W of the protrusion 6 in the tire axial direction be less than 2.0 mm.

It is conceivable that the linear pattern portion 7 is provided with a concave portion instead of the protruding portion 6. However, when the concave portion is formed, the tip portion 5T of the block 5C is weakened, and rubber chipping or the like is likely to occur. It is hard to adopt.

Here, the above-mentioned linear pattern portion 7 needs to be formed by vulcanization molding, for example, as shown in FIG.
As shown in FIG. 1, a mold 10 for tire vulcanization molding is provided with a molding portion 11 capable of molding the above-mentioned protrusion 6.

In this example, the mold 10 moves in the tire radial direction and has a sector plate 10C having an inner surface engraved with a tread pattern forming pattern, and moves in the tire axial direction to form a tire side portion. It is a container type including side plates 10A and 10B.

Further, in this example, as shown in an enlarged scale in FIG. 8B, a molded portion 11 substantially equal to the cross section of the projection 6 is formed on the inner surface of the sector plate in accordance with the equator M of the mold. Has been established.

The molding portion 11 is recessed so as to coincide with the equator M of the mold, and as shown in FIG. The case where they are arranged in parallel is included. This small range MW can be usually 5% of the tread width TW, but is preferably 3% of the tread width TW in order to increase the uniformity inspection accuracy.
%, More preferably 1% of the tread width TW.

Therefore, as shown in FIG. 3 (A), the position of the equator CL of the tire raw cover d is stored with being accurately aligned with the position M of the equator of the mold 10, and after that, vulcanization is performed. In the case where the linear pattern portion 7 is pressed,
The pneumatic tire is formed so as to coincide with the tire equator C.

FIG. 4 shows another example of the mold. Mold 10
In this example, is a two-piece type consisting of a lower mold 10A and an upper mold 10B that are separated from each other at the equatorial plane of the mold. In this example, as shown in the enlarged view of FIG. 1B, the small grooves 11A and 11B which use the respective divided surfaces of the lower mold 10A and the upper mold 10B and are cut out of the divided surfaces.
Are aligned, so that the molded portion 11 substantially equal to the cross section of the projection 6 is provided in a concave shape in accordance with the equator M of the mold.

The molded portion 11 is recessed so as to coincide with the equator M of the mold.
Is included in the small range MW centered at the center.

The pneumatic tire of the present invention is turned around the tire axis at such a speed that the linear pattern portion 7 formed on the tread surface 2 can be visually checked, and the tire uniformity can be visually checked. Can be inspected.

In the inspection, for example, when the linear pattern portion 7 extends substantially along the tire equator C and is arranged along the tire circumferential direction, the linear pattern portion 7 causes deflection in the tire axial direction. Appear without. Conversely, when the linear pattern portion 7 does not extend substantially along the tire equator C or does not extend along the tire circumferential direction, the linear pattern portion 7 can be determined to be inferior in uniformity, such as causing deflection in the tire axial direction. Becomes

Note that such a pneumatic tire can be used for either a radial or bias pneumatic tire.
Its application is not limited to any one for passenger cars, trucks and buses, motorcycles, aircrafts and the like. Preferably, it can be adopted for pneumatic tires for passenger cars or motorcycles, which have a wide variety of tread patterns.

Another embodiment of the linear pattern portion 7 is shown in FIG.
(B) shows. In the present example, a straight line extends on both sides of the tire equator C (symmetrical position in this example) and substantially parallel to the tire equator C, and in this example, between the boundary portions 12 and 12 of the protrusions 6 with the tread surface. And at the boundary 12,
Preferably, the distance W1 between 12 is greater than 0.3 mm and less than 2.0 mm.

When the distance W1 between the boundary portions 12 and 12 is 0.3 mm or less, a satisfactory visual inspection cannot be performed at a high rate. In conjunction with the interruption in the tire circumferential direction, the inspection accuracy tends to be reduced.

Further, as shown in FIG. 5, the present invention can be applied to a pneumatic tire having a drain groove 16 extending in a V-shape on the tread surface.

[0053]

EXAMPLE A radial tire having a tire size of 225 / 50R16 and having a tread pattern as shown in FIG. 1 according to the present invention was changed in the size of a linear pattern portion 7 as shown in FIG. Molding was performed using a vulcanizing mold (Examples 1 and 2), and whether or not uniformity visual inspection was possible, and steering stability and pattern noise (both sensory evaluation by a driver running on a test course) were evaluated.
Table 1 shows the test results.

[0054]

[Table 1]

As a result of the test, in Examples 1 and 2,
The visibility of the linear pattern portion was good, and the uniformity inspection by visual inspection was easily performed. In addition, it was confirmed that, when the height and width of the protruding portion were too large, the linear pattern portion was effective in reducing pattern noise, but tended to reduce steering stability. Therefore, it is preferable that the protrusions have a height d larger than 0.2 mm and smaller than 1.0 mm and a width W in the tire axial direction larger than 0.3 mm and smaller than 2.0 mm. preferable.

Next, for comparison, an equatorial mark having a width of about 3 mm made of white paint at the equatorial position of the raw tire cover was compared with an example having the same pattern as that of the embodiment having no molded part for forming a linear pattern part. Upon vulcanization molding with a mold, it was found that the remaining marks were largely distorted due to the influence of the flow of rubber during vulcanization, and visual inspection was impossible.

[0057]

As described above, the present invention relates to a pneumatic tire having no grooves on the tread surface extending straight on the tire equator or rib-like rows extending straight on the tire equator.
Inspection of the tire uniformity can be easily performed visually.

Further, since the projection of the linear pattern portion provided substantially on the tire equator is grounded before the tip of the block, the impact sound of the block can be reduced, and the pattern noise can be reduced.

[Brief description of the drawings]

FIG. 1 is a development view of a tread pattern showing an embodiment of the present invention.

FIGS. 2A and 2B are cross-sectional views showing an embodiment of a linear projection.

3A is a sectional view of a mold, and FIG. 3B is a partially enlarged view thereof.

FIG. 4A is a sectional view of another mold, and FIG. 4B is a partially enlarged view thereof.

FIG. 5 is a development view of a tread pattern showing another embodiment of the present invention.

FIG. 6 is a development view of a tread pattern.

FIGS. 7A and 7B are developed views of a tread pattern for explaining a conventional technique.

FIG. 8 is a cross-sectional view of a raw tire cover illustrating a conventional technique.

FIG. 9 is a cross-sectional view of a pneumatic tire immediately after vulcanization for explaining a conventional technique.

FIGS. 10A and 10B are front views illustrating a visual inspection of a tire uniformity.

[Explanation of symbols]

 2 Tread surface 3 Vertical groove 4 Horizontal groove 5 Block 6 Projection 7 Linear pattern 10 Mold 11 Molding section 12 Boundary part C Tire equator L Length of linear pattern P Pitch of linear pattern W Width of projection d Projection height W1 Distance between boundaries

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B60C 11/00-11/11 B60C 19/00 B29D 30/00-30/68 B29D 33/42 B29D 35 / 02-35/14

Claims (3)

(57) [Claims] 1. A lateral groove crossing a tire equator is formed on a tread surface.
Rubber flow at the tire equator position
Makes uniformity inspection using the equator mark difficult
And a linear pattern portion for tire uniformity visual inspection having a protrusion extending substantially on the tire equator without providing an equatorial mark on the tread surface. Molded , and the linear pattern portion is formed as a single protrusion or a tire equator.
Protrusions that extend in a straight line parallel to the tire equator on both sides of the
A pneumatic tire characterized by the following: 2. The linear pattern portion comprises one projection.
At the same time, the length L in the tire circumferential direction is greater than 10 mm, and is arranged intermittently at an arrangement pitch of less than 10 times this length L, and the height d of the projection is greater than 0.2 mm. And 1.
The pneumatic tire according to claim 1, wherein the width W in the tire axial direction is smaller than 0 mm and the width W in the tire axial direction is larger than 0.3 mm and smaller than 2.0 mm. 3. The straight pattern portion is formed on both sides of the tire equator and between the protrusions extending in a straight line parallel to the tire equator and projecting from the tread surface, and furthermore, a distance W1 between the boundary portions. The pneumatic tire according to claim 1, wherein a is larger than 0.3 mm and smaller than 2.0 mm.