JP2014178270A - Tire abrasion detection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tire abrasion detection device capable of accurately performing abrasion detection of a tread part without depending on the internal state of a tire.SOLUTION: A tire abrasion detection device includes a power source 18, a pair of electrodes 19 away from each other in the axial direction of a tire 6 and bonded to the inner peripheral surface of the tire 6 in a mutually insulated state, and a measurement circuit 17 measuring electrostatic capacity between the electrodes 19 when applying voltage from the power source 18 to the pair of electrodes 19. The tire abrasion detection device also includes a temperature sensor 12 detecting the internal temperature of the tire 6. A sensor unit controller 14 corrects the electrostatic capacity measured by the measurement circuit 17 according to the tire internal temperature detected by the temperature sensor 12, and detects an abrasion state with the corrected electrostatic capacity.

Description

  The present invention relates to a tire wear detection device for detecting wear on a tread portion of a tire.

  Various devices have been proposed as tire wear detection devices for detecting wear of tires (specifically, tread portions). For example, as shown in FIG. 6, the tire wear detection device disclosed in Patent Literature 1 is installed in a vehicle body, a wear detector 82 embedded in a tread portion 81 of a tire 80, a sensor unit 84 provided in a wheel 83, and a vehicle body. Receiver unit (not shown). The wear detector 82 includes a piezoelectric element and a resonance circuit that generates a radio wave signal from a voltage signal generated by the piezoelectric element. In the wear detector 82, as wear of the tread portion 81 progresses, the impact that the piezoelectric element receives from the road surface increases, and the level of the voltage signal generated by the piezoelectric element also increases. For this reason, the level (intensity) of the radio signal generated by the resonance circuit also increases.

  The sensor unit 84 wirelessly transmits a pressure data signal indicating the internal air pressure of the tire 80, receives the radio signal generated by the wear detector 82, and generates a signal indicating the wear state of the tire 80 based on the received radio signal. Then, a signal indicating the wear state is wirelessly transmitted. The receiver unit receives a signal indicating the wear state from the sensor unit 84, and determines the wear state of the tread portion 81 based on the received signal.

JP 2011-189795 A

  By the way, in detecting the wear of the tread portion, it is desired to improve the detection accuracy. However, the detection accuracy of wear varies depending on the internal state of the tire, and there is a possibility that the wear detection cannot be performed accurately.

  An object of the present invention is to provide a tire wear detection device capable of accurately detecting wear on a tread portion without being influenced by the internal state of the tire.

  In order to solve the above problem, the tire wear detection device according to claim 1 is a tire wear detection device that is mounted inside a tire of a vehicle and detects wear on a tread portion of the tire, And a pair of electrodes that are spaced apart from each other and bonded to the inner circumferential surface of the tire, and a capacitance of the electrodes when a voltage is applied from the power source to the pair of electrodes. A measurement circuit; a wear detection unit capable of detecting a wear state of the tread portion based on a capacitance measured by the measurement circuit; and an internal state detection unit detecting an internal state of the tire. The detection unit corrects the capacitance measured by the measurement circuit according to the internal state of the tire detected by the internal state detection unit, and detects the wear state using the corrected capacitance. about The gist.

  According to this, when a voltage is applied to the pair of electrodes, lines of electric force are generated between the pair of electrodes. Since the area and distance of the pair of electrodes are constant, the number of electric lines of force leaking from the tire as a dielectric interposed between the electrodes is small as the wear of the tread portion does not progress, and the ratio of the tire Since the dielectric constant increases, the capacitance between the pair of electrodes increases. On the other hand, as the wear of the tire progresses, the amount of electric lines of force leaking from the tire increases and the relative permittivity of the tire decreases, so that the capacitance between the pair of electrodes decreases. The capacitance varies under the influence of the internal state of the tire, for example, temperature and humidity. For this reason, even if the wear of the tread is not progressing, the capacitance measured under the influence of temperature and humidity becomes smaller than the value that should be measured, and the wear state is accurately detected. There is a risk that it will not be possible. Therefore, the wear detector corrects the measured capacitance according to the internal state to obtain a capacitance that is free from the influence of the internal state, and wears using the corrected capacitance. Detection can be performed. Therefore, wear detection of the tread portion can be accurately performed without being influenced by the internal state of the tire.

Further, in the tire wear detection device, the internal state detection unit may be a temperature sensor that detects an internal temperature of the tire.
According to this, since the electrostatic capacity is greatly affected by the temperature in the tire, the temperature in the tire is measured by the temperature sensor, and the electrostatic capacity is corrected according to the temperature, so that the wear of the tread portion is reduced. Can be obtained more accurately.

  In the tire wear detection device, the wear detection unit corrects the measured capacitance using a correction table in which a plurality of internal temperatures are associated with correction coefficients set in advance for each internal temperature. May be.

According to this, the wear detection unit can easily correct the capacitance by using the correction table.
In the tire wear detection device, the wear detection unit may store a correction method for correcting the measured capacitance, and the correction method may be rewritable.

  According to this, even if the tire is new or not, or the tire manufacturer has the same environment (for example, the same temperature), the measured internal state of the tire (temperature in the tire) Differences occur. For this reason, by rewriting the correction method in accordance with the tire on which the tire wear detection device is installed, wear detection can be performed in a state in which a difference generated for each tire is reduced.

  Further, in the tire wear detection device, a tire sensor unit that is installed inside the tire, detects a state of the tire, and has a transmission unit that transmits the detected tire information; and a tire sensor unit that is installed in a vehicle body of the vehicle, The vehicle includes a tire condition monitoring device including a receiver unit that includes a receiving unit that receives tire information transmitted by the unit, and the power source, the measurement circuit, the internal condition detection unit, and the tire wear detection device, The wear sensor may be included in the tire sensor unit.

  According to this, it is possible to attach the tire wear detecting device to the inside of the tire simply by joining the pair of electrodes to the inner peripheral surface of the tire and installing the tire sensor unit inside the tire.

  According to the present invention, it is possible to accurately detect wear on the tread portion without being influenced by the internal state of the tire.

The schematic block diagram which shows the vehicle by which the tire condition monitoring apparatus of embodiment is mounted. The fragmentary perspective view which shows the electrode in a tire, and a tire sensor unit. The figure which shows the circuit structure of a tire sensor unit and a tire wear detection apparatus. (A) is a graph which shows the relationship between temperature and an electrostatic capacitance, (b) is a table | surface which shows a correction table. The figure which shows the tire wear detection apparatus which detects wear of a tread part. The figure which shows background art.

Hereinafter, an embodiment in which the tire wear detection device is embodied will be described with reference to FIGS.
As shown in FIG. 1, the tire condition monitoring apparatus includes four tire sensor units 3 that are respectively attached to four wheels 2 of the vehicle 1 and a receiver unit 4 that is installed on the vehicle body of the vehicle 1. Each wheel 2 includes a wheel portion 5 and a tire 6 attached to the wheel portion 5. A tire wear detection device is mounted inside the tire 6. The direction in which the central axis of the tire 6 extends is the axial direction of the tire 6, and the rotational direction of the wheel 2 is the rotational direction of the tire 6.

  As shown in FIGS. 2 and 3, the tire 6 includes a plurality of tread grooves 8 extending in the rotation direction in the axial direction, and includes a tread portion 7 in contact with the road surface between the tread grooves 8 adjacent in the axial direction. Each tire sensor unit 3 is installed on the inner peripheral surface of the tire 6 so as to be disposed in the internal space of the tire 6. Each tire sensor unit 3 detects a state of the corresponding tire 6 (in-tire pressure and in-tire temperature) and wear of the tread portion 7 and wirelessly transmits a signal including data indicating the detected tire state and wear state. Send.

  Each tire sensor unit 3 includes a pressure sensor 11, a temperature sensor 12, a sensor unit controller 14, a transmission circuit 16, a measurement circuit 17, and a power source 18 inside the case 3a, and a pair of electrodes 19 outside the case 3a. The pair of electrodes 19 are rectangular plates of the same size, and are joined to the inner peripheral surface of the tire 6 in a state where they are insulated from each other with an interval along the axial direction of the tire 6. In addition, the case 3 a is joined to the inner peripheral surface of the tire 6 so as to straddle the pair of electrodes 19.

  The tire sensor unit 3 operates by supplying power from the power source 18. The pressure sensor 11 detects the pressure in the corresponding tire 6 (in-tire pressure), and outputs the in-tire pressure data obtained by the detection to the sensor unit controller 14. The temperature sensor 12 as the internal state detection unit of the tire 6 detects the temperature in the corresponding tire 6 and outputs the temperature data in the tire obtained by the detection to the sensor unit controller 14.

  The sensor unit controller 14 includes a microcomputer including a CPU and a storage unit (RAM, ROM, etc.), and an ID code as identification information unique to each tire sensor unit 3 is registered in the storage unit. This ID code is information used to identify each tire sensor unit 3 in the receiver unit 4. The sensor unit controller 14 outputs tire pressure data and tire temperature data to the transmission circuit 16. The transmission circuit 16 as a transmission unit modulates data to generate an RF signal, and wirelessly transmits the RF signal from the transmission antenna 21.

  The pair of electrodes 19 is electrically connected to the power source 18 via the measurement circuit 17, and a voltage is applied to the pair of electrodes 19 by the power source 18. When a voltage is applied to the pair of electrodes 19, electric lines of force F are generated between the pair of electrodes 19, and electrons move between the pair of electrodes 19. Since the tire 6 as a dielectric is interposed between the pair of electrodes 19, an electrostatic capacity can be provided between the pair of electrodes 19. This capacitance depends on the amount of electric force lines F passing through the tire 6, and the amount of electric force lines F leaking from the tire 6 is so small that the wear of the tread portion 7 does not progress. Since the ratio increases, the capacitance between the pair of electrodes 19 increases. On the other hand, as the wear of the tread portion 7 progresses, the amount of electric lines of force F leaking from the tire 6 increases and the relative dielectric constant of the tire 6 decreases, so that the capacitance between the pair of electrodes 19 decreases.

  The measurement circuit 17 is electrically connected to the pair of electrodes 19, and the measurement circuit 17 detects the capacitance between the pair of electrodes 19 as a voltage. The measurement circuit 17 is signal-connected to the sensor unit controller 14, and the voltage signal measured by the measurement circuit 17 is output to the sensor unit controller 14.

  The storage unit of the sensor unit controller 14 stores an overall program that comprehensively controls the operation of the tire sensor unit 3. In addition, a threshold for comparison with the voltage (capacitance) measured by the measurement circuit 17 is stored in advance in the storage unit of the sensor unit controller 14. The threshold is set larger than the voltage (capacitance) detected when the wear of the tread portion 7 proceeds excessively. When the voltage detected by the measurement circuit 17 exceeds the threshold value, the sensor unit controller 14 generates an alarm signal and transmits it from the transmission circuit 16. On the other hand, the sensor unit controller 14 does not generate an alarm signal when the voltage detected by the measurement circuit 17 does not exceed the threshold value.

  Therefore, in this embodiment, the sensor unit controller 14 constitutes a wear detection unit that detects wear of the tread portion 7. In the present embodiment, the tire wear detection device includes a power source 18 provided in the case 3a of the tire sensor unit 3, a temperature sensor 12, a measurement circuit 17, a sensor unit controller 14 (a wear detection unit), And a pair of electrodes outside the case 3a. The tire sensor unit 3 is joined to the inner peripheral surface of the tire 6 in a state of straddling the pair of electrodes 19.

  Further, the sensor unit controller 14 corrects the electrostatic capacitance obtained by the measurement of the measurement circuit 17 based on the tire temperature data output from the temperature sensor 12. The capacitance is affected by the temperature (internal state) in the tire 6 where the pair of electrodes 19 are placed.

  As shown in FIGS. 4 (a) and 4 (b), assuming that the capacitance obtained when the temperature in the tire 6 is 20 ° C. is 100 (reference value), the static temperature decreases as the temperature decreases from 20 ° C. The capacitance decreases and the capacitance decreases as the temperature rises above 20 ° C. For example, when the temperature in the tire 6 is 0 ° C., the value is 0.8 smaller than the capacitance at 20 ° C. Therefore, a correction table is stored in the storage unit of the sensor unit controller 14 as a correction method for correcting the capacitance according to the temperature in the tire 6.

  As shown in FIG. 4B, the correction table is set based on data measured in advance through experiments or the like. In the correction table, the capacitance is associated with each of the plurality of tire temperatures. In the correction table, the capacitance at 20 ° C. is set as a reference value (100), and the difference in capacitance at each temperature with respect to the reference value is set as a correction coefficient. Then, the sensor unit controller 14 uses the correction table to add a correction coefficient to the obtained capacitance, and calculates a correction value for the capacitance. For example, at 0 ° C., a correction coefficient of 0.8 is added to the obtained capacitance.

  A plurality of types of correction tables (correction methods) are provided in advance according to the brand of the tire 6, and are selected according to the tire 6 on which the tire wear detection device (the tire sensor unit 3 and the electrode 19) is installed. The The correction table is stored in the storage unit of the sensor unit controller 14 before the tire wear detection device (the tire sensor unit 3 and the electrode 19) is installed in the tire 6. Further, when the tire 6 is replaced, it is rewritten with a correction table suitable for the tire 6 to be replaced.

  As shown in FIG. 1, the receiver unit 4 includes a receiver unit controller 33 and an RF receiver circuit 35 as a receiver. A display unit 38 is connected to the receiver unit controller 33. The receiver unit controller 33 is composed of a microcomputer including a CPU and a storage unit (ROM, RAM, etc.), and a program for comprehensively controlling the operation of the receiver unit 4 is stored in the storage unit. The RF receiving circuit 35 demodulates the RF signal received from each tire sensor unit 3 through the RF receiving antenna 32 and sends it to the receiver unit controller 33.

  Based on the RF signal and ID code from the RF receiving circuit 35, the receiver unit controller 33 grasps the tire pressure and the tire temperature of the tire 6 corresponding to the tire sensor unit 3 that is the transmission source. The receiver unit controller 33 causes the display 38 to display information on the tire pressure and the tire temperature. The indicator 38 is arranged in the visible range of the passenger of the vehicle 1 such as the passenger compartment, and the receiver unit controller 33 displays (notifies) abnormality in the tire pressure and the tire temperature on the indicator 38. In addition, when receiving a warning signal from the tire sensor unit 3, the receiver unit controller 33 displays a warning regarding the wear of the tire 6 on the display 38.

Next, the operation of the tire wear detection device will be described.
Now, as shown in FIG. 3, the temperature sensor 12 detects the temperature in the tire 6 and outputs the detected tire temperature data to the sensor unit controller 14. The sensor unit controller 14 applies a voltage to the pair of electrodes 19 at regular intervals. When a voltage is applied from the power source 18 to the pair of electrodes 19, electric lines of force F are generated between the pair of electrodes 19, and a capacitance can be provided between the pair of electrodes 19. Then, the measurement circuit 17 measures the capacitance and outputs the measured capacitance to the sensor unit controller 14.

  The sensor unit controller 14 derives a correction coefficient from the correction table according to the tire temperature data output from the temperature sensor 12 and adds the correction coefficient to the capacitance measured by the measurement circuit 17. Then, the sensor unit controller 14 compares the capacitance (correction value) obtained by the correction with a threshold value. If the threshold value is not exceeded, the sensor unit controller 14 does not generate the above-described alarm signal and transmits by the transmission circuit 16. No action is taken.

  On the other hand, as shown in FIG. 5, when the wear of the tread portion 7 progresses, the amount of electric lines of force F leaking from the tire 6 increases, and the capacitance between the pair of electrodes 19 decreases. If the capacitance (correction value) obtained by the correction exceeds the threshold value, the sensor unit controller 14 generates an alarm signal and causes the transmission circuit 16 to transmit the alarm signal. In the receiver unit 4, the alarm signal is received by the RF receiving circuit 35 through the RF receiving antenna 32. The alarm signal received by the RF receiving circuit 35 is output to the receiver unit controller 33, and the receiver unit controller 33 causes the display 38 to display an alarm regarding tire wear.

According to the above embodiment, the following effects can be obtained.
(1) The tire wear detection device detects the temperature in the tire by the temperature sensor 12 and corrects the measured capacitance according to the temperature in the tire. For this reason, it is possible to detect wear using a capacitance that eliminates the influence of the temperature inside the tire, and detects the wear state of the tread portion 7 regardless of the temperature inside the tire to detect the wear state with high accuracy. It becomes possible to do.

  (2) The tire wear detection device joins the pair of electrodes 19 to the inner peripheral surface of the tire 6 and wears the tread portion 7 based on a change in capacitance when a voltage is applied to the pair of electrodes 19. Can be detected. Therefore, it is possible to detect the wear of the tread portion 7 without burying a wear detecting device in the tire 6.

  (3) Since the capacitance is greatly affected by the temperature in the tire, the temperature in the tire is measured by the temperature sensor 12, and the capacitance is corrected according to the temperature in the tire, so that the wear on the tread portion 7 is worn. Can be obtained more accurately. As a result, the wear of the tread portion 7 can be determined more accurately.

  (4) As a method for correcting the capacitance, a correction table in which the tire internal temperature is associated with the correction coefficient was used. For this reason, for example, the sensor unit controller 14 can easily correct the capacitance as compared with the case where the capacitance is calculated and calculated.

  (5) Even if the tire 6 is a new one and not, and the manufacturer has the same environmental temperature, a difference occurs in the measured tire internal temperature. For this reason, by setting (rewriting) a correction table (correction method) according to the tire 6 on which the tire wear detection device is installed, wear detection can be performed in a state in which a difference that occurs for each tire 6 is reduced.

  (6) Among the tire wear detection devices, the temperature sensor 12, the measurement circuit 17, the power source 18, and the sensor unit controller 14 are provided in the case 3a of the tire sensor unit 3, and only the electrode 19 is provided outside the case 3a. Yes. The tire wear detection device can be easily attached to the inside of the tire 6 simply by joining the pair of electrodes 19 to the inner peripheral surface of the tire 6 and installing the tire sensor unit 3 in the tire 6.

  In addition, unlike the case where the tire wear detection device and the tire sensor unit 3 are provided separately in the tire 6, it is possible to avoid an increase in the number of components in the tire 6 and an increase in the amount of the tire 6.

In addition, you may change this embodiment as follows.
The pair of electrodes 19 need not have the same size and the same shape.
In the embodiment, a part of the tire wear detection device is provided in the case 3a of the tire sensor unit 3, the pair of electrodes 19 and the tire sensor unit 3 are integrated, and the tire wear detection device and the tire sensor unit 3 are integrated. However, it is not limited to this. The tire sensor unit 3 and the tire wear detection device may be provided in the tire 6 separately.

  In the embodiment, the correction table corresponding to the tire 6 is stored in the storage unit of the sensor unit controller 14 before the tire wear detection device is mounted inside the tire 6 together with the tire sensor unit 3. . For example, an NFC tag is mounted in the tire sensor unit 3. Then, in a mobile communication terminal (for example, a mobile device such as a smartphone, a mobile phone, an information portable terminal (PDA), or a notebook computer) equipped with an NFC reader / writer that performs short-range wireless communication with an NFC tag, the NFC reader / writer The correction table is transmitted wirelessly from the NFC tag to the tire sensor unit 3. In the tire sensor unit 3, the correction table is written in the storage unit of the sensor unit controller 14 by the NFC tag.

The means for wireless communication is not limited to the NFC tag and the NFC reader / writer, and may be Bluetooth or infrared communication, and is not particularly limited.
○ Although a correction table is used as a correction method, an arithmetic expression or the like may be used.

  ○ The temperature sensor 12 is used as the internal state detection unit and the capacitance is corrected according to the temperature inside the tire, but the humidity sensor is used as the internal state detection unit and the capacitance is corrected according to the humidity inside the tire. May be.

In the embodiment, the pair of electrodes 19 and the tire sensor unit 3 are integrated, but the positions of the pair of electrodes 19 and the tire sensor unit 3 may be different.
The tire wear detection device is not limited to the application to the tire 6 in the four-wheel vehicle 1 but may be applied to the tire in the two-wheel vehicle.

The transmission unit of the tire sensor unit 3 may be a transmission circuit that generates an LF signal instead of the transmission circuit 16 that generates an RF signal.
The receiving unit of the receiver unit 4 may be a low-frequency receiving circuit instead of the RF receiving circuit 35.

Next, the technical idea that can be grasped from the above embodiment and other examples will be described below.
(A) The correction method is a tire wear detection device that is rewritten before the tire wear device is mounted inside the tire.

  DESCRIPTION OF SYMBOLS 1 ... Vehicle, 3 ... Tire sensor unit, 4 ... Receiver unit, 6 ... Tire, 7 ... Tread part, 12 ... Temperature sensor as an internal state detection part, 14 ... Sensor unit controller as a wear detection part, 16 ... Transmission A transmission circuit as a unit, 17 a measurement circuit, 18 a power source, 19 an electrode, 35 an RF reception circuit as a reception unit.

Claims (5)

A tire wear detection device mounted on the inside of a vehicle tire for detecting wear on a tread portion of the tire,
Power supply,
A pair of electrodes that are spaced apart from each other and bonded to the inner circumferential surface of the tire in an insulated state;
A measurement circuit that measures the capacitance of the electrodes when a voltage is applied to the pair of electrodes from the power source;
A wear detection unit capable of detecting a wear state of the tread portion based on the capacitance measured by the measurement circuit;
An internal state detection unit for detecting an internal state of the tire,
The wear detection unit corrects the capacitance measured by the measurement circuit according to the internal state of the tire detected by the internal state detection unit, and detects the wear state using the corrected capacitance. A tire wear detection device.   The tire wear detection device according to claim 1, wherein the internal state detection unit is a temperature sensor that detects an internal temperature of the tire.   The tire according to claim 2, wherein the wear detection unit corrects the measured capacitance using a correction table in which a plurality of internal temperatures and correction coefficients set in advance for each internal temperature are associated with each other. Wear detection device.   The tire wear according to any one of claims 1 to 3, wherein a correction method for correcting the measured capacitance is stored in the wear detection unit, and the correction method is rewritable. Detection device.   A tire sensor unit that is installed inside the tire, detects a state of the tire, and has a transmission unit that transmits the detected tire information; and a tire sensor unit that is installed in the vehicle body of the vehicle and receives the tire information transmitted by the tire sensor unit The vehicle includes a tire condition monitoring device including a receiver unit including a receiving unit, and the power source, the measurement circuit, the internal state detection unit, and the wear detection unit of the tire wear detection device are the tire. The tire wear detection device according to any one of claims 1 to 4, wherein the sensor unit is provided.