JP5816587B2 - Tire wear state detection method and tire wear state detection device - Google Patents

Description

  The present invention relates to a method and apparatus for detecting the wear state of a running tire.

Conventionally, at least three types of monitoring rubber members having different colors from the rubber of the tread rubber layer are laminated and embedded at the bottom of the tread rubber layer, and an image of the tread is photographed by taking an image of the tire tread. And the method of monitoring the abrasion state of a tire by determining whether the data (color data) of the rubber member for monitoring is contained in the image is proposed (for example, refer patent document 1).
Also, an acceleration sensor is provided on the inner surface side of the inner liner portion of the tire to detect the radial acceleration of the tire, and the deformation obtained from the deformation time that is the time difference between two peaks corresponding to the bulging point appearing in this acceleration waveform A method for estimating the degree of tire wear from the relationship between the length X and the contact length L obtained from the contact time, which is the time difference between the two peaks corresponding to the contact point appearing in the differential waveform obtained by differentiating the acceleration waveform, is proposed. (For example, refer to Patent Document 2).

JP 2006-123703 A JP 2009-19950 A

However, in the method described in Patent Document 1, not only the tire needs to be processed, but also when the rubber having physical properties different from the rubber of the tread rubber layer is exposed on the tread surface, the grip force of the tire is reduced. There was a problem such as.
Further, in the method described in Patent Document 2, it is not only necessary to provide a transmitter, an antenna, and the like in the tire, but because the configuration is such that data of the acceleration sensor is sent to the vehicle body side by communication, noise is likely to enter and measurement is performed. The accuracy was not always sufficient.

  The present invention has been made in view of conventional problems, and an object of the present invention is to provide a method and an apparatus for detecting the wear state of a running tire without providing a sensor in the tire.

準静電界は磁界成分を含まず、また、電波のように伝搬する性質がなく、人や車両、物質の周りに静電気帯電電界のように分布し、その極性またはレベルが変化する。
本発明者らは、鋭意検討の結果、タイヤの摩耗状態によりタイヤと路面間の接触状態及び摩擦状態が異なることから、車体外表面の帯電電位の変化を検出することで、タイヤの摩耗状態を検知できることを見出し、本発明に至ったものである。 In general, it is known that a charging potential is generated between a tire and a road surface due to contact, separation, and friction between the tire and the road surface (for example, the background art of Japanese Patent Application Laid-Open No. 2011-225023). On the other hand, since the vehicle body and the tire are capacitively coupled, a potential corresponding to the charged potential generated between the tire and the road surface is generated on the outer surface of the vehicle body.
The electric field distributed on the tire surface or the outer surface of the vehicle body is one of the electric fields generated by the minute dipole antenna at the distance r shown in the following formula (1), and is obtained from the solution by the Maxwell equation. Formula (1) includes three elements constituting an electromagnetic field (a radiated electromagnetic field proportional to 1 / r, an induction electromagnetic field proportional to 1 / r ² , and a quasi-electrostatic field proportional to 1 / r ³ ), The third term is an electric field distributed on the tire surface or the outer surface of the vehicle body, and changes with time from the rolling of the tire as the vehicle travels.

The quasi-electrostatic field does not include a magnetic field component, does not have the property of propagating like radio waves, is distributed around a person, vehicle, or substance like an electrostatic charging electric field, and its polarity or level changes.
As a result of intensive studies, the present inventors have found that the tire wear state is detected by detecting the change in the charging potential on the outer surface of the vehicle body, because the contact state and the friction state between the tire and the road surface differ depending on the tire wear state. It has been found that it can be detected, and has led to the present invention.

The present invention is a method for detecting the wear state of a running tire, a detection step for detecting a charging potential distributed in a vehicle body by contact, separation and friction between the tire and a road surface, and the detection step. And a detection step of detecting the wear state of the tire from a change in the time change waveform accompanying a change in the tire wear state.
Thereby, the wear state of the tire can be detected without providing a sensor in the tire.
Moreover, since it is not necessary to transmit the detected data by radio | wireless etc., while being able to simplify an apparatus, the detection precision of a tire wear state improves.

Further, the present invention provides a specific peak number that is the number of specific peaks that appear in the time-varying waveform and whose charging potential change amount is a peak larger than the average value of amplitude per unit period, a plurality of times per unit period. A counting step for counting is provided, and the wear state of the tire is detected from the appearance frequency of the specific peak number in the detection step.
As described above, if the wear state of the tire is detected from the appearance frequency of the specific peak number obtained by counting the number of specific peaks appearing in the time-varying waveform a plurality of times per unit period, the detection accuracy of the tire wear state is further improved. Can be improved.

Further, the present invention is characterized in that, in the counting step, an RMS value per unit period is obtained from the time change waveform, and the RMS value is used as an average value of amplitude per unit period.
Thus, since the RMS value that changes depending on the road surface unevenness state and the vehicle speed is the average value of the amplitude per unit period, unnecessary peaks caused by the road surface unevenness state and the vehicle speed can be surely eliminated. The detection accuracy of the tire wear state can be further improved.

Further, in the counting step, the positive peak and the negative peak are extracted from the time change waveform in the counting step, and the positive peak amplitude value and the negative peak amplitude value are When the peak value difference exceeds the RMS value, the positive peak or the negative peak is determined as a specific peak, and the determined specific peak The specific peak number that is a number is counted, and in the detection step, a frequency distribution of the specific peak number per unit period is obtained, and the wear state of the tire is detected from the appearance frequency of the specific peak number.
Thereby, since the determination accuracy of the specific peak number is further improved, the appearance frequency of the specific peak number can be accurately obtained.

In the detection step, the frequency distribution of the specific peak number is approximated by a Weibull distribution in the detection step to calculate a scale parameter and a shape parameter of the probability density function of the Weibull distribution, and the calculated shape parameter Alternatively, the wear state of the tire is detected from the scale parameter and the shape parameter.
Thereby, since the difference in the frequency distribution of the specific peak number can be quantified, it is possible to easily determine the wear state of the tire.

Further, the present invention is an apparatus for detecting the wear state of a running tire, a detection unit for detecting a charged potential distributed on a vehicle body by contact, separation and friction between the tire and a road surface, and detection by the detection unit. A monitoring unit that monitors a time change waveform of the charged potential, and a detection unit that detects a wear state of the tire from a change in the time change waveform accompanying a change in the tire wear state, and the detection unit includes the time A counting means for counting a specific number of peaks, which is the number of specific peaks that appear in a change waveform and whose amount of change in charging potential is a peak larger than an average value of amplitude per unit period, a plurality of times per unit period; And detecting means for detecting the wear state of the tire from the appearance frequency of the number of peaks.
By adopting such a configuration, it is possible to realize a tire wear state detection device that can reliably detect the wear state of a tire without providing a sensor and a radio device on the tire.

  The summary of the invention does not list all necessary features of the present invention, and sub-combinations of these feature groups can also be the invention.

It is a figure which shows the structure of the tire wear condition detection apparatus which concerns on this embodiment. It is the schematic which shows the structure of a monitoring part and a detection part. It is a figure which shows an example of the time change waveform of a charging voltage. It is an enlarged view of the time change waveform of a charging voltage. It is a figure which shows an example of the histogram showing the frequency distribution of the frequency | count of appearance of a specific peak. It is a figure which shows the probability density function of a Weibull distribution. It is a histogram showing the time distribution waveform of the charging voltage of a new tire and the frequency distribution of the number of appearances of a specific peak. It is a histogram showing the time distribution waveform of the charging voltage of a worn tire and the frequency distribution of the number of appearances of a specific peak. It is a flowchart which shows the tire wear state detection method. It is a figure which shows the other structure of a reference electrode.

  Hereinafter, the present invention will be described in detail through embodiments, but the following embodiments do not limit the invention according to the claims, and all combinations of features described in the embodiments are included. It is not necessarily essential for the solution of the invention.

FIG. 1 is a diagram illustrating a configuration of a tire wear state detection device 1 according to the present embodiment.
The tire wear state detection device 1 includes a detection electrode 11, a reference electrode 12, a sensor amplifier 13, a charging waveform extraction means 14, an RMS (Root Mean Square) value calculation means 15, a peak counting means 16, and a peak frequency. A distribution creating means 17, a storage means 18, and a tire wear state detecting means 19 are provided.
Each means from the detection electrode 11 to the sensor amplifier 13 constitutes a detection unit 1A that detects a charging potential generated by contact, separation, and friction between the tire 2B and the road surface 3, and the charging waveform extraction unit 14 is detected by the detection unit 1A. The monitoring unit 1B that monitors the detected charging potential is configured, and each unit from the RMS value calculation unit 15 to the tire wear state detection unit 19 configures the detection unit 1C.

The monitoring unit 1B and the detection unit 1C are configured by a storage device such as a ROM or a RAM and a microcomputer program.
Specifically, as shown in FIG. 2, the monitoring unit 1 </ b> B and the detection unit 1 </ b> C are configured by connecting various hardware to a CPU (Central Processing Unit) 21 that controls the control. For example, a ROM (Read Only Memory) 22 and a RAM (Random Access Memory) 23 serving as a work memory of the CPU 21 are connected via a bus 24.
The ROM stores a measurement program and the like, and the RAM stores measurement data. The CPU 21 develops the measurement program in the RAM 23 and executes it.

The detection electrode 11 is a flat electrode, and is arranged with a predetermined gap with respect to the outer surface of the vehicle body 2A of the vehicle 2 and is capacitively coupled to the vehicle body 2A. In this example, by inserting a plate-shaped dielectric having a constant thickness in the gap between the outer surface of the vehicle body 2A and the detection electrode 11, the capacitance between the vehicle body 2A and the vehicle body 2A is increased. The size of the gap is ensured.
On the other hand, the reference electrode 12 is also made of a plate-like electrode, and is a resin such as acrylic or urethane attached so as to protrude from the upper end of the support base 2b provided on the anti-vibration base 2a provided on the outer surface of the vehicle body 2A. It attaches to the front-end | tip of the rod-shaped support bar 2c which consists of. The support base 2b is a cylindrical member in which an insulating member such as a plate-like wood is attached to the vibration isolation base 2a side and the support bar 2c.
Thus, the reference electrode 12 can be separated from the charged vehicle body 2A (for example, 100 mm or more), and the reference electrode 12 and the vehicle body 2A can be electrically insulated from each other. It can be kept at zero potential.

Since the charging potential of the vehicle body 2A periodically changes between the (+) side and the (−) side, as shown in FIG. 3, the charging potential that is the potential of the detection electrode 11 capacitively coupled to the vehicle body 2A is also Changes positive and negative in time.
Further, since the charging potential of the vehicle body 2A changes as the capacitance between the tire 2B and the road surface 3 changes, the capacitance between the tire 2B and the road surface 3 also changes the contact state and friction between the tire and the road surface. Varies depending on the size of When the tire wears, not only does the groove height decrease and the block rigidity changes, but the tread surface condition also changes, so the contact state between the tire and the road surface and the magnitude of friction also change. Therefore, the tire wear state can be detected by detecting the change in the charging potential.
The sensor amplifier 13 is an amplifier including, for example, a field effect transistor (FET), and amplifies and outputs a voltage between the detection electrode 11 and the reference electrode 12 (hereinafter referred to as a charging voltage).

The charging waveform extracting means 14 sequentially extracts a time-varying waveform of the charging voltage for each unit period (hereinafter referred to as a charging waveform) from the time-varying waveform of the charging voltage that is amplified by the sensor amplifier 13 and continuously output.
In this example, while the unit period is set to one round of the tire, the wear state of the running tire is detected using the time waveform data of the N rounds of the tire sequentially extracted by the charging waveform extracting means 14.
The RMS value calculation unit 15 calculates the RMS value of the extracted charging waveform for each tire lap and stores it in the storage unit 18.

The peak counting unit 16 includes a peak extracting unit 16a, a specific peak determining unit 16b, and a counting unit 16c, and counts the number of specific peaks included in the charging waveform. The specific peak will be described later.
The peak extraction unit 16a extracts the (+) side peak and the (−) side peak from the charging waveform.
The specific peak determination unit 16b calculates a peak value difference that is a difference between the amplitude value of the (+) side peak adjacent to the time and the amplitude value of the (−) side peak in time, and stores the peak value difference and the stored peak value difference. The RMS value stored in the means 18 is compared, and when the peak value difference is larger than the RMS value, the peak that is behind in time is determined as the specific peak.
Since the RMS value changes depending on the unevenness of the road surface and the vehicle speed, as in this example, if a peak having a peak value difference larger than the RMS value is determined as a specific peak, a threshold is set for the amplitude value difference, Rather than setting a peak whose amplitude value difference is larger than the threshold value as a specific peak, an unnecessary peak can be reliably excluded.
FIG. 4 is an enlarged view of FIG. 3, and the peak circled in the same figure is a specific peak.
The counting unit 16c counts the number of appearances of the specific peak. Counting the number of appearances is performed for each lap of the tire, and the count result is stored in the storage means 18. The number of appearances is counted for N times, that is, N charging waveforms, which is a preset number of times.

The peak frequency distribution creation means 17 includes a histogram creation means 17a and a distribution function approximation means 17b.
The histogram creation means 17a creates a histogram representing the frequency distribution of the number of appearances of the specific peak as shown in FIG. 5 using the data of the number of appearances of the specific peak for each rotation of the tire stored in the storage means 18. .

The distribution function approximating means 17b approximates the histogram representing the frequency distribution of the number of appearances of the specific peak created by the histogram creating means 17a by a Weibull distribution used mainly when statistically representing the destruction phenomenon of the object, A scale parameter η and a shape parameter m of the probability density function of the Weibull distribution shown in the following equation (2) are calculated.

The shape parameter m of the probability density function of the Weibull distribution is a parameter related to the shape of the distribution. As shown in FIG. 6A, when m is small, f (x) does not have a peak and decreases rapidly as x increases. When m is large, f (x) has a peak.
The scale parameter η is a parameter related to the position and height of the peak. As shown in FIG. 6B, when η is small, the coordinates of the peak position are small and the height is high. When η is large, the coordinates of the peak position are large and the height is low.
In this example, as will be described later, the tire wear state is detected using the scale parameter η and the shape parameter m.

The storage means 18 is composed of a ROM 22 and a RAM 23, and as described above, the RMS value of the charging waveform for each tire turn extracted by the RMS value calculation means 15 and the tire turn for each tire measured by the counting means 16c. The number of appearances of the specific peak is stored, and a MW map 18M indicating the relationship between the tire wear state, the scale parameter η, and the shape parameter m is stored.
In this example, the groove height H is used as an index of the tire wear state.
The M-W map 18M creates a histogram representing the frequency distribution of the number of appearances of a specific peak by running a test vehicle in which a plurality of types of tires having different tire heights, that is, different groove heights H, are run in advance. It can be created by approximating the histogram created for each height H with the probability density function of the Weibull distribution and obtaining the scale parameter η and the shape parameter m.
As the MW map 18M, for example, a curved surface H (η, m) in which the x axis is the scale parameter η, the y axis is the shape parameter m, and the z axis is the tire groove height, or the scale parameter η is [η −Δη / 2, η + Δη / 2], and a table in which data of the groove height H is written for each region where the shape parameter m is [m−Δm / 2, m + Δm / 2] can be used.

The tire wear state detection means 19 compares the scale parameter η and the shape parameter m of the probability density function of the Weibull distribution obtained by the peak frequency distribution creation means 17 with the MW map 18M stored in the storage means 18 to compare the tires. The groove height H, which is an indicator of the wear state of, is detected.
FIGS. 7A and 7B are histograms showing the time distribution waveform of the charging voltage and the frequency distribution of the number of appearances of a specific peak of a tire that is not worn (hereinafter referred to as a new article). B) is a histogram representing a time distribution waveform of a charging voltage of a worn tire (hereinafter referred to as a worn product) and a frequency distribution of the number of appearances of a specific peak. The new groove height is H ₀ = 7.5 mm, and the worn groove height is H = 2.5 mm.
When the new product histogram and the wear product histogram are approximated to the Weibull distribution shown by the thick curves in the figure, and the scale parameter η of the probability density function and the shape parameter m are compared, the scale parameter η of the probability density function is obtained for the new product. And the shape parameter m are both large (η = 11.0, m = 3.35), and in the wear product, both the scale parameter η and the shape parameter m are smaller than the new product (η = 6.40, m = 2.37). )
Therefore, by comparing the scale parameter η and the shape parameter m with the MW map 18M stored in the storage unit 18, it is possible to accurately detect the groove height, which is an index of the wear state of the tire.
That is, if the scale parameter and the shape parameter of the probability density function of the Weibull distribution obtained by the peak frequency distribution creating unit 17 are η _k and m _k , respectively, η _k + Δη / 2 ≧ η ≧ η _k + Δη / 2 and m _{If k} + Δm / 2 ≧ m ≧ m _k + Δm / 2, the groove height is detected as H _k . Here, H _k is the groove height when the scale parameter described in the MW map 18M is η _k and the shape parameter m _k .

Next, a method for detecting the tire wear state using the tire wear state detection device 1 will be described with reference to the flowchart of FIG.
First, the change in the charging potential of the vehicle body 2A, which changes with the change in the capacitance between the tire 2B and the road surface 3 of the traveling vehicle 2, the charging voltage of the detection electrode 11 capacitively coupled to the vehicle body 2A. Then, the charging waveform, which is the time-varying waveform of the charging voltage for each tire lap, is sequentially extracted from the time-varying waveform of the charging voltage (step S11).
Next, the RMS value of the extracted charging waveform for one round of the tire is calculated (step S12), and the number of appearances of a specific peak that is the number of specific peaks included in the charging waveform for one round of the tire is counted. (Step S13).
And it is investigated whether the count of the specific peak appearance frequency for tire N rotation was completed (step S14).

If the counting for N rotations is not completed, the process returns to step S11 to extract the next charging waveform and continue the operation of counting the number of appearances of the specific peak.
After the count for N rotations is completed, a histogram representing the frequency distribution of the number of appearances of the specific peak is created (step S15), and this histogram is approximated by the Weibull distribution to determine the scale parameter of the probability density function of the Weibull distribution. η and the shape parameter m are calculated (step S16).
Then, the calculated scale parameter η, the shape parameter m, and the MW map 18M are compared to detect the groove height of the running tire (step S17).
In this way, a histogram representing the frequency distribution of the number of appearances of the specific peak is created from the time-varying waveform of the charging voltage to obtain the scale parameter η and the shape parameter m of the probability density function of the Weibull distribution, and these scale parameter η and the shape parameter If m is used to detect the groove height, which is an index of the tire wear state, the influence of road surface unevenness and the influence of the vehicle speed can be eliminated, so that the tire wear state can be detected with high accuracy.

In the embodiment described above, a combination of the charging potentials of the four tires 2B is detected by detecting a change in the charging potential of the vehicle body 2A. However, the detection electrode 11 is, for example, a tire of each tire 2B. By providing the house 2C (see FIG. 1) and detecting the charging potential of the tire 2B, the wear state of each tire 2B can be detected.
In the above embodiment, the tire wear state is detected by comparing the scale parameter η calculated using the time-varying waveform of the charging voltage, the shape parameter m, and the MW map 18M. Threshold value K ₁ and threshold value K ₂ are set for each of the shape parameter m and wear, and if η ≧ K ₁ and m ≧ K _2, wear does not progress, and if η <K ₁ and m <K _2, wear progresses. It may be.

In the above-described embodiment, the detection electrode 11 is capacitively coupled to the vehicle body 2A disposed with a gap with respect to the outer surface of the vehicle body 2A, but may be disposed on the outer surface of the vehicle body 2A. Alternatively, the vehicle body 2A itself may be a conductor corresponding to the detection electrode.
In the above embodiment, the reference electrode 12 and the vehicle body 2A are electrically insulated from each other, and the reference electrode 12 is arranged far away from the vehicle body 2A. However, an electric field is formed inside the multiple electrode structure as shown in FIG. If the configuration is such that a singular region near zero is formed and the reference electrode 12 is arranged in this singular region, the potential of the reference electrode 12 can be stabilized and the reference electrode 12 can be arranged inside the vehicle body 2A. it can.
Specifically, four electrodes 31 to 34 (hereinafter referred to as “quadrupoles”) are arranged at each apex of a square, an AC signal having a constant frequency is applied to each of the electrodes 31 to 34, and positions at adjacent apexes. By inverting the phases of the electrodes 31-32, 32-33, 33-34, and 34-31, the electric field strength near the center of gravity of the square is set to 0 [V / m] or a value approximate thereto. be able to. Therefore, if the reference electrode 12 is disposed in the vicinity of the center of gravity, the reference electrode 12 can be set to a reference potential (zero potential) instead of the ground.
The multi-electrode structure is not limited to the above-described multipole element. For example, an electrode is arranged at each apex of a positive 2n (n is an even number of 2 or more) square, and a phase is not set in an electrode arranged at an adjacent apex. If the alternating current is inverted, the strength of the electric field near the center of gravity of the regular 2n square can be set to 0 [V / m] or a value approximate thereto.

  As mentioned above, although this invention was demonstrated using embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. It will be apparent to those skilled in the art that various modifications or improvements can be added to the embodiment. It is apparent from the claims that the embodiments added with such changes or improvements can be included in the technical scope of the present invention.

  According to the present invention, since the wear state of the running tire can be detected without providing a sensor in the tire, the wear state of the tire can be detected with high accuracy.

1 tire wear state detection device, 1A detection unit, 1B monitoring unit, 1C detection unit,
2 vehicle, 2A body, 2B tire, 2C tire house, 3 road surface,
11 sensing electrode, 12 reference electrode, 13 sensor amplifier,
14 charging waveform extracting means, 15 RMS value calculating means, 16 peak counting means,
16a peak extraction means, 16b specific peak determination means, 16c counting means,
17 peak frequency distribution creation means, 17a histogram creation means,
17b Distribution function approximation means, 18 storage means, 19 tire wear state detection means,
21 CPU, 22 ROM, 23 RAM, 24 buses.

Claims (6)

A detection step for detecting a charging potential distributed in the vehicle body by contact, separation and friction between the tire and the road surface;
A monitoring step of monitoring a time-varying waveform of the charging potential detected in the detection step;
A tire wear state detection method comprising: a detection step of detecting a wear state of the tire from a change in the time change waveform accompanying a change in the tire wear state. A counting step is provided for counting the number of specific peaks, which is the number of specific peaks that appear in the time-varying waveform and whose amount of change in charging potential is larger than the average amplitude per unit period, a plurality of times per unit period. ,
In the detection step,
The tire wear state detection method according to claim 1, wherein the wear state of the tire is detected from the appearance frequency of the specific peak number. In the counting step,
The tire wear state detection method according to claim 2, wherein an RMS value per unit period is acquired from the time change waveform, and the RMS value is used as an average value of amplitude per unit period. In the counting step,
Extracting a positive peak and a negative peak from the time change waveform, calculating a peak value difference that is a difference between an amplitude value of the positive peak and an amplitude value of the negative peak, When the peak value difference exceeds the RMS value, the positive peak or the negative peak is determined as a specific peak, and the specific peak number that is the number of the determined specific peaks is counted,
In the detection step,
The tire wear state detection method according to claim 3, wherein a frequency distribution of a specific peak number per unit period is obtained, and a wear state of the tire is detected from an appearance frequency of the specific peak number. In the detection step,
The frequency distribution of the specific peak number is approximated by the Weibull distribution, and the scale parameter and the shape parameter of the probability density function of the Weibull distribution are calculated.
The tire wear state detection method according to claim 4, wherein the wear state of the tire is detected from the calculated shape parameter or scale parameter and shape parameter. A detection unit for detecting a charging potential distributed in the vehicle body by contact, separation and friction between the tire and the road surface;
A monitoring unit for monitoring a time-varying waveform of the charging potential detected by the detection unit;
A detection unit that detects a wear state of the tire from a change in the time change waveform accompanying a change in the tire wear state;
The detection unit is
Counting means for counting the number of specific peaks, which is the number of specific peaks that appear in the time change waveform and whose amount of change in charging potential is a peak larger than the average value of amplitude per unit period, a plurality of times per unit period;
A tire wear state detection device, comprising: a detecting unit that detects a wear state of the tire from the appearance frequency of the specific peak number.

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