JP2012218595A - Assembly of pneumatic tire and rim - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an assembly of a pneumatic tire and the rim having a sound absorbing device for further reducing noise, by reducing cavity resonance in a tire cavity, by being configured such that a sound absorbing material forms a plurality of layer shapes in the tire circumferential direction, by adopting a material for permeating air as the sound absorbing material, in a sound absorbing structure in the tire cavity.SOLUTION: This assembly of the pneumatic tire and the rim forms the tire cavity 32 between the pneumatic tire and the rim by installing the pneumatic tire 30 in the rim 31. The assembly of the pneumatic tire and the rim has one or more sound absorbing devices 33 installed in an air valve 40 in the assembly and arranged so as to be capable of intercepting a space in the tire circumferential direction in the tire cavity. The sound absorbing device 33 has an installation part to the assembly inside, a front sound absorbing layer 36 constituted of a porous sound absorbing material and a rear sound absorbing layer 37 constituted of the porous sound absorbing material.

Description

  The present invention relates to a pneumatic tire and rim assembly that reduces road noise of a running vehicle.

  In recent years, there has been a demand for further reduction in noise and quietness with respect to noise during travel of vehicles such as automobiles. There are various types of noise generated when a vehicle such as an automobile travels. Among them, the noise generated by tires is a so-called road called “go” in a frequency range of 50 to 400 Hz when traveling on a rough road surface. There is noise, and this road noise is transmitted to the inside of the vehicle, which makes the passengers uncomfortable. Among such road noises, a phenomenon that has a large influence mainly on 200 to 250 Hz, and when a pneumatic tire is mounted on a rim, a cavity formed around the rim and surrounded by the tire and the rim constitutes an air column tube. Some air is generated by resonance vibration (cavity resonance).

  Therefore, as a technique for reducing resonance generated in the cavity inside the tire and reducing noise transmitted to the inside of the vehicle, as shown in Patent Documents 1 and 2 below, an object for sound absorption and sound insulation is arranged in the cavity. A method has been proposed.

  In the following Patent Document 1, in an assembly of a pneumatic tire and a rim, one or more rising portions that rise in the tire radial direction from the outer peripheral surface of the rim by the centrifugal force accompanying the rotation of the assembly and block the tire lumen are arranged. The rising portion has a structure including a sound absorbing portion made of a nonwoven fabric at least partially. The rising portion is not limited to being formed from a cut piece obtained by cutting the band base so long as it rises in the tire lumen and does not transmit sound waves. Has been. Further, it is shown that the band base is made of stretchable vulcanized rubber and has a thickness of 0.5 to 3 mm before rim mounting. Furthermore, it has been shown that the thickness of the nonwoven fabric is less than 10 mm.

  Patent Document 2 below shows a tire having a bubble layer that is bonded to the inner wall of the tire at two beads and is not bonded to the other portions, that is, at the sidewall and crown. And it is shown that this bubble layer is not mostly bonded to the inner wall of the tire, so that this bubble layer exhibits a damping action on the peak of the first cavity mode. That is, the porous sound-absorbing material is disposed in the tire cavity, and has a structure in which a reduction effect is obtained when sound is transmitted in the cross-sectional direction of the tire.

JP 2001-347807 A JP 2008-273517 A

  However, the sound absorbing structures described in Patent Documents 1 and 2 have a drawback that the sound absorbing effect is small because a material that does not transmit sound waves is used, and therefore noise reduction due to cavity resonance in the tire cavity is not sufficient. It was.

  Therefore, as a result of intensive research, the present inventor adopted a material that transmits sound while attenuating sound waves as a sound absorbing material in the sound absorbing structure in the tire cavity, and the sound absorbing material forms a plurality of layers in the tire circumferential direction. By constructing as described above, a pneumatic tire and rim assembly having a sound absorbing device capable of reducing cavity resonance in the tire cavity and further reducing noise has been developed.

  The pneumatic tire and rim assembly according to the present invention is a pneumatic tire and rim assembly that forms a tire cavity between the pneumatic tire and the rim by mounting the pneumatic tire on the rim. And having one or more sound absorbing devices that are attached to the assembly and arranged so as to block a space in the tire circumferential direction within the tire cavity, and the sound absorbing devices are connected to the inside of the assembly. It has an attachment part, a front sound-absorbing layer made of a porous sound-absorbing material and front and rear sound-absorbing layers made of a porous sound-absorbing material.

  In the above configuration, the acoustic impedances of the porous sound absorbing material of the front sound absorbing layer and the porous sound absorbing material of the rear sound absorbing layer may be different from each other.

  Furthermore, the said structure WHEREIN: It is good also as a structure which has an intermediate | middle sound absorption layer from which an acoustic impedance differs between a front part sound absorption layer and a rear part sound absorption layer.

  Furthermore, in the configuration having the intermediate sound absorbing layer, the intermediate sound absorbing layer may include an air layer.

  In the configuration having the intermediate sound absorbing layer, the front sound absorbing layer and the rear sound absorbing layer may be the same porous sound absorbing material.

  Further, in the structure having the intermediate sound absorbing layer, the assembly is provided with an air valve that is an air inlet, and the front sound absorbing layer and the rear sound absorbing layer are formed by continuously forming their side surfaces. It is good also as a structure which is formed by the thickness layer of the cylindrical body, and the one end part of this hollow cylindrical body is an attaching part with respect to the said air valve.

  The sound-absorbing mechanism of the porous sound-absorbing material is obtained by analyzing the phenomenon in which sound waves pass through the porous sound-absorbing material from the air. The sound waves from the air are first the boundary surface between the air layer and the porous sound-absorbing material layer. If it enters the interface, it is divided into a first reflected wave bounced off by the first interface and an internal approach wave entering the inside of the porous sound absorbing material layer. A part of the internal approach wave passes through the porous sound absorbing material and is released into the air while being attenuated by a part of the sound absorbing material changing from acoustic energy to thermal energy in the porous sound absorbing material. When passing through, the attenuated internal approach wave enters the second interface which is the boundary surface between the porous sound-absorbing material layer and the air layer, and the internal reflected wave and the first external emission wave bounced back by the second interface Divided. Among these, the internal reflected wave reciprocates between the first interface and the second interface, and each time it enters the first interface and the second interface, the minute amount of internal reflected wave and the porous material remaining inside the porous sound absorbing material layer. It splits into a minute amount of externally emitted wave emitted to the outside of the sound absorbing material layer, and the minute amount of internally reflected wave that remains inside the porous sound absorbing material layer every time the division is repeated attenuates as its acoustic energy changes to thermal energy, It will mute over time. Therefore, when sound waves are incident on the porous sound absorbing material from the air, only the first reflected wave and the first external emitted wave are obtained except for a negligible amount of the externally emitted wave.

  For example, when the porous sound absorbing material has one layer with respect to the propagation direction of the sound wave P, the interface has two locations, a first interface that enters the sound absorbing material from the air layer and a second interface that exits from the sound absorbing material to the air layer. Thus, sound waves are attenuated by thermal conversion only at one location of the sound absorbing material layer between the first interface and the second interface. Therefore, when the porous sound absorbing material is a single layer, in order to improve the noise reduction effect, the thickness of the sound absorbing material can only be increased, but the volume of the entire sound absorbing device composed of the porous sound absorbing material increases. There is.

  On the other hand, a sound absorbing material is formed by stacking a front sound absorbing layer a made of a porous sound absorbing material with respect to the propagation direction of the sound wave P and a rear sound absorbing layer b made of a porous sound absorbing material having a different acoustic impedance from the front sound absorbing layer a. In the case of two layers, the interfaces are from the first interface that is incident from the air layer to the front sound absorbing layer a, the second interface that is incident from the front sound absorbing layer a to the rear sound absorbing layer b, and the rear sound absorbing layer b. The sound wave is attenuated due to thermal conversion in three places with the third interface through the air layer, and the rear sound absorption layer between the front interface, the second interface, and the third interface between the first interface and the second interface. There are two places with the layer. The front sound absorbing layer a made of the porous sound absorbing material and the rear sound absorbing layer b having a different acoustic impedance from the front sound absorbing layer a may be bonded together. Therefore, in comparison with the above-mentioned case of the sound absorbing material 1 layer, the thickness of the sound absorbing material 1 layer is the same as the thickness of the sound absorbing material 2 layer obtained by adding the thickness of the rear sound absorbing layer b to the thickness of the front sound absorbing layer a. In the two-layer sound absorbing material, the number of times that the sound wave is split increases by at least the number of interfaces, and every time the sound wave is split, the sound wave passes through the sound absorbing material and is attenuated by heat conversion. large. In addition, since the number of interfaces increases as the number of layers to be stacked increases, attenuation is repeated with the division of sound waves, so that the noise reduction effect is further increased.

  Furthermore, when an air layer is interposed as an intermediate layer between the front sound-absorbing layer a made of a porous sound-absorbing material and the rear sound-absorbing layer b also made of a porous sound-absorbing material, the interface is located in front of the external air layer. A first interface that enters the sound absorbing layer a, a second interface that passes from the front sound absorbing layer a to the intermediate layer, a third interface that enters the rear sound absorbing layer b from the intermediate layer, and an external air layer from the rear sound absorbing layer b It becomes four places with the 4th interface which passes through, and attenuation by heat conversion at the time of passing through a sound-absorbing material becomes two places, front sound absorption layer a and rear sound absorption layer b. Therefore, in comparison with the case of the above-described one sound absorbing material, when the thickness of the sound absorbing material 1 layer is the same as the thickness of the front sound absorbing layer a plus the thickness of the rear sound absorbing layer b, two sound absorbing materials are used. If an air layer is provided between the two, the number of sound wave splits increases as the number of interfaces increases, and each time the sound wave splits, the sound wave passes through the sound absorbing material layer and is attenuated by heat conversion. growing. Also in the production, if one sound absorbing material layer is divided into two parts and arranged with an interval, an air layer is interposed as an intermediate layer between the front sound absorbing layer a and the rear sound absorbing layer b. There is an advantage that it can be manufactured easily. When the intermediate layer is formed of a new sound absorbing material having a different acoustic impedance from the front sound absorbing layer a and the rear sound absorbing layer b, the sound absorbing material 1 layer is further superimposed on the two sound absorbing materials. Since a new sound-absorbing material layer in which sound waves are attenuated by thermal conversion is added, the noise reduction effect is increased.

  From the above, if it is the same thickness as compared with the case of one layer of sound absorbing material, a laminated body with another sound absorbing material having different acoustic impedance is used, or one layer of sound absorbing material is divided into a plurality of layers. This will increase the noise reduction effect.

  By configuring the pneumatic tire and rim assembly of the present invention as described above, in the sound absorbing structure in the tire cavity, a material that transmits air is used as the sound absorbing material, and the sound absorbing material is arranged in the tire circumferential direction. Since it is configured so as to form a plurality of layers, a sound absorbing device that reduces cavity resonance in the tire cavity and can further reduce noise is provided.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partially omitted perspective view of a tire radial direction cross section according to Example 1 of the present invention. It is a schematic diagram which shows the structure of the sound-absorbing device which concerns on Example 1 of this invention. It is explanatory drawing which shows the permeation | transmission state of the sound wave in the sound absorber which concerns on Example 1 of this invention. It is a partially-omission perspective view of the tire radial direction cross section concerning Example 2 of the present invention. It is a schematic diagram of a tire radial direction cross section according to Example 2 of the present invention. It is a schematic diagram which shows the structure of the sound-absorbing material which concerns on Example 2 of this invention. It is explanatory drawing which shows the permeation | transmission state of the sound wave in the sound absorber which concerns on Example 2 of this invention. It is a schematic diagram of a tire circumferential direction cross section according to Example 2 of the present invention. It is a partially-omission perspective view of a tire radial direction cross section concerning Example 3 of the present invention. It is a schematic diagram of the tire radial direction cross section which concerns on Example 3 of this invention. It is a schematic diagram of a tire circumferential direction cross section according to Example 3 of the present invention.

  Preferred embodiments of a pneumatic tire and rim assembly according to the present invention will be described below in detail with reference to the accompanying drawings.

  1 to 3 relate to the first embodiment. In FIG. 1, reference numeral 10 denotes a pneumatic tire, 11 denotes a rim, and the tire includes a pneumatic tire 10 fitted into the rim 11. A cavity 12 is formed, and a sound absorbing device 13 is arranged on the rim 11 so as to block a space in the tire circumferential direction in the tire cavity. The sound absorbing device 13 includes a mounting portion 14 on the rim 11 and a sound absorbing material portion 15, and the sound absorbing material portion 15 includes a front sound absorbing layer 16 made of a porous sound absorbing material, and the front sound absorbing layer 16 and sound. A rear sound absorbing layer 17 made of a porous sound absorbing material having different impedance is laminated by adhesion. In addition, it is desirable to use urethane as the porous sound-absorbing material because it does not interfere with the rim assembly because it can be knocked down when the rim is assembled.

  With such a configuration, as shown in FIG. 2, sound waves generated by cavity resonance generated in the tire cavity pass through the front sound absorbing layer 16 and the rear sound absorbing layer 17. That is, when a sound wave enters the front sound absorbing layer 16 from the external air layer, as shown in FIG. 3, the first external emission wave and the front sound absorbing light reflected by the first interface 10A that is the surface of the front sound absorbing layer 16. It is divided into a first internal approach wave that enters the inside of the layer 16. The first internal approach wave that has entered the front sound absorbing layer 16 travels while being attenuated by thermal conversion, and enters the second interface 10B that is a boundary surface between the front sound absorbing layer 16 and the rear sound absorbing layer 17. The first internal approach wave incident on the second interface 10B is divided into a first internal reflected wave reflected by the second interface 10B and a second internal approach wave entering the rear sound absorbing layer 17. The second internal approach wave that has entered the rear sound absorbing layer 17 travels while being attenuated by thermal conversion, and enters the third interface 10 </ b> C formed by the back surface of the rear sound absorbing layer 17 and the external air layer. The second internal approach wave incident on the third interface 10C is divided into a minute external emission wave and a second internal reflected wave reflected by the third interface 10C.

  On the other hand, the first internally reflected wave reflected by the second interface 10B travels while being attenuated by thermal conversion in the front sound absorbing layer 16, and enters the first interface 10A. The first internal reflected wave incident on the first interface 10A is divided into a minute amount of externally emitted wave and a third internal reflected wave. The third internal reflected wave reflected by the first interface 10A then follows the same process as the first internal approach wave.

  Further, the second internally reflected wave reflected by the third interface 10C travels while being attenuated by thermal conversion in the rear sound absorbing layer 17, and enters the second interface 10B.

  As described above, when the sound wave enters the front sound absorbing layer 16 from the external air layer, the sound absorbing device 13 in this embodiment is divided into the first external emission wave and the first internal approach wave, and the first internal approach wave is Then, reciprocation is repeated between the first interface 10A and the second interface 10B, between the second interface 10B and the third interface 10C, and between the first interface 10A and the third interface 10C. Each time it passes through the sound absorbing layer 16 and the rear sound absorbing layer 17, it disappears while being attenuated by thermal conversion, and a small amount of externally emitted waves that are almost negligible are emitted from the first interface 10A and the third interface 10C to the outside. become. Therefore, the sound wave incident on the sound absorbing device 13 from the external air layer is substantially only the first external emission wave.

  In addition, if a material having a high sound absorbing effect is employed for the sound absorbing layer in which sound waves are first incident from the external air layer among the front sound absorbing layer 16 and the rear sound absorbing layer 17 constituting the sound absorbing device 13 described above, Since the first external emission wave becomes smaller, the cavity resonance in the tire cavity is further reduced. In addition, it is preferable to employ a material having a high sound absorbing effect for both the front sound absorbing layer 16 and the rear sound absorbing layer 17 without considering the directionality of sound waves due to cavity resonance in the tire cavity. Further, if a plurality of sound absorbing devices 13 in this embodiment are installed in the tire cavity, the sound absorbing device 13 has the same effect as described above, and the first external reflected wave remaining in the tire cavity is transmitted to other sound absorbing devices. The incident light is further attenuated, so that the sound absorption effect is enhanced and the cavity resonance in the tire cavity is further reduced.

  4 to 8 relate to Example 2. In FIGS. 4 and 5, 20 is a pneumatic tire, 21 is a rim, and an assembly in which the pneumatic tire 20 is fitted into the rim 21 is shown. A tire cavity 22 is sometimes formed, and a sound absorbing device 23 is disposed on the rim 21 so as to block a space in the tire circumferential direction in the tire cavity. The sound absorbing device 23 includes a mounting portion 24 on the rim 21 and a sound absorbing material portion 25. The sound absorbing material portion 25 is the same as the front sound absorbing layer 26 made of a porous sound absorbing material, and a rear sound absorbing material made of a porous sound absorbing material. An intermediate sound absorbing layer 28 having an acoustic impedance different from that of the layer 27 is provided. The intermediate sound absorbing layer in the present embodiment is an air layer, but a porous sound absorbing material having an acoustic impedance different from that of the front sound absorbing layer 26 and the rear sound absorbing layer 27 may be used. As the porous sound-absorbing material, it is desirable to use urethane as it can be knocked down when assembling the rim, so that it does not interfere with the rim assembly.

  With this configuration, as shown in FIG. 6, sound waves generated by cavity resonance generated in the tire cavity pass through the front sound absorbing layer 26, the intermediate sound absorbing layer 28, and the rear sound absorbing layer 27. That is, when a sound wave enters the front sound absorbing layer 26 from the external air layer, the first external emission wave and the front sound absorbing light reflected by the first interface 20A that is the surface of the front sound absorbing layer 26 are shown in FIG. The first internal approach wave that enters the layer 26 is divided. The first internal approach wave that has entered the front sound absorbing layer 26 travels while being attenuated by thermal conversion, and enters the second interface 20B formed by the back surface of the front sound absorbing layer 26 and the intermediate sound absorbing layer 28. The first internal approach wave incident on the second interface 20B is divided into a first internal reflected wave reflected by the second interface 20B and a first external advance wave that advances to the intermediate sound absorbing layer 28. The first external advancing wave that has advanced to the intermediate sound absorbing layer 28 travels through the intermediate sound absorbing layer 28 and enters the third interface 20 </ b> C that is the surface of the rear sound absorbing layer 27. The first external advancing wave incident on the third interface 20 </ b> C is divided into a first external reflected wave reflected by the third interface 20 </ b> C and a second internal incoming wave entering the rear sound absorbing layer 27. The second internal approach wave that has entered the rear sound absorbing layer 27 travels while being attenuated by thermal conversion, and enters the fourth interface 20D formed by the back surface of the rear sound absorbing layer 27 and the external air layer. The second internal approach wave incident on the fourth interface 20D is divided into a minute external emission wave and a second internal reflection wave that is reflected by the fourth interface 20D and enters the rear sound absorbing layer 27.

  On the other hand, the first internally reflected wave reflected by the second interface 20B enters the front sound absorbing layer 26, travels while being attenuated by thermal conversion, and enters the first interface 20A. The first internal reflection wave incident on the first interface 20A is divided into a minute external emission wave and a third internal reflection wave reflected by the first interface 20A. The third internal reflected wave reflected by the first interface 20A then follows the same process as the first internal approach wave.

  Further, the first externally reflected wave reflected by the third interface 20C travels through the intermediate sound absorbing layer 28 and enters the second interface 20B. The first external reflected wave incident on the second interface 20B is divided into a third internal incoming wave that enters the front sound absorbing layer 26 and a second external reflected wave that is reflected by the second interface 20B. The third internal approach wave that has entered the inside of the front sound absorbing layer 26 then follows the same process as the first internal reflected wave. Thereafter, the second external reflected wave follows the same process as the first external advancing wave.

  The second internal reflected wave reflected by the fourth interface 20D travels while being attenuated by thermal conversion in the rear sound absorbing layer 27, and enters the third interface 20C. The second internal reflection wave incident on the third interface 20C is divided into a fourth internal reflection wave reflected by the third interface 20C and a second external advance wave that advances to the intermediate sound absorbing layer 28. The fourth internal reflected wave reflected by the third interface 20C then follows the same process as the second internal approach wave. The second external advancing wave that has advanced to the intermediate sound absorbing layer 28 then follows the same process as the first external reflected wave.

  As described above, when the sound wave enters the front sound absorbing layer 26 from the external air layer, the sound absorbing device 23 in this embodiment is divided into the first external emission wave and the first internal approach wave, and the first internal approach wave is Then, between the first interface 20A and the second interface 20B, between the second interface 20B and the third interface 20C, between the third interface 20B and the fourth interface 20D, and between the first interface 20A and the third interface. 20C, reciprocating between the second interface 20B and the fourth interface 20D, and between the first interface 20A and the fourth interface 20D, and passing through the front sound absorbing layer 26 and the rear sound absorbing layer 27. Each time it disappears while being attenuated by thermal conversion, a negligible amount of externally emitted waves are emitted from the first interface 20A and the fourth interface 20D to the outside. Therefore, the sound wave incident on the sound absorbing device 23 from the external air layer is substantially only the first external emission wave.

  In addition, if a material having a high sound absorption effect is employed for the sound absorbing layer in which sound waves are first incident from the external air layer among the front sound absorbing layer 26 and the rear sound absorbing layer 27 constituting the sound absorbing device 23, Since the first external emission wave becomes smaller, the cavity resonance in the tire cavity is further reduced. In addition, it is preferable to employ a material having a high sound absorbing effect for both the front sound absorbing layer 26 and the rear sound absorbing layer 27 without considering the directionality of sound waves due to cavity resonance in the tire cavity. Furthermore, if a plurality of sound absorbing devices 23 in the present embodiment are installed in the tire cavity, the sound absorbing device 23 has the same effect as described above, and the first external reflected wave remaining in the tire cavity is transmitted to other sound absorbing devices. The incident light is further attenuated, so that the sound absorption effect is enhanced and the cavity resonance in the tire cavity is further reduced.

  In the case of the second embodiment, even when the single-layer sound-absorbing material is arranged with an interval, it can be regarded as a plurality of layers including an intermediate air layer. If the distance between the front sound absorbing layer 26 and the rear sound absorbing layer 27 is increased, it cannot be said that the front sound absorbing layer 26 and the rear sound absorbing layer 27 are opposed to each other. Since it is difficult to obtain the effect of transmitting a plurality of times (the reflected wave is directed to the inner surface of the tire, not to the opposing sound absorbing material), as shown in FIG. 8, it is within 30 ° from the central axis of the assembly. It is desirable to arrange the front sound absorbing layer 26 and the rear sound absorbing layer 27 at intervals.

[Comparison test]
Regarding the case where the intermediate sound absorbing layer 28 made of an air layer was provided between the front sound absorbing layer 26 and the rear sound absorbing layer 27, the following measurement was performed. That is, a microphone arranged in front of the speaker and a microphone arranged at a distance of 1 meter in the sound propagation direction are prepared, and a gap is provided between the two porous microphones having the same total thickness. A comparison test of attenuation of transmitted sound was conducted with and without spacing. The sound-absorbing materials 1 and 2 used as spaced in the comparative test are 100 mm wide, 150 mm high, and 15 mm thick, and the sound-absorbing material used as not spaced is 100 mm wide and high. The thickness is 150 mm and the thickness is 30 mm. This comparative test is a comparative test when not mounted on a tire, and represents “a reduction effect at 250 Hz” as an index. A higher index indicates a better reduction effect. The results are shown in Table 1.

  In addition, the following comparative test was performed. This comparative test is a comparative test when mounted on a tire. That is, for a sound absorbing material having a layer structure as an example and a sound absorbing material not having a layer structure as a comparative example, a tire having a size of 215 / 55R17 is assembled on a general automobile wheel having a rim size of 17 × 7-JJ (pneumatic pressure). 230 kPa). The sound absorbing materials 1 and 2 used in this comparative test are 100 mm wide, 150 mm high, and 15 mm thick. The sound absorbing material used as a case where there is no gap is 100 mm wide, 150 mm high, and 30 mm thick. It is. In the drum test, in a drum (outer periphery 5364.5 mm) having an uneven surface such as asphalt, while rotating the drum at a speed of 60 km / h, a load of 4.4 kN was applied to the tire in the drum direction, ) The force applied to the direction and longitudinal axes was measured, and the respective peak levels in the cavity resonance frequency range were compared. Note that vehicle interior noise at a frequency position of 500 Hz or less is mainly individual propagation transmitted through a structure (from the suspension to the body), and the tire axial force is related to vehicle interior noise. The “index of axial force energy” in this comparative test indicates that the lower the value, the better the reduction effect. The results are shown in Table 2.

  As a result, it was found that even when the sound absorbing material having the same thickness is disposed, the transmitted sound is reduced when the sound absorbing material is spaced.

  9 to 11 relate to the third embodiment. In FIG. 9, reference numeral 30 denotes a pneumatic tire, reference numeral 31 denotes a rim, and the tire is the assembly in which the pneumatic tire 30 is fitted into the rim 31. A cavity 32 is formed, and in the assembly, the sound absorbing device 33 is disposed so as to block the space in the tire circumferential direction in the tire cavity. The sound absorbing device 33 includes an attachment portion 34 to an air valve 40 that is an air inlet to the assembly and a sound absorbing material portion 35, and the sound absorbing material portion 35 includes a front sound absorbing layer 36 and a rear sound absorbing layer 37. However, it forms a hollow cylindrical shape made of a porous sound-absorbing material continuous on its side surface, and the hollow portion becomes the intermediate sound-absorbing layer 38. In addition, it is not restricted to a hollow cylinder shape, What is necessary is just a hollow cylinder shape. In addition, it is desirable to use urethane as the porous sound-absorbing material because it does not interfere with the rim assembly because it can be knocked down when the rim is assembled. When the sound absorbing device 33 is attached to the air valve 40, because the air valve 40 is an air inflow port, the inside is formed into a hollow cylinder as in the third embodiment, and the hole and the hollow portion of the air valve 40 are communicated with each other. This is reasonable in that it does not hinder air filling, and since there is an air valve 40 on the rim 31 side, it does not hinder tire assembly. It is desirable to have a one-point soft structure.

  With this configuration, as shown in FIGS. 10 and 11, sound waves generated by cavity resonance generated in the tire cavity pass through the front sound absorbing layer 36, the intermediate sound absorbing layer 38, and the rear sound absorbing layer 37. . This sound wave transmission state is the same as that described in the second embodiment. That is, when sound waves are incident on the front sound absorbing layer 36 from the external air layer, the first external emission wave and the front sound absorbing light reflected by the first interface 30A that is the surface of the front sound absorbing layer 36, as shown in FIG. The first internal approach wave that enters the layer 36 is divided. The first internal approach wave that has entered the front sound absorbing layer 36 travels while being attenuated by thermal conversion, and enters the second interface 30B formed by the back surface of the front sound absorbing layer 36 and the intermediate sound absorbing layer 38. The first internal approach wave incident on the second interface 30B is divided into a first internal reflected wave reflected by the second interface 30B and a first external advance wave that advances to the intermediate sound absorbing layer 38. The first external advancing wave that has advanced to the intermediate sound absorbing layer 38 travels through the intermediate sound absorbing layer 38 and enters the third interface 30 </ b> C that is the surface of the rear sound absorbing layer 37. The first external advancing wave incident on the third interface 30 </ b> C is divided into a first external reflected wave reflected by the third interface 30 </ b> C and a second internal incoming wave entering the rear sound absorbing layer 37. The second internal approach wave that has entered the rear sound absorbing layer 37 travels while being attenuated by heat conversion, and enters the fourth interface 30D formed by the back surface of the rear sound absorbing layer 37 and the external air layer. The second internal approach wave incident on the fourth interface 30D is divided into a minute external emission wave and a second internal reflection wave that is reflected by the fourth interface 30D and enters the rear sound absorbing layer 37. On the other hand, the first internally reflected wave reflected by the second interface 30B enters the front sound absorbing layer 36, travels while being attenuated by thermal conversion, and enters the first interface 30A. The first internal reflected wave incident on the first interface 30A is divided into a minute external emission wave and a third internal reflected wave reflected by the first interface 30A. The third internally reflected wave reflected by the first interface 30A then follows the same process as the first internally approaching wave. Further, the first externally reflected wave reflected by the third interface 30C travels through the intermediate sound absorbing layer 38 and enters the second interface 30B. The first external reflected wave incident on the second interface 30B is divided into a third internal incoming wave that enters the front sound absorbing layer 36 and a second external reflected wave that is reflected by the second interface 20B. The third internal approach wave that has entered the inside of the front sound absorbing layer 36 then follows the same process as the first internal reflected wave. Thereafter, the second external reflected wave follows the same process as the first external advancing wave. The second internally reflected wave reflected by the fourth interface 30D travels while being attenuated by thermal conversion in the rear sound absorbing layer 37 and enters the third interface 30C. The second internal reflected wave incident on the third interface 30C is divided into a fourth internal reflected wave reflected by the third interface 30C and a second external advancing wave that advances to the intermediate sound absorbing layer 38. The fourth internal reflected wave reflected by the third interface 30C then follows the same process as the second internal approach wave. The second external advancing wave that has advanced to the intermediate sound absorbing layer 38 then follows the same process as the first external reflected wave.

  As described above, when the sound wave enters the front sound absorbing layer 36 from the external air layer, the sound absorbing device 33 in this embodiment is divided into the first external emission wave and the first internal approach wave, and the first internal approach wave is Then, between the first interface 30A and the second interface 30B, between the second interface 30B and the third interface 30C, between the third interface 30B and the fourth interface 30D, and between the first interface 30A and the third interface. 30C, reciprocating between the second interface 30B and the fourth interface 30D, and between the first interface 30A and the fourth interface 30D, and passing through the front sound absorbing layer 36 and the rear sound absorbing layer 37. Each time it disappears while being attenuated by thermal conversion, a very negligible external emission wave is emitted from the first interface 30A and the fourth interface 30D to the outside. Therefore, the sound wave incident on the sound absorbing device 33 from the external air layer is substantially only the first external emission wave.

  Further, if a material having a high sound absorbing effect is adopted for the sound absorbing layer constituting the sound absorbing device 33, the first externally emitted wave is reduced, so that the cavity resonance in the tire cavity is further reduced. .

  Regarding the sound absorbing device 33 attached to the air valve 40, the following comparative test was performed when the sound absorbing device 33 was attached and when the sound absorbing device 33 was not attached. A tire of size 215 / 55R17 was assembled on a general automobile wheel having a rim size of 17 × 7-JJ (air pressure 230 kPa). In the drum test, in a drum (outer periphery 5364.5 mm) having an uneven surface such as asphalt, while rotating the drum at a speed of 60 km / h, a load of 4.4 kN was applied to the tire in the drum direction, ) The force applied to the direction and longitudinal axes was measured, and the respective peak levels in the cavity resonance frequency range were compared. Note that vehicle interior noise at a frequency position of 500 Hz or less is mainly individual propagation transmitted through a structure (from the suspension to the body), and the tire axial force is related to vehicle interior noise. The “index of axial force energy” in this comparative test indicates that the lower the value, the better the reduction effect. The results are shown in Table 3. In Table 3, the case where the sound absorbing device 33 is attached to the air valve 40 is described as “sound absorbing valve”, and the case where the sound absorbing device 33 is not attached to the air valve 40 is described as “normal valve”.

  As a result, the effect of reducing resonance generated in the tire internal cavity was clearly obtained even at one location in the cavity.

  In addition, the assembly of the pneumatic tire and the rim according to the present invention is not limited to the above-described embodiments, and various embodiments are possible without departing from the configurations described in the claims.

DESCRIPTION OF SYMBOLS 10 ... Pneumatic tire 11 ... Rim 12 ... Tire cavity 13 ... Sound absorption device 14 ... Attachment part 15 ... Sound absorption material part 16 ... Front sound absorption layer 17 ... Rear part Sound absorbing layer 10A ... first interface 10B ... second interface 10C ... third interface 20 ... pneumatic tire 21 ... rim 22 ... tire cavity 23 ... sound absorbing device 24 ... mounting part 25 ... sound absorbing material portion 26 ... front sound absorbing layer 27 ... rear sound absorbing layer 28 ... intermediate sound absorbing layer 20A ... first interface 20B ... second interface 20C ... third interface 20D ... 4th interface 30 ... Pneumatic tire 31 ... Rim 32 ... Tire cavity 33 ... Sound absorbing device 34 ... Mounting part 35 ... Sound absorbing material part 36 ... Front sound absorbing layer 37 ..Sound absorbing layer 38 ... Intermediate sound absorbing layer 30A ... First interface 30B ... Second field Surface 30C ... Third interface 30D ... Fourth interface 40 ... Air valve

Claims (6)

A pneumatic tire and rim assembly that forms a tire cavity between the pneumatic tire and the rim by attaching the pneumatic tire to the rim,
Having one or more sound absorbing devices mounted in the assembly and arranged to block a tire circumferential space in the tire cavity;
The sound absorbing device has a mounting portion inside the assembly, a front sound absorbing layer made of a porous sound absorbing material and front and rear sound absorbing layers made of a porous sound absorbing material in the tire circumferential direction. Pneumatic tire and rim assembly.   2. The pneumatic tire and rim assembly according to claim 1, wherein acoustic impedances of the porous sound absorbing material of the front sound absorbing layer and the porous sound absorbing material of the rear sound absorbing layer are different.   The pneumatic tire / rim assembly according to claim 1, further comprising an intermediate sound absorbing layer having different acoustic impedance between the front sound absorbing layer and the rear sound absorbing layer.   4. The pneumatic tire and rim assembly according to claim 3, wherein the intermediate sound absorbing layer includes an air layer.   5. The pneumatic tire and rim assembly according to claim 3, wherein the front sound absorbing layer and the rear sound absorbing layer are the same porous sound absorbing material.   The assembly is provided with an air valve that is an air inlet, and the front sound-absorbing layer and the rear sound-absorbing layer are formed by a thick layer of a hollow cylindrical body formed by continuously connecting their side surfaces, 6. The pneumatic tire and rim assembly according to claim 5, wherein one end of the hollow cylindrical body is a mounting portion for the air valve.

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