Wheel position detection device

Abstract

To provide a wheel position detection device which can perform accurate wheel position detection more quickly.SOLUTION: In order to perform acceleration measurement when a vehicle 1 is turning at a control unit 33, the instruction of measurement start timing Ts and measurement end timing Te is transmitted to each tire side communication apparatus 2a to 2d. In addition, at the control unit 33, a sensor angle α is calculated on the basis of the acceleration Gx and acceleration Gz, and a cumulative angle θ is calculated by accumulating the change in the sensor angle α from the measurement start timing Ts to the measurement end timing Te on the basis of the sensor angle α. Then, at the control unit 33, on the basis of a magnitude of the cumulative angle θ in each tire side communication apparatus 2a to 2d, the wheel to which each tire side communication apparatus 2a to 2d is identified as one of multiple wheels 5a to 5d.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a wheel position detection device that identifies and registers the wheel to which a tire-side communication device is attached based on data transmitted from the tire-side communication device attached to each wheel, and is suitable for application to a tire pressure monitoring system (hereinafter referred to as TPMS). [Background technology]

[0002] Conventionally, Patent Document 1 discloses a technology for detecting wheel position in a direct type TPMS using a detection signal from a wheel speed sensor. In this TPMS, it is detected that the wheel has reached a predetermined rotational position based on an acceleration detection signal from an acceleration sensor (hereinafter referred to as a G sensor) provided in a tire-side communication device on the wheel side, and the vehicle body side also detects the rotational position of the wheel when a wireless signal is received from the tire-side communication device. The wheel position is detected by monitoring the change in the relative angle between the rotational position of the wheel detected on the wheel side and the rotational position of the wheel detected on the vehicle body side based on the deviation of a predetermined number of data, and the wheel position is detected by determining that the variation from the initial value exceeds a permissible value. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2013-173384 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, when using the detection signal of the wheel speed sensor, since the detection signal of the wheel speed sensor has an error, it is difficult to detect the wheel position quickly and accurately.

[0005] An object of the present disclosure is to provide a wheel position detection device that is capable of detecting the wheel position more quickly and with higher accuracy. [Means for solving the problem]

[0006] One aspect of the present disclosure is a method for producing a semiconductor device comprising: A wheel position detection device applied to a vehicle (1), comprising: tire-side communication devices (2a-2d) attached to a plurality of wheels (5a-5d) each having a tire; and a vehicle-side communication device (3) provided on a vehicle body (6), Each tire-side communication device attached to each of the plurality of wheels includes: an acceleration sensor (22) for detecting a circumferential acceleration (Gx) and a radial acceleration (Gz) of the wheel to which each tire-side communication device is attached; a first control unit (23) that stores the detection results of the acceleration sensors and creates a frame that stores individual identification information assigned to each of the tire-side communication units; a first communication unit (24) that performs two-way communication with the vehicle-side communication device, including the transmission of the frame; The vehicle-side communication device includes: a second communication unit (32) that receives the frame and transmits an instruction signal to each of the tire-side communication devices; a second control unit (33) that determines which of the plurality of wheels the tire-side communication device that has transmitted the frame is attached to, and that associates and registers the relationship between the identification information and the plurality of wheels, the second control unit transmits a measurement start timing (Ts) and a measurement end timing (Te) to each of the tire-side communication devices so as to cause the tire-side communication devices to measure acceleration when the vehicle is in a turning state; the second control unit or the first control unit provided in each of the tire-side communication devices calculates the sensor angle based on the circumferential acceleration and the radial acceleration, taking the angle at which the tire-side communication device is located with respect to the wheel center (WO) of the wheel to which the tire-side communication device is attached as a sensor angle (α), and calculates, based on the sensor angle, a cumulative angle (θ) obtained by accumulating changes in the sensor angle from the measurement start timing (Ts) to the measurement end timing (Te) or a cumulative number of rotations that the tire-side communication device has rotated with respect to the wheel center, The second control unit identifies which of the plurality of wheels each of the tire-side communication devices is attached to, based on the accumulated angle in each of the tire-side communication devices or the magnitude of the accumulated angle.

[0007] In this way, when the vehicle is turning, the sensor angle of each tire-side communication device is calculated based on the circumferential acceleration and radial acceleration detected by the tire-side communication device. The accumulated angle and accumulated rotation count are calculated from the sensor angle, and wheel position detection is performed based on the fact that the accumulated angle and accumulated rotation count are different for each wheel depending on the wheel position.

[0008] In this way, it is possible to identify which of the multiple wheels each tire-side communication device is attached to, and to perform wheel position detection. Furthermore, since this type of wheel position detection can be performed without using the detection signal of the wheel speed sensor, it is possible to perform wheel position detection more quickly and with high accuracy without being dependent on errors in the detection signal of the wheel speed sensor.

[0009] In another aspect of the present disclosure, the second control unit or the first control unit provided in each of the tire-side communication devices calculates the sensor angle based on only one of the circumferential acceleration and the radial acceleration, taking the angle at which the tire-side communication device is located with respect to the wheel center (WO) of the wheel to which the tire-side communication device is attached as a sensor angle (α), and calculates, based on the sensor angle, a cumulative angle (θ) obtained by accumulating changes in the sensor angle between the measurement start timing (Ts) and the measurement end timing (Te) or a cumulative number of rotations that the tire-side communication device has rotated with respect to the wheel center, The second control unit identifies which of the plurality of wheels each of the tire-side communication devices is attached to, based on the accumulated angle in each of the tire-side communication devices or the magnitude of the accumulated angle.

[0010] In this way, when the vehicle is turning, the wheel position can be detected by calculating the cumulative angle and the cumulative number of rotations based on the acceleration of one axis detected by the acceleration sensor. This type of wheel position detection can be performed without using the detection signal of the wheel speed sensor, so it is possible to detect the wheel position more quickly and with high accuracy without being dependent on the error of the detection signal of the wheel speed sensor.

[0011] The reference symbols in parentheses attached to each component indicate an example of the correspondence between the component and specific components described in the embodiments described below. [Brief description of the drawings]

[0012] [Figure 1] 1 is a diagram showing a schematic configuration of a vehicle equipped with a TPMS having a wheel position detection function according to a first embodiment. [Figure 2A] FIG. 2 is a block diagram showing a tire-side communication device; [Figure 2B] FIG. 2 is a block diagram showing a configuration of a vehicle-side communication device; [Diagram 3]1 is a diagram showing the X-axis and Z-axis accelerations applied to the tire-side communication unit as the wheel rotates, and the sensor angle, which is the angle at which the tire-side communication unit is located with respect to the center of the wheel. FIG. [Figure 4A] 13 is a diagram showing time changes in acceleration along the X-axis and Z-axis and time changes in the sensor angle in a tire-side communication unit attached to a left wheel. FIG. [Figure 4B] 13 is a diagram showing time changes in acceleration along the X-axis and Z-axis and time changes in the sensor angle in a tire-side communication unit attached to a right wheel. FIG. [Diagram 5] 1 is a diagram showing the relationship between the state when a vehicle turns right and the turning radius of each wheel. FIG. [Figure 6] 13 is a graph showing the change over time in the X-axis acceleration and the change over time in the sensor angle for each of the four wheels. [Figure 7A] FIG. 2 is a diagram showing a situation in which a vehicle capable of performing wheel position detection is turning; [Figure 7B] FIG. 2 is a diagram showing a situation in which a vehicle capable of performing wheel position detection is turning; [Figure 8] 11 is a diagram showing an example of the time change in X-axis acceleration and sensor angle and the number of rotation periods in a tire-side communication unit attached to a left wheel. FIG. [Figure 9] 13 is a diagram showing the X-axis and Z-axis accelerations applied to the tire-side communication unit as the right wheel rotates, and the sensor angle at which the tire-side communication unit is located with respect to the wheel center. FIG. [Figure 10] 13 is a diagram showing an example of the time change in acceleration and sensor angle of the X-axis and Z-axis in a tire-side communication unit attached to a left wheel, and the number of rotation periods. FIG. [Figure 11] 13 is a diagram showing an example of the time change in X-axis and Z-axis acceleration and sensor angle and the number of rotation periods in a tire-side communication unit attached to a right wheel. FIG. [Figure 12A] 4 is a flowchart showing details of a wheel position detection process. [Figure 12B] 12B is a flowchart showing details of the wheel position detection process following FIG. 12A. [Figure 13]4 is a time chart when a wheel position detection process is executed. [Figure 14A] FIG. 11 is a waveform diagram of the sensor angle before correction. [Figure 14B] FIG. 11 is a waveform diagram of the sensor angle after correction. [Figure 15] 13 is a diagram illustrating a change in acceleration on the X-axis and the corresponding pre-correction angle and post-correction angle. FIG. [Figure 16A] 10 is a flowchart showing details of a wheel position detection process according to a second embodiment. [Figure 16B] 16B is a flowchart showing details of the wheel position detection process following FIG. 16A. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the following, including other embodiments described below, the same reference numerals will be used to denote the same or equivalent parts in each embodiment.

[0014] (First embodiment) A first embodiment will be described with reference to Fig. 1 to Fig. 13. In this embodiment, a TPMS to which a wheel position detection device is applied will be described as an example. Fig. 1 is a block diagram showing the overall configuration of the TPMS, with the top of the page being the front of the vehicle 1, the bottom being the rear of the vehicle 1, and the left-right direction of the figure being the left-right direction of the vehicle 1.

[0015] 1, the TPMS is mounted on a vehicle 1 and includes tire-side communication devices 2a to 2d, a vehicle-side communication device 3, and a display device 4. In this embodiment, the tire-side communication devices 2a to 2d and the vehicle-side communication device 3 among these constitute a wheel position detection device.

[0016] The tire-side communication devices 2a-2d are attached to the four wheels 5a-5d of the vehicle 1, respectively. The tire-side communication devices 2a-2d detect the air pressure of the tires attached to the wheels 5a-5d, and transmit detection signal data indicating the detection results stored in a frame. The tire-side communication devices 2a-2d are capable of two-way communication with the vehicle-side communication device 3, and when they receive an instruction from the vehicle-side communication device 3, they enter a wheel position detection mode and perform processing corresponding to the instruction, such as transmitting data required for wheel position detection (hereinafter referred to as position detection data).

[0017] On the other hand, the vehicle-side communication device 3 is attached to the vehicle body 6 of the vehicle 1, and receives frames transmitted from the tire-side communication devices 2a-2d, and performs various processes and calculations based on the detection signal data stored therein to determine tire pressure. When detecting wheel positions, the vehicle-side communication device 3 issues instructions to each of the tire-side communication devices 2a-2d to cause each of the tire-side communication devices 2a-2d to transmit frames including position detection data, and performs wheel position detection based on the data. Figures 2A and 2B show block configurations of the tire-side communication devices 2a-2d and the vehicle-side communication device 3.

[0018] As shown in FIG. 2A, each of the tire-side communication devices 2a to 2d includes a sensing unit 21, a G sensor 22, a control unit 23, a communication unit 24, and an antenna 25.

[0019] The sensing unit 21 includes, for example, a pressure sensor and a temperature sensor, and outputs a detection signal corresponding to the tire pressure and a detection signal corresponding to the temperature. For example, the sensing unit 21 outputs a detection signal corresponding to the tire pressure and a detection signal corresponding to the temperature at every predetermined sampling period.

[0020] The G sensor 22 detects acceleration accompanying the rotation of the wheels 5a-5d to which the tire-side communication devices 2a-2d are attached. In the present embodiment, the G sensor 22 detects biaxial acceleration. Specifically, assuming that the circumferential direction of the wheels 5a-5d is the X-axis direction and the radial direction is the Z-axis direction as shown in FIG. 3, the G sensor 22 detects biaxial acceleration in the X-axis direction and the Z-axis direction. Hereinafter, the acceleration in the X-axis direction, i.e., the circumferential acceleration, will be referred to as acceleration Gx, and the acceleration in the Z-axis direction, i.e., the radial acceleration, will be referred to as acceleration Gz.

[0021] The G sensor 22 also outputs a detection signal corresponding to the acceleration at a sampling period that is the same as or different from the sampling period of the sensing unit 21. More specifically, the G sensor 22 outputs a detection signal corresponding to the acceleration, with the direction in which the wheels 5a to 5d rotate in one direction being the positive direction, and the direction in which the wheels 5a to 5d rotate in the reverse direction being the negative direction. If the direction in which the right wheels 5b, 5d rotate when the vehicle 1 moves forward is the positive direction, the right wheels 5b, 5d will rotate in the opposite negative direction.

[0022] For example, in FIG. 3, it is assumed that the wheels 5a to 5d are the left wheels 5a and 5c, and the left side of the drawing corresponds to the front of the vehicle 1, and the right side of the drawing corresponds to the rear of the vehicle 1. In this case, when the vehicle 1 moves forward, the left wheels 5a and 5c rotate counterclockwise as indicated by the arrow A1 in the drawing, and the sensor angle α, which is the angle at which the tire-side communication devices 2a to 2d equipped with the G sensor 22 are positioned relative to the wheel center WO, changes. The sensor angle α can be expressed as 0° when the tire-side communication devices 2a to 2d are positioned at the rightmost position relative to the wheel center WO, -90° when they are positioned at the topmost position, ±180° when they are positioned at the leftmost position, and +90° when they are positioned at the topmost position. In the case of the left wheels 5a and 5c, the rightmost position relative to the wheel center WO corresponds to the rearmost side of the vehicle 1, and the leftmost position corresponds to the frontmost side of the vehicle 1.

[0023] For the right wheels 5b, 5d, the sensor angle α is indicated in the same way as for the left wheels 5a, 5c, but since the tire-side communication devices 2a-2d are attached to the wheels 5a-5d in the same direction, the correspondence with the front-rear direction of the vehicle 1 is reversed. In other words, the rightmost side with respect to the wheel center WO corresponds to the frontmost side of the vehicle 1, and the leftmost side corresponds to the rearmost side of the vehicle 1. In addition, when the vehicle 1 moves forward, the right wheels 5b, 5d rotate clockwise, which is the opposite direction to the arrow A1 in FIG. 3. For this reason, the output corresponding to the acceleration Gx detected by the G sensor 22 has opposite positive and negative signs for the right wheels 5b, 5d and the left wheels 5a, 5c.

[0024] However, in the following, for example, as shown in Figure 6 described later, in order to make it easier to compare the outputs of acceleration Gx detected by the G sensors 22 in each wheel 5a to 5d, the positive and negative signs may be the same for the right wheels 5b, 5d and the left wheels 5a, 5c.

[0025] The control unit 23 corresponds to a first control unit, and is configured by a microcomputer equipped with a CPU, a ROM, a RAM, an I / O, etc., and executes predetermined processes according to programs stored in the ROM or the like.

[0026] Specifically, the control unit 23 receives a detection signal related to the tire pressure from the sensing unit 21, processes the signal and, if necessary, manipulates it to create data indicating the tire pressure detection result (hereinafter, referred to as tire pressure data). The control unit 23 then stores the tire pressure data together with the ID information of each tire-side communication device 2a-2d in a frame to be transmitted, and then transmits the frame to the communication unit 24. This process of transmitting a signal to the communication unit 24 is executed, for example, at a predetermined regular transmission interval in accordance with the above program.

[0027] The control unit 23 is basically in a periodic transmission mode in which a frame containing data on tire pressure together with ID information is transmitted to the vehicle-side communication device 3 at a predetermined periodic transmission period. In addition, when the control unit 23 receives an instruction to start measuring acceleration from the vehicle-side communication device 3 based on two-way communication, the control unit 23 enters a wheel position detection mode and starts measuring the acceleration Gx and the acceleration Gz based on the detection signal of the G sensor 22 to detect the wheel position. The sampling period of the acceleration by the G sensor 22 is arbitrary, but is set to a period, for example, 10 ms, in which the acceleration can be measured multiple times during one rotation of the wheels 5a to 5d. In addition, based on an instruction from the vehicle-side communication device 3, the control unit 23 performs a process of storing the measured acceleration data as position detection data in a frame together with the ID information of each of the wheels 5a to 5d and transmitting the data.

[0028] Furthermore, when the control unit 23 receives an instruction from the vehicle-side communication device 3 based on the two-way communication to end the wheel position detection, the control unit 23 ends the measurement of the acceleration and ends the transmission of the frame storing the position detection data. Then, the control unit 23 switches from the wheel position detection mode to the periodic transmission mode and performs periodic transmission of the frame storing the data related to the tire pressure.

[0029] The communication unit 24 corresponds to a first communication unit that performs two-way communication with the vehicle-side communication device 3 through the antenna 25. Specifically, the communication unit 24 functions as an output unit that transmits a frame sent from the control unit 23 to the vehicle-side communication device 3 through the antenna 25, and as an input unit that receives an instruction signal indicating an instruction from the vehicle-side communication device 3. The communication form of the communication unit 24 is arbitrary, but the two-way communication between the tire-side communication devices 2a to 2d and the vehicle-side communication device 3 is, for example, communication based on the BLE (Bluetooth Low Energy) standard. Note that "Bluetooth" is a registered trademark.

[0030] The antenna 25 is a communication antenna corresponding to the communication mode of the communication unit 24, and is built in, for example, the tire-side communication devices 2a to 2d, and has a function of a transmitting / receiving antenna capable of two-way communication. Of course, the transmitting / receiving antenna function does not have to be realized by a single antenna, and may be separated into a transmitting antenna and a receiving antenna.

[0031] The tire-side communication devices 2a-2d thus configured are attached to, for example, the air injection valves of the wheels of the respective wheels 5a-5d, and are disposed so that the sensing units 21 are exposed to the inside of the tires. As a result, each of the tire-side communication devices 2a-2d detects the tire pressure and transmits a frame at each predetermined regular transmission cycle via the antenna 25. Furthermore, each of the tire-side communication devices 2a-2d transmits a frame storing position detection data based on an instruction from the vehicle-side communication device 3 when detecting the wheel position.

[0032] As shown in FIG. 2B, the vehicle-side communication device 3 includes an antenna 31, a communication unit 32, and a control unit 33.

[0033] The antenna 31 is a single common antenna that collectively receives frames transmitted from each of the tire-side communication devices 2a to 2d, and is fixed to the vehicle body 6. The antenna 31 may be provided only for the TPMS, but if an antenna provided for the smart entry system is used, it is possible to reduce the number of parts by standardizing the parts.

[0034] The communication unit 32 corresponds to a second communication unit that performs two-way communication with each of the tire-side communication devices 2a-2d through the antenna 31. Specifically, when the communication unit 32 receives a frame transmitted from each of the tire-side communication devices 2a-2d via the antenna 31, the communication unit 32 functions as an input unit that inputs the frame and sends it to the control unit 33. In addition, the communication unit 32 functions as an output unit that transmits an instruction signal indicating an instruction sent from the control unit 33 to the vehicle-side communication device 3.

[0035] The control unit 33 corresponds to a second control unit, and is configured by a microcomputer equipped with a CPU, ROM, RAM, I / O, etc., and executes predetermined processes according to programs stored in the ROM or the like.

[0036] Specifically, the control unit 33 performs wheel position detection processing based on an instruction from the vehicle-side communication device 3. That is, the control unit 33 receives frames storing position detection data from each of the tire-side communication devices 2a-2d through the communication unit 32. Then, the control unit 33 specifies to which of the four wheels 5a-5d each of the tire-side communication devices 2a-2d is attached, and registers the ID information given to each of the tire-side communication devices 2a-2d by linking it to the wheel position, i.e., the wheel to which the tire-side communication device 2a-2d is attached.

[0037] For example, when the user presses a wheel position detection start switch (not shown), the control unit 33 executes the wheel position detection process, and when the wheel position detection start condition is satisfied, outputs an instruction signal to start acceleration measurement, and executes the wheel position detection process. The details of this wheel position detection process will be described later, but this wheel position detection process associates and registers the wheel on which the tire side communication devices 2a-2d are attached with the ID information of each tire side communication device 2a-2d. Then, when this registration is completed, the control unit 33 ends the wheel position detection process, and outputs an instruction signal to each tire side communication device 2a-2d to instruct them to end acceleration measurement. As a result, the control unit 23 of each tire side communication device 2a-2d switches to a periodic transmission mode, and begins to periodically transmit a frame storing data related to tire pressure.

[0038] It is optional to output an instruction signal from the vehicle-side communication device 3 to each of the tire-side communication devices 2a-2d to instruct them to end the acceleration measurement. In other words, when the time when the wheel position detection process is expected to end has elapsed, the tire-side communication devices 2a-2d can automatically switch to a regular transmission period of frames for normal tire pressure detection.

[0039] The control unit 33 is also configured to receive detection signals from the steering angle sensor 7 and the gear position sensor 8, and these detection signals are used when performing wheel position detection processing. Furthermore, data related to vehicle speed is input to the control unit 33 from another on-board ECU 9 such as a meter ECU. Of course, even if the detection signals from the steering angle sensor 7 and the gear position sensor 8 are not directly input to the control unit 33, if another ECU detects the steering angle or gear position from these detection signals, the detection results may be transmitted from that ECU.

[0040] Furthermore, the control unit 33 performs various signal processing and calculations based on the data indicating the detection results stored in the received frame to determine the tire pressures, and outputs an electric signal corresponding to the determined tire pressures to the display 4. For example, the control unit 33 identifies the tire pressures of the wheels 5a-5d and outputs the data to the display 4. Alternatively, the control unit 33 compares the determined tire pressures with a predetermined threshold value Th, and when it detects that the tire pressures have decreased, outputs data to that effect to the display 4. In this way, the tire pressure data of the four wheels 5a-5d or a decrease in the tire pressure of any of the wheels 5a-5d is transmitted to the display 4.

[0041] 1, the display 4 is disposed in a location visible to the driver, and is constituted by, for example, a display and a warning lamp installed in the instrument panel of the vehicle 1. For example, when tire pressure data of each of the wheels 5a-5d is sent from the control unit 33, the display 4 displays the tire pressure of each of the wheels 5a-5d as a numerical value. Furthermore, when data indicating that the tire pressure has dropped is sent from the control unit 33, the display 4 notifies the driver of the drop in tire pressure by displaying that fact.

[0042] The TPMS to which the wheel position detecting device of this embodiment is applied is configured as described above.

[0043] Next, the operation of the TPMS of this embodiment will be described. Prior to that, however, a method of wheel position detection performed by the TPMS of this embodiment will be described.

[0044] [Method of detecting wheel position] In the TPMS of this embodiment, wheel position detection is performed based on the accelerations Gx and Gz obtained from the detection signals of the G sensor 22.

[0045] As described above, in FIG. 3, it is assumed that the wheels 5a to 5d are the left wheels 5a and 5c, the left side of the drawing is the front of the vehicle 1, and the right side of the drawing is the rear of the vehicle 1, and the tire-side communication devices 2b and 2d are present at a position where the sensor angle α is 0°, and the vehicle 1 moves forward. In this case, if the time changes of the acceleration Gx and the acceleration Gz are extracted by excluding the centrifugal acceleration component associated with the change in the running speed of the vehicle 1 and only the gravitational acceleration component, they are shown as a sine waveform that changes with time with the rotation of the wheels, as shown in the upper part of FIG. 4A. The acceleration Gx has a waveform that is delayed by a 1 / 4 period phase from the acceleration Gz. And, the time change of the sensor angle α of the tire-side communication devices 2b and 2d is a waveform that linearly shifts from 0° to -180° and linearly returns from 180° to 0°, as shown in the lower part of FIG. 4A. Therefore, the sensor angle α can be detected based on the waveforms of the acceleration Gx and the acceleration Gz.

[0046] Similarly, in the case of the right wheels 5b, 5d, the time changes of the accelerations Gx and Gz are shown as sine waveforms that change with the rotation of the wheels as shown in the upper part of Fig. 4B. The acceleration Gx has a waveform that leads the acceleration Gz by a quarter cycle phase. The time changes of the sensor angle α of the tire-side communication devices 2b, 2d have a waveform that linearly shifts from 0° to +180° and linearly returns from -180° to 0° as shown in the lower part of Fig. 4B. Therefore, the sensor angle α can be detected based on the waveforms of the accelerations Gx and Gz.

[0047] As shown in Fig. 5, when the vehicle 1 turns, the turning radius of each of the wheels 5a to 5d becomes different in comparison with the turning radius R of the vehicle center depending on the distance from the turning center to each of the wheels 5a to 5d. For example, as shown in Fig. 5, consider the case where the vehicle 1 turns clockwise around point O as the turning center.

[0048] The turning radius of each wheel 5a to 5d is r A , r B , r C , r D Then, r A >r C >r B >r D The following relationship holds. Therefore, a difference occurs in the number of rotations of each wheel 5a to 5d during turning. Therefore, if the acceleration Gx in each tire-side communication device 2a to 2d is represented by Gxa to Gxd, the time change of the accelerations Gxa to Gxd is represented by a sine waveform shown in the upper part of FIG. 6, and the phases become faster in the order of Gxa>Gxc>Gxb>Gxd. In other words, the phase of the acceleration Gxc is slightly slower than the acceleration Gxa, the phases of the accelerations Gxb and Gxd are even slower than the accelerations Gxa and Gxc, and the phase of the acceleration Gxd is slightly slower than the acceleration Gxb. Similarly, as shown in the lower part of FIG. 6, the time change of the sensor angles αa to αd of each tire-side communication device 2a to 2d also gradually differs between the wheels 5a to 5d.

[0049] Therefore, the magnitude of the accumulated angle obtained by accumulating the change in the sensor angle α of the tire-side communication devices 2a to 2d after the same time has elapsed from the start of measurement using the inner wheel difference of each wheel 5a to 5d, or the magnitude of the accumulated number of revolutions obtained by accumulating the number of revolutions, follows the order of the phase of the acceleration. In other words, when the vehicle 1 turns clockwise, the magnitude of the accumulated angle or the accumulated number of revolutions is in the following relationship: left front wheel 5a>left rear wheel 5c>right front wheel 5b>right rear wheel 5d. Conversely, when the vehicle 1 turns counterclockwise, the magnitude of the accumulated angle or the accumulated number of revolutions is in the following relationship: right front wheel 5b>right rear wheel 5d>left front wheel 5a>left rear wheel 5c.

[0050] Based on this relationship, by calculating the accumulated angle or the accumulated number of revolutions during a predetermined time while the vehicle 1 is turning, it becomes possible to perform wheel position detection as to which of the wheels 5a to 5d the tire-side communication devices 2a to 2d are attached. Examples of such turning are turning from an automobile maintenance facility 10 of a dealer or the like to enter the facility or an adjacent road 11 as shown in Fig. 7A, and turning right or left at an intersection 12 as shown in Fig. 7B. If wheel position detection is necessary when turning in such a manner, the user presses a wheel position detection start switch (not shown) to execute wheel position detection processing.

[0051] Furthermore, it is preferable that the wheel position detection is performed when the vehicle 1 is turning under the conditions of a steering angle of a certain level or more and a vehicle speed of a certain level or more, that is, when it is confirmed that the vehicle 1 is actually turning. Therefore, when the wheel position detection process is performed and the conditions of a steering angle of a certain level or more and a vehicle speed of a certain level or more are satisfied, it is preferable that the vehicle side communication device 3 instructs each of the tire side communication devices 2a to 2d to start measuring acceleration.

[0052] On the other hand, when the wheel position detection is completed, the acceleration measurement may be terminated. For this reason, when it is possible to identify which of the wheels 5a to 5d the tire side communication devices 2a to 2d are attached to when the wheel position detection process is executed, the vehicle side communication device 3 may instruct each of the tire side communication devices 2a to 2d to terminate the acceleration measurement. The acceleration measurement may also be terminated when data necessary for wheel position detection is obtained during turning. Or, when turning is completed after turning, the acceleration measurement may be terminated because data suitable for wheel position detection is no longer obtained. For this reason, when the steering angle becomes equal to or less than a certain value, or when the vehicle speed is maintained at or below a certain value for a certain period of time, the vehicle side communication device 3 instructs each of the tire side communication devices 2a to 2d to terminate the acceleration measurement. The reason why the condition for the vehicle speed to be equal to or less than a certain value is that the vehicle speed is maintained for or above a certain period of time is set as the condition for the vehicle speed to be equal to or below a certain value is that the vehicle may stop temporarily when turning right or left, and the acceleration measurement is not stopped until such a case.

[0053] In this way, wheel position detection can be performed based on the accumulated angle or the accumulated number of revolutions, but it is desirable that the acceleration data used in this case is for the same period, that is, the measurement start and end timings are the same. For this reason, it is necessary to synchronize the measurement start timing and measurement end timing of each tire-side communication device 2a to 2d. For example, the following methods (1) and (2) can be considered as the method for this.

[0054] (1) Immediately before sampling of acceleration measurement, clock synchronization is performed between each of the tire-side communication devices 2a-2d and the vehicle-side communication device 3. Then, when the vehicle-side communication device 3 issues a broadcast instruction to each of the tire-side communication devices 2a-2d, each of the tire-side communication devices 2a-2d simultaneously responds accordingly. Then, each of the tire-side communication devices 2a-2d measures acceleration from the start of measurement until receiving an instruction to end measurement, and further, each of the tire-side communication devices 2a-2d or the vehicle-side communication device 3 performs processing required for wheel position detection.

[0055] (2) When the conditions for starting wheel position detection are met, the vehicle-side communication device 3 broadcasts a measurement start command to each of the tire-side communication devices 2a-2d without synchronizing the clocks. Each of the tire-side communication devices 2a-2d responds individually within a certain time after receiving the measurement start command, and performs acceleration measurement until it receives a measurement start or measurement end command, while each of the tire-side communication devices 2a-2d or the vehicle-side communication device 3 performs the processing required for wheel position detection.

[0056] Either method (1) or (2) may be used, but method (1) requires a configuration for clock synchronization, although it can eliminate delays between the tire-side communication devices 2a-2d in data communication from the tire-side communication devices 2a-2d to the vehicle-side communication device 3. On the other hand, method (2) does not require clock synchronization, so delays occur between the tire-side communication devices 2a-2d in data communication from the tire-side communication devices 2a-2d to the vehicle-side communication device 3, but the configuration can be simplified because no technology for clock synchronization is required.

[0057] For this reason, in this embodiment, the method (2) is used to synchronize the measurement start timing and measurement end timing without synchronizing the clocks, and the accumulated angle or accumulated number of rotations is calculated.

[0058] The calculation of the cumulative angle or the cumulative number of rotations can also be performed by the following two methods, (a) and (b).

[0059] First, as a premise, the acceleration Gx changes like a sine waveform with the rotation of the wheel as shown in the upper part of Fig. 8. Regarding the sensor angle α, in the case of the left wheels 5a and 5c, it repeatedly changes from 180° to -180° in response to the change in the acceleration Gx as shown in the lower part of Fig. 8. The two methods (a) and (b) will be explained with reference to this figure.

[0060] (a) All angle information during the period Tcal from the measurement start timing Ts to the measurement end timing Te is calculated. Then, as shown in the lower part of Fig. 8, the cumulative angle θ is obtained by calculating the total angle change amount of the hatched part in the figure for the change in the sensor angle α from the measurement start timing Ts to the measurement end timing Te along the time axis. When calculating the cumulative number of rotations, it can be understood as a value proportional to the cumulative angle θ, that is, the value obtained by dividing the cumulative angle θ by 360°.

[0061] The calculation of the cumulative angle θ and the cumulative rotation number may be performed by the control unit 23 of each tire-side communication device 2a-2d, or may be performed by the control unit 33 by transmitting the acceleration data or the sensor angle α data from each tire-side communication device 2a-2d to the vehicle-side communication device 3.

[0062] (b) Since the above method (a) requires an enormous amount of calculation, only the sensor angle αs at the measurement start timing Ts and the sensor angle αe at the measurement end timing Te are calculated as shown in Fig. 8. Then, during the period Tcal between the measurement start timing Ts and the measurement end timing Te, the number of rotation periods N of the wheels 5a to 5d is counted from the acceleration data. Since the sensor angle α changes in a sine waveform, it is possible to count the number of times an arbitrary sensor angle α is set as a reference angle based on the reference angle, and the number of times the reference angle is reached, thereby counting the number of rotation periods N.

[0063] For example, when the reference angle is 180°, the number of times 180° is passed, that is, the number of rotation periods N based on the wheel rotation, can be calculated by detecting and counting the peaks of the acceleration Gx. The peaks of the acceleration Gx can be detected based on the acceleration Gx at the sampling point Sp shown in the upper part of FIG. 8. For example, the acceleration Gx at the sampling point Sp at an arbitrary time t is set as Gx(t), and Gx(t) is compared with the acceleration Gx one cycle ago, Gx(t-1), and the sign of the difference Gx(t)-Gx(t-1) is calculated. The peaks of the acceleration Gx can be detected based on the fact that this sign becomes +, +, -, -. Also, the number of rotation periods N can be calculated by counting the number of times the condition is satisfied, for example, that the acceleration goes from less than a certain acceleration to more than a certain acceleration.

[0064] The sensor angle α at each timing can be calculated using the acceleration Gz in addition to the acceleration Gx. This calculation method will be described using the right wheels 5b and 5d as an example.

[0065] When the right wheels 5b, 5d are rotating due to the forward movement of the vehicle 1, the components of the acceleration Gx and acceleration Gz measured by the G sensor 22 with respect to the sensor angle α at which the tire-side communication devices 2b, 2d are located are shown in FIG. 9. That is, the acceleration Gx is expressed as a component that forms a sensor angle α with respect to the gravitational acceleration component, and the acceleration Gz is expressed as a component that forms a sensor angle α with respect to the position of 0° on the far right side of the wheel center WO, that is, the far front side of the vehicle 1. Note that HPF(Gz) means that high-pass filtering has been performed on the detection signal of the acceleration Gz. By performing high-pass filtering on the acceleration Gz, the centrifugal acceleration component accompanying the change in the traveling speed of the vehicle 1 is removed.

[0066] Therefore, the sensor angle α is expressed as in Equation 1, and can be calculated using the two-axis acceleration Gx and acceleration Gz detected by the G sensor 22.

[0067]

number

[0068] First, in the case of the left wheels 5a and 5c, the accumulated angle θ is expressed as in Equation 2 using the number of rotation periods N, the sensor angle αs at the measurement start timing, and the sensor angle αe at the measurement end timing. Note that (A°) mod 360° means that when A° is an angle exceeding 360°, an integer multiple of 360° is subtracted to make it an angle less than 360°.

[0069] (Number 2) θ=(N-1)×360°+(αs+360°-αe)mod360° 10, if the acceleration Gx and the acceleration Gz change, the sensor angle αs is -90°, the sensor angle αe is -10°, and N=4, the accumulated angle θ will be calculated as 1360° as shown in Equation 3. Note that the accumulated number of rotations can be calculated by dividing the accumulated angle θ by 360°, and if the accumulated angle θ is 1360°, then 1360÷360=3.777· is the accumulated number of rotations.

[0070] (Number 3) θ=(4-1)×360°+{-90°+360°-(-10°)}=1360° On the other hand, in the case of the right wheels 5b and 5d, the accumulated angle θ is expressed as in Equation 4 using the number of rotation periods N, the sensor angle αs at the measurement start timing, and the sensor angle αe at the measurement end timing.

[0071] (Number 4) θ=(N-1)×360°+(αe+360°-αs)mod360° Therefore, when the acceleration Gx and the acceleration Gz change as shown in FIG. 11, if the sensor angle αs is 90°, the sensor angle αe is 10°, and N=4, the cumulative angle θ will be calculated as 1360° as shown in Equation 5.

[0072] (Number 5) θ=(4-1)×360°+{10°+360°-90°)}=1360° In this way, the accumulated angle θ or accumulated rotation number of each tire side communication device 2a-2d can be calculated, and based on the magnitude of the calculated value and the vehicle 1, it can be identified to which of the wheels 5a-5d each tire side communication device 2a-2d is attached, making it possible to detect the wheel position.

[0073] Fig. 12 is a flowchart showing details of the wheel position detection process based on the above-mentioned wheel position detection method. This wheel position detection process is executed by the control unit 33 at predetermined intervals, for example, when the user presses a wheel position detection start switch (not shown) during tire replacement. The details of the wheel position detection process will be described with reference to the time charts shown in Figs. 12 and 13 when the wheel position detection process is executed.

[0074] First, in step S100 in FIG. 12, the control unit 33 judges whether the vehicle 1 is turning. The conditions for this judgment may be set arbitrarily, but here, if the conditions of a certain steering angle or more and a certain vehicle speed or more are satisfied, it is judged that the vehicle 1 is turning. As shown in FIG. 13, a steering angle threshold is set, and if the steering angle is equal to or more than this steering angle threshold, it is judged that the steering angle is equal to or more than the certain steering angle. Similarly, as shown in FIG. 13, a speed threshold is set, and if the vehicle speed is equal to or more than this speed threshold, it is judged that the vehicle speed is equal to or more than the certain vehicle speed. This judgment is made based on the detection signal of the steering angle sensor 7 and data related to the vehicle speed transmitted from another ECU. If the judgment here is affirmative, the process proceeds to step S105, and if the judgment is negative, the process of step S100 is repeated.

[0075] In step S105, the timer t for measuring time in the control unit 23 is reset. Then, the process proceeds to step S110, where, as at time T1 in FIG. 13, the vehicle-side communication device 3 transmits an instruction signal to each of the tire-side communication devices 2a to 2d to start acceleration measurement. In response to this, the control unit 23 of each of the tire-side communication devices 2a to 2d switches from the periodic transmission mode to the wheel position detection mode. Then, the control unit 23 starts measuring the acceleration Gx and the acceleration Gz and counting the number of rotation periods N from the timing of receiving the instruction, and returns a response signal to the vehicle-side communication device 3 to respond that it has received the instruction to start measurement, and enters a reception standby state. As a result, a connection is established between each of the tire-side communication devices 2a to 2d and the vehicle-side communication device 3, and bidirectional communication is performed. In the case of BLE communication, even if each of the tire-side communication devices 2a to 2d is not in a reception standby state called a scan, communication is possible based on an advertisement signal, so that an instruction to start measurement can be transmitted to each of the tire-side communication devices 2a to 2d by utilizing this.

[0076] After that, in step S115, it is determined whether the timer t has reached a predetermined time Ta or more. The predetermined time Ta here is a time set to be greater than or equal to the maximum delay time assumed between the issuance of an instruction to start measurement and the tire-side communicators 2a to 2d starting acceleration measurement and returning a response signal, as shown in FIG. 13. If the timer t has reached the predetermined time Ta or more, it is assumed that a response signal has been returned from all of the tire-side communicators 2a to 2d, even if there is a delay in the return of the response signal. The process of this step is repeated until a positive determination is made in step S115, and if a positive determination is made in step S115, the process proceeds to step S120. Note that, in this case, a response signal is returned from each of the tire-side communicators 2a to 2d, but it may be determined simply that the predetermined time Ta is greater than or equal to the time when each of the tire-side communicators 2a to 2d is assumed to start acceleration measurement in response to an instruction, and the return of a response signal is optional.

[0077] In step S120, the same process as in step S100 is performed again to determine whether the conditions suitable for wheel position detection still exist. If the determination here is affirmative, the process proceeds to step S125, and if the determination is negative, the process returns to step S100.

[0078] In step S125, as shown in Fig. 13, the control unit 33 informs each of the tire-side communication devices 2a-2d that it is the measurement start timing Ts. Specifically, the control unit 33 transmits an instruction signal to each of the tire-side communication devices 2a-2d to acquire the rotation period number N and the start acceleration Gxs and start acceleration Gzs, which are the acceleration Gx and the acceleration Gz, as an instruction to perform various processes to be executed at the measurement start timing Ts. In response to this, the control unit 23 of each of the tire-side communication devices 2a-2d converts the start period number Ns, start acceleration Gxs, and start acceleration Gzs calculated by, for example, the above-mentioned method (b) into digital form and returns the digital data to the vehicle-side communication device 3, where it is received by the vehicle-side communication device 3.

[0079] Then, the process proceeds to step S130, where the control unit 33 calculates the sensor angle αs at the measurement start timing Ts based on the start acceleration Gxs and start acceleration Gzs of the data received in step S125, based on the above-mentioned formula 1. This process is performed for each received data, that is, for each tire-side communication device 2a-2d, and the sensor angle αs is calculated for each tire-side communication device 2a-2d. Then, the process proceeds to step S135, where it is determined whether the vehicle 1 has finished turning. This determination condition may be set arbitrarily, but here, it is determined that the vehicle 1 has finished turning if the condition that a steering angle or a vehicle speed of a certain level or less is maintained for a certain period of time or more is satisfied. This determination is also performed based on the detection signal of the steering angle sensor 7 and data related to the vehicle speed transmitted from another ECU.

[0080] The constant steering angle and constant vehicle speed here may be the same as those in steps S100 and S120, or may be values ​​smaller than those in steps S100 and S120 by a predetermined amount including a margin. If the condition in step S135 is satisfied, it is assumed that the situation will be one in which turning is to be ended. After this, the inner wheel difference becomes smaller and data suitable for wheel position detection cannot be obtained, so the data obtained up to this point is used for wheel position detection. If the answer here is positive, the process proceeds to step S140, and if the answer is negative, the process in step S135 is repeated.

[0081] In step S140, it is determined whether or not a predetermined time Tb or more has elapsed since the timer t was at the predetermined time Ta, that is, whether or not the elapsed time from the measurement start timing Ts is equal to or greater than the predetermined time Tb. The predetermined time Tb here is set as the minimum time from the measurement start timing Ts to the measurement end timing Te as shown in FIG. 13, and is set arbitrarily assuming the time required to collect acceleration data to the extent that the wheel position detection can be performed with high accuracy. As shown in FIG. 8 and the like, the period Tcal from the measurement start timing Ts to the measurement end timing Te is set to a period equal to or greater than the predetermined time Tb. If a positive determination is made here, the process proceeds to step S145, and if a negative determination is made, the process proceeds to step S175.

[0082] The processes of steps S135 and S140 are not essential, and only one of them may be performed. For example, only step S140 may be performed, and when a predetermined time Tb or more has elapsed from the predetermined time Ta, it may be determined that data sufficient for accurate wheel position detection is available, and the process proceeds to step S145 and subsequent steps. Also, wheel position detection may be performed using data available until the condition of step S135 is met.

[0083] In step S145, as shown in Fig. 13, the control unit 33 informs each of the tire-side communication devices 2a-2d that it is the measurement end timing Te. Specifically, the control unit 33 transmits an instruction signal to each of the tire-side communication devices 2a-2d to acquire the rotation period number N and the end period number Ne, which are the accelerations Gx and Gz, and the end accelerations Gxe and Gze, as an instruction to perform various processes to be executed at the measurement end timing Te. In response to this, the control unit 23 of each of the tire-side communication devices 2a-2d converts the end period number Ne, the end accelerations Gxe and Gze calculated by, for example, the method (b) described above into digital form and returns the digital data to the vehicle-side communication device 3, where it is received by the vehicle-side communication device 3.

[0084] Then, the process proceeds to step S150, where the control unit 33 calculates the sensor angle αe at the measurement end timing Te based on the end acceleration Gxe and the end acceleration Gze of the data received in step S145, based on the above-mentioned formula 1. Then, the process proceeds to step S155, where the left and right wheels 5a, 5c are determined as the left and right wheels. The left and right wheels 5a, 5c may be determined as the left and right wheels 5a, 5c as the left and right wheels 5b, 5d as the left and right wheels 5a, 5c, respectively. That is, the control unit 23 detects whether the vehicle 1 is traveling forward or backward from the detection signal of the gear position sensor 8, and determines which of the phases of the acceleration Gx and the acceleration Gz is advanced in the left and right wheels 5a, 5c and the right and left wheels 5b, 5d in response to the detection result. For example, as shown in FIG. 13, when the vehicle 1 is traveling forward, if the phase of the acceleration Gz is advanced by 90° with respect to the acceleration Gx, it can be determined that the left wheels 5a, 5c are the wheels to which the control unit 33 is attached. Also, if the phase is delayed by 90°, it can be determined that the right wheels 5b, 5d are the wheels to which the control unit 33 is attached. When the left / right determination is to be performed by the vehicle-side communication device 3, data indicating the phase difference between the acceleration Gx and the acceleration Gz is also returned from each of the tire-side communication devices 2a-2d when the instruction in step S145 is given. Alternatively, since each of the tire-side communication devices 2a-2d can perform left / right determination based on the phase difference between the acceleration Gx and the acceleration Gz, data on the determination result is returned from each of the tire-side communication devices 2a-2d when the instruction in step S145 is given.

[0085] If the determination here is affirmative, the process proceeds to step S160, and if the determination here is negative, the process proceeds to step S165.

[0086] In step S160, since the wheels are the left wheels 5a and 5c, the accumulated angle θ for the left wheels 5a and 5c is calculated. The accumulated angle θ can be calculated using the above-mentioned formula 2, and the number of rotation periods N in formula 2 is calculated as the difference between the end number of periods Ne obtained in step S145 and the start number of periods Ns obtained in step S125.

[0087] Similarly, in step S165, since the wheels are the right wheels 5b and 5d, the accumulated angle θ for the right wheels 5b and 5d is calculated. The accumulated angle θ can be calculated using the above-mentioned formula 4, and the number of rotation periods N in formula 4 is calculated as the difference between the end number of periods Ne obtained in step S145 and the start number of periods Ns obtained in step S125.

[0088] The processes in steps S150 to S165 described above are performed for each piece of received data, that is, for each of the tire-side communicators 2a to 2d. Therefore, the accumulated angle θ is calculated for each of the tire-side communicators 2a to 2d.

[0089] Next, the process proceeds to step S170, where wheel position detection is performed based on the accumulated angle θ for the four wheels and the steering angle information, i.e., the turning direction of the vehicle 1 indicated by the detection signal of the steering angle sensor 7. That is, if the vehicle 1 turns clockwise, the magnitude of the accumulated angle θ has a relationship of left front wheel 5a>left rear wheel 5c>right front wheel 5b>right rear wheel 5d. Conversely, if the vehicle 1 turns counterclockwise, the magnitude of the accumulated angle θ has a relationship of right front wheel 5b>right rear wheel 5d>left front wheel 5a>left rear wheel 5c. Based on this relationship, it is possible to identify which of the four wheels 5a-5d each of the four tire-side communication devices 2a-2d is attached to. For this reason, the ID information stored in the frame of each tire-side communication device 2a-2d is registered by linking it to the wheel position, i.e., the wheel to which the tire-side communication device 2a-2d is attached. In this way, various calculations and determination processes are performed during the period Tc from the measurement end timing Te in FIG. 13, and the identification of the wheel position is completed. Then, the process proceeds to step S175, where the vehicle-side communication device 3 transmits an instruction to each of the tire-side communication devices 2a-2d to end measurement, as shown at time T2 in Fig. 13, and the wheel position detection process is terminated. Then, upon receiving this instruction, each of the tire-side communication devices 2a-2d ends the acceleration measurement and releases the reception standby state.

[0090] Although the accumulated angle θ is used to detect the wheel position here, the wheel position can also be detected in the same manner using the accumulated number of rotations, which is a value proportional to the accumulated angle θ.

[0091] After this, the control unit 23 of each tire-side communication device 2a-2d switches from the wheel position detection mode to the periodic transmission mode. Then, each tire-side communication device 2a-2d transmits a frame storing data on tire pressure together with ID information to the vehicle-side communication device 3 at a predetermined periodic transmission cycle. When this is transmitted to the control unit 33 via the antenna 31, the control unit 33 performs various signal processing and calculations to obtain the tire pressure, and identifies which of the wheels 5a-5d the tire pressure belongs to from the ID information stored in the frame. Then, the control unit 33 outputs an electric signal corresponding to the obtained tire pressure to the display device 4. As a result, the display device 4 displays the tire pressure in a form that identifies which of the wheels 5a-5d the tire pressure belongs to, or displays a drop in the tire pressure, thereby making it possible to inform the user of the tire condition.

[0092] As described above, in the TPMS of this embodiment, when the vehicle 1 is in a turning state, the sensor angle α of each of the tire-side communicators 2a-2d is calculated based on the acceleration Gx and the acceleration Gz detected by the tire-side communicators 2a-2d. Then, the accumulated angle θ and the accumulated rotation number are calculated from the sensor angle α, and wheel position detection is performed based on the fact that the accumulated angle θ and the accumulated rotation number are different values ​​for each of the wheels 5a-5d depending on the wheel position.

[0093] In this way, it is possible to identify which of the four wheels 5a-5d each of the four tire-side communication devices 2a-2d is attached to, and to perform wheel position detection. Furthermore, since such wheel position detection can be performed without using the detection signals of the wheel speed sensors, it is possible to perform wheel position detection more quickly and with high accuracy without being dependent on errors in the detection signals of the wheel speed sensors.

[0094] Second embodiment The second embodiment will be described. The second embodiment is different from the first embodiment in that wheel position detection can be performed based on uniaxial acceleration, and other aspects are the same as the first embodiment, so only the differences from the first embodiment will be described.

[0095] In the above first embodiment, a method of detecting wheel position when two-axis acceleration is detected by the G sensor 22 is described. In this embodiment, however, wheel position detection based on one-axis acceleration detected by the G sensor 22 will be described.

[0096] Even if the G sensor 22 can detect acceleration along only one axis, or even if the G sensor 22 detects acceleration along two axes, the wheel position can be detected by using only one of the axes.

[0097] When the acceleration Gx is used, as shown in Fig. 9, the acceleration Gx is expressed as a component that forms a sensor angle α with respect to the component of the gravitational acceleration. Therefore, the absolute value of the sensor angle α can be calculated as shown in Equation 6. Here, sgn means a sign function, and sgn(B) is a function that is 1 when B>0, 0 when B=0, and -1 when B<0. dGx / dt is the time differential value of the acceleration Gx, that is, the amount of change in the acceleration Gx per unit time, and may be the amount of change in the acceleration Gx between adjacent sampling points.

[0098]

number

[0099]

number

[0100] In addition, in the waveform of FIG. 14B, the positive and negative signs are reversed from the waveform of the sensor angle α in the case of the actual right wheels 5b and 5d, but there is no effect on the cumulative angle θ and the cumulative number of revolutions. Conversely, since the waveform of the sensor angle α of the right wheels 5b and 5d and the waveform of the sensor angle α of the left wheels 5a and 5c can be aligned, it is possible to calculate the cumulative angle θ and the cumulative number of revolutions using the same calculation formula, for example, Formula 2, and the calculation process can be simplified. Also, here, when the pre-correction angle gradually increases with time change, a negative sign is added to the pre-correction angle to obtain the post-correction angle, but when the pre-correction angle gradually decreases with time change, a negative sign may be added to the pre-correction angle to obtain the post-correction angle. In other words, only when the pre-correction angle gradually increases or decreases with time change, a correction is performed to add a negative sign to the pre-correction angle to obtain the post-correction angle, which can be used as the actual sensor angle α.

[0101] However, when obtaining the sensor angle α corresponding to the acceleration detected by the G sensor 22, it is necessary to determine whether or not to add a minus sign to the absolute value of the sensor angle α. This determination is performed as follows. Note that, although the description here assumes that the wheel position is detected using the acceleration Gx, the same applies when the acceleration Gz is used.

[0102] As shown in FIG. 15, the acceleration Gx that is the acceleration along the X-axis has a sine waveform. Therefore, based on the relationship between the acceleration Gx(t) at the sampling point Sp1 and the accelerations Gx(t-1) and Gx(t+1) at the sampling points Sp0 and Sp2 in the sampling periods before and after it, it is possible to determine whether to attach a minus sign.

[0103] State 1 indicates the relationship Gx(t-1) < Gx(t) < Gx(t+1), that is, the state where the acceleration Gx gradually increases. In this state, at the sampling point Sp1, the angle before correction is in the process of gradually decreasing with time change. Therefore, since it is not necessary to perform correction with a minus sign for the angle before correction, the angle before correction is directly treated as the angle after correction. Here, the correction coefficient is set to 1, and the sensor angle α × 1 is used as the angle after correction.

[0104] State 2 indicates the relationship Gx(t-1) < Gx(t), Gx(t+1), that is, the state where the acceleration Gx reaches the peak between the sampling point Sp1 and the sampling point Sp2. Also in this state, at the sampling point Sp1, the angle before correction is still in the process of gradually decreasing with time change. Therefore, since it is not necessary to perform correction with a minus sign for the angle before correction, similar to State 1, the angle before correction is directly treated as the angle after correction.

[0105] State 3 indicates the relationship Gx(t-1) ≤ Gx(t+1) < Gx(t), that is, the state where the acceleration Gx reaches the peak around the sampling point Sp1. In this state, at the sampling point Sp1, the angle before correction is in the situation just before switching from decreasing to increasing with time change, but it is still not necessary to attach a minus sign to the angle before correction. Therefore, similar to State 1, the angle before correction is directly treated as the angle after correction.

[0106] State 4 indicates the state where the relationship Gx(t + 1) < Gx(t - 1) ≤ Gx(t + 1) holds, that is, the state where the acceleration Gx reaches its peak between sampling point Sp0 and sampling point Sp1. In this state, at sampling point Sp1, since the angle before correction switches from decreasing to increasing with time change, it is necessary to perform a correction by attaching a minus sign to the angle before correction. Therefore, the angle after correction is calculated by attaching a minus sign to the angle before correction. Here, the correction coefficient is set to -1, and the sensor angle α × (-1) is taken as the angle after correction.

[0107] State 5 indicates the state where the relationship Gx(t + 1) < Gx(t) < Gx(t - 1) holds, that is, the state where the acceleration Gx gradually decreases. In this state, at sampling point Sp1, since the angle before correction is gradually increasing with time change, it is necessary to perform a correction by attaching a minus sign to the angle before correction. Therefore, similar to State 4, the angle after correction is calculated by attaching a minus sign to the angle before correction.

[0108] To sum up, whether to attach a minus sign to the sensor angle α at sampling point Sp1 is determined by the magnitude relationship between sampling points Sp0 and Sp2 in the sampling periods before and after that. In States 1 and 2 in Fig. 15, since Gx(t - 1) < Gx(t + 1), a minus sign is not required; in States 4 and 5, since Gx(t - 1) > Gx(t + 1), a minus sign is required. In State 3, Gx(t - 1) and Gx(t + 1) are the same or have almost no difference, but if Gx(t - 1) < Gx(t + 1), a minus sign is not required, and if Gx(t - 1) > Gx(t + 1), a minus sign is required.

[0109] In this way, based on the one-axis acceleration detected by the G sensor 22, the actual sensor angle α can be calculated. And once the actual sensor angle α is obtained, wheel position detection can be performed in the same manner as in the first embodiment based on this.

[0110] FIG. 16 is a flowchart showing details of the wheel position detection process of the present embodiment. This wheel position detection process is executed by the control unit 33 at a predetermined cycle when the user presses a start switch for wheel position detection (not shown) during tire replacement or the like.

[0111] First, in steps S200 to S220 of FIG. 16, the same processing as steps S100 to S120 of FIG. 12 in the first embodiment is performed. Then, proceeding to step S225, the control unit 33 transmits an instruction signal to each tire-side communication device 2a to 2d to acquire the start cycle number Ns and acquire the start acceleration Gxs for three sampling cycles. Regarding the start acceleration Gxs for three sampling cycles, with the signal transmission timing as the measurement start timing Ts, the start acceleration Gxs(t) at the measurement start timing Ts and the start accelerations Gxs(t-1) to Gxs(t+1) for three cycles including before and after it are used. In response to this, from the control units 23 of each tire-side communication device 2a to 2d, for example, the start cycle number Ns and the start acceleration Gxs calculated by the method (b) described above are converted into data and returned to the vehicle-side communication device 3, and are received by the vehicle-side communication device 3.

[0112] Subsequently, proceeding to step S230, the start accelerations Gxs(t-1) and Gxs(t+1) at the sampling cycles before and after the measurement start timing Ts are compared to determine whether the relationship Gxs(t-1) < Gxs(t+1) is satisfied.

[0113] Here, if an affirmative determination is made, proceeding to step S235, since it is not necessary to attach a minus sign to the angle before correction, the sensor angle αs at the measurement start timing Ts is calculated based on Equation 8.

[0114]

Equation

[0115]

Number

[0116] Note that the processes of steps S230 to S240 are performed for each received data, that is, for each of the tire-side communication devices 2a to 2d.

[0117] After that, in steps S245 and S250, the same processes as steps S135 and S140 in FIG. 12 in the first embodiment are performed. Then, if an affirmative determination is made in step S250, the process proceeds to step S255, and if a negative determination is made, the process proceeds to step S285.

[0118] In step S255, the control unit 33 transmits an instruction signal to each of the tire-side communication devices 2a to 2d to instruct the acquisition of the number of end cycles Ne and the acquisition of the end acceleration Gxe for three sampling cycles. For the end acceleration Gxe for three sampling cycles, the signal transmission timing is defined as the measurement end timing Te, and it means the end acceleration Gxe(t) at the measurement end timing Te and the end accelerations Gxe(t - 1) to Gxe(t + 1) for three cycles including the ones before and after it. In response to this, from the control units 23 of each of the tire-side communication devices 2a to 2d, for example, the number of end cycles Ne and the end acceleration Gxe calculated by the method (b) described above are converted into data and returned to the vehicle-side communication device 3 and received by the vehicle-side communication device 3.

[0119] Then, the process proceeds to step S260, where the end accelerations Gxe(t - 1) and Gxe(t + 1) at the sampling cycles before and after the measurement end timing Te are compared to determine whether the relationship Gxe(t - 1) < Gxe(t + 1) is satisfied.

[0120] Here, if an affirmative determination is made, the process proceeds to step S265. Since there is no need to attach a minus sign to the angle before correction, the sensor angle αe at the measurement end timing Te is calculated based on Equation 10.

[0121]

Number

[0122]

number

[0123] The processes in steps S255 to S270 are also performed for each received data, that is, for each tire-side communication device 2a to 2d.

[0124] Then, the process proceeds to step S275 to calculate the accumulated angle θ. At this time, since the corrected angle α is a value that gradually decreases with time regardless of whether it is the left wheels 5a, 5c or the right wheels 5b, 5d, as shown in Fig. 14B, the accumulated angle θ can be calculated from Equation 2 for both the left wheels 5a, 5c and the right wheels 5b, 5d.

[0125] 12 in the first embodiment, wheel position detection is performed based on the accumulated angle θ of the four wheels and steering angle information, i.e., the turning direction of the vehicle 1 indicated by the detection signal of the steering angle sensor 7. Then, when it is determined which of the four wheels 5a-5d each of the four tire-side communication devices 2a-2d is attached to, the ID information stored in the frame of each tire-side communication device 2a-2d is linked to the wheel position and registered. Finally, the process proceeds to step S285, where the vehicle-side communication device 3 transmits an instruction to each tire-side communication device 2a-2d to end measurement, and the wheel position detection process is terminated.

[0126] Although the accumulated angle θ is used to detect the wheel position here, the wheel position can also be detected in the same manner using the accumulated number of rotations, which is a value proportional to the accumulated angle θ.

[0127] Thereafter, similarly to the first embodiment, tire air pressure detection is performed while identifying which of the wheels 5a to 5d each of the tire-side communication devices 2a to 2d is attached to based on the result of wheel position detection.

[0128] As described above, when the vehicle 1 is in a turning state, the wheel position can be detected by calculating the cumulative angle θ and the cumulative number of rotations based on the one-axis acceleration detected by the G sensor 22. This provides the same effects as the first embodiment.

[0129] In addition, when wheel position detection is performed based on one-axis acceleration as in this embodiment, there is no need to perform left / right judgment, and when acceleration Gx is used, there is no need to perform high-pass filter processing as in the case of using acceleration Gz, which allows for simplification of the system. However, when wheel position detection is performed using two-axis acceleration Gx and acceleration Gz as in the first embodiment, a larger amount of acceleration data is used, so the sensor angle α can be calculated with higher accuracy, and more accurate wheel position detection is possible.

[0130] (Other embodiments) Although the present disclosure has been described based on the above-described embodiment, it is not limited to the embodiment, and includes various modifications and modifications within the equivalent range. In addition, various combinations and forms, and other combinations and forms including only one element, more than one element, or less than one element, are also within the scope and concept of the present disclosure.

[0131] (i) For example, in each of the above embodiments, the wheel position is detected using the accumulated angle θ. However, the wheel position may be detected using the accumulated number of rotations.

[0132] (ii) In the above embodiments, an example of inputting an instruction to start wheel position detection is when a user presses a wheel position detection start switch (not shown) when changing tires, but the start instruction may be input in another form. For example, wheel position detection may be performed when an automobile repair shop inputs an instruction to start wheel position detection using a tool. Furthermore, wheel position detection may be performed when a start switch such as an ignition switch is pressed if the vehicle 1 has not been started for a predetermined time or more.

[0133] (iii) In each of the above embodiments, an example has been given in which clock synchronization between each tire-side communication device 2a-2d and the vehicle-side communication device 3 is not performed immediately before sampling of acceleration measurement, but clock synchronization may also be performed.

[0134] (iv) In each of the above embodiments, each of the tire-side communication devices 2a to 2d acquires the rotation period number N and the acceleration Gx, transmits the data to the vehicle-side communication device 3, and the sensor angle α is calculated by the vehicle-side communication device 3. However, each of the tire-side communication devices 2a to 2d may also calculate the sensor angle α and transmit the data on the rotation period number N and the sensor angle α to the vehicle-side communication device 3.

[0135] (v) In the above embodiments, when calculating the sensor angle αs at the measurement start timing Ts and the sensor angle αe at the measurement end timing Te, the acceleration Gx at the sampling points Sp before and after the timing, Gx(t-1), Gx(t), and G(t+1), are used. This is also merely an example, and the acceleration Gx at the three sampling points Sp, the second previous and the one before the timing, may be used. In addition, the acceleration Gx at the three sampling points Sp, the one after and the two after the timing, may be used. In addition, the sensor angle α may be calculated using the acceleration Gx at two or four or more sampling points Sp1, not limited to three sampling points Sp.

[0136] (vi) In the above embodiments, the wheel position detection device provided for the vehicle 1 having four wheels 5a to 5d has been described, but the present disclosure can be similarly applied to a vehicle having a larger number of wheels. In that case, too, the accumulated angle θ and the accumulated number of rotations are the largest for the front wheel, which is the outer wheel of the turn, and the smallest for the rear wheel, which is the inner wheel of the turn. In this way, the order of the magnitude of the accumulated angle θ and the accumulated number of rotations is determined according to the wheel position, so that the wheel position detection can be performed based on that order.

[0137] (vii) In each of the above embodiments, one of the conditions for starting acceleration measurement is when a steering angle of a certain level or more has occurred. However, if the steering angle is expressed as a positive value for a left turn and a negative value for a right turn, the start condition may simply be when the absolute value of the steering angle is greater than or equal to a certain level.

[0138] (viii) The control unit and the method described in the present disclosure may be realized by a dedicated computer provided by configuring a processor and a memory programmed to execute one or more functions embodied in a computer program. Alternatively, the control unit and the method described in the present disclosure may be realized by a dedicated computer provided by configuring a processor with one or more dedicated hardware logic circuits. Alternatively, the control unit and the method described in the present disclosure may be realized by one or more dedicated computers configured by a combination of a processor and a memory programmed to execute one or more functions and a processor configured with one or more hardware logic circuits. In addition, the computer program may be stored in a computer-readable non-transitory tangible recording medium as instructions executed by a computer. [Explanation of symbols]

[0139] 1...vehicle, 2a to 2d...tire side communication device, 3...vehicle side communication device, 4...display 5a to 5d...wheel, 6...vehicle body, 7...steering angle sensor, 8...gear position sensor, 9...vehicle-mounted ECU 21: sensing unit, 22: G sensor, 23: control unit, 24: communication unit, 25: antenna 31...antenna, 32...communication unit, 33...control unit

Claims

1. A wheel position detection device applied to a vehicle (1), comprising: tire-side communication devices (2a to 2d) attached to a plurality of wheels (5a to 5d) each having a tire; and a vehicle-side communication device (3) provided on a vehicle body (6), Each tire-side communication device attached to each of the plurality of wheels includes: an acceleration sensor (22) for detecting a circumferential acceleration (Gx) and a radial acceleration (Gz) of the wheel to which each tire-side communication device is attached; a first control unit (23) that stores the detection results of the acceleration sensors and creates a frame that stores individual identification information assigned to each tire-side communication device; a first communication unit (24) that performs two-way communication with the vehicle-side communication device, including the transmission of the frame; The vehicle-side communication device includes: a second communication unit (32) that receives the frame and transmits an instruction signal to each of the tire-side communication devices; a second control unit (33) that determines which of the plurality of wheels the tire-side communication device that has transmitted the frame is attached to, and that associates and registers the relationship between the identification information and the plurality of wheels, the second control unit transmits a measurement start timing (Ts) and a measurement end timing (Te) to each of the tire-side communication devices so as to cause the tire-side communication devices to measure acceleration when the vehicle is in a turning state; the second control unit or the first control unit provided in each of the tire-side communication devices calculates the sensor angle based on the circumferential acceleration and the radial acceleration, taking an angle at which the tire-side communication device is located with respect to a wheel center (WO) of the wheel to which the tire-side communication device is attached as a sensor angle (α), and calculates, based on the sensor angle, a cumulative angle (θ) obtained by accumulating changes in the sensor angle between the measurement start timing (Ts) and the measurement end timing (Te) or a cumulative number of rotations that the tire-side communication device has rotated with respect to the wheel center, The second control unit identifies which of the plurality of wheels each of the tire-side communication devices is attached to, based on the accumulated angle in each of the tire-side communication devices or the magnitude of the accumulated angle.

2. 2. The wheel position detection device according to claim 1, wherein the second control unit or the first control unit provided in each of the tire-side communication devices performs a left / right determination to identify whether the wheel to which the tire-side communication device is attached is a left wheel (5 a, 5 c) or a right wheel (5 b, 5 d) based on the turning direction of the vehicle as well as the phase of the circumferential acceleration and the radial acceleration, calculates the sensor angle based on the result of the left / right determination and the circumferential acceleration and the radial acceleration, calculates a number of rotation periods (N) of the wheel to which the tire-side communication device is attached during the period from the measurement start timing to the measurement end timing, and calculates the accumulated angle or the accumulated number of rotations based on the sensor angle and the number of rotation periods.

3. 3. The wheel position detection device according to claim 1, wherein the second control unit transmits an instruction signal to start the acceleration measurement when it determines that the vehicle is turning, and notifies the measurement start timing when a predetermined time (Ta) at which each of the tire-side communication devices is expected to start the acceleration measurement in response to the instruction signal has elapsed, and further notifies the measurement end timing when it determines that the vehicle has finished turning.

4. A wheel position detection device applied to a vehicle (1), comprising: tire-side communication devices (2a to 2d) attached to a plurality of wheels (5a to 5d) each having a tire; and a vehicle-side communication device (3) provided on a vehicle body (6), Each tire-side communication device attached to each of the plurality of wheels includes: an acceleration sensor (22) for detecting one of a circumferential acceleration (Gx) and a radial acceleration (Gz) of the wheel to which each tire-side communication device is attached; a first control unit (23) that stores the detection results of the acceleration sensors and creates a frame that stores individual identification information assigned to each tire-side communication device; a first communication unit (24) that performs two-way communication with the vehicle-side communication device, including the transmission of the frame; The vehicle-side communication device includes: a second communication unit (32) that receives the frame and transmits an instruction signal to each of the tire-side communication devices; a second control unit (33) that determines which of the plurality of wheels the tire-side communication device that has transmitted the frame is attached to, and that associates and registers the relationship between the identification information and the plurality of wheels, the second control unit transmits a measurement start timing (Ts) and a measurement end timing (Te) to each of the tire-side communication devices so as to cause the tire-side communication devices to measure acceleration when the vehicle is in a turning state; the second control unit or the first control unit provided in each of the tire-side communication devices calculates the sensor angle based on only one of the circumferential acceleration and the radial acceleration, taking an angle at which the tire-side communication device is located with respect to a wheel center (WO) of the wheel to which the tire-side communication device is attached as a sensor angle (α), and calculates, based on the sensor angle, a cumulative angle (θ) obtained by accumulating changes in the sensor angle from the measurement start timing (Ts) to the measurement end timing (Te) or a cumulative number of rotations that the tire-side communication device has rotated with respect to the wheel center, The second control unit identifies which of the plurality of wheels each of the tire-side communication devices is attached to based on the accumulated angle in each of the tire-side communication devices or the magnitude of the accumulated angle.

5. The second control unit or the first control unit provided in each of the tire-side communication devices, 5. The wheel position detection device according to claim 4, further comprising: a pre-correction angle indicated by an absolute value of the sensor angle is obtained from one of the circumferential acceleration and the radial acceleration; a correction is performed by adding a negative sign to the pre-correction angle only in one of the cases where the pre-correction angle gradually increases with time or where the pre-correction angle gradually increases with time to obtain a post-correction angle; the post-correction angle is used as the actual sensor angle; and a number of rotation periods (N) of a wheel to which the tire-side communication device is attached is calculated during a period from the measurement start timing to the measurement end timing, and the accumulated angle or the accumulated rotation number is calculated based on the sensor angle and the number of rotation periods.

6. 6. The wheel position detection device according to claim 4, wherein the second control unit transmits an instruction signal to start the acceleration measurement when it determines that the vehicle is turning, and notifies the measurement start timing when a predetermined time (Ta) at which each of the tire-side communication devices is expected to start the acceleration measurement in response to the instruction signal has elapsed, and further notifies the measurement end timing when it determines that the vehicle has finished turning.

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