Resilient tires and wheels – Tires – resilient – Anti-skid devices
Reexamination Certificate
2001-07-18
2004-09-28
Maki, Steven D. (Department: 1733)
Resilient tires and wheels
Tires, resilient
Anti-skid devices
C152S209180, C152S902000
Reexamination Certificate
active
06796348
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a pneumatic tire, and in particular, to a pneumatic tire having a block pattern which can provide good off-road performance, on-snow performance, and on-road traveling performance.
2. Description of the Related Art
As shown in
FIG. 5
, in order to improve off-road traveling performance, tires for passenger and four-wheel drive vehicles generally employ a block pattern structure in which a tread
100
has circumferential grooves
102
which extend in zigzags in the circumferential direction of the tire in order to increase the number of the longitudinal and lateral edge factor, and has transverse grooves
104
which extend in the tire axial direction from the vertices or the sides of these zigzags.
To describe this tread pattern in more detail, the tread
100
is provided with a pair of circumferential grooves
106
which are formed parallel to a tire equatorial plane CL between the pair of circumferential grooves
102
, and which are formed linearly and have constant widths.
A large number of transverse grooves
108
, which are inclined with respect to the circumferential direction of the tire, are formed, substantially in the circumferential direction of the tire, at the region between the pair of circumferential grooves
106
. Further, a plurality of center blocks
110
are formed thereby.
An auxiliary groove
112
, which is narrow and is inclined in the direction opposite to the transverse grooves
108
, is formed in the center block
110
such that two sub-blocks are formed. Further, a plurality of sipes
113
are formed in the center block
110
.
A plurality of second blocks
114
are formed in the region between the circumferential groove
102
and the circumferential groove
106
. An auxiliary groove
116
, which is narrow and is inclined in the same direction as the transverse grooves
104
, is formed in the second block
114
, so as to form two sub-blocks. A plurality of sipes
118
are formed in the second block
114
.
A large number of shoulder blocks
120
are formed at the outer sides of the circumferential grooves
102
in the widthwise direction of the tire. An auxiliary groove
122
, which is inclined in the same direction as the transverse grooves
104
, and a plurality of sipes
124
are formed in the shoulder block
120
.
The transverse grooves
108
and the transverse grooves
104
at the left and right sides are inclined upwardly toward the right. Further, the center blocks
110
, the second blocks
114
, and the shoulder blocks
120
are disposed such that adjacent blocks have a phase difference in the circumferential direction of the tire therebetween.
Note that W in the drawings denotes the ground contact width.
In this type of pneumatic tire, in order to improve the on-road traveling performance, the rigidity is increased and the performances are maintained by making the blocks larger and by ensuring, with the negative ratio being 45% or less, the sufficient ground contact surface.
When the tread surface of the tread
100
is divided into a center tread region, which is located between the (two) circumferential grooves
102
, and side tread regions, which are positioned at the outer sides of the center tread region in the widthwise direction, the pitch number ratio of the blocks of the center tread region and the both side tread regions is set to be 1:1.
In a conventional pneumatic tire such as that shown in
FIG. 5
, usually, in order to ensure the off-road and on-snow performances, a large number of longitudinal and lateral edge factor (sipes and the like) are formed in the tread.
However, an increase in the number of edge factor in the block leads to a decrease in block rigidity and relates to a deterioration in on-road performances.
Thus, in order to prevent the rigidity from decreasing, there are many cases in which the block is set to be large. However, when the blocks at the side tread regions of the tread surface are large, a problem arises in that pattern noise becomes markedly worse.
In recent years, as vehicles have become more high-power, the need has arisen for tires to exhibit even higher levels of on-road and off-road performances.
Thus, a pneumatic tire having the tread pattern shown in
FIG. 6
was conceived as an improvement on the traveling properties of the pneumatic tire having the tread pattern shown in FIG.
5
.
In the tread pattern shown in
FIG. 6
, reference numeral
12
is a tread;
14
L,
14
R are circumferential grooves;
16
L,
16
R,
24
L,
24
R, and
28
are transverse grooves;
18
L,
18
R are shoulder blocks;
34
L,
34
R,
36
L,
36
R,
38
L,
38
R,
41
and
42
are auxiliary grooves;
30
L,
30
R are second blocks;
32
is a center block;
22
L,
22
R,
40
L,
40
R and
44
are sipes; and W is the ground contact width.
The feature of the pattern shown in
FIG. 6
is that the number of transverse groove components is greater than in the pattern shown in FIG.
5
. Note that the center blocks
32
and the second blocks
30
have absolutely no portions which overlap in the tire axial direction when viewed in the circumferential direction of the tire.
The pneumatic tire having the tread pattern shown in
FIG. 6
does exhibit an improvement in performances as compared to the pneumatic tire having the tread pattern of
FIG. 5
, but the improvement is still insufficient.
SUMMARY OF THE INVENTION
In view of the aforementioned, an object of the present invention is to provide a pneumatic tire having a block pattern which can provide, in particular, good off-road performance, on-snow performance, and on-road traveling performance, altogether.
A first aspect of the present invention is a pneumatic tire comprising: a circumferential groove extending along a circumferential direction of the tire, and provided within a region which is 10 to 40% of a ground contact width from one ground contact end of a tread in the widthwise direction toward a tire equatorial plane; another circumferential groove extending along the circumferential direction of the tire, and provided within a region which is 10 to 40% of the ground contact width from another ground contact end of the tread in the widthwise direction toward the tire equatorial plane; at least two rows of blocks which, when a region between the pair of circumferential grooves is defined as a center tread region, are divided, in at least the center tread region, by a plurality of transverse grooves extending substantially in a tire axial direction; first reinforcing portions provided integrally with tire-widthwise-direction other side end portions of first blocks located at tire-widthwise-direction one side among the at least two rows of blocks, such that the first reinforcing portions are connected to block side surfaces of the first block and adjacent transverse groove bottom portions; and second reinforcing portions provided integrally with tire-widthwise-direction one side end portions of second blocks located at the tire-widthwise direction other side which are adjacent to the first blocks, such that the second reinforcing portions are connected to block side surfaces of the second block and adjacent transverse groove bottom portions, wherein at least a portion of each first reinforcing portion faces the second block with the transverse groove therebetween in the circumferential direction of the tire and overlaps the second block in the tire widthwise direction; at least a portion of each second reinforcing portion faces the first block with the transverse groove therebetween in the circumferential direction of the tire and overlaps the first block in the tire widthwise direction; and a height of the first reinforcing portion decreases as the first reinforcing portion is distanced from the first block, and a height of the second reinforcing portion decreases as the second reinforcing portion is distanced from the second block.
In accordance with the above-described first aspect, the following excellent effects are achieved.
(1) Because the pair of circumferential grooves is provided in the t
Bridgestone Corporation
Maki Steven D.
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