JP2008087628A - Pneumatic tire and tire mold - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of entirely exerting a stone non-biting property by appropriately shaping a protrusion formed at the channel bottom, and a tire mold for molding the pneumatic tire. <P>SOLUTION: At the channel bottom 9a of a circumferential groove 9 formed on a tread surface, a protrusion 10 is formed extending along the extending direction of the circumferential groove 9, and a communication rubber part 13 having a communication hole 18 for making a protrusion forming part 16 communicate with a groove wall forming part 17 of a groove forming skeleton 15 arranged at a tire mold is arranged at least at either of the side wall of the protrusion 10 and the groove wall 9b of the circumferential groove 9. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a pneumatic tire in which a protrusion is provided on a groove bottom of a groove portion of a tread surface, and a tire mold for molding the pneumatic tire.

  The tread surface of a pneumatic tire is usually provided with groove portions such as circumferential grooves and lateral grooves and land portions divided by the groove portions, and various tread patterns according to required tire performance and use conditions are provided. It is formed. When running on a gravel road that is not leveled, the groove on the road may get caught on the road, and when the tire rolls in such a state, the force that pushes and widens the groove is repeated. There was a problem that the stones that acted or the sandwiched stones entered the groove bottom and caused damage such as cracks at the groove bottom.

  For this problem, as described in the following Patent Documents 1 to 3, a protrusion extending along the extending direction of the groove is provided on the groove bottom of the groove, thereby preventing stone biting. Proposed. However, as a precondition thereof, it is necessary that the shape of the ridge is appropriately formed, and if the ridge is chipped, the stone biting resistance is not sufficiently exhibited.

By the way, the tread pattern of the tire is formed by the molding surface portion of the tire molding die, and the groove portion is formed by pressing the groove forming bone protruding from the molding surface portion against the tread surface of the green tire. Accordingly, by forming the ridge forming portion in the groove bottom forming portion of the groove forming bone, unvulcanized rubber is applied to the ridge forming portion from the groove bottom side of the tire (the groove bottom forming portion side of the tire mold). The protrusions as described above can be integrally provided. However, if the rubber formation in the ridge forming portion is insufficient, the ridge may be chipped and the like, and the stone biting resistance may not be sufficiently exhibited, resulting in a product defect.
Japanese Patent Laid-Open No. 10-35224 JP 2000-185525 A JP 2002-29218 A

  The present invention has been made in view of the above circumstances, and the purpose thereof is a pneumatic tire capable of sufficiently exhibiting stone biting resistance by appropriately forming the shape of the protrusion provided on the groove bottom, and its The object is to provide a tire mold for molding a pneumatic tire.

  The above object can be achieved by the present invention as described below. That is, the pneumatic tire of the present invention is a pneumatic tire in which a groove portion and a land portion divided by the groove portion are provided on a tread surface, and the groove bottom of the groove portion extends along the extending direction of the groove portion. And a communication rubber portion formed by a communication hole that communicates the groove forming portion and the groove wall forming portion of the groove forming bone provided in the tire mold. And at least one of the groove walls of the groove. According to such a configuration, the supply of the unvulcanized rubber to the ridge forming portion at the time of forming the tread pattern is performed not only from the groove bottom side but also from the groove wall side through the communication hole. The formation of the shape is appropriately made, and the stone biting resistance by the protrusions can be sufficiently exhibited.

  In the above, it is preferable that the communication rubber portion has a line protrusion formed by the communication hole and extending toward a tip side of the protrusion on a side surface of the protrusion. According to this configuration, the unvulcanized rubber supplied through the communication hole is smoothly filled on the tip side of the ridge forming portion, and the shape of the tip side portion of the ridge is more appropriately formed. Thus, the stone biting resistance due to the protrusions can be sufficiently exhibited.

  Further, the tire molding die of the present invention is the tire molding die in which the groove forming bone for forming the groove portion of the tread surface protrudes from the molding surface portion for forming the tread pattern of the pneumatic tire. The bone is recessed in the groove bottom forming portion that forms the groove bottom of the groove portion, the groove wall forming portion that forms the groove wall of the groove portion, and the groove bottom forming portion, and the groove portion extends to the groove bottom. A ridge forming portion that forms a ridge extending along the existing direction, and a communication hole that communicates the ridge forming portion and the groove wall forming portion. As a result, when forming the tread pattern, the unvulcanized rubber is supplied to the protrusion forming part from the groove bottom side of the tire and also supplied from the groove wall side through the communication hole. The unvulcanized rubber is smoothly filled in the ridge, and the shape of the protrusion is appropriately formed.

  In the above, it is preferable that the communication hole has a groove portion that faces a side wall of the protrusion forming portion and extends toward a distal end side of the protrusion forming portion. With this configuration, the unvulcanized rubber supplied through the communication hole is smoothly filled on the tip side of the ridge forming portion, and the shape of the tip side portion of the ridge is more appropriately formed.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a half sectional view of a tire meridian showing an example of a pneumatic tire according to the present invention. FIG. 2 is a development view of the tread surface of the pneumatic tire. FIG. 3 is an enlarged perspective view of a part of FIG.

  In the present embodiment, as shown in FIGS. 1 and 2, circumferential grooves 9 as groove portions are continuously provided in the tire circumferential direction on the tread surface which is the outer circumferential side surface of the tread portion 7, and the circumferential direction thereof. Land portions divided by the grooves 9 are provided as rib patterns based on the ribs 5. Of the four circumferential grooves 9, the ridges 10 extend along the tire circumferential direction, which is the extending direction of the circumferential grooves 9, on the groove bottom 9 a of the circumferential groove 9 located on the outermost side in the tire width direction. It is installed.

  As shown in FIG. 3 in an enlarged manner, the ridge 10 includes a top portion 11 that constitutes a central portion and an upper portion in the height direction, and a base portion 12 that constitutes a lower portion in the height direction. The top portion 11 protrudes toward the tire outer peripheral side, and in the present embodiment, has a vertically long cross-sectional substantially rectangular shape. The base part 12 is narrower than the top part 11, and is interposed between the top part 11 and the groove bottom 9a so as to connect them together.

  The communication rubber portion 13 has a plate shape between the side surface of the protrusion 10 and the groove wall 9b, and is integrally connected to the lower portion of the top portion 11 and the side surface of the base portion 12, the groove wall 9b, and the groove bottom 9a. Is provided. As shown in FIG. 2, the communication rubber portion 13 is preferably spaced apart by 10 to 50 mm, more preferably 30 to 40 mm along the extending direction of the circumferential groove 9.

  The circumferential groove 9, the protrusion 10, and the communication rubber part 13 are formed by groove forming bones 15 as shown in FIG. The groove forming bone 15 protrudes from a molding surface part of a tire mold for molding a tread pattern of a pneumatic tire and has a shape corresponding to the circumferential groove 9. The groove forming bone 15 includes a groove bottom forming portion 14 that forms the groove bottom 9a, a groove wall forming portion 17 that forms the groove wall 9b, a ridge forming portion 16 that forms the ridge 10, and a ridge forming portion. The side surface of 16 and the groove wall formation part 17 are connected, and the communication hole 18 which forms the communication rubber part 13 is provided.

  The ridge forming portion 16 is recessed from the groove bottom forming portion 14 toward the root side of the groove forming bone 15 and has a shape corresponding to the ridge 10. That is, it is provided on the root side of the groove forming bone 15, and is provided narrower than the first forming portion 16 a on the distal end side of the groove forming bone 15 and the first forming portion 16 a that forms the crown portion 11. And a second forming portion 16 b that forms the base portion 12. The communication hole 18 is provided in a slit shape on the distal end side of the groove forming bone 15.

  The groove forming bone 15 is depressed by the tread surface of the green tire to form the circumferential groove 9. At that time, the uncured rubber is supplied from the groove bottom 9a side (groove bottom forming part 14 side) to the protrusion forming part 16 to project the protrusions 10, but in the present invention, the communication holes 18 are formed. Since the unvulcanized rubber is also supplied from the groove wall 9b side, the unvulcanized rubber is smoothly supplied to the ridge forming portion 16, facilitating rubber filling, and the shape of the ridge 10 is appropriately formed. The

  In the present invention, the cross-sectional shape of the ridge is not particularly limited, and a conventionally known shape such as a rectangular cross-section having a substantially constant width can be applied without limitation, but like the ridge 10 of the present embodiment, the top of the head 11 and a base 12 that is narrower than the top 11 is particularly useful. In such a shape, since the entrance of the ridge forming portion 16 provided in the groove forming bone 15 becomes narrow, it is difficult to smoothly supply unvulcanized rubber, and the shape formation of the top portion 11 is particularly concerned. According to the present invention, the rubber filling to the protrusion forming portion 16 is facilitated as described above, and the shape of the crown portion 11 is appropriately formed.

  In the present embodiment, as shown in FIG. 3, the ridge line portion 11 a on the tire outer peripheral side of the top portion 11 is formed with a curved surface having an arcuate cross section. Therefore, it becomes easier to fill the protrusions 16 with rubber, and the shape of the crown 11 can be appropriately formed.

  In addition, according to the protrusion 10, the stone biting property superior to the conventional one can be exhibited. That is, as shown in FIG. 5, when the pebbles S are sandwiched between the groove wall 9 b and the ridge 10, the top 11 is easily tilted around the narrow base 12, and the ridge 10 is Since it deforms and deforms as a whole, a reaction force that pushes up the pebbles S on the side surfaces of the ridges 10 is likely to occur based on the deformation restoring force of the ridges 10, and the ridges 10 discharge the pebbles S out of the grooves. It works like this.

  In addition, since the crown portion 11 easily tilts, the pebbles S cannot be held strongly, and the pebbles S are easily discharged out of the groove by the centrifugal force when rolling the tire. In addition, in the state where the pebbles S are sandwiched, the interval between the groove wall 9b on the left side of the example and the top 11 is narrow, and the intrusion of pebbles into this gap is suppressed. On the other hand, in the ridge having a certain width, the side surface of the ridge is locally deformed and held so as to wrap the pebbles, so the reaction force as described above hardly occurs and the pebbles easily come out. I can't.

  Further, since the base 12 is narrower than the top 11, it is possible to ensure a large volume on the groove bottom 9 a side of the circumferential groove 9, maintaining drainage even in a state where wear has progressed, and excellent Wet performance can be demonstrated.

  In the present embodiment, the side surface of the base 12 is formed in a shape constricted by a curved surface having an arcuate cross section, and the radius of the arc is preferably 0.5 to 2.0 mm. When the pebbles S are sandwiched, the parietal portion 11 can be easily and reliably tilted around the constricted portion of the base portion 12. In addition, since the base 12 is narrower than the top 11, the arc can be formed with a relatively large diameter, and a groove bottom crack starting from the root of the protrusion 10 can be effectively suppressed. .

  The side surface of the base portion 12 is smoothly connected to the side surface of the top portion 11 and the groove bottom 9a. From this, the flexibility of the bending deformation of the ridge 10 is increased, and a reaction force for discharging the pebbles S is easily obtained, and there is no portion where the distortion is easily concentrated, and the root of the ridge 10 is the starting point. Groove bottom cracks can be suppressed.

  In the present embodiment, the upper surface of the communication rubber portion 13 is inclined toward the tire outer peripheral side from the groove wall 9 b toward the protrusion 10. Thereby, the supply of unvulcanized rubber to the ridge forming portion 16, in particular, the supply to the first forming portion 16 a that forms the crown portion 11 is smoothly performed, and rubber filling becomes easier. Moreover, since the tilting of the crown 11 is not hindered, the stone biting resistance by the ridges 10 can be sufficiently exhibited.

  Here, as shown in FIG. 3, when the groove depth of the circumferential groove 9 is D and the height of the protrusion 10 is H, the ratio H / D of the height H to the groove depth D is 0.2. <H / D <0.5 is preferably satisfied, and 0.3 <H / D <0.4 is more preferable. When this H / D is 0.2 or less, the usefulness of the rubber filling smoothing effect of the ridge forming portion 16 is reduced, and the cost for improving the stone biting resistance tends to be reduced. On the other hand, if H / D is 0.5 or more, the drainage performance may be reduced and the WET performance may be impaired.

  Further, when the maximum width of the top portion 11 of the ridge 10 is W1 and the minimum width of the base portion 12 is W2, the ratio W2 / W1 of the minimum width W2 to the maximum width W1 is 0.5 ≦ W2 / W1 ≦ 0.9. Is preferably satisfied, and more preferably 0.7 ≦ W2 / W1 ≦ 0.8. If this W2 / W1 is less than 0.5, there is a concern that the resistance when the vulcanization is finished and the mold is released from the tire mold becomes large, and the base portion 12 is easily broken. On the other hand, when W2 / W1 exceeds 0.9, the protrusion 10 is flexibly bent and hardly deformed, and there is a tendency that the margin for improving the stone biting resistance tends to be small.

  Further, when the groove bottom width of the circumferential groove 9 is W3, the ratio W1 / W3 of the maximum width W1 to the groove bottom width W3 preferably satisfies 0.2 ≦ W1 / W3 ≦ 0.6, and 0.3 More preferably, ≦ W1 / W3 ≦ 0.5 is satisfied. When W1 / W3 is less than 0.2, the reaction force generated on the protrusion 10 tends to be small, and when W1 / W3 exceeds 0.6, the protrusion 10 tends to bend and be difficult to deform. .

  The pneumatic tire of the present invention is the same as a conventional pneumatic tire except that the above-described protrusions and communication rubber portions are provided in the groove portion of the tread surface, and any known materials, shapes, structures, manufacturing methods, etc. Can also be employed in the present invention. However, it is effective as a heavy-duty pneumatic tire to be mounted on gravel roads where pebbles are scattered and trucks and construction vehicles that have a lot of opportunities to move on leveling grounds, because it can exhibit resistance to biting stones by ridges. .

  In the present embodiment, an example of a heavy duty pneumatic tire is shown. In this tire, as shown in FIG. 1, the carcass ply 1 is wound around the bead core 3 and the rubber filler 4 arranged in the bead portion 2 from the inside to the outside, and the winding end is rubber. The filler 4 is disposed in the middle of the oblique side. The pad 6 is provided so as to sandwich the winding end of the carcass ply 1 together with the rubber filler 4.

  The carcass ply 1 is composed of one or a plurality of plies in which steel cords, high-strength organic fiber cords, and the like are arranged in the tire radial direction. The bead core 3 is made of a laminate of a bead wire and a covering rubber, and the rubber filler 4 is made of a hard rubber having a substantially triangular cross section whose bottom is an arc.

  A belt layer 8 is disposed on the tire outer periphery side of the carcass ply 1 of the tread portion 7, and a belt reinforcing layer is disposed on the outer periphery as necessary. The rubber hardness of the tread rubber is not particularly limited as long as it is normally used, and the tread pattern as described above is formed on the tread surface. Inner liner rubber for maintaining air pressure is provided on the inner peripheral side of the carcass ply 1, and side wall rubber is provided on the outer peripheral side of the carcass ply 1 between the tread portion 7 and the bead portion 2.

  In the tread pattern illustrated in FIG. 2, the central rib 5 near the tire equator line CL and the ribs 5 on both sides thereof are provided with closed sipes for the purpose of improving the WET performance. The shape of the rib 5 is not particularly limited. For example, the rib 5 may be divided by a circumferential groove extending zigzag. In such a case, a protrusion extending in a zigzag shape or a wave shape is provided along the extending direction of the circumferential groove.

  In the heavy load pneumatic tire, the groove bottom width W3 of the circumferential groove 9 is 7 to 16 mm or 10 to 12 mm, the groove depth D of the circumferential groove 9 is 10 to 20 mm or 14 to 16 mm, and the circumferential groove 9 The groove wall angle [theta] is 0 to 20 [deg.]. At this time, as an example of the dimensions of the protrusion 10, the height H is 5 to 7 mm, the maximum width W1 of the top 11 is 3 to 5 mm, and the minimum width W2 of the base 12 is 2.5 to 3.0 mm. Can be mentioned.

[Other Embodiments]
(1) FIG. 6 is a perspective sectional view showing an example of another embodiment of the present invention, in which the communicating rubber portion 13 extends toward the tip side of the ridge 10 on the side surface of the ridge 10. The configuration is the same as that of the above-described embodiment except that. The communication rubber portion 13 is formed by a groove forming bone 15 as shown in FIG. 7, and the communication hole 18 provided in the groove forming bone 15 faces the side wall of the ridge forming portion 16. And it has the groove part 18a extended toward the front end side of the protrusion formation part 16. As shown in FIG. When forming the tread pattern, the unvulcanized rubber supplied through the communication hole 18 is smoothly filled into the tip side of the ridge forming portion 16 through the groove portion 18a, so that the shape of the top portion 11 is further increased. Done appropriately.

  The protrusion 13a preferably has a gradually reduced protrusion height on the tip side of the protrusion 10, and similarly the groove 18a preferably has a gradually reduced depth on the tip side of the protrusion forming part 16, As a result, the appearance of the protrusion 10 is improved. In the example shown in the figure, the protrusion 13a reaches the ridge line portion 11a on the tire outer periphery side of the top portion 11, so that the shape formation of the top portion 11 becomes better, but for example, the center of the top portion 11 in the height direction. It may be terminated at the portion, and an improvement effect corresponding to that may be obtained.

  (2) In the above-described embodiment, the example in which the plate-like communication rubber portion is provided so as to be integrally connected to the lower portion of the top and the side surface of the base portion, the groove wall, and the groove bottom is shown. Is not limited to this, and may be as shown in FIG. The protrusion 40 includes a top portion 41 and a base portion 42, and is provided with a columnar communication rubber portion 46 that extends from the groove wall 9 b toward the side surface of the top portion 41.

  This communication rubber portion 46 is formed by the communication hole 19 of the groove forming bone 15 as shown in FIG. 9, and the unvulcanized rubber is directly supplied to the portion corresponding to the top 41 of the protrusion forming portion 16. For this reason, the shape of the top 41 is better formed. The communication rubber portion 46 is cut at any point when vulcanization is finished and released from the tire mold, and is provided in at least one of the side surface of the top portion 41 and the groove wall 9b.

  (3) In the above-described embodiment, an example in which the tread pattern is a rib pattern has been shown. However, the present invention is not limited to this, and the pattern may include a part or all of a block as a land portion. The groove part provided with the protrusion may be a lateral groove or an inclined groove. However, since the occurrence of stone biting is remarkable in the circumferential groove, it is preferable that the protrusion is provided at the groove bottom of at least one circumferential groove.

  (4) In the above-described embodiment, the example in which the protrusion and the communication rubber portion are provided only in the circumferential groove located on the outermost side in the tire width direction is shown. However, the present invention is not limited to this, for example, the tire width direction center side You may provide only in the groove part located in, or may provide in all the groove parts of a tread surface. Moreover, in this invention, you may provide a communication rubber part in the both sides of a protrusion.

The tire meridian half sectional view showing an example of a pneumatic tire according to the present invention Development view of the tread surface of the pneumatic tire 1 is an enlarged perspective view of a part of FIG. The perspective sectional view showing the bone for slot formation provided in the tire mold concerning the present invention Cross-sectional view of relevant parts showing a state where pebbles are sandwiched in the groove of a pneumatic tire The perspective sectional view showing the pneumatic tire concerning another embodiment of the present invention. The perspective sectional view showing the bone for slot formation provided in the tire mold concerning another embodiment of the present invention. The perspective sectional view showing the pneumatic tire concerning another embodiment of the present invention. The perspective sectional view showing the bone for slot formation provided in the tire mold concerning another embodiment of the present invention.

Explanation of symbols

5 rib 7 tread portion 9 circumferential groove 9a groove bottom 9b groove wall 10 ridge 11 head top portion 11a ridge line portion 12 base portion 13 communicating rubber portion 14 groove bottom forming portion 15 groove forming bone 16 ridge forming portion 17 groove wall forming portion 18 Communication hole D Groove depth H of circumferential groove S Height of ridge S Pebble W1 Maximum width W2 Top width W3 Minimum width W3 Groove bottom width of circumferential groove

Claims (4)

In a pneumatic tire provided with a groove part and a land part divided by the groove part on the tread surface,
The groove bottom of the groove part is provided with a protrusion extending along the extending direction of the groove part, and the communication for communicating the protrusion forming part of the groove forming bone provided in the tire mold and the groove wall forming part. A pneumatic tire characterized in that a communicating rubber portion formed by a hole is provided on at least one of a side surface of the protrusion and a groove wall of the groove portion.   2. The pneumatic tire according to claim 1, wherein the communication rubber portion includes a ridge formed by the communication hole and extending toward a tip side of the ridge on a side surface of the ridge. In the tire molding die in which the groove forming bone for forming the groove portion of the tread surface protrudes from the molding surface portion that forms the tread pattern of the pneumatic tire.
The groove forming bone is recessed in the groove bottom forming portion that forms the groove bottom of the groove portion, the groove wall forming portion that forms the groove wall of the groove portion, and the groove bottom forming portion, A tire molding die comprising: a ridge forming portion that forms a ridge extending along an extending direction of the groove portion; and a communication hole that communicates the ridge forming portion and the groove wall forming portion.   The tire forming die according to claim 3, wherein the communication hole has a groove portion facing a side wall of the protrusion forming portion and extending toward a tip side of the protrusion forming portion.

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