Transmitter, receiver, transmitting and receiving system, and wheel position determination method

Abstract

A transmitter (31) is mounted on each of a plurality of wheels (11) of a vehicle (10). Each transmitter (31) transmits transmission data to a receiver (50). Each transmitter (31) comprises a power source (38), a transmitter storage unit (37) configured to store identification information of the transmitter (31), and a transmission control unit (35). The transmission control unit (35) generates pre-transmission data having the same data length as the transmission data in accordance with a predetermined frame format, and transmits, as the transmission data, data obtained by adding data not included in the frame format to a specific bit in the pre-transmission data.

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 tire pressure monitoring system disclosed in Patent Document 1 includes a transmitter and a receiver. The transmitter is provided in a tire. The receiver is provided in a vehicle body. The transmitter transmits transmission data to the receiver. The receiver receives the transmission data. The receiver monitors the tire pressure.

[0003] JP 2019-43333 A

[0004] If the amount of data included in the transmission data increases, the length of the transmission data may increase, which may result in an increase in the power consumption of the transmitter.

[0005] According to a first aspect of the present disclosure, there is provided a transmitter mounted on each of a plurality of wheels of a vehicle and configured to transmit transmission data to a receiver. The transmitter includes a power source, a transmitter storage unit configured to store identification information of the transmitter, and a transmission control unit. The transmission control unit is configured to generate pre-transmission data having the same data length as the transmission data according to a predetermined frame format, and to transmit the data obtained by adding data not included in the frame format to specific bits in the pre-transmission data as the transmission data. The transmission control unit transmits the data obtained by adding the data not included in the frame format of the pre-transmission data to the specific bits of the pre-transmission data. The receiver restores the data not included in the frame format from the transmission data. The data length of the transmission data can be shortened compared to when transmitting transmission data including data not included in the frame format. Increased power consumption by the transmitter can be suppressed.

[0006] For the transmitter, the data not included in the frame format is wheel position determination data for causing the receiver to perform wheel position determination to determine to which of the plurality of wheels the transmitter is attached.

[0007] Regarding the transmitter, the specific bit is an error detection code or an error correction code. Regarding the transmitter, the transmitter includes a pressure sensor configured to detect tire pressure. The specific bit is an error detection code for pressure data. The error detection code for pressure data is pressure mirror data obtained by inverting a bit of pressure data indicating the pressure detected by the pressure sensor.

[0008] For the transmitter, the specific bit is the identification information. According to a second aspect of the present disclosure, there is provided a receiver configured to receive transmission data transmitted from a transmitter mounted on each of a plurality of wheels of a vehicle. The receiver includes a receiver memory configured to store identification information of the transmitter, and a reception control unit. The transmission data is obtained by adding data not included in the frame format to specific bits in pre-transmission data generated according to a predetermined frame format. The pre-transmission data has the same data length as the transmission data. The reception control unit is configured to restore the data not included in the frame format from the identification information stored in the receiver memory or the transmission data.

[0009] The reception control unit restores data that is not included in the frame format from the transmission data. This makes it possible to obtain data that is not included in the frame format in addition to data that is included in the transmission data. This increases the amount of data that the reception control unit can obtain without increasing the data length of the transmission data. This makes it possible to shorten the data length of the transmission data compared to when the transmitter transmits transmission data that includes data that is not included in the frame format. This makes it possible to prevent the power consumption of the transmitter from increasing.

[0010] In the receiver, the data not included in the frame format is wheel position determination data used to determine which of the plurality of wheels the transmitter is attached to, and the reception control unit is configured to perform the wheel position determination from the wheel position determination data.

[0011] In the above receiver, the reception control unit is configured to calculate the difference between the error detection code calculated from the transmission data and the error detection code included in the transmission data as the data not included in the frame format, or to calculate mirror data of the pressure data included in the transmission data from the pressure data and calculate the difference between the calculated mirror data and the pressure mirror data included in the transmission data as the data not included in the frame format.

[0012] In the above receiver, the reception control unit is configured to calculate the difference between the identification information stored in the receiver memory unit and the identification information included in the transmission data as the data not included in the frame format.

[0013] According to a third aspect of the present disclosure, there is provided a transmission / reception system including a transmitter mounted on each of a plurality of wheels of a vehicle and configured to transmit transmission data to a receiver, and a receiver configured to receive the transmission data. The transmitter includes a power source, a transmitter memory configured to store identification information of the transmitter, and a transmission control unit. The transmission control unit is configured to generate pre-transmission data having the same data length as the transmission data according to a predetermined frame format, and to transmit data obtained by adding data not included in the frame format to specific bits in the pre-transmission data as the transmission data. The receiver includes a receiver memory configured to store the identification information, and a reception control unit. The reception control unit is configured to restore the data not included in the frame format from the identification information stored in the receiver memory or the transmission data.

[0014] The transmission control unit adds data not included in the frame format of the pre-transmission data to specific bits of the pre-transmission data and transmits the data as transmission data. The receiver restores the data not included in the frame format from the transmission data. The data length of the transmission data can be shortened compared to when transmitting transmission data including data not included in the frame format. Increased power consumption of the transmitter can be suppressed.

[0015] According to a fourth aspect of the present disclosure, there is provided a wheel position determination method in which a receiver determines to which of a plurality of wheels each of transmitters attached to a plurality of wheels of a vehicle is attached, the wheel position determination method including the steps of: each of the transmitters generating pre-transmission data having the same data length as transmission data in accordance with a predetermined frame format; each of the transmitters adding wheel position determination data for causing the receiver to perform wheel position determination to a specific bit in the pre-transmission data and transmitting the obtained data as the transmission data; the receiver restoring the wheel position determination data from identification information of the transmitter or the transmission data; and the receiver performing wheel position determination, which determines to which of the plurality of wheels each of the transmitters is attached based on the wheel position determination data.

[0016] The transmitter adds data not included in the frame format of the pre-transmission data to specific bits of the pre-transmission data and transmits the data as transmission data. The receiver restores the data not included in the frame format from the transmission data. The data length of the transmission data can be shortened compared to when transmitting transmission data including data not included in the frame format. The power consumption of the transmitter can be suppressed from increasing.

[0017] FIG. 1 is a schematic diagram showing an example of a transmission / reception system. FIG. 2 is a diagram showing an ABS of a vehicle equipped with the transmission / reception system of FIG. 1. FIG. 3 is a schematic configuration diagram showing the transmitter of FIG. 1. FIG. 4 is a flowchart showing a specific angle transmission process performed by the transmission control unit of FIG. 3. FIG. 5 is a diagram showing a frame format of pre-transmission data generated in the specific angle transmission process of FIG. 4. FIG. 6 is a diagram showing wheel position determination data generated in the specific angle transmission process of FIG. 4. FIG. 7 is a flowchart showing wheel position determination process performed by the reception control unit of FIG. 1. FIG. 8 is a diagram showing variations in pulse count values ​​obtained in the wheel position determination process of FIG. 7. FIG. 9 is a diagram showing examples of pressure data and pressure mirror data. FIG. 10 is a diagram showing an example of wheel position determination data. FIG. 11 is a diagram showing an example of a difference between pressure mirror data included in transmission data and mirror data of pressure data calculated from the transmission data. FIG. 12 is a diagram showing a frame format of pre-transmission data in a second embodiment. FIG. 13 is a diagram showing an example of pre-transmission data in the second embodiment. FIG. 14 is a diagram showing an example of a difference between an error detection code included in transmission data and an error detection code calculated from the transmission data. FIG. 15 is a diagram showing an example of an ID code included in transmission data in a third embodiment. Fig. 16 is a diagram showing an example of transmission data in the third embodiment. Fig. 17 is a diagram showing an error detection code calculated using an ID code registered in the receiver. Fig. 18 is a diagram showing an example of the difference between the ID code included in the transmission data and the ID code registered in the receiver.

[0018] First Embodiment A first embodiment of a transmitter, a receiver, a transmission / reception system, and a wheel position determination method will be described.

[0019] As shown in Fig. 1, the transmission / reception system 30 is mounted on a vehicle 10. The vehicle 10 has four wheels 11. Each wheel 11 has a wheel 12 and a tire 13 attached to the wheel 12. In the following description, the right front wheel, the left front wheel, the right rear wheel, the left rear wheel, and the right rear wheel will be referred to as FR, FL, RR, and RL, respectively.

[0020] The vehicle 10 is equipped with an anti-lock brake system (hereinafter referred to as ABS) 20. The ABS 20 includes an ABS controller 25 and rotation sensor units 21 to 24 corresponding to the four wheels 11, respectively. The first rotation sensor unit 21 corresponds to the left front wheel FL, and the second rotation sensor unit 22 corresponds to the right front wheel FR. The third rotation sensor unit 23 corresponds to the left rear wheel RL, and the fourth rotation sensor unit 24 corresponds to the right rear wheel RR. The ABS controller 25 is, for example, a microcomputer, and determines the rotation angle of each wheel 11 based on signals from the rotation sensor units 21 to 24.

[0021] As shown in FIG. 2 , each of the rotation sensor units 21 to 24 includes a gear 26 that rotates integrally with the wheel 11 and a detector 27 disposed opposite the outer circumferential surface of the gear 26. The gear 26 has a plurality of teeth spaced at equal angular intervals on its outer circumferential surface. The gear 26 has 48 teeth. The detector 27 detects pulses generated by the rotation of the gear 26. The ABS controller 25 is wired to the detector 27 and calculates the rotation angle of each wheel 11 based on the pulse count values ​​detected by each detector 27. Specifically, the ABS controller 25 counts the rising and falling edges of the pulses generated by the detector 27. The ABS controller 25 divides the counted number of pulses by 96, which is the number of pulses required for one rotation of the gear 26, to obtain a pulse count value. Furthermore, by dividing 360 degrees by the number of pulses generated by the detector 27 during one rotation of the wheel 11, it is possible to determine the number of degrees the gear 26 has rotated per pulse count value. The pulse count value ranges from 0 to 95, and the rotation angle of the wheel 11 can be calculated from the pulse count value.

[0022] <Transmission and Reception System> As shown in Fig. 1 , the transmission and reception system 30 includes a transmitter 31 mounted on each of the four wheels 11, and a receiver 50 installed on the vehicle 10. The transmitter 31 is attached to the wheel 11 so as to be disposed in the interior space of the tire 13. The transmitter 31 may be fixed to a tire valve, or may be fixed to the wheel 12 or the tire 13. The transmitter 31 detects the condition of the corresponding tire 13 and wirelessly transmits transmission data including detected information about the tire 13 to the receiver 50. The transmission and reception system 30 monitors the condition of the tire 13 by receiving the transmission data transmitted from the transmitter 31 with the receiver 50. The transmission and reception system 30 is a tire condition monitoring system.

[0023] 3, each transmitter 31 includes a pressure sensor 32, a temperature sensor 33, an acceleration sensor 34, a transmission control unit 35, a battery 38, a transmission antenna 39, and a transmission circuit 40. The transmitter 31 operates using power supplied from the battery 38. The transmission control unit 35 comprehensively controls the operation of the transmitter 31. The battery 38, which serves as the power source for the transmitter 31, may be a primary battery, or may be a power storage device such as a secondary battery or a capacitor.

[0024] The pressure sensor 32 detects the air pressure of the corresponding tire 13. The temperature sensor 33 detects the temperature inside the corresponding tire 13. The acceleration sensor 34 is attached so as to be able to detect centrifugal acceleration. The acceleration sensor 34 has a detection axis and detects acceleration in the direction of the detection axis. The acceleration sensor 34 is attached to the wheel 11 so that the detection axis faces vertically downward when the transmitter 31 is located at the lowest position of the wheel 11. The acceleration sensor 34 is only required to be able to detect at least centrifugal acceleration, and may be a uniaxial acceleration sensor or a multiaxial acceleration sensor.

[0025] The transmission control unit 35 includes a processor 36 and a transmitter memory unit 37. The processor 36 is, for example, a central processing unit (CPU), a graphics processing unit (GPU), or a digital signal processor (DSP). The transmitter memory unit 37 includes a random access memory (RAM) and a read-only memory (ROM). The transmitter memory unit 37 stores program code or instructions configured to cause the processor to execute processing. The transmitter memory unit 37, i.e., the computer-readable medium, includes any available medium accessible by a general-purpose or special-purpose computer. The transmission control unit 35 may be configured by a hardware circuit such as an application-specific integrated circuit (ASIC) or a field-programmable gate array (FPGA). The transmission control unit 35, 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.

[0026] The transmitter storage unit 37 stores ID codes, which are data indicating unique identification information for each transmitter 31. As appropriate, the ID code of the transmitter 31 attached to the left front wheel FL is referred to as FLID, the ID code of the transmitter 31 attached to the right front wheel FR is referred to as RFID, the ID code of the transmitter 31 attached to the left rear wheel RL is referred to as RLID, and the ID code of the transmitter 31 attached to the right rear wheel RR is referred to as RRID. The transmitter storage unit 37 stores various programs for controlling the transmitters 31.

[0027] The transmission control unit 35 generates transmission data and outputs the generated transmission data to the transmission circuit 40. The transmission circuit 40 modulates the transmission data. The modulated transmission data is transmitted from the transmission antenna 39 as a radio signal. The radio signal can be said to be a signal that includes the transmission data. The radio 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.

[0028] The transmitter 31 performs a specific angle transmission process to transmit transmission data when the rotation angle of the wheel 11 reaches a predetermined specific angle. The specific angle transmission process may be performed, for example, when the vehicle 10 is stopped for a predetermined time or longer. The predetermined time is set to a time longer than the time required to change the position of the wheel 11, such as by tire rotation, or the time required to replace the wheel 11. The predetermined time is, for example, several tens of minutes to several hours.

[0029] Whether the vehicle 10 is moving can be determined from the acceleration detected by the acceleration sensor 34. As the vehicle speed increases, the centrifugal acceleration acting on the acceleration sensor 34 increases. If the acceleration detected by the acceleration sensor 34 is equal to or greater than the moving determination threshold, the transmission control unit 35 determines that the vehicle 10 is moving. On the other hand, if the acceleration detected by the acceleration sensor 34 is less than the moving determination threshold, the transmission control unit 35 determines that the vehicle 10 is stopped. Taking into account tolerances and the like, the moving determination threshold is set to a value greater than the acceleration detected by the acceleration sensor 34 when the vehicle 10 is stopped.

[0030] The specific angle transmission process will be described. As shown in Fig. 4, in step S1, the transmission control unit 35 detects the state of the tire 13. More specifically, the transmission control unit 35 acquires the detection result from the pressure sensor 32. The transmission control unit 35 acquires the detection result from the temperature sensor 33. The state of the tire 13 includes the pressure of the tire 13 and the temperature of the tire 13.

[0031] Next, in step S2, the transmission control unit 35 generates pre-transmission data. The pre-transmission data is generated according to a predetermined frame format. As shown in FIG. 5, the frame format includes an ID code, pressure data, temperature data, status, pressure mirror data, and an error detection code. This frame format is used, for example, as transmission data for existing transmitters available on the market. The frame format may also include a preamble.

[0032] The ID code is the ID code of the transmitter 31 that transmits the transmission data. The pressure data indicates the pressure detected by the pressure sensor 32. The temperature data indicates the temperature detected by the temperature sensor 33. The status indicates the state of the transmitter 31. The pressure mirror data is data in which the bits of the pressure data are inverted. The pressure mirror data is used in the receiver 50 to check whether there is an error in the pressure data. The pressure mirror data is an error detection code for the pressure data. The error detection code is calculated from each data included in the frame format. The error detection code is, for example, a CRC (Cyclic Redundancy Check). For example, the error detection code is the remainder obtained by dividing the ID code, pressure data, temperature data, status, and pressure mirror data by a generating polynomial. The transmission control unit 35 generates pre-transmission data by storing the data in the frame format.

[0033] Next, in step S3, the transmission control unit 35 detects the specific angle by acquiring the detection result of the acceleration sensor 34. Centrifugal acceleration and gravitational acceleration act on the detection axis of the acceleration sensor 34. If only gravitational acceleration is considered, gravitational acceleration always acts in the vertically downward direction. The orientation of the detection axis changes as the wheel 11 rotates. Therefore, the gravitational acceleration component detected by the acceleration sensor 34 changes as the wheel 11 rotates. Unless the vehicle 10 suddenly accelerates or stops, the change in centrifugal acceleration during one rotation of the wheel 11 is extremely small. Therefore, the change in acceleration detected by the acceleration sensor 34 during one rotation of the wheel 11 can be essentially considered to be a change in the gravitational acceleration component due to a change in the orientation of the detection axis.

[0034] When only gravitational acceleration is taken into consideration, the gravitational acceleration component detected by the acceleration sensor 34 varies between +1 G and −1 G during one rotation of the wheel 11. The gravitational acceleration component detected when the detection axis faces vertically downward is +1 G. The gravitational acceleration component detected when the detection axis faces vertically upward, which is the opposite direction to the vertically downward, is −1 G. When the position of the acceleration sensor 34 changes due to the rotation of the wheel 11 so that it crosses the position where the detection axis faces vertically upward, the acceleration detected by the acceleration sensor 34 changes from a decrease to an increase. More specifically, when the position of the acceleration sensor 34 changes from a position where the detection axis faces vertically downward to a position where the detection axis faces vertically upward, the acceleration detected by the acceleration sensor 34 decreases. On the other hand, when the position of the acceleration sensor 34 changes from a position where the detection axis faces vertically upward to a position where the detection axis faces vertically downward, the acceleration detected by the acceleration sensor 34 increases. The transmission control unit 35 acquires the detection result of the acceleration sensor 34 at predetermined intervals. Each time the transmission control unit 35 acquires the detection result of the acceleration sensor 34, it compares it with the previous value. If the detection result of the acceleration sensor 34 is higher than the previous value, it is considered an increase. If the detection result of the acceleration sensor 34 is lower than the previous value, it is considered a decrease. The transmission control unit 35 determines that the transmitter 31 is located at a specific angle of the wheel 11 when the pattern of decreases and increases matches a predetermined pattern. For example, the transmission control unit 35 determines that the transmitter 31 is located at a specific angle when the detection result of the acceleration sensor 34 changes from a decrease to an increase. In this manner, the transmission control unit 35 detects that the transmitter 31 is located at a specific angle. In this embodiment, the specific angle is set to two positions. If the transmitter 31 is located at the highest position of the wheel 11, which is defined as 0°, the specific angles are, for example, 0° and 180°. That is, the transmission data is transmitted when the transmitter 31 detects that it is at the top position of the wheel 11 and when the transmitter 31 detects that it is at the bottom position of the wheel 11. The specific angle may be one position.

[0035] Next, in step S4, the transmission control unit 35 generates wheel position determination data. As shown in FIG. 6, the wheel position determination data includes determination result data, transmission angle data, and frame number data. The determination result data indicates whether or not a specific angle was detected in step S3. The transmission angle data indicates the specific angle. For example, if multiple specific angles are set and transmission data is transmitted at each of the multiple specific angles, the transmission angle data indicates at which specific angle the transmission data was transmitted. The frame number data indicates the sequence of the frame to be transmitted.

[0036] Next, in step S5, the transmission control unit 35 generates transmission data. The transmission data is generated by adding the wheel position determination data to a specific bit in the pre-transmission data. In this embodiment, the specific bit is pressure mirror data. Therefore, the pressure mirror data included in the transmission data is data obtained by adding the wheel position determination data to the pressure mirror data of the pre-transmission data.

[0037] Next, in step S6, the transmission control unit 35 transmits the transmission data. If the specific angle has been detected, the transmission data is transmitted at the specific angle. <Receiver> As shown in FIG. 1, the receiver 50 includes a reception control unit 51, a receiving circuit 54, and a receiving antenna 55. A display 56 mounted on the vehicle 10 is connected to the reception control unit 51.

[0038] The reception control unit 51 includes a processor 52 and a receiver memory unit 53. The processor 52 is, for example, a CPU, a GPU, or a DSP. The receiver memory unit 53 includes RAM and ROM. The receiver memory unit 53 stores program code or instructions configured to cause the processor to execute processing. The receiver memory unit 53, i.e., the computer-readable medium, includes any available medium accessible by a general-purpose or special-purpose computer. The reception control unit 51 may be configured with a hardware circuit such as an ASIC or FPGA. The reception control unit 51, 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.

[0039] The receiving circuit 54 demodulates the radio signals received from each transmitter 31 via the receiving antenna 55, and outputs the transmission data from the transmitter 31 to the receiving control unit 51. This allows the receiving control unit 51 to acquire the transmission data.

[0040] The reception control unit 51 determines the state of the tire 13, such as the pressure and temperature inside the tire 13, based on the transmission data output from the receiving circuit 54. If an abnormality occurs in the tire 13, the reception control unit 51 may display a notification on the display 56.

[0041] The ID codes of the four wheels 11 are registered in the receiver 50. The ID codes are registered by storing the ID codes of the transmitters 31 attached to the four wheels 11 in the receiver storage unit 53. In this way, the transmitters 31 are associated with the receiver 50.

[0042] Here, there are cases where it is desired to identify which tire 13 of the four wheels 11 the received transmission data relates to. For example, there are cases where it is desired to display on the display 56 which tire 13 a pressure abnormality has occurred in, among the four wheels 11, or where it is desired to display on the display 56 the pressure of the tire 13 corresponding to each position of the wheel 11. In such cases, it is necessary to identify which wheel 11 the received transmission data relates to. In other words, the reception control unit 51 needs to associate the ID code of each transmitter 31 with the position of the wheel 11.

[0043] <Wheel Position Determination Process> The wheel position determination process for determining which of the four wheels 11 each transmitter 31 is attached to will be described. The wheel position determination process is performed, for example, when the vehicle 10 is started by a start switch that switches the vehicle 10 between a running state and a stopped state. The running state of the vehicle 10 is a state in which the vehicle 10 can be driven by operating the accelerator pedal. The stopped state of the vehicle 10 is a state in which the vehicle 10 does not drive even when the accelerator pedal is operated.

[0044] The wheel position determination process will now be described. As shown in Fig. 7, in step S11, the reception control unit 51 acquires the transmission data.

[0045] Next, in step S12, the reception control unit 51 acquires the pulse count values ​​of the rotation sensor units 21 to 24 from the ABS controller 25 upon receiving the transmission data.

[0046] Next, in step S13, the reception control unit 51 restores the wheel position determination data. The reception control unit 51 restores the wheel position determination data based on the transmitted data. The reception control unit 51 calculates mirror data of the pressure data using the same method as when calculating pressure mirror data of data before transmission. The reception control unit 51 can acquire pressure data from the transmitted data. The reception control unit 51 calculates mirror data of the pressure data by inverting the bits of the pressure data. The reception control unit 51 determines the difference between the pressure mirror data included in the transmitted data and the calculated mirror data of the pressure data as wheel position determination data. The reception control unit 51 can recognize a specific angle from the wheel position determination data.

[0047] Next, in step S14, the reception control unit 51 performs wheel position determination. Each time transmission data is acquired, pulse count values ​​are collected in association with the ID code included in the transmission data. As a result, there are rotation sensor units 21 to 24 corresponding to each transmitter 31 with small variations in pulse count values. This is because the rotation speed of each wheel 11 differs due to the influence of the differential gear, etc. The relative positions of the transmitters 31 attached to each wheel 11 change as the vehicle 10 travels. On the other hand, when the transmitter 31 transmits transmission data at a specific angle, the rotation angle of each of the four wheels 11 is synchronized with the rotation angle at which transmission data is transmitted from one of the four transmitters 31.

[0048] The reception control unit 51 determines which of the four wheels 11 each transmitter 31 is attached to based on the variation in the pulse count values ​​collected each time transmission data is acquired. For example, suppose that the result shown in FIG. 8 is obtained when pulse count values ​​are acquired from each rotation sensor unit 21-24 in association with the FLID. In the example shown in FIG. 8, the variation in the pulse count values ​​detected by the first rotation sensor unit 21 corresponding to the left front wheel FL is the smallest. Therefore, it can be determined that the transmitter 31 of the FLID is attached to the left front wheel FL.

[0049] When the collected pulse count values ​​fall within a predetermined range, the reception control unit 51 associates the rotation sensor units 21 to 24 that detected the pulse count values ​​with the transmitter 31. The predetermined range is a range that is set in consideration of variations in pulse count values, and is used to determine the rotation sensor units 21 to 24 with small variations in pulse count values.

[0050] The reception control unit 51 determines to which of the four wheels 11 the transmitters 31 for FLID, RFID, RLID, and RRID are attached. The reception control unit 51 then associates the four ID codes with the positions of the wheels 11 and stores the association in the receiver storage unit 53. The processing of steps S11 to S14 is repeated each time transmission data is received until the association between all transmitters 31 and the positions of the wheels 11 has been identified. When the association between the four ID codes and the positions of the wheels 11 has been completed by the processing of step S14, the reception control unit 51 ends the wheel position determination processing.

[0051] When multiple specific angles are set, as in this embodiment, it is necessary to determine at which specific angle the transmission data was sent. The reception control unit 51 can determine at which specific angle the transmission data was sent from the restored wheel position determination data.

[0052] The reception control unit 51 may collect pulse count values ​​for each specific angle and perform wheel position determination for each specific angle. In this case, the determination result for any one specific angle may be used, or a determination result may be used when the determination results for multiple specific angles match. Alternatively, multiple specific angles may be considered as a single specific angle by adding pulse count values ​​corresponding to the differences between the multiple specific angles. For example, if the specific angles are 0° and 180°, 48 may be added to or subtracted from the pulse count value when transmission data transmitted at 180° is acquired. Because a pulse count value of 48 corresponds to 180° in the rotational direction of the wheel 11, wheel position determination can be performed by considering the specific angle as 0°.

[0053] As described above, in the transmission / reception system 30, the transmission control unit 35 performs the specific angle transmission process, and the reception control unit 51 performs the wheel position determination process. In this way, the transmitter 31 and the receiver 50 execute the wheel position determination method.

[0054] [Operation of First Embodiment] Assume that the values ​​shown in Fig. 9 are obtained as the pressure data and pressure mirror data of the pre-transmission data. The pressure data and pressure mirror data shown in Fig. 9 are each 8-bit data. The pressure data is expressed as 11001101 in binary notation. The pressure mirror data is expressed as 00110010 in binary notation. The ID code, temperature data, status, and error detection code are omitted from Fig. 9.

[0055] Assume that the data shown in Figure 10 is generated as wheel position determination data. The wheel position determination data shown in Figure 10 is 8-bit data, with the upper 2 bits being determination result data, the lower 4 bits being frame number data, and the 2 bits between the determination result data and the frame number data being transmission angle data. In the example shown in Figure 10, the wheel position determination data is 01100010 in binary notation. Assume that 01 in the determination result data indicates successful detection of the specific angle. Assume that 10 in the transmission angle data indicates that the specific angle is 180°. Assume that 0010 in the frame number data indicates that this is the second frame.

[0056] In this case, the wheel position determination data expressed in hexadecimal notation, 0x62, is added to the pressure mirror data of the data before transmission, which is expressed in hexadecimal notation, 0x32. As a result, the pressure mirror data of the transmission data becomes 0x94. The transmitter 31 transmits transmission data whose pressure mirror data is 0x94.

[0057] The receiver 50 receives the transmission data. The pressure data is the same in the pre-transmission data and the transmission data. Therefore, the reception control unit 51 can calculate mirror data of the pressure data from the received transmission data. As shown in FIG. 11 , the mirror data of the pressure data calculated by the reception control unit 51 is 0x32. Since the pressure mirror data included in the transmission data is 0x94, the difference is 0x62. The reception control unit 51 acquires 0x62 as the wheel position determination data. 0x62 is 01100010 in binary. Therefore, the wheel position determination data generated by the transmission control unit 35 has been restored. The reception control unit 51 uses this wheel position determination data to perform wheel position determination. More specifically, wheel position determination is performed by collecting pulse count values ​​for each specific angle determined from the wheel position determination data.

[0058] [Effects of the First Embodiment] (1-1) The transmission control unit 35 transmits, as transmission data, data obtained by adding data not included in the frame format of the pre-transmission data to specific bits in the pre-transmission data. The reception control unit 51 can obtain the data not included in the frame format by restoring the data not included in the frame format from the transmission data. Therefore, the data length of the transmission data can be shortened compared to when transmitting transmission data obtained by adding data not included in the frame format as additional bits to the pre-transmission data. Since the power consumption of the transmitter 31 can be suppressed from increasing, the life of the battery 38 can be extended.

[0059] (1-2) The data not included in the frame format is wheel position determination data. The transmitter 31 can transmit the wheel position determination data to the receiver 50 without increasing the data length of the transmission data.

[0060] When adding the specific angle transmission function to an existing transmitter 31, it is necessary to add wheel position determination data to the frame format used by the existing transmitter 31. In this case, not only does the data length of the transmission data increase, which increases power consumption, but it also requires re-acquisition of radio wave authentication. In contrast, by adding the wheel position determination data to an existing specific bit in the transmission data as in the embodiment, the data length of the transmission data does not change. Therefore, it is possible to have the receiver 50 acquire the wheel position determination data without changing the frame format used by the existing transmitter 31. This eliminates the need to re-acquire radio wave authentication.

[0061] (1-3) The specific bit to which data not included in the frame format is added is pressure mirror data. The pressure mirror data can be calculated from the pressure data included in the transmission data. This makes it easy to restore the data in the receiver 50.

[0062] (1-4) The reception control unit 51 restores data that is not included in the frame format from the transmission data. This makes it possible to acquire data that is not included in the frame format in addition to data that is included in the transmission data. This increases the amount of data that the reception control unit 51 can acquire without increasing the data length of the transmission data. Because the data length of the transmission data is not increased, it is possible to prevent an increase in power consumption by the transmitter 31. This makes it possible to extend the life of the battery 38.

[0063] (1-5) The reception control unit 51 determines the wheel position from the restored wheel position determination data, thereby determining which wheel 11 each transmitter 31 is attached to.

[0064] (1-6) The reception control unit 51 calculates mirror data of the pressure data from the pressure data included in the transmission data, and calculates the difference between the calculated mirror data and the pressure mirror data included in the transmission data as data not included in the frame format. Because the transmission data includes pressure data, the reception control unit 51 can calculate the mirror data of the pressure data. The pressure mirror data included in the transmission data is obtained by adding data not included in the frame format to the pressure mirror data of the data before transmission. Therefore, the difference calculated as described above can be calculated as data not included in the frame format.

[0065] Second Embodiment A second embodiment of the transmitter, receiver, transmission / reception system, and wheel position determination method will be described. In the second embodiment, the processes performed by the transmitter and receiver are different. The hardware configurations of the transmitter and receiver are the same as those of the first embodiment.

[0066] In the second embodiment, the transmission control unit 35 performs the processes of steps S1 to S6. As shown in FIG. 12, the frame format used to generate the pre-transmission data in step S2 includes an ID code, pressure data, temperature data, status, and an error detection code. The error detection code is, for example, the remainder when the ID code, pressure data, temperature data, and status are divided by a generator polynomial. Except for the frame format of the pre-transmission data in step S2, the processes performed in steps S1 to S4 and S6 are the same as those in the first embodiment.

[0067] In step S5, the transmission control unit 35 generates transmission data by adding the wheel position determination data to the error detection code of the data before transmission. The specific bit in the second embodiment is the error detection code. Therefore, the error detection code included in the transmission data is data obtained by adding the wheel position determination data to the error detection code of the data before transmission.

[0068] The reception control unit 51 performs the processes of steps S11 to S14. In step S13, the reception control unit 51 restores wheel position determination data based on the transmitted data. The reception control unit 51 calculates an error detection code using the same method as when calculating the error detection code for the pre-transmission data. The reception control unit 51 can acquire the ID code, pressure data, temperature data, and status from the transmitted data. These data are the same as the data used by the transmission control unit 35 when calculating the error detection code for the pre-transmission data. The reception control unit 51 calculates the error detection code as the remainder when dividing the ID code, pressure data, temperature data, and status by a generating polynomial. The generating polynomial is the same as the one used when calculating the error detection code for the pre-transmission data. The reception control unit 51 determines the difference between the error detection code included in the transmitted data and the calculated error detection code as wheel position determination data. The reception control unit 51 can recognize the specific angle from the wheel position determination data. Steps S11, S12, and S14 are the same as those in the first embodiment.

[0069] [Operation of the Second Embodiment] Assume that the data shown in Fig. 13 is generated as pre-transmission data. "Hex" means hexadecimal, "dec" means decimal, and "bin" means binary. If the ID code is 12345678, the pressure is 200 kPaG, the temperature is 25 °C, and the status is 00000000, the error detection code is 32 in hexadecimal notation.

[0070] As in the first embodiment, it is assumed that the data shown in Figure 10 is generated as wheel position determination data. In this case, the wheel position determination data 0x62 is added to the error detection code 0x32 of the data before transmission. As a result, the error detection code of the transmission data becomes 0x94. The transmitter 31 transmits the transmission data with the error detection code 0x94.

[0071] The receiver 50 receives the transmission data. The ID code, pressure data, temperature data, and status are the same in the pre-transmission data and the transmission data. Therefore, the reception control unit 51 can obtain the ID code, pressure data, temperature data, and status from the received transmission data. Then, an error detection code can be calculated from the ID code, pressure data, temperature data, and status included in the transmission data. As shown in FIG. 14 , the error detection code calculated by the reception control unit 51 is 0x32. Because the error detection code included in the transmission data is 0x94, the difference is 0x62. The reception control unit 51 obtains 0x62 as the wheel position determination data. 0x62 is 01100010 in binary. Therefore, the wheel position determination data generated by the transmission control unit 35 has been restored. The reception control unit 51 uses this wheel position determination data to perform wheel position determination.

[0072] [Effects of Second Embodiment] In the second embodiment, the following effects can be obtained in addition to the effects (1-1), (1-2), (1-4), and (1-5) of the first embodiment.

[0073] (2-1) The specific bit to which data not included in the frame format is added is an error detection code. The error detection code can be calculated from the data included in the transmission data. This makes it easy for the receiver 50 to restore the data.

[0074] (2-2) The reception control unit 51 calculates the difference between the error detection code calculated from the transmission data and the error detection code included in the transmission data as data not included in the frame format. The transmission data includes the data used by the transmission control unit 35 when calculating the error detection code of the data before transmission, so the reception control unit 51 can calculate the error detection code. The error detection code included in the transmission data is obtained by adding the data not included in the frame format to the error detection code of the data before transmission. Therefore, the difference calculated as described above can be calculated as data not included in the frame format.

[0075] [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 second embodiment. The hardware configurations of the transmitter and the receiver are the same as those in the first embodiment.

[0076] The transmission control unit 35 performs the processes of steps S1 to S6. In step S5, the transmission control unit 35 generates transmission data by adding the wheel position determination data to the ID code of the pre-transmission data. The specific bits in the third embodiment are the ID code. Steps S1 to S4 and S6 are the same as those in the second embodiment.

[0077] The reception control unit 51 performs the processes of steps S11 to S14. In step S13, the reception control unit 51 restores wheel position determination data from the ID code. The reception control unit 51 calculates an error detection code using the ID code registered in the receiver 50 and the pressure data, temperature data, and status data included in the transmission data. The error detection code included in the transmission data is an error detection code calculated using the error detection code of the data before transmission, i.e., the ID code before the wheel position determination data is added. Therefore, when an error detection code is calculated using the four ID codes registered in the receiver 50, the error detection code calculated using one of the four ID codes matches the error detection code included in the transmission data. The reception control unit 51 can determine that the ID code used to calculate the error detection code that matches the error detection code included in the transmission data is the ID code of the sender of the transmission data. The reception control unit 51 calculates the wheel position determination data by calculating the difference between the sender's ID code among the ID codes registered in the receiver 50 and the ID code included in the transmission data. Steps S11, S12, and S14 are the same as those in the second embodiment.

[0078] [Operation of Third Embodiment] As shown in Figure 15, the ID code of the transmitter 31 that transmits transmission data is assumed to be 12345678 in hexadecimal notation. The wheel position determination data is assumed to be 62 in hexadecimal notation. In this case, the ID code included in the transmission data is 123456DA. As shown in Figure 16, the transmitter 31 transmits transmission data whose ID code is 123456DA in hexadecimal notation and whose error detection code is 32 in hexadecimal notation.

[0079] The receiver 50 receives the transmitted data. The pre-transmission data and the transmitted data have the same pressure data, temperature data, status, and error detection code. The receiver 50 also has registered therein the ID code of the transmitter 31. Therefore, the reception control unit 51 can calculate the error detection code using the ID code registered in the receiver 50.

[0080] The receiver 50 has registered therein at least ID codes corresponding to the number of wheels 11. The ID code of the transmitter 31 attached to the spare tire may also be registered. When the reception control unit 51 calculates an error detection code using all of the registered ID codes, an error detection code that matches the error detection code included in the transmission data is found. For example, as shown in FIG. 17 , assume that four ID codes, 12345678, 12345567, 12345688, and 123459AB, in hexadecimal notation, are registered in the receiver 50. In this case, the error detection code calculated using 12345678 is 32 in hexadecimal notation, the error detection code calculated using 12345567 is 21 in hexadecimal notation, the error detection code calculated using 12345688 is 31 in hexadecimal notation, and the error detection code calculated using 123459AB is F5 in hexadecimal notation. In this way, the error detection code calculated using 12345678 matches the error detection code included in the transmission data. Therefore, the ID code of transmitter 31 that is the source of the transmission data is 12345678.

[0081] 18, the reception control unit 51 calculates the difference between 12345678, the ID code used to calculate the error detection code that matches the error detection code included in the transmission data, and 123456DA, the ID code included in the transmission data. The difference is 62 in hexadecimal notation. Therefore, the wheel position determination data obtained is 62 in hexadecimal notation, or 01100010 in binary notation.

[0082] [Effects of the Third Embodiment] In the third embodiment, the following effects can be obtained in addition to the effects (1-1), (1-2), (1-4), and (1-5) of the first embodiment.

[0083] (3-1) The specific bits to which data not included in the frame format is added are an ID code. The ID code is registered in the receiver 50. Therefore, the ID code of the sender of the transmitted data can be obtained from the error detection code included in the transmitted data and the error detection code calculated from the registered ID code. Then, the difference between the ID code included in the transmitted data and the ID code of the sender can be calculated as data not included in the frame format.

[0084] [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.

[0085] In the first embodiment, the specific bit to which data not included in the frame format is added may be an error detection code. In each embodiment, the data not included in the frame format that is added to the specific bit may be any data. The data not included in the frame format may be the angle advanced from the detection of the specific angle at the time of transmitting the transmission data, or the delay time from the detection of the specific angle at the time of transmitting the transmission data. The data not included in the frame format may be the reliability of the transmission data. The data not included in the frame format may be information about the wheel 11. The information about the wheel 11 may be, for example, the size of the wheel 11. The data not included in the frame format may be acceleration data indicating the acceleration detected by the acceleration sensor 34.

[0086] In the second embodiment, if the frame format includes an error correction code, the specific bit may be the error correction code. In this case, the transmission control unit 35 and the reception control unit 51 may perform the same processing on the error correction code as they did on the error detection code in the second embodiment. The error correction code may be, for example, a Hamming code.

[0087] In each embodiment, the error detection code may be other than a CRC. For example, the error detection code may be a checksum. In each embodiment, various power generating elements may be used as the power source for the transmitter 31. Even if a component capable of charging or generating power is used as the power source, there is a limit to the amount of power that can be used. Therefore, it is preferable to reduce the power consumption due to the transmission of transmission data.

[0088] In each embodiment, the vehicle 10 may be, for example, a two-wheeled vehicle as long as it has a plurality of wheels 11. In each embodiment, the receiver 50 may be a mobile terminal carried by a passenger of the vehicle 10.

[0089] In each embodiment, the wheel position determination data may include rotation direction data that indicates whether the rotation direction of the wheel 11 is clockwise or counterclockwise.

[0090] 10...vehicle, 11...wheel, 13...tire, 30...transmitting / receiving system, 31...transmitter, 32...pressure sensor, 35...transmission control unit, 37...memory unit for transmitter, 38...battery which is an example of a power source, 50...receiver, 51...reception control unit, 53...memory unit for receiver.

Claims

1. A transmitter configured to be mounted on each of a plurality of wheels of a vehicle and transmit transmission data to a receiver, the transmitter comprising: a power source; a transmitter storage unit configured to store identification information of the transmitter; and a transmission control unit, wherein the transmission control unit generates pre-transmission data having the same data length as the transmission data according to a predetermined frame format, and transmits, as the transmission data, data obtained by adding data not included in the frame format to specific bits in the pre-transmission data.

2. The transmitter according to claim 1, wherein the data not included in the frame format is wheel position determination data for causing the receiver to perform wheel position determination for determining on which of the plurality of wheels the transmitter is mounted.

3. The transmitter according to claim 1 or 2, wherein the specific bits are error detection codes or error correction codes.

4. The transmitter according to claim 1 or 2, wherein the transmitter includes a pressure sensor configured to detect the pressure of a tire, the specific bits are error detection codes of pressure data, and the error detection codes of the pressure data are pressure mirror data obtained by inverting bits of pressure data indicating the pressure detected by the pressure sensor.

5. The transmitter according to claim 1 or 2, wherein the specific bits are the identification information.

6. A receiver configured to receive transmission data transmitted from transmitters mounted on each of a plurality of wheels of a vehicle, the receiver comprising: a receiver storage unit configured to store identification information of the transmitter; and a reception control unit, wherein the transmission data is obtained by adding data not included in the frame format to specific bits in pre-transmission data generated according to a predetermined frame format, the pre-transmission data having the same data length as the transmission data, and the reception control unit is configured to restore the data not included in the frame format from the identification information stored in the receiver storage unit or the transmission data.

7. The data not included in the frame format is wheel position determination data used for the transmitter to perform wheel position determination for determining on which of the plurality of wheels the transmitter is mounted, and the reception control unit is configured to perform the wheel position determination from the wheel position determination data. The receiver according to claim 6.

8. The reception control unit is configured to calculate, as the data not included in the frame format, the difference between the error detection code calculated from the transmission data and the error detection code included in the transmission data, or calculate mirror data of the pressure data included in the transmission data from the pressure data, and calculate, as the data not included in the frame format, the difference between the calculated mirror data and the pressure mirror data included in the transmission data. The receiver according to claim 6 or claim 7.

9. The reception control unit is configured to calculate, as the data not included in the frame format, the difference between the identification information stored in the receiver storage unit and the identification information included in the transmission data. The receiver according to claim 6 or claim 7.

10. A transmission-reception system including a transmitter configured to be mounted on each of a plurality of vehicle wheels and transmit transmission data to a receiver, and a receiver configured to receive the transmission data, wherein the transmitter includes a power source, a transmitter storage unit configured to store identification information of the transmitter, and a transmission control unit, and the transmission control unit is configured to generate pre-transmission data having the same data length as the transmission data according to a predetermined frame format, and transmit, as the transmission data, data obtained by adding data not included in the frame format to specific bits in the pre-transmission data. The receiver includes a receiver storage unit configured to store the identification information and a reception control unit, and the reception control unit is configured to restore the data not included in the frame format from the identification information stored in the receiver storage unit or the transmission data. The transmission-reception system.

11. A wheel position determination method in which a receiver determines on which of a plurality of wheels of a vehicle each transmitter mounted on the plurality of wheels is mounted, the wheel position determination method comprising: each of the transmitters generating pre-transmission data having the same data length as transmission data according to a predetermined frame format; each of the transmitters transmitting, as the transmission data, data obtained by adding wheel position determination data for causing the receiver to perform wheel position determination to specific bits in the pre-transmission data; the receiver restoring the wheel position determination data from the identification information of the transmitter or the transmission data; and the receiver performing wheel position determination to determine on which of the plurality of wheels each of the transmitters is mounted from the wheel position determination data.

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