Wheel position detection device and tire air pressure monitoring system

Abstract

This wheel position detection device is provided with a tire sensor (2) for detecting, as a first rotation angle, the angle of a position where the tire sensor (2) is present on the basis of a gravitational acceleration component included in a detection signal of an acceleration sensor (22). The wheel position detection device is provided with an in-vehicle unit (3) that detects, as a second rotation angle, the rotation angle of a wheel (5a-5d) based on an output signal from a wheel angle sensor (11a-11d). The tire sensor and the in-vehicle unit, upon establishment of connection therebetween, perform periodic communication at a predetermined communication interval. The tire sensor notifies the in-vehicle unit of tire position information corresponding to the first rotation angle, through the periodic communication at a predetermined timing. The in-vehicle unit identifies the position of the wheel to which the tire sensor is attached, on the basis of the second rotation angle and the tire position information notified from the tire sensor.

Description

Wheel position detection device, tire pressure monitoring system CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based on Japanese Patent Application No. 2024-45196 filed on March 21, 2024 and Japanese Patent Application No. 2024-99788 filed on June 20, 2024, the contents of which are incorporated herein by reference.

[0002] The present disclosure relates to a wheel position detection device and a tire pressure monitoring system (hereinafter also referred to as TPMS) including the wheel position detection device.

[0003] Patent Document 1 discloses a technology for obtaining information indicating the position of a gear tooth based on a detection signal from a wheel speed sensor that detects the passage of a gear tooth, and for identifying which wheel a tire sensor that detects tire air pressure is attached to based on the obtained information.

[0004] Specifically, frames are transmitted when the tire sensor is positioned at a predetermined angle relative to the center of the wheel while the wheel is rotating, and the wheel speed sensor acquires the wheel tooth position when the frame is received by an onboard device installed on the vehicle body. A tolerance for variation is set based on the wheel tooth position when the frame is received, and if the wheel tooth position when a subsequent frame is received is outside the tolerance for variation, the wheel is excluded from the candidates for the wheel to which the tire sensor that transmitted the frame is attached. The remaining wheels are then registered as the wheels to which the tire sensor that transmitted the frame is attached.

[0005] Patent No. 5477368

[0006] In the system described in Patent Document 1, a frame is transmitted by one-way communication from the tire sensor to the vehicle-mounted device each time the tire sensor attached to each wheel reaches a predetermined angular position. With this type of communication, radio wave interference can occur because the vehicle-mounted device has no idea when the frame is transmitted from the tire sensor.

[0007] Therefore, the inventors considered a configuration in which the vehicle-mounted device and the tire sensor are capable of two-way communication, and with a connection established between them, the vehicle-mounted device sends a signal requesting the amount of wheel rotation each time the wheel rotates a certain angle, and receives a response signal to the request signal from the tire sensor.

[0008] This configuration reduces radio wave interference, but in addition to sending and receiving signals containing information to identify the wheel on which the tire sensor is attached, regular communication is required to maintain the connection between the onboard device and the tire sensor, which increases the communication load.

[0009] An object of the present disclosure is to provide a wheel position detection device and a tire pressure monitoring system that can reduce communication load and suppress radio wave interference.

[0010] According to one aspect of the present disclosure, a wheel position detection device is applied to a vehicle having a plurality of wheels including tires attached to a vehicle body, and includes: acceleration sensors provided on the plurality of wheels and outputting detection signals corresponding to acceleration including a gravitational acceleration component that changes with the rotation of the wheels, the tire sensor using the acceleration sensors to detect a first rotation angle or a physical quantity correlating with the first rotation angle, the first rotation angle indicating the position of the tire sensor when any position in the circumferential direction of the wheels is set to 0°; and an on-board device provided on the vehicle body and detecting, as a second rotation angle, a wheel rotation angle based on output signals of wheel angle sensors provided corresponding to each of the plurality of wheels, the tire sensor and the on-board device being configured to perform periodic communication at a predetermined communication interval when a connection between them is established, the tire sensor being configured to notify the on-board device of tire position information corresponding to the first rotation angle or the physical quantity through periodic communication at a predetermined timing, and the on-board device including a position identification unit that identifies the position of the wheel to which the tire sensor is attached, based on the second rotation angle and the tire position information notified from the tire sensor.

[0011] In this way, if the onboard device and the tire sensor are configured to be able to communicate bidirectionally, it is possible to identify the position of the wheel on which the tire sensor is installed while suppressing radio wave interference. In particular, the wheel position detection device disclosed herein is configured to send and receive signals containing information for identifying the wheel on which the tire sensor is attached through periodic communication after a connection is established, thereby reducing the communication load.

[0012] Therefore, it is possible to realize a wheel position detecting device that can suppress radio wave interference while reducing the communication load.

[0013] FIG. 1 is an overall configuration diagram of a TPMS according to a first embodiment. FIG. 2 is a block configuration diagram of a tire sensor. FIG. 3 is a block configuration diagram of an on-vehicle device. FIG. 4 is a timing chart for explaining wheel position detection in the TPMS according to the first embodiment. FIG. 5 is a flowchart showing the flow of control processing executed by the on-vehicle device according to the first embodiment. FIG. 6 is an explanatory diagram for explaining the number of rotations of the wheels according to the traveling speed of the vehicle. FIG. 7 is a timing chart for explaining wheel position detection during low-speed traveling. FIG. 8 is a flowchart showing the flow of control processing executed by the tire sensor according to the first embodiment. FIG. 9 is a timing chart for explaining wheel position detection in the TPMS according to the second embodiment. FIG. 10 is a flowchart showing the flow of control processing executed by the tire sensor according to the second embodiment. FIG. 11 is a timing chart for explaining sensor output in a two-axis acceleration sensor. FIG. 12 is a timing chart for explaining wheel position detection in the TPMS according to the third embodiment. FIG. 13 is a flowchart showing the flow of control processing executed by the on-vehicle device according to the third embodiment. FIG. 14 is an explanatory diagram for explaining setting of a reference amount according to the traveling speed of the vehicle. FIG. 15 is a flowchart showing the flow of control processing executed by the tire sensor according to the third embodiment. Fig. 10 is an explanatory diagram for explaining acceleration measured by an acceleration sensor with centrifugal acceleration components reduced. Fig. 11 is a flowchart showing the flow of control processing executed by an in-vehicle device of a fourth embodiment. Fig. 12 is a flowchart showing the flow of control processing executed by a tire sensor of a fourth embodiment. Fig. 13 is a flowchart showing the flow of control processing executed by a tire sensor of a fifth embodiment. Fig. 14 is a flowchart showing the flow of control processing executed by an in-vehicle device of a fifth embodiment. Fig. 15 is a flowchart showing the flow of control processing executed by an in-vehicle device of a sixth embodiment. Fig. 16 is a flowchart showing the flow of control processing executed by a tire sensor of a sixth embodiment.

[0014] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the following embodiments, parts that are the same as or equivalent to those described in the preceding embodiments will be given the same reference numerals, and their description may be omitted. Furthermore, in the embodiments, when only some of the components are described, the components described in the preceding embodiments can be applied to the remaining components. The following embodiments can be partially combined with each other, even if not specifically stated, as long as there is no particular problem with the combination.

[0015] (First embodiment) This embodiment will be described with reference to Figures 1 to 8. Figure 1 is a diagram showing the overall configuration of a TPMS having an auxiliary function for tire pressure replenishment. The up-down direction on the paper surface of Figure 1 corresponds to the front-rear direction of a vehicle 1, and the left-right direction on the paper surface corresponds to the left-right direction of the vehicle 1. The TPMS in this embodiment will be described with reference to this figure.

[0016] As shown in FIG. 1, the TPMS is mounted on a vehicle 1 and includes a tire sensor 2, an on-board device 3 including an electronic control unit for the TPMS (hereinafter referred to as a TPMS-ECU), and a meter 4.

[0017] The TPMS includes a wheel position detection device that detects wheel positions. This wheel position detection device detects wheel positions using each tire sensor 2 provided in the TPMS and the onboard device 3, as well as information from an electronic control unit for brake control (hereinafter referred to as brake ECU 10). The brake ECU 10 acquires wheel speed pulses obtained from detection signals of wheel angle sensors 11a to 11d provided corresponding to each wheel 5a to 5d, and transmits this information to the onboard device 3 for wheel position detection.

[0018] The wheel angle sensors 11a to 11d are generally referred to as wheel speed sensors. These sensors output, as wheel speed pulses, signals corresponding to the tooth positions of gears that rotate with the axles. However, here, they are referred to as "wheel angle sensors" because they are used to obtain the angles at which the tire sensors 2 are positioned relative to the central axes of the wheels 5a to 5d. The angles at which the tire sensors 2 are positioned relative to the central axes of the wheels 5a to 5d are simply referred to as the "angle of the tire sensor 2." In the following, when the four tire sensors 2 are to be distinguished from one another, they may be referred to as tire sensors 2A, 2B, 2C, and 2D. When the four wheels 5a to 5d are to be distinguished from one another, they may be referred to as the left front wheel FL, the right front wheel FR, the left rear wheel RL, and the right rear wheel RR.

[0019] As shown in Figure 1, tire sensors 2 are attached to each wheel 5a-5d, detect the air pressure of the tires attached to the wheels 5a-5d, and transmit tire pressure information indicating the detection results stored in a frame. An on-board device 3 is attached to the vehicle body 6 of the vehicle 1, receives the frames transmitted from the tire sensors 2, and performs various processes and calculations based on the information stored therein to detect tire pressure. The tire sensors 2 transmit frames using, for example, FSK (frequency shift keying), and the on-board device 3 receives and demodulates the frames to read the information in the frames.

[0020] As shown in FIG. 2, the tire sensor 2 includes a sensing unit 21, an acceleration sensor 22, a first microcomputer 23, and a sensor communication unit 24, and each unit is driven by power supplied from a battery (not shown).

[0021] The sensing unit 21 includes a pressure sensor 21a and a temperature sensor 21b, and outputs detection signals corresponding to the tire pressure and temperature. The acceleration sensor 22 is used to detect the position of the tire sensor 2 itself on the wheels 5a to 5d to which the tire sensor 2 is attached, that is, to detect the rotation angle of the tire sensor 2 and the vehicle speed.

[0022] The acceleration sensor 22 of this embodiment is configured as a one-axis acceleration sensor. The acceleration sensor 22 outputs a detection signal corresponding to, for example, the acceleration acting on the wheels 5a to 5d when the wheels 5a to 5d rotate, in the radial direction of each wheel 5a to 5d, i.e., in two directions perpendicular to the circumferential direction.

[0023] The first microcomputer 23 constitutes the control unit of the tire sensor 2 and includes a CPU, memories such as ROM and RAM, an I / O, etc. The first microcomputer 23 executes predetermined processes according to programs stored in the built-in memory. The memory stores individual ID information including unique identification information for identifying each tire sensor 2 and vehicle-specific identification information for identifying the vehicle.

[0024] For example, the first microcomputer 23 receives detection signals from the pressure sensor 21a and the temperature sensor 21b, processes the signals, and if necessary, modifies them, and stores the information about the tire pressures in a frame together with ID information of each tire sensor 2. The first microcomputer 23 also monitors detection signals from the acceleration sensor 22 and performs vehicle motion determination, which determines the angle of each tire sensor 2 and whether the vehicle 1 is moving. After creating a frame, the first microcomputer 23 transmits the frame from the sensor communication unit 24 to the in-vehicle device 3 based on the result of the vehicle motion determination. Hereinafter, information about tire pressures will also be simply referred to as tire information.

[0025] The first microcomputer 23 repeatedly transmits frames at a predetermined timing, for example, while the vehicle 1 is traveling. The first microcomputer 23 determines whether the vehicle 1 is traveling based on the detection result of the acceleration sensor 22.

[0026] Because the acceleration sensor 22 outputs a detection signal corresponding to the rotation of each wheel 5a-5d, the detection signal contains a gravitational acceleration component during vehicle travel, resulting in a signal with an amplitude corresponding to wheel rotation. Therefore, the position of the acceleration sensor 22, i.e., the angle of the tire sensor 2, can be determined based on this amplitude. In this embodiment, the tire sensor 2 detects the angle of its own position as a first rotation angle or a physical quantity correlated to the first rotation angle using the first microcomputer 23 based on the gravitational acceleration component contained in the detection signal from the acceleration sensor 22. For example, the first rotation angle is defined as the angle at which the tire sensor 2 is positioned when any angle in the circumferential direction about the central axis of the wheel 5a-5d of the tire sensor 2 is 0°, e.g., when the tire sensor 2 is positioned at its lowest position. In this case, the first rotation angle can be expressed as 180° when the tire sensor 2 is positioned at its apex, and 90° and 270° when the tire sensor 2 is positioned at its horizontal position, respectively. Furthermore, the physical quantity correlated to the first rotation angle can be, for example, the detection signal of the acceleration sensor 22 itself.

[0027] Furthermore, the first microcomputer 23 transmits tire position information corresponding to the first rotation angle from the sensor communication unit 24 to the vehicle-mounted device 3 at a predetermined timing. When the first microcomputer 23 of this embodiment receives a request signal requesting notification of tire position information from the vehicle-mounted device 3, it stores the tire position information in a frame and transmits the frame as a response signal to the request signal.

[0028] The sensor communication unit 24 includes a first transmission / reception circuit 241 and a first communication antenna 242. The first transmission / reception circuit 241 is a communication circuit that performs bidirectional communication with the in-vehicle device 3 via the first communication antenna 242. The first transmission / reception circuit 241 performs wireless communication based on a communication method such as BLE. BLE is an abbreviation for Bluetooth (registered trademark) Low Energy. Note that the first transmission / reception circuit 241 may perform wireless communication based on a communication method other than BLE.

[0029] The first communication antenna 242 is an antenna for two-way communication with the vehicle-mounted device 3. The tire sensor 2 is provided with the sensor communication unit 24, which enables two-way communication with the vehicle-mounted device 3, rather than being limited to one-way communication from the tire sensor 2 to the vehicle-mounted device 3.

[0030] The tire sensor 2 configured in this manner detects the tire air pressure and the temperature inside the tire, and while the vehicle 1 is running, repeatedly transmits frames through the communication antenna 25 provided in each tire sensor 2 at timings when the angle of the tire sensor 2 reaches a predetermined angle.

[0031] Meanwhile, the on-vehicle device 3 is provided in the vehicle body 6. As shown in Fig. 3, the on-vehicle device 3 includes an on-vehicle communication unit 31, a second microcomputer 33, and the like. The on-vehicle device 3 acquires the number of edges or tooth positions indicated by the number of teeth of gears that rotate together with each of the wheels 5a to 5d by acquiring wheel speed pulses from the brake ECU 10 via an in-vehicle LAN (Local Area Network) such as a CAN (Controller Area Network), as will be described later. In the following description, the number of edges will be used as an example of gear information, but the number of teeth can also be used.

[0032] The in-vehicle communication unit 31 includes a second communication antenna 311 and a second transmission / reception circuit 312. The second communication antenna 311 is an antenna for performing bidirectional communication with each tire sensor 2. The second communication antenna 311 is used not only to receive frames transmitted from each tire sensor 2 but also to transmit request signals to each tire sensor 2. The second communication antenna 311 may be an internal antenna disposed within the main body of the in-vehicle device 3, or may be an external antenna with wiring extending from the main body.

[0033] The second transmission / reception circuit 312 is a communication circuit that communicates bidirectionally with each tire sensor 2 via the second communication antenna 311. The second transmission / reception circuit 312 performs wireless communication based on a communication method such as BLE. The second transmission / reception circuit 312 functions as an input unit that inputs transmission frames received from each tire sensor 2 via the second communication antenna 311 and sends the frames to the second microcomputer 33. When the second transmission / reception circuit 312 receives a frame via the second communication antenna 311, it transmits the received signal to the second microcomputer 33.

[0034] The second microcomputer 33 constitutes a control unit in the on-board device 3 and includes a CPU, an on-board memory M such as ROM or RAM, an I / O, etc. The second microcomputer 33 executes wheel position detection processing and tire air pressure detection processing in accordance with the programs stored in the on-board memory M.

[0035] In the wheel position detection process, wheel position detection is performed to identify which of the wheels 5a to 5d the tire sensor 2 is attached to. Specifically, the second microcomputer 33 performs wheel position detection based on rotation information of the wheels 5a to 5d based on wheel speed pulses obtained from the brake ECU 10 and tire position information obtained from each tire sensor 2.

[0036] The second microcomputer 33 acquires wheel speed pulses, which are output signals from the wheel angle sensors 11a to 11d provided corresponding to each of the wheels 5a to 5d, at a predetermined interval, for example, every 10 ms, from the brake ECU 10. The second microcomputer 33 converts the amount of change in the wheel speed pulses acquired from the wheel angle sensors 11a to 11d into the rotational angle of each of the wheels 5a to 5d, and detects the converted rotational angle as the second rotational angle. Note that if the integrated value of the wheel speed pulses (a value corresponding to the second rotational angle) is periodically transmitted from the brake ECU 10 or the like via the CAN, the in-vehicle device 3 may detect the second rotational angle based on that information.

[0037] The second microcomputer 33 detects the wheel positions based on tire position information corresponding to the first rotation angle included in the frame transmitted from each tire sensor 2 and the second rotation angle based on the output signal of each wheel angle sensor 11 a to 11 d. This wheel position detection enables the vehicle-mounted device 3 to identify which wheel 5 a to 5 d each tire sensor 2 is attached to. The specific method of wheel position detection processing will be described in detail later.

[0038] The tire pressure detection process involves detecting the tire pressures of the wheels 5a to 5d to which the tire sensors 2 are attached. Specifically, based on the results of wheel position detection, the second microcomputer 33 associates and stores the ID information of each tire sensor 2 with the position of each wheel 5a to 5d to which the tire sensor 2 is attached. The second microcomputer 33 then calculates a tire pressure equivalent value at a predetermined temperature based on the ID information and tire information stored in the transmission frame from each tire sensor 2, thereby detecting the tire pressure of each wheel 5a to 5d. An electrical signal corresponding to the tire pressure detection result is then output to the meter 4 via an in-vehicle LAN such as a CAN. For example, the second microcomputer 33 outputs a signal indicating the tire pressure of each wheel 5a to 5d to the meter 4. The second microcomputer 33 also detects a decrease in tire pressure by comparing the tire pressure with a predetermined threshold value, and when a decrease in tire pressure is detected, outputs a signal to that effect to the meter 4. This notifies the meter 4 that the tire pressure of one or more of the four wheels 5a to 5d has dropped, and the meter 4 displays this information.

[0039] The meter 4 is a display unit provided in the vehicle cabin that displays various information. The meter 4 displays various information when the power is on, specifically when an accessory switch (hereinafter referred to as ACC) or a start switch such as an ignition switch is turned on. The display on the meter 4 is basically performed when the power is on.

[0040] 1, the meter 4 is placed in a location visible to the driver, and may be, for example, a multi-information display installed in the instrument panel of the vehicle 1, a display of a navigation device, or the like. When the meter 4 receives a signal indicating a drop in tire air pressure from, for example, the second microcomputer 33 in the in-vehicle device 3, the meter 4 notifies the driver of the drop in tire air pressure of the wheel in question by displaying a display indicating the drop in tire air pressure while identifying the wheel in question.

[0041] Here, we will explain wireless communication between the tire sensor 2 and the on-board device 3. The tire sensor 2 and the on-board device 3 communicate wirelessly with each other based on BLE. BLE-based wireless communication allows for broadcast communication, which is unidirectional communication, and connection communication, which is bidirectional communication.

[0042] Broadcast communication, also known as connectionless communication, is a communication method in which data is sent unilaterally without checking the status of the other party before starting communication. Since broadcast communication does not require confirmation from the other party, control is simple and it is easy to improve communication speed, but in systems consisting of multiple communication devices such as TPMS, there is a risk of radio interference.

[0043] On the other hand, connection communication is a communication method in which a virtual connection (a virtual dedicated communication path) is established with the other party before communication begins, and data is sent and received through the established connection. In connection communication, for example, one master device establishes connections with multiple slave devices, and communication with each slave device can be performed in a time-division manner under the control of the master device, so interference does not occur.

[0044] When connection communication is initiated, for example, a connection request for initiating connection communication is transmitted from the tire sensor 2 to the vehicle-mounted device 3, and when the vehicle-mounted device 3 receives this frame, it transmits a frame for performing a connection procedure to the tire sensor 2. When the tire sensor 2 receives this frame, a connection is established. In other words, connection communication is initiated. In this way, when the vehicle-mounted device 3 receives a connection request, a connection is established by transmitting and receiving a frame for performing a connection procedure. However, hereinafter, it will simply be said that the vehicle-mounted device 3 establishes a connection when it receives a connection request. In this type of connection communication, the vehicle-mounted device 3 acts as the master, and the tire sensor 2 acts as the slave.

[0045] Once a connection is established between the tire sensor 2 and the vehicle-mounted device 3, the connection is maintained by performing periodic communication at a predetermined communication interval. The communication interval can be set arbitrarily between 7.5 milliseconds and 6 seconds, for example.

[0046] Specifically, the in-vehicle communication unit 31 of the in-vehicle device 3 transmits a periodic request signal as a command through periodic communication to request a response from the tire sensor 2, and after transmitting the periodic request signal, receives a periodic response signal as a response from the tire sensor 2. Furthermore, upon receiving the periodic request signal, the sensor communication unit 24 of the tire sensor 2 transmits a periodic response signal in response to the periodic request signal through periodic communication.

[0047] The tire sensor 2 is configured to notify the vehicle-mounted device 3 of tire position information corresponding to the first rotation angle through periodic communication at a predetermined timing. The vehicle-mounted device 3 identifies the positions of the wheels 5a to 5d to which the tire sensors 2 are attached, based on the tire position information notified from the tire sensor 2 and the second rotation angle calculated based on the wheel speed pulses. In this embodiment, a functional unit in the vehicle-mounted device 3 that performs the function of identifying the positions of the wheels 5a to 5d to which the tire sensors 2 are attached constitutes the "position identification unit 331."

[0048] Next, the wheel position detection process performed by the TPMS of this embodiment will be described in detail with reference to Figures 4 to 8. The wheel position detection process is performed using the tire sensors 2 and the on-board device 3 provided in the TPMS, as well as information from the brake ECU 10. The wheel position detection process of this embodiment starts when the start switch IG of the vehicle 1 is turned on.

[0049] First, to provide an overview of wheel position detection, the vehicle-mounted device 3 periodically acquires gear information from the wheel angle sensors 11a to 11d provided for each of the wheels 5a to 5d from the brake ECU 10. The vehicle-mounted device 3 then converts the count value of the wheel speed pulses (the number of pulses in this example) into the rotation angle of each of the wheels 5a to 5d, as shown in the upper part of Figure 4, and calculates the converted rotation angle as the second rotation angle. The second rotation angle is calculated for each of the wheels 5a to 5d.

[0050] Once a connection is established with the tire sensor 2, the vehicle-mounted device 3 transmits a periodic request signal requesting notification of tire position information at a predetermined communication interval. In this example, the communication interval is set to a relatively long 5 seconds, long enough for the wheels 5a to 5d to rotate multiple times even when driving at low speed. This longer communication interval has the advantage of reducing the frequency of communication between the vehicle-mounted device 3 and the tire sensor 2, making it easier to communicate with other devices, such as smartphones, in parallel.

[0051] Each time the vehicle-mounted device 3 transmits a periodic request signal, it stores the second rotation angle at the time of transmission of the periodic request signal as the request angle in the vehicle-mounted memory M. Then, based on the request angle and the output signals of the wheel angle sensors 11 a to 11 d, the vehicle-mounted device 3 calculates, as the second rotation amount, the rotation amount of the wheels 5 a to 5 d during the periodic transmission period from the transmission of the previous periodic request signal to the transmission of the current periodic request signal.

[0052] When the tire sensor 2 receives a periodic request signal requesting notification of tire position information, the amount of rotation of the wheels 5a to 5d during the periodic reception period from the reception of the previous periodic request signal to the reception of the current periodic request signal is calculated as the first amount of rotation based on the change in the first rotation angle.

[0053] Each tire sensor 2 counts the number of peaks in the sensor output of the acceleration sensor 22 during the regular reception period. Specifically, as shown in the lower part of Fig. 4, each tire sensor 2 counts "-1 G" as a peak in the sensor output of the acceleration sensor 22. Note that each tire sensor 2 may be configured to count "+1 G" as a peak in the sensor output of the acceleration sensor 22, or to count both "+1 G" and "-1 G" as peaks.

[0054] Each tire sensor 2 calculates the first rotation amount by multiplying the number of peak counts by the periodic angle at which the peak appears. As long as the first rotation amount can be compared with the second rotation amount, it may be expressed as the number of rotations of the wheels 5a to 5d, the amount of change in the rotation angle of the wheels 5a to 5d, or both the number of rotations and the rotation angle of the wheels 5a to 5d (for example, A rotations + B degrees). Each tire sensor 2 may count either "+1 G" corresponding to the maximum value of the sensor output of the acceleration sensor 22 or "-1 G" corresponding to the minimum value as a peak, or may count both as peaks.

[0055] Then, each tire sensor 2 notifies the vehicle-mounted device 3 of the tire position information to which the first rotation amount has been added through a periodic response signal in response to a periodic request signal requesting notification of tire position information. That is, upon receiving the periodic request signal, each tire sensor 2 transmits a frame including the tire position information to which the first rotation amount has been added as a periodic response signal.

[0056] When the vehicle-mounted device 3 receives a periodic response signal from each tire sensor 2, it identifies the position of each wheel 5a-5d on which the tire sensor 2 is installed based on the magnitude relationship between the difference between the first and second rotation amounts. For example, the vehicle-mounted device 3 extracts a first rotation amount that satisfies an error condition that is established when the difference between the first and second rotation amounts is within a predetermined angle error range, and identifies the position of each wheel 5a-5d on which the tire sensor 2 is installed based on the first rotation amount that satisfies the error condition. After identifying which wheel 5a-5d each tire sensor 2 is attached to, the vehicle-mounted device 3 then stores the ID information of each tire sensor 2 in association with the position of the wheel 5a-5d on which it is attached. This completes wheel position detection.

[0057] Next, specific processing executed by the vehicle-mounted device 3 and the tire sensor 2 when detecting the wheel position will be described with reference to Figures 5 and 6. The control flow shown in Figure 5 is executed by the vehicle-mounted device 3 when the start switch IG changes from off to on.

[0058] 5, in step S100, the vehicle-mounted device 3 starts receiving various signals including connection requests and frames from the tire sensors 2. Then, in step S105, the vehicle-mounted device 3 determines whether or not a connection request for performing connection communication has been received from each tire sensor 2. If the result of this determination is negative, the process returns to the determination processing of step S105.

[0059] If the determination result in step S105 is positive, in step S110, the vehicle-mounted device 3 establishes a connection (i.e., a virtual dedicated communication path) with each tire sensor 2. Specifically, the vehicle-mounted device 3 transmits a frame for performing a connection procedure to each tire sensor 2. When the tire sensor 2 receives this frame, a connection is established.

[0060] When a connection with each tire sensor 2 is established, the vehicle-mounted device 3 acquires the traveling speed of the vehicle 1 based on the amount of change in the wheel speed pulse per predetermined time, etc., in step S115. Then, in step S120, the vehicle-mounted device 3 determines the communication pattern of a signal requesting tire position information from the tire sensor 2, depending on the traveling speed of the vehicle 1.

[0061] Here, as shown in FIG. 6, the rotation speed of the wheels 5a to 5d increases as the traveling speed of the vehicle 1 increases. When the vehicle 1 is traveling at a low speed, the rotation speed of the wheels 5a to 5d is low. For example, when the vehicle 1 is equipped with tires of "tire size: 225 / 45R17" and traveling at a speed of 10 km / h, the wheels 5a to 5d rotate only seven times during the five-second communication interval, and it is difficult for a significant difference to occur in the rotation speed of each of the wheels 5a to 5d. Furthermore, when the vehicle 1 is stopped, there is no difference in the rotation speed of each of the wheels 5a to 5d.

[0062] Considering these points, it is desirable that the in-vehicle device 3 be configured to increase the interval at which it transmits periodic request signals requesting notification of tire position information as the number of rotations of the wheels 5 a to 5 d in a predetermined period decreases. The interval at which it transmits periodic request signals requesting notification of tire position information can be changed, for example, by transmitting multiple empty packet periodic request signals after transmitting a periodic request signal requesting notification of tire position information, as shown in FIG.

[0063] In this embodiment, the vehicle-mounted device 3 determines the communication pattern of the signal requesting tire position information from the tire sensor 2 so that the slower the traveling speed of the vehicle 1, the more frequently the periodic request signal that becomes an empty packet is transmitted.

[0064] Here, while the vehicle 1 is stopped, the on-board device 3 may be configured to transmit periodic request signals that become empty packets until the vehicle 1 resumes traveling. It is desirable that the on-board device 3 set a slave latency when the traveling speed of the vehicle 1 becomes zero, thereby omitting the transmission of periodic response signals from each tire sensor 2, thereby suppressing unnecessary operation of each tire sensor 2.

[0065] Next, in step S125, the vehicle-mounted device 3 sets a timer for periodic communication. This timer is set to expire when the communication interval has elapsed. Then, in step S130, the vehicle-mounted device 3 determines whether it is time to request notification of tire position information.

[0066] If it is the request timing to request notification of tire position information, the vehicle-mounted unit 3 stores the second rotation angle at the time of transmitting the periodic request signal in the vehicle-mounted memory M as the request angle in step S135, and transmits the periodic request signal in step S140.

[0067] Next, in step S145, the vehicle-mounted device 3 receives periodic response signals in response to the periodic request signals from each tire sensor 2. Then, in step S150, the vehicle-mounted device 3 performs a process of determining the position of the wheel to which the tire sensor 2 is attached.

[0068] Specifically, the vehicle-mounted device 3 determines, based on the change in the request angle and the second rotation angle, the amount of rotation of each of the wheels 5a-5d during the periodic reception period from the reception of the previous periodic request signal to the reception of the current periodic request signal, as the first amount of rotation.The vehicle-mounted device 3 then determines the positions of the wheels 5a-5d on which the tire sensors 2 are installed, based on the magnitude relationship between the difference between the first amount of rotation and the second amount of rotation indicated by the tire position information.When the vehicle-mounted device 3 has completed determining the positions of the wheels 5a-5d on which the tire sensors 2 are installed, the process proceeds to step S155.

[0069] On the other hand, if it is not the timing to request notification of tire position information, the vehicle-mounted device 3 transmits a periodic request signal that is an empty packet in step S160 without storing the second rotation angle or calculating the second rotation amount. Then, in step S165, the vehicle-mounted device 3 receives periodic response signals in response to the periodic request signal from each tire sensor 2. When the vehicle-mounted device 3 has completed receiving the periodic response signals, the process proceeds to step S155.

[0070] In step S155, the vehicle-mounted device 3 determines whether the timer for periodic communication has timed out. The vehicle-mounted device 3 waits until the timer for periodic communication has timed out, and when the timer has timed out, the process returns to step S115.

[0071] Next, specific processing executed by the tire sensor 2 when detecting the wheel position will be described with reference to Fig. 8. The control flow shown in Fig. 8 is periodically executed by each of the tire sensors 2A to 2D.

[0072] 8, in step S200, the tire sensor 2 transmits a connection request for connection communication with the vehicle-mounted device 3. Then, in step S205, the tire sensor 2 determines whether a connection with the vehicle-mounted device 3 has been established. The tire sensor 2 returns to step S200 until a connection is established, and once the connection is established, the tire sensor 2 proceeds to step S210.

[0073] In step S210, the tire sensor 2 detects acceleration using the acceleration sensor 22, and in step S215, determines whether the acceleration has passed its peak. If the acceleration has passed its peak, in step S220, the tire sensor 2 adds "1" to the number of times the peak has passed, and proceeds to step S225. If the acceleration has not passed its peak, the tire sensor 2 skips step S220 and proceeds to step S225.

[0074] Here, the number of times the peak passes has a correlation with the amount of rotation of the wheels 5 a to 5 d. In the tire sensor 2 of this embodiment, the number of times the peak passes is calculated as a first amount of rotation that indicates the amount of rotation of the wheels 5 a to 5 d during the periodic reception period from the reception of the previous periodic request signal to the reception of the current periodic request signal.

[0075] In step S225, the tire sensor 2 determines whether or not it has received a command transmitted from the vehicle-mounted device 3. If it has not received a command, the tire sensor 2 returns to step S210, and if it has received a command, the tire sensor 2 proceeds to step S230 and determines whether the command is a periodic request signal requesting tire position information.

[0076] If the command is a periodic request signal requesting notification of tire position information, the tire sensor 2 notifies the vehicle-mounted device 3 of the tire position information including the first rotation amount through a request response signal in step S235. Then, the tire sensor 2 resets the peak pass count to "0" in step S240, and returns to step S210.

[0077] If the command is not a periodic request signal requesting notification of tire position information, the tire sensor 2 determines in step S245 whether the periodic request signal will be an empty packet. If the periodic request signal is an empty packet, the tire sensor 2 transmits a periodic response signal that will be an empty packet in step S250. If the periodic request signal is not an empty packet, the tire sensor 2 returns to step S210. Note that a periodic response signal that is an empty packet is a signal that does not include tire position information.

[0078] As described above, the tire sensor 2 and the in-vehicle device 3 that constitute the wheel position detection device are configured to perform periodic communication at a predetermined communication interval once a connection between them is established. The tire sensor 2 is configured to notify the in-vehicle device 3 of tire position information corresponding to the first rotation angle through periodic communication at a predetermined timing. The in-vehicle device 3 includes a position identification unit 331 that identifies the positions of the wheels 5a to 5d to which the tire sensors 2 are attached, based on the second rotation angle and the tire position information notified from the tire sensor 2.

[0079] In this way, if the onboard device 3 and the tire sensors 2 are configured to be able to communicate bidirectionally, the positions of the wheels 5a-5d on which the tire sensors 2 are installed can be identified while suppressing radio wave interference. In particular, the wheel position detection device of this embodiment is configured to send and receive signals containing information for identifying the wheels 5a-5d on which the tire sensors 2 are attached through periodic communication after a connection is established, thereby reducing the communication load. Therefore, the configuration of this embodiment makes it possible to realize a wheel position detection device and TPMS that can suppress radio wave interference while suppressing the communication load.

[0080] The wheel position detecting device and the TPMS of this embodiment also have the following features.

[0081] (1) The vehicle-mounted device 3 includes an on-board communication unit 31 that transmits a periodic request signal requesting a response from the tire sensor 2 through periodic communication and receives a periodic response signal from the tire sensor 2 after transmitting the periodic request signal. The tire sensor 2 includes a sensor communication unit 24 that, upon receiving the periodic request signal, transmits a periodic response signal in response to the periodic request signal through periodic communication. The vehicle-mounted device 3 stores a second rotation angle at the time of transmission of the periodic request signal requesting notification of tire position information as a request angle in the on-board memory M. The vehicle-mounted device 3 is also configured to calculate, based on the request angle and the output signal of the wheel angle sensor, the amount of rotation of the wheels 5a to 5d during the periodic transmission period from the transmission of the previous periodic request signal to the transmission of the current periodic request signal as the second rotation amount. When the tire sensor 2 receives the periodic request signal requesting notification of tire position information, the tire sensor 2 calculates, based on a change in the first rotation angle, the amount of rotation of the wheels 5a to 5d during the periodic reception period from the reception of the previous periodic request signal to the reception of the current periodic request signal. The tire sensor 2 is also configured to notify the vehicle-mounted device 3 of tire position information including the first rotation amount through a periodic response signal in response to the current periodic request signal. The position identification unit 331 of the vehicle-mounted device 3 identifies the position of the wheel 5a to 5d to which the tire sensor 2 is attached based on the magnitude relationship of the difference between the first rotation amount and the second rotation amount.

[0082] In this way, if the vehicle-mounted device can grasp the amount of rotation of the wheels 5a to 5d during the regular transmission period and the amount of rotation of the wheels 5a to 5d during the regular reception period, the position of the wheels 5a to 5d to which the tire sensor 2 is attached can be identified based on the magnitude relationship of the difference between the amounts of rotation.

[0083] (2) In situations where the rotation of the wheels 5a-5d is suppressed, such as during slow driving or a temporary stop, it is difficult to identify the positions of the wheels 5a-5d to which the tire sensors 2 are attached, because differences in the amount of rotation of each wheel 5a-5d are unlikely to occur. In light of this, it is desirable that the in-vehicle device 3 be configured to increase the intervals at which it transmits periodic request signals requesting notification of tire position information, the fewer the number of rotations of the wheels 5a-5d in a predetermined period. This configuration reduces the communication load between the in-vehicle device 3 and the tire sensors 2 compared to when a periodic request signal is transmitted to request notification of tire position information to which the first amount of rotation is added.

[0084] (3) When the tire sensor 2 does not receive a notification requesting tire position information through a periodic request signal, the tire sensor 2 transmits a periodic response signal that does not include tire position information. This reduces the transmission of unnecessary packets, which contributes to reducing the communication load and power consumption of the tire sensor 2.

[0085] (Variant of the first embodiment) It is desirable that the vehicle-mounted device 3 is configured to change the interval at which it transmits a periodic request signal requesting notification of tire position information depending on the traveling speed of the vehicle 1, but this is not limited to this, and the vehicle-mounted device 3 may be configured to transmit a periodic request signal requesting notification of tire position information at a fixed communication interval.

[0086] The tire sensor 2 may be configured to transmit a signal including tire position information as a periodic response signal even when there is no notification requesting tire position information through a periodic request signal.

[0087] Second Embodiment Next, the wheel position detection process performed by the TPMS of a second embodiment will be specifically described with reference to Figures 9 to 11. In this embodiment, differences from the first embodiment will be mainly described.

[0088] When a connection is established with the tire sensor 2, the vehicle-mounted device 3 transmits a periodic request signal as a command at a predetermined communication interval to request a response from the tire sensor 2. In this example, the communication interval is set to a relatively short interval of 50 milliseconds, which is short enough that the wheels 5a to 5d do not make one rotation even when the vehicle is traveling at high speed.

[0089] After transmitting the periodic request signal, the vehicle-mounted device 3 receives a periodic response signal from the tire sensor 2 as a response, and each time it transmits a periodic response signal, it stores the second rotation angle at the time of receiving the periodic response signal in the vehicle-mounted memory M as the reception angle.

[0090] On the other hand, when the tire sensor 2 receives a periodic request signal requesting notification of tire position information, it transmits a periodic response signal in response to the periodic request signal. As shown in Fig. 9, the tire sensor 2 adds tire position information including peak information indicating that the peak has occurred to the periodic response signal that is transmitted immediately after the first rotation angle corresponding to the peak of the sensor output of the acceleration sensor 22 is reached.

[0091] When the vehicle-mounted device 3 receives the periodic response signal containing the tire position information from each tire sensor 2, it identifies the positions of the wheels 5a-5d on which the tire sensors 2 are installed based on the magnitude relationship between the first rotation angle identified by the peak information and the angle at the time of reception. For example, the vehicle-mounted device 3 extracts the tire sensors 2 that satisfy an error condition that is established when the difference between the first rotation angle identified by the peak information and the angle at the time of reception falls within a predetermined angle error range, and identifies the positions of the wheels 5a-5d on which the tire sensors 2 are installed based on the tire sensors 2 that satisfy the error condition. After identifying the wheels 5a-5d on which each tire sensor 2 is installed, the vehicle-mounted device 3 stores the ID information of each tire sensor 2 in association with the position of the wheel 5a-5d on which it is installed. This completes wheel position detection.

[0092] Next, specific processing executed by the vehicle-mounted device 3 and the tire sensor 2 when detecting the wheel position will be described with reference to Figures 10 and 11. The control flow shown in Figure 10 is executed by the vehicle-mounted device 3 when the start switch IG changes from off to on.

[0093] 10 , in step S300, the vehicle-mounted device 3 starts receiving various signals including connection requests and frames from the tire sensors 2. Then, in step S305, the vehicle-mounted device 3 determines whether or not a connection request for performing connection communication has been received from each tire sensor 2. If the result of this determination is negative, the process returns to the determination processing of step S305.

[0094] If the determination result in step S305 is positive, in step S310, the vehicle-mounted device 3 establishes a connection with each tire sensor 2. Specifically, the vehicle-mounted device 3 transmits a frame for performing a connection procedure to each tire sensor 2. When the tire sensor 2 receives this frame, a connection is established.

[0095] When a connection is established with each tire sensor 2, the vehicle-mounted device 3 sets a timer for periodic communication in step S315. This timer is set to expire when the communication interval has elapsed. Then, the vehicle-mounted device 3 transmits a periodic request signal in step S320.

[0096] Next, in step S325, the vehicle-mounted device 3 receives periodic response signals in response to the periodic request signals from each tire sensor 2. At this time, the vehicle-mounted device 3 stores the second rotation angle at the time of receiving the periodic response signal in the vehicle-mounted memory M as the reception angle.

[0097] Next, in step S330, the vehicle-mounted device 3 determines whether tire position information is added to the periodic response signal. If tire position information is added to the periodic response signal, the vehicle-mounted device 3 performs processing to determine the wheel positions on which the tire sensors 2 are attached in step S335. Specifically, the vehicle-mounted device 3 determines the positions of the wheels 5a to 5d on which the tire sensors 2 are attached based on the magnitude relationship between the angle at the time of reception and the first rotation angle indicated by the tire position information. Once the vehicle-mounted device 3 has completed determining the positions of the wheels 5a to 5d on which the tire sensors 2 are attached, the process proceeds to step S340.

[0098] On the other hand, if tire position information is not added to the periodic response signal, the vehicle-mounted device 3 skips step S335 and proceeds to step S340. When proceeding to step S340, the vehicle-mounted device 3 determines whether the timer for periodic communication has timed out. The vehicle-mounted device 3 waits until the timer for periodic communication has timed out, and when the timer has timed out, returns to step S315.

[0099] Next, specific processing executed by the tire sensor 2 when detecting the wheel position will be described with reference to Fig. 11. The control flow shown in Fig. 11 is periodically executed by each of the tire sensors 2A to 2D.

[0100] 11 , in step S400, the tire sensor 2 transmits a connection request for connection communication with the vehicle-mounted device 3. Then, in step S405, the tire sensor 2 determines whether a connection with the vehicle-mounted device 3 has been established. The tire sensor 2 returns to step S400 until a connection is established, and once the connection is established, the tire sensor 2 proceeds to step S410.

[0101] In step S410, the tire sensor 2 detects acceleration using the acceleration sensor 22, and in step S415, determines whether the acceleration has passed its peak. If the acceleration has passed its peak, in step S420, the tire sensor 2 sets a peak-passing flag indicating that the peak has been passed to "1." If the acceleration has not passed its peak, the tire sensor 2 skips step S420 and proceeds to step S425.

[0102] In step S425, the tire sensor 2 determines whether or not a command has been received from the vehicle-mounted device 3. If the tire sensor 2 has not received a command, the process returns to step S410, and if the tire sensor 2 has received a command, the process proceeds to step S430, where the tire sensor 2 determines whether the command is a periodic request signal requesting tire position information.

[0103] If the command is a periodic request signal requesting notification of tire position information, the tire sensor 2 proceeds to step S435, and if the command is not a periodic request signal requesting notification of tire position information, the tire sensor 2 returns to step S410. In step S435, the tire sensor 2 determines whether the peak passage flag is "1".

[0104] If the peak passage flag is "1", the tire sensor 2 transmits a periodic response signal to which the tire position information is added in step S440. Then, in step S445, the tire sensor 2 sets the peak passage flag to "0" and returns to step S410.

[0105] On the other hand, if the peak passing flag is not "1", the tire sensor 2 transmits a periodic response signal that is an empty packet in step S450. Thereafter, the tire sensor 2 returns to step S410. Note that the periodic response signal that is an empty packet is a signal that does not include tire position information.

[0106] The rest of the system is the same as in the first embodiment. The system of this embodiment can obtain the same effects as in the first embodiment that are achieved by a configuration common to or equivalent to the first embodiment.

[0107] The wheel position detecting device of this embodiment also has the following features.

[0108] (1) The vehicle-mounted device 3 includes an on-board communication unit 31 that transmits a periodic request signal requesting a response from the tire sensor 2 through periodic communication and receives a periodic response signal from the tire sensor 2 after transmitting the periodic request signal. The vehicle-mounted device 3 stores the second rotation angle at the time of receiving the periodic response signal as a reception angle in the on-board memory M. The tire sensor 2 includes a sensor communication unit 24 that transmits a periodic response signal in response to the periodic request signal through periodic communication upon receiving the periodic request signal. The tire sensor 2 adds tire position information including peak information indicating that the peak has occurred to the periodic response signal transmitted immediately after the first rotation angle corresponding to the peak of the sensor output of the acceleration sensor 22 is reached. The position identification unit 331 identifies the position of the wheel 5a-5d to which the tire sensor 2 is attached based on the magnitude relationship between the reception angle and the first rotation angle identified by the peak information.

[0109] This makes it possible to identify the position of the wheels 5a to 5d to which the tire sensor 2 is attached based on the magnitude relationship between the first rotation angle corresponding to the peak of the sensor output of the acceleration sensor 22 and the second rotation angle at the time of receiving the response signal notifying the first rotation angle.

[0110] (2) During the period from when the tire sensor 2 transmits the periodic response signal including the tire position information until the first rotation angle corresponding to the peak is reached, the tire sensor 2 transmits a signal that does not include the tire position information as the periodic response signal. This reduces the transmission of unnecessary packets. This contributes to reducing the communication load and the power consumption of the tire sensor 2.

[0111] (Modification of the Second Embodiment) The acceleration sensor 22 may be configured to be able to detect a first acceleration and a second acceleration different from the first acceleration. For example, the acceleration sensor 22 may be configured as a two-axis acceleration sensor that outputs a detection signal corresponding to the radial acceleration of each of the wheels 5 a to 5 d as the first acceleration and a detection signal corresponding to the circumferential acceleration of each of the wheels 5 a to 5 d as the second acceleration.

[0112] 12 is a time chart showing an example of changes in the first acceleration and the second acceleration output from the acceleration sensor 22. In Fig. 12, the first acceleration is indicated by a solid line, and the second acceleration is indicated by a dashed line.

[0113] If the acceleration sensor 22 is configured as a biaxial acceleration sensor, the sensor output of the acceleration sensor 22 will have multiple peaks during one rotation of the wheels 5a to 5d. In this configuration, the tire sensor 2 may transmit a response signal with tire position information attached multiple times during one rotation of the wheels 5a to 5d. For example, the tire sensor 2 may transmit a periodic response signal immediately after the first acceleration reaches a peak of "-1 G" and the first rotation angle corresponding to the peak is reached, and may also transmit a periodic response signal immediately after the second acceleration reaches a peak of "-1 G" and the first rotation angle corresponding to the peak is reached. Note that the tire sensor 2 needs to add tire position information, including rotation angle information for distinguishing between the first acceleration peak and the second acceleration peak, to the periodic response signal in addition to the peak information.

[0114] This increases the frequency with which the tire position information is notified to the vehicle-mounted device 3, thereby enabling the positions of the wheels 5a to 5d to which the tire sensors 2 are attached to be identified more quickly. Furthermore, by including rotation angle information corresponding to the peaks in the tire position information, each peak can be distinguished. The tire sensor 2 may be configured to count "+1 G" in the first acceleration and the second acceleration as a peak, or to count both "+1 G" and "-1 G" in the first acceleration and the second acceleration as peaks.

[0115] In addition, the tire sensor 2 of the second embodiment may also be configured to transmit a signal including tire position information as a periodic response signal during the period from when the periodic response signal including tire position information is transmitted until the first rotation angle corresponding to the peak is reached.

[0116] Third Embodiment Next, a third embodiment will be described with reference to Figures 13 to 16. In this embodiment, differences from the first embodiment will be mainly described.

[0117] Once a connection is established with the tire sensor 2, the vehicle-mounted device 3 transmits a periodic request signal at a predetermined communication interval to request a response from the tire sensor 2. In this example, the communication interval is set to a relatively short interval of 50 milliseconds.

[0118] 13, the vehicle-mounted device 3 is configured to request notification of tire position information from the tire sensor 2 through a periodic request signal every time the amount of change in the second rotation angle reaches a predetermined specified angle. The vehicle-mounted device 3 is also configured to store the second rotation angle at the time of transmitting the periodic request signal requesting notification of tire position information in the vehicle-mounted memory M as a requested angle.

[0119] On the other hand, when the tire sensor 2 is requested to notify tire position information through a periodic request signal, it notifies the vehicle-mounted device 3 of the tire position information through a periodic response signal, with the first rotation angle at the time of receiving the periodic request signal added as the current angle.

[0120] The position identification unit 331 of the vehicle-mounted device 3 identifies the positions of the wheels 5a-5d on which the tire sensors 2 are mounted based on the magnitude relationship between the current angle notified through the periodic response signal and the requested angle. The vehicle-mounted device 3 extracts, for example, those wheels that satisfy an error condition that is established when the difference between the current angle and the requested angle is within a predetermined angle error range, and identifies the positions of the wheels 5a-5d on which the tire sensors 2 are mounted based on those that satisfy the error condition. After identifying which wheels 5a-5d each tire sensor 2 is mounted on, the vehicle-mounted device 3 then stores the ID information of each tire sensor 2 in association with the position of the wheel 5a-5d on which it is mounted. This completes wheel position detection.

[0121] Next, specific processing executed by the vehicle-mounted device 3 and the tire sensor 2 when detecting the wheel position will be described with reference to Figures 14 to 16. The control flow shown in Figure 14 is executed by the vehicle-mounted device 3 when the start switch IG changes from off to on.

[0122] 14, in step S500, the vehicle-mounted device 3 starts receiving various signals including connection requests and frames from the tire sensors 2. Then, in step S505, the vehicle-mounted device 3 determines whether or not a connection request for performing connection communication has been received from each tire sensor 2. If the result of this determination is negative, the process returns to the determination processing of step S505.

[0123] If the determination result in step S505 is positive, in step S510, the vehicle-mounted device 3 establishes a connection with each tire sensor 2. Specifically, the vehicle-mounted device 3 transmits a frame for performing a connection procedure to each tire sensor 2. When the tire sensor 2 receives this frame, a connection is established.

[0124] When a connection is established with each tire sensor 2, the vehicle-mounted device 3 resets the angle pulse count to "0" in step S515. The angle pulse count is a count value of wheel speed pulses output by the wheel speed sensor.

[0125] Next, in step S520, the vehicle-mounted device 3 acquires the traveling speed of the vehicle 1 based on the amount of change in the wheel speed pulse per predetermined time, etc. In step S525, the vehicle-mounted device 3 determines a specified angle for specifying the timing of requesting the tire sensors 2 to notify tire position information, in accordance with the traveling speed of the vehicle 1.

[0126] Here, the specified angle needs to be equal to or greater than the change in the rotation angle of the wheels 5a to 5d during the communication interval. For example, if a vehicle 1 equipped with tires of "tire size: 225 / 45R17" travels at a speed of 40 km / h, the wheels 5a to 5d will rotate 100 degrees during the 50 millisecond communication interval. In this case, the specified angle needs to be set to 100 degrees or greater.

[0127] 15, the amount of change in the rotation angle of the wheels 5a to 5d during the communication interval increases as the traveling speed of the vehicle 1 increases. For this reason, it may be possible to set the specified angle to a large angle so that the vehicle can also travel at high speeds.

[0128] However, if the specified angle is too large, the frequency of performing the wheel position identification process for identifying the wheel position where the tire sensor 2 is attached decreases, which is undesirable because it increases the time required to complete identification of the wheel position where the tire sensor 2 is attached.

[0129] Taking these factors into consideration, the vehicle-mounted device 3 is configured to change the specified angle in accordance with the traveling speed of the vehicle 1. For example, the vehicle-mounted device 3 determines the specified angle so that it increases in stages in accordance with the traveling speed of the vehicle 1, as shown by the dashed line in Fig. 15 .

[0130] Frequent changes to the specified angle in response to acceleration or deceleration of the vehicle 1 may impair communication stability, and therefore it is desirable that the in-vehicle device 3 determine the specified angle so that it increases stepwise in accordance with the traveling speed of the vehicle 1. In particular, it is desirable that hysteresis be set in the process of changing the specified angle so that the traveling speed when the specified angle is increased is a predetermined speed higher than the traveling speed when the specified angle is decreased.

[0131] After determining the specified angle in this manner, the vehicle-mounted device 3 sets a timer for periodic communication in step S530. This timer is set to expire when the communication interval has elapsed. Then, in step S535, the vehicle-mounted device 3 determines whether the angle pulse count has reached a value corresponding to the specified angle.

[0132] When the angle pulse count reaches a value corresponding to the specified angle, the vehicle-mounted device 3 determines whether the timer has timed out in step S540. The vehicle-mounted device 3 waits until the timer has timed out, and when the timer has timed out, the process proceeds to step S545.

[0133] In step S545, the vehicle-mounted device 3 stores the current second rotation angle in the vehicle-mounted memory M as the requested angle at the time of transmitting the periodic request signal, and in step S550, transmits a periodic request signal requesting notification of tire position information.

[0134] Next, in step S555, the vehicle-mounted device 3 receives periodic response signals in response to the periodic request signals from each tire sensor 2. Then, in step S560, the vehicle-mounted device 3 performs processing to determine the positions of the wheels on which the tire sensors 2 are attached. Specifically, the vehicle-mounted device 3 determines the positions of the wheels 5a to 5d on which the tire sensors 2 are attached based on the magnitude relationship between the requested angle and the current angle indicated by the tire position information. Once the vehicle-mounted device 3 has completed determining the positions of the wheels 5a to 5d on which the tire sensors 2 are attached, the process proceeds to step S515.

[0135] On the other hand, if the angle pulse count does not reach a value corresponding to the specified angle, the vehicle-mounted device 3 proceeds to step S565. After proceeding to step S565, the vehicle-mounted device 3 determines whether the timer for periodic communication has timed out. The vehicle-mounted device 3 waits until the timer for periodic communication has timed out, and if the timer has timed out, proceeds to step S570.

[0136] In step S570, the vehicle-mounted device 3 transmits a periodic request signal that is an empty packet. Then, in step S575, the vehicle-mounted device 3 receives a periodic response signal in response to the periodic request signal from each tire sensor 2, and then returns to step S530.

[0137] Next, specific processing executed by the tire sensor 2 when detecting the wheel position will be described with reference to Fig. 16. The control flow shown in Fig. 16 is periodically executed by each of the tire sensors 2A to 2D.

[0138] 16, in step S600, the tire sensor 2 transmits a connection request for connection communication with the vehicle-mounted device 3. Then, in step S605, the tire sensor 2 determines whether a connection with the vehicle-mounted device 3 has been established. The tire sensor 2 returns to step S600 until a connection is established, and once the connection is established, the tire sensor 2 proceeds to step S610.

[0139] In step S610, the tire sensor 2 determines whether or not a command has been received from the vehicle-mounted device 3. If no command has been received, the tire sensor 2 waits until a command is received, and if a command has been received, the tire sensor 2 proceeds to step S615 and determines whether the command is a periodic request signal requesting tire position information.

[0140] If the command is a periodic request signal requesting notification of tire position information, in step S620, the tire sensor 2 determines the first rotation angle at the time of receiving the periodic request signal as the current angle based on the sensor output of the acceleration sensor 22. Then, in step S625, the tire sensor 2 transmits a periodic response signal to which tire position information including the current angle has been added, and then returns to step S610.

[0141] On the other hand, if the command is a periodic request signal that does not request notification of tire position information, the tire sensor 2 further determines whether the command is a periodic request signal that becomes an empty packet. If the command is a periodic request signal that becomes an empty packet, the tire sensor 2 transmits a periodic response signal that becomes an empty packet in step S635, and then returns to step S610. If the command is not a periodic request signal that becomes an empty packet, the tire sensor 2 skips step S635 and returns to step S610. Note that a periodic response signal that becomes an empty packet is a signal that does not include tire position information.

[0142] The rest of the system is the same as in the first embodiment. The system of this embodiment can obtain the same effects as in the first embodiment that are achieved by a configuration common to or equivalent to the first embodiment.

[0143] The wheel position detecting device of this embodiment also has the following features.

[0144] (1) The vehicle-mounted device 3 requests the tire sensor 2 to notify it of tire position information through a periodic request signal each time the amount of change in the second rotation angle reaches a predetermined specified angle. The vehicle-mounted device 3 also stores the second rotation angle at the time of transmitting the periodic request signal requesting notification of tire position information as the requested angle in the vehicle-mounted memory M. When notification of tire position information is requested through the periodic request signal, the tire sensor 2 notifies the vehicle-mounted device 3 of tire position information, to which the first rotation angle at the time of receiving the periodic request signal is added as the current angle through a periodic response signal. The position identification unit 331 identifies the positions of the wheels 5a to 5d to which the tire sensors 2 are attached, based on the magnitude relationship between the current angle notified through the periodic response signal and the requested angle. This allows the positions of the wheels 5a to 5d to which the tire sensors 2 are attached to be identified based on the magnitude relationship between the current angle and the requested angle.

[0145] (2) After requesting notification of tire position information through a periodic request signal, the vehicle-mounted device 3 does not request notification of tire position information through a periodic request signal until the amount of change in the second rotation angle reaches a specified angle. This reduces the communication load between the vehicle-mounted device 3 and the tire sensor 2 compared to when tire position information is constantly requested from the tire sensor 2.

[0146] (3) When the tire sensor 2 does not receive a notification requesting tire position information through a periodic request signal, the tire sensor 2 transmits a periodic response signal that does not include tire position information. This reduces the transmission of unnecessary packets, which contributes to reducing the communication load and power consumption of the tire sensor 2.

[0147] (4) The on-board device 3 increases the specified angle as the traveling speed of the vehicle 1 increases. Since the amount of change in the rotation angle of the wheels 5a to 5d during one communication interval increases as the traveling speed of the vehicle 1 increases, it is desirable to increase the specified angle as the traveling speed of the vehicle 1 increases.

[0148] (Variation of the third embodiment) The vehicle-mounted device 3 may also be configured to request notification of tire position information through a periodic request signal during the period from when the vehicle-mounted device 3 requests notification of tire position information through a periodic request signal until the change in the second rotation angle reaches a specified angle.

[0149] It is desirable that the tire sensor 2 transmits a signal that does not include tire position information as a periodic response signal when there is no notification requesting tire position information through a periodic request signal, but this is not required.

[0150] It is desirable that the on-board device 3 increases the specified angle as the traveling speed of the vehicle 1 increases, but this is not necessarily required. In other words, the on-board device 3 may set the specified angle to a fixed value regardless of the traveling speed of the vehicle 1.

[0151] Fourth Embodiment Next, a fourth embodiment will be described with reference to Figs. 17 to 20. In this embodiment, differences from the third embodiment will be mainly described. Fig. 17 shows the change in acceleration measured by the acceleration sensor 22 provided in the tire sensor 2 when the vehicle 1 accelerates from a stopped state to a constant speed.

[0152] The centrifugal acceleration acting on the tire sensor 2 changes in response to the acceleration or deceleration of the vehicle 1. This centrifugal acceleration is the magnitude of the centrifugal force acting on an object expressed in the form of acceleration. The centrifugal acceleration is expressed in units of "relative centrifugal acceleration RCF" expressed as a ratio to the Earth's gravitational acceleration. This relative centrifugal acceleration RCF is expressed, for example, by the following formula F2. In the following formula F2, "r" indicates the distance from the center of rotation to the object (i.e., the radius), and "N" indicates the number of rotations per minute. RCF = "centrifugal acceleration" / "Earth's gravitational acceleration" ≈ 1.118 x r x N ２ x10 －６ [G] ...(F2)

[0153] For example, in a vehicle 1 in which a tire sensor 2 is mounted integrally with an air valve on a tire with a tire size of "225-45R17," the relative centrifugal acceleration RCF when traveling at "100 km / h" is approximately 168 G. This is a very large value relative to the change in gravitational acceleration of ±1 G. In a tire with a tire size of "225-45R17," the tire radius is approximately 317 mm, and the wheel radius is approximately 216 mm.

[0154] 17, when the vehicle speed changes, the periods of centrifugal acceleration and gravitational acceleration change constantly, and therefore calculation of the rotation angles of the wheels 5a to 5d based on the acceleration measured by the acceleration sensor 22 tends to become complicated and error prone. Note that even if the peak of the sensor output of the acceleration sensor 22 can be detected, it is difficult to accurately determine the rotation angles of the wheels 5a to 5d unless the center of the waveform of the sensor output can be identified.

[0155] On the other hand, Figure 18 shows the acceleration measured by the acceleration sensor 22 after the centrifugal acceleration component has been removed. As shown in Figure 18, if the centrifugal acceleration component can be removed from the acceleration measured by the acceleration sensor 22, the rotation angles of the wheels 5a to 5d can be accurately determined from the waveform of the sensor output.

[0156] Taking these factors into consideration, the TPMS of this embodiment is configured to perform a correction on the tire sensor 2 side to reduce the centrifugal acceleration component from the acceleration measured by the acceleration sensor 22 using the centrifugal acceleration information notified from the in-vehicle device 3.

[0157] Specific processing executed by the vehicle-mounted device 3 when detecting the wheel position will be described below with reference to FIG. 19. The control flow shown in FIG. 19 is executed by the vehicle-mounted device 3 when the start switch IG changes from OFF to ON. Note that the processing of steps S500A to S545Aa and S555A to S575A shown in FIG. 19 is the same as the processing of steps S500 to S545 and S555 to S575 described in the third embodiment. Therefore, in this embodiment, description of the processing of steps S500A to S545Aa and S555A to S575A will be omitted.

[0158] As shown in FIG. 19, in step S545Aa, the vehicle-mounted device 3 stores the current second rotation angle in the vehicle-mounted memory M as the requested angle at the time of transmitting the periodic request signal, and proceeds to step S545Ab.

[0159] In step S545Ab, the vehicle-mounted device 3 calculates the centrifugal acceleration component acting on the acceleration sensor 22. For example, if the tire sensor 2 is integrated with the air valve, the vehicle-mounted device 3 calculates the centrifugal acceleration component from the wheel rotation speed and wheel radius, or from the traveling speed, tire radius, and wheel radius of the vehicle 1. Furthermore, if the tire sensor 2 is provided inside the tire tread, the vehicle-mounted device 3 calculates the centrifugal acceleration component from the wheel rotation speed and tire radius, or from the traveling speed and tire radius of the vehicle 1.

[0160] Next, in step S550A, the vehicle-mounted device 3 transmits a periodic request signal to request notification of tire position information. Specifically, the vehicle-mounted device 3 transmits a periodic request signal to the tire sensor 2, to which information on the centrifugal acceleration component is added as centrifugal angular velocity information.

[0161] Next, specific processing executed by the tire sensor 2 when detecting the wheel position will be described with reference to FIG. 8. The control flow shown in FIG. 20 is periodically executed by each of the tire sensors 2A to 2D. Note that the processing in steps S600A to S615A and S625A to S635A shown in FIG. 20 is the same as the processing in steps S600 to S615 and S625 to S635 described in the third embodiment. Therefore, in this embodiment, description of the processing in steps S600A to S615A and S625A to S635A will be omitted.

[0162] 20, in step S615A, the tire sensor 2 determines whether the command notified from the vehicle-mounted device 3 is a periodic request signal. If the command notified from the vehicle-mounted device 3 is a periodic request signal, the tire sensor 2 proceeds to step S620Aa.

[0163] In step S620Aa, the tire sensor 2 detects the acceleration acting on the tire sensor 2 using the acceleration sensor 22. In step S620Ab, the tire sensor 2 performs a correction to reduce the centrifugal acceleration component from the acceleration detected by the acceleration sensor 22, using the centrifugal acceleration information added to the periodic request signal. In step S620Ac, the tire sensor 2 determines the first rotation angle at the time of receiving the periodic request signal as the current angle, based on the value obtained by subtracting the centrifugal acceleration component from the acceleration detected by the acceleration sensor 22. In step S625A, the tire sensor 2 transmits a periodic response signal to which tire position information including the current angle has been added, and then returns to step 610A.

[0164] The rest of the system is the same as in the third embodiment. The system of this embodiment can obtain the same effects as in the third embodiment that are achieved by a configuration common to or equivalent to the third embodiment.

[0165] The wheel position detection device of this embodiment also has the following features: (1) The in-vehicle device 3 is configured to obtain, as centrifugal acceleration information, information regarding the centrifugal acceleration component acting on the tire sensor 2 when the amount of change in the second rotation angle reaches a specified angle, and to transmit the centrifugal acceleration information to the tire sensor 2 via a periodic request signal. The tire sensor 2 also performs correction to reduce the centrifugal acceleration component included in the detection signal output by the acceleration sensor 22 based on the centrifugal acceleration information notified from the in-vehicle device 3, and obtains the first rotation angle based on the corrected detection signal as the current angle. This allows the tire sensor 2 to accurately identify the peak of the sensor output of the acceleration sensor 22 and the current angle, even when the vehicle 1 is accelerating or decelerating.

[0166] (Variation of Fourth Embodiment) In the wheel position detection device of the fourth embodiment, the on-board device 3 is configured to determine the centrifugal acceleration component itself acting on the tire sensor 2, but this is not limited to this. For example, the wheel position detection device may be configured such that the on-board device 3 notifies the tire sensor 2 of information correlated with the centrifugal acceleration component as centrifugal acceleration information, and the tire sensor 2 uses the centrifugal acceleration information to determine the centrifugal acceleration component acting on the tire sensor 2. Specifically, the on-board device 3 may be configured to notify the tire sensor 2 of the radius and wheel rotation speed, which are variables shown in Formula F2, as centrifugal acceleration information. Alternatively, the radius, which is a variable shown in Formula F2, may be registered in advance in a memory or the like of the tire sensor 2, and the on-board device 3 may be configured to notify the tire sensor 2 of only the wheel rotation speed as centrifugal acceleration information.

[0167] Fifth Embodiment Next, a fifth embodiment will be described with reference to Fig. 21 and Fig. 22. In this embodiment, differences from the third embodiment will be mainly described.

[0168] The TPMS of this embodiment performs a correction on the vehicle-mounted device 3 side to reduce the centrifugal acceleration component from the sensor output of the acceleration sensor 22, and determines the current angle of the tire sensor 2 based on the value obtained by reducing the centrifugal acceleration component from the sensor output of the acceleration sensor 22.

[0169] The specific processing executed by the tire sensor 2 when detecting the wheel position will be described below with reference to FIG. 21. The control flow shown in FIG. 21 is periodically executed by each of the tire sensors 2A to 2D. Note that the processing in steps S600B to S610B, S630B, and S635B shown in FIG. 21 is the same as the processing in steps S600 to S610, S630, and S635 described in the third embodiment. Therefore, in this embodiment, a description of the processing in steps S600B to S610B, S630B, and S635B will be omitted.

[0170] 21 , when the tire sensor 2 receives a command from the vehicle-mounted device 3, the tire sensor 2 proceeds to step S615B. In step S615B, the tire sensor 2 determines whether the command is a periodic request signal requesting tire position information. If the command is a periodic request signal requesting notification of tire position information, the tire sensor 2 proceeds to step S620B.

[0171] In step S620B, the tire sensor 2 detects the acceleration acting on the tire sensor 2 using the acceleration sensor 22 as a physical quantity correlated with the first rotation angle of the tire sensor 2. Then, in step S625B, the tire sensor 2 transmits a periodic response signal to which tire position information including the sensor output of the acceleration sensor 22 has been added, and then returns to step S610.

[0172] Next, specific processing executed by the vehicle-mounted device 3 when detecting the wheel position will be described with reference to FIG. 22. The control flow shown in FIG. 22 is executed by the vehicle-mounted device 3 when the start switch IG changes from OFF to ON. Note that the processing of steps S500B to S550B and S560B to S575B shown in FIG. 22 is the same as the processing of steps S500 to S550 and S560 to S575 described in the third embodiment. Therefore, in this embodiment, description of the processing of steps S500B to S550B and S560B to S575B will be omitted.

[0173] 22, in step S555Ba, the vehicle-mounted device 3 receives periodic response signals in response to the periodic request signals from each tire sensor 2. Then, in step S555Bb, the vehicle-mounted device 3 obtains centrifugal acceleration information as information relating to the centrifugal acceleration component acting on the acceleration sensor 22. The method for obtaining the centrifugal acceleration information is the same as that described in the fourth embodiment, and therefore will not be described again.

[0174] Next, in step S555Bc, the vehicle-mounted device 3 determines the first rotation angle at the time of receiving the periodic request signal as the current angle based on a value obtained by subtracting the centrifugal acceleration component from the acceleration detected by the acceleration sensor 22 and added to the periodic response signal. Then, in step S560B, the vehicle-mounted device 3 performs processing to determine the position of the wheel to which the tire sensor 2 is attached.

[0175] The rest of the system is the same as in the third embodiment. The system of this embodiment can obtain the same effects as in the third embodiment that are achieved by a configuration common to or equivalent to the third embodiment.

[0176] The wheel position detection device of this embodiment also has the following features. (1) When a request for tire position information is received via a periodic request signal, the tire sensor 2 is configured to notify the vehicle-mounted device 3 of tire position information including a detection signal output by the acceleration sensor 22 as a physical quantity correlated with the first rotation angle. The vehicle-mounted device 3 obtains, as centrifugal acceleration information, information regarding a centrifugal acceleration component acting on the tire sensor 2 when the change in the second rotation angle reaches a specified angle. The vehicle-mounted device 3 then performs correction to reduce the centrifugal acceleration component included in the detection signal output by the acceleration sensor 22 based on the centrifugal acceleration information, and obtains, as the current angle, the first rotation angle based on the corrected detection signal. This also enables the vehicle-mounted device 3 to accurately determine the current angle of the tire sensor 2 even when the vehicle 1 is accelerating or decelerating.

[0177] Sixth Embodiment Next, a sixth embodiment will be described with reference to Fig. 23 and Fig. 24. In this embodiment, differences from the second embodiment will be mainly described.

[0178] The TPMS of this embodiment is configured to perform a correction on the tire sensor 2 side to reduce the centrifugal acceleration component from the acceleration measured by the acceleration sensor 22 using the centrifugal acceleration information notified from the vehicle-mounted device 3.

[0179] Specific processing executed by the vehicle-mounted device 3 when detecting the wheel position will be described below with reference to FIG. 23. The control flow shown in FIG. 23 is executed by the vehicle-mounted device 3 when the start switch IG changes from OFF to ON. Note that the processing in steps S300A to S310A and S320A to S340A shown in FIG. 23 is the same as the processing in steps S300 to S310 and S320 to S340 described in the second embodiment. Therefore, in this embodiment, a description of the processing in steps S300A to S310A and S320A to S340A will be omitted.

[0180] 23, in step S315Aa, the vehicle-mounted device 3 sets a timer for periodic communication. In step S315Ab, the vehicle-mounted device 3 obtains centrifugal acceleration information, which is information relating to the centrifugal acceleration component acting on the acceleration sensor 22. The method for obtaining the centrifugal acceleration information is the same as that described in the fourth embodiment, and therefore, a description thereof will be omitted. Then, in step S320A, the vehicle-mounted device 3 transmits a periodic request signal requesting notification of tire position information.

[0181] Next, specific processing executed by the tire sensor 2 when detecting the wheel position will be described with reference to FIG. 24. The control flow shown in FIG. 24 is periodically executed by each of the tire sensors 2A to 2D. Note that the processing in steps S400A, S405A, and S415A to S450A shown in FIG. 24 is the same as the processing in steps S400, S405, and S415 to S450 described in the third embodiment. Therefore, in this embodiment, description of the processing in steps S400A, S405A, and S415A to S450A will be omitted.

[0182] 24 , when a connection is established between the tire sensor 2 and the vehicle-mounted device 3, the tire sensor 2 proceeds to step S410Aa. In step S410Aa, the vehicle-mounted device 3 determines whether or not a command corresponding to the periodic request signal has been received from the vehicle-mounted device 3. If the tire sensor 2 has received the periodic request signal from the vehicle-mounted device 3, the tire sensor 2 proceeds to step S410Ab, and if the tire sensor 2 has not received the periodic request signal from the vehicle-mounted device 3, the tire sensor 2 proceeds to step S415A.

[0183] In step S410Ab, the tire sensor 2 detects the acceleration acting on the tire sensor 2 using the acceleration sensor 22. In step S410Ac, the tire sensor 2 uses the centrifugal acceleration information added to the periodic request signal to perform a correction to reduce the centrifugal acceleration component from the acceleration detected by the acceleration sensor 22. In step S415A, the tire sensor 2 determines whether the acceleration has passed its peak based on the value obtained by subtracting the centrifugal acceleration component from the acceleration detected by the acceleration sensor 22.

[0184] The rest of the system is the same as in the second embodiment. The system of this embodiment can obtain the same effects as in the second embodiment that are achieved by the configuration common to or equivalent to the second embodiment.

[0185] The wheel position detection device of this embodiment also has the following features: (1) The in-vehicle device 3 is configured to obtain, as centrifugal acceleration information, information regarding the centrifugal acceleration component acting on the tire sensor 2 when transmitting the periodic request signal, and to transmit the centrifugal acceleration information to the tire sensor 2 via the periodic request signal. The tire sensor 2 performs a correction to reduce the centrifugal acceleration component included in the detection signal output by the acceleration sensor 22 based on the centrifugal acceleration information notified from the in-vehicle device 3, and identifies the peak of the sensor output of the acceleration sensor 22 based on the corrected detection signal. This allows the tire sensor 2 to accurately identify the peak of the sensor output of the acceleration sensor 22 even when the vehicle 1 is accelerating or decelerating.

[0186] (Variation of Sixth Embodiment) In the wheel position detection device of the sixth embodiment, the on-board device 3 is configured to determine the centrifugal acceleration component acting on the tire sensor 2, but this is not limiting. For example, the wheel position detection device may be configured such that the on-board device 3 notifies the tire sensor 2 of information correlated with the centrifugal acceleration component as centrifugal acceleration information, and the tire sensor 2 uses the centrifugal acceleration information to determine the centrifugal acceleration component acting on the tire sensor 2. Specifically, the on-board device 3 may be configured to notify the tire sensor 2 of the radius and wheel rotation speed as centrifugal acceleration information. Alternatively, the radius may be registered in advance in the tire sensor 2, and the on-board device 3 may be configured to notify the tire sensor 2 of the wheel rotation speed as centrifugal acceleration information.

[0187] In the wheel position detection device of the sixth embodiment, the in-vehicle device 3 may acquire the sensor output of the acceleration sensor 22 from the tire sensor 2 as a physical quantity correlated with the first rotation angle, and perform a correction to reduce the centrifugal acceleration component included in the acquired sensor output. This allows the in-vehicle device 3 to identify the peak of the sensor output of the acceleration sensor 22, and therefore allows the tire sensor 2 to determine whether the peak of the sensor output of the acceleration sensor 22 is appropriately identified.

[0188] Other Embodiments Although typical embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments and can be modified in various ways, for example, as follows.

[0189] In the above embodiment, a wheel position detection device provided for a vehicle 1 having four wheels 5a to 5d has been described, but the present invention can also be applied to a vehicle 1 having more wheels.

[0190] In the above-described embodiment, the vehicle-mounted device 3 is configured to acquire information from the wheel angle sensors 11a to 11d from the brake ECU 10, but this is not limited to this and the vehicle-mounted device 3 may acquire the information from an ECU other than the brake ECU 10.

[0191] In the above-described embodiments, it goes without saying that the elements constituting the embodiments are not necessarily essential unless they are specifically stated as essential or are clearly considered essential in principle.

[0192] In the above-described embodiments, when numerical values ​​such as the number, values, amounts, ranges, etc. of components of the embodiments are mentioned, they are not limited to the specific numbers unless they are specifically stated as essential or are clearly limited to a specific number in principle.

[0193] In the above-described embodiments, when referring to the shapes, positional relationships, etc. of components, etc., the shapes, positional relationships, etc. are not limited to those unless otherwise specified or when they are fundamentally limited to specific shapes, positional relationships, etc.

[0194] The controller and method of the present disclosure may be implemented on a special-purpose computer by configuring a processor and memory programmed to perform one or more functions embodied in a computer program. The controller and method of the present disclosure may be implemented on a special-purpose computer by configuring a processor with one or more dedicated hardware logic circuits. The controller and method of the present disclosure may be implemented on one or more special-purpose computers configured with a processor and memory programmed to perform one or more functions in combination with a processor configured with one or more hardware logic circuits. The computer program may also be stored on a computer-readable non-transitory tangible storage medium as instructions executed by a computer.

[0195] [Aspects of the present disclosure]

[0196] [First Aspect] A wheel position detection device applied to a vehicle (1) having a vehicle body (6) and a plurality of wheels (5a, 5b, 5c, 5d) including tires attached thereto, comprising: a tire sensor (2) including acceleration sensors (22) provided on the plurality of wheels and outputting detection signals corresponding to acceleration including a gravitational acceleration component that changes with rotation of the wheels, the tire sensor (2) detecting, by using the acceleration sensors, a first rotation angle or a physical quantity correlating with the first rotation angle, which indicates a position of the tire sensor when an arbitrary position in a circumferential direction of the wheels is defined as 0°; and an on-board device (3) provided on the vehicle body and detecting, as a second rotation angle, a rotation angle of the wheel based on output signals of wheel angle sensors (11a, 11b, 11c, 11d) provided corresponding to each of the plurality of wheels, the tire sensor and the on-board device being configured to perform periodic communication at a predetermined communication interval when a connection between them is established, and the tire sensor being configured to notify the on-board device of tire position information corresponding to the first rotation angle or the physical quantity through the periodic communication at a predetermined timing, The vehicle-mounted device includes a position identification unit (331) that identifies the position of the wheel to which the tire sensor is attached based on the second rotation angle and the tire position information notified from the tire sensor.

[0197] [Second Aspect] The vehicle-mounted device includes an on-board communication unit (31) that transmits a periodic request signal requesting a response from the tire sensor through the periodic communication and receives a periodic response signal that is a response from the tire sensor after transmitting the periodic request signal, the tire sensor includes a sensor communication unit (24) that, upon receiving the periodic request signal, transmits the periodic response signal in response to the periodic request signal through the periodic communication, the vehicle-mounted device is configured to store the second rotation angle at the time of transmitting the periodic request signal requesting notification of the tire position information as a request angle in an on-board memory (M), and to determine, based on the request angle and an output signal of the wheel angle sensor, the rotation amount of the wheel during a periodic transmission period from the transmission of the previous periodic request signal to the transmission of the current periodic request signal, as the second rotation amount, the tire sensor is configured, upon receiving the periodic request signal requesting notification of the tire position information, to determine, based on a change in the first rotation angle, an amount of rotation of the wheel during a periodic reception period from reception of the previous periodic request signal to reception of the current periodic request signal, as a first amount of rotation, and to notify the vehicle-mounted device of the tire position information to which the first amount of rotation has been added via the periodic response signal in response to the current periodic request signal; and the position identification unit is configured to identify the position of the wheel to which the tire sensor is attached, based on the magnitude relationship of the difference between the first amount of rotation and the second amount of rotation.

[0198] [Third Aspect] The wheel position detection device according to the second aspect, wherein the on-board device is configured to increase the interval at which the periodic request signal for requesting notification of the tire position information is transmitted as the number of rotations of the wheel within a predetermined period decreases.

[0199] [Fourth Aspect] The wheel position detection device according to the second or third aspect, wherein the tire sensor transmits a signal that does not include the tire position information as the periodic response signal when there is no notification requesting the tire position information through the periodic request signal.

[0200] [Fifth Aspect] The wheel position detection device according to the first aspect, wherein the on-board device includes an on-board communication unit (31) that transmits a periodic request signal requesting a response from the tire sensor through the periodic communication and receives a periodic response signal that is a response from the tire sensor after transmitting the periodic request signal, and is configured to store the second rotation angle at the time of receiving the periodic response signal as a reception angle in an on-board memory (M); the tire sensor includes a sensor communication unit (24) that, upon receiving the periodic request signal, transmits the periodic response signal in response to the periodic request signal through the periodic communication, and is configured to transmit the periodic response signal immediately after reaching the first rotation angle corresponding to the peak of the sensor output of the acceleration sensor, together with the tire position information including peak information indicating that the sensor output of the acceleration sensor has peaked; and the position identification unit identifies the position of the wheel to which the tire sensor is attached based on the magnitude relationship of the difference between the reception angle and the first rotation angle identified by the peak information.

[0201] [Sixth Aspect] The wheel position detection device according to the fifth aspect, wherein the acceleration sensor is capable of detecting a first acceleration and a second acceleration different from the first acceleration, and the tire sensor adds the tire position information, including the peak information and rotational angle information for distinguishing between the peak of the first acceleration and the peak of the second acceleration, to each of the periodic response signals transmitted immediately after the first rotational angle corresponding to the peak of the first acceleration and the periodic response signals transmitted immediately after the first rotational angle corresponding to the peak of the second acceleration, and transmits the tire position information.

[0202] [Seventh Aspect] The wheel position detection device according to the fifth or sixth aspect, wherein the tire sensor transmits a signal that does not include the tire position information as the periodic response signal during a period from when the tire sensor transmits the periodic response signal that includes the tire position information until the tire sensor reaches the first rotation angle that corresponds to the peak.

[0203] [Eighth Aspect] The wheel position detection device according to any one of the fifth to seventh aspects, wherein the on-board device is configured to obtain, as centrifugal acceleration information, information relating to a centrifugal acceleration component acting on the tire sensor when the periodic request signal is transmitted, and to transmit the centrifugal acceleration information to the tire sensor via the periodic request signal, and the tire sensor performs a correction to reduce the centrifugal acceleration component included in the detection signal output by the acceleration sensor based on the centrifugal acceleration information notified from the on-board device, and identifies a peak of the sensor output of the acceleration sensor based on the corrected detection signal.

[0204] [Ninth Aspect] The vehicle-mounted device includes an on-board communication unit (31) that transmits a periodic request signal requesting a response from the tire sensor through the periodic communication, and receives a periodic response signal that is a response from the tire sensor after transmitting the periodic request signal; the tire sensor includes a sensor communication unit (24) that, upon receiving the periodic request signal, transmits the periodic response signal in response to the periodic request signal through the periodic communication; the vehicle-mounted device is configured to request the tire sensor to notify the tire position information through the periodic request signal every time an amount of change in the second rotation angle reaches a predetermined specified angle, and to store the second rotation angle at the time of transmitting the periodic request signal requesting notification of the tire position information as a requested angle in an on-board memory (M); and the tire sensor is configured, upon requesting notification of the tire position information through the periodic request signal, to notify the vehicle-mounted device of the tire position information including the first rotation angle or the physical quantity at the time of receiving the periodic request signal through the periodic response signal. The wheel position detection device according to a first aspect, wherein the position identification unit identifies the position of the wheel to which the tire sensor is attached based on a magnitude relationship of a difference between the first rotational angle notified through the periodic response signal or the first rotational angle corresponding to the physical quantity as a current angle.

[0205] [Tenth Aspect] The wheel position detection device according to the ninth aspect, wherein the on-board device does not request notification of the tire position information through the periodic request signal until an amount of change in the second rotation angle reaches the specified angle after requesting notification of the tire position information through the periodic request signal.

[0206] [Eleventh Aspect] The wheel position detection device according to the ninth or tenth aspect, wherein the tire sensor transmits a signal that does not include the tire position information as the periodic response signal when there is no notification requesting the tire position information through the periodic request signal.

[0207] [Twelfth Aspect] The wheel position detecting device according to any one of the ninth to eleventh aspects, wherein the on-board device increases the specified angle as the speed of the vehicle increases.

[0208] [Thirteenth Aspect] The wheel position detection device according to any one of the ninth to twelfth aspects, wherein the on-board device is configured to obtain, as centrifugal acceleration information, information on a centrifugal acceleration component acting on the tire sensor when an amount of change in the second rotation angle becomes the specified angle, and to transmit the centrifugal acceleration information to the tire sensor via the periodic request signal, and the tire sensor performs a correction to reduce the centrifugal acceleration component included in the detection signal output by the acceleration sensor based on the centrifugal acceleration information notified from the on-board device, and obtain, as the current angle, the first rotation angle based on the corrected detection signal.

[0209] [14th Aspect] The wheel position detection device according to any one of the 9th to 12th aspects, wherein the tire sensor is configured to notify the vehicle-mounted device of the tire position information, including the detection signal output by the acceleration sensor as the physical quantity, when notification of the tire position information is requested through the periodic request signal, and the vehicle-mounted device obtains, as the centrifugal acceleration information, information on the centrifugal acceleration component acting on the tire sensor when the amount of change in the second rotational angle reaches the specified angle, and performs correction to reduce the centrifugal acceleration component included in the detection signal output by the acceleration sensor based on the centrifugal acceleration information, and obtains, as the current angle, the first rotational angle based on the corrected detection signal.

[0210] [15th Aspect] A tire pressure monitoring system including the wheel position detection device according to any one of the first to fourteenth aspects, wherein the tire sensor creates a frame including information about the tire pressure and transmits the frame at a predetermined notification timing, and the on-board device, upon receiving the frame from the tire sensor, associates the information about the tire pressure included in the frame with the position of the wheel on which the tire sensor that transmitted the frame is installed, and stores the information.

Claims

1. A wheel position detection device applicable to a vehicle (1) in which a plurality of wheels (5a, 5b, 5c, 5d) including tires are attached to a vehicle body (6), The system includes an acceleration sensor (22) provided on multiple wheels that outputs a detection signal corresponding to acceleration including a gravitational acceleration component that changes with the rotation of the wheels, and a tire sensor (2) that uses the acceleration sensor to detect a first rotation angle indicating the position of itself when any position in the circumferential direction of the wheel is set to 0°, or a physical quantity correlated with the first rotation angle, The vehicle includes an on-board unit (3) that is provided on the vehicle body and detects the rotation angle of the wheel as a second rotation angle based on the output signals of wheel angle sensors (11a, 11b, 11c, 11d) provided corresponding to each of the plurality of wheels, The tire sensor and the in-vehicle device are configured to communicate periodically at predetermined communication intervals once a connection between them is established. The tire sensor is configured to notify the in-vehicle device of the tire position information corresponding to the first rotation angle or the physical quantity through the periodic communication at a predetermined timing. The aforementioned in-vehicle device is A positioning unit (331) that identifies the position of the wheel to which the tire sensor is attached based on the second rotation angle and the tire position information notified from the tire sensor, The vehicle includes an on-board communication unit (31) that transmits a periodic request signal requesting a response from the tire sensor via the aforementioned periodic communication, and receives a periodic response signal which is a response from the tire sensor after the transmission of the periodic request signal, The tire sensor includes a sensor communication unit (24) that, upon receiving the periodic request signal, transmits the periodic response signal to the periodic request signal through the periodic communication, The in-vehicle device is configured to store the second rotation angle at the time of transmission of the periodic request signal requesting notification of the tire position information as the requested angle in the in-vehicle memory (M), and to determine the amount of rotation of the wheel during the periodic transmission period from the transmission of a past periodic request signal to the transmission of the current periodic request signal as the second rotation amount based on the requested angle and the output signal of the wheel angle sensor. The tire sensor is configured to, upon receiving the periodic request signal requesting notification of the tire position information, determine the amount of rotation of the wheel during the periodic reception period from the reception of a past periodic request signal to the reception of the current periodic request signal, based on the change in the first rotation angle, as the first rotation amount, and to notify the in-vehicle device of the tire position information, including the first rotation amount, through the periodic response signal to the current periodic request signal. The position determination unit is a wheel position detection device that determines the position of the wheel to which the tire sensor is attached based on the relationship between the magnitude of the difference between the first rotation amount and the second rotation amount.

2. The wheel position detection device according to claim 1, wherein the in-vehicle unit is configured such that the transmission interval of the periodic request signal requesting notification of the tire position information is increased as the number of wheel rotations during a predetermined period decreases.

3. The wheel position detection device according to claim 1, wherein the tire sensor transmits a signal that does not include the tire position information as the periodic response signal if there is no notification requesting the tire position information via the periodic request signal.

4. A wheel position detection device applicable to a vehicle (1) in which a plurality of wheels (5a, 5b, 5c, 5d) including tires are attached to a vehicle body (6), The system includes an acceleration sensor (22) provided on multiple wheels that outputs a detection signal corresponding to acceleration including a gravitational acceleration component that changes with the rotation of the wheels, and a tire sensor (2) that uses the acceleration sensor to detect a first rotation angle indicating the position of itself when any position in the circumferential direction of the wheel is set to 0°, or a physical quantity correlated with the first rotation angle, The vehicle includes an on-board unit (3) that is provided on the vehicle body and detects the rotation angle of the wheel as a second rotation angle based on the output signals of wheel angle sensors (11a, 11b, 11c, 11d) provided corresponding to each of the plurality of wheels, The tire sensor and the in-vehicle device are configured to communicate periodically at predetermined communication intervals once a connection between them is established. The tire sensor is configured to notify the in-vehicle device of the tire position information corresponding to the first rotation angle or the physical quantity through the periodic communication at a predetermined timing. The aforementioned in-vehicle device is A positioning unit (331) that identifies the position of the wheel to which the tire sensor is attached based on the second rotation angle and the tire position information notified from the tire sensor, The vehicle includes an on-board communication unit (31) that transmits a periodic request signal requesting a response from the tire sensor via the aforementioned periodic communication, and receives a periodic response signal which is a response from the tire sensor after the transmission of the periodic request signal, The system is configured to store the second rotation angle at the time of receiving the periodic response signal in the on-board memory (M) as the reception angle. The tire sensor includes a sensor communication unit (24) that, upon receiving the periodic request signal, transmits the periodic response signal to the periodic request signal via periodic communication, and is configured to notify the in-vehicle device of the tire position information, including peak information indicating that the sensor output of the acceleration sensor has reached a peak, through the periodic response signal transmitted immediately after the first rotation angle corresponding to the peak of the sensor output of the acceleration sensor is reached. The position determination unit is a wheel position detection device that determines the position of the wheel to which the tire sensor is attached based on the relationship between the magnitude of the difference between the reception angle and the first rotation angle determined by the peak information.

5. The acceleration sensor is capable of detecting a first acceleration and a second acceleration different from the first acceleration. The wheel position detection device according to claim 4, wherein the tire sensor transmits the periodic response signal transmitted immediately after reaching the first rotation angle corresponding to the peak of the first acceleration and the periodic response signal transmitted immediately after reaching the first rotation angle corresponding to the peak of the second acceleration, with the tire position information, which includes the peak information and rotation angle information for distinguishing between the peak of the first acceleration and the peak of the second acceleration added to each of them.

6. The wheel position detection device according to claim 4, wherein the tire sensor transmits a signal that does not include the tire position information as the periodic response signal during the period from when it transmits the periodic response signal including the tire position information until it reaches the first rotation angle corresponding to the peak.

7. The in-vehicle device is configured to obtain information regarding the centrifugal acceleration component acting on the tire sensor when transmitting the periodic request signal as centrifugal acceleration information, and to transmit the centrifugal acceleration information to the tire sensor via the periodic request signal. The wheel position detection device according to claim 4, wherein the tire sensor performs a correction to reduce the centrifugal acceleration component included in the detection signal output by the acceleration sensor based on the centrifugal acceleration information notified from the in-vehicle device, and identifies the peak of the sensor output of the acceleration sensor based on the corrected detection signal.

8. A wheel position detection device applicable to a vehicle (1) in which a plurality of wheels (5a, 5b, 5c, 5d) including tires are attached to a vehicle body (6), The system includes an acceleration sensor (22) provided on multiple wheels that outputs a detection signal corresponding to acceleration including a gravitational acceleration component that changes with the rotation of the wheels, and a tire sensor (2) that uses the acceleration sensor to detect a first rotation angle indicating the position of itself when any position in the circumferential direction of the wheel is set to 0°, or a physical quantity correlated with the first rotation angle, The vehicle includes an on-board unit (3) that is provided on the vehicle body and detects the rotation angle of the wheel as a second rotation angle based on the output signals of wheel angle sensors (11a, 11b, 11c, 11d) provided corresponding to each of the plurality of wheels, The tire sensor and the in-vehicle device are configured to communicate periodically at predetermined communication intervals once a connection between them is established. The tire sensor is configured to notify the in-vehicle device of the tire position information corresponding to the first rotation angle or the physical quantity through the periodic communication at a predetermined timing. The aforementioned in-vehicle device is A positioning unit (331) that identifies the position of the wheel to which the tire sensor is attached based on the second rotation angle and the tire position information notified from the tire sensor, The vehicle includes an on-board communication unit (31) that transmits a periodic request signal requesting a response from the tire sensor via the aforementioned periodic communication, and receives a periodic response signal which is a response from the tire sensor after the transmission of the periodic request signal, The tire sensor includes a sensor communication unit (24) that, upon receiving the periodic request signal, transmits the periodic response signal to the periodic request signal through the periodic communication, The in-vehicle device is configured to request notification of the tire position information from the tire sensor via the periodic request signal whenever the amount of change in the second rotation angle reaches a predetermined specified angle, and to store the second rotation angle at the time of transmission of the periodic request signal requesting notification of the tire position information as the requested angle in the in-vehicle memory (M). The tire sensor is configured to notify the in-vehicle device of the tire position information, including the first rotation angle or the physical quantity at the time of receiving the periodic request signal, via the periodic response signal when notification of the tire position information is requested via the periodic request signal. The position determination unit determines the position of the wheel to which the tire sensor is attached, based on the relationship of the magnitude of the difference between the current angle and the requested angle, using the first rotation angle notified through the periodic response signal or the first rotation angle corresponding to the physical quantity as the current angle.

9. The wheel position detection device according to claim 8, wherein the in-vehicle unit requests notification of the tire position information via the periodic request signal, but does not request notification of the tire position information via the periodic request signal until the amount of change in the second rotation angle reaches the specified angle.

10. The wheel position detection device according to claim 8, wherein the tire sensor transmits a signal that does not include the tire position information as the periodic response signal if there is no notification requesting the tire position information via the periodic request signal.

11. The wheel position detection device according to claim 8, wherein the on-board unit increases the specified angle as the vehicle speed increases.

12. The in-vehicle device is configured to obtain information regarding the centrifugal acceleration component acting on the tire sensor when the change in the second rotation angle reaches the specified angle, as centrifugal acceleration information, and to transmit the centrifugal acceleration information to the tire sensor via the periodic request signal. The wheel position detection device according to claim 8, wherein the tire sensor performs a correction to reduce the centrifugal acceleration component included in the detection signal output by the acceleration sensor based on the centrifugal acceleration information notified from the in-vehicle device, and determines the first rotation angle based on the corrected detection signal as the current angle.

13. The tire sensor is configured to notify the in-vehicle device of the tire position information, including the detection signal output by the acceleration sensor as a physical quantity, when notification of the tire position information is requested via the periodic request signal. The wheel position detection device according to claim 8, wherein the in-vehicle device obtains information regarding the centrifugal acceleration component acting on the tire sensor when the change in the second rotation angle reaches the specified angle as centrifugal acceleration information, performs a correction to reduce the centrifugal acceleration component included in the detection signal output by the acceleration sensor based on the centrifugal acceleration information, and determines the first rotation angle based on the corrected detection signal as the current angle.

14. A tire pressure monitoring system including a wheel position detection device according to any one of claims 1 to 13, The tire sensor creates a frame containing information regarding the tire pressure and transmits the frame at a predetermined notification timing. The in-vehicle device, upon receiving the frame from the tire sensor, stores information regarding the air pressure of the tire contained in the frame and the position of the wheel on which the tire sensor that transmitted the frame is located, in a linked manner, as a tire pressure monitoring system.