Tire wheel position detection device and tire pressure monitoring system with the tire wheel position detection device

Abstract

Tire wheel position detection device applied to a vehicle (1) having a vehicle body (6) equipped with a plurality of tire wheels (5a-5d), each of the tire wheels (5a-5d) having a tire, wherein the tire wheel position detection device comprises: a transmitter (2) attached to each of the tire wheels (5a-5d) and comprising a control device (23) which generates and transmits a frame containing unique identification information; wherein: the transmitter (2) includes an accelerometer (22) which outputs a detection signal based on an acceleration including a gravitational acceleration component, wherein the gravitational acceleration component varies by rotating the tire wheel (5a-5d) to which the transmitter (2) is attached; the control device (23) of the transmitter (2) detects an angle of the transmitter (2) based on the gravitational acceleration component included in the detection signal of the accelerometer (22) and repeatedly transmits the frame at times where the angle is a predetermined transmission angle, where any circumferential position of the tire wheel (5a-5d), centered with respect to a central axis of the tire wheel (5a-5d) to which the transmitter (2) is attached, is an angle of 0 degrees; and a receiver (3) attached to the vehicle body (6) and including a control unit (33) configured to perform tire wheel position detection by performing the following steps: Receiving the frames transmitted by the transmitters (2) via a receiving antenna (31) and then Select from the candidate identification information included in the framework, specifying the candidates to be registered, and Identify, from the candidate identification information, the candidate identification information that matches the transmitters (2) attached to the tire wheels (5a-5d) of the vehicle (1), and Storing the tire wheels (5a-5d) and the identification information of the transmitters (2) attached to the tire wheels (5a-5d) in combination with each other Obtaining gear information specifying tooth positions of gears (12a-12d) based on detection signals from tire wheel speed sensors (11a-11d), wherein the tire wheel speed sensors (11a-11d) detect the passage of teeth of the gears (12a-12d) rotating in coordination with the tire wheels (5a-5d), each gear having a circumferential surface with the tooth sections and sections between the tooth sections to alternately exhibit different magnetic resistance values, the tooth sections being conductive bodies; Defining an acceptable range of variation based on the tooth positions at a given time when the frame is received; if the tooth positions at a frame reception time after setting the permissible variation range are outside the permissible variation range, eliminate the tire wheel (5a-5d) of tire wheel candidates that is connected to the transmitter (2) that transmitted the frame; and Identify and register one remaining tire wheel (5a-5d) as the tire wheel (5a-5d) to which the transmitter (2) is attached that transmitted the frame; and wherein the control device (33) of the receiver (3) includes: a preliminary fixer (S240) that performs a preliminary fixation of each individual candidate identification information prior to registration when the tire wheel (5a-5d) to which the transmitter (2) transmitting the frame is attached is identified on the basis of the tooth positions which are within the permissible range of variation; a determination device (S245) which, after preliminary fixing, determines whether the tooth positions at a time of receipt of the frame including the preliminary fixed candidate identification information are within the permissible range of variation; a counter (S250) which, after preliminary fixing, measures the number of frame receptions including the preliminary fixed candidate identification information, where the tooth positions remain within the permissible range of variation; a first determining device (S255) that determines whether the number of receptions is equal to or greater than a first predetermined value; a register (S260, S261) which, if the number of receptions is equal to or greater than the first predetermined value, definitively determines and records the provisionally fixed candidate identification information as the identification information of the identified tire wheel (5a-5d); a determination mechanism (S251) that determines whether a multitude of the provisionally established candidate identification information exists; and a second determination device (S270) which, when the number of provisionally fixed candidate identification information is determined to be two or more, determines whether the number of receptions is equal to or greater than a second predetermined value, wherein the second predetermined value is greater than the first predetermined value, wherein If the number of receptions is equal to or greater than the second predetermined value, the register definitively determines and registers the provisionally fixed candidate identification information as the identification information of the identified tire wheel (5a-5d).

Description

TECHNICAL AREA

[0001] The present disclosure relates to a tire position detection device for automatically detecting the position of a target tire on a vehicle. The present disclosure is suitably applicable to a direct tire pressure monitoring system. BACKGROUND OF THE INVENTION

[0002] There is one type of tire pressure monitoring system (TPMS) that is direct. Direct TPMS is configured so that a transmitter with a pressure sensor or other sensor is attached directly to a tire. An antenna and a receiver are also mounted on the vehicle. When a detection signal is sent by the sensor, the transmitter receives the signal through the antenna to measure the tire pressure.

[0003] When using the aforementioned direct TPMS, it is necessary to determine whether the transmitted data is for a specific vehicle and on which wheel the transmitter is mounted. Therefore, the data sent by the transmitter includes ID information to determine whether the transmitted data is for the specific vehicle or for another vehicle, and on which wheel the transmitter is mounted.

[0004] To identify the transmitter's position from the ID information contained in the transmitted data, it is necessary to link each transmitter's ID information to the position of each tire and to pre-register this link in the receiver. For example, the ID information of a transmitter on the subject vehicle is registered by reading a barcode on the transmitter with a barcode reader and registering an ID using the barcode reader. However, using this method requires a barcode reader and increases the labor hours needed to read the barcode of the transmitter attached to each tire.

[0005] The relationship between a transmitter's ID information and a tire's position must be re-registered in the receiver whenever, for example, a tire is rotated or replaced with winter tires. This prevents a user from changing tires independently. Therefore, there is a need for a system that automatically registers the ID information. In this regard, a technology for automatically registering ID information is proposed, for example, in JP 5 585 595 B2.

[0006] More precisely, a device described in JP 5 585 595 B2 receives an acceleration detection signal output by an accelerometer attached to a transmitter on a tire wheel, uses the received acceleration detection signal to detect that the tire wheel is at a predetermined rotational position (angle of rotation), and then causes the tire wheel to transmit a frame. When a registration procedure is performed accordingly by the user, a tire wheel speed sensor detects the passage of teeth of a gear rotating in accordance with the tire wheel and identifies the tire wheel's position based on the change in the teeth's positions at the time the frame is received.

[0007] The tire position can alternatively be identified by switching to an ID registration mode to register the ID information of a transmitter, transmitting predetermined radio waves from a vehicle body to the transmitter using a trigger device, and causing the transmitter to send response data to a receiver synchronously with the radio waves. Another alternative method for identifying the tire position involves attaching a dual-axis accelerometer to each transmitter, identifying left and right tires based on a detection signal from the dual-axis accelerometer, and identifying front and rear tires based on the received signal strength with which a frame from each transmitter is received by the receiver.Another alternative is to place an antenna near each tire wheel, measure the strength (RSSI) of the received radio waves when the antenna receives a frame, and register a high-strength value as the ID information of a tire wheel near the antenna.

[0008] Reference is also made to EP 2 810 797 A1, US 2014 / 0 207 329 A1, DE 11 2013 003 908 T5 and DE 11 2013 000 606 T5, which were identified as prior art. OVERVIEW OF THE INVENTION

[0009] If the aforementioned ID information of a transmitter is to be automatically registered, all ID information contained in the received frames is handled as ID information candidates for registration (hereinafter referred to as candidate IDs). The ID information of the transmitter of the subject vehicle, or the transmitter located on the subject vehicle, is then selected from the candidate IDs. Accordingly, the candidate IDs are stored in the memory of a TPMS ECU, and the ID information of the subject vehicle's transmitter is then selected from the candidate IDs. Finally, the selected ID information is registered in association with a tire.

[0010] However, the ID information of a transmitter from another vehicle can be erroneously identified as the ID information of a transmitter from the subject vehicle. Such a situation can occur if a frame is received from the transmitter of the other vehicle before a frame is received from the transmitter of the subject vehicle, and no frame is received from the transmitter of the subject vehicle for an extended period. In particular, if a frame from the transmitter of the other vehicle is registered as the candidate IDs in a situation where no frame is received from the transmitter of the subject vehicle, the positions of the teeth corresponding to the registered candidate IDs can quickly vary significantly at a given frame reception time.Therefore, there is a possibility that ID information exhibiting a slight variation in tooth positions could be inadvertently selected from the candidate IDs and identified as the ID information of the subject vehicle's sender. In such a case, it is undesirable to simply fix the ID information as the ID information of the subject vehicle's sender.

[0011] Meanwhile, even when using the alternative methods described above, a similar problem to the one described above can occur, as the ID information of the other vehicle's transmitter may be incorrectly registered as the ID information of the subject vehicle's transmitter. Furthermore, the method using the trigger device requires the use of a trigger device, which must be installed as an additional part. Similarly, the method using the dual-axis accelerometer requires the use of a dual-axis accelerometer, which must be installed as a highly functional additional part. Finally, the method of placing the antenna near each tire wheel requires the use of an antenna, which must be installed for each tire wheel. This results in an increase in the number of units required and therefore an increase in costs.

[0012] In light of the foregoing circumstances, one objective of the present disclosure is to provide a tire position detection device capable of registering ID information from a transmitter of a subject vehicle with increased accuracy. A further objective is to provide a tire pressure monitoring system incorporating such a tire position detection device.

[0013] The problem is solved by the subject matter of the independent claims. Advantageous further developments can be found in the dependent claims.

[0014] A tire position detection device in a first aspect of the present disclosure is applied to a vehicle having a vehicle body equipped with a plurality of tire wheels, each tire wheel having a tire, wherein the tire position detection device comprises: a transmitter attached to each of the tire wheels and including a first control unit that generates and transmits a frame containing unique identification information; and a receiver attached to the vehicle body and including a second control unit that detects tire position by receiving the frames transmitted by the transmitters via a receiving antenna and then selecting from the identification information contained in the frames candidate identification information indicating candidates to be registered.and identifying from the candidate identification information, the candidate identification information that matches the transmitters attached to the vehicle's wheels, and storing the wheel identification information and the identification information of the transmitters attached to the wheels in association with each other. The transmitter includes an accelerometer that outputs a detection signal based on acceleration including a gravitational acceleration component, the gravitational acceleration component varying by rotating the wheel to which the transmitter is attached. The transmitter's first control unit detects an angle of the transmitter based on the gravitational acceleration component included in the accelerometer's detection signal and transmits the frame repeatedly at times where the angle is a predetermined transmission angle, where any circumferential position of the wheel,which is centered with respect to a central axis of the tire wheel to which the transmitter is attached, is an angle of 0 degrees. The receiver's second control unit performs tire wheel position detection by obtaining gear information, specifying the tooth positions of gears, based on detection signals from tire wheel speed sensors, wherein the tire wheel speed sensors detect the passage of teeth of the gears that rotate in coordination with the tire wheels, each gear having a circumferential surface with the tooth sections and sections between the tooth sections to exhibit alternatingly different magnetic resistance values.wherein the tooth sections are conductive bodies; establishing an allowable range of variation based on the tooth positions at a frame reception time; if the tooth positions at a frame reception time after establishing the allowable range of variation are outside the allowable range of variation, eliminating the tire wheel of tire wheel candidates associated with the transmitter that transmitted the frame; and identifying and registering one remaining tire wheel as the tire wheel to which the transmitter that transmitted the frame is attached. The second control device includes: a preliminary fixer that performs a preliminary fix of each candidate identification piece of information prior to registration when the tire rim to which the transmitter that transmitted the frame is attached is identified based on the tooth positions.which lie within the permissible range of variation; a determination device that, after preliminary fixing, determines whether the tooth positions at a frame reception time, including the preliminary fixed candidate identification information, are within the permissible range of variation; a counter that, after preliminary fixing, measures the number of frame receptions, including the preliminary fixed candidate identification information, at which the tooth positions remain within the permissible range of variation; a first determination device that determines whether the number of receptions is equal to or greater than a first predetermined value; and a register that, if the number of receptions is equal to or greater than the first predetermined value, definitively determines and records the preliminary fixed candidate identification information as the identification information of the identified tire wheel.

[0015] As described above, even if the candidate identification information is identified as the identification information of the transmitter on one of the subject vehicle's tires at the time of tire position acquisition, the identified candidate identification information is not immediately determined and recorded. First, the identified candidate identification information is provisionally established. If the identified candidate identification information is found to be relatively accurate, it is determined and recorded. Thus, relatively accurate candidate identification information can be recorded as the identification information of the transmitter on each of the subject vehicle's tires. This prevents the identification information of a transmitter from another vehicle from being erroneously identified as the identification information of a transmitter on the subject vehicle.

[0016] A tire position detection device in a second aspect of the present disclosure is applied to a vehicle having a vehicle body equipped with a plurality of tire wheels, each tire wheel having a tire, wherein the tire position detection device comprises: a transmitter attached to each of the tire wheels and including a first control unit that generates and transmits a frame containing unique identification information; and a receiver attached to the vehicle body and including a second control unit that detects tire position by: receiving the frames transmitted by the transmitters via a receiving antenna and then selecting from the identification information contained in the frame candidate identification information indicating candidates to be registered.and identifies from the candidate identification information, the candidate identification information that matches the transmitters attached to the vehicle's wheels, and stores the wheel identification information and the identification information of the transmitters attached to the wheels in association with each other. The transmitter includes an accelerometer that outputs a detection signal based on acceleration, including a gravitational acceleration component, the gravitational acceleration component varying by rotating the wheel to which the transmitter is attached. The transmitter's first control unit detects an angle of the transmitter based on the gravitational acceleration component included in the accelerometer's detection signal and transmits the frame repeatedly at times when the angle is a predetermined transmission angle.where any circumferential position of the tire wheel, centered with respect to a central axis of the tire wheel to which the transmitter is attached, is an angle of 0 degrees. The receiver's second control unit performs tire wheel position sensing: obtaining gear information specifying the tooth positions of gears, based on sensing signals from tire wheel speed sensors that detect the passage of teeth of the gears rotating in coordination with the tire wheels, each gear having a circumferential surface with tooth segments and sections between the tooth segments to exhibit alternatingly different magnetic resistance values.wherein the tooth sections are conductive bodies; establishing an allowable range of variation based on the tooth positions at a frame reception time; if the tooth positions at a frame reception time after establishing the allowable range of variation are outside the allowable range of variation, eliminating the tire wheel of tire wheel candidates associated with the transmitter that transmitted the frame; and identifying and registering one remaining tire wheel as the tire wheel to which the transmitter that transmitted the frame is attached. The second control device includes: a preliminary fixer that performs a preliminary fix of each candidate identification piece of information prior to registration when the tire rim to which the transmitter that transmitted the frame is attached is identified based on the tooth positions.which lie within the permissible range of variation; a determination device that, after preliminary fixing, determines whether the tooth positions at a given frame reception time, including the preliminary fixed candidate identification information, lie within the permissible range of variation; a counter that, after preliminary fixing, measures the number of frame receptions, including the preliminary fixed candidate identification information, at which the tooth positions remain within the permissible range of variation; a count difference determination device that, if multiple preliminary fixed candidate identification information sets exist, determineswhether a difference between the largest number of receptions and the second largest number of receptions among the respective numbers of receptions of the frames including the provisionally fixed candidate identification information is equal to or greater than a predetermined value; and a register which, if the difference is determined to be equal to or greater than the predetermined value, definitively determines and records the candidate identification information exhibiting the largest number of receptions as the identification information of the identified tire wheel.

[0017] As described above, when multiple candidate identification information sets for a tire wheel are provisionally recorded, one of the candidate identification sets is identified as the correct identification information for a transmitter on that tire wheel based on the difference in the number of receptions of the candidate identification information sets, or more precisely, the difference in the number of receptions between the highest and second-highest number of receptions. Thus, relatively accurate candidate identification information sets can be registered as the identification information for the transmitter of each tire wheel on the subject vehicle. This prevents the identification information of a transmitter from another vehicle from being erroneously identified as the identification information of a transmitter on the subject vehicle.

[0018] A tire pressure monitoring system comprises a tire wheel position detection device according to a first and second aspect of the present disclosure. The transmitter includes a sensor section that outputs a detection signal based on the tire pressure, which is attached to each of the tire wheels; the first control unit allows the sensor section to perform signal processing of the detection signal, stores tire pressure information derived from the detection signal in the frame, and transmits the frame to the receiver; and the receiver causes the second control unit to detect the tire pressure attached to each of the tire wheels from the tire pressure information. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The foregoing and other tasks, features, and advantages of the present disclosure will become clearer from the following detailed description with reference to the accompanying drawings. In the drawings: Fig. Figure 1 is a diagram representing an overall configuration of a tire pressure monitoring system to which a tire wheel position detection device according to a first embodiment is applied; Fig. 2A is a block diagram representing a transmitter configuration; Fig. 2B is a block diagram representing a configuration of a TPMS ECU 3; Fig. Figure 3 is a time diagram illustrating how the calculation of the tire wheel position is performed; Fig. 4 is a pictogram that represents changes in gear information; Fig. 5A is a schematic diagram representing a tire wheel position determination logic; Fig. 5B is a schematic diagram representing a tire wheel position determination logic; Fig. 5C is a schematic diagram representing a tire wheel position determination logic; Fig. 6A is a table that represents the result of the tire wheel position evaluation of ID 1; Fig. 6B is a table that represents the result of the tire wheel position evaluation of ID 2; Fig. 6C is a table that represents the result of the tire wheel position evaluation of ID 3; Fig. 6D is a table that represents the result of the tire wheel position evaluation of ID 4; Fig. 7 is a flowchart that represents a registration start determination process; Fig. Figure 8 is a flowchart illustrating an ID determination process according to the first embodiment; Fig. 9 is a flowchart illustrating the ID determination processing according to a second embodiment; Fig. Figure 10 is a flowchart illustrating the ID determination processing according to a third embodiment; and Fig. Figure 11 is a flowchart illustrating the ID determination processing according to a fourth embodiment. DESCRIPTION OF THE EXECUTION FORMS

[0020] Embodiments of the present disclosure are now described with reference to the accompanying drawings. In the following description of individual embodiments, identical or equivalent elements are designated with the same reference numerals. (First embodiment)

[0021] A first embodiment of the present disclosure will now be described with reference to the attached drawings. Fig. Figure 1 is a diagram representing an overall configuration of a TPMS to which a tire wheel position detection device according to the first embodiment is applied. The upward direction in Fig. 1 corresponds to the forward direction of a vehicle 1 and the downward direction in Fig. 1 corresponds to the reverse direction of vehicle 1. The TPMS according to the present embodiment is described below with reference to Fig. 1 described.

[0022] As in Fig. As illustrated in Figure 1, the TPMS installed in the vehicle 1 includes transmitters 2, a TPMS ECU 3, and a display instrument 4. The TPMS ECU is an ECU for the TPMS and is designed to function as a receiver. The tire wheel position detection device identifies the tire wheel positions using the transmitters 2 and the TPMS ECU 3, which are included in the TPMS, and obtains gear information from a brake control ECU (hereinafter referred to as the brake ECU) 10. The gear information is derived from the detection signals of the tire wheel speed sensors 11a-11d, which are provided for the tire wheels 5 (5a-5d).

[0023] As in Fig. As illustrated in Figure 1, the transmitters 2 are attached to the tire wheels 5a-5d. The transmitters 2 detect the tire pressures of the tires mounted on the tire wheels 5a-5d, store tire pressure information indicating the detection result and ID information specific to each transmitter 2 in a frame, and transmit the frame. The TPMS ECU 3 is mounted on a vehicle body 6 of the vehicle 1. The TPMS ECU 3 receives the frame transmitted by each transmitter 2 and achieves tire wheel position detection and tire pressure detection by, for example, performing various processing operations and calculations based on a detection signal stored in the frame.

[0024] Transmitters 2 generate a frame, for example, using FSK (frequency shift keying). The TPMS ECU 3 demodulates the frame to read the data within it and performs tire position and tire pressure measurements. Fig. 2A and Fig. 2B are block diagrams showing the configurations of transmitter 2 and TPMS ECU 3.

[0025] As in Fig. As shown in Figure 2A, the transmitters 2 each comprise a sensor section 21, an accelerometer 22, a microcomputer 23, a transmitting circuit 24, and a transmitting antenna 25. These elements are powered by electrical energy supplied by a battery (not shown).

[0026] The sensor section 21 includes, for example, a diaphragm pressure sensor 21a and a temperature sensor 21b. The sensor section 21 outputs a detection signal based on tire pressure and a detection signal based on temperature. The accelerometer 22 is used to detect its position on the tire wheels 5a-5d connected to the transmitters 2, or on the tire wheels 5a-5d to which the transmitters 2 are attached, that is, to detect the positions of the transmitters 2 and the speed of the vehicle. In the present embodiment, the accelerometer 22 outputs a detection signal based on an acceleration exerted on the tire wheels 5a-5d during their rotation, exerted in both radial directions perpendicular to the circumferential directions.

[0027] The microcomputer 23 is a generally known type that includes, for example, a control unit (first control unit). The microcomputer 23 performs predetermined processing in accordance with a program stored in a memory of the control unit. The memory of the control unit stores individual ID information, which includes transmitter-specific identification information for identifying transmitters 2 and vehicle-specific identification information for identifying a subject vehicle.

[0028] The microcomputer 23 receives a tire pressure detection signal from the sensor section 21, processes the detection signal, reprocesses the result of the signal processing as needed, and stores the resulting tire pressure information in a frame along with the ID information of each transmitter 2. Furthermore, the microcomputer 23 monitors the detection signal from the accelerometer 22, detects the position (position angle) of a transmitter 2 on the tire wheel 5a-5d to which the transmitter 2 is attached, and detects the vehicle speed. When a frame is generated, the microcomputer 23 transmits the frame (data) from the transmitting antenna 25 to the TPMS ECU 3 via the transmitting circuit 24, based on the transmitter position detection and the vehicle speed detection.

[0029] More precisely, when vehicle 1 is moving, microcomputer 23 initiates a frame transmission. Microcomputer 23 repeats the frame transmission at a time when the detection signal from accelerometer 22 indicates that accelerometer 22 has a predetermined angle. Whether vehicle 1 is moving is determined based on the result of the vehicle speed detection. The angle of accelerometer 22 is determined based on the result of the transmitter position detection, which is derived from the detection signal of accelerometer 22.

[0030] This means that the microcomputer 23 detects the vehicle speed using the detection signal from the accelerometer 22. If the vehicle speed is equal to or greater than a predetermined speed (for example, 5 km / h), the microcomputer 23 determines that the vehicle is traveling. The output of the accelerometer 22 includes an acceleration based on centrifugal force (centrifugal acceleration). The vehicle speed can be calculated by integrating the centrifugal acceleration and multiplying the result by a coefficient. Therefore, the microcomputer 23 removes a gravitational acceleration component from the output generated by the accelerometer 22 to determine the centrifugal acceleration and then calculates the vehicle speed based on the centrifugal acceleration.

[0031] Furthermore, since the accelerometer 22 outputs a detection signal based on the rotation of each tire wheel 5a-5d, the detection signal includes the gravitational acceleration component while the vehicle 1 is moving. Thus, the detection signal has an amplitude based on the tire wheel rotation. For example, the amplitude of the detection signal is a negative maximum amplitude when the transmitter 2 is positioned above the central axis of the tire wheel 5a-5d, zero when the transmitter 2 is flush with the central axis, and a positive maximum amplitude when the transmitter 2 is positioned below the central axis. Therefore, the position of the accelerometer 22 can be detected based on the amplitude.Additionally, the angle at which the transmitter 2 is positioned, that is, the angle formed by the accelerometer 22, can be determined under the assumption that the angle formed by the accelerometer 22 is 0°, for example, if the accelerometer 22 is positioned above the central axis of the tire wheel 5a-5d.

[0032] Consequently, each transmitter 2 initiates a frame transmission as soon as the predetermined vehicle speed is reached, or when the accelerometer 22 is positioned at the predetermined angle after the predetermined vehicle speed has been reached. The frame transmission is then repeated at a time when the angle formed by the accelerometer 22 is equal to the angle at which the first frame transmission is performed. The frame transmission can be performed every time the angle formed by the accelerometer 22 is equal to the angle at which the first frame transmission is performed. However, considering battery life, it is preferred that the frame transmission be performed, for example, at predetermined time intervals (e.g., at 15-second intervals), without continuously performing the frame transmission every time the aforementioned angle is reached.

[0033] The transmitting circuit 24 functions as an output section that transmits a frame from the microcomputer 23 to the TPMS ECU 3 via the transmitting antenna 25. For example, RF band radio waves are used for frame transmission.

[0034] The transmitter, configured as described above, is attached, for example, to an air inflation valve of each tire 5a-5d and positioned such that the sensor section 21 is exposed to the inside of a tire. The transmitter 2 detects the tire pressure of a tire connected to it. When the predetermined vehicle speed is exceeded, as mentioned above, the transmitter 2 repeatedly performs a frame transmission through the transmitting antenna 25 attached to the transmitter 2 at a time when the predetermined angle is reached by the accelerometer 22 of each tire 5a-5d. Subsequently, the transmitter 2 can perform a frame transmission successively at a time when the predetermined angle is reached by the accelerometer 22 of each tire 5a-5d. However, the transmission intervals should be increased to conserve battery life.Therefore, if a time period presumably required for tire position detection has elapsed, a tire position determination mode is replaced by a periodic transmission mode. In periodic transmission mode, frame transmission is performed at longer, fixed time intervals (for example, at intervals of one minute) to periodically transmit a tire pressure signal to the TPMS ECU 3. In this case, for example, any desired delay can be set for each transmitter 2 to delay the transmission time of each transmitter 2. This avoids a situation in which the TPMS ECU 3 cannot receive signals from a large number of transmitters 2 due to radio wave interference.

[0035] As in Fig. As shown in Figure 2B, the TPMS ECU 3 comprises a receiving antenna 31, a receiving circuit 32, and a microcomputer 33. The TPMS ECU 3 obtains a gear position, specified by the number of tooth flanks (or the number of teeth) of a gear that rotates together with each tire wheel 5a-5d, by acquiring the gear information from the brake ECU 10, as described later, via a vehicle LAN such as a CAN.

[0036] The receiving antenna 31 is used to receive a frame transmitted by each transmitter 2. The receiving antenna 31 is attached to the vehicle body 6 and can be an internal antenna located in the body of the TPMS ECU 3, or an external antenna connected to the body of the TPMS ECU 3.

[0037] The receiving circuit 32 functions as an input section that inputs a frame received from each transmitter 2 via the receiving antenna 31 and delivers the frame to the microcomputer 33. After receiving a signal (frame) by the receiving antenna 31, the receiving circuit 32 transmits the received signal to the microcomputer 33.

[0038] The microcomputer 33 corresponds to a second control unit and performs tire wheel position detection in accordance with a program stored in a memory of the microcomputer 33. Specifically, the microcomputer 33 performs tire wheel position detection based on the relationship between the information acquired by the brake ECU 10 and the time at which a frame transmitted by each transmitter 2 is received. The tire wheel speed information of each tire wheel 5a-5d and the gear information of each tire wheel speed sensor 11a-11d, which are provided accordingly for the tire wheels 5a-5d, are obtained by the brake ECU 10 at predetermined time intervals (for example, at intervals of 10 milliseconds).

[0039] The gear information indicates the positions of the teeth of a gear that rotates with each tire wheel 5a-5d. The tire wheel speed sensors 11a-11d, each consisting, for example, of an electromagnetic transducer sensor facing the teeth of the gear, vary their detection signals based on the passage of the gear teeth. Detection signals output by tire wheel speed sensors 11a-11d of this type are quadratic pulse waves based on the passage of teeth. Therefore, the rise and fall of the quadratic pulse waves indicates the passage of the gear teeth.Therefore, the brake ECU 10 determines the number of tooth flanks of the gear from the number of rises and falls of the detection signal of each tire speed sensor 11a-11d; that is, it counts the number of tooth flank passages and delivers the current number of tooth flanks to the microcomputer 33 at predetermined time intervals as the gear information indicating the tooth positions. This allows the microcomputer 33 to determine the time at which a specific tooth of the gear passes through.

[0040] The number of tooth flanks is reset with each rotation of the gear. For example, if the gear has 48 teeth, a total of 96 tooth flanks (tooth flanks 0 to 95) are counted. When the counter reaches 95, it is reset to 0 (zero) and the counting continues.

[0041] It is assumed that the number of tooth flanks of the gear is transmitted from the brake ECU 10 to the microcomputer 33 as the gear information. Alternatively, however, the number of teeth, which is the count of tooth passes, can be transmitted as the gear information. Another alternative is to transmit the number of tooth flanks or teeth that have passed during a predetermined time period to the microcomputer 33, have the microcomputer 33 add the number of tooth flanks or teeth that passed during the predetermined time period to the number of tooth flanks or teeth that passed previously, and allow the microcomputer 33 to count the number of tooth flanks or teeth in such a cycle. That is, the microcomputer 33 should ultimately be able to obtain the number of tooth flanks or teeth as the gear information in such a cycle.Although the brake ECU 10 resets the number of tooth flanks (or teeth) of the gear each time the power supply is switched off, the brake ECU 10 resumes the measurement as soon as the power supply is switched back on or when a predetermined vehicle speed is reached after switching it on. Accordingly, even though a reset is performed each time the power supply is switched off, the same teeth are expressed by the same number of tooth flanks (or teeth) while the power supply is on.

[0042] The microcomputer 33 measures the frame reception time starting from the reception of a frame transmitted by each transmitter 2 and performs a wheel position detection based on the number of tooth flanks (or teeth) of the gear at the frame reception time, which is contained in the obtained information about the number of tooth flanks (or teeth) of the gear. Consequently, a wheel position detection can be performed to determine to which wheel 5a-5d each transmitter 2 is attached. A specific method for wheel position detection will be described in detail later.

[0043] Furthermore, based on the result of the tire wheel position detection, the microcomputer 33 stores the link between the ID information of each transmitter 2 and the position of a tire wheel 5a-5d associated with each transmitter 2. Subsequently, based on the ID information and tire pressure data stored in a frame transmitted by each transmitter 2, the microcomputer 33 detects the tire pressure of each tire wheel 5a-5d and outputs an electrical signal corresponding to the detected tire pressure to the display instrument via a vehicle LAN such as CAN. For example, the microcomputer 33 compares the tire pressure with a predetermined threshold Th to detect a decrease in tire pressure. Upon detecting a decrease in tire pressure, the microcomputer 33 outputs a signal indicating the decrease in tire pressure to the display instrument 4.In this way, counter 4 is informed which of the four tire wheels 5a - 5d a has experienced a reduction in tire pressure.

[0044] Display instrument 4 functions as an alarm. As in Fig. As illustrated in Figure 1, the display instrument 4 is positioned so that it is visible to a driver of the vehicle 1 and is, for example, a display instrument mounted on the dashboard of the vehicle 1. For example, when a signal indicating a decrease in tire pressure is transmitted from the microcomputer 33 in the TPMS ECU 3, the display instrument 4 notifies the driver of the decrease in tire pressure of a specific tire wheel by displaying information indicating the decrease in tire pressure while identifying the affected tire wheel 5a-5d.

[0045] The operations of the TPMS according to the present embodiment are now described. The following description of the TPMS operations is divided into two parts: one for tire position detection in the TPMS and the other for tire pressure detection in the TPMS. First, a specific method for tire position detection is described with reference to Fig. 3 to 6D described.

[0046] Transmitter 2 detects the vehicle speed and the angle of the accelerometer 22 of each wheel 5a-5d by enabling the microcomputer 23 to monitor the accelerometer 22's detection signal at predetermined sampling intervals based on the battery supply. When the predetermined vehicle speed is reached, the microcomputer 23 repeatedly performs a frame transmission at a time when the predetermined angle is reached by the accelerometer 22. Each transmitter 2 begins to perform a frame transmission at a time when, for example, the predetermined vehicle speed is reached or the predetermined angle is reached by the accelerometer 22 after the predetermined vehicle speed has been reached.Then, at a time when the angle formed by the accelerometer 22 becomes equal to the angle at the first frame transmission, each transmitter 2 performs a repeated frame transmission.

[0047] The gravitational acceleration component extracted from the detection signal of the accelerometer 22 is a Fig. Figure 3 shows a sine wave. The angle of the accelerometer 22 can be determined from the sine wave. Therefore, the frame transmission is carried out at a time when the sine wave indicates that the accelerometer 22 is at the same angle.

[0048] Meanwhile, the TPMS ECU 3 receives the gear information from the tire speed sensors 11a-11d, which are intended for the tire wheels 5a-5d, from the brake ECU 10 at predetermined intervals (for example, intervals of 10 milliseconds). After receiving a frame from each transmitter 2, the TPMS ECU 3 measures the frame reception time and obtains the number of tooth flanks (or teeth) of the gear at the frame reception time from the obtained gear information, which indicates the number of tooth flanks (or teeth) of the gear.

[0049] In the above case, the frame reception time of a frame transmitted by each transmitter 2 does not always coincide with the gear information acquisition cycle from the brake ECU 10. Therefore, the number of gear flanks (or gear teeth) specified by the gear information acquired in a cycle closest to, that is, immediately before or after, the frame reception time of the gear information acquisition cycles from the brake ECU 10 can be used as the number of gear flanks (or gear teeth) at the frame reception time. Alternatively, the number of gear flanks (or gear teeth) at the frame reception time can be calculated using the number of gear flanks (or gear teeth) specified by the gear information acquired in a cycle immediately before or after the frame reception time of the gear information acquisition cycles from the brake ECU 10.For example, an intermediate value of the number of gear flanks (or gear teeth) specified by the gear information obtained in a cycle immediately before or after the frame reception time can be used as the number of gear flanks (or gear teeth) at the frame reception time.

[0050] The operation described above for capturing the number of gear tooth flanks (or gear teeth) at frame reception time is repeated from each frame reception to perform wheel position detection based on the number of gear tooth flanks (or gear teeth) at the time a frame is received. More precisely, wheel position detection is performed by determining whether the change in the number of gear tooth flanks (or gear teeth) at frame reception time is within a predetermined range, based on the number of gear tooth flanks (or gear teeth) at the last frame reception time.

[0051] With respect to a tire wheel from which a frame is received, the frame is transmitted at a time when the predetermined angle is reached by the accelerometer 22. Therefore, the tooth positions, specified by the number of gear tooth flanks (or gear teeth), at the frame reception time essentially correspond to the last tooth positions. Consequently, the variation in the number of gear tooth flanks (or gear teeth) at the frame reception time is small and limited within the predetermined range. This also applies if the frame reception occurs multiple times. The variation in the number of gear tooth flanks (or gear teeth) at each frame reception time is within the predetermined range determined at the first frame reception time.Meanwhile, with respect to a tire wheel other than the tire wheel from which a frame is received, the tooth positions vary, which are specified by the number of gear tooth flanks (or gear teeth) at the time of frame reception of a frame transmitted from a transmitter 2 of another tire wheel.

[0052] This means that when the gears of the tire wheel speed sensors 11a-11d rotate in coordination with the tire wheels 5a-5d, the tooth positions of a tire wheel from which a frame is received essentially correspond to the tooth positions indicated by the number of gear tooth flanks (or gear teeth) at the frame reception time. However, the rotations of the tire wheels 5a-5d vary due to factors such as road conditions, turning, cornering, or lane changes. Therefore, the rotations of the tire wheels 5a-5d cannot be perfectly identical. Consequently, with respect to a tire wheel that differs from the tire wheel from which a frame is received, the tooth positions indicated by the number of gear tooth flanks (or gear teeth) at the frame reception time will vary.

[0053] Accordingly, with respect to a wheel that differs from the wheel from which the frame continuously receives data after the start of driving, in a state where the number of tooth flanks of gears 12a-12d is initially 0 (zero) when an ignition switch (IG) is turned on, the tooth positions, which are indicated by the number of gear tooth flanks (or gear teeth) at the frame reception time, vary as shown in Fig. Figure 4 illustrates the tire / wheel position detection, which is performed by determining whether the variation lies within the predetermined range.

[0054] For example, it is assumed that transmitter 2 is positioned at a first reception angle at the time of the first frame transmission, as in Fig. 5A is shown. It is also assumed that an allowable range of variation, which is a range in which the variation in the number of gear tooth flanks (or gear teeth) is allowed, is a value within a range of 180 degrees centered with respect to the first receiving angle (a range of the first receiving angle plus / minus 90 degrees). When it comes to the number of tooth flanks, the range is assumed to be a range of the number of tooth flanks plus / minus 24, centered with respect to the number of tooth flanks at the time of first receiving. When it comes to the number of teeth, the range is assumed to be a number of teeth plus / minus 12, centered with respect to the number of teeth at the time of first receiving. In this situation, as shown in Fig. As illustrated in Figure 5B, if the number of gear tooth flanks (or gear teeth) at the time of the second frame reception is within the permissible range of variation determined by the first frame reception, a wheel with that number of gear tooth flanks (or gear teeth) can match the wheel from which the frame is transferred. In this case, a true (correct) result is obtained.

[0055] However, in the above case as well, the permissible variation range is centrally determined with respect to the second reception angle, which is the angle of transmitter 2 at the time of the second frame reception. Thus, the permissible variation range corresponds to an angle of 180 degrees (± 90 degrees) centered with respect to the second reception angle. Therefore, an overlap between the permissible variation range of 180 degrees (± 90 degrees) centered with respect to the first reception angle, which is the previous permissible variation range, and the permissible variation range of 180 degrees (± 90 degrees) centered with respect to the second reception angle, results in a new permissible variation range (the number of tooth flanks ranges from 12 to 48). The new permissible variation range can be narrowed down to such an overlap range.

[0056] Therefore, as in Fig. As illustrated in Figure 5C, if the number of gear tooth flanks (or gear teeth) at the time of the third frame reception is outside the allowable range of variation determined by the first and second frame receptions, a wheel with that number of gear tooth flanks (or gear teeth) will not match the wheel from which the frame is transferred. In this case, a FALSE (incorrect) result is obtained. In the preceding example, even if the number of gear tooth flanks (or gear teeth) at the time of the third frame reception is within the allowable range of variation determined by the first frame reception, the result is determined as FALSE if the number of gear tooth flanks (or gear teeth) at the time of the third frame reception is outside the allowable range of variation determined by the first and second frame receptions.This makes it possible to determine on which of the tire wheels 5a-5d the transmitter 2, which sent the received frame, is attached.

[0057] That is, as in Fig. As illustrated in Figure 6A, the number of gear tooth flanks (or gear teeth) from a frame with ID 1 is obtained as the ID information at each time such a frame is received, and the obtained information is stored for each associated tire wheel (front left tire wheel FL, front right tire wheel FR, rear left tire wheel RL, rear right tire wheel RR). Each time the frame is received, it is determined whether the detected number of gear tooth flanks (or gear teeth) is within the permissible range of variation, and a tire wheel determined to be outside this range is eliminated from the tire wheel candidates associated with transmitter 2 that transmitted the frame. Finally, a tire wheel that is not eliminated is registered as the tire wheel associated with transmitter 2 that transmitted the frame.If the frame contains ID 1, the front right tire FR, the rear right tire RR and the rear left tire RL are successively eliminated from the candidates and the finally remaining front left tire FL is registered in conjunction with the ID information as the tire that is connected to or on which transmitter 2 is attached, which transmitted the frame.

[0058] As in Fig. As illustrated in Figures 6B to 6D, frames with IDs 2 to 4 are processed in the same way as the frame with ID 1. Consequently, the wheels of tires to which the transmitters 2, which transmitted the frames, are attached can be identified. Accordingly, all four wheels of tires to which the transmitters 2 are attached can be identified.

[0059] In the manner described above, it is determined which of the tire wheels 5a-5d each frame is connected to. Then the microcomputer 33 stores the ID information of each of the transmitters 2 that the frames have transmitted in conjunction with the position of the tire wheel to which each transmitter 2 is attached.

[0060] Furthermore, the TPMS ECU 3 receives a frame transmitted when a predetermined vehicle speed is reached and stores the gear information received at that time. However, if the vehicle speed is equal to or lower than a predetermined stop-start speed (e.g., 5 km / h), the TPMS ECU 3 discards the preceding gear information. Subsequently, when the vehicle resumes driving, the tire position detection is performed again in the manner described above.

[0061] Basic tire position detection is performed using the procedure described above. Therefore, the positions of the tires—namely, the front left tire (FL), the front right tire (FR), the rear left tire (RL), and the rear right tire (RR)—can be detected. If a frame transmitted by another vehicle is received during tire position detection, the ID information stored in that frame can be a candidate ID. That is, when tire position detection is performed, all ID information contained in received frames is treated as candidate IDs, and a transmitter 2 on the subject vehicle is selected from these candidate IDs. Accordingly, the candidate IDs are stored in the memory of the TPMS ECU 3, and a transmitter 2 on the subject vehicle is ultimately selected and registered from the stored candidate IDs.Under normal conditions, however, while a tire wheel position determination logic is used to determine the tire wheel position, there occurs a point in time when a frame transmitted by a transmitter on another vehicle does not coincide with the gear positions of the tire wheels 5a-5d of the subject vehicle. Consequently, only the ID information of one transmitter 2 is registered on the subject vehicle, while the registration of the ID information of a transmitter from another vehicle is avoided.

[0062] Under normal conditions, processing is based on the tire position determination logic, so the ID information of a transmitter from another vehicle lies outside the permissible range of variation. However, the ID information of a transmitter from another vehicle can be incorrectly identified as the ID information of transmitter 2 of the subject vehicle. This situation can occur, for example, if no frame is received from transmitter 2 of the subject vehicle for an extended period, so that a frame is received from a transmitter from another vehicle before a frame is received from transmitter 2 of the subject vehicle. In particular, if a frame from a transmitter from another vehicle is registered as a candidate ID in a situation where no frame is received from transmitter 2 of the subject vehicle, the registered candidate ID can soon deviate from the permissible range of variation.Thus, a candidate ID that inadvertently remains within the permissible range of variation could be identified as the ID information of sender 2 of the subject vehicle. In such a case, it is undesirable for such a candidate ID to be quickly determined and registered as the ID information of sender 2 of the subject vehicle.

[0063] Consequently, even if a candidate ID is identified as the ID information of a transmitter 2 on a tire 5a-5d of the subject vehicle, the present embodiment first makes a preliminary determination. If such a determination is subsequently found to be relatively accurate, the present embodiment registers such a candidate ID as the ID information of transmitter 2 of the subject vehicle. More precisely, the present embodiment performs methods described in the Fig. 7 and Fig. 8 are illustrated.

[0064] First, a Fig. The registration start determination processing shown in step 7 is performed to determine whether or not to enter an ID registration mode. In the ID registration mode, an ID determination processing process is performed, which is described in Fig. Figure 8 illustrates the process used to determine and register a relatively accurate candidate ID as the ID information of a sender 2 of the subject vehicle. The processing described in Figure 8 illustrates the following steps: Fig. 7 and Fig. The operations shown in 8 are performed at predetermined control intervals when the ignition switch (IG) is turned to power the TPMS ECU 3.

[0065] As in Fig. As illustrated in Figure 7, steps 100 to 130 are performed to determine whether the transition to ID registration mode is currently required.

[0066] More specifically, step 100 determines whether a request to switch to ID registration mode is generated by an external tool (not shown) that issues a tire position detection instruction. For example, the external tool sends a command to switch to ID registration mode to the TPMS ECU 3 using radio waves or an in-vehicle LAN (e.g., CAN).

[0067] Step 110 determines whether, for example, an execution switch (not shown) for tire position detection is activated to generate a request to transition to ID registration mode. The execution switch for tire position detection is, for example, mounted on the dashboard. When the execution switch is activated by a user, the request is transmitted to the TPMS ECU 3 via the vehicle's internal LAN, similar to a CAN bus.

[0068] Step 120 determines whether the ID information of transmitter 2 for each tire wheel 5a-5d is registered. If the vehicle has just been manufactured, the tire wheel position detection must be performed, as the ID information of each transmitter 2 is not yet registered.

[0069] In step 130, registered and unregistered ID information are compared based on the number of receptions to determine, for example, whether a tire change may have been performed. If a tire change has occurred, the tire position must also be recorded. For example, if the number of receptions of unregistered ID information is greater than the number of receptions of registered ID information by at least a predetermined value, step 130 determines that a tire change may have been performed.

[0070] Consequently, if the query is answered positively in any of steps 100 to 130, processing continues to step 140. In step 140, the transition to ID registration mode is performed, and the preceding processing ends. Conversely, if the query is answered negatively in all steps 100 to 130, processing returns to step 100 to repeat the preceding processing. The registration start determination processing for performing a tire position detection and determining whether or not to start the registration of the ID information of transmitter 2 of the subject vehicle is completed in the manner described above.

[0071] The ID determination processing is then carried out, which is described in Fig. Figure 8 illustrates this. First, step 200 determines whether ID registration mode is predominant. If the transition to ID registration mode occurs in step 140 of Fig. Once step 7 has been completed, the query in step 200 will be answered positively and the processing will proceed to step 205.

[0072] In step 205, RF reception occurs; that is, a frame transmitted in the form of RF radio waves is received, and processing proceeds to step 210. Step 210 determines whether the subject vehicle is moving. Here, tire position detection is performed by enabling the accelerometer 22 to detect any acceleration that occurs when the vehicle is moving. Accordingly, if the subject vehicle is not moving, it is excluded from tire position detection. Therefore, if the query in step 210 is answered positively, processing proceeds to step 215. Conversely, if the query is answered negatively, processing returns to step 205.

[0073] Whether the subject vehicle is moving can be determined, for example, by obtaining vehicle speed data from the brake ECU 10, since the brake ECU 10 calculates the vehicle speed based on the detection signals from the tire speed sensors 11a - 11d. Therefore, if, for example, a vehicle speed is generated, it can be determined that the vehicle is moving.

[0074] Step 215 determines whether the ID information stored in the currently received frame is an initially received ID. If the query in step 215 is answered positively, processing proceeds to step 220 and the initially received ID is registered as a candidate ID.

[0075] If, however, the query in step 215 is answered negatively, the ID information stored in the currently received frame is already registered as a candidate ID. In this case, processing continues to step 225. Step 225 determines whether the ID information stored in the currently received frame is provisionally fixed as the ID information of sender 2 of the subject vehicle.

[0076] When the ID information of sender 2 on a specific tire wheel 5a-5d is identified from candidate IDs based on the tire wheel position determination logic and then provisionally fixed, this means that the ID information is temporarily set as the ID information to be definitively fixed. If the ID information stored in a received frame is provisionally fixed, the ID information is most likely the ID information of sender 2 on a specific tire wheel, but it is still not definitively determined. If the ID information is provisionally fixed, this is indicated, for example, by a provisional fix flag in step 240, which is described later. Therefore, whether the ID information is provisionally fixed can be determined by checking if such a provisional fix flag is set.

[0077] If the query in step 225 is answered negatively, processing proceeds to step 230 and data about a registered candidate ID is updated. More precisely, a data update for tire wheel position detection is performed based on the tire wheel position determination logic, for example, by capturing the gear information of the candidate ID at the frame reception time and determining whether the number of gear tooth flanks (or gear teeth) specified by the obtained gear information is within the permissible range of variation. Accordingly, as described in the Fig. As illustrated in Figures 6A to 6D, the data is updated via a candidate ID each time a frame is received in order to perform tire wheel position detection.

[0078] The processing then continues with step 235, determining whether the tire wheel position is identified for the candidate ID. That is, as in Fig. As illustrated in Figures 6A to 6D, the process determines whether only one of the four tire wheels 5a-5d lies within the permissible range of variation for the candidate ID. If it is determined that only one tire wheel lies within the permissible range of variation, the processing proceeds to step 240. In step 240, the candidate ID is provisionally fixed as the ID information of sender 2 of a tire wheel identified as the one within the permissible range of variation. After completion of step 240, the processing returns to step 205. If, however, it is not determined that only one tire wheel lies within the permissible range of variation, the processing returns to step 205, and then steps 205 and beyond are repeated until the provisional fixation is achieved.

[0079] If the preliminary fix for the candidate ID was performed as described above, the query in step 225 will be answered positively. In such a case, processing continues with steps 245 and following, so that the preliminary fixed candidate ID is processed to increase accuracy.

[0080] More specifically, in step 245, tire wheel position detection is continuously performed for the provisionally fixed candidate ID based on the tire wheel position determination logic to determine whether the identified relevant tire wheel remains within the permissible range of variation. If the relevant tire wheel is within the permissible range of variation, processing proceeds to step 250, and the number of receptions after provisional fixing is updated by incrementing the count by one. After step 250 is completed, processing continues with step 255, which determines whether the number of receptions after provisional fixing is equal to or greater than a first predetermined value (e.g., three).When the number of receptions after the preliminary fix reaches the first predetermined value, processing proceeds to step 260, as it is highly likely that the preliminary fix candidate ID is the ID information of transmitter 2 on the relevant tire wheel. In step 260, the preliminary fix candidate ID is definitively determined and registered as the ID information of transmitter 2 on the relevant tire wheel.

[0081] However, if in step 245 the relevant tire wheel lies outside the permissible range of variation for the provisionally fixed candidate ID, it can be said that the provisionally fixed candidate ID is not the ID information of sender 2 of the relevant tire wheel. In this case, the processing therefore proceeds to step 265 and the provisional fix is ​​reset. After completion of step 265, the processing returns to step 205. In the manner described above, a relatively accurate candidate ID can be registered as the ID information of a sender 2 of each tire wheel 5a-5d of the subject vehicle.

[0082] After the tire position detection is complete as described above, the tire pressure detection is performed. More precisely, during tire pressure detection, each transmitter 2 transmits a frame at fixed time intervals. Each time a frame is transmitted by each transmitter 2, the TPMS ECU 3 receives the frames from four rotating tires. Based on the ID information stored in each frame, the TPMS ECU 3 identifies which transmitter 2, attached to a tire 5a-5d, transmitted the frame and reads the tire pressure of each tire 5a-5d from the tire pressure information. Thus, a decrease in the tire pressure of each tire 5a-5d can be detected to identify a tire 5a-5d with reduced tire pressure. When a tire pressure drop is detected, it is sent to the display instrument 4.The instrument 4 then notifies the driver of the decrease in tire pressure of a particular tire by displaying information indicating the decrease in tire pressure while identifying the affected tire wheel 5a-5d.

[0083] As previously described, the gear information, specifying the tooth positions of gears 12a-12d, is obtained at predetermined time intervals based on detection signals from the tire speed sensors 11a-11d, which detect the passage of the teeth of gears 12a-12d rotating in accordance with the tire wheels 5a-5d. The permissible variation range is then determined based on the tooth positions at the time of frame reception. If, after determining the permissible variation range, the tooth positions at the time of frame reception are outside the permissible variation range, a tire wheel attached to transmitter 2, which sent the linked frame, is eliminated from the candidates. Finally, one remaining tire wheel is registered as the tire wheel attached to transmitter 2, which transmitted the linked frame.Consequently, the tire wheel positions of the running tires can be identified without waiting until a large amount of data is collected.

[0084] Even if one of the candidate IDs is identified as the ID information of transmitter 2 on a specific tire 5a-5d of the subject vehicle during tire position detection, such a candidate ID is not immediately definitively determined and registered, but is provisionally fixed. If the candidate ID is later found to be relatively accurate, it is definitively determined and registered. In this way, a relatively accurate candidate ID can be registered as the ID information of a transmitter 2 on each tire 5a-5d of the subject vehicle. This further prevents the ID information of a transmitter from another vehicle from being erroneously identified as the ID information of a transmitter 2 of the subject vehicle.

[0085] Furthermore, since the ID information of transmitter 2 of each tire wheel 5a-5d can be registered in the manner described above, a trigger device with an antenna is not required for each tire wheel. This prevents an increase in the number of parts due to the need for additional components and thus avoids an increase in costs. In addition, a dual-axis accelerometer, which is a highly functional add-on component, does not need to be installed. (Second embodiment)

[0086] A second embodiment is now described. The second embodiment is similar to the first embodiment except for the method of determining the tire wheel position. Therefore, only the differences from the first embodiment are described below.

[0087] The first embodiment is configured under the assumption that only one candidate ID is identified as the ID information of sender 2 on a specific tire 5a-5d of the subject vehicle. Meanwhile, the second embodiment is configured to determine the tire position even if two or more candidate IDs are simultaneously identified as the ID information of sender 2 on a specific tire 5a-5d of the subject vehicle. More precisely, the second embodiment performs an ID determination process that is described in Fig. Figure 9 illustrates that, instead of the ID determination processing performed in the first embodiment and in Fig. 8 is illustrated. Steps 200 to 265 of Fig. 9 are the same as steps 200 to 265 of Fig. 8 and are not described redundantly.

[0088] First, steps 200 to 250 are carried out in the same way as in Fig. Step 8 is performed, and processing continues with step 251. In step 251, it is determined whether there are a multitude of fixed candidate IDs for the relevant tire wheel.

[0089] Tire wheel position detection, based on the tire wheel position determination logic, is performed for each candidate ID. A large number of candidate IDs may fall within the permissible range of variation defined for a specific tire wheel. In such a case, the query in step 251 is answered positively. If the query in step 251 is answered negatively, steps 255 and beyond are performed in the same manner as in the first embodiment. Conversely, if the query in step 251 is answered positively, processing proceeds to step 270.

[0090] In step 270, it is determined whether the number of receptions after preliminary fixing is equal to or greater than a second predetermined value (e.g., six). The second predetermined value is greater than the first predetermined value. If the number of receptions after preliminary fixing is equal to or greater than the second predetermined value, processing proceeds to step 260, as it is highly likely that the associated preliminary fixed candidate ID is the ID information of transmitter 2 on the relevant tire wheel. In step 260, the associated preliminary fixed candidate ID is definitively determined and registered as the ID information of transmitter 2 on the relevant tire wheel.

[0091] As described above, if multiple tentatively fixed candidate IDs exist for a given tire, the number of receptions for accuracy verification is set to be higher than if there were only one tentatively fixed candidate ID for that tire. More precisely, the number of receptions for accuracy verification is changed from the first predetermined value to the second predetermined value. Therefore, a second candidate ID that is incorrect, as the ID information of sender 2 of the relevant tire, can be outside the permissible range of variation while the data for the second predetermined value for the relevant tire is being updated. This further prevents the ID information of a sender from another vehicle from being incorrectly identified as the ID information of sender 2 of the subject vehicle. (Third embodiment)

[0092] A third embodiment is now described. This third embodiment is similar to the first, with the exception of the method for determining the tire / wheel position. Therefore, only the differences from the first embodiment are described below.

[0093] The third embodiment is configured to determine the tire wheel position in a manner different from that used in the second embodiment, even when two or more candidate IDs are simultaneously identified as the ID information of sender 2 of a specific tire wheel 5a-5d of the subject vehicle. More precisely, the third embodiment performs an ID determination process that is described in Fig. 10 is illustrated, instead of the ID determination processing that is performed in the first embodiment and in Fig. 8 is illustrated. Steps 200 to 250, 260 and 265 of Fig. 10 are the same as steps 200 to 250, 260 and 265 of Fig. 8 and are not described redundantly.

[0094] First, steps 200 to 250 are carried out in the same way as in Fig. As illustrated in Figure 8, the process is executed, and processing proceeds to step 256. In step 256, tentatively fixed candidate IDs for the relevant tire wheel are checked to determine if the difference between the highest number of receptions and the second-highest number of receptions is equal to or greater than a predetermined value (for example, three). If, in this case, only one tentatively fixed candidate ID exists for the respective tire wheel, step 256 is performed assuming that the second-highest number of receptions is 0 (zero). If the query in step 256 is successful, processing proceeds to step 260, since the candidate ID with the highest number of receptions is most likely the ID information of sender 2 of the relevant tire wheel.In step 260, the candidate ID with the highest number of receptions is definitively determined and registered as the ID information of transmitter 2 of the relevant tire wheel.

[0095] As described above, if a large number of tentatively fixed candidate IDs exist for a particular tire, the system determines which candidate ID represents the correct ID information of transmitter 2 of the relevant tire based on the difference between the number of candidate ID receptions, or more precisely, the difference between the highest and second-highest number of receptions. This also prevents the ID information of a transmitter from another vehicle from being incorrectly identified as the ID information of transmitter 2 of the subject vehicle. Furthermore, if multiple candidate IDs exist for a particular tire, the tire position detection is not completed until the candidate IDs are narrowed down to a single one.Therefore, if a frame containing a specific candidate ID is not received for an extended period, thus keeping the relevant candidate ID within the permissible range of variation, the time required to complete tire position detection can increase. However, the third embodiment determines the ID information of a transmitter 2 of the subject vehicle based on the difference between the number of candidate ID receptions. This reduces the time required to complete tire position detection. (Fourth embodiment)

[0096] A fourth embodiment is now described. This fourth embodiment is similar to the third, except for the method of determining the tire / wheel position. Therefore, only the differences from the third embodiment are described below.

[0097] If multiple candidate IDs are registered for a particular tire wheel, the third embodiment checks each of the tire wheels 5a-5d to determine whether the difference between the highest number of receptions and the second-highest number of receptions is equal to or greater than a predetermined value. In this case, if the difference is equal to or greater than the predetermined value, the third embodiment identifies and registers a candidate ID with the highest number of receptions as the ID information of transmitter 2 on the relevant tire wheel, without regard to the other tire wheels.Meanwhile, the fourth embodiment determines and registers a candidate ID that has the largest number of receptions as the ID information of transmitter 2 on the relevant tire wheel only if the difference between the largest number of receptions and the second largest number of receptions is equal to or greater than a predetermined value in each of the tire wheels 5a-5d.

[0098] More precisely, the fourth embodiment performs an ID determination process that is described in Fig. Figure 11 illustrates, instead of the ID determination processing performed in the first embodiment and in Fig. Figure 8 is illustrated. In the ID determination method according to the fourth embodiment, steps 257 and 261 of Fig. 11 instead of steps 256 and 260 of Fig. 10 executed. In Fig. Steps 11, except for steps 257 and 261, are the same as those in the third embodiment.

[0099] First, steps 200 to 250 are carried out in the same way as in Fig.As illustrated in Figure 10, the following steps are performed. In step 257, tentatively fixed candidate IDs for all four tire wheels 5a-5d are checked to determine if the difference between the highest number of receptions and the second-highest number of receptions is equal to or greater than a predetermined value (for example, three). If, in this case, there is only one tentatively fixed candidate ID for each of the four tire wheels 5a-5d, step 257 is performed assuming that the second-highest number of receptions is 0 (zero). If the query in step 257 is successful, the candidate ID with the highest number of receptions for each of the four tire wheels 5a-5d is most likely the ID information of sender 2 on the corresponding tire wheel. Therefore, processing proceeds to step 261.In step 261, the candidate ID that has the largest number of receptions for each of the four tire wheels 5a-5d is determined and registered as the ID information of sender 2 of the linked tire wheel.

[0100] As described above, if the difference between the highest number of receptions and the second-highest number of receptions is equal to or greater than the predetermined value at the same time in each of the four tire wheels 5a-5d, the relevant candidate ID is determined and registered as the ID information of transmitter 2 on the corresponding tire wheel. This further prevents the ID information of a transmitter from another vehicle from being erroneously identified as the ID information of transmitter 2 of the subject vehicle. That is, if the ID information of a transmitter from another vehicle is provisionally fixed as the ID information of transmitter 2 of the subject vehicle in any one of the four tire wheels 5a-5d, the condition that the difference between the highest number of receptions and the second-highest number of receptions must be equal to or greater than the predetermined value may not be met by the other tire wheels.In such a case, the number of receptions from one wheel containing the ID information of transmitter 2 of the subject vehicle can increase before the aforementioned condition is met by the other wheels, thus reversing the relationship between the number of receptions of the ID information of transmitter 2 of the subject vehicle and the number of receptions of the ID information of the other vehicle's transmitter. In such a situation, determining and registering the ID information for the first time when the condition is met by all wheels, rather than determining and registering the ID information each time the condition is met by a wheel, prevents the ID information of the other vehicle's transmitter from being erroneously identified as the ID information of transmitter 2 of the subject vehicle. (Alternative embodiments)

[0101] The present disclosure is not limited to the above embodiments, but the embodiments can be modified in a suitable manner.

[0102] In the aforementioned embodiments, the permissible variation range is continuously narrowed by changing it at each point in time during frame reception, but the permissible variation range, which is to be centrally determined with respect to the tooth positions, is assumed to be constant. Alternatively, the permissible variation range, which is to be centrally determined with respect to the tooth positions, can also be modified. For example, the change in tooth positions may increase with an increase in vehicle speed. Therefore, if the permissible variation range is increased with an increase in vehicle speed, a more precise permissible variation range can be determined. The longer the sampling intervals at which the accelerometer 22 detects acceleration, the lower the accuracy of detecting the time at which the accelerometer 22 reaches the predetermined angle.Therefore, a precise permissible range of variation can be determined by modifying the permissible range of variation accordingly. In such a case, since transmitter 2 knows the sampling intervals, it can transmit a frame containing data to determine the permissible range of variation.

[0103] Furthermore, in the aforementioned embodiments, the angle at which the frame transfer is carried out is such that, when the angle is 0°, the acceleration sensor 22 is arranged above and centered with respect to the central axis of each tire wheel 5a-5d. However, such a scheme is only an example. Alternatively, an angle of 0° can be considered any circumferential position of a tire wheel.

[0104] In the preceding embodiments, the TPMS ECU 3 obtains the gear information from the brake ECU 10. However, it is necessary for the TPMS ECU 3 to detect the number of gear tooth flanks or gear teeth as the gear information. Therefore, an alternative is to obtain the gear information from another ECU or to input the detection signals from the tire speed sensors 11a-11d and derive the number of gear tooth flanks or gear teeth from these detection signals. In particular, the preceding embodiments have been described assuming that the TPMS ECU 3 is separate from the brake ECU 10. Alternatively, these ECUs can be integrated into a single ECU. In such a case, the single ECU directly inputs the detection signals from the tire speed sensors 11a-11d and derives the number of gear tooth flanks or gear teeth from these detection signals.Additionally, in this case, the number of gear tooth flanks or gear teeth can be obtained constantly. Consequently, unlike a case where this information is obtained at predetermined intervals, tire wheel position detection can be performed based on the gear information obtained at the exact frame reception time.

[0105] Furthermore, the foregoing embodiments were described under the assumption that the tire position detection device is mounted in a vehicle 1 with four rotating tires 5a-5d. However, the tire position detection device described above is also applicable to a vehicle that has a larger number of rotating tires.

[0106] Furthermore, an alternative embodiment can be configured such that the tire wheel speed sensors 11a-11d detect the passage of teeth of a gear that rotates in accordance with the rotation of the tire wheels 5a-5d. Therefore, the gear can be configured such that a tooth section with a circumferential conductor alternates with a section between the teeth to exhibit different magnetic resistance values. In particular, the gear can be not only a general type having an outer section formed by convex and concave surfaces, that is, a conductive convex surface and a non-conductive space, but can also be, for example, a rotor switch formed by a conductive circumferential section and a non-conductive insulator (see, for example, JP-H10-048233A).

[0107] The steps shown in the accompanying drawings correspond to sections (means) for carrying out various processing operations. More precisely, a section for carrying out a processing operation in step 240 corresponds to a preliminary fixer (means for preliminary fixing), a section for carrying out a processing operation in step 245 corresponds to a determining device (after preliminary fixing determining device), and a section for carrying out a processing operation in step 250 corresponds to a counter (counting means).Furthermore, a section for performing processing in step 251 corresponds to a determination device (determination means), a section for performing processing in step 255 corresponds to a first determination device (first determination means), a section for performing processing in steps 256 and 257 corresponds to a count difference determination device (count difference determination means), and a section for performing processing in steps 260 and 261 corresponds to a register (registration means). Furthermore, a section for performing processing in step 270 corresponds to a second determination device (second determination means).

[0108] While the present disclosure has been described above in connection with embodiments, the present disclosure is not limited to the embodiments described above. For example, the scope of the present disclosure also includes an embodiment obtained by suitably combining technical elements disclosed in various embodiments.

Claims

[1] Tire wheel position detection device applied to a vehicle (1) having a vehicle body (6) equipped with a plurality of tire wheels (5a-5d), each of the tire wheels (5a-5d) having a tire, wherein the tire wheel position detection device comprises: a transmitter (2) attached to each of the tire wheels (5a-5d) and comprising a control device (23) which generates and transmits a frame containing unique identification information; wherein: the transmitter (2) includes an accelerometer (22) which outputs a detection signal based on an acceleration including a gravitational acceleration component, wherein the gravitational acceleration component varies by rotating the tire wheel (5a-5d) to which the transmitter (2) is attached; the control device (23) of the transmitter (2) detects an angle of the transmitter (2) based on the gravitational acceleration component included in the detection signal of the accelerometer (22) and repeatedly transmits the frame at times where the angle is a predetermined transmission angle, where any circumferential position of the tire wheel (5a-5d), centered with respect to a central axis of the tire wheel (5a-5d) to which the transmitter (2) is attached, is an angle of 0 degrees; and a receiver (3) attached to the vehicle body (6) and including a control unit (33) configured to perform tire wheel position detection by performing the following steps: Receiving the frames transmitted by the transmitters (2) via a receiving antenna (31) and then Select from the candidate identification information included in the framework, specifying the candidates to be registered, and Identify, from the candidate identification information, the candidate identification information that matches the transmitters (2) attached to the tire wheels (5a-5d) of the vehicle (1), and Storing the tire wheels (5a-5d) and the identification information of the transmitters (2) attached to the tire wheels (5a-5d) in combination with each other Obtaining gear information specifying tooth positions of gears (12a-12d) based on detection signals from tire wheel speed sensors (11a-11d), wherein the tire wheel speed sensors (11a-11d) detect the passage of teeth of the gears (12a-12d) rotating in coordination with the tire wheels (5a-5d), each gear having a circumferential surface with the tooth sections and sections between the tooth sections to alternately exhibit different magnetic resistance values, the tooth sections being conductive bodies; Defining an acceptable range of variation based on the tooth positions at a given time when the frame is received; if the tooth positions at a frame reception time after setting the permissible variation range are outside the permissible variation range, eliminate the tire wheel (5a-5d) of tire wheel candidates that is connected to the transmitter (2) that transmitted the frame; and Identify and register one remaining tire wheel (5a-5d) as the tire wheel (5a-5d) to which the transmitter (2) is attached that transmitted the frame; and wherein the control device (33) of the receiver (3) includes: a preliminary fixer (S240) that performs a preliminary fixation of each individual candidate identification information prior to registration when the tire wheel (5a-5d) to which the transmitter (2) transmitting the frame is attached is identified on the basis of the tooth positions which are within the permissible range of variation; a determination device (S245) which, after preliminary fixing, determines whether the tooth positions at a time of receipt of the frame including the preliminary fixed candidate identification information are within the permissible range of variation; a counter (S250) which, after preliminary fixing, measures the number of frame receptions including the preliminary fixed candidate identification information, where the tooth positions remain within the permissible range of variation; a first determining device (S255) that determines whether the number of receptions is equal to or greater than a first predetermined value; a register (S260, S261) which, if the number of receptions is equal to or greater than the first predetermined value, definitively determines and records the provisionally fixed candidate identification information as the identification information of the identified tire wheel (5a-5d); a determination mechanism (S251) that determines whether a multitude of the provisionally established candidate identification information exists; and a second determination device (S270) which, when the number of provisionally fixed candidate identification information is determined to be two or more, determines whether the number of receptions is equal to or greater than a second predetermined value, wherein the second predetermined value is greater than the first predetermined value, wherein If the number of receptions is equal to or greater than the second predetermined value, the register definitively determines and registers the provisionally fixed candidate identification information as the identification information of the identified tire wheel (5a-5d). [2] Tire wheel position detection device applied to a vehicle (1) having a vehicle body (6) equipped with a plurality of tire wheels (5a-5d), each of the tire wheels (5a-5d) having a tire, wherein the tire wheel position detection device comprises: a transmitter (2) attached to each of the tire wheels (5a-5d) and comprising a control device (23) which generates and transmits a frame containing unique identification information; wherein: the transmitter (2) includes an accelerometer (22) which outputs a detection signal based on an acceleration including a gravitational acceleration component, wherein the gravitational acceleration component varies by rotating the tire wheel (5a-5d) to which the transmitter (2) is attached; the control device (23) of the transmitter (2) detects an angle of the transmitter (2) based on the gravitational acceleration component included in the detection signal of the accelerometer (22) and repeatedly transmits the frame at times where the angle is a predetermined transmission angle, where any circumferential position of the tire wheel (5a-5d), centered with respect to a central axis of the tire wheel (5a-5d) to which the transmitter (2) is attached, is an angle of 0 degrees; and a receiver (3) attached to the vehicle body (6) and including a control unit (33) configured to perform tire wheel position detection by performing the following steps: Receiving the frames transmitted by the transmitters (2) via a receiving antenna (31) and then Select from the candidate identification information included in the framework, specifying the candidates to be registered, and Identifying from the candidate identification information, the candidate identification information matching the transmitters (2) attached to the tire wheels (5a-5d) of the vehicle (1), and Storing the tire wheels (5a-5d) and the identification information of the transmitters (2) attached to the tire wheels (5a-5d) in combination with each other Obtaining gear information specifying tooth positions of gears (12a-12d) based on detection signals from tire wheel speed sensors (11a-11d) detecting the passage of teeth of the gears rotating in coordination with the tire wheels (5a-5d), each gear having a circumferential surface with tooth sections and sections between the tooth sections to alternately exhibit different magnetic resistance values, the tooth sections being conductive bodies; Defining an acceptable range of variation based on the tooth positions at a given time when the frame is received; if the tooth positions at a frame reception time after setting the permissible variation range are outside the permissible variation range, eliminate the tire wheel (5a-5d) of tire wheel candidates that is connected to the transmitter (2) that transmitted the frame; and Identify and register one remaining tire wheel (5a-5d) as the tire wheel (5a-5d) to which the transmitter (2) is attached that transmitted the frame; and wherein the control device (33) of the receiver (3) includes: a preliminary fixer (S240) that performs a preliminary fixation of each individual candidate identification information prior to registration when the tire wheel (5a-5d) to which the transmitter (2) transmitting the frame is attached is identified on the basis of the tooth positions which are within the permissible range of variation; a determination device (S245) which, after preliminary fixing, determines whether the tooth positions at a time of receipt of the frame including the preliminary fixed candidate identification information are within the permissible range of variation; a counter (S250) which, after preliminary fixing, measures the number of frame receptions including the preliminary fixed candidate identification information, where the tooth positions remain within the permissible range of variation; a count difference determination device (S256, S257) which, when several of the provisionally fixed candidate identification information exist, determines whether a difference between the largest number of receptions and the second largest number of receptions among the respective numbers of receptions of the frames including the provisionally fixed candidate identification information is equal to or greater than a predetermined value; and a register (S260, S261) which, if the difference is determined to be equal to or greater than the predetermined value, definitively determines and registers the candidate identification information that has the largest number of receptions as the identification information of the identified tire wheel, where If for each of the tire wheels (5a-5d) it is determined that the difference is equal to or greater than the predetermined value, the register definitively determines and registers the candidate identification information that has the largest number of receptions as the identification information of the identified tire wheel (5a-5d). [3] Tire pressure monitoring system comprising a tire wheel position detection device according to one of claims 1 or 2, wherein: the transmitter (2) includes a sensor section (21) which outputs a detection signal based on the tire pressure, which is attached to each of the tire wheels (5a-5d), allows the control unit (23) of the transmitter (2) to perform signal processing of the detection signal from the sensor section (21), stores tire pressure information derived from the detection signal in the frame, and transmits the frame to the receiver (3); and the receiver (3) causes the control device (33) of the receiver (3) to detect the pressure of the tire attached to each of the tire wheels (5a-5d) from the tire pressure information.

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