Tire degradation estimation device and tire degradation estimation method

Abstract

A tire degradation inference method according to one embodiment of the present invention uses a tire degradation inference device arranged on the inner side of the tire, and comprises: a deformation speed measurement step (S11), measuring the deformation speed of the tire when the tire is rotating, i.e., the tire deformation speed, to obtain a time series change of the tire deformation speed; a calculation step (S12), calculating the peak value of the tire deformation speed according to the time series change of the tire deformation speed; and an inference step (S13), using the peak value of the tire deformation speed before the tire is stepped on or after the tire is stepped on in the time series change of the tire deformation speed, i.e., the first peak value, to infer the degree of degradation of the tire, thereby being able to infer the degree of degradation of the tire.

Description

Technical Field

[0001] The present invention relates to a tire degradation estimating device and a tire degradation estimating method for estimating the degree of degradation such as tire wear. Background Art

[0002] If the wear of the tire progresses, the grip performance when driving on a dry road surface and the drainage performance of draining water between the tire and the road surface when driving on a wet road surface will be reduced. Therefore, drivers and vehicle managers check the wear state of the tread by visual observation, and replace the tire before exceeding the usage limit in order to ensure safety performance. Although the tread wear mark provided in the groove of the tire is used in the inspection based on visual observation, the inspection operation is cumbersome, and there is also the risk of incorrect evaluation of the wear state. In the case of an incorrect evaluation, the tire with reduced performance will continue to be used, which is not preferred from the perspective of safety.

[0003] Therefore, a method of estimating the degree of tire wear by a method other than visual observation has been proposed. For example, Patent Document 1 describes a method of estimating the degree of tire wear stably and with high accuracy.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent No. 5111505 Summary of the invention

[0007] Problems that the invention will solve

[0008] The method described in Patent Document 1 calculates the tire deformation speed based on the tire radial acceleration, finds the tire rotation time, finds the deformation speed index based on the deformation speed and the rotation time, and calculates the degree of wear based on the magnitude of the index. In addition, in order to standardize the index of the tire deformation speed that varies with the rotation speed, it is multiplied or divided by the cube of the tire rotation time. This method determines the degree of wear by considering multiple data such as tire load, pressure, speed, and friction coefficient of the road surface, so the amount of calculation required to infer the degree of tire wear increases. Therefore, there is a problem that the power consumption of the tire degradation inference device increases.

[0009] Therefore, an object of the present invention is to provide a tire degradation estimating device and a tire degradation estimating method capable of estimating the degree of tire degradation by a method different from the conventional ones.

[0010] Means for solving problems

[0011] The present invention is based on the finding that the extent of tire degradation such as wear and flexibility reduction can be evaluated by using the deformation of the tire before stepping in (before contact) or after pushing out (after contact) and the deformation of the tire when contacting, and has the following configuration.

[0012] The tire degradation inference method of the present invention uses a tire degradation inference device arranged on the inner side of the tire, and is characterized in that the tire degradation inference method comprises: a deformation speed measurement step, measuring the tire deformation speed and obtaining a time series change of the tire deformation speed, wherein the tire deformation speed is the deformation speed of the tire when the tire is rotating; a calculation step, calculating the peak value of the tire deformation speed based on the time series change of the tire deformation speed; and an inference step, using the first peak value to infer the degree of degradation of the tire, wherein the first peak value is the peak value of the tire deformation speed before the tire is stepped on or after the tire is stepped out in the time series change of the tire deformation speed.

[0013] By using the first peak value, which is the peak value of the tire deformation speed before the stepping-in time or after the stepping-out time of the tire, the degree of tire deterioration can be estimated with high accuracy.

[0014] Alternatively, in the calculation step, the peak value of the tire deformation speed before the tire is stepped on or after the tire is pushed off, i.e., the first peak value, and the peak value of the tire deformation speed when the tire touches the ground, i.e., the second peak value, are calculated based on the time series changes, and in the inference step, the degree of degradation of the tire is inferred based on the ratio of the second peak value to the first peak value.

[0015] By calculating the second peak value in addition to the first peak value and estimating the degree of tire degradation using the ratio of the two, the influence of changes due to changes in external temperature, etc. can be suppressed, thereby improving estimation accuracy.

[0016] Alternatively, in the estimating step, the degree of deterioration of the tire may be estimated based on a first ratio obtained by dividing the first peak value before contact with the second peak value, or a second ratio obtained by dividing the first peak value after contact with the second peak value.

[0017] In the estimating step, it may be estimated that the tire is deteriorated when the ratio of the first peak value to the second peak value is 50% or less of a reference value.

[0018] The tire degradation inference method of the present invention is, as another embodiment, a tire degradation inference method using a tire degradation inference device arranged on the inner side of the tire, characterized in that the tire degradation inference method comprises: a deformation measurement step, measuring the deformation speed of the tire when the tire is rotating, and obtaining a time series change of the tire deformation obtained by integrating the tire deformation speed; a calculation step, determining the peak value of the tire deformation based on the time series change of the tire deformation; and an inference step, using a third peak value to infer the degradation degree of the tire, the third peak value being the peak value of the tire deformation before the tire is stepped on or after the tire is stepped out in the time series change of the tire deformation.

[0019] Alternatively, in the deformation measurement step, the third peak value of the tire deformation before stepping in or after pushing out and the fourth peak value of the tire deformation when the tire touches the ground are calculated based on the time series changes, and in the inference step, the degree of tire degradation is inferred based on the ratio of the third peak value to the fourth peak value.

[0020] The tire degradation inference device of the present invention is arranged on the inner side of the tire to identify the degradation state of the tire, and is characterized in that the tire degradation inference device comprises: a deformation measuring unit, which can measure the deformation of the tire when the tire is rotating; a calculation unit, which calculates the first peak value in the time series change of the tire deformation speed before the tire is stepped on or after the tire is stepped out based on the time series change of the tire deformation speed; and an inference unit, which uses the first peak value of the tire deformation speed to infer the degree of degradation of the tire.

[0021] Alternatively, the calculation unit may calculate a first peak value of the tire deformation speed before stepping on the tire or after pushing off the tire and a second peak value of the tire deformation speed when the tire touches the ground based on a time series change of the tire deformation speed, and the inference unit may use the first peak value and the second peak value of the tire deformation speed to infer the degree of degradation of the tire.

[0022] The deformation measuring unit may be a piezoelectric sensor formed in a sheet shape, arranged in contact with the inner side surface of the tire, and measures a deformation speed of the inner side surface of the tire, and the measured deformation speed is set as the tire deformation speed.

[0023] The piezoelectric sensor may include a first piezoelectric sensor and a second piezoelectric sensor, and the first piezoelectric sensor and the second piezoelectric sensor may have different sensitivities with respect to a deformation direction of the tire.

[0024] Alternatively, the first piezoelectric sensor may have a higher sensitivity in the width direction of the tire than the second piezoelectric sensor. For example, the first piezoelectric sensor may be formed into a rectangular shape when viewed from the normal direction and may be configured such that the length direction is the width direction of the tire, and the second piezoelectric sensor may be formed into a circular shape when viewed from the normal direction. The first piezoelectric sensor and the second piezoelectric sensor may also be configured on the same straight line along the rotation direction of the tire.

[0025] By configuring the piezoelectric sensor to include a first piezoelectric sensor and a second piezoelectric sensor having different sensitivities to the deformation direction of the tire, the difference between the outputs from the first and second piezoelectric sensors can be used to sense deformation in a specific direction such as the width direction of the tire.

[0026] Alternatively, the inference unit may infer the degree of tire degradation using the first peak value of the tire deformation speed before the tire is stepped on or after it is stepped on based on the measurement results of the first piezoelectric sensor, and the second peak value of the tire deformation speed when the tire touches the ground based on the measurement results of the second piezoelectric sensor.

[0027] The estimation unit may estimate the degree of tire deterioration based on a ratio of the first peak value to the second peak value or a difference between the first peak values ​​of tire deformation speeds based on measurement results of the first piezoelectric sensor and the second piezoelectric sensor.

[0028] With these configurations, the estimating unit can estimate the degree of tire degradation with high accuracy.

[0029] The tire deterioration estimation device may further include a communication unit capable of communicating with the outside, and a warning unit that issues a warning instruction when the estimation unit estimates that the tire has deteriorated.

[0030] When the estimation unit estimates that the tire is deteriorating, the warning unit can output a warning through the communication unit and notify the manager or driver of the vehicle.

[0031] Effects of the Invention

[0032] According to the present invention, by using the first peak value, it is possible to estimate the degree of tire degradation with high accuracy and with a small amount of calculation. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a flowchart of the tire degradation estimation method according to the first embodiment.

[0034] Figure 2(a) is a schematic diagram schematically showing deformation of a tire accompanying rotation, and (b) is a graph showing waveforms of changes in tire deformation speed (solid line) and deformation amount (dashed line).

[0035] Figure 3 This is a flowchart of a tire degradation estimation method according to the second embodiment.

[0036] Figure 4 This is a flowchart of a tire degradation estimation method according to a third embodiment.

[0037] Figure 5 This is a functional block diagram of a tire degradation estimation device.

[0038] Figure 6 (a) is a plan view schematically showing a configuration example of a strain measuring section of the tire deterioration estimation device, and (b) is a plan view schematically showing another configuration example of the strain measuring section.

[0039] Figure 7 It indicates schematically Figure 6 A perspective view of a deformation measuring unit in a state where the deformation measuring unit is arranged toward the inner side of the tire.

[0040] Figure 8 It is a top view schematically showing the deformation speed and direction of the inner side surface of the tire obtained by simulation.

[0041] Fig. 9 (a) is a plan view illustrating the rotation of the tire and the position (rotation angle) of the tire degradation estimation device, and (b) is a waveform showing the relationship between the rotation angle of the tire and the output voltage from the piezoelectric sensor of the deformation measurement unit.

[0042] Fig.10 The graphs show changes in the peak values ​​of waveforms of tires (new and used), where (a) is the measurement result of a rectangular piezoelectric sensor and (b) is the measurement result of a circular piezoelectric sensor.

[0043] Fig.11 The following are graphs showing changes in the peak values ​​of waveforms of tires (new and worn tires), wherein (a) is the measurement result of a rectangular piezoelectric sensor and (b) is the measurement result of a circular piezoelectric sensor. DETAILED DESCRIPTION

[0044] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In each of the drawings, the same components and processes (steps) are denoted by the same reference numerals, and description thereof will be appropriately omitted.

[0045] (First Embodiment)

[0046] like Figure 1As shown, the tire degradation estimation method of this embodiment is a tire degradation estimation method using a tire degradation estimation device disposed on the inner side of the tire, and includes a deformation speed measurement step (S11), a calculation step (S12), and an estimation step (S13). Each step is described below.

[0047] The deformation speed measuring step ( S11 ) is a step of measuring the deformation speed of the portion of the rotating tire 200 where the tire deterioration estimation device 100 is arranged, that is, the tire deformation speed. Figure 2 (a) is a front view schematically showing the deformation of the tire 200 when it is rotating. Figure 2 (b) is a waveform schematically showing the time series changes of the tire deformation speed and the tire deformation amount measured by the tire degradation estimation device 100 in the rotating tire 200. In this figure, the solid line shows the time series changes of the tire deformation speed, and the dotted line shows the time series changes of the tire deformation amount.

[0048] like Figure 2 As shown in (a), the tire degradation estimation device 100 measures the tire 200 by rotating the tire 200 and the deformation measurement unit 10 (see Figure 5 ) is repeated with respect to the road surface 50, the tire 200 is deformed. The deformation measuring unit 10 (refer to Figure 5 , Figure 7 ), and measuring the periodic deformation along with the rotation of the tire 200. The deformation speed measuring step measures the change of the periodic tire deformation speed of the tire 200. Figure 2 The graph (b) shows time on the horizontal axis and the tire deformation speed or tire deformation amount on the vertical axis. The solid line simplifies the waveform of the time series change of the tire deformation speed, and the dotted line simplifies the waveform of the time series change of the tire deformation amount.

[0049] In the calculation step (S12), the value (maximum value, minimum value) of the top (peak) of the wave in the waveform representing the time series change of the tire deformation speed, i.e., the peak value, is calculated based on the time series change of the tire deformation speed measured in the deformation speed measurement step. Here, the peak that brings the peak value of the tire deformation speed is classified into a peak (first peak) when the tire surface 202 corresponding to the portion of the inner side 201 of the tire 200 where the tire degradation estimation device 100 is arranged is not in contact with the road surface 50, and a peak (second peak) when it is in contact with the road surface 50. Figure 2 (a) and Figure 2 (b) These peaks are described.

[0050] like Figure 2 (a) and Figure 2As shown in (b), the peak when the tire surface 202 is not in contact with the road surface 50, that is, the first peak, is the peak before the stepping on ( Figure 2 (b) shows peaks a1 and a2) and peaks after push-off ( Figure 2 (b) is composed of peaks a5 and a6). When the tire surface 202 contacts the road surface 50, the deformation of the tire 200 becomes the largest ( Figure 2 (a)), before and after the center point of touchdown (hereinafter appropriately referred to as "the center point of touchdown C"), peaks a3 and a4 in opposite directions appear as the second peak ( Figure 2 (b)).

[0051] In the calculation step, the "first peak" before and after the tire touches the ground, that is, before stepping in or after pushing out, is found. Figure 2 As shown in (b), two peaks a1 and a2 appear before the peak a3 at the time of contact with the ground, and two peaks a5 and a6 appear after the peak a4 at the time of contact with the ground. Among these four peaks, the peaks a2 and a5 generated at positions close to the peaks a3 and a4 at the time of contact with the ground have larger absolute values ​​than the peaks a1 and a6, and are therefore easier to sense. Therefore, it is preferred to use the peaks a2 and a5 having the largest absolute values ​​of the tire deformation speed when the tire surface 202 is not in contact with the road surface 50, that is, before the tire steps in or after the tire steps out, as the first peak. In addition, in this specification, the peak on the same side as the peak a3 at the time of contact generated before the contact center point C is also referred to as the top peak, and the peak on the same side as the peak a4 at the time of contact generated after the contact center point C is also referred to as the bottom peak. For example, in Figure 2 In the waveform of (b), a1 and a5 of the first peak are top peaks, and a2 and a6 are bottom peaks.

[0052] The inference step (S13) is a step of inferring the degree of tire degradation using the value of the first peak in the time series change of the tire deformation speed calculated in the calculation step, that is, the first peak value. The index obtained using the first peak value is compared with the threshold value. When the index is less than the threshold value (Yes in S13), it is determined that the tire 200 is degraded (S14), and the tire degradation inference is terminated. When the index is greater than the threshold value (No in S13), the process returns to the deformation speed measurement step (S11).

[0053] The estimation step (S13) uses the first peak value to estimate the degree of tire degradation. Therefore, the calculation step (S12) obtains at least the first peak value among the peak values ​​of the tire deformation speed.

[0054] Here, refer to Fig. 9 (b) Regarding the waveform representing the relationship between the rotation angle of the tire and the output voltage from the piezoelectric sensor of the deformation measuring unit, Fig. 9(b) shows the situation of new tires and used tires. Fig. 9 As can be seen from (b), there is almost no difference in the output values ​​of the new and used products in the peak values ​​a3 and a4 at the time of contact with the ground, while there is a difference in the peak values ​​a1, a2, a5, and a6 before and after contact with the ground. That is, it can be seen that the maximum value of the deformation speed of the tire before and after contact with the ground sensitively reflects the degree of deterioration of the tire 200, especially the change in characteristics such as hardness caused by the deterioration, compared to the contact with the ground when the tire 200 contacts the ground. Therefore, by using the peak value of the tire deformation speed before and after the contact with the ground obtained in the calculation step, i.e., the first peak value, to infer the degree of deterioration of the tire, the deterioration state of the tire can be inferred with high accuracy. For example, by detecting that the peak value of peak a2 or the peak value of peak a5 is below a predetermined threshold value, and the peak value of peak a2 or peak a5 is below a predetermined ratio relative to the initial value of each peak value, it is inferred that the tire 200 has deteriorated. The predetermined ratio can be set to, for example, 40 to 60%, 50%, etc.

[0055] (Second Embodiment)

[0056] like Figure 3 As shown, the tire degradation estimation method of this embodiment is different from the first embodiment in that it includes a calculation step (S22) instead of the above-mentioned calculation step (S12). The calculation step (S22) calculates the second peak value of the tire deformation speed when the tire contacts the ground in addition to the first peak.

[0057] The second peak is the peak with the largest peak value on the top side and the bottom side. In the calculation step (S22), the second peak value is calculated in addition to the first peak value, so that the first peak value and the second peak value can be used in the estimation step (S23). As a result, in estimating the degree of tire degradation, the influence of changes in tire characteristics caused by external temperature changes, etc. can be considered, thereby improving the estimation accuracy.

[0058] like Figure 2 As shown in (b), the second peak is generated in the opposite direction of the waveform before and after the center point C of the tire contact. Figure 2 In the waveform of (b), peaks a3 and a4 before and after the contact center point C where the deformation of the tire 200 is the largest are second peaks, and the values ​​of the deformation speed in these peaks are second peak values. The second peak values ​​are the maximum values ​​of the deformation speed of the tire in the opposite directions when the tire contacts the ground.

[0059] In the present embodiment, in the calculation step (S22), the second peak value is calculated in addition to the first peak value. Therefore, in the inference step (S23) after the calculation step (S22), the index obtained using the first peak value and the second peak value can be used for inference of tire degradation. By using the second peak value in addition to the first peak value, the influence of factors other than the degree of tire degradation can be suppressed, and the accuracy of the inference can be improved. For example, in a low temperature environment, all materials tend to harden, so their output waveforms change similarly to the output waveforms at normal temperature. Therefore, even in the case where the first peak value and the second peak value change due to changes in the external environment, the ratio of the second peak value to the first peak value is the same. In contrast, in the case of wear, only the tread rubber is ground, which increases the influence of the steel wire, so the output waveforms are no longer similar. Therefore, as long as the ratio of the second peak value to the first peak value is used as an index, the influence of the external temperature environment can be suppressed.

[0060] In the estimation step (S23), in order to estimate the degree of deterioration of the tire 200, for example, Figure 2 The first ratio is obtained by dividing the peak value of peak a2 (first peak) by the peak value of peak a3 (second peak) in (b), or the second ratio is obtained by dividing peak a5 (first peak) by peak a4 (second peak). These are examples of combinations of the first peak and the second peak, and combinations other than these may be used. In addition, the ratio obtained by dividing the second peak by the first peak may be used.

[0061] Regarding the inference step (S23), for example, when the ratio of the first peak value to the second peak value becomes less than a predetermined ratio relative to the reference value, it is determined that the tire is deteriorated (S14). When it is not less than a predetermined ratio relative to the reference value, the process returns to the deformation speed measurement step (S11) and continues to measure the time series change of the tire deformation speed. As a reference value, the ratio of the first peak value to the second peak value of the tire (new product) before use (initial value) can be cited. The predetermined ratio can be set to an appropriate value depending on the type of tire, etc., but can be set to 40 to 60%, 50%, for example.

[0062] <Third Embodiment>

[0063] The tire degradation degree estimation method of the present embodiment replaces the time series change of the tire deformation speed ( Figure 2 (b) solid line), using the time series change of the tire deformation ( Figure 2 The third peak of the tire deformation amount is determined by the dotted line in (b), and the degree of tire degradation is inferred.

[0064] like Figure 4 As shown, the tire degradation degree estimation method according to the present embodiment includes a deformation amount measurement step ( S31 ), a calculation step ( S32 ), and an estimation step ( S33 ).

[0065] The deformation measurement step (S31) is a step of measuring the time series change of the tire deformation, for example, measuring the deformation speed of the tire when the tire is rotating, integrating the tire deformation speed to measure the tire deformation. Thus, a waveform of the time series change of the tire deformation represented by the dotted line in the figure can be obtained.

[0066] Regarding the calculation step (S32), the peak value of the tire deformation is determined based on the time series change of the tire deformation. Figure 2 As shown in (b) of FIG. 1 , the waveform of the time-series change in tire deformation has peaks b1 and b2 before stepping in, a peak b3 when the deformation is the largest when the tire touches the ground, and peaks b4 and b5 after stepping out.

[0067] The third peak among the peaks b1 to b5 is b1, b2, b4, and b5. Like the first peak in the first embodiment, the third peak of the tire deformation sensitively reflects the change in the elasticity of the tire accompanying the degradation. Therefore, in the inference step (S33), the third peak of the tire deformation is used, and when the obtained index is below the threshold, it is determined that the tire is degraded (S14), so that the degradation degree of the tire can be inferred with high accuracy.

[0068] In addition, in the calculation step (S32), in addition to the third peak value, a fourth peak value with the largest deformation amount may also be obtained. By using the fourth peak value in addition to the third peak value, the influence of temperature changes, etc. can be suppressed, as with the tire deformation speed, so the inference accuracy in the inference step (S33) is improved. In the inference step (S33), as an indicator for evaluating the degree of deterioration of the tire 200, a value obtained by dividing the third peak value by the fourth peak value may also be used. In this case, for example, when the indicator is less than a prescribed ratio (threshold value) relative to the initial value (Yes in S33), it is determined that the tire is deteriorated, and when it is not less than a prescribed ratio (threshold value) relative to the initial value (No in S33), the deformation measurement step (S31) is returned, and the calculation step (S32) and the inference step (S33) are repeated.

[0069] (Fourth Embodiment)

[0070] Figure 5 2 is a functional block diagram of the tire degradation estimation device 100 according to the present embodiment. The tire degradation estimation device 100 is disposed on the inner side surface 201 of the tire 200 (see Figure 2 (a)) to discern the degree of deterioration of the tire, and includes a deformation measuring unit 10, a calculating unit 21, and an estimating unit 22.

[0071] The deformation measuring unit 10 can measure the deformation speed of the tire while the tire 200 is rotating, and can use, for example, a sheet-shaped piezoelectric sensor having a structure in which a piezoelectric layer formed by dispersing piezoelectric particles in a matrix of a synthetic resin and sandwiched by an electrode layer. The deformation measuring unit 10 is arranged in contact with the inner side surface of the tire 200, measures the deformation speed of the inner side surface of the tire, and outputs the measurement result as the tire deformation speed to the calculation unit 21.

[0072] The calculation unit 21 calculates the peak value in the time series change of the tire deformation speed based on the time series change of the tire deformation speed measured by the deformation measurement unit 10. Figure 2 In the waveform of the time series change of the tire deformation speed shown by the solid line in (b), the peaks a1 and a2 before the tire is stepped on (before contact), the peaks a5 and a6 (first peak) after the tire is pushed out (after contact), the peaks a3 and a4 (second peak) at contact, etc. are calculated. The calculation of the peak value can be obtained from the data of the time series change of the tire deformation speed or by image analysis of the waveform of the time series change.

[0073] The estimation unit 22 estimates the degree of degradation of the tire 200 using the first peak value calculated by the calculation unit 21 .

[0074] The calculation unit 21 and the estimation unit 22 are part of the control unit 20 that is responsible for various controls of the tire degradation estimation device 100. Figure 5 As shown, the control unit 20 includes a warning unit 23 for notifying that the tire has deteriorated, and outputs a signal for warning that the tire has deteriorated when the degree of deterioration of the tire estimated by the estimation unit 22 is less than a predetermined threshold. A CPU (central processing unit) or the like may be used as the control unit 20, and the calculation unit 21, the estimation unit 22, and the warning unit 23 may be configured as software functions.

[0075] The tire degradation estimation device 100 of the present embodiment includes a storage unit 30 and a communication unit 40 in addition to the deformation measurement unit 10 and the control unit 20 described above. Various data are recorded in the storage unit 30, and these recorded data are referred to when the control unit 20 estimates the degradation state of the tire or issues a warning. As data stored in the storage unit 30, for example, a table showing the relationship between the index used in the evaluation and the degree of degradation of the tire can be listed. The estimation unit 22 can estimate the degradation state of the tire 200 with high accuracy by comparing the index based on the first peak value calculated by the calculation unit 21 with the information stored in the storage unit 30. In addition, the storage unit 30 can also use a storage unit provided in an external device such as a vehicle body 300 that can communicate with the tire degradation estimation device 100.

[0076] Based on the time series change of the tire deformation speed measured by the deformation measuring unit 10, the first peak value of the tire deformation speed before and after the part where the deformation measuring unit 10 is provided is calculated. Figure 2 In the waveform of the time series change of the tire deformation speed shown by the solid line in (b), the apex of the peaks a1 and a2 before the tire is stepped on (before touching the ground) and the peaks a5 and a6 when the tire is pushed off (after touching the ground) is calculated, that is, the first peak value which is the maximum value of the deformation speed in each peak.

[0077] The estimation unit 22 estimates the degree of deterioration of the tire 200 using the first peak value calculated by the calculation unit 21. Figure 2 As shown in (b), in the waveform representing the time series change of the tire deformation speed, the maximum peaks a3 and a4 are respectively generated on the top side and the bottom side when the tire touches the ground. The present invention can estimate the deterioration state of the tire 200 with high accuracy by using the values ​​of the first peaks, i.e., peaks a1, a2, a5 and / or a6, generated before and after (before and after the tire touches the ground) of the maximum peaks a3 and a4 on the top side and the bottom side, respectively.

[0078] The estimation unit 22 may also calculate a second peak value of the tire deformation speed when the tire contacts the ground in addition to the first peak value, and estimate the degree of tire degradation using the first peak value and the second peak value. For example, the value obtained by dividing the first peak value by the second peak value may be used as an indicator to evaluate the degree of tire degradation.

[0079] In this case, it is preferable to use the maximum value of the tire deformation speed before or after the tire contacts the ground in the first peak in combination with the maximum value of the tire deformation speed when the tire contacts the ground, that is, the second peak. Figure 2 The values ​​(a2 / a3), (a2 / a4), (a5 / a3) and (a5 / a4) obtained by dividing the peak value of peak a2 or peak a5 by the peak value of peak a3 or peak a4 in (b) are used as indicators for evaluating the degree of deterioration of the tire.

[0080] Alternatively, the deformation measuring unit 10 may obtain a time series change in the tire deformation amount obtained by integrating the tire deformation speed instead of the tire deformation speed. In this case, the inference unit 22 calculates the third peak value of the tire deformation amount before the tire is stepped on or after the tire is stepped on, and the fourth peak value of the tire deformation amount when the tire is grounded, based on the time series change in the tire deformation amount, and infers the degree of tire degradation based on the ratio of the third peak value to the fourth peak value. For example, the value indicating Figure 2 In the waveform of the time series change of the tire deformation amount shown by the dotted line in (b), the value (b2 / b3 or b4 / b3) obtained by dividing the peak value of peak b2 or b4 (third peak) by the peak value of peak b3 (fourth peak) is used as an indicator for evaluating the degradation state of the tire 200.

[0081] The deformation measuring unit 10 can use a piezoelectric sensor formed in a sheet shape, for example. Figure 6 (a) and Figure 6 As shown in (b) of FIG. 2 , it is preferable to include a first piezoelectric sensor 11 and a second piezoelectric sensor 12 having a sensitivity different from that of the first piezoelectric sensor 11 with respect to the deformation direction of the tire 200 .

[0082] like Figure 6 As shown in (a), for example, the first piezoelectric sensor 11 may be formed into a rectangular shape when viewed from the normal direction (Z-axis direction), and the second piezoelectric sensor 12 may be formed into a circular shape when viewed from the normal direction. In this way, by setting the first piezoelectric sensor 11 to a shape having shape anisotropy in the X-axis direction and the Y-axis direction, and setting the second piezoelectric sensor 12 to a shape not having shape anisotropy in the X-axis and the Y-axis, it is possible to measure the deformation speed in a specific direction in addition to the size of the deformation of the tire in the portion where the deformation measuring unit 10 is provided. For example, when equal deformation occurs in all directions, the outputs of the first piezoelectric sensor 11 and the second piezoelectric sensor 12 are made equal, and if the deformation speed in the width direction of the tire is large, the output of the first piezoelectric sensor 11 is made greater than the output of the second piezoelectric sensor 12. Thus, the deformation direction of the tire can be determined based on the output difference between the first piezoelectric sensor 11 and the second piezoelectric sensor 12.

[0083] The inference unit 22 may also obtain the deformation speed in a specific direction using the difference between the output of the first piezoelectric sensor 11 and the output of the second piezoelectric sensor 12. In this case, since the difference between the outputs is small, the difference between the output of the first piezoelectric sensor 11 and the output of the second piezoelectric sensor 12 may be amplified for use.

[0084] For example, by arranging the length direction of the first piezoelectric sensor 11 in the width direction (W, Y axis direction) of the tire, the first piezoelectric sensor 11 can be used to measure the deformation of the tire in the width direction with high accuracy. As described later, the tire deforms greatly in the width direction before and after contact. Therefore, by using the first piezoelectric sensor 11, the deformation speed of the tire before and after contact can be measured with high accuracy. Figure 6 2 shows an example in which the strain measurement unit 10 includes both the first piezoelectric sensor 11 and the second piezoelectric sensor 12 , but the strain measurement unit 10 may be configured to include only one of the first piezoelectric sensor 11 or the second piezoelectric sensor 12 .

[0085] The aspect ratio (W1:L1) of the first piezoelectric sensor 11 is preferably 10:1 or more and 10:10 or less, more preferably 10:3 or more and 10:8 or less, and further preferably 10:4 or more and 10:6 or less, in order to measure the force applied in the width direction with high sensitivity and high accuracy and increase the output. In addition, it can also be configured to have a plurality of notches extending in the longitudinal direction (Y-axis direction).

[0086] The length W1 of the first piezoelectric sensor 11 in the tire width direction is preferably about 10 to 20 mm, and the shape of the first piezoelectric sensor 11 (length L1 in the rotation direction (circumferential direction) × length W1 in the width direction) may be, for example, 5 mm × 10 mm, 7 mm × 15 mm, etc. In addition, the diameter L2 of the first piezoelectric sensor 11 is preferably about 5 to 20 mm.

[0087] Figure 6 (b) is a top view schematically showing another configuration example of the deformation measuring unit. As shown in the figure, the first piezoelectric sensor 11 may also be configured as 2 to 5 piezoelectric sensors 11a, 11b, 11c of the same shape (rectangular) arranged in parallel along the rotation direction of the tire. With this configuration, the measurement accuracy of the deformation speed in the width direction is improved. In this case, the length W1 of the first piezoelectric sensor 11 in the width direction is equal to the length W1 of the piezoelectric sensors 11a, 11b, 11c in the width direction of the tire, and the length L1 of the first piezoelectric sensor 11 in the rotation direction of the tire becomes the sum of the lengths l of the piezoelectric sensors 11a, 11b, 11c (3l). In addition, Figure 6 (b) shows an example of using piezoelectric sensors 11a, 11b, and 11c of the same shape, but piezoelectric sensors of different shapes may be used. In addition, the piezoelectric sensors 11a, 11b, and 11c may be arranged so that gaps are formed between them.

[0088] Figure 7 The state where the deformation measuring unit 10 including the first piezoelectric sensor 11 and the second piezoelectric sensor 12 is provided on the inner side surface 201 of the tire 200 is schematically shown. As shown in the figure, the first piezoelectric sensor 11 and the second piezoelectric sensor 12 are preferably arranged on the same straight line along the rotation direction L of the tire 200. Thus, the influence of the position in the width direction W of the tire 200 on the first piezoelectric sensor 11 and the second piezoelectric sensor 12 can be suppressed. Therefore, the difference between the outputs from the first piezoelectric sensor 11 and the second piezoelectric sensor 12 can be measured with high accuracy.

[0089] The estimation unit 22 may use both peak values ​​based on the measurement results of the first piezoelectric sensor 11 and the second piezoelectric sensor 12 to estimate the degree of tire degradation, or may use only one of them.

[0090] In addition, the inference unit 22 may also infer the degree of tire degradation based on the difference between the first peak values ​​based on the measurement results of the first piezoelectric sensor 11 and the second piezoelectric sensor 12. The greater the deformation speed of the tire in the width direction, the greater the difference between the output of the first piezoelectric sensor 11, which has good sensitivity to deformation in the width direction (Y-axis direction), and the output of the second piezoelectric sensor 12, which has no difference in sensitivity to the deformation direction. The deformation speed in the width direction before and after contacting the ground changes greatly due to the change in characteristics caused by the deterioration of the tire. Therefore, by using the difference in output from sensors with different sensing sensitivities in the width direction of the tire, it is possible to sense the change in the deformation speed in the width direction and infer the degree of tire degradation with high accuracy.

[0091] The control unit 20 of the tire degradation estimation device 100 of the present embodiment includes a warning unit 23 for issuing a warning instruction when the estimation unit 22 estimates that the tire has degraded. The output from the estimation unit 22 and / or the output from the warning unit 23 is output to the vehicle body 300 via the communication unit 40. Based on the output from the estimation unit 22 and the warning unit 23, the degradation state of the tire 200 is displayed on a display device or the like provided on the vehicle body 300, or a warning based on sound or light is issued. The communication unit 40 may also output to a portable terminal such as a smartphone in addition to the vehicle body 300, or output to an external server or the like via a public communication line.

[0092] The information on the tire state obtained by the tire degradation estimation device 100 may be used alone or in combination with information obtained from other devices. Examples of other devices include a TPMS (Tire Pressure Monitoring System) that monitors the tire pressure of a vehicle.

[0093] In the above-mentioned embodiment, the tire degradation estimation device 100 having the deformation measurement unit 10, the control unit 20, the storage unit 30 and the communication unit 40 is described. However, this is an example, and the tire degradation estimation device 100 may be constituted by the deformation measurement unit 10 and the communication unit 40. In this case, the ECU (Electronic Control Unit) provided in the vehicle body 300 performs the functions of the control unit 20, the calculation unit 21, the estimation unit 22 and the warning unit 23. The communication unit 40 can use a storage unit provided in a device such as the vehicle body 300 that can communicate via a communication line. The ECU acquires information related to the degradation state of the tire by, for example, communicating with the tire degradation estimation device 100 using a wireless communication unit such as Bluetooth (a registered trademark) when the vehicle body 300 maintains a speed of about 40 to 60 km / h and receiving data for only a few seconds.

[0094] Example

[0095] <Tire strain characteristics>

[0096] Figure 8 Schematic diagram showing the simulation results of the strain characteristics, i.e., the deformation direction and deformation speed, generated on the inner side surface 201 of the rotating tire 200 before stepping in, when stepping in, when contacting, when pushing out, and after pushing out. The direction of the hollow arrow in the figure indicates the deformation direction, and the size indicates the deformation speed. The tire 200 tends to stretch in the rotation direction (L) and shrink in the width direction (W) due to the air pressure of the air sealed inside, but the extension in the rotation direction (L) is dominant when contacting, and the extension in the width direction (W) is dominant when stepping in and when pushing out.

[0097] The rotating (running) tire 200 is subjected to vertical loads caused by contact with the ground and centrifugal force caused by rotation or force caused by curvature deformation in the width direction of the tire. The tire 200 rotates, causing the contacting part to change periodically, so the vertical load applied to each part changes periodically. The behavior of the tire when contacting the ground with this force applied can be described as Figure 2 (a) and Figure 2 The peaks a3 and a4 shown in (b) are captured.

[0098] In the stepping-in and pushing-out portions before and just after the tire 200 contacts the road surface 50, the extension of the tire 200 in the rotation direction (L) slows down, and at the same time, the contraction in the width direction (W) slows down. As a result, the tire 200 stretches in the width direction under the centrifugal force caused by the rotation. By measuring the behavior of the tire 200 before stepping-in and after pushing-out with a piezoelectric sensor or the like, it is possible to obtain Figure 2 The peaks a1 and a2 (before stepping in) and the peaks a5 and a6 (after pushing out) in the output waveform of (b) are as follows. Before stepping in and after pushing out refer to the range within one cycle of the periodic deformation of the portion where the tire degradation estimation device 100 is provided, which is generated as the tire 200 rotates.

[0099] <Evaluation of new and used tires>

[0100] Fig. 9 (b) shows that the first piezoelectric sensor 11 (size 10 mm × 6 mm: 10 mm × 2 mm) with a rectangular plane shape is 3 groups, refer to Figure 6(b)) is arranged on the inner side surface 201 of the tire (new or used) 200 in such a way that its length direction is parallel to the width direction of the tire 200, and a graph (waveform) of the output voltage from the first piezoelectric sensor 11 as the tire 200 rotates is measured. The rotation angle X refers to the rotation angle Fig. 9 The angle formed by the straight line connecting the peak point of the tire 200 when touching the ground and the rotation center O of the tire 200 shown in (a) and the straight line connecting the rotation center O and the tire degradation estimation device 100 is set as negative (-) when stepping in and positive (+) when pushing out after touching the ground, based on the peak point when touching the ground. Fig. 9 The position of the tire degradation estimating device 100 is the first peak a3 at the time of contact with the ground shown in (b).

[0101] exist Fig. 9 In (b), the waveform obtained by measuring a new tire is represented by a solid line, and the waveform obtained by measuring a used tire is represented by a dotted line. In addition, the used tire has both changes in properties such as hardness and a reduction in thickness due to wear. According to the waveform in the figure, the maximum value of the output voltage (peaks a3 and a4) is obtained when the tire touches the ground on both the top and bottom sides, and multiple peaks (a1, a2, a5, a6) are obtained before and after the tire touches the ground. Although the peak values ​​of these peaks before and after the tire touches the ground are smaller than the peaks when the tire touches the ground, the difference between new tires and used tires is large. According to this result, by using the peaks before and after the tire touches the ground, the degree of tire deterioration can be evaluated with high accuracy.

[0102] <Influence of the shape of the piezoelectric sensor>

[0103] As the deformation measuring unit 10, in the following Table 1 and Fig.10 (a) shows that there are three groups of first piezoelectric sensors 11 (size 10mm×6mm: 10mm×2mm) with a rectangular planar shape, referring to Figure 6 The tire degradation estimation device 100 having the deformation measurement unit 10 configured in (b)) is arranged on the inner side of the tire (new and used) in such a way that the length direction of the first piezoelectric sensor 11 is parallel to the width direction of the tire and measures the output from the piezoelectric sensor.

[0104] [Table 1]

[0105]

[0106] As the deformation measuring unit 10, in Table 2 and Fig.10 (b) shows that the second piezoelectric sensor 12 (diameter 10 mm, see Figure 6(b) The tire degradation estimation device 100 including the deformation measurement unit 10 is arranged on the inner side of a tire (new or used) and measures the output from the second piezoelectric sensor 12.

[0107] [Table 2]

[0108]

[0109] <Evaluation of new tires before and after buffing>

[0110] As the deformation measuring unit 10, in Table 3 and Fig.11 (a) shows that there are three groups of first piezoelectric sensors 11 (size 10 mm×2 mm) with a rectangular planar shape, referring to Figure 6 The tire degradation inference device 100 having a deformation measuring unit 10 composed of (b)) is arranged on the inner side of a tire (new product) in such a way that the length direction of the first piezoelectric sensor 11 is parallel to the width direction of the tire, and the results are measured before (initial value: 0%) and after (30% and 50% of the total grinding) the rubber on the tire surface is shaved off to a specified thickness by polishing.

[0111] [Table 3]

[0112]

[0113] As the deformation measuring unit 10, in Table 4 and Fig.11 (b) shows that the second piezoelectric sensor 12 (diameter L2 = 10 mm, see Figure 6 , ) were placed on the inner side of tires (new and used) and the output from the piezoelectric sensor was measured.

[0114] [Table 4]

[0115]

[0116] Table 5 below shows the ratios of a2 / a3 and a5 / a4 in the results of Tables 1 to 4, as compared to the values ​​after deterioration (second-hand products or after polishing) and the values ​​when new products.

[0117] [Table 5]

[0118]

[0119]

[0120] Fig.10The graphs compare peak values ​​obtained by measuring new tires and used tires. (a) shows the measurement results using a rectangular piezoelectric sensor as a deformation measurement unit, and (b) shows the measurement results using a circular piezoelectric sensor.

[0121] The change in tire behavior accompanying tire degradation can be captured as a change in the peak value of the waveform of the tire deformation speed over time. Fig.10 (a) and Fig.10 As shown in (b), by using a rectangular piezoelectric sensor with a rectangular plane shape having good sensitivity in the width direction of the tire, the degree of tire degradation can be detected with high sensitivity. In addition, the peaks (a2, a5) before and after contact are larger than the peaks (a3, a4) at contact, and the difference in waveform between new tires and used tires is larger, so the degree of tire degradation can be detected with high sensitivity.

[0122] Fig.11 The graphs compare the peak values ​​measured after a new tire was forcibly worn out by buffing. As the deformation measuring unit, (a) shows the measurement result using a rectangular piezoelectric sensor, and (b) shows the measurement result using a circular piezoelectric sensor.

[0123] like Fig.11 (a)~ Fig.11 As shown in (b), the change in tire behavior accompanying the development of tire friction can be captured as the change in the peak of the waveform of the tire deformation speed over time. The piezoelectric sensor used for the measurement has good sensitivity in the width direction of the tire. There is no significant difference between the piezoelectric sensor with a rectangular plane shape and the piezoelectric sensor with a circular plane shape. The peaks (a3, a4) at the time of contact can sense the degree of tire wear development with higher sensitivity than the peaks (a2, a5) before and after contact.

[0124] like Fig.10 (a) Fig.10 (b) and Fig.11 (a) Fig.11As shown in (b), the peak with good sensitivity in the peak of the deformation rate of the tire is different depending on whether the deterioration of the tire is caused by a change in characteristics such as hardness or by wear. However, by dividing the first peak before and after touchdown by the second peak at touchdown (first peak / second peak, a2 / a3, a5 / a4) as an indicator of tire degradation, it is possible to sense either a characteristic change such as a change in flexibility over time or a reduction in the thickness of the rubber caused by wear to infer the deterioration state of the tire. That is, the value of (first peak / second peak) becomes smaller as the deterioration of the tire progresses, so by using the change from the initial value as an evaluation indicator, it is possible to infer either wear accompanied by degradation over time or rapid wear not accompanied by degradation over time. Therefore, the difference between new and used tires can be sensed with high accuracy, so it can be said that it is preferable to use a rectangular piezoelectric sensor as a deformation measuring unit.

[0125] Industrial Applicability

[0126] The present invention is useful as a method and apparatus for estimating the degree of tire degradation.

[0127] Description of Reference Numerals

[0128] 10: Deformation measurement department

[0129] 11, 11a, 11b, 11c: first piezoelectric sensor

[0130] 12: Second piezoelectric sensor

[0131] 20: Control Department

[0132] 21: Computing Department

[0133] 22: Inference Department

[0134] 23: Warning Department

[0135] 30: Storage

[0136] 40: Ministry of Communications

[0137] 50: Road surface

[0138] 100: Tire degradation estimation device

[0139] 200: Tires

[0140] 201: Inside side

[0141] 202: Tire surface

[0142] 300: Body

[0143] C: Ground center point

[0144] O: Center of rotation

[0145] X: Rotation angle

[0146] L: Rotation direction

[0147] W: Width direction

[0148] a1, a2, a5, a6: Peak (first peak)

[0149] a3, a4: peak (second peak)

[0150] b1, b2, b4, b5: Peak (third peak)

[0151] b3: Peak (fourth peak)

Claims

1. A tire degradation estimation device, arranged on the inner side of a tire to identify the degradation state of the tire, characterized in that: The tire degradation estimation device includes: a deformation measuring unit capable of measuring deformation of the tire while the tire is rotating; a calculation unit that calculates a first peak value in a time series change of the tire deformation speed before stepping in or after stepping out of the tire based on the time series change of the tire deformation speed; and an estimating unit that estimates a degree of deterioration of the tire using the first peak value of the tire deformation speed, The deformation measuring unit is a piezoelectric sensor formed in a sheet shape, arranged in contact with the inner side surface of the tire, and measures a deformation speed of the inner side surface of the tire, and the measured deformation speed is set as the tire deformation speed. The piezoelectric sensor includes a first piezoelectric sensor and a second piezoelectric sensor, and the first piezoelectric sensor and the second piezoelectric sensor have different sensitivities with respect to a deformation direction of the tire.

2. The tire degradation estimation device according to claim 1, wherein: The first piezoelectric sensor has higher sensitivity in the width direction of the tire than the second piezoelectric sensor.

3. The tire degradation estimation device according to claim 2, wherein: The first piezoelectric sensor is formed into a rectangular shape when viewed from the normal direction, and is arranged so that the length direction is the width direction of the tire. The second piezoelectric sensor is formed in a circular shape when viewed from a normal direction.

4. The tire degradation estimation device according to any one of claims 1 to 3, characterized in that: The first piezoelectric sensor and the second piezoelectric sensor are arranged on the same straight line along the rotation direction of the tire.

5. The tire degradation estimation device according to claim 1, wherein: The inference unit infers the degree of tire degradation using the first peak value of the tire deformation speed before stepping on the tire or after stepping off the tire based on the measurement results of the first piezoelectric sensor, and the second peak value of the tire deformation speed when the tire touches the ground based on the measurement results of the second piezoelectric sensor.

6. The tire degradation estimation device according to claim 5, characterized in that: The estimating unit estimates the degree of tire degradation based on a ratio of the first peak value to the second peak value.

7. The tire degradation estimation device according to claim 2, wherein: The estimation unit estimates the degree of deterioration of the tire based on a difference between the first peak values ​​of tire deformation speed based on measurement results of the first piezoelectric sensor and the second piezoelectric sensor.

8. The tire degradation estimation device according to claim 1, wherein: Also available: a communication unit capable of communicating with the outside; and The warning unit issues a warning instruction when the estimating unit estimates that the tire has deteriorated.

Images