JPH07228105A - Pneumatic tire - Google Patents

Abstract

(57) [Summary] [Purpose] To provide a pneumatic tire capable of improving performance on ice and snow. [Structure] A pneumatic tire with a block pattern,
The belt layer is made of a belt ply in which belt cords made of organic fibers or inorganic fibers are arranged at an angle of 20 ° to 35 ° with respect to the tire equator, while the tread portion has a JISA hardness of 50 ° or more and 65 ° or less. The radius of curvature of the tread is 1.05 times or more and 1.65 times the cross-sectional width of the tire in a normal state in which it is made of tread rubber and assembled to a regular rim with normal internal pressure applied and no load is applied. The maximum length in the tire circumferential direction of the tread contact surface where the tread surface comes into contact with the maximum width in the tire axial direction of the tread contact surface in the maximum load state in which the regular state and the specified maximum load of the tire are applied together with the following. 1.
A pneumatic tire characterized by being set to 3 times or more and 1.5 times or less.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire capable of improving its performance on ice and snow.

[0002]

2. Description of the Related Art In recent years, as tires traveling on ice and snow roads,
So-called studless tires without spikes are being used frequently. In such studless tires, in order to provide sufficient grip on ice and snowy roads, a large number of sipes are formed on the block to dig up the road surface with sipeing edges, etc. to increase the frictional force and to soften the tread portion. It is made of rubber and is used to increase the adhesive frictional force with the ice surface.

[0003]

However, the studless tire as described above can improve running performance on an ice and snowy road as compared with a normal radial tire, but is significantly inferior in performance on ice as compared with a spike tire. Since then, there has been a longing for further improvement in on-ice performance.

The inventor of the present invention pays attention to the shape of the tread contact surface of the pneumatic tire, and variously regulates and changes the cord angle of the belt ply, the rubber hardness of the tread rubber, and the radius of curvature of the tread portion for this shape. As a result of repeated studies, the maximum length of the tread contact surface in the tire circumferential direction is 1.
The present invention has been completed by finding that the feeling on ice is improved by setting the ratio to 3 times or more and 1.5 times or less.

An object of the present invention is to provide a pneumatic tire capable of further improving the performance on ice and snow roads.

[0006]

The present invention provides a carcass consisting of a carcass ply having a turnback portion from a tread portion to a sidewall portion and folded back at a bead core of a bead portion, and comprising a carcass ply in which organic fiber cords are arranged radially. A block provided with a belt layer arranged radially outward of the tire of the carcass and inside the tread portion, and provided with a longitudinal groove extending in the circumferential direction on the tread surface and a lateral groove intersecting with the longitudinal groove and extending to the tread edge. A pneumatic tire of a pattern, wherein the belt layer is made of a belt ply in which a belt cord made of an organic fiber or an inorganic fiber is arranged at an angle of 20 ° to 35 ° with respect to the tire equator, while the tread portion is Is it in a normal state with a tread rubber with a JIS A hardness of 50 ° or more and 65 ° or less, and with a regular internal pressure applied to the regular rim with a rim assembled? In unloaded condition without applying a load, 1 the curvature radius of the tread portion of the section width of the tire.
The maximum length in the tire circumferential direction of the tread contact surface with which the tread surface is in contact with the tread is the maximum length in the normal state and in the maximum load state in which the specified maximum load of the tire is applied. It is 1.3 times or more and 1.5 times or less than the maximum width of the contact surface in the tire axial direction.

It is desirable that the belt cord is a steel cord and is arranged at an angle of 25 ° to 35 ° with respect to the tire equator.

The tread rubber preferably has a JISA hardness of 50 ° or more and 60 ° or less.

[0009]

According to the present invention, the belt layer disposed radially outward of the carcass has a belt cord made of organic fibers or inorganic fibers at a relatively large angle with respect to the tire equator, more specifically, The belt ply, which is arranged at an angle of 20 ° to 35 °, which is larger than that of a normal radial tire, acts to improve the ability to wrap the protrusions.

When the angle of the belt cord with respect to the tire equator is smaller than 20 °, the maximum length in the tire circumferential direction of the tread contact surface where the tread surface contacts the ground can be made sufficiently large for handling feeling (touch feeling). However, if the angle exceeds 35 °, the hoop effect of the belt layer is reduced and the steering stability is adversely affected.

Further, the tread rubber of the tread portion is JIS A
By adopting a soft rubber material having a hardness of 50 ° or more and 65 ° or less, it acts in the direction of increasing the deformation amount of the tread rubber in the tire ground contact surface.

The tread rubber has a JIS A hardness of 50 °.
If it is less than 60 ° C, the rigidity of the tread portion is excessively reduced and the steering stability is impaired. On the contrary, if it is more than 65 °, the length of the tread contact surface in the tire circumferential direction can be sufficiently increased. Therefore, the grip power and the frictional force with the road surface tend to be insufficient, and the purpose of improving the performance on ice and snow cannot be fully achieved.

Furthermore, in a normal state in which the tire is assembled on a regular rim and a regular internal pressure is applied and no load is applied, the radius of curvature of the tread portion is 1.05 times or more the tire cross-sectional width and 1 It is less than or equal to 65 times. Considering that the radius of curvature of the tread portion with respect to the tire cross-section width is generally set to about 1.8 in the studless tire, it can be understood that the radius of curvature of the tread portion of the present invention is set small. Therefore, by reducing the radius of curvature of the tread with respect to the tire cross-sectional width, the tread acts to increase the ground contact pressure of the crown portion.

When the radius of curvature of the tread portion is smaller than 1.05 times the sectional width of the tire, the area of the tread contact surface tends to be excessively reduced, and the grip force tends to be insufficient, while conversely 1.65 times. If it is larger than this, the ground contact pressure of the crown portion cannot be sufficiently increased.

By organically combining the above constituent elements, the ground contact pressure of the crown portion of the tire is increased and the deformation amount of the tread rubber on the ground contact surface of the tire is increased. As a result, the tire circumference of the tread ground surface is increased. The maximum length in the direction may be a so-called longitudinally long tread contact surface having a maximum width in the tire axial direction of the tread contact surface.

Further, in the present invention, the tread ground contact surface is not limited to the vertically long one, and the ratio of the maximum length in the tire circumferential direction to the maximum width in the tire axial direction is 1.3 to 1. It has been found that the on-ice performance is remarkably improved by restricting the range to 5.

As described above, the tread contact surface is vertically elongated and the ratio of the maximum width to the maximum length is restricted, so that the feeling of contact of the tire on ice is significantly improved and the handling feeling is improved.

When the belt cord is a steel cord and is arranged at an angle of 25 ° to 35 ° with respect to the tire equator, the maximum length of the tread contact surface in the tire circumferential direction can be further increased. Therefore, it is possible to further improve the performance on ice and snow, especially the feeling (feeling of contact with ground) on ice.

The tread rubber JI of the tread portion
The SA hardness is preferably 50 ° or more and 60 ° or less in order to ensure the improvement of the performance on ice and snow.

The radius of curvature of the tread portion can be optimized by setting the radius of curvature to 200 mm or more and 300 mm or less when the tire has a sectional width of about 185 mm.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. 1 and 2, a pneumatic tire 1 includes a tread portion 2, a sidewall portion 3 extending from both ends thereof inward in the tire radial direction, and a bead portion 4 connected to an inner end of the sidewall portion 3 in the tire radial direction. Have and. Further, the pneumatic tire 1 has a body portion 6a that extends from the tread portion 2 through the sidewall portion 3 to the bead portion 4, and a turnback portion that is folded back around the bead core 5 of the bead portion 4 from the inner side to the outer side in the tire axial direction. A carcass 6 having 6b,
A belt layer 7 disposed inside the tread portion 2 and outside the carcass 6 in the radial direction.

In the pneumatic tire 1, the flatness ratio, which is the ratio of the tire height from the tire bead line to the tire section width W, is 70 to 80%, and the tread edges E, E are the distance in the tire axial direction. A certain tread width is set to 70% or more of the sectional width W of the tire.

The tread portion 2 has a JIS A hardness of 50.
By arranging the soft tread rubber 12 of not less than ° and not more than 65 °, more preferably not less than 50 ° and not more than 60 °, it is possible to facilitate the deformation of the tread rubber 12 within the tire ground contact plane. Table 1 shows the composition and physical properties of such tread rubber 12.

[0024]

[Table 1]

The carcass 6 comprises one or more carcass plies, in this embodiment two or more carcass plies, each having a carcass cord of radial or semi-radial arrangement which is inclined at an angle of 60 to 90 ° with respect to the tire equator C. Further, as the carcass cord, an organic fiber cord such as nylon, rayon, polyester, aromatic polyamide fiber is used.

The belt layer 7 comprises a plurality of belt plies 7A and 7B in this embodiment, and each belt ply is composed of:
In this embodiment, a belt cord made of an organic fiber such as nylon, rayon, polyester, or aromatic polyamide fiber is arranged at a relatively large angle of 20 to 35 ° with respect to the tire equator C, and adjacent belt cords are oriented so as to intersect each other. Will be distributed.

By thus arranging the cords of the belt ply at a large angle for a radial tire, the ability to wrap around the protrusions of the tire is improved.

On the tread surface 2A, in the present embodiment, a central vertical groove 9A bent in a zigzag shape on the tire equator C,
A vertical groove 9 consisting of a pair of zigzag vertical grooves 9B, 9B arranged at a distance on both sides in the tire axial direction, and a plurality of lateral grooves connecting the vertical groove 9B on the side and the tread edge E. 10 ... are provided.

Further, a vertical small groove 11 having a groove width smaller than those of the vertical grooves 9 and consisting of a straight groove is disposed between the central and side vertical grooves 9A and 9B.

On the tread surface 2A, there is formed a block pattern consisting of a plurality of blocks 14 separated by these vertical grooves 9, horizontal grooves 10, vertical small grooves 11 ...
In addition, a plurality of sipes 15 extending in the tire axial direction are circumferentially spaced apart from each other in the block 14.

Further, in this embodiment, the vertical groove 9 and the horizontal groove 10 are provided.
The groove depth is set in the range of 4 to 12% of the tread width, and the groove width is set in the range of 6 to 12% of the tread width. The groove depth of the lateral groove 10 is preferably set to be equal to or slightly shallower than the groove depth of the vertical groove 9.

Further, as shown in FIG. 1, the tread portion 2
Is a normal state in which the tire is assembled on a regular rim and a regular internal pressure is applied thereto, and in a no-load state in which no load is applied, the radius of curvature TR of the tread portion is 1.05 of the sectional width W of the tire.
It is more than twice and less than 1.65 times. As compared with general specifications of studless tires, the radius of curvature TR of the tread is set smaller, and as a result, the action of increasing the ground contact pressure of the crown portion 2B is obtained, and the cord angle of the belt ply and the tread rubber 12 are obtained. Combined with the JISA hardness of No. 2, the shape of the tread contact surface is deformed into a so-called longitudinal length that is longer in the tire circumferential direction than in the tire width direction.

For a pneumatic tire having a tire sectional width W of about 185 mm, the radius of curvature TR is 200 mm.
It should be at least 300 mm.

Further, when the pneumatic tire 1 is in the normal state and in the maximum load state in which the specified maximum load of the tire is applied, as shown in FIG. 2, the maximum tread surface 2A in which the tread surface 2A is in contact with the road surface is the maximum in the tire circumferential direction. The length Y is set to 1.3 times or more and 1.5 times or less of the maximum width X in the tire axial direction.

As described above, the tread contact surface 13 is vertically long and has a maximum width Y in the tire circumferential direction and a maximum length X in the tire axial direction.
By restricting the ratio between and, the feeling of contact of the tire on ice is significantly improved and the handling feeling is improved.

By forming the belt cord from a steel cord and arranging it at an angle of 25 ° to 35 ° with respect to the tire equator C, the maximum length Y of the tread contact surface 13 in the tire circumferential direction is further increased. It can be increased, and the performance on ice and snow can be further improved.

The maximum length Y of the tread contact surface 13 in the tire circumferential direction is 1.3 of the maximum width X in the tire axial direction.
If it is less than twice, the sufficient feeling of contact with the tire on ice will not be fed back to the driver's handling feeling, which is not preferable, while if it is more than 1.5 times, the rigidity of the tire will be remarkably reduced and the steering stability will be stable. It is not preferable because it deteriorates the sex.

[0038]

[Examples] Tires having a tire size of 185R148PR and having the structures shown in FIGS. 1 and 2 (Examples 1 to 6) were manufactured as prototypes, and tires other than the structure of the present invention (Comparative Examples 1 to 4) were prepared. We made prototypes and compared the performance. The test conditions are as follows.

(1) Steering performance Regarding the steering performance, the test tire was mounted on an ordinary indoor steering performance tester, and the cornering power was measured at a load of 525 and an internal pressure of 1.9 ksc.
It was displayed as an index as 00. The larger the number, the better.

(2) Braking performance on ice Each of the four test tires was mounted on a passenger car having a displacement of 1800 cc, and the braking distance was measured on ice at an outside air temperature of -5 ° C. The tire of Comparative Example 1 was indexed to 100. The larger the value, the better the braking.

(3) Snow climbing performance Each test tire 4 was mounted on a passenger car having a displacement of 1800 cc, and the climbing time in a 50 m section with an outside temperature of -5 ° C and a climbing gradient of 7% was measured. The tire of Comparative Example 1 was indexed to 100. The larger the value, the better the grade.

(4) Riding Comfort Performance The test tire was mounted on a fixed shaft for a normal vibration overhanging the projection in a room, and the axial load fluctuation during the riding over the projection was measured under a load of 525 kg. The tire of Comparative Example 1 is indexed to 100, and the larger the value, the better the riding comfort.

(5) Abrasion resistance performance Four test tires were mounted on a passenger car having a displacement of 1800 cc, traveled on a public road for 10,000 km, and the amount of change in groove depth was measured. The tire of Comparative Example 1 is indexed to 100, and the larger the value, the better the abrasion resistance. The test results are shown in Table 2.

[0044]

[Table 2]

As a result of the test, it was confirmed that the tires of Examples had improved braking performance on ice with almost no change in steering performance.

[0046]

As described above, the pneumatic tire of the present invention can further improve the performance on ice as compared with the conventional studless tire.

[Brief description of drawings]

FIG. 1 is a meridian sectional view of a tire showing an embodiment of the present invention.

FIG. 2 is a plan view of a tread contact surface.

[Explanation of symbols]

 2 tread part 3 sidewall part 4 bead part 5 bead core 6 carcass 7 belt layer 9 vertical groove 10 horizontal groove 11 vertical small groove 12 tread rubber 13 tread ground surface 14 block 15 siping

Claims (5)

[Claims] Claims: 1. A carcass comprising a carcass ply having a turnback part from a tread part to a sidewall part and being folded back at a bead core of a bead part, and a carcass ply having an organic fiber cord arranged radially, and a carcass outward in a tire radial direction. A pneumatic tire having a block pattern, which comprises a belt layer arranged inside the tread portion, and which is provided with a longitudinal groove extending in the circumferential direction on the tread surface and a lateral groove intersecting with the longitudinal groove and extending to the tread edge. The belt layer is made of a belt ply in which a belt cord made of an organic fiber or an inorganic fiber is arranged at an angle of 20 ° to 35 ° with respect to the tire equator, while the tread portion has a JIS A hardness of 50 ° or more and 65% or more.
In the normal state in which the tire is made of a tread rubber of ° or less and is assembled to the regular rim and the normal internal pressure is applied and no load is applied, the radius of curvature of the tread portion is 1.05 times or more the tire cross-sectional width and 1 The maximum length in the tire circumferential direction of the tread contact surface with which the tread surface is in contact is defined as the tire axis of the tread contact surface in the normal state and in the maximum load state in which the specified maximum load of the tire is applied. A pneumatic tire having a width of 1.3 times or more and 1.5 times or less of a maximum width in a direction. 2. The pneumatic tire according to claim 1, wherein the belt cord is a steel cord. 3. The pneumatic tire according to claim 2, wherein the belt cord is arranged at an angle of 25 ° to 35 ° with respect to the tire equator. 4. The pneumatic tire according to claim 2, wherein the tread rubber has a JISA hardness of 50 ° or more and 60 ° or less. 5. The pneumatic tire according to claim 2, wherein the radius of curvature of the tread portion is 200 mm or more and 300 mm or less.