JP7027845B2 - Tire pressure detector - Google Patents

Description

The present invention relates to a tire pressure detection device.

Conventionally, for example, in Patent Document 1, a direct type tire pressure detection device has been proposed. This type of tire pressure detection device has a configuration in which a transmitter equipped with, for example, a pressure sensor integrated with an air valve is directly attached to the wheel side to which the tire is attached, and an antenna and a receiver are attached to the vehicle body side. Will be done. Then, when data indicating the detection result of the pressure sensor is transmitted from the transmitter, the data is received by the receiver via the antenna, and tire pressure detection is performed. Then, when the automatically measured tire pressure drops below the specified value, a warning is given to the driver. As a result, the driver can be notified when a sudden puncture occurs while the vehicle is running or when the tire pressure is naturally reduced, and the vehicle can be run more safely.

Japanese Patent Application Laid-Open No. 2003-228787

However, since the transmitter is attached to the tire side separated from the vehicle body, the tire pressure is not detected during parking to reduce power consumption, and the tire is used when it is confirmed that the vehicle has started running. Pneumatic detection is performed. Therefore, in order for the user to check the state of the tire pressure, it is necessary to drive the vehicle, and the tire pressure cannot be confirmed before the running.

On the other hand, the present inventors detect the tire pressure even while parking and store the data in the receiver provided on the vehicle body side so that the tire pressure can be immediately notified when the user starts the vehicle. I am considering making it. However, in such a form, if the position of the transmitter when parked is the position of Null where the receiver cannot sufficiently receive the radio wave due to the radio wave propagation characteristics, the tire pressure is transmitted to the receiver. Can't. Therefore, in the end, it is not possible to notify the tire pressure before the vehicle travels.

In view of the above points, it is an object of the present invention to provide a tire pressure detection device capable of reliably detecting tire pressure while parking.

In order to achieve the above object, the tire pressure detecting device according to claim 1 comprises a transmitter / receiver (2a to 2d) provided on each of a plurality of wheels (5a to 5d) provided with tires, and a transmitter / receiver. A sensing unit (21) having a receiver (3, 7) for performing data communication between the receivers, and the transmitter / receiver having a pressure sensor (21a) for outputting a detection signal indicating the tire pressure of each of the plurality of wheels. A first control unit (22) that processes a detection signal indicating the tire pressure to create data related to the tire pressure, and a first transmission / reception unit (23) that transmits data related to the tire pressure. The machine has a second transmission / reception unit (32) for receiving data on the tire pressure, and a second control unit (33) for detecting the tire pressure based on the received data on the tire pressure. In such a configuration, the plurality of transceivers attached to each of the plurality of wheels can receive data on the tire pressure between the plurality of transceivers, and among the plurality of transceivers while parked. At least one transceiver, which has better communication with the receiver than the other transceiver, acts as a repeater and transmits data about the tire pressure of the other transceiver received by communication to the receiver.

In this way, the tire pressure is detected during parking. If the communication status with the receiver is not good for any of the transceivers, the data related to the tire pressure is transmitted to the receiver using the one with good communication status as a repeater. As a result, if the receiver cannot receive the data related to the tire pressure even if the data is transmitted, or if the reception condition is not good, the transmitter / receiver having a good reception condition can be transmitted to the receiver as a repeater. This makes it possible to reliably transmit the data regarding the tire pressure to the receiver even when the transceiver is in the Null position, for example. Therefore, it is possible to provide a tire pressure detecting device capable of reliably detecting the tire pressure while parking.

The reference numerals in parentheses of each of the above means indicate an example of the correspondence with the specific means described in the embodiment described later.

It is a figure which showed the whole structure of the tire pressure detection device which concerns on 1st Embodiment. It is a figure which showed the block composition of a transmitter / receiver. It is a figure which showed the block composition of a receiver. It is a figure which showed the state of the data communication using a repeater. It is a figure which showed the state of the data communication using the repeater following FIG. 4A. It is a figure which showed the state of the data communication using the repeater following FIG. 4B. It is a figure which showed the state of the data communication using the repeater following FIG. 4C. It is a figure which showed the state of the data communication using the repeater following FIG. 4D. It is a figure which showed the state of the data communication using the repeater following FIG. 4E. It is a figure which showed the state of the data communication using the repeater following FIG. 4F. It is a figure which showed the state of the data communication using the repeater following FIG. 4G. It is a flowchart of the process executed by the control part of each transceiver. It is a time chart of the process executed by the control unit of the receiver while parking. It is a flowchart which showed the details of the selection process of the best repeater. It is a flowchart which showed the detail of the repeater processing. It is a figure which showed the whole structure of the tire pressure detection device when the portable device is used.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In each of the following embodiments, the parts that are the same or equal to each other will be described with the same reference numerals.

(First Embodiment)
The first embodiment of the present invention will be described with reference to FIGS. 1 to 5. It should be noted that the upward direction on the paper surface of FIG. 1 corresponds to the front of the vehicle 1, the downward direction on the paper surface corresponds to the rear of the vehicle 1, and the left-right direction on the paper surface coincides with the left-right direction of the vehicle.

The tire pressure detection device shown in FIG. 1 is attached to the vehicle 1 and includes transceivers 2a to 2d, a receiver 3, and a display 4.

As shown in FIG. 1, the transceivers 2a to 2d are attached to the wheels 5a to 5d of the vehicle 1, and detect the air pressure of the tires attached to the wheels 5a to 5d, and the detection result and the tire air pressure are measured. Data on tire pressure indicating that the tire pressure has dropped is transmitted. Further, the receiver 3 is an on-board unit attached to the vehicle body 6 side of the vehicle 1, and detects a decrease in tire pressure or tire pressure by receiving data on tire pressure transmitted from transceivers 2a to 2d. Further, the transceivers 2a to 2d and the receiver 3 according to the present embodiment are capable of performing not only communication from the transceivers 2a to 2d to the receiver 3 but also vice versa. Further, it is assumed that bidirectional communication can be performed between the transceivers 2a to 2d. Therefore, data communication between the receiver 3 and the transceivers 2a to 2d is possible, and a part of the transceivers 2a to 2d communicates with the transceivers 2a to 2d through the other part. It is also possible to communicate.

Various forms of two-way communication can be applied, such as Bluetooth communication including BLE (abbreviation of Bluetooth Low Energy) communication, wireless LAN (abbreviation of Local Area Network) such as wifi, and Sub-GHz communication. , Ultra wideband communication, ZigBee, etc. can be applied. "Bluetooth" is a registered trademark. Hereinafter, the detailed configurations of the transceivers 2a to 2d and the receiver 3 will be described with reference to FIGS. 2 and 3.

As shown in FIG. 2, the transceivers 2a to 2d are configured to include a sensing unit 21, a control unit 22, a bidirectional communication unit 23, a battery 24, and an antenna 25, and are based on the power supply from the battery 24. Each part is driven.

The sensing unit 21 is configured to include, for example, a pressure sensor 21a, a temperature sensor 21b, and an acceleration sensor 21c. The pressure sensor 21a outputs a detection signal according to the tire pressure. The temperature sensor 21b outputs a detection signal according to the temperature inside the tire. The acceleration sensor 21c outputs a detection signal corresponding to the acceleration generated by the rotation of the tire, for example, the radial acceleration of each wheel 5a to 5d. Then, the sensing unit 21 transmits the detection signals output by the pressure sensor 21a, the temperature sensor 21b, and the acceleration sensor 21c to the control unit 22.

Of these, the detection signal according to the tire pressure and the detection signal according to the temperature inside the tire are used for tire pressure detection, and the detection signal according to the acceleration is whether the vehicle 1 is running or parked. Used for judgment.

The control unit 22 corresponds to the first control unit and has a configuration including a memory 22a and a timer 22b. Although only the memory 22a and the timer 22b are shown here, the control unit 22 is configured by a well-known microcomputer equipped with a CPU, ROM, RAM, I / O, etc., and is predetermined according to the stored program of the memory 22a. Executes the processing of. The memory 22a in the control unit 22 stores ID information including transceiver-specific identification information for identifying the transceivers 2a to 2d and vehicle-specific identification information for identifying the own vehicle. .. Further, the unique information predetermined between the transceivers 2a and 2d and the unique information predetermined between the transceivers 2a and 2d and the receiver 3 are also used for calculating the error rate, which will be described later. It is stored in the memory 22a. The unique information here may be the same or different.

The control unit 22 receives the detection signal output from the sensing unit 21, processes the signal, and processes it as necessary. Then, the control unit 22 stores the data indicating the detection result of the tire pressure and the tire internal temperature used for the tire pressure detection in the frame together with the ID information of the transceivers 2a to 2d, and stores the frame at a predetermined timing. It is sent to the bidirectional communication unit 23. Further, the frame also includes unique information predetermined by the transceivers 2a to 2d and the receiver 3 as necessary. Further, the control unit 22 itself may determine the decrease in tire pressure. In that case, the control unit 22 also stores data indicating whether or not the tire pressure has dropped in the frame and sends it to the bidirectional communication unit 23. For example, the control unit 22 compares the tire air pressure when converted to a predetermined reference temperature with a predetermined warning threshold value Th, and when it detects that the tire air pressure has dropped to the warning threshold value Th or less, the tire pressure drop has occurred. The data indicating that is stored in the frame. Then, the control unit 22 transmits a frame to the receiver 3 through the bidirectional communication unit 23.

In the following description, the data indicating the detection result of the tire air pressure and the tire internal temperature and the data indicating the presence or absence of the occurrence of the tire air pressure decrease are referred to as the tire air pressure data. However, it is not always necessary for the data on tire pressure to include all of these data, only one of the data showing the detection result of the tire pressure and the temperature inside the tire and the data showing the presence or absence of a decrease in the tire pressure. May be.

Further, the control unit 22 has a relay function that plays a role of a repeater when the other transceivers 2a to 2d and the receiver 3 communicate with each other, and the receiver 3 that uses the other transceivers 2a to 2d as a repeater. It also has a relay source function to communicate with.

The control unit 22 issues a repeater instruction when communication with the receiver 3 is not good, and relays so that communication with the receiver 3 is performed via the repeater. Perform instruction processing. The case where the communication with the receiver 3 is not performed well means that the response signal does not arrive from the receiver 3 within a certain period even if the frame is transmitted, or the response sent from the receiver 3 is performed. This applies when the signal does not meet certain conditions. When the response signal does not satisfy a certain condition, for example, when the reception strength when the transceivers 2a to 2d receive the response signal is equal to or less than the specified value, or when the response signal does not include the reception completion signal. There are cases and so on. Further, the response signal includes the unique information determined in advance between the transmitter / receiver 2a to 2d and the receiver 3, and the unique information included in the response signal and the unique information stored in the transceivers 2a to 2d. Even when the error rate collated with the information is equal to or less than the threshold value, a certain condition is not satisfied. In these cases, the control unit 22 transmits a relay trigger instructing the other transceivers 2a to 2d to serve as a repeater. As a result, the frame is transmitted to the receiver 3 via the repeater. The error rate is an index indicating the communication status, and is, for example, a data demodulation rate.

On the contrary, the control unit 22 performs repeater processing in which the receiver 3 becomes a repeater in response to a request if the receiver 3 can receive the repeater satisfactorily. Specifically, when the frame is accurately received, the control unit 22 waits for the reception of the relay trigger, and when the relay trigger is received, the control unit 22 activates the relay function and becomes itself as a repeater. As a result, the control unit 22 relays the data communication between the transmitter / receiver 2a to 2d (hereinafter referred to as the relay source) and the receiver 3 that have transmitted the relay trigger, and relates to the tire pressure transmitted from the relay source. The data is received by the receiver 3. Further, since a plurality of transceivers 2a to 2d can be repeaters, the control unit 22 is the first determination index when selecting which is the best repeater when it becomes a repeater. The reception strength and error rate of the frame transmitted from the repeater are detected. Then, as a repeater, the control unit 22 includes the data of the first determination index in the frame transmitted by the relay source and transmits the data to the receiver 3.

In this way, the control unit 22 issues a repeater instruction if the transmitted frame is not satisfactorily received by the receiver 3, and a relay instruction so that the frame transmission is performed to the receiver 3 via the repeater. Performs processing and repeater processing in which it becomes a repeater.

Further, the control unit 22 uses the acceleration detection result to determine whether or not the vehicle is running. For example, when the acceleration sensor 21c outputs a detection signal corresponding to the radial acceleration of each wheel 5a to 5d, the control unit 22 removes the center of gravity acceleration component from the detection signal and extracts the centrifugal acceleration component. This change in the centrifugal acceleration component indicates the rotational state of the tire. Therefore, the control unit 22 detects that the vehicle 1 is traveling based on the generation of the centrifugal acceleration component, or detects the vehicle speed based on the change in the centrifugal acceleration component.

The control unit 22 transmits frames to the receiver 3 at regular transmission cycles. The periodic transmission cycle may be constant, but since it can be determined whether or not the vehicle is running based on the acceleration detection result, the periodic transmission cycle is changed between running and parking, and the vehicle is parked. Has a longer periodic transmission cycle than during driving. Further, when a decrease in tire pressure occurs during traveling, the periodic transmission cycle may be further changed by itself or based on a request from the receiver 3.

Further, in the present embodiment, each of the above-mentioned processes is not performed while the vehicle is running, but is performed only while the vehicle is parked. Unlike when the vehicle is parked, the wheels 5a to 5d are rotated while the vehicle is running, so that the positions of the transceivers 2a to 2d change. Therefore, even if the frame transmission is performed when the transceivers 2a to 2d come to the Null position and cannot be received by the receiver 3, the receiver 3 can receive the frame at the time of the next frame transmission or the like. It will be like. Therefore, each of the above-mentioned processes may be performed not only while the vehicle is parked but also while the vehicle is running, but here, it is performed only while the vehicle is parked. Then, while the vehicle is running, the control units 22 of the transceivers 2a to 2d do not perform the above-mentioned processing, and simply send the receiver 3 to the receiver 3 at each periodic transmission cycle during the running, as in the conventional case. The operation of transmitting a frame is performed.

The bidirectional communication unit 23 corresponds to the first transmission / reception unit, and performs data communication with the receiver 3 and other transceivers 2a to 2d through the antenna 25. Specifically, the bidirectional communication unit 23 functions as an output unit that transmits a frame transmitted from the control unit 22 as a radio wave toward the receiver 3. The bidirectional communication unit 23 also functions as an input unit for receiving data arriving as radio waves from the receiver 3 and other transceivers 2a to 2d. Although the bidirectional communication unit 23 is described here as one configuration, the bidirectional communication unit 23 may be configured separately for the transmission unit and the reception unit. The process of sending a signal from the control unit 22 to the bidirectional communication unit 23 is performed according to the above program.

The battery 24 supplies electric power to the sensing unit 21, the control unit 22, and the like, and receives the electric power from the battery 24 to collect data on the tire pressure in the sensing unit 21 and the control unit 22. Various operations are executed.

The transceivers 2a to 2d configured in this way are attached to, for example, air injection valves in the wheels of the wheels 5a to 5d, and the sensing unit 21 is arranged so as to be exposed inside the tire. As a result, the transceivers 2a to 2d detect the tire pressure of the corresponding wheel and transmit the frame through the antenna 25 provided in each of the transceivers 2a to 2d.

On the other hand, as shown in FIG. 3, the receiver 3 has a configuration including an antenna 31, a bidirectional communication unit 32, and a control unit 33.

The antenna 31 is provided in the vehicle body 6 and receives frames sent from the transceivers 2a to 2d, and transmits data by transmitting radio waves for transmitting data to the transceivers 2a to 2d. It is for doing. Here, the antenna 31 is composed of one common antenna that comprehensively performs transmission / reception to / from the transceivers 2a to 2d, but may be provided for each of the transceivers 2a to 2d. , It may be configured separately for transmission and reception.

The bidirectional communication unit 32 corresponds to a second transceiver unit, and functions as an input unit that inputs a frame transmitted from each of the transceivers 2a to 2d by the antenna 31 and sends it to the control unit 33. Fulfill. The bidirectional communication unit 32 also functions as an output unit that transmits data to the transceivers 2a to 2d in accordance with instructions from the control unit 33. Although the bidirectional communication unit 32 is configured to be capable of both transmission and reception here, the transmission unit and the reception unit may be configured separately.

The control unit 33 corresponds to the second control unit and has a configuration including a memory 33a and a timer 33b. Although only the memory 33a and the timer 33b are shown here, the control unit 33 is configured by a well-known microcomputer equipped with a CPU, ROM, RAM, I / O, etc., and is predetermined according to a program stored in the memory 33a. Executes the processing of. Specifically, the control unit 33 operates based on the power supply from a power source such as a battery (not shown), controls frame reception and data transmission in the bidirectional communication unit 32, and various types related to tire pressure detection. Perform processing.

For example, the control unit 33 performs reception processing, relay communication processing, pressure detection processing, and the like as various processes related to tire pressure detection.

In the reception process, processing for receiving frames from the transceivers 2a to 2d is performed. When the ignition (hereinafter referred to as IG) switch corresponding to the vehicle start switch is turned on, electric power is supplied to the receiver 3 from a power source such as a battery. At this time, as a reception process, the receiver 3 is always in a state of being able to receive the frames transmitted from the transceivers 2a to 2d. As a result, the receiver 3 can receive the frame transmission from each of the transceivers 2a to 2d. Since data communication from the receiver 3 to the transceivers 2a to 2d is also possible, when frame reception is performed, the ID information of the transceivers 2a to 2d stored in the received frame is attached. Then, data including a reception completion signal and the like can be sent.

On the other hand, when the IG switch is turned off and the vehicle is parked, the power supply from the power supply to the receiver 3 is turned off, so that the receiver 3 normally receives the frame in which data is transmitted from the transceivers 2a to 2d. Can not do it. Therefore, as a reception process, the control unit 33 wakes up based on the power supply from the power supply at predetermined time intervals when the IG switch is turned off, and the frame in which data is transmitted from the transceivers 2a to 2d. To be able to receive. For example, the timer 33b is set to measure the time even when the IG switch is turned off, and the memory 33a stores a program that switches to a state in which frame reception is possible only during a predetermined period at predetermined time intervals.

The predetermined period referred to here means a period from the completion of receiving the frame data transmitted from the transceivers 2a to 2d to the detection of the tire pressure of each wheel 5a to 5d. As described above, the transceivers 2a to 2d determine whether the vehicle is running or parked based on the detection signal of the acceleration sensor 21c, and periodically transmit the vehicle when the vehicle is running and when the vehicle is parked. The cycle is changing. During the predetermined period here, the frame transmitted from each transceiver 2a to 2d or the frame transmitted through the repeater is received according to the periodic transmission cycle during parking, and the tire pressure detection based on them is performed. It is the period until completion.

The relay communication process is a process of performing data communication with a relay source through a repeater. Specifically, the control unit 33 receives the frame transmitted from the relay source through the repeater, and notifies the relay source that the frame has been received. Further, as described above, a plurality of transceivers 2a to 2d can serve as repeaters. Therefore, the control unit 33 calculates the reception intensity and the error rate when the frame from the repeater is received as the second determination index, and then the best repeater based on the first determination index and the second determination index. Is selected. Regarding the error rate here, the unique information determined in advance between the transmitter / receiver 2a to 2d as the repeater and the receiver 3 is collated with the unique information included in the frame sent from the repeater. It can be obtained by.

In the pressure detection process, the tire pressure is obtained by performing various signal processing and calculations based on the data related to the tire pressure stored in the frame received from the bidirectional communication unit 32. Then, an electric signal corresponding to the obtained tire pressure is output to the display 4. For example, the control unit 33 compares the obtained tire pressure with a predetermined warning threshold Th, and when it detects that the tire pressure has dropped to the predetermined warning threshold Th or less, a signal to that effect is displayed on the display 4. Output. Further, when the tire pressure is detected by the transceivers 2a to 2d, the tire pressure drop is generated in the display 4 based on the data indicating that the tire pressure drop included in the received frame has occurred. You can also tell that.

Further, when the control unit 33 obtains the tire pressures of the four wheels 5a to 5d, the control unit 33 can output the tire pressures to the display 4 in association with the wheels 5a to 5d. In the memory 33a, the ID information of the transceivers 2a to 2d arranged on the wheels 5a to 5d is stored in association with the positions of the wheels 5a to 5d. Therefore, the control unit 33 recognizes which of the wheels 5a to 5d the receiver 2a to 2d is attached to the received frame by collating with the ID information stored in the frame, and the tire pressure is increased. You can identify the lowered wheel. Based on this, when a tire pressure drop occurs, the lowered wheel is identified and output to the display 4. Further, even when the tire pressure drop does not occur, the obtained tire pressure may be associated with each wheel 5a to 5d and output to the display 4.

In this way, the tire pressure of any one of the four wheels 5a to 5d has decreased, or the tire pressure of each of the four wheels 5a to 5d is transmitted to the display 4.

However, when the IG switch is off, that is, when the vehicle is parked, it is unlikely that the user will confirm it even if it is displayed on the display 4, and it is not effective. Therefore, when the IG switch is off, the output to the display 4 is not performed, and the obtained tire pressure or the decrease in the tire pressure is stored as data, and the display 4 is immediately displayed when the IG switch is off. Is enabled to output. In addition, if the tire pressure is requested multiple times during parking, the latest data is updated.

As shown in FIG. 1, the display 4 is arranged in a place where the driver can see it, and is composed of, for example, an alarm lamp or a display installed in the instrument panel of the vehicle 1. When a signal indicating that the tire pressure has decreased is sent from the control unit 33 of the receiver 3, for example, the display 4 displays the signal to that effect and notifies the driver of the decrease in the tire pressure. Alternatively, when the tire pressure of each of the four wheels 5a to 5d is transmitted from the receiver 3, the tire pressure of each wheel is displayed in correspondence with each wheel 5a to 5d.

In the present embodiment, the display 4 is used as a warning unit for giving a warning to the driver. However, in addition to the display 4 that gives a visual warning, a speaker or the like that gives an auditory warning. May be used as a warning unit.

As described above, the tire pressure detection device according to the present embodiment is configured. Subsequently, the operation of the tire pressure detection device of the present embodiment will be described.

For example, when an ignition switch (not shown) is turned on, the receiver 3 or the like is operated based on the power supply from the battery. As a result, the control unit 33 waits for the frame transmitted from the transceivers 2a to 2d to be received. On the other hand, in each of the transceivers 2a to 2d, the sensing unit 21, the control unit 22, and the like are driven based on the power supply from the battery 24, and data on the tire pressure in the sensing unit 21 is collected at each predetermined control cycle. And various processes in the control unit 22 are executed. Then, the control unit 22 determines whether the vehicle is running or parked based on the detection signal of the acceleration sensor 21c, and stores data on the tire pressure at each periodic transmission cycle according to the determination result. The frame is sent.

Based on this, in the receiver 3, the tire pressure is detected by the control unit 33 performing the pressure detection process. Specifically, the frame is received by the receiver 3, and the tire pressures of the wheels 5a to 5d are detected based on the data on the tire pressures stored in the frame. Then, based on this detection result, the tire pressure is displayed or the tire pressure has dropped is displayed through the display 4.

At this time, since the wheels 5a to 5d are rotated while the vehicle is running, the positions of the transceivers 2a to 2d change. Therefore, even if the frame transmission is performed when the transceivers 2a to 2d come to the Null position and cannot be received by the receiver 3, the receiver 3 can receive the frame at the time of the next frame transmission or the like. It will be like. Further, while the vehicle is running, frame reception is performed with a relatively short periodic transmission cycle. Therefore, while the vehicle is traveling, the transceivers 2a to 2d simply perform a frame transmission to the receiver 3 at each periodic transmission cycle during traveling, as in the conventional case. Further, when the tire pressure drops during traveling, the periodic transmission cycle can be further changed to a shorter cycle based on the request from the receiver 3 or itself.

On the other hand, while parking, there is a possibility that one of the transceivers 2a to 2d is in the position of Null and the transmitted frame is not received by the receiver 3. Therefore, each process including the above-mentioned relay instruction process, repeater process, relay communication process, and receive process is executed. Hereinafter, each process executed by the control unit 22 of the transceivers 2a to 2d and the control unit 33 of the receiver 3 will be described. Prior to that, the operation flow of the transceivers 2a to 2d and the receiver 3 will be described. It will be described with reference to 4A to 4H. In FIGS. 4A to 4H, the frame transmitted from the transceiver 2b of the left front wheel 5b is not received by the receiver 3, and the frames transmitted from the transceivers 2a, 2c, and 2d of the remaining wheels 5a, 5c, and 5d are The case where it is received by the receiver 3 is taken as an example.

First, as shown in FIG. 4A, during parking, frame transmission is performed from the transceivers 2a to 2d at each periodic transmission cycle set during parking. This will be received by the receiver 3, but if it is in the position of Null like the transceiver 2b of the left front wheel 5b, it is good even if the transmitted frame cannot be received by the receiver 3 or can be received. It may not be the communication status. On the other hand, when the receiver 3 receives the frame, as shown in FIG. 4B, the receiver 3 transmits a reception completion signal and a response signal containing unique information for obtaining an error rate together with the ID information stored in the received frame. As a result, the reception completion signal is transmitted to the transceivers 2a, 2c, and 2d by receiving the response signal. However, the transceiver 2b cannot receive the response signal. Or, even if reception is possible, for the transceiver 2b, the error rate when the unique information contained in the response signal and the unique information stored by itself are collated so that the reception strength of the response signal is equal to or less than the specified value. Is equal to or less than the threshold value, and the response signal does not satisfy a certain condition.

As a result, the transceiver 2b recognizes that the communication status with the receiver 3 is not good. Therefore, as shown in FIG. 4C, the transceiver 2b is another transceiver as a relay source based on the fact that the response signal does not reach within a certain period or the response signal does not satisfy a certain condition. A relay trigger is transmitted to 2a, 2c, and 2d. This relay trigger is received, for example, by the transceivers 2a and 2d of the right front wheel 5a and the left rear wheel 5d, which are relatively close to the left front wheel 5b. Then, the transceivers 2a and 2d that have received the relay trigger become repeaters, and as shown in FIG. 4D, activation information indicating that the relay function has been activated is transmitted to the transceiver 2b which is the relay source. In this way, the activation information can be notified to the transceiver 2b that has transmitted the relay trigger.

When this activation information reaches the transceiver 2b, as shown in FIG. 4E, information to be relayed to the transceivers 2a and 2d that can be relayed from the transceiver 2b (hereinafter referred to as relay information), for example, the receiver 3 first. Sends a frame containing the same tire pressure data that was sent to. As a result, the transceivers 2a and 2d detect the reception strength and the error rate when the frame from the transceiver 2b is received. The reception intensity and the error rate detected here are the first determination indexes. Then, each of the transceivers 2a and 2d stores these reception intensities and error rates in the frame in addition to the data related to the tire pressure sent from the transceiver 2b, and transmits them toward the receiver 3 as shown in FIG. 4F. do.

After that, when the receiver 3 receives the frames transmitted from the transceivers 2a and 2d, the receiver 3 detects the reception strength and the error rate when the frames from the transceivers 2a and 2d are received. .. Further, in the receiver 3, which of the transceivers 2a and 2d is the best repeater based on the first determination index and the second determination index with the reception intensity and the error rate detected here as the second determination index. Select. Here, the transceiver 2d is selected as the best repeater.

Then, as shown in FIG. 4G, the receiver 3 has selection data with the ID information of the one selected as the best repeater among the transceivers 2a and 2d, and data such as a response signal transmitted to the transceiver 2b. And send. Based on this, it is confirmed that the transceiver 2a is not the best repeater and the relay function is stopped, and the transceiver 2d is confirmed to be the best repeater and is shown in FIG. 4H. As shown, the data transmitted from the receiver 3 is transmitted to the transmitter / receiver 2b. As a result, data communication is relayed between the transmitter / receiver 2b and the receiver 3 with the transceiver 2d as the best repeater. After that, when the data communication between the transmitter / receiver 2b and the receiver 3 is completed, the communication end signal is sent from the receiver 3 to the transceiver 2b, and further, the end trigger is sent from the receiver 3 to the transceiver 2d. Will be sent. As a result, the transceiver 2d stops the relay function, and the relay between the transceiver 2b and the receiver 3 ends.

In this way, when the transmitted frame is not received by the receiver 3 for any of the transceivers 2a to 2d, the other transceivers 2a to 2d serve as repeaters, and the repeater and the receiver 3 are used. Performs data communication with. Hereinafter, each process executed by the control unit 22 of the transceivers 2a to 2d and the control unit 33 of the receiver 3 in order to perform such an operation will be described with reference to FIGS. 5 to 8.

First, with reference to FIG. 5, a process executed by the control unit 22 of the transceivers 2a to 2d during parking will be described.

First, as shown in step S100, the control unit 22 uses the timer 22b to start counting the first timer. The first timer referred to here measures the time corresponding to the periodic transmission cycle. The time measured by the first timer differs depending on whether the vehicle is running or parked, but here, the case where the vehicle is parked will be described. After that, the process proceeds to step S105, it is determined whether or not the first timer has reached the periodic transmission cycle Ta, and when the periodic transmission cycle Ta is reached, the process proceeds to step S110, and if not, the count of the first timer is counted until it is reached. continue. Then, when the process proceeds to step S110, the control unit 22 acquires a detection signal according to the tire air pressure and a detection signal according to the tire internal temperature from the sensing unit 21, and based on this, stores a frame in which data related to the tire air pressure is stored. It is created and transmitted from the bidirectional communication unit 23. At this time, if the transmitted frame is received by the receiver 3, the response signal including the reception completion signal and the unique information for error rate calculation together with the ID information of the transceivers 2a to 2d that can be received from the receiver 3. Will be sent.

Therefore, the process proceeds to step S115, and the control unit 22 starts counting the second timer using the timer 22b. The second timer referred to here measures the period in which it is assumed that the response signal will be transmitted from the receiver 3 after the frame transmission is performed. After that, if the control unit 22 proceeds to step S120 to determine whether or not the response signal from the receiver 3 is received, and receives the response signal before the second timer reaches the specified time Tb in step S125. , Step S130. Then, in step S130, the control unit 22 determines whether or not the communication status with the receiver 3 is good based on the response signal.

Here, the control unit 22 makes a negative determination when the response signal does not satisfy a certain condition, and makes an affirmative determination when the response signal satisfies a certain condition. When certain conditions are not satisfied, when the reception completion signal is not included, or when the reception strength of the response signal is less than or equal to the specified value, the unique information contained in the response signal and the transceivers 2a to 2d are stored. For example, the error rate when collating with the unique information that has been used is less than or equal to the threshold value. If an affirmative determination is made in step S130, the communication status with the receiver 3 is good, and the frame transmitted by itself is transmitted to the receiver 3. Therefore, the process proceeds to step S135 to proceed to the first timer and the first timer. 2 Reset the timer and end the process. Of the transceivers 2a to 2d in this way, those determined to have good communication with the receiver 3 can serve as repeaters. Therefore, the control unit 22 relays as shown in FIG. 8 to be described later. The device processing will be executed.

On the other hand, if a negative determination is made in step S130, the relay instruction processing shown in steps S140 and subsequent steps is executed. Specifically, in step S140, the control unit 22 resets the second timer, starts counting the third timer using the timer 22b, and then proceeds to step SS145 to transmit a relay trigger. When the relay trigger is transmitted, the third timer here will transmit the activation information of the relay function from the transceivers 2a to 2d which are the repeaters, that is, the data indicating that the relay is possible. It measures the expected period.

In step S150, the control unit 22 determines whether or not the activation information has been received, and if the activation information is received before the third timer reaches the specified time Tc in step S155, the process proceeds to step S160. Then, the control unit 22 transmits the same frame that was initially transmitted to the receiver 3 to the repeater. As a result, the repeater can exert the relay function, and it becomes possible to transmit the data related to the tire pressure to the receiver 3 in a better communication condition than when the frame is transmitted directly from the repeater to the receiver 3. .. After that, the frame transmitted via the repeater is received by the receiver 3, and finally the communication end signal indicating that the data communication is completed is sent from the receiver 3. Therefore, when the control unit 22 determines that the communication end signal has been received in step S165, the control unit 22 proceeds to step S170 to reset the first timer and the third timer and end the process. In this way, when the communication status between the transceivers 2a and 2d is not good, the transmitters and receivers 2a and 2d execute the relay instruction process and instruct the other transceivers 2a and 2d to act as repeaters. It can be put out and communicated with the receiver 3 through the repeater.

If the activation information does not arrive even after the specified time Tc has elapsed after the transmission of the relay trigger, it is assumed that the relay cannot be performed. In this case, the control unit 22 determines that the relay is not possible, proceeds to step S170, performs the above-mentioned processing, and promptly ends the communication with the receiver 3 and the other transceivers 2a to 2d. This is intended to reduce power consumption. Even in this case, since each of the above processes is repeated when the periodic transmission cycle Ta is reached again, the frame transmission from the transceivers 2a to 2d is performed again at that time, and the tire pressure is detected. Will be

Next, with reference to FIG. 6, a process executed by the control unit 33 of the receiver 3 while parking will be described.

First, as a reception process, the control unit 33 starts counting the fourth timer using the timer 33b in step S200, and then determines whether or not the fourth timer has reached the specified time Td in step S205. The specified time Td referred to here determines the frequency of tire pressure detection during parking, and tire pressure detection during parking is performed at each specified time Td.

If an affirmative determination is made in step S205, the process proceeds to step S210, and the control unit 33 starts counting the fifth timer using the timer 33b. The fifth timer referred to here determines the time limit for detecting the tire pressure during parking. When the count of the fifth timer is started, the process proceeds to step S215, and the control unit 33 determines whether or not the frame transmitted from the transceivers 2a to 2d has been received in step S215. If the frame has not been received, this determination is repeated until the fifth timer reaches the specified time Te in step S220 and times out. If a time-out occurs, the fifth timer is reset in step S280 to end the process.

Then, when the frame is received, the process proceeds to step S225, and it is determined whether or not the data stored in the frame includes the first determination index. If the first determination index is not included, the received frame is transmitted without the repeater, and if the first determination index is included, the received frame is transmitted via the repeater. It was conveyed. Therefore, if a negative determination is made in step S225, the process proceeds to step S230 and a response signal is transmitted. Specifically, the reception strength when the frame is received is obtained, and the response signal is created according to the reception strength. For example, if the reception strength is equal to or higher than the threshold value, it is assumed that reception is possible in good communication conditions, and a response signal including a reception completion signal is transmitted. Further, if the reception strength is equal to or less than the threshold value, it may not be possible to receive in good communication conditions. Therefore, a response signal including predetermined unique information between the transceivers 2a to 2d is used. Send. Based on this response signal, as described above, the transceivers 2a to 2d are performing the process of step S130 in FIG.

After that, the process proceeds to step S235, and it is determined whether or not the frame transmitted from all the transceivers 2a to 2d, that is, the data regarding the tire pressure for four wheels has been received, and the data regarding the tire pressure for four wheels is received. The process from step S215 is repeated until. Then, when the data regarding the tire pressures for the four wheels are gathered, the process proceeds to step S240, the fifth timer is reset, and the process is completed.

On the other hand, when the received frame contains the first determination index, the frame is transmitted via the repeater. In this case, the process proceeds to step S245, the fifth timer is reset, and then the process further proceeds to step S250. Then, in step S250, as the second determination index, the reception strength when the frame is received and the unique information stored in the frame are collated with the unique information stored in the memory 33a to calculate the error rate. This process is performed for each repeater when a plurality of frames including the first determination index are received, that is, when frames from a plurality of repeaters are received. After that, the process proceeds to step S255, and when frames from a plurality of repeaters have been received, the best repeater is selected from the first determination index and the second determination index in each repeater.

The best repeater is selected by the best repeater selection process. The best repeater selection process will be described with reference to FIG. 7.

The best repeater is selected based on the reception intensity and the error rate included in the first judgment index and the second judgment index. When the reception strength is larger than the first threshold value, it is a case where the communication condition is good without checking the error rate. Further, when the reception strength is larger than the second threshold value but smaller than the first threshold value, it may not be possible to say that the communication condition is good. In that case, check the error rate and it is good. It is necessary to confirm whether or not the communication status is good. Further, when the reception strength is smaller than the second threshold value, it cannot be said that the communication condition is good. Based on these, the best repeater will be selected.

Specifically, as shown in step S300 in FIG. 7, the control unit 33 has a repeater that satisfies the condition that the reception intensity in both the first determination index and the second determination index is larger than the first threshold value. Is determined. If an affirmative determination is made here, the process proceeds to step S305, and the repeater satisfying the conditions is set as the best repeater. When there are a plurality of repeaters that satisfy the conditions, the reception intensities included in the first determination index and the reception intensities included in the second determination index of each repeater are compared, and the largest one is the best. Set it as a repeater and end the process. At this time, if the repeater having the higher reception strength is different between the first judgment index and the second judgment index, for example, the one with the higher reception strength included in the second judgment index is set as the best repeater. .. In this case, which of the first determination index and the second determination index is prioritized is determined by the radio wave environment of the vehicle and the like. In terms of radio wave propagation characteristics, there are few obstacles to data communication between the transceivers 2a and 2d, so those who are considered to have many obstacles, such as between the transceivers 2a and 2d and the receiver 3. It is preferable to give priority to the characteristics. Therefore, the one with the higher reception strength of the second determination index is preferentially selected as the best repeater.

If a negative determination is made in step S300, the process proceeds to step S310, and the control unit 33 determines whether or not there is a repeater whose reception intensity in the first determination index is larger than the second threshold value. If an affirmative determination is made here, the process proceeds to step S315, and the control unit 33 selects a repeater whose reception intensity in the first determination index is larger than the second threshold value as the first best repeater. When there are a plurality of applicable repeaters, the control unit 33 selects the repeater having the higher reception strength in the first determination index as the first best repeater. If a negative determination is made here, the process proceeds to step S320, and the control unit 33 compares the error rates in the first determination index and selects the largest repeater as the first best repeater.

Further, the process proceeds to step S325, and the control unit 33 determines whether or not there is a repeater whose reception intensity in the second determination index is larger than the second threshold value. If an affirmative determination is made here, the process proceeds to step S330, and the control unit 33 selects a repeater whose reception intensity in the second determination index is larger than the second threshold value as the second best repeater. When there are a plurality of applicable repeaters, the control unit 33 selects the repeater having the higher reception strength in the second determination index as the second best repeater. If a negative determination is made here, the process proceeds to step S335, and the control unit 33 compares the error rates in the second determination index and selects the largest repeater as the second best repeater.

Then, the process proceeds to step S340, and the control unit 33 determines whether or not the first best repeater and the second best repeater match. Here, if they match, the process proceeds to step S350, and the control unit 33 selects the repeater selected as the first best repeater and the second best repeater as the final best repeater. If they do not match, the process proceeds to step S345, and the control unit 33 selects the second best repeater as the final best repeater in preference to the first best repeater. At this time, which of the first best repeater and the second best repeater is prioritized is determined by the radio wave environment in the vehicle and the like. In terms of radio wave propagation characteristics, there are few obstacles to data communication between the transceivers 2a and 2d, so those who are considered to have many obstacles, such as between the transceivers 2a and 2d and the receiver 3. It is preferable to give priority to the characteristics. Therefore, the second best repeater is prioritized over the first best repeater.

In this way, the repeater having a good communication condition is determined based on the first determination index and the second determination index, and the repeater having the best communication condition is selected as the best repeater. If the repeater with the best communication status is different between the first determination index and the second determination index, the best repeater with the best communication status in the second determination index is prioritized. It has been selected for.

In this way, in the receiver 3, the one that can relay communication most stably from the transceivers 2a to 2d is selected as the best repeater, and the information cannot be received in frames among the transceivers 2a to 2d. It is possible to establish stable communication by being transmitted to other things. Further, by determining the best repeater in this way, even if the radio wave propagation characteristics change due to the change in the position of each transceiver 2a to 2d, the one with the best communication condition is set as the best repeater each time. Can be selected. The selection of the best repeater may be made based on only one of the reception strength and the error rate. However, by selecting based on both of these, it is possible to select the best repeater among the transceivers 2a to 2d that can be relayed more stably.

As described above, the best repeater processing is completed, and the process proceeds to step S260 in FIG. Then, a response signal to be transmitted to the relay source is transmitted with data indicating that the repeater has become the best repeater, such as ID information of the transmitter / receiver 2a to 2d selected as the best repeater. For example, if the tire pressure of the relay source can be detected satisfactorily from the frame sent through the repeater, a response signal including the reception completion signal is transmitted, and if it cannot be detected satisfactorily, the tire pressure data is again obtained. Sends a response signal requesting. Then, in step S265, the control unit 33 communicates with the relay source via the best repeater and detects the tire pressure of the relay source. Since each repeater can grasp whether or not it has been selected as the best repeater based on the response signal transmitted from the receiver 3, if it is selected as the best repeater, the relay function is continued. If it is not selected, the relay function will be stopped. As a result, the relay function of the repeater, which is not the best repeater, can be stopped promptly, so that the power consumption can be reduced.

After that, the process proceeds to step S270, and the control unit 33 determines whether or not the communication with the relay source unit has ended, that is, whether or not the tire pressure of the relay source unit has been detected, and until a positive determination is made, step S265. Repeat the process of. Then, when the communication with the relay source unit is completed, the control unit 33 transmits a relay end signal to the relay source unit, then proceeds to step S275, and causes the repeater to transmit an end trigger indicating the end of the relay. As a result, the best repeater stops the relay function, and the communication between the relay source and the receiver 3 is terminated. At this time, by transmitting the end trigger from the receiver 3, the power consumption of the transceivers 2a to 2d can be reduced.

Subsequently, with reference to FIG. 8, the repeater processing executed by the control unit 22 of the transceivers 2a to 2d which can be a repeater will be described. As described above, this process is executed for the transceivers 2a to 2d that have completed the process of step S135 shown in FIG.

First, as shown in step S400, the control unit 22 starts counting the sixth timer using the timer 22b. The sixth timer referred to here measures the time corresponding to the periodic transmission cycle set during parking. After that, the process proceeds to step S405, the control unit 22 determines whether or not the relay trigger has been received, and if the sixth timer receives the relay trigger before the specified time Tf is reached in step S410, the process proceeds to step S415. ..

Here, the relay trigger may be issued when the frame is transmitted from the transceivers 2a to 2d other than itself. Therefore, if the relay trigger is not received for the time corresponding to the periodic transmission cycle, it is considered that the other transceivers 2a to 2d have not requested the relay. Therefore, if the relay trigger is not received before the 6th timer reaches the specified time Tf, a timeout occurs and the process proceeds to step S420, the 6th timer is reset, and the process ends.

Then, in step S415, the control unit 22 transmits activation information indicating that the relay function has been activated in accordance with the reception of the relay trigger, and then proceeds to step S425 to reset the sixth timer. When the activation information transmitted at this time is received by the relay source, the frame storing the data related to the air pressure and the unique information is transmitted again as shown in step S160 shown in FIG. Therefore, in step S430, the control unit 22 receives the relay information, that is, the frame transmitted from the relay source.

After that, the process proceeds to step S435, and the control unit 22 detects the reception intensity and the error rate when the frame from the relay source is received as the first determination index. The error rate is obtained by collating the predetermined unique information with the received unique information between the transceivers 2a and 2d. Then, the process proceeds to step S440, and the control unit 22 transmits to the receiver 3 a frame in which the reception intensity and the error rate are added to the data related to the tire pressure sent from the relay source, together with its own ID information.

Subsequently, the process proceeds to step S445, and the control unit 22 starts counting the seventh timer using the timer 22b. The seventh timer referred to here is set at a time when it is assumed that a response signal is returned from the receiver 3 when data is transmitted from the repeater to the receiver 3. After that, the process proceeds to step S450, if the control unit 22 determines whether or not the response signal from the receiver 3 has been received, and receives the response signal before the seventh timer reaches the specified time Tg in step S455. , Step S460. If it cannot be received, a timeout occurs and the process proceeds to step S465, the seventh timer is reset, and the process ends.

In step S460, the control unit 22 determines whether or not its own ID information is included in the response signal received from the receiver 3. As described above, the best repeater is selected by the receiver 3, and the ID information of the best repeater is attached to the response signal. Therefore, if the affirmative determination is made in step S460, since the repeater itself is the best repeater, the process proceeds to step S465 to relay the communication between the receiver 2 and the relay source. Then, in step S470, the control unit 22 continues relaying until the end trigger indicating that the communication with the relay source unit has ended is received from the receiver 3, and when the end trigger is received, the repeater process ends.

Further, if a negative determination is made in step S460, since the repeater itself is not the best repeater, the process proceeds to step S475 to reset the seventh timer, stop the relay function, and end the repeater process.

As described above, the tire pressure detection device of the present embodiment can detect the tire pressure even while parking. Then, if the receiver 3 on the vehicle body side cannot receive the data related to the tire pressure for any of the transceivers 2a to 2d, or if the reception condition is not good, the other transceivers 2a to 2d are used as repeaters. I am trying to tell the receiver 3. Thereby, for example, even when the transceivers 2a to 2d are in the position of Null, the data regarding the tire pressure can be reliably transmitted to the receiver 3.

Therefore, it is possible to provide a tire pressure detection device that can reliably receive data in the receiver 3 even while parking. Since the tire pressure can be detected while the vehicle is parked, the tire pressure can be detected without the user running the vehicle, and the tire pressure can be notified to the user earlier. For this reason, for example, when the tire pressure is low, the user can know it before the vehicle travels and can adjust the air pressure, so that it is possible to further improve the safety of vehicle travel. Become.

Specifically, when a frame storing data related to tire pressure is transmitted from the transceivers 2a to 2d, a response signal is transmitted from the receiver 3 in response to the transmission. If the response signal does not arrive from the receiver 3 within a certain period of time, it is assumed that the communication with the receiver 3 has not been performed well, and the communication with the receiver 3 via the repeater is performed. The relay trigger is transmitted from the relay source as it is done. Similarly, when the reception strength of the response signal is below the threshold value, or when the error rate when collating the unique information included in the response signal with the unique information stored in the transceivers 2a to 2d is below the threshold value. Also sends a relay trigger. As a result, the relay functions of the transceivers 2a to 2d, which are repeaters, can be activated, and communication between the relay source and the receiver 3 becomes possible via the repeater.

(Other embodiments)
The present invention is not limited to the above-described embodiment, and can be appropriately modified within the scope of the claims.

(1) For example, in the above embodiment, the receiver 3 mounted on the vehicle can detect the tire pressure even during parking when the start switch for enabling the vehicle to start, such as the IG switch, is turned off. The case of doing this is given as an example. However, this is just an example. For example, when a user uses a portable device such as a smartphone or a tool used in an automobile maintenance shop as a receiver, the tire pressure can be detected by the same method. That is, as shown in FIG. 9, the mobile device 7 functions as a receiver 3 and further as a display 4, and the result is displayed while the mobile device 7 detects the tire pressure. By doing so, the user does not need to turn on the start switch to display the display on the display 4, but the tire pressure detection result performed during parking can be detected in advance through the portable device 7. Can be known.

Further, when the tire pressure is detected through the portable device 7, the waiting time may be long until the frames are transmitted from the transceivers 2a to 2d in each periodic transmission cycle during parking.

Therefore, in this case, the mobile device 7 issues a start trigger to the transceivers 2a to 2d, and causes the transceivers 2a to 2d to transmit a frame including data related to the tire pressure even if the transmission / receiver cycle is not periodic. It is preferable to do so. Then, if any of the transmitters / receivers 2a to 2d that could not receive the frame in the mobile device 7, the other one that could receive the receiver is used as a repeater to relay the communication reliably. It becomes possible to convey the detection result of the tire pressure to the portable device 7. By doing so, it becomes possible to detect the tire pressure in a shorter time by using the portable device 7. Of course, transmitting the activation trigger to the transceivers 2a to 2d in this way so that the tire pressure can be detected regardless of the periodic transmission cycle is not limited to the case of using the portable device 7, and the receiver 3 is tired. The same is possible when transmitting air pressure.

If there are transceivers 2a to 2d that could not receive the activation trigger even if the start trigger is issued from the mobile device 7, the transmitter / receiver 2a to 2d include data on the tire pressure unless the periodic transmission cycle is reached. No frame transmission. Therefore, if there is a wheel for which the data on the tire pressure does not reach within a certain period of time, that fact may be displayed on the portable device 7.

(2) Further, in the above embodiment, when any one of the plurality of transceivers 2a to 2d transmits data regarding the tire pressure to the receiver 3, the communication condition with the receiver 3 is better than that of the other. Any form may be used as long as any of them is used as a repeater.

For example, in the above embodiment, the repeaters of the transmitters / receivers 2a to 2d are the repeaters having the most communication status among the repeaters capable of receiving the frames transmitted from the relay source. On the other hand, among the transceivers 2a to 2d that can be repeaters, the one closest to the repeater is selected as the repeater, and the one closest to the receiver 3 is selected as the repeater. May be. In this way, the repeater may be determined in advance, and if the repeater is selected in advance in this way, the power consumption required for selecting the repeater can be reduced.

Further, when the mobile device 7 is used, if the reception intensity is measured by the transceivers 2a to 2d when the radio wave is transmitted from the portable device 7, such as when the activation trigger is transmitted from the mobile device 7, each transceiver 2a The distance between ~ 2d and the mobile device 7 can be grasped. Therefore, even when the mobile device 7 is used, the one closest to the portable device 7 among the transceivers 2a to 2d can be selected as the repeater.

(3) As the transceivers 2a to 2d, those attached to the air injection valve have been described as an example, but they may be provided in other places. Further, the acceleration sensor 21c is not limited to the one that detects the acceleration in the tire radial direction.

As an example, as the transceivers 2a to 2d, a tire-side device called a tire mount sensor arranged on the back surface of the tire tread can also be applied. When the transmitters / receivers 2a to 2d are tire mount sensors, the detection signal output by the acceleration sensor 21c can also be used as a detection signal according to the magnitude of vibration in the tire tangential direction. In this case, the output voltage waveform that becomes the detection signal of the acceleration sensor 21c takes a maximum value at the start of ground contact when the portion of the tire tread corresponding to the arrangement portion of the acceleration sensor 21c begins to touch the ground as the tire rotates. Further, the output voltage waveform takes a minimum value at the end of ground contact when the portion of the tire tread corresponding to the arrangement portion of the acceleration sensor 21c is not grounded as the tire rotates. Therefore, it is possible to detect that the vehicle is running based on the detection signal of the acceleration sensor 21c.

In the case where the tire mount sensor is used as the transmitter / receiver 2a to 2d, the case where the acceleration sensor 21c detects the vibration in the tire tangential direction has been described, but even if the vibration in another direction, for example, the tire radial direction is detected, You can do the same.

Further, when the tire mount sensor is used as the transceivers 2a to 2d, a piezoelectric element can be used instead of the acceleration sensor 21c. Since the piezoelectric element generates an output voltage according to the stress, the output voltage having the same waveform as that of the acceleration sensor 21c is generated as the tire tread is deformed. Therefore, it is possible to detect that the vehicle 1 is running by using the output voltage of the piezoelectric element as a detection signal.

Further, when the tire mount sensor is used as the transmitter / receiver 2a to 2d, the tire pressure can be detected based on the detection signal of the acceleration sensor 21c or the piezoelectric element. That is, the length of the tire contact patch can be obtained by multiplying the period from the time when the detection signal of the acceleration sensor 21c or the piezoelectric element takes the maximum value to the time when the detection signal takes the minimum value by the tire rotation speed. Since the length of the tire contact patch changes according to the tire pressure, the tire pressure can be calculated based on the length of the tire contact patch. Therefore, when the tire pressure is calculated in this way, the acceleration sensor 21c or the piezoelectric element functions as a pressure sensor.

Further, also in the first embodiment, although the example of detecting the acceleration in the tire radial direction, that is, the acceleration in the centrifugal direction is shown by the acceleration sensor 21c, the acceleration in the tire tangential direction may be detected. Since the acceleration in the tire tangential direction also increases or decreases with the running of the vehicle 1, it is possible to detect whether the vehicle 1 is running or parked based on the acceleration.

(4) In the above first embodiment, the case where the tire pressure detection using the relay function is performed while parking is described, but it can also be carried out while the vehicle is running. However, the first timer in step S100 of FIG. 5 is set differently between when the vehicle is running and when the vehicle is parked. Therefore, while the vehicle is running, the first timer is set with a periodic transmission cycle shorter than that during parking, and frame transmission is repeatedly performed before the second timer measured in step S115 reaches the specified time Tb. .. Therefore, if the complaint is repeatedly transmitted while the vehicle is running, the data related to the tire pressure will be transmitted to the receiver 3 at some timing, and in that case, the relay function is not used while the vehicle is running. I'm done.

(5) Further, in each of the above embodiments, the portion of the tire pressure detection device provided on the vehicle body 6 side is comprehensively described as the receiver 3, but the receiver 3 is not necessarily one configuration. Is also good. For example, the antenna 31 and the bidirectional communication unit 32 that perform the reception function and the control unit 33 that performs the tire pressure detection function may be provided at different locations.

2a-2d Transceiver 3 Receiver 4 Display 5a-5d Wheels 7 Portable equipment 21 Sensing unit 22, 33 Control unit 23, 32 Two-way communication unit 24 Battery

Claims (14)

A tire having a transceiver (2a to 2d) provided on each of a plurality of wheels (5a to 5d) provided with tires, and a receiver (3, 7) for performing data communication between the transceivers. It is an air pressure detector
The transmitter / receiver has a sensing unit (21) having a pressure sensor (21a) that outputs a detection signal indicating the tire pressure of each of the plurality of wheels, and the tire pressure by processing the detection signal indicating the tire pressure. It has a first control unit (22) for creating data related to the tire pressure, and a first transmission / reception unit (23) for transmitting data related to the tire pressure.
The receiver has a second transmission / reception unit (32) for receiving data on the tire pressure, and a second control unit (33) for detecting the tire pressure based on the received data on the tire pressure. ,
The plurality of transceivers attached to each of the plurality of wheels can receive data regarding the tire pressure between the plurality of transceivers, and while the vehicle is parked, the other of the plurality of transceivers. At least one transceiver, which has better communication status with the receiver than the transceiver, acts as a repeater and transmits data regarding the tire pressure of the other transceiver received by communication to the receiver. ,
The first control unit causes the receiver to transmit data on the tire pressure at predetermined periodic transmission cycles (Ta) through the first transmission / reception unit.
When the receiver receives the data regarding the tire pressure, the receiver transmits a response signal.
When the response signal is not received or the response signal does not satisfy a certain condition, the first control unit determines that the communication condition with the receiver is not good, and relays itself as a relay source. As a device, a tire pressure detecting device that transmits a relay trigger instructing the transmitter / receiver to be the repeater to a transmitter / receiver different from the relay source among the plurality of transceivers . When the response signal does not satisfy a certain condition, the reception strength of the response signal is equal to or less than a specified value, or unique information is determined in advance between each of the plurality of transceivers and the receiver. The tire pressure detecting device according to claim 1 , wherein the response signal includes the unique information and the error rate obtained by collating the two unique information is equal to or less than the threshold value. When the first control unit of the different transceiver receives the relay trigger, the first control unit itself becomes the repeater and transmits the relay trigger to indicate that the relay function has been activated based on the relay trigger. The tire pressure detecting device according to claim 1 or 2 , which is transmitted to the relay source device. If the first control unit of the relay source unit does not receive the relay trigger during the specified period (Tc), it determines that the relay is not possible and terminates communication with the receiver and the different transmitter / receiver. The tire pressure detecting device according to claim 3 , wherein the data regarding the tire pressure is transmitted again after the time of the periodic transmission cycle. 3 . The described tire pressure detector. The repeater transmits data related to the tire pressure and unique information predetermined with the repeater.
When the repeater receives the data regarding the tire pressure and the unique information from the relay source, in addition to the data regarding the tire pressure, as a determination index, the reception intensity at the time of reception and the unique information are described in advance. The tire pressure detecting device according to claim 5 , wherein the error rate obtained by collating with the unique information determined with the repeater is transmitted to the receiver. In the receiver, the second control unit receives the data sent from the repeater, and when there are a plurality of the repeaters, the best repeater is the one with the best communication condition among the plurality of repeaters. The tire pressure detecting device according to claim 6 , wherein the response signal is transmitted with data indicating that the repeater has become the best repeater. The data sent from the repeater includes unique information predetermined between the repeater and the receiver.
The second control unit
The determination index included in the data sent from the repeater is used as the first determination index.
When the data regarding the tire pressure and the unique information from the repeater are received, as the second determination index, the reception strength at the time of reception, the unique information, and the unique information determined in advance between the repeater and the repeater are used. To find the error rate obtained by collating
The tire pressure detection device according to claim 7 , wherein the repeater having a good communication condition is selected as the best repeater based on the first determination index and the second determination index. The second control unit makes the second determination when the first determination index and the second determination index differ in the repeater having the best communication condition among the plurality of repeaters. The tire pressure detecting device according to claim 8 , wherein the index having the best communication condition is selected as the best repeater. Of the plurality of repeaters, the repeater that has not become the best repeater stops the relay function when it grasps that it has become the best repeater based on the response signal. 9. The tire pressure detecting device according to any one of 9. The tire pressure detecting device according to any one of claims 7 to 10 , wherein the best repeater transmits the response signal to the relay source when the response signal is received. One of claims 1 to 11 , when the second control unit receives data on the tire pressure of the repeater, it sends an end trigger indicating the end of relay to the repeater to stop the relay function. The tire pressure detection device according to one. The tire pressure detection device according to any one of claims 1 to 12 , wherein the receiver is an on-board unit (3) provided on a vehicle body . The tire pressure detection device according to any one of claims 1 to 12 , wherein the receiver is a portable device (7).

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