JP4445307B2 - Heavy duty radial tire - Google Patents

Description

  The present invention relates to a heavy-duty radial tire that is particularly suitable as a winter tire, and that can prevent block chipping while ensuring necessary snow and ice performance.

  In winter tires used in winter, in general, a block pattern with high snow biting properties is used to secure grip on snowy roads, and siping is formed on the blocks, and the siping and block edge effects (road surface excavation) Friction) and adhesion friction ensure performance on ice (see, for example, Patent Document 1).

Japanese Patent Application Laid-Open No. 11-20212

  In order to improve the performance on ice, the number of blocks and siping are increased. However, this conversely causes a decrease in block rigidity, which causes a problem that block breakage is likely to occur. Therefore, conventionally, block development of each block, particularly circumferential rigidity, is regulated based on, for example, load capacity and the like has been designed and developed so as not to become a predetermined value or less.

  However, as a result of the inventor's research, even when the block rigidity is sufficiently secured, block chipping may occur, and in particular, the tendency of block chipping to block rows arranged in the tread center region where the ground pressure becomes high It turns out that there is. As a result of further research, this block chipping is also greatly affected by the shape of the ground plane, and especially the shorter the ground contact length, in other words, the greater the force acting on the block row with fewer blocks in the ground plane, It was clarified that block chipping easily occurs even when the block rigidity is high.

  In view of this, the present invention is based on restricting the block row rigidity, which is the product of the number of blocks in the ground plane of the block row and the block stiffness, in the block row arranged in the tread center area. An object of the present invention is to provide a heavy duty radial tire capable of more reliably suppressing block chipping while ensuring performance.

In order to achieve the above object, the invention of claim 1 of the present application provides a central longitudinal main groove passing through the tire equator and longitudinal longitudinal main grooves on both sides thereof, whereby the tread surface is formed into the central longitudinal main groove. 4 ribs, a center side rib between the outer vertical main groove and a shoulder side rib between the outer vertical main groove and the tread edge,
In addition, the center-side rib has a circumferential shallow groove formed of a longitudinal narrow groove or siping extending in the circumferential direction, an inner lateral groove connecting the central longitudinal main groove and the circumferential shallow groove, and the outer longitudinal groove. An outer horizontal groove connecting the main groove and the circumferential shallow groove, an inner block row in which inner blocks Bi between the inner horizontal grooves are juxtaposed in the circumferential direction, and an outer block between the outer lateral grooves Bo forms an outer block row juxtaposed in the circumferential direction,
Moreover, the inner block Bi and the outer block Bo are divided into three block pieces in the circumferential direction by siping extending in the width direction,
Grounding for each block row in which the inner block Bi and the outer block Bo are grounded in a grounding surface that is grounded in a normal load state in which the normal rim is assembled and the normal internal pressure is filled and the normal load M is applied. The product of the number of blocks Ni and No and the circumferential rigidity (unit: N / mm) Gi and Go of the inner block Bi and the outer block Bo is respectively calculated as the block row rigidity RGi (= Ni × Gi) of the inner block row. ), Where the block row rigidity RGo (= No × Go) of the outer block row is a value Pi (= RGi / M) obtained by dividing the block row rigidity RGi, RGo by the normal load M (unit kN), Po (= RGo / M) is in the range of 9.0 to 16.0 (1 / mm) , respectively.

  In the invention of claim 2, the ratio Wbo / Wbi between the maximum width Wbi of the inner block Bi in the tire axial direction and the maximum width Wbo of the outer block Bo in the tire axial direction is 0.95 to 1.05. It is characterized by being.

  In the invention of claim 3, the total number n of the blocks Bi and Bo in the inner block row and the outer block row is set to 68 to 86, and the circumference of the inner block Bi and the outer block Bo is increased. Among the three block pieces in the direction, the circumferential lengths Lbi2 and Lbo2 of the inner block pieces are the ratios Lbi2 / Lbi and Lbo2 / Lbo to the circumferential lengths Lbi and LBo of the blocks Bi and Bo, respectively, 0.15. It is characterized by -0.35.

  In the invention of claim 4, the shoulder side rib is formed in a block pattern, and the ratio WLc / WLs between the maximum width in the tire axial direction WLc of the center side rib and the maximum width in the tire axial direction WLs of the shoulder side rib is 0. .95 to 1.02.

  The “regular rim” is a rim determined for each tire in the standard system including the standard on which the 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 specified by the tire for each tire. The maximum air pressure in the case of JATMA, the maximum value described in the table “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” in the case of TRA, If it is ETRTO, it means "INFLATION PRESSURE". The “regular load” is the load specified by the standard for each tire. The maximum load capacity shown in the table “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” is the maximum load capacity for JATMA and TRA for TRA. In the case of ETRTO, it means a load obtained by multiplying "LOAD CAPACITY" by 0.88.

  Since the present invention is configured as described above, it is possible to more reliably suppress block chipping while ensuring the necessary performance on snow and ice.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a sectional view showing a tread portion when the heavy-duty radial tire of the present invention is a winter tire, and FIG. 2 is a development view showing the tread pattern developed on a plane.

  1 and 2, a heavy-duty radial tire 1 (hereinafter referred to as tire 1) includes, in a tread portion 2, a central longitudinal main groove 3 passing on the tire equator C, and longitudinal main grooves 4 and 4 on both sides thereof. Thus, the tread surface has a center side rib 5 between the central vertical main groove 3 and the outer vertical main groove 4, and a shoulder side rib 6 between the outer vertical main groove 4 and the tread edge Te. It is divided into four ribs.

  As shown in FIGS. 3 and 4, the center-side rib 5 includes a circumferential shallow groove 8 formed of a vertical narrow groove or siping extending in the circumferential direction, and the circumferential shallow groove 8 and the longitudinal main groove in the center. An inner horizontal groove 9 that connects the groove 3 and an outer horizontal groove 10 that connects the circumferential shallow groove 8 and the outer vertical main groove 4 are arranged. As a result, the center-side rib 5 includes an inner block row 12 in which inner blocks Bi between the inner lateral grooves 9 and 9 are juxtaposed in the circumferential direction, and an outer block Bo between the outer lateral grooves 10 and 10. It is further divided into outer block rows 13 juxtaposed in the circumferential direction.

  Here, the longitudinal main grooves 3 and 4 are groove bodies having a groove width Wg (shown in FIG. 1) of 3 mm or more, have a linear shape or a zigzag shape (including a wave shape), and are continuous in the tire circumferential direction. . The groove width g is preferably 5 mm or more from the viewpoint of on-snow performance, and in this example, the groove width g is 8 mm. Further, the groove depth Dg of the longitudinal main grooves 3 and 4 is preferably 9 mm or more, and more preferably 15 mm or more. In this example, a groove depth of 20 mm is illustrated. The shallow groove 8 in the circumferential direction is a narrow and shallow groove body having a groove width Ws continuously extending in the tire circumferential direction of less than 3 mm, and the groove depth Ds is equal to 1 of the groove depth Dg. It is set to a range smaller than 0 times, preferably 0.4 to 0.9 times.

  The lateral grooves 9 and 10 have a groove width center line extending at an angle of 30 ° or less, preferably 15 ° or less with respect to the tire axial direction. The groove width Wy (shown in FIG. 2) and the groove depth Dy (shown in FIG. 1) are not particularly restricted, but from the viewpoint of performance on snow, the groove width Wy is 3 mm or more, and further 5 mm or more. preferable. The groove depth Dy is equal to or less than the groove depth Dg. In this example, a shallow bottom portion substantially equal to the groove depth Dg is formed in the vicinity of the intersecting position with the longitudinal main grooves 3 and 4, and the shallow shallow in the circumferential direction. The case where the deep bottom part substantially equal to the said groove depth Ds is provided near the crossing position with the groove | channel 8 is illustrated.

  Next, two sipings 15i and 15o extending in the width direction are arranged in the inner and outer blocks Bi and Bo, respectively, so that the inner block Bi is changed into three block pieces Bi1, Bi2 and Bi3, and The outer block Bo is divided into three block pieces Bo1, Bo2 and Bo3. The sipings 15i and 15o may be linear, but it is preferable that the sipings 15i and 15o be bent in a zigzag shape or a substantially Z shape as in this example in order to suppress a decrease in block rigidity in the tire axial direction. In particular, the circumferential length between the sipings 15i, 15i (ie, the circumferential length Lbi2 of the inner block piece Bi2) and the circumferential length between the sipings 15o, 15o (ie, the circumferential length of the inner block piece Bo2). When the length Lbo2) is gradually decreased toward the circumferential shallow groove 8 side, the movement of the inner block pieces Bi2 and Bo2 in the tire axial direction can be more restrained, which is preferable for the block rigidity. .

  Here, from the viewpoint of uneven wear, the ratio Wbo / Wbi between the maximum width Wbi in the tire axial direction of the inner block Bi and the maximum width Wbo in the tire axial direction of the outer block Bo is 0.95 to 1.05. If it is out of this range, uneven wear such as so-called rib punching wear in which any one of the inner and outer blocks Bi and Bo wears earlier than the other tends to occur.

  For the same purpose, the ratio Lbi2 / Lbi between the circumferential length Lbi2 of the inner block piece Bi2 and the circumferential length Lbi of the inner block Bi, and the circumferential length Lbo2 of the inner block piece Bo2 The ratio Lbo2 / Lbo with the circumferential length Lbo of the outer block Bo is preferably in the range of 0.15 to 0.35, respectively. When the ratio Lbi2 / Lbi and the ratio Lbo2 / Lbo are each less than 0.15, the block rigidity of the inner block pieces Bi2, Bo2 is smaller than the block pieces Bi1, Bi3, Bo1, Bo3 on both sides. Therefore, the wear of the inner block pieces Bi2 and Bo2 will remain with a non-uniform delay compared to the other block pieces Bi1, Bi3, Bo1 and Bo3. On the other hand, if it exceeds 0.35, the rigidity of the three block pieces Bi1, Bi2, Bi3 and the block pieces Bo1, Bo2, Bo3 will be close, and the heel will be applied to each block piece Bi1, Bi2, Bi3, Bo1, Bo2, Bo3. It tends to generate uneven wear such as & toe wear. If the circumferential lengths Lbi2, Lbo2, Lbi, and Lbo are not constant as in this example, the average value of the maximum value and the minimum value in the circumferential length of the block piece Bi2 is Lbi2. Lbo2 is the average value of the maximum and minimum values in the circumferential length of the block piece Bo2, and Lbi is the average value of the maximum and minimum values in the circumferential length of the inner block Bi, and the circumferential length of the outer block Bo is Let Lbo be the average of the maximum and minimum values.

  In the present embodiment, in order to suppress the block missing of the inner and outer blocks Bi and Bo, the following restriction is performed.

Specifically, first, the tread surface is grounded to a flat surface in a normal load load state in which the tire 1 is assembled on a normal rim and filled with a normal internal pressure and a normal load M is applied. On the ground contact surface 20 (shown in FIG. 5) at this time, the number of ground blocks Ni and No to be grounded by the inner block Bi and the outer block Bo are obtained for each block row. In the case of a block pattern tire, in order to reduce pattern noise, for example, the circumferential length of the block in the block row and the interval (width of the lateral groove) may be changed in the block row. In such a case, the total number of blocks in the block row is n, the tire circumference of the circumferential line passing through the width center of the block row is TL, and the contact length at the width center of the block row on the ground contact surface 20 is FL. Then, the number N of ground blocks is approximated by the following equation.
N = n × (FL / TL)
The total number n of the inner and outer block rows 12 and 13 is the same. In the case of a heavy duty radial tire, the total number n of blocks is preferably in the range of 68 to 86.

  Next, the circumferential rigidity (unit: N / mm) Gi and Go of the inner and outer blocks Bi and Bo are obtained, respectively. As shown schematically in FIG. 6, the circumferential rigidity G is obtained by applying a circumferential force Kx to the block surface BS, and the movement amount X when the block surface BS moves in the circumferential direction and the circumferential force Kx. It can be determined as the ratio Kx / X. At this time, for example, a circumferential force Kx is applied via a metal plate or the like fixed to the block surface BS with an adhesive or the like so that a vertical load does not act on the block B. The circumferential rigidity G may be obtained by computer analysis based on information such as the block shape size, the siping shape size, and the Young's modulus of the rubber of the block. In addition, when the circumferential direction rigidity G differs for every block B, let the average of the circumferential direction rigidity of each block B be the circumferential direction rigidity G.

  Then, the product of the number of ground blocks Ni, No and the circumferential rigidity Gi, Go is calculated as the block row rigidity RGi (= Ni × Gi) of the inner block row, and the block row rigidity RGo ( = No × Go), and Pi (= RGi / M) and Po (= RGo / M) obtained by dividing the block row rigidity RGi and RGo by the normal load M (unit kN) are 9.0 to 16 respectively. Restricted to the range of 0.0.

  This is because block chipping is greatly affected by the ground contact length FL of the ground contact surface 20, and the shorter the ground contact length FL, the greater the force acting on each block, resulting in greater deformation and damage such as block chipping. This is because it occurs. Therefore, by using the block row stiffness RG, which is the product of the number N of grounding blocks and the circumferential stiffness G, as a parameter, it is possible to more accurately grasp the occurrence of block chipping.

  Here, if the values Pi (= RGi / M) and Po (= RGo / M) are less than 9.0, the block row rigidity RGi and RGo are insufficient, and the blocks Bi and Bo are likely to be missing. Become. On the other hand, when the values Pi and Po exceed 16.0, respectively, the block row rigidity RGi and RGo are excessive, and the total number n of blocks is increased, and the groove depth Dy of the lateral grooves 9 and 10 is increased. It leaves plenty of room and can further improve the performance on snow and ice. In other words, it means that the performance on snow and ice is insufficient at present. Therefore, the values Pi and Po are more preferably set to a lower limit value of 9.5 or more and an upper limit value of 14.5 or less.

  Next, in this example, as shown in FIG. 1, the shoulder-side rib 6 also includes a longitudinal narrow groove 21 extending in the circumferential direction, and an inner lateral groove connecting between the longitudinal narrow groove 21 and the outer longitudinal main groove 4. 22 and an outer lateral groove 23 connecting the vertical narrow groove 21 and the tread edge Te to form a two-row block pattern. The shoulder side rib 6 preferably has a ratio WLc / WLs of 0.95 to 1.02 between the maximum width WLs in the tire axial direction and the maximum width WLc in the tire axial direction of the center side rib 5. This keeps the ground pressure balanced and suppresses uneven wear. If the ratio WLc / WLs is smaller than 0.95, so-called rib punching wear tends to occur at the center side rib 5 early, and conversely, if it exceeds 1.02, the shoulder side rib 6 wears off the shoulder. Tends to occur. In this example, the shoulder side rib 6 is provided with a sub-part 6B comprising a row of easily deformable tongue pieces 25 having a thickness of 5 mm or less extending along the tread edge Te for the purpose of enhancing the wandering performance. In this case, the width of the main part 6A excluding the sub part 6B is adopted as the maximum width WLs of the shoulder side rib 6.

  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.

  Prototype heavy-duty radial tires with tire sizes 275 / 80R22.5 and 295 / 70R22.5 based on the tread pattern shown in Fig. 2 and having the specifications shown in Table 1, and evaluated the anti-blocking chipping performance of each sample tire did.

  In addition, the example product and the conventional product change the circumferential rigidity Gi and Go of the blocks Bi and Bo only by the difference in the groove depth Dy in the lateral grooves 9 and 10 and the siping depth Dt of the sipings 15i and 15o. Yes.

(1) Block chip resistance:
A test tire was mounted on a drive shaft of a GVW 2.5 ton, 2-D4 vehicle and a user using a fixed volume, and the condition of the block missing after traveling 50,000 km was inspected. The evaluation was made in three stages: ×: generation of block chipping, Δ: generation of cracks at the groove bottom / sipe bottom, and ○: generation of cracks.

It is sectional drawing of the tread part which shows one Example of the radial tire for heavy loads of this invention. It is an expanded view which shows the tread pattern. It is a top view which expands and shows a center side rib. It is a perspective view which shows a center side rib with a shoulder side rib. It is a diagram which shows a ground plane. It is a diagram explaining the circumferential direction rigidity of a block.

Explanation of symbols

3 Central vertical main groove 4 Outer vertical main groove 5 Center side rib 6 Shoulder side rib 8 Horizontal groove 10 in the circumferential shallow groove 9 Outer horizontal groove 12 Outer block row 13 Outer block row 15i, 15o Siping 20 Contact Ground Bi1, Bi2, Bi3 block pieces Bo1, Bo2, Bo3 block pieces

Claims (4)

By providing a central vertical main groove that passes through the tire equator and outer vertical main grooves on both sides of the central tread surface, the center side rib between the central vertical main groove and the outer vertical main groove, the outer Divided into 4 ribs with shoulder side ribs between vertical main groove and tread edge,
In addition, the center-side rib has a circumferential shallow groove formed of a longitudinal narrow groove or siping extending in the circumferential direction, an inner lateral groove connecting the central longitudinal main groove and the circumferential shallow groove, and the outer longitudinal groove. An outer horizontal groove connecting the main groove and the circumferential shallow groove, an inner block row in which inner blocks Bi between the inner horizontal grooves are juxtaposed in the circumferential direction, and an outer block between the outer lateral grooves Bo forms an outer block row juxtaposed in the circumferential direction,
Moreover, the inner block Bi and the outer block Bo are divided into three block pieces in the circumferential direction by siping extending in the width direction,
Grounding for each block row in which the inner block Bi and the outer block Bo are grounded in a grounding surface that is grounded in a normal load state in which the normal rim is assembled and the normal internal pressure is filled and the normal load M is applied. The product of the number of blocks Ni and No and the circumferential rigidity (unit: N / mm) Gi and Go of the inner block Bi and the outer block Bo is respectively calculated as the block row rigidity RGi (= Ni × Gi) of the inner block row. ), Where the block row rigidity RGo (= No × Go) of the outer block row is a value Pi (= RGi / M) obtained by dividing the block row rigidity RGi, RGo by the normal load M (unit kN), A heavy-duty radial tire characterized in that Po (= RGo / M) is in a range of 9.0 to 16.0 (1 / mm) .
  The ratio Wbo / Wbi between the maximum width Wbi in the tire axial direction of the inner block Bi and the maximum width Wbo in the tire axial direction of the outer block Bo is 0.95 to 1.05. The radial tire for heavy loads according to 1.   In the three block pieces in the circumferential direction of the inner block Bi and the outer block Bo, the total number n of the blocks Bi and Bo in the inner block string and the outer block string is 68 to 86. The circumferential lengths Lbi2 and Lbo2 of the inner block pieces are such that the ratios Lbi2 / Lbi and Lbo2 / Lbo with respect to the circumferential lengths Lbi and LBo of the blocks Bi and Bo are 0.15 to 0.35, respectively. The heavy duty radial tire according to claim 1 or 2, characterized by the above-mentioned.   The shoulder side rib is formed in a block pattern, and the ratio WLc / WLs of the tire side axial maximum width WLc of the center side rib and the tire side axial maximum width WLs of the shoulder side rib is 0.95 to 1.02. The heavy duty radial tire according to any one of claims 1 to 3.

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