JP2023066795A - Tire position detection system - Google Patents

Abstract

To determine a tire position in which a detector is installed, while suppressing electric power consumed by the detector installed in a tire mounted on a vehicle.SOLUTION: A tire position detection system comprises a detector having an acceleration sensor that detects acceleration in a tire radial direction and a monitoring unit. The detector performs sampling of output of the acceleration sensor at a predetermined sampling cycle (a step S44) and outputs a result of the sampling to the monitoring unit (a step S45). The monitoring unit, when the result of the sampling received from the detector is the result of sampling performed during turning of a vehicle, calculates a tire rotation amount Rg ( a tire rotation amount in a predetermined period of time) based on acceleration, on the basis of the result of the sampling (a step S28), and determines a tire position in which the detector is installed, on the basis of the tire rotation amount Rg based on the acceleration (steps S30-S33).SELECTED DRAWING: Figure 7

Description

The present disclosure relates to a system for determining tire positions where detectors installed on tires mounted on a vehicle are installed.

Conventionally, there is a direct system as one of systems (TPMS: Tire Pressure Monitoring System) for monitoring the air pressure of tires. In this type of TPMS, a detector provided with a sensor such as a pressure sensor is installed directly on the side of the wheel on which the tire is attached. In addition, the vehicle body is equipped with an antenna and a receiver. When the sensor detection signal is transmitted from the wheel side detector, the detection signal is received by the receiver via the antenna, and the tire pressure is measured. detection is performed.

In such a direct-type TPMS, a device for determining on which tire, left or right, a detector installed in a tire is installed is disclosed in Japanese Patent Application Laid-Open No. 2005-147709, for example. . In this device, the detector installed in the tire has an acceleration sensor that detects the acceleration in the radial direction (centrifugal direction) of the tire, and the detector measures the time for one tire rotation based on the output of the acceleration sensor. , the measured tire rotation time is transmitted to the receiver on the vehicle body side as the tire rotation speed. A control unit is connected to the receiver on the vehicle body side, and this control unit determines the tire rotation speed based on the vehicle speed and tire size, and when the determined tire rotation speed and steering angle are equal to or greater than a predetermined value. First, the tire rotation speed received from the detector is compared with the magnitude relationship, and based on the result, it is determined on which tire, the left or right, the detector is installed.

JP-A-2005-147709

In order to determine the tire position where the detector is installed using the device disclosed in Japanese Patent Application Laid-Open No. 2005-147709, the detector uses the output of the built-in acceleration sensor to determine the time for the tire to make exactly one rotation. It is necessary to measure accurately.

In order to accurately measure the time it takes the tire to make exactly one rotation using the output of the acceleration sensor, the time required for the output of the acceleration sensor to change by one wavelength (more specifically, the time included in the output of the acceleration sensor It is necessary to accurately measure the time required for the gravitational acceleration component to change by one wavelength from the initial value at the start of measurement and return to the initial value. Therefore, it is necessary for the detector to constantly monitor the output of the acceleration sensor during the period when the output of the acceleration sensor changes by one wavelength. We are anxious about electric power increasing.

The present disclosure has been made to solve the above-described problems, and its object is to reduce the power consumption of detectors installed on tires mounted on a vehicle, and to detect tire positions where detectors are installed. is to determine

A tire position detection system according to one aspect of the present disclosure includes a detector having an acceleration sensor that detects radial acceleration of a tire mounted on a vehicle, and a monitoring unit configured to receive information from the detector. Prepare. The detector performs sampling processing for sampling the output of the acceleration sensor at predetermined intervals for a predetermined period, and outputs the result of the sampling processing to the monitoring unit. The monitoring unit calculates a tire rotation amount for a predetermined period based on the result of the sampling process when the result of the sampling process received from the detector is the result of sampling during turning of the vehicle, and calculates the tire rotation amount for the predetermined period. Determination processing is performed to determine the tire position where the detector is installed based on the amount of tire rotation.

According to the above aspect, the amount of tire rotation for a predetermined period is calculated based on the output of the acceleration sensor, instead of measuring the time required for the tire to rotate exactly once, and the detector detects the amount of tire rotation for the predetermined period. determines the tire position where the is installed. Therefore, it is not necessary to accurately measure the time it takes for the tire to rotate exactly once, and it is not necessary to constantly activate the detector at high frequency during the time it takes for the output of the acceleration sensor to change by one wavelength. As a result, the tire position where the detector is installed can be determined while suppressing the power consumption of the detector.

According to the present disclosure, it is possible to determine the tire position where the detector is installed while suppressing the power consumption of the detector installed on the tire mounted on the vehicle.

It is a figure which shows the structure of a vehicle typically. It is a block diagram which shows the structure of a detector. FIG. 4 is a diagram for explaining directions in which an acceleration sensor detects acceleration; FIG. 4 is a diagram schematically showing the waveform of the gravitational acceleration component superimposed on the acceleration G when the tire rotates at a constant speed; It is a figure for demonstrating the content of the sampling process by a detector. FIG. 4 is a diagram showing the difference between inner and outer wheels when the vehicle is turning to the left; FIG. 10 is a flowchart (part 1) showing an example of a processing procedure performed by a detector and a monitoring unit; FIG. 2 is a flowchart (part 2) showing an example of a processing procedure performed by a detector and a monitoring unit;

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. The same or corresponding parts in the drawings are denoted by the same reference numerals, and the description thereof will not be repeated.

<Overall composition>
FIG. 1 is a diagram schematically showing the configuration of a vehicle 10 to which a tire position detection system according to this embodiment is applied.

Specifically, the vehicle 10 includes front tires 11 and 12 and rear tires 13 and 14 .

Furthermore, the vehicle 10 is equipped with a system (TPMS) for monitoring the air pressure of each tire. Specifically, the vehicle 10 includes a plurality of detectors 31 to 34 each detecting tire pressure, and a TPMS receiver 40 . Detectors 31 and 32 are installed on wheels of front tires 11 and 12, respectively. Detectors 33 and 34 are installed on wheels of rear tires 13 and 14, respectively. Each of the detectors 31 to 34 may be formed integrally with, for example, a valve for drawing air into each tire.

Each of the detectors 31 to 34 detects the air pressure of each tire and outputs a UHF (Ultra High Frequency) band radio signal (hereinafter also simply referred to as "UHF signal") including the detection result. The UHF signal output by each of the detectors 31-34 includes at least information indicating a unique ID number for identifying each detector 31-34 in addition to information indicating the tire pressure. The TPMS receiver 40 can monitor the air pressure of each tire by receiving the UHF signal output by each of the detectors 31-34.

Each of the detectors 31 to 34 is activated when a predetermined activation condition is satisfied, detects the air pressure of each tire, and includes a detection result in a UHF (Ultra High Frequency) band radio signal (hereinafter simply referred to as "UHF signal"). ) is output. It should be noted that the "predetermined activation condition" is set in advance so as to be satisfied regularly or irregularly. Thereby, the detectors 31 to 34 can be intermittently activated at mutually different timings.

The front tires 11 and 12 and the rear tires 13 and 14 have the same specification and configuration so that tire rotation can be performed. Therefore, the detectors 31 to 34 have the same configuration. In the following description, the detectors 31 to 34 are also referred to as "detector 30" without distinguishing between them when there is no need to distinguish between the detectors 31 to 34.

The TPMS receiver 40 is provided on the vehicle body side of the vehicle 10 . The TPMS receiver 40 comprises an antenna A 1 and a monitoring unit 45 . Antenna A1 is configured to be able to receive UHF signals transmitted from each detector 30 . A monitoring unit 45 monitors the air pressure of each tire based on the UHF signal received by antenna A1. The monitoring unit 45 includes a storage section 46 and a processing section 47 .

The processing unit 47 includes a processor such as a CPU (Central Processing Unit) (not shown), a memory, and an input/output buffer. The memory includes ROM (Read Only Memory) and RAM (Random Access Memory). The processor expands a program stored in ROM into RAM and executes it. Various processes executed by the processing unit 47 are described in the programs stored in the ROM.

Information indicating the tire position where each detector 30 is arranged, information indicating the tire air pressure, etc. are stored in the storage unit 46 in association with the ID number of each detector 30 . In this embodiment, a total of four tire positions (left front, right front, left rear, right rear) are set in advance, and the ID number of each detector 30 is associated with one of the tire positions. ing. For example, the ID number of the detector 31 is associated with the tire position "front left", and the ID number of the detector 34 is associated with the tire position "rear right".

When the UHF signal is received from each detector 30, the monitoring unit 45 refers to the information stored in the storage unit 46 to specify the tire position of the ID number included in the UHF signal, and the specified tire position. is updated with the tire pressure contained in the UHF signal. For example, when the monitoring unit 45 receives a UHF signal containing the ID number of the detector 34, the monitoring unit 45 refers to the corresponding relationship between the ID number and the tire position stored in the storage unit 46 to obtain the information contained in the UHF signal. The tire position of the identified ID number is specified as "rear right", and the specified "rear right" air pressure is updated with the tire pressure included in the UHF signal.

The TPMS receiver 40 can cause the display unit 60 to display the information on the correspondence relationship between tire positions and tire pressures stored in the storage unit 46 . The display unit 60 is arranged at a position that can be visually recognized by the driver. The display unit 60 is arranged, for example, on an in-vehicle instrument panel.

If the tire pressure included in the received UHF signal is equal to or less than the low pressure threshold, the monitoring unit 45 causes the display unit 60 to display a warning and the tire position where the tire pressure is equal to or less than the low pressure threshold. The TPMS receiver 40 performs this tire air pressure determination process for each received UHF signal, and monitors the air pressure of each tire. This allows the driver to recognize in real time the position of the tire that has fallen below the low pressure threshold.

Further, vehicle 10 according to the present embodiment is provided with steering angle sensor 71 , shift position sensor 72 , and vehicle speed sensor 74 . The steering angle sensor 71 detects the steering angle and steering direction of the vehicle 10 . The shift position sensor 72 detects the shift position (forward position, reverse position, parking position, neutral position, etc.) operated by the user. A vehicle speed sensor 74 detects the rotation speed of the output shaft of the vehicle 10 as the vehicle speed. These sensors output detection results to the monitoring unit 45 .

Further, vehicle 10 according to the present embodiment is provided with initiators 51 and 52 for starting each detector 30 . Each initiator 51 , 52 is electrically connected to the TPMS receiver 40 . The initiator 51 is arranged near the front tires 11 and 12 and used to activate the detectors 31 and 32 . The initiator 52 is arranged near the rear tires 13 and 14 and used to activate the detectors 33 and 34 .

The initiators 51 and 52 have the same configuration. In the following description, the initiators 51 and 52 are also referred to as the "initiator 50" without distinguishing between them, unless the initiators 51 and 52 need to be distinguished from each other.

The initiator 50 includes an antenna (not shown), and is configured to be capable of outputting an LF (Low Frequency) band radio signal (hereinafter also simply referred to as an "LF signal") from the antenna. The initiator 50 transmits LF signals containing command information to each detector 30 based on commands from the monitoring unit 45 .

<Configuration of detector 30>
FIG. 2 is a block diagram showing the configuration of the detector 30. As shown in FIG. The detector 30 includes a controller 35, a pressure sensor 38, an acceleration sensor (G sensor) 39, an antenna L1, a receiving circuit CR, an antenna A2, and a transmitting circuit CT.

The controller 35 includes a storage section 36 and a processing section 37 . The processing unit 37 includes a processor such as a CPU (not shown), a memory, and an input/output buffer. The memory includes ROM and RAM. The processor expands a program stored in ROM into RAM and executes it. Programs stored in the ROM describe various processes to be executed by the processing unit 37 .

A unique ID number is stored in the storage unit 36 for each detector 30 shown in FIG. For example, the storage unit 36 included in the detector 33 of FIG. 1 stores "01" as an ID number. In addition, "02" is stored as an ID number in the storage unit 36 included in the detector 34 of FIG. In this manner, the ID number unique to each detector 30 is stored in the storage section 36 in each detector 30 .

The pressure sensor 38 detects tire air pressure and outputs the detection result (hereinafter also referred to as “tire air pressure P”) to the controller 35 . The acceleration sensor 39 detects acceleration (force) acting on the detector 30 and outputs a detection result (hereinafter also referred to as “acceleration G”) to the controller 35 . In addition to pressure sensor 38 and acceleration sensor 39, detector 30 may further include a temperature sensor for detecting tire temperature.

Antenna L1 receives an LF signal transmitted from initiator 50 . The LF signal received by antenna L1 is sent to controller 35 via receiver circuit CR. By receiving the LF signal from the receiving circuit CR, the controller 35 can recognize the information contained in the LF signal and the received signal strength indicator (RSSI) of the LF signal.

The controller 35 controls the transmission circuit CT to output the UHF signal from the antenna A2. The UHF signal includes information indicating the acceleration G in addition to information indicating the ID number and the tire pressure P stored in the storage unit 36 .

As described above, the detector 30 is activated and outputs a UHF signal at the timing when a predetermined activation condition is satisfied. The detector 30 is provided with a battery (not shown) and operates on electric power supplied from the battery. Since this battery cannot be easily charged from the outside, the operating time of the detector 30 is minimized for detection. It is desirable to reduce the power consumption of the device 30 . From this point of view, the activation condition of the detector 30 is set in advance so as to minimize the activation frequency of the detector 30 . For example, the activation condition of the detector 30 includes a timer activation condition that a timer (not shown) measures that a predetermined timer time has elapsed since the previous stop, and the acceleration G detected by the acceleration sensor 39 is a specific value ( For example, it includes an acceleration start condition such as a maximum value or minimum value).

The "timer time" used in the above-described timer activation condition may be a fixed value, or may be a variable value that varies according to the acceleration G, for example. For example, the controller 35 determines whether the tires are rotating based on the acceleration G, which is the detection result of the acceleration sensor 39, and if the tires are not rotating and is in a stopped state, the timer time is relatively long. Set the time (for example, several minutes, or even longer several hours), and set the timer time to a relatively short time (for example, several seconds, or even shorter several millimeters) when the tires are rotating. seconds). Also, the time for one activation of the detector 30 (time from activation to next deactivation) may be limited to a relatively short time (for example, several milliseconds).

Also, the period during which each detector 30 can receive the LF signal from the initiator 50 is limited to the period during which each detector 30 is in the active state or the period during which each detector 30 is in the standby state. The activation conditions for the detector 30 also include an initiator activation condition that an LF signal has been received from the initiator 50 in the standby state. Since a small amount of power is consumed by the detector 30 even during a period when the detector 30 is in a standby state (hereinafter also referred to as a "standby period"), from the viewpoint of suppressing the power consumption of the detector 30, the detector Thirty standby periods are set intermittently. For example, the standby period may be set in a relatively long period (for example, about several minutes), and one standby period may be limited to a relatively short period of time (for example, about several milliseconds).

<Detection direction of acceleration sensor (G sensor) 39>
FIG. 3 is a diagram for explaining directions in which the acceleration sensor 39 detects acceleration. A detector 30 having an acceleration sensor 39 is fixed at a predetermined location on the wheel WH of each tire. FIG. 3 schematically shows the state when the detector 30 is positioned at "12 o'clock", "3 o'clock", "6 o'clock", and "9 o'clock" when the tire is viewed from the right side of the vehicle. It is shown.

The acceleration sensor 39 is a uniaxial acceleration sensor that detects acceleration in one direction. In the present embodiment, the detection axis (acceleration detection direction) of the acceleration sensor 39 is set in the tire radial direction (centrifugal direction). That is, the acceleration sensor 39 detects acceleration in the tire radial direction (centrifugal acceleration).

The acceleration sensor 39 is configured to detect acceleration acting away from the center of rotation of the tire as a positive value, and detect acceleration acting toward the center of rotation of the tire as a negative value. In this case, the acceleration G detected by the acceleration sensor 39 is a value obtained by superimposing the centrifugal acceleration of the tire on the gravitational acceleration component that varies depending on the rotation angle of the tire. That is, the gravitational acceleration component superimposed on the acceleration G is "-1 G" (G: gravitational acceleration) when the detector 30 is at the "12 o'clock" position, Sometimes it will be "+1G" and it will be "0G" when the detector 30 is at the "3 o'clock" or "9 o'clock" position.

FIG. 4 is a diagram schematically showing the waveform of the gravitational acceleration component superimposed on the acceleration G when the tire rotates at a constant speed. As shown in FIG. 4, when the tire rotates at a constant speed, the gravitational acceleration component superimposed on the acceleration G becomes a sinusoidal waveform whose cycle is the time for one rotation of the tire. The output waveform of the acceleration sensor 39 has a value obtained by adding centrifugal acceleration to the gravitational acceleration component. The period will approximately match the period of the gravitational acceleration component.

<Tire position determination processing>
As described above, each tire is of the same specification and construction so that the tires can be rotated with each other. That is, when tire rotation is performed, the TPMS receiver 40 cannot specify the tire position where each detector 30 is installed only from the ID number included in the UHF signal.

Therefore, in the present embodiment, the tire position where each detector 30 is installed is determined by the following procedure.

First, the detector 30 performs "sampling processing" for sampling the output of the acceleration sensor 39 at a predetermined period Ts and a predetermined sampling period Ps, and outputs the result to the monitoring unit 45 as tire acceleration information. Next, the monitoring unit 45 determines the tire position where the detector 30 is installed based on the tire acceleration information received from the detector 30 when the tire acceleration information is the result of the sampling process performed during vehicle turning. "Determination processing" for determining is performed. In the following description, an example of determining whether each detector 30 is installed on the left or right tire of the vehicle 10 will be mainly described in the determination process.

The sampling process performed by the detector 30 and the determination process performed by the monitoring unit 45 will be described in detail below. Normally, in order to suppress the power consumption of the detector 30, the standby period of the detector 30 (the period during which the LF signal from the initiator 50 can be received) is intermittently set.

The monitoring unit 45 determines whether or not there is an indication that the vehicle 10 will turn based on the output of the vehicle speed sensor 74, for example, and detects a continuous standby request via the initiator 50 when there is an indication that the vehicle 10 will turn. output to the device 30 continuously for a certain period of time.

When the detector 30 receives a continuous standby request from the initiator 50 during the standby period, the detector 30 changes the standby period setting mode from an intermittent standby mode in which the standby period is intermittently set to a continuous standby period. Switch to the continuous standby mode that you want to set. During the continuous standby mode, the detector 30 is ready to continuously receive commands (LF signals) from the initiator.

After that, the monitoring unit 45 determines whether or not the vehicle 10 actually turns based on the output of the steering angle sensor 71, and sends a measurement start command to the detector 30 via the initiator 50 when the vehicle 10 turns. Output. Then, the detector 30 performs the above-described "sampling process" when receiving a measurement start command from the initiator 50 during the continuous standby mode.

FIG. 5 is a diagram for explaining the content of sampling processing by the detector 30. FIG. As in FIG. 4, FIG. 5 shows the waveform of the gravitational acceleration component superimposed on the acceleration G when the tire rotates at a constant speed.

As described above, the monitoring unit 45 continuously outputs the continuous standby request for a certain period of time when there is a sign that the vehicle 10 will turn. When the detector 30 receives the continuous standby request from the initiator 50 during the standby period in the intermittent standby mode, the detector 30 changes the setting mode of the standby period to the continuous standby mode. This allows the detector 30 to continuously receive commands (LF signals) from the initiator 50 .

The monitoring unit 45 outputs a measurement start command when the vehicle 10 actually turns. The detector 30 performs "sampling processing" when receiving a measurement start command from the initiator 50 during the continuous standby mode. In the sampling process, as described above, the output of the acceleration sensor 39 is sampled at the predetermined period Ts and the predetermined sampling period Ps.

Here, the sampling period Ps is set to a value less than half the output waveform period (hereinafter also referred to as "acceleration period Pg") of the acceleration sensor 39 according to the so-called sampling theorem. , when converting an analog signal to a digital signal, by sampling at a frequency higher than twice the frequency component contained in the original analog signal, the original analog signal can be reproduced from the sampled digital signal. Therefore, by sampling the acceleration G (output of the acceleration sensor 39) at the sampling period Ps, the sampled data can be used to reproduce the original waveform of the acceleration G. In order to increase it, it is practically desirable to set the sampling period Ps to less than a quarter of the acceleration period Pg.

Since the detector 30 cannot grasp the acceleration period Pg (tire rotation speed) in real time, the sampling period Ps is set in advance so that it is approximately less than half the acceleration period Pg during vehicle turning. It is decided. Conversely, if the sampling period Ps is determined, the maximum tire rotation speed at which the original analog signal can be reproduced is determined. is discarded on the monitoring unit 45 side.

In other words, the permissible vehicle speed during turning of the vehicle is preset to a predetermined value (for example, several km/h), and the sampling period Ps is preset to a value less than half the acceleration period Pg during running at the permissible vehicle speed. be set. Since the original acceleration waveform cannot be reproduced with the acceleration data collected by the sampling process performed while the vehicle is traveling at a speed exceeding the allowable vehicle speed, the data is discarded by the monitoring unit 45 and the above determination process is performed. avoid

If the detection accuracy of the acceleration sensor 39 is not sufficient, only the beginning and end of the sampling process are sampled at high frequency (for example, several millisecond cycles), and a plurality of data are statistically processed (average value, minimum Multiplicative interpolation) may be used to improve the detection accuracy of the acceleration G at the beginning and end of the sampling process.

Further, the predetermined period Ts during which the sampling process is performed does not necessarily have to be a fixed value, and the number of sampling processes does not necessarily have to be one. For example, when one measurement start command is received, after the first sampling process is performed for a first period Ts1 (for example, 3 seconds), the second sampling process is performed for a second period Ts2 (for example, 6 seconds), Among the data collected by these sampling processes, highly reliable data may be used, or data obtained by statistically processing the data collected by these sampling processes may be used.

The detector 30 stores the result of sampling processing in the storage unit 36 . Then, the detector 30 outputs the result of the sampling process as tire acceleration information at the next output timing.

The monitoring unit 45 reproduces the waveform of the acceleration G detected by the acceleration sensor 39 from the tire acceleration information (result of sample processing) received from the detector 30, and detects the waveform of the reproduced acceleration G for a predetermined period Ts (sampling The amount of rotation of the tire during the period during which the process was performed is calculated. Hereinafter, the amount of rotation of the tire during the predetermined period Ts calculated from the waveform of the acceleration G is also referred to as "amount of tire rotation Rg based on the acceleration G". For example, in the example shown in FIG. 5, the waveform of the acceleration G for approximately 2.5 wavelengths is included in the predetermined period Ts and the tire rotates 2.5 times, so the tire rotation amount Rg based on the acceleration G is Approximately 900° (=360°×2.5 rotations). Since the tire rotation amount Rg based on the acceleration G is calculated based on the output of the acceleration sensor 39 actually installed on the tire, the value reflects the influence of the difference between the inner and outer wheels while the vehicle is turning.

It should be noted that while the vehicle is turning, the vehicle speed is relatively low and it is assumed that the centrifugal acceleration contained in the acceleration G has little effect. The centrifugal acceleration applied to the detector 30 may be estimated from the output, and the acceleration G may be corrected with the estimated centrifugal acceleration.

Furthermore, the monitoring unit 45 calculates the rotation amount of the tire for a predetermined period Ts from the output of the vehicle speed sensor 74 . Hereinafter, the tire rotation amount for the predetermined period Ts calculated from the output of the vehicle speed sensor 74 is also referred to as "tire rotation amount Rv based on the vehicle speed". Since the tire rotation amount Rv based on the vehicle speed is calculated based on the output of the vehicle speed sensor 74 which is not installed on the tire, it is a value that does not reflect the influence of the difference between the inner and outer wheels when the vehicle turns.

The monitoring unit 45 determines which of the left and right tires of the vehicle 10 the detector 30 is installed on, based on the magnitude relationship between the tire rotation amount Rg based on the acceleration G and the tire rotation amount Rv based on the vehicle speed.

FIG. 6 is a diagram showing the inner and outer wheel difference when the vehicle 10 is turning to the left. When the vehicle 10 is turning left, the left tire 13 is the inner wheel and the right tire 14 is the outer wheel. In this case, when the tire rotation amount Rg based on the acceleration G is smaller than the tire rotation amount Rv based on the vehicle speed, it can be determined that the detector 30 is installed on the inner wheel side tire 13 . When the tire rotation amount Rg based on the acceleration G is larger than the tire rotation amount Rv based on the vehicle speed, it can be determined that the detector 30 is installed on the outer wheel side tire 14 .

When the vehicle 10 is turning to the right, the left tire 13 is the outer wheel and the right tire 14 is the inner wheel. Therefore, when the tire rotation amount Rg based on the acceleration G is smaller than the tire rotation amount Rv based on the vehicle speed, it can be determined that the detector 30 is installed on the inner wheel side tire 14 . When the tire rotation amount Rg based on the acceleration G is larger than the tire rotation amount Rv based on the vehicle speed, it can be determined that the detector 30 is installed on the outer wheel side tire 13 .

FIG. 7 is a flow chart showing an example of a processing procedure performed by the detector 30 and the monitoring unit 45. As shown in FIG. This flowchart is executed, for example, when the shift position of vehicle 10 is the forward position.

First, based on the output (vehicle speed) of the vehicle speed sensor 74, the monitoring unit 45 determines whether or not there is a sign that the vehicle 10 will turn (step S20). For example, when the vehicle speed suddenly decreases, the monitoring unit 45 can assume that the vehicle 10 has decelerated before the intersection, so that the vehicle 10 may thereafter determine that there is a sign that the vehicle 10 will turn. . Further, for example, when the vehicle speed is 0, the monitoring unit 45 assumes that the vehicle 10 is stopped at an intersection. good too.

If it is not determined that there is an indication that vehicle 10 will turn (NO in step S20), monitoring unit 45 skips subsequent processes and ends the process.

When it is determined that there is an indication that the vehicle 10 will turn (YES in step S20), the monitoring unit 45 causes the initiator 50 to continuously output the LF signal including the continuous standby request for a certain period of time (step S21).

Next, the monitoring unit 45 determines whether the vehicle 10 actually turns based on the output of the steering angle sensor 71 (step S22). When the vehicle 10 turns (YES in step S22), the monitoring unit 45 causes the initiator 50 to output an LF signal including a measurement start command (step S24).

Next, the monitoring unit 45 stores the turning information of the vehicle 10 in the storage section 46 (step S25). The turning information includes information such as the turning direction of the vehicle 10, turning time, and turning vehicle speed.

On the other hand, when the detector 30 receives the LF signal containing the continuous standby request from the initiator 50 (step S40), the standby period setting mode is changed from the intermittent standby mode to the continuous standby mode (step S40). S41). When the detector 30 receives the LF signal including the measurement start instruction from the initiator 50 during the continuous standby mode (step S42), the standby period setting mode is returned to the intermittent standby mode (step S43), The sampling process described above is performed (step S44). Specifically, the detector 30 samples the acceleration G at a predetermined period Ts and a predetermined sampling period Ps, and stores the result in the storage section 36 . The detector 30 outputs the result of the sampling process as tire acceleration information at the next output timing (step S45).

Upon receiving the tire acceleration information from the detector 30 (step S26), the monitoring unit 45 reads out the turning information stored in the storage unit 46 in step S25, and determines whether the turning vehicle speed included in the turning information is less than the allowable vehicle speed. It is determined whether or not (step S27). This allowable vehicle speed is the vehicle speed that is the basis for determining the sampling period Ps, as described above.

If the turning vehicle speed exceeds the allowable vehicle speed (NO in step S27), the original acceleration waveform cannot be accurately reproduced from the received tire acceleration information, so the monitoring unit 45 discards the tire acceleration information and terminates the process. do.

If the turning vehicle speed is less than the allowable vehicle speed (YES in step S27), the monitoring unit 45 reproduces the original acceleration waveform based on the acceleration data included in the tire acceleration information, and determines the acceleration G from the reproduced acceleration waveform. A tire rotation amount Rg is calculated (step S28).

Next, the monitoring unit 45 calculates the tire rotation amount Rv based on the vehicle speed from the turning vehicle speed included in the turning information (step S29).

Next, the monitoring unit 45 determines whether or not the tire rotation amount Rg based on the acceleration G is greater than the tire rotation amount Rv based on the vehicle speed (step S30).

If the tire rotation amount Rg based on the acceleration G is greater than the tire rotation amount Rv based on the vehicle speed (YES in step S30), the monitoring unit 45 detects that the detector 30 that has transmitted the tire acceleration information is on the outer tire during turning. It is determined that they are arranged (step S31).

If the tire rotation amount Rg based on the acceleration G is smaller than the tire rotation amount Rv based on the vehicle speed (NO in step S30), the monitoring unit 45 detects that the detector 30 that has transmitted the tire acceleration information is on the inner tire during turning. It is determined that they are arranged (step S32).

Next, the monitoring unit 45 determines on which tire, left or right, of the vehicle 10 the detector 30 is installed, based on the turning direction included in the turning information (step S33).

Specifically, in the case where it is determined in step S31 that the detector 30 is located on the outer tire, the monitoring unit 45 determines that the detector 30 is positioned on the right tire when the turning direction is left. If the turning direction is right, it is determined that the detector 30 is positioned on the left tire. In addition, in the case where it is determined in step S32 that the detector 30 is arranged on the inner tire, the monitoring unit 45 arranges the detector 30 on the left tire when the turning direction is left. If the turning direction is right, it is determined that the detector 30 is located on the right tire.

As described above, the tire position detection system according to this embodiment includes the detector 30 having the acceleration sensor 39 that detects the acceleration G in the tire radial direction, and the monitoring unit 45 . The detector 30 samples the output of the acceleration sensor 39 at a predetermined period Ts and a predetermined sampling period Ps, and outputs the result to the monitoring unit 45 . When the sampling result received from the detector 30 is the result of sampling performed while the vehicle 10 is turning, the monitoring unit 45 detects the tire rotation amount Rg (the tire rotation amount for the predetermined period Ts) based on the acceleration G based on the sampling result. rotation amount) is calculated, and the tire position where the detector 30 is installed is determined based on the tire rotation amount Rg based on the acceleration G.

Based on the output of the acceleration sensor 39, the above system does not measure the time required for the tire to rotate exactly once, but calculates the amount of tire rotation for a predetermined period of time Ts. Determine the tire position where 30 is installed. Therefore, it is not necessary to accurately measure the time it takes for the tire to rotate exactly once, and it is not necessary to constantly activate the detector 30 at a high frequency during the time it takes for the output of the acceleration sensor 39 to change by one wavelength. As a result, the tire position where the detector 30 is installed can be determined while suppressing the power consumption of the detector 30 .

In particular, in the tire position detection system according to the present embodiment, the amount of tire rotation calculated from the acceleration G is not limited to one rotation, and may be more than one rotation. Even if the difference between the inner and outer rings is very small, it is possible to make an accurate determination.

In addition, in the tire position detection system according to the present embodiment, since the tire rotation amount for the "predetermined period Ts" is calculated from the sampling result of the acceleration G, the acceleration G is accurately measured at the first and last sampling. Although it is necessary to measure, it is not necessary to measure the acceleration G so accurately during sampling between the beginning and the end. That is, according to the so-called sampling theorem, the intermediate sampling period Ps may be set to about half the output waveform period of the acceleration sensor 39 to increase the frequency of intermediate sampling. As a result, the detector 30 does not need to be activated frequently during sampling, and the power consumption of the detector 30 can be kept low.

Furthermore, in the present embodiment, monitoring unit 45 outputs a measurement start command to detector 30 via initiator 50 when vehicle 10 turns. The detector 30 performs sampling processing of the acceleration G when receiving a measurement start command from the initiator 50 . As a result, the sampling process of the acceleration G can be performed at the timing when the vehicle 10 is actually turning, so wasteful sampling process can be suppressed. As a result, power consumption of the detector 30 can be further reduced.

Furthermore, in this embodiment, the detector 30 intermittently sets a standby period during which the LF signal from the initiator 50 can be received. The monitoring unit 45 determines whether or not there is an indication that the vehicle 10 will turn based on the vehicle speed (output of the vehicle speed sensor 74), and if it is determined that there is an indication that the vehicle 10 will turn, issues a continuous standby request. It is continuously output to the detector 30 through the initiator 50 for a certain period of time. When the detector 30 does not receive a continuous standby request from the initiator 50, it intermittently sets a continuous standby period (intermittent standby mode), and receives a continuous standby request from the initiator 50 during the standby period. If received, the standby period is continuously set (continuous standby mode). Thus, when there is no indication that the vehicle 10 will turn, the standby period is set at a low frequency to suppress the power consumption of the detector 30, and when there is an indication that the vehicle 10 will turn, the standby period is set. Setting with a higher frequency makes it possible to prepare for receiving a measurement start command from the initiator 50 .

[Modification 1]
In the above-described embodiment, an example in which the tire position detection system according to the present disclosure is applied to the vehicle 10 including the initiator 50 has been described, but the tire position detection system according to the present disclosure may be applied to a vehicle that does not include the initiator 50. .

Without the initiator 50, it is difficult for the monitoring unit 45 to forcibly activate the detector 30 to sample the acceleration G when the vehicle 10 turns.

Therefore, in Modification 1, the detector 30 determines whether or not there is a sign that the vehicle 10 will turn based on the output (acceleration G) of the acceleration sensor 39, and determines that there is a sign that the vehicle 10 will turn. When the determination is made, sampling processing is performed and the result is output to the monitoring unit 45 . The monitoring unit 45 then determines the tire position where the detector 30 is installed based on the sampling process results received from the detector 30 .

FIG. 8 is a flow chart showing an example of a processing procedure performed by the detector 30 and the monitoring unit 45 according to Modification 1. As shown in FIG. This flowchart is also executed, for example, when the shift position of the vehicle 10 is the forward position, similar to the flowchart of FIG. 7 described above.

The flowchart shown in FIG. 8 is obtained by deleting steps S20, S21, S24, S40, S41, and S43 of the flowchart shown in FIG. 7, replacing steps S22 and S42 with steps 22A and S42A, respectively, and adding step S35. be. The other steps shown in FIG. 8 (steps with the same numbers as the steps shown in FIG. 7) have already been described, and detailed description thereof will not be repeated here.

First, the detector 30 determines whether or not there is a sign that the vehicle 10 will turn based on the output (acceleration G) of the acceleration sensor 39 (step S42A). For example, when the acceleration G increases from 0, there is a possibility that the stopped vehicle 10 will exit the intersection or the parking lot and turn. . Further, for example, when the tire rotation speed ascertained from the fluctuation period of the acceleration G suddenly decreases, it is assumed that the vehicle 10 decelerates before entering the intersection. It is determined that there is a sign that it will.

If it is not determined that there is an indication that vehicle 10 will turn (NO in step S42A), detector 30 skips the subsequent processes and ends the process.

If it is determined that there is a sign that vehicle 10 will turn (YES in step S42A), detector 30 performs the sampling process described above and stores the result in storage unit 36 (step S44). Thus, in the present modification 1, the detector 30 does not perform the sampling processing triggered by the reception of the measurement start command from the monitoring unit 45, but based on the output of the acceleration sensor 39 (acceleration G). The sampling process is triggered by the fact that the vehicle 10 has determined that there is a sign that the vehicle 10 will turn.

In step S44, the detector 30 stores sampling time information (information on the time when sampling was performed) in the storage unit 36 together with the result of the sampling process.

Then, the detector 30 outputs the result of the sampling process together with the sampling time information as tire acceleration information at the next output timing (step S45).

On the other hand, the monitoring unit 45 determines whether or not the vehicle 10 turns regardless of the sampling process of the detector 30 (step S22A). If vehicle 10 does not turn (NO in step S22A), monitoring unit 45 shifts the process to step S26.

When the vehicle 10 turns (YES in step S22A), the monitoring unit 45 stores the turning information of the vehicle 10 in the storage section 46 (step S25). The turning information includes information such as the turning direction of the vehicle 10, turning time, and turning vehicle speed, as described above. After that, the monitoring unit 45 shifts the process to step S26.

When the monitoring unit 45 receives the tire acceleration information from the detector 30 (step S26), the monitoring unit 45 reads the turning information stored in the storage unit 46 in step S25, and stores the tire acceleration information in the turning time zone included in the turning information. is included (step S35).

If the sampling time period is not included in the turning time period (NO in step S35), the tire acceleration information is not the result of sampling performed while vehicle 10 is turning. Skip and end processing.

When the sampling time period is included in the turning time period (YES in step S35), the processing from step S27 onwards is executed and determination is made.

As described above, the tire position detection system according to the present disclosure may be applied to vehicles that do not include the initiator 50 . That is, the detector 30 side predicts the turn of the vehicle 10, performs sampling processing, outputs the result to the monitoring unit 45, and the monitoring unit 45 side selects the result of the actual sampling processing during the turning of the vehicle, The data may be used for determination processing.

Note that in the first modification, the detector 30 performs the sampling processing triggered by the fact that the detector 30 itself has determined that there is a sign that the vehicle 10 is turning. Therefore, the sampling processing is actually performed while the vehicle is turning. It is also assumed that there is no Therefore, the predetermined period Ts of the sampling process is periodically switched to a plurality of slightly longer periods (for example, 3 seconds, 10 seconds, and 30 seconds) to increase the probability that the sampling process is actually performed while the vehicle is turning. You may do so.

[Modification 2]
In the above-described embodiment, the tire rotation amount Rv based on the vehicle speed is compared with the tire rotation amount Rg based on the acceleration G in step S30 of FIG.

However, the object to be compared with the tire rotation amount Rg based on the acceleration G in step S30 of FIG. 7 is not necessarily limited to the tire rotation amount Rv based on the vehicle speed.

For example, in step S30 of FIG. 7, the tire rotation amount Rg based on the acceleration G of one of the left and right tires and the tire rotation amount Rg based on the acceleration G of the other left and right tires may be compared. That is, it may be determined which one of the left and right tires or the other tire has the larger tire rotation amount Rg during the predetermined period Ts while the vehicle is turning. For example, when comparing the tire rotation amount Rg based on the acceleration G of one of the left and right rear tires and the tire rotation amount Rg based on the acceleration G of the other left and right rear tires, the larger tire rotation If it is determined that the detector 30 corresponding to the amount Rg is arranged on the outside tire and the detector 30 corresponding to the smaller tire rotation amount Rg is arranged on the inside tire, good.

Further, since the amount of tire rotation during turning differs between the steerable front tires 11 and 12 and the non-steerable rear tires 13 and 14, in step S30 of FIG. It is also possible to compare the tire rotation amounts Rg based on the above, and determine the tire positions where the detectors 30 for the four wheels are arranged from the comparison result.

For example, if the tires are attached at the same position in the overall length direction of the vehicle 10 (for example, left and right tires attached to the front wheels, or left and right tires attached to the rear wheels), the above-mentioned Thus, since there is a difference in the amount of rotation between the inner side and the outer side during turning, the mounting position of the tire can be determined by comparing the difference in the amount of rotation. Also, among the tires attached at different positions in the overall length direction of the vehicle 10, the tires attached to the same side along the overall length direction of the vehicle (for example, the front and rear tires on the right side of the vehicle, or the front and rear tires on the left side of the vehicle). ), the inner ring difference also occurs during turning. Therefore, the tire positions where the detectors 30 for four wheels are arranged may be determined by comparing the amount of rotation of each tire during turning.

[Modification 3]
In the above-described embodiment, an example has been described in which the detector 30 itself stops the sampling process after performing the sampling process for the predetermined period Ts.

However, the sampling process may be stopped when the detector 30 receives a measurement stop command from the initiator 50 . In this case, not only the start timing of the sampling process by the detector 30 but also the stop timing of the sampling process can be controlled by the monitoring unit 45 that can recognize that the vehicle is turning. Therefore, since only the period during which the vehicle is turning can be set as the period for the sampling process, the accuracy of the determination process can be improved.

It should be considered that the embodiments disclosed this time are illustrative in all respects and not restrictive. The scope of the present disclosure is indicated by the scope of the claims rather than the above description, and is intended to include all modifications within the scope and meaning of equivalents of the scope of the claims.

The exemplary embodiments and modifications thereof described above are specific examples of the following aspects.
(1) A tire position detection system according to the present disclosure includes a detector having an acceleration sensor that detects radial acceleration of a tire mounted on a vehicle, and a monitoring unit configured to receive information from the detector. Prepare. The detector performs sampling processing for sampling the output of the acceleration sensor at predetermined intervals for a predetermined period, and outputs the result of the sampling processing to the monitoring unit. The monitoring unit calculates a tire rotation amount for a predetermined period based on the result of the sampling process when the result of the sampling process received from the detector is the result of sampling during turning of the vehicle, and calculates the tire rotation amount for the predetermined period. Determination processing is performed to determine the tire position where the detector is installed based on the amount of tire rotation.

According to the above aspect, the amount of tire rotation for a predetermined period is calculated based on the output of the acceleration sensor, instead of measuring the time required for the tire to rotate exactly once, and the detector detects the amount of tire rotation for the predetermined period. determines the tire position where the is installed. Therefore, it is not necessary to accurately measure the time it takes for the tire to rotate exactly once, and it is not necessary to constantly activate the detector at high frequency during the time it takes for the output of the acceleration sensor to change by one wavelength. As a result, the tire position where the detector is installed can be determined while suppressing the power consumption of the detector.

(2) In one aspect, the predetermined period is set to a value less than half the output waveform period of the acceleration sensor.

According to the above aspect, since the amount of tire rotation for a predetermined period is calculated, it is not necessary to measure the acceleration so accurately as compared to the case of measuring the time taken for the tire to rotate exactly once. In view of this point, the "predetermined period" in which the detector samples the output of the acceleration sensor is set to the extent that the output waveform of the acceleration sensor can be reproduced according to the so-called sampling theorem, that is, about half the output waveform period of the acceleration sensor. Sampling frequency can be rough. As a result, the power consumption of the detector can be kept low.

(3) In one aspect, the predetermined period is set to a value less than half the output waveform period of the acceleration sensor when the vehicle turns at the first vehicle speed. The monitoring unit determines whether the result of the sampling process received from the detector is information during vehicle turns below the first vehicle speed. The monitoring unit performs a determination process when the result of the sampling process received from the detector is information that the vehicle is turning at less than the first vehicle speed. The monitoring unit does not perform the determination process if the result of the sampling process received from the detector is not the information that the vehicle is turning at less than the first vehicle speed.

According to the above aspect, the predetermined cycle (the cycle in which the detector samples the output of the acceleration sensor) is set in advance to a value less than half the output waveform cycle of the acceleration sensor when the vehicle turns at the first vehicle speed. . Then, the monitoring unit determines whether or not the result of the sampling process is information indicating that the vehicle is turning at a speed lower than the first vehicle speed, and whether or not to perform the determination process is determined according to the determination result. That is, if the result of the sampling process is information about the vehicle turning at the first vehicle speed or higher, the output waveform of the acceleration sensor cannot be accurately reproduced from the information, and the tire rotation amount cannot be calculated with high accuracy. Therefore, the monitoring unit does not perform determination processing. As a result, it is possible to prevent the determination process from being performed even when the tire rotation amount calculation accuracy is poor.

(4) In one aspect, the detector further comprises an initiator that outputs a command signal to the detector. The monitoring unit outputs a measurement start command to the detector via the initiator when the vehicle turns. The detector performs sampling processing when receiving a measurement start command from the initiator.

According to the above aspect, since the sampling process can be performed at the timing when the vehicle is actually turning, the sampling process by the detector is performed unnecessarily even when the determination process by the monitoring unit is not performed. can be suppressed. Therefore, the power consumption of the detector can be further reduced.

(5) In one aspect, the detector intermittently sets a standby period during which a signal from the initiator can be received. The monitoring unit determines whether or not there is a sign that the vehicle will turn based on the vehicle speed, and if it is determined that there is a sign that the vehicle will turn, a standby request is sent to the detector via the initiator for a certain period of time. output. The detector sets the standby period at the first frequency when no standby request is received from the initiator during the standby period. When a standby request is received from the initiator during the standby period, the standby period is set to a second frequency higher than the first frequency, and when a measurement start command is received from the initiator during the standby period, sampling processing is performed. do

According to the above aspect, when there is no sign of the vehicle turning, the power consumption of the detector is suppressed by setting the standby period of the detector to a low first frequency, and when there is a sign of the vehicle turning. By setting the standby period of the detector at a higher second frequency, it is possible to prepare for receiving the measurement start command from the initiator.

(6) In one aspect, the detector determines whether or not there is an indication that the vehicle will turn based on the output of the acceleration sensor, and performs sampling processing when it is determined that there is an indication that the vehicle will turn. . The monitoring unit determines whether the results of the sampling process received from the detector include information during vehicle turns. The monitoring unit performs determination processing when the result of the sampling processing received from the detector includes information on vehicle turning. The monitoring unit does not perform the determination process if the sampling process result received from the detector does not include the information that the vehicle is turning.

According to the above aspect, even if there is no initiator, the detector side determines whether or not there is a sign that the vehicle will turn based on the output of the acceleration sensor, and determines that there is a sign that the vehicle will turn. Sampling processing is performed when Therefore, even if there is no initiator, unnecessary sampling processing by the detector can be suppressed as much as possible, so power consumption of the detector can be kept low.

(7) In one aspect, the detector further has a pressure sensor that detects tire air pressure in addition to the acceleration sensor.

According to the above aspect, the detector can be used to monitor tire pressure in addition to determining the tire position at which the detector is located.

(8) In one aspect, in the determination process, the monitoring unit determines on which tire, left or right, of the vehicle, the detector is installed.

According to the above aspect, it is possible to determine on which tire, left or right, the detector is installed on the vehicle.

10 vehicle, 11, 12, 13, 14 tire, 31, 32, 33, 34 detector, 35 controller, 36, 46 storage unit, 37, 47 processing unit, 38 pressure sensor, 39 acceleration sensor, 40 TPMS receiver, 45 monitoring unit, 51, 52 initiator, 60 display unit, 71 steering angle sensor, 72 shift position sensor, 74 vehicle speed sensor, A1, A2, L1 antenna, CR receiving circuit, CT transmitting circuit, WH wheel.

Claims (8)

a detector having an acceleration sensor that detects radial acceleration of a tire mounted on a vehicle;
a monitoring unit configured to receive information from the detector;
The detector performs a sampling process of sampling the output of the acceleration sensor for a predetermined period and at a predetermined cycle, and outputs the result of the sampling process to the monitoring unit;
The monitoring unit is
calculating the tire rotation amount for the predetermined period based on the result of the sampling process when the result of the sampling process received from the detector is the result of sampling during turning of the vehicle;
A tire position detection system that performs determination processing for determining a tire position where the detector is installed based on the calculated tire rotation amount for the predetermined period. 2. The tire position detection system according to claim 1, wherein said predetermined period is set to a value less than half the output waveform period of said acceleration sensor. The predetermined cycle is set to a value less than half the output waveform cycle of the acceleration sensor when the vehicle turns at a first vehicle speed,
The monitoring unit is
determining whether the result of the sampling process received from the detector is information indicating that the vehicle is turning at less than the first vehicle speed;
performing the determination process when the result of the sampling process received from the detector is information indicating that the vehicle is turning at less than the first vehicle speed;
3. The tire position detection system according to claim 1, wherein said determination processing is not performed when the result of said sampling processing received from said detector is not information indicating that the vehicle is turning at less than said first vehicle speed. Further comprising an initiator that outputs a command signal to the detector,
the monitoring unit outputs a measurement start command to the detector via the initiator when the vehicle turns;
The tire position detection system according to any one of claims 1 to 3, wherein said detector performs said sampling process when receiving said measurement start command from said initiator. The detector intermittently sets a standby period during which a signal from the initiator can be received,
The monitoring unit is
determining whether there is a sign that the vehicle will turn based on the vehicle speed;
continuously outputting a standby request to the detector via the initiator for a certain period of time when it is determined that there is a sign that the vehicle will turn;
The detector is
setting the standby period at a first frequency when the standby request is not received from the initiator during the standby period;
setting the standby period at a second frequency higher than the first frequency when the standby request is received from the initiator during the standby period;
5. The tire position detection system according to claim 4, wherein said sampling process is performed when said measurement start command is received from said initiator during said standby period. The detector is
determining whether there is a sign that the vehicle will turn based on the output of the acceleration sensor;
performing the sampling process when it is determined that there is a sign that the vehicle will turn;
The monitoring unit is
determining whether the result of the sampling process received from the detector includes information on vehicle turning;
performing the determination process when the result of the sampling process received from the detector includes information that the vehicle is turning;
4. The tire position detection system according to any one of claims 1 to 3, wherein said determination processing is not performed when the result of said sampling processing received from said detector does not include information on vehicle turning. The tire position detection system according to any one of claims 1 to 6, wherein said detector further includes a pressure sensor for detecting tire air pressure in addition to said acceleration sensor. The tire position detection system according to any one of claims 1 to 7, wherein in the determination process, the monitoring unit determines on which left or right tire of the vehicle the detector is installed.

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