JP4517765B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire mounted on a passenger car or a heavy-duty vehicle, and more particularly to a pneumatic tire that equalizes circumferential rigidity on a tread surface that employs a variable pitch arrangement.

  Depending on the tread pattern on the surface of the pneumatic tire, a peculiar noise called pattern vibration noise is generated when the vehicle is running. Therefore, in order to level the pattern excitation sound generated from the tire (to eliminate the peak point of the sound in a certain speed range), it is common practice to employ a variable pitch arrangement as a block pattern. . Here, the variable pitch arrangement refers to a block arrangement in which a plurality of blocks having different pitch lengths are connected around the tire surface, and is a single block pattern arrangement.

  However, when this variable pitch arrangement is adopted for the block pattern, the block rigidity in the circumferential direction becomes non-uniform due to the pitch length of each block being different. And when rigidity becomes non-uniform | heterogenous, it will become easy to generate | occur | produce uneven wear. Specifically, for example, block punching, and heel and toe wear in which one side in the circumferential direction of the minimum pitch portion wears are conspicuous. This is especially true for tires with heavy loads and forces, such as heavy duty pneumatic tires. Even if variable pitch arrangement is adopted, the pitch variation ratio (maximum pitch length / minimum pitch length) is large. Can not be adopted. For this reason, there is a limit to the above-described pattern excitation sound leveling.

  Therefore, recently, several inventions have been disclosed in order to balance the counterfeit characteristics of noise suppression and uneven wear resistance. For example, the invention is such that the block portion having a large groove wall angle of the circumferential main groove is small and the small block portion is large (for example, Patent Document 1), or the block portion having a large groove depth of the circumferential main groove is deep and small block. An invention (for example, Patent Document 2) in which the portion is shallow is disclosed.

JP 2003-072319 A JP 2003-002013 A

  However, in the conventional pneumatic tire described above, when the groove wall angle of the main groove portion is changed according to the size of the block portion, the block stiffness in the tire width direction is affected, but the block stiffness in the circumferential direction is directly affected. The contribution is considered small. In addition, there is a limit to the change of the groove wall angle due to the relationship with the main groove depth. In particular, if the groove bottom radius of the flat main outer groove is small, cracks are likely to occur. In addition, when the groove depth of the circumferential main groove is changed, the effect of reinforcing the rigidity is similarly small, and it is not realistic if the standard or the like (groove depth, outer shape) is taken into consideration.

  Therefore, the present invention has been made in view of the above, and in a pneumatic tire having a block pattern arranged in a variable pitch, a noise peak leveling is performed using a technique of forming a bottom raised portion in a lateral groove between blocks. The purpose is to balance the two characteristics of anti-wear and uneven wear resistance.

  In order to achieve the above object, a pneumatic tire according to claim 1 is a pneumatic tire having a block pattern arranged in a variable pitch, and is a block adjacent in the circumferential direction with at least one block row arranged in the circumferential direction. A bottom raised portion that is convex at the bottom of the lateral groove between the blocks and that connects the blocks in the circumferential direction, next to the first block having the smallest pitch length and the first block The rigidity of the raised portion connecting the second block having a large pitch length is such that the rigidity of the raised portion connecting the second block and the third block having the next largest pitch length is connected to the second block. It is designed to be relatively larger than the rigidity.

  Since the raised bottom portion connects the blocks, it affects the difficulty of deformation of the connected blocks in the circumferential direction. And the rigidity of the raised portion connecting the first block having the relatively smallest pitch length and the second block having the second largest pitch length after the first block has the second block. If the rigidity of the bottom raising part connecting the third block having the second largest pitch length next to the second block is relatively large, the unevenness in rigidity of the blocks having different pitch lengths may be It is compensated by the magnitude of the rigidity and smoothed.

  Here, rigidity means compression rigidity, bending rigidity, and torsional rigidity. Therefore, the rigidity can be changed depending on the longitudinal elastic modulus and the lateral elastic modulus of the material. The rigidity is also affected by the cross-sectional secondary moment and the cross-sectional secondary pole moment, and these can be changed by the shape of the bottom-up portion, that is, the width in the tire width direction, the height, and the side wall angle in the tire circumferential direction. Further, if the cross-sectional area is increased in accordance with the change in the shape, the amount of deformation of the bottom-up portion and the block is also reduced.

  Further, the pneumatic tire according to claim 2 is a pneumatic tire having a block pattern arranged in a variable pitch, and is a bottom portion of a lateral groove between blocks adjacent in the circumferential direction in at least one block row arranged in the circumferential direction. And has a raised bottom portion that connects the blocks in the circumferential direction, and the rigidity of the raised portion that connects the blocks having a relatively small pitch length and the same pitch length is the pitch length. Is relatively larger than the rigidity of the raised bottom portion connecting the same blocks, and the block having a relatively large pitch length and the block having a relatively small pitch length are adjacent to each other. The rigidity of the raised portion is the rigidity when the blocks having the relatively small pitch length and the same pitch length are connected to each other. It is obtained by way.

  This invention is characterized by the relationship between the rigidity of the raised portion at the location where blocks having the same pitch length are continuous in the circumferential direction and the stiffness of the raised portion at the location where blocks having different pitch lengths are adjacent to each other, among the blocks of the variable pitch arrangement. There is. That is, there is a portion where blocks having the same pitch length are continuous, such as small-small-small-medium-medium-large-large-large, and the pitch lengths of small-medium and medium-large differ. The connection between the blocks is characterized by preferentially adopting the rigidity of the raised portion when the blocks having a relatively small pitch length are connected. The definition of rigidity and the magnitude of rigidity can be changed by the shape of the bottom raised portion, that is, the width in the tire width direction, the height, and the side wall angle in the tire circumferential direction, as in the first aspect of the invention.

  The pneumatic tire according to claim 3 is configured such that, in the pneumatic tire, the rigidity is adjusted by a size of a sectional area in a tire width direction of the bottom raised portion.

  When the cross-sectional area when the bottom raised portion is cut in the tire width direction is increased, the cross-sectional secondary moment and the cross-sectional secondary pole moment are also increased, so that the bending stiffness and torsional stiffness applied to the bottom raised portion can be increased. Therefore, by changing the cross-sectional area according to the pitch length of the blocks to which the bottom raised portions are connected, it is possible to compensate for the non-uniform rigidity of the blocks themselves and to smooth the rigidity of the blocks arranged in a variable pitch.

  Further, in the pneumatic tire according to claim 4, in the pneumatic tire, the size of the cross-sectional area in the tire width direction is adjusted by the size of the width in the tire width direction of the raised portion. .

  If the height of the bottom raised portion is set to a height that takes into account functions such as drainage of the lateral groove, and if this is constant, the cross-sectional area in the tire width direction can be adjusted by adjusting the width in the tire width direction. Thereby, the magnitude | size of the rigidity of a bottom raising part can be determined. Therefore, by changing the size of the width according to the pitch length of the blocks connected to the bottom raised portion, it is possible to compensate for nonuniform rigidity of the blocks themselves and smooth the rigidity of the blocks arranged in a variable pitch.

  Further, in the pneumatic tire according to claim 5, in the pneumatic tire, the size of the cross-sectional area in the tire width direction is adjusted by the height of the bottom raised portion.

  Considering the case where the cross-section of the raised part to which a bending moment or torsion moment is applied is a substantially square, a substantially triangular shape, or a combination thereof, a cross-sectional secondary moment that is one element of bending stiffness and a cross-section that is an element of torsional stiffness The secondary pole moment is characterized by being proportional to the cube of the height. Therefore, even if the change in the height is small, the rigidity changes greatly. In other words, there is an advantage that the height adjustment area of the bottom raised portion for changing the rigidity according to the pitch length can be small.

  Further, in the pneumatic tire according to claim 6, in the pneumatic tire, the size of the cross-sectional area in the tire width direction is such that the upper surface width in the tire width direction of the bottom raised portion is constant, and the sidewall angle in the tire width direction of the bottom raised portion. It is designed to be adjusted by the size of.

  A tire width direction side wall is a side wall of a bottom raised portion facing the tire main groove, and when there is no main groove at the tire end portion, it means a side wall in the tire width direction of the bottom raised portion. Moreover, the said angle means the angle from the perpendicular with respect to the bottom face of a bottom raising part, and is set to 0 degree | times when the bottom raising part is standing upright. When the side wall is increased, the cross-sectional area is also increased, and finally the rigidity of the raised portion is increased. Therefore, by changing the magnitude of the angle according to the pitch length of the blocks to which the bottom raised portions are connected, the rigidity of the blocks themselves can be compensated for unevenness and the rigidity of the entire blocks arranged in a variable pitch can be smoothed.

Further, in the pneumatic tire according to claim 7, in the pneumatic tire, the rigidity is adjusted by a lateral elastic modulus and a longitudinal elastic modulus of a rubber material used for the bottom raised portion. is there.

The transverse elastic modulus and longitudinal elastic modulus of the rubber material used for the bottom raised portion directly affect the rigidity of the bottom raised portion. Therefore, by selecting a material having a large coefficient, the rigidity of the bottom raised portion is determined, the unevenness of the rigidity of the block itself is compensated, and the rigidity of the entire blocks arranged in the variable pitch is smoothed.

  The pneumatic tire according to the present invention equalizes and smoothes the rigidity of each block against the circumferential shearing force applied to the tread surface portion, and suppresses uneven wear such as heel and toe wear and block punching wear. As a result, it is possible to achieve a trade-off between noise reduction (noise peak leveling by variable pitch arrangement) and uneven wear resistance.

  Below, the example of the pneumatic tire concerning the present invention is described in detail based on a drawing. Note that the present invention is not limited to the embodiments.

  FIG. 1 is a developed view showing a tread surface having block patterns arranged in a variable pitch. In the figure, the horizontal direction is the tire circumferential direction, and the vertical direction is the developed width direction. This pneumatic tire has four main grooves 2 in the tire circumferential direction of the tread surface 1, and many blocks 4 are formed so as to be partitioned into lateral grooves 3 in the tire width direction. The blocks 4 are arranged in a variable pitch, and the blocks 4 having different pitch lengths are arranged in the tire circumferential direction. In order to show the difference in the pitch length of each block 4, as a representative, the size of the pitch length from the bottom to the third column is added in alphabetical letters.

  The blocks 4 in the third row from the bottom have three types of pitch lengths, and are A, B, and C in descending order of the pitch length. Similarly, the blocks 4 in the second row from the bottom also have three kinds of pitch lengths, and are A ′, B ′, and C ′ in descending order of the pitch length. Furthermore, the block 4 in the lowermost row also has three types of pitch lengths, A ″, B ″, and C ″ in descending order of the pitch length. Between the blocks 4 adjacent to each other in the circumferential direction, there is a raised portion 5 which is convex at the bottom of the lateral groove and connects the blocks 4 in the circumferential direction.

  The bottom raised portion 5 has its rigidity changed according to the pitch length of the blocks 4 to be connected. Specifically, taking the row of blocks 4 at the bottom as an example, the rigidity in the tire width direction of the bottom raised portion 12 that connects the C ″ blocks 4 having a relatively small pitch length is a relatively large pitch length. It is made larger than the rigidity of the bottom raising part 10 which connects the blocks 4 of A ″. Thereby, the rigidity of the bottom raising part 5 which connects the blocks 4 of C ″ becomes relatively large.

  Further, the rigidity of the raised portion 11 at the location where the block 4 of A ″ having a relatively large pitch length and the block 4 of B ″ having a relatively small pitch length are adjacent to the block 4 is relatively the pitch length. Rigidity corresponding to a small B ″ block. The rigidity corresponding to the block refers to the rigidity employed when the blocks 4 are connected to each other. Here, there is only one block 4 of B ″, but if this is continuous, it means the rigidity to be adopted.

  In other words, in the present invention, among the blocks of the variable pitch arrangement, the relationship between the rigidity of the raised portion where the blocks having the same pitch length continue in the circumferential direction and the rigidity of the raised portion where the blocks having different pitch lengths are adjacent to each other There is a feature. That is, there is a portion where blocks having the same pitch length are continuous, such as small-small-small-medium-medium-large-large-large, and the pitch lengths of small-medium and medium-large differ. The connection between the blocks is characterized in that priority is given to the rigidity of the raised portion when the blocks having a relatively small pitch length are connected. If there is at least one block row having such characteristics, the rigidity is even and smoothed within that range, and uneven wear such as heel and toe wear can be avoided.

  The reason why the bottom raised portion is employed as described above is that, when the block 4 having a relatively small pitch length and the block 4 having a relatively large pitch length are connected, the rigidity of the block 4 itself is larger than when the relatively large blocks 4 are connected to each other. This is because the value becomes low and compensates for smoothing. Here, the rigidity means compression rigidity (stiffness), bending rigidity (stiffness), and torsional rigidity (stiffness). Therefore, the rigidity can be changed depending on the longitudinal elastic modulus and the lateral elastic modulus of the material. In addition, the rigidity is affected by the cross-sectional secondary moment and the cross-sectional secondary moment of the object, which can be changed depending on the shape of the raised portion, that is, the width in the tire width direction, the height, and the side wall angle in the tire circumferential direction. it can.

  Table 1 shows the magnitude of the rigidity of the raised bottom portion used when three types of blocks having different pitch lengths are connected to each other. The vertical and horizontal columns in the table represent the pitch length of the blocks, and have a relationship of A> B> C. Moreover, S, M, and L represent the magnitude | size of the rigidity of the bottom raising part which connects the said blocks, and have a relationship of L> M> S. As shown in the table, the rigidity of the raised portion when the blocks A having a relatively large pitch length are connected to each other is S. That is, the connecting portion is formed to have a relatively small rigidity. In the case of a combination of blocks A-B, BB, and B-A, the rigidity of the raised portion is set to medium M. In the case of a combination of blocks A-C, B-C, C-C, C-B, and C-A, a relatively large L is set as the rigidity of the raised portion.

  It is realistic to make the bottom raised part have the rigidity of the above size according to the pitch length of the block to be connected, but if you want to strictly smooth the rigidity of the whole tire, Depending on the pitch length of each block, the rigidity of the bottom raised portion may be changed in nine combinations which are all combinations.

  For example, when the magnitude of the rigidity of the raised portion connecting the blocks is represented by six types of symbols having a relationship of XL> L> MB> MA> S> XS, XS and A rigid bottom-up portion of S is used to connect the AB and B-A blocks. In addition, a rigid bottom-up portion that becomes an MB is used for the connection between the BB blocks. For connection of blocks C-A and A-C, a rigid bottom-up portion serving as MA is used, and for connection of blocks C-B and BC, a rigid bottom-up portion serving as L is used. Finally, the connection between the CC blocks can be set finely, such as using a rigid raised portion that becomes XL. Here, an example of selecting the rigidity of the raised portion is given, and it is not absolutely necessary to do as described above, but is averaged over the entire circumference of the tire by the pitch lengths of A, B, and C. Thus, the rigidity of the bottom raised portion can be changed and set flexibly.

  Table 2 shows the magnitude of the rigidity of the raised bottom portion used when connecting four types of blocks having different pitch lengths. The vertical and horizontal columns in the table represent the pitch length of the blocks, and have a relationship of A> B> C> D. Further, S, M, L, and XL represent the magnitude of the rigidity of the raised portion that connects the blocks, and there is a relationship of XL> L> M> S. As shown in the table, the rigidity of the bottom raised portion basically maintains the same regularity as in Table 1, and the difference in the rigidity of each block itself is compensated by the magnitude of the rigidity of the bottom raised portion. Even in this case, if it is desired to strictly smooth the rigidity of the entire tire, the rigidity of the raised portion may be changed in 16 combinations that are all combinations according to the pitch length of each block to be connected. Good. Thus, the present invention can be employed even when the number of different pitch lengths in the variable pitch arrangement increases.

  FIG. 2 is an explanatory diagram showing blocks arranged in a variable pitch and a bottom-up portion whose cross-sectional area is changed. This figure shows a raised portion that connects blocks A, B, and C in the order of increasing pitch length in the circumferential direction. As described above, the present invention changes the rigidity of the raised portion according to the pitch length. The change in the rigidity can also be realized by changing the cross-sectional area when the bottom-up portion is cut in the tire width direction. This is because when the cross-sectional area is increased, the cross-sectional secondary moment and the cross-sectional secondary pole moment are also increased, so that the bending stiffness and torsional stiffness applied to the bottom raised portion can be increased. Therefore, by changing the cross-sectional area in accordance with the pitch length of the blocks to which the bottom-up portions are connected, it is possible to compensate for uneven rigidity of the blocks themselves and smooth the rigidity of the blocks arranged in a variable pitch. Moreover, if the said cross-sectional area becomes large, the deformation | transformation ratio of a bottom raising part will also become small and can suppress the deformation | transformation of a block.

  More specifically, the size of the cross-sectional area is adjusted by the size of the width in the tire width direction of the bottom raised portions 8 and 9. For example, the tire width direction width a of the raised portion 8 that connects the block 6 having a relatively small pitch length C and the block 7 having a relatively medium pitch length B in the circumferential direction is the pitch length. It is set to be larger than the width c in the tire width direction of the bottom raised portion 9 that connects the block 7 being B and the block 13 being A having a relatively large pitch length in the circumferential direction.

  The height of the bottom raised portions 8 and 9 is set in consideration of ensuring the function of drainage and the like of the lateral groove, and when it is constant, the width in the tire width direction can be adjusted to adjust the cross-sectional area in the tire width direction. . Thereby, the magnitude | size of the rigidity of a bottom raising part can be determined. Therefore, by changing the size of the width according to the pitch length of the blocks to which the bottom raised portions are connected, it is possible to compensate for uneven rigidity of the blocks themselves and to smooth the rigidity of the blocks arranged in a variable pitch.

  Generally speaking, the above-described relationship of the bottom-up portion is a bottom-up connecting the first block 6 having the relatively smallest pitch length and the second block 7 having the next largest pitch length after the first block 6. The rigidity (the width in the tire width direction) of the portion 8 is the rigidity (the width in the tire width direction) of the bottom raised portion 9 that connects the second block 7 and the third block 13 having the next largest pitch length after the second block 7. ) Is relatively larger.

  FIG. 3 is an explanatory view showing a combination example of the pitch arrangement and the width in the tire width direction of the bottom-up portion. The upper row shows an arrangement 14 of pitch lengths having a relationship of A> B> C, and the lower row shows an arrangement of widths in the tire width direction of bottom raised portions having a relationship of a> b> c. As shown in the figure, when blocks having the same pitch length are continuous, the width a in the tire width direction of the raised portion connecting the blocks of C ″ having a relatively small pitch length is relatively The width c is larger than the width c of the raised portion connecting the blocks A ″ having a large pitch length. Thereby, the rigidity of the bottom raising part which connects the block of C '' becomes relatively large.

  In addition, the width of the raised portion at the location where the block of A ″ having a relatively large pitch length and the block of B ″ having a relatively small pitch length are adjacent to the block is relatively small. It is set as the width b of the raising part which connects the block of B ''. If there is at least one block row having such characteristics, the rigidity is smoothed within that range, and uneven wear such as heel and toe wear can be avoided.

  Although not shown, the size of the cross-sectional area can be increased or decreased even at the height of the bottom-up portion. Considering the case where the cross-section of the raised part to which a bending moment or torsion moment is applied is a substantially square, a substantially triangular shape, or a combination thereof, a cross-sectional secondary moment that is one element of bending stiffness and a cross-section that is an element of torsional stiffness The secondary pole moment is characterized by being proportional to the cube of the height. Therefore, even if the change in the height is small, the rigidity changes greatly. In other words, there is an advantage that the height adjustment area of the bottom raised portion for changing the rigidity according to the pitch length can be small. However, the height of the bottom raised portion is preferably lower than the height of the block in order to ensure functions such as drainage of the lateral groove.

  FIG. 4 is an explanatory view showing blocks arranged in a variable pitch and a bottom-up portion in which the tire circumferential side wall angle is changed. This figure shows a bottom-up portion that connects blocks A, B, and C in the order of increasing pitch length in the circumferential direction as in FIG. The tire circumferential direction side wall angle θa of the bottom raising portion 8 that connects the block 6 having a relatively small pitch length C and the block 7 having a relatively medium pitch length B in the circumferential direction has a pitch length of B Is greater than the tire circumferential side wall angle θc of the bottom raised portion 9 that connects the block 7 and the block 13 having a relatively large pitch length in the circumferential direction. In addition, a tire width direction side wall is a side wall of the bottom raising part which faces a tire main groove, and when there is no main groove in a tire edge part, it means the side wall of the bottom raising part in the tire width direction. In addition, as shown in the figure, the angle refers to an angle from a perpendicular to the bottom surface of the raised portion, and 0 degree when the raised portion is upright.

  When the height of the bottom raised portions 8 and 9 and the width of the upper surface are constant, the cross-sectional area in the tire width direction can be adjusted by adjusting the tire circumferential side wall angle. Thereby, the magnitude | size of the rigidity of a bottom raising part can be determined. Therefore, by changing the size of the side wall angle in accordance with the pitch length of the blocks connected to the bottom raised portion, uneven rigidity of the blocks themselves can be compensated, and the rigidity of the entire blocks arranged in the variable pitch array can be smoothed.

  Generally speaking, the above-described relationship of the bottom-up portion is a bottom-up connecting the first block 6 having the relatively smallest pitch length and the second block 7 having the next largest pitch length after the first block 6. The tire circumferential side wall angle of the portion 8 is relative to the tire circumferential direction side wall angle of the bottom raised portion 9 that connects the second block 7 and the third block 13 having the next largest pitch length after the second block 7. It will be big.

  FIG. 5 is an explanatory view showing a combination example of the pitch arrangement and the tire circumferential side wall angle of the raised bottom portion. In the upper row, an array 14 of pitch lengths having a relationship of A> B> C is described, and in the lower row, an array 16 of tire circumferential direction side wall angles of the bottom raised portion having a relationship of θa> θb> θc is described. These arrangements are the same as the width in the tire width direction in FIG. 3. If there is even one such row of blocks, the rigidity is smoothed within that range, and uneven wear such as heel and toe wear can be avoided.

Although not shown in the drawing, the rigidity of the bottom raised portion can be adjusted by appropriately selecting a rubber material used for the bottom raised portion. The transverse elastic modulus and longitudinal elastic modulus of the rubber material used for the bottom raised portion directly affect the rigidity of the bottom raised portion. Therefore, by selecting a material having a large coefficient, the rigidity of the raised portion is determined, the unevenness of the rigidity of the blocks having different pitch lengths is compensated, and the rigidity of the entire blocks arranged in the variable pitch is smoothed. be able to.

  Table 3 shows the results of the noise resistance test and uneven wear resistance test of this example. Here, in the noise test, the tire of the present example set as shown in FIG. 1 and FIG. 2 with a pneumatic pressure of 700 kPa mounted on a rim of 22.5 × 7.50 using a 10-t truck having a loading weight of 10 t as a test vehicle. Was mounted on all wheels of the truck. The evaluation is performed by measuring the overall (full frequency range) noise level every 5 km / h between the coasting speeds of 40 km / h and 80 km / h, and calculating the sound pressure (dB) of 60 km / h on the regression line of the measured values. The reciprocal number was expressed as an index using the conventional example as 100. In the uneven wear resistance test, a tire similar to the above is mounted on the drive shaft of the truck, the degree of heel and toe wear after traveling 50000 km on the same evaluation course, the reciprocal is calculated, and the reciprocal is calculated. The example was indexed with the conventional example as 100.

  As shown in the table, the pneumatic tire according to this example was able to improve the uneven wear resistance index without deteriorating the noise performance index as compared with the conventional example. As described above, in the pneumatic tire according to the present invention, the rigidity of the block pattern as a whole is made uniform, and the difference in deformation amount with respect to the circumferential shear force received by the tread tread during tire rolling is also reduced. As a result, in a pneumatic tire having a block pattern having a so-called variable pitch arrangement, it has an excellent feature that it is possible to achieve both anti-noise characteristics such as noise reduction (noise peak leveling by variable pitch arrangement) and uneven wear resistance. .

  As described above, the pneumatic tire according to the present invention can be applied to a pneumatic tire mounted on a heavy-duty vehicle such as a passenger car or a tire / bus, and is related to production and use of the tire.

It is an expanded view which shows the tread surface which has a block pattern. It is explanatory drawing which shows a block and the raising part which changed the cross-sectional area. It is explanatory drawing which shows the example of a combination of the pitch arrangement | sequence and the width | variety of a bottom raising part. It is explanatory drawing which shows a block and the bottom raising part which changed the side wall angle. It is explanatory drawing which shows the example of a combination of a pitch arrangement | sequence and the side wall angle of a bottom raising part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tread surface 2 Main groove 3 Horizontal groove 4 Block 5, 8, 9, 10, 11, 12 Bottom raising part 6, 7, 13 Block A, B, C Pitch length a, b, c Tire width direction width | variety (theta) a, (theta) c Tire circumference Directional side wall angle

Claims (7)

In a pneumatic tire having a block pattern arranged in a variable pitch,
It is at least one row of blocks arranged in the circumferential direction, and has a raised portion that forms a convex shape at the bottom of a lateral groove between adjacent blocks in the circumferential direction and connects the blocks in the circumferential direction. The rigidity of the raised portion connecting the smallest first block and the second block having the second largest pitch length next to the first block is next to the second block and the second block. A pneumatic tire characterized in that it is relatively larger than the rigidity of the raised bottom portion connecting the third block having a large pitch length. In a pneumatic tire having a block pattern arranged in a variable pitch,
It is at least one block row arranged in the circumferential direction, has a convex shape at the bottom of the lateral groove between adjacent blocks in the circumferential direction, and has a raised portion for connecting the blocks in the circumferential direction, and the pitch length is relatively The rigidity of the raised bottom portion connecting the blocks having the same pitch length is relatively larger than the rigidity of the raised bottom portion connecting the same blocks, and the pitch length is relatively large. The rigidity of the raised portion where the block having a relatively large length and the block having a relatively small pitch length are adjacent to each other connects the blocks having a relatively small pitch length and the same pitch length. A pneumatic tire characterized by the rigidity when   The pneumatic tire according to claim 1, wherein the rigidity is adjusted by a size of a cross-sectional area of the bottom raised portion in a tire width direction.   The pneumatic tire according to claim 3, wherein the size of the cross-sectional area in the tire width direction is adjusted by the size of the width in the tire width direction of the raised portion.   The pneumatic tire according to claim 3, wherein the size of the cross-sectional area in the tire width direction is adjusted by the height of the raised bottom portion.   The size of the cross-sectional area in the tire width direction is adjusted by a size of a side wall angle in the tire width direction of the bottom raised portion with a top surface width in the tire width direction of the bottom raised portion being constant. Pneumatic tire. The pneumatic tire according to claim 1, wherein the magnitude of the rigidity is adjusted by a lateral elastic modulus and a longitudinal elastic modulus of a rubber material used for the raised bottom portion.

Images