JP2007216885A - Pneumatic tire, and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire having excellent cutting resistance of a groove bottom. <P>SOLUTION: By providing a fiber-reinforced layer 18 on groove bottoms 14B of a plurality of main grooves 14 in the width direction formed in a tread part 12, any cut in the groove bottoms 14B caused by sharp rock or the like is absorbed by the fiber-reinforced layer 18, and reach of the cut to a belt layer or to a vicinity of the belt layer is suppressed. Thus, cut separation with the cut of the groove bottom 14B as a starting point is suppressed, and excellent cutting resistance of the groove bottom 14B is realized. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire for a construction vehicle used on a road surface that is susceptible to trauma, such as a bad road or a construction site, and a method for manufacturing the pneumatic tire.

  Conventionally, in a pneumatic tire for a construction vehicle having a so-called lug pattern in which a large number of lug grooves are arranged at predetermined intervals in the tire circumferential direction, the cut resistance is excellent for improving the cut resistance. Using a tread rubber (for example, Patent Document 1), increasing the tread gauge (deep groove), reducing the cut reaching the belt layer, and when the cut reaches the belt layer, the cut separation spreads from the cut Is generally reduced.

For this reason, in the market with high cutability in recent years, the separation from cuts received by the land due to the above-mentioned measures is decreasing. However, as the number of cuts received by the land decreases and the life cycle of the tire extends, the proportion of cut separation starting from the cut to the groove bottom by sharp rocks is increasing. However, the present situation is that almost no measures are taken against the separation starting from the cut injured in the groove bottom.
Japanese Patent Laid-Open No. 06-199103

Now, the tread gauge of the tread portion 102 of a general construction vehicle tire is a gauge B from the groove bottom 104B of the groove 104 to the belt layer than the gauge A from the land surface tread to the belt layer 105 as shown in FIG. Is thinner. For this reason, when the groove bottom 104B is cut by the sharp rock 103 or the like, the groove bottom 104B has a lower effect of buffering this cut than the land portion, so that the cut easily reaches the belt layer 105. was there.
If the vehicle continues running with such a cut, a large stress is repeatedly applied to the tip of the cut under the rolling load of the tire, and cracks or delamination along the surface of the outermost layer of the belt layer from this tip So-called cut separation occurs. Even if the cut does not reach the belt layer, if the cut is received to a position close to the belt layer, cut separation occurs under rolling load of the tire.

Here, the gauge B from the groove bottom to the belt layer was increased to try to prevent the cut by sharp rocks from reaching the belt layer. However, the tread gauge of the entire tire becomes very thick. The heat generation performance is worse and not realistic.
For these reasons, it has been a difficult problem to ensure sufficient cut resistance at the groove bottom.

  In view of the above facts, an object of the present invention is to provide a pneumatic tire excellent in cut resistance at the groove bottom and a method for manufacturing a pneumatic tire for manufacturing such a pneumatic tire. .

  In order to achieve the above object, a plurality of pneumatic tires according to claim 1 of the present invention are provided in a tread portion that contacts a road surface, a main groove having a groove depth of 70 to 200 mm, and a tire radius of the tread portion. A belt layer provided on the inner side in the direction, and a fiber reinforcing layer provided on the groove bottom of the main groove and extending in the longitudinal direction of the main groove.

Next, the effect of the pneumatic tire according to claim 1 will be described.
By providing a fiber reinforcement layer at the groove bottom of the main groove, cuts to the groove bottom due to sharp rocks can be buffered or prevented by the fiber reinforcement layer, so that this cut can reach the belt layer or the vicinity of the belt layer. Can be suppressed. Thereby, the cut separation starting from the cut at the groove bottom is suppressed. Therefore, the tire of the present invention is excellent in cut resistance at the groove bottom.
In addition, even when the cut is shallow (when the cut does not reach the belt layer), a large stress is repeatedly applied to the tip of the cut under the rolling load of the tire, and the cut progresses toward the belt layer. However, since the fiber reinforcing layer suppresses the stress, the progress of the cut can be suppressed. Therefore, the cut bottom resistance at the groove bottom is excellent.
Furthermore, even if the cut to the groove bottom reaches the belt layer or the vicinity of the belt layer, the surface of the outermost layer of the belt layer starts from the tip of the cut so that the fiber reinforcing layer suppresses a large stress acting on the tip of the cut. It is possible to suppress the progress of cracks or peeling along the surface. Therefore, the cut separation resistance is excellent.

  The pneumatic tire according to claim 2 of the present invention is the pneumatic tire according to claim 1, wherein the width of the main groove when new is W1 in the cross section perpendicular to the longitudinal direction of the main groove. When the width of the fiber reinforcing layer measured in parallel with the groove width measuring direction of the main groove is W2, 0.1W1 ≦ W2 ≦ W1 is satisfied.

Next, the effect of the pneumatic tire of Claim 2 is demonstrated.
If the relationship between W1 and W2 is 0.1W1 ≧ W2, the range of reinforcing the groove bottom with the fiber reinforcing layer is too narrow, and if W2 ≧ W1, the reinforcing effect of the fiber reinforcing layer on the groove bottom is saturated. End up. Therefore, it is preferable that the relationship between W1 and W2 satisfies 0.1W1 ≦ W2 ≦ W1.

  The pneumatic tire according to claim 3 of the present invention is the pneumatic tire according to claim 1 or 2, wherein the main groove extends in the tire width direction, the groove width on the tread end side is the widest, and the fiber The reinforcing layer is provided at least on the tread end side of the main groove.

Next, the effect of the pneumatic tire according to claim 3 will be described.
Since the groove width on the tread end side of the main groove is wider than other portions, sharp rocks or the like are likely to enter deeply on the tread end side, and the cut easily reaches the belt layer or the vicinity of the belt layer. For this reason, cut resistance can be effectively improved by providing a fiber reinforcement layer in the red end side.

  The pneumatic tire according to a fourth aspect of the present invention is the pneumatic tire according to the third aspect, wherein the length of the groove bottom center of the main groove is L1, and the fiber reinforcing layer is measured in the longitudinal direction of the main groove. When the length of L2 is L2, 0.25L1 ≦ L2 ≦ L1 is satisfied.

Next, the effect of the pneumatic tire of Claim 4 is demonstrated.
If the relationship between L1 and L2 is 0.25L1 ≧ L2, the range of reinforcing the groove bottom with the fiber reinforcing layer is too narrow, and if L2 ≧ L1, the reinforcing effect of the fiber reinforcing layer on the groove bottom is saturated. End up. Therefore, the relationship between L1 and L2 preferably satisfies 0.25L1 ≦ L2 ≦ L1.

  A pneumatic tire according to a fifth aspect of the present invention is the pneumatic tire according to any one of the first to fourth aspects, wherein the fiber reinforcing layer includes steel fibers.

Next, the effect of the pneumatic tire of Claim 5 is demonstrated.
Since the fiber reinforcing layer includes steel fibers, the cut to the groove bottom by sharp rocks or the like can be further buffered or prevented due to the high elastic modulus of the steel fibers, so that the cut resistance is further improved. In addition, since the steel fiber has low elongation, it is possible to further suppress the stress acting on the cut when rolling the tire under load, and further improve the cut progress resistance from the groove bottom to the belt layer, and also improve the cut separation resistance. Even better.

  A pneumatic tire according to a sixth aspect of the present invention is the pneumatic tire according to any one of the first to fourth aspects, wherein the fiber reinforcing layer includes an organic fiber.

Next, the effect of the pneumatic tire of Claim 6 is demonstrated.
Since the fiber reinforcing layer includes organic fibers, the cut to the groove bottom by sharp rocks or the like can be further buffered or prevented due to the high elastic modulus of the organic fibers, and therefore the cut resistance of the groove bottom is further improved. In addition, since the organic fibers have low elongation, the stress acting on the cut can be further suppressed during rolling load of the tire, and the cut progress resistance from the groove bottom to the belt layer is further improved, and the cut separation resistance is also improved. Even better.
In addition, even if water enters the fiber reinforcement layer from the groove bottom cut, the fiber does not rust and the rigidity does not decrease, so the groove bottom cut resistance and cut progress resistance can be maintained for a long time. it can.

  A pneumatic tire according to a seventh aspect of the present invention is the pneumatic tire according to any one of the first to fourth aspects, wherein the fiber reinforcing layer includes a non-woven fabric.

Next, the effect of the pneumatic tire of Claim 7 is demonstrated.
Since the fiber reinforcing layer includes a nonwoven fabric, it is possible to further buffer or prevent the cut to the groove bottom by sharp rocks or the like, so that the groove bottom cut resistance is further improved. Moreover, since the fiber of the nonwoven fabric suppresses the stress acting on the cut when the tire is loaded with load, the cut progress resistance from the groove bottom to the belt layer is further improved, and the cut separation resistance is further improved.
The non-woven fabric can be aligned in one direction or random depending on the production method, and thereby the releasability from the rubber and its own strength can be controlled. Therefore, by using a nonwoven fabric for the fiber reinforcement layer, the releasability from rubber and the strength can be controlled.

  The method for manufacturing a pneumatic tire according to claim 7 of the present invention includes a step of previously forming a groove extending in the longitudinal direction of the main groove at a position where the main groove is formed on the surface of the green tire formed by assembling the tire constituent members. And a step of disposing the fiber reinforcing layer according to any one of claims 1 to 7 on a surface of a groove bottom of the groove formed in the green tire, and an upper mold of the mold in the groove of the green tire. And a step of combining the main groove bones forming the main groove formed on the inner surface of the lower mold and loading them into a vulcanization molding machine.

Next, the effect of the pneumatic tire of Claim 7 is demonstrated.
Before vulcanization molding, a groove extending in the longitudinal direction of the main groove is formed at a position where the main groove is formed on the surface of the green tire, and a fiber reinforcing layer is disposed at the groove bottom of the groove. Next, the groove and each main groove bone on the inner surface of the mold are arranged together. By providing the groove, the arrangement position of the fiber reinforcement layer becomes clear and the arrangement work becomes easy, and also the displacement of the fiber reinforcement layer during the expansion of the vulcanization molded bladder is suppressed, so that the fiber reinforcement The accuracy of the arrangement position of the layers is improved.

  In addition, since the main groove bones enter the tread rubber by this groove and the amount of rubber to be removed thereafter is small, the pressing force by each main groove bone is small, and the belt wave and the belt wave by the pressing force to the belt member inside the tread rubber and The unevenness of the belt gauge can be suppressed as small as possible, and further, the joining of the joining portion is ensured.

  In addition, this groove makes it possible to apply upper and lower mold vulcanization molding machines, making the structure of the vulcanization molding machine simple, requiring less installation space, and keeping equipment costs low. it can. In particular, if the pneumatic tire is a large tire, the installation space and the equipment cost are greatly reduced.

  The pneumatic tire of the present invention has excellent groove bottom cut resistance. Moreover, the manufacturing method of the pneumatic tire of this invention can manufacture the pneumatic tire which is excellent in the cut resistance of a groove bottom.

[First Embodiment]
(Configuration) Next, a first embodiment of the pneumatic tire of the present invention and a method for manufacturing the pneumatic tire will be described with reference to FIG. The pneumatic tire 10 of the present embodiment (hereinafter simply referred to as the tire 10) is a tire for construction vehicles, the tire size is 40.00R57, and the internal structure is a structure of a general radial tire. Therefore, the description of the internal structure is omitted.

(Tread, groove)
As shown in FIG. 1A, the outermost layer of the tire 10 is provided with a tread portion 12 having a tread tread surface 12S that contacts the road surface. The tread portion 12 is formed by a tread rubber 13. The tread rubber 13 is preferably made of rubber having excellent cut resistance. Further, the tread portion 12 is provided with a plurality of width direction main grooves 14 which are symmetrical with respect to the equator plane CL (dashed line) at regular intervals in the tire circumferential direction. The width direction main groove 14 extends from both tread ends 12E of the tread portion 12 toward the equator plane CL.
A circumferential shallow groove 16 is provided on the equator plane CL of the tread portion 12 along the equator plane CL. The circumferential direction shallow groove 16 and each width direction main groove 14 are connected. A belt layer 15 is provided on the inner side in the tire radial direction of the tread portion 12.

Note that the width direction main groove 14 of the present embodiment has a groove width that decreases from the tread end 12E toward the equator plane CL.
Moreover, the groove depth of the width direction main groove 14 is 70-200 mm, and the groove depth is 97 mm in this embodiment.

(Reinforcing layer)
One fiber reinforcing layer 18 is provided on the surface of the groove bottom 14B of the width direction main groove 14 as shown in FIG. As shown in FIG. 2A, the fiber reinforcement layer 18 extends from the tread end 12E side toward the equator plane CL. Further, the fiber reinforcing layer 18 is a monofilament of the fiber 20 or a cord (or multifilament) formed by twisting a plurality of monofilaments arranged in parallel and coated with a coating rubber. The fiber reinforcement layer 18 of the present embodiment is a fiber made of steel 20 and, specifically, a plurality of 0.98 mm diameter steel cords twisted with steel monofilaments are arranged in parallel and covered with a coating rubber. It is a thing. The number of steel cords to be driven is 12.7 / 25 mm. In FIG. 1, the fiber 20 is not shown. In the present embodiment, the steel cord is inclined with respect to the tire circumferential direction.

In a cross section perpendicular to the longitudinal direction of the width-direction main groove 14 (FIG. 1B), the fiber reinforcement layer 18 is measured by measuring the width of the width-direction main groove 14 at the time of a new product in parallel with the W1 and groove width W1 measurement directions. When W2 is W2, it is preferable that 0.1W1 ≦ W2 ≦ W1 is satisfied.
Furthermore, when the length of the center (center line RCL) of the groove bottom 14B of the width direction main groove 14 is L1, and the length of the fiber reinforcement layer 18 measured in the longitudinal direction of the width direction main groove 14 is L2, 0.25L1 It is preferable to satisfy ≦ L2 ≦ L1.

In addition, although the width W2 of the fiber reinforcement layer 18 of this embodiment is uniformly set as shown in FIG. 2A, the width W2 is not limited to this, and the width W2 is always constant with respect to the groove width W1. It may be acceptable. In FIG. 2A, the fiber 20 is shown as a solid line.
Moreover, the fiber reinforcement layer 18 may be 5-10 mm away from the surface of the groove bottom 14B.

(Manufacturing method) Next, a manufacturing method of the tire 10 according to this embodiment will be described below. As described above, the tire 10 has the same structure as that of a general radial tire, and the process of forming a green tire in which the tire constituent members are assembled is the same as the manufacturing process of a general radial tire. Therefore, the description is omitted. In addition, since the manufacturing method of the pneumatic tire of this embodiment is substantially the same as the manufacturing method of the pneumatic tire described in Unexamined-Japanese-Patent No. 2001-105511, only a different point shall be described.

Prior to vulcanization molding by a mold vulcanization molding machine composed of upper and lower halves, a groove that becomes the width direction main groove 14 after vulcanization molding is formed on the surface of the green tire. This forming operation is performed while melting rubber on the surface of the green tire using a cutter that is heated by energizing the blade portion.
Next, the fiber reinforcing layer 18 is attached to the groove bottom of the formed groove. As described above, the fiber reinforcement layer 18 is a reinforcement layer in which steel cords (fibers 20) are arranged in parallel and covered with a coating rubber in this embodiment.
Then, the width direction main groove 14 for vulcanization molding of the width direction main groove 14 provided in the upper mold and the lower mold of the mold is aligned with the groove of the green tire, and the green tire is placed in the vulcanization molding machine. Load and perform vulcanization molding. Thereafter, the green tire is vulcanized and molded into the tire 10, the groove becomes the width direction main groove 14, and the fiber reinforcing layer 18 is disposed on the groove bottom 14B.

(Operation) Next, the operation of the tire 10 of the first embodiment will be described.
Since the fiber reinforcement layer 18 is provided on the groove bottom 14B of the width direction main groove 14, the cut to the groove bottom 14B by the sharp rock 30 or the like can be buffered by the fiber reinforcement layer 18 as shown in FIG. The cut can be prevented from reaching the belt layer 15 or the vicinity of the belt layer 15. Thereby, cut separation starting from the cut of the groove bottom 14B is suppressed. Therefore, the tire 10 is excellent in cut resistance of the groove bottom 14B.

Even when the cut is shallow (when the cut does not reach the vicinity of the belt layer), a large stress is repeatedly applied to the tip of the cut under the load-loaded rolling of the tire 10, so the cut is directed toward the belt layer 15. However, since the fiber reinforcement layer 18 suppresses stress, the progress of the cut can be suppressed. Therefore, it is excellent in cut progress resistance of the groove bottom 14B.
Further, even if the cut to the groove bottom 14B reaches the belt layer 15 or the vicinity of the belt layer 15, the fiber reinforcing layer 18 suppresses a large stress acting on the tip of the cut, so that the belt layer 15 starts from the tip of the cut. It can suppress that a crack thru | or peeling progress along the surface of the outermost layer. Therefore, the cut separation resistance is excellent.

  Since the fiber 20 of the fiber reinforcing layer 18 is a steel fiber, the cut to the groove bottom 14B by the sharp rock 30 or the like can be further buffered or prevented due to the high elastic modulus of the steel fiber, and the cut resistance is further improved. Moreover, since the steel fiber has low elongation, it is possible to suppress stress acting in the cord direction of the steel cord. In the present embodiment, since the steel cord is inclined in the tire circumferential direction, it is possible to suppress the stress related to the tip of the cut under the rolling load of the tire, and from the groove bottom 14B to the belt layer 15. The cut progress resistance is further improved, and the cut separation resistance is further improved.

  Since the groove width W1 on the tread end 12E side of the width direction main groove 14 is wider than other portions, the sharp rock 30 or the like is likely to enter deeply on the tread end 12E side, and the cut is made by the belt layer 15 or the belt layer 15. It is easy to reach the vicinity. For this reason, cut resistance can be effectively improved by providing the fiber reinforcement layer 18 in the tread end 12E side.

  If the relationship between the groove width W1 and the width W2 is 0.1W1 ≧ W2, the range in which the fiber bottom 14B of the width direction main groove 14 is reinforced by the fiber reinforcing layer 18 is too narrow, and if W2 ≧ W1, the fiber reinforcement The reinforcing effect on the groove bottom 14B of the layer 18 is saturated. Therefore, the relationship between the groove width W1 and the width W2 preferably satisfies 0.1W1 ≦ W2 ≦ W1.

  Further, if the relationship between the length L1 and the length L2 is 0.25L1 ≧ L2, the range in which the fiber bottom 14B of the width direction main groove 14 is reinforced by the fiber reinforcing layer 18 is too narrow, and if L2 ≧ L1. The reinforcing effect on the groove bottom 14B of the fiber reinforcing layer 18 is saturated. Therefore, the relationship between the length L1 and the length L2 preferably satisfies 0.25L1 ≦ L2 ≦ L1.

Next, the effect | action of the manufacturing method of the tire 10 of 1st Embodiment is demonstrated.
Before vulcanization molding, a groove extending in the longitudinal direction of the width direction main groove 14 is formed at a position where the width direction main groove 14 is formed on the surface of the green tire, and the fiber reinforcement layer 18 is disposed on the groove bottom of the groove. . Next, the grooves and the main groove bones in the width direction on the inner surface of the mold are arranged together. By providing the groove, the arrangement position of the fiber reinforcement layer 18 is clarified and the arrangement work is facilitated, and also the displacement of the fiber reinforcement layer 18 is suppressed during the expansion of the vulcanization molded bladder. The accuracy of the arrangement position of the fiber reinforcement layer 18 is improved.

  Further, since each groove in the width direction main groove enters the tread rubber 13 by this groove, and the amount of rubber to be removed thereafter is small, the pressing force by each width direction main groove is small, and the belt member inside the tread rubber 13 is applied to the belt member. The unevenness of the belt wave and the belt gauge due to the pressing force can be suppressed as small as possible, and further, the joining of the joining portion is ensured.

  In addition, this groove makes it possible to apply upper and lower mold vulcanization molding machines, making the structure of the vulcanization molding machine simple, requiring less installation space, and keeping equipment costs low. it can. In particular, if the tire is a large tire, the installation space and equipment cost will be greatly reduced.

[Second Embodiment]
(Configuration) Next, a second embodiment of the pneumatic tire of the present invention will be described. Note that the pneumatic tire of this embodiment is also a pneumatic tire for construction vehicles (the tire size is also 40.00R57) as in the pneumatic tire of the first embodiment, and the description thereof will be given in the first embodiment. Only the different configuration will be described. The second embodiment is different from the first embodiment in that the fiber 20 of the fiber reinforcement layer 18 of the first embodiment is an organic fiber instead of a steel fiber, and the details will be described below. Show.

(Reinforcing layer)
The fiber reinforcing layer 18 of the present embodiment is a fiber 20 made of organic fibers. Specifically, for example, an aromatic polyamide fiber (Kevlar: trade name), an aliphatic polyamide fiber, etc. (nylon: trade name), A plurality of cords in which monofilaments such as polyester fibers are twisted are arranged in parallel and covered with a coating rubber. In the present embodiment, the organic fiber cord is inclined with respect to the tire circumferential direction.

(Operation) Next, the operation of the second embodiment will be described.
Since the fiber 20 of the fiber reinforcement layer 18 is an organic fiber cord, the cut to the groove bottom 14B by the sharp rock 30 or the like can be further buffered or prevented due to the high elastic modulus of the organic fiber, and the cut resistance of the groove bottom 14B is improved. Even better. Moreover, since the organic fiber has low elongation, it is possible to suppress the stress acting in the cord direction of the organic fiber cord. In this embodiment, since the organic fiber cord is inclined in the tire circumferential direction, it is possible to suppress the stress related to the tip of the cut under load-load rolling of the tire, and from the groove bottom 14B to the belt layer 15. The cut progress resistance is further improved, and the cut separation resistance is further improved. Further, even if water enters the fiber reinforcing layer 18 from the cut of the groove bottom 14B, the fiber 20 is not rusted and the rigidity is not lowered. Therefore, the cut resistance and cut progress resistance of the groove bottom 14B are increased for a long time. Can be maintained.

[Third Embodiment]
(Configuration) Next, a third embodiment of the pneumatic tire of the present invention will be described. In addition, the pneumatic tire of this embodiment is also a pneumatic tire for construction vehicles (the tire size is also 40.00R57) similarly to the pneumatic tires of the first and second embodiments. Only the configuration different from the embodiment will be described. In the third embodiment, instead of arranging the fibers 20 of the fiber reinforcement layer 18 of the first embodiment in parallel and covering them with rubber, the point of using a non-woven fabric is the difference from the first embodiment. Is shown below.

(Reinforcing layer)
The fiber reinforcement layer 18 of the present embodiment is obtained by coating a nonwoven fabric formed of monofilaments of fibers 20 with a coating rubber. The fibers 20 may be organic fibers, steel fibers, or other fibers.

(Operation) Next, the operation of the third embodiment will be described.
Since the fiber reinforcement layer 18 includes a nonwoven fabric, the cut to the groove bottom 14B by the sharp rock 30 or the like can be further buffered or prevented, and the cut resistance of the groove bottom 14B is further excellent. Further, since the nonwoven fabric fibers 20 suppress the stress acting on the cut when the tire 10 is loaded under load, the cut resistance from the groove bottom 14B to the belt layer 15 is further improved, and the cut separation resistance is further improved. Excellent. Moreover, the nonwoven fabric can arrange | position the direction of the fiber 20 to one direction according to a manufacturing method, or can make it random, and this can control peelability from rubber | gum and own intensity | strength. Therefore, by using a non-woven fabric for the fiber reinforcement layer 18, the releasability from rubber and the strength can be controlled.

[Other Embodiments]
In the first to third embodiments, one layer of the fiber reinforcement layer 18 is arranged on the groove bottom 14B of the width direction main groove 14, but two layers are arranged side by side on the groove bottom 14B as shown in FIG. 2 (B). Alternatively, three or more layers may be arranged side by side. Moreover, as shown in FIG.2 (C), the fiber reinforcement layers 18 may be arrange | positioned 2 layers, and you may arrange | position 3 layers or more. 2C, when the fiber reinforcing layers 18 are arranged so as to overlap each other, the reinforcing effect on the cut is improved and the cut resistance is further improved by arranging the fibers 20 in a direction in which the fibers 20 cross each other. In addition, when the fiber reinforcement layers 18 are arranged side by side as shown in FIGS. 2B and 2C or are arranged in an overlapping manner, the fiber reinforcement layers 18 of the first to third embodiments are used. May be arranged in combination. In the case of arranging the fiber reinforcement layer 18 arranged n sheets, the length of each of the fiber-reinforced layer and a length of L2 _1, L2 ₂ ~L2 _n, the total length of the length L2 ₁ ～L2 _n and L2 To do.

  In the first and second embodiments, the fiber reinforcing layer 18 has a structure in which monofilaments or multifilaments of the fibers 20 are arranged in parallel and covered with a coating rubber. However, the present invention is not limited to this structure. Alternatively, a structure in which a woven fabric using multifilaments of weft and warp is covered with a coating rubber may be used.

Further, in the first to second embodiments, the tread pattern of the tire 10 is configured by the width direction main groove 14 and the circumferential direction shallow groove 16, but a configuration other than this configuration may be used. As shown in FIG. 4, a line connecting the ends on the equator plane CL side of the width direction main groove 14 on both sides with respect to the equator plane CL in the tire circumferential direction is defined as a boundary line BL (two-dot chain line). A widthwise narrow groove 26 that extends in the tire width direction and connects to the end of the widthwise main groove 14 may be provided therebetween.
In the first to third embodiments, the pneumatic tire of the present invention is used for construction vehicles, but may be used for other than construction vehicles.

(Test example)
In order to confirm the performance improvement effect of the pneumatic tire of the present invention, one type of pneumatic tire of an example according to the first embodiment of the present invention and one type of pneumatic tire of a comparative example are prepared and sharp. A test was conducted to evaluate the cut penetration resistance when a protrusion was stepped on.
In this evaluation test of cut penetration resistance, each test tire is first mounted on a standard rim in the applicable size specified in the 2005 version of TRA YEAR BOOK issued by the TRA Association of Tires and Rim in the United States. 100% of the maximum load (maximum load capacity) and the air pressure (maximum air pressure) corresponding to the maximum load in the application size / ply rating defined in BOOK is filled as the internal pressure. Next, the center of the tip of a regular triangular cutter having a width of about 15% of the maximum tread width is placed on the bottom of the main groove in the width direction at a position inside the tire width direction by X% of the maximum tread width from the tread ground contact edge. Press and cut until the tip of the cutter reaches the belt. The energy required for this cutting is measured at eight positions on the circumference of the tire, and the average value is taken as the measured value.

In addition, the structure of the tire of an Example and the tire of a comparative example is shown in Table 1, and the value of X and a measured value are shown in Table 2. Moreover, the measured value is displayed as an index when the tire of the comparative example is set to 100, and the larger the numerical value, the better the result.
In addition, the tread ground contact here means that a pneumatic tire is attached to a standard rim in the applicable size specified in the 2005 TRA YEAR BOOK issued by the TRA Association of Tires and Rim in the United States, and is attached to the TRA YEAR BOOK. The outermost ground contact in the tire width direction when the maximum load (maximum load capacity) and the air pressure corresponding to the maximum load (maximum air pressure) are filled as internal pressure and the maximum load is applied. Refers to the part. In addition, when there is a standard in the place of use or the manufacturing place, it follows each standard. Further, the maximum tread width refers to the distance between the tread grounding ends.

Example: A pneumatic tire according to the first embodiment shown in FIG.
Comparative Example: A pneumatic tire obtained by removing the fiber reinforcing layer from the tire of the example. The tire size is the same as in the example (40.00R57).

  From the results of Table 1, it became possible to provide a pneumatic tire mainly for construction vehicles for running on rough land, which is excellent in cut penetration resistance at the groove bottom when a sharp protrusion is stepped on according to the present invention.

(A) It is the figure which showed the tread pattern of the pneumatic tire for construction vehicles which concerns on 1st Embodiment. (B) It is a BB line sectional view of Drawing 1 (A). (A) It is the top view which expanded the width direction main groove of the pneumatic tire for construction vehicles which concerns on 1st Embodiment. (B) It is the top view to which the width direction main groove of the pneumatic tire for construction vehicles concerning other embodiments was expanded. (C) It is the top view to which the width direction main groove of the pneumatic tire for construction vehicles concerning other embodiments was expanded. It is the figure which looked at the state where the groove bottom of the pneumatic tire for construction vehicles concerning a 1st embodiment buffers a sharp rock cut with a fiber reinforcement layer in the section perpendicular to the longitudinal direction of the main groove. It is the figure which showed the tread pattern of the pneumatic tire for construction vehicles which concerns on other embodiment. It is the figure which looked at the state where the groove bottom of the conventional pneumatic tire for construction vehicles was damaged with a sharp rock in the cross section perpendicular to the longitudinal direction of the main groove.

Explanation of symbols

10 Pneumatic tires for construction vehicles (pneumatic tires)
12 tread part 14 width direction main groove (main groove)
14B Groove bottom 15 Belt layer 18 Fiber reinforcement layer 20 Fiber (steel fiber, organic fiber)
CL equatorial plane (tire equatorial plane)
RCL width direction main groove groove bottom center line

Claims (8)

A plurality of treads that are in contact with the road surface, a main groove having a groove depth of 70 to 200 mm;
A belt layer provided on the inner side in the tire radial direction of the tread portion;
A fiber reinforcing layer provided at the groove bottom of the main groove and extending in the longitudinal direction of the main groove;
A pneumatic tire characterized by comprising:   In a cross section perpendicular to the longitudinal direction of the main groove, when the width of the main groove when new is W1, the width of the fiber reinforcing layer measured in parallel with the groove width measurement direction of the main groove is W2, The pneumatic tire according to claim 1, wherein 0.1W1 ≦ W2 ≦ W1 is satisfied. The main groove extends in the tire width direction, and the groove width on the tread end side is the widest,
The pneumatic tire according to claim 1, wherein the fiber reinforcing layer is provided at least on the tread end side of the main groove.   The length of the groove bottom center of the main groove is L1, and the length of the fiber reinforcement layer measured in the longitudinal direction of the main groove is L2, and satisfies 0.25L1 ≦ L2 ≦ L1. Item 4. The pneumatic tire according to Item 3.   The pneumatic tire according to claim 1, wherein the fiber reinforcing layer includes steel fibers.   The pneumatic tire according to claim 1, wherein the fiber reinforcing layer includes organic fibers.   The pneumatic tire according to claim 1, wherein the fiber reinforcing layer includes a non-woven cloth. A step of previously forming a groove extending in the longitudinal direction of the main groove at a position where the main groove of the surface of the green tire formed by assembling the tire constituent member is formed;
Placing the fiber reinforcing layer according to any one of claims 1 to 7 on the surface of the groove bottom of the groove formed in the green tire;
Loading the groove of the green tire into the vulcanization molding machine by combining the main groove bones forming the main groove formed on the inner surface of the upper mold and the lower mold of the mold; and
A method for producing a pneumatic tire, comprising:

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