JP3764366B2 - Tire manufacturing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a tire that can shorten the vulcanization time by utilizing preheating by induction heating.
[0002]
[Prior art]
As a method for vulcanizing a tire, generally, as shown in FIG. 6, a vulcanizing device including a molding die a and a bladder b that presses the tire raw cover T against the inner surface a1 is used. Heating is performed by heat from the tire surface that conducts heat from a heater c built in a and a heat medium (for example, steam or the like) filled in the bladder b.
[0003]
However, since rubber has a low thermal conductivity, it takes time for heat to be transferred to the center thereof, and there is a problem that the vulcanization time becomes long particularly in a thick portion. If the center portion is to be finished with optimum vulcanization, the tire surface portion tends to be overvulcanized, which is not preferable.
[0004]
Therefore, the present inventor has proposed in Japanese Unexamined Patent Publication No. 2000-61963 to preheat the tread part and the bead part, which are thick parts, by induction heating to shorten the vulcanization time in the main vulcanization. .
[0005]
As schematically shown in FIG. 7, this uses a heating coil e in which a conductive wire circulates in a spiral through the bottom of the bead and the tread portion, and the electromagnetic induction action causes the tread portion Tt and the bead portion Tb. An embedded tire reinforcing member (for example, a breaker cord and a bead core) is induction-heated.
[0006]
At this time, the tread portion Tt and the bead portion Tb are different in rubber thickness and the steel amount of the tire reinforcing member to be embedded, and this difference is also different for each tire type (including size). Therefore, in order to vulcanize the tire more uniformly, it is necessary to individually control the temperature rise of the tread portion Tt and the bead portion Tb in the preliminary heating.
[0007]
[Problems to be solved by the invention]
Therefore, in the above-mentioned publication, a tread portion Tt is obtained by sticking a sheet-like temperature adjusting conductive material to the tire surface on the side where the temperature rise is slow, for example, the tread side, and increasing the heat generation amount of induction heating. And the rising temperature of the bead portion Tb are controlled.
[0008]
However, with such a temperature adjusting conductive material, the degree of freedom of temperature control is small, and it is difficult to perform temperature control according to the type of tire with high accuracy. In addition to making the sticking work inconvenient, it also becomes a factor that hinders temperature measurement during preheating.
[0009]
Therefore, the present invention uses a bead heating coil for heating a bead part and a tread heating coil for heating a tread part, and the tread part and the bead part are based on the individual adjustment of the amount of heat generated by the high frequency power supply device. Each temperature rise speed and set temperature can be accurately controlled with a wide degree of freedom, and can be preheated uniformly and quickly according to the type of tire. It aims at providing the manufacturing method of the tire which can achieve prevention of the overvulcanization in the.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, the invention of claim 1 is a tire manufacturing method in which a tread part and a bead part of a tire raw cover are preheated prior to the main vulcanization.
A tread portion is formed by an induction heating device including a bead heating coil for heating the bead portion, a tread heating coil for heating the tread portion, and a high frequency power supply device capable of individually adjusting heat generated by the bead heating coil and the tread heating coil. And the bead portion are preheated and then the mold is vulcanized.
[0011]
According to a second aspect of the present invention, the bead heating coil includes an annular portion in which a conductive wire is substantially concentric with the tire, and the tread heating coil has a conductive wire having a substantially spiral shape with a different diameter in the radial direction. And a plurality of spiral coil portions that are wound and connected side by side in the tire circumferential direction.
[0012]
In the invention of claim 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 further includes a lower bead heating coil portion, The heating coil portion is characterized in that its 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.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram conceptually showing an induction heating apparatus 1 used in the tire manufacturing method of the present invention.
[0014]
In FIG. 1, an induction heating device 1 is a heating device that preheats a tread portion Tt and a bead portion Tb of a tire raw cover T prior to the main vulcanization, and a bead heating coil 2 for heating the bead portion. , A tread heating coil 3 for heating the 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.
[0015]
As shown in FIG. 5, the tire raw cover T includes a tread portion Tt, a pair of sidewall portions Ts extending inward in the tire radial direction from both ends thereof, and a bead core 30 positioned at the inner ends thereof. Further, a carcass 31 is bridged between the bead cores 30 and 30, and a breaker 32 is disposed outside the carcass 31 and inside the tread portion Tt.
[0016]
Here, as the bead core 30, a ring-shaped body in which steel bead wires are wound in a plurality of layers is used. The breaker 32 includes a plurality of steel breaker cords arranged at an angle of, for example, 70 ° or less with respect to the tire circumferential direction (usually 1, 2 for motorcycle tires, 2 normally for passenger tires, heavy load) In heavy duty tires, usually three or four plies are formed.
[0017]
Therefore, the tire raw cover T is provided with breaker cords on the tread portion Tt and the bead portion Tb, which have a large thickness and require a long heating time, and are made of steel tire reinforcing members 33 that can generate heat by electromagnetic induction. And buried as a bead wire.
[0018]
As schematically shown in FIG. 1, the raw tire cover T is horizontally held by a supporting means 6 attached to the induction heating device 1 so as to be rotated horizontally around the tire shaft center. In this example, the supporting means 6 includes a tray-like receiving base 7 that receives the lower bead portion Tb, and a supporting base 8 that pivotally supports the receiving base 7 around the tire axis, The cradle 7 is driven by an electric motor M through a transmission means 9 having a known configuration using, for example, a pulley, a belt, or the like.
[0019]
Next, the bead heating coil 2 of the induction heating device 1 includes an upper bead heating coil portion 2U for heating the bead portion Tb on the tire raw cover T and a lower bead portion Tb as shown in FIG. Each of the bead heating coil portions 2U and 2L includes an annular portion 11 that circulates the conductive wire 10 substantially concentrically with the tire. In the present example, the annular portion 11 is illustrated with the conductive wire 10 wound twice, but the number of turns is not particularly limited and can be set as appropriate according to demand.
[0020]
In this example, in order to facilitate the setting of the tire raw cover T, the inner diameter of the annular portion 11U in the upper bead heating coil portion 2U is made larger than the diameter of the tread portion Tt of the tire raw cover T, The inner diameter of the annular portion 11L in the lower bead heating coil portion 2L is set smaller than the diameter of the tread portion Tt. Thereby, the tire raw cover T can be suspended from above and set on the cradle 7 through the upper annular portion 11U.
[0021]
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 with a different diameter in the radial direction. It is formed by winding.
[0022]
As the spiral coil portion 12, it is preferable that the spiral coil portion 12 is formed in a rectangular spiral shape as shown in a flat plane in FIG. 3 in order to uniformly arrange the spiral coil portions 12 in the circumferential direction. It can also be made spiral. Further, in the spiral coil portion 12, the inner end in the radial direction of the spiral is electrically connected to the outer end in the radial direction of the spiral in the adjacent spiral coil portion 12 through the joint portion 14. The number of turns of the spiral coil portion 12 is not particularly limited, and can be set as appropriate according to demand.
[0023]
Here, as shown in FIG. 4, the bead heating coil 2 generates a magnetic field GA extending between the annular portions 11U and 11L through the inside of the annular shape in the tire axial direction, and dielectrically heats the bead core 30. The tread heating coil 3 generates a magnetic field GB extending through the tread portion Tt substantially at right angles to the tread surface, and dielectrically heats the breaker 32.
[0024]
The receiving base 7 and the supporting base 8 of the support means 6 must be formed of a non-metallic material so as not to generate heat by the magnetic fields GA and GB, and the electric motor M includes the annular portions 11U and 11L. In addition, it is desirable that the spiral coil portion 12 be installed at least outward in the tire radial direction so as to eliminate the influence of the magnetic fields GA and GB as much as possible.
[0025]
Next, the high-frequency power supply device 4 is formed of a first power supply unit 4A connected to the bead heating coil 2 and a second power supply unit 4A connected to the tread heating coil 3, and the first power supply unit 4A The power supply unit 4A connects the upper and lower bead heating coil units 2U and 2L in series. The first and second power supply units 4A and 4B can individually adjust the output and frequency of the high-frequency current, thereby individually adjusting the heat generated by the bead heating coil 2 and the tread heating coil 3. The frequency of the high-frequency current used for induction heating is usually in the range of 50 Hz to 1 MHz. However, when the frequency is high, the so-called skin effect tends to be large and temperature unevenness tends to be strong, and therefore preferably in the range of 1 KHz to 500 KHz. More preferably, it is desirable to use in a low frequency range of 10 to 40 KHz.
[0026]
In this example, 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, and the temperature. The case where the control means 16 which performs the output control (including ON / OFF) of the high-frequency power supply device 4 by the measurement data of the sensors 15A and 15B is illustrated.
[0027]
Next, a tire manufacturing method using the induction heating device 1 will be described. This manufacturing method includes a preheating step in which the tread portion Tt and the bead portion Tb are preheated by induction heating prior to the main vulcanization. In this preheating step, the tire raw cover T is first suspended from above. Set on cradle 7.
[0028]
Thereafter, the tire raw cover T is rotated around the tire axis by the electric motor M, and the high-frequency power supply device 4 is operated, and the tire reinforcing member 33 is generated by the magnetic fields GA and GB generated by the bead heating coil 2 and the tread heating coil 3. Is heated by induction (self-heating), and the thick tread portion Tt and bead portion Tb are effectively heated from the inside.
[0029]
At this time, due to the rotation of the tire raw cover T, temperature unevenness in the tire circumferential direction is suppressed, and the temperature distribution can be made more uniform.
[0030]
Further, in order to raise the temperature of the tread portion Tt and the bead portion Tb to a desired set temperature within the same time as much as possible, that is, 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 considering the subsequent main vulcanization, the set temperature of the tread portion Tt is set according to the tire type (including size). For example, it can be set higher by about 10 degrees than the set temperature of the portion Tb.
[0031]
In this example, the surface temperature of each of the tread portion Tt and the bead portion Tb is constantly measured by the temperature sensors 15A and 15B, and the outputs of the first and second power supply portions 4A and 4B are controlled in accordance with the respective temperature rising speeds. is doing. When the set temperature is reached, the output is switched to a low output for keeping the temperature, and the set temperature is maintained until the vulcanizing apparatus for the main vulcanization is ready.
[0032]
As mentioned above, although especially preferable embodiment of this invention was explained in full detail, this invention is not limited to embodiment of illustration, It can deform | transform and implement in a various aspect.
[0033]
【Example】
A tire raw cover for a passenger car having a tire size of 195 / 65R15 shown in FIG. 5 was prototyped and preheated under the following conditions using the induction heating apparatus shown in FIGS.
・ Frequency of the high frequency power supply: 20 to 30 KHz
・ Set temperature (tread / upper and lower beads): 80 ° C / 80 ° C
[0034]
In the heating time of about 300 seconds, the tread portion and the upper and lower bead portions could be uniformly heated to the set temperature of 80 ° C. substantially simultaneously and in the circumferential direction.
[0035]
When this was vulcanized by main heating using a conventional vulcanizer, the standard vulcanization time of 10 minutes in the past could achieve a reduction of 75 seconds.
[0036]
【The invention's effect】
As described above, the present invention uses a bead heating coil for heating the bead part and a tread heating coil for heating the tread part, and the amount of generated heat is individually adjusted by the high frequency power supply device. The temperature increase speed and set temperature of each bead part can be controlled with a wide degree of freedom and with high precision, and can be preheated uniformly and quickly according to the type of tire. Moreover, it is possible to achieve a short time in the main vulcanization and prevention of overvulcanization on the tire surface.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view conceptually showing an embodiment of an induction heating device used in a 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 an expanded spiral coil portion of a tread heating coil.
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 that is preferably used in the present invention.
FIG. 6 is a cross-sectional view illustrating a conventional vulcanizing apparatus.
FIG. 7 is a schematic view showing a conventional induction heating apparatus for preheating.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Induction heating apparatus 2 Bead heating coil 2U, 2L Bead heating coil part 3 Tread heating coil 4 High frequency power supply device 10, 13 Conductive wire 11 Annular part 12 Spiral coil part T Tire raw cover Tt Tread part Tb Bead part

Claims (3)

A tire manufacturing method for preheating a tread portion and a bead portion of a raw tire cover prior to main vulcanization, comprising: a bead heating coil for heating a bead portion, a tread heating coil for heating a tread portion, and the bead A tire characterized by pre-heating the tread portion and the bead portion and then vulcanizing the die by an induction heating device including a high frequency power supply device capable of individually adjusting the heat generated by the heating coil and the tread heating coil. Manufacturing method. The bead heating coil includes an annular portion in which a conductive wire circulates substantially concentrically with the tire, and the tread heating coil is wound around the conductive wire in a substantially spiral shape with different diameters in the radial direction and in the tire circumferential direction. The tire manufacturing method according to claim 1, further comprising a plurality of spiral coil portions arranged side by side and connected to each other. The bead heating coil heats the bead portions on both sides of the tire raw cover and is arranged above and below the preheating device, and includes a lower bead heating coil portion, and the upper bead heating coil portion has an inner diameter. The tire manufacturing method according to claim 1 or 2, wherein the diameter of the tread portion of the raw tire cover is larger than that of the tread portion, and the lower bead heating coil portion is smaller than the diameter of the tread portion.

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