JP2012187958A - Tire air pressure monitoring system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tire air pressure monitoring system that can secure accuracy for specifying the tire position when the tire position is specified from the received signal strength of the tire air pressure signal.SOLUTION: A battery voltage obtaining part 22 is provided in a tire communication instrument 4, and the voltage of a battery 12 is monitored. When the tire communication instrument 4 transmits a tire air pressure signal Stp, the battery voltage data Dc is contained in the tire air pressure signal Stp and is transmitted to a vehicle body 5. When a TPMS receiver 13 receives the tire air pressure signal Stp, a received signal strength measuring part 20 measures the received signal strength at this time. A received signal strength correcting part 24 corrects the measured received signal strength by the battery voltage data Dc, and specifies the tire position by the received signal strength after the correction.

Description

  The present invention relates to a tire air pressure monitoring system that monitors the air pressure of each tire based on a tire air pressure signal wirelessly transmitted from a tire air pressure detecting means attached to each tire.

  In recent years, vehicles tend to be equipped with a tire pressure monitoring system that monitors the tire pressure of each tire during traveling for the purpose of ensuring the safety of the traveling vehicle. The tire pressure monitoring system attaches a tire communication device to each tire and wirelessly transmits a tire pressure signal detected by the tire communication device to the vehicle body. The vehicle body monitors the tire air pressure based on the tire air pressure signal received from the tire communicator, and notifies the driver of a low pressure alarm when confirming that a low pressure tire is present.

  In the tire pressure monitoring system, it is necessary to grasp from which tire the tire pressure signal received by the vehicle body is transmitted. As a method for specifying a tire position, for example, a technique for specifying a tire position from a received signal strength indicator (RSSI: Received Signal Strength Indicator) when a vehicle body receives a tire air pressure signal has been devised (see Patent Document 1, etc.). If this method is used, there is no need to attach an initiator for starting the tire communication device to each tire house, and there are advantages such as simplification of the system configuration and reduction of parts costs.

JP 2006-312342 A

  By the way, for example, in a tire communication device, when the battery decreases, the transmission intensity of radio waves tends to decrease. The output intensity of the tire communication device is also affected by the tire temperature. For this reason, a difference occurs in the measurement result between the received signal strength measured at the normal time and the received signal strength measured at the time of battery deterioration of the tire communication device or when the tire temperature rises. Therefore, even if the tire position is specified from the received signal strength of the tire air pressure signal with the aim of reducing the number of parts, there is a problem that the tire position cannot be detected with high accuracy.

  An object of the present invention is to provide a tire pressure monitoring system capable of ensuring the accuracy of tire position specification when specifying the tire position from the received signal strength of the tire pressure signal.

  In order to solve the above problems, in the present invention, tire pressure detection means for detecting tire pressure is attached to each tire, a tire pressure signal is transmitted to the vehicle body from the tire pressure detection means wirelessly, and the tire pressure signal is In a tire air pressure monitoring system that monitors the tire air pressure while specifying the position of the tire based on the received signal strength when the vehicle body receives, an acquisition means for acquiring a variation factor value of the transmission intensity of the tire air pressure signal; The present invention is summarized by comprising correction means for correcting the received signal intensity based on the variation factor value acquired by the acquisition means.

  According to the configuration of the present invention, when the tire communication device wirelessly transmits the tire pressure signal to the vehicle body to monitor the tire pressure, the fluctuation factor value of the tire pressure signal is acquired by the acquisition unit. Then, the received signal strength when the vehicle body receives the tire pressure signal is corrected by the correction means based on the variation factor value. Therefore, in the case of this example, the tire position is determined based on the received signal strength that is highly reliable as a value, that is, the received signal strength derived from the variation factor value. For this reason, when specifying a tire position from the received signal strength of a tire air pressure signal, it is possible to ensure the accuracy of specifying the tire position.

  In the present invention, the acquisition means is a power supply voltage notification means for detecting a power supply voltage of the tire air pressure detection means and wirelessly notifying the vehicle body of the power supply voltage as the variation factor value. The gist is to correct the received signal intensity measured in the vehicle body on the vehicle body side based on the power supply voltage. According to this configuration, since the received signal strength is corrected based on the power supply voltage of the tire communication device, even if the power supply voltage of the tire communication device is reduced and the transmission strength of the tire communication device is reduced, It is possible to obtain the received signal intensity having the same value as when the power supply voltage is not lowered. Therefore, even if the power supply voltage of the tire communication device is lowered, it is possible to ensure the accuracy of specifying the tire position.

  In the present invention, the acquisition means is tire temperature notification means for detecting the temperature of the tire and wirelessly notifying the vehicle body of the detected temperature value as the variation factor value, and the correction means is measured in the vehicle body. The gist is to correct the received signal intensity on the vehicle body side based on the detected temperature value of the tire. According to this configuration, since the received signal strength is corrected based on the temperature of the tire communication device, even if the temperature of the tire communication device increases and the transmission strength of the tire communication device decreases, the tire temperature is reduced. It becomes possible to obtain the received signal strength of the same value as when it is not increased. Therefore, even if the tire communication device fluctuates in temperature, it is possible to ensure the accuracy of specifying the tire position.

  In the present invention, the acquisition means is a correction coefficient notification means for determining a correction coefficient for correcting the received signal strength based on the variation factor value and notifying the correction body of the correction coefficient wirelessly, The gist of the correction means is to correct the received signal intensity measured in the vehicle body on the vehicle body side based on the correction coefficient. According to this configuration, for example, the received signal strength can be corrected by a simple calculation such as simply multiplying by a coefficient, so that the correction process can be simplified.

  In the present invention, the acquisition means is transmission intensity notifying means for actually measuring the transmission intensity of the tire air pressure signal and notifying the transmission body wirelessly to the vehicle body, and the correcting means is the transmission intensity and its reference value. And the received signal intensity measured on the vehicle body is corrected by the difference on the vehicle body side. According to this configuration, the received signal intensity can be corrected with the actually measured characteristic value, so that the correction accuracy is improved. Therefore, the effect of improving the accuracy of tire position determination is increased.

  ADVANTAGE OF THE INVENTION According to this invention, the precision of tire position specification at the time of specifying a tire position from the received signal strength of a tire air pressure signal is securable.

The lineblock diagram of the tire pressure monitoring system of a 1st embodiment. The schematic diagram which shows the arrangement | positioning place of a TPMS receiver. The graph which shows the relationship between the radio wave transmission intensity | strength of a tire communication apparatus, and a battery voltage. The flowchart which shows the communication sequence of a tire pressure monitoring system. The graph which shows the relationship between the radio wave transmission intensity | strength of the tire communication apparatus of 2nd Embodiment, and tire temperature. The flowchart which shows the communication sequence of a tire pressure monitoring system. The block diagram of the tire pressure monitoring system of 3rd Embodiment. The flowchart which shows the communication sequence of a tire pressure monitoring system. The block diagram of the tire pressure monitoring system of 4th Embodiment. Explanatory drawing which illustrated the difference in the transmission intensity of a tire communication machine. The flowchart which shows the communication sequence of a tire pressure monitoring system.

(First embodiment)
A tire air pressure monitoring system according to a first embodiment of the present invention will be described below with reference to FIGS.

  As shown in FIG. 1, the vehicle 1 is equipped with a tire pressure monitoring system (TPMS: Tire Pressure Monitoring System) 3 that monitors the tire pressure of each tire 2 (2a to 2d). The tire pressure monitoring system 3 detects the tire pressure and the like with a tire communication device 4 attached to each tire 2a to 2d, and wirelessly transmits the detection result to the vehicle body 5 as a tire pressure signal Stp. The vehicle body 5 confirms the tire air pressure from the tire air pressure signal Stp and notifies the driver of the result. Note that the tire communication device 4 corresponds to tire air pressure detecting means.

  The tire communication device 4 is provided with a controller 6 that manages the tire communication device 4 in an integrated manner. In the memory 7 of the controller 6, tire IDs are registered as unique IDs of the tires 2a to 2d. The tire communication device 4 includes a pressure sensor 8 that detects tire air pressure, a temperature sensor 9 that detects tire temperature, and an acceleration sensor 10 that detects rotation of the tire 2, and these are connected to the controller 6. These sensors output detection signals to the controller 6. The controller 6 is connected to a transmitter 11 capable of transmitting a radio wave in the UHF (Ultra High Frequency) band. The tire communication device 4 is provided with a battery 12 as a power source for the tire communication device 4. The battery 12 corresponds to a power source.

  The vehicle body 5 is provided with a receiver (hereinafter referred to as a TPMS receiver) 13 that monitors the air pressure of the tire 2 based on the tire air pressure signal Stp received from the tire communication device 4. The TPMS receiver 13 is provided with a tire air pressure monitoring ECU (Electronic Control Unit) 14 that comprehensively manages the operation of the TPMS receiver 13 and a receiver 15 that can receive radio waves in the UHF band. In the memory 16 of the tire pressure monitoring ECU 14, a plurality of tire IDs of the respective tires 2a to 2d are registered. The receiving unit 15 includes an antenna 17a and a receiving circuit 17b that demodulates and amplifies received radio waves. For example, a display unit 18 installed on an in-vehicle instrument panel or the like is connected to the TPMS receiver 13.

  The controller 6 is provided with a wireless transmission control unit 19 that wirelessly transmits information necessary for the TPMS receiver 13 to determine the tire pressure from the transmission unit 11 to the vehicle body 5. When the wireless transmission control unit 19 detects that the tire 2 enters the rotation state (the vehicle 1 is in the traveling state) based on the detected acceleration value (acceleration signal) output from the acceleration sensor 10, the wireless transmission control unit 19 transmits the tire air pressure signal Stp. To start. That is, the tire pressure monitoring system 3 of this example is a direct method in which the tire communication device 4 transmits the tire pressure signal Stp to the vehicle body 5 by itself while the vehicle is traveling. In addition to the tire ID, the tire air pressure signal Stp includes a detected pressure value (pressure signal) acquired from the pressure sensor 8 and a detected temperature value (temperature signal) acquired from the temperature sensor 9. Each tire communication device 4 transmits radio waves with a time difference so that radio transmission does not overlap with other tire communication devices 4.

  As shown in FIG. 2, the TPMS receiver 13 of the present example enables each tire communication device 4 to determine the tire position based on the received signal strength indicator (RSSI) when the tire pressure signal Stp is received. The distances L1 to L4 from... Are arranged at different positions. In the case of this example, the distance L1 between the tire communication device 4a of the right front tire 2a and the receiver 13 is the smallest, followed by the distance L2 between the tire communication device 4b and the receiver 13 of the left front tire 2b, and the right rear tire 2c. The distance L3 between the tire communication device 4c and the receiver 13 and the distance L4 between the tire communication device 4d and the receiver 13 of the left rear tire 2d increase in this order.

  As shown in FIG. 1, the tire pressure monitoring ECU 14 is provided with a received signal strength measuring unit 20 that measures the received signal strength of the received radio wave received by the receiving unit 15. In addition, the tire pressure monitoring ECU 14 is provided with a tire position specifying unit 21 that specifies a tire position based on the received signal strength measured by the received signal strength measuring unit 20.

  When the TPMS receiver 13 receives the tire pressure signal Stp, the received signal strength measuring unit 20 measures the received signal strength of the tire pressure signal Stp. Subsequently, the tire position specifying unit 21 performs ID collation with the tire ID included in the tire air pressure signal Stp, and based on the received signal strength measured by the received signal strength measuring unit 20, the tire of the tire ID Identify the location. That is, if the received signal strength takes a value according to the distance L1, it is determined as the right front tire 2a. If the received signal strength takes a value according to the distance L2, it is determined as the left front tire 2b, and the received signal strength conforms to the distance L3. If the value is determined to be the right rear tire 2c, the received signal strength is determined to be the left rear tire 2d if the received signal intensity is a value according to the distance L4. When the tire pressure monitoring ECU 14 identifies the tire position of the tire ID, the tire pressure monitoring ECU 14 compares the detected pressure value included in the tire air pressure signal Stp with the low pressure threshold value to confirm the tire air pressure of the tire ID.

  The tire pressure monitoring ECU 14 of this example sets a low pressure threshold value based on the detected temperature value (tire temperature) in the tire pressure signal Stp. This is because an optimum low pressure threshold is set according to the tire temperature because the tire air pressure naturally increases as the tire temperature increases. Then, the tire air pressure monitoring ECU 14 compares the tire pressure with the low pressure threshold value set according to the tire temperature, and if the tire air pressure is less than the constant pressure threshold value, the low pressure tire is displayed on the display unit 18 in association with the tire position. To do.

  The tire pressure monitoring system 3 of the present example is provided with a correction function for correcting the received signal intensity according to the voltage of the battery 12 of the tire communication device 4 (hereinafter referred to as the battery voltage). This is because, as shown in FIG. 3, when the battery voltage (remaining battery level) decreases in the tire communication device 4, the transmission intensity of radio waves tends to be weakened. This is because the tire position is accurately determined by correcting the received signal intensity based on the battery voltage.

  In this case, as shown in FIG. 1, the controller 6 includes a battery voltage acquisition unit 22 that acquires a battery voltage. When the tire communication device 4 transmits the tire pressure signal Stp, the battery voltage acquisition unit 22 acquires the battery voltage data Dc by confirming the voltage of the battery 12, for example. In addition, the battery voltage acquisition part 22 comprises an acquisition means (battery voltage notification means), and the battery voltage data Dc comprises a fluctuation factor value.

  The controller 6 is provided with a battery voltage notification unit 23 that wirelessly transmits the battery voltage data Dc acquired by the battery voltage acquisition unit 22 to the vehicle body 5. When the tire communication device 4 transmits the tire pressure signal Stp to the vehicle body 5, the battery voltage notification unit 23 includes the battery voltage data Dc in the tire pressure signal Stp and transmits the tire pressure signal Stp to the vehicle body 5. The battery voltage notification unit 23 constitutes acquisition means (power supply voltage notification means).

  The tire pressure monitoring ECU 14 is provided with a received signal strength correction unit 24 that corrects the received signal strength based on the battery voltage data Dc transmitted from the tire communication device 4. The received signal strength correcting unit 24 corrects the received signal strength measured by the received signal strength measuring unit 20 with the battery voltage data Dc, and outputs the corrected received signal strength to the tire position specifying unit 21 for reception after correction. The tire position is specified by the signal strength. The received signal strength correction unit 24 constitutes a correction unit.

Next, operation | movement of the tire pressure monitoring system 3 of this example is demonstrated using FIG.
In step 101, when the tire communication device 4 transmits the tire pressure signal Stp, the battery voltage acquisition unit 22 acquires the battery voltage data Dc by checking the voltage of the battery 12.

  In step 102, when the tire communication device 4 transmits the tire pressure signal Stp, the battery voltage notification unit 23 adds the battery voltage data Dc to the tire pressure signal Stp and wirelessly transmits the tire pressure signal Stp. The tire pressure signal Stp is a signal including a start bit 25 indicating the start of the signal, a tire ID, tire information 26 (detected pressure value, detected temperature value), battery voltage data Dc, and an end bit 27 indicating the end of the signal. ing.

In step 103, the vehicle body 5 receives the tire pressure signal Stp by the TPMS receiver 13.
In step 104, the received signal strength measuring unit 20 measures the received signal strength when the receiving unit 15 receives the tire air pressure signal Stp.

  In step 105, the received signal strength correcting unit 24 corrects the received signal strength measured by the received signal strength measuring unit 20 based on the battery voltage data Dc included in the tire air pressure signal Stp. As the correction process, for example, the correction amount is determined according to the value of the battery voltage. For example, the received signal strength is corrected by multiplying the actual received signal strength by this correction amount. Then, the received signal strength correcting unit 24 outputs the corrected received signal strength to the tire position specifying unit 21.

  In step 106, the tire position specifying unit 21 specifies the tire position of the tire ID included in the tire air pressure signal Stp based on the corrected received signal strength. At this time, the tire position specifying unit 21 performs ID collation with the received tire ID, and confirms whether or not the tire ID is registered in its own memory 16. If the tire ID is registered, the tire position of the tire ID is specified based on the corrected received signal intensity.

  In step 107, the tire pressure monitoring ECU 14 determines whether or not the detected pressure value of the received tire ID is less than a low pressure threshold value. At this time, if the detected pressure value is less than the low pressure threshold, the process proceeds to step 108, and if the detected pressure value is not less than the low pressure threshold, the process proceeds to step 109.

  In step 108, if the detected pressure value is less than the low pressure threshold value, the tire air pressure monitoring ECU 14 issues a low pressure alarm on the display unit 18. The low pressure alarm displays, for example, the tire 2 having a low pressure on the display unit 18 together with its position.

  In step 109, if the detected pressure value is not less than the low pressure threshold value, the tire air pressure monitoring ECU 14 ends the process without doing anything. That is, the process ends without executing the low pressure alarm.

  As described above, in this example, the battery voltage of the tire communication device 4 is measured, the battery voltage data Dc is wirelessly transmitted to the TPMS receiver 13, and the actually measured received signal strength is corrected with the battery voltage data Dc. For this reason, even if the battery voltage of the tire communication device 4 decreases and the transmission intensity of the tire air pressure signal Stp decreases, the decrease is corrected, so that the tire pressure is determined from the received signal intensity of the tire air pressure signal Stp. Even when the position is specified, the tire position can be obtained with high accuracy.

According to the configuration of the present embodiment, the following effects can be obtained.
(1) The battery voltage data Dc of the tire communication device 4 is included in the tire pressure signal Stp, and the received signal strength of the tire pressure signal Stp measured by the TPMS receiver 13 is corrected by the battery voltage data Dc. For this reason, even when the tire position is determined from the received signal strength of the tire air pressure signal Stp, the tire position can be specified with a suitable received signal strength, so that the accuracy of specifying the tire position can be ensured. it can.

  (2) When the battery voltage of the tire communication device 4 decreases, the radio wave transmission intensity of the tire communication device 4 tends to decrease. However, in this example, since the battery voltage is monitored by the tire communication device 4 and the received signal strength is corrected based on the battery voltage data Dc, the same value as when the battery voltage of the tire communication device 4 is not lowered is obtained. It is possible to determine the tire position based on the received signal strength. Therefore, even if the battery voltage of the tire communication device 4 decreases, the accuracy of specifying the tire position can be ensured.

  (3) Since the correction calculation of the received signal strength is executed on the TPMS receiver 13 side, it is not necessary to provide the tire communication device 4 with the function of the correction calculation. Therefore, the structure of the tire communication device 4 is not complicated.

(Second Embodiment)
Next, a second embodiment will be described with reference to FIGS. The second embodiment is an example in which the received signal strength correction method described in the first embodiment is changed, and other basic portions are the same. Therefore, the same parts as those in the first embodiment are denoted by the same reference numerals, detailed description thereof is omitted, and only different parts are described in detail.

  By the way, the transmitter 11 of the tire communication device 4 is generally configured by a group of semiconductor parts. For this reason, it is known that when the temperature of the transmitter 11 increases as the temperature of the tire communication device 4 increases, the output intensity of the radio wave of the transmitter 11 tends to decrease as shown in FIG. . For this reason, when the tire position is specified from the received signal strength of the tire air pressure signal Stp, it is understood that the tire position determination accuracy can be ensured by correcting the received signal strength with the temperature of the tire communication device 4 (that is, the tire temperature). . The wireless transmission control unit 19 constitutes acquisition means (tire temperature notification means).

  The received signal strength correction unit 24 of this example corrects the received signal strength based on the tire temperature and the battery voltage. Thus, the reason why the received signal intensity is corrected by the two parameters of the tire temperature and the battery voltage is that this can correct the received signal intensity more accurately. Of course, the received signal may be corrected only at the tire temperature, but in this example, an example in which the received signal intensity is corrected by both the tire temperature and the battery voltage will be described.

  Next, operation | movement of the tire pressure monitoring system 3 of this example is demonstrated using FIG.3, FIG.5 and FIG.6. In this example, only the portion for correcting the received signal strength is different from that of the first embodiment, so only this portion will be extracted and described.

In step 201, the reception signal strength correction unit 24 corrects the reception signal strength of the tire pressure signal Stp based on the detected temperature value and the battery voltage data Dc included in the tire pressure signal Stp. At this time, the radio wave transmission intensity of the transmission unit 11 when the voltage of the battery 12 is the reference voltage V0 shown in FIG. 3 is calculated as Pv0, and the radio wave transmission intensity of the transmission unit 11 when the voltage of the battery 12 is V1 is calculated as Pv1. . Further, the radio wave transmission intensity of the transmission unit 11 when the tire temperature shown in FIG. 5 is the reference temperature T0 is calculated as Pto, and the radio wave transmission intensity of the transmission unit 11 when the tire temperature is T1 is calculated as Pt1. Then, assuming that the received signal strength actually measured by the received signal strength measuring unit 20 is Ea, the received signal strength correcting unit 24 corrects the received signal strength using the following equation (A).
Ea × (Pv0 / Pv1) × (Pt0 / Pt1) (A)
The corrected received signal strength is calculated as a value corresponding to V0 and T0, and as a result, it is obtained as a value according to the current tire temperature and battery voltage. Therefore, if the tire position is specified based on the corrected received signal intensity, the tire position can be determined with a suitable received signal intensity, so that the accuracy of specifying the tire position can be ensured.

According to the configuration of the present embodiment, the following effects can be obtained in addition to the same effects as (1) and (3) of the first embodiment.
(4) Using the detected temperature value output from the temperature sensor 9, the received signal strength of the tire air pressure signal Stp is corrected. For this reason, even if the transmission unit 11 of the tire communication device 4 tends to increase in temperature and the transmission intensity of radio waves tends to decrease, the received signal intensity is corrected with the detected temperature value. The tire position can be determined. Therefore, the accuracy of specifying the tire position can be ensured without being affected by the temperature rise of the transmitter 11.

  (5) Since the received signal strength of the tire pressure signal Stp is corrected by both the tire temperature and the battery voltage, the received signal strength can be derived with a more accurate value. Therefore, the effect is further enhanced in ensuring the accuracy of specifying the tire position.

(Third embodiment)
Next, a third embodiment will be described with reference to FIGS. In the third embodiment, only the parts different from the first embodiment will be described in detail.

  As shown in FIG. 7, the controller 6 is provided with a data acquisition unit 31 that acquires data necessary to calculate the transmission intensity. When the tire communication device 4 transmits the tire pressure signal Stp, the data acquisition unit 31 acquires the battery voltage data Dc from the battery 12 and acquires the detected temperature value from the temperature sensor 9. In addition, the data acquisition unit 31 measures the elapsed time from the start of use of the battery 12 with a counter or the like, and measures the use time of the battery 12. The data acquisition unit 31 constitutes an acquisition unit.

  The memory 7 of the controller 6 stores correction coefficients α and β used when correcting the transmission intensity of the tire pressure signal Stp. By the way, the power supply voltage varies depending on the voltage value and the date of use in the usage environment. In addition, the rate of decrease in battery power varies depending on the years of use in the usage environment. The battery voltage correction coefficient α in this example is set as a correction coefficient for eliminating these variations. Further, the transmission intensity of the transmission unit 11 has output variations in the transmission unit 11 (for each tire communication device 4) with respect to the temperature. Therefore, the temperature correction coefficient β of this example is set as a correction coefficient for eliminating this variation. When the tire pressure signal Stp is transmitted, the data acquisition unit 31 calculates correction coefficients α and β to be used based on the tire pressure, the tire temperature, the usage time of the battery 12, and the like.

  The controller 6 is provided with a correction coefficient notification unit 32 that wirelessly transmits the correction coefficients α and β to be used to the vehicle body 5. The correction coefficient notification unit 32 determines the correction coefficients α and β to be used based on the battery voltage and the tire temperature at that time, and puts them on the tire air pressure signal Stp and notifies the vehicle body 5 of the correction coefficients. The correction coefficient notification unit 32 constitutes acquisition means (correction coefficient notification means).

  The received signal strength correcting unit 24 corrects the received signal strength measured by the received signal strength measuring unit 20 based on the correction coefficients α and β received from the tire communication device 4, and specifies the corrected received signal strength as a tire position. The tire position is specified based on the received signal strength after correction.

Next, operation | movement of the tire pressure monitoring system 3 of this example is demonstrated using FIG.
In step 301, when the tire communication device 4 transmits the tire pressure signal Stp, the data acquisition unit 31 acquires the battery voltage data Dc by checking the voltage of the battery 12.

In step 302, the data acquisition unit 31 acquires a detected temperature value from the temperature sensor 9.
In step 303, the data acquisition unit 31 acquires the battery voltage correction coefficient α and the temperature correction coefficient β to be used at this time from the acquired detected temperature value and the usage time of the battery 12.

In step 304, when the tire communication device 4 transmits the tire pressure signal Stp, the correction coefficient notification unit 32 adds the correction coefficients α and β to the tire pressure signal Stp and wirelessly transmits the tire pressure signal Stp.
The vehicle body 5 receives the tire pressure signal Stp by the TPMS receiver 13 (step 103), and measures the received signal strength (step 104).

In step 305, the received signal strength correcting unit 24 corrects the received signal strength measured by the received signal strength measuring unit 20 based on the correction coefficients α and β included in the tire air pressure signal Stp. At this time, as a correction process, if the actually measured received signal intensity is Ea, a correction value is calculated by the following equation (B), for example.
Ea × α × β (B)
Since subsequent steps 106 to 109 are the same as those in the first embodiment, the description thereof is omitted.

  As described above, in the present example, when the tire communication device 4 transmits the tire pressure signal Stp, the tire communication device 4 of the tire communication device 4 is based on the battery voltage data Dc, the detected temperature value, the battery voltage correction coefficient α, and the temperature correction coefficient β. Correct the transmission strength. For this reason, it is possible to correct the received signal intensity by a simple calculation using the correction coefficients α and β. Therefore, even if a measure for deriving the received signal strength with an accurate value is taken, the processing load on the TPMS receiver 13 can be reduced.

According to the configuration of the present embodiment, in addition to the same effects as (1) of the first embodiment, the following effects can be obtained.
(6) Since the received signal intensity is corrected by the correction coefficients α and β, the correction process can be performed with a simple calculation.

(Fourth embodiment)
Next, a fourth embodiment will be described with reference to FIGS. The fourth embodiment is a modification of the correction method of the third embodiment, and this embodiment will be described in detail only for different parts.

  As shown in FIG. 9, the transmission unit 11 is provided with a transmission intensity measurement circuit 35 that measures the transmission intensity of the radio wave transmitted from the transmission unit 11. When the tire pressure signal Stp is transmitted from the transmission unit 11, the transmission intensity measurement circuit 35 measures the transmission intensity of the radio wave before the radio wave is radiated (or during radio wave transmission), and uses the measured transmission intensity data Dk. Output to the controller 6.

  The controller 6 is provided with a transmission intensity notification unit 36 that wirelessly communicates the transmission intensity data Dk measured by the transmission intensity measurement circuit 35 to the vehicle body 5. When the tire communicator 4 transmits the tire pressure signal Stp, the transmission strength notification unit 36 notifies the vehicle body 5 of the transmission strength data Dk on the end of the signal. The transmission strength notification unit 36 constitutes acquisition means (transmission strength notification means).

  The reception signal strength correction unit 24 determines whether or not the tire air pressure signal Stp is transmitted with an appropriate transmission strength based on the transmission strength data Dk received from the tire communication device 4. By the way, as shown in FIG. 10, if the tire communication devices 4a to 4c have a sufficient power supply voltage, the transmission strength data Dk notifying the transmission strength close to Full is transmitted, whereas the tire having a low power supply voltage. From the communication device 4d, transmission strength data Dk for notifying low transmission strength is transmitted. Therefore, the TPMS receiver 13 can know the transmission capability of the tire communication device 4 by confirming the value of the transmission intensity data Dk.

  Therefore, the received signal strength correction unit 24 obtains a difference between the received transmission strength data Dk and a reference value (transmission strength that can be obtained when the transmission capability is Full), and corrects the received signal strength based on this difference. . The received signal strength correction unit 24 outputs the corrected received signal strength to the tire position specifying unit 21 and specifies the tire position based on the corrected received signal strength.

Next, operation | movement of the tire pressure monitoring system 3 of this example is demonstrated using FIG.
In step 401, in the process in which the transmission unit 11 transmits the tire pressure signal Stp, the transmission strength measurement circuit 35 measures the transmission strength of the tire pressure signal Stp.

In step 402, the transmission strength notification unit 36 acquires transmission strength data Dk from the transmission strength measurement circuit 35.
In step 403, when the tire communication device 4 transmits the tire pressure signal Stp, the transmission strength notification unit 36 adds the transmission strength data Dk to the tire pressure signal Stp and wirelessly transmits it.

The vehicle body 5 receives the tire pressure signal Stp by the TPMS receiver 13 (step 103), and measures the received signal strength (step 104).
In step 404, the reception signal strength correction unit 24 corrects the reception signal strength measured by the reception signal strength measurement unit 20 based on the transmission strength data Dk included in the tire air pressure signal Stp. That is, the received signal strength correction unit 24 obtains a difference between the transmission strength data Dk and the reference value, and corrects the received signal strength based on this difference. At this time, as a correction process, for example, a difference is obtained as a certain coefficient, and a correction value is calculated by multiplying the actual reception signal strength by this coefficient.

Since subsequent steps 106 to 109 are the same as those in the first embodiment, the description thereof is omitted.
As described above, in this example, the transmission intensity measurement circuit 35 is provided in the transmission section 11, and the tire pressure signal Stp transmitted from the transmission section 11 is actually measured by the transmission intensity measurement circuit 35. Then, the actually measured transmission strength data Dk is transmitted to the TPMS receiver 13, and the received signal strength is corrected based on the difference between the transmission strength data Dk and the reference value. Therefore, it is possible to calculate the actual received signal strength with a value close to the ideal value, which is highly effective in improving the accuracy of tire position determination.

According to the configuration of the present embodiment, in addition to the same effects as (1) of the first embodiment, the following effects can be obtained.
(7) The transmission unit 11 is provided with a transmission intensity measurement circuit 35, the transmission intensity that the transmission unit 11 can actually transmit is measured by the transmission intensity measurement circuit 35, and the received signal intensity is corrected based on the actually measured transmission intensity data Dk. . Therefore, the accuracy of the tire position determination can be improved.

Note that the embodiment is not limited to the configuration described so far, and may be modified as follows.
In each embodiment, the variation factor value is not limited to the battery voltage data Dc, the detected temperature value, the usage time of the battery 12, and the like. In short, any value may be used as long as it causes a change in received signal strength.

In each embodiment, the power source is not limited to the battery 12 and may be a capacitor, for example.
In each embodiment, the tire pressure monitoring system 3 is not limited to the direct method, and may be an indirect method, for example.

In each embodiment, the frequency of the radio wave of the tire pressure monitoring system 3 is not limited to UHF, and other bands such as LF (Low Frequency) may be used.
The correction calculation of the received signal strength is not limited to being performed on the vehicle body 5 side. For example, the correction calculation may be performed on the tire communication device 4 side, and the calculation result may be notified to the vehicle body 5.

  In the third embodiment, the correction coefficient is not limited to the battery voltage and the temperature, but may be a coefficient for correcting a voltage variation with respect to the temperature, for example. The correction coefficients α and β may be any data.

In each embodiment, the tire air pressure detecting means is not limited to the name of the tire communication device 4 and may be a tire valve, for example.
Next, technical ideas that can be grasped from the above-described embodiment and other examples will be described below together with their effects.

  (A) In any one of claims 1 to 5, the acquisition means detects a power supply voltage of the tire air pressure detection means, and notifies the vehicle body of the power supply voltage as the variation factor value; and Tire temperature notification means for detecting the temperature of the tire and notifying the vehicle body of the detected temperature value as the variation factor value, and the correction means uses the received signal intensity measured in the vehicle body as the power supply voltage and Correction is performed on the vehicle body side based on the detected temperature value. According to this configuration, the received signal strength can be set to a more suitable value, so that the accuracy of specifying the tire position can be improved.

  (B) In any one of claims 1 to 5 and the technical idea (A), the correction unit calculates an ideal received signal intensity based on the variation factor value acquired by the acquisition unit, and performs the calculation. The result is notified to the vehicle body wirelessly. According to this configuration, it is not necessary to perform correction calculation of the received signal strength on the vehicle body side, so that the processing load on the vehicle body can be reduced.

  2 (2a to 2d) ... tyre, 3 ... tyre air pressure monitoring system, 4 (4a to 4d) ... tyre communication device as tire air pressure detecting means, 5 ... vehicle body, 12 ... battery as power source, 19 ... acquisition means (tire) Wireless transmission control unit constituting temperature notification means), 22 battery voltage acquisition unit constituting acquisition means (battery voltage notification means), 23 battery voltage notification part constituting acquisition means (power supply voltage notification means), 24 ... Received signal intensity correction unit constituting correction means, 31... Data acquisition part constituting acquisition means, 32... Correction coefficient notification part constituting acquisition means (correction coefficient notification means), 36... Acquisition means (transmission intensity notification means) Transmission strength notifying unit, Stp... Tire pressure signal, Dc... Battery voltage data constituting variation factor values, .alpha., .Beta.

Claims (5)

A tire pressure detection means for detecting tire pressure is attached to each tire, a tire pressure signal is transmitted to the vehicle body wirelessly from the tire pressure detection means, and based on the received signal strength when the tire pressure signal is received by the vehicle body, In a tire air pressure monitoring system for monitoring the air pressure of a tire while specifying the position of the tire,
Obtaining means for obtaining a variation factor value of the transmission intensity of the tire pressure signal;
A tire pressure monitoring system, comprising: correction means for correcting the received signal intensity based on the variation factor value acquired by the acquisition means. The acquisition means is a power supply voltage notification means for detecting a power supply voltage of the tire air pressure detection means and notifying the vehicle body of the power supply voltage as the variation factor value wirelessly,
The tire pressure monitoring system according to claim 1, wherein the correction unit corrects the received signal intensity measured in the vehicle body on the vehicle body side based on the power supply voltage. The acquisition unit is a tire temperature notification unit that detects the temperature of the tire and wirelessly notifies the vehicle body of the detected temperature value as the variation factor value,
The tire pressure monitoring system according to claim 1 or 2, wherein the correction means corrects the received signal intensity measured in the vehicle body on the vehicle body side based on a detected temperature value of the tire. The acquisition means is a correction coefficient notifying means for determining a correction coefficient for correcting the received signal intensity based on the variation factor value and notifying the vehicle body of the correction coefficient wirelessly,
2. The tire pressure monitoring system according to claim 1, wherein the correction unit corrects the reception signal intensity measured in the vehicle body on the vehicle body side based on the correction coefficient. 3. The acquisition means is a transmission intensity notification means for measuring the transmission intensity of the tire pressure signal and notifying the vehicle body of the transmission intensity wirelessly,
The said correction | amendment means calculates | requires the difference of the said transmission strength and its reference value, and correct | amends the said received signal strength measured in the said vehicle body with the said difference in the said vehicle body side. Tire pressure monitoring system.

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