Abstract:
The purpose of the present invention is to inhibit deterioration in the external appearance of a sound suppressor, even when used in cold areas. This sound-suppressor-equipped pneumatic tire includes: a pneumatic tire provided with a tread section; and a sponge-like sound suppressor which is affixed to a tire inner cavity-side surface of the tread section, and which extends in the peripheral direction of the tire. In the sound suppressor, a plurality of slits are formed in an exposed surface which faces the tire inner cavity.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a pneumatic tire with a noise damper and a noise damper for a tire, and in particular, relates to a pneumatic tire in which deterioration in the appearance of a noise damper is prevented. 
       BACKGROUND ART 
       [0002]    Conventionally, a pneumatic tire with a sponge-like noise damper attached to a surface on the side of a tire cavity of the tread portion is well known in order to reduce road noise of tires. 
         [0003]    When the above pneumatic tire is used in cold climates, moisture in the air in the tire cavity may freeze and expand in the noise damper. This phenomenon causes a large number of cracks on the noise damper and brings a problem that aggravates its appearance. 
       CITATION LIST 
     Patent Literature 
       [0004]    Patent literature 1: Japanese Unexamined Patent Application Publication No. 2007-112395 
       SUMMARY OF INVENTION 
     Technical Problem 
       [0005]    The present invention has been made in view of circumstances as described above, and has a major object to provide a pneumatic tire with a noise damper and a noise damper for a tire capable of preventing deterioration in appearance of the noise damper, even when used in cold climates, by basically improving an exposed surface of the noise damper. 
       Solution to Problem 
       [0006]    The present invention provides a pneumatic tire with a noise damper including a pneumatic tire having a tread portion, a circumferentially extending sponge-like noise damper being fixed to a surface on a side of a tire cavity of the tread portion, and the noise damper being provided with a plurality of slits on an exposed surface of the tire cavity. 
         [0007]    In the pneumatic with a noise damper according to the present invention, preferably, the slits have a depth in a range of less than 50% of a thickness of the noise damper. 
         [0008]    In the pneumatic with a noise damper according to the present invention, preferably, the depth is in a range of from 2 to 5 mm. 
         [0009]    In the pneumatic with a noise damper according to the present invention, preferably, the slits are arranged at pitches of from 2 to 10 mm in a circumferential direction of the tire. 
         [0010]    In the pneumatic with a noise damper according to the present invention, preferably, the slits are inclined at an angle of less than 20 degrees with respect to an axial direction of the tire. 
         [0011]    In the pneumatic with a noise damper according to the present invention, preferably, the slits include a first slit and a second slit extending in a direction intersecting with the first slit. 
         [0012]    In the pneumatic with a noise damper according to the present invention, preferably, the first slit intersects with the second slit. 
         [0013]    Furthermore, the present invention provides a belt-like and sponge-like noise damper for a tire to be fixed to a surface on a side of a tire cavity of a tread portion of a pneumatic tire along a circumferential direction, the noise damper including a mounting surface for the tread portion and an exposed surface located in an opposite side of the mounting surface, and the exposed surface being provided with a plurality of slits. 
         [0014]    In the noise damper for a tire according to the present invention, preferably, the slits have a depth in a range of less than 50% of a thickness of the noise damper. 
         [0015]    In the noise damper for a tire according to the present invention, preferably, the depth is in a range of from 2 to 5 mm. 
         [0016]    In the noise damper for a tire according to the present invention, preferably, the slits are arranged at pitches of from 2 to 10 mm in a circumferential direction of the tire. 
         [0017]    In the noise damper for a tire according to the present invention, preferably, the slits are inclined at an angle of less than 20 degrees with respect to an axial direction of the tire. 
         [0018]    In the noise damper for a tire according to the present invention, preferably, the slits include a first slit and a second slit extending in a direction intersecting with the first slit. 
         [0019]    In the noise damper for a tire according to the present invention, preferably, the first slit intersects with the second slit. 
       Advantageous Effects of Invention 
       [0020]    The pneumatic tire with a noise damper according to the present invention includes a circumferentially extending sponge-like noise damper fixed to the tread portion on the side of the tire cavity. The noise damper is provided with a plurality of slits on an exposed surface of the tire cavity. Since the slits can open or close by themselves so as to follow expansion deformation of the noise damper based on freezing the moisture in the noise damper in cold climates for example, cracks on the noise damper can be prevented. Furthermore, even when a crack occurs on the noise damper, the slits can make the crack inconspicuous. Therefore, the pneumatic tire with a noise damper according to the present invention can prevent deterioration in the appearance of the noise damper. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0021]      FIG. 1  is a cross-sectional view illustrating a pneumatic tire with a noise damper in accordance with an embodiment of the present invention. 
           [0022]      FIG. 2  is a circumferential cross-sectional view of the pneumatic tire with a noise damper of  FIG. 1 . 
           [0023]      FIG. 3  is a plan view illustrating the noise damper in accordance with the present embodiment. 
           [0024]      FIG. 4  is a plan view illustrating a noise damper in accordance with another embodiment. 
           [0025]      FIG. 5  is a plan view illustrating a noise damper in accordance with yet another embodiment. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0026]    Hereinafter, an embodiment of the present invention will be explained based on the drawings.  FIG. 1  illustrates a cross-sectional view including a tire axis of a pneumatic tire with a noise damper T placed in a standard state in accordance with an embodiment of the present invention. As illustrated in  FIG. 1 , the pneumatic tire with a noise damper T according to the embodiment is suitably used as a passenger car tire, for example. 
         [0027]    Here, the standard state is such that the tire is mounted on a standard wheel rim (not illustrated) with a standard pressure, and is loaded with no tire load. As used herein, unless otherwise noted, a dimension of each portion of the tire refers a value measured under the standard state. 
         [0028]    As used herein, the standard wheel rim is a wheel rim officially approved or recommended for the tire by standards organizations, wherein the standard wheel rim is the “standard rim” specified in JATMA, the “Measuring Rim” in ETRTO, and the “Design Rim” in TRA or the like, for example. Furthermore, the standard pressure is a standard pressure officially approved or recommended for the tire by standards organizations, wherein the standard pressure is the “maximum air pressure” in JATMA, the “Inflation Pressure” in ETRTO, and the maximum pressure given in the “Tire Load Limits at Various Cold Inflation Pressures” table in TRA or the like, for example. In case of a passenger car tire, however, the standard pressure is defined as 180 kPa. 
         [0029]    The pneumatic tire with a noise damper T includes a pneumatic tire (hereinafter simply referred to as “tire”)  1  having a toroidal shape and a circumferentially extending noise damper  10  fixed to a surface  2   b  of tire  1  on the side of a tire cavity N. 
         [0030]    The tire  1  is configured as a tubeless tire, and includes a tread portion  2 , a pair of sidewall portions  3  each extending radially inwardly from each end of the tread portion, and bead portions  4  each provided with a radially inner side of each sidewall portions  3  and each having a bead core  5  therein. 
         [0031]    The tread portion  2  includes a belt layer  7  and a tread rubber  9  disposed radially outward of the belt layer  7 . The tread rubber  9  comes into contact with the ground and is provided with a groove G for draining. 
         [0032]    The tire  1  in accordance with the present embodiment includes a carcass  6 , the belt layer  8  and an inner liner layer  8 . 
         [0033]    The carcass  6  is configured as at least one, one in this embodiment, carcass ply  6 A. The carcass ply  6 A includes a main portion  6   a  and turn-up portions  6   b.  The main portion  6   a,  for example, extends from the tread portion  2  to the bead cores  5  of the bead portions  4  through the sidewall portions  3 . The turn-up portions  6   b  are continued to the main portion  6   a,  and are wound up around the bead cores  5  from the axially inside to the outside of the tire. 
         [0034]    The carcass ply  6 A is configured as a cord ply that includes carcass cords covered with a topping rubber. The carcass cords are oriented at an angle of from 70 to 90 degrees with respect to the tire equator C, for example. Preferably, an organic fiber cord such as rayon, nylon, polyethylene naphthalate (PEN), aramid and the like may be used for the carcass cords. 
         [0035]    A bead apex rubber Ba that extends radially outwardly from the bead core  5  and is made of a hard rubber is disposed between the main portion  6   a  and one of the turn-up portions  6   b  of the carcass ply  6 A in each bead portion. 
         [0036]    The belt layer  7  includes at least one belt ply, two belt plies  7 A and  7 B in this embodiment, having a belt cord oriented at an angle of from 5 to 45 degrees with respect to the tire equator C, for example. For the belt cord, a steel cord is preferably employed, for example. 
         [0037]    The inner liner layer  8  is disposed radially inward of the inner carcass ply  6 A. In this embodiment, the inner liner layer  8  extends continuously between the pair of bead portions  4  and  4 . The inner liner layer  8  is made of a rubber with air impermeable property to prevent air leakage from the tire cavity N. In this embodiment, the inner liner layer  8  forms the surface  2   b  of tire  1  on the side of a tire cavity N. 
         [0038]    The noise damper  10 , for example, is made of a spongy material of porousness with very small holes at its inside and surfaces. The spongy material, for example, is made of rubber or synthetic resin each having an open-cell or closed-cell structure. In the noise damper  10  according to the embodiment, a polyurethane sponge with an open-cell structure is employed. The porous noise damper  10  can absorb vibration energy of the air in the tire cavity N, and thus reduce road noise by preventing cavity resonance. 
         [0039]      FIG. 2  illustrates a circumferential cross-sectional view of the pneumatic tire with a noise damper T. As illustrated in  FIG. 2 , the noise damper  10  according to the present embodiment is configured as a long belt shaped body, and then is formed in an annular shape along the circumferential direction of the tire. In  FIG. 2 , both ends  10   e  and  10   e  of the noise damper  10  are butt-jointed. Alternatively, the both ends  10   e  and  10   e  may be apart from one another. The noise damper  10  can reduce the road noise effectively over the circumferential direction of the tire. 
         [0040]    As illustrated in  FIG. 1 , the noise damper  10 , in the cross-sectional view of the tire, has a flat rectangular shape having an axial width Wa greater than a thickness (ta) in the radial direction of the tire. Such a noise damper  10  can prevent cracks that are caused by vibration or rolling of the tire  1  since the noise damper  10  ensures high rigidity. In order to further improve the effects, the thickness (ta) of the noise damper  10  is preferably in a range of from 0.1 to 0.5 times of the width Wa. 
         [0041]    The cross sectional shape of the noise damper  10  is not limited to a rectangular shape, but may be employed a trapezoidal shape, triangular shape and bullet shape, semi-circular shape and the like, for example. Preferably, the cross sectional shape of the noise damper  10  is configured as symmetrical with respect to the radial line that passes the axially center position of the noise damper. In this embodiment, the noise damper  10  is arranged so that the axial center position is located on the tire equator C. 
         [0042]    It is not particularly limited, but an axial width Wa of the noise damper  10  is preferably in a range of from 30% to 70% of the tread width TW in order to reduce road noise effectively. The thickness (ta) of the noise damper  10  is preferably in a range of from 5 to 50 mm. 
         [0043]    The tread width TW is defined as an axial distance between the tread edges which are axially outermost edges of the ground contact patch that occurs when the tire under the standard state is loaded with a standard tire load at a camber angle of zero. The standard tire load is a tire load officially approved for the tire by standards organizations on which the tire is based, wherein the standard load is the “maximum load capacity” in JATMA, the “Load Capacity” in ETRTO, and the maximum value given in the above-mentioned table in TRA or the like. 
         [0044]    In this embodiment, the noise damper  10  includes a mounting surface  11  to be fixed to the surface  2   b  on the side of the tire cavity N of the tread portion  2  and an exposed surface  12  located in an opposite side of the mounting surface  11 . That is, the exposed surface  12  faces the tire cavity N. 
         [0045]    In this embodiment, the exposed surface  12  includes an axial surface  12   a  extending in the axial direction of the tire and a pair of side surfaces  12   b  and  12   b  each extending in the radial direction to connect the axial surface  12   a  with the mounting surface  11 . 
         [0046]      FIG. 3  illustrates a plan view of the noise damper  10 . As illustrated in  FIG. 3 , the axial surface  12   a  is provided with a plurality of slits  15 . Since the slits  15  can open or close by themselves so as to follow expansion deformation of the noise damper  10  based on freezing the moisture in the noise damper  10  in cold climates for example, cracks on the noise damper  10  can be prevented. Furthermore, even when a crack occurs on the noise damper  10 , the slits  15  can make the crack inconspicuous. Therefore, the present invention can prevent deterioration in the appearance of the noise damper  10  by providing the slits  15 . 
         [0047]    In this embodiment, the slits  15  extend in a straight shape. The slits  15  may open or close themselves in the same direction over the whole length of the slits  15  to offer a large deformation thereof due to freezing. This makes it possible to further prevent cracks from occurring. 
         [0048]    When the widths W 1  of the slits  15  are too large, there is a possibility that effect to reduce road noise may not be obtained owing to a reduced volume of the noise damper  1 . Preferably, the widths of the slits  15  are equal to or less than 2 mm. The slits  15  may be formed as a cut that has substantially no width in order to make cracks inconspicuous. However, the widths W 1  of the slits  15  are preferably equal to or more than 0.5 mm in order to ensure opening/closing deformation of the slits smoothly based on freezing of moisture of the noise damper  10 . 
         [0049]    The slits  15  are preferably provided such that the slits  15  extend from axially both ends  10   a  and  10   a  of the noise damper  10  and have an axial length not less than 20% of the axial width Wa of the noise damper  10 . That is, the noise damper  10  has small rigidity in axially both end portions as compared with an axially middle portion. Thus, there is high possibility that cracks occur on the axially both end portions of the noise damper  10 . Accordingly, it would effectively obtain the effect preventing cracks by providing the slits  15  in the above mentioned manner. In this embodiment, the slits  15  are in communication with the both ends  10   a  and  10   a  of the noise damper  10 . 
         [0050]    Preferably, the slits  15  have a depth D 1  (illustrated in  FIG. 1 ) in a range of not more than 50% of the thickness (ta) of the noise damper  10 . When the depth D 1  of the slits  15  is more than 50% of the thickness (ta) of the noise damper  10 , cracks or chipping may occur on the noise damper  10  owing to shortage of rigidity of the noise damper  10 . 
         [0051]    When the depth D 1  of the slits  15  is too small, the effect to prevent cracks may be lower since the opening/closing deformation of the noise damper  10  becomes small during freezing the moisture in the noise damper  10 . Thus, the depth D 1  of the slits  15  is preferably in a range of from 2 to 5 mm. 
         [0052]    When the circumferential pitches P 1  of the slits  15  is more than 10 mm, the effect that prevents cracks when freezing and that makes cracks inconspicuous tends to be lower. When the circumferential pitches P 1  of the slits  15  is less than 2 mm, cracks or chipping may occur on the noise damper  10  owing to shortage of rigidity of the noise damper  10 . Preferably, the circumferential pitches P 1  of the slits  15  is in a range of from 2 to 10 mm. 
         [0053]    As the present embodiment, the noise damper  10  having an annular shape tends to have lower rigidity in the axial direction than the circumferential direction. Thus, there is high possibility that axially extending cracks occur in the noise damper  10 . Accordingly, the slits  15  are preferably provided to have an angle θ 1  of not more than 20 degrees with respect to the axial direction of the tire. In this embodiment, the slits  15  have the angle θ 1  of zero degrees. 
         [0054]      FIG. 4  illustrates a plan view of the noise damper  10  in accordance with another embodiment. As illustrated in  FIG. 4 , the slits  15  provided on the exposed surface  12  of the noise damper  10  include first slits  16  and second slits  17  extending in a direction intersecting with the first slits  16 . Such a slit can follow expansion deformation of the noise damper  10  in various directions occurring when freezing, and can further prevent cracks from the noise damper  10 . In this embodiment, the first slits  16  and the second slits  17  are arranged alternately in the circumferential direction of the tire. Note that the present invention is not limited to the present embodiment. Alternatively, the slits  15  may be arranged so that a group having a plurality of circumferentially successive first slits  16  and another group having a plurality of circumferentially successive second slits  17  are arranged alternately in the circumferential direction of the tire. 
         [0055]      FIG. 5  illustrates a plan view of the noise damper  10  in accordance with yet another embodiment. As illustrated in  FIG. 5 , the exposed surface  12  is provided with the first slits  16  and the second slits  17  which intersect with each other. In the slits  15  according to the present embodiment, one first slit  16  and one second slits  17  adjacent the first slit  16  can open or close themselves to follow the expansion deformation of the noise damper  10  so as to further prevent cracks of the noise damper  10  from occurring. 
         [0056]    The absolute value of the difference |θ 2 -θ 3 | between an angle θ 2  of the first slits  16  relative to the axial direction of the tire and an angle θ 3  of the second slits  17  relative to the axial direction of the tire is preferably not more than 10 degrees, more preferably not more than 5 degrees. Thus, the first slits  16  and the second slits  17  can open and close themselves in the circumferential direction of the tire in good balance when the expansion deformation is caused by freezing of the water in the noise damper  10 . In particular, this embodiment can prevent an axially extending crack from occurring. Accordingly, deterioration in appearance of the noise damper  10  can be suppressed. 
         [0057]    In order to open the first slits  16  or the second slit  17  in the circumferential direction more widely, the angles θ 2  and θ 3  relative to the axial direction of the first slits  16  and the second slits  17  respectively are preferably not more than 45 degrees, more preferably not more than 20 degrees. 
         [0058]    In order to further improve the effects as described above, circumferential pitches P 2  of the first slits  16  are preferably equal to circumferential pitches of the second slit  17 . Preferably, the pitches P 2  of the first slits  16  are in a range of from 2 to 10 mm. Preferably, the first slits  16  and the second slits  17  have a depth in a range of not more than 50% of the thickness (ta) in the radial direction of the noise damper  10 , more preferably in a range of from 2 to 5 mm. 
         [0059]    While a particularly preferred embodiments of the present invention have been described in detail, the present invention is not be limited to the embodiments as shown, but it may be carried out by modifying to various aspects. 
       EXAMPLE 
       [0060]    Passenger car tires 215/45R17 having a basic structure as illustrated in  FIG. 1  and  FIG. 2  were manufactured based on details shown in Table 1, and were tested. Major common specifications of each test tire and test methods are as follows: 
         [0061]    Noise damper width Wa: 100 mm 
         [0062]    Noise damper thickness ta: 30 mm 
         [0063]    Noise damper: ether-based polyurethane sponge (ESH2 manufactured by INOAC CORPORATION) 
         [0064]    First slit and second slit depths: 5 mm 
         [0065]    First slit pitches P2 and second slit pitches P3: 5 mm 
         [0066]    Note that Ref. 1 and Ref. 2 have no slits. 
       Anti-Cracking Performance 
       [0067]    Each test tire was run on a drum test machine with a diameter of 1.7 m under the following conditions. Then, developmental state of cracks of the noise damper was confirmed after the rim had been removed. The results are indicated in five-point method with scored, regarding crack generation state, by the evaluation methods described below. The larger the value, the better the performance is. Note that each test tire with a noise damper moistened with 50 cc of water was left in a freezer at −30 degrees C. for twelve hours prior to the test. 
         [0068]    Rim: 17×7.0JJ 
         [0069]    Internal pressure: 220 kPa 
         [0070]    Tire load: 4.2 kN 
         [0071]    Speed: 60 km/h 
         [0072]    Running time: 5 minutes 
       Evaluation Method for Crack Generation State 
       [0073]    1: Crack with over 50 mm length occurred. 
         [0074]    2: No cracks with over 50 mm length, but five or more cracks occurred. 
         [0075]    3: No cracks with over 50 mm length, but one to four crack(s) occurred. 
         [0076]    4: Crack symptoms exist. 
         [0077]    5: No crack symptoms exist. 
       Appearance Performance 
       [0078]    After the above mentioned test, appearance of each noise damper of each test tire was checked. The results are indicated using a score based on appearance of the exposed surface, wherein Ex. 1 is set to five points. The larger the value, the better the performance is. 
         [0000]    
       
         
               
               
               
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
             
             
               
                   
                 Ref. 1 
                 Ex. 1 
                 Ex. 2 
                 Ex. 3 
                 Ex. 4 
                 Ex. 5 
                 Ex. 6 
                 Ex. 7 
                 Ex. 8 
                 Ex. 9 
                 Ex. 10 
               
               
                   
               
               
                 Figure illustrating slit shape 
                 — 
                 FIG. 3 
                 FIG. 3 
                 FIG. 3 
                 FIG. 3 
                 FIG. 3 
                 FIG. 3 
                 FIG. 3 
                 FIG. 3 
                 FIG. 3 
                 FIG. 3 
               
               
                 Slit depth (mm) 
                 — 
                 5 
                 1 
                 2 
                 10 
                 25 
                 5 
                 5 
                 5 
                 5 
                 5 
               
               
                 Slit pitches P1 (mm) 
                 — 
                 2 
                 2 
                 2 
                 2 
                 2 
                 1 
                 10 
                 15 
                 2 
                 2 
               
               
                 Slit angle θ1 (deg.) 
                 — 
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
                 20 
                 25 
               
               
                 Crack generating state [five 
                 1 
                 4 
                 3 
                 4 
                 4 
                 4 
                 4 
                 4 
                 4 
                 4 
                 3 
               
               
                 point method: larger is better] 
               
               
                 Appearance 
                 2 
                 5 
                 4 
                 5 
                 5 
                 4 
                 4 
                 5 
                 4 
                 4 
                 3 
               
               
                 [Score: larger is better] 
               
               
                   
               
             
          
           
               
                   
                   
                 Ref. 2 
                 Ex. 11 
                 Ex. 12 
                 Ex. 13 
                 Ex. 14 
                 Ex. 15 
                 Ex. 16 
                 Ex. 17 
               
               
                   
                   
               
               
                   
                 Figure illustrating slit shape 
                 — 
                 FIG. 5 
                 FIG. 5 
                 FIG. 5 
                 FIG. 5 
                 FIG. 5 
                 FIG. 5 
                 FIG. 5 
               
               
                   
                 First slit angle θ2 (deg.) 
                 — 
                 45 
                 45 
                 45 
                 45 
                 20 
                 20 
                 20 
               
               
                   
                 Second slit angle θ3 (deg.) 
                 — 
                 45 
                 35 
                 30 
                 55 
                 20 
                 10 
                 30 
               
               
                   
                 Crack generating state [five point 
                 1 
                 4 
                 4 
                 3 
                 3 
                 4 
                 4 
                 3 
               
               
                   
                 method: larger is better] 
               
               
                   
                 Appearance 
                 1 
                 5 
                 4 
                 3 
                 4 
                 4 
                 4 
                 4 
               
               
                   
                 [Score: larger is better] 
               
               
                   
                   
               
             
          
         
       
     
         [0079]    From the test results, it was confirmed that the example tires suppress deterioration in appearance of the noise damper as compared with the reference tires. 
       REFERENCE SIGNS LIST 
       [0080]      1  Pneumatic tire 
         [0081]      2  Tread portion 
         [0082]      2   b  Surface of tread portion on tire cavity side 
         [0083]      10  Noise damper 
         [0084]      12  Exposed surface 
         [0085]      15  Slit 
         [0086]    N Tire cavity