JPH0440179B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing a tire that can improve drainage performance and durability by providing a plurality of incisions of varying depth over substantially the entire width of the tread surface after vulcanization. Generally, in order to improve the braking force and turning performance of a tire on a wet road surface, it is necessary to effectively eliminate water interposed between the tread surface and the road surface. Therefore, the rib type or lug type is mainly adopted as the tread pattern, and the zigzag-shaped main groove extending in the circumferential direction has a large groove width and groove depth, and extends from the main groove to the tread end. Drainage performance is improved by providing wide horizontal grooves. On the other hand, in such tires, especially steel radial tires for heavy vehicles, due to the heavy load and ground pressure distribution of the tread, so-called railway wear occurs along the convex portions on both edges sandwiching the main groove. There are problems such as wear, so-called heel-and-toe wear in which uneven wear occurs at the rear end of the block in the running direction, or so-called shoulder-drop wear in which wear progresses at the tread shoulder portion compared to the center of the tread. For example, railway wear can be prevented by providing narrow horizontal grooves at regular intervals along both edges of the main groove, and shoulder drop wear can be prevented by providing a large number of narrow horizontal grooves at both ends of the tread. However, since such horizontal grooves have conventionally been formed at the same time as vulcanization by installing a thin blade protruding into the mold in advance, the width of the groove should be reduced from the perspective of preventing deformation of the blade. There is a limit to
As a result, there was a problem in that the decrease in the rigidity of the tread portion actually deteriorated the wear resistance or had an adverse effect on the drainage performance. The purpose of the present invention is to provide a tire manufacturing method capable of solving such problems, and after molding a green cover tire and vulcanizing it, the tread surface of the tire is vulcanized over almost the entire width of the tread surface of the tire. It is characterized by providing a plurality of incisions that are inclined at an angle with respect to the width direction and whose depth varies in the width direction. An embodiment of the present invention will be described below with reference to the drawings. First, an example of a tire obtained by the tire manufacturing method of the present invention will be described. Fig. 1 shows an expanded view of the right half of the tread portion 2 of the tire 1, and Fig. 2 shows an A-A cross section thereof. In the tire 1, a zigzag-shaped main groove 4 continuous in the circumferential direction is provided on the tread surface 3 at the center and both sides, and the tread portion 2 is connected to a tread center portion 5 and a pair of left and right treads. A carcass 7 consisting of cords arranged at an angle of 80° to 90° with respect to the equator C of the tire, and a steel carcass on which the tread portion 2 is arranged. The tire 1 is provided with a belt layer 8 made of cord, and a large number of incisions 9 inclined with respect to the equator C of the tire are provided in the circumferential direction over the entire width of the tread portion 2. The tire is manufactured by forming the green cover tire, vulcanizing it, and then forming the incisions 9 therein. The raw cover tire has a toroidal shape in which a carcass 7, a belt layer 8, a bead part (not shown), and a tread part 2 are assembled on a forming drum, and this is placed in a mold by a conventional method and vulcanized. After that, a cut 9 is made in the original tire taken out from the mold using a knife. Here, the cuts 9 are the main grooves 4 and 4 of the tread portion 2, which are carved by a sharp and relatively thin knife, bit, grindstone, saw blade, etc., with a thickness of about 3 mm or less.
This is a cut that crosses the ridge between the grooves, and can be formed without substantially having a groove width, and is provided obliquely to the equator C of the tire over the entire width of the tire 1 as described above. The lateral grooves of conventional tires, which are formed at the same time as vulcanization in a mold equipped with blades, have relatively wide groove widths because they cannot be made narrow in principle. In the tire 1, since the groove width of the notch 9 can be made so small that it can be practically ignored, both edges of the notch 9 are strongly pressed against each other due to compressive stress acting within the ground contact surface. It functions as if it were a continuous, integrated rubber layer, and by improving rigidity, it can prevent a decrease in wear resistance. In addition, in response to bending stress that occurs near the ground contact edge, the notches 9 can be flexibly deformed, making it possible to effectively disperse and alleviate the stress, which prevents shoulder drop wear of the tread portion 2, etc. This improves the spring-off and depression, that is, the grip. In addition, both edges of the cut 9 that is opened during bending and deformation cut the water film, thereby improving drainage in the direction of the main groove 4. To enhance this effect, cut 9
It is preferable that the angle is substantially linear over the entire width of the tread portion 2 and inclined at an angle of 30° to 90°, preferably 50° to 80° with respect to the equator C of the tire. If the inclination angle of the notches 9 is too small, the effect of preventing uneven wear will be reduced and the effect of improving wet grip properties will be reduced. Next, in the present invention, the depth d of the cut changes in the width direction of the tread, as shown in FIG. 3, which shows the cross section taken along line BB in FIG. 1, and in FIG. 4, which shows the cross section taken along line C-C in FIG. In the B-B cross section shown in Figure 3, the cutting depth increases from the tread end in the direction of the equator C, whereas in the CC cross section shown in Figure 4, the cutting depth increases from the tread end in the equator C direction. Cut depth is reduced. The incisions made at regular intervals in the circumferential direction of the tire are arranged so that the depth thereof increases and decreases in the equator C direction alternately.
This arrangement strengthens the tread rubber at the bottom of the cut and prevents damage to the tread rubber. In addition, in the present invention, it is also possible to use incisions with uniform depth in the width direction and incisions with varying depths.
Here, the depth d of the cut 9 is the groove depth D of the main groove 4.
The distance L between the notches 9 is in the range of 5 to 50 mm, preferably 10 to 30 mm. If an excessively large number of notches 9 are provided, the rigidity of the tread 2 will be reduced and the handling stability and wear resistance will be impaired. Note that the notches 9 can be arranged at irregular intervals in addition to regular intervals in the circumferential direction, and can also be formed so as to periodically repeat several kinds of intervals. Furthermore, several types of cuts with different groove depths d may be mixed. Note that the cut 9 is made by normal machining from the viewpoint of productivity and processing accuracy.
Furthermore, the cutting is done using an automatic cutting machine that can adjust the cutting position and angle. For example, this machine includes a tire mounting means for supporting the tire around a predetermined axis, a cutting means for forming an incision over the entire width of the tire tread, and a cutting means for cutting the surface of the tire tread. It includes a means for moving in the width direction, and a predetermined incision is made on the surface of the tread portion by suppressing the interlocking of the latter means. As described above, in the tire manufacturing method of the present invention, the incisions are made after the tire is vulcanized, so that the incisions can be formed to have a narrow width with substantially no groove width. For this reason, compressive stress creates a strong pressure contact between the notches within the ground contact surface, and they behave as if they were a continuous rubber band, and against bending stress near the contact edge, they jump without any unreasonable stress due to the notch effect acting on them. , it becomes possible to step on it, and rolling resistance and wear resistance are improved. Furthermore, the notches opened by the bending deformation of the tread rubber cut the water film, effectively draining water toward the main groove, and improving wet grip performance. In addition, there is no need to perform complicated processing such as installing blades to form horizontal grooves on the mold, which reduces mold costs, and allows users to freely change the shape and dimensions of the cut to suit their needs. There are advantages that can be achieved. The manufacturing method of the present invention can be applied to various types of tires such as passenger car tires and heavy vehicle tires, such as rib type, lug type, and blot type. There are 2 to 5 of them. Suitable for use in steel radial tires for truck buses. Example 1 shown in FIGS. 1, 2, 3, and 4.

[Table] 000R20 steel radial tires were made with cuts according to the specifications shown in Table 1 so that the direction of change in depth was alternately reversed, and characteristics such as wear resistance and wet grip were evaluated. Shown in the table.
It is clear that the tire manufactured by the tire manufacturing method of the present invention has improved various characteristics. Note 1: As shown in Figure 1. However, those with no incisions Note 2 Measured using a trailer tester under wet conditions on JARI's general test track, and shown as a relative value to the comparative example. The larger the value, the better. Note 3: The distance traveled until the tread wears 1 mm in an actual vehicle driving test is shown as a relative value. Note 4 Measured using a rolling resistance tester.

[Brief explanation of drawings]

FIG. 1 is a partial plan view illustrating a tire obtained by the manufacturing method of the present invention, and FIGS. 2, 3, and 4 are sectional views AA, BB, and C-C. It is a diagram. 1... Tire, 2... Tread portion, 3... Tread surface, 4... Main groove, 9... Notch, C... Tire equator.

Claims (1)

[Claims] 1. After forming a raw cover tire and vulcanizing it,
A method for manufacturing a tire, comprising providing a plurality of incisions over substantially the entire width of the tread surface of the tire at angles oblique to the equator of the tire and varying in depth in the width direction. 2. The method of manufacturing a tire according to claim 1, wherein the incisions are substantially linear and provided at equal intervals in the circumferential direction of the tire. 3. The method of manufacturing a tire according to claim 1, wherein the incision is inclined at an angle of 30° to 90° with respect to the equator of the tire. 4 The above-mentioned cuts are 5 to 50 in the circumferential direction of the tire.
The method for manufacturing a tire according to claim 1, wherein the tires are provided at intervals of mm. 5. The method of manufacturing a tire according to claim 1, wherein the tread surface of the tire has two to five zigzag-shaped main grooves continuous in the circumferential direction. 6. The method for manufacturing a tire according to claim 5, wherein the depth of the cut is in a range of 50 to 110% of the depth of the main groove. 7. The method of manufacturing a tire according to claim 1, wherein the tire is a steel radial tire for trucks and buses.