WO2015025204A1

WO2015025204A1 - Vehicle wheel information acquiring device

Info

Publication number: WO2015025204A1
Application number: PCT/IB2014/001515
Authority: WO
Inventors: Yuji Taki
Original assignee: Toyota Jidosha Kabushiki Kaisha
Priority date: 2013-08-20
Filing date: 2014-08-13
Publication date: 2015-02-26
Also published as: JP2015039892A

Abstract

A sensor unit (10) transmits a sensor ID, a tire pressure (P), a tire temperature (T), and a sensor rotation flag Fsen that is switched depending on a rotation speed of a vehicle wheel (W) at constant time intervals. A vehicle wheel ECU (50) extracts a sensor ID in which the sensor rotation flag Fsen varies within a predetermined time TO from plural unspecified radio signals (SI 2 to SI 9) when a vehicle running flag Fecu that is switched depending on a vehicle speed V varies (YES in S11), and stores the extracted sensor ID as the sensor ID of the sensor unit (10) of the host vehicle (S21) when the number of extracted sensor IDs is equal to the number of vehicle wheels (=4) (YES in S20).

Description

VEHICLE WHEEL INFORMATION ACQUIRING DEVICE

BACKGROUND OF THE INVENTION

1. Field of the Invention .

[0001] The present invention relates to a vehicle wheel information acquiring device that includes a vehicle wheel sensor fixed to a vehicle wheel and a vehicle-body-side device fixed to a vehicle body and that causes the vehicle-body-side device to acquire a vehicle wheel state by causing the vehicle wheel sensor to transmit the vehicle wheel state such as a tire pressure to the vehicle-body-side device using a radio signal.

2: Description of Related Art

[0002] As an example of the vehicle wheel information acquiring device, a tire pressure detector is known which notifies a driver of tire pressure information. The tire pressure detector includes a vehicle wheel sensor that detects a tire pressure for each vehicle wheel and is configured to transmit the tire pressure information from the vehicle wheel sensors using a radio signal, to cause a vehicle-body-side device to receive the radio signal, and to acquire the tire pressure information. When it is determined on the basis of the received tire pressure information that the tire pressure is lowered, the vehicle-body-side device displays the details thereof through the use of an alarm to notify a driver of the details.

[0003] In such a tire pressure detector, since it is determined whether the radio signal received by the vehicle-body-side device is transmitted from the vehicle wheel sensor of a host vehicle, the radio signal includes a sensor ID which is identification information of the vehicle wheel sensor in addition to the tire pressure information. Accordingly, even when the radio signal transmitted from a vehicle wheel sensor of another vehicle is received, the vehicle-body-side device can exclude the information of the radio signal from the another vehicle on the basis of the sensor ID and thus can appropriately monitor the tire pressure information of the host vehicle. The sensor ID is registered in advance in the vehicle-body-side device in a vehicle factory.

[0004] When a user owns multiple sets of tires (tires with a wheel) such as summer tires and winter tires, the vehicle wheel sensors are also replaced whenever the tires are replaced. When a tire or a wheel is replaced in a tire shop or the like and the vehicle wheel sensor is out of order, the vehicle wheel sensor is replaced. In this way, when the vehicle wheel sensor is replaced with a new vehicle wheel sensor, the sensor ID of the vehicle wheel sensor is not matched with the sensor ID stored in the vehicle-body-side device. Accordingly, the user needs to re-register the sensor ID through the use of a vehicle dealer whenever replacing the vehicle wheel sensor.

[0005] In order to solve this problem, techniques of automatically determining vehicle wheel sensors of a host vehicle and registering the sensor IDs thereof are disclosed in Japanese Patent Application Publication No. 2013-6473 (JP 2013-6473 A) and Japanese Patent Application Publication No. 2006-21716 (JP 2006-21716 A).

[0006] For example, in the device disclosed in JP 2013-6473 A, a vehicle wheel sensor has an acceleration sensor incorporated therein, detects a vehicle speed on the basis of the detected value of the acceleration sensor, and sets a transmission starting condition of a radio signal to a timing at which the vehicle speed is greater than a predetermined speed (20 km/h) and a predetermined time elapses after the vehicle speed reaches the predetermined speed. The vehicle wheel sensor transmits a radio signal including its own sensor ID, tire pressure information at that time, and the elapsed time information until the radio signal is transmitted after the vehicle speed reaches the predetermined speed, when the transmission starting condition is established. Thereafter, the vehicle wheel sensor transmits its own sensor ID and the tire pressure information at that time with a predetermined cycle. The vehicle-body-side device specifies the sensor ID of the host vehicle on the basis of the timing at which the vehicle speed reaches the predetermined speed and the elapsed time information included in the received radio signal.

[0007] In the device disclosed in JP 2006-21716 A, a vehicle wheel sensor has a centrifugal switch that is turned on when the vehicle speed is equal to or greater than a predetermined speed (30 km/h), and transmits a counted value of the time in which the centrifugal switch is turned on along with the tire pressure information. On the other hand, a vehicle-body-side device starts an entry mode when the vehicle speed is equal to or greater than the predetermined speed in an automatic ID registration mode, and stores all the sensor IDs of the received radio signals for only a predetermined time. Hereafter, an inappropriate sensor ID is excluded from the sensor IDs stored in the entry mode on the basis of a relationship between the vehicle speed and the counted time value, and the remaining final sensor IDs of four wheels are registered.

[0008] However, in the device disclosed in JP 2013-6473 A, the radio signal is not transmitted when the vehicle speed is not greater than the predetermined speed. Accordingly, the tire pressure information at that time is not transmitted. Accordingly, it cannot be determined whether the tire pressure is appropriate at the time of starting and running the vehicle or at the time of stopping of the vehicle. When the timing of transmitting a radio signal is set as described above only in the mode in which the sensor IDs are automatically registered, the vehicle-body-side device needs to understand whether a current mode is the automatic registration mode of a sensor ID. In this case, since the vehicle wheel sensor has to have a configuration for receiving mode information from the vehicle-body-side device and needs to switch the processes depending on the mode, the system configuration of the tire pressure detector is complicated.

[0009] In the device disclosed in JP 2006-21716 A, since all the sensor IDs of the radio signals received after the vehicle speed reaches the predetermined speed are stored and then the inappropriate sensor IDs are excluded from the sensor IDs stored in the entry mode on the basis of the relationship between the vehicle speed and the counted time value to narrow the sensor IDs of the host vehicle, it takes time to specify the sensor IDs of the host vehicle. It is also necessary to transmit time information indicating the counted time value.

[0010] In this way, in the above-mentioned devices, there is room for improvement in the process of determining a sensor ID of a host vehicle. SUMMARY OF THE INVENTION

[0011] An object of the present invention is to easily determine a sensor ID of a host vehicle.

[0012] An aspect of the present invention relates to a vehicle wheel information acquiring unit including:^' a vehicle wheel sensor that is fixed to each vehicle wheel of a host vehicle and that is configured to detect a vehicle wheel state and to transmit vehicle wheel state data indicating the detected vehicle wheel state along with a sensor ID using a radio signal; and a vehicle-body-side device that is fixed to a vehicle body of the host vehicle and that is configured to receive radio signals transmitted from a plurality of unspecified vehicle wheel sensors, to acquire the vehicle wheel state, which is detected by the vehicle wheel sensor specified by a registered sensor ID, from the received radio signals, and to perform a process corresponding to the detected vehicle wheel state. Each vehicle wheel sensor includes a vehicle wheel rotation state detecting unit that detects a vehicle wheel rotation state of the vehicle wheel to which the vehicle wheel sensor is fixed, and a transmitter unit that normally periodically transmits a radio signal including the sensor ID, the vehicle wheel state data, and vehicle wheel rotation state data indicating the vehicle wheel rotation state. The vehicle-body-side device includes a vehicle running state variation detecting unit that detects a variation of a running state of the host vehicle, a vehicle wheel rotation state variation detecting unit that detects a variation of the vehicle wheel rotation state at the time of first reception after the variation of the running state of the host vehicle is detected relative to the vehicle wheel rotation state at the time of reception immediately before the variation of the running state of the host vehicle is detected for each sensor ID included in the radio signals transmitted from the plurality of unspecified vehicle wheel sensors when the variation of the running state of the host vehicle is detected by the vehicle running state variation detecting unit, and a sensor ID determining unit that determines and registers the sensor IDs of the vehicle wheel sensors of the host vehicle on the basis of the variation of the vehicle wheel rotation state detected by the vehicle wheel rotation state variation detecting unit.

[0013] In the present invention, the vehicle wheel sensor is fixed to each vehicle wheel and the vehicle-body-side device is fixed to the vehicle body. The vehicle wheel sensor detects the vehicle wheel state and transmits the vehicle wheel state data indicating the detected vehicle wheel state along with the sensor ID using the radio signal. For example, the vehicle wheel sensor includes a tire pressure sensor that detects the tire pressure and transmits information indicating the detected tire pressure along with the sensor ID using the radio signal. The sensor ID is identification information for specifying the vehicle wheel sensor. The vehicle-body-side device receives the radio signal transmitted from plural unspecified vehicle wheel sensors, acquires the vehicle wheel state detected by the vehicle wheel sensor specified by the registered sensor ID from the received radio signal, and performs a process corresponding to the vehicle wheel state. Accordingly, the vehicle wheel state detected by the vehicle wheel sensor of the host vehicle can be acquired on the basis of the registered sensor ID.

[0014] When the vehicle sensor is replaced, it is necessary to change the registered sensor ID. The vehicle wheel information acquiring device according to the present invention has , a function of determining the radio signals transmitted from the vehicle wheel sensors installed in the host vehicle out of the radio signals transmitted from plural unspecified vehicle wheel sensors, that is, a. function of determining the sensor IDs of the host vehicle out of the sensor IDs included in the received radio signals.

[0015] In order to implement the function, each vehicle wheel sensor includes a vehicle wheel rotation state detecting unit and a transmitter unit. The vehicle wheel rotation state detecting unit detects the vehicle wheel rotation state of the vehicle wheel to which the vehicle wheel sensor is fixed. For example, the vehicle wheel rotation state detecting unit detects a rotation speed of the vehicle wheel. The transmitter unit normally periodically transmits a radio signal including the sensor ID, the vehicle wheel state data, and the vehicle wheel rotation state data indicating the vehicle wheel rotation state.

[0016] On the other hand, the vehicle-body-side device includes a vehicle running state variation detecting unit, a vehicle wheel rotation state variation detecting unit, and a sensor ID determining unit. When the sensor ID included in a radio signal is the sensor ID of a vehicle wheel sensor of the host vehicle, the vehicle wheel rotation state varies with the variation in the running state of the host vehicle. The radio signals are transmitted from the vehicle wheel sensors at constant time intervals. Accordingly, when the variation of the running state of the host vehicle is detected, it is possible to determine whether the vehicle wheel rotation state varies with the variation of the running state of the host vehicle by comparing the vehicle wheel rotation state at the preceding time of reception with the vehicle wheel rotation state at the subsequent time of reception.

[0017] Therefore, the vehicle running state variation detecting unit detects the variation of the running state of the host vehicle. The vehicle wheel rotation state variation detecting unit detects the variation of the vehicle wheel rotation state at the time of the first reception after the variation of the running state of the host vehicle is detected relative to the vehicle wheel rotation state at the time of the reception immediately before the variation of the running state of the host vehicle is detected for each sensor ID included in the radio signals transmitted from the plurality of unspecified vehicle wheel sensors when the variation of the running state of the host vehicle is detected by the vehicle running state variation detecting unit. The sensor ID determining unit determines and registers the sensor IDs of the vehicle wheel sensors of the host vehicle on the basis of the variation of the vehicle wheel rotation state detected by the vehicle wheel rotation state variation detecting unit.

[0018] In this way, according to the present invention, since the radio signal including the vehicle wheel rotation state data are normally periodically transmitted, the vehicle wheel state may be monitored using, the radio signals without any change or the sensor IDs of the vehicle wheel sensors of the host vehicle may be determined. Therefore, it is possible to determine the sensor IDs of the vehicle wheel sensors of the host vehicle without lowering the function of monitoring the vehicle wheel state. The function can be implemented with a simple communication system without using the function of controlling the vehicle wheel sensors by the vehicle-body-side device.

[0019] When the variation of the running state of the host vehicle is detected, the variation of the vehicle wheel rotation state at the time of the first reception after the variation of the running state of the host vehicle is detected relative to the vehicle wheel rotation state at the time of the reception immediately before the variation of the running state of the host vehicle is detected is detected. Accordingly, it is not necessary to transmit time information as in the device according to the related art and it is thus possible to rapidly detect the variation of the vehicle wheel rotation state. As a result, it is possible to rapidly complete the determination of the sensor IDs of the vehicle wheel sensors.

[0020] As a result, according to the present invention, it is possible to easily determine the sensor IDs of the host vehicle.

[0021] The vehicle wheel rotation state detecting unit may detect a vehicle wheel rotation speed, the vehicle wheel rotation state data may be a flag indicating whether the vehicle wheel rotation speed is equal to or greater than a predetermined rotation speed, and the vehicle wheel rotation state variation detecting unit may detect a variation of the flag.

[0022] - By employing this configuration, since the flag indicating whether the vehicle wheel rotation speed is equal to or greater than a predetermined rotation speed is transmitted as the vehicle wheel rotation state data, it is possible to shorten the transmission time of the radio signal for each transmission time. Accordingly, it is possible to reduce power consumption of the vehicle wheel sensors. The received intensity of the radio signal in the vehicle-body-side device varies depending on a revolution position of the vehicle wheel sensor around an axle and thus there may be a reception-disabled area in which the radio signal cannot be received depending on the revolution position. In this case, when the transmission time for each transmission is long, the revolution position of the vehicle wheel sensor is likely to pass through the reception-disabled area during communications and thus a reception rate of the radio signal in the vehicle-body-side device is lowered. On the contrary, in the present invention, since the transmission time for each transmission can be shortened, it is possible to enhance the reception rate of the radio signal in the vehicle-body-side device. The vehicle wheel rotation state variation detecting unit has a configuration for detecting the variation of the flag and thus the process thereof is simplified.

[0023] The vehicle running state variation detecting unit may detect an increasing variation in which the vehicle speed varies from a speed lower than a predetermined vehicle speed to a speed higher than the predetermined vehicle speed and a decreasing variation in which the vehicle speed varies from a speed higher than the predetermined vehicle speed to a speed lower than the predetermined vehicle speed. The sensor ID determining unit may determine the sensor IDs of the vehicle wheel sensors of the host vehicle on the basis of the variation of the flag and the variation direction of the flag at the time of the first reception after the variation of the running state of the host vehicle is detected relative to the flag at the time of the reception just before the variation is detected whenever the increasing variation or the decreasing variation is detected.

[0024] Both the increasing variation and the decreasing variation in which the vehicle speed crosses the predetermined vehicle speed are detected by the vehicle running state variation detecting unit. By setting the predetermined vehicle speed to a vehicle speed corresponding to a predetermined rotation speed for switching the flag, when the variation of the vehicle speed is detected, the flag included in the radio signal transmitted from the vehicle wheel sensor of the host vehicle varies until the time corresponding to the transmission time interval of the radio signal elapses after the variation is detected. By using this fact, the sensor ID determining unit determines the sensor IDs of the vehicle wheel sensors of the host vehicle on the basis of the variation and the variation direction of the flag at the time of the first reception after the variation of the running state of the host vehicle is detected relative to the flag at the time of the reception immediately before the variation is detected whenever the increasing variation or the decreasing variation of the vehicle speed is detected.

[0025] Accordingly, since the sensor IDs of the vehicle wheel sensors of the host vehicle are determined even at the time of the decreasing variation as well as at the time of the increasing variation of the vehicle speed, the determination process can be rapidly terminated. In addition, since the sensor IDs are determined on the basis of the variation of the flag and the variation direction of the flag, high determination accuracy is obtained with a simple process. Here, the variation direction of the flag represents a direction in which the vehicle wheel rotation speed varies with respect to the predetermined rotation speed. Therefore, it has only to be determined whether the vehicle wheel rotation speed varies from a speed lower than the predetermined rotation speed to a speed higher than the predetermined rotation speed or whether the vehicle wheel rotation speed varies from a speed higher than the predetermined rotation speed to a speed lower than the predetermined rotation speed.

[0026] The transmitter unit may transmit a radio signal in which the vehicle wheel state data is temporarily replaced with data indicating a magnitude of the vehicle wheel rotation speed only when the vehicle wheel state satisfies a predetermined condition.

[0027] When data indicating the magnitude of the vehicle wheel rotation speed is used to determine the sensor IDs of the vehicle wheel sensors of the host vehicle, it is possible to improve determination accuracy. In this case, it is necessary to include the data indicating the magnitude of the vehicle wheel rotation speed in the radio signal to be transmitted from the vehicle wheel sensor. In this case, the communication time is extended by the data. Accordingly, in the present invention, the transmitter unit transmits a radio signal in which the vehicle wheel state data is temporarily replaced with the data indicating the magnitude of the vehicle wheel rotation speed. As a result, it is possible to transmit data helpful for determination of the sensor IDs while suppressing an increase in communication time. In addition, the transmitter unit replaces the data only when the vehicle wheel state satisfies a predetermined condition. Accordingly, for example, only when a notification non^requested condition in which there is small necessity for notifying the user of the , vehicle wheel state is satisfied, replacement of the data can be performed. As a result, in situations in which there is necessity for notifying the user of the vehicle wheel state, the replacement of the data can be inhibited and thus there is no interference in use.

[0028] The vehicle wheel state data may include tire pressure data and tire temperature data, and the transmitter unit may transmit a radio signal in which host data is temporarily replaced with the data indicating the magnitude of the vehicle wheel rotation speed using one of the tire pressure data and the tire temperature data as the host data.

[0029] By employing this configuration, one of the tire pressure data and the tire temperature data is temporarily replaced with the data indicating the magnitude of the vehicle wheel rotation speed and the resultant data is transmitted. Accordingly, it is possible to transmit data helpful for determination of the sensor IDs while suppressing an increase in communication time.

[0030] The host data may be tire pressure data, and the predetermined condition may be set to a condition ih which the tire pressure at the time of currently transmitting the radio signal is equal to or greater than the tire pressure at the time of previously transmitting the radio signal.

[0031] By employing this configuration, only when the tire pressure at the time of currently transmitting the radio signal is equal to or greater than the tire pressure at the time of previously transmitting the radio signal, the tire pressure data is temporarily replaced with the data indicating the magnitude of the vehicle wheel rotation speed and the resultant data is transmitted. Accordingly, the replacement of the data is performed when the decrease in the tire pressure is not detected, and thus there is no interference in use.

[0032] The host data may be tire temperature data, and the predetermined condition may be set to a condition in which the tire temperature at the time of currently transmitting the radio signal is in a predetermined temperature range.

[0033] By employing this configuration, only when the tire temperature at the time of currently transmitting the radio signal is in the predetermined temperature range, the tire temperature data is temporarily replaced with the data indicating the magnitude of the vehicle wheel rotation speed and the resultant data is transmitted. Accordingly, the replacement of the data is performed when the tire is not overheated, and thus there is no interference in use.

[0034] . The vehicle wheel state data may include tire pressure data. The vehicle-body-side device may include a pressure-employing sensor ID determining unit that determines whether the tire pressure is equal to or greater than a predetermined determination tire pressure for each sensor ID included in the radio signals transmitted from the plurality of unspecified vehicle wheel sensors and that specifies the sensor IDs in which the tire pressure is equal to or greater than the predetermined determination tire pressure as the sensor IDs of the vehicle wheel sensors of the host vehicle. The predetermined determination tire pressure may be set to a value greater than a normally-used tire pressure range.

[0035] After the user raises the tire pressure of the host vehicle to a value equal to or greater than the determination pressure higher than the normally-used tire pressure range in advance, the pressure-employing sensor ID determining unit is activated. The pressure-employing sensor ID determining unit determines whether the tire pressure is equal to or greater than the determination pressure for each sensor ID included in the radio signals transmitted from the plural unspecified vehicle wheel sensors, and specifies the sensor IDs in which the tire pressure is equal to or greater than the determination pressure as the sensor IDs of the vehicle sensors of the host vehicle. Accordingly, it is possible to easily determine the sensor IDs of the vehicle wheel sensors of the host vehicle using the tire pressure data. : ^'

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Features, advantages, and technical and industrial significance of exemplary embodiments of the invention will be described below with reference to the accompanying drawings, in which like numerals denote like elements, and wherein:

FIG. 1 is a diagram schematically illustrating a configuration of a vehicle wheel information acquiring device according to an embodiment of the present invention;

FIG. 2 is a functional block diagram illustrating a sensor unit and a vehicle wheel ECU according to a first embodiment;

FIG. 3 is a flowchart illustrating a host vehicle ID determining routine according to the first embodiment;

FIG. 4 is a graph illustrating variations of a vehicle running flag and a sensor rotation flag according to the first embodiment;

FIG. 5 is a graph illustrating a relationship between a vehicle wheel rotation angle and a signal intensity;

FIG. 6 is a flowchart illustrating transmission data switching routine 1 according to a second embodiment;

1 FIG. 7 is a diagram illustrating transmission patterns in transmission data switching routine 1 ;

FIG. 8 is a flowchart illustrating transmission data switching routine 2 according to .the second embodiment;

FIG. 9 is a diagram illustrating transmission patterns in transmission data switching routine 2;

FIG. 10 is a flowchart illustrating a host vehicle ID determining routine according to a third embodiment; and

FIG. 11 is a flowchart illustrating a high-pressure host vehicle ID determining routine according to the third embodiment.

DETAILED DESCRIPTION OF EMBODIMENTS

[0037] Hereinafter, a vehicle wheel information acquiring device of a vehicle according to an embodiment of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a diagram schematically illustrating a configuration of a vehicle wheel information acquiring device according to the embodiment. The vehicle wheel information acquiring device is a device for notifying a driver of tire pressure information and includes a tire pressure sensor unit 10 (hereinafter, referred to as sensor unit 10) fixed to each vehicle wheel W and a vehicle wheel information processing unit 50 (hereinafter, referred to as vehicle wheel ECU 50) fixed to a vehicle body B. FIG. 2 is a functional block diagram illustrating the sensor units 10 and the vehicle wheel ECU 50 according to a first embodiment. The sensor units 10 disposed in four wheels have the same function and thus one thereof is illustrated.

[0038] Each sensor unit _.10 is attached to a tire air injection valve of the corresponding vehicle wheel W. The sensor unit 10 includes a pressure sensor 11, a temperature sensor 12, an acceleration sensor 13, a control unit 20, an antenna 14, and a battery 15. The pressure sensor 11 detects the pressure of the corresponding tire and outputs a detection signal indicating the pressure P to the control unit 20. The temperature sensor 12 detects the temperature of the corresponding tire and outputs a detection signal indicating the tire temperature T to the control unit 20. The acceleration sensor 13 detects an acceleration in a centrifugal direction of the corresponding vehicle wheel W or an acceleration in the circumferential direction of the corresponding vehicle wheel W and outputs a detection signal indicating the acceleration G to the control unit 20.

[0039] The acceleration sensor 13 is provided to detect a rotation speed of the corresponding vehicle wheel W. When the vehicle wheel W rotates, the sensor unit 10 including the acceleration sensor 13 also revolves around an axle. Accordingly, a gravitational acceleration is added to the output of the acceleration sensor 13, and a ripple waveform with one turn of the vehicle wheel W as one cycle is formed. Accordingly, by extracting a ripple component of the acceleration G, it is possible to detect the time required for one turn of the vehicle wheel W, that is, the rotation speed of the vehicle wheel W, by the cycle of the ripple component.

[0040] The control unit 20 includes a microcomputer and a communication circuit as principal parts and includes a timing setting unit 21 that sets the timing of transmitting a radio signal, a sensor rotation flag setting unit 22 that sets a sensor rotation flag Fsen to be described later, an ID storage unit 23 that stores a sensor ID as identification information for specifying the sensor unit 10, and a transmitter unit 24 that generates a radio signal and transmits the generated radio signal via the antenna 14, in terms of the functions thereof.

[0041] The transmission timing of the radio signal is always set at intervals of a constant time TO. Accordingly, the timing setting unit 21 includes a timer and outputs a transmission command to the transmitter unit 24 whenever the predetermined time TO elapses on the basis of the counted value of the time. The transmission command is also output to the sensor rotation flag setting unit 22. The predetermined time TO which is the transmission time interval of the radio signal is set to 1 minute in this embodiment, but is preferably set to 1 minute to 2 minutes.

[0042] The sensor rotation flag setting unit 22 sets a sensor rotation flag Fsen indicating a determination result on whether the rotation speed Vw of the vehicle wheel W is higher than a predetermined set rotation speed Vwref. Specifically, the sensor rotation flag setting unit 22 computes the rotation speed Vw of the vehicle wheel W with a predetermined short cycle on the basis of the ripple component of the acceleration G detected by the acceleration sensor 13. When a transmission command is input from the timing setting unit 21 , the sensor rotation flag setting unit 22 compares the vehicle wheel rotation speed Vw at that time with the set rotation speed Vwref, sets the sensor rotation flag Fsen to "1" when the vehicle wheel rotation speed Vw is equal to or greater than the set rotation speed Vwref, and sets the sensor rotation flag Fsen to "0" when the vehicle wheel rotation speed Vw is less than the set rotation speed Vwref. Therefore, the sensor rotation flag Fsen can be implemented by a one-bit signal indicating "0" or "1". The sensor rotation flag setting unit 22 outputs the set sensor rotation flag Fsen to the transmitter unit 24. Here, a hysteresis can be provided to the set, rotation speed Vwref to set a dead zone of the sensor rotation flag Fsen so as not to hunt the sensor rotation flag Fsen.

[0043] When the transmission command is input from the timing setting unit 21 , the transmitter unit 24 reads the tire pressure P output from the pressure sensor 11 , the tire temperature T output from the temperature sensor 12, the sensor rotation flag Fsen output from the sensor rotation flag setting unit 22, and the sensor ID stored in the ID storage unit 23, generates transmission data indicating the sensor ID, the tire pressure P, the tire temperature T, and the sensor rotation flag Fsen, and transmits a radio signal obtained by modulating the transmission data via the antenna 14. The tire pressure P, the tire temperature T, and the sensor rotation flag Fsen are newest information at the time of transmitting the radio signal.

[0044] The battery 15 supplies power to electrical loads in the sensor unit 10.

[0045] The sensor unit 10 in this embodiment can only transmit information to the vehicle wheel ECU 50 (cannot perform interactive communication) and normally periodically transmits the radio signal. Therefore, the sensor unit 10 performs the process of transmitting the radio signal in a unilateral way regardless of a mode (to be described later) that is performed by the vehicle wheel ECU 50.

[0046] The vehicle wheel ECU 50 will be described below. The vehicle wheel ECU 50 includes a microcomputer and a communication circuit as principal parts, and includes a receiver unit 51, a data processing unit 52, a host vehicle ID storage unit 53, a sensor ID determination command unit 54, and a sensor ID automatic registering unit 60. The vehicle wheel ECU 50 is connected to an alarm 100 and an initialization switch 110 disposed in the vicinity of a driver seat.

[0047] The receiver unit 51 is connected to an antenna 90, receives the radio signals transmitted from the sensor units 10 of the host vehicle via the antenna 90, and also recei ves radio signals transmitted from sensor units 10 of another vehicle when the another vehicle is present in the vicinity of the host vehicle via the antenna 90. That is, the receiver unit 51 receives radio signals transmitted from plural unspecified sensor units 10. The receiver unit 51 extracts data indicating the sensor ID, the tire pressure P, the tire temperature T, and the sensor rotation flag Fsen from a received signal whenever the radio signal is received. The receiver unit 51 receives a mode signal from the sensor ID determination command unit 54, and outputs the extracted data indicating the sensor ID, the tire pressure P, and the tire temperature T when the mode signal indicating a vehicle wheel information monitor mode to the data processing unit 52. When the mode signal indicates a sensor ID determination mode, the receiver unit 51 outputs the sensor ID and the sensor rotation flag Fsen to the sensor ID automatic registering unit 60.

[0048] The data processing unit 52 determines whether the tire pressures P associated with only the registered sensor IDs are in an appropriate range on the basis of the data input from the receiver unit 51 and the sensor IDs of four wheels (referred to as registered sensor IDs) stored in the host vehicle ID storage unit 53. That is, it is not determined whether the tire pressures P associated with sensor IDs other than the registered sensor IDs are in the appropriate range. When the tire pressure P of at least one of four wheels is not in the appropriate range, the data processing unit 52 outputs a tire pressure inappropriateness signal to the alarm 100. In this case, the data processing unit 52 may correct the appropriate range of the tire pressure P depending on the tire temperature T. The data processing unit 52 determines whether the tire temperature T associated with the registered sensor IDs is an abnormal high temperature, and outputs tire overheat information to another vehicle controller not illustrated when the overheated state of the tire is detected. The detection of the tire temperature T and the processing based on the tire temperature T do not need to be performed necessarily.

[0049] When the tire pressure inappropriateness signal is input, the alarm 100 notifies the driver that the tire pressure is not normal by lighting an indication lamp. Accordingly, when the vehicle wheel information monitor mode is set, the driver can normally know whether the tire pressure of the host vehicle is appropriate.

[0050] The sensor ID determination command unit 54 is connected to the initialization switch 110, and switches the vehicle wheel information monitor mode to the sensor ID determination mode when the operation of the initialization switch 110 is detected. These two modes are identified by a mode signal. The sensor ID determination command unit 54 outputs the mode signal to the sensor ID automatic registering unit 60 and the receiver unit 51. When a determination completion signal is input from a host vehicle ID determining unit 64 to be described later, the sensor ID determination command unit 54 switches the mode signal from the sensor ID determination mode to the vehicle wheel information monitor mode.

[0051] When a sensor unit 10 fixed to . a vehicle wheel W is replaced due to replacement of a tire, disorder of the sensor unit 10, or the like, the sensor ID of the sensor unit 10 is changed and thus it is necessary to change the registration of the sensor ID of the host vehicle understood by the vehicle wheel ECU 50 side. That is, it is necessary to change the registered sensor ID stored in the, host vehicle ID storage unit 53. In this case, the user operates the initialization switch 110. Accordingly, the sensor ID automatic registering unit 60 is started, automatically determines the sensor ID of the sensor unit 10 fixed to the vehicle wheel W of the host vehicle, and updates the registered sensor ID stored in the host vehicle ID storage unit 53 to the automatically-determined sensor ID.

[0052] The sensor ID determination command unit 54 may be configured to switch the vehicle wheel information monitor mode to the sensor ID determination mode by the operation of turning on an ignition switch in addition to the operation of the initialization switch 110. Accordingly, even when the user forgets the operation, the automatic registration of the sensor ID may be performed at the time of starting the vehicle.

[0053] At the time of re-registering a sensor ID, when the sensor ID included in a radio signal to be transmitted is read and the sensor ID is registered as a new sensor ID, a sensor ID included in a radio signal transmitted from a sensor unit 10 of another vehicle may be registered. Accordingly, it is necessary to determine whether the sensor ID of the received radio signal is transmitted from the sensor unit 10 of the host vehicle or is transmitted from the sensor unit 10 of another vehicle.

[0054] The sensor ID automatic registering unit 60 is a functional unit that automatically sets and registers the sensor IDs of the host vehicle after performing the determination.

[0055] The sensor ID automatic registering unit 60 includes a vehicle speed detecting unit 61, a vehicle running flag setting unit 62, a received ID and rotation flag temporary storage unit 63, and a host vehicle ID determining unit 64, and is activated in a period in which the mode signal output from the sensor ID determination command unit 54 indicates the sensor ID determination mode.

[0056] The vehicle speed detecting unit 61 detects a vehicle speed Vb. The vehicle Vb can be acquired by receiving the vehicle speed information used by another vehicle controller such as a brake controller by CAN communication or the like.

[0057] The vehicle running flag setting unit 62 sets a vehicle running flag Fecu indicating the determination result on whether the vehicle runs at a predetermined speed or higher on the basis of the vehicle speed Vb detected by the vehicle speed detecting unit 61. Specifically, the vehicle running flag setting unit 62 reads the vehicle speed Vb detected by the vehicle speed detecting unit 61 with a predetermined short cycle and compares the read vehicle speed Vb with a set vehicle speed Vbref at that time. The vehicle running flag setting unit 62 sets the vehicle running flag Fecu to "1 " when the vehicle speed Vb is equal to or greater than the set vehicle Vbref, and sets the vehicle running flag Fecu to "0" when the vehicle speed Vb is less than the set vehicle speed Vref. Accordingly, the vehicle running flag Fecu can be implemented by a one-bit signal indicating "0" or "1".

[0058] The set vehicle speed Vbref is set to a vehicle corresponding to a set rotation speed Vwref used in the sensor rotation flag setting unit 22 of the sensor unit 10, that is, a value corresponding to the vehicle when the vehicle wheel W rotates at the set rotation speed Vwref. The vehicle running flag setting unit 62 outputs the set vehicle running flag Fecu to the host vehicle ID determining unit 64. Here, a hysteresis can be provided to the set vehicle speed Vbref to set a dead zone of the vehicle running flag Fecu so as not to hunt the vehicle running flag Fecu.

[0059] The received ID and rotation flag temporary storage unit 63 receives plural unspecified sensor IDs and the sensor rotation flag Fsen output from the receiver unit 51 and stores the newest sensor rotation flag Fsen for each sensor ID. Accordingly, whenever a sensor ID and a sensor rotation flag Fsen are input from the receiver unit 51 , the received ID and rotation flag temporary storage unit 63 updates the sensor rotation flag Fsen corresponding to the sensor ID. That is, when the receiver unit 51 receives the radio signal transmitted from plural unspecified sensor units 10 of another vehicle and the like, the received ID and rotation flag temporary storage unit 63 stores and updates the sensor rotation flags Fsen corresponding to the sensor IDs of the received radio signals in correlation with the sensor IDs. Here, the received ID and rotation flag temporary storage unit 63 starts storage of the sensor IDs and the sensor rotation flag Fsen when the vehicle wheel information monitor mode is switched to the sensor ID determination mode, and deletes the stored data when the sensor ID determination mode is switched to the vehicle wheel information monitor mode.

[0060] The host vehicle ID determining unit 64 performs a host vehicle ID determining process. FIG. 3 is a flowchart illustrating the host vehicle ID determining routine which is performed by the host vehicle ID determining unit 64. This routine is started when the mode signal output from the sensor ID determination command unit 54 is switched from the vehicle wheel information monitor mode to the sensor ID determination mode.

[0061] First, the host vehicle ID determining unit 64 determines whether the vehicle running flag Fecu is switched in step SI 1. The host vehicle ID determining unit 64 reads the newest vehicle running flag Fecu set with a predetermined short cycle by the vehicle running flag setting unit 62, compares the currently-read vehicle running flag Fecu with the previously-read vehicle running flag Fecu, and determines whether the vehicle running flag Fecu is switched ("0"-»"l" or "l"->"0"). That is, it is determined whether an increasing variation and a decreasing variation of the vehicle speed in which the vehicle speed Vb crosses the set vehicle speed Vbref is detected.

[0062] The host vehicle ID determining unit 64 repeatedly performs these processes. When the switching of the vehicle running flag Fecu is detected (YES in step Sl l), the host vehicle ID determining unit 64 reads the newest sensor rotation flag Fsen for every sensor ID stored in the received ID and rotation flag temporary storage unit 63 in step S I 2. At this time, the host vehicle ID determining unit 64 stores the switching direction of the vehicle running flag Fecu (acceleration direction: "0"→"1" or deceleration direction: "Γ→"0").

[0063] The vehicle wheel ECU 50 receives all the radio signals transmitted from the sensor units O, but these received radio signals cannot be said to be transmitted from the sensor units 10 of the host vehicle. For example, the radio signals transmitted from the sensor units 10 of another vehicle located in the vicinity of the host vehicle are also received. Therefore, it is necessary to specify the sensor IDs of the host vehicle out of the received sensor IDs.

[0064] The running states of the host vehicle and another vehicle are different from each other, or are temporarily equal to each other but become different from each other in the way. Accordingly, when the vehicle running flag Fecu is switched but the sensor rotation flag Fsen is not switched with the switching, it can be estimated that the sensor ID correlated with the sensor rotation flag Fsen is not transmitted from a sensor unit 10 of the host vehicle. Here, since the radio signal is transmitted at intervals of a predetermined time TO, the switching of the sensor rotation flag Fsen is delayed from the switching of the vehicle running flag Fecu. Accordingly, it is necessary to perform the estimation after the delay time.

[0065] When reading the sensor rotation flags Fsen of all the sensor IDs in step SI 2, the host vehicle ID determining unit 64 substitutes the value of the sensor rotation flag Fsen for an on-switching rotation flag Fsenl for each sensor ID and stores the flag value in step S13 (Fsenl <— Fsen). The on-switching rotation flag Fsenl indicates the value of the sensor rotation flag Fsen when the vehicle running flag Fecu is switched. Since the switching of the sensor rotation flag Fsen is delayed from the switching of the vehicle running flag Fecu, the on-switching rotation flag Fsenl indicates the vehicle wheel rotation state at the time of receiving the radio signal immediately before the switching of the vehicle running flag Fecu is detected.

[0066] Subsequently, the host vehicle ID determining unit 64 sets a determination timer, that is, starts counting of the determination timer, in step S I 4. In step S I 5, it is determined whether the determination tinier expires. When the determination time does not expire, the host vehicle ID determining unit 64 reads the newest vehicle running flag Fecu set by the vehicle running flag setting unit 62 and determines whether the vehicle running flag Fecu is switched, in step S I 6. When the vehicle running flag Fecu is not switched, the host vehicle ID determining unit 64 returns the routine to step SI 5. On the other hand, when the vehicle running flag Fecu is switched before the determination time expires, the host vehicle ID determining unit 64 returns the routine to step SI 2. In this case, the value of the on-switching rotation flag Fsenl is cleared.

[0067] The time counted by the determination timer is set to a predetermined time TO which is the transmission time interval of the radio signal, or a time (Τ0+α) obtained by adding a margin a to the predetermined time TO. When the radio signal of the sensor unit 10 of the host vehicle is received, the sensor rotation flag Fsen is switched with the switching of the vehicle running flag Fecu with a time delay. This time delay is the predetermined time TO at most. Accordingly, when the received radio signal is transmitted from a sensor unit 10 of the host vehicle, the switching of the sensor rotation flag Fsen will be detected after the predetermined time TO. The determination time is, a set time for waiting for the time delay. Here, the margin a is set to a time shorter than the predetermined time TO.

[0068] The host vehicle ID determining unit 64 repeatedly performs these processes, and reads the sensor rotation flag Fsen for every sensor ID stored in the received ID and rotation flag temporary storage unit 63 in step S17 when the expiration of the determination timer is detected (YES in step S I 5). The sensor rotation flag Fsen is updated with the newest value during the counting of the determination timer. Here, the received ID and rotation flag temporary storage unit 63 deletes the sensor ID, with which the radio signal associated is not received in the predetermined time TO, and the sensor rotation flag Fsen thereof.

[0069] Subsequently, in step SI 8, the host vehicle ID determining unit 64 substitutes the value of the sensor rotation flag Fsen for a time-up rotation flag Fsen2 for each sensor ID (Fsen2<— Fsen). The time-up rotation flag Fsen2 indicates the vehicle wheel rotation state at the time of receiving a first ratio signal after the switching of the vehicle running flag Fecu is detected. Subsequently, in step S19, the host vehicle ID determining unit 64 determines whether the sensor rotation flag Fsen is switched in the same direction as the vehicle running flag Fecu detected in step Sl l for every sensor ID. In this case, the host vehicle ID determining unit 64 performs the determination on the basis of the on-switching rotation flag Fsenl and the time-up rotation flag Fsen2.

[0070] For example, when the switching of the vehicle running flag Fecu in the acceleration direction ("0"— >"\") is detected in step Sl l , it is determined that a variation is present for the sensor ID in which the on-switching rotation flag Fsenl is "0" and the time-up rotation flag Fsen2 is "1". It is .determined that no variation is present for the other sensor IDs. When the switching of the vehicle running flag Fecu in the deceleration direction ("1"—"0") is detected in step Sl l, it is determined that a variation is present for the sensor ID in which the on-switching rotation flag Fsenl is "1" and the time-up rotation flag Fsen2 is "0". It is determined that no variation is present for the other sensor IDs.

[0071] Subsequently, in step S20, the host vehicle ID determining unit 64 determines whether the number of sensor IDs in which the sensor rotation flag Fsen is switched within the period counted by the determination timer is equal to the number of vehicle wheels (=4). When the same number of sensor IDs as the number of vehicle wheels varies, the host vehicle ID determining unit 64 estimates that the sensor IDs corresponding to the four wheels are the sensor IDs of the sensor units 10 attached to the vehicle wheels W of the host vehicle, registers (updates and stores) the sensor IDs in the host vehicle ID storage unit 53, and ends this routine in step S21. The host vehicle ID determining unit 64 outputs a determination end signal to the sensor ID determination command unit 54. Accordingly, the sensor ID determination command unit 54 switches the mode signal from the sensor ID determination mode to the vehicle wheel information monitor mode.

^• [0072] On the other hand, when it is determined in step S20 that the number of sensor IDs in which the sensor rotation flag Fsen is switched is not equal to the number of vehicle wheels (=4), the host vehicle ID determining unit 64 returns the routine to step S I 1. For example, when another vehicle runs in parallel with the host vehicle, the sensor rotation flag Fsen of the another vehicle is switched similarly to the host vehicle. In this case, the number of sensor IDs in which the sensor rotation flag Fsen is switched is five or more. However, by repeatedly performing this routine, the sensor IDs of the sensor units 10 of the host vehicle can be finally specified, j

[0073] FIG. 4 is a diagram illustrating the switching of the vehicle running flag Fecu and the sensor rotation flag Fsen. At the time tl, the vehicle running flag Fecu is switched from "0" to "1". In this case, the sensor IDs in which the sensor rotation flag Fsen is switched within the predetermined time TO from the switching of the vehicle running flag Fecu are five of ID1 to ID5. In this case, since the number of sensor IDs in which the sensor rotation flag Fsen is switched is five, the determination result of step S20 is "NO". The host vehicle ID determining unit 64 returns the routine to step S l l and waits until the next vehicle running flag Fecu is switched. At time t2, the vehicle running flag Fecu is switched from "1" to "0". The sensor IDs in which the sensor rotation flag Fsen is switched within the predetermined time TO from time t2 are four of ID1 to ID4. Accordingly, the sensor IDs of the sensor units of the host vehicle are determined to be ID1 to ID4.

[0074] Here, the received signal intensity of the vehicle wheel ECU 50 varies depending on the rotation position of the vehicle wheel W (the revolution position of the sensor unit 10 around the axle) when the sensor unit 10 transmits the radio signal. Accordingly, when the processes of steps S l l to S20 are repeated plural times and the same determination result is repeatedly obtained, the sensor ID of the sensor unit 10 of the host vehicle can be determined.

[0075] The timing of starting the host vehicle ID determining routine that is performed by the host vehicle ID determining unit 64 can be set to a time point at which the vehicle speed Vb is equal to or greater than the set vehicle speed Vbref. In this case, the timing at which the determination result of step Sl l is firstly "YES" is the time point at which the vehicle speed Vb becomes less than the set vehicle speed Vbref. For example, when the host vehicle is parked in a large parking lot, the radio signals transmitted from the sensor units 10 of a lot of vehicles are received. However, when the deceleration is detected after the host vehicle starts running, the number of radio signals transmitted from the other vehicles can be reduced. Accordingly, it is possible to more easily determine the sensor IDs.

[0076] When the sensor IDs of the transmitted radio signals are checked in the sensor ID determination mode and the received sensor IDs are equal to those registered in the host vehicle ID storage unit 53, it is not necessary to perform the host vehicle ID determining routine.

[0077] In the above-mentioned vehicle wheel information acquiring device according to the first embodiment, since radio signals including the vehicle wheel information (the tire pressure and the tire temperature), the sensor IDs, and the sensor rotation flags Fsen are normally periodically transmitted from the sensor units 10, the vehicle wheel ECU 50 may monitor the vehicle wheel state (the tire pressure and the tire temperature) using the transmitted radio signals, or may determine the sensor IDs of the sensor units 10 of the host vehicle. Accordingly, it is possible to determine the sensor IDs of the sensor units 10 of the host vehicle without lowering the function of monitoring the vehicle wheel state.

[0078] The function of causing the vehicle wheel ECU 50 to control the sensor units 10 is not necessary. That is, in order to determine the sensor IDs, it is not necessary to provide the sensor units 10 with a function of receiving a command from the vehicle wheel ECU 50 or a function of performing a process corresponding to the command. Accordingly, determination of the sensor IDs can be implemented by a simple communication system.

[0079] Since the sensor rotation flag Fsen is used as the vehicle wheel rotation state data, it is possible to shorten the transmission time for each transmission of a radio signal. Accordingly, it is possible to reduce the power consumption of the sensor units 10 and thus to reduce the frequency of interchanging a battery. It is also possible to enhance a reception rate of a radio signal in the vehicle wheel ECU 50.

[0080] The variation of the sensor rotation flag Fsen at the time of first receiving the radio signal after the variation of the vehicle running flag Fecu is detected relative to the sensor rotation flag Fsen at the time of receiving the radio signal immediately before the variation of the vehicle running flag Fecu is detected is detected. Accordingly, it is possible to rapidly detect the variation of the vehicle wheel rotation state without transmitting the time information. Since the sensor IDs are determined in both the increasing variation and the decreasing variation of the vehicle speed, it is possible to rapidly terminate the determination process. Since the determination is performed in consideration of the switching direction of the sensor rotation flag Fsen, it is possible to achieve high determination accuracy.

[0081] As a result, the vehicle wheel information acquiring device according to the first embodiment can easily automatically determine the sensor IDs.

[0082] Second Embodiment

A vehicle wheel information acquiring device according to a second embodiment will be described below. In the vehicle wheel information acquiring device according to the second embodiment, vehicle wheel rotation speed information is added to the radio signal transmitted from the sensor unit 10. In the first embodiment, the radio signal transmitted from the sensor'' unit 10 includes the sensor ID, the tire pressure P, the tire temperature T, and the sensor rotation flag Fsen, but when the vehicle wheel rotation speed information (information indicating the magnitude of the vehicle wheel rotation speed) is included in the radio signal at the time of determining the sensor ID of the host vehicle, it is possible to perform accurate determination.

[0083] However, when the vehicle wheel rotation speed information is added, the amount of data of the radio signal increases by as much. Accordingly, the time for transmitting the radio signal from the sensor unit 10 extends and extra power is necessary, thereby affecting the battery lifetime. Since the transmission time for each transmission extends, the angle by which the vehicle wheel W rotates during the transmission increases. Since the sensor unit 10 revolves around the axle along with the vehicle wheel W, the received intensity of the radio signal in the vehicle wheel ECU 50 varies depending on the revolution position thereof. FIG. 5 illustrates a relationship between the rotation position (0° to 360°) of the vehicle wheel W and a received signal intensity index. As can be seen from this drawing, the received signal intensity depends on the rotation position of the vehicle wheel W (the revolution position of the sensor unit 10) and may be lower than a reception limit depending on the rotation position of the vehicle wheel W. Accordingly, when the transmission time for each transmission extends, the revolution position of the sensor unit is likely to pass through the reception-disabled area in which the radio signal cannot be received by the vehicle wheel ECU 50 during the transmission and thus the reception rate of the radio signal is lowered. Particularly, when the vehicle runs at a high speed, the rotation angle by which the vehicle wheel W rotates in the same time is large and thus this influence becomes marked.

[0084] Therefore, in order to suppress an increase in the amount of data of the radio signal, the sensor unit 10 of the second embodiment alternately replaces one of the tire pressure data and the tire temperature data with the vehicle wheel rotation speed data and transmits the resultant data. FIG. 6 is a flowchart illustrating transmission data switching routine 1 that is performed by the transmitter unit 24 of the sensor unit 10 as an example thereof. In transmission data switching routine 1 , the tire pressure data and the vehicle wheel rotation speed data are alternately switched.

[0085] In step S41, the transmitter unit 24 determines whether the timing of transmitting the radio signal arrives. The transmitter unit 24 waits until a transmission command is input from the timing setting unit 21 , and determines whether the current transmission is odd-numbered iri step S42 when the transmission command is input (YES in step S41). When the current transmission is odd-numbered (YES in step S42), the transmitter unit 24 selects transmission pattern 1 in step S43. As illustrated in FIG. 7, transmission pattern 1 is a pattern in which a radio signal including the sensor ID, the tire pressure P, the tire temperature T, and data indicating the sensor rotation flag Fsen is transmitted.

[0086] On the other hand, when the current transmission is even-numbered (NO in step S42), it is determined in step S44 the current tire pressure P(n) is equal to or greater than the previously-transmitted tire pressure P(n-l). The transmitter unit 24 stores the previously-transmitted tire pressure P(n-l) and performs the determination by comparing the current tire pressure P(n) read from the tire pressure sensor 11 with the stored tire pressure P(n-l). When the current tire pressure P(n) is equal to or greater than the previously-transmitted tire pressure P(n-l), the transmitter unit 24 selects transmission pattern 2 in step S45. As illustrated in FIG. 7, transmission pattern 2 is a pattern in which a radio signal including the sensor ID, the vehicle wheel rotation speed Vw, the tire temperature T, and data indicating the sensor rotation flag Fsen is transmitted. That is, the transmission pattern including the vehicle wheel rotation speed Vw instead of the tire pressure P is selected. On the other hand, when the current tire pressure P(n) is less than the previously-transmitted tire pressure P(n-l) (NO in step S44), transmission pattern 1 is selected.

[0087] When the transmission pattern is selected in this way, the transmitter unit 24 generates transmission data based on the transmission pattern in step S46, modulates the transmission data into a radio signal, and transmits the radio signal via the antenna 14 in step S47. Here, when transmission pattern 2 is selected, the transmitter unit 24 reads the vehicle wheel rotation speed Vw computed by the sensor rotation flag setting unit 22 and generates the transmission data. When he radio signal is transmitted in step S47, the transmitter unit 24 returns the routine to step S41 and repeats the above-mentioned processes.

[0088] Therefore, according to the second embodiment, since the tire pressure data is replaced with the vehicle wheel rotation speed data and the resultant data is transmitted every other time, it is possible to transmit the vehicle wheel rotation speed data without increasing the amount of data of the radio signal to be transmitted every other time. Accordingly, the second embodiment can be implemented without causing a decrease in battery lifetime. Since the transmission time for each transmission does not increase, the reception rate of the radio signal in the vehicle wheel ECU 50 is not lowered:

0089] Only when the condition in which the tire pressure P(n) is equal to or greater than the previously-transmitted tire pressure P(n-l) is satisfied, the tire pressure data is replaced with the vehicle wheel rotation speed data and the resultant data is transmitted. Accordingly, the function of alarming a low tire pressure which is the original object can be maintained. That is, since the replacement of data is inhibited in a situation in which there is necessity for notification to the user, there is no interference in use.

[0090] Accordingly, it is possible to accurately determine the sensor IDs using the vehicle wheel rotation speed data. For example, the vehicle wheel ECU 50 performs the following processes in addition to the first embodiment. When the vehicle wheel rotation speed Vw is included in the radio signal at the time of receiving the radio signal, the receiver unit 51 outputs the vehicle wheel rotation speed Vw to the host vehicle ID determining unit 64. When the vehicle wheel rotation speed Vw is input from the receiver unit 51, the host vehicle ID determining unit 64 reads the vehicle speed Vb detected by the vehicle speed detecting unit 61 and compares the vehicle speed Vb with the vehicle wheel rotation speed Vw in the same unit. When the difference therebetween is greater than a reference value, a process of excluding the sensor ID of the radio signal from the candidates of the host vehicle is performed at that time.

[0091] Similarly, the tire temperature data may be replaced with the vehicle wheel rotation speed data and the resultant data rnay be transmitted every other time. FIG. 8 is a flowchart illustrating transmission data switching routine 2 that is performed by the transmitter unit 24 of the sensor unit 10 as an example thereof. In transmission data switching routine 2, the tire pressure data and the vehicle wheel rotation speed data are alternately switched. The same processes as illustrated in FIG. 6 will be referenced by the same reference numerals and description thereof will not be repeated.

[0092] When the current transmission is odd-numbered in step S42, the transmitter unit 24 selects transmission pattern 1 in step S43. As illustrated in FIG. 9 (FIG. 7), transmission pattern 1 is a pattern in which a radio signal including the sensor ID, the tire pressure P, the tire temperature T, and data indicating the sensor rotation flag Fsen is transmitted. On the other hand, when the current transmission is even-numbered, the transmitter unit 24 reads the tire temperature T detected by the temperature sensor 12 and determines whether the tire temperature T is included in a predetermined set temperature range (Trefl to Tref2) in step S54. The set temperature range is a normal temperature range in which the detection of the tire pressure is less affected and is set to, for example, a range of 0°C to 40°C. When the tire temperature is included in the set temperature range, the transmitter unit 24 selects transmission pattern 3 in step S55. As illustrated in FIG. 9, transmission pattern 3 is a pattern in which a radio signal including the sensor ID, the tire pressure P, the vehicle wheel rotation speed Vw, and data indicating the sensor rotation flag Fsen is transmitted. That is, the transmission pattern including the vehicle wheel rotation speed Vw instead of the tire temperature T is selected. On the other hand, when the current tire temperature T departs from the set temperature range (Trefl to Tref2) (NO in step S54), transmission pattern 1 is selected.

[0093] In transmission data switching routine 2, since the tire temperature data and the vehicle wheel rotation speed data are alternately transmitted, it is possible to transmit the vehicle wheel rotation speed data without increasing the amount of data of the radio signal to be transmitted every other time. Accordingly, the second embodiment can be implemented without causing a decrease in battery lifetime. Since the transmission time for each transmission does not increase, the reception rate of the radio signal in the vehicle wheel ECU 50 is not lowered.

[0094] In this case, only when the condition in which the tire temperature is included in the normal temperature range is satisfied, the tire temperature data is replaced with the vehicle wheel rotation speed data and the resultant data is transmitted. Accordingly, the detection of the tire pressure is less affected and the function of detecting an overheated state of the tire can be maintained.

[0095] Accordingly, as described above, it is possible to accurately determine the sensor IDs using the vehicle wheel rotation speed data. Here, when the data indicating the vehicle wheel rotation speed Vw is transmitted (in transmission pattern 2 or transmission pattern 3), the sensor rotation flag Fsen may be skipped. This is because the vehicle wheel rotation speed Vw serves as the sensor rotation flag Fsen.

[0096] Third Embodiment

A vehicle wheel information acquiring device according to a third embodiment will be described below. In the vehicle wheel information acquiring device according to the third embodiment, another sensor ID determining function is added to the vehicle wheel information acquiring devices according to the first and second embodiments. In the third embodiment, a user raises the tire pressure to an ID determination-enabling pressure higher than a normal usage range in advance at the time of registering sensor IDs, and the sensor unit 10 fixed to a tire in which the tire pressure is high in the host vehicle ID determining process is determined as the host vehicle ID.

[0097] FIG. 10 is a flowchart illustrating the host vehicle ID determining routine that is performed by the host vehicle ID determining unit 64. When the user operates the initialization switch 110 and switches the mode signal output from the sensor ID determination command unit 54 to the sensor ID determination mode, the host vehicle ID determining unit 64 of the third embodiment displays a selection screen of the host vehicle ID determination mode on a display not illustrated in step S61. A screen for causing the user to select a normal-pressure ID determination mode and a high-pressure ID determination mode is displayed in the selection screen. The host vehicle ID determining unit 64 waits the operation of selecting the determination mode in step S62, and performs the high-pressure host vehicle ID determining routine illustrated in FIG. 11 in step S70 when the user selects the high-pressure ID determination mode (YES in step S63). On the other hand, when the user selects the normal-pressure ID determination mode (NO in step S63), the host vehicle ID determining unit 64 performs the normal-pressure host vehicle ID determining routine in step S10. The normal-pressure host vehicle ID determining routine is the same as the host vehicle ID determining routine illustrated in FIG. 3.

[0098] When the user selects the high-pressure ID determination mode, the user raises the tire pressures of four wheels of the host vehicle to the ID determination-enabling pressure in advance. The ID determination-enabling pressure is set to a pressure corresponding to the detection upper limit of the tire pressure sensor 11 incorporated in the sensor unit 10. The tire pressure sensor 11 can detect a pressure in a range of about 0 kPa to 350 kPa (relative pressure). Accordingly, since the detected value does not reach the upper limit in the normally-used tire pressure range, the. sensor ID of the host vehicle in which the detected value reaches the upper limit.

[0099] When the high-pressure host vehicle ID determining routine is started, the host vehicle ID determining unit 64 sets the determination timer and starts the counting in step S71. The time counted by the determination timer is set to a predetermined time TO which is the transmission time interval of the radio signal, or a time (Τ0+α) obtained by adding a margin a to the predetermined time TO. Subsequently, the host vehicle ID determining unit 64 reads the sensor ID and the tire pressure P of the radio signal received by the receiver unit 51 in correlation with each other in step S72. Since the receiver unit 51 receives plural unspecified radio signals, the sensor IDs and the tire pressures P read by the host vehicle ID determining unit 64 are not limited to those of the host vehicle.

[0100] The host vehicle ID determining unit 64 determines whether time is up in step S73, and returns the routine to step S72 and repeatedly performs the above-mentioned processes when time is not up.

[0101] When the determination time expires (YES in step S73), the host vehicle ID determining unit 64 extracts the sensor IDs in which the tire pressure P is equal to or greater than a threshold value Phigh out of all read data in step S74. The threshold value Phigh is set to a value greater than the normally-used tire pressure range, that is, the detection upper limit of the tire pressure sensor 11 in this embodiment. Accordingly, the sensor IDs extracted in step S74 can be estimated to be the sensor IDs of the sensor units 10 of the host vehicle. Subsequently, in step S75, the host vehicle ID determining unit 64 determines whether the number of extracted sensor IDs is equal to the number of vehicle wheels (=4). When the number of extracted sensor IDs is equal to the number of vehicle wheels, the host vehicle ID determining unit 64 determines that the extracted sensor IDs are the sensor IDs of the sensor units 10 of the host vehicle in step S76, updates and stores the sensor IDs in the host vehicle ID storage unit 53, and ends this routine.

[0102] When the user adjusts the tire pressure to the ID determination-enabling pressure in advance, it is possible to appropriately determine the sensor IDs. However, when the adjustment of the tire pressure is not appropriate, the determination result of step S75 is "NO". In this case, the host vehicle ID determining unit 64 switches the determination mode to the normal -pressure host vehicle ID determination mode in step S77 and then ends this routine. Accordingly, the host vehicle ID determining routine illustrated in FIG. 3 is started. Here, when the determination result of step S75 is :NO" and four sensor IDs cannot be determined even by repeatedly performing the processes of steps S71 to S75 multiple times, the determination mode may be switched to the. normal-pressure host vehicle ID determination mode.

[0103] According to the third embodiment, even when the vehicle does not run, it is possible to satisfactorily determine the sensor IDs of the sensor units 10 of the host vehicle using the tire pressure data. Since the normal-pressure host vehicle ID determination mode can also be selected, the convenience of the user not desiring the adjustment of the tire pressure is not lowered.

[0104] While the vehicle wheel information acquiring device according to this embodiment, the present invention is not limited to the embodiment and can be modified in various forms without departing from the gist of the present invention.

[0105] For example, in this embodiment, the tire pressure and the tire temperature are acquired as the vehicle wheel information but a configuration in which only one thereof is acquired may be employed. Another vehicle wheel information may be acquired.

[0106] In this embodiment, the alarm 100 employs the indication lamp for alarming abnormality of the tire pressure, but the tire pressure of each tire may be displayed by numerical values or an appropriateness determination may be displayed. In this case, it is necessary to estimate the arrangement (front-right wheel, front-left wheel, rear-right wheel, or rear-left wheel) of each sensor unit 10, but one of various methods known in the related art can be employed for the estimation of the arrangements of the sensor units 10.

[0107] In the second embodiment, the configuration in which the vehicle wheel state data (the tire pressure data or the tire temperature data) is alternately replaced with the vehicle wheel rotation speed data is employed, but it is not necessary to alternately replace the data and the transmission number ratio thereof can be set to be arbitrary.

[0108] The sensor units 10 of this embodiment can only transmit data to the vehicle wheel ECU 50, but, for example, a configuration in which bidirectional communication with the vehicle wheel ECU 50 is possible may be employed. The sensor unit's 10 of this embodiment are configured to transmit a radio signal with a constant cycle TO regardless of the rotation states of the vehicle wheels, but, for example, a configuration in which the transmission cycle of a radio signal differs when the vehicle wheels do not rotate and when the vehicle wheels rotate may be employed.

Claims

L A vehicle wheel information acquiring unit comprising:

a vehicle wheel sensor that is fixed to each vehicle wheel of a host vehicle and that is configured to detect a vehicle wheel state and to transmit vehicle wheel state data indicating the detected vehicle wheel state along with a sensor ID using a radio signal; and a vehicle-body-side device that is fixed to a vehicle body of the host vehicle and that is configured. to receive radio signals transmitted from a plurality of unspecified vehicle wheel sensors, to acquire the vehicle wheel state, which is detected by the vehicle wheel sensor specified by a registered sensor ID, from the received radio signals, and to perform a process corresponding to the detected vehicle wheel state,

wherein each vehicle wheel sensor includes

a vehicle wheel rotation state detecting unit that detects a vehicle wheel rotation state of the vehicle wheel to which the vehicle wheel sensor is fixed, and

a transmitter unit that normally periodically transmits a radio signal including the sensor ID, the vehicle wheel state data, and vehicle wheel rotation state data indicating the vehicle wheel rotation state, and

wherein the vehicle-body-side device includes

a vehicle running state variation detecting unit that detects a variation of a running state of the host vehicle,

a vehicle wheel rotation state variation detecting unit that detects a variation of the vehicle wheel rotation state at the time of first reception after the variation of the running state of the host vehicle is detected relative to the vehicle wheel rotation state at the time of reception immediately before the variation of the running state of the host vehicle is detected for each sensor ID included in the radio signals transmitted from the plurality of unspecified vehicle wheel sensors when the variation of the running state of the host vehicle is detected by the vehicle running state variation detecting unit, and

a sensor ID determining unit that determines and registers the sensor IDs of the vehicle wheel sensors of the host vehicle on the basis of the variation of the vehicle wheel rotation state detected by the vehicle wheel rotation state variation detecting unit.

2. The vehicle wheel information acquiring device according to claim 1, wherein the vehicle wheel rotation state detecting unit detects a vehicle wheel rotation speed,

wherein the vehicle wheel rotation state data is a flag indicating whether the vehicle wheel rotation speed^' is equal to or greater than a predetermined rotation speed, and

wherein the vehicle wheel rotation state variation detecting unit detects a variation of the flag.

3. The vehicle wheel information acquiring device according to claim 2, wherein the vehicle running state variation detecting unit detects an increasing variation in which the vehicle speed varies from a speed lower than a predetermined, vehicle speed to a speed higher than the predetermined vehicle speed and a decreasing variation in which the vehicle speed varies from a speed higher than the predetermined vehicle speed to a speed lower than the predetermined vehicle speed, and

wherein the sensor ID determining unit determines the sensor IDs of the vehicle wheel sensors of the host vehicle on the basis of the variation of the flag and the variation direction of the flag at the time of the first reception after the variation of the running state of the host vehicle is detected relative to the flag at the time of the reception immediately before the variation is detected whenever the increasing variation or the decreasing variation is detected.

4. The vehicle wheel information acquiring device according to claim 2 or 3, wherein the transmitter unit transmits a radio signal in which a vehicle wheel state data is temporarily replaced with data indicating the magnitude of the vehicle wheel rotation speed only when the vehicle wheel state satisfies a predetermined condition.

5. The vehicle wheel information acquiring device according to claim 4, wherein the vehicle wheel state data includes tire pressure data and tire temperature data, and

.wherein the transmitter unit transmits a radio signal in which host data is temporarily replaced with the data indicating the magnitude of the vehicle wheel rotation speed using one of the tire pressure data and the tire temperature data as the host data.

6. The vehicle wheel information acquiring device according to claim 5, wherein the host data is tire pressure data, and

wherein the predetermined condition is set to a condition in which the tire pressure at the time of currently transmitting the radio signal is equal to or greater than the tire pressure at the time of previously transmitting the radio signal.

7. The vehicle wheel information acquiring device according to claim 5, wherein the host data is tire temperature data, and

wherein the predetermined condition is set to a condition in which the tire temperature at the time of currently transmitting the radio signal is in a predetermined temperature range.

8. The vehicle wheel information acquiring device according to any one of claims 1 to 7, wherein the vehicle wheel state data includes tire pressure data,

wherein the vehicle-body-side device includes a pressure-employing sensor ID determining unit that determines whether the tire pressure is equal to or greater than a predetermined determination tire pressure for each sensor ID included in the radio signals transmitted from the plurality of unspecified vehicle wheel sensors and that specifies the sensor IDs in which the tire pressure is equal to or greater than the predetermined determination tire pressure as the sensor IDs of the vehicle wheel sensors of the host vehicle, and

wherein the predetermined determination tire pressure is set to a value greater than a normally-used tire pressure range.