Patent Description:
Conventionally, there has been known an apparatus in which an acceleration sensor (accelerometer) is mounted inside a tire/wheel assembly in which a tire is mounted on a rim wheel, and the speed and traveling distance of a vehicle mounted with the tire/wheel assembly are calculated based on acceleration data detected by the acceleration sensor (See Patent Literature and <CIT>).

Specifically, a sensor unit including an acceleration sensor is attached to the rim wheel as integrated with the air valve. Attention is also drawn to the disclosures of <CIT> and <CIT>.

Recently, an acceleration sensor is also used for detecting the road surface condition, but in such a case, it is preferable to mount the acceleration sensor on the inner surface of the tread of the tire.

When the acceleration sensor is mounted on the inner surface of the tread, when a part of the tread corresponding to the mounting position of the acceleration sensor touches the ground, the part of the tread is deformed, so that the detected acceleration (centrifugal acceleration) in the tire radial direction is momentarily largely dropped.

Therefore, an object of the present invention is to provide a tire state detection system, a tire state detection method, and a tire state detection program capable of detecting a tire state without being affected by the grounding of a portion of the tread corresponding to the mounting position of the acceleration sensor even when the acceleration sensor is mounted on the inner surface of the tread of the tire.

One aspect of the present invention is a tire state detection system as claimed in claim <NUM>.

One aspect of the present invention is a tire state detection method as claimed in claim <NUM>.

One aspect of the present invention is a tire state detection program as claimed in claim <NUM>.

Hereinafter, an embodiment will be described based on the drawings. It should be noted that the same or similar reference numerals are given to the same functions and structures, and the description thereof will be omitted as appropriate.

<FIG> is an overall schematic configuration diagram of a tire state detection system <NUM> according to the present embodiment. As shown in <FIG>, the tire state detection system <NUM> comprises a sensor unit <NUM> and a processing device <NUM>.

The tire state detection system <NUM> includes an acceleration sensor mounted on the inner surface of a tread <NUM> of the pneumatic tire <NUM> (Tire).

Specifically, as will be described later, the sensor unit <NUM> includes various sensors and batteries for detecting acceleration in a predetermined direction, such as in the tire radial direction.

The sensor unit <NUM> is mounted on the inner surface of the tread <NUM> of the pneumatic tire <NUM>. <FIG> shows a cross-sectional shape in the tire width direction of the pneumatic tire <NUM> assembled to a rim wheel. The sensor unit <NUM> may also include a sensor for detecting temperature and pressure (tire pressure) in addition to acceleration.

One sensor unit <NUM> may be provided in the tire circumferential direction. In view of the fact that the ground contact surface of the tread <NUM> is deformed when the vehicle turns left and right, the sensor unit <NUM> is preferably provided at the center of the tread <NUM> in the tire width direction.

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

The processing device <NUM> is usually provided in a vehicle on 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 a vehicle. Alternatively, the processing device <NUM> may be implemented on a server computer connected via a wireless communication network, rather than on a vehicle.

<FIG> is a functional block diagram of the tire state detection system <NUM>. As shown in <FIG>, the sensor unit <NUM> includes an acceleration sensor <NUM> and a communication unit <NUM>. The processing device <NUM> includes a communication unit <NUM>, an acceleration data acquisition unit <NUM>, an acceleration data extraction unit <NUM>, and a calculation unit <NUM>.

The acceleration sensor <NUM> detects acceleration in a predetermined direction of the pneumatic tire <NUM>. In the present embodiment, the acceleration sensor <NUM> detects acceleration of the pneumatic tire <NUM> in the tire radial direction, specifically, centrifugal acceleration (May be called centrifugal force).

As the acceleration sensor <NUM>, a general-purpose acceleration sensor such as a <NUM>-axis acceleration sensor may be used.

In the present embodiment, the acceleration sensor <NUM> does not necessarily have to be constantly activated, but may be activated at a measurement interval T (See <FIG>, e.g., every <NUM> seconds) to detect a predetermined number of accelerations.

The communication unit <NUM> and the communication unit <NUM> execute radio communication between the sensor unit <NUM> and the processing device <NUM>. The radio communication method by the communication unit <NUM> is not particularly limited. For example, the communication method includes a method using a frequency (UHF, etc.) used in TPMS (tire pressure monitoring system) or the like, and a method in accordance with the standard of short-range wireless communication.

The communication unit <NUM> can communicate with a control device such as an ECU of a vehicle on which the pneumatic tire <NUM> is mounted, or with the outside of the vehicle via a wireless communication network.

The acceleration data acquisition unit <NUM> acquires acceleration data detected by the acceleration sensor <NUM>. Specifically, the acceleration data acquisition unit <NUM> acquires the acceleration data at each predetermined acquisition interval.

<FIG> shows an example of acceleration data acquired by the sensor unit <NUM>. Specifically, <FIG> shows an example of acceleration data in the tire radial direction acquired by the acceleration sensor <NUM>.

In <FIG>, the section in which the acceleration is greatly reduced roughly corresponds to the grounding time Tc at which the mounting position of the sensor unit <NUM> (Acceleration sensor <NUM>) and the portion of the tread <NUM> corresponding to the mounting position are grounded on the road surface R (See <FIG>). The rotation period Tr indicates a time for one rotation of the pneumatic tire <NUM>.

The acceleration data acquisition unit <NUM> acquires acceleration data at each acquisition interval Tac (predetermined acquisition interval), and acquires the value of acceleration in the tire radial direction detected by the acceleration sensor <NUM>.

The acquisition interval Tac is optional, but is preferably set as follows in consideration of the power consumption of the acceleration sensor <NUM> and the accuracy of the vehicle speed and traveling distance calculated by the calculation unit <NUM>. <MAT> <MAT>.

As shown in (Expression <NUM>), the acquisition interval Tac is preferably shorter than the rotation period Tr. That is, the acquisition interval Tac may vary depending on the speed of the vehicle on which the pneumatic tire <NUM> (Sensor unit <NUM>) is mounted.

The acquisition interval Tac is preferably longer than the grounding time Tc. By satisfying (Expression <NUM>) and (Expression <NUM>), the acceleration data can be acquired without fail while the pneumatic tire <NUM> rotates once, and the acceleration data acquired in a state where the mounting position of the sensor unit <NUM> and the corresponding part of the tread <NUM> are grounded can be suppressed to <NUM> time.

It is not always necessary to satisfy both of (Expression <NUM>) and (Expression <NUM>), and only one of them may be satisfied.

Furthermore, the acceleration data acquisition unit <NUM> may repeat the acquisition of <NUM> or more acceleration data continuously acquired for each acquisition interval Tac (For example, <NUM> seconds. ) for each measurement interval T (See <FIG>, e.g., every <NUM> seconds). That is, the acceleration data acquisition unit <NUM> may repeatedly acquire the predetermined number of acceleration data of <NUM> or more at each measurement interval T.

The acceleration data acquisition unit <NUM> can adjust the acquisition interval Tac according to the diameter size of the pneumatic tire <NUM>. Specifically, the acceleration data acquisition unit <NUM> increases the acquisition interval Tac as the diameter size of the pneumatic tire <NUM> increases, and decreases the acquisition interval Tac as the diameter size of the pneumatic tire <NUM> decreases. Thus, acceleration data can be acquired at appropriate timing corresponding to the diameter size (tire size) of the pneumatic tire <NUM>.

The acceleration data extraction unit <NUM> extracts appropriate acceleration data for calculation in the calculation unit <NUM> from a plurality of acceleration data acquired by the acceleration data acquisition unit <NUM>.

Specifically, the acceleration data extraction unit <NUM> extracts intermediate acceleration data from the continuous <NUM> or more acceleration data acquired sequentially by the acceleration data acquisition unit <NUM>.

The intermediate acceleration data is one or a plurality of acceleration data indicating an intermediate acceleration excluding the maximum acceleration data indicating at least the maximum acceleration and the minimum acceleration data indicating the minimum acceleration.

The acceleration data extraction unit <NUM> generates a set of discrete acceleration data by extracting the acceleration data in this manner.

More specifically, it is preferable that the acceleration data extraction unit <NUM> extracts median acceleration data corresponding to a median from the continuous <NUM> or more acceleration data acquired sequentially by the acceleration data acquisition unit <NUM>.

By using the median value of the acceleration data rather than the average value of the plurality of acceleration data, the influence of the instantaneous drop of acceleration due to the grounding of the tread <NUM> can be eliminated.

The calculation unit <NUM> executes calculation using the intermediate acceleration data extracted by the acceleration data extraction unit <NUM>. Specifically, the calculation unit <NUM> executes calculation using the median acceleration data.

In the present embodiment, the calculation unit <NUM> calculates the speed or traveling distance of the vehicle on which the pneumatic tire <NUM> is mounted.

<FIG> is a diagram schematically showing a variable used for calculating the speed or the traveling distance of the vehicle and a side surface of the pneumatic tire <NUM>.

As shown in <FIG>, the tire outer surface <NUM> a of the pneumatic tire <NUM> rolls in contact with the road surface R. The sensor unit <NUM> is mounted on a tire inner surface <NUM> a of the pneumatic tire <NUM>. As described above, the sensor unit <NUM> is provided with the acceleration sensor <NUM> (See <FIG>).

The calculation unit <NUM> uses the acceleration (a) based on the acceleration data extracted by the acceleration data extraction unit <NUM> to calculate the rotational speed of the tire inner surface <NUM> b (Vi), that is, the rotational speed of the acceleration sensor <NUM>.

Specifically, the calculation unit <NUM> uses the to calculate the rotational speed (Vi), and further calculates the angular velocity (ω). ri is a radius from the center of the pneumatic tire <NUM> to the tire inner surface <NUM> a. [Formula <NUM>] <MAT>.

The calculation unit <NUM> uses the (Expression <NUM>) to calculate the rotational speed of the tire outer surface <NUM> a (Vo) and the vehicle speed (Vv). [Formula <NUM>] <MAT>.

Here, the traveling distance (L) of the vehicle can generally be calculated using (Expression <NUM>), but as described above, the traveling distance (L) is affected by a momentary drop in acceleration due to the grounding of the tread <NUM>, and since the acceleration sensor <NUM> needs to be constantly activated, power consumption also increases. [Formula <NUM>] <MAT>.

Therefore, in the present embodiment, as described above, the calculation unit <NUM> calculates the vehicle speed (Vv) and the traveling distance (L) using the median value (an) of the acceleration indicated by at least <NUM> continuous acceleration data acquired for each acquisition interval Tac (see <FIG>).

Specifically, the calculation unit <NUM> uses the (Expression <NUM>) to calculate the vehicle speed (Vv) and the traveling distance (L). [Formula <NUM>] <MAT>.

The calculation unit <NUM> calculates the vehicle speed (Vv) and the traveling distance (L) using the median values (an) of the plurality of accelerations acquired at each measurement interval T.

The calculation unit <NUM> calculates the traveling distance (L) by assuming that the vehicle travels at the same speed during the measurement interval T (For example, as described above, for <NUM> seconds).

Next, the operation of the tire state detection system <NUM> will be described. Specifically, the operation of the tire state detection system <NUM> for calculating the vehicle speed (Vv) and the traveling distance (L) will be described.

<FIG> shows the calculation operation flow of the vehicle speed (Vv) and the traveling distance (L) by the tire state detection system <NUM>.

As shown in <FIG>, the tire state detection system <NUM> (Specifically, the processing device <NUM>, same as below) acquires acceleration data at each predetermined acquisition interval (S <NUM>).

Specifically, as shown in <FIG>, the tire state detection system <NUM> acquires a plurality of acceleration data for each acquisition interval Tac. More specifically, the tire state detection system <NUM> acquires continuous acceleration data of <NUM> or more.

In the example shown in <FIG>, the acceleration data D1, the acceleration data D2, and the acceleration data D3 are acquired. As described above, the acceleration data D1, the acceleration data D2, and the acceleration data D3 indicate acceleration in the tire radial direction (centrifugal acceleration).

The tire state detection system <NUM> extracts intermediate acceleration data in which the magnitude of acceleration is intermediate from the plurality of acquired acceleration data (S <NUM>).

Specifically, the tire state detection system <NUM> extracts acceleration data D3 corresponding to a median value from the acceleration data D1, the acceleration data D2, and the acceleration data D3.

That is, the tire state detection system <NUM> excludes the acceleration data D2 (Maximum acceleration data) indicating the maximum acceleration and the acceleration data D1 (minimum acceleration data) indicating the minimum acceleration from among the acceleration data D1, the acceleration data D2 and the acceleration data D3, and extracts the acceleration data D3 (intermediate acceleration data).

The tire state detection system <NUM> calculates the rotational speed (Vo) of the pneumatic tire <NUM> using the extracted acceleration data (S <NUM>).

Specifically, the tire state detection system <NUM> applies the acceleration data D3 (median value) to the above-described (Expression <NUM>) to calculate the rotational speed (Vo).

The tire state detection system <NUM> uses the calculated rotational speed (Vo) to calculate the vehicle speed (Vv) and the traveling distance (L) of the vehicle on which the pneumatic tire <NUM> is mounted (S <NUM>).

Specifically, the tire state detection system <NUM> applies the calculated rotational speed (Vo) to the above-described (Expression <NUM>) to calculate the vehicle speed (Vv) and the traveling distance (L).

According to the embodiment described above, the following effects can be obtained. Specifically, according to the tire state detection system <NUM>, intermediate acceleration data excluding the maximum acceleration data and the minimum acceleration data is extracted from the <NUM> or more acceleration data sequentially acquired. Further, the vehicle speed (Vv) or the traveling distance (L) is calculated using the extracted intermediate acceleration data.

Therefore, even when the acceleration sensor <NUM> (Sensor unit <NUM>) is mounted on the inner surface of the tread <NUM> and the detected acceleration in the tire radial direction (centrifugal acceleration) drops momentarily and greatly, the tire state can be detected without being affected by the ground contact of the part of the tread <NUM> corresponding to the mounting position of the acceleration sensor <NUM> such as the rotational speed (Vo) of the pneumatic tire <NUM>.

In the present embodiment, the median acceleration data corresponding to the median is extracted from the sequential acceleration data of <NUM> or more.

Therefore, the rotational speed (Vo) can be estimated with high accuracy while eliminating the influence of the instantaneous drop of acceleration due to the grounding of the tread <NUM>. Thus, the vehicle speed (Vv) and the traveling distance (L) can be more accurately calculated.

In this embodiment, the acquisition interval Tac (predetermined acquisition interval) can be shorter than the time for one revolution of the pneumatic tire <NUM> (rotation period Tr).

Therefore, since the acceleration data is always acquired during one rotation of the pneumatic tire <NUM>, the rotational speed (Vo) can be estimated with higher accuracy. Thus, the vehicle speed (Vv) and the traveling distance (L) can be more accurately calculated.

In this embodiment, the acquisition interval Tac can be longer than the grounding time Tc of the acceleration sensor <NUM> (Sensor unit <NUM>) and the corresponding portion of the tread <NUM>.

Therefore, while the pneumatic tire <NUM> rotates once, the acceleration data acquired in a state where the portion of the tread <NUM> corresponding to the mounting position of the sensor unit <NUM> is grounded can be suppressed to at most <NUM> time. This may eliminate the possibility that the acceleration data is extracted as a median value (intermediate acceleration data). Thus, the vehicle speed (Vv) and the traveling distance (L) can be more accurately calculated.

In the present embodiment, the acquisition interval Tac can be adjusted according to the diameter size of the pneumatic tire <NUM>.

Therefore, acceleration data can be acquired at an appropriate timing according to the diameter size of the pneumatic tire <NUM> (tire size). As a result, the vehicle speed (Vv) and the traveling distance (L) can be calculated more accurately.

In this embodiment, the acceleration sensor <NUM> does not necessarily have to be constantly activated, but may be activated at a measurement interval T (see <FIG>) to detect a predetermined number of accelerations.

Therefore, when there is an influence due to the momentary drop of acceleration caused by the grounding of the tread <NUM>, the power consumption of the sensor unit <NUM> can be suppressed, that is, the accuracy of the vehicle speed (Vv) and the traveling distance (L) can be maintained while the consumption of the battery is suppressed.

While the contents of the present invention have been described in accordance with the above embodiments, it will be apparent 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 median value is used among <NUM> or more acceleration data, but when the tire state detection system <NUM> acquires more acceleration data, the median value may not necessarily be used. Specifically, the tire state detection system <NUM> may use intermediate acceleration data excluding the maximum acceleration data and the minimum acceleration data.

Furthermore, the three or more acceleration data may not necessarily be sequentially acquired. That is, as long as the three or more acceleration data satisfy the above-mentioned (Expression <NUM>) and (Expression <NUM>), the acceleration data may not necessarily be acquired continuously.

In the above-described embodiment, the vehicle speed (Vv) and the traveling distance (L) are calculated, but only one of them may be calculated. Further, in the case of calculation using the rotational speed (Vo), for example, acceleration or deceleration of the vehicle may be calculated in addition to the vehicle speed (Vv) and the traveling distance (L).

In the above-described embodiment, the acceleration sensor <NUM> detects acceleration in the tire radial direction, but may detect acceleration in the tire circumferential direction. In this case, the processing device <NUM> may calculate the rotational speed (Vo) based on the acceleration in the tire circumferential direction.

Claim 1:
A tire state detection system (<NUM>) using an acceleration sensor (<NUM>) mounted on an inner surface of a tread (<NUM>) of a tire (<NUM>), comprising:
an acceleration data acquisition unit (<NUM>) for acquiring acceleration data detected by the acceleration sensor (<NUM>) at every predetermined acquisition interval (Tac);
the system being characterized in further comprising:
an acceleration data extraction unit (<NUM>) for extracting intermediate acceleration data (D3) indicating an intermediate acceleration by excluding maximum acceleration data (D2) indicating a maximum acceleration and minimum acceleration data (D1) indicating a minimum acceleration from three or more acceleration data sequentially acquired by the acceleration data acquisition unit (<NUM>); and
a calculation unit (<NUM>) for executing a calculation using the intermediate acceleration data (D3) extracted by the acceleration data extraction unit (<NUM>).