JPH061119A - Pneumatic tire for iced and snowy road - Google Patents

Abstract

PURPOSE:To improve cornering performance without impairing driving and braking performance when traveling straight by forming sipes in a reversed V shape with the center section in the tire cross direction taken as an apex and lugs in a V shape in a tread surface and making the inclination of sipes in the lateral direction 5 deg. to 25 deg. and the inclination of lug grooves 120 deg. to 40 deg.. CONSTITUTION:In a tire for iced and snowy roads whose groove area ratio is 20 to 50%, and whose snow traction index ST1 is 160 to 250, a main groove 10 of the equator in the peripheral direction, V-shaped lug grooves 20 extending from the end of a tread ground contacting section to the center, and reversed V-shaped sipes 30 are provided in a tread surface T. The sipes 30 are made their respective inclination alpha to be 5 deg. to 25 deg., and the lug grooves 20 are made their respective lateral inclination alpha to be 10 deg. to 40 deg.. When rhog is (overall groove length when projected in the lateral direction)/(ground contact widthXperipheral length) (1/mm), rhos is (overall sipe length when projected in the lateral direction)/(ground contact widthXperipheral length)(1/mm), and Dg is average groove depth(mm), ST1=-6.8+2202rhog+672rhos+7.6Dg. Therefore, traveling performance on iced and snowy road can be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvement of a pneumatic tire for ice and snow roads, and more particularly to a pneumatic tire for ice and snow roads having improved cornering performance without deteriorating driving / braking performance when traveling straight ahead. is there.

[0002]

2. Description of the Related Art In recent years, regulations on spike pollution such as dust and noise have become strict, and as the regulated area expands, a studless tire for snow running on ice and snow roads has been developed. Taking a bath. Most of these studless tires have improved running performance on ice and snow roads due to the edge effect of sipes and lug grooves formed on the tread.

FIG. 2 is an explanatory plan view showing an example of a tread pattern of a conventional studless tire. In FIG. 2, a plurality of main grooves 1 formed in the tire circumferential direction EE ′ on the tread surface T and a plurality of main grooves 1 formed in the lateral direction (the direction perpendicular to the tire equator line) intersecting with the main grooves 1. A block pattern is formed by the sub-grooves 2, and each block is provided with a block pattern in order to improve athletic performance on a snowy road.
A plurality of sipes 3 are arranged in the lateral direction.

The groove area ratio of this conventional studless tire is 20 to 50%, which is the same as that of a normal snow tire (tire for ice and snow roads).
(STI) is in the range of 160-250. However,
The above-mentioned conventional studless tire has excellent driving / braking properties because the sipe 3 is at a right angle to the traveling direction of the tire during straight running, but the sipe 3 tilts with respect to the traveling direction of the tire during cornering. There was a problem that the edge effect of No. 3 decreased and the cornering performance was hindered.

That is, in this conventional studless tire, although the driving / braking performance when going straight on an icy snow road is improved by the edge effect of the sipes 3 formed on the block, when the tire turns, the road surface is Since the edge effect of the sipe 3 with respect to the pressure from is not sufficiently exerted, the cornering performance is temporarily deteriorated, and the tire slips side by side.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems in the conventional studless tires, and it is possible to improve cornering performance without lowering driving / braking performance when traveling straight ahead. It is intended to provide an improved pneumatic tire for ice and snow roads.

[0007]

The present invention has a groove area ratio of 20.
-50%, a snow traction index (STI) represented by the following formula (I) of 160 to 250 for ice and snow roads, and having an inverted V shape with the center in the tire width direction as the apex on the tread surface. A plurality of sipes are provided over both ground contact ends, a plurality of lug grooves are provided in a V shape with the tire width direction central portion as an apex, and the inclination angle α of the sipes with respect to the lateral direction is 5 ° to 25 °. The feature is that the inclination angle β of the lug groove with respect to the lateral direction is set to 10 ° to 40 °.

STI = −6.8 + 2202ρg + 672ρs + 7.6Dg (I) where ρg: (total groove length projected in the lateral direction) / (contact width ×
Perimeter) (1 / mm) ρs: (Total sipe length projected in the lateral direction) / (Grounding width x circumference) (1 / mm) Dg: Average groove depth (mm) Thus, in the present invention, Since the sipe is provided in the inverted V shape and the lug groove is provided in the V shape, the edge effect of the sipe and the lug groove is not substantially reduced as compared with the case where the sipe is provided in the lateral direction. The driving / braking performance is not substantially reduced.

Further, since the inclination angle α of the sipe with respect to the lateral direction is set to 5 to 25 °, when the tire turns on the road surface on ice and snow, the sipe of the tire shoulder portion, which has a particularly high ground contact pressure, is directed toward the traveling direction of the vehicle. Since it is close to a right angle, you can fully exert the edge effect of Sipe,
The cornering performance of the tire can be improved.
In addition, the inclination angle β of the lug groove with respect to the lateral direction is 10
Since it was set to -40 °, the lug groove becomes parallel to the traveling direction of the vehicle when the tire turns on the road surface on ice and snow, so that the rigidity in the traveling direction of the vehicle can be sufficiently maintained,
Does not deteriorate cornering performance.

Therefore, the pneumatic tire for ice and snow roads of the present invention can improve the cornering performance without impairing the driving and braking performances on the ice and snow roads, and particularly when turning on a hard road surface such as on ice. Side slip has disappeared,
Extremely good running performance on snow and ice. Here, the sipe is a thin notch cut from the tread surface into the inside of the tire and has a thickness of 2 mm or less. It is preferably 1 mm or less. The sipe inclination angle α is an angle with respect to the tire lateral direction of a line connecting one end and the other end of the sipe, and is an average value of the sipe angles. The lug groove is a sub-groove that is normally arranged on the tread surface in the tire width direction. The lug groove is wider and deeper than the sipe. The inclination angle β of the lug groove is an angle formed by a line connecting the groove center point of the ground contact width end portion and the other end portion center points with respect to the tire lateral direction.

The structure of the present invention will be described in detail below with reference to the drawings. FIG. 1 shows an example of a tread pattern of a pneumatic tire for ice and snow roads according to the present invention, in which a tread surface T is arranged at a tire center line (equatorial line) and in a tire circumferential direction EE '. Main groove 10 extending to
A large number of lug grooves 20 continuously extending in the tire width direction from one tread ground contact end to almost the center of the tread, and a sipe 30 continuously or intermittently extending in the tire width direction from the main groove 10 to the tread ground contact end. It is provided. Sipe
The reference numeral 30 extends in an inverted V shape from the main groove 10 of the center line to the apex and extends over both ground ends. Further, the lug groove 20 is provided in a V shape with the vicinity of the main groove 10 as an apex.

The groove area ratio of the tire is in the range of 20 to 50%, and the snow traction index (STI) is
It is specified in the range of 160 to 250 respectively. Here, the groove area ratio of the tire indicates the ratio of the groove ground contact surface to the total ground contact area (ground contact width x circumference) of the tread surface.
If it is less than 50%, the athletic performance on snow of the tire decreases, and if it exceeds 50%, the athletic performance on ice of the tire decreases.

Here, the snow traction index
(STI) is an index indicating the performance level on snow calculated from the lateral direction component of the groove and sipe length on the surface of the tread pattern and the groove depth described in SAE Paper 820345, and more specifically, the above formula ( It is represented by I).
If this STI is smaller than 160, good ice-snow road running performance will not be exhibited, and if it is larger than 250, the tire rigidity will decrease, and dry road running performance will be impaired.

The groove width of the center main groove 10 is usually 4 to 10 m.
The m and groove depth are usually set in the range of 9.0 to 12.0 mm. The groove width of the lug groove 20 is usually 4 to 10 mm, and the groove depth is
Usually, it is set in the range of 9.0 to 12.0 mm. The groove width of the sipe 30 is usually 0.4 to 2 mm, and the groove depth is usually set to the range of 50 to 100% of the center main groove 10 or the lug groove 20. The inclination angle α of the sipe 30 is in the range of 5 ° to 25 °. When α is less than 5 °, the edge effect during cornering is reduced and the cornering performance is deteriorated, and when α exceeds 25 °, the edge effect during straight traveling is decreased and the driving / braking performance is deteriorated.

The inclination angle β of the lug groove 20 extends in the direction opposite to the sipe 30 from the viewpoint of drainage, and the inclination angle β with respect to the lateral direction is in the range of 10 ° to 40 °. If it is less than 10 °, the rigidity of the block on the outside of the tire, where the contact pressure is high in the tire tread when cornering, is low with respect to the force in the vehicle flowing direction. This reduces the sipe's edge effect,
Cornering performance is reduced. If it exceeds 40 °, the same effect as that of less than 10 ° will occur, and the edge effect of the groove at the time of straight traveling will decrease, resulting in deterioration of driving and braking performance.

[0016]

EXAMPLES Test tires 1-2 shown in Table 1, conventional tires shown in Table 2, comparative tires 1-2, tires 1 of the present invention
For No. 2, the braking performance on ice and the turning performance on ice were evaluated. The results are shown in Table 1 and Table 2, respectively. in this case,
The tire size was 185/70 R13 85Q, and the tread pattern shown in FIG. 1 was formed on the tread surface. Here, groove area ratio: 35%, STI 200, groove width of sipe 30: 0.8 mm,
Groove depth: 8 mm, groove width of lug groove 20: 7 mm, groove depth: 10.5 m
m.

Evaluation method of braking performance on ice : Air pressure 1.9 kgf
It was mounted on an FF car (front engine front-wheel drive) with an engine of 1800 cc at a rim of 13 x 5 1 / 2JJ with a rim of 13 cm / ² cm, and it was running on the ice at an initial speed of 40 km / h and braking. The braking performance was evaluated by measuring the braking distance. The on-ice performance is shown as an index with the reciprocal of the braking distance being 100 for the conventional tire or the reference tire. The larger the number, the better.

Evaluation method of turning performance on ice : Air pressure 1.9 kgf
/ cm ² , rim 13 × 5 1 / 2JJ, mounted on an FF vehicle (front engine front wheel drive) with an engine of 1800 cc, swiveling on an ice disk with a radius of 30 m, the time required for a certain measurement section Was measured. Displayed as an index with 100 for conventional tires or reference tires. The larger the number, the better.

[0019]

[0020] From Table 1, when the inclination angle α of the sipe is 15 °,
It can be seen that both performances are excellent. Further, it can be seen from Table 2 that the tires 1 and 2 of the present invention have excellent turning performance on ice while maintaining the braking performance on ice. From the above results, it is clear that the pneumatic tire for ice and snow roads of the present invention has improved cornering performance without impairing the driving / braking performance when traveling straight ahead.

[0021]

As described above in detail, the pneumatic tire for ice and snow roads according to the present invention has improved cornering performance without impairing the driving and braking performances on the ice and snow roads. The skid when turning on a hard road such as ice has been eliminated, and the running performance on snow and ice is extremely excellent.

[Brief description of drawings]

FIG. 1 is an explanatory plan view showing an example of a tread pattern of a pneumatic tire for ice and snow roads of the present invention.

FIG. 2 is an explanatory plan view showing an example of a tread pattern of a conventional studless tire.

[Explanation of symbols]

 T Tread surface 10 Main groove 20 Lug groove 30 Sipe

Claims (1)

[Claims] 1. A groove area ratio of 20 to 50% and a snow traction index (STI) represented by the following formula (I) is 1.
In the tires of 60 to 250, a plurality of sipes are provided on the tread surface in an inverted V shape with the central portion in the tire width direction as the apex over both ground contact ends, and in the V shape with the central portion in the tire width direction as the apex. Pneumatic tire for ice and snow roads, in which the sipe has an inclination angle α of 5 ° to 25 ° with respect to the lateral direction and the lug groove has an inclination angle β of 10 ° to 40 ° with respect to the lateral direction. STI = -6.8 + 2202ρg + 672ρs + 7.6Dg (I) where ρg: (total groove length projected in the lateral direction) / (contact width x
Perimeter) (1 / mm) ρs: (Total sipe length projected in the lateral direction) / (Contact width x perimeter) (1 / mm) Dg: Average groove depth (mm)