JP3273772B2 - studless tire - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a studless tire having both improved performance on ice and improved resistance to uneven wear.

[0002]

2. Description of the Related Art Conventionally, a studless tire has conventionally formed a large number of sipes in a block pattern having excellent traction properties, and mainly has an adhesive frictional force due to contact between a block surface and an ice surface, and digs a road surface by an edge of the block or siping. The performance on ice is secured by the action of frictional force (edge effect).

On the other hand, in order to further improve the performance on ice, for example, as shown conceptually in FIGS. 5A and 5B, the vicinity of the tire equator C is placed on the tread surface a in the tire circumferential direction. , A central vertical main groove b extending on both sides of the central vertical main groove b, an intermediate vertical main groove c arranged on both sides of the central vertical main groove b and continuous in the tire circumferential direction, and both of the intermediate vertical main grooves. An outer vertical main groove d which is arranged on the outside and is continuous in the tire circumferential direction is provided. Between the intermediate vertical main groove c having a relatively high ground contact pressure and the outer vertical main groove d, the outer main groove is continuous in the tire circumferential direction. A rib / block pattern in which a rib e is formed and the other is a block f has been proposed. Such a rib / block pattern increases the contact area and the adhesive frictional force, and also forms a large number of sipes s on the rib e to dig up the road surface by the edge thereof to increase the frictional force.

[0004]

However, in the tire having the rib / block pattern, it is desired that the rib e be formed with a relatively small width in order to secure required performance on snow. In order to increase the surface friction coefficient and the edge component, the pitch interval p of the sipes s
Needs to be as small as possible to form a large number of sipings s.

[0005] As a result, the rigidity of the rib e becomes too small as compared with the rigidity of the other blocks f, and as shown in FIG. There is a problem in that so-called mohawk-cut uneven wear (hereinafter, such uneven wear may be referred to as “mohawk wear”) occurs in which fi is unevenly worn (indicated by hatching).

Therefore, the present invention provides a rib e as described above,
A stepped siping provided with a small middle part on both sides of the deep part and a shallow part with a smaller depth than this medium part is arranged alternately left and right. With
On the basis of regulating the depth of the siping and the pitch interval, respectively, with the aim of providing a studless tire that can improve the performance on ice while maintaining the performance on snow, and that can effectively suppress the occurrence of the Mohawk abrasion. I have.

[0007]

According to the first aspect of the present invention, there is provided a central vertical main groove extending continuously in the tire circumferential direction in the vicinity of the tire equator on the tread surface. An intermediate longitudinal main groove arranged on both sides of the longitudinal main groove and extending continuously in the tire circumferential direction, and an outer longitudinal main groove arranged on both outer sides of the intermediate longitudinal main groove and extending continuously in the tire circumferential direction. To form a land portion consisting of a row of ribs or blocks between each vertical main groove and between the outer vertical main groove and the tread edge,
A middle rib extending continuously in the tire circumferential direction between the intermediate vertical main groove and the outer vertical main groove is provided with a siping crossing the middle rib, and the siping is a deep portion where a deepest portion continues. The bottom portion is opened by the outer vertical main groove and the middle bottom portion having a depth smaller than the deep bottom portion, and the other side is opened by the middle vertical main groove and the shallow bottom portion which is shallower than the middle bottom portion. A stepped first siping provided, a stepped portion provided with a shallow portion opened in the outer vertical main groove in a deep portion, and an intermediate bottom portion opened in the intermediate vertical main groove on the other side. While the first and second sipes are alternately arranged at a circumferential pitch interval Pc in the range of 0.028 to 0.04 times the tread contact width W, The siping depth Ds3 of the deep bottom portion is set to 0.70-0. 0 times, the siping depth Ds2 in said bottom portion, the groove depth D of the circumferential main grooves from 0.40 to 0.
60 times, and the siping depth Ds1 of the shallow portion is:
The depth D of the vertical main groove is 0.04 to 0.35 times.

According to a second aspect of the present invention, the middle rib has a rib width Wr in the tire axial direction and a tread contact width W.
2. The studless tire according to claim 1, wherein the thickness is 0.07 to 0.30 times as large as the studless tire.

Here, the "tread contact width" means the maximum width in the tire axial direction of the tread contact surface to be contacted when a tire is rim-assembled on a regular rim, filled with a regular internal pressure, and loaded with a regular load. I do. Also "Regular rim"
Is a rim defined for each tire in the standard system including the standard on which the tire is based.
Standard rim for ATMA, "Design R for TRA"
im "or" Measuring Rim "for ETRTO.

[0010] The "normal internal pressure" is the air pressure specified for each tire in a standard system including the standard on which the tire is based. TIRE LOAD LIMITS AT VARIOU
Maximum value, ETR described in "S COLD INFLATION PRESSURES"
In the case of TO, it is "INFLATION PRESSURE", but in the case of tires for passenger cars, it is 180 kPa. Further, "regular load" is a load defined by each standard for each tire in a standard system including the standard on which the tire is based,
JATMA: maximum load capacity, TRA: table
TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSUR
The maximum value described in "ES" or "LOAD CAPAC for ETRTO"
ITY ".

According to a third aspect of the present invention, in the first and second sipings, a length L3 of the deep bottom portion in the tire axial direction is set to 0.
40 to 0.9 times, the length L in the tire axial direction of the midsole portion
2 is 0.05 to 0.3 times the length L, and the length L1 of the shallow portion in the tire axial direction is 0.05 to 0.3 times the length L.
3. The studless tire according to claim 1, wherein the studless tire is tripled.

According to a fourth aspect of the present invention, the middle vertical main groove forms a linear groove, so that the sidewall of the middle rib on the tire equator side has a linear shape, and the outer vertical main groove has a linear shape. The studless tire according to any one of claims 1 to 3, wherein the rib (Wr) in the tire axial direction of the middle rib repeatedly increases and decreases in the circumferential direction by making the groove a non-linear groove.

According to a fifth aspect of the present invention, in the studless tire according to any one of the first to fourth aspects, the land portion other than the middle rib is a row of blocks in which blocks are arranged in a circumferential direction. It is.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings, taking a studless tire for a passenger car as an example. FIG. 1 is a development view in which a tread surface of a studless tire (hereinafter, may be simply referred to as “tire”) 1 of the present embodiment is developed. In the figure, a tire 1 is provided on a tread surface 2, a central vertical main groove 3 extending continuously in the tire circumferential direction in the vicinity of a tire equator C, and arranged on both sides of the central vertical main groove 3. Middle longitudinal main grooves 4, 4 extending continuously in the circumferential direction, and outer longitudinal main grooves 5, 5 arranged on both outer sides of the intermediate longitudinal main grooves 4 and extending continuously in the tire circumferential direction; Six circumferential land portions R are formed between the vertical main grooves and between the outer vertical main grooves 5 and the tread edge E. In the present embodiment, the central vertical main groove 3 and the intermediate vertical main groove 4 are linearly extending.
Extends on the tire equator C, but is not limited to this embodiment. The vertical main groove may be formed in a zigzag or wavy shape.
Needless to say, the tire may deviate from the tire equator C.

In the present embodiment, the land portion R is composed of a row of ribs or blocks. At least between the intermediate vertical main groove 4 and the outer vertical main groove 5 is substantially in the tire circumferential direction. A middle rib 6 extending continuously is formed. In the present embodiment, the tread surface 2 is formed as a rib / block pattern by configuring the land portion R other than the middle rib 6 by a block row B in which blocks are arranged in a circumferential direction via a lateral groove Y. Is shown.

In the present invention, each of the vertical main grooves 3, 4, 5
The width, depth, and the like of the lateral groove Y are not particularly limited, but dimensions similar to those of a conventional general studless tire can be adopted. For example, in the case of a studless tire for a passenger car, a groove width WG (shown in FIG. 2) having a range of 5 to 25 mm and a groove depth D (shown in FIG. 2) having a range of 8 to 15 mm are particularly preferable. In this example,
The groove depth D of the vertical main groove is about 12 mm, which is substantially equal to the groove depth of the horizontal groove Y. In addition, the tire 1 of this example has the land portion R with respect to the entire area TA of the ground contact surface due to the formation of the middle rib 6.
Land ratio (AA / TA), which is the ratio of the total surface area AA of
It is set higher than that of the block pattern consisting only of the conventional blocks, and the adhesive friction force is improved by increasing the actual contact area.

In this embodiment, since the middle vertical main groove 4 forms a linear groove, the tire equatorial-side wall wall 6i of the middle rib 6 has a linear shape, and the outer vertical main groove 5 has a non-linear shape. By way of example, the ribs W of the middle rib 6 in the tire axial direction repeatedly increase and decrease in the circumferential direction.
Such an increase or decrease in the rib width Wr is effective for increasing the rib rigidity, and furthermore, the tread edge E of the middle rib 6.
By forming the side wall 6o on the side in a zigzag shape, an edge effect on an icy road can be expected. In particular, in this example, in the side wall 6o of the middle rib 6, the maximum width portion K1 and the minimum width portion K2 are brought close to each other, and the space between the maximum width portion K1 and the minimum width portion K2 is inward in the tire axial direction. It is preferable to provide a side wall having a saw-toothed portion connected by a convex arc K3 in that a higher edge effect can be exhibited.

Further, a siping 7 is formed on the middle rib 6 so as to cross the middle rib 6. The siping 7 has a notch shape having a width of 1.5 mm or less (about 0.3 mm in this example), and both ends are opened by the middle vertical main groove 4 and the outer vertical main groove 5. It is particularly preferable that the siping 7 is formed along the tire axial direction. However, the siping 7 may be inclined in a range of about ± 30 ° with respect to the tire axial direction. Although the siping 7 is schematically shown as extending straight in the tire axial direction in this example, a zigzag, wavy, or saw blade is provided at an intermediate position of the siping 7 in the tire axial direction in order to increase its edge component. A meandering portion (not shown) that is curved in various shapes such as a rectangular shape and a rectangular uneven shape can be formed.

The siping 7 is formed of stepped first and second sipings 10 and 11, and the first and second sipings 10 and 11 have a tread contact width W of 0.028 to 0.028. They are arranged alternately in the circumferential direction with a pitch interval Pc in the range of 0.04 times.

As shown in FIG. 2, a cross section along the siping of the first siping 10 has an opening at the deep bottom portion 10A where the deepest portion (the portion where the siping is deepest) continues. An intermediate bottom portion 10B having a depth smaller than that of the deep bottom portion 10A is provided on the other side with a shallow bottom portion 10C which is opened by the intermediate vertical main groove 4 and is shallower than the intermediate bottom portion 10B. I have. Each portion is illustrated as being connected via an arc portion 15 in order to prevent stress concentration.

As shown in FIG. 3, the second siping 11 has a cross section along the siping.
1A, the shallow bottom portion 11C opening with the outer vertical main groove 5
Is provided on the other side with the middle bottom portion 11B which is opened by the middle vertical main groove 4. That is, the second siping 11 is provided with a shallow bottom portion 11C and a middle bottom portion 11B opposite to the first siping 10.

As described above, the first and second sipings 10,
Numeral 11 is formed in a stepped shape in which middle bottom portions 10B and 11B and shallow bottom portions 10C and 11C are provided on both sides of the deep bottom portions 10A and 11A, respectively. Accordingly, both side edges of the middle rib 6 are reinforced, and even when the first and second sipes 10 and 11 are arranged at the small pitch interval Pc, the rigidity of the middle rib 6 can be improved. Large deformation in the tire circumferential direction and the tire axial direction is effectively suppressed. As a result, it is possible to effectively suppress the Mohawk abrasion in which abrasion is concentrated on the inner edge in the tire axial direction of the blocks on both sides thereof while effectively exhibiting the edge effect.

The first and second sipings 10, 11
Are medium bottom portions 10B, 11B and shallow bottom portions 10C, 11C
Are different from each other, for example, the deep bottom portion 1
Compared to the case where both sides of 0A and 11A have the same depth, it is advantageous for both the effect of improving the rigidity of the rib and the edge effect. Moreover, since the first and second sipes 10 and 11 are alternately arranged, the rigidity of the side edge of the rib 6 is made uniform, and uneven wear can be suppressed more effectively.

Here, in order to exhibit the above-described effects, in the first and second sipes 10 and 11, the siping depth Ds3 of the deep bottom portions 10A and 11A is set as follows.
0.70 to 0.80 of the groove depth D of the vertical main groove 4 or 5
Times, the siping depth Ds of the middle bottom portions 10B, 11B
2 is 0.40 to 0.60 times the groove depth D, and the siping depth Ds1 of the shallow portions 10C and 11C is 0.04 to 0.35 times the groove depth D. Is required.

When the siping depth Ds3 is (0.80 ×
D), the siping depth Ds2 is (0.60 ×
D), or the siping depth Ds1 is (0.
In the case of larger than 35 × D), the siping is too deep to keep the rigidity of the middle rib 6 high, and the inner edge side of the adjacent land portion R (block row B) in the tire axial direction is not good. The uneven wear suppression effect such as uniform wear is not achieved. Conversely, the siping depth Ds3 is (0.7
0 × D) and the siping depth Ds2 is (0.40
× D) or the siping depth Ds1 is (0.
If it is less than 04 × D), the siping tends to be shallow and the edge effect becomes insufficient, so that the performance on ice cannot be improved.

If the pitch interval Pc of the siping is less than (0.028 × TW), the number of sipings is remarkably increased, and it becomes difficult to maintain the rigidity of the rib 6 high, and the effect of suppressing uneven wear can be achieved. Disappears. Conversely, if the pitch interval Pc is greater than (0.04 × TW), the number of sipings will be significantly reduced, and it will not be possible to expect an improvement in on-ice performance such as a sufficient length of the edge component cannot be secured.

Here, the first and second sipes 10, 1
In FIG. 1, when the length L3 of the deep portions 10A and 11A is extremely large, or when the lengths L2 and L1 of the middle portions 10B and 11B and the shallow portions 10C and 11C are extremely small, the rigidity of the rib 6 decreases. The effect of suppressing uneven wear tends to decrease. Conversely, the length L3 of the deep portion 10A, 11A
Is too small, or when the lengths L2 and L1 of the middle bottom portions 10B and 11B and the shallow bottom portions 10C and 11C are too large, it is difficult to obtain an edge effect particularly on an icy road, and the ice road running performance is reduced. Cheap.

From this viewpoint, although not particularly limited, for example, the first and second sipings 10, 11
In the above, the substantial length L3 of the deep bottom portions 10A and 11A in the tire axial direction is 0.40 to 0.90 times the length L of the sipes 10 and 11 in the tire axial direction, and the middle bottom portion 10B , 11B by 0.05 to 0.30 times the length L, the shallow bottom portion 10C,
The length L1 in the tire axial direction of 1C is set to 0.0
Preferably, it is 5 to 0.30 times. by this,
The performance on ice and the uneven wear resistance can be more reliably and significantly improved.

Further, according to the present invention, the rib width W of the middle rib 6 is set so as to maintain the performance on snow higher while effectively exhibiting such performance on ice and uneven wear resistance.
It is desirable that r be 0.07 to 0.30 times, more preferably 0.08 to 0.15 times the tread contact width TW. When the rib width Wr is less than (0.07 × TW),
The increase in the contact area due to the middle rib 6 is reduced,
The effect of increasing the adhesive frictional force tends to decrease relatively. On the other hand, when it exceeds (0.30 × TW), it becomes difficult to obtain the traction force on snowy roads, and the snowy road running performance tends to decrease relatively. is there.

The siping depth Ds is set such that the rib width Wr of the middle rib 6 repeatedly increases and decreases in the circumferential direction.
1, Ds2, Ds3, pitch interval Pc, groove width Wg, and rib width Wr can be changed on one circumference of the tire. In such a case, it is particularly desirable that both the maximum value and the minimum value are regulated within the above range.

In the other circumferential land portions R formed as the block rows B, sipes 20 are formed in each block, similarly to a conventional studless tire.
The siping 20 may be formed in a stepped shape similar to the sipings 10 and 11, but in this embodiment, the siping 20 having a constant depth is employed.

[0032]

EXAMPLE A studless tire having a tread pattern shown in FIG. 1 and having a tire size of 175 / 80R14 was prototyped based on the specifications shown in Table 1, and the performance on ice, the performance on snow, and the resistance to uneven wear described below were tested. evaluated. As a comparative example 1, as shown in FIG. 4, a siping in which only a middle bottom portion is provided on one side of a deep bottom portion is employed.

(1) Performance on Ice The test tire was subjected to an internal pressure (180 kpa) and a rim (14 × 5).
Under J), it is mounted on four wheels of a passenger car (FF car: 1800cc), runs on a icy road at a constant speed of 40km / H in an environment of 0 ° C, and suddenly brakes with a four-wheel lock. The braking distance until the vehicle stopped was measured, and the reciprocal of the braking distance was used to evaluate Comparative Example 1 by an index of 100. The larger the value, the better the performance on ice.

(2) Performance on Snow The above vehicle was used and the snow-covered road (depth: 3
0mm), and the straight running stability performance and the turning performance at that time were evaluated by a driver's feeling by a 10-point scale. The higher the value, the better.

(3) Uneven wear resistance performance A test drum having a dry pavement pseudo surface is run on a test tire, and the reciprocal of the uneven wear amount after traveling 1000 km is indicated by an index. The index is set to 100 in Comparative Example 1, and the larger the numerical value, the better the wear resistance.

[0036]

[Table 1]

[0037]

As described above, the studless tire of the present invention can improve the performance on ice while maintaining the performance on snow, and furthermore, has an unevenness such as Mohawk wear in which the land adjacent to the middle rib is locally worn. Wear can be effectively suppressed.

[Brief description of the drawings]

FIG. 1 is a developed view showing a tread pattern of a tire according to an embodiment of the present invention.

FIG. 2 is a sectional view showing a first siping.

FIG. 3 is a sectional view showing a second siping.

FIG. 4 is a sectional view showing a siping used in Comparative Example 1.

FIGS. 5A and 5B are diagrams illustrating a conventional technique.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Studless tire 2 Tread surface 3 Central vertical main groove 4 Middle vertical main groove 5 Outside vertical main groove 6 Middle rib 7 Siping 10 First siping 11 Second siping 10A, 11A Deep bottom portion 10B, 11B Medium Bottom part 10C, 11C Shallow bottom part C Tire equator R Land part TW Tread contact width Ds3 Deep bottom part siping depth D Vertical main groove groove depth Ds2 Middle bottom part siping depth Ds1 Shallow bottom part siping depth Wr Rib width of middle rib L3 Length of deep portion in tire axis direction L2 Length of middle portion in tire axis direction L1 Length of shallow portion in tire axis direction

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B60C 11/12

Claims (5)

(57) [Claims] 1. A central longitudinal main groove extending continuously in the tire circumferential direction near the tire equator on the tread surface, and arranged on both sides of the central longitudinal main groove and continuously extending in the tire circumferential direction. A middle vertical main groove extending and outer vertical main grooves arranged on both outer sides of the intermediate vertical main groove and extending continuously in the tire circumferential direction are provided, and the vertical main grooves between and outside the vertical main grooves and the tread are provided. A land portion consisting of a row of ribs or blocks is formed between the end edge and a middle rib extending continuously in the tire circumferential direction between the intermediate vertical main groove and the outer vertical main groove. Along with a siping crossing the middle rib, the siping opens the outer vertical main groove at the deepest part where the deepest part continues and opens the middle bottom part with a depth smaller than the deepest part at the other side. Stepped shape with a shallow bottom portion that is opened at the middle vertical main groove and shallower than the middle bottom portion A stepped second siping having a first siping and a shallow portion opening in the outer vertical main groove at a deeper portion and an intermediate bottom portion opening at the intermediate vertical main groove on the other side; And the first and second sipings are defined by a tread contact width W.
Are alternately arranged at a circumferential pitch interval Pc in a range of 0.028 to 0.04 times the sipe depth Ds3 of the deep bottom portion, which is 0.70 to 0.75 of the groove depth D of the vertical main groove. 0.80 times, the sipe depth Ds2 of the middle bottom portion is 0.40 times the groove depth D of the vertical main groove.
~ 0.60 times and the siping depth Ds of the shallow part
1. A studless tire characterized in that 1 is 0.04 to 0.35 times the groove depth D of the vertical main groove. 2. The studless tire according to claim 1, wherein the middle rib has a rib width Wr in the tire axial direction of 0.07 to 0.30 times the tread contact width W. 3. In the first and second sipings, the length L3 of the deep bottom portion in the tire axial direction is 0.40 to 0.9 times the length L of the siping in the tire axial direction, and The length L2 of the portion in the tire axial direction is set to 0.05 to
The studless tire according to claim 1 or 2, wherein the length L1 of the shallow portion in the tire axial direction is set to 0.05 to 0.3 times the length L. 4. The intermediate vertical main groove forms a linear groove, so that a sidewall of the middle rib on the tire equator side is linear, and the outer vertical main groove is a non-linear groove. The studless tire according to any one of claims 1 to 3, wherein the rib width Wr of the middle rib in the tire axial direction repeatedly increases and decreases in the circumferential direction. 5. The studless tire according to claim 1, wherein the land portion other than the ribs of the middle is a block row in which blocks are arranged in a circumferential direction.