JPH0994831A - Vulcanization molding mold and radial tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the generation of rubber flash by forming a notch part for the volume corresponding to excess volume in the inside end part of a rib extending from the mating faces on both sides of each segment. SOLUTION: It is necessary that the ratio d/L of the depth (d) of a notch to the length L of the bottom 4b of a notch part 4 formed in the rib 2-1 of a segment 1-1 is 0.2-1.0. The end of the notch part 4 is preferably chamfered at an angle ϕ of 30-60 deg.. The volume VR of the notch part 4 before notching which is chamfered at an angle ϕ is given by equation I, where VEX=VR, d/L is 0.2-1.0, and the length of the bottom 4b of the notch part 4 is L, the depth is (d), and a chamfer angle ϕ are set up. For example, the length L of the bottom 4b is arranged, and the length L of the bottom 4b, the depth (d), and the chamfer angle ϕ are set up to meet equation II.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is capable of reciprocating radial movement between an operating position where vulcanization molding is performed on an unvulcanized tire and a non-operating position where a tire after vulcanization molding is taken out is taken out. A vulcanization mold having a large number of divided segments, the inner surface of each segment having ribs forming circumferential grooves in the tread rubber of the tire, and a pair of bead parts and a pair vulcanized and molded by this mold. And a tread portion continuous in a toroidal shape between the both sidewall portions, and the tread rubber of the tread portion is provided with a circumferential groove.

[0002]

2. Description of the Related Art Pneumatic radial tires (hereinafter referred to as radial tires or simply tires) used in vehicles such as passenger cars, trucks and buses, which often travel at relatively high speed on paved road surfaces, have a high level of uniformity characteristics. In order to meet this requirement, it is indispensable to apply a so-called split mold to the mold used in the vulcanization molding process. Therefore, the vulcanization molding mold for the radial tire to be used for the above vehicle is required. It has become common to use split molds.

The split mold is composed of a number of parts,
Of these, only a large number of divided segments, which mainly serve to directly vulcanize and mold the tread rubber portion of the unvulcanized tire, are taken out, and a simplified schematic plan view is shown in FIG.
Segment 1 shown by a solid line in FIG. 8 is in an operating position when vulcanization molding is performed on an unvulcanized tire (not shown),
The segment 1 indicated by a chain double-dashed line indicates that the tire (not shown) after vulcanization molding is in a non-operating position when taken out.

The segment 1, which is usually divided into 7 to 9 (8 in the illustrated example), extends from the non-operating position to the operating position.
It is configured to be movable in the radial direction shown by the double-ended arrows A and B by engaging with and interlocking with means (not shown), and a large number of divided segments 1 are merged at the operating position. The mating surface P is adjusted so that there is almost no gap between adjacent segments 1 including the end surface of the rib 2 for forming a groove in the tread rubber. The double-headed arrows A and B indicate the central axis C of the segment 1 in the operating position.
Head to (indicated by dots in the figure). The inner peripheral surface of the united segment 1 in the operating position excluding the rib portion forms a surface of rotation about the central axis C.

In FIG. 8, ribs 2 provided on the inner surface of each segment 1 are ridges for forming circumferential grooves in the tread rubber when vulcanizing and molding an unvulcanized tire. The circumferential groove here, a straight groove extending along the circumference of the tire tread or extending diagonally across the circumference, and a bent groove extending in the same manner as above by bending the straight groove in a zigzag shape,
The straight groove includes a curved groove formed by bending a part or the whole, and the same applies hereinafter.

When the segment 1 provided with the rib 2 forming the circumferential groove moves in the direction of the arrow B from the non-operating position to the operating position, the tread rubber of the unvulcanized tire loaded inside the segment 1 is As is clear from the figure, the end face 2 _EP of each rib 2 bites diagonally. In other words, the end faces 2 _EP of the segments 1 adjacent to each other have the orthogonal movement component with respect to the same mating face P shown by the solid line, and the mating face P
Move toward and match.

[0007]

The main purpose of using a split mold at a significantly higher cost is to minimize changes in member shape, member position, etc. between the unvulcanized tire state and the product tire, This is because it is possible to realize a high degree of uniformity, and therefore the outer diameter of the unvulcanized tire is set to a value as close as possible to the inner peripheral surface diameter of the operating position segment 1. This means that the rib 2 first digs into the tread rubber, and the end face 2 of the adjacent rib 2 described above
_EP by movement of the quadrature component with respect to the mating surface P, the end face 2 _EP
Extrude the tread rubber toward each other as if scraping it off.

A part of the extruded rubber flows and stops on the mating surface P which still forms a space, and after all, after the vulcanization and molding, the circumferential groove located on the mating surface P has a relatively large volume "extrusion". "Rubber", so to speak, forms a rubber burr. This rubber flash not only impairs the appearance of the tire and deteriorates the commercial property, but also increases the noise level due to the rubber flash when the tire is used, deteriorates drainage on wet road surface, and further travels. On the way, crack nuclei occur near the rubber flash. This core causes a crack failure as the tire travel distance increases, and eventually leads to a marked decrease in tire life.

As a means for avoiding performance deterioration and crack failure due to this rubber flash, the specification relating to Japanese Patent Application No. 62-73674 discloses a rib (protrusion) provided in a segment for forming a groove of a tread rubber. Have proposed a tire molding die in which the inner portion is cut out at the end positions where they contact each other, and in the specification relating to Japanese Patent Application No. 62-73675 and Japanese Patent Application Laid-Open No. 1-208206, JI.
For tires without rubber burrs in which the wear indicator with a height of 1.6 mm provided on the groove bottom of the tread rubber (protrusion from the groove bottom) was fitted to the notch position proposed by the former specification according to the provisions of SD4230. Disclosure.

However, since the height of the wear indicator is regulated to a constant 1.6 mm regardless of the tire type,
For various groove depths and groove widths of various radial tires, it is inevitable that it will be impossible to deal with all by forming the wear indicator by the rib notch portion disclosed in the above specification and publication. Absent. This is because the amount of rubber sandwiched between the ribs 12 and the end faces 12 _EP when the segment 10 is moved to the operating position, as described above, is not large because there is a large difference in actual fact.
Therefore, it often happens that a bare failure occurs in the wear indicator portion due to insufficient rubber amount, or rubber flash still occurs due to insufficient cutout portion volume.

Therefore, an object of the present invention is to ensure that rubber burrs are generated without causing other problems even in circumferential grooves having various groove depths and groove widths across a wide variety of radial tires. It has a vulcanization mold with controllable segments and excellent appearance quality with absolutely no rubber burrs, and high groove bottom durability with no deterioration due to rubber burrs or groove bottom cracking. To provide a radial tire having a level.

[0012]

In order to achieve the above object, the vulcanization molding die according to the present invention is such that, in the die described at the beginning, the mating surfaces (P) of the segments adjacent to each other in the operating position are The approach angle (θ) formed by the rib end face including the rib end face and forming the rib end face with respect to the radial direction of the segment movement and the radius of the inner end edge of the rib end face at the operating position with respect to the central axis of the united segment are defined as follows. A distance that is subtracted from 1/2 of the outer diameter of the unvulcanized tire at the first contact position, and contour specifications that determine the area included in the height of the rib end surface from the inner edge corresponding to the above distance. Based on the above, while the segments are moved inward by the above distance and united, the volumes produced by the rib end faces of the adjoining mating surfaces (P) are mutually calculated, and the calculated volumes are calculated. Surplus To a volume, again notches of volume fraction corresponding to the excess volume, the depth (d)
The value (d / L) of the cutout bottom length (L) is 0.
It is characterized in that it is formed at the inner tip portion of the rib extending from the mating surfaces (P) on both sides of each segment within the range of 2 to 1.0.

In actually manufacturing the die, chamfering is preferably performed along the bottom edge of the cutout portion in the rib end surface.

Further, the radial tire according to the present invention is
In the tire described at the beginning as well, by the vulcanization molding die described above, the same number as the number of the die segments is formed on the circumferential groove bottom with the same protrusions as the rib cutouts. It is characterized by being formed.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment according to the present invention will be described in detail below with reference to FIGS. FIG. 1 is a plan view showing two adjacent segments 1 taken out in the non-operating position shown in FIG. In FIG. 1, the arc center (actually, the central axis) C of the united segment 1 in the operating position is the arc center of each segment 1 which is separated by moving each segment 1 in the radial direction (direction of arrow A) by a distance Dm. Move to Cm.

This center Cm lies on the circle E for all the segments 1 that make up the whole. A line segment connecting the center C and the center Cm, or an extension line le extending outward in the radial direction, and 2
The angle θ between the intermediate position of the mating surfaces P facing each other and the straight line lm passing through the center C does not change for the segment 1 in the operating position. This is because the straight line le does not change even at this position, and the straight line lm passes through the mating surface P of the segment 1.

While moving the segment 1 from the non-operating position to the operating position, the end face (straight line in the figure) 2 _EP of the rib 2 on the mutual mating surface P of the segment 1 is moved by the center Cm with respect to the straight line lm. A vertical line length component (horizontal movement component) from is included. That is, this lateral movement component has a negative slope (−) even after the end face 2 _EP comes into contact with the tread rubber 3 t of the unvulcanized tire 3 of which a part of the side surface is shown in FIG. 1.
It decreases under the relationship between the straight line Cm-C having tan θ) and the straight line lm, and becomes zero when the center Cm coincides with the center C. This state will be described below with reference to FIG. 2 which is a partially enlarged view of FIG.

FIG. 2 shows in a solid line how the segment 1 moves in the direction of arrow B and the innermost side surface 2s of the rib 2 comes into contact with the outer peripheral surface 3ts of the tread rubber 3t. Rib 2 with radius of curvature Rr in segment 1
FIG. 2 is a partial plan view of FIG. 1 showing the innermost side surface 2s of FIG. More precisely, half of the unvulcanized tire outer diameter, i.e. the maximum radius of curvature of the outer peripheral surface 3ts of the tread rubber 3t is set larger than the radius of curvature Rr of the innermost surface 2s, the end face 2 _EP tread rubber 3t 3 shows a state when the outer peripheral surface 3ts is first contacted.

The inner edge of the end surface 2 _EP of the rib 2 is indicated by reference numeral 2e, and when both segments 1 move in the direction of arrow B (see FIG. 1) and merge, the inner edge 2e on both sides of the straight line lm is a point. Match at X (actually line X). The line segment between the inner edges 2e on both sides at the position shown and the point X is the inner edge 2 of the end face 2 _EP.
e is a straight line that should travel inside the tread rubber 3, and the angle θ formed by this straight line and the straight line lm is, so to speak, the approach angle θ. Therefore, the inner edge 2e stops at the point X while maintaining the approach angle θ, that is, reducing the distance to the straight line lm. When stopped, the straight line lm is on the mating surface P.

Here, the distance h from the intersection point Y to the point X of the straight line lm and the line segment connecting both inner end edges 2e is the vertical movement component of the inner end 2e which is orthogonal to the horizontal movement component mentioned above, that is, the tread rubber bite depth of the inner edge 2e, within errors negligible in practice, out of the unvulcanized tire at a position where the end face 2 _EP is first contacted with the outer peripheral surface 3ts of the tread rubber 3t From the diameter Rt, it can be calculated by h = Rt-Rr.

FIG. 3 shows a partial cross section of the tread rubber 3t in the width direction by a plane including the straight line lm and the central axis C in FIG. 2, a part of the mating surface P of the segment 1 and the end surface 2 of the rib 2.
Shown together with _EP . The segment 1 portion shown by the solid line in FIG. 3 is in the same position as the portion similarly shown in FIG. 2, and the segment 1 portion shown by the two-dot chain line is in the operating position.

Here, the rib end surface 2 at the biting depth h
The inner edge width w of the rib end surface 2 _EP and the inclination angle α of both side surfaces are used as contour specifications for determining the area of _EP , and the approach angle θ and the bite depth h described above are added to each segment While 1 moves toward the inside by a distance h and merges, one side volume V _EX among the volumes created by the rib end surfaces 2 _EP of the mating surfaces P adjacent to each other is:

[Formula 1] V_EX= {(W / 2) + (h / 3) tan α} h²・ Tan θ can be calculated as (1). The inner edge width w is small on both ends.
Approximately with an appropriate degree that there is no practical problem even when attaching an arc
This one side volume V_EXThe value of can be used. Still above
Although the description is omitted when the inclination angle is different on both sides,
Similarly, volume V _EXAsk for.

The volume V _EX calculated by the above equation is taken as the tread rubber surplus volume, and the rib 2 which has been described as a uniform rib 2 height at least in the vicinity of the mating surface P is added to the tread rubber surplus volume V _EX . A notch corresponding to the corresponding volume is provided at the inner tip portion of the rib 2 extending from the mating surfaces P on both sides of each segment 1. Details of this notch are shown in FIGS. 4 (a) and 4 (b).

FIG. 4 (a) shows the notch portion 4 provided in the rib 2-2 of the segment 1-1 shown in a plan view like FIG. 2, and FIG. 4 (b) is a front view in FIG. The notch 4 provided in the rib 2-2 of the segment 1-1 shown is shown.
In FIGS. 4A and 4B, the ratio d / L of the notch depth d to the length L of the bottom 4b of the notch portion 4 is 0.2 to.
It must be in the range of 1.0. Further, it is preferable to chamfer the end of the notch portion 4 at an angle φ within the range of 30 to 60 °.

Notch 4 with chamfer angle φ
The volume V _R before the notch is

V _R = (w + d · tan α) dL + {(w / 2) + (d / 3) tan α} d ² · cotφ ... (2) Here, assuming V _EX = V _R , the value of the ratio d / L is 0.
Within the range of 2 to 1.0, the length L of the bottom 4b of the cutout portion 4, the depth d, and the chamfer angle φ are set. For example, bottom 4b
Arrange the length L of

[Equation 3] L = {(w / 2) (h ² · tan θ-d ² · cot φ) + tan α (h ³ · tan θ-d ³ · cot φ) / 3} / {d (w + d · tan α)} ······ Set the length L of the bottom 4b, the depth d and the chamfer angle φ so as to satisfy (3).

By providing the notch 4 described above, the end of the notch 4 of the rib 2-2 is first unvulcanized while the segments 1-1 are moved to the operating position and merged. Furthermore enters in contact with the outer peripheral surface 3tS of the tread rubber 3t tire 3, then the rubber 3t to contact similarly have inner edge 2e-1 rib end surface 2 _EP -1 of both mating surfaces P adjacent to each other I will enter. At this time, the rubber 3t flows from the end portion of the cutout portion 4 toward the cutout portion 4 and fills the space portion of the cutout portion 4.

Here, if V_EX≤V_RIf so, V_EX<
V_RIn the case of, cutting of rib 2-2 of united segment 1-1
Between the notch 4 and the outer peripheral surface 3ts of the tread rubber 3t
(V _R-V_EX), A void portion corresponding to the volume of
Air enters this void (the air bubble-shaped air reservoir after vulcanization molding).
State) or bare (do not contact the mold due to air accumulation
There is a problem such as vulcanization of the rough rubber part
I will. Therefore, in order to avoid this kind of defect occurrence,
It is necessary to eliminate all voids, so V _EX= V_R
Must. Of course V_EX> V_RThen rubber burrs are raw
It is impossible because it is twisted.

Further, as shown in FIG. 5 (a), which shows the cross section near the notch 4 together with the tread rubber 3t cross section, the rib end surface 2
_It is more effective to chamfer along the bottom edge of the notch 4 in _EP- 1. This chamfering effect is shown in FIG. 5 (b) showing how the tread rubber 3t is flowing toward the cutout portion 4, and the tread rubber inside the cutout portion 4 under the state where the segment 1-1 is completely united. It is shown in FIG.5 (c) which shows the state of 3t. A series of FIG.
As is clear from (c), the flowing rubber 3t accumulates in the chamfered portion before flowing between the rib end faces 2 _EP −1,
It is possible to completely avoid the behavior of biting the rubber 3t between the matched rib end surfaces 2 _EP −1.

FIG. 6A shows a cross section of the notch 4 which is not chamfered as in FIG. 5A. In addition, FIG.
FIG. 5 (c) shows flows of tread rubber 3t corresponding to FIGS. 5 (b) and 5 (c), respectively. FIG. 6C shows that even under the condition of V _EX = V _R described above, the rubber 3t biting behavior may sometimes occur depending on the rubber flow conditions and the characteristics of the rubber, and this behavior is By properly chamfering the above, it can be completely prevented.

[0030] described above, using a vulcanizing metal mold or vulcanization metal mold with chamfered along the notched portion 4 bottom edge per the mold comprises a segment 1-1 satisfying V _EX = V _R Then, the unvulcanized tire 3 is vulcanized and molded to obtain a radial tire having the same number of divided segments as the protrusions having the same shape as the notch 4 of the rib 2-2 in the circumferential groove.

[0031]

EXAMPLE As one example, the rib 2-2 of the nine-segment segment 1-1 has an inner edge width w of 8 mm, and the rib 2-2
In the case where the inclination angle α of both side surfaces is 7 °, the depth L of cutout 4 bottom 4b obtained from V _EX = V _R and the cutting depth h = Rt−Rr are used as parameters. The relationship of the notch depth d (mm) is shown in FIG. 7 as a diagram. The chamfer angle φ was 45 °.

In the embodiment according to FIG. 7, in this case, the outer diameter (2 × Rt) of the unvulcanized tire 3 is set to the rib height 8 which forms the radius of curvature Rr of the united segment 1-1 in the operating position. It was set to reach the 59% position of 5 mm. That is, the biting depth h is 5.0 mm.

From the diagram shown in FIG. 7, within the range of each notch 4 bottom length L (mm) and notch depth d (mm) which can be taken at h = 5.0 mm (represented by a thick solid line). , The Mooney viscosity value of the tread rubber 3t and the rib 2-2
In consideration of the biting speed (about 2 mm / sec) into the rubber 3t, the length L of the bottom 4b of the notch 4 was set to 2.4 mm and the notch depth d was set to 1.5 mm. As described above, the diagram illustrated in FIG. 7 has a great advantage that the optimum value can be selected in consideration of other conditions.

Vulcanization molding production of radial tires was carried out using the vulcanization molding die having the nine divided segments 1-1 having the above-mentioned cutouts 4, and the number of samplings of product tires was 1
When 00 pieces were observed, there were no places where rubber burrs were generated on the protrusions of the circumferential groove. Furthermore, as a result of conducting an experiment to actually run this product tire, it is possible to confirm a reduction in noise level (noise reduction) and an improvement in wet performance in comparison with a tire having a rubber burr in a conventional wear indicator, Further, as a matter of course, even when the tread rubber was worn to the limit of its use, no failure such as cracks was found in the protrusions of the circumferential groove.

[0035]

According to the present invention, the conventional vulcanization molding that absorbs the rubber flash generated on the mating surface by aligning the mating surfaces of the plurality of divided segments in the split mold with the wear indicator position provided in the circumferential groove. The mold cannot handle a wide variety of radial tires with various groove depths, and rubber burrs still occur, which causes an increase in running noise level, deterioration of wet performance, and cracking of the rubber burrs. It is possible to provide a vulcanization molding die and a radial tire that can advantageously solve the problem that the tire life is inevitably reduced. .

[Brief description of drawings]

FIG. 1 is a plan view illustrating a reciprocating movement of a segment.

FIG. 2 is a partial plan view illustrating a relationship between a segment moving to an operating position and a tread rubber.

FIG. 3 is a view showing a front view of the segment shown in FIG. 2 and a cross-sectional view of the tread rubber together.

FIG. 4 is a plan view and a front view of a segment according to the present invention.

FIG. 5 is a partial cross-sectional view illustrating the operation of the embodiment according to the present invention.

FIG. 6 is a partial cross-sectional view explaining the operation of another embodiment.

FIG. 7 is a diagram showing the relationship between the bottom length and the depth of the cutout portion according to the present invention.

FIG. 8 is a plan view for explaining the operation of a large number of divided segments.

[Explanation of symbols]

1, 1-1 segment 2, 2-1 rib 2 _EP , 2 _EP -1 rib end face 2e inner end edge of rib end face 2s innermost side face of rib 2 3 unvulcanized tire 3t tread rubber 3ts tread rubber outer peripheral face 4 cut Notch 4b Notch bottom L L Notch bottom length d Notch depth P Mating surface h Biting depth w Inner edge width of rib end face θ Entry angle α Rib side inclination angle

Claims (3)

[Claims] 1. A plurality of divided segments that can be reciprocally moved in a radial direction between an operating position where vulcanization molding is performed on an unvulcanized tire and an inoperative position where a tire after vulcanization molding is completed are taken out. In a vulcanization molding die in which each segment has a rib that forms a circumferential groove in the tread rubber of the tire, the mating surfaces (P) of the adjacent segments in the operating position match each other, including the rib end surface. , The entrance angle (θ) formed by the rib end face with respect to the radial direction of the segment movement, and the radius of the inner end edge of the rib end face with respect to the central axis of the united segment in the operating position, at the position where the end edge first contacts. Based on the distance subtracted from 1/2 of the outer diameter of the unvulcanized tire and the contour specifications that define the area of the rib end surface included in the height from the inner edge corresponding to the above distance, each segment Distance The volumes produced by the rib end faces of the mating surfaces (P) adjacent to each other are calculated separately while moving toward the inner side of the scale and merged, and the calculated volume is defined as the tread rubber surplus volume, and the surplus volume is re-established. In a notch portion having a volume corresponding to, the value of the ratio (d / L) between the depth (d) and the length (L) of the notch bottom is within a range of 0.2 to 1.0, A vulcanization mold, which is formed at an inner tip portion of a rib extending from the mating surfaces (P) on both sides of each segment. 2. The vulcanization molding die according to claim 1, wherein chamfering is performed along a bottom edge of the cutout portion in the rib end surface. 3. A radial tire comprising a pair of beads, a pair of sidewalls, and a tread portion continuous in a troid shape between the sidewalls, wherein the tread rubber of the tread portion has a circumferential groove. The vulcanization molding die described in Item 1 or 2 is characterized in that the same number as the number of the die segments is formed on the circumferential groove bottom with projections having the same shape as the rib cutouts. Radial tires.