JP2024051286A - Tire building device and tire manufacturing method - Google Patents

Abstract

[Problem] To improve the uniformity of a tire after vulcanization. [Solution] A tire building apparatus 10 disclosed herein includes a pair of calender rolls 30, a building drum 70, and stretching mechanisms 35, 75. The pair of calender rolls 30 are arranged at a predetermined interval. A rubber strip 95 is transported between the pair of calender rolls 30 and rolled. The rubber strip 95, transported from the pair of calender rolls 30 along a predetermined transport path, is wound around the building drum 70. The stretching mechanisms 35, 75 stretch the rubber strip 95 along the transport path. The stretching mechanisms 35, 75 are provided on the transport path. The stretching mechanisms 35, 75 include a control device 80 that controls the elongation rate of the rubber strip 95 based on the circumferential length of the calender rolls 30 and the circumferential length of the building drum 70. [Selected Figure] Figure 2

Description

The present invention relates to a tire building device and a tire manufacturing method.

JP 2018-151870 A discloses a method for calculating winding conditions when winding a band-shaped rubber strip in a spiral shape around a wound body. The calculation method disclosed in the publication includes a step of inputting constraint conditions for winding the rubber strip into a computer, a step of inputting a first objective function for identifying an error of the rubber member from a target cross-sectional shape into the computer, and a step of the computer searching for at least one optimal solution of the winding conditions that satisfies at least the first objective function under the constraint conditions based on an optimization algorithm. It is said that this calculation method can stably form an annular rubber member having a target cross-sectional shape.

JP 2018-151870 A

By the way, when rubber strips are wound around a forming drum and molded, we would like to improve the uniformity of the tire after vulcanization.

The tire building device disclosed herein includes a pair of calendar rolls arranged at a predetermined interval between which the rubber strip is transported and rolled, a building drum around which the rubber strip transported from the pair of calendar rolls along a predetermined transport path is wound, and a stretching mechanism provided on the transport path for stretching the rubber strip along the transport path. The stretching mechanism includes a control device that controls the elongation rate of the rubber strip based on the circumference of the calendar rolls and the circumference of the building drum.

Using a tire building machine with this configuration improves the uniformity of the tire after vulcanization.

FIG. 1 is a perspective view of the row cover 90. FIG. FIG. 2 is a schematic diagram of the tire building apparatus 10. FIG. 3 is a schematic diagram of the rubber strip 95 . FIG. 4 is a schematic diagram of the rubber strip 95 .

An embodiment of the present invention will be described below with reference to the drawings. Note that the present invention is not limited to the following embodiment. Each drawing is a schematic drawing and does not necessarily reflect the actual product. Also, each drawing shows only an example, and does not limit the present invention unless otherwise specified. Also, the same reference numerals are appropriately used for members and parts that perform the same function, and duplicate explanations are omitted. The directions of up, down, left, right, front, and rear are respectively represented by arrows U, D, L, R, F, and Rr in the drawings. Here, the directions of up, down, front, and rear are determined merely for convenience of explanation, and do not limit the present invention unless otherwise specified.

<Low Cover 90>
Fig. 1 is a perspective view of a low cover 90. The low cover 90 is an unvulcanized tire before vulcanization and is also called a raw tire. The low cover 90 is a cylindrical member in which unvulcanized sidewall rubber and tread rubber are bonded to a base material such as a bead wire, a carcass, a breaker, and a wire. As shown in Fig. 1, the low cover includes a first cover 91 that constitutes the inner surface and the side surface, and a second cover 92 that constitutes the outer surface.

The first cover 91 is a cylindrical member. The first cover 91 includes, for example, an inner liner, a carcass, and a pair of sidewall rubbers 91a. The first cover 91 further includes a pair of beads at its radially inner end.

The second cover 92 is a cylindrical member. The second cover 92 is molded so that the inner diameter is larger than the outer diameter of the first cover 91. The second cover 92 includes, for example, a breaker, a band, a base rubber, and a tread rubber. The second cover 92 is molded, for example, by winding the breaker, band, and base rubber in that order onto a molding drum, and then winding the tread rubber onto the base rubber.

The following describes, as an example, a method for molding the rubber member 92a included in the low cover 90 using the tire molding device 10. In this embodiment, the rubber member 92a is a member that constitutes the tread rubber of the second cover 90. The rubber member 92a is formed by winding and overlapping a rubber strip 95 (see FIG. 2) along the circumferential direction of the low cover 90. The rubber strip 95 is a long, slender rubber member that is narrower than the rubber member 92a.

<Tire building device 10>
FIG. 2 is a schematic diagram of the tire building apparatus 10. FIG. 2 shows a state in which the rubber strip 95 is conveyed toward the building drum 70 along the conveying path. In FIG. 2, the conveying direction of the rubber strip 95 and the rotating direction of the building drum 70 are indicated by arrows. As shown in FIG. 2, the tire building apparatus 10 includes a pair of calender rolls 30, a building drum 70, and stretching mechanisms 35 and 75. The stretching mechanisms 35 and 75 are mechanisms provided on the conveying path to be described later, and stretch the rubber strip 95 along the conveying path. The tire building apparatus 10 further includes a first roller 40 and a second roller 60. The tire building apparatus 10 includes guide rollers 55 to 58 and a festoon 50 between the first roller 40 and the second roller 60.

The tire manufacturing method realized by using the tire building apparatus 10 includes a step of conveying the rubber strip 95 along a conveying path and a step of winding the rubber strip 95 around the building drum 70. At least one of the steps of conveying the rubber strip 95 and winding the rubber strip 95 around the building drum 70 includes stretching the rubber strip 95 along the conveying path. In this embodiment, both the step of conveying the rubber strip 95 and the step of winding the rubber strip 95 around the building drum 70 each include stretching the rubber strip 95 along the conveying path. The tire building apparatus 10 and the tire manufacturing method will be described below.

In the process of conveying the rubber strip 95, the rubber strip 95 is conveyed from the pair of calendar rolls 30 along a predetermined conveying path. In this embodiment, the conveying path of the rubber strip 95 is set by the calendar rolls 30, the first roller 40, the festoon 50, the guide rollers 55 to 58, the second roller 60, and the molding drum 70. The tire building device 10 also includes a control device 80 that controls the conveying speed of the rubber strip 95. The rubber strip 95 is first extruded from the extruder 20.

<Extruder 20>
The extruder 20 extrudes the rubber strip 95. The extruder 20 is a device for extruding the rubber material that is the material of the rubber strip 95 while kneading it. Although detailed illustration is omitted, the extruder 20 includes a cylinder, a screw, and a discharge port. The cylinder accommodates the rubber material. The screw is provided inside the cylinder, and is configured so that the rubber material accommodated in the cylinder can be extruded while being kneaded while rotating. The discharge port is an opening through which the rubber material extruded by the screw is discharged. The rubber material as the rubber strip 95 extruded from the extruder 20 is transported toward the calender roll 30.

<Calendar Roll 30>
The calender rolls 30 are a pair of rolls between which the rubber strip 95 is transported and rolled. The pair of calender rolls 30 are arranged at a predetermined interval. The rubber strip 95 is passed between the pair of calender rolls 30, so that the thickness, surface properties, and the like of the rubber strip 95 can be adjusted. The interval between the calender rolls 30 can be appropriately set depending on the configuration of the rubber member to be molded, the number of turns of the rubber strip 95 wound around the molding drum 70, the composition of the rubber strip 95, and the like. The pair of calender rolls 30 may be configured so that conditions can be appropriately set depending on the type of rubber material, the type of rubber member to be molded, and the like. For example, the pair of calender rolls 30 may be replaced or the interval may be changed depending on the conditions of the rubber strip 95.

The calendar roll 30 is a cylindrical roller. The calendar roll 30 is supported so that it can rotate in the circumferential direction. A control device 80 is connected to the calendar roll 30. In this embodiment, the rotation of the calendar roll 30 is controlled by the control device 80. Therefore, the conveying speed of the rubber strip 95 conveyed between the pair of calendar rolls 30 is controlled by the control device 80. The conveying speed can be determined by the number of rotations and the circumference of the roll. The rubber strip 95 conveyed between the pair of calendar rolls 30 is conveyed toward the first roller 40.

<First roller 40>
The first roller 40 is provided downstream of the calender roll 30 in the conveying path. The first roller 40 is a cylindrical roller. The first roller 40 is supported so as to be rotatable in the circumferential direction. The first roller 40 can be a roller for applying a required tension to the rubber strip 95 passed between the pair of calender rolls 30. In this embodiment, a pair of first rollers 40 is provided. The rubber strip 95 is passed between the pair of first rollers 40. The interval between the pair of first rollers 40 can be set narrower than the interval between the pair of calender rolls 30. The interval between the pair of first rollers 40 is appropriately set according to the thickness of the target rubber strip 95, etc.

In this embodiment, a control device 80 is connected to the first roller 40, and the rotation of the first roller 40 is controlled by the control device 80. Therefore, the conveying speed of the rubber strip 95 conveyed between the pair of first rollers 40 is controlled by the control device 80.

In this embodiment, the speed at which the rubber strip 95 is transported along the first roller 40 is set to be faster than the speed at which it is transported between the pair of calendar rolls 30. By setting the transport speed of the rubber strip 95 at the first roller 40 faster than that of the calendar roll 30, tension is applied to the rubber strip 95 between the calendar roll 30 and the first roller 40. By applying tension to the rubber strip 95, the dimensions, shape, etc. of the rubber strip 95 can be adjusted. In addition, by setting the gap between the pair of first rollers 40 narrower than the gap between the pair of calendar rolls 30, tension is easily applied to the rubber strip 95.

The rubber strip 95 is stretched along the conveying direction by applying tension to the rubber strip 95 due to the difference in conveying speed. In this embodiment, the stretching mechanism 35 that stretches the rubber strip 95 is realized by the calendar roll 30, the first roller 40, and the control device 80 that controls the rotation of these. The stretching mechanism 35 stretches the rubber strip 95 due to the difference between the speed at which the rubber strip 95 is conveyed between the pair of calendar rolls 30 and the speed at which the rubber strip 95 is conveyed along the first roller 40. The stretching mechanism 35 stretches the rubber strip 95 between the calendar roll 30 and the first roller 40. In this embodiment, the control device 80 controls the elongation rate of the rubber strip 95 by controlling the rotation (e.g., the number of rotations) of the calendar roll 30 and the first roller 40. In this specification, the ratio of the length of the rubber strip after it has been stretched to the length before it has been stretched is referred to as the "elongation rate". The elongation rate of the rubber strip 95 stretched in the stretching mechanism 35 is represented by, for example, the difference between the conveying speed of the first roller 40 and the conveying speed of the calender roll 30, the ratio of the conveying speeds, etc. In this embodiment, when the conveying speed of the calender roll 30 is set to 100, the elongation rate of the rubber strip 95 stretched in the stretching mechanism 35 is represented by the following formula.
Elongation rate=difference in conveying speed between the first roller 40 and the calender roll 30×0.01+1

The rubber strip 95 transported between the pair of first rollers 40 is hung on guide rollers 55, 56 and transported toward the festoon 50. In this embodiment, the guide rollers 55 are a pair of rollers between which the rubber strip 95 passes. The rubber strip 95 that has passed between the guide rollers 55 is transported toward the guide roller 56. Here, multiple guide rollers 56 are provided. The angle at which the rubber strip 95 is transported to the festoon 50 is adjusted by the guide rollers 56.

<Festoon 50>
The rubber strip 95 transported in the transport direction is accumulated in the festoon 50. The festoon 50 includes a plurality of upper rollers 51 and a plurality of lower rollers 52. The plurality of upper rollers 51 are arranged in the front-rear direction at predetermined intervals above the festoon 50. The plurality of lower rollers 52 are arranged in the front-rear direction at predetermined intervals below the festoon 50. The rubber strip 95 is alternately wound around the plurality of upper rollers 51 and the plurality of lower rollers 52 while reciprocating in the up-down direction.

At least one of the upper roller 51 and the lower roller 52 is configured to be drivable in the vertical direction by a drive device (not shown). This allows the distance between the upper roller 51 and the lower roller 52 to be adjusted.

In this embodiment, the upper roller 51 is fixed at approximately the same height as the guide rollers 56, 57. The lower roller 52 is configured to be drivable in the vertical direction by a drive device. By adjusting the distance between the upper roller 51 and the lower roller 52, the length of the rubber strip 95 passing through the festoon 50 is adjusted. In this way, the rubber strip 95 is accumulated in the festoon 50 and then transported toward the forming drum 70. This allows the rubber strip 95 to be transported with a stable tension regardless of the supply amount or transport speed.

The rubber strip 95 hung on the upper roller 51 and lower roller 52 of the festoon 50 is hung on a guide roller 57 provided downstream of the festoon 50. In this embodiment, multiple guide rollers 57 are provided. The rubber strip 95 hung on the guide roller 57 is hung on a guide roller 58 and transported toward the second roller 60. The angle at which the rubber strip 95 is transported to the second roller 60 is adjusted by the guide roller 58.

<Second Roller 60>
The second roller 60 is provided upstream of the forming drum 70 in the conveying path. The second roller 60 is a cylindrical roller. The second roller 60 is supported so as to be rotatable in the circumferential direction. In this embodiment, the second roller 60 is a pair of rollers arranged at an interval in the front-rear direction. A conveying belt 61 is hung on the pair of second rollers 60. The conveying belt 61 is composed of a band-shaped rubber sheet that is wider than the rubber strip 95. The conveying belt 61 is a so-called endless belt formed in a ring shape. The rubber strip 95 is placed on the conveying belt 61 and conveyed toward the forming drum 70. In addition, a roller, belt, etc. for pressing the rubber strip 95 conveyed on the conveying belt 61 may be provided near the conveying belt 61.

The conveyor belt 61 is driven by the rotation of the second roller 60. Therefore, the conveying speed of the rubber strip 95 conveyed on the conveyor belt 61 is determined by the number of rotations and the circumference of the second roller 60. In this embodiment, the second roller 60 is connected to a control device 80, and the rotation of the second roller 60 is controlled by the control device 80. Note that the pair of second rollers 60 may be controlled by the control device 80 so that both of them rotate at a set number of rotations. Also, one of the pair of second rollers 60 may be controlled by the control device 80 so that it rotates at a set number of rotations. In this case, the other roller may be rotated passively by the rotation being transmitted via the conveyor belt 61.

The speed at which the rubber strip 95 is conveyed along the second roller 60 (in other words, the conveying speed of the rubber strip 95 conveyed on the conveyor belt 61 hung on the second roller 60) is controlled by the control device 80. The conveying speed of the rubber strip 95 is not particularly limited. In this embodiment, the speed of the rubber strip 95 conveyed along the second roller 60 is set to be approximately the same as the speed at which it is conveyed between the calendar rolls 30. For example, the control device 80 can control the rotation of each roller so that the product of the circumference and the number of rotations of the second roller 60 is approximately the same as the product of the circumference and the number of rotations of the calendar roll 30. By setting the conveying speeds of the calendar roll 30 and the second roller 60 to be approximately the same, the rubber strip 95 is less likely to bend or pull unnecessarily, and conveyance becomes more stable.

The rubber strip 95 transported on the conveyor belt 61 is passed to the conveyor belt 63 provided downstream of the conveyor belt 61. The conveyor belt 63 is an endless belt made of a band-shaped rubber sheet wider than the rubber strip 95, just like the conveyor belt 61. The conveyor belt 63 is hung on a pair of rollers 62. The rotation of the rollers 62 is controlled by the control device 80. The rotation of the rollers 62 is set so that the conveying speeds of the conveyor belt 63 and the conveyor belt 61 are approximately the same. The rubber strip 95 transported on the conveyor belt 63 is transported toward the forming drum 70. A pressing roller 64 for pressing the rubber strip 95 against the forming drum 70 may be provided between the conveyor belt 63 and the forming drum 70.

<Molding drum 70>
The molding drum 70 is a drum on which the rubber strip 95 transported along the above-mentioned transport path is wound. The molding drum 70 is a cylindrical drum and has an outer peripheral surface on which the rubber strip 95 is wound. The circumferential length and diameter of the molding drum 70 can be determined based on the dimensions of the raw cover 90 to be molded, etc. The molding drum 70 is configured to be rotatable in the circumferential direction. The molding drum 70 is also configured to be movable in the axial direction. In the process of winding the rubber strip 95, the molding drum 70 is rotated and reciprocated along the axial direction, and the rubber strip 95 is wound and overlapped. Therefore, the rubber strip 95 is wound and overlapped in the axial and radial directions on the outer peripheral surface of the molding drum 70.

The forming drum 70 can move in the axial direction at a predetermined constant speed. As a result, the rubber strip 95 wound around the forming drum 70 is wound sequentially along the axial direction on the forming drum 70 with the widthwise ends overlapping with the previously wound rubber strip 95. The rubber strip 95 is wound in a predetermined range on the forming drum 70. The range around which the rubber strip 95 is wound is appropriately set according to the width of the rubber member 92a. When the rubber strip 95 is wound in a predetermined range on the forming drum 70, the forming drum 70 moves at the same speed in the opposite direction. As a result, the rubber strip 95 is wound and overlapped on the previously wound rubber strip 95. The rubber strip 95 is wound and overlapped a predetermined number of times on the forming drum 70, and the rubber member 92a of the row cover 90 is formed.

A control device 80 is connected to the forming drum 70. The control device 80 controls the rotation of the forming drum 70. The speed at which the rubber strip 95 is transported (wrapped) on the forming drum 70 is set to a speed faster than the speed at which it is transported along the second roller 60. In other words, the rotation is set so that the transport speed of the rubber strip 95 on the forming drum 70 is faster than that of the transport belt 63, whose transport speed is set by the second roller 60. Therefore, when the rubber strip 95 is wound around the forming drum 70, it is wound under tension. This makes it less likely that gaps will occur between the rubber strip 95 and the forming drum 70 and between the overlapping rubber strips 95.

In this manner, the rubber strip 95 is wound around the forming drum 70 in a state where tension is applied due to the difference in conveying speed. Therefore, the rubber strip 95 is wound around the forming drum 70 in a state where it is stretched along the circumferential direction of the forming drum 70. In this embodiment, the stretching mechanism 75 that stretches the rubber strip 95 is realized by the second roller 60, the forming drum 70, and the control device 80 that controls the rotation of these. In other words, the stretching mechanism 75 stretches the rubber strip 95 due to the difference between the speed at which the rubber strip 95 is conveyed along the second roller 60 and the speed at which the rubber strip 95 is conveyed on the forming drum 70. The stretching mechanism 75 stretches the rubber strip 95 on the forming drum 70. In this embodiment, the control device 80 controls the rotation of the second roller 60 and the forming drum 70 to control the stretch rate of the rubber strip 95. The stretch rate of the rubber strip 95 stretched in the stretching mechanism 75 is expressed, for example, by the difference between the conveying speed at the second roller 60 and the conveying speed at the forming drum 70, the ratio of the conveying speeds, or the like. In this embodiment, the elongation rate of the rubber strip 95 stretched by the stretching mechanism 75 when the conveying speed of the second roller 60 is taken as 100 is expressed by the following formula.
Elongation rate=difference in conveying speed between the forming drum 70 and the second roller 60×0.01+1

In the above-described embodiment, the tire building apparatus 10 includes a stretching mechanism 35 realized by the calendar roll 30, the first roller 40, and a control device 80 that controls the rotation of these. The tire building apparatus 10 includes a stretching mechanism 75 realized by the second roller 60, the building drum 70, and a control device 80 that controls the rotation of these. Therefore, the final stretch rate of the rubber strip 95, which is compared between the rubber strip 95 passed between the calendar rolls 30 and the rubber strip 95 wound around the building drum 70, is expressed as the product of the stretch rate stretched in the stretching mechanism 35 and the stretch rate stretched in the stretching mechanism 75.

The tire building apparatus 10 is not particularly limited as long as the control device 80 controls the elongation rate of the rubber strip 95 based on the circumference of the calendar roll 30 and the circumference of the building drum 70. For example, the tire building apparatus 10 does not necessarily have to include both the stretching mechanism 35 and the stretching mechanism 75. The tire building apparatus 10 may include only one of the stretching mechanism 35 and the stretching mechanism 75. In addition, the stretching mechanism 35 and the stretching mechanism 75 do not have to be controlled by the same control device 80. For example, the tire building apparatus 10 may set the conveying speed and the elongation rate of the rubber strip 95 by separate control devices.

However, if the rubber strip has thickness variations along the conveying direction, the rubber strip wound around the forming drum may also have thickness variations. Due to thickness variations in the rubber strip, the formed raw cover may have uneven thickness portions. If uneven thickness portions are formed in the raw cover, uneven portions may also occur in the final product, the tire after vulcanization, and there is a concern that the so-called uniformity may deteriorate. According to the inventor's knowledge, the rubber strip may have unavoidable thickness variations due to runout caused by the assembly of the calendar rolls and tension applied to the rubber strip. Such thickness variations may occur periodically in the conveying direction of the rubber strip.

Figures 3 and 4 are schematic diagrams of a rubber strip 95. In Figure 3, the rubber strip 95 passing between the calender rolls 30 is shown. In Figure 4, the rubber strip 95 wound along the axial direction of the forming drum 70 (see Figure 2) is shown. In Figure 3, the conveying direction of the rubber strip 95 and the rotation direction of the calender rolls 30 are indicated by arrows. Note that Figures 3 and 4 are drawn schematic and do not reflect actual dimensions.

The rubber strip 95 passed through the calender rolls 30 has a relatively thin portion 95a and a relatively thick portion 95b. The inventor's study revealed that the thickness pattern of the rubber strip 95 can be formed periodically at approximately regular intervals in the conveying direction of the rubber strip 95. For example, the thickness pattern of the rubber strip 95 can be formed in part due to the calender roll 30 vibrating when it rotates. For this reason, the relatively thin portion 95a and the relatively thick portion 95b of the rubber strip 95 can be formed every time the calender roll 30 rotates. In other words, the pattern of the thin portion 95a and the thick portion 95b of the rubber strip 95 can be formed periodically with the circumference of the calender roll 30 being one period. When the rubber strip 95 is wound and overlapped, if the thin portion 95a or the thick portion 95b is concentrated in the circumferential direction of the forming drum 70, the difference in thickness with other portions can be amplified.

In the above-described embodiment, the control device 80 of the stretching mechanism 35, 75 controls the elongation rate of the rubber strip 95 by controlling the transport speed of the rubber strip 95 transported along the calendar roll 30, the first roller 40, the second roller 60, and the molding drum 70. The control device 80 controls the elongation rate of the rubber strip 95 based on the circumferential length of the calendar roll 30 and the circumferential length of the molding drum 70. In this embodiment, the control device 80 stores the circumferential length of the calendar roll 30 and the circumferential length of the molding drum 70 in advance. The control device 80 may be configured to be able to input the circumferential length of the calendar roll 30 and the circumferential length of the molding drum 70.

In the above-described embodiment, the tire building device 10 includes a pair of calendar rolls 30, a building drum 70, and stretching mechanisms 35, 75. The pair of calendar rolls 30 are arranged at a predetermined interval. The rubber strip 95 is transported between the pair of calendar rolls 30 and rolled. The rubber strip 95 transported from the pair of calendar rolls 30 along a predetermined transport path is wound around the building drum 70. The stretching mechanisms 35, 75 stretch the rubber strip 95 along the transport path. The stretching mechanisms 35, 75 are provided on the transport path. The stretching mechanisms 35, 75 include a control device 80 that controls the elongation rate of the rubber strip 95 based on the circumferential length of the calendar rolls 30 and the circumferential length of the building drum 70.

With this tire building device 10, the elongation rate of the rubber strip 95 can be controlled according to the circumferential length of the calendar roll 30 and the circumferential length of the building drum 70 so that the thickness patterns of the rubber strip 95 do not overlap in the circumferential direction. This makes it possible to disperse the thickness differences in the circumferential direction of the building drum 70 even when the rubber strip 95 has thin portions 95a and thick portions 95b. As a result, the thickness variation of the raw cover 90 is reduced, and uniformity is improved in the vulcanized tire.

For example, by controlling the elongation rate based on the circumference of the calendar roll 30 and the circumference of the forming drum 70, it is possible to disperse the thickness variation of the rubber strip 95 on the forming drum 70. In the embodiment shown in FIG. 4, the conveying speed is controlled so that the thick portions 95a and the thin portions 95b are slightly shifted each time the rubber strip 95 is wound around one revolution. In this way, it is possible to control the elongation rate so that the patterns of the thin portions 95a and the thick portions 95b on the outer circumferential surface of the forming drum 70 do not match in the axial direction.

The inventors used the tire building device described above to prototype low covers by varying the transport speed of the rubber strip. Here, the speed of the calendar roll and the speed of the second roller were set to the same speed, which was taken as the reference speed (100). The speed of the calendar roll and the speed of the second roller were the same in each example. The inventors vulcanized the manufactured low covers and vulcanized and molded tires. Here, five tires of size 265/65R17 were prototyped for each example (examples 1 to 5).

The uniformity of the prototype tires was inspected. Here, an automatic uniformity measuring machine was used to measure the RFV (Radial Force Uniformity). The measured RFV data was subjected to order analysis using a computer. The order analysis may be performed according to a known analysis method. In the order analysis, the first to ninth order components were calculated, and the average value of the order components was calculated for each example. Table 1 below shows the implementation conditions and results for each example.

The "elongation rate" in Table 1 indicates the ratio of elongation of the rubber strip rolled by the calendar roll before it is attached to the forming drum. The elongation rate in Table 1 is calculated from the conveying speeds of the calendar roll, the first roller, the second roller, and the forming drum. Here, the elongation rate in Table 1 is calculated from the difference between the speed of the calendar roll and the conveying speed of the first roller, and the difference between the conveying speeds of the second roller and the forming drum. When the conveying speed of the calendar roll is set to 100, the elongation rate at the forming drum is expressed by the following formula.
Elongation rate = (difference in conveying speed between the first roller and the calendar roll x 0.01 + 1) x (difference in conveying speed between the forming drum and the second roller x 0.01 + 1)

"Period" in Table 1 indicates the value of the circumference of the forming drum relative to the product of the circumference of the calendar roll and the elongation rate.

In examples 1 and 3, where the period is far from an integer, the higher order (sixth and above) components of the RFV were suppressed to 10 or less. On the other hand, in examples 2, 4, and 5, where the period is close to an integer, high values were detected in the higher order components of the RFV. In example 2, where the period is 7.99, the eighth order component of the RFV was 22.1. In example 4, where the period is 6.99, the seventh order component of the RFV was 15.4. In example 5, where the period is 6.04, the sixth order component of the RFV was 23.4. From this, it can be seen that when the period is close to an integer, the order components of the RFV corresponding to that period become high, which can reduce uniformity.

In the control device of the tire molding device disclosed herein, the conveying speeds of the calendar roll, the first roller, the second roller, and the molding drum can be set. In addition, the control device is configured to be able to control the elongation rate of the rubber strip from the conveying speeds of the calendar roll, the first roller, the second roller, and the molding drum. For example, the control device is configured to store the circumference of the calendar roll and the circumference of the molding drum, and to be able to confirm the circumference of the molding drum relative to the product of the circumference of the calendar roll and the elongation rate. For this reason, the control device can control the conveying speed and adjust it so that the circumference of the molding drum relative to the product of the elongation rate and the circumference of the calendar roll does not become an integer. The conveying speed setting may be set in advance before the rubber strip is conveyed. In addition, the conveying speed may be automatically set during the conveyance of the rubber strip so that the circumference of the molding drum relative to the product of the circumference of the calendar roll and the elongation rate does not become a preset value (for example, an integer, etc.). By controlling the circumference of the molding drum relative to the product of the elongation rate and the circumference of the calendar roll so that it does not become an integer, unevenness in the thickness of the raw cover due to the periodicity of the calendar roll is less likely to occur. As a result, the uniformity of the tire after vulcanization can be further improved.

From the results shown in Table 1 above, the uniformity of the vulcanized tire can be improved by setting the circumference of the forming drum relative to the product of the circumference of the calendar roll and the elongation rate to a value that is 0.05 or more away from an integer. The circumference of the forming drum relative to the product of the circumference of the calendar roll and the elongation rate may be set to a value that is 0.1 or more away from an integer, for example, or may be set to a value that is 0.15 or more away from an integer.

In another trial by the inventor, the tire cover of Example 6 was prototyped by using the tire molding device described above, setting the conveying speed so that the circumference of the molding drum was 7.5 times the product of the circumference of the calendar roll and the elongation rate. Also, the tire cover of Example 7 was prototyped by setting the conveying speed so that the circumference of the molding drum was 7.2 times the product of the circumference of the calendar roll and the elongation rate. The manufactured tire cover was vulcanized, and the tires of Examples 6 and 7 were vulcanized and molded. The RRO (Radial Run Out) of each tire prototyped here was measured using an automatic uniformity measuring device and a computer similar to the device used in measuring the RFV of Examples 1 to 5. The measured RRO was subjected to order analysis, and the order components from 1st to 20th were calculated. Among the order components from 1st to 20th of the RRO, the difference between the tire of Example 6 and the tire of Example 7 was the largest in the 15th order component. The 15th component of the RRO in Example 7 was 43% lower than the 15th component of the RRO in Example 6.

From this, when the circumference of the forming drum for the product of the circumference of the calendar roll and the elongation rate is an integer + 0.5 times, the uniformity of the order component corresponding to twice that value (15, which is twice 7.5, in Example 6) may decrease. From this, it can be seen that the RRO of the order component can be suppressed by controlling the conveying speed of the rubber strip so that the circumference of the forming drum for the product of the elongation rate and the circumference of the calendar roll is not the sum of an integer and 0.5. From this result and the result of Table 1, by controlling the conveying speed of the rubber strip so that the circumference of the forming drum for the product of the elongation rate and the circumference of the calendar roll is not an integer multiple of 0.5, the raw cover may be less likely to have uneven parts due to the periodicity of the calendar roll. As a result, the uniformity of the vulcanized tire may be further improved. For example, the circumference of the forming drum for the product of the circumference of the calendar roll and the elongation rate may be set to a value that is 0.1 or more away from an integer + 0.5, or may be set to a value that is 0.15 or more away from it.

The above describes various aspects of the technology disclosed herein. However, the technology disclosed herein is not limited to the above-mentioned form unless otherwise specified. For example, in the tire molding device described above, the rubber strip is wound and overlapped on the molding drum, but is not limited to such a form. For example, the above-mentioned technology is also applicable to the case where the rubber strip is wound around a rubber member (e.g., a breaker, a band, a base rubber, etc.) wound around the molding drum. In this case, the elongation rate of the rubber strip can be controlled by using the circumference of the rubber member wound around the molding drum as the above-mentioned "circumference of the molding drum". Furthermore, when the rubber strip conveyed to the molding drum is overlapped on the previously wound rubber strip, the elongation rate of the rubber strip may be controlled by using the circumference taking into account the thickness of the previously wound rubber strip as the "circumference of the molding drum".

The various configurations of the embodiments mentioned above can be combined as appropriate as long as they do not interfere with each other. This specification includes the following inventions, but the following inventions are not limited to the above-mentioned embodiments.

The present invention (1) relates to a tire building apparatus. The tire building apparatus according to the present invention (1) comprises:
a pair of calender rolls arranged at a predetermined interval between which the rubber strip is conveyed and rolled;
a forming drum on which the rubber strip transported from the pair of calendar rolls along a predetermined transport path is wound;
a stretching mechanism provided on the transport path to stretch the rubber strip along the transport path,
The stretching mechanism includes a control device that controls the elongation rate of the rubber strip based on the peripheral length of the calendar roll and the peripheral length of the forming drum.

The present invention (2) is a tire building apparatus according to the present invention (1),
The rubber strip further includes a first roller that is provided downstream of the calender rolls in the conveying path and conveys the rubber strip at a speed faster than a speed at which the rubber strip is conveyed between the pair of calender rolls,
The stretching mechanism stretches the rubber strip by a difference between a speed at which the rubber strip is transported between the pair of calender rolls and a speed at which the rubber strip is transported along the first roller.

The present invention (3) is a tire building apparatus according to the present invention (1),
Further, a second roller is provided upstream of the forming drum in the conveying path and conveys the rubber strip at a speed slower than a speed at which the rubber strip is conveyed on the forming drum,
The stretching mechanism stretches the rubber strip by the difference between the speed at which the rubber strip is conveyed along the second roller and the speed at which the rubber strip is conveyed over the forming drum.

The present invention (4) is a tire building apparatus according to the present invention (1),
a first roller that is provided downstream of the calender rolls in the conveying path and conveys the rubber strip at a speed faster than a speed at which the rubber strip is conveyed between the pair of calender rolls;
a second roller that is provided upstream of the forming drum in the conveying path and conveys the rubber strip at a speed slower than the speed at which the rubber strip is conveyed on the forming drum;
The stretching mechanism stretches the rubber strip by the difference between the speed at which the rubber strip is transported between the pair of calendar rolls and the speed at which the rubber strip is transported along the first roller, and by the difference between the speed at which the rubber strip is transported along the second roller and the speed at which the rubber strip is transported over the forming drum.

The present invention (5) is a tire building apparatus in any combination with any of the present inventions (1) to (4),
The control device controls the conveying speed of the rubber strip so that the product of the elongation rate and the circumference of the calendar roll is not an integer.

The present invention (6) is a tire building apparatus in any combination with any of the present inventions (1) to (4),
The control device controls the transport speed of the rubber strip so that the peripheral length of the forming drum relative to the product of the elongation rate and the peripheral length of the calendar roll is a value that is 0.05 or more away from an integer.

The present invention (7) is a tire building apparatus in any combination with any of the present inventions (1) to (4),
The control device controls the transport speed of the rubber strip so that the peripheral length of the forming drum relative to the product of the elongation rate and the peripheral length of the calendar roll is not an integer multiple of 0.5.

The present invention (8) relates to a method for manufacturing a tire. The tire manufacturing method according to the present invention (8) includes the steps of:
A step of conveying a rubber strip along a predetermined conveying path from a pair of calender rolls arranged at a predetermined interval toward a forming drum;
and winding the rubber strip transported along the transport path around the forming drum,
At least one of the conveying step and the winding step includes stretching the rubber strip along the conveying path,
The elongation of the rubber strip is controlled based on the circumference of the calender rolls and the circumference of the forming drum.

REFERENCE SIGNS LIST 10 Tire building device 20 Extruder 30 Calender rolls 35, 75 Stretching mechanism 40 First roller 50 Festoon 60 Second roller 61 Conveyor belt 70 Building drum 80 Control device 90 Row cover 95 Rubber strip

Claims (8)

a pair of calender rolls arranged at a predetermined interval between which the rubber strip is conveyed and rolled;
a forming drum on which the rubber strip transported from the pair of calendar rolls along a predetermined transport path is wound;
a stretching mechanism provided on the transport path to stretch the rubber strip along the transport path,
The tire building apparatus includes a control device, wherein the stretching mechanism controls the elongation rate of the rubber strip based on the circumferential length of the calendar roll and the circumferential length of the building drum. The rubber strip further includes a first roller that is provided downstream of the calender rolls in the conveying path and conveys the rubber strip at a speed faster than a speed at which the rubber strip is conveyed between the pair of calender rolls,
2. The tire building apparatus according to claim 1, wherein the stretching mechanism stretches the rubber strip by a difference between a speed at which the rubber strip is transported between the pair of calendar rolls and a speed at which the rubber strip is transported along the first roller. Further, a second roller is provided upstream of the forming drum in the conveying path and conveys the rubber strip at a speed slower than a speed at which the rubber strip is conveyed on the forming drum,
2. The tire building apparatus of claim 1, wherein the stretching mechanism stretches the rubber strip by a difference between a speed at which the rubber strip is conveyed along the second roller and a speed at which the rubber strip is conveyed over the building drum. a first roller that is provided downstream of the calender rolls in the conveying path and conveys the rubber strip at a speed faster than a speed at which the rubber strip is conveyed between the pair of calender rolls;
a second roller that is provided upstream of the forming drum in the conveying path and conveys the rubber strip at a speed slower than the speed at which the rubber strip is conveyed on the forming drum;
2. The tire building apparatus according to claim 1, wherein the stretching mechanism stretches the rubber strip by a difference between a speed at which the rubber strip is transported between the pair of calendar rolls and a speed at which the rubber strip is transported along the first roller, and a difference between a speed at which the rubber strip is transported along the second roller and a speed at which the rubber strip is transported over the building drum. The tire building device according to any one of claims 1 to 4, wherein the control device controls the conveying speed of the rubber strip so that the product of the elongation rate and the circumference of the calendar roll and the circumference of the building drum is not an integer. The tire building device according to any one of claims 1 to 4, wherein the control device controls the transport speed of the rubber strip so that the circumference of the building drum relative to the product of the elongation rate and the circumference of the calendar roll is a value that is 0.05 or more away from an integer. The tire building device according to any one of claims 1 to 4, wherein the control device controls the conveying speed of the rubber strip so that the circumference of the building drum relative to the product of the elongation rate and the circumference of the calendar roll is not an integer multiple of 0.5. A step of conveying a rubber strip along a predetermined conveying path from a pair of calender rolls arranged at a predetermined interval toward a forming drum;
and winding the rubber strip transported along the transport path around the forming drum,
At least one of the conveying step and the winding step includes stretching the rubber strip along the conveying path,
A method for manufacturing a tire, wherein the elongation rate of the rubber strip is controlled based on the circumference of the calendar roll and the circumference of the building drum.

Images