JP2003112320A - Tire manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately control the respective temperature rising speeds or set temperatures of a tread part and a bead part in preheating with the wide degree of freedom. SOLUTION: In the tire manufacturing method for preheating a tire green cover T, the tread part Tt and the bead part Tb are preheated by an induction heating device 1 equipped with a bead heating coil 2, a tread heating coil 3 and a high frequency power supply device 4 capable of individually adjusting the respective coils 2 and 3 in generation of heat.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tire manufacturing method capable of shortening vulcanization time by utilizing preheating by induction heating.

[0002]

2. Description of the Related Art As a method of vulcanizing a tire, generally, as shown in FIG. 6, a vulcanizing apparatus including a molding die a and a bladder b for pressing a raw tire cover T on an inner surface a1 thereof is used. The heating is performed by the heat from the tire surface that conducts heat from the heat medium (for example, steam) filled in the heater c and the bladder b built in the molding die a.

However, since rubber has a low thermal conductivity, it takes a long time for heat to be transferred to its central portion, and there is a problem that the vulcanization time becomes long particularly in a thick portion. Further, if the center portion is to be optimally vulcanized, the tire surface portion tends to be overvulcanized, which is not preferable.

Therefore, the inventor of the present invention disclosed in Japanese Patent Laid-Open No. 2000-6
In 1963, it is proposed that the tread portion and the bead portion, which are thick portions, be preheated by induction heating to shorten the vulcanization time in the main vulcanization.

This one uses a heating coil e formed by spirally winding a conductive wire through a bead bottom part and a tread part, as schematically shown in FIG. 7, and by its electromagnetic induction action, a tread part Tt and a bead. A tire reinforcing member (for example, a breaker cord and a bead core) embedded in the portion Tb is induction-heated.

At this time, the tread portion Tt and the bead portion Tb
And, there is a difference in the rubber thickness and the amount of steel of the tire reinforcing member to be embedded, and this difference also differs for each type of tire (including size). Therefore, in order to more uniformly vulcanize the tire, in the preheating, the tread portion Tt
It is necessary to individually control the temperature rise between the bead portion Tb and the bead portion Tb.

[0007]

Therefore, in the above publication, a sheet-shaped temperature adjusting conductive material is attached to the tire surface on the side where the temperature rises slowly, for example, the tread side, and the amount of heat generated by induction heating is increased. Is controlled to increase the temperatures of the tread portion Tt and the bead portion Tb.

However, such a temperature-adjusting conductive material has a small degree of freedom in temperature control, and it is difficult to perform temperature control with high accuracy according to the type of tire. Moreover, in addition to making the sticking work inconvenient, it becomes a factor that hinders temperature measurement during preheating.

Therefore, the present invention uses a bead heating coil for heating the bead portion and a tread heating coil for heating the tread portion, and the heat generation amount of each is individually adjusted by the high frequency power supply device, and the tread portion is basically adjusted. The temperature rising rate and the set temperature of each of the beads and the bead can be accurately controlled with a wide degree of freedom and can be uniformly and quickly preheated according to the type of tire, and the time required for the main vulcanization can be shortened. It is an object of the present invention to provide a tire manufacturing method capable of achieving overvulcanization prevention on the tire surface.

[0010]

In order to achieve the above object, the invention of claim 1 is a method of manufacturing a tire in which a tread portion and a bead portion of a tire raw cover are preheated prior to main vulcanization. There is a bead heating coil for bead heating,
After preheating the tread portion and the bead portion by an induction heating device including a tread heating coil for heating the tread portion, and a high frequency power supply device capable of individually adjusting heat generation by the bead heating coil and the tread heating coil. It is characterized by mold vulcanization.

Further, in the invention of claim 2, the bead heating coil has an annular portion in which a conductive wire is wound substantially concentrically with the tire, and the tread heating coil has a conductive wire radially wound in a substantially spiral shape. It is characterized by comprising a plurality of spiral coil portions which are wound differently and which are arranged and connected in the tire circumferential direction.

According to the invention of claim 3, the bead heating coil includes bead heating coil portions for heating the bead portions on both sides of the tire raw cover and arranged above and below the preheating device. The upper bead heating coil portion is characterized in that the inner diameter thereof is larger than the diameter of the tread portion of the tire raw cover, and the lower bead heating coil portion is smaller than the diameter of the tread portion.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below.
This will be described together with the illustrated example. FIG. 1 is a diagram conceptually showing an induction heating device 1 used in the tire manufacturing method of the present invention.

In FIG. 1, an induction heating apparatus 1 is a heating apparatus for preheating the tread portion Tt and the bead portion Tb of the tire raw cover T prior to the main vulcanization, and the bead portion for heating the bead portion. It comprises a heating coil 2, a tread heating coil 3 for heating a tread portion, and a high frequency power supply device 4 capable of individually adjusting each heat generated by the bead heating coil 2 and the tread heating coil 3.

As shown in FIG. 5, the tire raw cover T is provided with a tread portion Tt, a pair of sidewall portions Ts extending inward in the tire radial direction from both ends thereof, and an inner end portion thereof. A bead portion Tb reinforced with a bead core 30 is provided. A carcass 31 is bridged between the bead cores 30 and 30, and a breaker 32 is arranged outside the carcass 31 and inside the tread portion Tt. .

Here, as the bead core 30, a ring-shaped body in which a steel bead wire is wound in a plurality of layers is used. Further, the breaker 32 includes a steel breaker cord, for example, 70 in the tire circumferential direction.
It is formed from a plurality of plies arranged at an angle of ° or less (usually 1, 2 for motorcycle tires, usually 2 for passenger car tires, usually 3, 4 for heavy duty tires).

Therefore, in the tire raw cover T, the tire reinforcing member 33 made of steel capable of generating heat by the electromagnetic induction action is provided on the tread portion Tt and the bead portion Tb, which have a large thickness and require a long heating time. It is embedded as a breaker cord and bead wire.

As shown in FIG. 1, the tire raw cover T is horizontally held by a supporting means 6 attached to the induction heating device 1 in a horizontally placed state and rotatably around the tire axis. In this example, the supporting means 6 includes a tray-shaped receiving base 7 for receiving the lower bead portion Tb, and a supporting base 8 for rotatably supporting the receiving base 7 around the tire axis. The pedestal 7 is driven by the electric motor M via a transmission means 9 having a well-known structure using, for example, a pulley and a belt.

Next, the bead heating coil 2 of the induction heating device 1 has an upper bead heating coil portion 2U for heating the bead portion Tb on the tire raw cover T, as shown in FIG.
And a lower bead heating coil portion 2L for heating the lower bead portion Tb, and each bead heating coil portion 2U, 2L is formed with an annular portion 11 that circulates the conductive wire 10 substantially concentrically with the tire. . In this example, as the annular portion 11,
Although the conductive wire 10 is illustrated as being wound twice, the number of turns is not particularly limited and can be appropriately set according to requirements.

Further, in this example, in order to facilitate setting of the raw tire cover T, the inner diameter of the annular portion 11U in the upper bead heating coil portion 2U is set to be larger than the diameter of the tread portion Tt of the raw tire cover T. In addition, the inner diameter of the annular portion 11L in the lower bead heating coil portion 2L is set to be smaller than the diameter of the tread portion Tt. As a result, the tire raw cover T can be hung from above and set on the pedestal 7 through the upper annular portion 11U.

The tread heating coil 3 is formed by connecting a plurality of spiral coil portions 12 side by side in the tire circumferential direction, and each spiral coil portion 12 has a conductive wire 13 having a substantially spiral shape and a radial diameter. It is formed by winding differently.

It is preferable that the spiral coil portion 12 is formed in a rectangular spiral shape as shown in FIG. 3 when it is developed in a plane, in order to uniformly arrange the spiral coil portions 12 in the circumferential direction. Alternatively, it may have a circular spiral shape. Further, in the spiral coil portion 12, the inner end of the spiral in the radial direction and the outer end of the adjacent spiral coil portions 12 in the radial direction of the spiral are electrically connected via the joint portion 14. The number of turns of the spiral coil section 12 is not particularly limited, and can be appropriately set according to requirements.

Here, the bead heating coil 2 is shown in FIG.
As shown in, a magnetic field GA extending between the annular portions 11U and 11L through the inside of the annular portion and extending in the tire axial direction is generated, and the bead core 30 is dielectrically heated. Further, the tread heating coil 3 generates a magnetic field GB that extends through the tread portion Tt substantially at right angles to the tread surface, and dielectrically heats the breaker 32.

It should be noted that the receiving table 7 and the supporting table 8 of the supporting means 6 do not generate heat due to the magnetic fields GA and GB.
It is necessary to form a non-metallic material, and the electric motor M
Is the annular portions 11U and 11L and the spiral coil portion 12
Of the magnetic field G
It is desirable to eliminate the effects from A and GB as much as possible.

Next, the high frequency power supply device 4 is composed of a first power supply section 4A connected to the bead heating coil 2 and a second power supply section 4A connected to the tread heating coil 3. The first power supply unit 4A connects the upper and lower bead heating coil units 2U and 2L in series. Further, the first and second power supply units 4A and 4B can individually adjust the output and frequency of the high-frequency current, whereby the heat generation by the bead heating coil 2 and the tread heating coil 3 can be individually adjusted. The frequency of the high-frequency current used for induction heating is usually in the range of 50 Hz to 1 MHz, but if the frequency is high, the so-called skin effect is large and temperature unevenness is strong, and therefore the range of 1 KHz to 500 KHz is preferable. More preferably, it is desirable to use in a low frequency range of 10 to 40 KHz.

In this embodiment, as shown in FIG. 1, the induction heating device 1 is provided with temperature sensors 15A and 15B such as infrared temperature sensors for measuring the surface temperatures of the tread portion Tt and the bead portion Tb in a non-contact manner. , This temperature sensor 15
Control means 16 for performing output control (including ON / OFF) of the high frequency power supply device 4 based on the measurement data of A and 15B.
The case where and are provided is illustrated.

Next, a method of manufacturing a tire using the induction heating device 1 will be described. This manufacturing method includes a preliminary heating step of preheating the tread portion Tt and the bead portion Tb by induction heating prior to the main vulcanization. In this preliminary heating step, first, the tire raw cover T is hung from above. Set it on the cradle 7.

Thereafter, the raw tire cover T is rotated around the tire shaft center by the electric motor M, the high frequency power supply device 4 is operated, and the magnetic fields GA and GB generated by the bead heating coil 2 and the tread heating coil 3 cause
The tire reinforcing member 33 is induction-heated (self-heating), and the thick tread portion Tt and bead portion Tb are effectively heated from the inside.

At this time, the rotation of the raw tire cover T suppresses the temperature unevenness in the tire circumferential direction, and makes the temperature distribution more uniform.

Further, the tread portion Tt and the bead portion Tb are heated to a desired set temperature in the same time as possible.
That is, in order to raise the temperature as efficiently as possible, the heat generated by the bead heating coil and the tread heating coil is individually adjusted. Normally, the set temperatures of the tread portion Tt and the bead portion Tb are the same, but in consideration of the subsequent main vulcanization, the set temperature of the tread portion Tt is set according to the tire type (including size). Than the set temperature of section Tb
For example, it can be set higher by about 10 degrees.

In this example, the temperature sensors 15A, 15
The surface temperatures of the tread portion Tt and the bead portion Tb are constantly measured by B, and the outputs of the first and second power supply portions 4A and 4B are controlled according to the respective temperature rising speeds. Further, when the respective set temperatures are reached, the output is switched to the low output for heat retention, and the set temperature is maintained until the vulcanizer for main vulcanization is ready.

Although a particularly preferred embodiment of the present invention has been described above in detail, the present invention is not limited to the illustrated embodiment, and various modifications can be made and implemented.

[0033]

EXAMPLE Tire size 195 / 65R15 shown in FIG.
The tire raw cover for passenger cars was manufactured as a prototype and preheated under the following conditions using the induction heating device shown in FIGS.・ Frequency of high frequency power supply: 20-30KHz ・ Set temperature (tread part / upper and lower bead parts): 80 ° C
/ 80 ° C

With the heating time of about 300 seconds, the tread portion and the upper and lower bead portions could be heated to the set temperature of 80 ° C. substantially simultaneously and uniformly in the circumferential direction.

When this was vulcanized by main heating using a conventional vulcanizer type, the standard vulcanization time was 10 minutes, but a reduction of 75 seconds could be achieved.

[0036]

As described above, the present invention uses the bead heating coil for heating the bead portion and the tread heating coil for heating the tread portion, and individually adjusts the heat generation amount of each by the high frequency power supply device. Therefore, the temperature rising rate and the set temperature of each of the tread portion and the bead portion can be accurately controlled with a wide degree of freedom, and preheating can be performed uniformly and quickly depending on the type of tire. Further, it is possible to achieve shortening of time in main vulcanization and prevention of overvulcanization on the tire surface.

[Brief description of drawings]

FIG. 1 is a sectional view conceptually showing one embodiment of an induction heating device used in the tire manufacturing method of the present invention.

FIG. 2 is a perspective view showing the bead heating coil and the tread heating coil.

FIG. 3 is a diagram showing a spiral coil portion of a tread heating coil in an expanded manner.

FIG. 4 is a schematic diagram showing a magnetic field generated by a bead heating coil and a tread heating coil.

FIG. 5 is a cross-sectional view showing an example of a tire raw cover suitably used in the present invention.

FIG. 6 is a sectional view illustrating a conventional vulcanizing apparatus.

FIG. 7 is a schematic view showing a conventional induction heating device for preheating.

[Explanation of symbols]

1 Induction heating device 2 bead heating coil 2U, 2L bead heating coil 3 tread heating coil 4 High frequency power supply 10, 13 Conductive wire 11 Ring part 12 spiral coil T tire raw cover Tt tread section Tb bead part

Claims (3)

[Claims] 1. A method of manufacturing a tire in which a tread portion and a bead portion of a tire raw cover are preheated prior to main vulcanization, comprising a bead heating coil for heating a bead portion and a tread heating for heating a tread portion. Vulcanizing the mold after preheating the tread portion and the bead portion with an induction heating device including a coil and a high-frequency power supply device capable of individually adjusting heat generated by the bead heating coil and the tread heating coil. And a method for manufacturing a tire. 2. The bead heating coil comprises an annular portion formed by winding a conductive wire substantially concentrically with a tire, and the tread heating coil winds the conductive wire in a substantially spiral shape with different diameters in a radial direction. The method for manufacturing a tire according to claim 1, further comprising a plurality of spiral coil portions that are connected to each other in a circumferential direction of the tire. 3. The bead heating coil heats the bead portions on both sides of the tire raw cover and is disposed above and below the preheating device, and includes upper and lower bead heating coil portions, and an upper bead heating coil portion. 3. The tire according to claim 1 or 2, wherein the inner diameter is larger than the diameter of the tread portion of the tire raw cover, and the lower bead heating coil portion is smaller than the diameter of the tread portion. Manufacturing method.