JP2010058554A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of efficiently and certainly suppressing uneven wear of an intermediate land part by simple management work. <P>SOLUTION: Assuming a load to be applied being a half of a regular load and an internal pressure by air to be filled being a half of a regular internal pressure, in a contact patch that contacts a road surface, when a contact length of an intermediate land part 6 along the tire circumferential direction is Lc, a contact length of intermediate land parts 7, 8 along the tire circumferential direction is Lm, and a contact length of intermediate land parts 9, 10 on both sides along the tire circumferential direction is Ls, the size relation among the contact lengths is set as Lm≥Lc>Ls. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire that is used for a vehicle such as a light truck and suppresses uneven wear of a tread portion.

Generally, in a vehicle such as a small truck, there is a problem that so-called uneven wear occurs in which a part of each land portion row formed in the tread portion is worn most.
For example, in an empty small truck, when the load applied to the pneumatic tire is low, the main pressure is reduced to increase the ground contact area and the vehicle is traveling straight ahead. There has been a problem of uneven wear in which the wear of the intermediate land portion arranged between the both end land rows at the outermost end in the width direction is most advanced.
In order to suppress this uneven wear, conventionally, a technique has been proposed in which the ratio between the contact lengths of each land portion row is set within a predetermined range (see, for example, Patent Document 1).

In the technique described in Patent Document 1, the contact length along the circumferential direction of the central land portion row is L, the contact length at the outermost end in the tire width direction of both land portions row is A, and both land portions 0.02 ≦ (A−B) /L≦0.1, and 0. 0 when the contact length at a predetermined position of the row is B and the contact length at a predetermined position of the intermediate land portion row is C. The ground contact length is defined so as to satisfy 02 ≦ (C−B) /L≦0.1.
WO 2006/001290 publication

  However, in the conventional pneumatic tire described above, since the relationship between the contact lengths of each land portion row is very complicated, there is a problem that the management of the contact length is very complicated and the work load becomes large. .

  Therefore, the present invention has been made in view of such a situation, and provides a pneumatic tire capable of efficiently and reliably suppressing uneven wear of intermediate land rows with simple management work. With the goal.

In order to solve the above-described problems, the present invention has the following features. First, in the first feature of the present invention, a central land portion row (central land portion row 6) arranged at the center in the tire width direction by a plurality of main grooves (main grooves 2 to 5) extending along the tire circumferential direction. And both side land portion rows (both side land portion rows 9 and 10) arranged on both sides on the outermost side in the tire width direction, and an intermediate land portion row (between these central land portion rows and both side land portion rows ( The intermediate land portion rows 7, 8) are pneumatic tires formed in the tread portion (tread portion 1), where the load to be applied is ½ of the normal load, and the internal pressure by the air to be filled is 1 of the normal internal pressure. / 2, the contact length along the tire circumferential direction of the central land row is Lc, and the contact length along the tire circumferential direction of the intermediate land row is Lm, , When the ground contact length along the tire circumferential direction of the both side land rows is Ls, It has set the size relationship to Lm ≧ Lc> Ls.
As described above, by simply setting the contact length dimension, it is possible to efficiently suppress uneven wear in which the progress degree of wear of the intermediate land portion row is larger than that of other land portion rows.

  In another feature, when the load to be loaded is a normal load and the internal pressure of the air to be filled is a normal internal pressure, the magnitude relationship between the contact lengths is set to Lm ≧ Lc> Ls.

  In other features, the loss tangent tan δ at 60 ° C. of the tread rubber forming the tread portion (tread portion 1) is 0.22 or less.

  In another feature, the magnitude relationship of the contact length is set to Lm> Lc.

  ADVANTAGE OF THE INVENTION According to this invention, the pneumatic tire which can suppress the uneven wear of a middle land part row | line | column efficiently and reliably by simple management work can be provided.

  Next, an embodiment of a pneumatic tire according to the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic and ratios of dimensions and the like are different from actual ones.

  Accordingly, specific dimensions and the like should be determined in consideration of the following description. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

  FIG. 1 is a development view of a tread portion of a pneumatic tire according to an embodiment of the present invention.

  In the tread portion 1 of the pneumatic tire according to the present embodiment, a total of four main grooves 2, 3, 4, and 5 are formed along the tire circumferential direction. These main grooves 2 to 5 are arranged at a predetermined interval in the tire width direction, and the first main groove 2, the second main groove 3, the third main groove 4 and the first main groove 2 from the vehicle inner side toward the vehicle outer side. 4 main grooves 5 are formed.

  With these first main groove to fourth main groove, the tread portion 1 has a central land portion row 6 disposed in the center in the tire width direction and a middle portion disposed in a pair on both sides of the central land portion row 6 in the tire width direction. The land portion rows 7 and 8 and the both side land portion rows 9 and 10 disposed on both sides in the tire width direction of the intermediate land portion rows 7 and 8 are defined.

  In addition, circumferential narrow grooves 11 extending in the tire circumferential direction along the tire equator line CL passing through the center in the tire width direction are formed in the center of the central land portion row 6, and both ends of the central land portion row 6 in the tire width direction are formed. A plurality of lateral grooves 12 and 13 extending along the tire width direction are formed in the portion at predetermined intervals in the tire circumferential direction. Further, a plurality of sub-grooves 14 and 15 extending substantially parallel to the lateral grooves 12 and 13 are formed in the intermediate land portion rows 7 and 8 at predetermined intervals in the tire circumferential direction. Furthermore, circumferential grooves 16 and 17 are formed in the both-side land portion rows 9 and 10 in a broken line shape at a predetermined interval along the circumferential direction.

  FIG. 2 is a schematic view showing a ground contact surface of the pneumatic tire according to the embodiment of the present invention. In addition, this pneumatic tire has shown the contact surface in the initial state which has not yet worn out.

  In the present embodiment, the load applied to the pneumatic tire is ½ of the normal load, and the air pressure due to the air to be filled is ½ of the normal internal pressure. Here, the normal load and the normal internal pressure shall conform to an industry standard for each region where the pneumatic tire is produced or used, for example, STANDARDS MANUAL issued by ETRTO (European Tire and Rim Technical Organization). For example, the normal internal pressure of a pneumatic tire in the case of a single wheel having a size of 205 / 70R15C is 450 kPa, and the normal load is 950 kg.

  Further, among the contact surfaces that contact the road surface, the contact length along the tire circumferential direction of the central land row 6 is Lc, and the contact length along the tire circumferential direction of the intermediate land rows 7 and 8 is Lc. Let Lm be the contact length along the tire circumferential direction of the both-side land portion rows 9 and 10 as Ls. Here, Lc is a contact length in the center of the central land portion row 6 in the tire width direction, and Lm is a contact length in the center of the intermediate land portion rows 7 and 8 in the tire width direction. Further, the Ls is a portion that is 2/3 from the outer end in the tire width direction with respect to the width dimension along the tire width direction of both land portions rows 9 and 10 (that is, a portion that is 1/3 from the inner end in the tire width direction). ) Shows the ground contact length. In this case, the relationship between the contact lengths is set such that Lm ≧ Lc> Ls.

  That is, the ground contact length Lm of the intermediate land portion rows 7 and 8 is the same as or longer than the contact length Lc of the central land portion row 6. Further, the ground contact length Lc of the central land portion row 6 is set to be longer than the contact length Ls of the both-side land portion rows 9 and 10. FIG. 2 shows an example in which Lm> Lc> Ls is set.

  Here, for each of the contact lengths Lm, Lc, and Ls, well-known and commonly used means such as changing the rigidity of the crown R and the belt can be appropriately used. For example, when the air pressure due to the air to be filled is ½ of the normal internal pressure, if the crown R of the central land portion row 6 is increased, the ground contact length Lc of the central land portion row 6 can be shortened. If the crown R of the rows 9 and 10 is reduced, the ground contact length Ls of the both-side land portion rows 9 and 10 can be shortened. Further, if a belt having high rigidity in the tire circumferential direction is disposed near the central land portion row in the tread portion 1, the ground contact length Lc of the central land portion row 6 can be shortened.

  The loss tangent tan δ at 60 ° C. of the tread rubber forming the tread portion 1 is set to 0.22 or less in the case of a low rolling resistance tire. Note that the rolling resistance of the tire can be improved by reducing tan δ.

  This loss tangent means G ″ / G ′, which is the ratio of the loss shear modulus (G ″) to the storage shear modulus (G ′), and is represented by tan δ. It is a numerical value indicating how much energy is absorbed and converted into heat when the rubber material is deformed, and the measurement is performed using a dynamic viscoelasticity measuring device. The larger the value of the loss tangent tan δ, the more the deformation energy is absorbed, and the impact resilience becomes smaller in the impact buffer test.

  In a pneumatic tire, if the value of tan δ is greater than 0.22, the rolling resistance of the tire will increase, so tan δ at 60 ° C. is preferably set to 0.22 or less. In this case, it is preferable that the relationship between the contact lengths is Lm> Lc. The reason is that a tread rubber having a tan δ value of 0.22 or less has a small coefficient of friction with the road surface, and slip easily occurs. As a result, when Lm <Lc, the slip of the intermediate land portion rows 7 and 8 becomes larger with respect to the central land portion row 6, and uneven wear of the intermediate land portion rows 7 and 8 is likely to occur. is there.

<Action / Effect>
(1) In the embodiment of the present invention, the plurality of main grooves extending along the tire circumferential direction are arranged on the central land portion row arranged at the center in the tire width direction and on both sides on the outermost side in the tire width direction. The pneumatic land tires formed in the tread portion are the two land land rows and the intermediate land row arranged between the central land rows and the two land land rows. ½, the internal pressure due to the air to be filled is ½ of the normal internal pressure, and among the contact surfaces that contact the road surface, the contact length along the tire circumferential direction of the central land row is Lc, and the intermediate land When the ground contact length along the tire circumferential direction of the partial row is Lm and the ground contact length along the tire circumferential direction of the both-side land portion rows is Ls, the relationship between the contact lengths of the respective rows is represented by Lm ≧ Lc > Ls is set.
As described above, by managing the simple contact length, it is possible to efficiently and reliably suppress uneven wear in which the progress degree of wear of the intermediate land portion row is larger than that of other land portion rows.

  For example, if the load on the pneumatic tire is very small, such as in small trucks, where the internal pressure of the pneumatic tire is reduced without carrying luggage and the vehicle is mainly traveling straight, the central land row There is a problem that so-called uneven wear is likely to occur in the middle land portion row provided between the two land portion rows and the middle land portion row.

  Here, as described in the background art, conventionally, the ground contact length of the central land portion row is L, the ground contact length of the both land portion rows is A, and the contact length of the both land portion rows is B. When the ground contact length of the intermediate land portion row is C, 0.02 ≦ (A−B) /L≦0.1 and 0.02 ≦ (C−B) /L≦0.1 Uneven wear of the intermediate land section was prevented by the technology that specified the contact length to satisfy.

  However, according to the present invention, the uneven wear of the intermediate land portion row can be efficiently suppressed by the management of the contact length that is significantly simpler than before.

  (2) In the embodiment of the present invention, when the load to be applied is a normal load and the internal pressure due to the air to be filled is a normal internal pressure, the relationship between the contact lengths is expressed as Lm ≧ Lc>. Ls is set. Thus, even when the load load and the internal pressure are set to the normal load and the normal internal pressure, it is preferable to set the contact length so that Lm ≧ Lc> Ls. Also in this case, the uneven wear of the intermediate land portion row can be efficiently suppressed by the management of the contact length that is significantly simpler than before.

  (3) The rolling resistance can be reduced by setting the loss tangent tan δ at 60 ° C. of the tread rubber forming the tread portion to 0.22 or less.

  (4) Further, when the loss tangent tan δ is 0.22 or less, if the magnitude relation of the contact length is set to Lm> Lc, uneven wear of the intermediate land portion rows 7 and 8 can be suppressed.

<Other embodiments>
As described above, the contents of the present invention have been disclosed through the embodiments of the present invention. However, it should not be understood that the descriptions and drawings constituting a part of this disclosure limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.
For example, in the above-described embodiment, the load applied to the pneumatic tire is ½ of the normal load, and the air pressure due to the air to be filled is ½ of the normal internal pressure. However, the present invention is not limited to this, and even when the load to be applied is the same as the normal load and the air pressure by the air to be filled is the same as the normal internal pressure, the relationship between the contact lengths of the land rows is Lm ≧ It is preferable that Lc> Ls.

  As described above, the present invention naturally includes various embodiments that are not described herein. Therefore, the technical scope of the present invention is determined only by the invention specifying matters according to the scope of claims reasonable from the above description.

Next, in order to clarify the effect of the present invention, the results of tests performed using the pneumatic tires according to Conventional Examples 1 and 2 and Invention Example 1 will be described. Specifically, in Example 1, the contact length of each land portion row in a new-state pneumatic tire is detected, and in Example 2, the tire rolling resistance index after traveling a predetermined distance is detected. Then, the level difference due to wear between each land portion row after traveling a predetermined distance was detected.
[Example 1]
The configurations of the pneumatic test tires according to Conventional Examples 1 and 2 and Example 1 are as follows.

  The tire sizes of the test tires were 205 / 70R15C 106S in both Conventional Examples 1 and 2 and Example 1, the wheel size was 15 × 6JJ, the internal pressure was 225 kPa, and the load was 475 kg. These internal pressures are 1/2 of the normal internal pressure (450 kPa), and the load is 1/2 of the normal load (950 kg). The normal internal pressure and the normal load are values for a single wheel.

  The pneumatic tire in this state was attached to the vehicle, and the contact length along the tire circumferential direction of each land portion row was measured. The results are shown in Table 1 below.

  As is clear from Table 1, in the pneumatic tires according to the conventional examples 1 and 2, Lc> Lm> Ls, that is, the contact length Lc of the central land portion row is the longest, and the contact length Lm of the intermediate land portion row Is the next longest, and the ground contact length Ls of the both side land rows is the shortest.

  On the other hand, in the pneumatic tire according to Example 1 of the present invention, Lm> Lc> Ls, that is, the contact length Lm of the middle land portion row is the longest, the contact length Lc of the central land portion row is the next longest, The ground contact length Ls of the substring was the shortest.

The loss tangent tan δ at 60 ° C. of the tread rubber forming the tread portion was 0.25 in Conventional Example 1, 0.15 in Conventional Example 2, and 0.15 in the present invention example.
[Example 2]
Next, in Example 2, the tire rolling resistance index was detected.

The tire size and wheel size of the test tire were the same as those in Example 1, the internal pressure was 200 kPa, and the load was 4.3 kN. This pneumatic tire was mounted on a vehicle and allowed to run at a speed of 80 km / hour. As a result, as shown in Table 1, Invention Example 1 showed better results than Conventional Example 1.
[Example 3]
Next, in Example 3, the level difference due to wear between the land portion rows was detected.

  The tire size and wheel size of the test tire were the same as those in Example 1, the internal pressure was 200 kPa, and the load was 4.3 kN. The pneumatic tire was mounted on a vehicle and traveled a distance of 36,000 km at a speed of 80 km / hour. The tire side force input was 0 kN and the camber angle was 0 °. The results are shown in Table 1.

  Here, the step amounts H1 and H2 will be briefly described with reference to FIG.

  FIG. 3 is a schematic diagram showing a cross-section of the land portion row in a state where the wear of the intermediate land portion row has progressed, and a belt disposed in the tread portion is omitted.

  A difference in height along the tire radial direction between the tire radial direction outer end of the central land portion row 6 and the tire radial direction outer end of the intermediate land portion row 7 is defined as a step amount H1. Further, the difference in height along the tire radial direction between the tire radial direction outer end of the intermediate land portion row 7 and the tire radial direction outer end of the both-side land portion row 9 is defined as a step amount H2.

  As shown in Table 1, it was found that Example 1 of the present invention has smaller step amounts H1 and H2 than that of Conventional Example 2, and the degree of wear of the intermediate land rows 7 and 8 is small. Thus, Invention Example 1 showed better results than Conventional Example 2.

It is an expanded view which shows the tread part of the pneumatic tire which concerns on embodiment of this invention. It is the schematic which shows the contact surface of the pneumatic tire which concerns on embodiment of this invention. It is the schematic which shows the cross section of the state which abrasion of the middle land part row | line | column advanced.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Tread part 2, 3, 4, 5 ... Main groove 6 ... Central land part row | line | column 7,8 ... Middle land part row | line | column 9,10 ... Both-side land part row | line | column 11 ... Circumferential narrow groove | channel 12, 13 ... Horizontal groove | channel 14,15 ... sub-groove 16, 17 ... circumferential groove

Claims (4)

A plurality of main grooves extending along the tire circumferential direction, a central land portion row disposed in the center in the tire width direction, both side land portion rows disposed on both sides on the outermost side in the tire width direction, the central land portion row, and A pneumatic tire in which a middle land portion row disposed between the both side land portion rows is formed in a tread portion,
The contact length along the tire circumferential direction of the central land portion row among the contact surfaces that contact the road surface, assuming that the load to be applied is 1/2 of the normal load and the internal pressure due to the air to be filled is 1/2 of the normal internal pressure. Lc, the ground contact length along the tire circumferential direction of the intermediate land portion row is Lm, and the ground contact length along the tire circumferential direction of the both side land portion rows is Ls. A pneumatic tire characterized in that the magnitude relationship is set to Lm ≧ Lc> Ls.   2. The air according to claim 1, wherein when the load to be applied is a normal load and the internal pressure due to the air to be filled is a normal internal pressure, the magnitude relationship of the contact length is set to Lm ≧ Lc> Ls. Enter tire.   3. The pneumatic tire according to claim 1, wherein a loss tangent tan δ at 60 ° C. of the tread rubber forming the tread portion is 0.22 or less.   The pneumatic tire according to claim 3, wherein the magnitude relation of the contact length is set to Lm> Lc.

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