Patent Description:
Conventionally, a technique has been known in which an acceleration sensor mounted on inside surface of a pneumatic tire (tire) assembled to a rim wheel is used to detect acceleration (i.e., equivalent to centrifugal force) of tire radial direction, and the wear amount of the tire, specifically, the tread portion is estimated based on a time series waveform of the detected acceleration and a waveform obtained by differentiating the time series waveform. This technology focuses on the fact that the deformation speed of the tread portion at the time of ground contact changes as the tread portion wears.

<CIT> discloses an acceleration sensor installed on the inner surface in the inner liner region of a tire to detect the acceleration of the tread in the radial direction of the tire. The peak level on the leading edge side or the trailing edge side of the tread appearing in the differentiated waveform of the detected acceleration is calculated and used as an index of deformation speed of the tread. The degree of wear of the tire is estimated on the basis of the calculated index of deformation speed and an M-V map showing a predetermined relationship between the degree of tire wear and the index of deformation speed.

<CIT> discloses an acceleration sensor provided on an inner surface side of an inner liner part of the tire. Acceleration of tread in the tire radial direction is detected to calculate and its differential waveform, and a grounding time t which is an interval between two peaks appearing in this differential wave form is calculated. A period of one peak is calculated as a rotation time, and a velocity of a tire is calculated from the rotation time T.

<CIT> discloses an acceleration sensor provided on the inner surface side of an inner liner part of the tire, and an acceleration waveform in the tire diameter direction of a tire tread is detected, and a deformation time being a time between two peaks corresponding to a swelling point appearing in the acceleration waveform is calculated. A deformation length which is an index of a grounding out-of-plane deformation range of the tire is calculated, and a grounding time which is a time between two peaks corresponding to the ground contact end of the tread appearing in a differential waveform which is a time-series waveform of a differentiated value of the acceleration is calculated, and a grounding length which is an index of a deflection amount of the tire is calculated. The abrasion degree of the tire is estimated based on the calculated deformation length and grounding length and a map showing a relation between the deformation length corresponding to the abrasion degree of the tire and the grounding length, determined beforehand.

<CIT> discloses a method and system for monitoring and measuring the amount of deflection of a pneumatic tire wherein said monitoring system in the tire detects tire sidewall deflection by measuring the length of the tire contact patch area relative to the total circumference of the tire. The embedded sensor device generates a signal which varies as it passes through the tire contact patch within the tire on a moving vehicle. If the vehicle is moving at a constant speed, the ratio of time which the sensor spends inside the contact patch to the time the sensor spends outside the contact patch is proportional to tire deflection. Sensor electrical signals are digitized and counted to determine deflection, tire speed and the number of tire revolutions to improve performance of both the tire and the vehicle.

<CIT> discloses a judging part of the tire abrasion state judging device provides actual acceleration generated in the tire circumferential direction by an acceleration sensor when a rotating tire grounds. Additionally, it provides abrasion causing threshold value to be a standard for abrasion judgement set against standard acceleration generated in the tire circumferential direction from a memory part when the tire in a non-abrasion state grounds. The abrasion state of the tire is judged by comparing the detected actual acceleration and the abrasion causing
threshold value with each other in accordance with at least either one of size of an output value of the acceleration, changing gradient of the output value and a peak interval in acceleration increase.

Since the above-described technique for estimating the amount of wear of a tire uses acceleration in tire radial direction, there is a problem that the estimation accuracy deteriorates when a vehicle equipped with a tire mainly travels at a low speed (For example, about <NUM>/h).

Specifically, at low speed, the acceleration (centrifugal force) of tire radial direction decreases, and the signal-to-noise ratio (S/N) deteriorates. Therefore, it becomes difficult to accurately detect the change of the deformation speed of the tread portion, and the estimation accuracy of the wear amount decreases.

Therefore, the present invention has been made in view of such a situation, and it is an object of the present invention to provide a tire wear amount estimation system, a tire wear amount estimation program, and a tire wear amount estimation method, which can achieve a high estimation accuracy of a wear amount even when traveling mainly at a low speed.

According to a first aspect of the invention there is provided a tire wear amount estimation system as recited in claim <NUM>.

According to a second aspect of the invention there is provided a tire wear amount estimation program as recited in claim <NUM>.

According to a third aspect of the invention there is provided a tire wear amount estimation method as recited in claim <NUM>.

Embodiments will be described below with reference to the drawings. It should be noted that the same functions and configurations are denoted by the same or similar reference numerals, and the description thereof is appropriately omitted.

<FIG> is an overall schematic configuration diagram of a tire wear amount estimation system <NUM> according to an embodiment. As shown in <FIG>, the tire wear amount estimation system <NUM> includes a sensor unit <NUM> and a processing device <NUM>.

The sensor unit <NUM> is provided in inside of a tread portion <NUM> of the pneumatic tire <NUM>.

<FIG> shows a cross-sectional shape of the pneumatic tire <NUM> assembled to a rim wheel <NUM> along a tire width direction. The tread portion <NUM> is a part in contact with the road surface R when the pneumatic tire <NUM> mounted on the vehicle (not shown) rolls on the road surface R (Not shown in <FIG>, see <FIG>), and a tread pattern corresponding to the type of the vehicle and required performance is formed on the tread portion <NUM>.

Although only one pneumatic tire <NUM> is shown in <FIG>, the sensor unit <NUM> is preferably provided on each pneumatic tire mounted on the vehicle. However, the sensor unit <NUM> may not necessarily be provided in all pneumatic tires mounted on the vehicle.

In this embodiment, the sensor unit <NUM> is provided on inside surface of the pneumatic tire <NUM>. Specifically, the sensor unit <NUM> is attached to a surface of an inner liner (not shown) for preventing leakage of a gas such as air filled in an internal space of the pneumatic tire <NUM> assembled to the rim wheel <NUM>.

The sensor unit <NUM> is not necessarily provided on inside surface of the pneumatic tire <NUM>. For example, some or all of the sensor unit <NUM> may be embedded within the pneumatic tire <NUM>.

In the present embodiment, the sensor unit <NUM> is provided at the center of the tread portion <NUM> in the tire width direction. The sensor unit <NUM> may be provided at a place other than the tread portion <NUM>, for example, the tire side portion <NUM>. In the present embodiment, one sensor unit <NUM> is provided in the tire circumferential direction, but a plurality of sensor units <NUM> may be provided in the tire circumferential direction.

As will be described later, the sensor unit <NUM> includes various sensors including a strain sensor, a battery, a wireless communication function, and the like.

The processing device <NUM> realizes wireless communication with the sensor unit <NUM> and acquires a signal output from the sensor unit <NUM>. The processing device <NUM> is implemented by hardware such as a communication module including a processor, memory, and antenna.

The processing device <NUM> is usually provided in a vehicle to which the pneumatic tire <NUM> is mounted. In this case, the processing device <NUM> may be implemented by an electronic control unit (ECU) mounted on the vehicle. Alternatively, the processing device <NUM> may be implemented not on a vehicle but on a server computer (which may be referred to as a network cloud) connected via a wireless communication network.

<FIG> is a functional block diagram of the tire wear amount estimation system <NUM>. Specifically, <FIG> is a functional block diagram of the sensor unit <NUM> and the processing device <NUM>.

As shown in <FIG>, the sensor unit <NUM> includes an internal pressure sensor <NUM>, a temperature sensor <NUM>, a strain sensor <NUM>, and a communication unit <NUM>.

The internal pressure sensor <NUM> detects the internal pressure (air pressure) of the pneumatic tire <NUM> assembled to the rim wheel <NUM>. The temperature sensor <NUM> detects the temperature of the inner surface of the tread portion <NUM>.

The sensor unit <NUM> may not include the internal pressure sensor <NUM> and the temperature sensor <NUM>. Alternatively, the sensor unit <NUM> may include an acceleration sensor.

The strain sensor <NUM> detects strain generated in the tread portion <NUM>. Specifically, the strain sensor <NUM> detects strain in the tire circumferential direction.

As described above, the sensor unit <NUM> is provided on inside surface of the pneumatic tire <NUM>, more specifically, the tread portion <NUM> (or inside the pneumatic tire <NUM>), and the strain sensor <NUM> is also provided on inside surface of the tread portion <NUM> (or inside the pneumatic tire <NUM>).

Specifically, the strain sensor <NUM> can detect the amount of strain (bending moment) generated when the tread portion <NUM> contacts the road surface R.

When the pneumatic tire <NUM> rolls and comes into contact with the road surface R, the arcuate tread portion <NUM> in the tire side view is deformed substantially linearly by the load. Specifically, focusing on the position of the specific tread portion <NUM> in the tire circumferential direction, bending deformation occurs in the tread portion <NUM> at the timing of stepping on the road surface R, and the tread portion deforms substantially linearly in the state of contact with the road surface R. In addition, bending deformation occurs again at the timing of kicking out from the road surface R, and thereafter, the shape returns to the original arc shape.

That is, the stepping of the tread portion <NUM> onto the road surface R may be interpreted as a timing at which the predetermined position of the tread portion <NUM> in the tire circumferential direction is brought into contact with the road surface R by the rolling motion of the tread portion <NUM>. The kicking out of the tread portion <NUM> from the road surface R may be interpreted as a timing at which the predetermined position of the tread portion <NUM> in the tire circumferential direction is separated from the road surface R by the rolling motion of the tread portion <NUM>.

In the present embodiment, the strain detected by the strain sensor <NUM> may correspond to the deformation amount Δl when the load is applied divided by the original length l (Δl/l) as generally interpreted. In practice, the strain sensor <NUM> can output a voltage (unit: mV) corresponding to the microstrain (µε).

The amount of strain detected by the strain sensor <NUM> may be interpreted as a bend amount. The strain sensor <NUM> may be, for example, a piezoelectric sensor, but may be referred to as a strain sensor or a strain gauge. The number of elements constituting the strain sensor (gauge) and the gauge length are not particularly limited.

The communication unit <NUM> executes wireless (radio) communication with the processing device <NUM>. The wireless communication system of the communication unit <NUM> is not particularly limited. For example, as a communication scheme, a method using a frequency (such as UHF) used in a tire pressure monitoring system (TPMS) or the like, or a method in accordance with a short-range wireless communication standard can be mentioned.

The communication unit <NUM> modulates the signals (voltage, etc.) output from the internal pressure sensor <NUM>, the temperature sensor <NUM>, and the strain sensor <NUM> according to a predetermined modulation scheme, and transmits the modulated signals to the processing device <NUM> via radio signals. The communication unit <NUM> may also transmit control data or the like transmitted from the processing device <NUM> via a radio signal to the internal pressure sensor <NUM>, the temperature sensor <NUM>, and the strain sensor <NUM> as necessary.

The battery <NUM> supplies power necessary for the operation of the internal pressure sensor <NUM>, the temperature sensor <NUM> and the strain sensor <NUM>. More specifically, although the type of the battery <NUM> is not particularly limited, it is preferable that the sensor unit <NUM> is constituted by a primary battery or the like capable of being continuously driven for a long period of time (For example, one year or more).

As shown in <FIG>, the processing device <NUM> includes a communication unit <NUM>, a signal acquisition unit <NUM>, a wear estimation unit <NUM>, and an output unit <NUM>.

The communication unit <NUM> executes wireless communication with the sensor unit <NUM>. Similar to the communication unit <NUM>, the wireless communication system of the communication unit <NUM> is not particularly limited. Further, the communication unit <NUM> can perform communication with a control device such as an ECU of the vehicle to which the pneumatic tire <NUM> is mounted or with the outside of the vehicle via a wireless communication network.

The signal acquisition unit <NUM> acquires a signal output from a sensor group constituting the sensor unit <NUM>. Specifically, the signal acquisition unit <NUM> acquires signals output from the internal pressure sensor <NUM>, the temperature sensor <NUM>, and the strain sensor <NUM>.

In particular, the signal acquisition unit <NUM> acquires a strain signal output from the strain sensor <NUM>. The signal acquisition unit <NUM> constitutes a strain signal acquisition unit.

Specifically, the signal acquisition unit <NUM> acquires a voltage value corresponding to the microstrain (µε) detected by the strain sensor <NUM> as a strain signal. The signal acquisition unit <NUM> may directly acquire µε as a strain signal if possible, such as when the strain sensor <NUM> or the communication unit <NUM> supports output of µε.

The wear estimation unit <NUM> estimates the wear state of the tread portion <NUM> using the strain signal (µε) acquired by the signal acquisition unit <NUM>. The wear state of the tread portion <NUM> estimated by the wear estimation unit <NUM> typically includes a wear amount (unit: mm) of the tread portion <NUM>, but may also include a residual amount (residual groove amount) of a groove portion formed on the tread portion <NUM>, a wear rate based on the pneumatic tire <NUM> when new (start of use), and the like. Alternatively, it may be an estimated travel distance (or time) until the pneumatic tire <NUM> reaches its use limit due to wear.

The wear estimation unit <NUM> estimates the wear state of the tread portion <NUM> based on the strain signal (Bo) output at the timing of kicking out from the road surface R of the ground contact area Ac (see <FIG>) of the tread portion <NUM> corresponding to the strain sensor <NUM> and the reference value of the strain signal.

Specifically, the wear estimation unit <NUM> uses the strain signal (Bi) output at the timing of stepping on the road surface of the ground contact area Ac as the reference value.

The start time of estimating the wear state of the tread portion <NUM> is typically when the pneumatic tire <NUM> is new, but the start time of estimating the wear state of the tread portion <NUM> may also be used for the pneumatic tire <NUM> which has been used over a certain distance and the wear of the tread portion <NUM> has progressed to a certain extent.

The wear estimation unit <NUM> can determine the estimated wear amount of the tread portion <NUM> based on the difference between the strain signal (Bo (w)) output at the timing of kicking out of the ground contact area Ac from the road surface R and the reference value, or the ratio between Bo (w) and the reference value.

Thus, the wear estimation unit <NUM> determines the estimated wear amount of the tread portion <NUM> based on the difference between Bo (w) and the reference value.

The wear estimation unit <NUM> determines the estimated wear amount of the tread portion <NUM> by associating the difference or the ratio with the wear amount (or the residual groove amount).

The wear estimation unit <NUM> may adjust the estimated wear amount of the tread portion <NUM> using the ratio between the value of the strain signal (Bo (n)) when the pneumatic tire <NUM> is new and the above-mentioned reference value.

For example, the wear estimation unit <NUM> adjusts the ratio of Bo (n) to Bi (n) based on the value of the strain signal when the pneumatic tire <NUM> is new. Specifically, the wear estimation unit <NUM> adjusts the value of Bo (n)/Bi (n) based on the strain signal when the pneumatic tire <NUM> is new to "<NUM>" even when the value is other than "<NUM>" (such processing is called "offset processing").

In practice, the wear estimation unit <NUM> adjusts all the values of Bo (n)/Bi (n) to "<NUM> " based on the number of sensor units <NUM> that perform communication with the processing device <NUM>, that is, the strain signals in the new state of tire corresponding to the number of pneumatic tires <NUM> mounted on the vehicle.

The wear estimation unit <NUM> determines an estimated wear amount of the tread portion <NUM> on the basis of the ratio when the pneumatic tire <NUM> is new and the ratio when the pneumatic tire <NUM> is used for traveling a certain distance and worn.

A specific example of the offset processing when the pneumatic tire <NUM> is new will be described later.

The wear estimation unit <NUM> may perform machine learning using the time-series waveform of the strain signal acquired by the signal acquisition unit <NUM>. Specifically, the wear estimation unit <NUM> can create a wear estimation model by executing machine learning with the wear amount as an object variable using the feature amount relating to the peak value of the strain signal.

The characteristic quantity relating to the peak value of the strain signal includes, for example, a ratio or difference between the peak value of the strain signal at the stepping timing and the kicking timing of the pneumatic tire <NUM>, or a ratio or difference between the peak value of the strain signal at the kicking timing when the pneumatic tire <NUM> is new and when the wear is estimated. That is, the wear estimation unit <NUM> can execute machine learning by using "the amount of wear of the tread portion <NUM>" as an objective variable and "an index value related to the size of the peak on the kick out side of the time-series waveform of the strain signal" as an explanatory variable. The index value may be any value (ratio or difference) related to the peak of the strain signal (µε) output at the timing of kicking out related to the reference value.

The feature amount may be estimated based on one time (one revolution) of time series waveforms, or the accuracy of estimating the wear state of the tread portion <NUM> may be enhanced by applying statistical methods such as average, median, and outlier processing based on a plurality of times of time series waveforms. Since the feature amount can vary depending on the type (Internal structure, tread pattern, etc.) of the pneumatic tire <NUM> and the tire size, it is preferable that the machine learning is executed for each type and tire size. By advancing such machine learning, it is possible to estimate the wear state of the tread portion <NUM> with high accuracy, for example, even in the case of a new tire size which has never been obtained before.

Further, since the index value (feature value) can vary depending on load, speed, temperature, internal pressure, and the like, the wear estimation unit <NUM> may increase the accuracy of estimating the wear state of the tread portion <NUM> by combining a signal output from the internal pressure sensor <NUM> or the temperature sensor <NUM> (or an acceleration sensor) with a strain signal.

The wear estimation unit <NUM> may supplement or substitute the estimation of the wear state described above by using a learning model (wear estimation model) obtained by executing machine learning.

The output unit <NUM> outputs information on the wear state of the tread portion <NUM> estimated by the wear estimation unit <NUM>. More specifically, the output unit <NUM> can output the amount of wear of the tread portion <NUM>, the amount of remaining grooves, the wear rate of the pneumatic tire <NUM> relative to the new one, and the running distance (or time) until the use limit is reached.

For example, the output unit <NUM> may display a warning (alert) on a display device provided in the vehicle indicating that the amount of wear (or the rate of wear) has exceeded a threshold, or that the amount of remaining grooves and the travel distance (or time) have fallen below the threshold, or may notify the warning by a voice guidance and/or an alarm sound.

The output unit <NUM> may display or report information or a warning about the internal pressure or temperature based on signals from the internal pressure sensor <NUM> and the temperature sensor <NUM>.

Next, the operation of the tire wear amount estimation system <NUM> will be described. Specifically, the operation of estimating the wear amount of the tread portion <NUM> by the tire wear amount estimation system <NUM> will be described.

<FIG> shows the pneumatic tire <NUM> provided with the strain sensor <NUM> and an example of output of a strain signal by the strain sensor <NUM>. Specifically, <FIG> shows an example of a time-series waveform of microstrain (µε) detected by the strain sensor <NUM> provided on inside surface of the pneumatic tire <NUM> (tread portion <NUM>).

As shown in <FIG>, when the pneumatic tire <NUM> rolls along the road surface R in the traveling direction, the ground contact area Ac of the tread portion <NUM> where the strain sensor <NUM> is installed also comes into contact with the road surface R.

A ground contact area Ac which is a part of inside surface of the tread portion <NUM> receives compressive stress at the stepping timing to the road surface R. As a result, Bi, which is a strain in the compression direction ("+ " direction in the figure), is generated in the ground contact area Ac. In the present embodiment, the strain sensor <NUM> detects strain in the tire circumferential direction.

Thereafter, when the area of the tread portion <NUM> facing the ground contact area Ac contacts the road surface R, the ground contact area Ac receives tensile stress. As a result, strain occurs in the tensile direction ("-" direction in the figure) in the ground contact area Ac. Thereafter, Bo, which is a strain in the compression direction, is generated again in the ground contact area Ac at the kicking timing from the road surface R.

As described above, the strain at the stepping timing is expressed as Bi, and the strain at the kicking timing is expressed as Bo. The strain of the pneumatic tire <NUM> when it is new is referred to as Bo (n) and Bi (n), and the strain of the pneumatic tire <NUM> at an arbitrary time point in the use process (That is, when the wear state is estimated,) is referred to as Bo (w) and Bi (w).

<FIG> shows an output example of a strain signal when the pneumatic tire <NUM> is new. <FIG> shows an output example of a strain signal when the pneumatic tire <NUM> is worn.

As shown in <FIG>, the values (µε) of Bi (n) and Bo (n) when the pneumatic tire <NUM> is new are approximately the same.

As shown in <FIG>, the value of Bi (w) after the pneumatic tire <NUM> is worn is not significantly different from the value of Bi (n). On the other hand, the value of Bo (w) is clearly smaller than the value of Bo (n).

The wear amount estimation system <NUM> estimates the wear state of the tread portion <NUM> by utilizing such a feature that the peak value of the strain (Bo (w)) at the kicking out timing of inside surface of the tread portion <NUM> decreases by wear progress.

<FIG> shows an estimation operation flow of the wear amount of the pneumatic tire <NUM> (tread portion <NUM>) by the tire wear amount estimation system <NUM>.

As shown in <FIG>, the tire wear amount estimation system <NUM>, in this embodiment, the processing device <NUM> acquires a time series waveform of the strain signal (µε) (S <NUM>). More specifically, the processing device <NUM> acquires time series waveforms (µε) as shown in <FIG>.

As described above, in the present embodiment, only one sensor unit <NUM> is provided in the tire circumferential direction, and the processing device <NUM> acquires time-series waveforms having peak values (Bi, Bo) of strain signals of the stepping timing and the kicking timing as shown in <FIG> for each rotation of the pneumatic tire <NUM>.

The processing device <NUM> may acquire one time-series waveform as shown in <FIG> to estimate the wear amount, but it is preferable to acquire a plurality of time-series waveforms to estimate the wear amount as described above. In addition, at the time of acceleration/deceleration of the vehicle on which the pneumatic tire <NUM> is mounted, since noise mixed into the strain signal increases, it is preferable to use a time-series waveform acquired in a state where a change in the vehicle speed is small.

The processing device <NUM> detects the peak value (Bo (w)) of the strain signal of the kicking out timing by using the acquired time series waveform (S <NUM>). Specifically, the processing device <NUM> detects the peak µε of the kicking out timing based on the output (voltage) value from the strain sensor <NUM> corresponding to the peak of the kicking out timing strain signal.

The processing device <NUM> compares the detected Bo (w) with a reference value (S <NUM>). Specifically, the processing device <NUM> can use, as a reference value, a peak value (Bi (n) or Bi (w)) of the strain signal at the stepping timing.

The processing device <NUM> estimates the wear amount of the tread portion <NUM> using the detected Bo (w) and any of the reference values described above (S <NUM>).

Specifically, the processing device <NUM> can estimate the amount of wear of the tread portion <NUM> based on the difference between Bn (w) and the reference value or the ratio between Bn (w) and the reference value.

More specifically, the processing device <NUM> can estimate the amount of wear of the tread portion <NUM> based on any of the following.

Further, as described above, the processing device <NUM> may estimate not only the amount of wear of the tread portion <NUM>, but also other parameters, specifically, the residual amount of groove, the wear rate of the pneumatic tire <NUM> relative to the new one, or the distance (or time) that can be traveled before the limit of use is reached.

When estimating the estimated travel distance (or time), the processing device <NUM> may acquire information such as the accumulated travel distance and time from the ECU side of the vehicle, if necessary.

The processing device <NUM> determines whether or not an alert is necessary based on the estimated wear amount (S <NUM>). Specifically, the processing device <NUM> determines whether the wear amount (or wear rate) exceeds a threshold value. Alternatively, the processing device <NUM> may determine whether the residual groove amount and the travel distance (or time) described above are less than the threshold value.

If the estimated wear amount (or wear rate) exceeds a threshold value (Residual groove amount, running distance (or time) is below the threshold. ), the processing device <NUM> outputs an alert (S <NUM>).

Specifically, the processing device <NUM> may display the alert on a display device provided in the vehicle or may notify the alert by means of a voice guidance and/or an alarm sound.

As described above, the wear amount estimation system <NUM> (processing device <NUM>) can estimate the wear amount of the tread portion <NUM> using a strain signal (Bo (w)) at the kicking out timing or the like, but the accuracy of estimating the wear amount may be enhanced by executing the offset processing as follows.

Before the offset processing, variation in µε inevitably occurs due to individual difference of the pneumatic tire <NUM> or the like. Therefore, if the wear amount is estimated without performing the offset processing, it is possible to estimate that the wear has progressed, but there is a limit to accurately estimating the specific wear amount (mm) and the residual groove amount (mm).

Therefore, the ratio of the strain signal when the pneumatic tire <NUM> is new is adjusted using the ratio of Bo (w) and the reference value as described above. For example, the value of Bo (n)/Bi (n) based on the strain signal (Bo (n)) when the pneumatic tire <NUM> is new is adjusted to "<NUM>".

When the difference between Bo (w) and the reference value is used while executing the offset processing, the processing device <NUM> can estimate the wear amount of the tread portion <NUM> based on the following calculation formula.

When the ratio of Bo (w) to the reference value is used while performing such calibration, the processing device <NUM> can estimate the wear amount of the tread portion <NUM> based on the following calculation formula.

According to the embodiment described above, the following effects are obtained. Specifically, according to the tire wear amount estimation system <NUM>, the wear state of the tread portion <NUM> can be estimated based on the strain signal (Bo) output at the timing of kicking out of the ground contact area Ac of the strain sensor <NUM> from the road surface R and the reference value (Bi or Bo (n)) of the strain signal.

Since the strain signal shows the same tendency regardless of the traveling speed of the vehicle to which the pneumatic tire <NUM> is mounted, the amount of wear of the tread portion <NUM> can be estimated with high accuracy even when the vehicle is mainly traveling at a low speed (For example, about <NUM>/h).

In other words, according to the tire wear amount estimation system <NUM>, even if the vehicle on which the pneumatic tire <NUM> is mounted is mainly driven at a low speed, a high estimation accuracy of the wear amount can be achieved.

It is difficult to apply the conventional algorithm for estimating the wear state based on the time-series waveform of the acceleration as it is to the time-series waveform of the strain signal. Since the strain sensor <NUM> is more sensitive than the acceleration sensor, it picks up the irregularities of the road surface R, the dispersion of the peak on the tensile side at the time of grounding of the ground contact area Ac increases, and the dispersion of the wear feature amount, which is the gradient between the peak of the stepping (kicking out) timing and the peak at the time of grounding, also increases.

In the present embodiment, unlike the estimation algorithm of the wear state based on the time series waveform, a feature is found in which the peak value of the strain (Bo (w)) at the kicking out timing of inside surface of the tread portion <NUM> decreases with the wear progress, and the wear state of the tread portion <NUM> is estimated based on the feature.

The tire wear amount estimation system <NUM> uses a strain signal (Bi (n) or Bi (w)) at the stepping timing as a reference value of the strain signal.

Therefore, by applying an appropriate reference value according to the type or size of the pneumatic tire <NUM> or the like, the estimation accuracy of the wear state can be further improved.

In the present embodiment, the wear amount estimation system <NUM> can determine the estimated wear amount of the tread portion <NUM> based on the difference between the strain signal (Bo (w)) output at the timing of kicking out and the reference value (Bi (n), Bi (w)) or the ratio between Bo (w) and the reference value.

Therefore, by applying a method for determining an appropriate estimated wear amount according to the type or size of the pneumatic tire <NUM> or the like, the accuracy of estimating the wear state can be further enhanced. In particular, when the ratio of Bo (w) to the reference value is used, the deterioration of the estimation accuracy due to individual differences between the strain sensor <NUM> and the pneumatic tire <NUM>, variations in the internal pressure, and the like can be prevented.

In this embodiment, the wear amount estimation system <NUM> can adjust (calibrate) the estimated wear amount of the tread portion <NUM> by using the ratio between the value of the strain signal (Bo (n)) when the pneumatic tire <NUM> is new and the reference value.

Therefore, even when the detected µε varies due to individual difference of the pneumatic tire <NUM> or the like, the specific wear amount (mm) and the residual groove amount (mm) can be estimated with high accuracy by executing such calibration.

Although the contents of the present invention have been described with reference to the embodiments described above, it is obvious to those skilled in the art that the present invention is not limited to these descriptions and that various modifications and improvements are possible.

For example, in the above-described embodiment, the strain sensor <NUM> detects strain in the tire circumferential direction, but the strain sensor <NUM> detects a strain in the tire width direction or tire radial direction, and the processing device <NUM> may estimate the wear state of the tread portion <NUM> based on the detected strain.

In the above embodiment, the processing device <NUM> is realized on the ECU of a vehicle or on a server computer connected via a wireless communication network, but a part of the functional blocks constituting the processing device <NUM> may be provided on the ECU, and other functional blocks may be realized on the server computer.

The main functions of the processing device <NUM> may also be provided as a software program executable in a computer. In addition, the software program may be provided over a communications network or recorded on a computer readable recording medium such as an optical disk, hard disk drive, or flash memory.

<FIG> is an overall schematic configuration diagram of a tire wear amount estimation system <NUM> related to modified example. As shown in <FIG>, the processing device <NUM> (Some functions may be implemented by the ECU) mounted on a vehicle performs wireless communication with the sensor unit <NUM> mounted on the pneumatic tire <NUM>, performs wireless communication with a wireless base station <NUM>, and connects to a server computer <NUM> provided on a network cloud <NUM>.

When the data of the time-series waveform of the strain signal shown in <FIG> or the like is transmitted from the sensor unit <NUM> to the processing device <NUM>, the amount of data may be large and the battery <NUM> (see <FIG>) may be consumed quickly. Therefore, in such a case, the sensor unit <NUM> may extract the feature amount of the strain signal, specifically, Bo and Bi (µε), and transmit only the extracted Bo and Bi to the processing device <NUM> instead of the data of the time series waveform.

On the other hand, if the operating conditions such as the battery <NUM> are satisfied, the functions of the processing device <NUM> described in the above-described embodiment may be mounted in the sensor unit <NUM>.

Claim 1:
A tire wear amount estimation system (<NUM>) comprising:
a strain signal acquisition unit (<NUM>) that acquires a strain signal output from a strain sensor (<NUM>) provided on an inner surface or inside of a tire (<NUM>); and
a wear estimation unit (<NUM>) that estimates a wear state of a tread portion (<NUM>) by comparing the strain signal output (Bo(w)) at a timing of kicking out from a road surface (R) of the ground contact area (Ac) of the tread portion corresponding to the strain sensor with a reference value of the strain signal,
wherein the wear estimation unit uses, as the reference value, the strain signal output (Bi(n), Bi(w)) at a timing of stepping on the road surface of the ground contact area.