JP2013095096A - Method for designing tire-vulcanizing mold - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for designing a tire-vulcanizing mold capable of preventing deformation of a segment while preventing over-spew.SOLUTION: The method for designing a tire-vulcanizing mold including a plurality of segments divided in the tire circumferential direction for forming a tread forming surface annularly continued by joining divided surfaces of the segments, is provided. The method includes: a step for setting a segment model by dividing the segments into the finite number of elements; a step for aligning the divided surfaces of the segment model with each other, giving a boundary condition of allowing free expansion by invalidating contact between the divided surfaces, and making temperature and pressure act so as to perform free expansion simulation of the segment model; a step for obtaining an amount of overlap on a divided surface of a pair of segment models based on the free expansion simulation; a step for determining an initial gap between the segments based on the amount of overlap; and a step for designing the segments based on the initial gap.

Description

  The present invention relates to a method for designing a tire vulcanization mold that can prevent deformation of a segment while preventing overspewing.

  In general, a vulcanization mold for vulcanizing a pneumatic tire includes, for example, a plurality of fan-shaped segments 2 divided in the tire circumferential direction as shown in FIG. The segment 2 forms a tread molding surface 3 that is annularly continuous in the tire circumferential direction by combining the divided surfaces 2a. The tread molding surface 3 is pressed against the tread portion of the raw cover t formed using unvulcanized rubber by receiving heat and pressure, thereby forming a tread pattern. The following technologies have been proposed as related technologies.

JP 2004-216622 A JP 2007-62270 A JP 2008-194946 A

  Meanwhile, a relatively soft aluminum alloy or the like is used for the segment 2 described above in order to engrave a pattern reversal shape. On the other hand, during the vulcanization molding, the segment 2 is subjected to a large pressure due to the mold clamping for continuing the ring, and a large force acts on the divided surface 2a due to the expansion due to heat. For this reason, the segment 2 is likely to be worn or deformed on the divided surface 2a or the like in several months, and there is a problem in terms of durability.

  In order to solve such problems, it has been proposed to provide an initial gap between the divided surfaces 2a and 2a in an initial state in view of thermal expansion of the segment 2 until the segment is clamped. ing.

  However, the amount of such an initial gap is largely dependent on experiments and experience values, and appropriate values differ depending on the outer diameter of the tire, so that no effective improvement measures have been proposed yet.

  The present invention has been devised in view of the above problems. A segment model is set by dividing a segment into a finite number of elements, and the division planes of the segment model are aligned and aligned with each other. Free expansion simulation is performed under the boundary condition that enables free expansion by disabling contact on the divided surface, and the amount of overlap of the segment model on the divided surface is obtained from this free expansion simulation, and based on this amount of overlap The main purpose is to provide a tire vulcanization mold design method with excellent durability on the basis of determining the initial gap of the segment.

  The invention according to claim 1 of the present invention includes a plurality of segments divided in the tire circumferential direction, and a tire vulcanization mold in which an annularly continuous tread molding surface is formed by combining the divided surfaces of the segments. A step of dividing the segment into a finite number of elements and setting a segment model; aligning and aligning the division surfaces of the segment model with each other and disabling contact on the division surface; A boundary condition that allows free expansion is provided, and a step of performing free expansion simulation of the segment model by applying temperature and pressure, and an overlapping amount of the pair of segment models on the split surface from the free expansion simulation Determining an initial gap of the segment based on the overlap amount; and Characterized in that it comprises the step of designing a segment based on the cap.

  According to a second aspect of the present invention, in the tire vulcanization mold according to the first aspect, the overlap amount includes an overlap amount L1 inside the tire radial direction of the segment model and an overlap amount L2 outside the tire radial direction. It is a design method.

The invention according to claim 3 is the tire vulcanization mold design method according to claim 2, wherein the initial gap is determined using the following equation.
Initial gap G1 in the tire radial direction of the segment G1 = α · L1
Initial gap G2 on the outer side in the radial direction of the segment G2 = α · L2
(Α is a safety factor taking a value of 0.92 to 0.98.)

The invention according to claim 4 is the tire vulcanization mold design method according to claim 2, wherein the initial gap is determined using the following equation.
Initial gap G1 in the tire radial direction inside the segment = α · L1 + β (Ts−Tp)
Initial gap G2 on the outer side in the tire radial direction of the segment = α · L2 + β (Ts−Tp)
(Α is a safety factor taking a value of 0.92 to 0.98, β is the thermal expansion coefficient of the segment to be analyzed, Ta is the initial temperature of the free expansion simulation, and Tp is the temperature at the time of manufacturing the segment.)

  The present invention is a tire vulcanization mold design method comprising a plurality of segments divided in the tire circumferential direction, and forming a tread molding surface that is annularly continuous by combining the division surfaces of the segments, A step of setting a segment model by dividing a segment into a finite number of elements, and a boundary condition that enables free expansion by aligning and aligning the division surfaces of the segment model and disabling contact at the division surface And performing a free expansion simulation of the segment model by applying temperature and pressure, obtaining an overlap amount on the division plane of the segment model from the free expansion simulation, and based on the overlap amount Determining an initial gap for the segment; and determining a segment based on the initial gap. It is a tire vulcanization mold design method which comprises the steps of: total.

It is a partial exploded perspective view of a vulcanization metal mold. It is sectional drawing of a vulcanization mold. It is a flowchart which shows the process sequence of this embodiment. (A) is the perspective view which visualizes and shows a segment model, (b) is the side view. It is a side view of a segment model assembly in which segment models are arranged in an annular shape. It is a partial side view of the segment model assembly explaining a free expansion simulation. It is a perspective view which visualizes and shows a segment model etc. It is a typical side view of a segment model explaining free expansion simulation. It is a typical side view of a unit model to which a periodic boundary condition is applied. It is the stress distribution figure of the division surface of a segment model, (a) shows a prior art example, (b) shows the thing of an Example. It is a graph which shows the average value of the contact force in the division surface of a segment model. It is a side view explaining a segment.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
As shown in FIG. 12, the tire vulcanization mold subject to the design method of the present invention includes a plurality of segments 2 divided in the tire circumferential direction, and an annular shape obtained by matching the dividing surfaces 2a of the segments 2. A tread molding surface 3 is formed continuously.

  Also, as shown in FIGS. 1 and 2, the tire vulcanization mold M is used, for example, with the rotation axis of the raw cover t (tire) vertical, and is connected to the segment 2 and has a lower sidewall surface. It has a lower side ring 4a to be molded and an upper side ring 4b which is continuous with the upper side of the segment 2 and which forms the upper side wall surface. On the inner side in the tire radial direction of the upper and lower side rings 4b and 4a, upper and lower bead rings 5b and 5a are respectively connected.

  Further, the tire vulcanization mold M has a sector shoe 6 fitted to the outer side in the tire radial direction of the segment 2 and having a slope 6a, and a slope 7a facing the slope 6a of the sector shoe 6, and the sector shoe by descending. And an actuator ring 7 that presses the shoe 6 and the segment 2 inward in the tire radial direction to clamp the mold. Further, in the tire vulcanizing mold M, a lower plate 8a and an upper plate 8b are disposed below and above the side ring, respectively.

  In such a tire vulcanizing mold M, as is well known, by positioning the actuator ring 7 upward, the dividing surface 2a of each segment 2 is separated and expanded in diameter, and the upper side ring 4b and the upper bead The raw cover t is inserted with the ring 5b positioned at the top. Thereafter, the upper side ring 4b and the upper bead ring 5b are moved down together with the actuator ring 7 so that the divided surfaces 2a of the segments 2 are brought close to each other and the raw tire t is vulcanized.

  FIG. 3 shows an example of the processing procedure of the design method of the tire vulcanization mold according to the present embodiment, which will be described below in order. In the design method of the present embodiment, first, a segment model is set (step S1).

  4A is a perspective view showing the segment model 10 visualized, and FIG. 4B is a side view thereof. The segment model 10 is set as numerical data that can be handled by a computer by dividing the three-dimensional shape of the segment 2 to be analyzed into discrete elements 10a, 10b, 10c,. The Specifically, the node coordinate values, element shapes, and material characteristics of each element 10a, 10b, 10c... Are defined and stored in the computer.

  The material properties include the density, Young's modulus, damping coefficient, and the like of the metal material constituting the segment 2 to be analyzed. For each of the elements 10a, 10b, 10c,..., For example, a three-dimensional tetrahedron solid element is preferably used.

  As shown in FIG. 5, the segment model 10 of the present embodiment has a fan shape with a central angle of 40 °, and both end faces in the circumferential direction form a dividing surface E. Further, in the present embodiment, the segment models 10 are configured to form a segment model 11 composed of an annular body that is continuous 360 ° without a gap by aligning the division planes E of the nine segment models 10 in the circumferential direction. Has been modeled. In other words, in the present embodiment, the segment model 10 having a zero initial gap is formed by dividing the annular ring into nine equal parts.

  Next, as shown in FIG. 6, the dividing surfaces E of the segment model 10 are aligned and aligned with each other, and a boundary condition that allows free expansion by disabling each other's contact with the dividing surfaces E is given. Moreover, free expansion simulation of the segment model 10 is performed by applying temperature and pressure (step S2).

  In the embodiment shown in FIG. 6, the nine segment models 10 are aligned so as to contact each other at the dividing plane E, thereby setting the 360 ° continuous segment model assembly 11. Conditions for applying the temperature and pressure generated during vulcanization molding are given to the solid 11 and a free expansion simulation of the segment model 10 is performed.

  In the free expansion simulation, each segment model 10 is given a boundary condition that allows free expansion by disabling contact with each other on the dividing plane E. In a normal free expansion simulation, each segment model 10 expands by receiving heat. The elongation of the segment model 10 in the tire circumferential direction is constrained by another segment model 10 that is in contact via the dividing surface E, and serves to increase the pressure of the dividing surface E. However, in the free expansion simulation of the present embodiment, the contact between the segment models 10 and 10 adjacent in the tire circumferential direction is invalidated, and each segment model 10 can be freely expanded and deformed assuming that there is no contact between the two. It is said. However, in order to fix the position of each segment model 10, the center position CL of the segment model 10 in the tire circumferential direction is positioned so that it cannot be displaced.

  Further, in the free expansion simulation, as shown in FIG. 7, each of the tire vulcanization molds M is configured so that heat and pressure act on each segment model 10 in the same manner as in actual vulcanization molding. It is desirable to model a part using a finite number of elements, and to apply heat and pressure using these parts. In this embodiment, the lower and upper side rings 5a and 5b are modeled, the lower side ring models 12a and 12b, the sector shoe model 13 that models the sector shoe 6, and the actuator ring 7 are modeled. The actuator ring model 14 and the lower and upper plates 8a and 8b are modeled and the upper plate models 15a and 15b are included.

  Then, as shown in FIG. 7, the models are combined and the sector shoe model 13 is moved in the radial direction using the actuator ring model 14 in the same manner as the actual tire vulcanization mold M. A clamping force is applied to the model 10. Each model 12 to 15 has a temperature defined during tire vulcanization. As described above, when heat and pressure are applied to each segment model 10 in the same manner as the actual vulcanization mold M, it is useful to obtain a more accurate simulation result.

  In FIG. 8, the partial side view of the segment model assembly 11 which performed the free expansion simulation of this embodiment is shown. When a free expansion simulation is performed in which contact on the dividing surface E is invalidated as in the present embodiment, in each of a pair of adjacent segment models 10A and 10B, each of the dividing surfaces Ea and Eb is divided before expansion. It will be located on the other segment model side beyond the plane E. Thereby, the adjacent segment models 10A and 10B form overlapping portions that overlap each other.

  Next, in this embodiment, a computer calculates | requires the duplication amount in the division surface E of a pair of segment model 10A, 10B from the result of the said free expansion simulation (step S3). This is easily calculated from the node coordinates of each model. Further, as shown in FIG. 8, since the overlap amount L varies depending on the position in the tire radial direction, preferably, the segment model 10 has an innermost overlap amount L1 in the tire radial direction and an outermost radial direction in the tire radial direction. It is desirable to include the overlap amount L2.

  In the actual vulcanization mold M, the overlapping amounts L1 and L2 do not occur, but the pressure of the dividing surface 2a of the segment 2 increases based on this value, resulting in deformation of the segment 2 and the like. On the other hand, if the contact force of the dividing surface 2a of the segment 2 is too small, the rubber of the raw cover is sucked up from the dividing surface 2a of the segment 2 to generate excessive burrs and spews (hereinafter referred to as “over spew”). Sometimes called). Therefore, the segment 2 needs to be designed so that the amount of overlap when the free expansion simulation is performed is optimal.

  Therefore, in the present embodiment, the initial gap of the segment is determined based on the overlap amount (step S4). As described above, the initial gap does not act on the tire rotation axis O with respect to the center line CL in the tire circumferential direction of each segment (segment model 10) as shown in a side view of FIG. This is an initial gap before mold clamping formed between the divided surfaces E and E of adjacent segments (segment model 10) when aligned so as to pass and arranged in an annular shape. Note that the segment model assembly 11 shown in FIG. 5 has a zero initial gap.

In this embodiment, the computer determines the initial gap using the following equation.
Initial gap G1 in the tire radial direction of the segment G1 = α · L1
Initial gap G2 on the outer side in the radial direction of the segment G2 = α · L2
Here, L1 and L2 are overlapping amounts inside and outside in the tire radial direction obtained by the above-described free inflation simulation, and α is a safety factor that takes a value of 0.92 to 0.98.

  The inventors have conducted various experiments on how the relationship between the amount of overlap and the initial gap affects durability and overspew. As a result, by setting the initial gap to 92 to 98% of the overlapping amounts L1 and L2 of the segment model 10 obtained by the free expansion simulation, it is possible to suppress overspew while maintaining segment durability. And the safety factor α was set. However, it goes without saying that the present invention is not limited to such safety factor values.

Furthermore, as a preferred embodiment, the initial gap can be determined using the following equation.
Initial gap G1 in the tire radial direction inside the segment = α · L1 + β (Ts−Tp)
Initial gap G2 on the outer side in the tire radial direction of the segment = α · L2 + β (Ts−Tp)
Here, L1, L2, and α are the same as above, but β is the thermal expansion coefficient of the segment to be analyzed, Ta is the initial temperature of the free expansion simulation, and Tp is the temperature at the time of manufacturing the segment.

  In such a determination method, when the initial temperature Ta during the free expansion simulation is different from the temperature Tp at the time of manufacturing the segment, the initial gap is determined in consideration of the expansion amount of the segment corresponding to the temperature difference in advance. can do. Therefore, it is particularly effective for the design of a segment that can suppress the overspew while increasing the durability more reliably.

  In the above-described free expansion simulation, the segment model assembly 11 in which the segment models 10 are connected in a ring shape is used, but these are periodically repeated structures of a pair of segment models. Therefore, such a structure can reduce the number of elements to be calculated using a periodic boundary condition, for example, as shown in FIG. In the case of FIG. 9, the unit models 12 that are half of each of the pair of segment models 10 </ b> A and 10 </ b> B that are in contact with each other via the dividing surface E are periodically continuous. Accordingly, element deformation calculation and the like can be performed only for the unit model 12, and the calculation time can be shortened.

  As mentioned above, although embodiment of this invention was described in detail, this invention can be deform | transformed and implemented in a various aspect, without being limited to the said embodiment.

The effect of the present invention was confirmed by taking a tire vulcanization mold for forming a pneumatic tire having a tire size of 155R65 / 14 as an example. The main specifications are as follows.
・ Tire outer diameter: 553mm
・ Segment outer diameter: 690mm
Number of divisions: 9 equal divisions Young's modulus: 70.5 GPa
Poisson's ratio: 0.33
Density: 2.68 g / cm ³
・ Segment model (based on the shape of Fig. 4 (a) and (b))
Number of elements: 2684, number of nodes: 3672

The segment model was used to simulate free expansion. The amount of overlap was as follows.
Overlapping amount L1: 0.27mm inside the tire radial direction
Overlapping distance L2 in the tire radial direction: 0.32 mm

Next, 0.95 was adopted as the safety factor α, and the initial gap between segments was determined as follows.
<Example>
Initial gap G1 in the tire radial direction G1 = α × L1 = 0.26 mm
Initial gap G2 outside the tire radial direction G2 = α × L2 = 0.30 mm

Next, a segment model having this initial gap was defined, and a normal expansion simulation was performed in consideration of contact on the divided surface. Similarly, a similar expansion simulation was performed for a segment model with reference to a conventional segment having the following initial gap determined empirically.
<Conventional example>
Initial gap G1 in the tire radial direction G1 = 0.24mm
Initial gap G2 on the outer side in the tire radial direction = 0.30mm
The test results are shown in FIGS.

  FIG. 10 is a stress distribution diagram of the segmented surface of the segment model, where (a) is a conventional example and (b) is an example. The portion displayed in white indicates that the stress is large. As a result of the simulation, it can be seen that the divided surface of the segment model of the embodiment has a smaller area where a large stress is applied than that of the segment model of the conventional example.

  FIG. 11 is a graph showing the average value of the contact force acting on the dividing surface of each segment model. As is clear from FIG. 11, it was confirmed that the segment model of the example had a contact force less than half that of the conventional example. Note that when an actual segment was prototyped based on the segment model of the example, no overspew was found.

2 Segment 3 Tread molding surface 10 Segment model E Segment model split surface M Vulcanization mold

Claims (4)

A tire vulcanization mold design method comprising a plurality of segments divided in the tire circumferential direction, and forming a tread molding surface that is annularly continuous by combining the division surfaces of the segments,
Dividing the segment into a finite number of elements and setting a segment model;
Aligning and aligning the division surfaces of the segment model with each other, disabling contact at the division surface to provide boundary conditions that enable free expansion, and applying the temperature and pressure to free expansion of the segment model Performing a simulation,
Obtaining an overlap amount on the split surface of a pair of segment models from the free expansion simulation;
Determining an initial gap of the segment based on the amount of overlap;
And a step of designing a segment based on the initial gap.   2. The tire vulcanization mold design method according to claim 1, wherein the overlap amount includes an overlap amount L <b> 1 inside the tire radial direction of the segment model and an overlap amount L <b> 2 outside the tire radial direction. The method for designing a tire vulcanization mold according to claim 2, wherein the initial gap is determined using the following equation.
Initial gap G1 in the tire radial direction of the segment G1 = α · L1
Initial gap G2 on the outer side in the radial direction of the segment G2 = α · L2
(Α is a safety factor taking a value of 0.92 to 0.98.) The method for designing a tire vulcanization mold according to claim 2, wherein the initial gap is determined using the following equation.
Initial gap G1 in the tire radial direction inside the segment = α · L1 + β (Ts−Tp)
Initial gap G2 on the outer side in the tire radial direction of the segment = α · L2 + β (Ts−Tp)
(Α is a safety factor taking a value of 0.92 to 0.98, β is the thermal expansion coefficient of the segment to be analyzed, Ta is the initial temperature of the free expansion simulation, and Tp is the temperature at the time of manufacturing the segment.)