JP5993295B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire in which electric resistance of a tire is reduced while suppressing a decrease in steering stability.

  In recent years, a tire having a structure conceptually shown in FIG. 7 has been proposed in order to ensure the conductivity of the tire while improving the rolling resistance performance of the tire.

  Specifically, in order to reduce the rolling resistance performance, in the tread rubber a, the base part a1 and the cap part a2 which are the main parts thereof are formed of rubber containing silica with a small tangent loss tan δ. Further, in order to ensure the electrical conductivity of the tire, a through terminal portion a3 that penetrates the base portion a1 and the cap portion a2 in the tire radial direction and extends from the tread reinforcing cord layer b to the ground surface s is provided. For the part a3, for example, carbon-containing rubber having a low electrical resistance is used (see, for example, Patent Documents 1 and 2).

  And the penetration terminal part a3 of such a tire is generally distribute | arranged to the land part Yc near the tire equatorial plane Co from a viewpoint of grounding property. The “land portion Yc close to the tire equator plane Co” refers to the crown land portion Yc arranged on the tire equator plane Co when the tread portion is divided into five land portions Y as in this example. In the case of being divided into four land portions Y, it means the crown land portion Yc adjacent to the tire equatorial plane Co on both sides.

  However, as a result of the inventor's research, it has been found that such a tire is inferior in handling stability as compared with, for example, a tire in which the entire tread rubber a is formed of silica-containing rubber.

  As a result of further study on the cause, the following was found. That is, in the straight traveling state, the contact length (circumferential length) in the contact surface shape is usually the longest in the crown land portion Yc. The initial responsiveness during steering of the steering wheel is greatly influenced by the torsional rigidity of the crown land portion Yc having the longest ground contact length in the straight traveling state. Therefore, when the penetrating terminal portion a3 is provided in the crown land portion Yc, the rubber of the penetrating terminal portion a3 and the rubber of the base portion a1 and the cap portion a2 are blended differently and the torsional rigidity of the crown land portion Yc. It has been found that this causes a decrease in maneuvering stability.

  In a four-wheel vehicle, generally, the same tire is mounted on the front wheel and the rear wheel. However, a so-called negative camber angle that is inclined in a letter C when viewed from the front and rear is usually given to the rear wheels for the purpose of improving turning performance. Therefore, in the straight traveling state of the rear tire, unlike the front tire, the contact length tends to be longer in the land portion Yi inside the vehicle than the crown land portion Yc. Therefore, in the rear tire, when the through terminal portion a3 is provided in the land portion Yi inside the vehicle, the torsional rigidity of the land portion Yi is reduced, and the steering stability is lowered.

  Therefore, in the case of a tire having a through terminal portion a3, in order to suppress a decrease in steering stability, a through terminal portion is provided in the crown land portion Yc and the land portion Yi on the vehicle inner side than the crown land portion Yc. It is important not to form.

JP 2010-264959 A JP 2010-115935 A

  Therefore, the invention is based on the fact that the through-land terminal portion is not formed in the crown land portion and the land portion inside the vehicle from the crown land portion, and the torsional rigidity of the land portion having the longest ground contact length in the straight traveling state is provided. It is an object of the present invention to provide a pneumatic tire that suppresses a decrease and can suppress a decrease in steering stability due to the through terminal portion.

According to the first aspect of the present invention, the carcass extending from the tread portion through the sidewall portion to the bead core of the bead portion, and the carcass on the outer side in the tire radial direction and inside the tread portion, and further assembled to the rim. A tread reinforcing cord layer electrically connected to the rim, and a tread rubber disposed on the outer side in the tire radial direction of the tread reinforcing cord layer, and having a designated orientation for mounting on a vehicle Tire,
The tread rubber is adjacent to the outer side in the tire radial direction of the tread reinforcing cord layer and is made of a non-conductive rubber compounded with silica, and is adjacent to the outer side in the tire radial direction of the base portion. And a cap part made of non-conductive rubber compounded with silica, and one end exposed through the base part and the cap part to the grounding surface and the other end to the tread reinforcing cord layer Including a through terminal portion made of conductive rubber connected,
Moreover, the tread portion is provided with four circumferential main grooves extending in the tire circumferential direction in the tread portion, so that the crown land portion extending in the circumferential direction on the tire equatorial plane and the shoulder land portion extending along the tread end. And a total of five land portions consisting of a middle land portion disposed between the crown land portion and the shoulder land portion,
The penetrating terminal portion is arranged only in an outer middle land portion or an outer shoulder land portion arranged outside the vehicle when the vehicle is mounted.

  According to a second aspect of the present invention, the through terminal portion is disposed only in the outer middle land portion.

According to a third aspect of the present invention, the carcass extending from the tread portion through the sidewall portion to the bead core of the bead portion, and the rim when the carcass is arranged on the outer side in the tire radial direction and inside the tread portion and assembled to the rim, A pneumatic tire comprising an electrically conductive tread reinforcing cord layer and a tread rubber disposed on the outer side in the tire radial direction of the tread reinforcing cord layer, and the direction of mounting on the vehicle is designated.
The tread rubber is adjacent to the outer side in the tire radial direction of the tread reinforcing cord layer and is made of a non-conductive rubber compounded with silica, and is adjacent to the outer side in the tire radial direction of the base portion. And a cap part made of non-conductive rubber compounded with silica, and one end exposed through the base part and the cap part to the grounding surface and the other end to the tread reinforcing cord layer Including a through terminal portion made of conductive rubber connected,
Moreover, the tread portion is provided with three circumferential main grooves extending in the tire circumferential direction in the tread portion, so that a crown land portion extending in the circumferential direction on both sides of the tire equatorial plane and a shoulder land extending along the tread end. It is divided into a total of four land parts consisting of
The penetrating terminal portion is arranged only in an outer shoulder land portion arranged outside the vehicle when the vehicle is mounted.

  As described above, according to the present invention, in a tire having five land portions in the tread portion, the penetrating terminal portion is provided only on the outer middle land portion or the outer shoulder land portion disposed outside the vehicle when the vehicle is mounted. Forming. Further, in the tire having four land portions in the tread portion, the penetrating terminal portion is formed only in the outer shoulder land portion disposed outside the vehicle when the vehicle is mounted.

  That is, the through terminal portion is not formed in the land portion where the ground contact length is the longest in the straight traveling state. Therefore, it is possible to maintain the torsional rigidity in the land portion having the greatest influence on the initial responsiveness during steering of the steering wheel (the land portion having the longest ground contact length in the straight traveling state), and the steering stability caused by the through terminal portion. Can be suppressed.

It is sectional drawing which shows one Example of the pneumatic tire of this invention. It is sectional drawing which expands and shows a penetration terminal part. It is an expanded view which shows 1st Embodiment of the tread pattern. (A) is a conceptual diagram showing the shape of the contact surface when straight traveling in the front wheel tire, (B) is a conceptual diagram showing the shape of the contact surface when traveling straight in the rear tire. It is an expanded view which shows 2nd Embodiment of a tread pattern. 1 is a schematic cross-sectional view conceptually showing a tire electrical resistance measuring device. It is sectional drawing which shows an example of the conventional tire.

Hereinafter, embodiments of the present invention will be described in detail.
As shown in FIG. 1, the pneumatic tire 1 of the present embodiment includes a carcass 6 that extends from a tread portion 2 through a sidewall portion 3 to a bead core 5 of a bead portion 4, and the carcass 6 on the outer side in the tire radial direction. And a tread reinforcing cord layer 10 disposed inside the tread portion 2.

  The carcass 6 includes carcass folding portions 6b that are folded from the inner side to the outer side in the tire axial direction around the bead core 5 at both ends of the toroidal carcass main body portion 6a straddling the bead cores 5 and 5. The carcass 6 is formed of one or more carcass plies 6A in this example, in which an array of carcass cords arranged at an angle of, for example, 70 to 90 degrees with respect to the tire circumferential direction is covered with a topping rubber. . Further, a bead apex rubber 8 for bead reinforcement extending in a radially outward direction from the bead core 5 is disposed between the carcass main body portion 6a and the carcass folding portion 6b.

  In the present example, the tread reinforcing cord layer 10 is formed of a belt layer 7 placed on the carcass 6 and a band layer 9 placed on the outer side thereof.

  The belt layer 7 is composed of two or more belt plies 7A and 7B in this example, in which a belt cord array arranged at an angle of, for example, 15 to 40 degrees with respect to the tire circumferential direction is covered with a topping rubber. It is formed. The belt layer 7 enhances belt rigidity by crossing the belt cords between the plies, and reinforces substantially the entire width of the tread portion 2. The band layer 9 is formed of one or more band plies 9A, in this example, one band ply 9A in which a band cord wound spirally at an angle of 5 degrees or less with respect to the tire circumferential direction is covered with a topping rubber. The The band layer 9 constrains the belt layer 7 and improves handling stability, high-speed durability, and the like.

  The tread reinforcing cord layer 10 can be formed only by the belt layer 7 or can be formed only by the band layer 9. The belt cord and the band cord may be collectively referred to as a tread reinforcement cord, and the belt plies 7A and 7B and the band ply 9A may be collectively referred to as a tread reinforcement ply.

Here, on the outer side in the tire axial direction of the carcass 6, a sidewall rubber 3 </ b> G that forms the outer surface of the sidewall portion 3 and a clinch rubber 4 </ b> G that forms the outer surface of the bead portion 4 are disposed. The radially outer end of the sidewall rubber 3G is in contact with the tread reinforcing cord layer 10. The clinch rubber 4G has an outer end portion in the tire radial direction connected to the sidewall rubber 3G and an inner end portion in the tire radial direction in contact with the rim J. In this example, the rubber 3G, 4G, the topping rubber of the carcass ply 6A, and the topping rubber of the tread reinforcing ply are blended with carbon black as a rubber reinforcing agent in the same manner as a conventional general tire. It is made of conductive rubber having a volume specific electric resistance value of less than 1.0 × 10 ⁸ (Ω · cm). Therefore, in this example, the tread reinforcing cord layer 10 can be electrically connected to the rim J via the rubbers 3G, 4G and the carcass ply 6A. The conduction path from the tread reinforcing cord layer 10 to the rim J is not limited to this and can be variously set.

  Next, tread rubber 2 </ b> G is disposed outside the tread reinforcing cord layer 10 in the radial direction.

  The tread rubber 2G includes a base portion 11 adjacent to the tread reinforcing cord layer 10 on the outer side in the tire radial direction, a cap portion 12 adjacent to the base portion 11 on the outer side in the tire radial direction, and an outer surface constituting the ground contact surface 2S. And a through terminal portion 13 extending through the base portion 11 and the cap portion 12 inward and outward in the radial direction.

The base part 11 and the cap part 12 are made of non-conductive rubber. On the other hand, the through terminal portion 13 is made of conductive rubber, and as shown in an enlarged view in FIG. 2, one end 13a of the through terminal portion 13 is exposed to the ground plane 2S, and the other end 13b is the tread reinforcing cord. Connected to layer 10. As described above, the conductive rubber is defined as a rubber having a volume specific electrical resistance value of less than 1.0 × 10 ⁸ (Ω · cm), and a non-conductive rubber is defined as “a volume specific electrical resistance value of It is defined as rubber of 1.0 × 10 ⁸ (Ω · cm) or more.

  The ground contact surface 2S is a tread portion that comes into contact with a flat surface when a normal load is applied to a normal tire that is assembled with a normal rim and filled with a normal internal pressure and is grounded on a flat surface with a camber angle of 0 degrees. 2 surfaces. The outermost position in the tire axial direction on the ground contact surface 2S is referred to as a tread end Te.

  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 defined by the standard for each tire. If JATMA, the maximum air pressure, if TRA, the maximum value described in the table “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” Means "INFLATION PRESSURE", but in the case of passenger car tires, it is 180 kPa. The “regular load” is a load determined by the standard for each tire, and if it is JATMA, the maximum load capacity, and if it is TRA, the maximum value described in the table “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” If it is ETRTO, it is "LOAD CAPACITY".

  Further, as the non-conductive rubber for the base portion 11 and the cap portion 12, a silica-rich compound rubber containing a large amount of silica is used. Such a silica-rich compounded rubber improves wet grip performance in the cap portion 12 while improving rolling resistance performance. Further, in the base portion 11, while improving the rolling resistance performance, internal heat generation is reduced and damage such as belt end peeling is suppressed. Since the base portion 11 does not come into contact with the road surface, the requirements for wear resistance, cut resistance and the like are less than those of the cap portion 12. Therefore, in the base part 11, the silica compounding amount is increased as compared with the cap part 12, and the tangent loss tan δ1 of the base part 11 is set smaller than the tangent loss tan δ2 of the cap part 12.

  In this example, the base portion 11, the cap portion 12, and the through terminal portion 13 are formed by a so-called strip winding method in which tape-like rubber strips each having a predetermined rubber composition are spirally wound (described above). (See Patent Documents 1 and 2). However, various known forming methods can be employed, such as a rubber extrusion device having a multi-layered head, which can be extruded as an integrally extruded product in which the base portion 11, the cap portion 12, and the through terminal portion 13 are integrated. .

  The pneumatic tire 1 is designated for mounting on the vehicle. In a normal tire, the mounting direction to the vehicle is specified only when an asymmetric pattern is adopted as the tread pattern. However, in the case of the tire of the present invention, the direction of mounting on the vehicle is specified even in the case of a symmetrical pattern. This mounting direction is indicated by, for example, the display unit 15 provided on the sidewall unit 3.

  Next, as shown in FIG. 3, the tread portion 2 is provided with four circumferential main grooves 20 extending in the tire circumferential direction. Accordingly, the tread portion 2 includes a crown land portion Yc extending in the circumferential direction on the tire equatorial plane Co, a shoulder land portion Ys extending along the tread end Te, and between the crown land portion Yc and the shoulder land portion Ys. It is divided into a total of five land portions Y composed of middle land portions Ym.

  The land portion Y may be a circumferential rib extending continuously in the tire circumferential direction, or may be a block row in which a plurality of blocks divided by the lateral grooves 22 are arranged in the circumferential direction. In this example, the case where the crown land portion Yc is formed as a circumferential rib and the shoulder land portion Ys and the middle land portion Ym are formed as a block row is shown. The circumferential main grooves 20 and the lateral grooves 22 are of various conventional shapes and sizes (including groove width and groove depth).

  Of the five land portions Y, the penetrating terminal portion 13 is formed only in the outer middle land portion YmO or the outer shoulder land portion YsO arranged on the vehicle outer side when the vehicle is mounted, and the crown land portion The through terminal portion 13 is not formed in the middle land portion YmI or the inner shoulder land portion YsI disposed on the inside of the vehicle when Yc and the vehicle is mounted.

  This is based on the inventor's knowledge that the initial responsiveness during steering of the steering wheel is greatly influenced by the torsional rigidity of the land portion Y having the longest ground contact length in the straight traveling state. That is, in the case of a tire without a camber angle, such as a front wheel tire, as shown in FIG. 4A, the ground contact length of the crown land portion Yc is the other land portion as shown in the ground contact surface shape F in the straight traveling state. Therefore, the initial responsiveness during steering is greatly affected by the torsional rigidity of the crown land portion Yc. Therefore, if the penetrating terminal portion 13 is formed in the crown land portion Yc, the torsional rigidity of the crown land portion Yc is reduced. As a result, the initial responsiveness and thus the steering stability are greatly reduced. Therefore, in the case of a tire not provided with a camber angle, it is necessary to form the through terminal portion a3 in the land portion Y other than the crown land portion Yc in order to suppress a decrease in steering stability.

  On the other hand, a so-called negative camber angle that is inclined in a letter C when viewed from the front and rear is often given to the rear wheel tire. In this case, as shown in FIG. 4B, the contact surface shape F in the straight traveling state, the contact length of the inner land portion YmI or the outer shoulder land portion YsI disposed on the vehicle inner side than the crown land portion Yc. Becomes big. Therefore, in the case of a rear wheel tire to which a negative camber angle is given, in order to suppress a decrease in steering stability, the land portion Y other than the inner land portion YmI and the outer shoulder land portion YsI is penetrated. The terminal portion 13 needs to be formed.

  In general, in a four-wheel vehicle, since the same tire is mounted on the front wheel and the rear wheel, the above two conditions must be satisfied. Therefore, in 1st Embodiment, it becomes possible to suppress the fall of steering stability by forming the penetration terminal part 13 only in the outer middle land part YmO or the outer shoulder land part YsO.

  As a result of the inventor's research, when the through terminal portion 13 is formed on the outer shoulder land portion YsO, although it is effective in suppressing a decrease in steering stability, the rolling resistance performance is evaluated for the outer middle land portion YmO. It was found that the penetration terminal portion 13 was slightly inferior to the case where the penetration terminal portion 13 was formed. This is because the shoulder land portion Ys is the land portion where the movement is greatest at the time of rolling of the tire. Therefore, when the through terminal portion 13 having a high tangent loss tan δ is formed on the land portion, the heat generation becomes large and the rolling resistance performance is increased. Cause a decline. Therefore, it is most preferable to form the penetrating terminal portion 13 in the outer middle land portion YmO.

  Next, FIG. 5 illustrates a tread pattern of the tire 1 of the second embodiment. In the second embodiment, the tread portion 2 is provided with three circumferential main grooves 20 extending in the tire circumferential direction. Accordingly, the tread portion 2 is divided into a total of four land portions Y including a crown land portion Yc extending in the circumferential direction on both sides of the tire equatorial plane Co and a shoulder land portion Ys extending along the tread end Te. The

  For the same reason as in the first embodiment, the through terminal portion 13 is formed only on the outer shoulder land portion YsO arranged on the vehicle outer side when the vehicle is mounted, and the crown land portion Yc and the inner shoulder land portion YsI. Is not formed. Thereby, the fall of steering stability can be suppressed.

  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.

(1) A pneumatic tire (size: 235 / 45R18) having the internal structure shown in FIG. 1 and the tread pattern shown in FIG. 3 was prototyped according to the specifications shown in Table 1, and the conductivity and steering stability of each tire were And rolling resistance were measured. In each tire, a silica-rich non-conductive rubber was used for the cap part and the base part, and a carbon-rich conductive rubber was used for the through terminal part. The blending and the like are the same for each tire, and only the formation position of the through terminal portion is different. In the table, a land portion where the penetrating terminal portion is formed is indicated by ○, and a land portion where the penetrating terminal portion is not formed is indicated by ×. The parameters other than those shown in Table 1 are the same for each tire.

  In Comparative Example 1, silica-rich non-conductive rubber is used for the cap portion and the base portion, but no through terminal portion is formed.

<Conductivity>
As shown in FIG. 6, a metal plate 31 (electric resistance value is 10Ω or less) placed on an insulating plate 30 (electric resistance value is 10 ¹² Ω or more), a conductive tire mounting shaft 32, an electric resistance Using the measuring device including the measuring device 33, the electrical resistance value of the assembly of the test tire T and the rim J was measured in accordance with JATMA regulations. An electrical resistance value of 1.0 × 10 ⁸ Ω or less was defined as ok. Each test tire had a surface release agent and dirt sufficiently removed in advance and was sufficiently dry. Other conditions are as follows.
Rim material: Aluminum alloy Rim size: 18 × 7J
Internal pressure: 200 kPa
Load: 5.00kN
Test environment temperature (test room temperature): 25 ° C
Humidity: 50%
Measuring range of electric resistance measuring device: 10 ^{3 to} 1.6 × 10 ¹⁶ Ω
Test voltage (applied voltage): 1000V

<Steering stability>
Test tires run on a dry asphalt test course on all wheels of a vehicle (domestic 3500cc, FR vehicle) under the conditions of a rim (18 × 7J) and internal pressure (200 kPa). The following performance of the rear wheel tire was evaluated by an index with the comparative example 1 being 100, by sensory evaluation of the driver. The larger the value, the better the steering stability.

<Rolling resistance>
Using a rolling resistance tester, rolling resistance was measured under the following conditions. Evaluation was made with an index with Comparative Example 1 as 100. The larger the value, the better the rolling resistance.
Rims: 18x7J
Internal pressure: 200 kPa
Load: 5.00kN
Speed: 80km / h

(2) Similarly, a pneumatic tire (size: 235 / 45R18) having the internal structure shown in FIG. 1 and having the tread pattern shown in FIG. Steering stability and rolling resistance were measured. Other than the tread pattern, it is the same as (1).

表１、２に示すように、実施例のタイヤは、操縦安定性の低下を抑えながら導電性を確保しうるのが確認できる。

As shown in Tables 1 and 2, it can be confirmed that the tires of the examples can ensure conductivity while suppressing a decrease in steering stability.

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Tread part 2S Grounding surface 2G Tread rubber 3 Side wall part 4 Bead part 5 Bead core 6 Carcass 10 Tread reinforcement cord layer 11 Base part 12 Cap part 13 Through terminal part 20 Main circumferential groove J Rim Te Tread end Y Land Yc Crown Land Ym Middle Land Ys Shoulder Land

Claims (3)

A carcass extending from the tread portion through the sidewall portion to the bead core of the bead portion, and a tread that is disposed on the outer side in the tire radial direction of the carcass and inside the tread portion and is electrically connected to the rim when assembled to the rim. A pneumatic tire comprising a reinforcing cord layer and a tread rubber disposed on the outer side in the tire radial direction of the tread reinforcing cord layer, and the direction of mounting on the vehicle is designated,
The tread rubber is adjacent to the outer side in the tire radial direction of the tread reinforcing cord layer and is made of a non-conductive rubber compounded with silica, and is adjacent to the outer side in the tire radial direction of the base portion to constitute a grounding surface. In addition, a cap portion made of non-conductive rubber compounded with silica, and one end extending through the base portion and the cap portion are exposed to the ground surface, and the other end is connected to the tread reinforcing cord layer. Including a penetrating terminal made of conductive rubber,
Moreover, the tread portion is provided with four circumferential main grooves extending in the tire circumferential direction in the tread portion, so that the crown land portion extending in the circumferential direction on the tire equatorial plane and the shoulder land portion extending along the tread end. And a total of five land portions consisting of a middle land portion disposed between the crown land portion and the shoulder land portion,
The pneumatic tire according to claim 1, wherein the penetrating terminal portion is disposed only on an outer middle land portion or an outer shoulder land portion disposed on an outer side of the vehicle when the vehicle is mounted.   The pneumatic tire according to claim 1, wherein the penetrating terminal portion is disposed only on an outer middle land portion. A carcass extending from the tread portion through the sidewall portion to the bead core of the bead portion, and a tread that is disposed on the outer side in the tire radial direction of the carcass and inside the tread portion and is electrically connected to the rim when assembled to the rim. A pneumatic tire comprising a reinforcing cord layer and a tread rubber disposed on the outer side in the tire radial direction of the tread reinforcing cord layer, and the direction of mounting on the vehicle is designated,
The tread rubber is adjacent to the outer side in the tire radial direction of the tread reinforcing cord layer and is made of a non-conductive rubber compounded with silica, and is adjacent to the outer side in the tire radial direction of the base portion to constitute a grounding surface. In addition, a cap portion made of non-conductive rubber compounded with silica, and one end extending through the base portion and the cap portion are exposed to the ground surface, and the other end is connected to the tread reinforcing cord layer. Including a penetrating terminal made of conductive rubber,
Moreover, the tread portion is provided with three circumferential main grooves extending in the tire circumferential direction in the tread portion, so that a crown land portion extending in the circumferential direction on both sides of the tire equatorial plane and a shoulder land extending along the tread end. It is divided into a total of four land parts consisting of
The pneumatic tire according to claim 1, wherein the through terminal portion is disposed only on an outer shoulder land portion disposed on an outer side of the vehicle when the vehicle is mounted.

Images