JP2016022761A - Tire state detection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect an overload state of a tire taking an influence of a wheel load in addition to a tire inflation pressure into consideration.SOLUTION: Data including data indicating a grounding time of a tire 3, a tire ID and so on is transmitted from a tire side device 1. The data is received and the grounding time of the tire 3 is calculated by a vehicle side device 2, and a grounding length of the tire 3 at this time is calculated. An alarm threshold of a grounding length that is assumed that the tire 3 according to the tire ID is in an overload state is set, and it is determined whether the calculated grounding length of the tire 3 is equal to or more than the alarm threshold, so that the overload state of the tire is determined.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a tire state detection device that detects a tire state such as a decrease in tire air pressure based on a detection signal from a vibration detection unit provided in the tire.

  Conventionally, in Patent Document 1, a technique has been proposed in which an acceleration sensor is embedded in the back surface of a tire tread and tire pressure is estimated based on a detection signal of the acceleration sensor. Specifically, when an acceleration sensor using the piezoresistive effect is embedded in the back surface of the tire tread, the timing corresponding to the location where the acceleration sensor is arranged in the tire tread and the timing at which it does not come into contact with the tire rotation. A vibration peak is placed on the detection signal (hereinafter, the timing of grounding is referred to as the start of grounding, and the timing at which the grounding stops is referred to as the end of grounding). For this reason, conventionally, the contact length corresponding to the length in the tire traveling direction of the tire contact surface is calculated from the distance between two vibration peaks generated at the start of contact and the end of contact and the vehicle speed, and the length of the contact length is calculated. The tire pressure is estimated based on the above.

U.S. Patent No. 20110113876

  As described above, conventionally, the tire air pressure is estimated based on the length of the contact length, and a decrease in the tire air pressure is determined only by whether or not the tire air pressure is below a predetermined threshold, and the tire is excessively recessed. It is determined that an overload condition has occurred. However, in the case where the tire is excessively depressed and reaches an overload state, not only a decrease in tire air pressure but also a wheel load applied due to a vehicle weight, a loaded weight, or the like is affected. For this reason, it is necessary to determine that the tire is overloaded in consideration of not only the tire air pressure but also the influence of the wheel load applied to each wheel.

  In view of the above points, an object of the present invention is to provide a tire state detection device that can detect an overload state of a tire in consideration of the influence of wheel load in addition to tire air pressure.

  In order to achieve the above object, according to the first to fourth aspects of the present invention, a signal processing unit (13) for outputting data relating to the contact length with the road surface of the tire (3) and a transmitter for transmitting data relating to the contact length. (15), a tire side device (1), a receiver (21) that receives data on the contact length transmitted from the transmitter, and a calculation unit (22c) that calculates the contact length from the data on the contact length. And a threshold setting unit (22b) that sets a warning threshold of a contact length corresponding to a tire ID that is individual identification information of a tire that represents a tire load index, and the contact length calculated by the calculation unit is equal to or greater than the warning threshold The vehicle-side device (2) having a determination unit (22d) that determines that the tire is in an overloaded state is provided.

  In this way, the alarm threshold is set to the contact length that is assumed that the tire corresponding to the road index is overloaded, and it is determined whether or not the calculated contact length of the tire is greater than or equal to the alarm threshold. Thus, the tire overload state is determined. Thereby, even if the tire air pressure and the wheel load are not detected, it is possible to set an alarm threshold that takes into account both the tire air pressure and the wheel load. Therefore, it is possible to determine and alert the tire overload state from both the tire air pressure and the wheel load.

  In addition, the code | symbol in the bracket | parenthesis of each said means shows an example of a corresponding relationship with the specific means as described in embodiment mentioned later.

It is the figure which showed the block configuration of the whole tire state detection apparatus 100 concerning 1st Embodiment of this invention. It is a cross-sectional schematic diagram of the tire 3 with which the tire side apparatus 1 was attached. It is an output voltage waveform figure of vibration power generation element 11 at the time of tire rotation. It is the graph which showed the relationship between a load index (Load Index), tire air pressure, and a maximum permissible load. It is the figure which showed the relationship between tire pressure and wheel load. It is the figure which showed an example of the wheel load applied to a vehicle. It is the figure which showed the block configuration of the whole tire state detection apparatus 100 concerning 2nd Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiments, parts that are the same or equivalent to each other will be described with the same reference numerals.

(First embodiment)
With reference to FIGS. 1-6, the tire condition detection apparatus concerning this embodiment is demonstrated. The tire condition detection device according to the present embodiment responds to a decrease in tire air pressure or a wheel load based on a contact length of a contact surface of a tire provided on each wheel of the vehicle, that is, a length of the contact surface in the tire traveling direction. It is used to detect an overload condition of a tire.

  As shown in FIG. 1, the tire state detection device 100 is configured to include a tire-side device 1 provided on the tire side and a vehicle-side device 2 provided on the vehicle body side. The tire state detection device 100 transmits data such as contact time data as contact length data indicating a tire load state from the tire side device 1, and the vehicle side device 2 receives data transmitted from the tire side device 1, Based on the data, a tire overload state is detected. Specifically, the tire side device 1 and the vehicle side device 2 are configured as follows.

  As shown in FIG. 1, the tire side device 1 is configured to include a vibration power generation element 11, a power supply circuit 12, a signal processing unit 13, an information storage unit 14, and a transmitter 15, as shown in FIG. 2. It is provided on the back side of the tread 31 of the tire 3.

  The vibration power generation element 11 outputs a detection signal corresponding to the vibration in the direction in contact with the circular orbit drawn by the tire side device 1 when the tire 3 rotates, that is, in the tire tangential direction (direction of arrow X in FIG. 2). This constitutes a vibration detecting unit. In the case of this embodiment, in addition to outputting a detection signal corresponding to the vibration in the tire tangential direction by the vibration power generation element 11, the vibration energy is converted into electric energy, and the power source of the tire side device 1 is generated based on the vibration energy. ing. For this reason, the vibration power generation element 11 is disposed so as to generate power with respect to vibration in the tire tangential direction. As the vibration power generation element 11, for example, an electrostatic induction type power generation element (electret), a piezoelectric element, a friction type, a magnetostriction type, or an electromagnetic induction type element can be applied. In addition, other devices such as an acceleration sensor may be used as long as the detection signal corresponding to the vibration in the tire tangential direction not taking into account the power generation application is output.

  For example, when an electrostatic induction type power generation element is used as the vibration power generation element 11, if the upper electrode charged positively by electrostatic induction is vibrated in the horizontal direction with respect to the lower electrode having a negative charge, Electricity is generated by changing the electric charge due to electrical induction and generating electromotive force. Based on such power generation by the vibration power generation element 11, the power source of the tire side device 1 is generated, and a detection signal corresponding to the magnitude of vibration in the tire tangential direction is generated.

  That is, when a vehicle equipped with the tire condition detection device 100 travels, vibrations occur in the tread 31 of the tire 3 due to various factors such as the rotational movement of the tire 3 and the unevenness of the road surface. When this vibration is transmitted to the vibration power generation element 11, power generation by the vibration power generation element 11 is performed, and when this vibration is transmitted to the power supply circuit 12, a power source for the tire side device 1 is generated. In addition, since the output voltage at the time of power generation by the vibration power generation element 11 changes according to the magnitude of vibration, the signal processing unit uses the output voltage of the vibration power generation element 11 as a detection signal representing the magnitude of vibration in the tire tangential direction. 13 to tell. The output voltage of the vibration power generation element 11 is an alternating voltage because the upper electrode reciprocates due to vibration.

  The power supply circuit 12 is a circuit for storing power based on the output voltage of the vibration power generation element 11 to generate a power source and supplying power to the signal processing unit 13 and the transmitter 15, and includes a rectifier circuit 12a and a power storage circuit 12b. It is set as the structure provided with.

  The rectifier circuit 12a is a known circuit that converts an alternating voltage output from the vibration power generation element 11 into a direct current. The AC voltage output from the vibration power generation element 11 is DC converted by the rectifier circuit 12a and output to the power storage circuit 12b. The rectifier circuit 12a may be a full-wave rectifier circuit or a half-wave rectifier circuit.

  The power storage circuit 12b is a circuit for storing the DC voltage applied from the rectifier circuit 12a, and is configured by a capacitor or the like. The output voltage of the vibration power generation element 11 is stored in the power storage circuit 12b via the rectifier circuit 12a, and power to the signal processing unit 13 and the transmitter 15 included in the tire side device 1 is obtained using the voltage stored here as a power source. Supplying. In addition, since the power supply circuit 12 includes the power storage circuit 12b, when the vibration power generation element 11 is generating excessive power, the surplus is stored, and when the power generation amount is insufficient, the shortage is stored. It comes to be able to compensate.

  The signal processing unit 13 uses the output voltage of the vibration power generation element 11 as a detection signal representing vibration data in the tire tangential direction, and processes the detection signal to obtain data related to tire air pressure, which is transmitted to the transmitter 15. Play a role to communicate. That is, the signal processing unit 13 determines the grounding time of the vibration power generation element 11 during rotation of the tire 3 (that is, the vibration power generation element 11 of the tread 31 of the tire 3 based on the time change of the output voltage of the vibration power generation element 11. The contact time of the part corresponding to the arrangement location) is measured. Since the ground contact time of the vibration power generation element 11 is data relating to the ground contact length on the ground contact surface of the tire 3 and data representing the tire air pressure, the data representing the ground contact time is transmitted to the transmitter 15.

  Specifically, the signal processing unit 13 is configured by a known microcomputer including a CPU, a ROM, a RAM, an I / O, and the like, and performs the above processing according to a program stored in the ROM. And the signal processing part 13 is provided with the peak detection part 13a and the contact time measurement part 13b as a function part which performs those processes.

  The peak detector 13 a detects the peak value of the detection signal represented by the output voltage of the vibration power generation element 11. The output voltage waveform of the vibration power generation element 11 during tire rotation is, for example, the waveform shown in FIG. As shown in this figure, the output voltage of the vibration power generation element 11 reaches the maximum value at the start of grounding when the portion corresponding to the arrangement position of the vibration power generation element 11 of the tread 31 starts to ground as the tire 3 rotates. Take. The peak detector 13a detects the start of grounding at which the output voltage of the vibration power generation element 11 takes a maximum value as the timing of the first peak value. Further, as shown in FIG. 3, when the tire 3 rotates, the portion of the tread 31 corresponding to the position where the vibration power generation element 11 is disposed is grounded from the state where the vibration power generation element 11 is not grounded. Output voltage takes the minimum value. The peak detector 13a detects the end of grounding when the output voltage of the vibration power generation element 11 takes a minimum value as the timing of the second peak value.

  The vibration power generation element 11 takes the peak value at the above timing for the following reason. That is, when the portion of the tread 31 corresponding to the placement location of the vibration power generation element 11 comes into contact with the rotation of the tire 3, the portion of the tire 3 that has been substantially cylindrical in the vicinity of the vibration power generation element 11 is It is pressed and deformed into a flat shape. By receiving the impact at this time, the output voltage of the vibration power generation element 11 takes the first peak value. Further, when the portion of the tread 31 corresponding to the place where the vibration power generation element 11 is disposed is separated from the grounding surface as the tire 3 rotates, the tire 3 is released from pressing in the vicinity of the vibration power generation element 11 and is planar. To return to a substantially cylindrical shape. By receiving an impact when the shape of the tire 3 returns to the original shape, the output voltage of the vibration power generation element 11 takes the second peak value. In this way, the vibration power generation element 11 takes the first and second peak values when the grounding starts and when the grounding ends, respectively. Moreover, since the direction of the impact when the tire 3 is pressed and the direction of the impact when released from the press are opposite directions, the sign of the output voltage is also opposite.

  Then, the peak detection unit 13a extracts detection signal data including the timings of the first and second peak values and transmits the detection signal data to the contact time measurement unit 13b. Here, the detection signal data including the timing of the first and second peak values indicates the detection signal itself during a predetermined period including the period from the first peak value to the second peak value. . At this time, the time setting for a predetermined period including the period from the first peak value to the second peak value can be set to, for example, one rotation of the tire. For the period of one rotation of the tire, assuming that the vehicle speed at which the tire 3 is to be overloaded, for example, when the vehicle speed range is 40 to 120 km / h or less, data of at least one rotation of the tire in the speed range is included. It is time to enter. In the case of a speed range of 40 to 120 km / h, it is set to a time (for example, 250 ms) in which the tire rotates once or more at a minimum speed of 40 km / h. Further, it may be from the timing when the first peak value is reached to the timing when the first peak value is next set. Here, the detection signal data including the timings of the first and second peak values are extracted and transmitted to the contact time measuring unit 13b by the peak detection unit 13a, but the first and second peak values are obtained. Only the data relating to the timing may be transmitted to the contact time measuring unit 13b.

  The grounding time measurement unit 13b measures the grounding time of the vibration power generation element 11 based on the data transmitted from the peak detection unit 13a. Specifically, the contact time measurement unit 13b measures the time interval between the timing of the first peak value and the timing of the second peak value from the data transmitted from the peak detection unit 13a. Thereby, the grounding time of the vibration power generation element 11 is measured. At this time, when a plurality of first peak values and second peak values are included in the transmitted data, for example, the timing of the maximum value of the first peak values and the second peak value immediately thereafter The time interval between the timings is measured. Conversely, when the transmitted data includes a plurality of first peak values and second peak values, the timing of the smallest one of the second peak values and the timing of the first peak value immediately before the second peak value are included. You may measure the time interval between.

  For example, when a detection signal is sent for a time when the tire is rotated once or more at the lowest speed in the speed range (40 to 120 km / h), the maximum value among them is detected as the first peak value. In addition, a minimum value is detected from a certain time after the timing of the maximum value, for example, a time shorter than one rotation of the tire of 120 km / h and longer than a contact time assumed at 40 km / h (for example, 30 ms). It detects as a 2nd peak value. The time difference between the timing at which the first peak value is reached and the timing at which the second peak value is reached can be set as the ground contact time.

  Thus, in the signal processing unit 13, the ground detection time of the vibration power generation element 11 is measured by the peak detection unit 13a and the ground time measurement unit 13b. Then, the signal processing unit 13 outputs grounding time data, which is data regarding the grounding time, to the transmitter 15 as data regarding the grounding length.

  The information storage unit 14 is a part that stores individual identification information (hereinafter referred to as a tire ID) assigned to each tire type, and transmits the tire ID to the transmitter 15 and transmits it together with the data representing the contact length. Wireless transmission is performed from the machine 15 toward the vehicle side device 2. The tire ID here is, for example, a road index attached to each tire. The road index represents the maximum load load allowed for the tire 3 as a numerical value, and is a value determined according to the type of the tire 3.

  The transmitter 15 wirelessly transmits data representing the contact time transmitted from the signal processing unit 13 to the vehicle side device 2 together with the tire ID transmitted from the information storage unit 14. Communication between the transmitter 15 and the receiver 21 included in the vehicle-side device 2 can be performed by a known short-range wireless communication technology such as Bluetooth (registered trademark). The timing for transmitting the data representing the contact time is arbitrary, but may be, for example, when the contact time per rotation of the tire 3 can be acquired. Moreover, it is good also as a structure which transmits, after accumulating the data for multiple rotations of the tire 3. FIG. In that case, since the operating rate of the transmitter 15 can be suppressed, the power consumed by the transmitter 15 can be reduced.

  In addition, about the data showing contact time, it is made to send with the specific recognition information (ID information) of the wheel previously equipped for every tire 3 with which the vehicle was equipped. The position of each wheel can be specified by a well-known wheel position detection device that detects where the wheel is attached to the vehicle, so by transmitting data representing the ground contact time together with the ID information to the vehicle side device 2, It is possible to determine which wheel data.

  On the other hand, the vehicle side device 2 is configured to include a receiver 21 and an arithmetic processing unit 22, and receives data including the contact time and the tire ID transmitted from the tire side device 1. The overload state of the tire 3 of each wheel is determined by performing various processes based on the data.

  The receiver 21 is a device for receiving data including the contact time transmitted by the tire side device 1 and data including a tire ID. Data representing the contact time received by the receiver 21 and data including the tire ID and the like are sequentially output to the arithmetic processing unit 22 each time it is received.

  The arithmetic processing unit 22 is configured by a known microcomputer including a CPU, ROM, RAM, I / O, and the like, and performs the above-described various processes in accordance with programs stored in the ROM. And the arithmetic processing part 22 is set as the structure which has the vehicle speed acquisition part 22a, the threshold value setting part 22b, the calculating part 22c, and the determination part 22d as a function part which performs those processes.

  For example, the vehicle speed acquisition unit 22a acquires vehicle speed data calculated by an in-vehicle ECU (electronic control unit) based on detection signals of a vehicle speed sensor and a wheel speed sensor through CAN (Controller Area Network) communication that is an in-vehicle network, The vehicle speed is acquired.

  The threshold setting unit 22b sets a warning threshold for each type of the tire 3 based on the tire ID included in the data received by the receiver 21. With reference to FIG. 4 and FIG. 5, the relationship between tire ID and an alarm threshold value is demonstrated.

  As described above, the tire ID indicates, for example, a road index indicating the maximum allowable load as a numerical value. The relationship between the road index and the tire pressure is expressed as a relationship shown in FIG. 4, for example. The threshold setting unit 22b stores the relationship shown in FIG. 4 by a map or an arithmetic expression, and can set an alarm threshold according to a road index indicated by a tire ID. For example, the tire 3 mounted on the wheel is 87Q with 215 / 45R17 (tire width 215 mm, flatness 45%, rim diameter 17 inches, road index 87, speed display Q (= maximum speed 160 km / h)) Is represented as follows.

  That is, when the load index is 87, the maximum load load allowed as a wheel load is 400 kg when the tire air pressure is 140 kPa. When the tire air pressure is 150 kPa, the maximum load load allowed as a wheel load is 415 kg. Thus, the maximum load load increases as the tire air pressure increases. In other words, even if the tire air pressure is an appropriate pressure, it can be said that if a wheel load exceeding the maximum load load is applied, the tire 3 is excessively depressed and is in an overload state. The relationship between the tire air pressure and the maximum load load when the load index is 87 is the relationship shown in FIG. 5, and the contact length of the tire 3 at the line indicating this relationship differs in the tire air pressure and the maximum load load. However, the value was almost constant (145 mm). In other words, when the dent amount of the tire 3 is large and overloaded, if the vehicle continues to run for a long time, there is a possibility of a burst, and this corresponds to the dent amount of the tire 3 at that time. The ground contact length to be basically becomes a constant value.

  Therefore, if the contact length that is assumed to be overloaded is set as the alarm threshold, the wheel load exceeds the maximum load load even if the tire pressure is appropriate, and the wheel load is the maximum load load. Even if it is less than the threshold value, it is possible to set an alarm threshold value corresponding to both cases where the tire air pressure is low. In this way, by setting the contact length assumed that the tire 3 is in an overload state as an alarm threshold according to the load index, an alarm threshold that takes into account both tire air pressure and wheel load is set. Is possible. In other words, it is possible to make an alarm by determining an overload state from both the tire pressure and the wheel load.

  The calculation unit 22c is a part that calculates the contact length of the tire 3. The calculation unit 22c calculates the contact length of the tire 3 from the data representing the contact time sent from the tire-side device 1 and the vehicle speed data acquired by the vehicle speed acquisition unit 22a. Is calculated. Specifically, the contact length of the tire 3 is calculated by multiplying the vehicle speed by the contact time. For example, when the vehicle speed is 60 km / h and the contact time is 6 msec, the contact length = 10 cm by multiplying them. And can be calculated.

  The determination unit 22d is configured to calculate the contact length of the tire 3 calculated by the calculation unit 22c using the alarm threshold for the contact length set by the threshold setting unit 22b and the data representing the contact time transmitted from the tire side device 1 during traveling. From these, the overload state of the tire 3 is determined. Specifically, the calculated contact length of the tire 3 is compared with an alarm threshold value, and when the contact length becomes equal to or greater than the alarm threshold value, it is determined that the tire 3 is in an overload state. When the overload state of the tire 3 is determined, for example, an alarm is given through an alarm device (not shown), or a display indicating that the tire 3 is in an overload state is made through a display provided on the instrument panel. As a result, the driver can recognize that the tire 3 is in an overloaded state.

  At this time, using the ID information for each wheel included in the data sent from the tire-side device 1, an alarm is given in a form that specifies which wheel the tire 3 is in an overload state. Also good.

  As described above, in the tire state detection device 100 according to the present embodiment, data representing the contact time of the tire 3 and data including the tire ID and the like are transmitted from the tire-side device 1. In addition, the vehicle-side device 2 receives it, calculates the contact time of the tire 3, and calculates the contact length of the tire 3 at that time. And the alarm threshold value which is the contact length assumed that the tire 3 corresponding to the tire ID is in an overload state is set, and it is determined whether or not the calculated contact length of the tire 3 is equal to or greater than the alarm threshold value. By doing so, the overload state of the tire 3 is determined.

  Thus, by setting the alarm threshold corresponding to the tire ID, it is possible to set the alarm threshold considering both the tire air pressure and the wheel load even if the tire air pressure and the wheel load are not detected. . Therefore, it is possible to determine and alert the overload state of the tire 3 from both the tire pressure and the wheel load.

  For example, as in the vehicle shown in FIG. 6, there may be a case where the appropriate load is different between the front, rear, left and right wheels, such as the left front wheel 485 kg, the right wheel 475 kg, the left rear wheel 356 kg, and the right rear wheel 355 kg. . In such a vehicle, if the same tire 3 of 215 / 45R17 87Q is mounted on all four wheels and the tire pressure is 140 kPa, for example, the contact length of the tire 3 of the rear wheels is set to the alarm threshold value. Less than. However, since the ground contact length of the tire 3 for the two front wheels is equal to or greater than the warning threshold, a warning is issued for the two front wheels.

  Thus, even if the tire pressure is the same, the alarm threshold value differs depending on the wheel load. And according to the tire condition detection apparatus 100 of the present embodiment, since the alarm threshold is set taking into account both the tire pressure and the wheel load, the overload condition of the tire 4 from both the tire pressure and the wheel load. It becomes possible to determine and alert. For example, when the wheel load is 485 kg as in the left front wheel, it is necessary to warn even if the air pressure is about 200 kPa as shown in FIG. On the other hand, according to the tire state detection device 100 of the present embodiment, even in such a case, the left wheel tire can be alarmed when the contact length becomes equal to or greater than the alarm threshold for the left wheel. An alarm can be given when the air pressure reaches about 200 kPa. Therefore, not only the tire pressure but also the wheel load as compared with the conventional device that issues an alarm when the tire pressure simply falls below a predetermined pressure threshold (for example, 180 kPa, which is 25% lower than the appropriate pressure 240 kPa). In consideration, it becomes possible to give an alarm from an earlier stage.

  Further, even when a genuine tire is replaced with another tire, the tire ID is sent from the tire side device 1 attached to the replaced tire 3 to the vehicle side device 2, and an alarm threshold is set according to the tire ID. Is set. Therefore, unlike the case where the alarm threshold value is uniformly set regardless of the type of the tire 3 or the like, the alarm threshold value can be set according to the type of the tire 3 after the replacement even if the tire is replaced. It becomes possible to determine the overload state.

(Second Embodiment)
A second embodiment of the present invention will be described. In the present embodiment, a pressure sensor is added to the first embodiment, and the others are the same as those in the first embodiment. Therefore, only the parts different from the first embodiment will be described.

  As shown in FIG. 7, in the tire state detection device 100 according to the present embodiment, the tire side device 1 includes a pressure sensor 16 that detects tire air pressure. The pressure sensor 16 outputs a detection signal corresponding to the tire pressure, and transmits this detection signal to the transmitter 15. The transmitter 15 uses the detection signal corresponding to the tire air pressure as data indicating the tire air pressure, or calculates the tire air pressure from the detection signal, and uses the calculation result as data indicating the tire air pressure, along with data related to the contact length, etc. To the side device 2. The vehicle-side device 2 receives this data, and it is possible to further calculate the wheel load from the contact length calculated by the calculation unit 22c and the tire air pressure. That is, the contact length varies depending on the tire pressure and the wheel load. If the contact length can be calculated, if one of the tire pressure and the wheel load is known, the other can be obtained.

  Therefore, the calculation unit 22c calculates the contact length and the tire air pressure based on the data sent from the tire side device 1, for example, a map showing the relationship between the contact length, the tire air pressure and the wheel load stored in advance. The wheel load can be calculated based on the calculation formula. Thereby, when the tire 3 is in an overload state, it is possible to determine the cause of the occurrence, that is, whether the wheel load is excessive or the tire air pressure is reduced, It is possible to alarm together with the judgment result. Therefore, the user can determine whether it is necessary to adjust the tire pressure, or whether the loading amount is excessive or the loading state is biased, and it is necessary to review the loading.

(Other embodiments)
The present invention is not limited to the embodiment described above, and can be appropriately changed within the scope described in the claims.

  For example, in the tire side device 1, when the tire ID is not registered in the information storage unit 14, the user may register the tire ID in the information storage unit 14, or the tire ID input unit in the vehicle side device 2. May be provided separately so that the tire ID can be registered directly in the vehicle-side device 2.

  DESCRIPTION OF SYMBOLS 1 ... Tire side apparatus, 2 ... Vehicle side apparatus, 3 ... Tire, 11 ... Vibration power generation element, 12 ... Electric power supply circuit, 13 ... Signal processing part, 13a ... Peak detection part, 13b ... Grounding time measurement part, 14 ... Information Storage unit, 15 ... Transmitter, 16 ... Pressure sensor, 21 ... Receiver, 22 ... Calculation processing unit, 22a ... Vehicle speed acquisition unit, 22b ... Threshold setting unit, 22c ... Calculation unit, 22d ... Determination unit

Claims (4)

A tire side device (1) having a signal processing unit (13) for outputting data relating to a contact length with a road surface in the tire (3), and a transmitter (15) for transmitting data relating to the contact length;
A receiver (21) that receives data related to the contact length transmitted from the transmitter, a calculation unit (22c) that calculates the contact length from the data related to the contact length, and the tire that represents a road index of the tire A threshold value setting unit (22b) for setting a warning threshold value of the contact length corresponding to the tire ID as individual identification information of the tire, and the tire when the contact length calculated by the calculation unit is equal to or greater than the warning threshold value. A tire state detection device comprising: a vehicle side device (2) having a determination unit (22d) for determining that the vehicle is in an overload state. The tire side device is:
A vibration detection unit (11) that is attached to the back surface of the tread (31) in the tire and outputs a detection signal corresponding to the magnitude of vibration of the tire,
In the signal processing unit, based on a detection signal of the vibration detection unit, data representing a ground contact time of a portion corresponding to an arrangement position of the vibration detection unit in the tread during one rotation of the tire is related to the ground contact length. Output as data,
The vehicle side device
The receiver receives data representing the contact time as data relating to the contact length, and the calculation unit calculates the contact length of the tire based on the data representing the contact time and the vehicle speed. The tire state detection device according to claim 1, wherein: The tire side device is:
An information storage unit (14) for storing the tire ID;
The tire condition detection device according to claim 1, wherein the transmitter transmits the tire ID stored in the information storage unit together with the data related to the contact length. The tire side device is:
A pressure sensor (16) for detecting tire air pressure, which is air pressure in the tire,
In the transmitter, the data indicating the detection result of the pressure sensor is transmitted together with the data related to the contact length,
The vehicle side device
Receiving data indicating the detection result of the pressure sensor;
The calculation unit calculates a wheel load from the contact length and the tire air pressure indicated by the detection result of the pressure sensor,
The determination unit determines whether or not the tire is in an overload state, and determines whether the cause of the overload state is the tire air pressure or the wheel load. Item 4. The tire condition detection device according to any one of Items 1 to 3.

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