JP5161478B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire that is suitably mounted on a rally vehicle that travels on rough terrain, particularly a wet unpaved road surface.

  Pneumatic tires that are suitable for rally vehicles have a traction to transmit driving force to the road surface and a side grip that suppresses the skidding of the tire to improve the running time by firmly gripping the unpaved road surface. Sex is important.

  Therefore, in Patent Document 1, for example, as shown in FIG. 7A, a long block a that is long in the tire circumferential direction is arranged in the tread outer region ys that faces the outer side of the vehicle when the vehicle is mounted. At the same time, it has been proposed to place horizontally long blocks b in the tread inner region yu with an emphasis on traction.

Japanese Patent Laid-Open No. 11-268506

However, even when the tire has such a pattern, for example, when driving on a road surface with an extremely low coefficient of friction μ (hereinafter sometimes referred to as an ultra-low μ road surface) such as a wet unpaved road surface or a road surface with a lot of gravel. You can't expect much on the side grip during cornering. Therefore, in recent years, as shown schematically in FIG. 7 (B), only the horizontally long block b can be used to specialize in traction, and the running time can be shortened by the high traction while sacrificing the lateral grip. Proposed.

  The present invention relates to the improvement of the tread pattern using only such a horizontally long block, and while maintaining excellent traction by the horizontally long block, it is possible to ensure a lateral grip property, particularly an ultra-low μ road surface. An object of the present invention is to provide a pneumatic tire that can further improve the running time.

In order to achieve the above object, the invention of claim 1 of the present application includes a plurality of longitudinal main grooves extending continuously in the tire circumferential direction in the tread portion, and between the longitudinal main grooves and between the longitudinal main grooves and the tread edge. A pneumatic tire in which a plurality of block rows in which the blocks are spaced apart in the tire circumferential direction are formed in the tread portion by providing a plurality of transverse grooves extending in between,
Each of the blocks has a ratio L / of a block length L that is the maximum length in the tire circumferential direction on the block tread surface where the block contacts the road surface and a block length W that is the maximum length in the tire axial direction on the block tread surface. W is a horizontally long block of 0.3 to 0.6,
The vertical main groove includes an outer vertical main groove arranged on the outermost side of the vehicle when the vehicle is mounted, and an inner vertical main groove arranged on the innermost side of the vehicle,
The opening portions of the lateral groove on one side and the other side in the tire axial direction that open across the outer vertical main groove are the outer sides of the blocks arranged on the other side and one side in the tire axial direction of the outer vertical main groove. The vertical block edge facing the vertical main groove has a block edge facing portion that faces the outer vertical main groove across the outer longitudinal main groove, and of the circumferential length of the opening, While making the block edge facing ratio, which is the ratio occupied by the circumferential length, greater than 50%,
The opening portions of the lateral groove on one side and the other side in the tire axial direction that open across the inner longitudinal main groove are the inner portions of the blocks arranged on the other side and one side in the tire axial direction of the inner longitudinal main groove. The block edge facing ratio with respect to the vertical block edge facing the vertical main groove is 50% or less, or 0%.

  According to a second aspect of the present invention, the vertical main groove includes the outer vertical main groove, an inner vertical main groove, and a central vertical main groove extending on the tire equator.

  According to a third aspect of the present invention, the block edge facing ratio of the opening portion of the lateral groove on one side and the other side in the tire axial direction that opens across the outer vertical main groove, and the central vertical main groove opens. The block edge facing ratios of the openings of the lateral grooves on one side and the other side in the tire axial direction are 100%, respectively.

  According to a fourth aspect of the present invention, the inner vertical main groove has a groove width smaller than that of other vertical main grooves.

  In the invention of claim 5, in each block row, the smallest tread area where the block tread area where the block contacts the road surface is the smallest tread area where the block tread area is the largest. It is a feature.

  In the invention of claim 6, the outer block row arranged on the outermost side of the vehicle when mounted on the vehicle has an average area of the block tread surface larger than an average value of the block tread areas in the other block rows. It is characterized by that.

In the invention of claim 7, in each of the block rows, the groove width of the narrowest lateral groove is 90% or more of the groove width of the widest lateral groove. In the invention according to claim 8, the lateral block has lateral block edges on both sides in the tire circumferential direction at an angle θ of 10 ° or less with respect to the tire axial direction, and protrudes in the tire circumferential direction on one lateral block edge side. One substantially horizontally long rectangular protrusion is formed, and one substantially horizontally long rectangular recess is formed on the other lateral block edge side at a position substantially opposite to the protrusion in the tire circumferential direction. With reference to the reference line J passing through the approximate center of the block and parallel to the vertical block edges on both sides in the tire axial direction of the block, the one side portion in the tire axial direction from the reference line J is compared with the other side portion. It is characterized by a shape that is displaced in the tire circumferential direction.

  As described above, the present invention employs a block pattern in which horizontally long blocks having a ratio L / W of 0.3 to 0.6, which is the aspect ratio / width ratio, are used, and thus exhibits excellent traction. Particularly in rally vehicles, a negative camber is provided in order to keep the tire posture in cornering correctly. Therefore, at the time of straight traveling, the tread inner region is greatly involved in the traction characteristics in the straight traveling, such as the center of the tire contact pressure shifts to the inner region of the tread that is inside the vehicle from the tire equator.

  Therefore, in the present invention, in order to particularly increase the traction force in the inner region of the tread, the block edge facing ratio in the opening is reduced to 50% or less in the lateral groove that opens to intersect with the longitudinal main groove. Here, when the block edge facing ratio is 50% or less, the horizontal grooves arranged on both sides of the inner vertical main groove are arranged in a substantially horizontal state without being greatly displaced in the circumferential direction. Therefore, the mud etc. in the horizontal groove are easily stepped and solidified, such as the lateral grooves on both sides are connected, and the mud mud etc. that has been tucked together is mutually coupled to increase the strength. As a result, not only the edge effect by the horizontally long block, but also the traction force can be increased by increasing the shearing force of the mud soil that has been compacted.

  On the other hand, for the tread outer region that is greatly involved in skidding during cornering, the block edge facing ratio at the opening is increased to more than 50% in the lateral groove that opens across the outer vertical main groove. When the block edge facing ratio is larger than 50%, the lateral grooves arranged on both sides of the outer longitudinal main groove have a substantially staggered arrangement in which they are greatly displaced in the circumferential direction. Accordingly, mud soil or the like that has been stepped and solidified in the lateral groove is blocked by the opposing block wall surface, and an axial (lateral) shearing force can be obtained. In particular, since the mud soil that has been compacted is horizontally long, the shearing force in the axial direction becomes large. In addition, since the lateral groove is opened facing the block wall surface, the edge effect is enhanced, for example, the edge of the block wall surface is easily caught on the road surface.

  And, by these interactions, it is possible to sufficiently secure the lateral grip property while exhibiting excellent traction properties, and it is possible to improve the running time especially on the ultra-low μ road surface.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a development view showing a tread pattern in the case where the pneumatic tire of the present invention is a tire for a rally vehicle mounted on a rally vehicle.

  As shown in FIG. 1, the pneumatic tire 1 according to this embodiment includes a plurality of longitudinal main grooves 3 extending continuously in the tire circumferential direction on the tread portion 2, and the longitudinal main grooves 3, 3 and the longitudinal main grooves. A block pattern comprising a plurality of lateral grooves 4 extending between the groove 3 and the tread edge T, whereby a plurality of block rows R in which the blocks 5 are spaced apart in the tire circumferential direction are arranged in the tread portion 2. Is formed.

  In the case of a tire for a rally vehicle such as this example, the land ratio (S / S0) in the block pattern is in the range of 44 to 48% from the viewpoint of running performance on both the soft road and the hard road. preferable. The land ratio (S0 / S) is the total block with respect to the total area S0 of the outer surface of the tread portion 2 (the total area of the outer surface of the tread portion 2 when all the vertical main grooves 3 and the horizontal grooves 4 are filled). It is defined by the ratio of the total sum S of the block tread areas. Further, the number of blocks 5 arranged in each block row R, that is, the number of pitches is the same as that in each block row R. In the case of tires for rally vehicles, a range of 40 to 60 is preferable.

  Next, the vertical main groove 3 includes an outer vertical main groove 3s arranged on the outermost side of the vehicle when the vehicle is mounted and an inner vertical main groove 3u arranged on the innermost side of the vehicle. In this example, the vertical main groove 3 is composed of a total of three main main grooves 3s, 3u, and a central vertical main groove 3c arranged between them and extending on the tire equator C. The case is illustrated.

The lateral groove 4 is
(1) A block row composed of the outer blocks 5s by crossing the land area Zs between the outer tread edge Ts disposed on the vehicle outer side and the outer vertical main groove 3s. A plurality of outer lateral grooves 4s as Rs;
(2) By crossing the land area Zm between the outer vertical main groove 3s and the central vertical main groove 3c, the land area Zm is a plurality of block rows Rm composed of the inner blocks 5m. 4m horizontal groove in the book,
(3) By crossing the land area Zn between the central vertical main groove 3c and the inner vertical main groove 3u, the land area Zn becomes a block row Rn composed of the inner blocks 5n. A lateral groove 4n in the book;
(4) By crossing the land area Zu between the inner vertical main groove 3u and the inner tread edge Tu arranged on the inner side of the vehicle, the land area Zu is made up of a block row composed of the inner blocks 5u. It is composed of a plurality of transverse grooves 4u which are Ru. The vertical main grooves 3s, 3c, and 3u are collectively referred to as the vertical main grooves 3, and the horizontal grooves 4s, 4m, 4n, and 4u are collectively referred to as the horizontal grooves 4, and the blocks 5s, 5m, 5n, and 5u are collectively referred to. This is called block 5.

  Each block 5 has a longitudinal / longitudinal ratio L / W of a block length L in the tire circumferential direction and a block length W in the tire axial direction, as representatively represented by the block 5m in FIG. It is formed by a horizontally long block having an aspect ratio in the range of 0.3 to 0.6. The “block length L” in the tire circumferential direction is defined as the maximum length in the tire circumferential direction on the block tread surface where the block 5 contacts the road surface, and the “block length W” in the tire axial direction is defined as It is defined as the maximum length in the tire axial direction on the block tread.

  Such a horizontally long block has a large edge component in the tire axial direction, and a large shearing force can be obtained from mud or the like in which the lateral groove 4 is long and solidified inside thereof. Can generate power. If the ratio L / W exceeds 0.6, the above-mentioned effect due to the landscape orientation will not be sufficiently exerted, and conversely, even if the ratio is less than 0.3, the block becomes excessively elongated and the block rigidity tends to be insufficient. Similarly, the traction force cannot be obtained effectively because the block collapses in a crumbled state during driving or braking.

  Next, as the block 5, in this example, the longitudinal block edges 6 and 6 on both sides in the tire axial direction facing the longitudinal main groove 3 are substantially parallelogram shapes that are inclined at an angle α with respect to the tire circumferential direction. However, it may have a substantially rectangular shape with the angle α being 0 °. This angle α is preferably 20 ° or less, and more preferably 15 ° or less. If the angle α exceeds 20 °, the block pattern has a directionality, and is used for the left wheel to ensure straight running stability. The versatility tends to be impaired, such as the need for two types of tires and tires for the right wheel.

  When the vertical block edge 6 on the tire axial direction side is inclined, the vertical main groove 3 can be regarded as a zigzag groove in which the vertical block edge 6 forms a zigzag element. Thus, the longitudinal main groove 3 can be formed as the zigzag groove or as a linear groove with the angle α being 0 °. When the vertical block edge 6 is inclined as in this example, the groove width Wg of the vertical main groove 3 is the tire axial direction between the tire circumferential direction lines X and X passing through the intermediate point 6M of the vertical block edge 6. Is defined as the distance. The groove width Wg of the longitudinal main groove 3 is preferably in the range of 5 to 10% of the tread width TW (shown in FIG. 1) from the viewpoint of running performance on both the soft road and the hard road.

  Moreover, it is preferable that the horizontal block edges 7 and 7 on both sides in the tire circumferential direction of the block 5 are arranged at an angle θ of 10 ° or less with respect to the tire axial direction. That is, the lateral grooves 4 are preferably arranged at the angle θ. If the angle θ exceeds 10 °, it becomes difficult to reduce the ratio L / W to 0.6 or less, for example, the block length L in the tire circumferential direction increases. Directionality occurs in the block pattern, and the versatility tends to be impaired.

  In the block 5 of the present example, a substantially horizontally long projection 8 that protrudes in the tire circumferential direction is formed on one side of the horizontal block edge 7, and the projection on the side of the other horizontal block edge 7. A substantially horizontally-long rectangular recess 9 is formed at a position substantially opposite to 8. The protrusion amount δ1 of the protrusion 8 and the recess amount δ2 of the recess 9 are substantially equal, and the block 5 of this example passes through the approximate center of the block 5 and is centered on a reference line J parallel to the vertical block edge 6. As described above, the tire has a shape in which the one side portion in the tire axial direction is displaced from the reference line J in the tire circumferential direction as compared with the other side portion. Providing such projections 8 and recesses 9 can increase the total edge length of the block 5, which is advantageous for traction and lateral grip. The protrusion amount δ1 of the protrusion 8 and the recess amount δ2 of the recess 9 are each preferably in the range of 10 to 20% of the block length L in the tire circumferential direction, and if less than 10%, the total edge length is sufficient. An increase cannot be expected. Conversely, if it exceeds 20%, there arises a problem that the block rigidity is lowered.

  Next, in the tire 1 of the present embodiment, as shown in FIGS. 3 and 4 in an enlarged manner, the opening 10 of the lateral groove 4 on one side and the other side in the tire axial direction that opens across the outer vertical main groove 3s. The vertical block edge 6 facing the outer vertical main groove 3s in the block 5 disposed on the other side and one side in the tire axial direction of the outer vertical main groove 3s is the outer vertical main groove 3s. The block edge facing ratio PS is the ratio of the block edge facing portion 11 that is opposed to the block edge and is occupied by the circumferential length QS of the block edge facing portion 11 in the circumferential length PS of the opening 10. / QS is greater than 50%. Further, the opening 10 of the transverse groove 4 on one side and the other side in the tire axial direction that opens across the inner longitudinal main groove 3u is disposed on the other side and one side in the tire axial direction of the inner longitudinal main groove 3u. The block edge facing ratio PU / QU with respect to the vertical block edge 6 facing the inner vertical main groove 3u in the block 5 is set to 50% or less, or 0%.

More specifically, as shown in FIG. 3, the outer longitudinal main grooves 3s are arranged on one side (in this example, the vehicle outer side) and the other side (in this example, the vehicle inner side) in the tire axial direction. An inner lateral groove 4m is disposed, and the outer lateral groove 4s and the inner lateral groove 4m include openings 10s and 10m that open to intersect with the outer longitudinal main groove 3s. The opening 10s of the outer horizontal groove 4s is opposed to the vertical block edge 6m of the inner block 5m disposed inside the outer vertical main groove 3s with the outer vertical main groove 3s interposed therebetween. It has a block edge facing portion 11s. The block edge facing ratio PSs / QSs, which is the ratio occupied by the circumferential length QSs of the block edge facing portion 11s in the circumferential length PSs of the opening 10s, is larger than 50%. Similarly, the opening 10m of the inner horizontal groove 4m is sandwiched between the outer vertical main groove 3s and the vertical block edge 6s of the outer block 5s arranged on the vehicle outer side of the outer vertical main groove 3s. An opposing block edge facing portion 11m is provided. The block edge facing ratio PSm / QSm, which is the ratio occupied by the circumferential length QSm of the block edge facing portion 11m in the circumferential length PSm of the opening 10m, is greater than 50%. The block edge facing ratio PSs / QSs and PSm / QSm are collectively referred to as block edge facing ratio PS / QS.

  On the other hand, as shown in FIG. 4, the lateral grooves 4n in the inner longitudinal main groove 3u are arranged on one side in the tire axial direction (in this example, the vehicle outer side) and the other side (in this example, the vehicle inner side), The lateral groove 4u includes openings 10n and 10u that open across the longitudinal main groove 3u. The opening 10n of the inner horizontal groove 4n is opposed to the vertical block edge 6u of the inner block 5u disposed on the vehicle inner side of the inner vertical main groove 3u with the inner vertical main groove 3u interposed therebetween. A block edge facing portion 11n. The block edge facing ratio PUn / QUn, which is the ratio occupied by the circumferential length QUn of the block edge facing portion 11n in the circumferential length PUn of the opening 10n, is 50% or less, or 0%. . Similarly, the opening 10u of the inner horizontal groove 4u is sandwiched between the inner vertical main groove 3u and the vertical block edge 6n of the inner block 5n arranged on the vehicle outer side of the inner vertical main groove 3u. It has the block edge opposing part 11u which opposes. The block edge facing ratio PUu / QUIu, which is the ratio occupied by the circumferential length QUu of the block edge facing portion 11u in the circumferential length PUu of the opening 10u, is 50% or less, or 0%. . The block edge facing ratio PU / QUn and PUu / Qu are collectively referred to as the block edge facing ratio PU / QU.

  In this example, as shown in FIG. 5, the block edge facing ratio PC / QC of the opening 10 of the lateral groove 4 on one side and the other side in the tire axial direction that crosses the central longitudinal main groove 3c and opens is also 50%. It is bigger. That is, the lateral grooves 4m and 4n arranged on one side (in this example, the vehicle outer side) and the other side (in this example, the vehicle inside) of the central vertical main groove 3c are the central vertical main grooves 3c. Opening portions 10m and 10n that cross and open. The opening 10m of the inner horizontal groove 4m is opposed to the vertical block edge 6n of the inner block 5n disposed on the vehicle inner side of the central vertical main groove 3c with the central vertical main groove 3c interposed therebetween. A block edge facing portion 11m. The block edge facing ratio PCm / QCm, which is the ratio of the circumferential length QCm of the block edge facing portion 11m in the circumferential length PCm of the opening 10m, is greater than 50%. Similarly, the opening 10n of the inner horizontal groove 4n is sandwiched between the central vertical main groove 3c and the vertical block edge 6m of the central block 5m disposed on the vehicle outer side of the central vertical main groove 3c. It has the block edge opposing part 11n which opposes. The block edge facing ratio PCn / QCn, which is the ratio of the circumferential length QCn of the block edge facing portion 11n in the circumferential length PCn of the opening 10n, is greater than 50%. Block edge facing ratio PCm / QCm and PCu / QCu are collectively referred to as block edge facing ratio PC / QC.

  As described above, in a rally vehicle, a negative camber is provided in order to keep the tire posture correctly in cornering. For this reason, cornering is completed, and in the straight acceleration state where the vehicle is standing up, the tread inner region yu moves to the tread inner region yu on the inner side of the tread, which is inside the vehicle from the tire equator. The involvement of is great.

  Therefore, in order to particularly increase the traction force in the tread inner region yu and improve the acceleration performance, the block edge facing ratio PU / in the opening portions 10n and 10u of the lateral grooves 4n and 4u that open to intersect the inner longitudinal main groove 3u. QU has been reduced to 50% or less respectively.

  Here, when the block edge facing ratio PU / QU is 50% or less, the lateral grooves 4n and 4u are arranged in a substantially side-by-side state without being greatly displaced in the circumferential direction. Then, the lateral grooves 4n and 4u on both sides are connected side by side to increase the volume, making it easier for the mud and the like in the lateral groove to be compacted and increasing the volume of the mud and the like that have been compacted. As a result, not only the edge effect due to the horizontally long block, but also the shearing force of the mud that has been squeezed is increased, and the traction force can be increased.

  On the other hand, with respect to the tread outer side region ys that is greatly involved in the side slip during cornering, the block edge facing ratio PS / QS at the opening portions 10s and 10m of the transverse grooves 4s and 4m that intersect with the outer longitudinal main groove 3s is 50, respectively. It is higher than%. When the block edge facing ratio PS / QS is greater than 50%, the lateral grooves 4s and 4m are arranged in a substantially staggered arrangement with a large displacement in the circumferential direction. Therefore, mud or the like that has been squeezed within the lateral grooves 4s and 4m is blocked by the opposing block wall surface 5S, and an axial (lateral) shearing force can be obtained. In particular, since mud or the like is stepped and consolidated horizontally, the shearing force in the axial direction becomes large. Moreover, since the lateral grooves 4s and 4m are opened facing the block wall surface 5S, the road surface is easily caught on the edge (that is, the vertical block edge 6) of the block wall surface 5S, and the edge effect is enhanced.

  And, by these interactions, it is possible to sufficiently secure the lateral grip property while exhibiting excellent traction properties, and it is possible to improve the running performance particularly on an ultra-low μ road surface. From the viewpoint of improving the running performance, it is preferable that the block edge facing ratio PS / QS is set to 100% in the openings 10 s and 10 m of the transverse grooves 4 s and 4 m intersecting the outer longitudinal main groove 3 s. At this time, it is more preferable that the width center i of each of the openings 10s and 10m and the intermediate point 6M of the vertical block edges 6m and 6s facing each other are on the same axial line. In addition, in the openings 10n and 10u of the horizontal grooves 4n and 4u intersecting the inner vertical main groove 3u, the block edge facing ratio PU / QU is preferably as small as possible with 30% or less. Further, in the openings 10m and 10n of the transverse grooves 4m and 4n intersecting the longitudinal main groove 3c, it is preferable that the block edge facing ratio PC / QC is 100%. At this time, it is more preferable that the width centers i of the openings 10m and 10n and the intermediate points 6M of the vertical block edges 6n and 6m facing each other are on the same axial line.

  Next, during the initial small rudder angle when the vehicle starts to turn from the straight traveling state, the center of the contact pressure is at the center of the tread, so that the central vertical main groove 3c acts effectively. Thereafter, during cornering, the center of ground pressure shifts to the outside of the vehicle, so that the outer vertical main groove 3s acts effectively. Therefore, as in this example, the groove widths Wgs and Wgc of the outer vertical main groove 3s and the central vertical main groove 3c are made larger than the groove width Wgu of the inner vertical main groove 3u, that is, Wgs> Wgu. By setting Wgc> Wgu, it is possible to improve the catching of the edge in the lateral direction, and it is possible to improve the response of the steering from the initial stage to the large steering angle. From the viewpoint of improving the responsiveness, the groove width Wgc is preferably in the range of 90 to 110%, more preferably 100% of the groove width Wgs. On the other hand, if the groove width Wgu is too narrow, the contact pressure tends to be non-uniform and uneven wear tends to occur. Therefore, the lower limit value of the groove width Wgu is 50% or more of the groove width Wgs and 50% of the groove width Wgc. % Or more is preferable.

  Further, when traveling on an ultra-low μ road surface, the slip ratio of the tire becomes very high. Therefore, in this example, in each block row R, the minimum tread area SAmin that is the tread area of the smallest block having the smallest block tread area (tread area) is 80 of the maximum tread area SAmax that is the tread area of the widest maximum block. The block 5 having a relatively uniform size with a small variation in the tread area such as% or more is arranged. Also in the horizontal grooves 4 arranged in each block row R, the groove width Wymin of the narrowest narrow groove having the narrowest groove width Wy is 90% or more of the groove width Wymax of the widest widest horizontal groove. The lateral grooves 4 having a relatively small width are arranged.

  Thus, in each block row R, by arranging the blocks 5 having a relatively uniform size and the lateral grooves 4 having a relatively uniform width, the ground pressure at the lateral block edge 7 can be equalized. As a result, the edge of the horizontal block edge 7 can be used effectively, that is, the edge effect can be enhanced, traction on a high ultra-low μ road surface can be improved, and slip can be suppressed. In addition, the uneven wear resistance can be improved by equalizing the contact pressure.

  A large load is applied to the outer block row Rs during cornering. Therefore, the average value SAs of the block tread areas of the blocks 5s arranged in the outer block row Rs is the average of the block tread areas of the blocks 5m, 5n, 5u arranged in the other block rows Rm, Rn, Ru. From the viewpoint of durability, it is preferable to increase the block strength to be larger than the values SAm, SAn, and SAu. In particular, it is more preferable that the average value SAu in the block row Ru in which the load is small during cornering is the smallest, and the average values SAm and SAn are set equal to each other in the remaining block rows Rm and Rn. More preferably.

  Further, with respect to the groove width Wy of the lateral groove 4, from the viewpoint of the balance between traction and lateral grip properties, the groove width Wys of the lateral grooves 4s, 4m, 4n, 4u arranged in each block row Rs, Rm, Rn, Ru. When the average values of Wym, Wyn, and Wyu are WAs, WAm, WAn, and WAu, respectively, it is preferable that WAs = WAm = WAn ≦ WAu. However, it is more preferable to satisfy WAs ≦ WAm = WAn ≦ WAu in consideration of the load movement during the cornering described above.

  As mentioned above, although especially preferable embodiment of this invention was explained in full detail, this invention is not limited to embodiment of illustration, It can deform | transform and implement in a various aspect.

A pneumatic tire for a rally vehicle having a tire size of 195 / 65R15 was made on the basis of the specifications shown in Table 1, tested for running performance on uneven terrain of each sample tire, and compared with each other. FIG. 6 illustrates the tread pattern of the tire used for the test, and each tire is substantially the same as the following specifications except for the block arrangement.
・ Block shape ---- Horizontal rectangle ・ Block aspect ratio L / W ---- 0.42
・ Land ratio (S / S0) ---- 45%
・ Number of block pitches ---- 49
・ Vertical main groove width (Wgs, Wgc, Wgu) ----- 7mm
・ Groove width of lateral groove (Wys, Wym, Wyn, Wyu) ----- 9.5mm

(1) Test Each tire was mounted on all wheels of a rally racing four-wheel drive vehicle with a displacement of 2000 cc with a rim (6.5 J) and internal pressure (210 kPa). Two time trials were performed on the lap, 2km), and the best running time and average running time were compared. The running performance at that time was evaluated by a five-point method based on the driver's sensuality. The following items were evaluated for running performance.
・ Traction performance, braking performance,
・ Initial responsiveness, behavior stability when entering cornering,
-Gripping and rudder following during cornering-Traction at cornering exit, front / rear balance-Responsiveness and front / rear balance at high speeds-Others (rigidity, grounding feeling, controllability)

It is an expanded view which shows one Example of the tread pattern of the pneumatic tire of this invention. It is a top view which expands and shows a block. It is a top view explaining the block edge opposing rate in the opening part of the horizontal groove which crosses an outer vertical main groove. It is a top view explaining the block edge opposing rate in the opening part of the horizontal groove which crosses an inner vertical main groove. It is a top view explaining the block edge opposing rate in the opening part of the horizontal groove which crosses the center vertical main groove. FIG. 3 is a development view showing a tread pattern of a tire used in the test of Table 1. (A), (B) is a development view of a conventional tread pattern for explaining the background art. It is an expanded view which shows an example of the tread pattern of the conventional tire.

Explanation of symbols

2 Tread part 3, 3s, 3c, 3u Vertical main groove 4, 4s, 4m, 4n, 4u Horizontal groove 5, 5s, 5m, 5n, 5u Block 6, 6s, 6m, 6n, 6u Vertical block edge 10, 10s, 10m 10n, 10u Opening 11, 11s, 11m, 11n, 11u Block edge facing part C Tire equator R, Rs, Rm, Rn, Ru Block row T Tread edge

Claims (8)

The tread portion is provided with a plurality of vertical main grooves extending continuously in the tire circumferential direction and a plurality of horizontal grooves extending between the vertical main grooves and between the vertical main grooves and the tread edge. A pneumatic tire in which a plurality of block rows in which the blocks are spaced apart in the tire circumferential direction is formed,
Each of the blocks has a ratio L / of a block length L that is the maximum length in the tire circumferential direction on the block tread surface where the block contacts the road surface and a block length W that is the maximum length in the tire axial direction on the block tread surface. W is a horizontally long block of 0.3 to 0.6,
The vertical main groove includes an outer vertical main groove arranged on the outermost side of the vehicle when the vehicle is mounted, and an inner vertical main groove arranged on the innermost side of the vehicle,
The opening portions of the lateral groove on one side and the other side in the tire axial direction that open across the outer vertical main groove are the outer sides of the blocks arranged on the other side and one side in the tire axial direction of the outer vertical main groove. The vertical block edge facing the vertical main groove has a block edge facing portion that faces the outer vertical main groove across the outer longitudinal main groove, and of the circumferential length of the opening, While making the block edge facing ratio, which is the ratio occupied by the circumferential length, greater than 50%,
The opening portions of the lateral groove on one side and the other side in the tire axial direction that open across the inner longitudinal main groove are the inner portions of the blocks arranged on the other side and one side in the tire axial direction of the inner longitudinal main groove. A pneumatic tire characterized in that a block edge facing ratio with respect to a vertical block edge facing the vertical main groove is set to 50% or less or 0%.   2. The pneumatic tire according to claim 1, wherein the vertical main groove includes the outer vertical main groove, an inner vertical main groove, and a central vertical main groove extending on the tire equator.   Block edge facing ratio of the opening portion of the lateral groove on one side and the other side in the tire axial direction that opens across the outer vertical main groove, and one side and the other side in the tire axial direction that opens across the central vertical main groove The pneumatic tire according to claim 2, wherein a block edge facing ratio of each of the lateral groove openings is 100%.   The pneumatic tire according to any one of claims 1 to 3, wherein the inner vertical main groove has a groove width smaller than that of other vertical main grooves.   5. The minimum tread area with the smallest block tread area where the block contacts the road surface in each block row is 80% or more of the maximum tread area with the largest block tread area. The pneumatic tire according to any one of the above.   2. The outer block row arranged on the outermost side of the vehicle when mounted on the vehicle has an average area of block treads that is larger than an average value of block tread areas in other block rows. The pneumatic tire in any one of -5.   The pneumatic tire according to any one of claims 1 to 6, wherein in each of the block rows, a groove width of the narrowest lateral groove is 90% or more of a groove width of the widest lateral groove. The laterally long blocks are arranged such that the lateral block edges on both sides in the tire circumferential direction are at an angle θ of 10 ° or less with respect to the tire axial direction,
On one side of the horizontal block edge is formed a substantially horizontally-long rectangular protrusion protruding in the tire circumferential direction, and on the other side of the horizontal block edge, the protrusion is substantially opposed to the protrusion in the tire circumferential direction. By forming one substantially horizontally-long rectangular recess, the tire axis extends from the reference line J around the reference line J passing through the approximate center of the block and parallel to the vertical block edges on both sides in the tire axial direction of the block. The pneumatic tire according to any one of claims 1 to 7, wherein the pneumatic tire has a shape in which a direction one side portion is displaced in a tire circumferential direction as compared with the other side portion.

Images