This nonprovisional application is based on Japanese Patent Application No. 2021-188357 filed with the Japan Patent Office on Nov. 19, 2021, the entire contents of which are hereby incorporated by reference.
The present disclosure relates to a tire position determination system.
In a tire pressure monitoring system (TPMS) in a vehicle, a detector has conventionally been attached to each of a plurality of tires. The detector attached to each of the plurality of tires transmits pneumatic pressure information to a processing device such as an ECU attached to a vehicle body.
Some TPMS's are provided with an auto location function to automatically determine to which tire among a plurality of tires a detector is attached. For example, Japanese Patent Laying-Open No. 2019-48547 discloses a tire state information detection system that determines to which tire of double tires used in a truck and the like a detector is attached.
Among such TPMS's, there is a system including an initiator. The initiator transmits a command signal to a tire at a prescribed tire position. The detector transmits a response signal to a processing device such as an ECU provided on a vehicle body side based on reception of the command signal from the initiator. The processing device determines attachment of the detector that has transmitted the response signal to a tire at the prescribed tire position.
When the initiator is provided at each of a plurality of tire positions, however, cost may increase. On the other hand, when a single initiator is used to transmit a command signal to a plurality of detectors, the processing device provided on the vehicle body side may not be able to determine from which detector it receives the response signal.
The present disclosure was made to solve the problem described above, and an object thereof is to determine a tire position of each of a plurality of tires with the use of a single initiator.
A tire position determination system according to one aspect of the present disclosure is a tire position determination system provided in a vehicle including a first tire and a second tire different from the first tire. The tire position determination system includes an initiator that transmits a command signal, a first detector attached to the first tire, the first detector transmitting a detection signal when the first detector receives the command signal, a second detector attached to the second tire, the second detector transmitting a detection signal when the second detector receives the command signal, and a monitoring unit configured to receive the detection signal. A first distance between the first tire and the initiator is equal to or shorter than a second distance between the second tire and the initiator. Each of the first detector and the second detector includes an acceleration sensor that detects an acceleration in a direction orthogonal to a revolution axis direction. The detection signal includes a detection value from the acceleration sensor. When the monitoring unit receives the detection signal from the first detector or the second detector, the monitoring unit performs determination processing for determining whether a detector that has transmitted the detection signal is the first detector or the second detector based on positional relation between the detector that has transmitted the detection signal and the initiator estimated from the detection value from the acceleration sensor included in the received detection signal.
According to the aspect above, with the use of a value of the acceleration detected by each detector in addition to signal intensity of the detection signal received from each detector, a larger number of statuses of revolution of each tire can be specified. As variations of the statuses of revolution are wider, a larger number of tire positions can be specified. The tire position determination system thus determines a tire position of each of a plurality of tires with the use of a single initiator.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.
An embodiment of the present disclosure will be described in detail below with reference to the drawings. The same or corresponding elements in the drawings have the same reference characters allotted and description thereof will not be repeated.
<Overall Configuration>
Vehicle 100 according to the first embodiment is a vehicle including tires 11 and 12 on a front side which are steering wheels and tires 13 to 16 on a rear side which are non-steering wheels. Tires 11 to 16 are each in such a form that a single tire is attached at a single tire attachment position. A direction FR shown in
In the description below, a vertical direction when vehicle 100 is arranged on the plane is defined as a “Z-axis direction,” a direction perpendicular to the Z-axis direction, in the direction of forward travel of vehicle 100, is defined as a “positive direction along an X axis,” and a direction perpendicular to an X-axis direction is defined as a “Y-axis direction.” Hereafter, a positive direction along a Z axis in each figure may be referred to as an upper side and a negative direction along the Z axis may be referred to as a lower side, the positive direction along the X axis may be referred to as a front side and a negative direction along the X axis may be referred to as a rear side, and a positive direction along a Y axis may be referred to as a right side and a negative direction along the Y axis may be referred to as a left side.
Vehicle 100 includes a system that monitors a pneumatic pressure of each tire (TPMS). Specifically, vehicle 100 includes a plurality of tire detectors 31 to 36 each detecting a tire pressure, initiators 61 and 62, and a TPMS receiver 40. Tire detectors 31 to 36 are attached to wheels of tires 11 to 16, respectively. Tire detectors 31 to 36 may each be formed integrally with a valve for intake of air into each tire. Tire detectors 31 to 36 may each be formed separately from the valve.
Each of tire detectors 31 to 36 is activated when a prescribed activation condition is satisfied, and detects a pneumatic pressure of each tire and transmits a radio signal in an ultra high frequency (UHF) band (which is also simply referred to as a “UHF signal” below) that includes a result of detection. The “prescribed activation condition” is set in advance to be satisfied regularly or irregularly. Tire detectors 31 to 36 are thus intermittently activated at timings different from one another and transmit UHF signals.
The UHF signals outputted from tire detectors 31 to 36 include information indicating specific ID numbers for identifying at least respective tire detectors 31 to 36. Specifically, the UHF signals outputted from tire detectors 31 to 36 include ID numbers “01” to “06”, respectively.
The UHF signals outputted from tire detectors 31 to 36 each include information representing a tire pressure in addition to the information indicating the ID number. As TPMS receiver 40 receives the UHF signal outputted from each of tire detectors 31 to 36, it can monitor a pneumatic pressure of each tire.
Tires identical in specifications and construction are employed as tires 11 to 16 for allowing tire rotation. Therefore, tire detectors identical in configuration are adopted also for tire detectors 31 to 36. When tires 11 to 16 do not have to be described as being distinguished from one another, tires 11 to 16 are simply referred to as a “tire 10” below. When tire detectors 31 to 36 do not have to be described as being distinguished from one another, tire detectors 31 to 36 are simply referred to as a “tire detector 30.” Tires 11 to 16 are identical in tire diameter.
TPMS receiver 40 is provided on a vehicle body side of vehicle 100. TPMS receiver 40 includes a monitoring unit 45 that monitors a pneumatic pressure of each tire. Monitoring unit 45 includes a storage 46, a processing unit 47, and an antenna A1. Antenna A1 is configured to receive a UHF signal transmitted from tire detector 30. Monitoring unit 45 accepts the UHF signal received by antenna A1.
Processing unit 47 includes a processor such as a not-shown central processing unit (CPU), a memory, and an input and output buffer. The memory includes a read only memory (ROM) and a random access memory (RAM). The processor develops a program stored in the ROM on the RAM and executes the same. Various types of processing performed by processing unit 47 are described in the program stored in the ROM.
Information indicating a position of a tire where each tire detector 30 is attached and information indicating a tire pressure are stored in storage 46 as being brought in correspondence with an ID number of each tire detector 30. In the first embodiment, six tire positions (a front left side, a front right side, a rear first-row left side, a rear first-row right side, a rear second-row left side, and a rear second-row right side) in total are stored in correspondence with the respective ID numbers of tire detectors 30.
Specifically, the tire position “front left side” is brought in correspondence with the ID number “01” and the tire position “front right side” is brought in correspondence with the ID number “02”. The tire position “rear first-row left side” is brought in correspondence with the ID number “03” and the tire position “rear first-row right side” is brought in correspondence with the ID number “04”. The tire position “rear second-row left side” is brought in correspondence with the ID number “05” and the tire position “rear second-row right side” is brought in correspondence with the ID number “06”. When tires are rotated and monitoring unit 45 detects attachment at different tire positions, monitoring unit 45 updates relation between the ID number and the tire position.
When monitoring unit 45 receives a UHF signal, it checks the ID number included in the UHF signal against the ID number stored in storage 46, and obtains the tire position brought in correspondence with the ID number. Monitoring unit 45 updates the pneumatic pressure at the obtained tire position with the tire pressure included in the UHF signal.
For example, when monitoring unit 45 receives the UHF signal including the ID number “01”, it refers to correspondence between the ID number “01” and the tire position stored in storage 46. In storage 46, the “front left side” is brought in correspondence with the ID number “01” as the tire position. Monitoring unit 45 updates the pneumatic pressure on the “front left side” with the tire pressure included in the UHF signal.
TPMS receiver 40 can have information on correspondence between the tire position and the tire pressure stored in storage 46 shown on a display 52. Display 52 is arranged at a position where a driver can visually recognize the same. Display 52 is arranged, for example, in an instrument panel within the vehicle.
Monitoring unit 45 determines whether or not the tire pressure included in the received UHF signal is equal to or lower than a low-pressure threshold value. When the tire pressure is equal to or lower than the low-pressure threshold value, monitoring unit 45 has the tire position where the tire pressure has become the low-pressure threshold value shown on display 52 together with a warning. TPMS receiver 40 determines the tire pressure each time it receives the UHF signal and monitors each pneumatic pressure of the tire. The driver can thus recognize in real time the position of the tire the tire pressure of which has become equal to or lower than the low-pressure threshold value.
Initiators 61 and 62 for activating tire detectors 33 to 36 on the rear side are electrically connected to TPMS receiver 40. Initiator 61 is arranged in the vicinity of tire 13 on the left side in the rear first row and used for activation of tire detectors 33 and 35. Initiator 62 is arranged in the vicinity of tire 14 on the right side in the rear first row and used for activation of tire detectors 34 and 36.
Initiators 61 and 62 identical in configuration are adopted. When initiators 61 and 62 do not have to be described as being distinguished from each other, they are also denoted as an “initiator 60” below without being distinguished from each other.
Initiator 60 includes a not-shown antenna, and is configured to output a radio signal in a low frequency (LF) band (which is also simply referred to as an “LF signal” below) from the antenna. Initiator 60 transmits the LF signal to tire detector 30 based on an instruction from monitoring unit 45. The LF signal is a command signal for instructing tire detector 30 to perform a specific operation.
Each tire detector 30 can receive the LF signal from initiator 60. Each tire detector 30 is configured to output a UHF signal when the prescribed activation condition described above is satisfied. The “prescribed activation condition” in the first embodiment includes reception of the LF signal. In other words, each tire detector 30 transmits the UHF signal on condition that it receives the LF signal.
Relation between each tire position and the position of initiator 61 or 62 is stored in storage 46. For example, a tire position closest to initiator 61 being “rear first-row left” and a tire position second closest thereto being “rear second-row left” are stored in storage 46.
<Configuration of Tire Detector 30>
An exemplary configuration of tire detector 30 will be described below with reference to
Controller 85 includes a storage 86 and a processing unit 87. Processing unit 87 includes a processor such as a not-shown CPU, a memory, and an input and output buffer. The memory includes a ROM and a RAM. The processor develops a program stored in the ROM on the RAM and executes the same. Various types of processing performed by processing unit 87 are described in the program stored in the ROM.
In storage 86, an ID number specific for each tire detector 30 shown in
Antenna L1 receives the LF signal transmitted from initiator 61 or 62. Controller 85 accepts the LF signal received by antenna L1 through reception circuit CR. Reception circuit CR detects reception intensity of the LF signal received by antenna L1.
Reception circuit CR outputs a voltage in accordance with radio wave intensity (received signal strength indicator (RSSI) signal) of the inputted LF signal. Controller 85 obtains intensity (which is referred to as an “RSSI value” below) of the received signal (radio wave) resulting from A/D conversion of this voltage. The RSSI value in the first embodiment is obtained as a voltage ratio [dBμV] to 1 μV. The unit of the RSSI value may be a voltage [V] or power [W]. Reception circuit CR is configured not to receive the LF signal lower than radio wave intensity M but to receive the LF signal equal to or higher than radio wave intensity M.
Controller 85 controls transmission circuit CT to transmit a UHF signal from antenna A2. Controller 85 outputs the UHF signal at timing when a prescribed activation condition is satisfied. Tire detector 30 is provided with a not-shown battery, and operates with electric power supplied from the battery. This battery is constructed not to readily externally be charged. Therefore, in tire detector 30 in the first embodiment, desirably, operating time is minimized to suppress power consumption by tire detector 30.
From this point of view, the “prescribed activation condition” is set in advance to suppress a frequency of activation of tire detector 30 as much as possible. For example, the prescribed activation condition may include such a timer-based activation condition that a timer has counted lapse of prescribed timer time since previous stop and such an acceleration-based activation condition that a result of detection (which is also referred to as an “acceleration G” below) by acceleration sensor 39 has attained to a specific value (for example, a maximum value or a minimum value).
The “timer time” used as the timer-based activation condition described above may be set to a fixed value or a variable value that varies with acceleration G. For example, controller 85 may determine whether or not a tire is revolving based on acceleration G which represents the result of detection by acceleration sensor 39 and change the set timer time.
In tire detector 30 in the first embodiment, the prescribed activation condition includes reception of the LF signal from initiator 60. Tire detector 30 transmits a UHF signal including detection information representing an ID number, a tire pressure P, acceleration G, and an RSSI value to monitoring unit 45 by being triggered by reception of the LF signal.
Pressure sensor 38 detects a tire pressure and outputs a result of detection (which is also referred to as “tire pressure P” below) to controller 85. Acceleration sensor 39 detects an acceleration in a uniaxial direction generated in a direction orthogonal to a revolution axis direction of tire 10 and outputs a result of detection to controller 85. Acceleration sensor 39 in the first embodiment has a revolution circumferential direction of tire 10 as a detection direction. Tire detector 30 may further include a temperature sensor that detects a tire temperature in addition to pressure sensor 38 and acceleration sensor 39.
<Detection Value from Acceleration Sensor 39>
Arrangement 1h represents arrangement of tire detector 33 when tire 13 revolves by 0 degrees clockwise from the state of arrangement 12h. 0 degrees in
Arrangement 3h represents arrangement of tire detector 33 when tire 13 revolves by 0 degrees clockwise from the state of arrangement 2h. Arrangement 3h is referred to as arrangement at “+90 degrees” below.
As described with reference to
In the example in
When tire detector 33 is at arrangement 8h or arrangement 10h the detection value from acceleration sensor 39 is +√ 3/2 G. When tire detector 33 is at arrangement 7h or arrangement 11h, the detection value from acceleration sensor 39 is +½ G. When tire detector 33 is at arrangement 12h or arrangement 6h, the detection value from acceleration sensor 39 is 0 G.
When tire detector 33 is at arrangement 1h or arrangement 5h, the detection value from acceleration sensor 39 is −½ G. When tire detector 33 is at arrangement 2h or arrangement 4h, the detection value from acceleration sensor 39 is −√ 3/2 G. Depending on a direction of attachment of tire detector 33, positive and negative signs of the acceleration of gravity as the detection value shown in
Tire detector 33 transmits the UHF signal including the detection value from acceleration sensor 39 to monitoring unit 45. Monitoring unit 45 can estimate arrangement of tire detector 33 based on the detection value from acceleration sensor 39. As shown in
Estimation of arrangement of tire detector 33 based on the detection value from acceleration sensor 39 in the first embodiment will more specifically be described. As described with reference to
Initiator 61 is arranged on the side of the positive direction in the X-axis direction of tire 13. When arrangement of tire detector 33 is on the side close to initiator 61, the detection values from acceleration sensor 39 are all positive. When arrangement of tire detector 33 is on the side distant from initiator 61, the detection values from acceleration sensor 39 are all negative. By determining whether the detection value from acceleration sensor 39 included in the received UHF signal is positive or negative, monitoring unit 45 can determine whether tire detector 33 is arranged on the side close to or distant from initiator 61.
Monitoring unit 45 can obtain at least two arrangements as arrangement candidates for tire detector 33 based on the detection value from acceleration sensor 39. For example, when monitoring unit 45 finds the detection value from acceleration sensor 39 as +√ 3/2 G, tire detector 33 obtains arrangement 8h and arrangement 10h as arrangement candidates. Alternatively, when monitoring unit 45 finds the detection value from acceleration sensor 39 as −½ G, tire detector 33 obtains arrangement 1h and arrangement 5h as arrangement candidates.
When the detection value from acceleration sensor 39 is +1 G, monitoring unit 45 estimates that tire detector 33 is in arrangement 9h. When the detection value from acceleration sensor 39 is −1 G, monitoring unit 45 estimates that tire detector 33 is in arrangement 3h. For tire detector 35 attached to tire 15 as well, relation between arrangement of tire detector 35 and the detection value from acceleration sensor 39 is similar to relation between the arrangement of tire detector 33 and the detection value from acceleration sensor 39 described with reference to
Acceleration sensor 39 of tire detector 30 in the first embodiment may detect the acceleration generated in revolution diameter direction RD3 (centrifugal direction). When the acceleration generated in revolution diameter direction RD3 is detected, detection values from acceleration sensor 39 are in line symmetry with respect to the Z-axis that passes through central point CP3. Therefore, monitoring unit 45 is unable to determine whether or not tire detector 30 is arranged in the region close to the initiator only based on the positive and negative signs of the detection value from acceleration sensor 39.
When acceleration sensor 39 detects the acceleration generated in revolution diameter direction RD3, monitoring unit 45 detects the acceleration consecutively two times at intervals at least shorter than a period of revolution of tire 10 by ninety degrees. Since monitoring unit 45 can thus uniquely determine arrangement of tire detector 30 based on the detection value from acceleration sensor 39, it can determine whether or not tire detector 30 is arranged in the region close to the initiator.
<As to Attenuation of Radio Wave Intensity>
Radio wave intensity H may correspond to the “first threshold value” in the present disclosure. Radio wave intensity L may correspond to the “second threshold value” in the present disclosure.
A width Wd3 represents a width of a range of possible distances between tire detector 33 and initiator 61. A width Wd5 represents a width of a range of possible distances between tire detector 35 and initiator 61. Arrangement of tire detectors 33 and 35 changes with revolution of tires 13 and 15. Therefore, distances between tire detectors 33 and 35 and initiator 61 change within the ranges of width Wd3 and Wd5. Width Wd3 and Wd5 can be estimated from arrangement of initiator 61 and tires 13 and 15 and the tire diameter of tires 13 and 15.
As shown in
Monitoring unit 45 in the first embodiment determines the tire position of tire 10 to which tire detector 30 is attached based on the RSSI value. More specifically, when monitoring unit 45 receives the UHF signal including the RSSI value equal to or higher than radio wave intensity H, it determines that the UHF signal has been transmitted from tire detector 33 attached to tire 13 close to initiator 61. When monitoring unit 45 receives the UHF signal including the RSSI value lower than radio wave intensity L, it determines that the UHF signal has been transmitted from tire detector 35 attached to tire 15 distant from initiator 61.
When monitoring unit 45 receives the UHF signal including the RSSI value equal to or higher than radio wave intensity L and lower than radio wave intensity H, it may not be able to determine the tire position of tire detector 30 that has transmitted the UHF signal. An example in which the monitoring unit is unable to determine the tire position will be described by referring to a distance D1 and a distance D2.
Distance D1 is a distance which is included within width Wd3 and relatively close to width Wd5. Distance D2 is a distance which is included within width Wd5 and relatively close to width Wd3. According to the graph shown in
Though radio wave intensity of the LF signal attenuates with the graph shown in
When the RSSI value included in the UHF signal is equal to or higher than radio wave intensity L and lower than radio wave intensity H, in consideration of the error, monitoring unit 45 is unable to determine the tire position only based on the RSSI value. When monitoring unit 45 in the first embodiment receives the UHF signal including radio wave intensity equal to or higher than radio wave intensity L and lower than radio wave intensity H, it determines the tire position with a tire position determination method which will be described later.
A distance D3 represents a distance between tire detector 33 at arrangement 3h and tire detector 33 at arrangement 9h. Since tire 13 and tire 15 are identical in tire diameter, distance D3 is defined also as a distance between tire detector 35 at arrangement 3h and tire detector 35 at arrangement 9h. A distance D4 represents a distance between tire detector 33 at arrangement 3h and tire detector 35 at arrangement 9h.
Though distances D3 and D4 in
A line LnL is a line that shows in a simplified manner, a boundary at which reception intensity attains to radio wave intensity L when it is assumed that the amount of attenuation follows the graph shown in
A distance between a central point CP1 of initiator 61 and central point CP3 of tire 13 may correspond to the “first distance” in the present disclosure. A distance between central point CP1 of initiator 61 and a central point CP5 of tire 15 may correspond to the “second distance” in the present disclosure.
When the tire position determination system in the first embodiment receives the UHF signal including radio wave intensity equal to or higher than radio wave intensity L and lower than radio wave intensity H, it determines the tire position based on arrangement of tire detector 30 estimated from the detection value from acceleration sensor 39.
When vehicle 100 has stopped traveling (YES in step S101), initiator 61 is instructed to transmit the LF signal at radio wave intensity T1 (step S102). Initiator 61 receives the transmission instruction and transmits the LF signal at radio wave intensity T1. Each of tire detectors 33 and 35 transmits the UHF signal in response to reception of the LF signal.
Monitoring unit 45 receives the UHF signal (step S103). Monitoring unit 45 determines whether or not the RSSI value included in the received UHF signal is equal to or higher than radio wave intensity H (step S104). When the RSSI value is equal to or higher than radio wave intensity H (YES in step S104), monitoring unit 45 determines that the UHF signal has been transmitted from tire detector 33 of tire 13 attached at the tire position close to initiator 61 (step S105). In other words, monitoring unit 45 determines that the tire position of tire detector 30 that has transmitted the UHF signal received in step S103 is “rear first-row left.”
When the RSSI value is lower than radio wave intensity H (NO in step S104), monitoring unit 45 determines whether or not the RSSI value included in the received UHF signal is lower than radio wave intensity L (step S106). When the RSSI value is lower than radio wave intensity L (YES in step S106), monitoring unit 45 determines that the UT-IF signal has been transmitted from tire detector 35 of tire 15 attached at the tire position distant from initiator 61 (step S107). In other words, monitoring unit 45 determines that the tire position of tire detector 30 that has transmitted the UHF signal received in step S103 is “rear second-row left.”
When the RSSI value is not lower than radio wave intensity L (NO in step S106), monitoring unit 45 determines whether or not the detection value from acceleration sensor 39 included in the UHF signal received in step S103 is positive (step S108). In other words, monitoring unit 45 determines whether or not tire detector 30 is arranged in the region in tire 10 close to the initiator based on the detection value from acceleration sensor 39. Monitoring unit 45 can thus estimate positional relation between tire detector 30 and initiator 61 based on the detection value from acceleration sensor 39.
When the detection value from acceleration sensor 39 is positive (YES in step S108), monitoring unit 45 determines that the UHF signal in step S103 has been transmitted from tire detector 35 of tire 15 at the tire position distant from initiator 61 (step S109).
As shown in
When the detection value from acceleration sensor 39 is not positive (NO in step S108), monitoring unit 45 determines whether or not the detection value from acceleration sensor 39 included in the UHF signal received in step S103 is negative (step S110). In other words, monitoring unit 45 determines whether or not tire detector 30 is arranged in the region distant from the initiator in tire 10 based on the detection value from acceleration sensor 39. Monitoring unit 45 can thus estimate positional relation between tire detector 30 and initiator 61 based on the detection value from acceleration sensor 39.
When the detection value from acceleration sensor 39 is negative (YES in step S110), monitoring unit 45 determines that the UHF signal in step S103 has been transmitted from tire detector 33 in tire 13 at the tire position close to initiator 61 (step S111). Monitoring unit 45 can determine that the tire position of tire detector 30 that has transmitted the UHF signal received in step S103 is “rear first-row left.”
When the detection value from acceleration sensor 39 is not negative (NO in step S110), monitoring unit 45 quits the process without determining the tire position. This is because, even based on the detection value from acceleration sensor 39, monitoring unit 45 is unable to determine the tire position when tire detector 30 is in arrangement 12h or arrangement 6h.
Thus, in the first embodiment, even when monitoring unit 45 receives the UHF signal including the RSSI value lower than radio wave intensity H and equal to or higher than radio wave intensity L, it can determine the tire position based on arrangement of tire detector 30 estimated from the detection value from acceleration sensor 39. The tire position determination system in the first embodiment can thus determine the tire position of each of tire 13 and tire 15 with the use of single initiator 61, without providing the initiator for each of tire 13 and tire 15.
In the first embodiment, tire 13 is arranged between initiator 61 and tire 15. Initiator 61, however, is not necessarily arranged at the position shown in
The tire position determination system in the modification of the first embodiment determines radio wave intensities L and H defined as the threshold values in accordance with arrangement of initiator 61 and tires 13 and 15. As shown in
In the tire position determination system in the modification of the first embodiment, line LnL represents a boundary line in contact with tire 13. In other words, radio wave intensity L is set such that tire 13 is not included but at least a part of tire 15 is included in a range lower than radio wave intensity L.
In the modification of the first embodiment, the region close to initiator 61 in tire 13 is a region where radio wave intensity is equal to or higher than radio wave intensity H and the region distant from initiator 61 in tire 13 is a region where radio wave intensity is lower than radio wave intensity H. The region close to initiator 61 in tire 15 is a region where radio wave intensity is equal to or higher than radio wave intensity L and the region distant from initiator 61 in tire 15 is a region where radio wave intensity is lower than radio wave intensity L.
Thus, even in an example in which initiator 61 is arranged as in
In the modification of the first embodiment, in the tire position determination system, initiator 61 may be arranged equidistantly from the tire center of tire 13 and the tire center of tire 15. In this case, in the tire position determination system, when a combination of the RSSI value in the signal received from tire detector 33 and the detection value from acceleration sensor 39 of tire detector 33 is identical to a combination of the RSSI value in the signal received from tire detector 35 and the detection value from acceleration sensor 39 of tire detector 35, monitoring unit 45 may discard data representing the RSSI value and the detection value from acceleration sensor 39, and when the combinations of the RSSI value and the detection value from acceleration sensor 39 are different from each other, monitoring unit 45 may specify the tire position.
In the first embodiment described above, an example in which radio wave intensity T1 at which both of tire detectors 33 and 35 are able to sufficiently receive the LF signal even in consideration of attenuation of the LF signal is set as transmission intensity is described. In a second embodiment, an example in which initiator 61 sets as transmission intensity, radio wave intensity T2 at which only tire detector 33 is able to receive the LF signal in consideration of attenuation of the LF signal will be described. In the second embodiment, description of the configuration similar to that in the tire position determination system in the first embodiment will not be repeated.
As shown in
When tire detector 35 receives the LF signal due to an error caused in the amount of attenuation, tire detector 35 is arranged in the region close to initiator 61, and in this case, both of tire detectors 33 and 35 may receive the LF signal. When tire detector 35 is in the region distant from initiator 61, it is arranged at a position distant from line LnM. Therefore, even when an error is caused in the amount of attenuation, tire detector 35 is unable to receive the LF signal. In this case, only tire detector 33 receives the LF signal.
In the second embodiment, a method of determining a tire position based on a detection value from acceleration sensor 39 even when tire detector 35 receives the LF signal due to an error as shown in
The tire position determination system in the second embodiment has the LF signal transmitted with transmission intensity thereof being set to radio wave intensity T2, and determines the tire position based on arrangement of tire detector 30 estimated from the detection value from acceleration sensor 39.
When vehicle 100 has stopped traveling (YES in step S201), initiator 61 is instructed to transmit the LF signal at radio wave intensity T2 (step S202). Initiator 61 receives the transmission instruction and transmits the LF signal at radio wave intensity T2. When each of tire detector 33 and tire detector 35 receives the LF signal, it transmits the UHF signal.
Monitoring unit 45 receives the UHF signal (step S203). Monitoring unit 45 determines whether or not the detection value from acceleration sensor 39 included in the received UHF signal is negative (step S204). In other words, monitoring unit 45 determines whether or not tire detector 30 that has transmitted the UHF signal received in step S203 is arranged in the region distant from the initiator in tire 10.
When the detection value from acceleration sensor 39 is not negative (NO in step S204), monitoring unit 45 quits the process. When the detection value is not negative, tire detector 30 that has transmitted the UHF signal in step S203 is arranged in the region close to initiator 61. As described above, when an error is caused in the amount of attenuation and when tire detector 35 is arranged in the region close to initiator 61 in tire 15, tire detector 35 may receive the LF signal and transmit the UHF signal.
Therefore, when monitoring unit 45 receives the UHF signal from tire detector 30 arranged in the region close to initiator 61, it is unable to determine the tire position and quits the process as shown in
When the detection value from acceleration sensor 39 is negative (YES in step S204), monitoring unit 45 can determine that the UHF signal received in step S203 has been transmitted from tire detector 33 and determines that the tire position is “rear first-row left” (step S206). As shown in
Then, monitoring unit 45 has initiator 61 transmit the LF signal the transmission intensity of which is set to radio wave intensity T1 (step S207). Monitoring unit 45 determines whether or not it receives the UHF signal with an ID number different from the ID number included in the UHF signal received in step S203 (step S208). When monitoring unit 45 does not receive the UHF signal including the different ID number (NO in step S208), the process returns to step S207 and monitoring unit 45 has initiator 61 transmit the LF signal again.
When monitoring unit 45 receives the UHF signal including the different ID number (YES in step S208), it can determine that the UHF signal with the different ID number has been transmitted from tire detector 35 and determines that the tire position is “rear second-row left” (step S209). Monitoring unit 45 has the tire position “rear second-row left” and the ID number received at a branch in step S208 stored in storage 46 in correspondence with each other.
Thus, the tire position determination system in the second embodiment can determine a plurality of tire positions with the use of single initiator 61 based on the detection value from acceleration sensor 39, also when it has initiator 61 transmit the LF signal the transmission intensity of which is set to radio wave intensity T2.
Tire 13 is arranged between initiator 61 and tire 15 also in the second embodiment. Initiator 61, however, is not necessarily arranged at the position shown in
Thus, even in an example where initiator 61 is arranged as in
Though monitoring unit 45 determines the tire position based on whether radio wave intensity is equal to or higher than radio wave intensity H or lower than radio wave intensity L in the first embodiment, it may determine the tire position based on whether radio wave intensity is higher than radio wave intensity H or equal to or lower than radio wave intensity L.
<Modification in Connection with the Number of Tires>
In the first embodiment and the second embodiment, a configuration including one axle in front and two axles in rear in which two tire positions of tires 13 and 15 aligned in the X-axis direction are determined is described. Vehicle 100, however, may be constructed to include three or more axles in rear. Monitoring unit 45 in the first embodiment can determine three more tire positions by newly setting a threshold value in addition to radio wave intensity H and radio wave intensity L.
More specifically, in the tire position determination system, when a further tire is arranged on the side of the negative direction along the X axis of tire 15 shown in
When monitoring unit 45 receives the UHF signal including the RSSI value at radio wave intensity equal to or higher than radio wave intensity set as the new threshold value, it can determine from tire detector 30 of which of tire 15 and the tire arranged on the side of the negative direction along the X axis of tire 15 the UHF signal has been transmitted, based on the detection value from acceleration sensor 39. Thus, even in an example where the number of tires is increased to three or more, by increase of the threshold value, monitoring unit 45 can determine the tire position.
It should be understood that the embodiments disclosed herein are illustrative and non-restrictive in every respect. The scope of the present disclosure is defined by the terms of the claims rather than the description above and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.
The illustrative embodiments and the modifications thereof described above are specific examples of aspects below.
(1) A tire position determination system according to one aspect of the present disclosure is a tire position determination system provided in a vehicle including a first tire and a second tire different from the first tire. The tire position determination system includes an initiator that transmits a command signal, a first detector attached to the first tire, the first detector transmitting a detection signal when the first detector receives the command signal, a second detector attached to the second tire, the second detector transmitting a detection signal when the second detector receives the command signal, and a monitoring unit configured to receive the detection signal. A first distance between the first tire and the initiator is equal to or shorter than a second distance between the second tire and the initiator. Each of the first detector and the second detector includes an acceleration sensor that detects an acceleration in a direction orthogonal to a revolution axis direction. The detection signal includes a detection value from the acceleration sensor. When the monitoring unit receives the detection signal from the first detector or the second detector, the monitoring unit performs determination processing for determining whether a detector that has transmitted the detection signal is the first detector or the second detector based on positional relation between the detector that has transmitted the detection signal and the initiator estimated from the detection value from the acceleration sensor included in the received detection signal.
According to the aspect above, when the monitoring unit is unable to determine the tire position only based on reception intensity, it can determine the tire position based on whether or not the tire detector is arranged in the region close to the initiator. The tire position determination system can thus determine the tire position of each of the plurality of tires with the use of a single initiator.
(2) In one aspect, the detection signal further includes reception intensity of the command signal from the initiator. The monitoring unit has the initiator transmit the command signal. When the reception intensity included in the received detection signal is equal to or higher than a first threshold value, the monitoring unit determines that the detector that has transmitted the detection signal is the first detector. When the reception intensity included in the received detection signal is lower than a second threshold value, the monitoring unit determines that the detector that has transmitted the detection signal is the second detector. When the reception intensity included in the received detection signal is lower than the first threshold value and equal to or higher than the second threshold value, the monitoring unit performs the determination processing.
According to the aspect above, even when the distance between tire detector 33 and tire detector 35 is short in tire 13 and tire 15, the tire position determination system can determine the tire position by estimating arrangement of tire detector 33 and tire detector 35.
(3) In one aspect, the first threshold value and the second threshold value are determined in accordance with arrangement of the initiator, the first tire, and the second tire.
According to the aspect above, the tire position determination system can determine an appropriate threshold value based on arrangement of the initiator, the first tire, and the second tire.
(4) In one aspect, the first threshold value is set such that the second tire is not included but at least a part of the first tire is included in a range where attenuated intensity of the command signal is equal to or higher than the first threshold value, and the second threshold value is set such that the first tire is not included but at least a part of the second tire is included in a range where attenuated intensity of the command signal is lower than the second threshold value.
According to the aspect above, radio wave intensities L and H can be determined based on the distances between initiator 61 and tires 13 and 15 and attenuation of the LF signal.
(5) In one aspect, the monitoring unit has the initiator transmit the command signal at first radio wave intensity. When the monitoring unit estimates based on the detection value from the acceleration sensor included in the received detection signal that the detector that has transmitted the detection signal is not arranged in a region close to the initiator in the first tire or the second tire, the monitoring unit determines that the detector that has transmitted the detection signal is the first detector. When the monitoring unit estimates based on the detection value from the acceleration sensor included in the received detection signal that the detector that has transmitted the detection signal is arranged in the region close to the initiator in the first tire or the second tire, the monitoring unit discards the detection signal. The first radio wave intensity is set such that the second tire is not included but the first tire is included in a range where attenuated intensity of the command signal is equal to or higher than a third threshold value, and the first detector or the second detector is configured to be unable to receive the command signal at reception intensity lower than the third threshold value and to be able to receive the command signal at reception intensity equal to or higher than the third threshold value.
According to the aspect above, the tire position determination system can determine the tire position by causing transmission of the LF signal transmission intensity of which is set to radio wave intensity T2.
(6) In one aspect, the first tire is arranged between the initiator and the second tire.
According to the aspect above, the region close to initiator 61 and the region distant from initiator 61 in tires 13 and 15 can suitably be determined.
Though embodiments of the present invention have been described, it should be understood that the embodiments disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.
Number | Date | Country | Kind |
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2021-188357 | Nov 2021 | JP | national |