JPS6345949B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention is a radial tire that improves the uniformity of finished tires by measuring the circumferential length of the crown portion of a raw tire and controlling it within a specified range when molding a radial tire. It relates to a tire molding method. (Prior art and problems to be solved by the invention) Since the structure of a radial tire is such that the cords of the breaker layer arranged on the carcass layer are arranged at an angle close to the circumferential direction, the manufacturing method is inevitably cylindrical. A two-step method is used in which the bead part, carcass layer, and sidewall rubber are stretched and molded on a shaped former, the diameter of which is expanded to transform it into a toroid shape, and the breaker layer and tread layer are pasted and molded on the crown part. It's on.
In such a forming method, when the carcass layer is deformed into a toroidal shape, stress concentration may occur locally in the carcass cord, and a uniform expansion diameter cannot necessarily be obtained, resulting in tires with various outer circumferences. In other words, the main factors that determine the outer circumference of a toroidal carcass are the spacing between the bead wires placed on the former, the inflation pressure, and the inflation time, but even if these are adjusted appropriately, all of a specific size will have the same outer circumference. It is extremely difficult to do so. Therefore, when a tread layer cut to a certain length is applied to tires with different circumferences, unevenness will occur on the outer surface of the crown of the finished tire, resulting in radial force variation or lateral force variation. Characteristics such as variation are significantly reduced. In order to solve this problem, there is a method of cutting the length of each tread according to the outer circumference of the molded tire, but this method not only reduces work efficiency, but also
Since the length is adjusted by visual inspection by the operator, the operator must be skilled in order to improve the molding accuracy, and furthermore, there is a natural limit to that accuracy. SUMMARY OF THE INVENTION It is an object of the present invention to provide a radial tire molding method that solves these problems and can efficiently mold a uniform tire with high precision. (Means for Solving the Problems) The present invention places a carcass layer together with other constituent members on a forming drum, deforms it into a toroid shape, and attaches a breaker layer or a tread layer to the crown portion of the toroid. In the method of forming a radial tire to form a tire, (a) the step of measuring the circumference of the tire crown before pasting the breaker layer; and (b) the step of measuring the circumference of the tire crown if the circumference is outside the specified range. This is a radial tire molding method that includes the steps of: controlling the pressure within a specified range using inflation pressure, etc. (Example) An example of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram showing a system for the molding method of the present invention. In the figure, a green tire 1 has a carcass layer 2 assembled together with bead wires 3 and sidewalls 4 on a forming drum 5, and is deformed into a toroidal shape. Thereafter, the length of one circumference of the green tire 1 is measured to check whether the expansion diameter of this toroidal carcass is uniform. The length (L) of one circumference of the outer surface of the raw tire 1 can be calculated using the following formula. L=∫ ² 〓 ₀ γ(θ)dθ Here, γ is the radius to the outer surface of the green tire, which is the rotation angle expressed in radians. Here, if a minute rotation angle △θ is taken to perform numerical integration, the numerical integration can be obtained by N△θ=2π, L= _N 〓 ⁱ⁼¹ , γi△θ. Here, N is the number of divisions for numerical integration, and L is the length of one round. Also, γi is the tire radius at the i-th point. Here, the method for finding γi is as follows. That is, in FIG. 1, a displacement meter 7 is installed near the crown of the green tire, and the distance d from the displacement meter to the outer surface of the green tire is measured. γi is the distance d from the distance R from the tire rotation axis to the displacement meter.
It is calculated as the value obtained by subtracting the As shown in FIG. 3, the displacement meter used in the present invention includes a fourth differential transformer that causes a detection roller 11 attached to a movable part 10 to follow the rotation of the tire outer surface and measure the radial variation thereof. As shown in the figure, a displacement meter that irradiates a laser beam from a laser oscillator 12 onto an object to be measured 13 and detects the reflected light with an image sensor 14, or as shown in FIG. It is possible to use a displacement meter or the like that emits a light beam, detects it with an image camera placed on the reflection side, and measures the change in height of the upper end of the object to be measured 13, and can also be of either a contact type or a non-contact type. good. Using these displacement meters, the distance d to the outer surface of the raw tire is obtained as a waveform signal for one revolution of the tire, as shown in FIG. In the figure, the horizontal axis shows the tire rotation angle, the vertical axis shows the distance d to the outer surface of the raw tire, P corresponds to the tire concave part, T corresponds to the tire convex part,
A indicates the amplitude of the waveform. This waveform signal is then A/
The data is input to the D converter 15, where each tire radius γi of one tire circumference is converted into a digital value, and this is input to the computer 16, where the circumference of the tire is calculated by the numerical integration described above. If this calculated value is outside the specified range, the internal pressure of the raw tire is adjusted by controlling the internal pressure filling solenoid valve 18 and the internal pressure release solenoid valve 19 by the solenoid valve controller 17, and the circumference of the raw tire is adjusted. Set within the specified range. This control method is shown in FIG. 7 as a flowchart. In the figure, first, after the diameter of a green tire is inflated, the internal pressure is maintained at a predetermined value, and the circumferential length of one round of the green tire is measured using the method described above. If this measured value is smaller than the specified upper limit and larger than the specified lower limit, that is, within the specified numerical range, the process moves to the next breaker layer pasting process without the need for correction. Next, if the measured value of the circumference of the raw tire is larger than the specified upper limit, the amount to reduce the internal pressure of the raw tire is calculated according to the difference, and the solenoid valve 19 is intermittently operated to set the internal pressure. decrease to. After that, the circumference of the raw tire is measured again. Next, if the measured value of the circumference of the raw tire is smaller than the specified lower limit, calculate how much the internal pressure of the raw tire should be increased according to the difference, and intermittently operate the solenoid valve 18 to fill the internal pressure. Raise to the set internal pressure. After that, the circumference of the raw tire is measured again. Adjustment of the internal pressure is repeated in this manner until the circumference of the raw tire falls within a predetermined range. Note that this internal pressure adjustment is monitored by a pressure sensor 20. Since the green tire obtained in this way always has a circumference within a certain range, even when a breaker layer or tread layer is attached in the next step, the joints at both ends will be almost constant. High precision molding becomes possible and the uniformity of the finished tire improves. In addition to the method of directly measuring the circumference of a green tire as in the present invention, there are methods of measuring the tire radius using a phototube method, or converting this into a circumference. Because of these changes, it is difficult to mold with high precision. In the present invention, in addition to controlling the tire internal pressure as described above in order to adjust the circumferential length of the tire, it is also possible to adjust the bead spacing (W in FIG. 1) when deforming into a toroidal shape. Below are the results of measuring the circumferential runout at the center of the crown of the finished tires formed by molding 10 steel radial tires with a tire size of 10.00R20-14PR using the method described below. Runout measurement was carried out with the tire mounted on a rim of size 7.00T x 20, with an internal pressure of 7.25Kg.
Measurements were made using a differential transformer at f/cm ² . The results are shown in Table 1. In Example 1 of the present invention, a breaker layer was pasted on a toroidal carcass layer using a molding machine equipped with the mechanism shown in FIG. 1, and then the runout waveform on the tire equator was measured. The number of divisions (N) for numerical integration is 60, and the range of the specified upper limit value and specified lower limit value is 1 mm. After controlling the circumferential length by adjusting the internal pressure, a tread was attached, and the product was manufactured through normal vulcanization and finishing steps. On the other hand, Comparative Example 1 was manufactured in the same manner as in the example except that the circumferential length was controlled.

【table】

[Table] As is clear from the table, in Example 1 of the present invention, it is clear that the average value and standard deviation of the amplitude are small, and the uniformity is considerably improved. (Effects) As described above, the present invention measures the circumference of the crown portion of the carcass layer expanded in a toroidal shape during the radial tire molding process, compares the measured value with a predefined value, and detects deviations outside the specified range. In this case, it is controlled within the specified range using expansion force, etc.
This makes it possible to make all the carcass circumferences of tires of the same size the same, making it possible to greatly improve the uniformity of finished tires.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing the system of the molding method of the present invention, Fig. 2 is a schematic diagram showing the radius change of a green tire, Figs. 3 to 5 are displacement meters, and Fig. 6 is a diagram showing the tire runout waveform. The figure shown in FIG. 7 shows a flowchart of the molding method of the present invention. DESCRIPTION OF SYMBOLS 1... Tire, 2... Carcass layer, 5... Forming drum, 7... Displacement meter, 16... Calculator, 17...
... Controller, 18, 19 ... Solenoid valve, 20
...Internal pressure sensor.

Claims (1)

[Claims] 1. Place the carcass layer together with other constituent members on a forming drum, deform it into a toroid shape,
A method for forming a radial tire in which a green tire is formed by pasting a breaker layer and a tread layer on the crown part includes the steps of (a) measuring the circumference of the tire crown before pasting the breaker; ) A method for forming a radial tire, comprising the step of: controlling the circumference within the specified range by using inflation pressure, etc., if the circumference is outside the specified range.