JP2022101835A - Manufacturing method of pneumatic tire - Google Patents

Abstract

To provide a manufacturing method of a pneumatic tire excellent in appearance, while intending to optimize a vulcanization time, by measuring an accurate vulcanization temperature for every tire during a vulcanization step.SOLUTION: At least one of segments that a tire-molding metal mold has is provided with a projection portion for forming a groove portion to a tread portion of a green tire, and a temperature sensor for measuring a temperature of the tread portion during a vulcanization step. The temperature sensor is arranged toward the inside from the outside in a radial direction inside the projection portion, at least a portion of the tip end protrudes to the radial direction inside with respect to a tip end of the protrusion portion, when a maximum width of the protrusion portion is set to WP and a maximum width of the temperature sensor projected from the tip end of the projection portion is set to Ws, 1≤(Ws/WP)≤4, and the vulcanization step is carried out while measuring a temperature of the treading portion, by burying the temperature sensor projected from the tip end of the projection portion in the treading portion.SELECTED DRAWING: Figure 3

Description

The present invention relates to a method for manufacturing a pneumatic tire, which comprises a vulcanization step of heating and vulcanizing an unvulcanized raw tire in a tire molding mold.

When manufacturing pneumatic tires, which are rubber products, the vulcanization process is the most time-consuming process, and efforts are still being made to shorten the vulcanization process time. On the other hand, if the vulcanization of the rubber part is insufficient in the vulcanization process, the air generated by the vulcanization reaction of the rubber remains in the vulcanized rubber, and such residual air causes tire failure at the product stage. May be. Therefore, in a normal tire production site, considering that the temperature of raw unvulcanized tires, which are raw materials, the temperature inside the mold, the atmospheric temperature, etc., vary due to seasonal factors, etc., all variations in the vulcanization process are taken into consideration. The time required for the vulcanization process is set by adding the extra time in consideration of.

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

For example, Patent Document 1 below describes a method for manufacturing a pneumatic tire, which includes at least a step of embedding a permittivity measuring probe in a shoulder portion of a tread portion of a raw tire in a vulcanization step.

Japanese Unexamined Patent Publication No. 2016-203555

As a result of diligent studies by the present inventors, in the method described in Patent Document 1, the pneumatic tire obtained after the vulcanization step has an embedding mark corresponding to the embedding portion of the dielectric constant measuring probe. There was a problem that the appearance of the pneumatic tire was deteriorated.

The present invention has been made in view of the above circumstances, and an object of the present invention is to measure the accurate vulcanization temperature of each tire during the vulcanization process, thereby optimizing the vulcanization time and excellent appearance. The purpose is to provide a method for manufacturing a pneumatic tire.

The above object can be achieved by the present invention as described below. That is, the present invention is a method for manufacturing a pneumatic tire including a vulcanization step of heating and vulcanizing an unvulcanized raw tire in a tire molding mold, wherein the tire molding mold is unvulcanized. The tread mold portion is provided with at least a tread mold portion that can be pressure-contacted with the tread portion of the raw tire, and the tread mold portion has a plurality of segments that are divided in the circumferential direction and can move in the radial direction of the raw tire. At least one of the segments includes a protrusion for forming a groove in the tread portion of the raw tire and a temperature sensor for measuring the temperature of the tread portion during the vulcanization step, and the temperature sensor is inside the protrusion. Is arranged from the outside in the radial direction to the inside, at least a part of the tip thereof protrudes radially inward from the tip of the protruding portion, the maximum width of the protruding portion is _WP , and the tip of the protruding portion is When the maximum width of the temperature sensor protruding from the tire is W _s , 1 ≦ (W _s / _WP ) ≦ 4, and in the vulcanization step, the temperature sensor protruding from the tip of the protruding portion is read onto the tread. The present invention relates to a method for manufacturing a pneumatic tire, which is carried out while measuring the temperature of the tread portion by burying the tire in the portion.

In the method for manufacturing a pneumatic tire, the height of the protruding portion is preferably 2 mm or more.

In the method for manufacturing a pneumatic tire, it is preferable that the maximum width Wb of the protruding portion is 5 mm or more.

In the method for manufacturing a pneumatic tire, it is preferable that the maximum width Ws of the temperature sensor protruding from the tip of the protruding portion is within 5 mm.

In the method for manufacturing a pneumatic tire, it is preferable that the temperature sensor is a platinum resistance temperature detector.

The tire molding die used in the method for manufacturing a pneumatic tire according to the present invention includes a protruding portion for forming a groove in the tread portion of a raw tire, and a temperature sensor for measuring the temperature of the tread portion during the vulcanization process. To prepare for. Further, the temperature sensor is arranged from the radial outside to the inside in the protrusion, and at least a part of the tip thereof protrudes radially inward from the tip of the protrusion. Since the tire molding die used in the present invention has such a configuration, in the pneumatic tire manufactured after the vulcanization step, an embedding mark caused by the temperature sensor is formed in the vicinity of the bottom surface of the groove portion. That is, since no large buried mark is left on the tread portion of the tread portion of the pneumatic tire, it is possible to manufacture the pneumatic tire having excellent appearance.

A tire meridian sectional view showing an example of an unvulcanized raw tire to be heat-vulcanized in the present invention. Cross-sectional view conceptually showing a tire molding die used in the present invention. Cross-sectional view conceptually showing the state of the protrusion and the temperature sensor provided in the tire molding die used in the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a cross-sectional view of a tire meridian showing an example of an unvulcanized raw tire that is heat-vulcanized in the present invention. The raw tire 9 shown here has a pair of bead portions 1, a sidewall portion 2 extending outward in the tire radial direction from each of the bead portions 1, and a tread surface connected to each tire radial outer end of the sidewall portion 2. It is a pneumatic tire provided with a tread portion 3 constituting the above. An annular bead core 1a is arranged in the bead portion 1.

The carcass layer 4 reaches the bead portion 1 from the tread portion 3 via the sidewall portion 2, 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 ° with respect to the tire circumferential direction with topping rubber.

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

The tread rubber 6 may be configured with only one layer, or may be configured with 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 thereof.

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

In the vulcanization molding of the raw tire 9, a tire molding die (hereinafter, also simply referred to as “mold”) is used. FIG. 2 shows a cross-sectional view conceptually showing a tire molding die. The raw tire 9 is set in the mold 10 in an unvulcanized state, and the vulcanization step is performed by applying heat and pressure to the raw tire 9 in the mold 10.

The mold 10 includes at least a tread mold portion 11 that can be pressed against the tread portion 3 of the raw tire 9. In the present embodiment, the mold 10 includes a tread mold portion 11 in contact with the tread surface of the raw tire 9, a lower mold portion 12 in contact with the outer surface of the tire facing downward, and an upper mold portion 13 in contact with the outer surface of the tire facing upward. To prepare for. These are configured to be freely displaceable between the mold-fastened state and the mold open state by an opening / closing mechanism (not shown) installed around them, and the structure of such an opening / closing mechanism is well known. The tread mold portion 11 is further divided into a plurality of segments in the circumferential direction, and is movable in the radial direction of the raw tire 9 arranged in the mold 10. Further, the mold 10 is provided with a platen plate (not shown) having a heat source such as an electric heater or a steam jacket, whereby each mold portion is heated.

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

In the central mechanism 14, a medium supply path 21 for supplying a heating medium into the bladder 15 is vertically extended, and a ejection port 22 is formed at the upper end of the medium supply path 21. A heating medium supplied from the heating medium supply source 23 and a supply pipe 24 through which the pressure medium supplied from the pressure medium supply source 26 flows are connected to the medium supply path 21. 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 a high-temperature high-pressure fluid in which a heating medium and a pressurized medium in the bladder 15 are mixed is extended up and down, and is provided at the upper end of the medium discharge path 31. A collection port 32 is formed. A discharge pipe 34 through which a high-temperature high-pressure fluid flows is connected to the medium discharge passage 31, and a blow valve 33 for operating the opening / closing of the discharge pipe 34 is provided in the discharge pipe 34. 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 into the inside of the bladder 15 via the medium supply path 21.

FIG. 3 shows a cross-sectional view conceptually showing the state of the protrusion and the temperature sensor included in the tire molding die used in the present invention. As shown in FIG. 3, at least one of the segments Sg constituting the mold 10 measures the temperature of the protruding portion P for forming a groove portion in the tread portion 3 of the raw tire and the temperature of the tread portion 3 during the vulcanization step. It is equipped with a temperature sensor S. The temperature sensor S is arranged in the protrusion P from the radial outside to the inside. In addition, although two or more protrusions P for forming a groove in the tread portion 3 are usually arranged in the mold 10, the temperature sensor S may be arranged in only one of the plurality of protrusions P. Often, it may be arranged on two or more protrusions P. The temperature sensor S is fixed by, for example, a fixing means (not shown) included in the segment Sg, and can be installed so as to extend in the tire radial direction of the raw tire toward the inner peripheral surface side. The "inner peripheral surface side" means the center side of the raw tire 9 when the raw tire 9 is set in the mold 10. As the fixing means for fixing the temperature sensor S, for example, the outer peripheral surface side may be configured with a double nut or the like, and the inner peripheral surface side may be configured with a screw structure.

As shown in FIG. 3, at least a part of the tip of the temperature sensor S protrudes radially inward from the tip of the protruding portion P. A resistance temperature detector is disposed at the tip of the temperature sensor S, and the temperature of the tread portion 3 can be measured at the tip portion. As the resistance temperature detector, it is preferable to use a platinum resistance temperature detector because of its excellent sensitivity. A lead wire is connected to the resistance temperature detector, and voltage information (temperature information) is transmitted to a recorder (not shown).

As a method of embedding (inserting) the temperature sensor S in the tread portion 3 during the vulcanization step, for example, the axial direction of the temperature sensor S and the radial direction of the raw tire 9 coincide with at least one of the segments Sg. , The protrusion P and the temperature sensor S are arranged so that the temperature sensor S is inserted into the tread portion 3 of the raw tire 9 at the same time as the segment Sg moves in the tire radial direction during the vulcanization process. You may. When the temperature sensor is embedded in the tread portion, a considerable load is normally applied to the temperature sensor, and there is a concern that the temperature sensor may be damaged in some cases. However, as shown in FIG. 3, in the present invention, only the tip of the temperature sensor S protrudes from the protrusion P, and the temperature sensor S is disposed in the protrusion P except for the tip and is protected. There is. Therefore, even if the temperature sensor S is repeatedly embedded (inserted) in the tread portion 3, it is possible to significantly reduce the occurrence of damage to the temperature sensor S.

In particular, in the mold 10 used in the present invention, when the maximum width of the protruding portion P is WP and the maximum width of the temperature sensor S protruding from the tip of the protruding portion _P is W _s , 1 ≦ (W _s / _WP ). ) ≤ 4, so that the buried marks caused by the temperature sensor are formed near the bottom surface of the groove, and the buried marks are relatively small and almost inconspicuous. Therefore, the appearance of the manufactured pneumatic tire is excellent. In order to keep the buried marks relatively small, the maximum width Ws of the temperature sensor _S is preferably 5 mm or less, and more preferably 2 to 5 mm.

In the pneumatic tire obtained after the vulcanization step, a groove corresponding to the protrusion P on which the temperature sensor S is arranged is formed in the tread portion 3. The wider the groove width of the groove, the more the groove bottom of the groove. The buried marks of the temperature sensor formed in the tire are less noticeable. Therefore, the protruding portion P is preferably a wide groove formed in the tread portion 3, for example, a protruding portion for forming a main groove. In order to keep the burial marks relatively small, the maximum width Wp of the protrusion _P is preferably 5 mm or more, and more preferably 5 to 20 mm. Further, in order to keep the buried mark relatively small, the height HP of the protruding portion _P corresponding to the depth of the groove formed on the tread surface of the tread portion is preferably 5 mm or more, preferably 5 to 20 mm. It is more preferable to have.

The protrusion height _HST of the tip of the temperature sensor S protruding from the tip of the protrusion P is preferably designed to exceed 0 mm in order to measure the temperature of the tread portion 3, and is designed to exceed 5 mm. Is more preferable. Further, if the H _ST is too long, a hole corresponding to the buried portion of the temperature sensor S is formed in the groove bottom of the tread portion 3, so that the appearance may be deteriorated, and the buried mark may be deteriorated when the tire is running. There is an increased risk of foreign matter such as pebbles getting caught in the tire. Therefore, the H _ST is preferably designed to be 20 mm or less, and more preferably 15 mm or less.

According to the method for manufacturing a pneumatic tire according to the present invention, an unvulcanized raw tire can be heated and vulcanized while accurately measuring the temperature of the tread portion, so that the tire can be tired without setting an extra safety time. The end point of the vulcanization process can be reliably determined for each. In addition, since it is possible to design the buried mark corresponding to the buried part of the temperature sensor of the manufactured tire to be very small, foreign matter such as pebbles gets caught, which causes cracks on the tread surface of the pneumatic tire. The possibility of tire treading can be significantly reduced.

It is possible to adopt the structure adopted in each of the above embodiments in any other embodiment. The specific configuration of each part is not limited to the above-described embodiment, and various modifications can be made without departing from the gist of the present disclosure.

Example 1
In order to specifically show the configuration and effect of the present invention, a sample tire (tire size: 275 / 70R22.5) was vulcanized using the vulcanization die 10 shown in FIG. At that time, as shown in FIG. 3, a temperature sensor S (platinum resistance temperature detector) connected to the high-precision digital data logger is arranged in the protruding portion P for forming the main groove, and the temperature of the tread portion 3 is measured. While doing so, the vulcanization process was carried out. The protrusion height H _ST of the tip of the temperature sensor S protruding from the tip of the protrusion P is 15 mm, the maximum width Ws of the temperature sensor _S is 5 mm, the height HP of the protrusion _P is 25 mm, and the maximum width of the protrusion. W _p was designed to be 15 mm, and (W _s / _WP ) was designed to be 3. After that, a pneumatic tire was manufactured by carrying out a vulcanization step using a vulcanization die 10.

Comparative Example 1
A pneumatic tire was manufactured by the same method as in Example 1 except that the temperature sensor was not arranged (the temperature of the tread portion was not measured during the vulcanization step). In addition, Comparative Example 1 corresponds to a conventionally known production method, and the vulcanization step was carried out by adding a margin time considering all variations in the vulcanization step.

Comparative Example 2
Example 1 Except that the temperature sensor was designed so as to be embedded in the tread of the tread instead of being arranged in the protruding portion, and the vulcanization step was carried out while measuring the temperature of the tread. A pneumatic tire was manufactured by the same method as above. The length of the portion embedded in the tread portion of the temperature sensor was 15 mm, and a hole corresponding to this portion was formed on the tread portion of the tread portion.

[Tire appearance]
The appearance of the manufactured pneumatic tire was evaluated based on the presence or absence of protruding rubber generated from the buried marks of the temperature sensor. If there is a large protruding rubber on the tread tread, it looks bad and needs to be removed. The results are shown in Table 1.

[Vulcanization productivity]
The vulcanization time is defined as the time from the time when the raw tire 9 is set in the mold 10 to the time when the mold 10 is opened and the vulcanization process is completed, and the vulcanization time in Comparative Example 1 is 100. Expressed as an index. The lower the value, the better the vulcanization productivity. The results are shown in Table 1.

From the results in Table 1, it can be seen that the production method of Example 1 can produce a pneumatic tire having excellent appearance while optimizing the vulcanization time. On the other hand, in the manufacturing method of Comparative Example 2, it can be easily understood that the appearance is deteriorated because the buried mark of the temperature sensor is formed on the tread surface of the tread portion.

S temperature sensor P protrusion

Claims (5)

A method for manufacturing a pneumatic tire, which includes a vulcanization step of heating and vulcanizing an unvulcanized raw tire in a tire molding die.
The tire molding die is provided with at least a tread mold portion that can be pressure-welded to the tread portion of an unvulcanized raw tire.
The tread mold portion is divided in the circumferential direction and has a plurality of segments that are movable in the radial direction of the raw tire.
At least one of the segments comprises a protrusion for forming a groove in the tread portion of the raw tire and a temperature sensor for measuring the temperature of the tread portion during the vulcanization step.
The temperature sensor is arranged from the radial outside to the inside in the protrusion, and at least a part of the tip thereof protrudes radially inward from the tip of the protrusion.
When the maximum width of the protruding portion is _WP and the maximum width of the temperature sensor protruding from the tip of the protruding portion is W _s , 1 ≦ (W _s / _WP ) ≦ 4.
A method for manufacturing a pneumatic tire, wherein the vulcanization step is carried out while measuring the temperature of the tread portion by embedding the temperature sensor protruding from the tip of the protruding portion in the tread portion. .. The method for manufacturing a pneumatic tire according to claim 1, wherein the height of the protruding portion is 2 mm or more. The method for manufacturing a pneumatic tire according to claim 1 or 2, wherein the maximum width Wb of the protruding portion is 5 mm or more. The method for manufacturing a pneumatic tire according to any one of claims 1 to 3, wherein the maximum width Ws of the temperature sensor protruding from the tip of the protruding portion is within 5 mm. The method for manufacturing a pneumatic tire according to any one of claims 1 to 4, wherein the temperature sensor is a platinum resistance temperature detector.

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