JPH10138713A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the travelling performance on an icy road surface by adopting a round shoulder connecting a tread part to a buttress part with a circular-arc, and providing a specific circumferential groove extending over about the full length of the periphery of a tire. SOLUTION: With the tire, a tread face 2 and the outside surface of a buttress part 4 are connected through a joint circular-arc part 5, and a tread width TW in the tireaxial direction between intersections P of a virtual line 2V as an extension of the tread face 2 and a vertual line 4V as an outward and radial extension of the contour of the outside surface of the buttress part, is structured to form 80% of the sectional width of the tire. In this case, the joint circular-arc part 5 is formed as a small circular-arc having the length of 6 to 20% of the tread width and a curvature R, and a 3 to 7mm deep D circumferential groove 6 extending over about the full length of the periphery of the tire is provided in the buttress part 4. A groove wall 6A of the circumferential groove 6 on the side face of the tread fase is tip-angled from a tire-radial line N at an angle of θ of 0 to 15 degrees in the opposite direction to the buttress face. A groove edge E0 at which the groove wall 6A and the tire-outside surface intersect, is positioned at a position at which the distance (a) in the tire-axial direction from the intersection P is 7% or less of the tread width, and which is located outside the intersection P in the tire-axial direction.

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 running performance on a smooth icy road.

[0002]

2. Description of the Related Art Since the use of spiked tires has been banned for preventing road damage and dust pollution, pneumatic tires called so-called studless tires have been widely used in snowy areas and the like. In recent years, such pneumatic tires have adopted a block pattern in which a large number of blocks are formed on a tread surface, in addition to the development of a tread rubber material or the like which can maintain flexibility even in a low-temperature environment, and a large number of blocks are used. The performance on snow is greatly improved by the provision of siping.

[0003] However, pneumatic tires without spikes are still inferior to spiked tires in terms of running performance on slippery icy roads. Therefore, conventionally, many proposals have been made to improve the running performance on ice of this type of pneumatic tire.

Generally, in order to increase the adhesive friction between an icy road and a tire, as shown in FIG. 5, the tire T is increased by increasing the ratio of the tread width TW to the tire sectional width W.
It is preferable to substantially increase the ground contact area of the road surface.

[0005] However, in the tire T in which the tread width TW is increased with respect to the tire cross-sectional width W, the tread edge tends to be squared and the rigidity tends to be high. Easy to occur,
In addition, there is a problem that cornering responsiveness is reduced on icy and snowy roads, and the vehicle is hard to bend.

[0006] To solve these problems,
As shown by a dashed line in FIG. 5, an arc r having a relatively large radius of curvature is formed between the tread portion and the sidewall portion of the tire.
It has also been proposed to use a round shoulder.

[0007]

However, although the tire having the round shoulder can exhibit an effect in, for example, the ability to get over a rut, the tire tends to reduce the contact area of the tread, so that the cornering limit speed is reduced. A new problem arises.

[0008] As described above, the conventional tires have a problem that they have poor rideability on ruts and are hard to bend on icy or snowy roads or have low cornering limits.

The present invention has been made in view of the above problems, and employs a round shoulder in which a tread portion and a buttress portion are connected by an arc on the premise of increasing the ratio of the tread width to the tire cross-sectional width. In addition, by providing a specific circumferential groove that extends almost all around the tire in the buttress part, it is possible to reduce cornering limit performance while taking advantage of good rutting ability by round shouldering, cornering responsiveness on icy roads The aim is to provide no pneumatic tires.

Conventionally, a recess formed by recessing the outer surface of the tire is formed in the buttress portion of the tire.
Japanese Patent Publication No. 6-22302 and Japanese Patent Publication No. 5-81442 have been proposed, but both proposals have been made under the problem of improving the workability at the time of tire tread rehabilitation. It is not arranged all around,
Nothing suggests the subject of the present invention and the circumferential groove.

Japanese Patent Application Laid-Open No. H08-113010 discloses that a circumferential groove is provided in a buttress portion of a tire, but this groove is a fine groove formed to improve the appearance of a shoulder portion. It is. Therefore, these proposals also basically differ from the circumferential groove of the present invention in the problem and the configuration.

[0012]

Means for Solving the Problems In the present invention, claim 1 is provided.
According to the invention described above, in a meridional section of the tire in a state where the tire is assembled to a regular rim and filled with a regular internal pressure, a tread surface and a buttress portion outer surface which is a tire radially outer portion of a sidewall portion are joined with a circular arc. The tire shaft between the intersection points P, P, which are connected via a portion and extend a virtual line extending the contour of the tread surface outward in the axial direction and a virtual line extending the contour of the outer surface of the buttress portion radially outward. The tread width TW, which is the distance in the direction, is 80 times the tire cross-sectional width W.
% Of the tread width TW, wherein the joint arc portion is formed by a small arc having a radius of curvature R of 6 to 20% of the tread width TW.
One circumferential groove extending substantially the entire circumference of the tire with a groove depth D of about 7 mm, and the outer groove wall on the side close to the tread surface of the circumferential groove is 0 ° or The outer groove edge where the outer groove wall intersects with the tire outer surface at an angle θ of greater than 0 ° and equal to or less than 15 ° and the inclination of the buttress surface, and the tire between the intersection P The axial distance a is 7% or less of the tread width TW, and the intersection P
Are located on the outer side in the tire axial direction.

Here, the "regular rim" and "regular internal pressure"
Conforms to standards such as JIS and JATMA. Further, the groove depth D of the circumferential groove can be specified by measuring in a direction perpendicular to the buttress surface.

According to a second aspect of the present invention, the tread surface has a tread rubber having a JISA hardness of 55 degrees or less that comes into contact with a road surface and extends to the tire outer surface from the tread surface to the buttress portion. A lateral groove for dividing the circumferential groove in the tire circumferential direction is formed.

[0015]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a meridional section of a pneumatic tire assembled to a regular rim and filled with a regular internal pressure.

In this embodiment, a pneumatic tire is
A carcass 7 composed of a radial structure ply in which fiber cords are arranged at an angle of 75 to 90 ° with respect to the tire equator, and two inner and outer belt plies 9A and 9B composed of a steel cord arranged radially outside the carcass 7 A studless tire having a belt layer 9 made of a rubber is illustrated.

Also, as shown in FIGS. 1 and 3, the pneumatic tire has a tread surface 2 on which a soft tread rubber G having a JISA hardness of 55 degrees or less, which is in contact with a road surface, is disposed. By providing a plurality of main grooves 10 extending and a plurality of lateral grooves 11 extending in a direction intersecting with the main grooves 10, a block pattern in which blocks 12 are arranged in the tire circumferential direction on the tread surface 2 is formed.

Each block 12 is formed with a zigzag siping S which bends and extends in the tire axial direction, for example, so that it can exert an edge effect particularly on an icy road to improve running performance.

Further, in this embodiment, the pneumatic tire includes a tread surface 2 composed of a single arc and a sidewall portion 3.
And the outer surface of the buttress portion 4, which is the outer portion in the tire radial direction, is smoothly connected through the joint arc portion 5,
The tread width TW is set so as to occupy 80% or more of the tire sectional width W.

Here, the “tread width TW” is defined as an imaginary line 2V obtained by extending the contour of the tread surface 2 outward in the axial direction.
The contour of the outer surface of the buttress portion 4 is defined as a distance in the tire axial direction between intersections P, P with an imaginary line 4V extending outward in the radial direction.

As described above, since the tread width TW occupies 80% or more of the tire sectional width W, it is useful to increase a tread width direction ground contact area, and it is possible to increase frictional force on an icy road. Becomes Conversely, the tread width T
In a tire having W smaller than 80% of the tire cross-sectional width W, the contact width is small, and a satisfactory frictional force cannot be obtained when traveling on an icy road.

On the premise of such a pneumatic tire,
In the present invention, the size of the radius of curvature R of the connecting arc portion 5 is limited in relation to the tread width TW, and the buttress portion 4 is provided with one circumferential groove 6 extending substantially over the entire circumference of the tire. It is characterized by:

First, the radius of curvature R of the joint arc 5 is:
On the premise that the tread width TW is wider than before, it is necessary to set the tread width TW to 6 to 20% of the tread width TW.

That is, the radius of curvature R of the joint arc 5
If it is less than 6% of the tread width TW, the tread edge becomes square, and even if the circumferential groove 6 is provided, it is not possible to improve the rutability, and if it exceeds 20%, the tread width is increased. This is because despite the widening of the TW, the effect of increasing the contact width can hardly be expected, and the braking performance on ice and the cornering limit speed cannot be improved.

When importance is attached to the ability to cross over the rut, the radius of curvature R of the connecting arc 5 is preferably set to 12 to 20% of the tread width TW. Conversely, if the braking performance on ice is emphasized, For example, it is preferable to set 6 to 11%.

It is conceivable that the tread surface 2 and the outer surface of the buttress portion are formed into a tapered slope. However, in this case, the running performance on icy and snowy roads is reduced due to a decrease in the ground contact width, so that it cannot be adopted. .

As described above, when the radius of curvature R of the joint circular arc portion 5 is set, it is possible to expect the improvement of the bridging ability and the cornering responsiveness due to the round shoulder. However, the cornering limit speed is inevitably reduced only by this. Therefore, it is necessary to provide the circumferential groove 6 having a specific shape in the buttress portion 4.

Such a circumferential groove 6 mainly increases the outer surface of the tire effectively when a slip angle is given to the tire to prevent a decrease in the contact area, thereby preventing other performances from deteriorating. The groove depth D, the angle θ of the outer groove wall 6A, the axial distance a between the outer groove edge Eo and the intersection P, and the like are described below. Need to be identified.

First, the circumferential groove 6 shown in FIG.
Needs to be set to about 3 to 7 mm and provided on substantially the entire circumference of the tire.

If the groove depth D is less than 3 mm, the rigidity of the shoulder portion centering on the connecting arc 5 cannot be reduced during cornering, and the cornering limit speed decreases. Since the rigidity of the shoulder portion is significantly reduced, a linear feeling when riding over a rut is lost, and a decrease in cornering limit speed cannot be suppressed.

If the circumferential groove 6 is not provided on substantially the entire circumference of the tire, the change in the contact width over the entire circumference of the tire during cornering is not stable, and the cornering limit speed decreases.

The reason why the circumferential groove 6 is provided "almost" all around the tire is as shown in FIG.
However, since the circumferential groove 6 may be divided in the tire circumferential direction by extending from the tread surface 2 to the buttress portion 4, the circumferential groove 6 may be completely connected to the entire circumference of the tire. It may be divided in the tire circumferential direction by a lateral groove or the like.

Next, since the groove depth D of the circumferential groove 6 is set to 3 to 7 mm, the tread surface 2 of the circumferential groove 6 is set.
The outer groove wall 6A on the side close to the tire is formed to be inclined at an angle θ of 0 ° or more than 0 ° and 15 ° or less with respect to the tire radial line N in a direction opposite to the inclination of the buttress surface. is necessary.

If the angle θ of the outer groove wall 6A is less than 0 °, the shoulder cannot be effectively grounded at the time of cornering, and the cornering limit speed decreases. When the vehicle travels on a road surface, rubber tears occur in the vicinity of the circumferential groove 6 and durability is reduced. Preferably, the angle θ is set to 10 to 15 °.

The groove wall 6B on the side of the circumferential groove 6 remote from the tread surface 2 can be arbitrarily determined, but is preferably in the normal direction to the buttress surface 4 or ± 2 from this.
It is preferable to form at an angle of 0 °.

The tire axial distance a between the outer groove edge Eo where the outer groove wall 6A of the circumferential groove 6 intersects the tire outer surface and the intersection point P is 7% of the tread width TW.
When it is larger than 0, it is necessary to be located outside the intersection point P in the tire axial direction.

The distance a in the tire axial direction between the outer groove edge Eo and the intersection P can specify the position of the circumferential groove 6, and when this distance a is less than 0 mm, that is, the intersection P If it is located further inward in the tire axial direction, a decrease in the cornering limit speed can be prevented, but the responsiveness of the cornering decreases due to the tendency of the shoulder portion SH to be squared. The rigidity of the shoulder portion 5 becomes too high, and the cornering limit speed decreases.

The outer groove edge Eo and the inner groove edge Ei where the inner groove wall 6B of the circumferential groove 6 and the tire outer surface intersect.
It is preferable that the groove width GW of the circumferential groove, which is the distance between them, is set to, for example, 4% or more, preferably 5% or more of the tread width TW.

If the groove width GW is less than 4% of the tread width TW, clogging of the groove due to stone biting or the like is likely to occur, and the circumferential groove 6 tends to be unable to function effectively.

FIG. 4 shows another embodiment of the present invention. As shown in this example, the circumferential grooves 6S and 6L adjacent to each other via the lateral groove 11 have different groove widths GW. Thus, in the circumferential grooves 6S and 6L adjacent to each other via the lateral groove 11, in addition to the groove width GW, the groove depth D, the inclination angle θ of the outer groove wall, the curvature radius R of the joint arc portion, The distance a can be made different, and further, an appropriate pattern or a narrow groove may be formed on the buttress surface, for example, in the tire radially inner portion of the circumferential groove 6.

[0041]

[Example] The tire size is 195 / 65R15,
A pneumatic tire having the structure shown in FIGS. 1 to 3 and having dimensions R, D, θ, a and the like of each part changed as shown in Table 1 (Examples 1 to 17), and a tire other than the present invention. Tires (Comparative Examples 1 to 17) were also prototyped, and a test for evaluating performance was performed.

In the test, a test tire was mounted on a 2000cc rear-wheel drive vehicle produced in Japan, and the test driver's feeling was used to observe wobbling of the vehicle when riding over a rut. Cornering response performance when observing the vehicle's ease of turning when cornering is applied, cornering limit performance when observing the limit speed at which the vehicle can turn on icy and snowy roads, and lack of rubber around the circumferential groove when traveling on dry asphalt road surface A test such as dry road durability performance was conducted as required, and a very good case was evaluated as ◎, a generally good case was evaluated as ○, and a bad case was evaluated as ×.

Separately from the feeling test, a sudden braking for locking the tires on a slippery icy road at a speed of 15 km / h is performed, and a braking performance test on ice on ice is performed to measure a braking distance from the start of braking to the stop of the vehicle. Also performed as needed. In this test, the performance was evaluated by an index with the performance of Comparative Example 1 where the radius of curvature R of the joint arc portion was set to 0 as 100. The higher the value, the better. Table 1 shows the test results.

[0044]

[Table 1]

[0045]

[0046]

[0047]

The results of the test show that the tires of the examples have improved running performance on icy roads without reducing any of the rutability, cornering responsiveness on icy roads and cornering limit performance. Is shown.

[0049]

According to the pneumatic tire of the present invention, the circumferential groove provided in the buttress portion makes it possible to prevent the cornering limit performance from deteriorating while taking advantage of the good overriding property and cornering responsiveness due to the round shoulder.

[Brief description of the drawings]

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

FIG. 2 is an enlarged contour view of an end of a tread portion.

FIG. 3 is an enlarged perspective view of an end of a tread portion.

FIG. 4 is an enlarged perspective view of an end portion of a tread portion showing another embodiment of the present invention.

FIG. 5 is a meridional sectional view of a pneumatic tire illustrating a conventional technique.

[Explanation of symbols]

2 Tread surface 2V A virtual line extending the contour of the tread surface outward in the axial direction 3 Side wall portion 4 Buttress portion 4V A virtual line extending the contour of the outer surface of the buttress portion radially outward 5 Joint arc portion 6 Circumferential groove 6A Outside Groove edge 10 Main groove 11 Lateral groove TW Tread width P Intersection point of an imaginary line extending the contour of the tread surface outward in the axial direction and an imaginary line extending the contour of the outer surface of the buttress portion radially outward R Curvature radius θ Angle of inclination of outer groove wall D Depth of circumferential groove a Distance between outer groove edge and intersection P in tire axial direction

Claims (2)

[Claims] In a tire meridional section in a state where a tire is assembled to a regular rim and filled with a regular internal pressure, a tread surface and an outer surface of a buttress portion which is a radially outer portion of a sidewall portion in a tire radial direction are joined arcs. And a tire axis between intersections P and P of a virtual line extending the contour of the tread surface outward in the axial direction and a virtual line extending outward in the radial direction of the contour of the buttress portion. The tread width TW, which is the distance in the direction, is a pneumatic tire occupying 80% or more of the tire cross-sectional width W, and the joint arc portion is a small arc having a radius of curvature R of 6 to 20% of the tread width TW. The buttress portion is provided with one circumferential groove extending substantially all around the tire at a groove depth D of 3 to 7 mm, and an outer groove wall on the side close to the tread surface of the circumferential groove. Is a tire At the angle θ of 0 ° or more than 0 ° and 15 ° or less with respect to the radial direction line, the buttress surface is inclined in a direction opposite to the inclination of the buttress surface, and the outer groove edge where the outer groove wall and the tire outer surface intersect is , The distance a in the tire axial direction from the intersection P is the tread width T.
A pneumatic tire, which is located at 7% or less of W and outside of the intersection point P in the tire axial direction. 2. The JIS according to claim 2, wherein the tread surface is in contact with a road surface.
A hardness has a tread rubber of 55 degrees or less,
The pneumatic tire according to claim 1, wherein a lateral groove that extends from the tread surface to the buttress portion to divide the circumferential groove in a tire circumferential direction is formed on an outer surface of the tire.