JP2019081514A - Pneumatic tire for heavy load - Google Patents

Abstract

To provide a pneumatic tire for a heavy load that can prevent occurrence of a bare by improving air flow between a vulcanization molding die and an external surface of a raw tire.SOLUTION: A pneumatic tire for a heavy load 1 has, on a surface of a sidewall part 3, a serration part 10 in which a plurality of ridges 11 extending in a tire radial direction are arranged side by side in a tire circumferential direction, and a convex vent line 50 that extends in the tire circumferential direction to connect with each ridge 11. The ridges 11 have their pitches changing in the tire circumferential direction.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a heavy duty pneumatic tire.

  Conventionally, in a pneumatic tire for a passenger car, there is known a technique of forming a serration portion in order to suppress a bear which easily occurs on the outer surface of a sidewall portion in vulcanization molding (see, for example, Patent Document 1) ).

  However, in the heavy load pneumatic tire, because the height of the tire is large, only by providing the serration portion on the outer surface of the sidewall portion, it is possible between the vulcanized mold and the outer surface of the green tire. In some cases, trapped air can not be discharged sufficiently, and further improvement is expected.

JP 2001-163 018 A

  The present invention has been devised in view of the above-described actual situation, and is intended for heavy load which can improve the flow of air between the vulcanized mold and the outer surface of the green tire and suppress the generation of the bear. The main purpose is to provide a pneumatic tire.

  According to the present invention, a serration portion in which a plurality of ridges extending in the tire radial direction are arranged in parallel in the tire circumferential direction on the surface of a sidewall portion, and a convex vent line extending in the tire circumferential direction and connected to each ridge Wherein the pitch of the ridges varies in the circumferential direction of the tire.

  In the heavy load pneumatic tire according to the present invention, the serration portion includes a first serration portion and a second serration portion alternately arranged in a tire circumferential direction, and the pitch of the second serration portion is the first serration portion. Preferably, the pitch is smaller than the pitch in one serration portion.

  In the heavy load pneumatic tire according to the present invention, it is preferable that the pitch of the second serration portion is 0.5 to 0.8 times the pitch of the first serration portion.

  In the heavy load pneumatic tire according to the present invention, a spew suctioned up by a vent hole of a tire vulcanizing mold is formed in the vent line, and the second serration portion is the sidewall in a tire side portion. It is desirable that the region be formed in a region including radiation connecting the tire rotation axis and the spew when the part is viewed from the front.

  In the heavy load pneumatic tire according to the present invention, the second serration portion is preferably formed in an area of 10 ° to 20 ° on one side and the other side in the tire circumferential direction from the radiation.

  In the heavy load pneumatic tire according to the present invention, the height of the vent line from the bead base line is preferably 25 to 35% of the tire height.

  In the heavy load pneumatic tire according to the present invention, it is preferable that the serration portion is formed in the region of 50 to 65% of the tire height outside the tire radial direction from the vent line.

  The heavy load pneumatic tire according to the present invention has a serration portion in which a plurality of ridges extending in the tire radial direction are arranged in parallel in the tire circumferential direction on the surface of the sidewall portion and a convex portion extending in the tire circumferential direction and connected to each ridge And the like. That is, in the vulcanizing mold of the heavy load pneumatic tire, the radial shallow groove for forming the ridge of the serration portion communicates with the circumferential groove for forming the vent line. And since the pitch of the ridge changes in the tire circumferential direction, the pitch of the radial shallow grooves also changes in the tire circumferential direction. That is, the serration portion includes a region in which the ridges are roughly arranged and a region in which the ridges are densely arranged. Then, in the region where the ridges are densely arranged, the width of the radial shallow groove is narrow and the depth thereof is shallow, the flow of air flowing through the radial shallow groove becomes fast, and the generation of the bare is suppressed. In addition, the shadow of the serration portion changes in the tire circumferential direction, and the appearance performance of the heavy load pneumatic tire is improved.

1 is a perspective view showing an embodiment of a heavy load pneumatic tire according to the present invention. FIG. 2 is a meridional cross-sectional view of the heavy load pneumatic tire of FIG. 1; FIG. 3 is a meridional cross-sectional view showing the heavy load pneumatic tire of FIG. 2 together with a vulcanized mold. BRIEF DESCRIPTION OF THE DRAWINGS It is sectional drawing which cut | disconnects and shows the vulcanized molding die and green tire in the initial stage of a vulcanization molding process in a tire circumferential direction. It is a side view of the heavy duty pneumatic tire of FIG. (A) And (b) is sectional drawing which shows the variation of the shape of the serration part of FIG.

Hereinafter, an embodiment of the present invention will be described based on the drawings.
FIG. 1 is a perspective view of a heavy load pneumatic tire 1 of the present embodiment. The heavy load pneumatic tire (hereinafter sometimes simply referred to as “tire”) 1 of the present embodiment includes a tread portion 2, a sidewall portion 3 and a bead portion 4.

  FIG. 2 is a tire meridional cross-sectional view including a tire rotation axis in a normal state. Here, the normal state is a non-loaded state in which the tire is rim-assembled on a normal rim and filled with a normal internal pressure. Hereinafter, the dimensions and the like of each part of the tire are values measured in this normal state unless otherwise mentioned.

  The “regular rim” is a rim that defines the standard for each tire in the standard system including the standard on which the tire is based, for example, “standard rim” for JATMA, “Design Rim” for ETRA, and TRA If it is "Measuring Rim".

  The "normal internal pressure" is the air pressure specified by each standard in the standard system including the standard to which the tire is based, and in the case of JATMA, the "maximum air pressure", and in the case of TRA, the table "TIRE LOAD LIMITS The maximum value described in "AT VARIOUS COLD INFlation PRESSURES" is "INFLATION PRESSURE" in the case of ETRTO.

  As shown in FIG. 2, the heavy load tire (hereinafter sometimes referred to simply as “tire”) 1 of the present embodiment is a toroid from the tread portion 2 through the sidewall portion 3 to the bead core 5 of the bead portion 4. And a belt layer 7 disposed radially outward of the carcass 6 and inward of the tread portion 2.

  The carcass 6 is formed of, for example, one carcass ply 6A in which a steel carcass cord is arranged at an angle of 70 to 90 degrees with respect to the tire circumferential direction. The carcass ply 6A is provided with a series of folded back portions 6b that are bent outward from the inside in the tire axial direction around the bead cores 5 at both ends of the main body portion 6a straddling between the pair of bead cores 5,5.

  A belt layer 7 is disposed radially outside the carcass 6 and inside the tread portion 2. The belt layer 7 is formed, for example, of at least two belt plies using a steel belt cord. In this example, a first belt ply 7A in which the belt cords are arranged at an angle of, for example, 60 ± 15 ° with respect to the tire circumferential direction, and the belt cords are laminated on the outer side thereof, for example A four-sheet structure is exemplified which includes second to fourth belt plies 7B to 7D arranged at a small angle of 35 °.

  The bead core 5 has, for example, a core body having a polygonal cross-sectional shape (for example, a hexagonal cross-sectional shape) in which a bead wire made of steel is wound in multiple rows and multistages.

  Bead apex rubber 8 is provided on the outer side of bead core 5 in the tire radial direction. The bead apex rubber 8 is disposed between the body portion 6a of the carcass ply 6A and the folded back portion 6b, and tapers from the bottom surface connected to the outer surface in the tire radial direction of the bead core 5 toward the outer end in the tire radial direction. Grow in shape.

  As shown in FIGS. 1 and 2, a serration portion 10 and a vent line 50 extending continuously in the tire circumferential direction are formed on the outer surface of the sidewall portion 3.

  The serration portion 10 includes a plurality of ridges 11 extending in the tire radial direction. The ridges 11 are arranged in parallel in the tire circumferential direction. The ridges 11 may be inclined with respect to the tire radial direction.

  The vent line 50 protrudes outward in the axial direction of the tire and extends continuously in the circumferential direction of the tire. The vent line 50 is connected to the ridge 11.

  The vent line 50 of the present embodiment is connected to each ridge 11 at an inner end 11 i of the ridge 11 in the tire radial direction. The vent line 50 may be connected to the ridge 11 at an outer end 11 o of the ridge 11 in the tire radial direction. Further, the vent line 50 may be connected to the ridge 11 between the inner end 11i and the outer end 11o.

  FIG. 3 shows the heavy load pneumatic tire 1 together with a vulcanized mold 100. In the vulcanization molding die 100 of the heavy load pneumatic tire 1, the radial direction shallow groove 111 for forming the ridge 11 of the serration portion 10 communicates with the circumferential direction groove 150 for forming the vent line 50. Therefore, in the side wall portion 3 in the vulcanization forming step, the air trapped between the vulcanization forming mold 100 and the green tire is vulcanized and formed through the radial direction shallow groove 111 and the circumferential direction groove 150 sequentially It is discharged to the outside of the mold 100. As described above, in the heavy load pneumatic tire 1, it is important to enhance the air discharge performance of the radial shallow groove 111 because the height of the tire is larger than that of a passenger car tire.

  As shown in FIG. 1, the pitch of the ridges 11 changes in the tire circumferential direction. For example, the serration portion 10 of the present embodiment includes a first serration portion 20 in which the ridges 11 are roughly arranged and a second serration portion 30 in which the ridges 11 are closely arranged. It is.

  FIG. 4 is a cross-sectional view showing the green tire 1R of the vulcanized mold 100 and the heavy duty pneumatic tire 1 at an early stage of the vulcanizing process, cut in the circumferential direction of the tire.

  The radial direction shallow groove 111 functions as a discharge groove for discharging the air between the outer surface of the green tire 1R and the tire molding surface of the vulcanization molding die 100. Since the pitch of the ridges 11 changes in the tire circumferential direction, the width of the radially shallow groove 111 is narrower and the depth is shallower in the second serrated portion 30 compared to the first serrated portion 20. As a result, in the second serration portion 30, the flow of air flowing in the radial direction shallow groove 111 is accelerated, and the generation of the bear is suppressed. Further, compared to the first serration portion 20, in the second serration portion 30, the density of the radial direction shallow groove 111 is high, so that more air can be discharged, and the generation of the bear is suppressed.

  Further, the shadow of the serration portion 10 changes in the tire circumferential direction, and the appearance performance of the heavy load pneumatic tire 1 is improved.

  As shown in FIG. 1, the first serrations 20 and the second serrations 30 are alternately arranged in the tire circumferential direction. As a result, the second serrations 30 excellent in air discharge performance at the time of vulcanization molding are distributed substantially uniformly in the tire circumferential direction. For this reason, the generation of the bear is prevented in the entire sidewall portion 3.

  The pitch P2 of the ridges 11 in the second serration portion 30 is preferably 0.5 to 0.8 times the pitch P1 of the ridges 11 in the first serration portion 20. When the pitch P2 is less than 0.5 times the pitch P1, the ridge height Q2 is insufficient, and the air discharge performance is deteriorated after the convex portion 112 of the second serration portion 30 abuts on the outer surface of the green tire 1R. There is a risk of In addition, the shadow of the second serration portion 30 may be blurred, and the appearance performance of the heavy load pneumatic tire 1 may be degraded. On the other hand, when the pitch P2 exceeds 0.8 times the pitch P1, the number of ridges 11 may be reduced, and the air discharge performance may be deteriorated.

  As shown in FIG. 3, in the circumferential groove 150 of the vulcanizing mold 100, a vent hole 151 for discharging the air in the circumferential groove 150 to the outside of the vulcanizing mold 100 is formed. There is. Along with this, the spew 51 sucked up by the vent hole 151 of the vulcanizing mold 100 is formed in the vent line 50 of the heavy load pneumatic tire 1.

  In the present embodiment, since the air discharge performance at the time of vulcanization molding is enhanced by the second serration portion 30, the generation of the bear can be suppressed even if the number of the vent holes 151 is reduced. Therefore, the appearance performance of the heavy duty pneumatic tire 1 can be improved by reducing the number of the spew 51. Moreover, in the process of cutting the spew 51 after the vulcanization process, the production efficiency is improved by reducing the spew 51 to be cut, and the spew 51 to be disposed of after cutting can be reduced.

  In the present embodiment, the pitch P1 of the ridges 11 in the first serration portion 20 is constant, and the pitch P2 of the ridges 11 in the second serration portion 30 is also constant. The pitch P1 may change in the tire circumferential direction, and the pitch P2 may also change in the tire circumferential direction. For example, the pitch P1 of the first serration portion 20 may gradually decrease or increase toward both ends in the tire circumferential direction in a range smaller than the pitch P2, and the pitch P2 of the second serration portion 30 may be a pitch P2 It may increase or decrease gradually toward both ends in the tire circumferential direction as long as it is smaller.

  FIG. 5 is a side view of the heavy load pneumatic tire 1. The second serration portion 30 is formed in a region including the radiation RL connecting the tire rotation axis O and the spew 51 when the sidewall portion 3 is viewed from the front in the tire side surface portion. As a result, the exhaust path from the air discharge space E of the second serration portion 30 (see FIG. 4) to the vent hole 151 via the circumferential groove 150 is shortened, and the air discharge performance during vulcanization molding is further enhanced. And the generation of bears is suppressed.

  It is desirable that the second serration portion 30 be formed in a region where the radiation angle θ2 is 10 ° to 20 ° on one side and the other side in the tire circumferential direction from the radiation RL.

  If the radiation angle θ2 is less than 10 °, there is a possibility that a region where the air discharge performance at the time of vulcanization molding can be enhanced can not be sufficiently obtained. When the radiation angle θ2 exceeds 20 °, when the green tire 1R comes in contact with the mold at the initial stage of the vulcanization process, the air discharging effect may be reduced. In addition, since the shade in the second serration unit 30 is blurred, the design of the entire serration unit 10 may be affected.

  In the heavy load pneumatic tire 1 of the form shown in FIG. 5, the second serration portion 30 is formed in the region of the radiation angle 2 · θ2. Similarly, the first serration portion 20 is formed in the region of the radiation angle 2 · θ1. Then, the radiation angle θ2 is equal to the radiation angle θ1. The radiation angle θ2 may be different from the radiation angle θ1.

  As shown in FIG. 2, the height H 0 of the vent line 50 from the bead base line BL is desirably 25 to 35% of the tire height H. If the height H0 is less than 25% of the tire height H, the serration portion 10 and the vent line 50 are located in a region where the strain of the bead portion 4 is large, and the surface of the serration portion 10 and the vent line 50 may be cracked. is there. When the height H0 exceeds 35% of the tire height H, the vent line 50 is disposed away from the vicinity of the tip portion of the bead apex rubber 8 in which a recess tends to occur in the green tire 1R, and air at the time of vulcanization molding There is a possibility that the emission performance can not be sufficiently improved.

  It is desirable that the serration portion 10 be formed in the region of 50 to 65% of the tire height H outside the vent line 50 in the tire radial direction. That is, 50 to 65% of the tire height H of the tire radial direction length H1 of the serration part 10 is desirable. If the height H1 is less than 50% of the tire height H, there is a possibility that the air discharge performance during vulcanization molding can not be sufficiently enhanced. When the height H1 exceeds 65% of the tire height H, when the green tire 1R comes in contact with the mold in the initial stage of the vulcanization process, the air discharging effect may be reduced. In addition, the serration portion 10 is positioned in a region where distortion of the buttress portion is large, and a crack may occur on the surface of the serration portion 10.

  In FIG. 6, (a) and (b) are cross-sectional views showing variations of the shape of the serration portion 10 of FIG. In the embodiment shown in FIG. 6A, the serration portion 10 has a trapezoidal ridge 11A in which the tip end of the cross section cut in the tire circumferential direction is angular. Such a serration portion 10 is clearly shaded, and enhances the appearance performance of the heavy load pneumatic tire 1. In the embodiment shown in FIG. 6B, the serration portion 10 has a trapezoidal ridge 11B in which the tip of the cross section cut in the tire circumferential direction is rounded. Such a serration portion 10 has a good rubber filling property, and the generation of a bear is suppressed. In addition, the serration portion 10 may have a triangular-shaped ridge in which the tip of the cross section cut in the tire circumferential direction is sharp.

  The ridge 11A may be formed in one of the first serration portion 20 and the second serration portion 30, and the ridge 11B may be formed in the other, and the ridge 11A and the ridge 11B may be formed in the first serration portion 20 and the second serration portion 30. May be mixed.

  As mentioned above, although the heavy load pneumatic tire of the present invention was explained in detail, the present invention is changed into various modes, without being limited to the above-mentioned concrete embodiment, and is carried out.

A heavy load pneumatic tire of size 315 / 80R22.5 having the basic structure of FIG. 2 was produced on the basis of the specifications of Tables 1 and 2 and the bare suppressing performance and appearance performance of each sample tire were tested. The main common specifications and test methods of each sample tire are as follows.
Carcass ply cord: steel Carcass ply: 1 Belt ply cord: steel Belt ply: 4 sheets

<Bear suppression performance>
One thousand samples of each sample tire were produced, and the generation of the bare after vulcanization molding was visually inspected. The result is expressed by the bear incidence rate, and the smaller the value, the better.

<Appearance performance>
The evaluator 1 sensory-evaluated the appearance of the pattern of the serration part 1 m away from each sample tire. A result is represented by the score which sets Example 1 to 100, and it is so favorable that a numerical value is large.

  As is clear from Table 1, it has been confirmed that the heavy load pneumatic tire of the example has significantly improved bear suppressing performance and appearance performance as compared with the comparative example.

  A heavy load pneumatic tire of size 315 / 80R22.5 having the basic structure of FIG. 2 was produced on the basis of the specifications of Table 2, and the bear suppressing performance and the crack resistance performance of each sample tire were tested. The main common specification of each sample tire and the test method regarding the bare restraint performance are the same as described above. The test method regarding crack resistance performance is as follows.

<Crack resistance performance>
Each sample tire is installed in a rim of 22.5 x 9.00, traveled for 600 km with a drum type running test machine under the conditions of internal pressure: 900 kPa, load: 4000 kg, speed: 90 km / h, side wall part The crack of was visually confirmed by the evaluator. A result is represented by the score which sets Example 10 to 100, and it is so favorable that a numerical value is large.

1: Heavy load pneumatic tire 3: Side wall portion 10: Serration portion 11: Ridge 20: First serration portion 30: Second serration portion 50: Vent line 51: Spew BL: Bead baseline H: Tire height H0: Height H1: Height P1: Pitch P2: Pitch RL: Radiation θ1: Radiation angle θ2: Radiation angle

Claims (7)

For heavy load, the surface of the sidewall portion has a serration portion in which a plurality of ridges extending in the tire radial direction are aligned in the tire circumferential direction, and a convex vent line extending in the tire circumferential direction and connected to each ridge A pneumatic tire,
The pitch of the ridges varies in the circumferential direction of the tire,
Heavy duty pneumatic tire. The serration portion includes a first serration portion and a second serration portion alternately arranged in the tire circumferential direction,
The heavy duty pneumatic tire according to claim 1, wherein the pitch in the second serration portion is smaller than the pitch in the first serration portion.   The heavy duty pneumatic tire according to claim 2, wherein the pitch in the second serration portion is 0.5 to 0.8 times the pitch in the first serration portion. In the vent line, spew sucked up at the vent hole of the tire vulcanizing mold is formed,
The heavy load according to claim 2 or 3, wherein the second serration portion is formed in a region including a radiation connecting the tire rotation axis and the spew when the sidewall portion is viewed from the front on the tire side surface portion. Heavy duty pneumatic tire.   The heavy duty pneumatic tire according to claim 4, wherein the second serration portion is formed in an area of 10 ° to 20 ° on one side and the other side in the tire circumferential direction from the radiation.   The heavy duty pneumatic tire according to any one of claims 1 to 5, wherein the height of the vent line from the bead base line is 25 to 35% of the tire height.   The heavy duty pneumatic tire according to claim 6, wherein the serration portion is formed in an area of 50 to 65% of the tire height outward in the tire radial direction from the vent line.

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