JP2005145113A - Tire position detecting system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately identify whether the tire having a mounted sensor unit is a front wheel or a rear wheel in reference to a receiving level of a signal transmitted in a wireless manner from the sensor unit fixed to the tire of a vehicle. <P>SOLUTION: A vehicle 1 has, at each of its front side and rear side, receivers 20a, 20b for receiving signals transmitted in a wireless manner from each of the sensor units 10 (10a, 10b, 10c, 10d) installed at each of the tires 2 (a left front wheel 2a, a right front wheel 2b, a left rear wheel 2c and a right rear wheel 2d). A control device 30 compares values of a receiving signal level at the front receiver 20a and a receiving signal level at the rear receiver 20b for the same sensor unit. When the receiving signal level at the front receiver 20a is higher, it is judged that the sensor unit is mounted at the front wheel. In turn, when the receiving signal level at the rear receiver 20b is higher, it is judged that the sensor unit is mounted at the rear wheel. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a tire position detection device that receives a signal wirelessly transmitted from a sensor unit attached to a tire of a vehicle and determines the position of the tire on which the sensor unit is mounted based on a received signal level.

  There is known a tire pressure monitoring system that monitors the air pressure of a vehicle tire (hereinafter referred to as tire pressure) and issues a warning to a driver or the like when the tire pressure is lower than a specified pressure value. The tire pressure monitoring system has a tire pressure monitoring device installed in the vehicle body and a tire pressure detection device (sensor unit) installed in each tire. The tire pressure detection device includes a tire pressure sensor that detects tire pressure, a wireless transmission unit, a battery power source, and the like, and wirelessly transmits the detected tire pressure information and tire-specific identification information. The tire pressure monitoring device receives information wirelessly transmitted from each tire pressure detection device and monitors the tire pressure of each tire (see Patent Document 1 and Patent Document 2).

For the purpose of discriminating between the right wheel and the left wheel of a vehicle, an acceleration sensor is provided on both wheels, and information that distinguishes the left and right wheels is transmitted (Patent Document). 3).
Japanese National Patent Publication No. 10-508264 Japanese National Patent Publication No. 08-505939 Special table 2003-527608 gazette

  In order to notify not only the decrease in tire pressure but also the position of the tire where the tire pressure has decreased (for example, the front left wheel, the front right wheel, the rear left wheel, the rear right wheel), the identification information of the tire pressure detection device And a tire position (for example, front left wheel, front right wheel, rear left wheel, rear right wheel) where the tire pressure detection device is installed must be associated (four wheel position detection).

  When the tire pressure detection device transmits information that distinguishes the left and right wheels or transmits the rotation direction information of the tire, the right wheel and the left wheel are received by receiving such information. Discrimination is possible.

  Regarding the separation of the front and rear tires, it is conceivable that a receiving device is installed in front of (or behind) the vehicle and is determined based on the strength (reception signal level) of the received radio wave. However, when the variation in the transmission output of the tire pressure detection device is large or when the variation in the transmission output is large, there is a possibility of making an erroneous determination.

  Further, in the configuration in which only one receiving device is installed in the vehicle, when the vehicle is large, either the front or the rear can be received, but the other may not be received.

  The present invention has been made to solve such a problem, and an object of the present invention is to provide a tire position detection device that can accurately determine the position of a tire on which a sensor unit is mounted based on a received signal level. And

  In order to solve the above problems, in the tire position detecting device according to the present invention, a receiving device that receives a signal transmitted wirelessly from a sensor unit installed in each tire of a vehicle is arranged separately in the front-rear direction of the vehicle. The front wheel for comparing the received signal level at the front receiving device and the received signal level at the rear receiving device for the same sensor unit to determine whether the tire on which the sensor unit is installed is a front wheel or a rear wheel -It has a rear wheel discrimination means.

  In the tire position detecting device according to the present invention, two receiving devices are spaced apart from each other in the front-rear direction of the vehicle, the received signal levels of both receiving devices are compared for the same sensor unit, and the sensor unit is installed from the comparison result. Since it is determined whether the tire is a front wheel or a rear wheel, erroneous determination of the tire position can be eliminated.

  Further, since the two receiving devices are spaced apart from each other in the front-rear direction of the vehicle, any of the receiving devices can receive signals wirelessly transmitted from each sensor unit even in a vehicle having a long wheel length. .

  Hereinafter, the best mode for carrying out the invention will be described based on examples.

  FIG. 1 is a diagram showing a configuration of a tire pressure monitoring system to which a tire position detecting device according to the present invention is applied. The tire pressure monitoring system TPMS includes each sensor unit 10a, 10b, 10c, 10d installed in each tire 2a, 2b, 2c, 2d of the vehicle 1, a receiving device 20a disposed on the front side of the vehicle 1, The receiving device 20 b disposed on the rear side of the vehicle 1, the control device 30, and the display device 40 are included. The receiving device 20a and the control device 30 may be configured as an integrated device. The receiving device 20a, the control device 30, and the display device 40 may be configured as an integrated device.

  FIG. 2 is a diagram showing a block configuration of the sensor unit. The sensor unit 10 (10a to 10d) includes a tire pressure sensor 11 that detects tire pressure, a rotation sensor 12 that detects rotation and a rotation direction of the tire, a CPU unit 13, an RF unit 14, and a transmission antenna 15. And a battery 16 for supplying power to each part. The rotation sensor 12 is configured using, for example, an acceleration sensor.

  The CPU unit 13 is configured using a one-chip microcomputer or the like that incorporates a CPU, ROM, RAM, EEPROM, A / D converter, and the like. The CPU unit 13 captures the output of the tire pressure sensor 11 at predetermined time intervals and performs temperature compensation of the tire pressure as necessary. The CPU unit 13 detects the tire rotation direction based on the output of the rotation sensor 12. When the output of the rotation sensor 12 does not change, the CPU unit 13 determines that the vehicle is in a stopped state. The CPU 13 may be configured to measure the time for one tire rotation (tire rotation speed) based on the output of the rotation sensor 12. The CPU 13 holds identification information (ID information) unique to each sensor unit 10 in, for example, an EEPROM.

  FIG. 3 is a diagram illustrating an example of a format of data wirelessly transmitted from the sensor unit. As shown in FIG. 3, the CPU unit 13 generates a series of transmission data including a header, a function, identification information (ID), tire pressure information, tire rotation direction information, an error correction code, and the like, and supplies the transmission data to the RF unit 14. To do. The RF unit 14 generates a signal obtained by modulating a carrier wave having a predetermined carrier frequency by a predetermined modulation method based on the transmission data, and wirelessly transmits the signal from the transmission antenna 15. If the CPU 13 determines that the vehicle is in a stopped state based on the output of the rotation sensor 12, the CPU 13 performs data transmission, for example, every hour. If the CPU 13 determines that the vehicle is in a running state, the CPU 13 transmits data at intervals of several seconds to several minutes.

  FIG. 4 is a diagram illustrating a block configuration of the receiving apparatus. The receiving device 20 (20a, 20b) includes a receiving antenna 21, a receiving unit 22, a signal processing unit 23, and an output unit 24. The receiving unit 22 demodulates the high frequency signal received by the receiving antenna 21. A binary signal (data) obtained by demodulation is supplied to the signal processing unit 23. The reception unit 22 includes a reception signal level detection unit 25. The reception signal level detection unit 25 outputs a voltage signal corresponding to the reception signal level. A voltage signal corresponding to the received signal level is supplied to the signal processing unit 23.

  The signal processing unit 23 decodes the binary signal (data) supplied from the receiving unit 22 and extracts each information of identification information (ID), tire pressure information, and tire rotation direction information. The signal processing unit 23 includes an A / D converter, and converts a voltage signal corresponding to the reception signal level into reception signal level data.

  The output unit 24 supplies identification information (ID), tire pressure information, tire rotation direction information, and received signal level data to the control device 30 in a predetermined signal transmission format. The output unit 24 includes an in-vehicle LAN interface circuit and the like, and controls each information of identification information (ID), tire pressure information, tire rotation direction information and received signal level data via an in-vehicle LAN system (not shown). 30 may be supplied.

  FIG. 5 is a diagram showing a block configuration of the control device. The control device 30 is configured using a one-chip microcomputer equipped with a CPU, ROM, RAM, EEPROM, serial data communication unit, and the like. The control device 30 includes a tire position detection unit 31 and a tire pressure monitoring unit 32. The tire position detection unit 31 includes a left wheel / right wheel discrimination unit 33 and a front wheel / rear wheel discrimination unit 34. The left wheel / right wheel discriminating means 33 discriminates left and right based on the tire rotation direction information supplied from the receiving device 20.

  The front wheel / rear wheel discriminating means 34 discriminates before and after by comparing the received signal level data supplied from the receiving devices 20a and 20b. The front wheel / rear wheel discriminating means 34 compares the magnitude relationships of the received signal levels at the front and rear receiving devices 20a and 20b with respect to the same sensor unit 10, that is, the same identification information (ID). When the reception signal level at the front receiving device 20a is high, it is determined that the sensor unit is installed on the front wheel. When the reception signal level at the rear receiving device 20b is high, it is determined that the sensor unit is installed on the rear wheel.

  The tire position detection unit 31 manages the identification information (ID) of the sensor unit 10 and the determined tire position (left front wheel, right front wheel, left rear wheel, right rear wheel) in association with each other. The tire position detection unit 31 may write the identification information (ID) and the tire position in an EEPROM or the like. When the tire position detection unit 31 obtains the identification information (ID) of the sensor unit 10 for all four tire positions, the tire position detection unit 31 checks whether the same identification information (ID) is registered repeatedly in a plurality of tire positions. To do. If duplicate registration is detected, the tire position detection unit 31 may display the fact on the display device 40. The tire position detection unit 31 may treat the latest determination result as valid and delete data already registered for the same identification information (ID).

  The tire pressure monitoring unit 32 monitors the tire pressure detected by each sensor unit 10, and causes the display device 40 to display the abnormal content including the tire position when a tire pressure drop or the like occurs.

  The display device 40 is configured by using a plurality of lamps or light emitting diodes that visually display the tire position and the abnormality of the tire pressure. The display device 40 may be provided in the instrument panel. The display device 40 may be configured using a display device that can display characters, images, and the like. Furthermore, instead of providing a dedicated display device, a tire status may be displayed using a display device such as a navigation system.

  As shown in FIG. 1, two receivers 20a and 20b are spaced apart from each other in the front-rear direction of the vehicle, and the received signal levels at both receivers 20a and 20b are compared for the same sensor unit 10, and the comparison result is obtained. It is determined whether the tire on which the sensor unit 10 is installed is a front wheel or a rear wheel. Thereby, the position of the tire can be correctly determined even if the transmission power differs for each sensor unit.

  In addition, since the receiving devices 20a and 20b are respectively arranged in front and rear of the vehicle, even if the transmission power of each sensor unit 10 is small in a vehicle having a large wheel length, a signal from each sensor unit 10 can be received. it can.

It is a figure which shows the structure of the tire pressure monitoring system to which the tire position detection apparatus which concerns on this invention is applied. It is a figure which shows the block configuration of a sensor unit. It is a figure which shows an example of the format of the data transmitted wirelessly from a sensor unit. It is a figure which shows the block configuration of a receiver. It is a figure which shows the block configuration of a control apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Vehicle 2 (2a, 2b, 2c, 2d) Tire 10 (10a, 10b, 10c, 10d) Sensor unit 20 (20a, 20b) Receiving device 21 Receiving antenna 22 Receiving portion 23 Signal processing portion 24 Output portion 30 Control device 31 Tire position detection unit 32 Tire pressure monitoring unit 33 Left wheel / right wheel discrimination means 34 Front wheel / rear wheel discrimination means 40 Display device

Claims (1)

A receiving device that receives a signal transmitted wirelessly from a sensor unit installed in each tire of the vehicle is arranged separately in the front-rear direction of the vehicle,
Front wheel to determine whether the tire on which the sensor unit is installed is a front wheel or a rear wheel by comparing the received signal level at the front receiving device with the received signal level at the rear receiving device for the same sensor unit A tire position detection device comprising rear wheel discrimination means.

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