Tire position determination system

Abstract

The present invention relates to a tire position determination system. A starter is used to determine the tire position of each of a plurality of tires. The tire position determination system is provided on a vehicle having a first tire and a second tire, and comprises a starter for sending a command signal, a first detector mounted on the first tire, a second detector mounted on the second tire, and a monitoring unit. The distance between the first tire and the starter is less than the distance between the second tire and the starter. The first detector and the second detector each include an acceleration sensor. The detection signal includes a detection value of the acceleration sensor. The monitoring unit uses the positional relationship between the detector and the starter estimated based on the detection value of the acceleration sensor to perform determination processing for determining the position of the first tire and the position of the second tire.

Description

Technical Field

[0001] The present disclosure relates to a tire position determination system. Background Art

[0002] Conventionally, in a system for monitoring the air pressure of a vehicle's tires (TPMS: Tire Pressure Monitoring System), a detector is mounted on each of a plurality of tires. The detector mounted on each of the plurality of tires transmits air pressure information to a processing device such as an ECU mounted on the vehicle body.

[0003] In such TPMS, there is a system with an automatic positioning function that automatically determines which tire of multiple tires a detector is installed on. For example, Patent Document 1 (Japanese Patent Publication No. 2019-48547) discloses a tire state information detection system that determines which tire of a dual tire used in a truck or the like a detector is installed on.

[0004] In addition, there is a system with a starter in such TPMS. The starter sends a command signal to a specified tire position. Based on the command signal received from the starter, the detector sends a response signal to a processing device such as an ECU provided on the vehicle body side. The processing device determines that the detector that sent the response signal is installed on a tire at a specified tire position.

[0005] Patent Document 1: Japanese Patent Application Publication No. 2019-48547

[0006] However, if starters are provided for multiple tire positions, the cost may increase. On the other hand, when one starter is used to send command signals to multiple detectors, the processing device provided on the vehicle body side may not be able to determine from which detector the response signal is received. Summary of the invention

[0007] The present disclosure has been made to solve the above-mentioned problems, and an object of the present disclosure is to determine the tire position of each of a plurality of tires using one starter.

[0008] A tire position determination system according to one embodiment of the present disclosure is a tire position determination system provided in a vehicle having a first tire and a second tire different from the first tire. The tire position determination system comprises: a starter that sends a command signal; a first detector that is mounted on the first tire and sends a detection signal when receiving the command signal; a second detector that is mounted on the second tire and sends a detection signal when receiving the command signal; and a monitoring unit that is configured to receive the detection signal. The first distance between the first tire and the starter is less than the second distance between the second tire and the starter. The first detector and the second detector each include an acceleration sensor that detects acceleration in a direction orthogonal to the rotation axis. The detection signal includes a detection value of the acceleration sensor. When the monitoring unit receives a detection signal from the first detector or the second detector, the monitoring unit uses the positional relationship between the detector that sends the detection signal and the starter that is estimated based on the detection value of the acceleration sensor included in the received detection signal to perform a determination process to determine whether the detector that sends the detection signal is the first detector or the second detector.

[0009] According to the above method, in addition to the signal strength of the detection signal received from each detector, the value of the acceleration detected by each detector is also used, thereby being able to identify more rotation conditions for each tire, and by diversifying the change of the rotation condition, being able to identify more tire positions. Thus, the tire position determination system uses one actuator to determine the tire position of each of the plurality of tires.

[0010] According to the present disclosure, the tire position of each of a plurality of tires can be determined using one actuator. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 This is a diagram schematically showing the configuration of a vehicle to which the tire position determination system according to the first embodiment is applied.

[0012] Figure 2 is a side view of the vehicle.

[0013] Figure 3 : is a block diagram showing an example of the structure of a tire detector.

[0014] Figure 4 FIG. 1 is a diagram showing an example of the appearance of a tire detector.

[0015] Figure 5 This is a conversion diagram of the arrangement of the tire detector when the tire rotates.

[0016] Figure 6 This is a graph showing an example of attenuation when the radio wave intensity T1 is used as the transmission intensity.

[0017] Figure 7It is the appearance description of the starter and tire. Figure 6 Figure of the diagram shown.

[0018] Figure 8 This is a flowchart showing an example of tire position determination processing in the first embodiment.

[0019] Fig. 9 This is a diagram for explaining the configuration of the starter in a modified example of the first embodiment.

[0020] Fig.10 This is a graph showing an example of attenuation when the radio wave intensity T2 is used as the transmission intensity.

[0021] Fig.11 It is the appearance description of the starter and tire. Fig.10 Figure of the diagram shown.

[0022] Fig.12 This is a flowchart showing an example of tire position determination processing in the second embodiment.

[0023] Fig.13 This is a diagram for explaining the configuration of the starter in a variation of Implementation Example 2.

[0024] Description of Reference Numerals

[0025] 1h~12h…configuration; 10~16…tire; 30~36…tire detector; 38…pressure sensor; 39…acceleration sensor; 40…TPMS receiver; 45…monitoring unit; 46, 86…storage unit; 47, 87…processing unit; 52…display unit; 60~62…starter; 85…controller; 100…vehicle; A1, A2, L1…antenna; CP1, CP3, CP5…center point; CR…receiving circuit; CT…transmitting circuit; D1~D4…distance; FR…direction; G…acceleration; H, L, M, R1, R2, T1, T2…radio wave intensity; LnH, LnL, LnM…line; P…tire pressure; RD1…rotation axial direction; RD2…rotation circumferential direction; RD3…rotation radial direction; WH…wheel; Wd3, Wd5…width. DETAILED DESCRIPTION

[0026] Hereinafter, the embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In addition, the same reference numerals are given to the same or corresponding parts in the drawings, and their description will not be repeated.

[0027] [Implementation Method 1]

[0028] <Overall structure>

[0029] Figure 11 is a diagram schematically showing a configuration of a vehicle 100 to which the tire position determination system according to the first embodiment is applied.

[0030] The vehicle 100 in the first embodiment is a vehicle having tires 11 and 12 on the front side as steering wheels and tires 13 to 16 on the rear side as non-steering wheels. Each of the tires 11 to 16 is mounted at one tire mounting position. Figure 1 The direction FR shown is the forward direction of the vehicle 100. In addition, the tires 13 to 16 may be dual tires in which two tires are mounted at one tire mounting position.

[0031] In the following description, the vertical direction when the vehicle 100 is arranged on a plane is referred to as the "Z-axis direction", the direction perpendicular to the Z-axis direction and along the advancing direction of the vehicle 100 is referred to as the "positive direction of the X-axis", and the direction perpendicular to the X-axis direction is referred to as the "Y-axis direction". In addition, in the following, the positive direction of the Z-axis in each figure is sometimes referred to as the upper side, the negative direction of the Z-axis is referred to as the lower side, the positive direction of the X-axis is referred to as the front side, the negative direction of the X-axis is referred to as the rear side, the positive direction of the Y-axis is referred to as the right side, and the negative direction of the Y-axis is referred to as the left side.

[0032] The vehicle 100 is provided with a system (TPMS) for monitoring the air pressure of each tire. Specifically, the vehicle 100 is provided with a plurality of tire detectors 31 to 36 for respectively detecting the air pressure of the tires, starters 61 and 62, and a TPMS receiver 40. The tire detectors 31 to 36 are respectively mounted on the wheels of the tires 11 to 16. The tire detectors 31 to 36 may be formed integrally with a valve for sucking air into each tire. In addition, the tire detectors 31 to 36 may also be formed separately from the valve.

[0033] Each of the tire detectors 31 to 36 is activated when a predetermined activation condition is satisfied, detects the air pressure of each tire, and transmits a radio wave signal (hereinafter also referred to as a "UHF signal") in the UHF (Ultra High Frequency) band containing the detection result. The "predetermined activation condition" is preset to be satisfied regularly or irregularly. Thus, each of the tire detectors 31 to 36 is intermittently activated at different timings to transmit the UHF signal.

[0034] The UHF signals outputted by the tire detectors 31 to 36 include at least information indicating a unique ID number for identifying the tire detectors 31 to 36. Specifically, the UHF signals outputted by the tire detectors 31 to 36 include ID numbers "01" to "06", respectively.

[0035] The UHF signals outputted from the tire detectors 31 to 36 include information indicating the tire air pressure in addition to the information indicating the ID number. The TPMS receiver 40 receives the UHF signals outputted from the tire detectors 31 to 36 , thereby monitoring the air pressure of each tire.

[0036] Tires 11 to 16 use the same specifications and structure so that the tires can rotate. Therefore, tire detectors 31 to 36 also use the same structure. Hereinafter, when there is no need to distinguish between tires 11 to 16, tires 11 to 16 are simply referred to as "tire 10". In addition, when there is no need to distinguish between tire detectors 31 to 36, tire detectors 31 to 36 are simply referred to as "tire detector 30". The tire diameters of the tires 11 to 16 are the same.

[0037] The TPMS receiver 40 is provided on the vehicle body side of the vehicle 100. The TPMS receiver 40 includes a monitoring unit 45 for monitoring the air pressure of each tire. The monitoring unit 45 includes a storage unit 46, a processing unit 47, and an antenna A1. The antenna A1 is configured to be able to receive a UHF signal transmitted from the tire detector 30. The monitoring unit 45 receives the UHF signal received by the antenna A1.

[0038] The processing unit 47 is configured to include a processor such as a CPU (Central Processing Unit) not shown, a memory, and an input / output buffer. The memory includes a ROM (Read Only Memory) and a RAM (Random Access Memory). The processor expands the program stored in the ROM to the RAM for execution. The various processes executed by the processing unit 47 are described in the program stored in the ROM.

[0039] In the storage unit 46, information indicating the position of the tire on which each tire detector 30 is mounted and information indicating the tire pressure are stored in association with the ID number of each tire detector 30. In the first embodiment, a total of six tire positions (front left side, front right side, rear first row left side, rear first row right side, rear second row left side, and rear second row right side) are stored corresponding to the ID number of each tire detector 30.

[0040] Specifically, the tire position "front left side" is associated with ID number "01", and the tire position "front right side" is associated with ID number "02". In addition, the tire position "rear first column left side" is associated with ID number "03", and the tire position "rear first column right side" is associated with ID number "04". In addition, the tire position "rear second column left side" is associated with ID number "05", and the tire position "rear second column right side" is associated with ID number "06". When it is detected that the tire is rotated and installed in a different tire position, the monitoring unit 45 updates the relationship between the ID number and the tire position.

[0041] When the monitoring unit 45 receives the UHF signal, it compares the ID number included in the UHF signal with the ID number stored in the storage unit 46 to obtain the tire position associated with the ID number. The monitoring unit 45 updates the air pressure of the obtained tire position using the tire air pressure included in the UHF signal.

[0042] For example, when the monitoring unit 45 receives a UHF signal including the ID number "01", it refers to the correspondence between the ID number "01" and the tire position stored in the storage unit 46. In the storage unit 46, the tire position "front left" is associated with the ID number "01". The monitoring unit 45 updates the air pressure of the "front left" using the tire air pressure included in the UHF signal.

[0043] The TPMS receiver 40 can display the information of the correspondence between the tire position and the tire pressure stored in the storage unit 46 on the display unit 52. The display unit 52 is arranged at a position visible to the driver. The display unit 52 is arranged on, for example, an instrument panel in the vehicle.

[0044] The monitoring unit 45 determines whether the tire pressure included in the received UHF signal is below the low pressure threshold. If it is below the low pressure threshold, the monitoring unit 45 displays the tire position at the low pressure threshold together with the warning on the display unit 52. The TPMS receiver 40 determines the tire pressure every time it receives the UHF signal and monitors the air pressure of each tire. As a result, the driver can recognize the position of the tire below the low pressure threshold in real time.

[0045] Starters 61 and 62 for starting the rear tire detectors 33 to 36 are electrically connected to the TPMS receiver 40. Starter 61 is arranged near the left tire 13 of the first rear row and is used to start the tire detectors 33 and 35. Starter 62 is arranged near the right tire 14 of the first rear row and is used to start the tire detectors 34 and 36.

[0046] The starters 61 and 62 have the same structure. Hereinafter, when there is no need to distinguish between the starters 61 and 62, they are described as "starter 60" without distinguishing between them.

[0047] Starter 60 includes an antenna (not shown) and is configured to output a radio wave signal in the LF (Low Frequency) band (hereinafter also referred to as an "LF signal"). Starter 60 transmits the LF signal to tire detector 30 based on a command from monitoring unit 45. The LF signal is a command signal for causing tire detector 30 to perform a specific operation.

[0048] Each tire detector 30 can receive the LF signal from the starter 60. In addition, each tire detector 30 is configured to output a UHF signal when the above-mentioned predetermined start condition is satisfied. The "predetermined start condition" in the first embodiment includes receiving the LF signal. That is, each tire detector 30 transmits the UHF signal on the condition that the LF signal is received.

[0049] The storage unit 46 stores the relationship between each tire position and the position of the starters 61 and 62. For example, the storage unit 46 stores that the tire position closest to the starter 61 is "the first rear row left side" and the tire position next closest is "the second rear row left side".

[0050] Figure 2 is a side view of the vehicle 100. Figure 2 , the vehicle 100 is shown when viewed from the negative direction side of the Y axis. The starters 61 and 62 are respectively arranged on the positive direction side of the X axis of the rear tires 13 and 14. That is, the tire 13 is arranged between the starter 61 and the tire 15. In addition, the tire 14 is arranged between the starter 62 and the tire 16.

[0051] <Structure of Tire Detector 30>

[0052] Below, use Figure 3 and Figure 4 An example of the configuration of tire detector 30 will be described. Figure 3 is a block diagram showing an example of the structure of the tire detector 30. Figure 3 As shown, tire detector 30 includes controller 85 , pressure sensor 38 , acceleration sensor (G sensor) 39 , antennas L1 and A2 , receiving circuit CR, and transmitting circuit CT.

[0053] The controller 85 includes a storage unit 86 and a processing unit 87. The processing unit 87 is configured to include a processor such as a CPU (not shown), a memory, and an input / output buffer. The memory includes a ROM and a RAM. The processor expands the program stored in the ROM to the RAM for execution. Various processes performed by the processing unit 87 are described in the program stored in the ROM.

[0054] The storage unit 86 stores the Figure 1 The ID numbers shown are unique to each tire detector 30. In the storage unit 86 of the tire detectors 31 to 36, "01" to "06" are stored as ID numbers, respectively.

[0055] The antenna L1 receives the LF signal transmitted by the starters 61, 62. The controller 85 receives the LF signal received by the antenna L1 via the receiving circuit CR. The receiving circuit CR detects the reception strength of the LF signal received by the antenna L1.

[0056] The receiving circuit CR outputs a voltage (RSSI (Received Signal Strength Indicator) signal) corresponding to the radio wave strength of the input LF signal. The controller 85 performs A / D conversion on the voltage and obtains the strength of the received signal (radio wave) (hereinafter referred to as "RSSI value"). The RSSI value in embodiment 1 is obtained as a voltage ratio "dBuV" relative to 1uV. In addition, the unit of the RSSI value can be voltage "V" or power "W". The receiving circuit CR is configured not to receive LF signals with a radio wave strength less than M, but to be able to receive LF signals with a radio wave strength greater than M.

[0057] The controller 85 controls the transmission circuit CT to transmit the UHF signal from the antenna A2. The controller 85 outputs the UHF signal when a predetermined start condition is satisfied. The tire detector 30 includes a battery (not shown) and operates with power supplied from the battery. The battery is configured so that it cannot be easily charged from the outside. Therefore, in the tire detector 30 of the first embodiment, it is preferable to reduce the operating time as much as possible to suppress the power consumption of the tire detector 30.

[0058] From this point of view, the "predetermined activation condition" is pre-set to minimize the activation frequency of tire detector 30. For example, the predetermined activation condition may include a timer activation condition in which a predetermined timer time has passed since the last stop time measured by a timer, an acceleration activation condition in which the detection result of acceleration sensor 39 (hereinafter also referred to as "acceleration G") reaches a specific value (e.g., a maximum value or a minimum value), and the like.

[0059] The “timer time” used for the timer start condition may be a fixed value or a variable value that changes according to the acceleration G. For example, the controller 85 may determine whether the tire is rotating based on the acceleration G detected by the acceleration sensor 39 and change the set timer time.

[0060] In tire detector 30 of Embodiment 1, the predetermined activation condition includes receiving an LF signal from starter 60. Upon receiving the LF signal, tire detector 30 transmits a UHF signal including detection information indicating an ID number, tire pressure P, acceleration G, RSSI value, etc. to monitoring unit 45.

[0061] The pressure sensor 38 detects the tire pressure and outputs the detection result (hereinafter also referred to as "tire pressure P") to the controller 85. The acceleration sensor 39 detects the acceleration in a uniaxial direction generated in a direction orthogonal to the rotation axis of the tire 10 and outputs the detection result to the controller 85. The acceleration sensor 39 of the first embodiment uses the rotation circumferential direction of the tire 10 as the detection direction. In addition to the pressure sensor 38 and the acceleration sensor 39, the tire detector 30 may also include a temperature sensor for detecting the tire temperature.

[0062] Figure 4 1 is a diagram showing an example of the appearance of the tire detector 30. The tire detector 30 is fixedly mounted on the wheel WH of the tire 10. The position of the tire detector 30 changes as the tire 10 rotates. Figure 4 , the rotation axial direction RD1, the rotation circumferential direction RD2, and the rotation radial direction RD3 of the wheel WH when the tire 10 rotates are shown. As described above, the acceleration sensor 39 of the tire detector 30 in the first embodiment is a uniaxial acceleration sensor with the rotation circumferential direction RD2 as the detection direction.

[0063] <Detection value of the acceleration sensor 39>

[0064] Figure 5 This is a diagram showing a transition of the arrangement of tire detector 33 when tire 13 rotates. Figure 5 The figure shows the transition of the arrangement of tire detector 33 when viewing tire 13 from the positive side in the Y-axis direction (outside of vehicle 100 ). Figure 5 Indicates the detection value of the acceleration sensor 39 when the vehicle 100 is stopped.

[0065] exist Figure 5, configurations 1h to 12h are shown as 12 pattern configuration examples of tire detectors 33. Configuration 12h of tire detector 33 is a configuration in which tire detector 33 is located on a rotation radial direction RD3 from center point CP3 of tire 13 toward the positive direction of the Z axis. Hereinafter, configuration 12h is referred to as a "0 degree" or "+360 degree" configuration.

[0066] Arrangement 1h is the arrangement of tire detector 33 when tire 13 is rotated by θ degrees in the clockwise direction from the state of arrangement 12h. Figure 5 The angle θ in the figure is 30 degrees. Hereinafter, the configuration 1h is referred to as the "+30 degree" configuration. In addition, the configuration 2h is the configuration of the tire detector 33 when the tire 13 is rotated clockwise by θ degrees from the state of the configuration 1h. Hereinafter, the configuration 2h is referred to as the "+60 degree" configuration.

[0067] In addition, configuration 3h is the configuration of tire detector 33 when tire 13 is rotated clockwise by θ degrees from the state of configuration 2h. Hereinafter, configuration 3h is referred to as a "+90 degree" configuration. Figure 5 , an example of arrangement of tire detectors 33 in 12 patterns of 0 degree (360 degrees), 30 degrees, +60 degrees, +90 degrees, +120 degrees, +150 degrees, +180 degrees, +210 degrees, +240 degrees, +270 degrees, +300 degrees, and +330 degrees is shown.

[0068] like Figure 4 As described above, the acceleration sensor 39 of the tire detector 33 is a uniaxial acceleration sensor that detects acceleration in only one direction, and uses the tire circumferential direction (rotational circumferential direction RD2) as the detection direction. Figure 5 As shown, when the tire detector 33 is in the configuration 3h (+90 degrees) or in the configuration 9h (+270 degrees), the gravity acceleration in the detection direction is maximum.

[0069] exist Figure 5 In the example of FIG. 1 , when the tire detector 33 is installed in the position of 9h, the detection value of the acceleration sensor 39 becomes +1G. That is, when the tire detector 33 is installed in the position of 3h, the detection value of the acceleration sensor 39 becomes -1G.

[0070] When the tire detector 33 is in the configuration 8h or the configuration 10h, the detection value of the acceleration sensor 39 is +√2 / 3 G. When the tire detector 33 is in the configuration 7h or the configuration 11h, the detection value of the acceleration sensor 39 is +1 / 2 G. When the tire detector 33 is in the configuration 12h or the configuration 6h, the detection value of the acceleration sensor 39 is 0 G.

[0071] When the tire detector 33 is in the configuration 1h or configuration 5h, the detection value of the acceleration sensor 39 becomes -1 / 2G. When the tire detector 33 is in the configuration 2h or configuration 4h, the detection value of the acceleration sensor 39 becomes -√2 / 3G. In addition, depending on the installation direction of the tire detector 33, Figure 5 The sign of the gravitational acceleration of the detected value shown may be reversed.

[0072] The tire detector 33 transmits a UHF signal including the detection value of the acceleration sensor 39 to the monitoring unit 45. The monitoring unit 45 can estimate the configuration of the tire detector 33 based on the detection value of the acceleration sensor 39. Figure 5 As shown, the detection values ​​of the acceleration sensor 39 are linearly symmetrical with the Y axis passing through the center point CP3 as the axis of symmetry.

[0073] The estimation of the arrangement of the tire detector 33 using the detection value of the acceleration sensor 39 in the first embodiment will be described in more detail. Figure 1 and Figure 2 As described above, the starter 61 is arranged on the positive direction side of the X-axis of the tire 13. Figure 5 When the straight line of the rotation radial direction RD3 from the center point CP3 of the tire 13 toward the positive direction of the Z axis is used as the boundary, the area of ​​the tire 13 can be divided into an area on the side close to the starter 61 and an area on the side far from the starter 61. Figure 5 In the example of , the arrangement 7h to the arrangement 11h are arranged in the region on the side close to the initiator 61 . The arrangement 1h to the arrangement 5h are arranged in the region on the side far from the initiator 61 .

[0074] The initiator 61 is arranged on the positive direction side of the X-axis direction of the tire 13. When the tire detector 33 is arranged on the side close to the initiator 61, all the detection values ​​of the acceleration sensor 39 are positive values. On the other hand, when the tire detector 33 is arranged on the side far from the initiator 61, all the detection values ​​of the acceleration sensor 39 are negative values. The monitoring unit 45 can determine whether the tire detector 33 is arranged on the side close to the initiator 61 or on the side far from the initiator 61 by determining the positive or negative of the detection value of the acceleration sensor 39 included in the received UHF signal.

[0075] Monitoring unit 45 can acquire at least two configurations as configuration candidates of tire detector 33 based on the detection value of acceleration sensor 39. For example, when the detection value of acceleration sensor 39 is +√2 / 3G, monitoring unit 45 acquires configuration 8h and configuration 10h as configuration candidates of tire detector 33. Furthermore, when the detection value of acceleration sensor 39 is -1 / 2G, monitoring unit 45 acquires configuration 1h and configuration 5h as configuration candidates of tire detector 33.

[0076] When the detection value of the acceleration sensor 39 is +1G, the monitoring unit 45 estimates that the tire detector 33 is in the configuration 9h. When the detection value of the acceleration sensor 39 is -1G, the monitoring unit 45 estimates that the tire detector 33 is in the configuration 3h. In addition, in the tire detector 35 mounted on the tire 15, the relationship between the configuration of the tire detector 35 and the detection value of the acceleration sensor 39 is also the same. Figure 5 The arrangement of the tire detector 33 described in and the relationship between the detection values ​​of the acceleration sensor 39 are the same.

[0077] In addition, the acceleration sensor 39 of the tire detector 30 in the first embodiment can also detect the acceleration generated in the rotation radial direction RD3 (centrifugal force direction). When detecting the acceleration generated in the rotation radial direction RD3, the detection values ​​of the acceleration sensor 39 are line symmetrical with the Z axis passing through the center point CP3 as the symmetry axis. Therefore, the monitoring unit 45 cannot determine whether the tire detector 30 is arranged in the area close to the starter based only on the positive and negative signs of the detection values ​​of the acceleration sensor 39.

[0078] When the acceleration sensor 39 detects the acceleration generated in the rotation radial direction RD3, the monitoring unit 45 continuously detects at least twice at an interval shorter than the period during which the tire 10 rotates 90 degrees. Thus, the monitoring unit 45 can uniquely determine the arrangement of the tire detector 30 based on the detection value of the acceleration sensor 39, and can therefore determine whether the tire detector 30 is arranged in an area close to the starter.

[0079] <About the attenuation of radio wave intensity>

[0080] Figure 6 This is a graph showing an example of attenuation when the radio wave intensity T1 is used as the transmission intensity. Figure 6 The horizontal axis represents the radiation distance (unit: m) of the LF signal from the initiator 61, and the vertical axis represents the radio wave strength (unit: W) of the LF signal. As the distance increases, the attenuation increases, and the radio wave strength of the LF signal gradually weakens. If the radiation distance of the LF signal sent from the initiator 61 increases, the attenuation of the radio wave strength of the LF signal increases. Figure 6 , the radio wave intensities L and H are shown. The radio wave intensity H is a radio wave intensity higher than the radio wave intensity L.

[0081] In addition, the electric field strength H may correspond to the "first threshold value" in the present disclosure, and the electric field strength L may correspond to the "second threshold value" in the present disclosure.

[0082] exist Figure 6, an example is shown in which the initiator 61 transmits the LF signal with the radio wave intensity T1 as the transmission intensity. Hereinafter, the radio wave intensity when the initiator 61 transmits is referred to as "transmission intensity". On the other hand, the radio wave intensity when the LF signal is attenuated and received by the tire detector 30 is referred to as "reception intensity". The radio wave intensity T1 is the radio wave intensity at which both the tire detectors 33 and 35 can fully receive the LF signal even if the LF signal is attenuated.

[0083] Width Wd3 is a width indicating a range in which the distance between tire detector 33 and starter 61 can be taken. Width Wd5 is a width indicating a range in which the distance between tire detector 35 and starter 61 can be taken. The arrangement of tire detectors 33 and 35 changes as tires 13 and 15 rotate. Therefore, the distance between tire detectors 33 and 35 and starter 61 changes within the range of widths Wd3 and Wd5. Widths Wd3 and Wd5 can be estimated based on the arrangement of starter 61 and tires 13 and 15 and the tire diameters of tires 13 and 15.

[0084] like Figure 6 As shown, the radio intensity H is the radio intensity corresponding to the distance from the center of the width Wd3. The radio intensity L is the radio intensity corresponding to the distance from the center of the width Wd5. The radio intensity H and L are stored in the storage unit 46 of the monitoring unit 45.

[0085] Monitoring unit 45 in Embodiment 1 uses the RSSI value to determine the tire position of tire 10 on which tire detector 30 is mounted. More specifically, when monitoring unit 45 receives a UHF signal including an RSSI value of radio wave strength H or higher, it determines that the UHF signal is transmitted from tire detector 33 mounted on tire 13 close to starter 61. When monitoring unit 45 receives a UHF signal including an RSSI value less than radio wave strength L, it determines that the UHF signal is transmitted from tire detector 35 mounted on tire 15 far from starter 61.

[0086] On the other hand, when monitoring unit 45 receives a UHF signal including an RSSI value having a radio intensity of at least L and less than radio intensity H, it may be unable to determine the tire position of tire detector 30 that transmitted the UHF signal. A case where the tire position cannot be determined using distances D1 and D2 will be described below.

[0087] The distance D1 is a distance included in the width Wd3 and is relatively close to the width Wd5. The distance D2 is a distance included in the width Wd5 and is relatively close to the width Wd3. Figure 6 In the graph shown, the reception intensity at a distance of D1 is the radio wave intensity R1, and the reception intensity at a distance of D2 is the radio wave intensity R2.

[0088] However, the strength of the LF signal is Figure 6 The graph shown is used as a reference for attenuation, but errors may occur due to various factors. That is, the attenuation of the LF signal wave strength is affected by the surrounding environment and may vary from Figure 6 Therefore, the reception intensity at the distance D1 may become the radio wave intensity R2, and the reception intensity at the distance D2 may become the radio wave intensity R1.

[0089] Taking the occurrence of errors into consideration, the monitoring unit 45 cannot determine the tire position based on the RSSI value alone when the RSSI value included in the UHF signal is greater than or equal to the radio wave intensity L and less than the radio wave intensity H. When the monitoring unit 45 of the first embodiment receives a UHF signal including a radio wave intensity greater than or equal to the radio wave intensity L and less than the radio wave intensity H, it determines the tire position using the tire position determination method described below.

[0090] Figure 7 Appearance description of using starter 61, tires 13, 15 Figure 6 The diagram shown in Figure. Figure 7 In, with Figure 2 Likewise, the state in which the starter 61 and the tires 13 and 15 are viewed from the negative direction side of the Y axis is shown.

[0091] Distance D3 is the distance between tire detector 33 in configuration 3h and tire detector 33 in configuration 9h. In addition, since tire 13 and tire 15 have the same tire diameter, distance D3 may also be the distance between tire detector 35 in configuration 3h and tire detector 35 in configuration 9h. Distance D4 is the distance between tire detector 33 in configuration 3h and tire detector 35 in configuration 9h.

[0092] exist Figure 7 In the figure, for the sake of convenience, distances D3 and D4 represent only the distances in the X-axis direction, but distances D3 and D4 are three-dimensional distances. Thus, since distance D4 is short when tire detector 33 and tire detector 35 are closest, an error occurs in the attenuation amount of the LF signal, resulting in a higher probability that both tire detector 33 and tire detector 35 receive the LF signal. That is, monitoring unit 45 may not be able to determine the tire position based on the RSSI value alone. In the first embodiment, distance D4 is a distance smaller than half of distance D2.

[0093] Line LnL is a simplified representation of the attenuation without considering the error. Figure 6 In the graph shown in FIG. 1 , the received intensity is the boundary line of the radio wave intensity L. Similarly, the line LnH is a simplified representation of the attenuation amount according to the condition that the error is not taken into account. Figure 6In the graph shown, the reception intensity is the boundary line of the radio wave intensity H.

[0094] Furthermore, the distance between the center point CP1 of the starter 61 and the center point CP3 of the tire 13 may correspond to the “first distance” in the present disclosure. The distance between the center point CP1 of the starter 61 and the center point CP5 of the tire 15 may correspond to the “second distance” in the present disclosure.

[0095] <Tire Position Determination in Embodiment 1>

[0096] When receiving a UHF signal having a radio intensity of not less than radio intensity L and less than radio intensity H, the tire position determination system in Embodiment 1 determines the tire position using the arrangement of tire detector 30 estimated from the detection value of acceleration sensor 39 .

[0097] Figure 8 1 is a flowchart showing an example of tire position determination processing in Embodiment 1. The monitoring unit 45 determines whether the vehicle 100 has stopped running (step S101). The monitoring unit 45 uses a vehicle speed sensor (not shown) to determine whether the vehicle 100 has stopped running. When the vehicle 100 has not stopped running ("No" in step S101), the monitoring unit 45 repeatedly performs the processing of step S101.

[0098] When the vehicle 100 stops running ("Yes" in step S101), a transmission command of an LF signal with a radio wave strength of T1 is issued to the starter 61 (step S102). The starter 61 receives the transmission command and transmits the LF signal with a radio wave strength of T1. In response to receiving the LF signal, the tire detectors 33 and 35 transmit UHF signals.

[0099] The monitoring unit 45 receives the UHF signal (step S103). The monitoring unit 45 determines whether the RSSI value included in the received UHF signal is equal to or greater than the radio wave strength H (step S104). When the RSSI value is equal to or greater than the radio wave strength H ("Yes" in step S104), the monitoring unit 45 determines that the UHF signal is transmitted from the tire detector 33 of the tire 13 installed at the tire position close to the starter 61 (step S105). That is, the monitoring unit 45 determines that the tire position of the tire detector 30 that transmitted the UHF signal received in step S103 is "the left side of the first rear row".

[0100] When the RSSI value is not equal to or greater than the radio wave intensity H (No in step S104), the monitoring unit 45 determines whether the RSSI value included in the received UHF signal is less than the radio wave intensity L (step S106). When the RSSI value is less than the radio wave intensity L (Yes in step S106), the monitoring unit 45 determines that the UHF signal is transmitted from the tire detector 35 of the tire 15 installed at the tire position far from the starter 61 (step S107). That is, the monitoring unit 45 determines that the tire position of the tire detector 30 that transmitted the UHF signal received in step S103 is "the second rear row left side".

[0101] When the RSSI value is not less than the radio wave intensity L ("No" in step S106), the monitoring unit 45 determines whether the detection value of the acceleration sensor 39 included in the UHF signal received in step S103 is a positive value (step S108). That is, the monitoring unit 45 uses the detection value of the acceleration sensor 39 to determine whether the tire detector 30 is arranged in the area close to the starter in the tire 10. In this way, the monitoring unit 45 can estimate the positional relationship between the tire detector 30 and the starter 61 using the detection value of the acceleration sensor 39.

[0102] When the detection value of acceleration sensor 39 is positive (YES in step S108 ), monitoring unit 45 determines that the UHF signal in step S103 is transmitted from tire detector 35 of tire 15 at a tire position far from starter 61 (step S109 ).

[0103] like Figure 7 As shown, between the line LnL and the line LnH, the tire detector 35 of the tire 15 is arranged in a region of the tire 15 close to the starter 61. On the other hand, between the line LnL and the line LnH, the tire detector 33 of the tire 13 is arranged in a region of the tire 13 far from the starter 61. Therefore, the monitoring unit 45 can determine that the tire position of the tire detector 30 that transmits the UHF signal received in step S103 is "the second rear row left side".

[0104] When the detection value of the acceleration sensor 39 is not a positive value (No in step S108), the monitoring unit 45 determines whether the detection value of the acceleration sensor 39 included in the UHF signal received in step S103 is a negative value (step S110). That is, the monitoring unit 45 uses the detection value of the acceleration sensor 39 to determine whether the tire detector 30 is arranged in the tire 10 in an area away from the starter. In this way, the monitoring unit 45 can estimate the positional relationship between the tire detector 30 and the starter 61 using the detection value of the acceleration sensor 39.

[0105] When the detection value of the acceleration sensor 39 is a negative value ("Yes" in step S110), the monitoring unit 45 determines that the UHF signal of step S103 is transmitted from the tire detector 33 of the tire 13 at the tire position close to the starter 61 (step S111). The monitoring unit 45 can determine that the tire position of the tire detector 30 that transmitted the UHF signal received in step S103 is "the left side of the first rear row".

[0106] If the detection value of the acceleration sensor 39 is not a negative value (No in step S110), the monitoring unit 45 does not determine the tire position and ends the process. That is, when the tire detector 30 is arranged at 12h or 6h, the monitoring unit 45 cannot determine the tire position even if the detection value of the acceleration sensor 39 is used.

[0107] Thus, in the first embodiment, the monitoring unit 45 can determine the tire position even when receiving a UHF signal including an RSSI value less than the radio wave intensity H and greater than the radio wave intensity L by using the configuration of the tire detector 30 estimated based on the detection value of the acceleration sensor 39. Thus, the tire position determination system in the first embodiment can determine the tire position of each of the tires 13 and 15 using one starter 61 without providing starters for each of the tires 13 and 15.

[0108] exist Figure 8 , the configuration in which the monitoring unit 45 causes the starter 61 to transmit the LF signal when the vehicle 100 stops is described. In one aspect, the monitoring unit 45 may cause the starter 61 to transmit the LF signal while the vehicle 100 is running. In this case, the monitoring unit 45 removes the centrifugal force generated by the running of the vehicle 100 from the detection value of the acceleration sensor 39, thereby obtaining only the gravitational acceleration. The monitoring unit 45 calculates the centrifugal force generated by the running of the vehicle 100 based on the speed of the vehicle 100 received from the speedometer (not shown).

[0109] <Variation of Embodiment 1>

[0110] In the first embodiment, the tire 13 is arranged between the starter 61 and the tire 15. However, the starter 61 is not limited to being arranged between the starter 61 and the tire 15. Figure 7 The positions shown can be configured in various positions.

[0111] Fig. 9 1 is a diagram for explaining the configuration of the starter 61 in a modified example of the first embodiment. Fig. 9 As shown in FIG. 1 , the starter 61 is disposed on the positive side of the Z axis of the tire 13. The concentric circles indicated by the dotted lines with the transmission circuit of the starter 61 as the center indicate the radio wave intensity of the LF signal.

[0112] In the tire position determination system of the modified example of the first embodiment, the radio wave intensities L and H serving as threshold values ​​are determined according to the arrangement of the starter 61 and the tires 13 and 15. Fig. 9 As shown, in the tire position determination system of the modification of the first embodiment, line LnH is a boundary line in contact with tire 15. That is, radio wave intensity H is set so that within a range of radio wave intensity H or higher, tire 15 is not included but at least a portion of tire 13 is included.

[0113] In the tire position determination system of the modification of Embodiment 1, line LnL is a boundary line in contact with tire 13. That is, radio wave intensity L is set so that within a range smaller than radio wave intensity L, tire 13 is not included but at least a portion of tire 15 is included.

[0114] In a modified example of the first embodiment, the area near the starter 61 in the tire 13 is an area with a radio wave intensity of H or more, and the area far from the starter 61 in the tire 13 is an area with a radio wave intensity of less than H. In addition, the area near the starter 61 in the tire 15 is an area with a radio wave intensity of L or more, and the area far from the starter 61 in the tire 15 is an area with a radio wave intensity of less than L.

[0115] Therefore, even if the starter 61 Fig. 9 In such a configuration, monitoring unit 45 can determine the tire position according to whether tire detectors 33 and 35 are disposed in an area close to starter 61 or in an area far from starter 61 when the RSSI value is less than radio wave intensity H and greater than radio wave intensity L. In this way, the tire position determination system in Embodiment 1 can be applied to places other than the placement of starter 61.

[0116] Furthermore, as a modification of the first embodiment, in the tire position determination system, the starter 61 may be arranged at the same distance from the tire center of the tire 13 and the tire center of the tire 15. In this case, in the tire position determination system, the monitoring unit 45 may discard the data indicating the RSSI value and the detection value of the acceleration sensor 39 when the combination of the RSSI value of the signal received from the tire detector 33 and the detection value of the acceleration sensor 39 of the tire detector 33 and the combination of the RSSI value of the signal received from the tire detector 35 and the detection value of the acceleration sensor 39 of the tire detector 35 are the same, and may identify the tire position when the combination of the RSSI value and the detection value of the acceleration sensor 39 is different.

[0117] [Implementation Method 2]

[0118] In the first embodiment, the radio wave intensity T1 at which both tire detectors 33 and 35 can sufficiently receive the LF signal even when the attenuation of the LF signal is taken into account is described as an example of the transmission intensity. In the second embodiment, the radio wave intensity T2 at which only tire detector 33 can receive the LF signal is described as an example of the transmission intensity of starter 61 taking into account the attenuation of the LF signal. In the second embodiment, the description of the same configuration as that of the tire position determination system in the first embodiment is not repeated.

[0119] Fig.10 This is a graph showing an example of attenuation when the radio wave intensity T2 is used as the transmission intensity. Fig.10 , the radio wave strength M is shown. The radio wave strength M is the radio wave strength indicating the boundary at which the tire detector 30 can receive the LF signal. That is, the tire detector 30 is configured to be able to receive LF signals with a radio wave strength of M or more, but cannot receive LF signals with a radio wave strength of less than M. The receiving circuit CR of the tire detector 30 is configured to receive the LF signal when the antenna L1 detects a LF signal with a radio wave strength of M or more. In addition, the radio wave strength M may correspond to the "third threshold value" in the present disclosure.

[0120] like Fig.10 As shown in FIG. 1 , the radio wave intensity T2 as the transmission intensity is set so that the radio wave intensity M that becomes the reception boundary due to the attenuation of the LF signal corresponds to a distance that is longer than the maximum distance of the width Wd3 and shorter than the minimum distance of the width Wd5. Thus, without considering various factors such as the surrounding environment, only the tire detector 33 can receive the LF signal. However, as described above, the attenuation amount of the radio wave intensity of the LF signal may vary depending on the surrounding environment, etc. Therefore, depending on the configuration of the tire detector 35, the LF signal with the radio wave intensity M as the transmission intensity may be received by the tire detector 35.

[0121] Fig.11 Appearance description of using starter 61, tires 13, 15 Fig.10 The line LnM is a line that simply shows the boundary where the radio wave intensity of the LF signal attenuates and becomes the radio wave intensity M. Fig.11 As shown, the radio wave intensity M is set so that the line LnM is arranged between tires 13 and 15. When tire detector 35 is arranged in an area close to the starter such as arrangement 9h, tire detector 35 receives the LF signal when the attenuation of the radio wave intensity of the LF signal is reduced due to the surrounding environment. Fig.11 In response to the tire detector 35 receiving the LF signal, the UHF signal is transmitted from the tire detector 35 .

[0122] When tire detector 35 receives the LF signal due to an error caused by the attenuation, tire detector 35 is arranged in an area close to initiator 61. In this case, both tire detectors 33 and 35 can receive the LF signal. When tire detector 35 is located in an area far from initiator 61, since it is arranged at a position far from line LnM, tire detector 35 cannot receive the LF signal even if an error caused by the attenuation occurs. In this case, only tire detector 33 receives the LF signal.

[0123] In implementation mode 2, if Fig.11 , a method of determining the tire position based on the detection value of the acceleration sensor 39 is described even when the tire detector 35 receives the LF signal due to an error. In addition, the radio wave intensity T2 may correspond to the "first radio wave intensity" in the present disclosure.

[0124] <Regarding Tire Position Determination in Embodiment 2>

[0125] The tire position determination system in the second embodiment transmits an LF signal using radio wave intensity M as the transmission intensity, and determines the tire position using the arrangement of tire detector 30 estimated from the detection value of acceleration sensor 39 .

[0126] Fig.12 2 is a flowchart showing an example of tire position determination processing in Embodiment 2. Monitoring unit 45 determines whether vehicle 100 has stopped running (step S201). If vehicle 100 has not stopped running (No in step S201), monitoring unit 45 repeats the processing of step S101.

[0127] When the vehicle 100 stops running ("Yes" in step S201), a transmission command of an LF signal with a radio wave strength of T2 is issued to the starter 61 (step S202). The starter 61 receives the transmission command and transmits the LF signal with a radio wave strength of T2. When the tire detectors 33 and 35 receive the LF signal, they transmit the UHF signal.

[0128] The monitoring unit 45 receives the UHF signal (step S203). The monitoring unit 45 determines whether the detection value of the acceleration sensor 39 included in the received UHF signal is a negative value (step S204). That is, the monitoring unit 45 determines whether the tire detector 30 that transmitted the UHF signal received in step S203 is arranged in an area of ​​the tire 10 away from the starter.

[0129] If the detection value of acceleration sensor 39 is not a negative value (No in step S204), monitoring unit 45 ends the process. That is, if it is not a negative value, tire detector 30 that transmits the UHF signal in step S203 is arranged in an area close to starter 61. As described above, when an error occurs in the attenuation amount, if tire detector 35 is arranged in an area close to starter 61 in tire 15, tire detector 35 can receive the LF signal and transmit the UHF signal.

[0130] Therefore, when the monitoring unit 45 receives a UHF signal from the tire detector 30 disposed in an area close to the starter 61, it is impossible to determine the tire position. Fig.12 That is, the monitoring unit 45 discards the data of the UHF signal received in step S203. In addition, the monitoring unit 45 may store the data of the UHF signal in the storage unit 46 without discarding it.

[0131] When the detection value of the acceleration sensor 39 is negative ("Yes" in step S204), the monitoring unit 45 can determine that the UHF signal received in step S203 is transmitted from the tire detector 33, and determine that the tire position is "the left side of the first rear row" (step S206). Fig.11 As shown, in a state where the tire detector 30 is arranged in an area far from the starter 61, the tire detector 33 is the only tire detector 30 that can receive the LF signal having the transmission strength of the radio wave strength M. At this time, the monitoring unit 45 stores the tire position "the first rear row on the left" in the storage unit 46 in association with the ID number included in the UHF signal received in step S203.

[0132] Next, the monitoring unit 45 causes the initiator 61 to transmit an LF signal with a radio wave intensity T1 as a transmission intensity (step S207). The monitoring unit 45 determines whether a UHF signal having an ID number different from the ID number included in the UHF signal received in step S203 is received (step S208). If a UHF signal having a different ID number is not received ("No" in step S208), the monitoring unit 45 returns the process to step S207 and causes the initiator 61 to transmit the LF signal again.

[0133] When a UHF signal with a different ID number is received ("Yes" in step S208), the monitoring unit 45 can determine that the UHF signal with a different ID number is transmitted from the tire detector 35, and determine that the tire position is "the second rear column left side" (step S209). That is, the monitoring unit 45 associates the tire position "the second rear column left side" with the ID number received in the branch of step S208 and stores it in the storage unit 46.

[0134] Thus, the tire position determination system of the second embodiment can determine the positions of a plurality of tires using one initiator 61 using the detection value of the acceleration sensor 39 even when the initiator 61 is caused to transmit the LF signal having the transmission intensity of the radio wave intensity M.

[0135] exist Fig.12 In the above description, the monitoring unit 45 is described as causing the starter 61 to send the LF signal when the vehicle 100 stops. Figure 8 Similarly, by removing the centrifugal force according to the speed of the vehicle 100 , the starter 61 is caused to transmit the LF signal while the vehicle 100 is running.

[0136] <Variation of Embodiment 2>

[0137] In the second embodiment, the tire 13 is also arranged between the starter 61 and the tire 15. However, the starter 61 is not limited to being arranged between the starter 61 and the tire 15. Figure 7 The positions shown can be configured in various positions.

[0138] Fig.13 This is a diagram for explaining the arrangement of the starter 61 in a modified example of the second embodiment. Fig.13 The initiator 61 is configured with Fig. 9 In a variation of implementation 2, as Fig.13 As shown in FIG. 1 , line LnM is disposed between line LnL and line LnH. That is, radio intensity M is a value obtained by adding radio intensity L to half of a value obtained by subtracting radio intensity L from radio intensity H.

[0139] Therefore, even if the starter 61 Fig.13 In such a configuration, the monitoring unit 45 can also determine the tire position when the transmission strength of the LF signal is set to the radio wave strength M. That is, in the tire position determination system of the second embodiment, the positions of multiple tires can be determined using one initiator 61. In this way, the tire position determination system of the second embodiment can be applied without being limited to the configuration of the initiator 61.

[0140] In the first embodiment, monitoring unit 45 determines the tire position based on whether the radio intensity is greater than or equal to H or less than L. However, the tire position may be determined based on whether the radio intensity is greater than H or less than L.

[0141] <Modification example related to the number of tires>

[0142] In the first and second embodiments, the structures of the front one axle and the rear two axles, that is, the structures for determining the positions of the two tires 13 and 15 arranged in the X-axis direction, are described, but the vehicle 100 may also have a structure of more than three rear axles. The monitoring unit 45 in the first embodiment sets a new threshold in addition to the radio wave intensity H and the radio wave intensity L, thereby enabling determination of more than three tire positions.

[0143] More specifically, in the tire position determination system, Figure 7 When a tire is further arranged on the negative side of the X-axis of the tire 15 shown, the radio wave intensity corresponding to the boundary line passing through the center point of the tire arranged on the negative side of the X-axis is set as a new threshold. When the UHF signal includes an RSSI value less than the radio wave intensity set as the new threshold, the monitoring unit 45 can determine that the UHF signal is transmitted from the tire arranged on the negative side of the X-axis of the tire 15.

[0144] Furthermore, when the monitoring unit 45 receives a UHF signal including an RSSI value having an intensity less than the radio intensity L and greater than the radio intensity set as the new threshold value, it can determine from the detection value of the acceleration sensor 39 whether the signal is transmitted from the tire 15 or from the tire detector 30 arranged on the negative side of the X-axis of the tire 15. In this way, the threshold value is increased even when the number of tires increases, and thus the monitoring unit 45 can determine the tire position even when the number of tires is three or more.

[0145] The embodiments disclosed this time should be considered as illustrative in all aspects and not limiting the present invention. The scope of the present disclosure is indicated by the claims rather than the above description, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0146] The exemplary embodiments and their modifications described above are specific examples of the following aspects.

[0147] (1) In a tire position determination system according to one embodiment of the present disclosure, the tire position determination system is a tire position determination system provided in a vehicle having a first tire and a second tire different from the first tire. The tire position determination system comprises: a starter that sends a command signal; a first detector that is mounted on the first tire and sends a detection signal when receiving the command signal; a second detector that is mounted on the second tire and sends a detection signal when receiving the command signal; and a monitoring unit that is configured to receive the detection signal. A first distance between the first tire and the starter is less than or equal to a second distance between the second tire and the starter. The first detector and the second detector each include an acceleration sensor that detects acceleration in a direction orthogonal to the rotation axis. The detection signal includes a detection value of the acceleration sensor. When the monitoring unit receives a detection signal from the first detector or the second detector, the monitoring unit performs a determination process of determining whether the detector that sends the detection signal is the first detector or the second detector, using the positional relationship between the detector that sends the detection signal and the starter estimated based on the detection value of the acceleration sensor included in the received detection signal.

[0148] According to the above aspect, when the tire position cannot be determined based on the reception strength alone, the monitoring unit can determine the tire position based on whether the tire detector is arranged in an area close to the initiator. Thus, the tire position determination system determines the tire position of each of a plurality of tires using one initiator.

[0149] (2) In one embodiment, the detection signal further includes a reception strength of a command signal from the initiator. The monitoring unit causes the initiator to send the command signal, and when the reception strength included in the received detection signal is greater than a first threshold, the monitoring unit determines that the detector sending the detection signal is the first detector, and when the reception strength included in the received detection signal is less than a second threshold, the monitoring unit determines that the detector sending the detection signal is the second detector, and when the reception strength included in the received detection signal is less than the first threshold and greater than the second threshold, the monitoring unit performs a determination process.

[0150] According to the above aspect, the tire position determination system can estimate the arrangement of tire detectors 33 and 35 in tires 13 and 15 , and determine the tire positions even when the distance between tire detectors 33 and 35 is shortened.

[0151] (3) In one embodiment, the first threshold value and the second threshold value are determined according to the arrangement of the starter, the first tire, and the second tire.

[0152] According to the above aspect, the tire position determination system can determine an appropriate threshold value according to the arrangement of the starter, the first tire, and the second tire.

[0153] (4) In one embodiment, the first threshold is set so as to exclude the second tire but include at least a portion of the first tire within a range where the attenuated intensity of the command signal is greater than the first threshold, and the second threshold is set so as to exclude the first tire but include at least a portion of the second tire within a range where the attenuated intensity of the command signal is less than the second threshold.

[0154] According to the above aspect, the radio wave intensities L and H can be determined based on the distance between the starter 61 and the tires 13 and 15 and the attenuation of the LF signal.

[0155] (5) In one embodiment, the monitoring unit causes the starter to send a command signal with a first radio wave strength, and when it is estimated using the detection value of the acceleration sensor included in the received detection signal that the detector sending the detection signal is not arranged in the area close to the starter in the first tire or the second tire, the monitoring unit determines that the detector sending the detection signal is the first detector, and when it is estimated using the detection value of the acceleration sensor included in the received detection signal that the detector sending the detection signal is arranged in the area close to the starter in the first tire or the second tire, the detection signal is discarded. The first radio wave strength is set to include the first tire but not the second tire within a range where the intensity of the command signal after attenuation becomes greater than a third threshold, and the first detector or the second detector is configured to be unable to receive a command signal with a reception intensity less than the third threshold, but to be able to receive a command signal with a reception intensity greater than the third threshold.

[0156] According to the above aspect, the tire position determination system can determine the tire position by transmitting the LF signal with the radio wave intensity M as the transmission intensity.

[0157] (6) In one embodiment, the first tire is arranged between the starter and the second tire.

[0158] According to the above aspect, the area close to the starter 61 and the area far from the starter 61 in the tires 13 and 15 can be appropriately determined.

Claims

1. A tire position determination system, the tire position determination system being provided in a vehicle having a first tire and a second tire different from the first tire, characterized in that: have: Starter, sending command signal; a first detector, mounted on the first tire, and sending a detection signal upon receiving the command signal; a second detector, mounted on the second tire, and sending a detection signal upon receiving the command signal; as well as a monitoring unit configured to receive the detection signal, A first distance between the first tire and the starter is less than a second distance between the second tire and the starter, The first detector and the second detector each include an acceleration sensor for detecting acceleration in a direction orthogonal to the rotation axis. The detection signal includes a detection value of the acceleration sensor. When the monitoring unit receives the detection signal from the first detector or the second detector, the monitoring unit uses the positional relationship between the detector that sends the detection signal and the starter estimated based on the positive and negative values ​​of the detection value of the acceleration sensor included in the received detection signal to perform a determination process to determine whether the detector that sends the detection signal is the first detector or the second detector. The detection signal also includes the reception strength of the command signal from the initiator, The monitoring unit performs the following actions: causing the initiator to send the command signal, When the reception strength included in the received detection signal is greater than or equal to a first threshold, it is determined that the detector sending the detection signal is the first detector, When the reception strength included in the received detection signal is less than a second threshold, it is determined that the detector sending the detection signal is the second detector, The determination process is performed when the reception intensity included in the received detection signal is smaller than the first threshold value and equal to or greater than the second threshold value.

2. The tire position determination system according to claim 1, characterized in that: The monitoring unit performs a determination process of determining whether the detector sending the detection signal is the first detector or the second detector, using the transmission strength when the initiator sends the command signal or the reception strength when the detector receives the command signal from the initiator.

3. The tire position determination system according to claim 1, characterized in that: The first threshold value and the second threshold value are determined according to the arrangement of the starter, the first tire, and the second tire.

4. The tire position determination system according to claim 1, characterized in that: The first threshold is set so that the second tire is not included but at least a part of the first tire is included in a range in which the intensity of the command signal after attenuation is equal to or greater than the first threshold. The second threshold is set so as to exclude the first tire and include at least a portion of the second tire within a range where the attenuated intensity of the command signal is smaller than the second threshold.

5. The tire position determination system according to claim 3, characterized in that: The first threshold is set so that the second tire is not included but at least a part of the first tire is included in a range in which the intensity of the command signal after attenuation is equal to or greater than the first threshold. The second threshold is set so as to exclude the first tire and include at least a portion of the second tire within a range where the attenuated intensity of the command signal is smaller than the second threshold.

6. The tire position determination system according to any one of claims 1 to 5, characterized in that: The first tire is arranged between the starter and the second tire.

7. A tire position determination system, the tire position determination system being provided in a vehicle having a first tire and a second tire different from the first tire, characterized in that: have: Starter, sending command signal; a first detector, mounted on the first tire, and sending a detection signal upon receiving the command signal; a second detector, mounted on the second tire, and sending a detection signal upon receiving the command signal; as well as a monitoring unit configured to receive the detection signal, A first distance between the first tire and the starter is less than a second distance between the second tire and the starter, The first detector and the second detector each include an acceleration sensor for detecting acceleration in a direction orthogonal to the rotation axis. The detection signal includes a detection value of the acceleration sensor. When the monitoring unit receives the detection signal from the first detector or the second detector, the monitoring unit uses the positional relationship between the detector that sends the detection signal and the starter estimated based on the positive and negative values ​​of the detection value of the acceleration sensor included in the received detection signal to perform a determination process to determine whether the detector that sends the detection signal is the first detector or the second detector. The monitoring unit performs the following actions: causing the starter to send the command signal at a first radio wave strength, When it is estimated that the detector sending the detection signal is not arranged in the area close to the starter in the first tire or the second tire using the detection value of the acceleration sensor included in the received detection signal, it is determined that the detector sending the detection signal is the first detector, When it is estimated that the detector that sent the detection signal is arranged in the area close to the starter in the first tire or the second tire using the detection value of the acceleration sensor included in the received detection signal, the detection signal is discarded; The first radio wave intensity is set so as to exclude the second tire and include the first tire within a range where the intensity of the command signal after attenuation becomes equal to or greater than a third threshold value, The first detector or the second detector is configured to be unable to receive the command signal having a reception intensity less than the third threshold value, but to be able to receive the command signal having a reception intensity greater than the third threshold value.

8. The tire position determination system according to claim 7, characterized in that: The monitoring unit performs a determination process of determining whether the detector sending the detection signal is the first detector or the second detector, using the transmission strength when the initiator sends the command signal or the reception strength when the detector receives the command signal from the initiator.

9. The tire position determination system according to claim 7 or 8, characterized in that: The first tire is arranged between the starter and the second tire.

Images