JP2016068834A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tire which is improved in noise performance while maintaining rolling resistance.SOLUTION: A pneumatic tire comprises: an inclined belt having a carcass which straddles a pair of bead parts in a toroidal shape, and composed of at least one layer of an inclined belt layer at the outside of a tire radial direction of the carcass; a peripheral belt which is composed of at least one layer of a peripheral belt layer; and a tread. In the peripheral belt, with a tire width-directional region including at least a tire equator, and having a width in a tire width direction which is not smaller than 0.2 times and not larger than 0.7 times of a maximum width of the peripheral belt in the tire width direction as a center region, the rigidity of any portion of the center region in a tire peripheral direction per unit width is set higher than the rigidity of any portion of adjacent both shoulder regions in the tire peripheral direction per unit width, and a width of one shoulder region is set at not smaller than 1.5 times and not larger than 8.0 times of a width of the other shoulder region.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a pneumatic tire with improved noise performance while maintaining rolling resistance performance.

  In recent years, the weight of tires has been reduced in order to reduce the rolling resistance of the tires. In such tires, the vibration attenuation of the running tires is reduced and the radiated sound emitted from the tires is increased. There is a tendency.

  As a method for reducing this radiated sound, Patent Document 1 discloses that in the circumferential belt layer disposed on the outer side in the tire radial direction of the carcass, the tire circumferential rigidity per unit width of any portion of the high rigidity region including the tire equator. Is also described as being higher than the rigidity in the tire circumferential direction per unit width in any part of the other region.

International Publication No. 2013/161296

  However, there is a demand for a tire that can suppress the radiated sound more effectively while maintaining the rolling resistance performance. Accordingly, an object of the present invention is to provide a tire having improved noise performance while maintaining rolling resistance performance.

The gist of the present invention is as follows.
(1) The pneumatic tire of the present invention has a carcass straddling a toroidal shape between a pair of bead portions, and a cord that is disposed on the outer side in the tire radial direction of the crown portion of the carcass and is inclined with respect to the tire circumferential direction. A circumferential direction comprising an inclined belt comprising at least one inclined belt layer and at least one circumferential belt layer having a cord disposed on the outer side in the tire radial direction of the crown portion of the carcass and extending along the tire circumferential direction A pneumatic tire comprising a belt and a tread disposed on the outer side in the tire radial direction of the circumferential belt,
The circumferential belt includes at least a tire equator, a tire width direction region having a tire width direction width of 0.2 to 0.7 times the maximum width in the tire width direction of the circumferential belt as a center region, The tire circumferential rigidity per unit width of any part of the center region is also higher than the tire circumferential rigidity per unit width of any part of the adjacent shoulder regions,
The width of one shoulder region is not less than 1.5 times and not more than 8.0 times the width of the other shoulder region. According to the pneumatic tire of the present invention, it is possible to provide a tire with improved noise performance while maintaining rolling resistance performance.

  In addition, said inclination belt layer is a belt layer which has a code | cord | chord which extends incline with respect to a tire circumferential direction, and a circumferential belt layer is a belt layer which has a code | cord | chord extended along a tire circumferential direction. Here, “extends along the tire circumferential direction” means that the cord is tired depending on the case where the cord is parallel to the tire circumferential direction or the result of forming a belt layer by spirally winding a strip coated with rubber on the cord. Including the case where it is slightly inclined with respect to the circumferential direction (the angle with respect to the tire circumferential direction is about 5 ° or less). The unit width is 3 mm in the tire width direction, and the tire circumferential rigidity is calculated from the number of cords per unit width, the strength per cord, the strength of rubber covering the cords, and the like.

(2) In the pneumatic tire of the present invention, it is preferable that the number of belt layers in the center region is larger than the number of the same layers in the shoulder region. According to this configuration, it is possible to more easily manufacture a tire with improved noise performance while maintaining rolling resistance performance.

(3) In the pneumatic tire of the present invention, it is preferable that a shoulder region having a smaller width in the tire width direction is disposed on the inner side in the vehicle mounting direction. According to this configuration, it is possible to improve the noise performance while maintaining the steering stability performance when traveling straight ahead.

  The width in the tire width direction and the like of the circumferential belt is measured with the tire mounted on the applied rim, filled with the specified internal pressure, and no load.

  `` Applicable rim '' refers to the standard rim specified in the following standards according to the tire size, `` specified internal pressure '' refers to the air pressure specified in accordance with the maximum load capacity in the following standards, “Maximum load capacity” refers to the maximum mass allowed to be loaded on a tire according to the following standards. The standard is an industrial standard effective in the area where tires are produced and used. In Japan, “Standard Rim” described in JATMA YEAR BOOK, and in Europe, “Measurement” described in ETRTO STANDARDDS MANUAL. “Rim”, in the United States, refers to “Design Rim” described in TRA YEAR BOOK.

  According to the present invention, it is possible to provide a pneumatic tire with improved noise performance while maintaining rolling resistance performance.

It is a width direction sectional view of the pneumatic tire concerning one embodiment of the present invention. It is a figure for demonstrating the effect | action of a comparative example. It is a figure for demonstrating the effect | action of this invention. It is a figure which shows the relationship between steering stability and the generation amount of a radiated sound.

  Hereinafter, a pneumatic tire of the present invention (hereinafter also simply referred to as a “tire”) will be described in detail with reference to the drawings.

  FIG. 1 shows a cross section in the width direction of a tire 10 according to an embodiment of the present invention. The tire 10 has at least one layer including a carcass 2 straddling a toroidal shape between a pair of bead portions 1 and a cord that is disposed on the outer side in the tire radial direction of the crown portion of the carcass 2 and is inclined with respect to the tire circumferential direction. An inclined belt 3 composed of two inclined belt layers (here, 3a and 3b), and at least one circumference having a cord disposed on the outer side in the tire radial direction of the crown portion of the carcass and extending along the tire circumferential direction The tire includes a circumferential belt 4 formed of directional belt layers (here, 4a and 4b) and a tread 6 disposed on the outer side of the circumferential belt 4 in the tire radial direction. The circumferential belt 4 includes at least a tire equator CL, and a tire width direction region having a tire width direction width Wc that is 0.2 to 0.7 times the maximum width in the tire width direction of the circumferential belt 4 is a center region. As C, the tire circumferential rigidity per unit width of any part of the center region C is also made higher than the tire circumferential rigidity per unit width of any part of both shoulder regions S1 and S2.

  In the present embodiment, the center region C of the circumferential belt 4 has a tire width direction width Wc that is 0.5 times the maximum width W of the circumferential belt 4 in the tire width direction. The shoulder regions S1 and S2 have different tire width direction widths Ws1 and Ws2, and the tire width direction width Ws1 of one shoulder region S1 is 2.0 times the tire width direction width Ws2 of the other shoulder region S2. It has become.

  In the tire of the present invention, as described above, the circumferential belt 4 includes at least the tire equator CL, and has a tire width not less than 0.2 times and not more than 0.7 times the maximum width W in the tire width direction of the circumferential belt 4. With the region having the direction width Wc as the center region C, the tire circumferential rigidity per unit width of any part of the center region C is also greater than the tire circumferential rigidity per unit width of any part of the adjacent shoulder region S. It is important that the width Ws1 of one shoulder region S1 is 1.5 times or more and 8.0 times or less than the width Ws2 of the other shoulder region S2.

  In general, in many passenger car tires, a shape in which a tread surface vibrates uniformly and greatly in a high frequency range of 400 Hz to 2 kHz in vibration modes such as a primary, secondary, and tertiary directions in a cross-sectional direction (in FIG. Loud radiated sound is generated. Therefore, if the circumferential rigidity of the tread width center is locally increased, it becomes difficult for the tread width center to spread in the tire radial direction and the tread surface spread (vibration amplitude) is suppressed. Radiated sound is reduced (indicated by broken lines in FIG. 2).

  In the tire of the present invention, the center region C of the circumferential belt 4 having relatively high rigidity is extended in the range of 0.2 to 0.7 of the maximum width W of the circumferential belt 4 in the tire width direction. Further, the tire width direction widths Ws1 and Ws2 of the shoulder regions S1 and S2 of the circumferential belt 4 are further varied in a range where the ratio Ws1 / Ws2 is 1.5 or more and 8.0 or less, that is, the tire equator. It is set as the structure which has arrange | positioned the circumferential belt 4 asymmetrically with respect to CL by the tire width direction sectional view. Therefore, the amplitude of the vibration mode that causes the radiated sound as described above is suppressed (indicated by a broken line in FIG. 2), and the vibration mode includes two vibration modes (a broken line and a one-dot chain line in FIG. 3). Separated). As a result, since the peak level of the sound is more effectively lowered, it is possible to further reduce the radiated sound generated from the tire.

  As described above, in the tire of the present invention in which the amplitude of the vibration generated in the tire itself is reduced and the peak level of the sound is reduced by separating the amplitude into different modes, other tire configurations, for example, inclined belt layers Irrespective of the size of the cord angle, the sound emitted from the tire can be reduced.

More specifically, for example, in a tire in which the cord angle of the inclined belt layer with respect to the tire circumferential direction is 35 ° or more, the radiated sound tends to be particularly loud because the inclined belt layer is in a deformation mode that uniformly vibrates. The deformation mode in which the inclined belt layer vibrates uniformly can be improved by applying the above-described configuration of the present invention, in particular, by providing a center region having a relatively high rigidity at a predetermined ratio. Further, by making the width in the tire width direction of the shoulder region having relatively low rigidity different between the one side and the other side, it is possible to separate the vibration modes and reduce the generation of radiated sound.
Similarly, even in a tire in which the cord angle of the inclined belt layer is less than 35 °, the effect of reducing radiated sound can be obtained by applying the configuration of the present invention.

  In addition, if the tire circumferential rigidity in the region including the tire equator CL is locally increased, the local shear strain of the top rubber (rubber forming the tread surface layer) increases, so that the damping of the vibration mode also increases. Become. Therefore, as in the present invention, the improvement to increase the rigidity in the tire circumferential direction in the center region C including the tire equator CL is a change in the direction in which the tire ring rigidity is increased and the eccentricity of the tire is suppressed. Difficult to deteriorate performance. Thus, the tire of the present invention can achieve both rolling resistance performance and noise performance.

  When the ratio Wc / W of the width Wc in the tire width direction of the center region C to the maximum width W in the tire width direction of the circumferential belt 4 is less than 0.2, the center region C having relatively high rigidity is small. If the tire vibration mode is not enough to be changed and if the ratio Wc / W is more than 0.7, the center area with high rigidity becomes too wide, and rather a large amplitude is generated and radiated sound is generated. In order to increase, the ratio Wc / W is set in the range of 0.2 to 0.7.

  Further, the vibration can be separated into different modes by making the tire width direction width Ws1 of one shoulder region different by 1.5 times or more the tire width direction width Ws2 of the other shoulder region. However, if the size exceeds eight times, the amplitude becomes large in the wide shoulder region (shoulder region S1 in the example of FIG. 1) and the radiated sound tends to increase.

  Note that the ratio Wc / W is not less than 0.3 and not more than 0.6, and the ratio Ws1 / Ws2 is not less than 2 and not more than 4 from the viewpoint of reducing the radiated sound by making the change of the tire vibration mode more reliable. More preferably.

  In the tire of the present invention, it is preferable that the number of the circumferential belt layers in the center region C is larger than the same number of layers in the shoulder region S. In order to increase the rigidity in the tire circumferential direction in the center region C of the circumferential belt 4, in addition to means for increasing the number of layers in the portion, the number of cords in the circumferential belt layer is increased. There are methods such as using a high-strength cord only in the portion corresponding to the center region, or increasing the rigidity of the ply coating rubber in the portion corresponding to the center region of the circumferential belt layer. In other words, a method of increasing the number of circumferential belt layers is preferable.

  From the viewpoint of sufficiently improving the noise performance, the tire circumferential rigidity per unit width of any part of the center region C of the circumferential belt 4 is also the tire circumferential direction per unit width of any part of the shoulder region S. The rigidity is preferably 1.3 times or more.

  The cords of the carcass 2, the inclined belt 3 and the circumferential belt 4 can be organic fiber cords such as aramid, polyethylene terephthalate or polyethylene naphthalate, and steel cords, for example.

In the tire of the present invention, a shoulder region having a small width in the tire width direction (shoulder region S2 in the example of FIG. 1) is disposed on the inner side in the vehicle mounting direction, that is, the inner side in the vehicle mounting direction. It is preferable to bias the highly rigid center region C. In this case, compared with the case where the shoulder region S2 is arranged on the outer side in the mounting direction, it is possible to improve the steering stability performance during straight traveling. This is because, in the center region C having relatively high rigidity, the contact length of the tread tends to be shortened. However, when the contact length of the tire half on the inner side in the vehicle mounting direction becomes shorter, stress acts on the inner side in the vehicle mounting direction. This is because a lateral force is generated from the pair of tires inward in the vehicle mounting direction.
When there is an appropriate vehicle mounting direction, the vehicle mounting direction is usually designated by a display or the like by marking on the tire.

Here, a test conducted to examine the relationship between the steering stability and the generation of radiated sound will be described.
That is, the tire T1 having no highly rigid center region C in the circumferential belt, the tire T2 having a ratio Wc / W of 0.5 around the tire equator CL, as shown in FIG. 2, and FIG. As shown, the tire T3 having a ratio Wc / W of 0.5 asymmetrically with respect to the tire equator CL is rolled on a flat belt, and the cornering rigidity when the steer angle is cut by 1 degree, The magnitude of the emitted sound was evaluated.

  The test results are shown in FIG. Here, in each of the tires T1 to T3, the average of the cornering rigidity is plotted when the flat belt speed is 60 kph and when the flat belt speed is 100 kph. The triangle mark indicates the tire T1, the square mark indicates the tire T2, and the circle mark indicates the tire T3, and one scale on the vertical axis is 1 dB. Therefore, in the tires T2 and T3 according to the embodiment of the present invention, it is understood that the generation of radiated sound is less by about 1 to 3 dB than the other tires T1 while maintaining the cornering rigidity. That is, in the tires T2 and T3 according to the embodiment of the present invention, it was confirmed that the noise performance could be improved while maintaining the cornering rigidity that contributes to the steering stability during cornering as the tire alone.

Also, these tires T1 to T3 are assembled to the applicable rim, and a tire / rim assembly filled with the specified internal pressure is mounted on the vehicle. It was evaluated by feeling. At this time, the tire / rim assembly of the tire T3 is mounted on the vehicle so that the shoulder region with a small width in the tire width direction is mounted on the vehicle so that the shoulder region is on the vehicle mounting inner side, and the shoulder region is on the vehicle mounting outer side. It was tested both when worn and when worn.
As a result, it was found that the former tire having increased rigidity on the inner side of the vehicle was superior in steering stability performance. This is considered to be due to the fact that the straight running stability is increased because a lateral force is generated inwardly when the vehicle is going straight. When the tire is attached to the vehicle, it is possible to expect not only rolling resistance performance and noise performance but also improvement in running performance represented by steering stability by making the tire asymmetrical with high rigidity on the inner side of the vehicle.

  As a means for improving the steering stability, for example, a means for increasing the rigidity in the tire width direction by increasing the angle of the inclined belt layers 3a and 3b with respect to the tire circumferential direction (for example, 35 ° or more). However, in the present embodiment, by arranging a shoulder region (shoulder region S2 in the example of FIG. 1) having a small width in the tire width direction on the inner side in the vehicle mounting direction, the tires of the inclined belt layers 3a and 3b. Even when the angle with respect to the circumferential direction is reduced (for example, less than 35 °), both noise performance and steering stability performance can be achieved.

  In the embodiment of FIG. 1, the circumferential belt layers 4 a and 4 b are disposed so as to cover the inclined belt 3. That is, the width W of the widest circumferential belt layer 4a is larger than the width of the widest inclined belt layer 3a. In this way, from the viewpoint of suppressing belt end separation, the width W of the widest circumferential belt layer 4a is made larger than the width of the widest inclined belt layer 3a, and further, The end portion and the end portion of the inclined belt layer 3a are preferably separated from each other by 5 mm or more in the tire width direction.

  As is clear from FIG. 1, in the present embodiment, the inclined belt layer 3a is formed on the carcass 2 (outer in the tire radial direction) straddling the toroidal space between the bead portions 1, and the narrower belt layer 3a is narrower on the 3a. In the inclined belt layer 3b, a circumferential belt layer 4a wider than 3a and 3b is disposed on the 3b, and a circumferential belt layer 4b narrower than 3a and 3b is disposed on the 4a.

  Examples of the present invention will be described below, but the present invention is not limited thereto. Invention tires and comparative tires (both tire sizes are 225 / 45R17) were prototyped under the specifications shown in Table 1 and evaluated for rolling resistance performance and noise performance.

  Each test tire has a carcass straddling in a toroidal shape between a pair of bead portions, and at least one layer of an inclination having a cord that is disposed on the outer side in the tire radial direction of the crown portion of the carcass and that is inclined with respect to the tire circumferential direction. An inclined belt composed of a belt layer; a circumferential belt composed of at least one circumferential belt layer having a cord disposed on the outer side in the tire radial direction of the crown portion of the carcass and extending along the tire circumferential direction; and the circumferential belt And a tread disposed on the outer side in the tire radial direction.

Inventive tires in this example all have a shoulder region (S2 in FIG. 1) with a small width in the tire width direction disposed inside the tire mounting direction.
“Rc / rs” in Table 1 means the ratio of the tire circumferential stiffness rc in the center region to the tire circumferential stiffness rs in the shoulder region.
“Cord angle” in Table 1 means the angle of the cord of the inclined belt layer with respect to the tire circumferential direction.

(Rolling resistance performance)
Each test tire was assembled to an applied rim and an internal pressure of 180 kPa was applied, and then the rolling resistance of the axle was determined using a drum testing machine (speed: 80 km / h) having a steel plate surface with a diameter of 1.7 m. This rolling resistance was measured according to ISO18164 using a smooth drum and force type. The results are shown in Table 1 as an increase rate (%) of the rolling resistance value of each test tire with respect to Comparative Example 1. The increasing rate of the rolling resistance value is a symmetrical narrow width reinforcing structure between the test tires having the same width Wc of the center region C to the maximum width W in the tire width direction of the circumferential belt 4 and the same Wc / W. The rate of increase in the comparison with the comparative example having a maximum of 2% was evaluated as maintaining the rolling resistance performance.

(Noise performance)
After assembling each test tire to the applicable rim, applying an internal pressure of 180 kPa, applying a load of 4.52 N on the running test drum, rotating it at 40 km, 60 km, 80 km, and 100 km per hour, moving the microphone with noise (noise) ) Level was measured and the average of these measurements was calculated. The results shown in Table 1 were evaluated by obtaining a difference from the noise level of the comparative example tire 1. A smaller value means less radiated sound and better noise performance. In addition, increase / decrease in the radiant volume compared with the comparative example which has a symmetrical narrow reinforcement structure between the test tires with the same ratio Wc / W was evaluated.

As shown in Table 1, a tire having a width in the tire width direction of 0.2 to 0.7 times the maximum width in the tire width direction of the circumferential belt 4 including at least the tire equator CL of the circumferential belt 4 With the width direction region as the center region C, the tire circumferential direction rigidity per unit width of any part of the center region C is greater than the tire circumferential direction rigidity per unit width of any part of the adjacent shoulder regions S1 and S2. In the tire of the present invention in which the width Ws1 of one shoulder region S1 is 1.5 times to 8.0 times the width Ws2 of the other shoulder region S2, the noise is maintained while maintaining the rolling resistance performance. It has been found that the performance can be reduced.
More specifically, between the test tires having the same ratio Wc / W, all the inventive examples reduced the radiation volume while maintaining the increase rate of rolling resistance to 2% or less as compared with the comparative example. I found out.
Further, not only when the cord angle of the inclined belt is 60 ° with respect to the tire circumferential direction, but also when the cord angle is 30 °, the rolling resistance is increased in comparison with the comparative example having the same cord angle. It was found that the radiation volume was reduced while maintaining the rate below 2%.

DESCRIPTION OF SYMBOLS 1 Bead part 2 Carcass 3 Inclined belt 3a, 3b Inclined belt layer 4 Circumferential belt 4a, 4b Circumferential belt layer 6 Tread 10 Pneumatic tire 20 Conventional pneumatic tire 7 Applicable rim C Center area CL Tire equator S1, S2 Shoulder region

Claims (3)

An inclined belt comprising a carcass straddling a toroidal shape between a pair of bead portions, and at least one inclined belt layer having a cord which is disposed on the outer side in the tire radial direction of the crown portion of the carcass and which is inclined with respect to the tire circumferential direction. A circumferential belt comprising at least one circumferential belt layer having a cord extending along the tire circumferential direction and disposed on the outer side in the tire radial direction of the crown portion of the carcass, and the tire radial direction of the circumferential belt A pneumatic tire comprising an outer tread,
The circumferential belt includes at least a tire equator, a tire width direction region having a tire width direction width of 0.2 to 0.7 times the maximum width in the tire width direction of the circumferential belt as a center region, The tire circumferential rigidity per unit width of any part of the center region is also higher than the tire circumferential rigidity per unit width of any part of the adjacent shoulder regions,
A pneumatic tire characterized in that the width of one shoulder region is not less than 1.5 times and not more than 8.0 times the width of the other shoulder region.   The pneumatic tire according to claim 1, wherein the number of layers of the circumferential belt layer in the center region is larger than the number of layers in the shoulder region.   The pneumatic tire according to claim 1, wherein the other shoulder region is disposed on a side that is on an inner side in a vehicle mounting direction.

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