JP7429546B2 - Tire molding mold and pneumatic tire manufacturing method - Google Patents

Description

The present invention includes a pair of bead portions, a sidewall portion extending outward in the tire radial direction from each of the bead portions, and a tread portion continuous to an outer end in the tire radial direction of each of the sidewall portions and forming a tread surface. The present invention relates to a tire mold for vulcanizing an unvulcanized green tire.

When manufacturing pneumatic tires, which are rubber products, the vulcanization process is the most time-consuming process, so efforts are still being made to shorten the time of the vulcanization process. On the other hand, if the rubber part is not sufficiently vulcanized during the vulcanization process, air generated by the rubber vulcanization reaction will remain in the vulcanized rubber, and this residual air can cause tire failure at the product stage. In some cases, Therefore, in normal tire production sites, we take into account the fact that, due to seasonal factors, for example, the temperature of the unvulcanized raw tire, the temperature inside the mold, the ambient temperature, etc. The time required for the vulcanization process is set by adding the margin time that takes into account the above.

However, setting a margin time is not preferable from the viewpoint of improving tire productivity, and it has been desired to determine the end of vulcanization for each tire and efficiently execute the vulcanization process.

Patent Document 1 below discloses that the impedance of a vulcanized sample is measured while the vulcanization process is progressing, and the optimal vulcanization is determined at the point when the rate of increase in the polymer resistance value Rp of the vulcanized sample suddenly slows down. A method for real-time vulcanization control of vulcanized samples is described, with a stop time. However, this method requires impedance measurement of the vulcanized sample by sandwiching the vulcanized sample between two electrodes, and since tires are usually a laminate of composite materials, this method cannot be used. It is difficult to apply it to tires during tire vulcanization.

Japanese Patent Application Publication No. 2003-211459

The present invention was made in view of the above circumstances, and its purpose is to accurately measure the temperature of a pneumatic tire during vulcanization in order to reliably determine the end point of the vulcanization process for each tire. It is an object of the present invention to provide a tire molding mold that has a temperature measurement probe with excellent durability, and a method for manufacturing a pneumatic tire using the tire molding mold.

The above object can be achieved by the present invention as described below. That is, the present invention provides a pair of bead portions, a sidewall portion extending outward in the tire radial direction from each of the bead portions, and a tread portion continuous to the outer end of each of the sidewall portions in the tire radial direction to form a tread surface. A tire molding mold for vulcanizing an unvulcanized green tire, comprising at least a tread mold part that can be pressed into contact with the tread part, the tread mold part being divided in the circumferential direction, It has a plurality of segments that are movable in the radial direction of the green tire, and at least one of the segments includes a fixing means for fixing an end of the temperature measurement probe on the outer circumference side, and a fixing means for fixing an end of the temperature measurement probe toward the inner circumference side. The extending temperature measurement probe insertion hole has an outer peripheral surface side end fixed by the fixing means, extends inside the temperature measurement probe insertion hole toward the inner peripheral surface side, and has an inner peripheral surface side end fixed to the inner peripheral surface side of the temperature measurement probe insertion hole. a temperature measuring probe attached in a position that allows it to be buried in the shoulder portion of the tread portion beyond the circumferential side edge, and a convex portion formed on the inner circumferential side side surface of the temperature measuring probe insertion hole and the temperature measuring probe; The present invention relates to a tire molding mold, characterized in that the temperature measuring probe is fixed by contacting the surface of the measuring probe.

In the tire mold, it is preferable that the temperature measurement probe is fixed by contacting the top of the convex portion with the surface of the temperature measurement probe.

In the above tire molding mold, the convex portion is formed in a range L1 in the depth direction from an end on the inner circumferential surface of the temperature measuring probe insertion hole, and the convex portion is formed on the inner circumferential surface side of the temperature measuring probe insertion hole. It is preferable that the depth L of the temperature measurement probe insertion hole from the end to the outer peripheral surface side end satisfies 0.02≦L1/L≦0.05.

It is preferable that the length of L1 is at least 5 mm or more.

In the tire molding mold described above, it is preferable that the temperature measuring probe has an outer diameter of 1 to 10 mm.

In the tire molding mold described above, it is preferable that the temperature measuring probe is a platinum resistance temperature detector.

Further, the present invention provides a method for manufacturing a pneumatic tire, including a vulcanization step of vulcanizing in any of the tire molding molds described above, wherein the vulcanization step includes the step of vulcanizing a pair of bead portions, A tread portion of an unvulcanized green tire, comprising a sidewall portion extending outward in the tire radial direction from each of the bead portions, and a tread portion continuous to the outer end in the tire radial direction of each of the sidewall portions and forming a tread surface. The present invention relates to a method for manufacturing a pneumatic tire, comprising the step of embedding a temperature measuring probe in the shoulder portion included in the tire to measure the temperature of the shoulder portion.

The tire molding die according to the present invention is a so-called "segmental mold" in which at least the tread mold part is divided in the circumferential direction, and at least one of the segments is equipped with the above-mentioned specific temperature measurement probe. This makes it possible to accurately measure the temperature of the pneumatic tire during vulcanization, particularly the temperature of the shoulder portion of the tread where vulcanization of the tire is most difficult to proceed.

In the tire molding die according to the present invention, the temperature measurement probe is pushed and embedded in the shoulder portion of the tread portion of the green tire. Generally, even if the rubber part that makes up the shoulder part is in an unvulcanized state, when the temperature measurement probe is pushed into the rubber, a large load is placed on the temperature measurement probe, and in some cases, the temperature measurement probe may be There is a risk of it becoming bent. However, in the tire molding die according to the present invention, the temperature measurement probe is fixed by the convex portion formed on the inner circumferential side surface of the temperature measurement probe insertion hole coming into contact with the surface of the temperature measurement probe. . This allows the temperature measurement probe to be held more stably compared to a configuration in which the outer circumferential end of the temperature measurement probe is fixed using only the fixing means, thereby preventing deformation such as curvature of the temperature measurement probe and increasing the temperature. The durability of the measurement probe can be improved.

In particular, in the tire molding die according to the present invention, when the temperature measuring probe is fixed by contacting the tops of the convex parts with the surface of the temperature measuring probe, the temperature measuring probes are fixed at the tops of the plurality of convex parts. It can be held more stably. In addition, since an air layer is formed between the adjacent convex portions and the surface of the temperature measurement probe, heat conduction from the mold to the temperature measurement probe can be further reduced. As a result, the temperature of the pneumatic tire during vulcanization can be measured more accurately.

Tire meridian cross-sectional view showing an example of a tire that can be manufactured according to the present invention A sectional view conceptually showing a tire molding die of the present invention A cross-sectional view conceptually showing a state in which a temperature measurement probe is embedded in a shoulder part in a segment constituting a tread mold part of a mold of the present invention.

Embodiments of the present invention will be described with reference to the drawings. The green tire 9 shown in FIG. 1 includes a pair of bead portions 1, a sidewall portion 2 extending outward in the tire radial direction from each bead portion 1, and a sidewall portion 2 continuous to the outer end of each sidewall portion 2 in the tire radial direction. This pneumatic tire includes a tread portion 3 that constitutes a tread surface. An annular bead core 1a is arranged in the bead portion 1.

The carcass layer 4 extends from the tread portion 3 via the sidewall portion 2 to the bead portion 1, and its end portion is folded back via the bead core 1a. The carcass layer 4 is composed of at least one carcass ply. The carcass ply is formed by covering a carcass cord extending at an angle of approximately 90 degrees with respect to the tire circumferential direction with topping rubber.

The belt layer 5 is bonded to the outside of the carcass layer 4 at the tread portion 3 and covered with tread rubber 6 from the outside. The belt layer 5 is composed of a plurality of (two in this embodiment) belt plies. Each belt ply is formed by covering belt cords extending obliquely with respect to the tire circumferential direction with topping rubber, and the belt cords are stacked so as to intersect in opposite directions between the plies.

The tread rubber 6 may be composed of only one layer, or may be composed of a so-called cap base structure having a base tread on the inner side in the tire radial direction and a cap tread located on the outer peripheral side of the base tread.

The raw tire 9 shown in FIG. 1 is an unvulcanized raw tire, and in the vulcanization process described later, it is shaped into the shape of a product tire (see FIG. 2), and its tread surface is coated with various treads. A pattern is formed.

In the vulcanization molding of the green tire 9, a tire molding mold (hereinafter also simply referred to as a "mold") according to the present invention is used. FIG. 2 shows a conceptual cross-sectional view of the tire molding die of the present invention. The green tire 9 is set in the mold 10 in an unvulcanized state, and the green tire 9 in the mold 10 is heated and pressurized to perform a vulcanization process.

The mold 10 includes at least a tread mold part 11 that can be pressed against the tread part 3 of the green tire 9. In this embodiment, the mold 10 includes a tread mold part 11 in contact with the tread surface of the green tire 9, a lower mold part 12 in contact with the tire outer surface facing downward, and an upper mold part 13 in contact with the tire outer surface facing upward. Equipped with These are configured to be freely displaceable between a mold-clamping state and a mold-opening state by an opening/closing mechanism (not shown) installed around them, and the structure of such opening/closing mechanism is well known. The tread mold part 11 is further divided into a plurality of segments in the circumferential direction, and is movable in the radial direction of the green tire 9 disposed within the mold 10. Furthermore, the mold 10 is provided with a platen plate (not shown) having a heat source such as an electric heater or a steam jacket, which heats each mold part.

At the center of the mold 10, a center mechanism 14 is provided coaxially with the tire, and around this a tread mold part 11, a lower mold part 12, and an upper mold part 13 are installed. The center mechanism 14 has a rubber bag-shaped bladder 15 and a center post 16 extending in the tire axial direction, and the center post 16 is provided with an upper clamp 17 and a lower clamp 18 for gripping the end of the bladder 15. ing.

A medium supply path 21 for supplying a heating medium into the bladder 15 extends vertically in the central mechanism 14, and an ejection port 22 is formed at the upper end of the medium supply path 21. The medium supply path 21 is connected to a supply pipe 24 through which a heating medium supplied from a heating medium supply source 23 and a pressurizing medium supplied from a pressurizing medium supply source 26 flow. The heating medium is supplied according to the opening/closing operation of the valve 25, and the pressurizing medium is supplied according to the opening/closing operation of the valve 28.

Further, in the central mechanism 14, a medium discharge path 31 for discharging the high temperature and high pressure fluid in which the heating medium and the pressurizing medium are mixed in the bladder 15 is vertically extended. A recovery port 32 is formed. A discharge pipe 34 through which high-temperature, high-pressure fluid flows is connected to the medium discharge path 31, and the discharge pipe 34 is provided with a blow valve 33 for opening and closing the blow valve 33. The pump 35 may use a method of forcibly circulating the high-temperature, high-pressure fluid so that the high-temperature, high-pressure fluid passing through the medium discharge path 31 is resupplied to the inside of the bladder 15 via the medium supply path 21.

Hereinafter, the segments 41 constituting the tread mold part 11 included in the mold 10 of the present invention will be described. FIG. 3 is a cross-sectional view conceptually showing a state in which a temperature measurement probe 44 is embedded in a shoulder portion 3S in a segment constituting a tread mold portion of a mold according to the present invention. In FIG. 3, the "inner peripheral surface side" means the side closer to the green tire 9 when the green tire 9 is set in the mold 10. The segment 41 is one in which the tread mold part 11 is divided into, for example, 6 to 12 parts in the circumferential direction, and each segment 41 is pressed into contact with the tread part 3 of the raw tire 9 by moving in the radial direction of the raw tire 9. It is possible. It is more preferable that the number of divisions of the segment 41 is an odd number within the range of 6 to 12.

At least one of the segments 41 is fixed by the fixing means 42 for fixing the temperature measuring probe 44, a temperature measuring probe insertion hole 43 extending from the fixing means 42 toward the inner peripheral surface side, and the temperature measuring probe 44 is fixed by the fixing means 42. The probe extends inside the insertion hole 43 toward the inner peripheral surface side, and is in a position where the inner peripheral surface end can be embedded in the shoulder portion 3S of the tread portion 3 beyond the inner peripheral surface side end I of the temperature measurement probe insertion hole 43. and a temperature measurement probe 44 attached thereto. Such temperature measurement probe 44 may be attached to one of the plurality of segments 41, may be attached to a plurality of segments 41, or may be attached to all segments 41.

The fixing means 42 for fixing the temperature measurement probe 44 is configured by, for example, a double nut on the outer circumference side and a threaded structure on the inner circumference side, thereby preventing the temperature measurement probe 44 from protruding from the temperature measurement probe hole 43. It can be designed so that the height can be adjusted.

A temperature measurement probe insertion hole 43 is formed on the inner peripheral surface side of the fixing means 42 . The temperature measurement probe insertion hole 43 is preferably arranged in the radial direction of the green tire 9, as will be described later. The inner peripheral surface side of the temperature measurement probe insertion hole 43 is open, and is designed so that the temperature measurement probe 44 can protrude into the cavity of the mold 10 and be buried in the shoulder part 3S of the tread part 3. .

The temperature measurement probe 44 has an end on the outer circumferential surface side fixed by the fixing means 42 and extends inside the temperature measurement probe insertion hole 43 toward the inner circumferential surface side. It is attached in such a manner that it can be embedded in the shoulder part 3S of the tread part 3 beyond the inner peripheral surface side edge I. As will be described later, the temperature measurement probe 44 is preferably arranged in the radial direction of the green tire 9. Furthermore, the cross-sectional shape of the temperature measurement probe 44 is not particularly limited, but is preferably circular.

As described above, since the segments 41 move in the radial direction of the green tire 9, if the temperature measurement probe 44 is also arranged in the radial direction of the green tire 9, when the temperature measurement probe 44 is buried in the shoulder portion 3S, , is preferable because the load is the least. When considering the reduction of the load on the temperature measurement probe 44, the deviation between the direction in which the segment 41 moves in the radial direction and the direction in which the temperature measurement probe 44 is arranged in the radial direction should be 3 degrees or less. is preferable, and more preferably 1° or less.

As shown in FIG. 3, in this embodiment, a convex portion 4M is formed on the side surface of the inner peripheral surface of the temperature measurement probe insertion hole 43, and the top of the convex portion 4M contacts the surface of the temperature measurement probe 44. , the temperature measurement probe 44 is fixed. According to this configuration, the temperature measurement probe 44 is stably held within the temperature measurement probe insertion hole 43, thereby preventing deformation such as curvature of the temperature measurement probe 44 and improving the durability of the temperature measurement probe 44. be able to. Further, since an air layer is formed between the adjacent convex portions 4M and the surface of the temperature measurement probe 44, heat conduction from the mold to the temperature measurement probe can be further reduced.

The convex portion 4M formed on the inner circumferential side surface of the temperature measurement probe insertion hole 43 may be formed anywhere on the inner circumferential side surface of the temperature measurement probe insertion hole 43; 43 is preferably formed from the inner circumferential surface side end I toward the outer circumferential surface side. Further, the convex portion 4M is formed in a range L1 in the depth direction from the inner peripheral surface side end I of the temperature measurement probe insertion hole 43, and extends from the inner peripheral surface side end I of the temperature measurement probe insertion hole 43 to the outer peripheral surface. It is preferable that the depth L of the temperature measurement probe insertion hole 43 to the side end O satisfies 0.02≦L1/L≦0.05. According to this configuration, the temperature measurement probe 44 is held more stably within the temperature measurement probe insertion hole 43, so deformation such as curvature of the temperature measurement probe 44 is more reliably prevented, and the durability of the temperature measurement probe 44 is improved. can further improve performance. The length L1 can be arbitrarily designed depending on the length of the temperature measurement probe 44, but is preferably 5 mm or more, for example.

In this embodiment, the inner diameter D2 at the outer peripheral surface side end O of the temperature measurement probe insertion hole 43 is designed to be larger than the inner diameter D1 at the inner peripheral surface side end I. According to this configuration, since a larger gap can be secured between the temperature measurement probe 44 and the temperature measurement probe hole 43 on the outer peripheral surface side, the temperature inside the shoulder part 3S of the tread part 3 can be measured by the temperature measurement probe 44. When doing so, it becomes possible to further reduce heat conduction from the mold 10 to the temperature measurement probe 44, and the temperature within the shoulder portion 3S of the tread portion 3 can be measured more accurately. In the temperature measurement probe insertion hole 43, when L2 is the length in the depth direction of the portion where the inner diameter is larger than D1, it is preferable that L2/L≦0.9. The outer diameter of the temperature measurement probe 44 is preferably about 1 to 10 mm, for example.

In the present invention, as a temperature measurement probe used to measure the vulcanization temperature, a resistance temperature detector that utilizes the property that the electrical resistance of metal changes with temperature changes can be used. Examples of such metals include platinum, nickel, and copper; however, in the present invention, platinum thermometers have a large resistance value change (sensitivity) to temperature changes, and as a result, platinum thermometers have very high sensitivity to temperature changes. Resistors can be particularly preferably used.

Next, the vulcanization step in the method for manufacturing a pneumatic tire of the present invention will be specifically explained.

First, as shown in FIG. 2, a green tire 9 is set in a mold 10, and the green tire 9 is shaped to approximate the inner shape of the mold 10 using an inflated bladder 15. Thereby, the green tire 9 is held by the bladder 15 and is applied to each of the tread mold part 11, the lower mold part 12, and the upper mold part 13. At this point, a temperature measuring probe is embedded in the slowest vulcanization part of the green tire 9. The slowest vulcanization section refers to a section of the tire where vulcanization is least likely to proceed, and usually refers to the shoulder section of the tread section 3. Particularly, in the shoulder portion, it is preferable to set the position where the thickness of the tread portion 3 becomes maximum, as measured along the normal line to the inner surface of the tread portion 3 after vulcanization, as the slowest vulcanization portion. In any case, in the present invention, a temperature measuring probe is embedded in the slowest vulcanization part of the green tire 9 in order to measure the vulcanization temperature at the slowest vulcanization part. As an embedding method, for example, the temperature measurement probe 44 is disposed at a position corresponding to the shoulder part of the tread mold part 11, and when the tread mold part 11 moves in the radial direction of the green tire 9 and the green tire 9 is placed. It is conceivable to design the temperature measurement probe 44 so that it is pushed into the green tire 9 and buried therein. The temperature measurement probe 44 embedded in the green tire 9 measures the temperature of the green tire 9 during the vulcanization process, and the tire is demolded from the mold 10 including the tread mold part 11 at the end of the vulcanization process. At this time, the temperature measurement probe may be simultaneously removed from the slowest vulcanization section.

Subsequently, outer heating is performed in which the mold 10 is heated to heat the tire 9 from the tire outer surface side, and inner heating is performed in which a high temperature heating medium is supplied to the bladder 15 in the mold 10 to heat the tire 9 from the tire inner surface side. The green tire 9 is vulcanized by heating. The mold 10 is heated in advance by the above-mentioned steam jacket or the like, thereby performing external heating. The inner side heating is performed by supplying a heating medium into the bladder 15 through the medium supply path 21 after shaping the tire 9 . After supplying the heating medium for a predetermined period of time, a pressurizing medium is subsequently supplied into the bladder 15 to pressurize the tire 9 at high pressure. As the heating medium, for example, steam or high temperature water is used, and as the pressurizing medium, for example, an inert gas such as nitrogen gas or steam is used.

The temperature measurement probe 44 can obtain time-series data on the temperature of the green tire during vulcanization. To acquire such time-series data, it is possible to use a high-precision digital data logger commonly available in the market (temperature resolution of about 0.001°C, accuracy of about ±0.005°C, minimum temperature value acquisition interval of 1 second). . By analyzing the acquired time series data, it is possible to reliably determine the end point of the vulcanization process for each tire.

After the vulcanization process is completed, the temperature measuring probe disposed inside the mold 10 is removed from the vulcanized tire while the mold 10 is left open. As a result, it is possible to determine the end point of vulcanization for each tire and to manufacture pneumatic tires while shortening the vulcanization time.

The present invention is not limited to the embodiments described above, and various improvements and changes can be made without departing from the spirit of the present invention.

Claims (6)

An unfinished tread comprising a pair of bead portions, a sidewall portion extending outward in the tire radial direction from each of the bead portions, and a tread portion continuous to the outer end of each of the sidewall portions in the tire radial direction and forming a tread surface. A tire molding mold for vulcanizing a raw sulfur tire,
At least a tread mold part that can be pressed into contact with the tread part,
The tread mold part is divided in the circumferential direction and has a plurality of segments movable in the radial direction of the green tire,
At least one of the segments includes a fixing means for fixing the outer circumferential surface side end of the temperature measurement probe, a temperature measurement probe insertion hole extending from the fixing means toward the inner circumferential surface side, and an outer circumferential surface side end by the fixing means. is fixed and extends inside the temperature measurement probe insertion hole toward the inner peripheral surface side, and the inner peripheral surface side end can be embedded in the shoulder portion of the tread portion beyond the inner peripheral surface side end of the temperature measurement probe insertion hole. Equipped with a temperature measurement probe attached in a comfortable position,
The temperature measurement probe is fixed by contacting the surface of the temperature measurement probe with a convex portion formed on a side surface of the inner peripheral surface of the temperature measurement probe insertion hole ,
The temperature measurement probe is fixed by the contact between the top of the protrusion and the temperature measurement probe surface , and an air layer is formed between the adjacent protrusion and the temperature measurement probe surface. A tire molding mold that is characterized by: The convex portion is formed in a range L1 in the depth direction from the inner peripheral surface side end of the temperature measurement probe insertion hole, and extends from the inner peripheral surface side end of the temperature measurement probe insertion hole to the outer peripheral surface side end. The tire molding die according to claim 1 , wherein the depth L of the temperature measurement probe insertion hole satisfies 0.02≦L1/L≦0.05. The tire molding die according to claim 2 , wherein the length of the L1 is at least 5 mm or more. The tire molding mold according to any one of claims 1 to 3 , wherein the temperature measuring probe has an outer diameter of 1 to 10 mm. The tire molding mold according to any one of claims 1 to 4 , wherein the temperature measuring probe is a platinum resistance temperature sensor. A method for manufacturing a pneumatic tire, comprising a vulcanization step of vulcanizing in a tire mold according to any one of claims 1 to 5 ,
The vulcanization step includes a pair of bead portions, a sidewall portion extending outward in the tire radial direction from each of the bead portions, and a tread portion that is continuous with the outer end of each of the sidewall portions in the tire radial direction to form a tread surface. A method for manufacturing a pneumatic tire, comprising the step of embedding a temperature measurement probe in a shoulder part included in a tread part of an unvulcanized green tire, and measuring the temperature of the shoulder part. .

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