JPS60230836A - Preparation of pneumatic radial tire - Google Patents

Abstract

PURPOSE:To reduce the vibration of a tire at the time of high speed running by enhancing the uniformity of the tire, by specifying the ratio of splice lap amount at the center part and that at the both right and left end parts in the splice part of a belt cover layer. CONSTITUTION:A belt cover layer 6 is arranged onto the outermost layer of a belt layer 5 in a second stage so that the direction of heat-shrinkable fiber cords 6a comes to almost 0 deg. with respect to the peripheral direction of a tire. At this time, in the splice lap amount b1 at the center part and that b2 at the both right and left end parts in the splice part 61 of the belt cover layer 6, b2 is formed in a range of 0.5b1-0.8b1. By this method, in the product tire E after the vulcanization of a green tire E1, the splice lap amounts at the both right and left end parts and the center part can be almost coincided, with each other.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention provides a belt cover layer on the outermost layer of the belt layer.
The present invention relates to an improvement in a method for manufacturing a pneumatic radial tire in which the direction of the heat-shrinkable fiber cords is arranged at approximately 0° with respect to the circumferential direction of the tire.

[Conventional technology]

Conventionally, radial tires with excellent high-speed performance, especially steel radial tires, have a belt cover layer on the outermost layer of the belt layer, which is made of heat-shrinkable fiber cords, in order to suppress the standing wave phenomenon in the trend section during high-speed running. It is arranged so that the direction is approximately 0° with respect to the tire circumferential direction.

However, when manufacturing a tire, this belt cover single layer has a splice portion 61 as shown in FIGS. 1 and 2 (al (bl), and this splice portion 61 is This locally high rigidity has a negative effect on the uniformity of the tire, and when a car is running at high speed, this poor uniformity is one of the causes of vehicle vibration and worsens the riding comfort, while spot wear, i.e. Various studies have revealed that localized abnormal wear occurs.

[Purpose of the invention]

The present invention was developed as a result of experiments and studies to solve the above-mentioned problems.

Therefore, an object of the present invention is to improve the uniformity of a tire equipped with a single-layer belt cover, particularly to reduce vibration during high-speed running to improve ride comfort, and to prevent the occurrence of spot wear. An object of the present invention is to provide a method for manufacturing a pneumatic radial tire.

[Structure of the invention]

That is, in the second stage of the manufacturing process of a pneumatic radial tire, the present invention arranges a heald cover layer on the outermost layer of the belt layer so that the direction of its heat-shrinkable fiber cords is approximately Oo with respect to the tire circumferential direction. In this case, if the amount of splice ramp at the center of the splice part of this belt cover single layer is s, and the amount of splice ramp at both left and right ends is b2, then the splice ramp at both left and right ends (Jb2 is 0.5b+~o, 8bl) The gist of this invention is a method for manufacturing a pneumatic radial tire characterized by the following.

First, the progress that led to the present invention will be explained along with experimental examples.

[Experimental Example 1] The inventors of the present invention found that, in the splice portion of the single layer of the belt cover, if the direction of the circumferential edge of the splice portion is inclined with respect to the tire circumferential direction, the rigidity changes locally rapidly. Focusing on the fact that the uniformity of the tire can be improved by making the change smooth without changing the shape of the tire, as shown in FIG. Then, the uniformity of the tire was measured by changing the inclination angle α of this edge measured from the acute angle side with respect to the tire circumferential direction and the amount of splice ramp.

The uniformity is measured by the dimensional run-out in the tire radial direction (hereinafter referred to as RRO) at the tire center and at the left and right shoulders.
al Run 0ut)].

Further, in this experimental example, 185/70HR14 steel radial tires were used, and the experimental results were summarized as the average value of 10 tires. (For some of the shoulders, the average value of the left and right shoulders was used.) As a result of the experiment, the experimental results shown in FIG. 5 were obtained.

In Figure 5, the vertical axis shows tire uniformity (RRO (am)), and the horizontal axis shows inclination angle α (°) and splice ramp amount (
, m) is the key.

Note that in the figure, the mark indicates a part of the shoulder, and the mark ○ indicates a part of the center.

As is clear from FIG. 5, if the inclination angle α of the circumferential edge of the splice portion 61 of the belt cover single layer 6 with respect to the tire circumferential direction is reduced, that is, the inclination direction of the circumferential edge of the splice portion 61 can be changed in the tire circumferential direction. The closer the RRO is to the smaller the
It can be seen that RRO becomes smaller.

As described above, this reduces the inclination angle α of the circumferential edge of the splice portion 61 of the belt cover layer 6 with respect to the tire circumferential direction. Alternatively, if the splice wrap amount is reduced, as shown in FIG. 4 (al and (b)),
This is because the rigidity of the splice portion 61 of the heald cover layer 6 can be smoothly changed in the circumferential direction.

Furthermore, when comparing the RRO of a part of the center and a part of the shoulder, if the values of the inclination angle and the amount of splice ramp are the same, the RRO of the part of the shoulder is larger. The accompanying decrease in RRO is also small.

This is because, as shown in FIG. 6, the lift rate experienced during vulcanization is higher in the center part than in the shoulder part due to the tread radius of the tire.

For this reason, in the second stage, when placing a single layer of heald cover on the outermost layer of the belt layer, the splice wrap amount b1 at the center (part of the center) in the splice part and the splice lamp at both left and right ends (part of the shoulder) are determined. The quantity b2 is made the same as shown in Fig. 7(a).
After vulcanization, as shown in Figure 7 (bl), the amount of splice wrap a2 at both left and right ends (part of the shoulder) where the lift rate is small is greater than the amount of splice wrap a1 of the center part (part of the center). This is because there will be more.

Therefore, when placing a single layer of belt cover on the outermost layer of the belt layer in the second stage as in the conventional method shown in FIG.
If the splice wrap amount b1 of the center part) is the same as the splice wrap amount b2 of both left and right ends (part of the shoulder), after vulcanization, as shown in FIG. The splice wrap amount a2 at the shoulder section (part of the shoulder) is larger than the splice wrap amount a1 at the center section (part of the center). Lamp amount a
1 means that the lift rate is smaller than the splice ramp amount a2 at both the left and right ends (part of the shoulder) where the lift rate is small. As a result, even if the inclination angle is simply reduced,
It is not possible to improve riding comfort and prevent spot wear during high-speed driving.

Therefore, the inventors of the present invention determined the splice ramp amount b2 at both left and right ends (part of the shoulder) of the splice portion when placing one layer of the belt cover on the outermost layer of the belt layer in the second stage. As shown in , the splice ramp amount b at the center (part of the center)
If the lift rate is increased compared to 1 in accordance with the lift rate during vulcanization, after vulcanization, as shown in Fig. 8(b), the lift rate at both left and right ends (part of the shoulder) where the lift rate is small will be increased. The splice ramp amount a2 and the center part where the lift rate is large (
It has been found that the splice wrap amount a1 of the center part) can be made to substantially match the splice wrap amount a1, and a preferable result can be obtained.

Therefore, the inventors of the present invention, based on the above-mentioned knowledge,
The following experiment was conducted.

[Experimental Example 2] In the second stage, when placing a belt cover layer on the outermost layer of the heald layer, the inclination angle α of the circumferential edge at the splice portion 61 of the belt cover layer 6 was set to 6.
While fixing the tire to 0°, fixing the splice ramp amount b1 at the center (part of the center) to 65 cranes, and varying the splice ramp amount b2 at both left and right ends (part of the shoulder), measure the uniformity of the tire. did.

Uniformity is measured by dimensional run-out in the tire radial direction of a part of the tire center and part of the left and right shoulders [hereinafter referred to as RRO (llad)].
ial Run 0ut)]. Further, in this experimental example, 185/70) IR14 steel radial tires were used, and the experimental results were summarized as the average value of 10 tires. (For the above shoulder part,
As a result of the experiment, the experimental results shown in FIG. 9 were obtained.

In FIG. 9, the vertical axis represents tire uniformity (RRO(+n)), and the horizontal axis represents b2/b1.

Note that in the figure, the mark indicates a part of the shoulder, and the mark ○ indicates a part of the center.

As is clear from Fig. 9, the RRO of a part of the shoulder is b
If the value of 2/b1 is less than 0.5, it will be significantly worse, or 0.
, when it exceeds 8, the RRO becomes significantly worse, and in the end, the RRO of the shoulder part has a value of b 2 / b 1 of 0.5.
It can be seen that good results can be obtained in the range of ~0.8.

This means that in the second stage of the pneumatic radial tire manufacturing process, the belt cover N6 is placed on the outermost layer of the belt layer 5 so that the direction of the heat-shrinkable fiber cord 6a is approximately Oo with respect to the tire circumferential direction. When arranging the belt cover, if the splice wrap amount b2 at both left and right ends (part of the shoulder) is set in the range of 0.5b+ to 0.8b+, the uniformity of a pneumatic radial tire with this type of belt cover placed in one layer will be greatly improved. In particular, it is found that vibrations during high-speed running can be reduced to improve riding comfort, and spot wear can be prevented from occurring.

Further, it is preferable that the amount of splice ramp at the center part of the splice portion 61 of the first layer 6 of the heald cover in the second stage is set in the range of 60 to 80. This is because if the splice ramp amount b1 of the center part (part of the center) is less than 60 mm, the splice portion 61 may open during vulcanization, and if it exceeds 80 mm, the splice ramp amount b1 is less than 60 mm. This is because an excessively large number increases the rigidity of the splice portion 61 and impairs uniformity, which is not preferable.

Further, the inclination angle α of the circumferential edge of the splice portion 61 of the belt cover single layer 6 is preferably set in the range of 15° to 60° as measured from the acute angle side with respect to the tire circumferential direction. This is because if the inclination angle α is less than 15°, the splice portion 61 becomes extremely long in the circumferential direction of the tire, making production practically difficult, and if it exceeds 60°, as is clear from the above-mentioned Experimental Example 1, This is because it is undesirable because it inhibits.

[Embodiments of the invention]

Hereinafter, the present invention will be specifically described by way of examples with reference to the drawings.

10 to 12 show examples of the present invention. Figure 11 is a partially cut-away perspective explanatory view showing the product tire after vulcanization of the same pneumatic radial tire, and Figures 12 (al (b) and (C) are respectively at the second stage in the manufacturing process of the pneumatic radial tire. , A part showing an example of the splice part of the heald cover layer when the belt cover layer is arranged on the outermost layer of the belt layer so that the direction of the heat-shrinkable fiber cord is approximately 0° with respect to the tire circumferential direction. FIG. 2 is a cutaway explanatory plan view.

In the figure, El indicates the green tire after the second stage in the manufacturing process of the pneumatic radial tire according to the embodiment of the present invention, and a pair of left and right bead portions 1,
A pair of left and right sidewall portions 2 connected to this bead portion 1
and the trend part 3 located between this side wall part 2.
A carcass layer 4 in which the angle of the cord 4a with respect to the tire circumferential direction is substantially 90 degrees is installed between the pair of left and right bead portions 1, and on the carcass layer 4 in the trend portion 3, A plurality of belt layers 5 whose cords 5a intersect with each other at an angle of 10° to 30° with respect to the direction.
Further, on the outermost layer of the belt layer 5, a belt cover layer 6 is arranged, in which a cord 6a made of a heat-shrinkable material is set at approximately 0° with respect to the tire circumferential direction.

In the present invention, especially in the second stage, a belt cover M is provided on the outermost layer of the belt layer 5.
When arranging the belt cover so that the direction of the heat-shrinkable fiber cord 6a is approximately 0° with respect to the tire circumferential direction, the amount of splice wrap at the center portion (part of the center) of the splice portion 61 of the belt cover layer 6 is determined by bl. If the splice wrap amount at both left and right ends (part of the shoulder) is b2, then the splice ramp amount b2 at both left and right ends is 0.5b.
+ to 0.8b+.

Therefore, when the above-mentioned green tire E1 is vulcanized, as shown in FIG. 11, in the product tire E after vulcanization, the splice ramp amount a2 at both left and right ends and the splice wrap amount a1 at the center are approximately equal. This type of belt cover can greatly improve the uniformity of pneumatic radial tires with a single-layer belt cover, and in particular, it can reduce vibration during high-speed driving and improve ride comfort, as well as reduce the occurrence of spot wear. In this embodiment, the belt cover layer 6 is arranged in one layer as shown in the figure, and a nylon cord is used for the cord 6a.

The first embodiment shown in FIGS. 10 and 12(a) is an example in which the circumferential end edge of the splice portion 61 in the belt cover single layer 6 is formed into a substantially semicircular shape in plan view.

Further, the second embodiment shown in FIG. 12 (bl) is an example in which the circumferential end edge of the splice portion 61 in the single layer 6 of the heald cover is formed into a substantially triangular shape in plan view.

Furthermore, the third embodiment shown in FIG. 12(C) is an example in which the circumferential end edge of the splice portion 61 in the belt cover single layer 6 is formed into a substantially trapezoidal shape in plan view.

The main specifications and RRO measurements of each of the above-mentioned embodiments are shown in Table 1 below.

(Margins below this page) [Effects of the Invention] As described above, in the second stage of the manufacturing process of a pneumatic radial tire, the present invention provides a layer of belt cover on the outermost layer of the belt layer in the direction of its heat-shrinkable fiber cords. When arranging the belt cover so that it is approximately Oo with respect to the tire circumferential direction, let bl be the splice ramp amount at the center and b2 be the splice ramp amount at both left and right ends in the splice portion of one layer of the belt cover. splice wrap amount b2 of 0.5b+~0.8b+
Since the tire is in the range of I can do it.

[Brief explanation of the drawing]

Fig. 1 is a perspective explanatory view showing an example of a splice part of a single layer of belt cover of a pneumatic radial tire, Fig. 2 (al is a plan view explanatory view of the same as above, fb) is an explanatory side view of the same as above, and (C) is an explanatory view of same as above as a side view. 3 is a perspective explanatory view showing another example of a splice portion of a single layer of belt cover of a pneumatic radial tire, FIG. 4(a) is an enlarged explanatory plan view of the same as above, FIG. Figure 5 is a diagram showing the results of Experimental Example 1, Figure 6 is an explanatory diagram showing the state of the belt layer and the heald cover layer after the second stage and vulcanization, and Figure 7 (al (bl) and Figure 8 (fal (b)). are explanatory diagrams showing the principle of the present invention, FIG. 9 is a diagram showing the results of Experimental Example 2, and FIGS.
Fig. 12 shows an embodiment of the present invention, Fig. 10 is a partially cutaway explanatory perspective view showing a green tire after the second stage in the manufacturing process of the pneumatic radial tire of the present invention, and Fig. 11 is the same as above. FIG. 12 is a partially cut-away perspective explanatory view showing the product tire after vulcanization of the pneumatic radial tire. One layer of held cover on the outer layer,
FIG. 2 is a partially cutaway explanatory plan view illustrating an example of a splice portion of a single-layer helmet cover when the direction of the heat-shrinkable fiber cord is arranged at approximately 0° with respect to the circumferential direction of the tire. 6... One layer of heald cover, 6a... Splice part. Agent: Patent Attorney Shin Ogawa - Patent Attorney Ken Noguchi Teru Patent Attorney Kazuhiko Saishita Figure 1 Figure 2 Rigidity

Claims (1)

[Claims] 1. In the second stage of the manufacturing process of a pneumatic radial tire, a belt cover layer is placed on the outermost layer of the belt layer so that the direction of the heat-shrinkable fiber cords is approximately 0° with respect to the tire circumferential direction. When arranging the belt cover, if the splice ramp amount at the center of the single-layer splice part of the belt cover is bl, and the splice wrap amount at both left and right ends is b2, then the splice wrap amount b2 at both left and right ends is 0.5b+~0. A method for manufacturing a pneumatic radial tire, characterized in that the pneumatic radial tire is in the range of .8b1. 2. The direction of the circumferential edge of the splice part of one layer of the belt cover is 15° to 60° measured from the acute angle side with respect to the tire circumferential direction.
A method for manufacturing a pneumatic radial tire according to claim 1, characterized in that: 3. The method for manufacturing a pneumatic radial tire according to claim 1, characterized in that the amount of splice lap at the center of the splice portion of the single layer of the belt cover is set to 60*n to 8o.