| Title of Invention | A PNEUMATIC RADIAL TIRE FOR PASSENGER CAR AND LIGHT TRUCK |
|---|---|
| Abstract | This invention relates to a pneumatic radial tire for passenger car and light truck comprises a radial carcass (1), a belt (2) superimposed about a crown portion of the carcass (2) and a tread (3) arranged on the belt (2), in which a cut protector (4) is arranged in a buttress portion so as to protrude outward therefrom in a rotating axial direction of the tire and provided in its inside with a reinforcing cord layer (5) having a modulus of elasticity of cord smaller than that of the cord in the carcass, and has a width (h) corresponding to 10-60% of a distance (H) ranging from an end of the tread (3) to a maximum width of the tire in the radial direction. |
| Full Text | - 1A - PNEUMATIC RADIAL TIRES This invention relates to a pneumatic radial tire for passenger cars and light trucks frequently running on rough road surface scattered with foreign substance such as stones or the like, and more particularly to a pneumatic radial tire comprising a carcass of a radial cord structure extending between a pair of bead cores, a belt superimposed about a crown portion of the carcass outward in a radial direction and a tread arranged on the belt outward in the radial direction. In general, the conventionally typical pneumatic radial tires for passenger car and light truck have been designed on the assumption that they are run on a good paved road. Therefore, when such a conventional pneumatic radial tire is run on a waste paved road or an unpaved road such as a farm road or the like as it is, it is apt to suffer a cut damage in a buttress portion by foreign substances scattered on the road such as sharp stones, glass pieces, metal pieces, bolts and the like. Further, the buttress portion may be subjected to cut damage when the tire rides over a curbstone or a road shoulder. In any case, when the tire having the cut damage in the buttress portion is used as it is, the cut damage grows up to the carcass and hence the tire is punctured or the carcass may be broken to induce a fatal burst failure. - 2 - In order to hardly cause the above cut damage, it is frequently attempted to increase a rubber gauge in an upper portion of a side rubber corresponding to the buttress portion. In this case, however, the tire weight itself is increased and hence there are caused troubles such as deterioration of fuel consumption and ride comfortability against vibrations, rise of production cost due to the increase of material cost and the like. It is, therefore, an object of the invention to solve the above troubles of the conventional technique and to provide a pneumatic radial tire for passenger car and light truck running on rough road surface which hardly causes the cut damage in the buttress portion without deteriorating various performances such as ride comfortability and the like. According to the invention, there is the provision of a pneumatic radial tire for passenger car and light truck comprising a carcass of a radial cord structure extending between a pair of bead cores, a belt superimposed about a crown portion of the carcass outward in a radial direction and a tread arranged on the belt outward in the radial direction, characterized in that (1) a cut protector is arranged in a buttress portion so as to protrude outward therefrom in a rotating axial direction of the tire, (2) the cut protector is provided in its inside with a reinforcing cord layer, (3) a modulus of elasticity of a cord in the reinforcing cord layer is smaller than that of a cord in the carcass, and (4) a width h of the cut - 3 - protector in radial direction corresponds to 10-60% of a distance H ranging from an end of the tread to a maximum width of the tire in the radial direction. In a preferable embodiment of the invention, the reinforcing cord layer is a canvas-like reinforcing cord layer. In this case, the resistance to crack growth can be improved. In another preferable embodiment of the invention, the modulus of elasticity of the cord in the reinforcing cord layer is 30-80 as an index based on that the modulus of elasticity of the cord in the carcass is 100. As a result of the inventors investigations, it has been confirmed that the cut damages created in the buttress portion of the tire under condition of running on a waste paved road or an unpaved road such as a farm road or the like concentrate in a zone ranging from an end of the tread to a maximum width of the tire and tend to be joined together in a radial direction of the tire rather than in a circumferential direction thereof. The pneumatic radial tire according to the invention is particularly provided in its buttress portion with the cut protector protruding outward in the rotating axial direction of the tire and including the reinforcing cord layer therein and having a width h in radial direction corresponding to 10-60% of a distance H from the end of the tread to the tire maximum width as mentioned above, so that the cut damage created in the buttress portion is prevented - 4 - to be grown up to the carcass and the diffusion of the cut damage is effectively controlled. Furthermore, in the pneumatic radial tire according to the invention, the modulus of elasticity of the cord in the reinforcing cord layer is smaller than that of the cord in the carcass, so that the cut damage is hardly caused in the buttress portion without deteriorating the ride comfortability against vibrations and it is possible to provide a pneumatic radial tire suitable for passenger car and light truck running on rough road surface. The invention will be described with reference to the accompanying drawing, wherein: Fig. 1 is a partly enlarged section view of an embodiment of the pneumatic radial tire according to the invention. There are provided an example tire according to the invention and a conventional tire each having a tire size of LT195R14. As shown in Fig. 1, the example tire comprises a carcass 1 of a radial cord structure extending between a pair of bead cores (not shown), a belt 2 superimposed about a crown portion of the carcass outward in a radial direction and a tread 3 arranged on the belt outward in the radial direction. In the example tire, a cut protector 4 protruding outward in a rotating axial direction of the tire is disposed in a buttress portion and is provided in its inside with a canvas-like reinforcing cord layer 5. - 5 - The canvas-like reinforcing cord layer 5 contains cords having a modulus of elasticity smaller than that of cords in the carcass 1. Further, the cut protector 4 has a width h in radial direction corresponding to 50% of a distance H ranging from an end of the tread to a maximum width of the tire in the radial direction thereof. In this case, the carcass 1 is comprised of plural polyester cords each having a modulus of elasticity of 740 kg/mm2 after a dipping treatment, and the canvas-like reinforcing cord layer 5 is comprised of plural nylon cords each having a modulus of elasticity of 436 kg/mm2 after the dipping treatment. Moreover, the kind of the cord used in each of the carcass and the reinforcing cord layer is not limited to the above embodiment. Even if the cords used in the carcass and the reinforcing cord layer are the same, the given relation in the modulus of elasticity of the cord between the carcass and the reinforcing cord layer can be obtained by properly selecting the cord diameter, the twisting structure, the dipping conditions and the like. On the other hand, the pneumatic tire of the conventional example has substantially the same structure as in the above example tire except that the cut protector 4 and the canvas-like reinforcing cord layer 5 are omitted. A protrusion impact test is carried out with respect to the example tire and conventional tire in order to evaluate the degree of cut damage in the buttress portion. - 6 - As a result of this test, when the impact number until the occurrence of fatal burst failure is represented by an index on the basis that the conventional tire is 100, the example tire is 180. On the other hand, the ride comfortability against vibrations is substantially the same level in both tires. As seen from the above, when the pneumatic radial tire according to the invention is compared with the conventional tire, the ride comfortability against vibrations is equal and the resistance to cut damage in the buttress portion is excellent. 7 WE CLAIM 1. A pneumatic radial tire for passenger car and light truck comprising a carcass (1) of a radial cord structure extending between a pair of bead cores, a belt (2) superimposed outwardly over a crown portion of the carcass (1) in a radial direction; and a tread (3) disposed outwardly on the belt (2) in the radial direction, characterized in that a cut protector (4) is provided in a buttress portion so as to protrude outwardly thereform in an axially rotating direction of the tire, a reinforcing cord layer (5) comprising a plurality of cords being interposed in an inside of side cut protector (4), and in that a modulus of elasticity of each of said cords of the reinforcing cord layer (5) is smaller than that of a cord in the carcass, and a width (h) of the cut protector (4) in a radial direction corresponds to 10-60% of a distance (H) measured from an end of the tread (3) to a maximum width of the tire in the radial direction. 2. A pneumatic radial tire as claimed in claim 1, wherein said reinforcing cord layer (5) is a canvas-like reinforcing cord layer having improved resistance to crack growth. 3. A pneumatic radial tire as claimed in claim 1, wherein said modulus of elasticity of the cord in the reinforcing cord layer (5) has a representative value between 30-80 when the modulus of elasticity of the cord in the carcass (1) is indexed at a value of 100. This invention relates to a pneumatic radial tire for passenger car and light truck comprises a radial carcass (1), a belt (2) superimposed about a crown portion of the carcass (2) and a tread (3) arranged on the belt (2), in which a cut protector (4) is arranged in a buttress portion so as to protrude outward therefrom in a rotating axial direction of the tire and provided in its inside with a reinforcing cord layer (5) having a modulus of elasticity of cord smaller than that of the cord in the carcass, and has a width (h) corresponding to 10-60% of a distance (H) ranging from an end of the tread (3) to a maximum width of the tire in the radial direction. |
|---|
00163-cal-1998-correspondence-1.1.pdf
00163-cal-1998-correspondence.pdf
00163-cal-1998-description(complete).pdf
00163-cal-1998-priority document(others).pdf
00163-cal-1998-priority document.pdf
163-cal-1998-granted-abstract.pdf
163-cal-1998-granted-acceptance publication.pdf
163-cal-1998-granted-claims.pdf
163-cal-1998-granted-correspondence.pdf
163-cal-1998-granted-description (complete).pdf
163-cal-1998-granted-drawings.pdf
163-cal-1998-granted-examination report.pdf
163-cal-1998-granted-form 1.pdf
163-cal-1998-granted-form 2.pdf
163-cal-1998-granted-form 3.pdf
163-cal-1998-granted-form 6.pdf
163-cal-1998-granted-letter patent.pdf
163-cal-1998-granted-priority document.pdf
163-cal-1998-granted-reply to examination report.pdf
163-cal-1998-granted-specification.pdf
163-cal-1998-granted-translated copy of priority document.pdf
| Patent Number | 194157 | ||||||||
|---|---|---|---|---|---|---|---|---|---|
| Indian Patent Application Number | 163/CAL/1998 | ||||||||
| PG Journal Number | 30/2009 | ||||||||
| Publication Date | 24-Jul-2009 | ||||||||
| Grant Date | 29-Apr-2005 | ||||||||
| Date of Filing | 02-Feb-1998 | ||||||||
| Name of Patentee | BRIDGESTONE CORPORATION | ||||||||
| Applicant Address | 10-1, KYOBASHI 1-CHOME, CHUO-KU, TOKYO | ||||||||
Inventors:
|
|||||||||
| PCT International Classification Number | B60C 11/04 | ||||||||
| PCT International Application Number | N/A | ||||||||
| PCT International Filing date | |||||||||
PCT Conventions:
|
|||||||||