Bridgestone Corporation

Bridgestone Tire Company Limited

Hisao Ushikubo

Misao Kawabata

Ichiro Takahashi

Toru Tsuda

Teruyuki Tominaga

Yutaka Yamaguchi

Hiroo Matsunaga

Katsutoshi Tani

Tadashi Yamazaki

Hiroshi Kojima

Kazunori Shinohara

Katsuhiko Kinoshita

Kazuo Obata

Tsuguyoshi Yamada

Touru Tsuda

A pneumatic tire having improved high-speed running performances is manufactured by conducting vulcanization of a green tire with a mold provided at a position corresponding to a given position between neighborhood of shoulder portion and neighborhood of bead portion with at least one protrusion which protrudes inside the mold and continuously extends in the circumferential direction of the mold and consists of a first arc segment having a center of curvature located outside from the inner surface of the mold and second arc segments each having a center of curvature located inside from the inner surface of the mold and smoothly connecting to the first arc segment at upper and lower ends in the radial direction of the mold.

Pneumatic radial tires

A high-speed running pneumatic radial tire comprises a cylindrical crown portion, a pair of sidewall portions extending inward therefrom, a radial carcass extending from one of the sidewall portions through the crown portion to the other sidewall portion, and a belt and a tread successively superimposed on the crown portion outward in the radial direction of the tire. The tread has plural rows of blocks defined by plural circumferential grooves and many lateral grooves, and the belt is comprised of at least two main crosscord belt layers and an auxiliary belt layer arranged thereon. The auxiliary belt layer is formed by spirally winding a rubberized ribbon ply of heat-shrinkable cords on the main belt layers, in which an overlapped amount of the ribbon ply is made large in a zone of the tread substantially corresponding to the block row than in a zone of the tread substantially corresponding to the circumferential groove.

Pneumatic radial tires for passenger cars

A high performance pneumatic radial tire comprises a toroidal carcass, a tread radially outside a crown portion of the carcass, a belt layer interposed between the carcass and the tread and having a same width of the tread, and an auxiliary layer arranged between the belt layer and the tread and covering the entire belt layer. organic cords are buried substantially parallel to an equatorial plane of the tire in the auxiliary layer, and land portions are defined between at least two circumferential main grooves formed in an outer surface portion of the tread and between the circumferential main grooves and axially opposite edges of the tread. In the tire, a rigidity of the tire corresponding to locations overlapping the circumferential main grooves is made smaller than that of portions corresponding to the land portions by, for example, constituting the auxiliary layer from at least two auxiliary plies comprising one auxiliary ply located on a radially innermost side and covering the belt layer over an entire width thereof, and cutting at least a radially outermost auxiliary ply at locations overlapping the circumferential main grooves among the auxiliary plies having portions overlapping the circumferential main groove.

High performance pneumatic radial tires

Method of making pneumatic radial tires

Automobile tire

To improve high-speed durability of the pneumatic tire formed with a directional tread such that transversal grooves are arranged into a herringbone pattern at regular intervals along the tire circumferential direction, the U-shaped cross section of each of the transversal grooves is formed in such a way that a radius (R.sub.1) of curvature of a step-out side corner between a side wall and a bottom of each transversal groove which is first brought into contact with the ground along a tire rotating direction is determined smaller than that (R.sub.2) of a kick-out side corner therebetween which is afterward brought into contact with the ground at a ratio of about 2 to 5.

Pneumatic tire with directional tread

Pneumatic tires are disclosed, which each comprise a pair of beads, a toroidal carcass composed of at least one carcass ply which extends between the beads and is composed of cords arranged substantially in a radial direction of the tire, a belt layer superimposed radially outside a crown portion of the carcass, a tread arranged radially outside of the belt layer to cover the belt layer, and an auxiliary layer which is arranged between the tread and the belt layer to cover the whole belt layer and is composed of an organic fiber cord arranged substantially in parallel with the tire circumferential direction. The tread is constituted by a tread central portion containing a tire equatorial plane, a pair of tread side edge portions covering the side edges of the belt layer, and a pair of tread intermediate portions between the tread central portion and the tread side edge portions. The auxiliary layer comprises a plurality of plies at at least widthwise opposite side edge portions, and is constituted by a continuous cord member comprising at least one rubberized cord which is spirally wound in the tire circumferential direction. The opposite ends of the cord member of the auxiliary layer are located radially inside the tread intermediate portion or portions of the tread.

Pneumatic tires including spirally wound auxiliary layer outside belt

When a radial tire is used at high speed (e.g. 250 km/h or more), tire blocks deform outward due to a centrifugal force applied to mass at the center of each block, so that contact pressure rises and therefore the tire is heated into blow out. To overcome this problem, the rubber thickness (gage) of the block partitioned by circumferential grooves and transverse grooves is reduced at the central area of the block. To reduce the rubber thickness, a shallow groove extending along the circumferential groove is formed in the middle of the block or a hole is formed at the center of the block.

Pneumatic radial tire suitable for use at high speed

A low profile pneumatic radial tire comprises at least one carcass ply containing cords arranged substantially at 90.degree. relative to a circumference of a tread, and a belt consisting of at least two belt layers which are composed of metal cords inclined relative to the circumference of the tread and intersected with one another between the adjacent belt layers and which are arranged upon a crown of the carcass. The tread surrounds the crown, and is provided with a pair of circumferential main grooves which are disposed symmetrically with respect to an equatorial plane of the tire and which divide a treading portion of the tread into a central region and axially opposite side regions and which are separated by a distance ranging from 45 to 65% of a maximum width of the tire in the state that the tire is assembled onto a normal rim and inflated at a normal internal pressure. The width of the belt ranges from 110 to 130% of a distance between intersections of an imaginary straight line which tangentially contracts with a top surface of a wear indicator projecting from a bottom of each of the circumferential grooves and which is drawn in parallel with a tire rotary axis and a tire contour line at axially opposite side regions of the tread, and the thickness of a tread rubber at maximum width edges of the tread ranges from 30 to 80% of that at the intersections.

Low profile pneumatic radial tires

To improve high-speed durability of a low-section pneumatic radial tire without producing tire separation at both belt ends and expansion at both tread sidewalls after the tire has been worn off to some extent, the tire belt structure disposed between the tire tread and the carcass is composed of two belt layers and a plurality of auxiliary layers. The auxiliary layers comprises a first auxiliary layer extending over the belt layers and at least second and third auxiliary layers arranged on both axially outside end of the tread in such a way that an axially outer end of each of the auxiliary layers extends to near the tread sidewall and an axially inner end of each of the auxiliary layers extends to or beyond under at least an axially outermost circumferential groove formed on the tread in step fashion extending from tread center to tread end or vice versa. Further, these auxiliary layers are formed by winding a ribbon including at least two heat-shrinkable fiber cords coated with a coating rubber in spiral fashion on the circumferential surface of the belt layers.

Low-section pneumatic radial tire

To improve the load supporting capability of a pneumatic safety tire and to prevent the tire bead portion from coming off from the rim seat both during run-flat (flat punctured tire) travel, the pneumatic safety tire comprises a pair of crescent-shaped cross-section reinforcing rubber layers each having the thicknest portion at the tire side portion and a pair of beak-shaped cross-section rim-fixed protruding hard-rubber members each disposed under the reinforcing rubber layer in such a way that annular circumferential bonding surfaces between the two are inclided axially outwardly or inwardly in annular wedge shape. Further, to prevent creases from being produced during green tire forming process and cracks from being produced during run-flat travel in or near the bonding surfaces, crescent-shaped reinforcing layer and the beak-shaped rim-fixed protruding members are extrusion-formed simultaneously before a green tire is formed.

Pneumatic safety tire

To obtain a uniform initial cord tension in an auxiliary layer of a radial tire made up of a toroidal carcass, a belt, the auxiliary layer and a tread rubber, the belt is formed by winding inextensible cords around a drum with a radius of curvature substantially the same as that of a tire tread. Further, when the belt is formed by winding the cords around a flat drum, the auxiliary layer is formed on the belt by winding a heat-shrinkable cord around the belt in spiral fashion in such a way as to apply a higher tension at both the ends of the belt layer than at the center thereof. The radial tire thus manufacture is excellent in high-speed tire durability and tire uniformity, without causing belt separation trouble at high speed.

Method of manufacturing radial tire

To improve the durability and the riding comfortableness of a pneumatic safety tire having at least one carcass ply, at least one belt layer, and a pair of crescent-shaped cross-section reinforcing layers, each of the reinforcing layers comprises a higher elastic rubber layer with a hardness of 70 to 85 in Shore A and an elastic modulus of 25 to 60 kg/cm.sup.2 and an anticrack rubber layer with a hardness of 55 to 70 in Shore A and an elastic modulus of 10 to 30 kg/cm.sup.2. The maximum thickness of the reinforcing layer is preferably 4 to 12 mm. Load applied to the tire during run-flat travel is supported mainly by the higher elastic rubber layer, and crack generation due to tire deformation is reduced by the presence of the anticrack rubber layer.

Growing community of inventors

Kodaira, Japan

Hisao Ushikubo