JP2005119614A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire which can improve the running performance on a bad road while maintaining the operation stability on a good road. <P>SOLUTION: Groove bottom block rows 6R composed of groove bottom blocks 6 are provided on a groove bottom 5 of a longitudinal main groove 3. The groove bottom block 6 has an approximate Z shape at which an end portion 14e of a first longitudinal portion 14 along one groove wall S1 on one side in the peripheral direction is connected to an end portion 15e of a second longitudinal portion 15 along the other groove wall S2 on the other side in the peripheral direction so as to have an overlapped portion 16. The groove bottom blocks 6 neighboring in the peripheral direction are arranged so as to have a peripheral gap Gy between the first longitudinal portions 14, 14 and between the second longitudinal portions 15, 15, and further so as to have a gap Gx in the axial direction of the tire between one first longitudinal portion 14 and the other second longitudinal portion 15. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a pneumatic tire in which a groove bottom block is provided at the bottom of a longitudinal main groove to improve traveling performance on rough roads such as muddy areas and snowy roads.

  Various tread patterns using tread grooves including vertical main grooves extending in the tire circumferential direction are formed in the tread portion of the tire. And in pneumatic tires such as winter tires, mud & snow tires, etc., in order to ensure the running performance on rough roads such as muddy areas and snowy roads, in addition to devising the pattern shape of the tread pattern, Increasing the groove volume or increasing the ratio of the groove area to the tread surface (groove area ratio) is performed.

  However, such an increase in the groove volume and groove area ratio is accompanied by a decrease in pattern rigidity and a contact area, so that steering stability on a good road is impaired and results are brought about. Accordingly, there is a limit to the increase in the groove volume and the groove area ratio, and it has been difficult to sufficiently improve the running performance on rough roads. Moreover, since the groove volume of the tread groove is reduced with the progress of wear, there is a problem that the running performance on a rough road is greatly lowered with the progress of wear.

JP 2001-253211 A JP 2001-63316 A

  Accordingly, the present invention is based on the provision of a groove bottom block having a predetermined shape at the groove bottom of the vertical main groove, and can improve driving performance on rough roads while maintaining steering stability on good roads. And it aims at providing the pneumatic tire which can suppress the fall of the running performance on the rough road accompanying wear progress.

In order to achieve the above object, the invention of claim 1 of the present application is characterized in that the groove of the vertical main groove extending in the tire circumferential direction disposed in the tread portion is spaced apart from the groove wall of the vertical main groove. Providing a groove bottom block row consisting of groove bottom blocks raised from the bottom and arranged in the groove length direction,
The groove bottom block has a width Wa smaller than 0.5 times the width WG of the groove bottom, and extends along a first vertically long portion extending along one groove wall and the other groove wall. And an overlapping portion in which the end portion on one side in the circumferential direction of the first vertically long portion and the end portion on the other side in the circumferential direction of the second vertically long portion face each other in the tire axial direction. And while making a substantially Z-shape connected at this overlapping part,
The groove bottom block row includes a circumferential gap Gy between the first vertically long portions and the second vertically long portions of the groove bottom blocks adjacent to each other in the circumferential direction, and the groove bottom block rows of the adjacent groove bottom blocks are adjacent to each other. The groove bottom block is arranged between the one vertically long portion and the second vertically long portion of the other groove bottom block with a tire axial gap Gx therebetween.

  According to a second aspect of the present invention, the groove bottom block has a height H from the groove bottom of 0.25 to 0.35 times the groove depth HG of the vertical main groove.

  In the invention of claim 3, the first vertically long portion of one groove bottom block adjacent to the circumferential direction and the second vertically long portion of the other groove bottom block have overlapping regions facing each other in the tire axial direction. It is a feature.

  According to a fourth aspect of the present invention, a length La in the circumferential direction of the first and second vertically long portions is 4.0 to 6.0 times the width Wa.

  In the invention of claim 5, the circumferential length Lb of the overlapping portion is 0.7 to 1.3 times the width Wa.

  In the invention of claim 6, the circumferential gap Gy between the first vertically long portions and the second vertically long portions of the groove bottom blocks adjacent in the circumferential direction is the first and second vertically long portions. It is characterized by being 0.3 to 0.7 times the circumferential length La.

  According to the invention of claim 7, the axial gap Gx between the first vertically long portion of one adjacent groove bottom block and the second vertically long portion of the other groove bottom block is set to 0. 0 of the width Wa. It is characterized by 3 to 0.7 times.

  Since the present invention is configured as described above, it is possible to improve running performance on bad roads while maintaining steering stability on good roads. In addition, excellent running performance on this rough road can be stably exhibited without being greatly influenced by the progress of wear.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a development view of a tread pattern when the pneumatic tire of the present invention is a mud and snow tire for a four-wheel drive vehicle, and FIG. 2 is a plan view of a groove bottom block.

  In FIG. 1, a pneumatic tire 1 includes a vertical main groove 3 extending in the tire circumferential direction in a tread portion 2, and a groove bottom block row including groove bottom blocks 6 on a groove bottom 5 of the vertical main groove 3. 6R is formed.

  In this example, the case where one longitudinal main groove 3 and 3 is arranged on each side of the tire equator C is illustrated, so that the tread portion 2 can be connected to the central land between the longitudinal main grooves 3 and 3. It is divided into a portion Rc and a shoulder land portion Rs between the vertical main groove 3 and the tread grounding edge Te. Further, the central land portion Rc is composed of two rows of blocks 9 composed of blocks 9 by a vertical narrow groove 7 extending on the tire equator C and a horizontal main groove 8 connecting between the vertical narrow groove 7 and the vertical main groove 3. Are formed. Further, the shoulder land portion Rs is composed of two rows composed of blocks 12 by a horizontal main groove 10 connecting the vertical main groove 3 and the tread grounding edge Te and a connecting groove 11 connecting the horizontal main grooves 10 and 10. What is formed in this block row is illustrated.

  In this example, the vertical main groove 3 is a straight groove extending continuously in a straight line. As shown in FIG. 3, the width WG of the groove bottom 5 is preferably 2 of the tread grounding width TW. -10%, more preferably 3-7%. The groove depth HG is preferably set to 8 to 15 mm, more preferably 10 to 13 mm. Such vertical main grooves 3 exhibit excellent drainage performance, while ensuring straight running stability on rough roads. In addition, the horizontal main grooves 8 and 10 and the connecting groove 11 have a width and a groove depth at the bottom of the groove which are the same as those of the vertical main groove 3 in order to secure grip performance on a rough road. Similarly, it is set to the range of 2 to 5% of the tread ground contact width TW and 8 to 13 mm.

  The “tread grounding width TW” is the tire axial direction between the tread grounding edges Te and Te when the tire is assembled on a regular rim and filled with a regular internal pressure and is loaded with a regular load and grounded on a flat surface. Means distance. The “regular rim” is a rim determined for each tire in a standard system including a standard on which a tire is based, for example, a standard rim for JATMA, “Design Rim” for TRA, Or ETRTO means “Measuring Rim”. The “regular internal pressure” is the air pressure defined by the standard for each tire. If JATMA, the maximum air pressure, if TRA, the maximum value described in the table “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” In the case of ETRTO, it means “INFLATION PRESSURE”, but in the case of a passenger car tire, it is 180 KPa. Furthermore, the “regular load” is a load that the standard defines for each tire. If it is JATMA, the maximum load capacity, if it is TRA, the maximum value described in the table “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES”, If it is ETRTO, it means “LOAD CAPACITY”, but in the case of passenger car tires, it is 0.88 times the value.

  In the present invention, at least one groove bottom 5 of the vertical main grooves 3, and in this example, the groove bottom 5 of each vertical main groove 3 is spaced from the groove wall S of the vertical main groove 3. A groove bottom block row 6 </ b> R is formed that is formed from the groove bottom blocks 6 that protrude from the groove bottom 5 and are arranged in the groove length direction (in the present example, the tire circumferential direction).

  As shown in an enlarged view in FIG. 2, the groove bottom block 6 includes a first vertically long portion 14 extending along one groove wall S1 of the vertical main groove 3 and a second wall extending along the other groove wall S2. And the vertically long portion 15. In addition, the groove bottom block 6 includes an overlapping portion 16 in which the end portion 14e on one circumferential side of the first vertically long portion 14 and the end portion 15e on the other circumferential side of the second vertically long portion 15 face each other in the tire axial direction. And is formed in a substantially Z-shape connected to each other at the overlapping portion 16.

  The first and second vertically long portions 14 and 15 have widths Wa1 and Wa2 (referred to collectively as width Wa) smaller than 0.5 times the width WG of the groove bottom, that is, Wa1 / WG. <0.5 and Wa2 / WG <0.5. In this example, the first and second vertically long portions 14 and 15 have a vertically long rectangular shape that is long in the groove length direction, and the circumferential lengths La1 and La2 (generally referred to as the circumferential length La). Is preferably 4.0 to 6.0 times the widths Wa1 and Wa2, ie, 4.0 ≦ La1 / Wa1 ≦ 6.0, 4.0 ≦ La2 / Wa2 ≦ 6.0. ing.

  Further, the groove bottom blocks 6 and 6 adjacent in the circumferential direction separate the circumferential gaps Gy1 and Gy2 between the first vertically long portions 14 and 14 and the second vertically long portions 15 and 15, respectively. The first vertically long portion 14 of the groove bottom block 6 and the second vertically long portion 15 of the other groove bottom block 6 are arranged with a tire axial gap Gx therebetween. At this time, in this example, the first vertically long portion 14 of the one groove bottom block 6 and the second vertically long portion 15 of the other groove bottom block 6 form an overlapping region J facing the tire axial direction. ing.

  As described above, the groove bottom block 6 has the first and second vertically long portions 14 and 15 formed in a vertically long rectangular shape and is connected by the overlapping portion 16, so that the width Wa 1 and Wa 2 are reduced. Sufficient directional rigidity can be secured. Therefore, while suppressing a reduction in the groove volume of the vertical main groove 3, the circumferential side wall surface of the groove bottom block 6 makes it possible to obtain traction force from snow or soil biting into the groove, and grip performance on rough roads. Can be improved. In particular, when the overlapping region J is provided between the groove bottom blocks 6 and 6, more groove bottom blocks 6 can be arranged, and the effect of improving grip performance on rough roads can be further enhanced. The groove bottom block 6 is substantially Z-shaped so that the overlapping region J can be formed.

  Further, since the groove bottom block 6 is formed on the groove bottom 5, the steering stability on the good road can be maintained, and the grip on the rough road can be maintained without being affected by the progress of wear of the tread portion 2. The property improvement effect can be exhibited stably. Moreover, it becomes possible to perform pattern design with a high degree of freedom.

  Here, in order to improve the grip performance on the rough road, the height H (shown in FIG. 3) of the groove bottom block 6 from the groove bottom 5 is set to the groove depth HG of the vertical main groove 3. It is preferable to make it 0.25 to 0.35 times. If it is less than 0.25 times, the height H is too small to obtain a sufficient traction force, and the effect of improving the grip performance on rough roads cannot be exhibited effectively. On the other hand, if it exceeds 0.35 times, the drainage performance tends to be lowered in the middle to final stage of wear.

  Further, when the ratios La1 / Wa1 and La2 / Wa2 are less than 4.0, the groove bottom block 6 is likely to cause chipping due to a decrease in strength such as insufficient circumferential rigidity. On the other hand, if it exceeds 6.0, the groove volume is unnecessarily reduced, which tends to impair the effect of improving grip performance on rough roads and the drainage performance.

  In this example, the widths Wa1 and Wa2 are the same, and the circumferential lengths La1 and La2 are the same, and the same grip performance improvement effect on a rough road can be exhibited in any tire rotation direction. The thing which has no directionality is illustrated. However, the widths Wa1 and Wa2 and the circumferential lengths La1 and La2 can be made different from each other within the range as required.

  Moreover, in the groove bottom block 6, in order to ensure the rigidity in the circumferential direction, it is preferable that the circumferential length Lb of the overlapping portion 16 is 0.7 to 1.3 times the width Wa. If it is less than double, the circumferential rigidity is insufficient. On the other hand, if it exceeds 1.3 times, the groove volume is unnecessarily reduced. When the widths Wa1 and Wa2 are different, the width Wa is treated as an average value (Wa1 + Wa2) / 2.

  The circumferential gaps Gy1 and Gy2 between the groove bottom blocks 6 and 6 adjacent to each other in the circumferential direction are 0.3 to 3 to the lengths La1 and La2 in the circumferential directions of the first and second vertically long portions 14 and 15, respectively. 0.7 times, that is, 0.3 ≦ Gy1 / La1 ≦ 0.7 and 0.3 ≦ Gy2 / La2 ≦ 0.7 are preferable. When the ratios Gy1 / La1 and Gy2 / La2 are smaller than 0.3, the shearing force of snow and soil biting into the circumferential gaps Gy1 and Gy2 becomes small. In either case, the grip improvement effect on rough roads tends to be reduced.

  Further, the axial gap Gx between the groove bottom blocks 6 adjacent to each other in the circumferential direction is preferably 0.3 to 0.7 times the width Wa. The soil removal property is reduced, and clogging is likely to occur in the gaps Gy1, Gy2, and Gx. On the other hand, if it exceeds 0.7 times, the widths Wa1 and Wa2 are substantially reduced, and the rigidity and strength of the groove bottom block 6 are lowered.

  Next, FIGS. 4A and 4B show another embodiment of the vertical main groove 3 and the groove bottom block row 6R. In this example, the case where the vertical main groove 3 is a zigzag groove is illustrated, and in FIG. 4A, the groove bottom block row 6R includes the first vertical elongated portion 14 having a parallelogram shape along the groove wall S1. The parallelogram-shaped second vertically long portion 15 along the groove wall S2 is formed by a substantially Z-shaped groove bottom block 6 connected by an overlapping portion 16 thereof. In this example, an example is shown in which, for example, two groove bottom blocks 6 are arranged in the zigzag half pitch Q without having the overlapping region J and without crossing the corner V of the zigzag.

  In FIG. 4B, the groove bottom block row 6R is formed to include a corner groove bottom block 6A that crosses the zigzag corner V. In the corner groove bottom block 6A, the first and / or second longitudinally long portions 14 and / or 15 crossing the corner V are bent in a square shape along the corner.

  As mentioned above, although especially preferable embodiment of this invention was explained in full detail, this invention can be deform | transformed and implemented in various aspects, without being limited to embodiment of illustration. For example, the groove bottom block row 6R may be formed in one of the plurality of vertical main grooves 3, and if the tread pattern also includes at least one vertical main groove 3, the book Without being limited to the examples, various patterns can be employed.

  A tire of tire size R215 / 55R17 was prototyped based on the specifications shown in Table 1 using the tread pattern shown in Fig. 1 as a basic pattern. Tested against time and compared the results.

(1) Grip performance on bad roads and snowy roads;
Grip performance when a test tire is mounted on all wheels of a vehicle (four-wheel drive 3000cc) with a rim (7JJ × 17) and internal pressure (210kPa) and running on a mud and soil-based test course mainly made of mud According to the sensory evaluation of the driver, the evaluation was made in four stages: ◎ (good), ○ (possible: new product level of conventional products), △ (inferior), and × (bad).

  As shown in the table, it can be confirmed that the tires of the examples can improve the grip performance on rough roads when new, and can maintain high grip performance even when worn by 50%.

It is an expanded view of the tread pattern which shows one Embodiment of the pneumatic tire of this invention. It is a top view which expands and shows the groove bottom block row | line | column. It is sectional drawing of the direction orthogonal to the groove length direction of a vertical main groove. (A), (B) is a top view which shows the other Example of a groove bottom block row | line | column.

Explanation of symbols

2 tread portion 3 vertical main groove 5 groove bottom 6 groove bottom block 6R groove bottom block row 14 first vertical portion 15 second vertical portion 16 overlapping portion J overlapping regions S1, S2 groove wall

Claims (7)

A groove bottom block that protrudes from the groove bottom and is arranged in the groove length direction at a groove bottom of the vertical main groove extending in the tire circumferential direction arranged in the tread portion and spaced from a groove wall of the vertical main groove. A groove bottom block row consisting of
The groove bottom block has a width Wa smaller than 0.5 times the width WG of the groove bottom, and extends along a first vertically long portion extending along one groove wall and the other groove wall. And an overlapping portion in which the end portion on one side in the circumferential direction of the first vertically long portion and the end portion on the other side in the circumferential direction of the second vertically long portion face each other in the tire axial direction. And while making a substantially Z-shape connected at this overlapping part,
The groove bottom block row includes a circumferential gap Gy between the first vertically long portions and the second vertically long portions of the groove bottom blocks adjacent to each other in the circumferential direction, and the groove bottom block rows of the adjacent groove bottom blocks are adjacent to each other. A pneumatic tire characterized in that a groove bottom block is arranged between a vertically long portion of one and a second vertically long portion of the other groove bottom block with a tire axial gap Gx therebetween.   The pneumatic tire according to claim 1, wherein the groove bottom block has a height H from the groove bottom of 0.25 to 0.35 times the groove depth HG of the longitudinal main groove.   The first vertically long portion of one groove bottom block adjacent to the circumferential direction and the second vertically long portion of the other groove bottom block have overlapping regions facing each other in the tire axial direction. The described pneumatic tire.   The pneumatic length according to any one of claims 1 to 3, wherein a length La in the circumferential direction of the first and second vertically long portions is 4.0 to 6.0 times the width Wa. tire.   The pneumatic tire according to any one of claims 1 to 4, wherein a circumferential length Lb of the overlapping portion is 0.7 to 1.3 times the width Wa.   The circumferential gap Gy between the first vertically long portions and the second vertically long portions of the groove bottom blocks adjacent to each other in the circumferential direction has a circumferential length La of the first and second vertically long portions. The pneumatic tire according to claim 1, wherein the pneumatic tire is 0.3 to 0.7 times.   The axial gap Gx between the first vertically long portion of one adjacent groove bottom block and the second vertically long portion of the other groove bottom block is 0.3 to 0.7 times the width Wa. The pneumatic tire according to any one of claims 1 to 6.

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