JP2000309206A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maximize and to enhance hydroplaning resistance and improve wet performance by restricting the groove volume ratio between vertical groove overall volume and lateral groove overall volume within a ground contact area of a tread. SOLUTION: This tire has, on its tread surface 2, a vertical groove 3 that runs in the circumferential direction of tire and a lateral groove 4 that runs with an inclination of 40 deg. or more in relation to the circumferential direction of tire. In such conditions where the tire is assembled with a regular rim, inflated with a regular internal pressure, applied with a regular load, and grounded on a flat surface, a ratio (Ga/Gc) between the overall volume of the vertical groove Gc within a ground contact area of the tread S and the overall volume of the lateral groove Ga within the ground contact area of the tread S is 0.25 to 0.35.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a pneumatic tire capable of improving wet performance.

[0002]

2. Description of the Related Art A pneumatic tire has a basic drain groove formed on a tread surface by a vertical groove extending in the tire circumferential direction and a plurality of lateral grooves extending in a direction intersecting the vertical groove. It is equipped as. The tire uses these vertical grooves and horizontal grooves to discharge moisture between the tire and the road surface to the outside of the tire to improve wet performance, and particularly to prevent a hydroplaning phenomenon and the like. In order to increase the drainage efficiency of the road surface, the sea ratio (sea rat) expressed as the ratio of the total surface area of all grooves to the total surface area of the tread portion
io) may be increased, but this degrades dry steering stability, abrasion resistance, and noise performance.

[0003] The present inventors have noticed from the results of various experiments that the hydroplaning occurrence speed differs depending on the individual tires even if the load applied to the tires and the above-mentioned sea ratio are the same. As a cause, it was found that the vertical grooves and the horizontal grooves had different contribution rates to the hydroplaning resistance performance. That is, even when the sea ratio is fixed, it has been found that the hydroplaning resistance can be significantly improved by optimizing the ratio of the groove volume of the vertical groove and the horizontal groove, and the present invention has been completed. Was.

As described above, the present invention provides a pneumatic tire capable of improving hydroplaning resistance, particularly suitable for a passenger car, based on optimizing the ratio of the groove volume of the vertical groove and the horizontal groove. It is intended to be.

[0005]

According to the first aspect of the present invention, a tread surface has a vertical groove extending in the tire circumferential direction and a lateral groove inclined at an angle of 40 ° or more with respect to the tire circumferential direction. The vertical groove total volume Gc in the tread ground contact surface which is arranged and rim assembled to the normal rim, filled with the normal internal pressure and loaded with the normal load and grounded on a flat surface, and the transverse groove total volume Ga in the tread contact surface And the groove volume ratio (Ga /
Gc) is a pneumatic tire with 0.25 to 0.35.

Here, the definitions used in this specification are as follows. First, a “regular rim” is a rim defined for each tire in a standard system including a standard on which a tire is based. For example, a standard rim for JATMA, a “Design Rim” for TRA, or an ETRT
If it is O, it will be "Measuring Rim". In addition, the "normal internal pressure" is the air pressure that each standard defines for each tire in a standard system including the standard on which the tire is based,
JATMA for maximum air pressure, TRA for table "TI
RE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURE
Maximum value described in "S", or "INFLATION P" for ETRTO
RESSURE ", but if the tire is for a passenger car, the pressure is 180 kPa. Further," regular load "is a load defined by each standard in the standard system including the standard on which the tire is based. Yes, maximum load capacity for JATMA, table "TIRE LOAD LIMITS A" for TRA
The maximum value described in "T VARIOUS COLD INFLATION PRESSURES" or "LOAD CAPACITY" for ETRTO.

[0007]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a development view of a tread portion of a pneumatic radial tire for a passenger car (hereinafter, may be simply referred to as “tire”) as a preferred embodiment of the present invention. The tire is on the tread surface 2,
The vehicle includes a plurality of vertical grooves extending in a tire circumferential direction, and a horizontal groove intersecting the vertical grooves.

In the present embodiment, the vertical groove 3 has four vertical main grooves 3a.
And two vertical sub-grooves 3b. The two vertical main grooves 3a are arranged on both sides of the tire equator C, respectively.
The vertical main groove 3a in this example is straight and extends continuously in the tire circumferential direction. Such a vertical main groove 3a can smoothly discharge to the rear of the travel without giving resistance to the drainage flowing in the groove. This vertical main groove 3a
The groove width GW1 is not particularly limited, but is, for example, 2 to 8% of the tread contact width, and more preferably 3 to 7%.
% Is desirable, and this example illustrates a value of about 6%. The vertical main groove 3a having such a groove width GW1
Is at least one or more, preferably 2
It is desirable to form more than four, more preferably four or more.

The vertical sub-grooves 3b of this embodiment are arranged one by one on each side of the tire equator C. The vertical sub-groove 3b of this example is also shown to extend straight and continuously in the tire circumferential direction. Although the groove width of the vertical sub-groove 3b is not particularly limited, for example, it is smaller than the groove width GW1 of the vertical main groove 3a and less than 2% of the tread contact width TW, more preferably. 1.5% or less. The vertical sub-groove 3b mainly contributes to the steering stability and the like by appropriately adjusting the rigidity of the tread surface 2, and is expected to slightly improve the drainage. In the present embodiment, the vertical sub-groove 3b has a groove width of about 1.5 mm.

The depth of these vertical grooves 3, especially the vertical main grooves 3a, is preferably at least 1.0 times, more preferably 1.3 times the groove width GW1, in order to ensure sufficient drainage. More preferably, it is desirable to secure 1.5 times or more. The groove depth of the vertical sub groove 3b can be variously determined.

On the tread surface 2, a central land portion 5 extending on the tire equator C, a pair of land portions 6, 6 disposed on both sides thereof, and a further outer portion thereof are formed by the vertical main groove 3a. , A pair of outer land portions 7, 7 are respectively defined.

The lateral groove 4 has a width of 40 with respect to the tire circumferential direction.
It extends at an angle θ of not less than ゜ and not more than 90 °. This angle θ is measured on the small angle side. The lateral groove 4 in this example has an inner end 4a in the tire axial direction at the center land portion 5, and extends from the tread contact end E on each side from there. In the present embodiment, the lateral grooves 4 are inclined in opposite directions on the left and right sides of the tire equator C, for example, as shown by an arrow A in FIG. It is preferable to specify it in order to enhance drainage. The groove width GW2 of the lateral groove 4 is, for example, 2 to 2 of the tread contact width TW.
It is desirable to be 7%, more preferably 2 to 6%, and in this example, it is about 2.3%. It is desirable that the groove depth is 1.0 times or more, preferably 1.3 times or more, more preferably 1.5 times or more of the groove width.

By these lateral grooves 4, the land portion 5 at the center of the tread surface 2 forms a continuous rib without any break in the tire circumferential direction, while the middle land portion 6 and the outer land portion 7
Each block B is defined as a row of blocks arranged in the circumferential direction of the tire. On the tread surface 2, the sea ratio represented by the total surface area of all grooves with respect to the total surface area of the tread portion (tread contact width TW × tire circumference) is approximately 25.
Set to ~ 35%. As a result, it is possible to suppress a remarkable reduction in wear resistance and a reduction in noise characteristics such as pattern noise during running, thereby preventing a reduction in various performances.

According to the present invention, the tire is rim-assembled on a regular rim, filled with a regular internal pressure, and a regular load is applied to the tire to make contact with a tread contact surface S (FIG. 1 shows an outline of the tread contact surface with a chain line). The groove volume ratio (Ga / Gc), which is the ratio of the total vertical groove volume Gc in ()) to the total horizontal groove volume Ga in the tread contact surface S, is set to 0.25 to 0.35. One.

The inventors conducted the following experiment to clarify the difference in the contribution ratio of the vertical groove 3 and the horizontal groove 4 to the hydroplaning. First, as shown in FIG. 4, a test tire (size: 2) was placed on a test course provided with a water pool Z having a length of 20 m on an asphalt road surface having a radius of 102 m.
15 / 55R16, rim 7JJ × 16, internal pressure 180KP
A test vehicle with a displacement of 3,000 cc equipped with a) was entered at a constant speed, and the minimum value of the lateral acceleration (lateral G) at that time was recorded using an acceleration pickup.

Further, the approach speed of the vehicle into the water pool Z is increased from 50 km / H to 90 km / H in steps of 10 km / H in steps, and the water depth of the water pool Z is 5 mm and 10 mm. Tested as type. Further, the test tire has a tread pattern shown in FIG.
The groove depth of each of the longitudinal grooves 3 and the lateral grooves 4 in the tread contact surface S is set by changing the groove depth of each of the lateral grooves 4 to 8 mm (4.7% of the tread contact width TW) and changing each groove width. A plurality of prototypes having different ratios (Ga / Gc) were produced. The groove volume ratio (Ga / Gc) was measured at six locations on the tire circumference, and the average value was used.

Next, as shown in FIG. 5, a vehicle entry speed V1 at max G / 2 which is half of the maximum lateral G (max G) is obtained from a graph showing a relationship between the lateral G and the vehicle entry speed.
This was compared and evaluated. That is, as a control tire, the ratio (Ga / Gc) between the total vertical groove volume Gc in the tread contact surface S and the horizontal groove total volume Ga in the tread contact surface.
However, as a conventional general value, a value set to about 0.76 is adopted, and the speed V1 of the control tire is used.
And the speed of each tire was compared and evaluated.

The test results are shown in FIGS. 2 and 3, respectively. In each figure, the horizontal axis indicates the total vertical groove width, the horizontal axis indicates the total horizontal groove width, and the control tire speed ratio of the plotted tires is also displayed. The “total vertical groove width” refers to the total volume (v) of each vertical groove in the tread contact surface S.
1, v2,...) To the total length (L1, L2,
..) And their respective groove depths (d1, d2,...) (V1 / (L1 · d1), v2 / (L2 · d2),
…)) And the unit is mm.

FIG. 2 shows the result when the water depth of the water pool Z is 5 mm, and the groove volume ratio (Ga / Gc) is about 0.2.
The optimum result is obtained near 5 and when the water depth of the water pool Z shown in FIG. 3 is 10 mm, the optimum result is obtained when the groove volume ratio (Ga / Gc) is about 0.35. I have. In general, in consideration of the fact that the vehicle often travels in a puddle portion having a water depth of 5 to 10 mm on a pavement asphalt road surface, the groove volume ratio (Ga / G
The value of c) is set in a range smaller than the conventional value, ie, 0.2
It is limited to the range of 5 to 0.35.

By designing the vertical groove 3 and the horizontal groove 4 so as to have such a groove volume ratio (Ga / Gc),
Hydroplaning resistance can be maximized and exhibited within a certain range of sea ratio, and wet performance can be significantly improved. As for the hydroplaning resistance, the vertical groove 5 contributes more than the horizontal groove 4,
Therefore, when the total vertical groove width is reduced, the hydroplaning resistance tends to decrease, so that the total vertical groove width is preferably 25 mm or more, preferably 30 mm or more, more preferably 35 mm or more, and still more preferably 40 mm or more. It is desirable to keep.

As the method of changing the groove volume ratio (Ga / Gc), a method of changing the groove width while keeping the groove depth of each of the grooves 3 and 4 constant, and a method of changing both the groove width and the groove depth are used. Various methods such as changing the number of the vertical grooves 3 and the horizontal grooves 4 and changing the inclination angle θ of the horizontal grooves 4 can be adopted.

While the embodiment of the present invention has been described above, the vertical grooves 3 and the horizontal grooves 4 may be appropriately bent such as in a zigzag shape or may be smoothly curved. As described above, the present invention is not limited to the illustrated embodiment and can be implemented by being modified into various modes.

[0023]

[Specific Example] A tire having a tire size of 215 / 55R16 and having the tread pattern shown in FIG. 1 was experimentally manufactured according to the following specifications, and the above-mentioned hydrowet resistance performance and noise performance were comparatively evaluated. The noise performance was determined in accordance with the automotive noise standard JASO Z 101-83 in accordance with the vehicle exterior noise test method. The vehicle was run at a speed of 60 km / h and the overall noise was measured. In addition, each evaluation is shown by the index which makes the conventional example 100. The higher the value, the better.

(Embodiment) Tread contact width 172 mm, vertical main groove groove width 7 mm, vertical main groove groove depth 8 mm vertical sub groove groove width 1 mm, vertical sub groove groove depth 4 mm vertical in tread ground plane Groove total volume Gc 3 × 10 ⁴ mm ³ Angle of horizontal groove 35 ° Groove width of horizontal groove 3 mm, groove depth of vertical groove 8 mm Total volume of horizontal groove in tread ground contact surface Ga 9.3 × 10 ³ mm ³ groove volume ratio (Ga /Gc)=0.31

(Conventional example) Tread contact width 172 mm, vertical main groove groove width 5 mm, vertical main groove groove depth 8 mm vertical sub groove groove width 1 mm, vertical sub groove groove depth 4 mm vertical in tread ground plane Groove total volume Gc 2.2 × 10 ⁴ mm ³ Angle of horizontal groove 35 ° Groove width of horizontal groove 6 mm, groove depth of vertical groove 8 mm Groove volume ratio (Ga / Gc) = 0.76 Total volume of horizontal groove in tread contact surface Table 1 shows the test results of Ga 1.7 × 10 ⁴ mm ³ .

[0026]

[Table 1]

As a result of the test, it was confirmed that the example of the present invention has improved hydroplaning resistance without causing any trouble such as noise performance.

[0028]

As described above, according to the present invention, the groove volume ratio (Ga / Gc), which is the ratio of the total vertical groove volume to the horizontal groove total volume in the tread contact surface, is restricted to a predetermined range. The wet performance can be greatly improved, for example, the hydroplaning resistance can be maximized and exhibited within a specific sea ratio.

[Brief description of the drawings]

FIG. 1 is a development view of a tread portion showing one embodiment of the present invention.

FIG. 2 is a graph showing a relationship between a total vertical groove width, a total horizontal groove width, and a hydroplaning test result when the water depth of a water pool is 5 mm.

FIG. 3 is a graph showing a relationship between a total vertical groove width, a total horizontal groove width, and a hydroplaning test result when the water depth of a water pool is 10 mm.

FIG. 4 is a plan view illustrating a hydroplaning test course.

FIG. 5 is a graph showing a relationship between a lateral G and an approach speed of a vehicle.

[Explanation of symbols]

 2 Tread surface 3 Vertical groove 4 Horizontal groove Gc Total vertical groove volume in tread ground plane Ga Total horizontal groove volume in tread ground plane GW1 Vertical groove width GW2 Horizontal groove width S Tread ground plane TW Tread ground width

Claims (1)

[Claims] A tread surface is provided with a longitudinal groove extending in the tire circumferential direction and a lateral groove inclined at an angle of 40 ° or more with respect to the tire circumferential direction, and is assembled to a regular rim and filled with a regular internal pressure. Moreover, the total volume Gc of the vertical grooves in the tread contact surface that is grounded on a plane by applying a regular load, and the total volume Ga of the horizontal grooves in the tread contact surface
The groove volume ratio (Ga / Gc), which is the ratio of
35. A pneumatic tire as 35.