JP4436146B2 - Passenger car tires - Google Patents

Description

  The present invention relates to a tire for a passenger car that is suitable for use at a high internal pressure, and can exhibit excellent rolling resistance performance while suppressing a decrease in ride comfort and steering stability.

  The air pressure actually used for passenger car tires is selected in consideration of the maximum load, mounting position, use conditions, vehicle characteristics, etc. in addition to the load capacity of the tire, and is normally used in the range of 180 to 250 kPa. Often.

  On the other hand, in recent years, for the purpose of reducing rolling resistance and improving the fuel efficiency of a vehicle, a high internal pressure of, for example, 250 kPa or more, further 300 kPa or more, with the maximum air pressure (350 kPa in the case of JATMA) determined by the standards of JATMA as an upper limit. It has been proposed to use tires.

  However, when the conventional tire is used at a higher air pressure, the longitudinal spring constant increases due to an increase in tire rigidity, resulting in a deterioration in ride comfort. In addition, since the tread profile in the tire meridional section is flattened and the contact length is reduced, there arises a problem that the steering stability is lowered, for example, the cornering power (CP) and the self-aligning torque (SAT) are reduced. Therefore, in order to reduce rolling resistance by using tires at a high internal pressure, it is necessary to minimize the decrease in ride comfort and steering stability due to the high internal pressure while maintaining running performance at normal internal pressure. Is essential.

  In Patent Document 1, in the state of filling with normal internal pressure, the ratio of the tread contact width to the total tire width is reduced, and the ratio of the belt width to the tread contact width is increased to reduce the rolling resistance while improving the riding comfort. Although it has been proposed to improve the driving stability and the like, there is no description about suppressing the decrease in riding comfort and driving stability due to the increase in the internal pressure used.

JP 2003-146015 A

  Therefore, the present invention reduces the ratio of the tread ground contact width to the nominal width of the tire and increases the ratio of the belt width to the tread ground contact width while increasing the camber amount of the tread in the 300 kPa filled state in the normal internal pressure filling state. The purpose is to provide a tire for passenger cars that can exhibit excellent rolling resistance performance and improve fuel efficiency while using tires at high internal pressures, while reducing the reduction in ride comfort and driving stability. It is said.

In order to achieve the above-mentioned object, the invention of claim 1 of the present application is folded around the bead core from the inside to the outside on both sides of the ply main body portion across the bead core of the bead portion from the tread portion to the sidewall portion. A carcass made of a carcass ply having a series of ply turn-up parts, a belt layer made up of a plurality of belt plies arranged inside the tread part and radially outside the carcass, and rises from the bead core in a tapered shape A passenger car tire having a bead apex rubber,
In a normal internal pressure state in which a tire is assembled on a normal rim and filled with a normal internal pressure, the tread contact width TW, which is the tire axial distance between the tread contact ends, is 0.55 to 0.65 of the nominal width W0 of the tire. And the belt width BW, which is the distance in the tire axial direction of the outer end of the belt ply of the maximum width of the belt layer, is greater than 1.0 times and less than 1.2 times the tread ground contact width TW. ,
The bead apex rubber is made of a hard rubber having a rubber hardness of 75 to 95 °,
The radial height H1 from the bead base line of the bead apex rubber is 0.8 to 1.8 times the radial height Hf from the bead base line of the rim flange of the regular rim,
The sidewall portion is provided with a rubber reinforcement layer that is continuous with the bead apex rubber and extends radially outward from the tire maximum width position K.
The rubber reinforcing layer has a rubber hardness of 75 to 95 ° and a thickness of 0.5 to 2.0 mm.
The rubber reinforcing layer has a radial height H3 from the bead base line of 1.1 to 1.4 times a radial height Hk from the bead base line at the tire maximum width position K , and
The rubber reinforcing layer has a radial overlap width W1 with the bead apex rubber of 3.0 mm or more , and a lower end portion of the rubber reinforcing layer is radially outward from a folded end of the ply folded portion. Terminate, and
In the 300 kPa internal pressure state filled with 300 kPa, the camber amount Ca, which is the distance in the tire radial direction from the tire equator point on the tread surface to the tread contact end, is 0.045 to 0 of the tread contact width TW in the normal internal pressure state. .070 times as a feature.

  The invention of claim 2 is characterized in that the belt width BW is 1.05 times or more of the tread ground contact width TW.

  Here, the “tread grounding end” means the outermost end in the tire axial direction of the tread grounding surface that can be grounded when a normal load is applied to the tire in the normal internal pressure state. The “regular rim” is a rim determined for each tire in the standard system including the standard on which the tire is based, for example, a standard rim for JATMA, “Design Rim” for TRA, or ETRTO means "Measuring Rim". The “regular internal pressure” is the air pressure specified by the tire for each tire. The maximum air pressure in the case of JATMA, the maximum value described in the table “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” in the case of TRA, In the case of ETRTO, it means “INFLATION PRESSURE”, but in the case of passenger tires, it is 180 kPa. The “regular load” is the load specified by the standard for each tire. The maximum load capacity shown in the table “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” is the maximum load capacity for JATMA and TRA for TRA. In the case of ETRTO, it means a load obtained by multiplying "LOAD CAPACITY" by 0.88.

  Since the present invention is configured as described above, it is possible to maintain the running performance at normal internal pressure, and in the use of a tire at high internal pressure, while exhibiting excellent rolling resistance performance, ride comfort and driving stability. Can be kept low.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a meridional sectional view showing a normal internal pressure state of a passenger car tire of the present invention.
In FIG. 1, a passenger car tire 1 is disposed on a carcass 6 extending from a tread portion 2 through a sidewall portion 3 to a bead core 5 of a bead portion 4, inside the tread portion 2 and radially outside the carcass 6. And at least a belt layer 7.

  The carcass 6 includes at least one carcass ply 6A in which carcass cords are arranged at an angle of, for example, 75 ° to 90 ° with respect to the tire circumferential direction, and in this example, one carcass ply 6A. An organic fiber cord such as rayon is preferably used. The carcass ply 6A includes a series of ply folding portions 6b that are folded back from the inside around the bead core 5 on both sides of the ply main body portion 6a straddling the bead cores 5 and 5, and the ply main body portion. A bead apex rubber 8 for bead reinforcement rising from the bead core 5 in a tapered shape is disposed between the 6a and the ply turn-up portion 6b.

  The bead apex rubber 8 is made of a hard rubber having a rubber hardness (durometer A hardness) of 75 to 95 °. In this example, the radial height H1 from the bead base line BL is set as the radial height of the rim flange. An example in which the bead portion 4 is slimmed by setting it as low as 0.8 to 1.8 times the Hf is illustrated. Thereby, bead durability and road noise performance are improved, aiming at weight reduction. The ply turn-up portion 6b has a radial height H2 that is smaller than the height H1 of the bead apex rubber 8 and not more than 1.2 times the height Hf of the rim flange. The occurrence of failure is suppressed.

  Further, in this example, in order to suppress a decrease in tire lateral rigidity due to downsizing of the bead apex rubber 8, the sidewall portion 3 has a rubber hardness of 75 to 95 ° and a thickness of 0.5 to 2.0 mm. A thin rubber reinforcing layer 10 is attached. The rubber reinforcing layer 10 is continuous with the bead apex rubber 8 and extends radially outwardly in contact with the outer side surface of the ply main body 6a in the tire axial direction. The direction is broken off. The radial height H3 of the rubber reinforcing layer 10 is preferably in the range of 1.1 to 1.4 times the radial height Hk of the tire maximum width position K. The rubber reinforcing layer 10 is integrated with the bead apex rubber 8 by setting the overlap width W1 in the radial direction with the bead apex rubber 8 to 3.0 mm or more.

  Next, the belt layer 7 is formed by a plurality of belt plies 7A, 7B in this example, in which belt cords are arranged at, for example, 10 to 35 ° with respect to the tire circumferential direction. By crossing each other, the belt rigidity is increased, and the tread portion 2 is strongly reinforced with a tagging effect. The outer belt ply 7B is narrower than the inner belt ply 7A, thereby relaxing the stress concentration acting on the belt outer end. A steel cord is suitable as the belt cord, but high modulus organic fiber cords such as polyethylene naphthalate (PEN), polyethylene terephthalate (PET), and aromatic polyamide may be used as necessary.

  In this example, for the purpose of improving high-speed durability, band cords of organic fibers such as nylon are arranged at an angle of 5 degrees or less with respect to the circumferential direction on the radially outer side of the belt layer 7. A band layer 9 is provided. As the band layer 9, a pair of left and right edge band plies that covers only the outer end portion in the tire axial direction of the belt layer 7 and a full band ply that covers substantially the entire width of the belt layer 7 can be used as appropriate. An example of one full band ply is shown.

  In the present invention, as shown in the enlarged view of the tread portion 2 in the normal internal pressure state in FIG. 2, the tread ground contact width TW, which is the distance in the tire axial direction between the tread ground contact Te, Te, is set to the tire nominal width W0. The range is 0.55 to 0.65 times that of a conventional tire (shown in FIG. 4). In a conventional tire, the tread contact width TW is generally set to be as wide as about 0.72 times or more than the nominal tire width W0.

  Such a narrow tread ground contact width TW is formed by providing the tread portion 2 with a ground raised portion 2A that forms a tread ground contact surface S by being raised at the center thereof. The contact bulge portion 2A bulges relative to the non-protrusion portion 2B that is continuous on the outer side in the tire axial direction, and the tread gauge thickness in the contact bulge portion 2A is determined by the tread gauge of a conventional tire. By setting the value substantially equal to the thickness, it is possible to ensure a conventional wear life. Further, the non-protruding portion 2B is thin, such as being connected to the sidewall portion 3 with substantially the same thickness, and the region from the tread grounding end Te to the tire maximum width position K is easily bent and deformed. For example, a high internal pressure of 300 kPa or more is applied. Even when filled, it is possible to suppress an increase in the longitudinal spring constant of the tire.

  At this time, the belt width BW which is the distance in the tire axial direction of the outer end 7e of the belt ply of the maximum width (in this example, the inner belt ply 7A) of the belt layer 7 is set to 1.0 of the tread grounding width TW. It is important to reinforce the tread portion 2 by increasing it to a range larger than twice and 1.2 times or less. If the belt width BW is 1.0 times or less of the tread ground contact width TW, the tread rigidity is insufficient, making it difficult to ensure the required handling stability, and the change in the tread profile due to air pressure becomes large. There is a tendency for a difference in steering stability or the like between the use of normal internal pressure and the use of high internal pressure. Further, if the belt width BW exceeds 1.2 times the tread ground contact width TW, it is disadvantageous for suppressing the longitudinal spring constant, and the distance from the tire surface of the outer end 7e becomes too small. It becomes easy to cause damage. Further, in the tire molding process, it becomes difficult to attach the tread rubber, and defects such as bears are likely to occur. From such a viewpoint, the lower limit value of the belt width BW is preferably 1.05 times or more, more preferably 1.10 times or more of the tread ground contact width TW, and the upper limit value is 1.15 times or less. Is preferred.

  Further, in the present invention, for example, when using a tire filled with a high internal pressure of 300 kPa or more, in order to minimize a decrease in steering stability, in a 300 kPa internal pressure state (shown in FIG. 3) filled with 300 kPa, The camber amount Ca, which is the distance in the tire radial direction from the tire equator point Cp on the tread surface 2S to the tread ground contact end Te, is restricted to a range of 0.045 to 0.070 of the tread ground contact width TW in a normal internal pressure state. The tread radius (radius of the tread surface 2S) is set to be rounder than that of the conventional tire.

  As a result, it is possible to suppress the tread profile from flattening when the high internal pressure is filled and reduce the contact length in the tire circumferential direction, and to prevent the cornering power (CP) and self-aligning torque (SAT) from decreasing. Is possible. And by synergistic effects, such as reducing the above-mentioned tread ground contact width TW, when using tires at high internal pressure, it is possible to suppress a decrease in ride comfort and steering stability while exhibiting excellent rolling resistance performance.

  If the camber amount Ca is less than 0.045 times the tread grounding width TW, the effect of improving the steering stability at the time of high internal pressure filling cannot be achieved. Conversely, if it exceeds 0.070 times, the shoulder portion slips at the time of grounding. It is easy to cause uneven wear. Accordingly, the lower limit value of the camber amount Ca is preferably 0.05 times or more of the tread ground contact width TW, and the upper limit value is preferably 0.06 times or less.

  In addition, according to the experiment result of the present inventor in Table 1 to be described later, when the air pressure is increased from 200 kPa to 300 kPa and used, the deterioration margin of the vertical spring constant (up ratio of the vertical spring constant) is compared with the conventional comparison. Compared to the tire of Example 1, it can be suppressed by about 5%, and the rolling resistance improvement allowance (rolling resistance reduction rate) can be improved by about 3%. That is, it is possible to achieve both the riding comfort and the handling stability and the rolling resistance.

  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.

  A tire having a tire size of 165 / 70R14 and having the configuration shown in FIG. 1 is made on the basis of the specifications shown in Table 1, and the longitudinal spring constant (200 kPa internal pressure state and 300 kPa internal pressure state) and rolling resistance (200 kPa internal pressure) of the sample tire. State and 300 kPa internal pressure state) and cornering power (300 kPa internal pressure state) were tested, and the results are shown in Table 1. In addition, the tread part in the 200 kPa internal pressure state of the conventional tire described in the comparative example 1 is shown in FIG.

(1) Longitudinal spring constant:
By measuring the vertical deflection when a longitudinal load (4.00 kN) is applied to the rim-assembled tire of 200 kPa internal pressure state and 300 kPa internal pressure state mounted on the regular rim, and by dividing the vertical load by this vertical deflection The longitudinal spring constant was determined and displayed as an index with the longitudinal spring constant of Comparative Example 1 at 200 kPa internal pressure as 100. The smaller the value, the lower the longitudinal spring constant and the better the ride comfort.

(2) Rolling resistance:
Using a rolling resistance tester, the rolling resistance under the conditions of speed (80 km / h) and load (4.00 kN) of the rim set in the 200 kPa internal pressure state and the 300 kPa internal pressure state was measured, and Comparative Example 1 in the 200 kPa internal pressure state was measured. It was displayed as an index with the rolling resistance as 100. The smaller the value, the lower the rolling resistance and the better.

(3) Cornering power:
Using an indoor tester, the cornering power of the rim set tire in the 300 kPa internal pressure state was measured, and displayed as an index with Comparative Example 1 in the 300 kPa internal pressure state taken as 100. The larger the value, the higher the cornering power and the better the steering stability.

  As shown in the table, it is confirmed that the tires of the examples can suppress the decrease in ride comfort and driving stability while exhibiting excellent rolling resistance performance and improving fuel efficiency when using tires at high internal pressure. it can.

It is sectional drawing which shows one Example of the tire for passenger cars of this invention. It is sectional drawing which expands and shows the tread part. It is a diagram which shows a tread profile in a 300 kPa internal pressure state. It is sectional drawing of the tread part in the 200 kPa internal pressure state of the conventional tire.

Explanation of symbols

2 Tread portion 2S Tread surface 3 Side wall portion 4 Bead portion 5 Bead core 6 Carcass 7 Belt layer 7A, 7B Belt ply Cp Tire equatorial point Te Tread grounding end

Claims (2)

A carcass made of a carcass ply having a series of ply turn-around portions that are turned from the inside to the outside on both sides of the ply main body portion across the bead core of the bead portion from the tread portion to the sidewall portion, and the tread A tire for a passenger car having a belt layer composed of a plurality of belt plies arranged inward of the carcass and radially outward of the carcass, and a bead apex rubber rising in a tapered shape from the bead core,
In a normal internal pressure state in which a tire is assembled on a normal rim and filled with a normal internal pressure, the tread contact width TW, which is the tire axial distance between the tread contact ends, is 0.55 to 0.65 of the nominal width W0 of the tire. And the belt width BW, which is the distance in the tire axial direction of the outer end of the belt ply of the maximum width of the belt layer, is greater than 1.0 times and less than 1.2 times the tread ground contact width TW. ,
The bead apex rubber is made of a hard rubber having a rubber hardness of 75 to 95 °,
The radial height H1 from the bead base line of the bead apex rubber is 0.8 to 1.8 times the radial height Hf from the bead base line of the rim flange of the regular rim,
The sidewall portion is provided with a rubber reinforcement layer that is continuous with the bead apex rubber and extends radially outward from the tire maximum width position K.
The rubber reinforcing layer has a rubber hardness of 75 to 95 ° and a thickness of 0.5 to 2.0 mm.
The rubber reinforcing layer has a radial height H3 from the bead base line of 1.1 to 1.4 times a radial height Hk from the bead base line at the tire maximum width position K , and
The rubber reinforcing layer has a radial overlap width W1 with the bead apex rubber of 3.0 mm or more , and a lower end portion of the rubber reinforcing layer is radially outward from a folded end of the ply folded portion. Terminate, and
In the 300 kPa internal pressure state filled with 300 kPa, the camber amount Ca, which is the distance in the tire radial direction from the tire equator point on the tread surface to the tread contact end, is 0.045 to 0 of the tread contact width TW in the normal internal pressure state. Passenger car tire characterized by having a .070 magnification.
  The tire for a passenger car according to claim 1, wherein the belt width BW is 1.05 times or more of the tread ground contact width TW.

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