JP4736645B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire suitable as a studless tire, and more specifically, by forming a narrow groove on a ground contact surface of a land portion partitioned by a tread portion, ensuring on-ice performance from a new article, and The present invention relates to a pneumatic tire in which narrow grooves are worn away at an early stage so that the original characteristics of tread rubber are exhibited at an early stage.

  Pneumatic tires for icy and snowy roads typified by studless tires are on the ice compared to tires that have completed running-in, because the original rubber grip is not exerted due to the release material, etc. in a new state where running-in is not carried out. There is a tendency for performance to be inferior. On the other hand, in the tire market, it is required to ensure the performance on ice from the time of a new article. Therefore, by applying surface processing to the ground contact surface of the land portion divided into tread portions, the initial performance on ice is ensured.

  As a specific example of such a technique for improving the performance on ice, by forming a number of narrow grooves in a specific direction on the ground contact surface of the land section divided into the tread portion, while ensuring the performance on ice from the new article, It has been proposed that the inherent characteristics of the tread rubber are exhibited at an early stage by causing the narrow grooves to wear away at an early stage (see, for example, Patent Document 1).

However, when the tread portion wears, the entire ground contact surface does not wear uniformly, and in particular, tires employing pitch variations may wear unevenly due to differences in block rigidity, resulting in heel and toe. There is a problem that uneven wear such as wear tends to occur.
JP 2004-34903 A

  The object of the present invention is to form a narrow groove on the ground contact surface of the land section divided into the tread portion, to ensure the performance on ice from a new article, and to wear the tread rubber at an early stage. An object of the present invention is to provide a pneumatic tire capable of preventing the occurrence of heel and toe wear when the original characteristics are exhibited at an early stage.

In order to achieve the above object, a pneumatic tire according to the present invention is a pneumatic tire in which a plurality of land portions arranged in a tire circumferential direction are defined in a tread portion, and variations in the tire circumferential pitch of these land portions are given. A plurality of narrow grooves are formed on the ground contact surface of the land portion, the depth of the narrow grooves is 0.1 mm to 0.8 mm, the width of the narrow grooves is 0.1 mm to 0.8 mm, The interval between the narrow grooves is 0.5 mm to 2.0 mm, and the depth of the narrow grooves is reduced in the land portion where the pitch is smaller than that in the land portion where the pitch is large.

Further, the pneumatic tire of the present invention for achieving the above object is a pneumatic tire in which a plurality of land portions arranged in the tire circumferential direction are defined in a tread portion, and variations in the tire circumferential pitch of these land portions are given. In the tire, a plurality of narrow grooves are formed on the ground contact surface of the land portion, the depth of the narrow grooves is 0.1 mm to 0.8 mm, and the width of the narrow grooves is 0.1 mm to 0.8 mm. The interval between the narrow grooves is 0.5 mm to 2.0 mm, and the interval between the narrow grooves is increased as the land portion has a smaller pitch than the land portion having a larger pitch.

Furthermore, the pneumatic tire of the present invention for achieving the above object is a pneumatic tire in which a plurality of land portions arranged in the tire circumferential direction are defined in the tread portion, and variations in the tire circumferential pitch of these land portions are given. In the tire, a plurality of narrow grooves are formed on the ground contact surface of the land portion, the depth of the narrow grooves is 0.1 mm to 0.8 mm, and the width of the narrow grooves is 0.1 mm to 0.8 mm. The interval between the narrow grooves is 0.5 mm to 2.0 mm, and the land portion having a smaller pitch than the land portion having a larger pitch has a smaller inclination angle with respect to the tire circumferential direction of the narrow groove. is there.

  In the present invention, in the pneumatic tire adopting the pitch variation, by forming a plurality of narrow grooves on the ground contact surface of the land portion, while ensuring on-ice performance from a new article, the narrow grooves are worn out early. In the pneumatic tires that employ pitch variations, the large-pitch land part may be more difficult to wear than the small-pitch land part. Proceed unevenly. Therefore, in order to alleviate uneven wear, the following configuration is adopted in forming the narrow groove.

In other words, by reducing the depth of the narrow groove in the land portion where the pitch is small compared to the land portion where the pitch is large, uneven wear in the pneumatic tire adopting the pitch variation is alleviated and uneven wear is prevented. can do. In this case, the pitch of the land portion is set to P1... Pn (n: arbitrary integer) in order from the largest, and the i-th and j-th largest pitches are Pi and Pj (1 ≦ i <j ≦ n), respectively. When the depths of the narrow grooves at the land portions of the pitches Pi and Pj are Pdi and Pdj, respectively,
(Pdi / Pdj) = α × (Pi / Pj)
α = 0.7-2.0
It is preferable to satisfy this relationship.

Also, by increasing the gap between the narrow grooves in the land portion where the pitch is small compared to the land portion where the pitch is large, uneven wear in the pneumatic tire adopting the pitch variation is alleviated and uneven wear is prevented. be able to. In this case, the pitch of the land portion is set to P1... Pn (n: arbitrary integer) in order from the largest, and the i-th and j-th largest pitches are Pi and Pj (1 ≦ i <j ≦ n), respectively. When the interval between the narrow grooves at the land portions of the pitch Pi and Pj is Ppi and Ppj, respectively,
(Ppj / Ppi) = β × (Pi / Pj)
β = 0.7-2.0
It is preferable to satisfy this relationship.

Furthermore, by reducing the inclination angle of the narrow groove with respect to the tire circumferential direction in the land portion with a smaller pitch compared to the land portion with a larger pitch, uneven wear in the pneumatic tire adopting the pitch variation is alleviated and uneven wear. Can be prevented. In this case, the pitch of the land portion is set to P1... Pn (n: arbitrary integer) in order from the largest, and the i-th and j-th largest pitches are Pi and Pj (1 ≦ i <j ≦ n), respectively. When the maximum inclination angles of the narrow grooves in the land portions of the pitches Pi and Pj are Pai and Paj, respectively,
(Pai / Paj) = γ × (Pi / Pj)
γ = 0.7 to 1.3
It is preferable to satisfy this relationship.

  In the present invention, the depth of the fine groove is 0.1 mm to 0.00 mm in order to ensure the performance on ice from the new article due to the presence of the fine groove and to exhibit the original characteristics of the tread rubber at an early stage by abrasion of the fine groove. The width of the narrow grooves is 0.1 mm to 0.8 mm, the distance between the narrow grooves is 0.5 mm to 2.0 mm, and the inclination angle of the narrow grooves with respect to the tire circumferential direction is 30 ° to 60 °. preferable.

  In the present invention, when a pneumatic tire for an icy and snowy road represented by a studless tire is configured, it is preferable to provide a plurality of sipes extending in the tire width direction in each land portion. The present invention provides a remarkable effect when applied to a pneumatic tire for icy and snowy roads, but can also be applied to a pneumatic tire for all seasons.

Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 shows a tread pattern of a pneumatic radial tire according to an embodiment of the present invention. In FIG. 1, CL is a tire equator.

  As shown in FIG. 1, a plurality of longitudinal grooves 2 extending in the tire circumferential direction and a plurality of lateral grooves 3 extending in the tire width direction are formed in the tread portion 1, and the tires are formed by the longitudinal grooves 2 and the lateral grooves 3. A plurality of land portions 4 arranged in the circumferential direction are partitioned. The land portion 4 may be a completely divided block as shown in the figure, or may be a block in which ribs continuous in the tire circumferential direction are partitioned into blocks. Here, five block rows are formed. A plurality of types of pitches (P1, P2, P3) are set in these land portions 4.

  A plurality of narrow grooves 5 are formed on the ground surface of the land portion 4. The narrow grooves 5 may be formed in all the land portions 4 on the circumference as shown in the figure, but can be formed in at least some of the land portions 4. For example, the land portion 4 having the smallest pitch may not be subjected to surface processing by the narrow groove 5. Moreover, although the narrow groove 5 may be formed in the whole area of the grounding surface of each land part 4 as shown in the figure, it can be formed in at least a part of the grounding surface.

  2 is a plan view showing an extracted land portion of the pneumatic radial tire of FIG. 1, and FIG. 3 is a cross-sectional view taken along the line XX of FIG. 2 and 3, the depth Pd of the narrow groove 5 is set in the range of 0.1 mm to 0.8 mm, and the width Pw of the narrow groove 5 is set in the range of 0.1 mm to 0.8 mm. The interval (pitch) Pp of the grooves 5 is set in the range of 0.5 mm to 2.0 mm, and the inclination angle Pa of the narrow grooves 5 with respect to the tire circumferential direction R is set in the range of 30 ° to 60 °. Usually, when the tire is new, impurities such as a release material adhere to the surface of the cap tread rubber, so that the original on-ice performance of the tire cannot be obtained, but the narrow groove 5 having the above dimensions is formed on the ground surface of the land portion 4. In this case, the presence of the narrow groove 5 ensures the performance on ice since a new article, and the wear of the narrow groove 5 allows the original characteristics of the tread rubber to be exhibited at an early stage.

  Since the pneumatic radial tire employs pitch variations, the land portion 4 with a large pitch tends to be less worn than the land portion 4 with a small pitch. Therefore, the wear of the tread portion 1 in the pneumatic tire adopting the pitch variation is made by relatively reducing the depth Pd of the narrow groove 5 in the land portion 4 of the small pitch which is more easily worn than the land portion 4 of the large pitch. The condition is made uniform to prevent heel and toe wear.

Here, the pitch of the land portion 4 is set to P1... Pn (n: arbitrary integer) in order from the largest, and the i-th and j-th largest pitches are Pi and Pj (1 ≦ i <j ≦ n), respectively. When the depths of the narrow grooves 5 in the land portions of the pitches Pi and Pj are Pdi and Pdj, respectively, the following relationship is satisfied.
(Pdi / Pdj) = α × (Pi / Pj)
α = 0.7-2.0

  By satisfying the above relationship, heel and toe wear can be more reliably prevented. If the variable α is smaller than 0.7, the rigidity difference between the land portion 4 with the large pitch Pi and the land portion 4 with the small pitch Pj cannot be reduced, and the effect of suppressing the heel and toe wear becomes small. On the contrary, if the variable α is larger than 2.0, the surface processing is performed in excess of the necessary amount for reducing the rigidity difference between the land portion 4 having the large pitch Pi and the land portion 4 having the small pitch Pj. In other words, the land portion 4 having the large pitch Pi wears faster, so that the effect of suppressing heel and toe wear is reduced.

  FIG. 4 shows a tread pattern of a pneumatic radial tire according to another embodiment of the present invention. In this embodiment, the same components as those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted.

  In FIG. 4, the pitch variation is adopted by relatively increasing the interval Pp (see FIG. 2) of the narrow grooves 5 in the small pitch land portion 4 that is more easily worn than the large pitch land portion 4. The wear state of the tread portion 1 in the tire is made uniform to prevent the occurrence of heel and toe wear.

Here, the pitch of the land portion 4 is set to P1... Pn (n: arbitrary integer) in order from the largest, and the i-th and j-th largest pitches are Pi and Pj (1 ≦ i <j ≦ n), respectively. When the intervals between the narrow grooves 5 in the land portions of the pitches Pi and Pj are Ppi and Ppj, respectively, the following relation is satisfied.
(Ppj / Ppi) = β × (Pi / Pj)
β = 0.7-2.0

  By satisfying the above relationship, heel and toe wear can be more reliably prevented. If the variable β is smaller than 0.7, the rigidity difference between the land portion 4 with the large pitch Pi and the land portion 4 with the small pitch Pj cannot be reduced, and the effect of suppressing the heel and toe wear becomes small. On the contrary, if the variable β is larger than 2.0, the surface processing is performed in excess of the necessary amount for reducing the rigidity difference between the land portion 4 with the large pitch Pi and the land portion 4 with the small pitch Pj. In other words, the land portion 4 having the large pitch Pi wears faster, so that the effect of suppressing heel and toe wear is reduced.

  FIG. 5 shows a tread pattern of a pneumatic radial tire according to still another embodiment of the present invention. In this embodiment, the same components as those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted.

  In FIG. 5, pitch variation is achieved by relatively reducing the inclination angle Pa (see FIG. 2) of the narrow groove 5 with respect to the tire circumferential direction in the small pitch land portion 4 that is more easily worn than the large pitch land portion 4. The wear state of the tread portion 1 in the pneumatic tire adopting the above is made uniform to prevent the occurrence of uneven wear.

Here, the pitch of the land portion 4 is set to P1... Pn (n: arbitrary integer) in order from the largest, and the i-th and j-th largest pitches are Pi and Pj (1 ≦ i <j ≦ n), respectively. When the maximum inclination angles of the narrow grooves 5 in the land portions of the pitches Pi and Pj are Pai and Paj, respectively, the following relationship is satisfied.
(Pai / Paj) = γ × (Pi / Pj)
γ = 0.7 to 1.3

  By satisfying the above relationship, heel and toe wear can be more reliably prevented. If the variable γ is smaller than 0.7, the rigidity difference between the land portion 4 with the large pitch Pi and the land portion 4 with the small pitch Pj cannot be reduced, and the effect of suppressing the heel and toe wear becomes small. On the contrary, if the variable γ is larger than 1.3, the surface processing is performed in excess of the necessary amount for reducing the rigidity difference between the land portion 4 with the large pitch Pi and the land portion 4 with the small pitch Pj. In other words, the land portion 4 having the large pitch Pi wears faster, so that the effect of suppressing heel and toe wear is reduced.

  In each of the embodiments described above, the narrow grooves 5 are disposed in the entire area of the tread portion 1, but these narrow grooves 5 can be selectively disposed in a specific region of the tread portion 1. For example, when a pneumatic tire is used under the condition that it is easily worn in the shoulder region of the tread portion 1 like a steered wheel, the narrow groove 5 is located on the inner side in the tire width direction from the position of 40% of the tread ground contact width from the tire equator CL. It is good to form only in the land part 4 divided into the center area | region. On the other hand, when a pneumatic tire is used under the condition that it is easily worn in the central region of the tread portion like a driving wheel, the narrow groove 5 is located around the outer side in the tire width direction from the position of 40% of the tread contact width from the tire equator CL. It is good to form only in the land part 4 divided into the area | region. In either case, it contributes to suppression of uneven wear. For example, in a rear-wheel drive vehicle, it is desirable to mount the former pneumatic tire on the front wheel and the latter pneumatic tire on the rear wheel.

  Note that the tread contact width here is in the tire axial direction measured with the tire mounted on a standard rim in accordance with the static load radius measurement method specified in the JATMA Yearbook (2005 edition). It is the contact width.

  Conventional example 1 in which a pneumatic tire having a block pattern with a tire size of 295 / 45R20 adopts pitch variations including three types of pitches P1 to P3, and only changes the processing conditions of the ground contact surface of the land portion composed of blocks. The tires of -2 and Examples 1-3 were produced.

  In Conventional Example 1, the ground contact surface of the land portion is a smooth surface. In Conventional Example 2, a plurality of narrow grooves are formed on the ground contact surface of the land, and the depths Pd1 to Pd3, the intervals Pp1 to Pp3, and the inclination angles Pa1 to Pa3 are made constant. On the other hand, in Examples 1 to 3, a plurality of narrow grooves are formed on the ground contact surface of the land, the intervals Pp1 to Pp3 and the inclination angles Pa1 to Pa3 are made constant, and only the depths Pd1 to Pd3 are changed. It is. Α, β, and γ are values when i = 1 and j = 3, respectively (the same applies hereinafter).

For these test tires, the amount of uneven wear due to heel and toe wear was measured by the following measurement method. In other words, the test tire is fitted to a wheel of rim size 20 × 10 J and mounted on an AWD vehicle with a displacement of 4700 cc with an air pressure of 240 kPa. After running 25 laps on the test course at 2 km, the amount of uneven wear due to heel and toe wear is circulated. Measurement was performed at the above 16 locations, and the average value was obtained. The measurement results are shown in Table 1.

  As can be seen from Table 1, the tires of Examples 1 to 3 have higher heel and toe than the case where no narrow grooves are provided (Conventional Example 1) and the case where uniform grooves are provided (Conventional Example 2). The amount of uneven wear due to wear was greatly reduced.

  Next, in a pneumatic tire having a block pattern with a tire size of 295 / 45R20, a pitch variation including three types of pitches P1 to P3 was adopted, and only the processing conditions of the ground contact surface of the land portion made of blocks were changed. Tires of Examples 4 to 6 were produced. In these Examples 4 to 6, a plurality of narrow grooves are formed on the ground contact surface of the land, the depths Pd1 to Pd3 and the inclination angles Pa1 to Pa3 are made constant, and only the intervals Pp1 to Pp3 are changed. is there.

For these test tires, the amount of uneven wear due to heel and toe wear was measured by the same measurement method as described above. The measurement results are shown in Table 2.

  As can be seen from Table 2, in the tires of Examples 4 to 6, the heel and toe are compared to the case where no narrow grooves are provided (Conventional Example 1) and the case where uniform grooves are provided (Conventional Example 2). The amount of uneven wear due to wear was greatly reduced.

  Next, in a pneumatic tire having a block pattern with a tire size of 295 / 45R20, a pitch variation including three types of pitches P1 to P3 was adopted, and only the processing conditions of the ground contact surface of the land portion made of blocks were changed. Tires of Examples 7 to 9 and Conventional Examples 3 to 4 were produced. In these examples 7 to 9, a plurality of narrow grooves are formed on the ground contact surface of the land, the depths Pd1 to Pd3 and the intervals Pp1 to Pp3 are made constant, and only the inclination angles Pa1 to Pa3 are changed. is there. Conventional Example 3 is contrasted with Example 9, and the ground contact surface of the land portion is a smooth surface. The conventional example 4 is contrasted with the ninth example, in which a plurality of narrow grooves are formed on the ground contact surface of the land portion, and the depths Pd1 to Pd3, the intervals Pp1 to Pp3, and the inclination angles Pa1 to Pa3 are respectively set. It is constant.

For these test tires, the amount of uneven wear due to heel and toe wear was measured by the same measurement method as described above. The measurement results are shown in Table 3.

  As can be seen from Table 3, in the tires of Examples 7 to 8, the heel and toe are compared to the case where no narrow grooves are provided (Conventional Example 1) and the case where uniform grooves are provided (Conventional Example 2). The amount of uneven wear due to wear was greatly reduced. In addition, the tire of Example 9 has a greater amount of uneven wear due to heel and toe wear than when no narrow groove is provided (Conventional Example 3) and when the narrow groove is provided uniformly (Conventional Example 4). It was reduced.

It is an expanded view which shows the tread pattern of the pneumatic radial tire which consists of embodiment of this invention. FIG. 2 is a plan view showing a land portion extracted from the pneumatic radial tire of FIG. 1. It is XX arrow sectional drawing of FIG. It is a tread pattern development view of a pneumatic radial tire according to another embodiment of the present invention. FIG. 6 is a development view of a tread pattern of a pneumatic radial tire according to still another embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tread part 2 Vertical groove 3 Horizontal groove 4 Land part 5 Narrow groove CL Tire equator P1-P3 Land pitch Pd Narrow groove depth Pw Narrow groove width Pp Narrow groove interval Pa Small groove inclination angle

Claims (10)

In a pneumatic tire that divides a plurality of land portions arranged in the tire circumferential direction in the tread portion and gives variations to the pitch in the tire circumferential direction of these land portions, a plurality of narrow grooves are formed on the ground contact surface of the land portion. Forming a depth of the narrow grooves of 0.1 mm to 0.8 mm, a width of the narrow grooves of 0.1 mm to 0.8 mm, an interval of the narrow grooves of 0.5 mm to 2.0 mm, and a pitch A pneumatic tire characterized in that the depth of the narrow groove is reduced in a land portion having a smaller pitch than that in a land portion having a large pitch. In a pneumatic tire that divides a plurality of land portions arranged in the tire circumferential direction in the tread portion and gives variations to the pitch in the tire circumferential direction of these land portions, a plurality of narrow grooves are formed on the ground contact surface of the land portion. Forming a depth of the narrow grooves of 0.1 mm to 0.8 mm, a width of the narrow grooves of 0.1 mm to 0.8 mm, an interval of the narrow grooves of 0.5 mm to 2.0 mm, and a pitch A pneumatic tire characterized in that the interval between the narrow grooves is increased in a land portion having a smaller pitch than in a land portion having a large pitch. In a pneumatic tire that divides a plurality of land portions arranged in the tire circumferential direction in the tread portion and gives variations to the pitch in the tire circumferential direction of these land portions, a plurality of narrow grooves are formed on the ground contact surface of the land portion. Forming a depth of the narrow grooves of 0.1 mm to 0.8 mm, a width of the narrow grooves of 0.1 mm to 0.8 mm, an interval of the narrow grooves of 0.5 mm to 2.0 mm, and a pitch A pneumatic tire characterized in that an inclination angle of the narrow groove with respect to a tire circumferential direction is reduced in a land portion having a smaller pitch than a land portion having a large pitch. P1... Pn (n: arbitrary integer) are set in order from the largest pitch of the land portion, and the i-th and j-th largest pitches are Pi and Pj (1 ≦ i <j ≦ n), respectively, and the pitch Pi , Pj when the depth of the narrow groove in the land portion is Pdi, Pdj,
(Pdi / Pdj) = α × (Pi / Pj)
α = 0.7-2.0
The pneumatic tire according to claim 1, wherein the relationship is satisfied. P1... Pn (n: arbitrary integer) are set in order from the largest pitch of the land portion, and the i-th and j-th largest pitches are Pi and Pj (1 ≦ i <j ≦ n), respectively, and the pitch Pi , Pj when the interval between the narrow grooves in the land portion is Ppi, Ppj,
(Ppj / Ppi) = β × (Pi / Pj)
β = 0.7-2.0
The pneumatic tire according to claim 2, wherein the relationship is satisfied. P1... Pn (n: arbitrary integer) are set in order from the largest pitch of the land portion, and the i-th and j-th largest pitches are Pi and Pj (1 ≦ i <j ≦ n), respectively, and the pitch Pi , Pj when the maximum inclination angle of the narrow groove in the land portion is Pai, Paj, respectively.
(Pai / Paj) = γ × (Pi / Pj)
γ = 0.7 to 1.3
The pneumatic tire according to claim 3, wherein the relationship is satisfied. The pneumatic tire according to any one of claims 1 to 6, wherein an inclination angle of the narrow groove with respect to a tire circumferential direction is 30 ° to 60 °.   The pneumatic tire according to any one of claims 1 to 7, wherein the narrow groove is formed only in a land portion defined in a central region on the inner side in the tire width direction from a position of 40% of the tread contact width from the tire equator.   The pneumatic tire according to any one of claims 1 to 7, wherein the narrow groove is formed only in a land portion partitioned in a peripheral region on the outer side in the tire width direction from a position of 40% of the tread contact width from the tire equator.   An automobile having the pneumatic tire according to claim 8 mounted on a front wheel and the pneumatic tire according to claim 9 mounted on a rear wheel.

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