Tire pressure monitoring system

Abstract

Tire pressure monitoring system that features: Wheel sensors (10), each comprising an air pressure sensor (11) for detecting a tire pressure (Px) and a transmitter (16) for repeatedly transmitting wheel information, which is information including tire pressure information representing the tire pressure (Px) detected by the air pressure sensor (11) and a unique sensor ID, as a radio signal and fixed and arranged on respective wheels (W) of a vehicle, and a vehicle body-side device (50, 100) comprising a receiver (51) for receiving the wheel information transmitted from the wheel sensors (10), respectively, an ID registration section (54) for registering the sensor IDs of the wheel sensors (10) used as targets for air pressure monitoring, and a reporting section (53, 100) for reporting the tire pressure information transmitted from the wheel sensor (10) specified by the sensor ID registered in the ID registration section (54) to a driver, and fixed and arranged on a vehicle body, wherein the vehicle body-side device (50, 100) comprises: a time measuring device (55) for measuring a non-reception period (T1, T2, T3, T4), which is a period of time during which the wheel information specified by the sensor ID is continuously not received, in a case where the wheel information specified by the sensor ID should be transmitted, for each sensor ID registered in the ID registration section (54), a malfunction reporting device (100) for reporting a malfunction to the driver of the vehicle when the non-reception period (T1, T2, T3, T4) exceeds a first set time (Tref1) for any of the sensor IDs registered in the ID registration section (54), a total time calculation device (57) for calculating a total non-reception period (Ttotal), which is a sum of the non-reception periods (T1, T2, T3, T4) for a specific number (n) of sensor IDs among the registered sensor IDs, the specific number (n) being greater than 1, an overwrite device (58) for starting discrimination processing for discriminating the sensor IDs of the wheel sensors (10) respectively arranged on the wheels (W) of the own vehicle from among many and unspecified sensor IDs received by the receiver (51) when the total non-reception period (Ttotal) exceeds a second set time (Tref2) shorter than a time period obtained by multiplying the specified number (n) by the first set time (Tref1), and for overwriting the sensor ID registered in the ID registration section (54) with the sensor ID discriminated by the discrimination processing.

Description

Technical area

[0001] The present invention relates to a tire pressure monitoring system comprising wheel sensors fixed to respective wheels and a vehicle body-side device that is fixed to a vehicle body and performs notification processing corresponding to a tire pressure with the vehicle body-side device by transmitting tire pressure information representing a tire pressure from each wheel sensor to the vehicle body-side device as a radio signal. State of the art

[0002] A tire pressure monitoring system (TPMS) is known for informing a driver of tire pressure information. The tire pressure monitoring system includes a tire pressure sensor unit (referred to as a wheel sensor) that detects tire pressure for each wheel. The system is configured to transmit tire pressure information as a radio signal from the wheel sensor and receive the radio signal via a vehicle body-side device to acquire the tire pressure information. If the tire pressure is determined to have decreased based on the received tire pressure information, the vehicle body-side device displays this information on a display to notify the driver.

[0003] The vehicle body-side device receives not only the radio signal transmitted from the wheel sensor installed in the wheel of the vehicle (own vehicle), but also the radio signal transmitted from the wheel sensor installed in many and unspecified vehicles. For this reason, in order to distinguish which wheel sensor the radio signal received by the vehicle body-side device is transmitted from, the radio signal contains, in addition to the tire pressure information, a sensor ID that constitutes distinguishing information unique to a wheel sensor.

[0004] The sensor ID of the wheel sensor disposed in the vehicle's wheel is registered in advance in a non-volatile memory of the vehicle body-side device. Therefore, the vehicle body-side device is configured to refer to the sensor ID stored in the non-volatile memory and acquire the tire pressure information included in the radio signal specified by this sensor ID as the tire pressure information of the vehicle's wheel (own vehicle).

[0005] JP 2013-23127 A proposes a device that registers a sensor ID of a wheel sensor disposed in a wheel of the vehicle (own vehicle) according to a wheel location. In this device, a user applies a push to tires of right and left front and rear wheels of a vehicle in a sequence described in documented work instructions. The wheel sensor disposed in each wheel includes an acceleration sensor and transmits its own sensor ID to the vehicle body-side device when this acceleration sensor detects the push applied by the user to the tire. Therefore, the sensor ID transmitted from each wheel sensor is transmitted to the vehicle body-side device in the order in which the user applies the tire, that is, the order described in the documented work instructions.Based on the order in which the sensor IDs are received, the vehicle body-side device acquires the correspondence between the sensor IDs and the wheel locations and stores the correspondence in the non-volatile memory. Therefore, in this device, overwriting of the sensor IDs is performed by manual user action.

[0006] Furthermore, a technology for distinguishing a sensor ID of the wheel sensor of the own vehicle from sensor IDs of radio signals transmitted from many unspecified wheel sensors and automatically registering them is known. For example, JP 2006-21716 A proposes a device that stores all sensor IDs of radio signals received until a predetermined time has elapsed since a radio signal was first transmitted from a wheel sensor (this period is called the entry period), and then searches for the sensor ID of the wheel sensor of the vehicle among the stored sensor IDs. In this device, a sensor ID assumed to be assigned to a wheel sensor of another vehicle rather than the vehicle (own vehicle) is eliminated from the sensor IDs stored as registration candidates during the entry period.Then, when the number of remaining sensor IDs becomes equal to the number of wheels of the own vehicle, the sensor IDs are registered as the sensor IDs of the wheel sensors of the own vehicle.

[0007] US 2010 / 0 302 063 A1 discloses a tire pressure monitoring system comprising: wheel sensors, each having an air pressure sensor for detecting a tire pressure and a transmitter for repeatedly transmitting wheel information, which is information including tire pressure information representing the tire pressure detected by the air pressure sensor and a unique sensor ID, as a radio signal, and fixed and arranged on respective wheels of a vehicle; and a vehicle body-side device comprising a receiver for receiving the wheel information transmitted from the wheel sensors, respectively, an ID registration section for registering the sensor IDs of the wheel sensors used as targets for air pressure monitoring, and a reporting section for reporting the tire pressure information transmitted from the wheel sensor specified by the sensor ID.which is registered in the ID registration section, to a driver and is fixed and arranged on a vehicle body, wherein the vehicle body-side device comprises: an overwrite device for performing discrimination processing for distinguishing the sensor IDs of the wheel sensors respectively arranged on the wheels of the own vehicle from among many and unspecified sensor IDs received by the receiver, and for overwriting the sensor ID registered in the ID registration section with the sensor ID distinguished by the discrimination processing.

[0008] US 2010 / 0 300 192 A1 describes a tire pressure monitoring system according to which the sensor IDs corresponding to the unmounted wheels (summer wheels or winter wheels) are registered and then identified when the summer wheels are replaced by winter wheels and vice versa.

[0009] DE 10 2007 043 638 A1 describes a tire pressure detecting device that determines whether an abnormality has occurred in a transmitter and outputs a retry trigger signal at a time different from a continuous transmission to determine whether the non-response state of the transmitter is caused by an abnormality in the transmitter or by something else. Summary of the invention

[0010] Generally, in a tire pressure monitoring system, when an ignition switch is turned on, an on-vehicle device starts operating. The on-vehicle device reads a sensor ID (called a registered sensor ID) stored in a non-volatile memory and, upon receiving a radio signal containing this registered sensor ID, acquires tire pressure information from this radio signal. For this reason, when a wheel sensor is replaced with another, it is necessary to overwrite the registered sensor ID stored in the non-volatile memory with the sensor ID of the replaced wheel sensor. Furthermore, generally, a complete wheel rotation is performed between summer and winter. Since a wheel sensor is replaced along with the wheel sensor, it becomes necessary to rewrite the sensor ID.In the following, “a tire swap” means a tire swap that includes a wheel.

[0011] In the device proposed in JP 2013-23127 A, user action is required to overwrite a sensor ID, which is not user-friendly. Since the overwrite operation of a sensor ID is only performed at the time of tire replacement, a user may not understand how to perform this operation and will contact a vehicle dealer. Furthermore, the user may forget that the overwrite operation of a sensor ID is required.

[0012] In a tire pressure monitoring system, a rule is defined according to which a user must be notified of a system malfunction when a situation occurs where tire pressure information cannot be reported for more than a specified period of time (for example, within 10 minutes, within 20 minutes, etc.). Therefore, the vehicle body-side device determines whether a state in which a wireless signal can be received outside of a specified period of time (referred to as a non-reception state) has persisted for each registered sensor ID, and illuminates a warning light when the non-reception state is detected.

[0013] By illuminating such a warning light, the device proposed in JP 2013-23127 A can also prompt a user to perform a sensor ID overwrite operation. However, the nuisance of the operation itself has not been eliminated.

[0014] A system having a function for automatically registering a sensor ID similar to the device proposed in JP 2006-21716A starts searching for a self-vehicle sensor ID simultaneously with illuminating a warning lamp when a non-reception condition is detected. Since the search for a self-vehicle sensor ID is initiated only after the stage of notifying a user of a malfunction, it takes a long time until the self-vehicle sensor ID is finally registered. Since the warning lamp continues to illuminate until the sensor ID is registered, the driver will feel inconvenienced.

[0015] The present invention has been made to solve the above problem, and its object is to provide a tire pressure monitoring system according to which inconvenience to the driver in tire pressure monitoring is prevented as much as possible.

[0016] The object is achieved with a tire pressure monitoring system according to the features of claim 1. The dependent claim is directed to a preferred development of the invention.

[0017] In this case, it is advantageous if the total time calculation device is designed to calculate a total non-reception period, which is a sum of the non-reception period for the sensor IDs of the right and left front and rear wheels of the vehicle, and the second setting time is set to a time period that is shorter than four times the first setting time.

[0018] The tire pressure monitoring system according to the present invention includes wheel sensors fixed and arranged on the respective wheels, and a vehicle body-side device fixed and arranged on the vehicle body. Each wheel sensor includes an air pressure sensor that detects a tire pressure, and a transmitter that repeatedly transmits wheel information, which is information representing the tire pressure detected by the air pressure sensor and includes a unique sensor ID, as a radio signal.

[0019] The vehicle body-side device includes a receiver that receives the wheel information transmitted from the respective wheel sensors, an ID registration section in which the sensor IDs of the wheel sensors used as targets for air pressure monitoring are registered, and a report section that reports to a driver the tire pressure information transmitted from the wheel sensor specified by the sensor ID registered in the ID registration section.

[0020] When a wheel sensor is replaced due to tire replacement, etc., the sensor IDs registered in the ID registration section are different from the sensor IDs of the wheel sensors actually installed on the wheels of the vehicle. Therefore, the vehicle body-side device is unable to detect the tire pressure of the vehicle. Generally, when a situation occurs in the tire pressure monitoring system where it is impossible to detect the tire pressure of the vehicle for a certain period of time or longer, it is necessary to notify a driver of a malfunction for each wheel. To handle this, the vehicle body-side device includes a timer and a malfunction reporting device.

[0021] The timer measures a non-reception period, which is a continuous period of time during which the wheel information specified by the sensor ID is continuously not received, in a case where the wheel information specified by the sensor ID should be transmitted, for each sensor ID registered in the ID registration section. The "case where the wheel information specified by the sensor ID should be transmitted" refers to a case where the wheel information is normally transmitted from the wheel sensor. For example, if a system is designed such that the wheel information is transmitted from the wheel sensor only when the vehicle is traveling at a predetermined vehicle speed or faster, this refers to a case where the vehicle is traveling at a predetermined vehicle speed or faster.For example, if a system is designed to transmit wheel information from the wheel sensor unconditionally, there will always be a case where the wheel information should be transmitted.

[0022] If the wheel sensors have been replaced and therefore the sensor IDs registered in the ID registration section differ from the sensor IDs of the wheel sensors installed in the wheels of the own vehicle, a state persists in which the wheel information of the sensor IDs registered in the ID registration section cannot be received. In such a case, the non-reception period measured by the time measuring device increases.

[0023] The malfunction reporting device reports a malfunction to the vehicle driver if the non-reception period exceeds a first set time for any of the sensor IDs. A malfunction reporting device may be a device for visually alerting the driver, such as a warning light illuminating or flashing, or may be a device for audibly alerting the driver, such as a warning buzzer or a voice announcement.

[0024] The case where the sensor IDs are not registered correctly due to wheel sensor replacement is different from a case where a system error has been generated. If the vehicle body-side device detects that the wheel sensors have been replaced at an early stage and overwrites the sensor ID registered in the ID registration section, the malfunction reporting device can be prevented from reporting a malfunction.

[0025] Typically, all four wheels are replaced during a tire replacement (for example, a change from summer tires to winter tires). Since a tire is replaced along with a wheel, all wheel sensors attached to the wheels are also replaced. For this reason, once a tire pressure monitoring system is started, the non-reception period for all sensor IDs of the right and left front and rear wheels registered in the ID registration section increases. If the non-reception periods of multiple sensor IDs registered in the ID registration section increase, it can be assumed that the wheel sensors were replaced due to a tire replacement. In particular, the reliability of such an assumption increases as the number of sensor IDs whose non-reception periods increases.

[0026] According to the invention, based on the increase in the non-reception periods of the sensor IDs of a plurality of wheel sensors, it is assumed that the wheel sensors have been replaced, and discrimination processing for distinguishing the sensor IDs of the wheel sensors arranged in the wheels of the own vehicle is started based on the assumption. For this purpose, the vehicle body-side device comprises a total time calculation device and an overwrite device.

[0027] The total time calculation means calculates a total non-reception period, which is a sum of the non-reception periods of a specific number of sensor IDs greater than 1 (a specific number of sensor IDs included in the sensor IDs registered in the ID registration section). In this case, it is advantageous to calculate the total non-reception period for the sensor IDs of four wheels (right and left front and rear wheels) mounted on the vehicle.

[0028] The overwriting unit starts discrimination processing for discriminating the sensor IDs of the wheel sensors each disposed in the wheels of the own vehicle among multiple and unspecified sensor IDs received by the receiver when the total non-reception period exceeds a second set time shorter than a time period obtained by multiplying the specific number by the first set time, and overwrites the sensor ID registered in the ID registration section with the sensor ID discriminated by the discrimination processing. When a state in which the wheel information cannot be received synchronously continues for a plurality of the sensor IDs registered in the ID registration section, the discrimination processing can be started at an early stage.

[0029] For this reason, it becomes possible to complete discrimination processing before the non-reception period for each sensor ID reaches the first set time, and it eliminates the need for the malfunction reporting device to report a malfunction. In this case, only the second set time needs to be determined taking into account the time required for discrimination processing. For example, the second set time may be set to a time shorter than a time obtained by subtracting the time required for discrimination processing from the first set time and multiplying a time obtained by the subtraction by the specific number.

[0030] As a result, according to the present invention, the driver can be prevented from feeling inconvenienced as much as possible. In a case where a failure of a particular wheel sensor, poor reception in the vehicle body-side device, etc. has occurred (i.e., when a malfunction that should be reported to a driver has occurred), the driver can be notified of a malfunction at a time when the non-reception period reaches the first set time. Therefore, the reliability of the system can be maintained.

[0031] In the above explanation, for the purpose of facilitating the understanding of the invention, reference numerals used in an embodiment are added in parentheses to the configuration of the invention according to the embodiment, but each component of the invention is not limited to the embodiment specified by the above reference numerals. Short description of the drawings Fig. 1 is a schematic diagram of a tire pressure monitoring system according to an embodiment of the present invention. Fig. 2 is a functional block diagram in a sensor unit and an ECU. Fig. 3 is a drawing of a display screen image (normal time) displayed by a display device. Fig. 4 is a drawing of a display screen image (tire pressure malfunction time) displayed by a display device. Fig. 5 is a drawing of a display screen image (start time) displayed by a display device. Fig. 6 is a drawing of a display screen image (non-reception malfunction time) displayed by a display device. Fig. Figure 7 is a flowchart of a non-receive period measurement routine. Fig. 8 is a flowchart of a non-reception malfunction detection routine. Fig. Figure 9 is a flowchart of a tire replacement guessing routine. Fig. 10 is a drawing showing a relationship between the rotation position, the transmission timing, and the pulse number of a sensor unit. Description of the embodiments

[0032] Hereinafter, a tire pressure monitoring system according to an embodiment of the present invention will be described with reference to the drawings. Fig. 1 shows the schematic configuration of the tire pressure monitoring system for a vehicle. The tire pressure monitoring system is a system for reporting tire pressure information of a tire to a driver and includes tire pressure sensor units 10 (hereinafter referred to as sensor units 10) fixed to respective wheels W, a tire pressure reporting control unit (hereinafter referred to as ECU 50) fixed to a vehicle body, and a display device 100. The sensor unit 10 corresponds to the wheel sensor of the present invention. In addition, a configuration consisting of the ECU 50 and the display device 100 corresponds to the vehicle body-side device of the present invention. Fig. 2 shows a functional block diagram in the sensor unit 10 and the ECU 50. Since all the sensor units 10 arranged in the respective wheels W have the same function, Fig. 2 just one of these.

[0033] The sensor unit 10 is attached to the tire air injection valve provided in a wheel rim of the wheel W. The sensor unit 10 includes an air pressure sensor 11, a temperature sensor 12, an acceleration sensor 13, an ID storage section 14, a transmission controller 15, a transmitter 16, and a battery 17, as shown in Fig. 2. These components 11 to 17 are contained in a housing and modularized.

[0034] The air pressure sensor 11 detects the air pressure of a tire and outputs a detection signal representing the air pressure Px to the transmission controller 15. The temperature sensor 12 detects the temperature of the tire and outputs a detection signal representing the tire temperature Tx to the transmission controller 15. The acceleration sensor 13 detects the acceleration in a direction of a centrifugal force of the wheel W and outputs a detection signal representing the acceleration Gx to the transmission controller 15. The ID storage section 14 is a non-volatile memory for storing the sensor IDs, which are discrimination information of the sensor units 10, and outputs the sensor IDs to the transmission controller 15.

[0035] The transmission controller 15 has a microcomputer as its main part, generates transmission data including the air pressure Px detected by the air pressure sensor 11, the tire temperature Tx detected by the temperature sensor 12, the acceleration Gx detected by the acceleration sensor 13, and the sensor ID stored in the ID storage section 14, and outputs it to the transmitter 16.

[0036] When the transmission data output from the transmission controller 15 is input, the transmitter 16 converts the transmission data into a radio signal and transmits it to the ECU 50 via a transmitting antenna 16a. The transmitter 16 transmits the above radio signal at the time the transmission data is input. Therefore, the timing at which the transmitter 16 transmits the radio signal is controlled by the transmission controller 15.

[0037] This transmitter 16 is only capable of transmitting to the ECU 50 (bidirectional communication is impossible) and unidirectionally transmits the above radio signal. Hereinafter, the information transmitted as a radio signal from the transmitter 16 (corresponding to the transmission data output from the transmission controller 15 to the transmitter 16) is referred to as wheel information.

[0038] The battery 17 supplies electrical energy for operation to respective electrical loads in the sensor unit 10 and serves as a power supply.

[0039] The transmission controller 15 adjusts the transmission timing of the radio signal based on the acceleration Gx detected by the acceleration sensor 13 and a transmission time interval. The acceleration sensor 13 used in the present embodiment detects the acceleration in a centrifugal force direction of the wheel W (diameter direction). Since the acceleration sensor 13 rotates together with the wheel W to which the acceleration sensor 13 is attached, the acceleration Gx in a centrifugal force direction is undulated due to the influence of gravity according to its own rotational position (rotational position of the sensor unit 10). This undulated component of the acceleration Gx in a centrifugal force direction is a gravitational acceleration component.

[0040] The gravitational acceleration component changes sinusoidally in a range from -1G to +1G while the wheel W rotates one revolution, as shown in Fig. 10 (G represents the Earth's gravitational acceleration). For this reason, the rotational position around the axle shaft of the sensor unit 10 can be detected from the value of the gravitational acceleration component included in the acceleration Gx detected by the acceleration sensor 13. In the present embodiment, the time at which the gravitational acceleration component becomes -1G, that is, the time at which the rotational position of the sensor unit 10 reaches its highest point, is set as the transmission time of the radio signal.

[0041] Since the transmission interval during the vehicle travel is short when the transmission timing of the radio signal is simply set based on the rotational position of the sensor unit 10, a transmission time interval condition is added so as to ensure a transmission time interval of a predetermined time (1 minute in the present embodiment). That is, a time at which the rotational position of the sensor unit 10 reaches a setting location for the first time after a predetermined time has elapsed since the last transmission of the radio signal (the top point in this example) is set as the transmission timing of the radio signal.

[0042] Furthermore, the transmission controller 15 transmits the radio signal at the above transmission timing when the vehicle speed is a fixed speed (for example, 20 km / h) or higher. The transmission controller 15 estimates the vehicle speed based on the acceleration Gx detected by the acceleration sensor 13. The vehicle speed can be estimated, for example, based on the wave period (ripple period) (pulsation period) of the gravitational acceleration component included in the acceleration Gx. In addition, the higher the vehicle speed becomes, the more the centrifugal force acting on the acceleration sensor 13 increases. Therefore, the vehicle speed can also be estimated from a value obtained by subtracting the gravitational acceleration component from the acceleration Gx.

[0043] Although in the present embodiment, the radio signal is transmitted only when the vehicle speed is equal to or greater than a fixed speed, this is not necessary, and the radio signal can also be transmitted when the vehicle speed is lower than the fixed speed. Since the sensor unit 10 does not rotate while the vehicle is stopped, the transmission timing cannot be adjusted based on the rotational position of the sensor unit 10. Therefore, in the case where the vehicle speed becomes lower than the fixed speed, for example, the transmission timing only needs to be adjusted in a fixed period of time.

[0044] The ECU 50 will be described below. The ECU 50 comprises a microcomputer and a communication circuit as its main body, and includes a receiver 51, a reception processing section 52, a notification controller 53, a registration ID storage section 54, an individual non-reception period measurement section 55, a non-reception malfunction determination section 56, a total non-reception period calculation section 57, and an ID discrimination / overwriting section 58 from a functional perspective. Furthermore, the ECU 50 is connected to the display device 100 located near a driver's seat. The ECU 50 starts its operation when an ignition switch is turned on and stops its operation when the ignition switch is turned off.

[0045] The receiver 51 receives the radio signal (wheel information) transmitted from each sensor unit 10 via a receiving antenna 51a. This receiver 51 receives the radio signals transmitted from the sensor units 10 fixed to the wheels W, not only of the own vehicle but also of many other vehicles, not specified. The reception processing section 52 extracts data representing the sensor ID, air pressure Px, tire temperature Tx, and acceleration Gx from the radio signal whenever the receiver 51 receives the radio signal. The reception processing section 52 outputs this data to the notification controller 53, the individual non-reception period measuring section 55, and the ID discrimination / overwriting section 58.

[0046] The notification controller 53 generates display data representing the air pressures Px of four wheels of the vehicle with respect to each wheel location based on the data input from the reception processing section 52 (the sensor ID, the air pressure Px, and the tire temperature Tx) and the sensor IDs of the four wheels stored in the registration ID storage section 54.

[0047] The registration ID storage section 54 is a non-volatile memory that stores the sensor IDs of the sensor units 10 mounted on the wheels W of the host vehicle, along with their wheel locations. The registration ID storage section 54 includes a left front wheel ID storage area 54FL for storing the sensor ID assigned to the sensor unit 10 of a left front wheel, a right front wheel ID storage area 54FR for storing the sensor ID assigned to the sensor unit 10 of a right front wheel, a left rear wheel ID storage area 54RL for storing the sensor ID assigned to the sensor unit 10 of a left rear wheel, and a right rear wheel ID storage area 54RR for storing the sensor ID assigned to the sensor unit 10 of a right rear wheel.

[0048] Hereinafter, the sensor IDs stored in the registration ID storage section 54 are referred to as registered sensor IDs. Specifically, when it is not necessary to distinguish between the registered sensor IDs according to the respective storage area, the sensor ID stored in the left front wheel ID storage area 54FL is referred to as registered sensor ID1, the sensor ID stored in the right front wheel ID storage area 54FR is referred to as registered sensor ID2, the sensor ID stored in the left rear wheel ID storage area 54RL is referred to as registered sensor ID3, and the sensor ID stored in the right rear wheel ID storage area 54RR is referred to as registered sensor ID4.

[0049] The notification controller 53 refers to a correspondence relationship between the registered sensor IDs and the wheel locations stored in the registration ID storage section 54, generates display data representing the air pressures Px of the four wheels corresponding to their wheel locations based on the data input from the reception processing section 52, and outputs the generated display data to the display device 100. Furthermore, the notification controller 53 compares the air pressure Px with a proper evaluation value Pref for each wheel, and outputs insufficient air pressure wheel location data identifying the wheel location where the air pressure is insufficient to the display device 100 when the air pressure Px is less than the proper evaluation value Pref.

[0050] Furthermore, the notification controller 53 determines whether the tire temperature Tx has become abnormally elevated based on the input tire temperature Tx and outputs tire overheat information to another vehicle controller (not shown) when a tire overheat condition is detected. Furthermore, the notification controller 53 may be configured to output tire overheat location data specifying the wheel location of the overheated tire to the display device 100. Furthermore, the notification controller 53 may be configured to correct the correct evaluation value Pref for determining the correctness of a tire pressure based on the tire temperature Tx.

[0051] The display device 100 includes a display arranged at a location visible from a driver's seat, a display driver that drives the display, and a display microcomputer that controls the display driver, and displays a tire pressure monitoring screen image on the display according to the display data output from, for example, the notification controller 53.

[0052] Fig. 3 represents a tire pressure monitoring screen image D displayed on the display of the display device 100. A vehicle body mark M1 representing a top view pattern of a vehicle body, air pressure value display sections M2 arranged corresponding to respective wheel locations and displaying numerical values ​​of the tire pressures, and a warning mark M3 for attracting a driver's attention are displayed on the tire pressure monitoring screen image D.

[0053] The display device 100 displays the numerical values ​​of the air pressures at the air pressure value display sections M2 based on the display data input from the notification controller 53. Furthermore, in the case where it is determined that a shortage of air pressure has occurred based on the insufficient air pressure wheel location data, it changes the display mode of the air pressure value display section M2 of the wheel in which the air pressure shortage has occurred (for example, its background color and character color can be changed) and turns on the warning mark M3, as shown in Fig. 4 is shown. Fig. Figure 4 shows an example where a tire pressure deficiency has occurred in the right front wheel. The warning mark M3 can only be seen by a driver when it is on, and cannot be seen by a driver when it is off. Therefore, along with the corresponding air pressure value, a driver can identify which wheel W is lacking air pressure.

[0054] Since the ECU 50 is started by turning on an ignition switch, it does not obtain the tire pressure information from the sensor unit 10 immediately after its start-up. In this case, the notification control 53 displays, as shown in Fig. 5, the notification controller 53 displays the "-" mark, etc., on the air pressure value display sections M2 of the tire pressure monitoring screen D, and reports that a state exists where the tire pressure has not yet been detected. At this time, the notification controller 53 does not turn on the warning mark M3.

[0055] When the non-reception malfunction detection signal output from the non-reception malfunction determination section 56, which will be described later, is input, the notification controller 53 changes the display mode of the "-" mark displayed on the air pressure value display section M2 (for example, its background color and character color can be changed) for the wheel W specified by the non-reception malfunction detection signal (non-reception malfunction determination flag, which will be described later), and turns on the warning mark M3. Fig. 6 shows an example where a non-reception malfunction is detected in all four wheels (right and left front and rear wheels).

[0056] The individual non-reception period measuring section 55 is a functional section that measures a non-reception period, which is a continuous period during which the wheel information is not received, for each registered sensor ID. Since the sensor unit 10 in the system of the present embodiment can transmit the wheel information while the vehicle is traveling at a fixed vehicle speed or faster, the individual non-reception period measuring section 55 measures a non-reception period when the vehicle is traveling at a vehicle speed not lower than a set vehicle speed Vref (which may be equivalent to the vehicle speed set as a condition for the sensor unit 10 to transmit the wheel information).

[0057] In addition, if the sensor unit 10 is configured to transmit the radio signal at a fixed period regardless of the vehicle speed, the individual non-reception period measuring section 55 only needs to measure the continuous period during which the wheel information cannot be received as the non-reception period regardless of the vehicle speed. That is, the individual non-reception period measuring section 55 measures the continuous period during which the wheel information containing the sensor ID included in the registered sensor ID cannot be received, in a case where the wheel information should normally be transmitted from the sensor unit 10.

[0058] Fig. 7 shows a non-reception period measurement routine performed by the individual non-reception period measurement section 55. The non-reception period measurement routine is performed in parallel for each of the four registered sensors ID1 to ID4 stored (registered) in the registration ID storage section 54. Although the non-reception period measurement routine for the registered sensor ID1 is explained here, the same applies to the other registered sensors ID2 to ID4. The non-reception period measurement routine is repeated at a predetermined short operating period.

[0059] In step S11, the individual non-receiving period measuring section 55 reads the vehicle speed detected by a vehicle speed sensor (not shown) and determines whether the vehicle speed V is not less than a set vehicle speed Vref. This set vehicle speed Vref is set to a vehicle speed at which the wheel information should be transmitted from the sensor unit 10, for example, 20 km / h. Since the sensor unit 10 will not transmit the wheel information when the vehicle speed V is less than the set vehicle speed Vref, the individual non-receiving period measuring section 55 once terminates this routine.

[0060] When the vehicle is traveling at the set vehicle speed Vref or faster, the individual non-reception period measuring section 55 determines in step S12 whether the wheel information including the registered sensor ID1 stored in the left front wheel ID storage area 54FL of the registration ID storage section 54 has been received. The reception processing section 52 outputs the sensor ID to the individual non-reception period measuring section 55 whenever the receiver 51 receives the wheel information. The individual non-reception period measuring section 55 determines in this step S12 whether the sensor ID identical to the registered sensor ID1 is output from the reception processing section 52.In this case, the individual non-reception period measuring section 55 reads the registered sensor ID1 stored in the left front wheel ID storage area 54FL and determines whether the sensor ID output from the reception processing section 52 is identical to the registered sensor ID1.

[0061] In step S12, the individual non-reception period measuring section 55 determines "No" if the sensor ID is not output from the reception processing section 52 or if the sensor ID output from the reception processing section 52 is different from the registered sensor ID1. In this case, the individual non-reception period measuring section 55 counts up a measurement time T1 of a non-reception timer of the registered sensor ID1 in step S13. This measurement time T1 represents the continuous period during which the wheel information including the registered sensor ID1 is not received. The initial value of the measurement time T1 is set to zero. The processing in step S13 is processing for incrementing the measurement time T1 by a period corresponding to the operation period during which the non-reception period measuring routine is repeated.

[0062] The individual non-receiving period measuring section 55 repeats such processing in a predetermined operation period. When the sensor ID identical to the registered sensor ID1 is output from the receiving processing section 52 (S12: Yes), the individual non-receiving period measuring section 55 resets the measurement time T1 in step S14. That is, when the wheel information specified by the registered sensor ID1 is received by the sensor unit 10, the measurement time T1 is reset (cleared to zero).

[0063] By repeating such processing, the individual non-reception period measuring section 55 calculates the measurement time T1, which is the continuous period during which the wheel information including the registered sensor ID1 cannot be received. The individual non-reception period measuring section 55 performs the same processing for the other registered sensor IDs, i.e., ID2 to ID4. Hereinafter, when the non-reception periods are individually specified with respect to the registered sensor ID1, ID2, ID3, and ID4, they will be referred to as non-reception periods T1, T2, T3, and T4.

[0064] Each sensor unit 10 transmits the wheel information as a radio signal for approximately one minute at a time. This wheel information may not necessarily be received by the ECU 50 every transmission due to a decrease in the reception intensity when the ECU 50 receives the radio signal (in a case where the reception intensity of the transmitted radio signal is below a reception limit), the influence of noise, a failure of the sensor unit 10, etc. If the wheel information including the registered sensor ID cannot be received by the ECU 50, the non-reception period increases.

[0065] In the tire pressure monitoring system according to the present embodiment, a rule is defined according to which a driver must be notified of a system malfunction when a situation exists in which tire pressure information cannot be reported within a certain period of time (for example, within 10 minutes) while the vehicle is traveling (at a vehicle speed at which the sensor unit 10 is defined as transmitting the wheel information). The continuous period during which the tire pressure information cannot be received is denoted by the non-reception period measured by the individual non-reception period measuring section 55.

[0066] Based on this non-reception period, the non-reception malfunction determination section 56 determines a system malfunction and outputs the non-reception malfunction determination flag, which is a signal representing the determination result, to the notification controller 53. Fig. 8 shows a non-reception malfunction determination routine performed by the non-reception malfunction determination section 56. The non-reception malfunction determination section 56 repeats the non-reception malfunction determination routine in a predetermined operating period. During the execution of the non-reception malfunction determination routine, the above non-reception period measurement routine is performed by the individual non-reception period measurement section 55.

[0067] When the non-reception malfunction determination routine starts, the non-reception malfunction determination section 56 reads the non-reception periods T1, T2, T3, and T4 currently measured by the individual non-reception period measuring section 55 in step S21. Then, in step S22, it is determined whether the non-reception period T1 with respect to the registered sensor ID1 is not greater than the first set time Tref. The first set time Tref1 is set to 10 minutes in the present embodiment.

[0068] If the non-reception period T1 is equal to or less than the first set time Tref, the non-reception malfunction determination section 56 sets the non-reception malfunction determination flag F1 to "0" in step S23. On the other hand, if the non-reception period T1 is greater than the first set time Tref1 (this state is referred to as a non-reception state), the non-reception malfunction determination flag F1 is set to "1" because it is a state where a driver needs to be notified of a system malfunction.

[0069] The non-reception malfunction determination section 56 similarly determines whether the non-reception periods T2 to T4 are not greater than the first set time Tref1 for the registered sensor IDs, i.e., -ID2 to -ID4 (S25, S28, S31). A non-reception malfunction determination flag F2 representing the non-reception state of the registered sensor ID2 is set to "0" when the non-reception period T2 is not greater than the first set time Tref1, and is set to "1" when T2 exceeds the first set time Tref1 (S26, S27). A non-reception malfunction detection flag F3 representing the non-reception state of the registered sensor ID3 is set to "0" when the non-reception period T3 is not greater than the first set time Tref1, and is set to "1" when T3 exceeds the first set time Tref1 (S29, S30).A non-reception malfunction detection flag F4 representing the non-reception state of the registered sensor ID4 is set to "0" when the non-reception period T4 is not greater than the first set time Tref1, and is set to "1" when T4 exceeds the first set time Tref1 (S32, S33).

[0070] The non-reception malfunction determination section 56 outputs the non-reception malfunction determination flags F1, F2, F3, and F4 to the notification controller 53. The notification controller 53 turns on the warning flag M3 of the display device 100 when at least one of the non-reception malfunction determination flags F1, F2, F3, and F4 is set to "1." Meanwhile, the tire location air pressure value display section M2, which is set to "1," is changed to "-" and its display mode is changed (for example, its background color and character color are changed). This allows the driver to be aware of the occurrence of a system malfunction.

[0071] When the sensor unit 10 is replaced, it becomes impossible to receive the radio signal containing the registered sensor ID of the removed sensor unit 10 (sensor ID stored in the registration ID storage section 54 at the time of replacement). For this reason, the non-reception malfunction flag F for the registered sensor ID of the wheel location where the sensor unit 10 was replaced is set to "1," and a system malfunction is reported to a driver via the display device 100.

[0072] The case where the registration of a sensor ID is incorrect due to replacement of the sensor unit 10 is different from the case where a failure has occurred in the system. As described later, the tire pressure monitoring system according to the present embodiment has a function of automatically discriminating the sensor ID of the sensor unit 10 of the own vehicle and storing it in the registration ID storage section 54. Therefore, when it can be estimated at an early stage that the sensor unit 10 has been replaced, by starting the automatic discrimination of the sensor ID of the sensor unit 10 of the own vehicle at that time and registering the correct sensor ID in the registration ID storage section 54 within the first set time (10 minutes), it becomes unnecessary to report a system malfunction.

[0073] Typically, all four wheels are replaced during tire replacement. Since a tire is replaced along with a wheel, all the sensor units 10 mounted on the wheels are also replaced. For this reason, once the ECU 50 is started, the respective non-reception periods (T1 to T4) for all the registered sensor IDs of the right and left front and rear wheels registered in the registration ID storage section 54 increase. If the non-reception periods (T1 to T4) of the four registered sensor IDs registered in the registration ID storage section 54 increase together, it can be assumed or presumed that the sensor units 10 were replaced due to tire replacement.

[0074] The total non-receiving period calculation section 57 is provided as a functional section that performs this assumption. Fig. 9 is a flowchart showing a tire replacement presumption routine performed by the total non-receiving period calculation section 57. The total non-receiving period calculation section 57 repeats the tire replacement presumption routine in a predetermined operating period. While the tire replacement presumption routine is being performed, the above non-receiving period measurement routine is performed by the individual non-receiving period measurement section 55.

[0075] Once the tire replacement presumption routine starts, the total non-reception period calculation section 57 reads the non-reception periods T1, T2, T3, and T4 currently measured by the individual non-reception period measurement section 55 in step S51. Then, in step S52, the total non-reception period calculation section 57 calculates the total non-reception period Ttotal (= T1 + T2 + T3 + T4), which is a sum of the non-reception periods T1, T2, T3, and T4.

[0076] Then, in step S53, the total non-reception period calculation section 57 determines whether the total non-reception period Ttotal exceeds a predetermined second set time Tref2. The second set time Tref2 is set to 10 minutes in the present embodiment.

[0077] When the vehicle travels at a speed equal to or greater than the set vehicle speed Vref after the four sensor units 10 are replaced by replacing the four tires simultaneously, all of the non-reception periods T1, T2, T3, and T4 increase (are not reset). For this reason, the total non-reception period Ttotal increases by four times each of the incremental speeds of the non-reception periods T1, T2, T3, and T4. Therefore, when the total non-reception period Ttotal reaches the second set time Tref2 (10 minutes), this is a stage where the non-reception state has actually only lasted 2.5 minutes (= 10 minutes / 4).That is, the actual time period during which the non-reception state continues synchronously for the four registered sensor IDs is a time period obtained by dividing the total non-reception period Ttotal by the number of sensor units 10 (number of registered sensor IDs).

[0078] If it is determined in step S53 that the total non-reception period Ttotal does not exceed the predetermined second set time Tref2, the total non-reception period calculation section 57 terminates the tire replacement presumption routine once. The total non-reception period calculation section 57 repeats the tire replacement presumption routine in a predetermined operation period. If the total non-reception period Ttotal exceeds the second set time Tref2 (10 minutes) (S53: Yes), the total non-reception period calculation section 57 outputs a self-vehicle ID discrimination initiation instruction to the ID discrimination / override section 58 in step S54 and terminates the tire replacement presumption routine.

[0079] For example, when the ECU 50 first starts (the tire pressure monitoring system starts) in a state where the four sensor units 10 have been replaced by replacing the four tires, and when the integrated time during which the vehicle is traveling at a speed equal to or greater than the set vehicle speed Vref exceeds 2.5 minutes, the self-vehicle ID discrimination initiation instruction is issued from the total non-reception period calculation section 57. Therefore, 7.5 minutes remain before the non-reception malfunction determination section 56 sets the non-reception malfunction determination flags F1, F2, F3, and F4 to "1" at this time. If the sensor IDs of the actually mounted sensor units 10 are registered in the registration ID storage section 54 within this remaining time (7.5 minutes), it is not necessary to turn on the warning flag M3 in the display device 100.This means there is no need to issue an unnecessary warning to a driver.

[0080] When the self-vehicle ID discrimination initiation instruction output from the total non-reception period calculation section 57 is input, the ID discrimination / override section 58 will perform self-vehicle ID discrimination processing, wheel location discrimination processing, and ID override processing. The self-vehicle ID discrimination processing is processing for specifying the sensor ID of the sensor unit 10 disposed in the wheel W of the self-vehicle from among many unspecified sensor IDs included in the received reception signal. The wheel location discrimination processing is processing for discriminating to which wheel W the sensor unit 10 corresponding to the sensor ID specified by the self-vehicle ID discrimination processing is mounted.The ID rewrite processing is processing for storing the sensor IDs whose wheel locations are located by the wheel location discrimination processing in the predetermined areas (54FL, 54FR, 54RL, 54RR) of the registration ID storage section 54. In addition, the own vehicle ID discrimination processing may also be performed in the wheel location discrimination processing.

[0081] The reception processing section 52 outputs the sensor ID contained in the radio signal to the ID discrimination / rewriting section 58 each time the radio signal is received. The ID discrimination / rewriting section 58 discriminates the sensor ID of the sensor unit 10 of the own vehicle from the sensor IDs output by the reception processing section 52 (own vehicle ID discrimination processing).

[0082] The self-vehicle ID discrimination processing may be performed as follows. For example, the ID discrimination / rewriting section 58 samples a plurality of the sensor IDs output from the reception processing section 52 for each sensor ID for a fixed period and determines that the sensor ID with a large sampling number (contained in the radio signal with a large number of receptions) is the sensor ID of the self-vehicle sensor unit 10. Alternatively, the self-vehicle ID discrimination processing may also be performed based on the reception intensity of the radio signal. For example, the reception processing section 52 outputs data representing the reception intensity of the radio signal in association with the sensor ID to the ID discrimination / rewriting section 58.The ID discrimination / overwriting section 58 samples a plurality of the reception intensities of the radio signals output from the reception processing section 52 for a fixed period, and determines that the sensor ID included in the radio signal having a large reception intensity is the sensor ID of the sensor unit 10 of the own vehicle among the sampled data.

[0083] In such self-vehicle ID discrimination processing, it is not necessary to limit the sensor IDs to four (number of wheels). This is because four sensor IDs can be finally specified through the wheel location discrimination processing, as described later.

[0084] The ID discrimination / override section 58 narrows down the candidate sensor IDs of the sensor units 10 of the own vehicle through the own-vehicle ID discrimination processing and then performs the wheel location discrimination processing. When performing the wheel location discrimination processing, the ID discrimination / override section 58 uses a pulse signal output from the wheel speed sensor 60.

[0085] The ID discrimination / override section 58 is connected to the wheel speed sensors 60 arranged on the four wheels, and inputs a number of pulse signals proportional to the wheel speed of each wheel W from the wheel speed sensor 60. The ID discrimination / override section 58 specifies the sensor IDs of the sensor units 10 at the four wheel locations based on a relationship between a count of the pulse signals output by the wheel speed sensors 60 and the time of reception of the radio signal (the time at which the ID discrimination / override section 58 receives the sensor ID from the reception processing section 52).

[0086] The wheel speed sensor 60 is arranged at each corresponding wheel W and outputs a predetermined number of pulse signals while the wheel W rotates one revolution. The wheel speed sensor 60 of the present embodiment outputs the pulse signal 96 times while the wheel W rotates one revolution. That is, the pulse signal is output whenever the wheel W rotates a fixed angle (3.75 degrees (= 360 / 96)).

[0087] The ID discrimination / override section 58 starts counting the pulse signals output from the wheel speed sensor 60 at any time, resets a pulse count value to "1," and resumes counting when the count value exceeds "96," which is the number of pulse signals for one rotation of the wheel. The pulse count value thus converted to a value of "96" or less is called a pulse number. For example, when the pulse count value increases like 95, 96, 97, 98, 99..., the pulse number is adjusted to change like 95, 96, 1, 2, 3... The pulse number becomes a value representing the remainder resulting from dividing the pulse count value by the number of pulse signals for one rotation of the wheel.

[0088] As mentioned above, the sensor unit 10 transmits the wheel information at a location where its own rotational position is the uppermost, that is, at a location where the gravitational acceleration component detected by the acceleration sensor 13 becomes -1G. Therefore, when the sensor unit 10 and the wheel speed sensor 60 are arranged on a common wheel W, the pulse number of each wheel W sampled upon receiving the wheel information transmitted from the sensor unit 10 becomes fundamentally constant.

[0089] Fig. Figure 10 is a diagram illustrating the relationship between the rotational position of the sensor unit 10 and the pulse rate in any wheel W. This example shows that the pulse rate of the right front wheel is indicated as a constant value of "3" when the rotational position of the sensor unit 10 always reaches the top position.

[0090] Respective wheels W do not necessarily rotate at the same speed, and the rotational speeds differ due to an inner ring difference, an outer wheel difference, and slippage. For this reason, the sampled pulse number fluctuates when the sensor unit 10 and the wheel speed sensor 60 do not correspond to a common wheel W.

[0091] Using such a principle, whenever the sensor ID is input as a candidate from the reception processing section 52, the ID discrimination / overwriting section 58 stores the pulse numbers of the respective wheel speed sensors 60 at that time in association with the sensor IDs. That is, the pulse numbers are sampled. Based on the pulse number of each wheel speed sensor 60 sampled for each sensor ID, the wheel W having the wheel speed sensor 60 with the smallest change in pulse number is specified as the wheel W to which the own sensor unit 10 is mounted. This determines the relationship between the sensor IDs of the sensor units 10 mounted on the wheels in the own vehicle and the wheel locations.

[0092] The ID discrimination / overwriting section 58 stores the determined relationship between the sensor IDs and the wheel locations in the registration ID storage section 54. That is, the registered sensor IDs stored in the ID storage areas 54FL, 54FR, 54RL, and 54RR are overwritten by the sensor IDs specified by the wheel location discrimination processing.

[0093] When the registered sensor IDs stored in the registered ID storage section 54 are overwritten, the non-reception periods with respect to the registered sensor IDs are reset (cleared to zero) at the time the wheel information including the overwritten sensor ID is subsequently transmitted. That is, in step S12 of the non-reception period measurement routine performed by the individual non-reception period measurement section 55, the subjects for determining the presence of radio signal reception are changed to the newly written registered sensor IDs. As a result, the non-reception periods are reset (S14) at the time the newly written sensor ID is input from the reception processing section 52 to the individual non-reception period measurement section 55 (S12: Yes).Therefore, the registered sensor IDs can be overwritten before the non-reception period reaches the first set time Tref1, and the warning flag M3 of the display device 100 can be prevented from being turned on.

[0094] According to the tire pressure monitoring system of the present embodiment explained above, the total non-reception period calculation section 57 totals the non-reception periods with respect to the four registered sensor IDs, and the ID discrimination / overwriting section 58 starts discrimination (searching) of the sensor ID of the sensor unit 10 of the own vehicle when the total non-reception period Ttotal reaches a second set time Tref2 (10 minutes). This second set time Tref2 is set to a time period shorter than a time period obtained by multiplying the first set time Tref1, which is used as a reference for reporting a non-reception malfunction, by the number of registered sensor IDs (Tref1 × 4).

[0095] When the four sensor units 10 are replaced similarly to the case of replacing a set of tires, discrimination (search) of the sensor ID of the sensor unit 10 of the own vehicle can be started before a non-reception malfunction is detected (in this example, at a stage where a 2.5-minute non-reception period has elapsed). Since the sensor ID discrimination, which also includes wheel location discrimination processing, is completed within 5 minutes, the registered sensor IDs can be overwritten before the non-reception period of each registered sensor ID reaches the first set time Tref1. Accordingly, since the warning flag M3 of the display device 100 is not turned on, inconvenience to a driver can be avoided.

[0096] On the other hand, if a case persists where the radio signal cannot be received due to other factors, such as poor radio signal reception, a failure of the sensor unit 10 itself, etc., the non-reception malfunction can be detected for each sensor unit 10 (each sensor ID) by the individual non-reception period measuring section 55. Therefore, when a system malfunction that should be reported to a driver occurs, the warning flag M3 of the display device 100 can be surely turned on to inform the driver that a malfunction has occurred. Therefore, the reliability of the system can be maintained.

[0097] Furthermore, when the sensor units 10 are replaced, the driver does not have to manually register new sensor IDs. This ensures user-friendliness.

[0098] Although the tire pressure monitoring system according to the present embodiment has been explained as described above, the present invention is not limited to the above embodiment, and various modifications of the present invention are possible as long as they do not deviate from the subject matter of the present invention.

[0099] Although the total non-reception period Ttotal is calculated for the registered sensor IDs of the four wheels (right and left front and rear wheels) in the present embodiment, for example, the total non-reception period Ttotal obtained by summing the non-reception periods of the registered sensor IDs of two wheels (two of the four wheels) or the total non-reception period Ttotal obtained by summing the non-reception periods of the registered sensor IDs of three wheels (three of the four wheels) can be obtained. In this case, it is advantageous if the second set time Tref2 is set to a time period shorter than a time period obtained by multiplying the number of registered sensor IDs as subjects whose non-reception periods are summed up (n = 2 or 3) by the first set time Tref1 (2 x Tref1 or 3 x Tref1).

[0100] Furthermore, in this case, it is advantageous if the registered sensor IDs that have a long non-reception period are selected as subjects whose non-reception periods are summed up. For example, it is advantageous if two registered sensor IDs that have the longest non-reception period are selected as subjects whose non-reception periods are summed up, and their non-reception periods are summed up when the number of registered sensor IDs as subjects is 2, and it is advantageous if three registered sensor IDs that have the longest non-reception period are selected as subjects whose non-reception periods are summed up, and their non-reception periods are summed up when the number of registered sensor IDs as subjects is 3.

[0101] In addition, the first set time Tref1 and the second set time Tref2 can be set arbitrarily. In this case, the second set time Tref2 can be set based on an assumption time Tx, which is a period of time assumed to be required to start discriminating the sensor IDs of the own vehicle and store them in the registration ID storage section 54. For example, when the number of registered sensor IDs as subjects whose non-reception periods are summed up (corresponding to the specific number of the present invention) is defined as n, it is preferable that the second set time Tref2 be set to a period shorter than (Tref1 - Tx) x n.

[0102] Furthermore, when registering sensor IDs, a manual registration function may be provided in addition to the automatic registration function. For example, a manual switch (not shown) is arranged at an arbitrary location of the vehicle, and the signal from the manual switch is input to the ID discrimination / override section 58. The ID discrimination / override section 58 performs the above processing (the self-vehicle ID discrimination processing, the wheel location discrimination processing, and the ID override processing) not only when the self-vehicle ID discrimination initiation instruction output from the total non-reception period calculation section 57 is input, but also when an operation signal is input from the manual switch.According to this modification, even if one of the sensor units 10 is replaced, the warning mark M3 can be prevented from being turned on by operating the manual switch immediately after starting the tire pressure monitoring system.

[0103] Although in the present embodiment, the ID discrimination / override section 58 performs the own-vehicle ID discrimination processing and the wheel location discrimination processing separately, the sensor IDs of the sensor units 10 of the own vehicle may be discriminated only by the wheel location discrimination processing.

[0104] Various techniques can also be used for the own-vehicle ID discrimination processing. For example, the ID discrimination / override section 58 also acquires data representing the accelerations Gx in addition to and associated with the sensor IDs from the reception processing section 52, and narrows down the candidate sensor IDs of the own vehicle based on these accelerations Gx and a motion state of the own vehicle.In this case, the ID discrimination / override section 58 compares an average wheel rotation state detected by the wheel speed sensor 60 when the sensor ID is input (when the radio signal containing the sensor ID is received by the receiver 51) with the wheel rotation state estimated from the acceleration Gx. If they differ greatly, it determines that the input sensor ID is not the sensor ID of the sensor unit 10 of the own vehicle and eliminates it from the candidate sensor IDs of the sensor units 10 of the own vehicle. If a transition of the acceleration Gx in any sensor ID (a transition of the acceleration Gx included in the radio signal received multiple times) differs from a transition of the average wheel rotation state detected by the wheel speed sensor 60.detected, it eliminates the sensor ID from the candidate sensor IDs of the sensor units 10 of the own vehicle. This corresponds, for example, to a case where the acceleration Gx does not change or decreases between two reception times, even if the wheel rotation speed of the own vehicle increases.

[0105] Although a display screen reports tire pressure information in the present embodiment, a display screen may not be used, that is, for example, a sound announcement device may be used to report the tire pressure information.

[0106] Although in the present embodiment, the pulse signal output from the wheel speed sensor 60 is directly input to the ECU 50 (ID discrimination / overwriting section 58), information representing the number of output pulse signals may be input to the ECU 50 from a brake control device (not shown) to which the pulse signals output from the wheel speed sensor 60 are input, and, for example, a wheel speed may be calculated. The brake control device counts the number of pulse signals output from the wheel speed sensor 60 in a predetermined time (for example, 30 milliseconds) and outputs information (wheel speed information) representing the counted number in a predetermined period of time. Therefore, the ECU 50 can accumulate the counted number of pulse signals output by the brake control device to detect the number of pulse signals.

[0107] Although in the present embodiment, the sensor IDs of the own vehicle are distinguished and registered according to wheel locations, it is not necessary to register the sensor IDs according to the wheel locations, and the sensor IDs of the own vehicle may be specified (discriminated) and registered among many and unspecified sensor IDs that are received. That is, there may be a system that does not monitor tire pressures in discrimination of the respective wheel locations. In this case, the registration ID storage section 54 may be configured to store only the number of sensor units 10 together, instead of storing the sensor IDs of the own vehicle in discrimination between the wheel locations. In addition, the respective sensor IDs stored in the registration ID storage section 54 may be used in step S12 of the non-reception malfunction determination routine executed in Fig. 7 shown.

[0108] Although the system according to the present embodiment is a system that monitors tire pressures of traveling wheels (right and left front and rear wheels), it may be configured to additionally provide a function for monitoring the tire pressure of an additional wheel. List of reference symbols 10 Sensor unit 11 Air pressure sensor 12 Temperature sensor 13 Accelerometer 14 ID memory part 15 Transmission control 16 channels 50 ECU 51 recipients 52 Reception processing section 53 Notification control 54 Registration ID storage section 55 Individual non-reception period measurement section 56 Non-reception malfunction detection section 57 Total non-receiving period calculation section 58 ID Discrimination / Override Section 60 wheel speed sensor 100 display device D Tire pressure monitoring screen F1, F2, F3, F4 Non-reception malfunction detection flag Gx acceleration Px air pressure M3 warning marking Tref1 first set time Tref2 second set time Ttotal Total non-reception period W bike

Claims

[1] Tire pressure monitoring system comprising: Wheel sensors (10), each comprising an air pressure sensor (11) for detecting a tire pressure (Px) and a transmitter (16) for repeatedly transmitting wheel information, which is information including tire pressure information representing the tire pressure (Px) detected by the air pressure sensor (11) and a unique sensor ID, as a radio signal and fixed and arranged on respective wheels (W) of a vehicle, and a vehicle body-side device (50, 100) comprising a receiver (51) for receiving the wheel information transmitted from the wheel sensors (10), respectively, an ID registration section (54) for registering the sensor IDs of the wheel sensors (10) used as targets for air pressure monitoring, and a reporting section (53, 100) for reporting the tire pressure information transmitted from the wheel sensor (10) specified by the sensor ID registered in the ID registration section (54) to a driver, and fixed and arranged on a vehicle body, wherein the vehicle body-side device (50, 100) comprises: a time measuring device (55) for measuring a non-reception period (T1, T2, T3, T4), which is a period of time during which the wheel information specified by the sensor ID is continuously not received, in a case where the wheel information specified by the sensor ID should be transmitted, for each sensor ID registered in the ID registration section (54), a malfunction reporting device (100) for reporting a malfunction to the driver of the vehicle when the non-reception period (T1, T2, T3, T4) exceeds a first set time (Tref1) for any of the sensor IDs registered in the ID registration section (54), a total time calculation device (57) for calculating a total non-reception period (Ttotal), which is a sum of the non-reception periods (T1, T2, T3, T4) for a specific number (n) of sensor IDs among the registered sensor IDs, the specific number (n) being greater than 1, an overwrite device (58) for starting discrimination processing for discriminating the sensor IDs of the wheel sensors (10) respectively arranged on the wheels (W) of the own vehicle from among many and unspecified sensor IDs received by the receiver (51) when the total non-reception period (Ttotal) exceeds a second set time (Tref2) shorter than a time period obtained by multiplying the specified number (n) by the first set time (Tref1), and for overwriting the sensor ID registered in the ID registration section (54) with the sensor ID discriminated by the discrimination processing. [2] Tire pressure monitoring system according to claim 1, wherein the total time calculation device (57) is designed to calculate a total non-reception period (Ttotal), which is a sum of the non-reception periods (T1, T2, T3, T4) for the sensor IDs of the right and left front and rear wheels of the vehicle, and the second setting time (Tref2) is set to a time period that is shorter than four times the first setting time (Tref1).

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