JP2022086312A - Method of designing knife blades for vulcanizing molds - Google Patents

Abstract

To provide a method for designing knife blades that can prevent damage.SOLUTION: A method for designing a knife blade on an arc-shaped segment comprising a vulcanization mold for a tire, comprises: a process S1 of inputting a tread rubber model having a siping corresponding to a knife blade discretized with finite elements into a computer; a process S2 of inputting a segment model having a knife blade model discretized with finite elements into the computer; a first process S3 of aligning the tread rubber model and the segment model in a pseudo-vulcanized state by fitting the knife blade model into the siping of the tread rubber model by the computer; a second process S4 in which the segment model in the pseudo-vulcanized state is moved outward in the tread radial direction from the tread rubber model by the computer to obtain the pseudo-vulcanization state; and a process of calculating the physical quantities acting on the knife blade model during the second process S4.SELECTED DRAWING: Figure 4

Description

The present invention relates to a method for designing a knife blade for a vulcanization die.

The following Patent Document 1 describes a pneumatic tire in which a plurality of sipings are arranged side by side on a tread surface. Such siping is formed by pushing a plurality of knife blades provided in the vulcanization die in the tire circumferential direction into the unvulcanized tread rubber during vulcanization molding of the tire.

Japanese Patent No. 4516415

When the knife blade is removed from the tread rubber after vulcanization molding, it may be damaged by contact with the tread rubber and / or a bending moment. It has been difficult to design a knife blade that can prevent such damage.

The present invention has been devised in view of the above circumstances, and an object of the present invention is to provide a method for designing a knife blade capable of preventing damage.

The present invention is a method for designing a knife blade provided in an arc-shaped segment constituting a vulcanization mold of a tire, and the tread rubber on which the siping corresponding to the knife blade is formed is dispersed by a finite number of elements. A step of inputting a tread rubber model having vulcanized siping to a computer and a segment model having a knife blade model in which the segment provided with the knife blade is discreteized by a finite number of elements are input to the computer. The first step in which the computer fits the knife blade model into the siping of the tread rubber model and aligns the tread rubber model and the segment model in a pseudo-vulcanized state. The computer moves the segment model in the pseudo-vulcanized state from the tread rubber model to the outside in the tread radial direction to obtain a pseudo-demolded state, and during the second step, the knife blade model is used. It is characterized by including a step of calculating the acting physical quantity.

In the method for designing a knife blade of the vulcanization die according to the present invention, the physical quantity may be stress.

In the method for designing a knife blade of the vulcanization die according to the present invention, the computer compares the physical quantity with a predetermined allowable value, and when the physical quantity exceeds the allowable value, the knife. Further steps may be included to change the design factors of the blade.

In the method for designing a knife blade for a vulcanization die of the present invention, it is possible to design a knife blade capable of preventing damage by adopting the above steps.

It is a perspective view which shows an example of the computer 1 for executing the design method of the knife blade of a vulcanization die. It is a partial cross-sectional view explaining an example of a vulcanization process. It is a partial cross-sectional view in the direction orthogonal to the axis of the tread molding die of FIG. It is a flowchart which shows an example of the processing procedure of the design method of the knife blade of a vulcanization die. It is a perspective view which shows an example of a tread rubber model and a segment model. It is sectional drawing explaining an example of the pseudo vulcanization state. It is sectional drawing explaining an example of the pseudo-release state. It is a flowchart which shows an example of the processing procedure of 2nd step. It is a contour diagram which shows an example of the stress of a knife blade model.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. It must be understood that the drawings include exaggerated representations and representations that differ from the dimensional ratio of the actual structure in order to aid in understanding the content of the invention. Further, throughout the embodiments, the same or common elements are designated by the same reference numerals, and duplicate description is omitted. Furthermore, the specific configurations shown in the embodiments and drawings are for understanding the contents of the present invention, and the present invention is not limited to the specific configurations shown.

[Computer]
A computer 1 is used as a method for designing a knife blade for a vulcanization die according to the present embodiment (hereinafter, may be simply referred to as a “design method”). FIG. 1 is a perspective view showing an example of a computer 1 for executing a method for designing a knife blade of a vulcanization die.

The computer 1 includes a main body 1a, a keyboard 1b, a mouse 1c, and a display device 1d. The main body 1a is provided with an arithmetic processing unit (CPU), a ROM, a working memory, a storage device such as a magnetic disk, disk drive devices 1a1, 1a2, and the like. The storage device stores in advance a processing procedure (program) for executing the design method of the present embodiment.

[Vulcanization mold]
FIG. 2 is a partial cross-sectional view illustrating an example of the vulcanization process. The tire 2 is manufactured by vulcanizing and molding an unvulcanized raw tire 3 according to a convention. Here, the unvulcanized term includes all aspects that have not reached complete vulcanization, and the so-called semi-vulcanized state is included in this "unvulcanized". A vulcanization die 5 is used for vulcanization molding.

The vulcanization die 5 of the present embodiment includes, for example, a tread forming die 6 having a tread forming surface 6s and a pair of sidewall forming dies 7 and 7 having a sidewall forming surface 7s. By fitting these tread molding dies 6 and sidewall molding dies 7 and 7, a molding surface 5s capable of molding the outer surface 2s of the tire 2 is formed.

The tread molding die 6 is configured to include a plurality of segments 8 divided in the tire circumferential direction. FIG. 3 is a partial cross-sectional view in a direction orthogonal to the axis (not shown) of the tread molding die 6 of FIG.

[segment]
Each segment 8 is formed in an arc shape (an arc shape that is convex outward in the radial direction of the tire) as in the conventional case. Each segment 8 is provided so as to be movable in and out of the tire radial direction.

On the molded surface 8s of the segment 8, a protrusion 9 (shown in FIGS. 2 and 3) for forming the groove 11 of the tire 2 and a knife blade 10 (shown in FIG. 3) for forming the siping 12 are provided. It is provided. As shown in FIG. 3, a plurality of knife blades 10 are provided in the tire circumferential direction, and project from the molded surface 8s of the segment 8 toward the tire 2 (raw tire 3). The protruding direction D2 of each knife blade 10 of the present embodiment is set to be parallel to the tire radial direction, but may be in an intersecting direction.

As shown in FIG. 2, at the time of vulcanization molding, after the raw tire 3 is inserted inside the vulcanization die 5, each segment 8 (tread molding die 6) shown in FIG. 3 is in the tire radial direction. Moved inside. As a result, the tread forming mold 6 in which the segments 8 are connected in an annular shape is assembled, the tread forming surface 6s capable of forming the tread surface of the tire 2 is formed, and the raw tire 3 is vulcanized (vulcanized state). .. The knife blade 10 is pushed into the unvulcanized tread rubber 4. As a result, the siping 12 is formed on the tread rubber 4.

After the vulcanization molding is completed, the vulcanization die 5 is opened by moving each segment 8 to the outside in the radial direction of the tire (mold release state). As a result, the knife blade 10 is pulled out from the tread rubber 4, and the tire (finished tire) 2 on which the siping 12 is formed is taken out. At this time, the knife blade 10 may receive contact (friction) and / or bending moment with the tread rubber 4.

In the present embodiment, a plurality of knife blades 10 having different angles (hereinafter, may be simply referred to as “pulling angles”) θ1 between the moving direction D1 of the segment 8 and the protruding direction D2 of the knife blade 10 are included. .. As the pull-out angle θ1 becomes larger, the contact (friction) and / or bending moment between the knife blade 10 and the tread rubber 4 becomes larger, which may cause damage.

In order to design the knife blade 10 that can prevent the above damage, for example, the design change of the knife blade 10 (for example, the shape, arrangement, material, etc. of the knife blade 10 are changed), trial manufacture, and evaluation are repeatedly performed. It is necessary, and it requires a lot of time and cost.

[Design method for knife blades for vulcanization dies]
In the design method of the present embodiment, the knife blade 10 is designed by using the computer 1 (shown in FIG. 1) in order to suppress the increase in time and cost required for the design as described above. FIG. 4 is a flowchart showing an example of a processing procedure of a method for designing a knife blade of a vulcanization die. FIG. 5 is a perspective view showing an example of the tread rubber model 15 and the segment model 19.

[Tread rubber model input process]
In the design method of the present embodiment, first, the tread rubber model 15 is input to the computer 1 (shown in FIG. 1) (step S1). In step S1, the tread rubber 4 (shown in FIG. 3) on which the siping 12 corresponding to the knife blade 10 is formed has a finite number of elements F (i) (i = 1, 2, ... ) Is discretized. As a result, in step S1, the tread rubber model 15 having siping 16 is set. The contour of the tread rubber 4 and the like can be specified, for example, based on the design factor (CAD data) of the tire 2. As the numerical analysis method, for example, a finite element method, a finite volume method, a difference method or a boundary element method can be appropriately adopted, but in the present embodiment, the finite element method is adopted.

As the element F (i), for example, a tetrahedral solid element, a pentahedral solid element, a hexahedral solid element, or the like is used. Each element F (i) has a plurality of nodes 17. Numerical data such as an element number, a node number 17, and a coordinate value of the node 17 are defined in each element F (i). Further, numerical data such as material properties (for example, elastic modulus, Poisson's ratio, density, etc.) of the tread rubber 4 shown in FIG. 2 are defined in each element F (i).

In the tread rubber model 15 of the present embodiment, only a part of the tread rubber 4 shown in FIGS. 2 and 3 in the tire circumferential direction is modeled. As a result, in the design method of the present embodiment, the number of elements F (i) to be calculated can be reduced, so that an increase in calculation time can be prevented. The tread rubber model 15 is not limited to such an aspect, and may be modeled over the entire circumference in the tire circumferential direction, for example. The tread rubber model 15 is stored in the computer 1.

[Segment model (knife blade model) input process]
Next, in the design method of the present embodiment, the segment model 19 having the knife blade model 18 is input to the computer 1 (shown in FIG. 1) (step S2). In step S2 of the present embodiment, based on the design factors of the knife blade 10 and the segment 8 shown in FIG. 3, the segment 8 provided with the knife blade 10 has a finite number of elements G (which can be handled by the numerical analysis method). i) Discretized by (i = 1, 2, ...). As a result, in step S2, the segment model 19 having the knife blade model 18 is set. The design factors for the knife blade 10 and segment 8 can be identified, for example, in CAD data.

For the element G (i), for example, the same element as the element F (i) can be used. Numerical data such as an element number, a node number 20, and a coordinate value of the node 20 are defined in each element G (i). Further, in each element G (i), numerical data such as material properties (for example, elastic modulus, Poisson's ratio, density, etc.) of the segment 8 and the knife blade 10 shown in FIG. 3 are defined.

In the present embodiment, the thickness of the segment model 19 is set to be small (in this example, in the shape of a plate). Further, in the segment model 19 of the present embodiment, only a part of the plurality of segments 8 (shown in FIG. 5) arranged in the tire circumferential direction is modeled so as to correspond to the tread rubber model 15. ing. As a result, the number of elements G (i) to be calculated can be reduced, so that an increase in calculation time can be prevented. The segment model 19 is not limited to such an embodiment, and may be set to have the same thickness as the actual segment 8, or all segments 8 may be modeled. The knife blade model 18 and the segment model 19 are stored in the computer 1 (shown in FIG. 1).

[First step]
Next, in the design method of the present embodiment, the computer 1 (shown in FIG. 1) inserts the knife blade model 18 into the siping 16 of the tread rubber model 15 to form the tread rubber model 15 and the segment model 19. Align to the pseudo-vulcanized state (first step S3). In the present embodiment, "aligning to the pseudo-vulcanized state" means the tread rubber model 15 and the segment based on the relative positions of the tread rubber 4 and the segment 8 in the actual vulcanized state shown in FIG. It is to align with the model 19. In the first step S3 of the present embodiment, the calculation of the vulcanization state (for example, the flow calculation such as rubber flow) is omitted, so that the increase in the calculation time can be suppressed. FIG. 6 is a cross-sectional view illustrating an example of a pseudo-vulcanized state. In FIG. 6, the elements F (i) and G (i) are omitted, and the outer surface side of the tread rubber model 15 is colored.

In the first step S3 of the present embodiment, first, the knife blade model 18 is fitted into the siping 16 of the tread rubber model 15. Next, in the first step S3, the relative positions (for example, the coordinate values in the X-axis direction, the Y-axis direction, and the Z-axis direction) between the tread rubber model 15 and the segment model 19 are in the vulcanized state shown in FIG. It is adjusted to the relative position between the tread rubber 4 and the segment 8. As a result, in the first step S3, the tread rubber model 15 and the segment model 19 are aligned in the pseudo-vulcanized state.

In the first step S3, the contact condition for preventing the tread rubber model 15 and the knife blade model 18 from slipping through may be invalidated prior to fitting the knife blade model 18 into the siping 16. As a result, the knife blade model 18 can slip through the tread rubber model 15 and can be smoothly fitted into the siping 16. After the knife blade model 18 is fitted into the siping 16, the contact conditions are effectively set.

[Second step]
Next, in the design method of the present embodiment, the computer 1 moves the segment model 19 in the pseudo-vulcanized state from the tread rubber model 15 to the outside in the tread radial direction to obtain a pseudo-demolded state (second step S4). ). In the present embodiment, "obtaining a pseudo-demolding state" means that the segment model 19 is referred to the tread rubber model 15 based on the relative position (not shown) between the tread rubber 4 and the segment 8 in the actual demolding state. It is to get the state moved from. Therefore, in the second step S4, the movement of the segment model 19 is calculated based on the actual movement direction D1 (shown in FIG. 3) of the segment 8. FIG. 7 is a cross-sectional view illustrating an example of a pseudo-release state. In FIG. 7, the state in which the segment model 19 is moved to the position indicated by the alternate long and short dash line is specified as a pseudo-release state.

When the moving direction D1 of the segment model 19 and the protruding direction D2 of the knife blade model 18 (that is, the protruding direction D2 of the knife blade 10 shown in FIG. 3) are not parallel, the knife blade model 18 is the tread rubber model 15. Contact. By such contact, the deformation calculation of the tread rubber model 15 and the knife blade model 18 is performed in the second step S4.

The deformation calculation of the tread rubber model 15 and the knife blade model 18 is based on the shapes and material properties of the elements F (i) and G (i) shown in FIG. 5, and the elements F (i) and G ( The mass matrix, stiffness matrix, and damping matrix of i) are created, respectively. Furthermore, each of these matrices is combined to form the matrix of the entire system. Then, the equations of motion are created by applying the various conditions, and these are calculated for each minute time (unit time T (x) (x = 0, 1, ...)). As a result, the deformation calculation of the tread rubber model 15 and the knife blade model 18 is performed.

Commercially available finite element analysis application software such as LS-DYNA manufactured by LSTC is used for the deformation calculation of the tread rubber model 15 and the knife blade model 18. The unit time T (x) is appropriately set according to the required simulation accuracy.

FIG. 8 is a flowchart showing an example of the processing procedure of the second step S4. In the second step S4 of the present embodiment, as shown in FIG. 7, a step S41 for moving the segment model 19, a step S42 for calculating a physical quantity acting on the knife blade model 18, and a pseudo-separation state are obtained. The step S43 for determining whether or not it is present is carried out. These steps S41 to S43 are carried out in the unit time T (x).

In the step S41 of the present embodiment, the deformation of the segment model 19 due to the contact between the tread rubber model 15 and the knife blade model 18 is calculated by moving along the moving direction D1. In step S42, the physical quantity acting on each element G (i) of the knife blade model 18 shown in FIG. 5 is calculated based on the deformation calculation in step S41. The physical quantity is appropriately set as long as the damage of the knife blade 10 can be evaluated. The physical quantity of this embodiment is the stress of the knife blade model 18. FIG. 9 is a contour diagram showing an example of the stress of the knife blade model 18. It can be evaluated that the knife blade 10 (shown in FIG. 3) is easily damaged in the place where the stress of the knife blade model 18 is large.

When it is determined in step S43 that a pseudo-release state (indicated by a two-dot chain line in FIG. 7) is obtained (“Y” in step S43), a series of processes in step S4 is completed. On the other hand, if it is determined in step S43 that the pseudo-release state has not been obtained (“N” in step S43), the unit time is advanced by one (step S44), and steps S41 to S43 are carried out again. Will be done. As described above, in the second step S4 of the present embodiment, the segment model 19 is moved from the pseudo-vulcanization state (shown in FIG. 6) to the pseudo-demolding state (shown in FIG. 7) and acts during the movement. The physical quantity of the knife blade model 18 can be calculated for each unit time T (x). The physical quantity is stored in the computer 1 (shown in FIG. 1).

Next, in the design method of the present embodiment, the computer 1 (shown in FIG. 1) compares the physical quantity with a predetermined allowable value (step S5). The permissible value can be appropriately set, for example, as long as it can evaluate the presence or absence of damage to the knife blade 10 (shown in FIG. 3). As the allowable value of this embodiment, the allowable stress of the material used for the knife blade 10 is set.

In step S5 of the present embodiment, the maximum calculated during the movement from the pseudo-vulcanization state (shown in FIG. 6) to the pseudo-demolding state (shown in FIG. 7) in each element G (i) of the knife blade model 18. It is determined whether or not the stress of is less than or equal to the allowable value.

When it is determined in step S5 that the physical quantity is equal to or less than the allowable value (“Y” in step S5), based on the design factor of the knife blade 10 (that is, the shape, arrangement, material, etc. of the knife blade model 18). , The knife blade 10 is designed and manufactured (step S6).

On the other hand, when it is determined in step S5 that the physical quantity exceeds the permissible value (“N” in step S5), the design factor of the knife blade 10 is changed (step S7), and steps S1 to S5 are repeated. Will be implemented. The design factors to be changed include, for example, the shape, arrangement and material of the knife blade 10 (knife blade model 18).

As described above, in the design method of the present embodiment, the segment model 19 is moved from the pseudo-vulcanization state (shown in FIG. 6) to the pseudo-demolding state (shown in FIG. 7) and acts on the knife blade model 18. Physical quantities can be calculated. Therefore, in the design method of the present embodiment, the design factor can be appropriately changed based on the physical quantity thereof, so that the knife blade 10 capable of preventing damage can be reliably designed.

In the design method of the present embodiment, the design factor of the knife blade 10 is changed until the physical quantity acting on the knife blade model 18 becomes equal to or less than the allowable value. Therefore, in the design method of the present embodiment, the knife blade 10 having high durability can be reliably designed.

In the design method of the present embodiment, the physical quantity acting on the knife blade model 18 is calculated using the computer 1 while changing the design factors of the knife blade model 18 without repeating the actual trial production of the knife blade 10. can do. Therefore, the design method of the present embodiment can efficiently design the knife blade 10 (that is, in a short time and at low cost).

Further, in the design method of the present embodiment, the physical quantity acting on the knife blade model 18 can be calculated without modeling the entire vulcanization die 5 (shown in FIG. 2), and the durability of the knife blade 10 can be calculated. You can evaluate sex. Therefore, in the design method of the present embodiment, the calculation time can be significantly shortened.

Although the particularly preferred embodiment of the present invention has been described in detail above, the present invention is not limited to the illustrated embodiment and can be modified into various embodiments.

Knife blades were designed and manufactured based on conventional procedures (ie, without using the procedures of FIGS. 4 and 8) (comparative examples).

On the other hand, based on the procedure of FIG. 4, a knife blade provided in the arcuate segment constituting the vulcanization die of the tire was designed (Example). In the examples, an early knife blade model was set based on the design factors of the conventional knife blade. Next, in the embodiment, the physical quantity acting on the knife blade model was calculated based on the procedure of FIG. 8, and the design factor of the knife blade was changed until the physical quantity was equal to or less than a predetermined allowable value. Then, a knife blade was manufactured based on a design factor in which the physical quantity was less than the allowable value.

Then, the raw tires were vulcanized and molded using the knife blades of Examples and Comparative Examples. Then, the number of tires until the knife blades were damaged and the damaged parts were visually confirmed. The common specifications are as follows.
Tire size: 295 / 80R22.5
Length of knife blade (comparative example) in the tire radial direction: 17.5 mm

In the comparative example, after vulcanizing 30 tires, the knife blade was damaged. The portion where the knife blade of the comparative example was damaged (cracked) coincided with the portion where the physical quantity exceeded the permissible value in the initial knife blade model of the example.

On the other hand, in the example, the knife blade was not damaged even after vulcanizing 1000 tires. Therefore, the example was able to design a knife blade capable of preventing damage as compared with the comparative example.

S1 Process for inputting the tread rubber model S2 Process for inputting the segment model S3 First step S4 Second step

Claims (3)

It is a design method of a knife blade provided in an arcuate segment constituting a vulcanization die of a tire.
A process of inputting a tread rubber model having a siping in which a tread rubber having a siping corresponding to the knife blade is discretized by a finite number of elements into a computer is used.
A step of inputting a segment model having a knife blade model in which the segment provided with the knife blade is discretized by a finite number of elements to the computer.
The first step in which the computer fits the knife blade model into the siping of the tread rubber model and aligns the tread rubber model and the segment model in a pseudo-vulcanized state.
A second step in which the computer moves the segment model in the pseudo-vulcanized state from the tread rubber model to the outside in the tread radial direction to obtain a pseudo-demolded state.
The second step includes a step of calculating a physical quantity acting on the knife blade model.
How to design a knife blade for a vulcanization die. The method for designing a knife blade of a vulcanization die according to claim 1, wherein the physical quantity is stress. Claim 1 or 2 further comprises a step in which the computer compares the physical quantity with a predetermined allowable value and changes the design factor of the knife blade when the physical quantity exceeds the allowable value. How to design a knife blade for a vulcanization die as described in.

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