Method for detecting abnormal position of uninflated tire

Abstract

To provide an appropriate detection method for an abnormal position of a non-pneumatic tire.SOLUTION: This detection method for an abnormal position of a non-pneumatic tire includes: a step at which noise generated by a non-pneumatic tire is measured from a side surface direction of the non-pneumatic tire by use of a microphone array including a plurality of microphones in the state that the non-pneumatic tire grounds and rotates on a ground plane; a step at which a rotation angle of the non-pneumatic tire from a reference point is measured; a step at which the sound pressure distribution on a side surface of the non-pneumatic tire is calculated from the noise by near distance field acoustic holography processing; and a step at which an abnormal position of the non-pneumatic tire is specified from the sound pressure distribution and the rotation angle.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a method for detecting an abnormal position in an unpneumatic tire, and more particularly to a method for identifying an abnormal position by performing sound source probing on an unpneumatic tire in synchronization with the rotation angle. [Background technology]

[0002] Tires are important components that support the load from a vehicle and affect the ride comfort, safety, etc. of the vehicle. Various methods have been available for inspecting the safety, etc. of tires. For example, Patent Document 1 discloses a method for identifying the source of an abnormal sound in a tread pattern using a microphone array installed ahead of the tire in the traveling direction. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5089253 Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, non-pneumatic tires, which do not require inflation, have been attracting attention. Non-pneumatic tires have the advantage of not requiring maintenance for issues such as loss of air pressure or punctures. However, non-pneumatic tires have a different configuration from pneumatic tires, and therefore may experience abnormalities specific to non-pneumatic tires, creating a need for an appropriate method for detecting abnormal positions. The method of Patent Document 1 does not consider detecting abnormal positions in non-pneumatic tires, and there is still room for improvement.

[0005] SUMMARY OF THE INVENTION An object of the present invention is to provide a method for detecting the abnormal position of an uninflated tire. [Means for solving the problem]

[0006] The method for detecting an abnormal position of a non-pneumatic tire according to the present invention is characterized by comprising the steps of: measuring noise generated by the non-pneumatic tire from the side direction of the non-pneumatic tire using a microphone array including a plurality of microphones while the non-pneumatic tire is in contact with the ground and rotating; measuring the rotation angle of the non-pneumatic tire from a reference point; calculating the sound pressure distribution on the side of the non-pneumatic tire from the noise using near-field acoustic holography processing; and identifying the abnormal position of the non-pneumatic tire from the sound pressure distribution and the rotation angle. [Effects of the Invention]

[0007] The detection method according to the present invention makes it possible to identify the abnormal position of an uninflated tire. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a side view of a non-pneumatic tire according to an example embodiment; [Figure 2] FIG. 1 is a block diagram of a detection device according to an embodiment. [Figure 3] FIG. 2 is a diagram illustrating the positional relationship between a non-pneumatic tire and a microphone array in an example embodiment. [Figure 4] FIG. 1 is a diagram showing a sound pressure distribution applied to the side of a non-pneumatic tire in an example embodiment. [Figure 5] FIG. 2 is a diagram illustrating reference points of a non-pneumatic tire in an example embodiment. [Figure 6] 1 is a flowchart illustrating an overall detection method according to an embodiment. [Figure 7] FIG. 4 is a diagram corresponding to FIG. 3 in another example of the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] An example of a detection method according to the present invention will be described in detail below with reference to the drawings. The embodiment described below is merely an example, and the present invention is not limited to the following embodiment. Furthermore, configurations formed by selectively combining the components of the multiple embodiments and variations described below are included in the present invention. In this specification, the "main rotation direction" of the non-pneumatic tire 1 refers to the rotation direction when a vehicle equipped with the non-pneumatic tire 1 moves forward. Furthermore, the term "substantially constant" is used as an example to describe a direction that is considered to be substantially constant, as well as completely constant.

[0010] A non-pneumatic tire 1, which is the subject of the present invention, will be described with reference to Fig. 1. Fig. 1 is a side view of a non-pneumatic tire 1 according to an example of an embodiment.

[0011] The non-pneumatic tire 1 has an inner ring 5, an outer ring 7, and a plurality of spokes 9. The outer shape of the non-pneumatic tire 1 is circular. The inner ring 5 is fixed to an axle of a vehicle. From the viewpoint of improving uniformity, the inner ring 5 preferably has, for example, a cylindrical shape with a substantially constant thickness.

[0012] The outer ring 7 is concentric with the inner ring 5 and is provided outside the inner ring 5 in the tire radial direction. From the viewpoint of improving uniformity, the outer ring 7 preferably has, for example, a cylindrical shape with a substantially constant thickness. The outer ring 7 includes, for example, a support layer 7a, a reinforcing layer 7b, and a tread layer 7c, in that order from the inside in the tire radial direction. As will be described later, the support layer 7a, together with the inner ring 5 and the spokes 9, constitutes a support structure that supports the load from the vehicle. The reinforcing layer 7b is composed of, for example, steel cords or cords made of fiber-reinforced plastics such as CFRP and GFRP arranged substantially parallel to the tire width direction, a cylindrical metal ring, or a high-modulus resin ring. The tread layer 7c is composed of, for example, rubber, resin, or the like, similar to conventional pneumatic tires, and may have a tread pattern on its outer circumferential surface, similar to conventional pneumatic tires.

[0013] The spokes 9 are arranged between the inner ring 5 and the outer ring 7, and connect the inner ring 5 and the outer ring 7 to each other. In FIG. 1, the spokes 9 are indicated by dot hatching. The spokes 9 have, for example, a plate shape. A plurality of spokes 9 are arranged in parallel in the tire circumferential direction, and there are gaps between the spokes 9. From the viewpoint of improving uniformity, it is preferable that these gaps be approximately constant.

[0014] 1, the spokes 9 linearly connect the inner ring 5 and the outer ring 7. The spokes 9 are inclined in the axial direction. For example, two adjacent spokes 9 may be inclined in opposite directions to each other in the axial direction.

[0015] The shape of the spokes 9 and the arrangement and number of the spokes 9 are not limited to the example of this embodiment. The spokes 9 may extend in a curved manner rather than linearly in the tire radial direction as shown in FIG. 1. Furthermore, the gaps between the spokes 9 may extend in a curved manner rather than linearly in the tire radial direction as shown in FIG. 1. The number of spokes 9 is, for example, 4 to 200.

[0016] The inner ring 5, the support layer 7a, and the spokes 9 constitute a support structure that supports the load from the vehicle. The material of the support structure is not particularly limited, but for example, the support structure is formed of an elastic material. For example, a thermoplastic elastomer such as a polyester elastomer, a crosslinked rubber such as natural rubber, or other resins (for example, a thermoplastic resin such as a polyethylene resin, or a thermosetting resin such as a polyurethane resin) may be used as the base material of the support structure. For example, a reinforcing material such as a fiber or a metal cord may be embedded inside the base material.

[0017] Next, with reference to Figures 2 to 7, a method for detecting an abnormal position of the non-pneumatic tire 1, more specifically, a method for identifying the abnormal position by performing sound source detection on the non-pneumatic tire in synchronization with the rotation angle, will be described.

[0018] 2 is a block diagram of a detection device 10 according to this embodiment. The detection device 10 includes a microphone array 12 that measures noise, and an acoustic holography device 14 that calculates a sound pressure distribution from the measured noise using near-field acoustic holography processing.

[0019] The detection device 10 further includes a rotation amount measuring device 16 that measures the amount of rotation of the non-pneumatic tire 1. The computer 18 is connected to the acoustic holography device 14 and the rotation amount measuring device 16, and by combining data obtained from these devices, the abnormal position of the non-pneumatic tire 1 is identified as described below. The detection device 10 may also include an output device 19 such as a display that displays the results of calculations by the computer 18.

[0020] Measurement of noise generated by the non-pneumatic tire 1 is performed while the non-pneumatic tire 1 is rotating and in contact with the road surface G, as shown in FIG. 3. The non-pneumatic tire 1 is in contact with the road surface G at the contact surface 20. FIG. 3 is a diagram showing the positional relationship between the non-pneumatic tire 1 and the microphone array 12 in an example of an embodiment. The direction of rotation is, for example, the main rotation direction R. It is preferable to measure the noise in an environment suitable for sound measurement, such as an anechoic chamber or a semi-anechoic chamber.

[0021] The detection method according to this embodiment is performed with the non-pneumatic tire 1 pressed against a road surface G and with a load applied to the non-pneumatic tire 1. In this embodiment, the road surface G is a flat belt, and the rotational speed of the non-pneumatic tire 1 can be controlled by changing the moving speed of the flat belt. The road surface G is not limited to a flat surface, and may be the curved surface of a drum.

[0022] The road surface G is preferably smooth. The road surface G preferably has a mean profile depth (MPD), which is a roughness index, of less than 0.3. The material of the road surface G is, for example, steel.

[0023] The microphone array 12 may be installed, for example, so as to cover substantially the entire side surface of the non-pneumatic tire 1. This makes it possible to measure noise generated from abnormal positions on the non-pneumatic tire 1 over the entire side surface of the non-pneumatic tire 1. Note that in FIG. 3 , the vicinity of the contact patch 20 of the non-pneumatic tire 1 is not covered by the lattice of the microphone array 12, but near-field acoustic holography processing, which will be described later, can be performed without any problems.

[0024] In this embodiment, a plurality of microphones 25 are arranged in a grid pattern to form the microphone array 12. In the example shown in Fig. 3, eight microphones 25 are arranged at approximately equal intervals in the vertical direction and eight microphones 25 are arranged at approximately equal intervals in the horizontal direction to form the microphone array 12. Note that the arrangement and number of microphones 25 that form the microphone array 12 are not limited to this example, and for example, the microphones 25 may be arranged in a pattern other than a grid pattern.

[0025] It is preferable that the vertical spacing s between the microphones 25 is substantially the same as the horizontal spacing t between the microphones 25. In other words, it is preferable that the lattice formed by the microphones 25 is a square lattice.

[0026] The distances s and t between the microphones 25 are preferably 25 mm to 85 mm, and more preferably 25 mm to 50 mm. This allows near-field acoustic holography processing to be performed while reducing the influence of normal running sounds, including noise derived from the tread pattern. The upper frequency limit of near-field acoustic holography depends on the distances s and t. The upper frequency limit of near-field acoustic holography is 6400 Hz when the distances s and t are 25 mm, 3200 Hz when the distances s and t are 50 mm, and 2000 Hz when the distances s and t are 85 mm. By setting the distances s and t within the above ranges, it is possible to measure noise generated from abnormal positions on the non-pneumatic tire 1 while avoiding frequencies where normal running sounds are dominant (below 2000 Hz).

[0027] The microphone 25 is, for example, a probe microphone. Examples of the probe microphone include those with a measuring tip having a diameter of 1 / 2, 1 / 4, or 1 / 8 inch. It is preferable that the distance between the side surface of the non-pneumatic tire 1 and the tip of the microphone 25 constituting the microphone array 12 is approximately the same as the intervals s and t.

[0028] The acoustic holography device 14 uses the measured noise to perform near-field acoustic holography processing to calculate the sound pressure distribution on the side surface of the non-pneumatic tire 1. As the acoustic holography device 14, a commercially available device can be used.

[0029] 4 is a diagram showing a sound pressure distribution applied to the side of a non-pneumatic tire 1 in one example of an embodiment. When the non-pneumatic tire 1 is rotated while being pressed against a road surface G, noise is generated from an abnormal position in the non-pneumatic tire 1. By applying the sound pressure distribution obtained by near-field acoustic holography processing to the side of the non-pneumatic tire 1, as shown in FIG. 4, the abnormal position in the non-pneumatic tire 1 is measured as a sound pressure increase portion 40 where sound pressure is increased in the sound pressure distribution.

[0030] In parallel with noise measurement, the detection device 10 measures the rotation amount of the non-pneumatic tire 1 using a rotation amount measurement device 16. Examples of the rotation amount measurement device 16 include a rotation pulse meter that obtains one pulse signal per tire rotation, and a wheel encoder that obtains multiple pulse signals per tire rotation.

[0031] As will be described later, a reference point 50 is set on the non-pneumatic tire 1, and then the amount of rotation of the non-pneumatic tire 1 is measured, thereby making it possible to measure the rotation angle from the reference point 50. This makes it possible to identify the abnormal position of the non-pneumatic tire 1 from the positional relationship between the sound pressure increase portion 40 and the reference point 50.

[0032] More specifically, noise is measured for each unit angle of the rotating non-pneumatic tire 1. At this time, noise measurement data for each unit angle is averaged to evaluate the sound pressure distribution for each unit angle. This unit angle is the resolution of the rotation angle of the non-pneumatic tire 1. It is preferable that the resolution of the unit angle be equal to or greater than the number of spokes of the non-pneumatic tire 1. For example, if the number of spokes is 100, it is preferable that the unit angle be 3.6 degrees or less.

[0033] There may be multiple sound pressure increase portions 40 on the side surface of the non-pneumatic tire 1. For sound pressure increase portions 40 on the side surface of the non-pneumatic tire 1 that are included in at least the rear quarter of the range in the direction of rotation from the position corresponding to the center of the contact patch 20, it is possible to estimate whether the abnormality is in the outer ring 7 or the spokes 9, as described below. Here, the center of the contact patch 20 refers to a point on the side surface of the non-pneumatic tire 1 that is equidistant from both ends of the contact patch 20.

[0034] If the angle θ formed by the line connecting the center of the sound pressure increase portion 40 and the center O of the non-pneumatic tire 1 and the perpendicular line drawn from the center O to the contact surface 20 is between 0° and 10°, it may be determined that an abnormality has occurred in the outer ring 7 corresponding to the sound pressure increase portion 40.

[0035] Possible abnormalities in the outer ring 7 include, for example, cracks occurring in the reinforcing layer 7b, separation between the reinforcing layer 7b and the tread layer 7c, and separation between the support layer 7a and the reinforcing layer 7b. The cause of the sound pressure increase portion 40 occurring in the above-mentioned part of the non-pneumatic tire 1 is presumed to be contact between the layers constituting the peeled outer ring 7 at the contact surface 20.

[0036] If the angle θ formed by the line connecting the center of the sound pressure increase portion 40 to the center O of the non-pneumatic tire 1 and the perpendicular line drawn from the center O to the contact surface 20 is between 10° and 60°, it may be determined that an abnormality has occurred in the spoke corresponding to the sound pressure increase portion 40.

[0037] When the angle θ is between 10° and 60°, the abnormality position in the spoke corresponding to the sound pressure increase portion 40 may be identified in the tire radial direction based on the distance L from the center O of the non-pneumatic tire 1 of the center P of the sound pressure increase portion 40. Note that when the angle θ is 10°, the abnormality may be identified as occurring in either the outer ring 7 or the spoke based on the distance L. More specifically, if the distance L is approximately the same as the radius of the outer ring 7, it may be identified that the abnormality has occurred in the outer ring 7, and if the distance L is smaller than the radius of the outer ring 7, it may be identified that the abnormality has occurred in the spoke.

[0038] Possible abnormalities in the spokes 9 include, for example, breaks or cracks in the spokes 9, and separation between the spokes 9 and the outer ring 7. The cause of the sound pressure increase portion 40 occurring in the above-mentioned portion of the non-pneumatic tire 1 is presumed to be that the non-pneumatic tire 1 is significantly deformed near the contact patch 20, causing buckling and contact of the abnormal portion of the spoke 9 in the above-mentioned portion rearward of the contact patch 20 in the direction of rotation.

[0039] 5 is a diagram illustrating a reference point 50 of a non-pneumatic tire 1 in one example of an embodiment. The reference point 50 is set, for example, between two adjacent spokes (9a, 9b) among the plurality of spokes 9. More specifically, the reference point 50 is set in a gap g between the connection portion 30a and the connection portion 30b where the adjacent spokes 9a and 9b connect to the outer ring 7, respectively. The reference point 50 is, for example, a point in the gap g that is equidistant from both the connection portion 30a and the connection portion 30b.

[0040] 6 is a flowchart showing the procedure of the detection method according to this embodiment. In step S1, the rotation angle of the non-pneumatic tire 1 from the reference point 50 is measured. Step S1 is performed by the rotation amount measuring device 16.

[0041] In step S2, the noise generated by the non-pneumatic tire 1 is measured from the side direction of the non-pneumatic tire 1. Step S2 is performed using a microphone array 12 including a plurality of microphones 25 as shown in FIG.

[0042] In step S3, near-field acoustic holography processing is performed from the noise obtained in step S2 to calculate the sound pressure distribution on the side of the non-pneumatic tire 1. Step S3 is performed by the acoustic holography device 14.

[0043] In step S4, the position of the abnormality in the non-pneumatic tire 1 is identified based on the rotation angle obtained in step S1 and the sound pressure distribution obtained in step S3. Furthermore, based on the positional relationship between the sound pressure increase portion 40 and the contact patch 20, it may be further determined whether the abnormality has occurred in the outer ring 7 or the spokes 9.

[0044] Steps S1 and S2 are performed in parallel. Steps S1 and S2 may be performed continuously. Alternatively, step S1 may be performed continuously while step S2 is performed intermittently, or step S2 may be performed continuously while step S1 is performed intermittently.

[0045] Step S3 may be performed in parallel with step S2 or after step S2 is completed. The detection method according to this embodiment ends with step S4, in which the sound pressure distribution and rotation angle data are analyzed to identify the abnormal position of the non-pneumatic tire 1.

[0046] Fig. 7 is a diagram showing the positional relationship between the non-pneumatic tire 101 and the microphone array 112 in another example of the embodiment. As shown in Fig. 7, the microphone array 112 is disposed facing the side of the non-pneumatic tire 101 over at least a quarter of the range rearward in the rotational direction from a position corresponding to the center of the contact patch 120. This allows the number of microphones to be reduced compared to when a microphone array is configured to cover the entire side of the non-pneumatic tire 101.

[0047] As described above, the detection method according to the present invention can appropriately detect the location of an abnormality in an unpneumatic tire. Furthermore, by performing a more detailed analysis, it is possible to estimate which part of the unpneumatic tire has an abnormality. [Explanation of symbols]

[0048] 1,101 Non-pneumatic tire, 5 inner ring, 7 outer ring, 9 spokes, 10 detection device, 12,112 microphone array, 14 acoustic holography device, 16 rotation amount measurement device, 18 calculation device, 19 output device, 20 contact surface, 25,125 microphone, 30a, 30b connection part, 40 sound pressure rise part, 50 reference point, θ angle

Claims

1. measuring noise generated by the non-pneumatic tire from a side direction of the non-pneumatic tire using a microphone array including a plurality of microphones while the non-pneumatic tire is in contact with the ground and rotating on the ground surface; calculating a sound pressure distribution on a side surface of the non-pneumatic tire from the noise by near-field acoustic holography processing; measuring a rotation angle of the non-pneumatic tire from a reference point; and identifying an abnormal position of the non-pneumatic tire from the sound pressure distribution and a rotation angle of the non-pneumatic tire from a reference point.

2. 2. The method for detecting an abnormal position of an unpneumatic tire according to claim 1, wherein the plurality of microphones in the microphone array are arranged in a grid pattern, and the microphones are spaced apart from one another at intervals of 25 mm to 85 mm.

3. 3. The method for detecting an abnormal position of a non-pneumatic tire according to claim 1, wherein the microphone array is arranged to face the side of the non-pneumatic tire within a range of at least one-quarter of the tire rearward in the direction of rotation from a position corresponding to the center of the contact patch.

4. The non-pneumatic tire has an inner ring, an outer ring provided on the outer side of the inner ring in the tire radial direction, and a plurality of spokes connecting the inner ring and the outer ring to each other, 4. The method for detecting an abnormal position of a non-pneumatic tire according to claim 1, wherein the reference point is set between two adjacent spokes of the plurality of spokes.

5. When the angle formed by the line connecting the center of the sound pressure increase portion and the center of the non-pneumatic tire and the perpendicular line drawn from the center of the non-pneumatic tire to the ground contact surface is defined as θ, If the angle θ is between 0° and 10°, it is determined that an abnormality has occurred in the outer ring corresponding to the portion where the sound pressure has increased, 5. The method for detecting an abnormal position in a non-pneumatic tire according to claim 4, wherein when the angle θ is between 10° and 60°, it is determined that an abnormality has occurred in the spoke corresponding to the portion where sound pressure has increased.

6. 6. The method for detecting an abnormal position in a non-pneumatic tire according to claim 5, further comprising the step of: when θ is between 10° and 60°, identifying an abnormal position in a spoke corresponding to the portion of increased sound pressure in the radial direction of the tire based on the distance from the center of the non-pneumatic tire to the center of the portion of increased sound pressure.

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