JP2006056459A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire suitably employed as a pneumatic tire with improved performance on snow, especially, as a studless pneumatic tire for a heavy load. <P>SOLUTION: In a tread face of the pneumatic tire, two inside vertical channels are formed on both sides of a tire equator C to extend in a circumferential direction of a tire, and two shoulder side vertical channels are formed outside the inside vertical channels to extend in the circumferential direction of the tire equator C. An inside block row constituted of inside blocks arranged on the tire equator C is formed by connecting between the inside vertical channels by means of inside horizontal channels, and intermediate block rows constituted of intermediate blocks which are arranged in parallel in the tire circumferential direction by connecting the inside vertical channels with the shoulder side vertical channels by means of the intermediate horizontal channels. Inside block recess parts are formed by cutting out both side faces facing the inside vertical channel of the inside blocks. An intermediate point in the tire circumferential direction of the inside block recess part is positioned between extended lines of both channel walls of the intermediate horizontal channel. The inside block has a sipe connecting, in a tire axial direction, both end faces opening at the inside block recess parts. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a pneumatic tire that can improve performance on snow, and more particularly to a pneumatic tire that can be suitably employed as a studless pneumatic tire for heavy loads.

  In winter pneumatic tires such as snow tires and studless tires for running on snow and ice road surfaces, a block pattern consisting of blocks partitioned by vertical grooves and horizontal grooves is adopted on the tread surface, and in the grooves The grip force and running performance on snow are being improved by the shearing force of the snow column that has been bitten and solidified, that is, the shearing reaction force that can act on the snow column.

  In terms of running performance on ice, siping in the circumferential direction of the tire is provided in a block whose tread surface is divided by vertical grooves and horizontal grooves, and the ratio between the length of the siping and the block area is selected, so that the performance on snow and on ice In particular, a studless pattern with improved skid resistance has been proposed (see, for example, Patent Document 1).

  In addition, various studless pneumatic tires that improve performance on snow and on ice, particularly on ice by arranging a plurality of sipings in the tire axial direction in the block are also known (for example, Patent Document 2). It has also been proposed to arrange a V-shaped siping in the block (Patent Document 3), and the performance on ice has been improved in recent years by the proposal of these studless patterns.

JP-A-7-205617 JP-A-1-101205 JP 2003-118320 A

  However, for pneumatic tires, particularly heavy-duty pneumatic tires that are used at high loads, there is always a need for further improvements in running performance on snow and ice.

  As a result of repeated research to satisfy this requirement, the present inventor formed a recess by cutting the side surface of the block arranged at the center of the tread portion, and formed the recess into a lateral groove of the block separating the vertical groove. It has been found that by making the snow columns facing each other in a cross shape, the shear strength of the snow columns can be increased, and by placing siping, the performance on snow can be improved. The purpose is to provide a pneumatic tire having a tread pattern that can improve performance on snow.

In order to achieve the above-mentioned object, the invention according to claim 1 of the present application includes two longitudinal grooves extending in the circumferential direction of the tire on both sides of the tire equator C on the tread surface, and outside the longitudinal grooves in the inside. Two shoulder-side longitudinal grooves extending in the tire circumferential direction are provided,
And an inner block row composed of inner blocks arranged on the tire equator C by connecting the inner grooves between the inner grooves with inner lateral grooves,
While forming the intermediate block row in which the intermediate blocks are juxtaposed in the tire circumferential direction by connecting the internal vertical groove and the vertical groove on the shoulder side with an intermediate horizontal groove,
Provided with an inner block recess cut out on both sides facing the inner longitudinal groove of the inner block,
And in the extension line of both groove walls of the intermediate lateral groove, the tire circumferential direction intermediate point of the inner block recess is located,
Moreover, the pneumatic tire is characterized in that siping is formed in the inner block by opening both side surfaces of the inner block with the inner block recesses and joining the inner block in the tire axial direction.

The invention according to claim 2 is characterized in that the intermediate block includes an intermediate block concave portion in which both side surfaces facing the longitudinal groove are cut out.
And the tire circumferential direction intermediate point of the said intermediate | middle block recessed part is located in the extension line of both the groove walls of the said inner side groove | channel.

According to a third aspect of the present invention, an inner longitudinal groove comprising a main longitudinal groove extending on the tire equator C in the tire circumferential direction and an auxiliary longitudinal groove extending outside in the tire circumferential direction on the tread surface. And providing a shoulder side longitudinal groove extending in the tire circumferential direction on the shoulder side outside the auxiliary longitudinal groove in the inside,
In addition, by connecting the inner main vertical groove and the inner sub vertical groove with the inner horizontal groove, the inner block row consisting of the inner blocks arranged in the tire circumferential direction is formed on both sides of the tire equator C. By forming an intermediate block row in which intermediate blocks arranged in parallel in the tire circumferential direction are formed by connecting the groove and the vertical groove on the shoulder side with an intermediate lateral groove,
A side faced to the inner main longitudinal groove of the inner block is cut out to provide an inner block recess,
And the tire circumferential direction middle point of the inner block recess is positioned within the extension line of both groove walls of the inner lateral groove facing the tire equator,
Moreover, the pneumatic tire is characterized in that siping is formed in the inner block by opening both side surfaces of the inner block with the inner block recesses and joining the inner block in the tire axial direction.

  The invention according to claim 4 is characterized in that the depth of the siping is 30% or more and 70% or less of the groove depth of the inner vertical groove at the opening end of the central block recess. In the invention according to No. 5, the lateral groove angle α, which is an angle with respect to the tire equator C, is 80 ° or more and less than 90 °, and the lateral grooves adjacent to the tire axial direction have different directions with respect to the tire equator C. Further, the invention according to claim 6 is characterized in that the sea / land ratio at the contact surface when the normal internal pressure is filled in the normal rim and the normal load is applied is 50 to 80%.

  When traveling on a snowy road surface, the snow in the groove is compressed by the contact pressure to form a snow column. The driving force acting on the tire causes a shear stress in the snow column, and the force that withstands the shear corresponds to the grip performance on the snow road surface. When the tire is grounded with a normal internal pressure and a normal load applied, the ground pressure generally increases at the center. A snow column that is effective within the tread contact surface, that is, a tread pattern that forms the snow column so as to maximize the shear stress increases the grip on the snow road surface. In addition, it is important for the tread pattern part away from the ground contact surface to discharge the snow in the groove to form a snow column when this part is newly grounded.

  In the invention according to claim 1, two inner vertical grooves extending in the circumferential direction on both sides across the equator plane and a shoulder-side vertical groove are provided, and an inner horizontal groove that connects between the inner vertical grooves, and an inner An intermediate horizontal groove that connects between the vertical groove and the vertical groove on the shoulder side is provided. The invention according to claim 3 includes a main longitudinal groove passing through the tire equator, a sub longitudinal groove on both sides thereof, and a shoulder side longitudinal groove. It also has an intermediate transverse groove that connects between the inner longitudinal groove and the auxiliary inner longitudinal groove. The block facing the inner main longitudinal groove has an inner block recess on the side surface, and a cross-shaped effective snow column can be formed by the longitudinal groove with the recess and the inner lateral groove. In the invention according to claim 2, the cross portion is formed also by the intermediate block concave portion on the side surface of the intermediate block, thereby increasing the number of snow columns having a cross section and improving the grip performance.

In the invention according to claim 3, the inner vertical groove is formed by the main vertical groove passing through the tire equator and the auxiliary vertical grooves on both sides thereof. Two are arranged from the inside. Further, the number of lateral grooves is determined so that each block in the central portion is formed in a rectangular shape having a tire axial length longer than the tire circumferential length.
In addition, a plurality of lateral grooves are arranged at least between the longitudinal grooves in the central portion, and many snow columns are formed to ensure a grip on the snow road surface.

  The block recesses are preferably cut into a rectangular shape so that the recesses cooperate with the horizontal grooves of the adjacent block rows in substantially the same position in the tire circumferential direction. A snow pillar can be formed.

  Also, the block recess is positioned within the extension line of both groove walls of the intermediate lateral groove, and the tire circumferential midpoint of the inner block recess is located or the tire circumferential midpoint of the inner block recess faces across the tire equator. It is located within the extension line of both the groove walls of the inner groove, and thus, the block recesses are arranged in a cross shape via the transverse groove and the longitudinal groove of the adjacent block row, and the transverse groove and the transverse groove are arranged on the axis. When the snow column formed by the lateral groove is formed in the ground contact surface by not arranging in a lined-up configuration, one end of the snow column is stopped at the adjacent block, and a compression effect in the tire axial direction occurs, and the snow column shear force Is increased.

  The block recess has an effect of fixing the formed snow column and helps increase the shear force of the snow column. In addition, the notch portion itself forms a snow column, and its edge portion improves on-snow performance. The snow column formed by the vertical groove, the horizontal groove, and the concave portion has a “cross shape” and exhibits a higher shearing force than a snow column in one direction.

  Also, at least one siping that is continuous from one notch to the other notch is provided. The siping provided between the notches opens at the ground end and closes at the center of the ground plane. With this function, when forming a snow column, more snow can be taken into the lateral groove than when there is no siping, which helps to compress the snow column. Furthermore, when the part leaves | separates from a ground surface, it is useful for discharge | emission of the snow taken in in the groove | channel. The siping in the notch not only has an effect on the formation and discharge of the snow column in the notch, but also has an effect on the formation and discharge of the snow column in the lateral groove in the tire axial direction of the notch. is there.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a tread according to an embodiment when a radial tire for trucks and buses having a tire size of 11R22.5-14PR (a heavy duty radial tire, abbreviated as a tire) is adopted as a pneumatic tire. FIG. 2 is a plan view in which a part of the pattern is developed. FIG. 2 is an enlarged view of a part of the block passing through the tire equator C and the intermediate block on the left side of FIG. 1, and FIG. 2 is a partial cross-sectional view along S. FIG. The tire has a well-known structure together with its constituent members.

  FIGS. 1 to 3 show a tread pattern in which a normal internal pressure state without a normal load is applied, and the tread surface is between the tread edges E and E in the standard state with a normal load added. And a ground plane to be grounded.

  In this specification, “regular rim” is defined in accordance with either a standard rim defined by JATMA, “Design Rim” defined by TRA, or “Measuring Rim” defined by ETRTO. Is determined in accordance with either the maximum air pressure defined by JATMA, the maximum value described in the TRA table “TIRE LOADILIMITS AT VARIOUS COLD INFRATION PRESURES”, or “INFLATION PRESSURE” defined by ETRTO. “Normal load” means the maximum load corresponding to the normal internal pressure in each standard.

  1 to 3, the tread surface T has two longitudinal grooves 2, 2 extending in the tire circumferential direction on both sides of the tire equator C, and the tire circumferential direction outside the longitudinal grooves 2, 2. Two longitudinal grooves 3 and 3 on the shoulder side are provided. Further, by connecting the inner vertical grooves 2 and 2 with the inner horizontal grooves 4, an inner block row 5G comprising inner blocks 5 on the tire equator C is formed. An intermediate block row 7G in which the intermediate blocks 7 are arranged in parallel in the tire circumferential direction is formed by joining the longitudinal grooves 3 on the shoulder side with intermediate horizontal grooves 6. As a result, the inner horizontal groove 3 and the intermediate vertical groove 6 are opened in the inner vertical groove 2, and the intermediate horizontal groove 6 is opened in the vertical groove 3 on the shoulder side.

  As a result, the inner block 5 has an upper wall surface 5c and a lower wall surface 5d (upper and lower sides) separated by side wall surfaces 5a and 5b on both sides facing the inner vertical groove 2 and inner grooves 4 and 4 on both ends in the circumferential direction. 1 is a substantially rectangular shape having the top and bottom when the tire equator C is defined as the top and bottom (the left and right are also the same), and the angle on the acute angle side of the upper wall surfaces 5c and 5d with respect to the tire circumferential line. Is the inclination angle α of the inner lateral groove 4 and the upper and lower wall surfaces 5c and 5d are equal and inclined in the same direction. The inclination angle α is set to 80 ° or more and less than 90 °, more preferably 83 ° or more and less than 90 °. This is because excessive inclination tends to decrease the strength of the snow column.

  Further, the side wall surfaces 5a and 5b are sloped so that the central portion in the circumferential direction protrudes outwardly in the tire axial direction near the middle position of the tire circumferential length, and the side wall surfaces 5a and 5b are notched in the central portion. The left and right inner block recesses 9a, 9b facing the inner vertical groove 2 (hereinafter sometimes referred to as the inner block recess 9 or the recess 9).

  Further, in the middle block 7, one side wall surface 7a facing the inner vertical groove 2, the other side wall surface 7b facing the shoulder side vertical groove 3, an upper wall surface 7c and a lower wall surface 7d facing the intermediate horizontal groove 6 are provided. In this embodiment, the side wall surfaces 7a and 7b extend linearly in the circumferential direction. The side wall surfaces 7a and 7b are notched at the center of the tire circumferential length, and the outer intermediate block concave portion 10a facing the inner vertical groove 2 and the intermediate block concave portion 10b facing the inner vertical groove 2 (sometimes In addition, intermediate block recess 10 or recess 10 is formed.

  Further, the upper wall surfaces 7c and 7d of the intermediate block 7 have an acute angle with respect to the tire circumferential direction line so that the inclination angle β of the intermediate lateral groove 6 is equal and inclined in the same direction. The inclination angle β is set to 80 ° or more and less than 90 °, and more preferably 83 ° or more and less than 90 ° to prevent a decrease in snow column strength. Also, the inclination angles are alternately arranged in the order of adjacent blocks, that is, the left middle block 7, the inner block 5, and the right inner block 7 arranged from the left side when the tire equator C in FIG. α and β can change the direction of inclination of the tire with respect to the tire circumferential direction to form a stronger snow column and improve the grip performance when going straight.

  On the other hand, the groove width Wg2 of the inner vertical groove 2 and the groove width Wg3 of the shoulder-side vertical groove 3 are larger than the groove width Wg3 of the inner vertical groove 2 with respect to the groove width Wg3 of the shoulder-side vertical groove 3. It is good to do. That is, the relationship of the groove width Wg2 <the groove width Wg3 is established, and thereby the life of the tire can be improved by increasing the contact area in the central portion where the contact pressure is generally high. The groove width Wg2 of the inner vertical groove 2 and the groove width Wg3 of the vertical groove 3 on the shoulder side are obtained by an average value when the groove width Wg changes in the tire circumferential direction, and the inner horizontal groove 4, It is calculated that the intermediate horizontal groove 6 is not opened by the vertical groove 2 and the vertical groove 3 on the shoulder side (the side of the block is virtually extended and closed). The recesses 9 and 10 are included. The ratio Wg2 / groove width Wg3 of the groove width Wg2 and the groove width Wg3 is set to be larger than 1 and about 0.6 or more, and the groove width Wg3 is 5 to 5 of the width (developed length) between the tread edges E and E. It is set to about 11%.

  Further, the groove width Wg4 of the inner horizontal groove 4 and the groove width Wg6 of the intermediate horizontal groove 6 are made larger than the groove width Wg6 of the inner horizontal groove 2. That is, the relationship of the groove width Wg4 <the groove width Wg6 is established, whereby the contact area of the central portion where the contact pressure is high can be increased to improve the tire life. The groove widths Wg4 and Wg6 of the lateral grooves 4 and 6 are calculated by calculating the average value in the length direction, similar to the longitudinal grooves 2 and 3, and the ratio Wg4 / groove width Wg6 of the groove width Wg4 and the groove width Wg6 is 1. It is larger and about 0.6 or more to improve the running performance on snow. The groove depths D2 and D3 of the vertical grooves 2 and 3 and the groove depths D4 and D6 with the horizontal grooves 4 and 6 are set to be approximately the same.

  On the other hand, the left and right intermediate lateral grooves 6 in FIG. 1 are circumferential lengths of the side wall surfaces 5a and 5b of the inner block 5 with the inner longitudinal grooves 2 being separated from each other inside (the tire equator C side). It opens facing the center. Further, the inner lateral groove 4 is separated from the inner longitudinal groove 2 on the left and right sides, for example, in the middle in the circumferential direction of the right side wall surface 7a of the intermediate block 6 adjacent to the left, and the intermediate block adjacent to the right. The left side wall surface 7b of 6 is opened to face the center in the circumferential direction.

  Further, as described above, the left and right inner block recesses 9a and 9b are provided at the center portion in the circumferential direction of the side wall surfaces 5a and 5b of the inner block 5, with the side wall surfaces 5a and 5b cut out at the center portion. Furthermore, also in the intermediate block 7, the intermediate block recesses 10a and 10b are formed in the center portion in the tire circumferential direction of the side wall surfaces 7a and 7b.

  As described above, the left and right intermediate lateral grooves 6 are opposed to the inner block concave portion 9a or the inner block concave portion 9b of the peripheral wall surface 5a of the inner block 5 with the inner vertical groove 2 therebetween on each inner side. ing. As a result, when traveling in the snow, the intermediate lateral groove 6, the inner vertical groove 2, the concave portion 9a, or the concave portion 9b can cooperate to form a cross-shaped groove portion, and this portion is newly grounded. The inner block recesses 9a and 9b can be stepped on to form a cross-shaped effective snow column and increase the shear resistance. It is possible to enhance the grip property and to discharge snow in the groove of the tread pattern portion that is separated from the grounding surface together with the separation surface.

  Further, in the case of this embodiment, the inner lateral groove 4 is opposed to the intermediate block recesses 10a and 10b of the intermediate block 6 adjacent to the left and right, for example, with the inner vertical groove 2 on the left and right. As a result, a cruciform and strong snow column can be formed as well, and the traction can be improved.

  Here, for example, “the lateral groove 6 faces the recess” means, for example, in the case of the intermediate lateral groove 6, extended lines w61 and w62 of both groove walls (intersection lines between the groove wall and the tread surface) of the intermediate lateral groove 6. It means that the tire circumferential direction intermediate point 9c of the inner block concave portion 9 is positioned within (also referred to as extension lines w1, w2). That is, the tire circumferential direction intermediate point 9c of the inner block recess 9 is located in a region between the extension lines w1 and w2, and the solid line f1 in FIG. 4 indicates that the tire circumferential direction intermediate point 9c is an extension line. When the center line wc passing through the center of w1 and w2 coincides with the center line wc, the broken line f2 indicates that when the tire circumferential direction middle point 9c of the inner block recess 9 coincides with the upper extension line w1, the alternate long and short dash line f3 indicates that the tire circumference The case where the direction intermediate point 9c is on the lower extension line w2 is shown. The relationship between the inner lateral groove 4 and the intermediate block recess 10 is the same. Also, the extension lines w41 and w42 of both the groove walls of the inner lateral groove 4 are sometimes abbreviated as extension lines w1 and w2.

  Preferably, the intermediate points 9c and 10c are centered on the center line wc of the extension lines w1 and w2 in the region Wa narrower than the groove widths Wg4 and Wg6 of the opposing lateral grooves 4 or lateral grooves 6. The intermediate points 9c and 10c of the recesses 9 and 10 are reduced to reduce the cross-shaped deformation, thereby improving the connectivity at each side of the cross and increasing the shearing force. The preferable region Wa refers to a range of 3/4, 1/2 times, more preferably 1/4 times the groove widths Wg4, Wg6 with the center line wc as the center.

  The extension lines w1 and w2 are defined as lines extending through the groove wall point at the middle point in the tire axial direction of the lateral groove and the opening end points of both groove walls, and each position when the lateral groove is excessively deformed. As described above, the extension line is obtained using a straight line or a curve smoothly passing through the center point in the circumferential direction as a groove wall line.

  Further, the respective circumferential maximum lengths L9 and L10 at the open ends of the inner block concave portions 9a and 9b and the intermediate block concave portions 10a and 10b are 0.5 to 0.5 of the groove width Wg6 and the groove width Wg4 of the opposed lateral grooves 6 and 4, respectively. The snow column strength is improved by 1.2 times, preferably about 0.8 to 1.1 times. The depth W9, W10 is also set to 0.2 to 1.0 times, preferably about 0.3 to 0.6 times the groove width Wg6 and groove width Wg4 of the opposing lateral grooves 6 and 4, respectively. Good.

  Further, the circumferential maximum lengths L9 and L10 and the depths W9 and W10 of the inner block recess 9 and the intermediate block recess 10 are set depending on the size of the blocks 5 and 7 in which the recesses 9 and 10 are formed. Yes. For example, the circumferential lengths L9 and L10 are 1/4 to 1 to 12 times the circumferential lengths L7 and L5 on the side walls of the intermediate block 7 and the inner block 5 in which the recesses 9 and 10 are provided. The depths W9 and W10 are set to 1/6 to 1 to 20 of the maximum widths W5 and W7 of the blocks 5 and 7. Whether the present invention is based on the groove width Wg of the opposing groove or the size of the block includes the case where one or both of them are satisfied.

  Further, as shown in FIGS. 2 and 3, for example, one siping S <b> 5 is formed in the inner block 5 to connect both side surfaces in the tire axial direction through the inner block recesses 9 a and 9 b. In this embodiment, the siping S5 is substantially flat through the upper end of the right inner tread recess 9a in FIG. 1 of the inner block 5 and through the lower end of the left inner tread recess 9b. It is continuous in a Z shape and has a straight line portion Ss between the inward points a and b of the bent portions on both sides.

  In addition, as shown in FIG. 3, the siping S5 is formed with a straight portion S1 having a bottom of the base that is inclined in the same direction as the upper end surface between the inward points a and b. The siping S opens toward the road surface when the inner block 5 comes in contact with the ground, and increases the length of the inner block recess 9 in the tire circumferential direction so that more snow is taken into the recess 9 and is closed within the contact surface. Thus, the snow taken into the recess 9 can be strongly compressed to form a relatively strong snow column. Further, when the inner block 5 is separated from the ground contact surface, it can be opened again, and the captured snow can be effectively discharged by loosening the restraint of the snow solidified inside.

  At that time, the snow column having a cross-shaped cross section is removed and discharged as a snow mass. Thus, not only the snow in the concave portion 9 but also the snow in the inner vertical groove 2 and the inner horizontal groove 4 are smoothly discharged. Make it possible. In this embodiment, as described above, the siping S5 is continuous through the upper end of the right inner tread recess 9a and the lower end of the left inner tread recess 9b. The length of the siping S5 can be increased and the above effect can be promoted as compared with the case where the gap between the lower ends is continuous.

  Furthermore, in the siping S5, it is easy for the opening at the grounding end of the inner lateral groove 4 and the opening of the siping S5 to interlock with the upper end surface of the inner block 5, that is, the inclination direction of the inner lateral groove 4 is the same. The snow removal effect can be demonstrated. In this example, the inner lateral groove 4 is inclined downward to the right in FIG. 1, and the siping S5 is similarly inclined as a whole.

  In the present embodiment, the intermediate block 7 also has, for example, one siping S7 with both side surfaces having open ends in the intermediate block recesses 10a and 10b. In this embodiment, the siping S7 is substantially flat through the upper end of the right inner tread recess 9a in FIG. 1 of the inner block 5 and through the lower end of the left inner tread recess 9b. It is continuous in a Z shape, has a straight line portion Ss between the inward points c and d of the bent portions on both sides, and is otherwise the same as the siping S5.

  As shown in FIG. 3, in the siping S5 arranged in the inner block 2, the depth Ds5 of the portion opened to the inner vertical groove 2 is 30% or more of the vertical groove depth D2 of the inner vertical groove 2 And it is preferable that it is 70% or less. If it is less than 30%, there are few siping openings at the above-mentioned grounding end, and the above-mentioned siping effect is hardly exhibited. On the other hand, if it exceeds 70%, the rigidity of the block is too low, and the snow column is liable to collapse. In order to prevent the collapse of the snow column, the angle of the straight line portion Ss is made larger than the upper and lower wall surfaces 7c and 7d. Similarly, the depth Ds7 of the portion of the siping S7 that opens to the vertical groove 2 is preferably 30% or more and 70% or less of the vertical groove depth D2 of the vertical groove 2 therein. Further, the depth Dss of the straight line portion Ss is set to be 40% or more and 80% or less of the depths Ds5 and Ds7 to prevent excessive movement of the blocks 5 and 7, and to prevent the collapse of the snow column. Prevents missing blocks when driving on the road.

  Further, the sea / land ratio at the contact surface when the normal rim is incorporated and the normal internal pressure is filled and the normal load is applied is 50 to 80%. This is because when the present invention is applied to a tread pattern of less than 50%, the block rigidity is too low and uneven wear tends to occur, and when it exceeds 80%, the groove area is too small and it is difficult to exert a grip on snow. More desirably, the ratio of the actual ground contact area to the total area within the ground contact surface in the standard state is 60% or more and 70% or less.

  FIG. 5 shows an inner longitudinal groove 2 composed of a main longitudinal groove 2A extending on the tire equator C in the tire circumferential direction and an auxiliary longitudinal groove 2B extending outside in the tire circumferential direction on the tread surface T. Another embodiment is shown in which a shoulder-side longitudinal groove 3 is provided and the shoulder side extends in the tire circumferential direction outside the sub-vertical groove 2B.

  Also, by connecting the inner main longitudinal groove 2A and the inner sub-vertical groove 2B with the inner lateral groove 4, an inner block row 5G composed of inner blocks 5 arranged in the tire circumferential direction on both sides of the tire equator C, An intermediate block 7 arranged in parallel in the tire circumferential direction by connecting the sub-vertical groove 2B (groove width: Wg3, groove depth D3) and the shoulder-side vertical groove 3 with an intermediate horizontal groove 6 is provided. An intermediate block row 7G is formed.

  Further, as in the above-described embodiment, the side surface of the inner block 5 facing the inner main longitudinal groove 2A is notched to provide the inner block recess 9, and the tire circumferential intermediate point 9c of the inner block recess 9 is defined as a tire. Two similar sipings S5 are provided in the extension lines w1 and w2 of both groove walls of the inner lateral groove 2 facing each other across the equator. The description of the above embodiment can be applied to the specific configuration of each part.

  Although the pneumatic tire has been described as a heavy duty radial tire, it can also be used as a tire of other categories such as a small bus / truck tire, a passenger tire, or a run-flat tire.

Hereinafter, tires to which the present invention was applied (Example tires) were made together with Comparative Example tires, and both were evaluated. Examples 1 to 4 and Comparative Example 1 are the embodiment shown in FIG. 1, Example 5 and Comparative Example 2 are the embodiments shown in FIG. 5 (however, Comparative Examples 1 and 2 are the recesses on the block side surface in the tires shown in FIGS. Tires (all not shown)). The results are shown in Table 1 (unit: mm, angle: degree).
The tire structure is common to each tire.
The test conditions are as follows.
<Snow Performance> A test tire is assembled on a rim of 22.5 × 7.50, filled with an internal pressure of 800 kPa, and mounted on all wheels of a 2-D vehicle with a load capacity of 8 t. Starting from a stop state on a 6% gradient uphill, the time until the vehicle travels 10 m is measured, and is expressed as the reciprocal of the time when Comparative Example 1 is taken as 100. Higher values indicate higher performance.
<Uneven wear resistance performance> A sample tire is assembled on a rim of 22.5 × 7.50, filled with an internal pressure of 800 kPa, mounted on all wheels of a 2-D-4 vehicle with a load capacity of 10 t, and a full load of 200 kN. The difference in the circumferential direction between the blocks after traveling 10,000 km is measured, and is represented by the reciprocal number when Comparative Example 1 is set to 100. Higher values indicate higher performance.

It is a top view which shows the tread pattern of one embodiment of this invention. It is the one part enlarged view. FIG. It is a plain diagram which expands and shows a recessed part position. It is a top view which illustrates the tread pattern of other embodiments.

Explanation of symbols

2 vertical groove 3 intermediate vertical groove 4 horizontal groove 5 internal block 6 intermediate horizontal groove 7 intermediate block 9 inner block concave part 10 intermediate block concave part 13, 14, 15 notch part BC central block C equatorial plane

Claims (6)

Provided on the tread surface are two longitudinal grooves extending in the tire circumferential direction on both sides of the tire equator C, and two shoulder-side longitudinal grooves extending in the tire circumferential direction outside the longitudinal grooves in the tread surface,
And an inner block row composed of inner blocks arranged on the tire equator C by connecting the inner grooves between the inner grooves with inner lateral grooves,
While forming the intermediate block row in which the intermediate blocks are juxtaposed in the tire circumferential direction by connecting the internal vertical groove and the vertical groove on the shoulder side with an intermediate horizontal groove,
Provided with an inner block recess cut out on both sides facing the inner longitudinal groove of the inner block,
And in the extension line of both groove walls of the intermediate lateral groove, the tire circumferential direction intermediate point of the inner block recess is located,
Moreover, the pneumatic tire is characterized in that siping is formed in the inner block by opening both side surfaces of the inner block by the inner block recesses and joining the inner block in the tire axial direction. The intermediate block includes an intermediate block recess that is cut out on both side faces facing the longitudinal groove in the inside,
The pneumatic tire according to any one of claims 1 to 3, wherein an intermediate point in the tire circumferential direction of the intermediate block recess is located in an extension line of both groove walls of the inner lateral groove. On the tread surface, there is provided an inner vertical groove composed of an inner vertical groove extending on the tire equator C in the tire circumferential direction and an outer auxiliary vertical groove extending on the outer side in the tire circumferential direction. With the shoulder side vertical groove extending in the tire circumferential direction on the shoulder side outside the groove,
In addition, by connecting the inner main vertical groove and the inner sub vertical groove with the inner horizontal groove, the inner block row consisting of the inner blocks arranged in the tire circumferential direction is formed on both sides of the tire equator C. Forming an intermediate block row 7 in which intermediate blocks arranged in parallel in the tire circumferential direction are arranged by connecting the groove and the vertical groove on the shoulder side with an intermediate lateral groove,
A side faced to the inner main longitudinal groove of the inner block is cut out to provide an inner block recess,
And the tire circumferential direction middle point of the inner block recess is positioned within the extension line of both groove walls of the inner lateral groove facing the tire equator,
Moreover, the pneumatic tire is characterized in that siping is formed in the inner block by opening both side surfaces of the inner block by the inner block recesses and joining the inner block in the tire axial direction.   The depth of the siping is 30% or more and 70% or less of the groove depth of the inner vertical groove at the opening end in the central block recess. Pneumatic tire described in Crab   The inner groove has a transverse groove angle α which is an angle with respect to the tire equator C of 80 ° or more and less than 90 °, and the lateral grooves adjacent to the tire axial direction have different directions with respect to the tire equator C. The pneumatic tire in any one of -4.   The pneumatic according to any one of claims 1 to 5, wherein the sea / land ratio at the ground contact surface is 50 to 80% when a normal rim is incorporated and a normal internal pressure is filled and a normal load is applied. tire.

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