JP2005157416A - Tire location detection unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately discriminate whether a tire attached with a sensor unit is at a front wheel or a rear wheel on the basis of receiving levels of radio signals transmitted from the sensor units mounted on tires of a vehicle. <P>SOLUTION: A receiving device 20 receiving radio signals transmitted from respective sensors 10 (10a, 10b, 10c, and 10d) mounted on respective tires 2 (a left-front wheel 2a, a right-front wheel 2b, a left-rear wheel 2c, and a right-rear wheel 2d) of the vehicle 1 is arranged on a front side of the vehicle. The receiving device 20 comprises a transmitted output level storage means registering discrimination information of the sensor unit and a transmitted output level of the sensor unit by corresponding with each other, a receiving signal level detection portion and a front wheel and rear wheel discrimination means. The front wheel and rear wheel discrimination means calculates compensated received signal levels compensating the received signal levels in response to the transmitted signal levels regarding respective sensor units, and determines whether each tire with the sensor unit is located at a front wheel or a rear wheel side on the basis of magnitude relationship of each calculated compensated receiving signal level. <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.

  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.

  In order to solve the above-described problems, in the tire position detection device according to the present invention, a receiving device that receives a signal wirelessly transmitted from a sensor unit installed in each tire of a vehicle is disposed on either the front side or the rear side of the vehicle. The reception device includes a transmission output level storage means in which identification information for identifying the sensor unit and a transmission output level of the sensor unit are registered in association with each other, and a reception signal level detection for detecting the reception signal level. And a sensor unit for each of the sensor unit and the sensor unit to obtain a corrected reception signal level obtained by correcting the reception signal level detected by the reception signal level detection unit according to the transmission output level. It has a front wheel / rear wheel discrimination means for judging whether the installed tire is a front wheel or a rear wheel. That.

  Further, in the tire position detection device according to the present invention, a receiving device that receives a signal wirelessly transmitted from a sensor unit installed in each tire of the vehicle is disposed on either the front side or the rear side of the vehicle, The receiving apparatus includes a transmission output level storing unit in which identification information for identifying a sensor unit and a transmission output level of the sensor unit are registered in association with each other, a received signal level detecting unit that detects a received signal level, a sensor For each unit, determine the level difference between the transmission output level and the reception signal level, and determine whether the tire on which the sensor unit is installed is the front wheel or the rear wheel based on the calculated level difference. A wheel discriminating means is provided.

  The tire position detection device according to the present invention corrects the reception signal level according to the transmission output level of the sensor unit, and the tire on which the sensor unit is installed is a front wheel or a rear wheel based on the corrected reception signal level. Determine if there is. Thereby, even if there is variation in the transmission output level of the sensor unit, the tire position can be accurately determined.

  Further, the tire position detection device according to the present invention determines whether the tire on which the sensor unit is installed is a front wheel or a rear wheel based on a level difference between the transmission output level and the reception signal level. Even if the transmission output level of the unit varies, the tire position can be accurately determined.

  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 is arranged on the front side of the vehicle 1 and each sensor unit 10 (10a, 10b, 10c, 10d) installed on each tire 2 (2a, 2b, 2c, 2d) of the vehicle 1 respectively. The receiving device 20 and the display device 40. Note that the receiving device 20 may be disposed on the rear side of the vehicle 1.

  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 takes in 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 includes a receiving antenna 21, a receiving unit 22, and a control unit 30. The receiving unit 22 demodulates the high frequency signal received by the receiving antenna 21. The binary signal (data) obtained by the demodulation is supplied to the control unit 30. The reception unit 22 includes a reception signal level detection unit 23. The reception signal level detection unit 23 outputs a voltage signal corresponding to the reception signal level. A voltage signal corresponding to the received signal level is supplied to the control unit 30.

  The control unit 30 is configured using a microcomputer system including a CPU, ROM, RAM, EEPROM, A / D converter, serial data communication unit, and the like. The control unit 30 includes a signal processing unit 31, a tire pressure monitoring unit 32, a tire position detection unit 33, a transmission output level storage unit 36, and an in-vehicle LAN interface unit 37.

  The signal processing unit 31 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 31 includes an A / D converter, and converts a voltage signal corresponding to the received signal level into received signal level data.

  The transmission output level storage means 36 is configured using, for example, an EEPROM. The transmission output level storage means 36 stores the identification information (ID) of each sensor unit 10a to 10d and the transmission output level in association with each other.

  When the control unit 30 is supplied with identification information (ID) and transmission output level data of each sensor unit 10a to 10d together with a registration request from a data writing device (not shown) via the in-vehicle LAN interface unit 37, each sensor The identification information (ID) of the units 10a to 10d and the transmission output level are associated with each other and written in the transmission output level storage means 36.

  When the sensor unit 10 is configured to transmit the transmission output level information, the control unit 30 stores the received transmission output level information in the transmission output level storage unit 36 in association with the identification information (ID). You may do it.

  Further, the control unit 30 registers the identification information (ID) and the received signal level received through the receiving antenna 21 and the receiving unit 22 in the transmission output level storage means 36 when a registration switch (not shown) is operated. You may do it. In this case, the received signal level is registered with a constant distance between the sensor unit 10 and the receiving device 20.

  The tire position detection unit 33 includes a left wheel / right wheel discrimination unit 34 and a front wheel / rear wheel discrimination unit 35. The left wheel / right wheel discriminating means 34 discriminates the left wheel / right wheel based on the tire rotation direction information supplied from the signal processing unit 31. The left wheel / right wheel discriminating means 34 holds the identification information (ID) and the discrimination result of the left wheel / right wheel in association with each other.

  The front wheel / rear wheel discriminating means 35 corrects the reception signal level data supplied from the signal processing unit 31 according to the transmission output level, and then determines the front wheel / rear wheel based on the corrected reception signal level. Make a decision. A specific example of front wheel / rear wheel discrimination is shown below.

  FIG. 5 is a diagram showing an example of contents registered in the transmission output level storage means. In the transmission output level storage means 36, the transmission output level of the sensor unit 10a of identification information (ID) A is a, the transmission output level of the sensor unit 10b of identification information (ID) B is b, and the identification information ( It is registered that the transmission output level of the sensor unit 10c of ID) C is c and the transmission output level of the sensor unit 10d of identification information (ID) D is d. Here, it is assumed that a <b <c <d.

  The front wheel / rear wheel discriminating means 35 sets the correction value when the signal from the sensor unit 10a having the lowest transmission output level is received to 0. The front wheel / rear wheel discriminating means 35 sets the correction value when the signal of the identification information (ID) B from the sensor unit 10b is received to a−b. Similarly, the correction value when the signal from the sensor unit 10c with the identification information (ID) C is received is set to ac, and the correction when the signal from the sensor unit 10d with the identification information (ID) D is received. Set the value to ad.

  The front wheel / rear wheel discriminating means 35 receives a signal from the identification information (ID) A, and assuming that the received signal level is Ra, a value Ra-0 obtained by subtracting the correction value 0 of the sensor unit 10a from Ra. The corrected received signal level. Similarly, if signals from identification information (ID) B, C, and D are received and the received signal levels are Rb, Rc, and Rd, respectively, corrected received signal levels Rb− (a -B), Rc (ac), Rd (ad) are obtained.

  The front wheel / rear wheel discriminating means 35 receives all signals from the four sensor units 10a to 10d, and corrects the received signal levels Ra-0, Rb- (ab), Rc (ac), Rd. When all of (a-d) are complete, the magnitude relationship of the corrected received signal level is compared, and it is determined that the two sensor units with the high corrected received signal level are installed on the tire on the front wheel side, It is determined that the two sensor units with low received signal levels after correction are installed on the tire on the rear wheel side.

  Note that the above determination is made when the receiving device 20 is disposed on the front side of the vehicle 1 and when the receiving device 20 is disposed on the rear side of the vehicle 1, the corrected received signal level is It is determined that the two high sensor units are installed in the rear wheel tire, and the two sensor units having low corrected reception signal levels are determined to be installed in the front tire, and the front wheel The rear wheel discriminating means 35 holds the identification information (ID) A to D of each sensor unit 10a to 10d in association with the discrimination result of the front wheel and the rear wheel.

  The tire position detector 33 is based on the left / right discrimination result by the left wheel / right wheel discrimination means 34 and the front / rear discrimination result by the front wheel / rear wheel discrimination means 35, and the tire position to which the sensor units 10 a to 10 d are attached. (Left front wheel, right front wheel, left rear wheel, right rear wheel) are recognized. The tire position detection unit 33 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 33 may write the identification information (ID) and the tire position in an EEPROM or the like. If the identification information (ID) of the sensor unit 10 is obtained for all four tire positions, the tire position detection unit 33 checks whether the same identification information (ID) is registered repeatedly in a plurality of tire positions. To do. The tire position detection unit 33 may display the fact on the display device 40 when duplicate registration is detected. The tire position detection unit 33 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.

  The front wheel / rear wheel discriminating means 35 obtains a level difference between the transmission output level and the reception signal level for each of the sensor units, and based on the obtained level difference, the tire on which the sensor unit is installed is a front wheel. You may make it judge whether it is a ring. For example, as shown in FIG. 5, the transmission output levels of the sensor units 10a to 10d are a, b, c, and d, respectively, and the reception signal levels of the sensor units 10a to 10d are Ra, Rb, Rc, and Let Rd be assumed.

  The front wheel / rear wheel discriminating means 35 has a level difference a−Ra between the transmission output level a of the sensor unit 10a and the reception signal level Ra of the sensor unit 10a, the transmission output level b of the sensor unit 10b and the reception signal level of the sensor unit 10b. Level difference b-Rb from Rb, level difference c-Rc between transmission output level c of sensor unit 10c and reception signal level Rc of sensor unit 10c, transmission output level d of sensor unit 10d and reception signal level of sensor unit 10d A level difference d-Rd from Rd is obtained.

  Then, the front wheel / rear wheel discriminating means 35 compares the obtained level difference of the four level differences, determines that the two sensor units having the small level differences are installed on the front wheel side tire, and determines the level difference. It is determined that the two large sensor units are installed on the rear wheel side tire.

  Note that the above determination is made when the receiving device 20 is arranged on the front side of the vehicle 1, and when the receiving device 20 is arranged on the rear side of the vehicle 1, two sensors having a high level difference are used. The unit is determined to be installed on the front wheel side tire, and the two sensor units having a low level difference are determined to be installed on the rear wheel side tire.

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 an example of the content registered into the transmission output level storage means.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Vehicle 2 (2a, 2b, 2c, 2d) Tire 10 (10a, 10b, 10c, 10d) Sensor unit 20 Receiving device 21 Receiving antenna 22 Receiving unit 23 Receiving signal level detecting unit 30 Control unit 31 Signal processing unit 32 Tire Pressure monitoring unit 33 Tire position detection unit 34 Left wheel / right wheel discrimination means 35 Front wheel / rear wheel discrimination means 36 Transmission output level storage means 40 Display device

Claims (2)

A receiving device that receives a signal wirelessly transmitted from a sensor unit installed in each tire of the vehicle is disposed on either the front side or the rear side of the vehicle,
The reception device includes transmission output level storage means in which identification information for identifying the sensor unit and the transmission output level of the sensor unit are registered in association with each other.
A received signal level detector for detecting the received signal level;
For each of the sensor units, a corrected reception signal level obtained by correcting the reception signal level detected by the reception signal level detection unit according to the transmission output level is obtained, and the sensor unit is based on the obtained correction reception signal level. A tire position detecting device comprising: a front wheel / rear wheel discriminating means for judging whether the tire on which the vehicle is installed is a front wheel or a rear wheel. A receiving device that receives a signal wirelessly transmitted from a sensor unit installed in each tire of the vehicle is disposed on either the front side or the rear side of the vehicle,
The reception device includes transmission output level storage means in which identification information for identifying the sensor unit and the transmission output level of the sensor unit are registered in association with each other.
A received signal level detecting means for detecting a received signal level;
For each of the sensor units, a level difference between the transmission output level and the reception signal level is obtained, and whether the tire on which the sensor unit is installed is a front wheel or a rear wheel based on the obtained level difference. A tire position detecting device comprising front wheel / rear wheel discriminating means for judging.

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