Transmitter, receiver, transmission / reception system, and wheel position determination method

Abstract

A receiver (40) receives transmission data that are transmitted from transmitters (21) which are respectively mounted to two wheels (11, 12) provided to a two-wheeled vehicle (10). The transmitters (21) each comprise an acceleration sensor (24) that is configured to detect acceleration in the Z-axis direction, which is the centrifugal direction of the wheels (11, 12). The receiver (40) comprises a reception control unit (41). The reception control unit (41) determines a stop of the two-wheeled vehicle (10), acquires the acceleration, which has been detected by the acceleration sensor (24), from the transmission data received by the receiver (40) after the stop of the two-wheeled vehicle (10), and uses the acceleration to determine whether the transmitters (21) are respectively mounted to the wheels (11, 12).

Description

Transmitter, receiver, transmitting / receiving system, and wheel position determining method

[0001] The present disclosure relates to a transmitter, a receiver, a transmitting and receiving system, and a wheel position determining method.

[0002] The transmission / reception system described in Patent Document 1 is mounted on a vehicle. The vehicle includes a plurality of wheels and a detection unit that detects the rotation angle of each wheel. The transmission / reception system includes a transmitter and a receiver. One transmitter is provided for each wheel. The transmitter transmits transmission data at a predetermined specific angle. When the receiver receives the transmission data, it determines the rotation angle of each wheel from the detection result of the detection unit. The receiver determines which wheel each transmitter is attached to based on the variation in the rotation angle of each wheel at the time of receiving the transmission data.

[0003] Japanese Patent Application Laid-Open No. 2014-227124

[0004] The transmitting and receiving system may be installed on a two-wheeled vehicle, and in this case, it may be necessary to determine which wheel each transmitter is attached to.

[0005] According to a first aspect of the present disclosure, there is provided a receiver configured to receive transmission data transmitted from transmitters attached to each of two wheels of a motorcycle. Each of the transmitters includes an acceleration sensor configured to detect acceleration in a Z-axis direction, which is the centrifugal direction of the wheel. The receiver includes a reception control unit. The reception control unit is configured to determine whether the motorcycle is stopped, obtain acceleration detected by the acceleration sensor from the transmission data received by the receiver after the motorcycle has stopped, and determine which of the wheels each of the transmitters is attached to based on the acceleration.

[0006] When parking a motorcycle, the front wheels are steered. Because the front wheels of a motorcycle are supported with a caster angle, steering generates a difference between the acceleration detected by the acceleration sensor in the transmitter for the front wheel and the acceleration detected by the acceleration sensor in the transmitter for the rear wheel. By utilizing this difference, the reception control unit can determine which wheel each transmitter is attached to.

[0007] In the receiver, the acceleration sensor is configured to detect acceleration in a Y-axis direction, which is an axial direction of the wheel. The reception control unit is configured to obtain the acceleration in the Y-axis direction from the transmission data received by the receiver after the two-wheeled vehicle has stopped, and to determine that the transmitter equipped with the acceleration sensor having the larger absolute value of the acceleration in the Y-axis direction is attached to the front wheel.

[0008] In the above receiver, the motorcycle has a detection unit configured to detect the rotation angle of the wheel, and the reception control unit is configured to obtain the acceleration in the Z-axis direction from the transmission data received by the receiver after the motorcycle has stopped, obtain the rotation angle from the detection unit after the motorcycle has stopped, and determine which wheel the transmitter is attached to by comparing the acceleration in the Z-axis direction obtained from the transmission data with a map that associates the rotation angle with the acceleration in the Z-axis direction.

[0009] In the receiver, the acceleration sensor is configured to detect acceleration in a Y-axis direction, which is an axial direction of the wheel. The reception control unit is configured to obtain the acceleration in the Y-axis direction from the transmission data received by the receiver after the two-wheeled vehicle has stopped, and to determine that a transmitter equipped with the acceleration sensor whose absolute value of the acceleration in the Y-axis direction is equal to or greater than a front wheel determination threshold is attached to the front wheel.

[0010] According to a second aspect of the present disclosure, there is provided a receiver configured to receive transmission data transmitted from transmitters attached to each of two wheels of a motorcycle. The motorcycle is equipped with a center stand. Each of the transmitters is equipped with an acceleration sensor configured to detect acceleration in a Z-axis direction, which is the centrifugal direction of the wheel. The receiver is equipped with a reception control unit. The reception control unit is configured to determine whether the motorcycle is stopped, obtain the acceleration in the Z-axis direction from the transmission data received by the receiver after the motorcycle has stopped, and determine that the transmitter equipped with the acceleration sensor whose acceleration in the Z-axis direction changes after the motorcycle has stopped is attached to the rear wheel.

[0011] If a motorcycle is equipped with a center stand, the rear wheel goes from a grounded state to a non-grounded state when the motorcycle is parked. As the rear wheel spins, the acceleration in the Z-axis direction fluctuates. Because the front wheel does not rotate, only the acceleration in the Z-axis direction detected by the acceleration sensor equipped in the transmitter on the rear wheel fluctuates. The reception control unit can determine that a transmitter equipped with an acceleration sensor that changes the acceleration in the Z-axis direction after the motorcycle has stopped is attached to the rear wheel. Therefore, the reception control unit can determine which wheel each transmitter is attached to.

[0012] According to a third aspect of the present disclosure, there is provided a transmitter mounted on each of two wheels of a motorcycle. The transmitter includes an acceleration sensor configured to detect acceleration in a Y-axis direction, which is the axial direction of the wheel, and acceleration in a Z-axis direction, which is the centrifugal direction of the wheel, and a transmission control unit. When the acceleration in the Z-axis direction is less than a threshold, the transmission control unit detects acceleration in the Y-axis direction and transmits transmission data including the acceleration in the Y-axis direction to a receiver, thereby causing the receiver to determine to which wheel each of the transmitters is mounted, using the acceleration in the Y-axis direction.

[0013] The transmission control unit transmits transmission data including acceleration in the Y-axis direction to the receiver, allowing the receiver to determine to which wheel each transmitter is attached. According to a fourth aspect of the present disclosure, there is provided a transmitter to be attached to each of two wheels of a motorcycle. The transmitter includes an acceleration sensor configured to detect acceleration in the Y-axis direction, which is the axial direction of the wheel, and acceleration in the Z-axis direction, which is the centrifugal direction of the wheel, and a transmission control unit. The transmission control unit is configured to determine whether the motorcycle is stopped based on the acceleration in the Z-axis direction, obtain the acceleration in the Y-axis direction from the acceleration sensor after the motorcycle has stopped, determine whether the absolute value of the acceleration in the Y-axis direction is equal to or greater than a front wheel determination threshold, and transmit the determination result to the receiver.

[0014] When parking a motorcycle, the front wheels are steered. As a result, the acceleration in the Y-axis direction detected by the acceleration sensor provided in the transmitter on the front wheel is greater than the acceleration in the Y-axis direction detected by the acceleration sensor provided in the transmitter on the rear wheel. Therefore, by determining whether the absolute value of the acceleration in the Y-axis direction is equal to or greater than the front wheel determination threshold, it is possible to determine whether the transmitter is attached to the front wheel or the rear wheel. By transmitting this determination result to the receiver, the receiver can determine which wheel each transmitter is attached to.

[0015] According to a fifth aspect of the present disclosure, there is provided a transmission / reception system including a transmitter mounted on each of two wheels of a motorcycle and a receiver configured to receive transmission data transmitted from the transmitter. Each of the transmitters includes an acceleration sensor configured to detect acceleration in a Z-axis direction, which is the centrifugal direction of the wheel. The receiver includes a reception control unit. The reception control unit is configured to determine whether the motorcycle is stopped, obtain the acceleration detected by the acceleration sensor from the transmission data received by the receiver after the motorcycle has stopped, and determine which of the wheels each of the transmitters is mounted on based on the acceleration.

[0016] There is a difference between the acceleration detected by the acceleration sensor attached to the front wheel transmitter and the acceleration detected by the acceleration sensor attached to the rear wheel transmitter. By utilizing this difference, the reception control unit can determine which wheel each transmitter is attached to.

[0017] According to a sixth aspect of the present disclosure, there is provided a wheel position determination method for determining, by a receiver, to which of two wheels a transmitter attached to each of two wheels of a motorcycle is attached. The wheel position determination method includes the steps of: each of the transmitters transmitting transmission data including acceleration; the receiver receiving the transmission data; determining, by the receiver, whether the motorcycle is stopped; the receiver obtaining, by the receiver, the acceleration from the transmission data received by the receiver after the motorcycle has stopped; and determining, by the receiver, which of the wheels each of the transmitters is attached to, based on the acceleration.

[0018] A difference occurs between the acceleration detected by the acceleration sensor attached to the transmitter on the front wheel and the acceleration detected by the acceleration sensor attached to the transmitter on the rear wheel. By utilizing this difference, the receiver can determine which wheel each transmitter is attached to.

[0019] FIG. 1 is a perspective view of a motorcycle. FIG. 2 is a side view of the motorcycle. FIG. 3 is a perspective view of a transmitter. FIG. 4 is a schematic diagram of a transmitting and receiving system. FIG. 5 is a flowchart of transmission control. FIG. 6 is a flowchart of wheel position determination control. FIG. 7 is a diagram showing the front and rear wheels when locked by the handlebar lock mechanism. FIG. 8 is a diagram showing the relationship between wheel angle and acceleration detected by an acceleration sensor. FIG. 9 is a flowchart of transmitter-side wheel position determination control. FIG. 10 is a diagram showing the relationship between wheel angle and acceleration detected by an acceleration sensor.

[0020] First Embodiment A first embodiment of a transmitter, a receiver, a transmission / reception system, and a wheel position determination method will be described.

[0021] 1 and 2 , a motorcycle 10 includes two wheels 11, 12, a stand 15, and a handlebar lock mechanism 16. Each wheel 11, 12 includes a wheel 13 and a tire 14 mounted on the wheel 13. The two wheels 11, 12 include a front wheel 11 and a rear wheel 12. The stand 15 supports the motorcycle 10 when the motorcycle 10 is stopped. The stand 15 is a side stand. The handlebar lock mechanism 16 prohibits rotation of the handlebar, for example, by locking the handlebar with a lock pin.

[0022] The two-wheeled vehicle 10 includes detection units 17, 18 that detect the rotation angles of the wheels 11, 12, and a vehicle control device 19 that acquires the detection results of the detection units 17, 18. The detection units 17, 18 are provided one for each wheel 11, 12. The detection unit 17 that corresponds to the front wheel 11 is the first detection unit 17. The detection unit 18 that corresponds to the rear wheel 12 is the second detection unit 18. The detection units 17, 18 generate pulses due to the rotation of a rotor that rotates integrally with the wheels 11, 12. The rotor is, for example, a gear with teeth arranged at equal angular intervals. With each rotation of the rotor, a certain number of pulses are generated in the detection units 17, 18. If the rotor is a gear, one rotation of the rotor generates pulses in the detection units 17, 18 equal to the number of teeth.

[0023] The vehicle control device 19 is configured, for example, by a microcomputer. The vehicle control device 19 acquires pulses from each of the detection units 17 and 18. The vehicle control device 19 counts the rising and falling edges of the pulses generated by the detection units 17 and 18. The vehicle control device 19 calculates the remainder obtained by dividing the counted number of pulses by the number of pulses counted for one rotation of the rotor, as a pulse count value. Because the number of pulses generated by the detection units 17 and 18 per one rotation of the rotor is fixed, the rotation angles of the wheels 11 and 12 can be calculated from the pulse count value. The rotation angles of the wheels 11 and 12 are absolute angles. The absolute angle is the angle from a reference position of the rotor. The reference position of the rotor can be recognized, for example, by forming a special shape on some of the gear teeth. The rotation angles of the wheels 11 and 12 are referred to as wheel angles as appropriate. The detection units 17 and 18 are, for example, wheel speed sensors used in an anti-lock braking system provided in the motorcycle 10.

[0024] <Transmitting / receiving system> The motorcycle 10 includes a transmitting / receiving system 20. The transmitting / receiving system 20 includes a transmitter 21 mounted on each of the wheels 11, 12, and a receiver 40. The transmitter 21 is attached to the wheels 11, 12 so as to be disposed in the interior space of the tire 14. The transmitter 21 may be fixed to a tire valve, or may be fixed to the wheel 13 or the tire 14. As shown in FIG. 3 , in this embodiment, the transmitter 21 is fixed to the tire valve. The transmitter 21 detects the condition of the corresponding tire 14 and wirelessly transmits transmission data including detected information about the tire 14 to the receiver 40. The transmitting / receiving system 20 monitors the condition of the tire 14 by receiving the transmission data transmitted from the transmitter 21 with the receiver 40. The transmitting / receiving system 20 is a tire condition monitoring system.

[0025] 4, each transmitter 21 includes a pressure sensor 22, a temperature sensor 23, an acceleration sensor 24, a transmission control unit 28, a transmission circuit 31, a transmission antenna 32, and a battery 33. The transmitter 21 operates using power supplied from the battery 33. The transmission control unit 28 comprehensively controls the operation of the transmitter 21. The battery 33, which serves as the power source for the transmitter 21, may be a primary battery, or may be a power storage device such as a secondary battery or a capacitor.

[0026] The pressure sensor 22 detects the air pressure of the corresponding tire 14. The temperature sensor 23 detects the temperature inside the corresponding tire 14. As shown in FIG. 3 , the acceleration sensor 24 is a three-axis acceleration sensor. The acceleration sensor 24 has an X-axis 25, a Y-axis 26, and a Z-axis 27. The X-axis 25, the Y-axis 26, and the Z-axis 27 are perpendicular to one another. The Y-axis 26 extends in the axial direction of the wheels 11, 12. The axial direction of the wheels 11, 12 is the direction in which the central axes of the wheels 11, 12 extend. The Z-axis 27 extends in the centrifugal direction of the wheels 11, 12. The centrifugal direction of the wheels 11, 12 is the direction toward the radial outside of the wheels 11, 12. The X-axis 25 extends in a direction perpendicular to the Y-axis 26 and the Z-axis 27.

[0027] The acceleration sensor 24 individually detects acceleration acting in three directions: the X-axis direction, which is the direction in which the X-axis 25 extends; the Y-axis direction, which is the direction in which the Y-axis 26 extends; and the Z-axis direction, which is the direction in which the Z-axis 27 extends. Acceleration in the Y-axis direction will be referred to as Y-axis acceleration, and acceleration in the Z-axis direction will be referred to as Z-axis acceleration. The Y-axis acceleration is acceleration in the axial direction of the wheels 11, 12. The Z-axis acceleration is centrifugal acceleration of the wheels 11, 12.

[0028] The transmission control unit 28 includes a processor 29 and a storage unit 30. The processor 29 may be, for example, a central processing unit (CPU), a graphics processing unit (GPU), or a digital signal processor (DSP). The storage unit 30 includes a random access memory (RAM) and a read-only memory (ROM). The storage unit 30 stores program code or instructions configured to cause the processor to execute processing. The storage unit 30, i.e., a computer-readable medium, includes any available medium accessible by a general-purpose or dedicated computer. The transmission control unit 28 may be configured with a hardware circuit such as an application-specific integrated circuit (ASIC) or a field-programmable gate array (FPGA). The transmission control unit 28, which is a processing circuit, may include one or more processors operating according to a computer program, one or more hardware circuits such as ASICs or FPGAs, or a combination thereof. The storage unit 30 stores an ID code, which is data indicating unique identification information of each transmitter 21.

[0029] The transmission control unit 28 generates transmission data and outputs the generated transmission data to the transmission circuit 31. The transmission data includes pressure data, temperature data, and an ID code. The pressure data indicates the pressure detected by the pressure sensor 22. The temperature data indicates the temperature detected by the temperature sensor 23. The transmission circuit 31 modulates the transmission data. The modulated transmission data is transmitted from the transmission antenna 32 as a wireless signal. The wireless signal can be said to be a signal including the transmission data. The wireless signal is a signal in a predetermined frequency band. The frequency band is, for example, the LF band, the MF band, the HF band, the VHF band, the UHF band, and the 2.4 GHz band.

[0030] The transmission control performed by the transmission control unit 28 will now be described. As shown in FIG. 5 , in step S1, the transmission control unit 28 determines whether the Z-axis acceleration is less than a threshold value. The threshold value is set to determine whether the motorcycle 10 is moving. As the speed of the motorcycle 10 increases, the centrifugal acceleration acting on the acceleration sensor 24 increases. Therefore, it is possible to determine whether the motorcycle 10 is moving from the Z-axis acceleration. The threshold value is set to a value greater than the Z-axis acceleration when the motorcycle 10 is stationary, taking into account tolerances and the like. If the Z-axis acceleration is less than the threshold value, the motorcycle 10 is stationary. If the Z-axis acceleration is equal to or greater than the threshold value, the motorcycle 10 is moving. If the determination result in step S1 is positive, the transmission control unit 28 proceeds to step S2. If the determination result in step S1 is negative, the transmission control unit 28 proceeds to step S4.

[0031] In step S2, the transmission control unit 28 determines whether the stop time during which the motorcycle 10 is stopped has exceeded a predetermined time. The predetermined time can be set to any time. For example, the predetermined time is set to a time longer than the time the motorcycle is temporarily stopped due to a traffic light. If the determination result of step S1 is positive, the transmission control unit 28 starts counting the stop time. The transmission control unit 28 continues counting the stop time while the determination result of step S1 remains positive. If the determination result of step S1 is negative, the transmission control unit 28 resets the stop time. If the determination result of step S2 is positive, the transmission control unit 28 ends transmission control. If the determination result of step S2 is negative, the transmission control unit 28 proceeds to step S3.

[0032] In step S3, the transmission control unit 28 detects the Y-axis acceleration. That is, the transmission control unit 28 detects the Y-axis acceleration when the two-wheeled vehicle 10 is stopped. In this embodiment, the transmission control unit 28 detects the Y-axis acceleration when the two-wheeled vehicle 10 is stopped and the time the two-wheeled vehicle 10 has been stopped is less than a predetermined time.

[0033] In step S4, the transmission control unit 28 transmits transmission data. If the Y-axis acceleration was detected in step S3, the transmission control unit 28 transmits transmission data including the Y-axis acceleration. If the determination result in step S1 is negative, the transmission control unit 28 transmits transmission data not including the Y-axis acceleration. Therefore, while the two-wheeled vehicle 10 is traveling, the transmission control unit 28 transmits transmission data not including the Y-axis acceleration. After the two-wheeled vehicle 10 comes to a stop, the transmission control unit 28 transmits transmission data including the Y-axis acceleration until a predetermined time has elapsed.

[0034] 4, the receiver 40 includes a reception control unit 41, a receiving circuit 44, and a receiving antenna 45. The receiver 40 may be mounted on the motorcycle 10, or may be a portable terminal carried by a rider of the motorcycle 10.

[0035] The reception control unit 41 includes a processor 42 and a storage unit 43. The processor 42 is, for example, a CPU, a GPU, or a DSP. The storage unit 43 includes RAM and ROM. The storage unit 43 stores program code or instructions configured to cause the processor 42 to execute processing. The storage unit 43, i.e., the computer-readable medium, includes any available medium accessible by a general-purpose or special-purpose computer. The reception control unit 41 may be configured with a hardware circuit such as an ASIC or FPGA. The reception control unit 41, which is a processing circuit, may include one or more processors operating according to a computer program, one or more hardware circuits such as an ASIC or FPGA, or a combination thereof.

[0036] The reception control unit 41 is configured to be able to acquire the wheel angle from the vehicle control device 19. The reception circuit 44 demodulates the radio signals received from each transmitter 21 via the reception antenna 45, and outputs the transmission data from the transmitter 21 to the reception control unit 41. This allows the reception control unit 41 to acquire the transmission data.

[0037] The reception control unit 41 determines the state of the tire 14, such as the pressure and temperature inside the tire 14, based on the transmission data output from the receiving circuit 44. If an abnormality occurs in the tire 14, the reception control unit 41 may notify the rider of the motorcycle 10. The notification may be made, for example, by displaying a message on a display, turning on a warning light, or sounding a warning buzzer.

[0038] Here, there are cases where it is desired to identify which tire 14 of the two wheels 11, 12 the received transmission data relates to. For example, there are cases where it is desired to distinguish which tire 14 of the two wheels 11, 12 the pressure abnormality in one tire 14 has occurred in and notify the tire 14. In such cases, it is necessary to identify which wheel 11, 12 the received transmission data relates to. In other words, the reception control unit 41 needs to associate the ID code of each transmitter 21 with the position of the wheel 11, 12.

[0039] The wheel position determination control for determining which of the two wheels 11, 12 each transmitter 21 is attached to will now be described. As shown in FIG. 6 , in step S11, the reception control unit 41 determines whether the two-wheeled vehicle 10 is stopped. Whether the two-wheeled vehicle 10 is stopped can be determined, for example, from the detection results of the detection units 17, 18. Whether the two-wheeled vehicle 10 is stopped can also be determined based on whether the transmitted data includes Y-axis acceleration. If the determination result in step S11 is negative, the reception control unit 41 ends the wheel position determination control. If the determination result in step S11 is positive, the reception control unit 41 proceeds to step S12.

[0040] In step S12, the reception control unit 41 acquires the transmission data. The transmission data acquired in step S12 is the transmission data received by the receiver 40 after the two-wheeled vehicle 10 has stopped.

[0041] Next, in step S13, the reception control unit 41 obtains acceleration from the transmission data obtained in step S12. In this embodiment, the reception control unit 41 obtains Y-axis acceleration from the transmission data obtained in step S12. The reception control unit 41 obtains Y-axis acceleration from the transmission data transmitted from each of the two transmitters 21. Therefore, the Y-axis acceleration acting on the front wheels 11 and the Y-axis acceleration acting on the rear wheels 12 are obtained.

[0042] Next, in step S14, the reception control unit 41 performs front / rear wheel determination. The front / rear wheel determination is a process of determining to which wheel 11, 12 each of the transmitters 21 is attached, based on the Y-axis acceleration acquired in step S13. That is, the reception control unit 41 determines whether each of the transmitters 21 is attached to the front wheel 11 or the rear wheel 12.

[0043] The transmission data transmitted by the transmitter 21 includes a Y-axis acceleration and an ID code. Therefore, the reception control unit 41 acquires the Y-axis acceleration in association with the ID code of each transmitter 21. The reception control unit 41 compares the absolute values ​​of the Y-axis accelerations. The reception control unit 41 determines that the transmitter 21 equipped with the acceleration sensor 24 that detected the Y-axis acceleration with the larger absolute value is attached to the front wheel 11. More specifically, the reception control unit 41 determines that the ID code associated with the Y-axis acceleration with the larger absolute value is the ID code of the transmitter 21 attached to the front wheel 11. The reception control unit 41 determines that the ID code that was not determined to be the ID code of the transmitter 21 attached to the front wheel 11 is the ID code of the transmitter 21 attached to the rear wheel 12.

[0044] In step S14, the reception control unit 41 may determine that the transmitter 21 equipped with the acceleration sensor 24 that detected the Y-axis acceleration with the smaller absolute value is attached to the rear wheel 12. Specifically, the reception control unit 41 may determine that the ID code associated with the Y-axis acceleration with the smaller absolute value is the ID code of the transmitter 21 attached to the rear wheel 12. The reception control unit 41 determines that the ID code that is not determined to be the ID code of the transmitter 21 attached to the rear wheel 12 is the ID code of the transmitter 21 attached to the front wheel 11. In this way, even if it is determined that the transmitter 21 equipped with the acceleration sensor 24 that detected the Y-axis acceleration with the smaller absolute value is attached to the rear wheel 12, it is ultimately determined that the transmitter 21 equipped with the acceleration sensor 24 that detected the Y-axis acceleration with the larger absolute value is attached to the front wheel 11.

[0045] The wheel position determination control identifies the ID code of the transmitter 21 attached to the front wheel 11 and the ID code of the transmitter 21 attached to the rear wheel 12. The reception control unit 41 stores the correspondence between each wheel 11, 12 and the ID code in the memory unit 43.

[0046] As described above, in the transmitting / receiving system 20, the transmission control unit 28 controls transmission, and the reception control unit 41 controls wheel position determination. In this way, the transmitter 21 and receiver 40 execute the wheel position determination method.

[0047] [Operation of the First Embodiment] When parking the motorcycle 10, the ignition is turned off after the motorcycle 10 is stopped. When parking the motorcycle 10, the front wheel 11 is steered. For example, when locking the handlebars using the handlebar lock mechanism 16, the handlebars are locked while being steered. The steering angle of the front wheel 11 at this time is, for example, 40° to 50°.

[0048] As shown in Figure 7, in the motorcycle 10, the front wheel 11 is supported with a caster angle, so steering the handlebars causes the central axis of the front wheel 11 to tilt relative to the horizontal. Therefore, when the handlebars are locked by the handlebar lock mechanism 16, the central axis of the front wheel 11 tilts relative to the horizontal. When steering the handlebars, the central axis of the rear wheel 12 does not tilt relative to the horizontal, or even if it does tilt, the amount of tilt is less than that of the front wheel 11. Furthermore, when the stand 15 is a side stand, supporting the motorcycle 10 on the stand 15 causes the central axes of the wheels 11, 12 to tilt relative to the horizontal. Figure 7 depicts the wheels 11, 12 without taking into account the tilt of the wheels 11, 12 due to the stand 15.

[0049] FIG. 8 shows the acceleration detected by the acceleration sensor 24 when the handlebar lock mechanism 16 is locked. Line L1 indicates the Y-axis acceleration of the acceleration sensor 24 provided in the transmitter 21 of the front wheel 11, and line L2 indicates the Y-axis acceleration of the acceleration sensor 24 provided in the transmitter 21 of the rear wheel 12. Because the central axis of the front wheel 11 is tilted with respect to the horizontal direction, a component of gravitational acceleration is detected by the Y-axis 26. As a result, the absolute value of the Y-axis acceleration of the acceleration sensor 24 provided in the transmitter 21 of the front wheel 11 is greater than zero. Because the stand 15 is a side stand, the central axis of the rear wheel 12 is tilted with respect to the horizontal direction. Therefore, a component of gravitational acceleration is also detected by the Y-axis 26 of the acceleration sensor 24 provided in the transmitter 21 of the rear wheel 12. However, the amount of tilt of the central axis of the rear wheel 12 with respect to the horizontal direction is smaller than the amount of tilt of the central axis of the front wheel 11 with respect to the horizontal direction. As a result, after the two-wheeled vehicle 10 has stopped, the absolute value of the Y-axis acceleration detected by the acceleration sensor 24 provided in the transmitter 21 on the front wheel 11 becomes larger than the absolute value of the Y-axis acceleration detected by the acceleration sensor 24 provided in the transmitter 21 on the rear wheel 12. The reception control unit 41 can determine from the Y-axis acceleration whether each of the transmitters 21 is attached to the front wheel 11 or the rear wheel 12.

[0050] [Effects of the First Embodiment] (1-1) When parking the motorcycle 10, the front wheel 11 is steered. In the motorcycle 10, the front wheel 11 is supported with a caster angle. Therefore, steering causes a difference between the acceleration detected by the acceleration sensor 24 provided in the transmitter 21 of the front wheel 11 and the acceleration detected by the acceleration sensor 24 provided in the transmitter 21 of the rear wheel 12. By utilizing this difference, the reception control unit 41 can determine to which wheel 11, 12 each of the transmitters 21 is attached. This determination can be made more easily than when determining to which wheel 11, 12 each of the transmitters 21 is attached using variations in the wheel angles acquired by the detection units 17, 18.

[0051] (1-2) The reception control unit 41 acquires the Y-axis acceleration from the transmission data received by the receiver 40 after the motorcycle 10 has stopped. The reception control unit 41 determines that the transmitter 21 equipped with the acceleration sensor 24 with the larger absolute value of the Y-axis acceleration is attached to the front wheel 11. By utilizing the change in the steering angle used to lock the handlebar lock mechanism 16, it is possible to determine whether each transmitter 21 is attached to the front wheel 11 or the rear wheel 12. Even if the motorcycle 10 does not have the detection units 17, 18, it is possible to determine whether each transmitter 21 is attached to the front wheel 11 or the rear wheel 12.

[0052] (1-3) When the Z-axis acceleration is less than a threshold value, the transmission control unit 28 detects the Y-axis acceleration and transmits transmission data including the Y-axis acceleration to the receiver 40. By transmitting the transmission data including the Y-axis acceleration to the receiver 40, the transmission control unit 28 can enable the receiver 40 to determine to which of the wheels 11, 12 each of the transmitters 21 is attached.

[0053] Because the wheel position determination control is performed after the two-wheeled vehicle 10 has stopped, there is no need to transmit data including Y-axis acceleration to the receiver 40 while the two-wheeled vehicle 10 is traveling. When there is no need to transmit data including Y-axis acceleration, the power consumption of the battery 33 can be reduced by not detecting the Y-axis acceleration.

[0054] Second Embodiment A second embodiment of a transmitter, a receiver, a transmission / reception system, and a wheel position determination method will be described. In the second embodiment, the processing performed by the transmitter and the receiver differs from that in the first embodiment. The hardware configurations of the transmitter and the receiver are the same as those in the first embodiment.

[0055] The transmission control unit 28 performs transmission control. In the transmission control, the transmission control unit 28 transmits transmission data including the Z-axis acceleration to the receiver 40. The transmission control unit 28 may transmit the transmission data including the Z-axis acceleration to the receiver 40 only when the Z-axis acceleration is less than a threshold value.

[0056] The reception control unit 41 performs wheel position determination control. The reception control unit 41 performs the same processes as in the first embodiment in steps S11 and S12. In step S13, the reception control unit 41 obtains the Z-axis acceleration from the transmitted data.

[0057] In step S14, the reception control unit 41 determines to which wheel 11, 12 each transmitter 21 is attached, based on the acquired Z-axis acceleration. The reception control unit 41 acquires the wheel angles from the detection units 17, 18. The reception control unit 41 determines to which wheel 11, 12 each transmitter 21 is attached by comparing the wheel angles acquired from the detection units 17, 18 and the Z-axis acceleration acquired from the transmission data with a map that associates wheel angles with Z-axis acceleration. The map is stored in a storage device that can be read by the reception control unit 41. The storage device is, for example, the storage unit 43.

[0058] In Figure 8, line L3 indicates the Z-axis acceleration of the acceleration sensor 24 provided on the transmitter 21 of the front wheel 11, and line L4 indicates the Z-axis acceleration of the acceleration sensor 24 provided on the transmitter 21 of the rear wheel 12. As can be seen from Figure 8, a difference occurs between the Z-axis acceleration of the acceleration sensor 24 provided on the transmitter 21 of the front wheel 11 and the Z-axis acceleration of the acceleration sensor 24 provided on the transmitter 21 of the rear wheel 12. Specifically, there is a phase shift in the sine wave indicating the correspondence between the wheel angle and the Z-axis acceleration. Furthermore, there is a difference in the maximum absolute value of the Z-axis acceleration. This is because, when the steering angle is increased with a caster angle, the positions of the apexes of the wheels 11 and 12 shift, and because the Z-axis 27 tilts relative to the direction of gravity, reducing the maximum value of the gravitational acceleration detected by the Z-axis 27. Therefore, by creating a map in advance that associates wheel angle with Z-axis acceleration and comparing this map with the Z-axis acceleration, it is possible to determine whether the transmitter 21 is attached to the front wheel 11 or the rear wheel 12.

[0059] The map may be a map in which the wheel angle is associated with the Z-axis acceleration detected by the acceleration sensor 24 provided in the transmitter 21 of either the front wheel 11 or the rear wheel 12. The map may be a map in which the wheel angle is associated with the Z-axis acceleration detected by the acceleration sensor 24 provided in each transmitter 21.

[0060] A case will be described in which a map is used in which the wheel angle is associated with the Z-axis acceleration detected by the acceleration sensor 24 provided in the transmitter 21 of either the front wheel 11 or the rear wheel 12. As an example, a case in which the wheel angle is associated with the Z-axis acceleration detected by the acceleration sensor 24 provided in the transmitter 21 of the rear wheel 12 will be described.

[0061] The reception control unit 41 acquires transmission data transmitted from the transmitters 21 attached to each wheel 11, 12 and acquires Z-axis acceleration from the transmission data. The reception control unit 41 also acquires the wheel angle from the second detection unit 18. The reception control unit 41 acquires the Z-axis acceleration corresponding to the wheel angle acquired from the second detection unit 18 from a map. The reception control unit 41 compares the Z-axis acceleration acquired from the map with the Z-axis acceleration acquired from the transmission data. The reception control unit 41 determines that the Z-axis acceleration acquired from the transmission data that has a smaller difference from the Z-axis acceleration acquired from the map is the Z-axis acceleration detected by the acceleration sensor 24 provided in the transmitter 21 of the rear wheel 12. The reception control unit 41 determines that the ID code associated with the Z-axis acceleration is the ID code of the transmitter 21 attached to the rear wheel 12. The reception control unit 41 determines that the ID code not determined to be the ID code of the transmitter 21 attached to the rear wheel 12 is the ID code of the transmitter 21 attached to the front wheel 11. For example, suppose the wheel angle obtained from the second detection unit 18 is 270°. In this case, the Z-axis acceleration of the acceleration sensor 24 provided in the transmitter 21 of the rear wheel 12 is 0. The reception control unit 41 determines that the Z-axis acceleration obtained from the transmission data that is closest to 0 is the Z-axis acceleration detected by the acceleration sensor 24 provided in the transmitter 21 of the rear wheel 12. Then, it determines that the ID code associated with the Z-axis acceleration closest to 0 is the ID code of the transmitter 21 attached to the rear wheel 12.

[0062] A case will be described in which a map that associates wheel angles with Z-axis acceleration detected by the acceleration sensors 24 provided in each transmitter 21 is used. The reception control unit 41 acquires transmission data transmitted from the transmitters 21 attached to each wheel 11, 12, and acquires the Z-axis acceleration from the transmission data. The reception control unit 41 also acquires wheel angles from each of the first detection unit 17 and the second detection unit 18.

[0063] The reception control unit 41 obtains from the map the Z-axis acceleration corresponding to the wheel angle obtained from the first detection unit 17. Then, the reception control unit 41 compares the Z-axis acceleration corresponding to the wheel angle obtained from the first detection unit 17 with the Z-axis acceleration obtained from the transmission data. The reception control unit 41 determines that the Z-axis acceleration obtained from the transmission data that has the smaller difference from the Z-axis acceleration obtained from the map is the Z-axis acceleration detected by the acceleration sensor 24 provided in the transmitter 21 of the front wheel 11.

[0064] The reception control unit 41 obtains from the map the Z-axis acceleration corresponding to the wheel angle obtained from the second detection unit 18. Then, the reception control unit 41 compares the Z-axis acceleration corresponding to the wheel angle obtained from the second detection unit 18 with the Z-axis acceleration obtained from the transmission data. The reception control unit 41 determines that the Z-axis acceleration obtained from the transmission data that has the smaller difference from the Z-axis acceleration obtained from the map is the Z-axis acceleration detected by the acceleration sensor 24 provided in the transmitter 21 of the rear wheel 12.

[0065] [Effects of the Second Embodiment] According to the second embodiment, the following effect can be obtained in addition to the effects of the first embodiment. (2-1) When parking the two-wheeled vehicle 10, the handlebars are locked by the handlebar lock mechanism 16. In this state, a difference occurs between the Z-axis acceleration of the acceleration sensor 24 provided in the transmitter 21 of the front wheel 11 and the Z-axis acceleration of the acceleration sensor 24 provided in the transmitter 21 of the rear wheel 12. There is a correlation between the wheel angle and the Z-axis acceleration. By creating a map of this correlation in advance, it is possible to use the map to determine whether each transmitter 21 is attached to the front wheel 11 or the rear wheel 12.

[0066] [Third Embodiment] A third embodiment of a transmitter, a receiver, a transmission / reception system, and a wheel position determination method will be described. In the third embodiment, the processing performed by the transmitter and the receiver is different from that in the first embodiment. The hardware configurations of the transmitter and the receiver are the same as those in the first embodiment.

[0067] The transmission control unit 28 performs transmitter-side wheel position determination control, which will be explained in detail below. As shown in FIG. 9, in step S21, the transmission control unit 28 determines whether the Z-axis acceleration is less than a threshold value. This determination is the same as the determination in step S1 in FIG. 5. Therefore, the transmission control unit 28 determines whether the two-wheeled vehicle 10 is stopped. If the determination result in step S21 is negative, the transmission control unit 28 ends the transmitter-side wheel position determination control. If the determination result in step S21 is positive, the transmission control unit 28 proceeds to step S22.

[0068] In step S22, the transmission control unit 28 determines whether the time the two-wheeled vehicle 10 has been stopped has exceeded a predetermined time. This determination is the same as the determination in step S2 in Fig. 5. If the determination result in step S22 is negative, the transmission control unit 28 ends the transmitter-side wheel position determination control. If the determination result in step S22 is positive, the transmission control unit 28 proceeds to step S23.

[0069] In step S23, the transmission control unit 28 determines whether the absolute value of the Y-axis acceleration is equal to or greater than the front wheel determination threshold. The front wheel determination threshold is a predetermined value. As described in the first embodiment, when the motorcycle 10 is stopped, the absolute value of the Y-axis acceleration detected by the acceleration sensor 24 provided in the transmitter 21 of the front wheel 11 is greater than the absolute value of the Y-axis acceleration detected by the acceleration sensor 24 provided in the transmitter 21 of the rear wheel 12. The front wheel determination threshold can be set arbitrarily within the range between the absolute value of the Y-axis acceleration detected by the acceleration sensor 24 provided in the transmitter 21 of the rear wheel 12 and the absolute value of the Y-axis acceleration detected by the acceleration sensor 24 provided in the transmitter 21 of the front wheel 11. If the absolute value of the Y-axis acceleration is equal to or greater than the front wheel determination threshold, the transmitter 21 is attached to the front wheel 11. If the absolute value of the Y-axis acceleration is less than the front wheel determination threshold, the transmitter 21 is attached to the rear wheel 12.

[0070] Next, in step S24, the transmission control unit 28 transmits transmission data including the determination result of step S23 to the receiver 40. That is, the transmission control unit 28 transmits data to the receiver 40 indicating whether the transmission control unit 28 is the transmitter 21 attached to the front wheel 11 or the transmitter 21 attached to the rear wheel 12. Because the transmission data includes an ID code, the determination result is associated with the ID code.

[0071] The reception control unit 41 acquires the determination result from the transmitted data. This makes it possible to determine whether each transmitter 21 is attached to the front wheel 11 or the rear wheel 12. The reception control unit 41 determines that the ID code associated with the determination result indicating that the transmitter 21 is attached to the front wheel 11 is the ID code of the transmitter 21 attached to the front wheel 11. The reception control unit 41 determines that the ID code that was not determined to be the ID code of the transmitter 21 attached to the front wheel 11 is the ID code of the transmitter 21 attached to the rear wheel 12.

[0072] [Effects of the Third Embodiment] (3-1) The transmission control unit 28 determines whether the transmitter 21 is attached to the front wheel 11 by determining whether the absolute value of the Y-axis acceleration is equal to or greater than the front wheel determination threshold. By transmitting this determination result to the receiver 40, the reception control unit 41 can associate the ID code with each of the wheels 11, 12.

[0073] [Fourth embodiment] A fourth embodiment of a transmitter, a receiver, a transmission / reception system, and a wheel position determination method will be described. In the fourth embodiment, the processing performed by the transmitter and the receiver is different from that in the first embodiment. The hardware configurations of the transmitter and the receiver are the same as those in the first embodiment.

[0074] The stand 15 is a center stand. The transmission control performed by the transmission control unit 28 is the same as in the second embodiment. That is, the transmission control unit 28 transmits transmission data including the Z-axis acceleration to the receiver 40 only when the Z-axis acceleration is less than a threshold value.

[0075] The reception control unit 41 performs wheel position determination control. The reception control unit 41 performs the same processes as in the first embodiment in steps S11 and S12. In step S13, the reception control unit 41 obtains the Z-axis acceleration from the transmitted data.

[0076] In step S14, the reception control unit 41 determines whether the acquired Z-axis acceleration has changed from the previous value, thereby determining to which wheel 11, 12 each transmitter 21 is attached. The reception control unit 41 determines whether the Z-axis acceleration has changed from the previous value for each ID code. The reception control unit 41 determines that the transmitter 21 equipped with the acceleration sensor 24 whose Z-axis acceleration changes is attached to the rear wheel 12.

[0077] If the stand 15 is a center stand, the rear wheel 12 goes from a grounded state to a non-grounded state when the motorcycle 10 is parked. The rear wheel 12 spins, causing a change in Z-axis acceleration. Because the front wheel 11 does not rotate, only the Z-axis acceleration detected by the acceleration sensor 24 provided in the transmitter 21 of the rear wheel 12 changes. The reception control unit 41 determines whether the Z-axis acceleration has changed for each ID code from the transmission data acquired after the motorcycle 10 has stopped. If only one of the Z-axis accelerations has changed after the motorcycle 10 has stopped, the reception control unit 41 determines that the ID code associated with that Z-axis acceleration is the ID code of the transmitter 21 attached to the rear wheel 12. The reception control unit 41 determines that an ID code different from the ID code of the transmitter 21 attached to the rear wheel 12 is the ID code of the transmitter 21 attached to the front wheel 11.

[0078] [Effects of the Fourth Embodiment] (4-1) When the stand 15 is a center stand, the rear wheel 12 goes from a ground-contact state to a non-ground-contact state when the motorcycle 10 is parked. The rear wheel 12 spins, causing the acceleration in the Z-axis direction to fluctuate. Because the front wheel 11 does not rotate, only the acceleration in the Z-axis direction detected by the acceleration sensor 24 provided in the transmitter 21 of the rear wheel 12 fluctuates. The reception control unit 41 can determine that a transmitter 21 equipped with an acceleration sensor 24 whose Z-axis acceleration fluctuates after the motorcycle 10 has stopped is attached to the rear wheel 12. Therefore, the reception control unit 41 can determine to which wheel 11, 12 each of the transmitters 21 is attached.

[0079] [Modifications] Each embodiment can be modified as follows: Each embodiment and the following modifications can be combined with each other to the extent that no technical contradiction occurs.

[0080] In the first embodiment, the stand 15 may be a center stand. When the stand 15 is a center stand, the motorcycle 10 is in an upright position. Therefore, the inclination of the central axes of the wheels 11, 12 relative to the horizontal direction is smaller than when the stand 15 is a side stand. Even when the stand 15 is a center stand, the inclination of the central axis of the front wheel 11 relative to the horizontal direction is greater than the inclination of the central axis of the rear wheel 12 relative to the horizontal direction.

[0081] In Figure 10, line L11 indicates the Y-axis acceleration of the acceleration sensor 24 provided in the transmitter 21 of the front wheel 11, and line L12 indicates the Y-axis acceleration of the acceleration sensor 24 provided in the transmitter 21 of the rear wheel 12. As can be seen from Figure 10, even when the stand 15 is a center stand, the absolute value of the Y-axis acceleration detected by the acceleration sensor 24 of the front wheel 11 is greater than the absolute value of the Y-axis acceleration detected by the acceleration sensor 24 of the rear wheel 12. Therefore, by using the same wheel position determination control as in the first embodiment, it can be determined whether each transmitter 21 is attached to the front wheel 11 or the rear wheel 12.

[0082] In the first embodiment, the reception control unit 41 may determine in step S14 that a transmitter 21 equipped with an acceleration sensor 24 whose absolute value of Y-axis acceleration is equal to or greater than the front wheel determination threshold is attached to the front wheel 11. In other words, the reception control unit 41 may perform the processing performed by the transmission control unit 28 in the third embodiment.

[0083] In the first embodiment, the transmission control unit 28 may detect the Y-axis acceleration regardless of the Z-axis acceleration and transmit transmission data including the Y-axis acceleration. That is, the transmission control unit 28 may transmit transmission data including the Y-axis acceleration to the receiver 40 even while the two-wheeled vehicle 10 is traveling.

[0084] In the third embodiment, the transmission control unit 28 does not need to perform the determination in step S22. That is, if the determination result in step S21 is positive, the process of step S23 may be performed.

[0085] In each embodiment, the acceleration sensor 24 may not have an X-axis 25. In each embodiment, the reference position of the rotor may be recognized by the receiver 40 when the transmitter 21 transmits transmission data at a constant wheel angle. Transmission of the transmission data at a constant wheel angle may be performed based on, for example, acceleration detected by the acceleration sensor 24.

[0086] 10...two-wheeled vehicle, 11...front wheel, 12...rear wheel, 17, 18...detection unit, 20...transmission and reception system, 21...transmitter, 24...acceleration sensor, 28...transmission control unit, 40...receiver, 41...reception control unit.

Claims

1. A receiver configured to receive transmission data transmitted from transmitters each mounted on one of two wheels of a two-wheeled vehicle, each of the transmitters comprising an acceleration sensor configured to detect acceleration in the Z-axis direction which is the centrifugal direction of the wheel, the receiver comprising a reception control unit, the reception control unit being configured to: determine the stop of the two-wheeled vehicle; acquire the acceleration detected by the acceleration sensor from the transmission data received by the receiver after the stop of the two-wheeled vehicle; and determine which wheel each of the transmitters is mounted on from the acceleration.

2. The acceleration sensor is configured to detect acceleration in the Y-axis direction which is the axial direction of the wheel, and the reception control unit is configured to: acquire the acceleration in the Y-axis direction from the transmission data received by the receiver after the stop of the two-wheeled vehicle; and determine that the transmitter including the acceleration sensor having a larger absolute value of the acceleration in the Y-axis direction among the transmitters is mounted on the front wheel. The receiver according to claim 1.

3. The two-wheeled vehicle has a detection unit configured to detect the rotation angle of the wheel, and the reception control unit is configured to: acquire the acceleration in the Z-axis direction from the transmission data received by the receiver after the stop of the two-wheeled vehicle; acquire the rotation angle from the detection unit after the stop of the two-wheeled vehicle; and determine which wheel the transmitter is mounted on by comparing a map associating the rotation angle with the acceleration in the Z-axis direction with the acceleration in the Z-axis direction acquired from the transmission data. The receiver according to claim 1.

4. The acceleration sensor is configured to detect acceleration in the Y-axis direction which is the axial direction of the wheel, and the reception control unit is configured to: acquire the acceleration in the Y-axis direction from the transmission data received by the receiver after the stop of the two-wheeled vehicle; and determine that the transmitter including the acceleration sensor having an absolute value of the acceleration in the Y-axis direction equal to or greater than a front wheel determination threshold is mounted on the front wheel. The receiver according to claim 1.

5. A receiver configured to receive transmission data transmitted from transmitters each attached to one of two wheels of a two-wheeled vehicle, the two-wheeled vehicle including a center stand, each of the transmitters including an acceleration sensor configured to detect acceleration in the Z-axis direction, which is the centrifugal direction of the wheel, the receiver including a reception control unit, the reception control unit determining a stop of the two-wheeled vehicle, obtaining the acceleration in the Z-axis direction from the transmission data received by the receiver after the stop of the two-wheeled vehicle, and determining that a transmitter including the acceleration sensor whose acceleration in the Z-axis direction fluctuates after the stop is attached to the rear wheel.

6. A transmitter attached to each of two wheels of a two-wheeled vehicle, the transmitter including an acceleration sensor configured to detect acceleration in the Y-axis direction, which is the axial direction of the wheel, and acceleration in the Z-axis direction, which is the centrifugal direction of the wheel, and a transmission control unit, the transmission control unit detecting the acceleration in the Y-axis direction when the acceleration in the Z-axis direction is less than a threshold value, and transmitting transmission data including the acceleration in the Y-axis direction to a receiver to cause the receiver to determine to which of the wheels each of the transmitters is attached using the acceleration in the Y-axis direction.

7. A transmitter attached to each of two wheels of a two-wheeled vehicle, the transmitter including an acceleration sensor configured to detect acceleration in the Y-axis direction, which is the axial direction of the wheel, and acceleration in the Z-axis direction, which is the centrifugal direction of the wheel, and a transmission control unit, the transmission control unit determining a stop of the two-wheeled vehicle from the acceleration in the Z-axis direction, obtaining the acceleration in the Y-axis direction from the acceleration sensor after the stop of the two-wheeled vehicle, determining whether or not the absolute value of the acceleration in the Y-axis direction is greater than or equal to a front-wheel determination threshold value, and transmitting a determination result to a receiver.

8. A transceiver system comprising a transmitter mounted on each of two wheels of a two-wheeled vehicle, and a receiver configured to receive transmission data transmitted from the transmitter, wherein each of the transmitters includes an acceleration sensor configured to detect acceleration in the Z-axis direction, which is the centrifugal direction of the wheel, the receiver includes a reception control unit, and the reception control unit is configured to determine a stop of the two-wheeled vehicle, acquire the acceleration detected by the acceleration sensor from the transmission data received by the receiver after the stop of the two-wheeled vehicle, and determine which of the wheels each of the transmitters is mounted on from the acceleration.

9. A wheel position determination method for determining by a receiver on which of two wheels of a two-wheeled vehicle a transmitter mounted on each of the two wheels is mounted, the wheel position determination method including: each of the transmitters transmitting transmission data including acceleration; the receiver receiving the transmission data; the receiver determining a stop of the two-wheeled vehicle; the receiver acquiring the acceleration from the transmission data received by the receiver after the stop of the two-wheeled vehicle; and the receiver determining on which of the wheels each of the transmitters is mounted from the acceleration.

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