JP4545018B2 - Pneumatic tire - Google Patents

Description

    The present invention relates to a pneumatic tire in which a belt reinforcing layer that overlaps a belt layer is disposed in a tread portion.

As conventional pneumatic tires, for example, those described in Patent Document 1 below are known.
JP 2002-46415 A

  This is a carcass layer whose ends in the width direction are folded around a bead core and extend in a toroidal shape, and is arranged radially outside the carcass layer, at the same angle within a range of 15 to 35 degrees with respect to the tire equator. A belt layer composed of two belt plies in which metal wire cords inclined in the opposite direction are embedded, a tread disposed radially outward of the belt layer, and between the belt layer and the tread And a belt reinforcing layer in which a reinforcing cord made of organic fibers extending substantially parallel to the tire equator is embedded.

  And this is a tread for pneumatic tires for high performance passenger cars, aircrafts, trucks, buses, etc. due to centrifugal force during high-speed running due to reinforcement cords extending substantially parallel to the tire equator in the belt reinforcement layer It is possible to suppress a large diameter growth of the entire part radially outward, thereby suppressing a change in the ground contact shape due to high speed traveling and realizing high steering stability in a high speed range.

  Here, when a pneumatic tire as described above is run under a load, the tread portion is repeatedly out of plane in the circumferential direction so that the radius of curvature is greatly reduced in the vicinity of the stepping position and the kicking position of the pneumatic tire. Bending deformation (bending deformation with the tire width direction as a crease), while the tread portion repeats in the circumferential direction so that the radius of curvature becomes infinite (flat) between the stepping position and the kicking position To bend out of plane.

    However, in the pneumatic tire as described above, a metal wire cord inclined at a small inclination angle with respect to the tire equator is embedded in the belt layer, and the tire equator is substantially embedded in the belt reinforcement layer. Since the reinforcing cords extending in parallel are embedded, when the pneumatic tire is filled with internal pressure, a large tension is generated in the metal wire cords in the belt layers and the reinforcing cords in the belt reinforcing layers. The circumferential bending stiffness of the layer and the belt reinforcing layer, that is, the combined value of these circumferential bending stiffnesses becomes high. As a result, the out-of-plane bending deformation in the circumferential direction at the time of grounding as described above is limited, and as a result, the longitudinal spring constant becomes a large value, the ride comfort is lowered, and the grounding length is shortened to reduce the grounding area. There was a problem that the driving stability in the low and medium speed range was reduced.

  An object of the present invention is to provide a pneumatic tire capable of improving both ride comfort and steering stability.

For this purpose, a carcass layer whose both ends in the width direction are folded around a bead core and extend in a toroidal shape, and a non-stretchable belt that is disposed radially outside the carcass layer and is inclined with respect to the tire equator S A belt layer composed of at least two belt plies in which a cord is embedded, a tread disposed radially outward of the belt layer, and a belt layer are disposed so as to overlap the belt layer, and substantially inside the tire equator S. A pneumatic tire including a belt reinforcing layer in which a non-stretchable reinforcing cord extending in parallel is embedded, and a belt embedded in a contact belt ply of the belt ply that is disposed in close contact with the belt reinforcing layer the diameter of the cord, by larger than the diameter of the belt cords embedded in the remaining belt plies, bending the circumferential direction of the contact belt ply Sex and by larger than circumferential bending stiffness of the remaining belt ply can be achieved.

  In the present invention, the circumferential bending stiffness of the belt ply, which is closely contacted with the belt reinforcing layer, is larger than the circumferential bending stiffness of the remaining belt plies, so the circumferential bending stiffness is high. The belt reinforcing layer having a value and the contact belt ply having the next highest bending stiffness in the circumferential direction after the belt reinforcing layer are gathered in the vicinity of the neutral axis of the bending located near the boundary. . As a result, the combined circumferential bending rigidity of the belt layer and the belt reinforcing layer is reduced, thereby reducing the longitudinal spring constant of the pneumatic tire and improving the ride comfort, and increasing the contact length and increasing the contact area. This increases the steering stability at all speeds.

On the other hand, when a belt ply with a circumferential bending stiffness greater than the remaining belt ply is arranged at a position away from the belt reinforcement layer, belt reinforcement with a high circumferential bending stiffness is provided on both sides of the neutral axis of bending. Since the sandwich structure in which the layers and the belt ply are located apart from each other is formed, the synthetic circumferential bending rigidity becomes a large value as in the conventional case, and as a result, such an arrangement structure cannot be used .

Embodiment 1 of the present invention will be described below with reference to the drawings.
In FIGS. 1 and 2, reference numeral 11 denotes a pneumatic radial tire for a passenger car that can run at high speed. The pneumatic tire 11 includes a pair of bead portions 13 each having a bead core 12 embedded therein, and a radial direction from the bead portions 13. Side wall portions 14 extending outward are provided, and a substantially cylindrical tread portion 15 that connects the outer ends in the radial direction of the side wall portions 14 is provided. The present invention may be applied to pneumatic tires for aircraft or trucks and buses.

  The pneumatic tire 11 has a carcass layer 18 that extends between the bead cores 12 in a toroidal shape and reinforces the side wall portions 14 and the tread portions 15. Both end portions of the carcass layer 18 in the width direction of the bead core 12 It is turned around from the axially inner side to the axially outer side. The carcass layer 18 is composed of at least one carcass ply 19 in this case, and the carcass ply 19 intersects the tire equator S at a cord angle of 70 to 90 degrees, that is, in a radial direction ( A large number of mutually parallel carcass cords 20 made of nylon, aromatic polyamide, steel, etc. (here, nylon) extending in the meridian direction are embedded.

  23 is a belt layer arranged radially outward of the carcass layer 18, and this belt layer 23 has at least two belt plies, here two belt plies 24, 25 in this order toward the radially outer side. It is configured by stacking. Here, a large number of mutually parallel non-stretchable belt cords 26 and 27 are embedded in the belt plies 24 and 25, respectively, and these belt cords 26 and 27 are made of stranded wires or monofilaments. . The belt cords 26 and 27 in the two belt plies 24 and 25 have the same inclination angle Z within the range of 15 to 35 degrees with respect to the tire equator S in order to maintain the in-belt rigidity at a high value. And at least two belt plies incline in opposite directions with respect to the tire equator S and cross each other.

  31 is a tread made of rubber disposed radially outside the carcass layer 18 and the belt layer 23. The outer surface (tread surface) of the tread 31 is continuously continuous in the circumferential direction in order to improve drainage performance. A plurality of extending main grooves 32, here, four main grooves 32 are formed. In addition, a large number of lateral grooves extending in the width direction or oblique direction may be formed on the outer surface of the tread 31.

  Reference numeral 35 denotes a belt reinforcing layer which is disposed on the tread portion 15 between the belt layer 23 and the tread 31 so as to overlap the belt layer 23 and covers the belt layer 23 with the full width. At least one belt reinforcing layer 35 (here, In this case, a non-stretchable reinforcing cord 37 extending substantially parallel to the tire equator S is embedded in the reinforcing ply 36. If the belt reinforcing layer 35 that covers the belt layer 23 with the full width is provided on the outer side in the radial direction of the belt layer 23 in this way, the entire tread portion 15 grows greatly in the radial direction outside due to the centrifugal force during high-speed running. It is strongly suppressed, and by this, changes in the ground contact shape during high-speed driving are suppressed, and high steering stability can be realized.

  Here, the belt reinforcing layer 35 described above is formed by, for example, winding a strip having a constant width, in which one or several reinforcing cords 37 are arranged side by side, and spirally wrapping the outer side of the belt layer 23 with the side ends in contact with each other. Can be molded. If the belt reinforcing layer 35 is formed in this way, the belt reinforcing layer 35 can be formed with high efficiency and high accuracy. The reinforcing cord 37 in the belt reinforcing layer 35 may be made of steel, but is preferably made of aromatic polyamide as in this embodiment. The reason for this is that, in this way, the diameter growth of the tread portion 15 can be strongly suppressed even when the tread portion 15 becomes high temperature due to high speed running while achieving weight reduction.

  When the pneumatic tire 11 as described above is run under a load, the tread portion 15 is repeatedly subjected to out-of-plane bending deformation in the vicinity of the stepping and kicking positions of the pneumatic tire 11 and between them. At this time, the belt layer 23 and the belt reinforcing layer 35 have a high circumferential bending rigidity due to the tension based on the internal pressure filling, so that the out-of-plane bending deformation is likely to be limited.

  However, in this embodiment, the circumferential bending stiffness of one of the belt plies 24, 25, here the belt ply 25, is made different from the circumferential bending stiffness of the remaining belt ply 24, The belt ply 25 is placed in close contact with the belt reinforcing layer 35 without any interposition between them, so that the close contact belt ply in close contact with the belt reinforcing layer 35, here the belt ply The circumferential bending stiffness of 25 is made larger than the circumferential bending stiffness of the remaining belt ply, here, the separation belt ply 24 furthest away from the belt reinforcing layer 35.

  As a result, the belt reinforcing layer 35 having a high circumferential bending stiffness and the contact belt ply 25 having the highest circumferential bending stiffness next to the belt reinforcing layer 35 are positioned near these boundaries. It will gather near the neutral axis. As a result, the composite circumferential bending rigidity of the belt layer 23 and the belt reinforcing layer 35 is reduced, and as a result, the vertical spring constant of the pneumatic tire 11 is reduced, and the thrust feeling when riding over the protrusion and the roughness on the rough road surface are reduced. The feeling and the like are reduced and the ride comfort is improved, and the contact length is increased, the contact area is increased, and the handling stability in the entire speed range is improved.

  On the other hand, when a belt ply having a circumferential bending rigidity larger than the remaining belt ply is arranged at a position away from the belt reinforcing layer 35, a belt having a high circumferential bending rigidity on both sides of the neutral axis of the bending. Since the reinforcing layer 35 and the belt ply are located apart from each other, the composite circumferential bending rigidity becomes a large value as in the conventional case.

Further, by making the diameter of the belt cord 27 embedded in the contact belt ply 25 larger than the diameter of the belt cord 26 embedded in the separation belt ply 24, the circumferential bending rigidity of the contact belt ply 25 is increased. It is larger than the circumferential bending rigidity of the separation belt ply 24. With this the diameter of the belt cord 27 in close contact with the belt ply 25 and the large, can increase the in-plane rigidity of the belt layer 23, in such a case, easily improved ride comfort, steering stability Can be made.

Also, while configuring the belt cords 27 are embedded in the adhesion belt ply 25 of steel, by forming the belt cords 26 are embedded in spaced belt plies 24 from grayed Las fibers, Young belt cords 27 The rate can be made larger than the Young's modulus of the belt cord 26, whereby the circumferential bending stiffness of the contact belt ply 25 can be made larger than the circumferential bending stiffness of the remaining separation belt ply 24.

  Thus, if the Young's modulus of the belt cord 27 in the contact belt ply 25 is larger than the Young's modulus of the belt cord 26 of the separation belt ply 24, the coating rubber thickness between the belt cords 26 and 27 can be changed. Therefore, the circumferential bending rigidity of the contact belt ply 25 can be easily made larger than the circumferential bending rigidity of the separation belt ply 24. If the belt cord 26 is made of the above-described material, the in-plane rigidity of the belt layer 23 can be maintained at a high value.

Here, circumferential tensile and compressive forces are generated at positions away from the neutral axis of bending due to the out-of-plane bending deformation of the tread portion 15 as described above. the belt plies 24 rather than the steel as described above, since the belt cord 26 consisting grayed lath fibers are embedded, these belt cord 26 causes functions only as a weak resistance to bending deformation plane previously described First, an out-of-plane bending deformation in the tread portion 15 is allowed. For this reason, the riding comfort and steering stability of the pneumatic tire 11 are hardly reduced by the tensile force and the compressive force.

  Furthermore, the driving interval of the belt cord 27 embedded in the contact belt ply 25 (the distance between the centers of adjacent belt cords) is set smaller than the driving interval of the belt cord 26 embedded in the separation belt ply 24. In other words, the circumferential bending stiffness of the contact belt ply 25 can be made larger than the circumferential bending stiffness of the separation belt ply 24 by densely driving. Thus, if the driving distance of the belt cord 27 in the contact belt ply 25 is made small, the in-plane rigidity of the belt layer 23 can be increased, but also in this case, ride comfort and handling stability can be easily achieved. Can be improved.

    3 and 4 are views showing Embodiment 2 of the present invention. In this embodiment, the belt reinforcing layer 40, which is slightly narrower than the belt layer 41, is disposed so as to overlap the belt layer 41 between the belt layer 41 and the carcass layer 18, and the belt layer 41 is replaced with the belt reinforcing layer 40. The belt ply 42 is disposed in close contact with the belt, the separation belt ply 44 farthest from the belt reinforcing layer 40, and the intermediate belt ply 43 disposed between the belt plies 42 and 44. ing.

  As a result, the contact belt ply 42, the intermediate belt ply 43, and the separation belt ply 44 are arranged in this order toward the radially outer side, but the circumferential bending rigidity of the belt plies 42, 43, and 44 is increased. Small in this order. As a result, the circumferential bending stiffness of the belt plies 42, 43, and 44 is the maximum value for the contact belt ply 42, the minimum value for the separation belt ply 44, and the intermediate value for the intermediate belt ply 43.

  Thus, also in this embodiment, since the belt reinforcing layer 40 and the contact belt ply 42 having high circumferential bending rigidity are gathered near the neutral axis of the bending, the combined circumferential direction of the belt layer 41 and the belt reinforcing layer 40 Bending rigidity is reduced, and ride comfort and handling stability are improved. Moreover, as described above, if the circumferential bending stiffness of the separation belt ply 44 farthest from the belt reinforcing layer 40 is the smallest of the belt plies 42, 43, 44, the belt ply having the smallest circumferential bending stiffness. Riding comfort and handling stability can be improved as compared with the case where is disposed on the belt reinforcement layer 40 side from the separation belt ply 44.

  In this embodiment, as described above, the belt reinforcement layer 40 is disposed between the belt layer 41 and the carcass layer 18, but when the belt reinforcement layer 40 is provided at such a position, The belt reinforcing layer 40 arranged on the inner side in the radial direction of the belt layer 41 can suppress the radial growth of the tread portion 15 to the outer side in the radial direction during high speed running. Steering stability at the time of high-speed traveling equivalent to when it is arranged outside in the direction can be ensured.

Next, Test Example 1 will be described. In this test, the conventional tire 1 as shown in FIGS. 1 and 2 in which the cord A is driven into the separation and contact belt ply at a distance of 1.2 mm (distance between the centers of adjacent belt cords), and the separation and contact belt. Cord B is driven into the contact belt ply with a distance of 1.2 mm, and the conventional tire 2 is the same as the conventional tire 1 except that the belt cord in the ply is changed to the cord B. in reference tire 1 as shown in FIG. 1 and 2 is embedded in a reference tire 2 is the same as in reference tire 1 except that the belt cords in spaced belt ply cord C, and belt cords in spaced belt plies and code D, close contact with the code E the belt cords of the belt in the ply other than the can as in the tire 1 is the same as in reference tire 1, away septum, in close contact belt ply 1.5mm Rutokodo implantation intervals, respectively, except for using 0.9mm were prepared in Reference tire 3 is similar to the conventional tire 1.

Further, as a comparative tire, the reference tires 1 and 2 are the same as the reference tires 1 and 2 except that the cords in the separation belt ply and the cords in the contact belt ply in the embodiment tire 1 are replaced. A comparative tire 4 similar to the reference tire 3 was also prepared except that the comparative tires 1, 2, and 3 were interchanged with each other, and the driving distance of the belt cords in the separation and contact belt ply was interchanged.

  Here, the cord A is a belt cord formed by twisting three steel filaments having a diameter of 0.3 mm, and the cord B is a belt cord having a diameter of 0.7 mm obtained by twisting aromatic polyamide filaments. C is a belt cord with a diameter of 0.7 mm twisted from glass fiber filaments, Cord D is a belt cord made by twisting two steel filaments with a diameter of 0.3 mm, and Cord E is 0.3 mm in diameter. It is a belt cord formed by twisting four steel filaments.

  Each of the aforementioned tires is a tire for a high-performance passenger car having a size of 245 / 55R17, and two carcass plies embedded with nylon cords that intersect the carcass layer of each tire at 90 degrees with the tire equator S. On the other hand, a reinforcing cord having a diameter of 0.7 mm formed by twisting aromatic polyamide filaments was embedded in the belt reinforcing layer at an interval of 1.0 mm. Further, the belt cord in the separation belt ply was inclined at 30 degrees on the upper right with respect to the tire equator S, and the belt cord in the contact belt ply was inclined at 30 degrees on the left with respect to the tire equator S.

Next, after filling each tire with an internal pressure of 220 kPa, a paint is applied to the outer surface of the tread portion, and the ground shape is transferred to the paper by pressing against a white paper while applying a load of 6 kN before the paint dries. did. Then, the contact length (the maximum length in the tire equator direction in the contact shape and the unit is mm) was measured from the contact shape of each tire, and the results are shown in Table 1. Here, a high belt reinforcing layer in the circumferential direction bending rigidity, adhesion exemplary tire belt ply in close contact arrangement, the contact length than the comparative tire placed away them is longer.

Next, after mounting each of the tires on a high-performance passenger car, the vehicle was run on a dry road circuit at a maximum speed of 200 km / h, and the steering stability was evaluated by a skilled test driver. Table 1 shows the score for each tire, with a maximum score of 100. Here, in the conventional tire 2, the in-belt rigidity is lowered, so that the steering stability is deteriorated even when the contact length is longer than that of the conventional tire 1. Further, a high belt reinforcing layer in the circumferential direction bending rigidity, exemplary tire in close contact disposed adhesion belt ply because contact Chicho becomes longer, evaluated from comparison tire placed away them is high.

Next, the joints of the bumpy road and the highway prepared for the test course were passed by the same passenger car as described above, and the vibration ride comfort was evaluated by a skilled test driver. Shows the evaluation are shown in Table 1 in 10 stages, since the conventional tire 2 are embedded belt cords made of aromatic polyamide in any of the belt in the ply, riding comfort is good, implementation tire The ride comfort of the car was almost as good.

  The present invention can be applied to the industrial field of pneumatic tires in which a belt reinforcing layer that overlaps the belt layer is disposed in the tread portion.

It is meridian sectional drawing which shows Embodiment 1 of this invention. It is a partially broken plan view of the tread portion. It is meridian sectional drawing which shows Embodiment 2 of this invention. It is a partially broken plan view of the tread portion.

11 ... Pneumatic tire 12 ... Bead core
18 ... Carcass layer 23 ... Belt layer
24 ... Separate belt ply 25 ... Contact belt ply
26, 27 ... belt cord 31 ... tread
35 ... Belt reinforcement layer 44 ... Separation belt ply S ... Tire equator Z ... Inclination angle

Claims (3)

A carcass layer whose both ends in the width direction are folded back around the bead core and extend in a toroidal shape, and a non-extensible belt cord which is disposed on the outer side in the radial direction of the carcass layer and which is inclined with respect to the tire equator S is embedded therein. A belt layer composed of at least two belt plies, a tread disposed on the outer side in the radial direction of the belt layer, and a non-extensible structure disposed so as to overlap the belt layer and extending substantially parallel to the tire equator S inside. In the pneumatic tire including the belt reinforcement layer in which the reinforcement cord is embedded , the diameter of the belt cord embedded in the contact belt ply of the belt ply in close contact with the belt reinforcement layer by than the diameter of the belt cords embedded in the belt in the ply and large, the circumferential bending stiffness of the contact belt ply, the remaining bell A pneumatic tire characterized by being larger than circumferential bending stiffness of the ply. The adhesion while the belt cords of the belt in the plies consist of steel, a pneumatic tire according to claim 1, wherein configuring the belt cords in the remaining belt ply fiberglass. The pneumatic tire according to claim 1, wherein a driving distance between belt cords embedded in the contact belt ply is smaller than a driving distance between belt cords embedded in the remaining belt plies.

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