JPH0485105A - Radial tire for passenger car - Google Patents

Abstract

PURPOSE:To improve puncture resistance by providing an edging rib protrusively on the buttress surface of a lug groove end part, then extending tread rubber to the starting point of the edging rib so as to cover side wall rubber, and providing a band layer from the specified position of the edging rib starting end part so as to cover a belt layer. CONSTITUTION:The end part of a buttress part 3 is provided with a slightly elevated edging rib 12 extended circumferentially, and tread rubber 13 is extended from a tread part 2 as far as outside the buttress part 3 so as to be disposed to cover side wall rubber 14, being bounded by a boundary face M inclined obliquely to the radial direction between a position underneath the starting point of the edging rib 12 and the end part H of a belt layer 9. The belt layer 9 is then provided with a band layer 15, formed of plural plies made of inorganic fiber cords such as nylon buried into topping rubber, disposed along the boundary face M from a position, spaced by the distance 3mm-7mm from the starting point F of the edging rib 12, as an origin.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a radial tire for passenger cars with improved puncture resistance.

[Conventional technology]

In recent years, an increasing number of passenger cars are capable of driving on so-called off-road roads other than on general roads. In tires used for such vehicles, the buttress portion S is
As shown in Figure 5, it is formed using a so-called sidewall over tread (SOT) structure in which sidewall rubber b overlaps the outside of tread rubber a, similar to that used for on-road driving, increasing the bonding strength between both rubbers and providing grip. The tread grooves were deepened to increase power. Therefore, the lug grooves (g) extending in the buttress portion are also formed to be wider and deeper than those of ordinary tires designed exclusively for on-road driving.

[Problem to be solved by the invention]

However, when driving off-road, the lug grooves g tend to become stoney, and as a result, cracks occur in the buff-less portions S, causing the tire to bank.

In order to improve puncture resistance, it is conceivable to increase the rubber thickness t at the lug groove bottom e in the buttress portion S, but by increasing the rubber thickness t, the tread portion becomes thick over almost the entire area. , the weight of the tire increases and the cost increases.

As a result of intensive research to improve tire puncture resistance without increasing the weight of the tire, the inventor developed a so-called tread overlay in which tread rubber made of hard rubber is layered on the outside of shoulder rubber in the buttress section, contrary to the conventional structure. The sidewall (TO3) structure increases the hardness of the rubber in the lug groove, and in addition, by interposing a reinforcing layer at the boundary between both rubbers, the locking properties of the buttress part are increased and impact resistance is increased. They discovered scales that have excellent puncture resistance.

The present invention is based on the fact that the tread rubber covers the sidewall rubber through the boundary surface connecting the starting point of the edge rib surface and the end of the belt layer, and also provides a band layer along the boundary surface. The objective is to provide a radial tire for passenger cars that has improved impact resistance and puncture resistance.

[Means to solve the problem]

The present invention includes a carcass that leaves a tread portion, a buttress portion and a sidewall portion, and folds around a bead core of a bead portion, and a belt layer disposed inside the tread portion and outside the carcass, and a belt layer provided on both sides of the tread portion. At the end of the buttress of the lug groove, a small-height edging rib is formed that protrudes from the buff tress surface and extends in the circumferential direction, and the tread rubber on the outside of the tread portion is formed between the starting point of the surface of the edging rib and the belt. The layer extends from the outside of the sidewall portion through a boundary surface oblique to the radial direction connecting the axial end of the tire and covers the sidewall rubber that is softer than the tread rubber, and extends from the starting point in the axial direction of the tire. This radial tire for a passenger car is provided with a band layer made of an organic fiber cord and extending along the boundary surface to the belt layer starting from a position separated by a distance of 3W or more and 7cm or less in the opposite direction.

[Effect]

The tread rubber of the tread part has a so-called TO5 structure that covers the sidewall rubber, which is softer than the tread rubber, through the interface connecting the edge decoration rib and the end of the belt layer, so the lug grooves formed on the tread surface The grooves are formed from hard rubber tread rubber, and the grooves have excellent impact resistance, and can prevent cracking of the grooves even in the case of stone bite, thereby increasing puncture resistance.

Furthermore, since a band layer made of organic fiber cords is arranged on the boundary surface and extends to the belt layer along the boundary surface, it prevents the impact from being transmitted to the carcass when biting stones and protects the carcass cord from damage. , the durability of the tread portion can be improved.

Furthermore, since the band layer's starting point is located at a regulated distance inward from the starting point of the boundary surface, the tread rubber and sidewall rubber are in close contact with each other in the vicinity of the tire's outer surface, preventing bonding. Because it is strong, it prevents peeling from the interface and improves durability.

In this way, in the present invention, each of the above-mentioned configurations is combined into one, and the impact resistance of the lug grooves in the buffless portion can be increased, and the puncture resistance can be improved.

〔Example〕 An embodiment of the present invention will be described below based on the drawings.

In FIG. 1.2, the radial tire 1 for a passenger car includes a carcass 7 that passes from the tread portion, passes through the buttress portion 3, the sidewall portion 4, and folds around the bead core 6 of the bead portion 5, and the inside of the tread portion 2 and the carcass 7. and a belt layer 9 disposed on the outside.

The tread portion 2 has buttress portions 3 from both sides thereof.
A tread groove G- including a plurality of lug grooves 11- extending at the end of the tire is arranged in the tire circumferential direction and the tire meridian direction, and a block pattern 21 is formed on the tread portion 2 by these tread grooves G-. .

The carcass 7 is made of organic fiber cords such as nylon, polyester, aromatic polyamide, etc.
It is formed by one or more carcass plies 7A and 7B, two carcass plies 7A and 7B in this embodiment, arranged side by side and inclined at an angle of 0 to 90 degrees.

In addition to organic fiber cords such as nylon, polyester, and aromatic polyamide, the belt layer 9 is made of one or more belt plies 9A, 9B, in this example, three belt plies 9A, 9B, in which steel cords are arranged side by side and inclined with respect to the tire equator C. It is formed by overlapping 9C.

Further, at the end of the buttress portion 3, a decorative rib 12 is formed which protrudes from the surface of the buttress portion, extends in the circumferential direction of the tire, and has a small height.

Tread rubber 13 is formed on the outside of the tread portion 2, and sidewall rubber 14 is formed on the outside of the sidewall portion 4 and the buttress portion 3, respectively.

The tread rubber 13 has, for example, a rubber composition shown in A to E in Table 1, and is made of hard rubber having a JISA hardness of 60 or more and 75 or less. Also, the side wall rubber 14 is
According to the rubber composition shown in Table 1 A1 to A4, the JISA
The hardness is in the range of 50 to 60 degrees. Therefore, the sidewall rubber 14 is formed as a softer rubber than the tread rubber 13.

The tread rubber 13 and the sidewall rubber 14 are bounded by a boundary surface M that is inclined obliquely with respect to the tire radial direction, which connects the surface of the edge decoration rib 12 as a starting point F and the tire axial end H of the belt layer. be combined.

If the hardness of the tread rubber 13 is less than 60 degrees, the buttress portion is likely to be damaged when stones bite, and if it exceeds 75 degrees, the rigidity of the tread portion 2 increases, increasing rolling resistance and reducing ride comfort. .

On the other hand, since the trimming ribs 12 are raised from the buttress portion 3, the stress on the outer surface of the trimming ribs 12 is reduced when the tire is deformed due to running.

Therefore, by locating the starting point F of the boundary surface M on the surface of the edge decoration rib 12, the force acting on the boundary surface M becomes small, and IAJl of both rubbers can be efficiently prevented.

A band layer 15 is disposed on the boundary surface M.

The band layer 15 is composed of one or more band plies, in this embodiment, one band ply, in which organic fiber cords such as nylon, polyester, aromatic polyamide, etc. are embedded in topping rubber.

Since the band ply is formed using an organic fiber cord, it can be elastically deformed even if an impact load is applied to the buttress part 3, such as when a stone gets caught in the lug groove 11. can be absorbed into the band layer 15 and the sidewall rubber 14 via the band layer 15.

It is preferable that the organic fiber cord has an initial elastic modulus in a range of 280 kg/2 or more and 3,700 kg/2 or less and 1 or less.

If the initial elastic modulus is less than 280kg+/■8, the buttress portion 3 will have an impact of 11? iii) The impact absorption capacity when heavy loads are applied is small, and the effect of providing the band layer 15 is not exhibited. Also, if the initial elastic modulus exceeds 3700 kg/■3, the rigidity of the band layer increases, and as a result, the entire tread portion 2 The rigidity increases, rolling resistance increases, and riding comfort decreases.

The number of organic fiber cords to be implanted is also preferably in the range of 45 to 60 per 5c11 for the above-mentioned reasons.

The band layer 15 is formed from a starting point P at a distance of 3 days or more and 7 cm or less from the starting point F of the boundary surface M located on the surface of the edge decoration rib 12 in the axial direction of the tire. In this embodiment, the end point Q of the band layer 15 is located at the end H of the belt layer 9.

In this way, by separating the starting point P of the band layer 15 from the starting point F of the boundary surface M by a distance 11L, the end of the band layer can be completely covered by both the tread rubber 13 and the sidewall rubber 14, Peeling of the band layer 15 can be prevented.

If the distance jlIL is less than 3 days, the band layer 15 is likely to peel off in the vicinity of its starting point P, and if it exceeds 7 days, the cord of the carcass 7 will be damaged near the starting point P due to stone bite in the lug groove 11. Durability decreases.

Further, in this embodiment, the buff dress portion 3 has the edge decoration rib 1.
The thickness TB between the groove bottom of the lug groove IO and the outer surface of the carcass at a position separated by 5 mm from the radially outer end of the outer surface along the outer surface toward the tire equator side is 4.5 m or more and 8.5 m or more.
The range is below ta.

When the thickness TB is less than 4.5 mm, the rubber thickness of the tread rubber 13 becomes thin, and the impact resistance at the groove bottom of the lug groove 10 decreases, while when it exceeds 8.5 mm, the tread rubber 13 becomes thin over the entire area. As a result, the tire weight increases and the cost increases.

FIG. 3(a) (false) shows another example in which the band layer is placed in a different position.

FIG. 3 (In the season, the band layer 15A extends from the starting point P of the above structure to the belt layer 9 along the boundary surface M, and its terminal end Q is between the inner surface of the belt layer 9 and the outer surface of the carcass 7. The end @Q is held between the belt layer 9 and the carcass 7 to prevent movement of the band layer 15A.

In addition, in Fig. 3, the terminal end Q of the band layer 15B covers the end H of the carcass 9, and it is possible to prevent the end part of the belt layer 9 from peeling off due to deformation of the tread part during running. can.

By configuring the band layer as shown in FIG. 3 (18) or (3), the durability of the tread portion 2 can be further improved.

〔Concrete example〕

(A) Tires with a tire size of P235/75 R15 having the structure shown in FIG. 1 and the specifications shown in Table 2 were prototyped (Examples 1 to 7), and their performance was tested. For comparison purposes, tires (Comparative Examples 1 to 4) with specifications other than those specified in the present invention were manufactured and tested.

The test is based on the specifications below.

(1) Buttress penetration energy test A sample tire was mounted on a rim of 6% J x 15, and 1.8 kg/cm was applied to the inner cavity.
The tire was subjected to an impact test using a pendulum impact tester I.

The pendulum impact test III is as shown schematically in Figure 4.
The tread surface of the sample tire T is gripped by a gripper K, and a pendulum N is applied to the groove bottom of a lug groove R located near the gripper to apply an impact load to the groove bottom. The impact energy can be changed by adjusting the weight of the weight W of the pendulum N, and the impact energy when a crack occurs at the bottom of the groove is measured.

The numerical values in the table are expressed as an index with Comparative Example 1 set as 100, and the larger the numerical value, the better.

(2) Durability of buffless part (2.45 when installed on a 6% J x 15 rim as in item 13)
When the tire was loaded with an internal pressure of ksr/- and a load of 1.5 times the maximum allowable load of the tire using a drum testing machine, and the tire was run for a distance of 30,000 km at a speed of 80 km/H, the buffless portion It was expressed as an index with 100 being the case where no damage was observed.

A value less than 100 indicates that damage has occurred.

(B) Regarding tires of the same size as the above item (A>),
We investigated the relationship between the hardness of each rubber, tread rubber and sidewall rubber, and buff stress penetration energy. In addition, during the investigation, the configuration of the band layer was kept constant as shown in Table 3. The energy test was conducted under the same conditions as in section (A).

As a result of the test, it was confirmed that the examples were superior to those of the comparative examples.

[Effects of the Invention] As described above, in the passenger car radial tire of the present invention, the tread rubber of the buff tress portion covers the sidewall rubber via the boundary surface connecting the starting point of the edge decoration rib surface and the end of the belt layer. Moreover, since the band layer is provided along the boundary surface, the impact resistance at the bottom of the lug groove can be improved, and the puncture resistance can be improved.

[Brief explanation of drawings]

FIG. 1 is a left half sectional view of a tire showing an embodiment of the present invention;
Figure 2 is a developed plan view illustrating the tread pattern;
3(a) to 3(b) are partial cross-sectional views showing other examples of band layers, FIG. 4 is a front view schematically showing an apparatus for measuring the penetration energy of lug grooves, and FIG. 5 is a conventional technique. FIG. 2-) Red part, 3- Buttress part, 4- Sidewall part 5- Bead part 6- Bead core,
7- carcass, 9- belt layer, 11- lug groove,
12-Edge rib, 13-.-Tread rubber, 1.1-
Sidewall rubber, 15--band layer, F--111 starting point, H--end of belt layer, L--distance,
M - interface, P - starting point, TB - thickness of buntless part from the groove bottom. Patent applicant Sumitomo Rubber Industries Co., Ltd. Agent
Patent Attorney Tadashi Naemura Figure 2 I! 1 Figure 3 (a) 'tx31''W (b) Figure 4 Figure 5

Claims (1)

[Claims] 1. A carcass that passes from the tread portion to the buttress portion, the sidewall portion, and is folded back around the bead core of the bead portion;
a belt layer disposed inside the tread part and outside the carcass, and a small-height edge decoration rib is formed at the buttress end of the lug groove on both sides of the tread part, protruding from the buttress surface and extending in the circumferential direction. At the same time, the tread rubber on the outside of the tread portion extends from the outside of the sidewall portion via a boundary surface oblique to the radial direction connecting the starting point of the surface of the edge decoration rib and the axial end of the belt layer. and covers the sidewall rubber, which is softer than the tread rubber, and extends 3 m inward in the axial direction of the tire from the starting point.
A radial tire for a passenger car, comprising a band layer made of an organic fiber cord and extending along the boundary surface to the belt layer starting from a position separated by a distance of 7 mm or more and 7 mm or more. 2. The buttress portion has a thickness of 4 mm between the groove bottom of the lug groove and the outer surface of the carcass at a position 5 mm apart from the radially outer end of the trim rib toward the tire equator along the outer surface. The radial tire for a passenger car according to claim 1, having a diameter of 5 mm or more and 8.5 mm or less.