Tire air pressure monitoring system

Abstract

To provide a tire air pressure monitoring system that can suppress frame interference from each sensor unit and a wasteful electricity consumption in the sensor unit.SOLUTION: A tire air pressure monitoring system includes sensor units 2a to 2d and an on-vehicle device 3. An on-vehicle control unit 33 of the on-vehicle device 3 transmits a response signal from an on-vehicle transmission / reception unit 32 when a bi-directional command is indicated on a frame. When detecting an error in tire air pressure during travel of a vehicle 1, a sensor control unit 22 for the sensor units 2a to 2d shifts to a high frequency transmission mode in which the number of transmissions of the frame per unit time is increased compared to a case where the tire air pressure is normal, and transmits the frame indicating the bi-directional commands. Then, the sensor control unit 22 receives a response signal with a sensor transmission / reception unit 23 after transmitting the frame indicating the bi-directional command, and shifts to a normal transmission mode in which the number of transmissions of the frame per unit time is small compared with the high frequency transmission mode.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a tire pressure monitoring system (hereinafter also referred to as TPMS). [Background technology]

[0002] Conventionally, there is known a technology in which, when an abnormality in tire air pressure is detected, the frequency of transmitting frames including the tire air pressure from a sensor unit attached to the tire to an in-vehicle device is increased to notify the driver of the abnormality in tire air pressure (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2015-189460 A Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, the TPMS described in Patent Document 1 is configured to increase the frequency of frame transmission from the sensor unit until a predetermined fixed time has elapsed since an abnormality in tire pressure was detected. In this manner, the state in which the frequency of frame transmission from the sensor unit is increased continues even after the tire pressure abnormality is notified to the vehicle-mounted device. This is undesirable because it promotes interference between frames from each sensor unit and results in unnecessary power consumption in the sensor unit.

[0005] An object of the present disclosure is to provide a TPMS capable of suppressing interference between frames from each sensor unit and unnecessary power consumption in the sensor units. [Means for solving the problem]

[0006] The invention described in claim 1 is A tire pressure monitoring system for monitoring tire pressure of a vehicle (1), comprising: a plurality of sensor units (2a to 2d) provided corresponding to a plurality of wheels (5a to 5d) including tires, An on-board device (3) provided on a vehicle body (6), Each of the plurality of sensor units includes a pressure sensor (21a) that outputs a detection signal indicating tire pressure, a first control unit (22) that processes the detection signal indicating tire pressure to create a frame indicating one of a unidirectional command and a bidirectional command, and transmits the frame at a predetermined transmission interval, and a first transmitting / receiving unit (23) that transmits the frame and receives a response signal transmitted from the vehicle-mounted device, the vehicle-mounted device has a second transceiver unit (32) that receives frames and transmits response signals, and a second control unit (33) that detects tire air pressures based on detection data stored in the frames received by the second transceiver unit; the second control unit is configured to cause the second transceiver unit to transmit a response signal when a bidirectional command is indicated in the frame; The first control unit is when an abnormality in tire pressure is detected based on a detection signal indicating the tire pressure while the vehicle is traveling, the vehicle transitions to a high frequency transmission mode in which the number of frame transmissions per unit time is increased compared to when the tire pressure is normal, and causes the first transceiver to transmit a frame indicating a bidirectional command; When the first transceiver receives a response signal after transmitting a frame indicating a bidirectional command, the mode transitions to a normal transmission mode in which the number of frame transmissions per unit time is smaller than in the high frequency transmission mode.

[0007] In this way, if the sensor unit is configured to transmit frames to the vehicle-mounted device more frequently when the sensor unit detects an abnormality in tire pressure, the abnormality in tire pressure can be appropriately notified to the vehicle-mounted device. In particular, the TPMS disclosed herein is configured to transmit frames to the vehicle-mounted device less frequently when the sensor unit receives a response signal from the vehicle-mounted device. This reduces the frequency of frame transmission from the sensor unit after the vehicle-mounted device is notified of the abnormality in tire pressure, thereby suppressing interference between frames from each sensor unit and unnecessary power consumption in the sensor unit.

[0008] Note that the reference symbols in parentheses attached to each component indicate an example of the correspondence between the component and specific components described in the embodiments described below. [Brief description of the drawings]

[0009] [Figure 1] 1 is a schematic configuration diagram of a TPMS according to an embodiment. [Diagram 2] FIG. 2 is a block diagram showing a configuration of a sensor unit. [Diagram 3] FIG. 2 is a block diagram showing a configuration of an in-vehicle device. [Figure 4] 4 is a flowchart showing the flow of a control process executed by a sensor control unit. [Diagram 5] 10 is an explanatory diagram for explaining the frequency of frame transmission in the sensor unit when the tire air pressure is abnormal. FIG. [Figure 6] 4 is a flowchart showing a flow of a control process executed by an in-vehicle controller. [Figure 7] 10 is an explanatory diagram for explaining the relationship between a change in the radio wave level of a signal received by an in-vehicle device when a wheel rotates once and a sensitivity level at which the in-vehicle device can receive the signal. [Figure 8] 10 is an explanatory diagram for explaining a response signal transmitted from an in-vehicle device when a frame indicating a bidirectional command is received. FIG. [Figure 9]13 is an explanatory diagram for explaining a modified example of a frame transmission mode in the sensor unit when the tire air pressure is abnormal. FIG. [Figure 10] 11 is an explanatory diagram for explaining a modified example of a transmission mode of a response signal transmitted from an in-vehicle device when a frame indicating a bidirectional command is received. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] An embodiment of the present disclosure will be described with reference to Figs. 1 to 8. In this embodiment, an example will be described in which the TPMS of the present disclosure is applied to a vehicle 1 having four wheels 5a to 5d. Note that the upper direction of Fig. 1 corresponds to the front of the vehicle 1, the lower direction corresponds to the rear of the vehicle 1, and the left-right direction corresponds to the left-right direction of the vehicle 1. In addition, when the four wheels 5a to 5d are to be described separately, the four wheels 5a to 5d may be referred to as a left front wheel FL, a right front wheel FR, a left rear wheel RL, and a right rear wheel RR.

[0011] 1 includes sensor units 2a to 2d, an in-vehicle device 3, and a display device 4. The display device 4 may be configured as a device dedicated to the TPMS, or may be configured as a device shared with a meter, a navigation system, etc.

[0012] As shown in FIG. 1, the sensor units 2a to 2d are attached to the wheels 5a to 5d of the vehicle 1, detect the air pressure and temperature of the tires attached to the wheels 5a to 5d, and transmit the detection signal data indicating the detection result stored in a frame. The vehicle-mounted device 3 is attached to the vehicle body 6 of the vehicle 1, receives the frame transmitted from the sensor units 2a to 2d, and detects the tire air pressure based on the detection signal stored therein. The sensor units 2a to 2d and the vehicle-mounted device 3 according to this embodiment are capable of two-way communication, which allows not only communication from the sensor units 2a to 2d to the vehicle-mounted device 3, but also vice versa. Therefore, the sensor units 2a to 2d can request the vehicle-mounted device 3 to transmit a response signal. Various forms of two-way communication can be applied. Hereinafter, the detailed configurations of the sensor units 2a to 2d and the vehicle-mounted device 3 will be described with reference to FIG. 2 and FIG. 3.

[0013] 2, the sensor units 2a to 2d are configured to include a sensing section 21, a sensor control section 22, a sensor transmitting / receiving section 23, a battery 24, and an antenna 25, and each section is driven based on power supply from the battery 24. In this embodiment, the sensor control section 22 corresponds to a "first control section," and the sensor transmitting / receiving section 23 corresponds to a "first transmitting / receiving section."

[0014] The sensing unit 21 includes, for example, a pressure sensor 21a, a temperature sensor 21b, and an acceleration sensor 21c. The pressure sensor 21a outputs a detection signal corresponding to the tire pressure. The temperature sensor 21b outputs a detection signal corresponding to the temperature inside the tire. The acceleration sensor 21c outputs a detection signal corresponding to the acceleration generated with the rotation of the tire, for example, the radial acceleration of each of the wheels 5a to 5d. 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 sensor control unit 22. Among these, the detection signal corresponding to the tire pressure and the detection signal corresponding to the temperature inside the tire are used to detect the tire pressure, and the detection signal corresponding to the acceleration is used to detect that the vehicle 1 is traveling.

[0015] The sensor control unit 22 is configured by a microcomputer equipped with a CPU, ROM, RAM, I / O, etc., and executes a predetermined process according to a program stored in the ROM, etc. The sensor control unit 22 stores ID information including sensor unit-specific identification information for identifying each of the sensor units 2a to 2d and vehicle-specific identification information for identifying the vehicle itself.

[0016] The sensor control unit 22 receives the detection signal output from the sensing unit 21, processes it, and processes it as necessary. The sensor control unit 22 stores data indicating the detection results of the tire pressure and the tire internal temperature used for tire pressure detection in a frame together with ID information of each of the sensor units 2a to 2d, and transmits the frame to the sensor transmitting / receiving unit 23 at a predetermined regular transmission interval. The sensor control unit 22 is also configured to determine whether or not a tire pressure drop has occurred in the frame, and the data is sent to the sensor transmitting / receiving unit 23. For example, the sensor control unit 22 compares the amount of change in the tire pressure with a predetermined specified amount of change, and if the amount of change in the tire pressure exceeds the specified amount of change, it determines that the tire pressure is abnormal, and stores data indicating that the tire pressure is abnormal in the frame.

[0017] In the following description, data indicating the detection results of tire pressure and internal tire temperature, and data indicating the presence or absence of an abnormality in tire pressure are referred to as detection data related to tire pressure. However, the detection data related to tire pressure does not necessarily need to include all of these data, and may include only one of the data indicating the detection results of tire pressure and internal tire temperature, and data indicating the presence or absence of an abnormality in tire pressure.

[0018] The sensor control unit 22 uses the detection result of the acceleration to determine whether the vehicle 1 is in a normal running state. For example, when the acceleration sensor 21c outputs a detection signal corresponding to the radial acceleration of each wheel 5a to 5d, the sensor control unit 22 removes the gravitational acceleration component from the detection signal and extracts the centrifugal acceleration component. The change in the centrifugal acceleration component indicates the rotation state of the tire. For this reason, the sensor control unit 22 detects that the vehicle 1 is in a normal running state based on the occurrence of the centrifugal acceleration component. In the case of this embodiment, the sensor control unit 22 determines that the vehicle 1 is in a normal running state if the centrifugal acceleration is equal to or greater than a certain value, and that the vehicle 1 is in a slow running / stopped state if it is less than the certain value. For example, the centrifugal acceleration occurring during low-speed running (slow running state) of about 20 km / h is set as a constant value. During low-speed running at this level, even if the frequency of tire pressure detection decreases, there is little danger, so the vehicle is considered to be in a slow running / stopped state even during low-speed running.

[0019] Furthermore, when the centrifugal acceleration is equal to or greater than a certain value and the vehicle 1 is determined to be in a normal driving state, the sensor control unit 22 basically performs one-way communication in which only frame transmission from the sensor units 2a to 2d is performed periodically. In this case, the sensor control unit 22 stores a one-way command in the frame and transmits the frame.

[0020] However, even in a normal driving state, when the sensor control unit 22 determines that there is an abnormality in the tire air pressure, it performs two-way communication to request a response from the vehicle-mounted device 3 in addition to transmitting frames from the sensor units 2a to 2d. In this case, the sensor control unit 22 stores a two-way command in a frame and transmits the frame.

[0021] The sensor transmitting / receiving unit 23 functions as an output unit that transmits the frame sent from the sensor control unit 22 to the vehicle-mounted device 3 as RF radio waves through the antenna 25. The sensor transmitting / receiving unit 23 also functions as an input unit that demodulates the response signal from the vehicle-mounted device 3 and sends it to the sensor control unit 22. The sensor transmitting / receiving unit 23 is described here as a single configuration, but the transmitting unit and the receiving unit may be configured separately. Here, the sensor transmitting / receiving unit 23 transmits and receives using radio waves in the UHF band of, for example, 300 MHz or 400 MHz, but the frequency band of radio waves to be used can be selected arbitrarily. The process of sending a signal from the sensor control unit 22 to the sensor transmitting / receiving unit 23 is performed according to the above program.

[0022] Battery 24 supplies power to sensing unit 21, sensor control unit 22, etc., and the power supply from battery 24 is used to collect data related to tire pressure in sensing unit 21 and to perform various calculations in sensor control unit 22. Here, the power supply unit is configured with battery 24, but the power supply unit can also be configured with a power generation device, a storage battery, etc., in addition to battery 24. When the power supply unit is configured with a power generation device, there are fewer problems with battery life compared to when battery 24 is used, but since it is difficult to generate large amounts of power, the issue of reducing power consumption is similar to when battery 24 is used.

[0023] The sensor units 2a to 2d thus configured are attached to the air injection valves of the wheels 5a to 5d, for example, and are arranged so that the sensing units 21 are exposed to the inside of the tires. As a result, the sensor units 2a to 2d detect the tire air pressure of the corresponding wheels and transmit frames at predetermined timing through the antennas 25 provided in the sensor units 2a to 2d.

[0024] 3, the in-vehicle device 3 includes an antenna 31, an in-vehicle transmitting / receiving unit 32, and an in-vehicle control unit 33. In this embodiment, the in-vehicle transmitting / receiving unit 32 corresponds to a "second transmitting / receiving unit", and the in-vehicle control unit 33 corresponds to a "second control unit".

[0025] The antenna 31 is provided on the vehicle body 6, and serves to receive frames sent from the sensor units 2a to 2d, and to transmit response signals to the sensor units 2a to 2d when a bidirectional command is included in the received frame. Here, the antenna 31 is configured as a single common antenna that generally performs transmission and reception with the sensor units 2a to 2d, but it may be provided for each of the sensor units 2a to 2d, or may be configured as separate antennas for transmission and reception.

[0026] When the frame transmitted from each of the sensor units 2a to 2d is received by the antenna 31, the in-vehicle transmitting / receiving unit 32 functions as an input unit that demodulates the frame and sends it to the in-vehicle control unit 33. The in-vehicle transmitting / receiving unit 32 also functions as an output unit that transmits a response signal to each of the sensor units 2a to 2d in accordance with an instruction from the in-vehicle control unit 33. Here, the in-vehicle transmitting / receiving unit 32 is configured to be capable of both transmission and reception, but the transmitting unit and the receiving unit may each be configured separately.

[0027] The on-board control unit 33 is configured by a microcomputer equipped with a CPU, a memory M including a ROM and a RAM, an I / O, etc., and executes various processes according to programs stored in the memory M. Specifically, the on-board control unit 33 operates based on the power supply from a battery (not shown), controls frame reception and response transmission in the on-board transceiver unit 32, and executes various processes related to tire pressure detection.

[0028] For example, the in-vehicle control unit 33 performs various processes related to tire pressure detection, such as an alarm determination process, as a prescribed process of the TPMS.

[0029] In the warning determination process, various signal processing and calculations are performed based on the detection data related to the tire pressure stored in the frame received from the in-vehicle transmitting / receiving unit 32, and an electrical signal corresponding to the tire pressure is output to the display device 4. In the warning determination process, the tire pressure is compared with a predetermined warning threshold, and if it is detected that the tire pressure has dropped below the predetermined warning threshold, a signal to that effect is output to the display device 4. In addition, if the sensor units 2a to 2d are detecting tire pressure, it is also possible to notify the display device 4 of the occurrence of a drop in tire pressure based on data indicating the occurrence of a drop in tire pressure contained in the received frame.

[0030] Furthermore, after the vehicle-mounted control unit 33 obtains the tire pressure of each of the four wheels 5a to 5d, the vehicle-mounted control unit 33 can output the tire pressure to the display device 4 in association with each wheel 5a to 5d. The memory M of the vehicle-mounted control unit 33 stores ID information of the sensor units 2a to 2d arranged on each wheel 5a to 5d in association with the position of each wheel 5a to 5d. Therefore, the vehicle-mounted control unit 33 can recognize which of the wheels 5a to 5d the sensor unit 2a to 2d is attached to by checking the received frame against the ID information stored in the frame, and can identify the wheel 5a to 5d whose tire pressure has decreased. Based on this, when a decrease in tire pressure occurs, the vehicle-mounted control unit 33 identifies the wheel 5a to 5d whose tire pressure has decreased and outputs it to the display device 4. Also, even if a decrease in tire pressure does not occur, the obtained tire pressure may be output to the display device 4 in association with each wheel 5a to 5d.

[0031] In this manner, a drop in tire pressure of any one of the four wheels 5a to 5d or the tire pressures of each of the four wheels 5a to 5d is transmitted to the display device 4.

[0032] 1, the display device 4 is disposed in a location visible to the driver, and is constituted by, 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 dropped is sent from the vehicle-mounted control unit 33 in the vehicle-mounted device 3, the display device 4 notifies the driver of the drop in tire pressure by displaying the signal. Alternatively, when the tire pressure of each of the four wheels 5a to 5d is transmitted from the vehicle-mounted device 3, the display device 4 displays the tire pressure corresponding to each wheel 5a to 5d.

[0033] In this embodiment, the display device 4 is used as a warning unit that warns the driver. However, in addition to a device that issues a visual warning like the display device 4, a device that issues an audible warning, such as a speaker, may also be used as the warning unit.

[0034] The vehicle-mounted device 3 configured as above is connected to other vehicle-mounted devices including a host ECU 7 and a DCM 8 via a communication network, such as a CAN, built in the vehicle 1. The host ECU 7 is a control device that controls, for example, the steering, acceleration, deceleration, etc. of the vehicle 1. The DCM 8 is a vehicle communication module that is capable of communicating information with a communication center via wireless communication. CAN is an abbreviation for Controller Area Network. Also, DCM is an abbreviation for Data Communication Module.

[0035] The vehicle-mounted device 3 can, for example, obtain other sensor information such as wheel speed pulses corresponding to the wheel angles of the wheels 5a to 5d from the host ECU 7, and transmit detection data related to tire pressure to devices other than the sensor units 2a to 2d. The vehicle-mounted device 3 can also receive requests from information terminals such as tablets and smartphones via a communication center or the like using the DCM 8, and transmit detection data related to tire pressure to the information terminals.

[0036] The TPMS configured as described above is designed so that if an abnormal decrease in tire air pressure occurs in any of the wheels 5a to 5d while the vehicle 1 is traveling, the abnormality in tire air pressure is quickly notified to the vehicle-mounted device 3 by frequently transmitting frames from the sensor units 2a to 2d.

[0037] Such a technique can be realized by increasing the frequency of frame transmission from the sensor units 2a to 2d to the vehicle-mounted device 3 until a certain period of time has elapsed since an abnormality in the tire air pressure has been detected.

[0038] However, in this case, frequent frame transmission continues even after the tire pressure abnormality has been notified to the vehicle-mounted device 3, which increases interference between the frames transmitted from each of the sensor units 2a to 2d and wastes the batteries 24 of each of the sensor units 2a to 2d.

[0039] In addition, the radio wave level of the signal received by the vehicle-mounted device 3 varies among the sensor units 2a to 2d depending on the positional relationship between the vehicle-mounted device 3 and the tires, the output difference between the sensor units 2a to 2d, and the like. For this reason, for example, if a unit that transmits frames frequently among the sensor units 2a to 2d can transmit a signal with the highest radio wave level to the vehicle-mounted device 3, there is a high possibility that the signal from the unit and the signals from other units that are mixed with the signal from the unit will not be transmitted to the vehicle-mounted device 3. In the worst case, the vehicle-mounted device 3 may not be able to receive signals from other units for a period until the high-frequency frame transmission is completed. In this case, if tire pressure abnormalities occur in succession in multiple sensor units 2a to 2d, the signals from the units will not be transmitted to the vehicle-mounted device 3 easily.

[0040] In consideration of these, the TPMS of this embodiment is configured to reduce the frequency of frame transmission from each of the sensor units 2a to 2d after the vehicle-mounted device 3 is notified of an abnormality in tire air pressure.

[0041] Specifically, when the sensor control unit 22 detects an abnormality in tire pressure based on a detection signal indicating the tire pressure while the vehicle 1 is traveling, the sensor control unit 22 transitions to a high-frequency transmission mode in which the number of frame transmissions per unit time is increased compared to when the tire pressure is normal. In the high-frequency transmission mode, the sensor control unit 22 causes the sensor transceiver unit 23 to transmit a frame indicating a bidirectional command instead of a unidirectional command. Then, when the sensor control unit 22 receives a response signal from the in-vehicle device 3 after transmitting the frame indicating the bidirectional command, the sensor control unit 22 transitions to a normal transmission mode in which the number of frame transmissions per unit time is reduced compared to the high-frequency transmission mode.

[0042] A specific tire-side processing flow executed by the sensor control unit 22 of this embodiment will be described below with reference to Fig. 4. The processing shown in Fig. 4 is executed by the sensor control unit 22 every time the vehicle 1 enters a normal driving state.

[0043] As shown in Fig. 4, first, in step S100, it is determined whether the amount of change in tire pressure is within a specified amount of change. The amount of change in tire pressure here is the difference between the value detected this time by the sensor units 2a to 2d and the value detected up to the previous time. The specified amount of change is set to the amount of change in tire pressure expected when an abnormality such as a flat tire occurs.

[0044] If the determination in step S100 is affirmative, the process proceeds to step S105, where the state of the reception flag indicating the history of reception of a response signal from the vehicle-mounted device 3 is set to "0." The sensor control unit 22 in this example sets the initial state of the reception flag to "0," and sets the state of the reception flag to "1" when a response signal is received from the vehicle-mounted device 3.

[0045] Then, the process proceeds to step S110, where a frame containing detection data on tire pressure according to the detection results of the pressure sensor 21a and the temperature sensor 21b is transmitted as tire information. At this time, a one-way command is stored in the frame, since the frame is transmitted when the tire pressure is determined to be normal while the vehicle 1 is traveling. Then, the process proceeds to step S115, where a timer is set to a normal interval of, for example, every 60 seconds, so that frame transmission is performed at regular transmission intervals set while the vehicle 1 is traveling.

[0046] Next, the process proceeds to step S120, where it is determined whether the acceleration is equal to or greater than a certain value. This process is repeated until the timer set to the normal interval in step S115 expires, and it is confirmed that the vehicle 1 is continuing to travel. Then, when the timer expires in step S125, the process returns to step S100.

[0047] As a result, if the tire pressure is determined to be normal while the vehicle 1 is traveling, a frame containing a one-way command is transmitted at a predetermined cycle set as a normal interval, as shown in the upper part of Fig. 5. If a negative determination is made in step S120, the state of the reception flag is set to the initial state of "0" in step S130, and this process ends.

[0048] On the other hand, if the determination in step S100 is negative, it is determined that the tire air pressure is abnormal, and the flow proceeds to step S 135. In this step S135, it is determined whether the state of the reception flag is "1".

[0049] If the state of the reception flag is "1", it means that a response signal has already been received from the vehicle-mounted device 3, so the process proceeds to step S110, where a frame containing the detection data regarding the tire pressure and the one-way command is transmitted as tire information.

[0050] If the reception flag is set to "0", the process proceeds to step S140, where a frame containing the tire pressure-related detection data and the two-way command is transmitted as tire information. This frame may or may not contain information indicating an abnormality in tire pressure.

[0051] Here, after transmitting a frame indicating a bidirectional command, the sensor units 2a to 2d enter a reception waiting state for receiving a response signal from the vehicle-mounted device 3 until a predetermined reception waiting time has elapsed. Note that the reception waiting time is set in consideration of the time required from transmitting a frame indicating a bidirectional command from the sensor units 2a to 2d until receiving a response signal from the vehicle-mounted device 3.

[0052] After transmitting the frame indicating the bidirectional command, the process proceeds to step S145, where it is determined whether or not a response signal has been received from the vehicle-mounted device 3. In this determination, if a response signal has been received from the vehicle-mounted device 3, a positive determination is made, and if a response signal has not been received, a negative determination is made.

[0053] If a response signal has been received, the process proceeds to step S150, where the state of the reception flag is set to "1." After that, the process returns to step S115, where the timer is set to a normal interval of, for example, every 60 seconds, so that frame transmission is performed at each regular transmission cycle that is set while driving. In other words, when the sensor control unit 22 receives a response signal at the sensor transceiver unit 23 after transmitting a frame indicating a bidirectional command, the sensor control unit 22 transitions to a normal transmission mode in which the number of frame transmissions per unit time is smaller than in the high-frequency transmission mode.

[0054] On the other hand, if a response signal has not been received, the process proceeds to step S155. In this step S155, the timer is set to an abnormality interval that is shorter than the normal interval, for example, every 10 seconds, so that the number of frame transmissions per unit time is greater than when the tire pressure is normal.

[0055] Next, the process proceeds to step S120, where it is determined whether the acceleration is equal to or greater than a certain value. This process is repeated until the timer set for the abnormality interval in step S155 times out, and it is confirmed that the vehicle 1 is continuing to travel. Then, when the timer times out in step S125, the process returns to step S100 again.

[0056] As a result, if the tire pressure is determined to be abnormal while the vehicle 1 is traveling, a frame containing a bidirectional command is transmitted at a predetermined period set as an abnormality interval, as shown in the lower part of Fig. 5. In other words, when the sensor control unit 22 detects an abnormality in the tire pressure while the vehicle 1 is traveling, the sensor control unit 22 transitions to a high-frequency transmission mode in which the number of frame transmissions per unit time is increased compared to when the tire pressure is normal, and transmits a frame indicating a bidirectional command. If a negative determination is made in step S120, the state of the reception flag is set to the initial state of "0" in step S130, and this process is terminated.

[0057] Next, the operation of the in-vehicle device 3 will be described with reference to a vehicle-side processing flow executed by the in-vehicle control unit 33 with reference to Fig. 6. The processing shown in Fig. 6 is executed by the in-vehicle control unit 33 when a start switch of the vehicle 1 is turned on. The start switch corresponds to, for example, an ignition switch in a vehicle equipped with an engine, and corresponds to a power switch in an electric vehicle.

[0058] 6, first, in step S200, a reception process for receiving various signals is started, whereby frames transmitted from the sensor units 2a to 2d are received.

[0059] Next, when a frame is received from each of the sensor units 2a to 2d, the process proceeds to step S205, where it is determined whether or not a command has been received, that is, whether or not a unidirectional command or a bidirectional command contained in the frame transmitted from the sensor units 2a to 2d has been received.

[0060] If either a unidirectional command or a bidirectional command has been received, the process proceeds to step S210, where it is determined whether the received command is a bidirectional command. If a frame transmitted from the sensor units 2a to 2d is received at the regular transmission cycle set in the normal interval, a unidirectional command is included, so a negative determination is made in step S210, and the process proceeds to step S215. In step S215, it is determined whether the ID information of the sensor unit 2a to 2d that transmitted the frame including the unidirectional command is registered in the memory M as an abnormality sensor ID indicating an abnormality in tire pressure.

[0061] If the ID information of the sensor units 2a to 2d that transmitted the frame including the one-way command is registered in the memory M as an abnormality occurring sensor ID, the process proceeds to step S220, where the abnormality occurring sensor ID registered in the memory M is cleared. Here, it is the ID information of the sensor units 2a to 2d that transmitted the frame including the one-way command that is cleared.

[0062] If the ID information of the sensor unit 2a to 2d that transmitted the frame including the one-way command is not registered in the memory M as an abnormality occurring sensor ID, the process skips step S220 and proceeds to step S225. Note that the process also proceeds to step S225 if a negative judgment is made in the judgment process of step S205.

[0063] In step S225, the above-mentioned alarm determination and display on the display device 4 are performed as the prescribed processing of the TPMS, and then the process proceeds to step S230. In step S230, it is determined whether the start switch of the vehicle 1 is on or not, and if the start switch is on, the process returns to step S205, and if the start switch is off, the process proceeds to step S235, where the signal reception process is stopped and this process is exited.

[0064] On the other hand, if a frame transmitted from the sensor units 2a to 2d is received at each transmission period set in the abnormality interval, the frame contains a bidirectional command, so that a positive determination is made in step S210 and the process proceeds to step S240.

[0065] In step S240, the current wheel angle of the sensor unit 2a-2d that transmitted the frame is stored as a reference angle in the memory M. The wheel angle is a rotation angle of each wheel 5a-5d about the axle, and is obtained based on the wheel speed pulse of each wheel 5a-5d obtained from the host ECU 7.

[0066] Thereafter, the process proceeds to step S245, and waits until the current wheel angle of the sensor unit 2a-2d that transmitted the frame becomes the reference angle stored in the memory M. When the current wheel angle of the sensor unit 2a-2d that transmitted the frame becomes the reference angle, the process proceeds to step S250, and the frame reception process is temporarily stopped, and a response signal is transmitted. That is, the in-vehicle control unit 33 causes the in-vehicle transmitting / receiving unit 32 to transmit a response signal at the timing when the wheel angle of the tire to which the sensor unit 2a-2d that transmitted the frame indicating the bidirectional command is attached becomes the reference angle stored in the memory M. The response signal is a response signal to the frame indicating the bidirectional command.

[0067] Thereafter, the process proceeds to step S255, where it is determined whether or not the ID information of the sensor units 2a to 2d that have transmitted the frame including the bidirectional command has been registered in the memory M as an abnormality occurring sensor ID.

[0068] If the ID information of the sensor units 2a to 2d that transmitted the frame including the bidirectional command is not registered in the memory M as an abnormality occurring sensor ID, proceed to step S260. In step S260, the ID information of the sensor units 2a to 2d that transmitted the frame including the bidirectional command is registered in the memory M as an abnormality occurring sensor ID, and proceed to step S270.

[0069] On the other hand, if the ID information of the sensor unit 2a-2d that transmitted the frame including the bidirectional command has already been registered in the memory M as an abnormality-occurring sensor ID, the process proceeds to step S265, where the vehicle-mounted transmitting / receiving unit 32 transmits a response signal. In other words, if the vehicle-mounted control unit 33 receives a frame indicating a bidirectional command two or more times from the same sensor unit 2a-2d, it is highly likely that the first response signal did not reach the sensor unit 2a-2d, so the vehicle-mounted control unit 33 transmits the response signal multiple times.

[0070] After the process of step S260 or step S265 is performed, the process proceeds to step S270, where the reception process of various signals is resumed, and then the process proceeds to step S225, where the above-mentioned TPMS regulation process is performed.

[0071] The TPMS of the present embodiment described above enables two-way communication between the sensor units 2a-2d provided on the wheels 5a-5d and the vehicle-mounted device 3 provided on the vehicle body 6. The vehicle-mounted control unit 33 of the vehicle-mounted device 3 is configured to transmit a response signal from the vehicle-mounted transceiver 32 when a two-way command is indicated in a frame transmitted from each of the sensor units 2a-2d. When the sensor control unit 22 of each of the sensor units 2a-2d detects an abnormality in tire pressure while the vehicle 1 is traveling, the sensor control unit 22 shifts to a high-frequency transmission mode and transmits a frame indicating a two-way command from the sensor transceiver 23. When the sensor control unit 22 receives a response signal at the sensor transceiver 23 after transmitting a frame indicating a two-way command, the sensor control unit 22 shifts to a normal transmission mode and transmits a frame indicating a one-way command from the sensor transceiver 23.

[0072] In this way, if the sensor units 2a to 2d are configured to transmit frames more frequently to the vehicle-mounted device 3 when they detect an abnormality in tire pressure, the abnormality in tire pressure can be properly communicated to the vehicle-mounted device 3.

[0073] In particular, the TPMS of this embodiment is configured to reduce the frequency of frame transmission from the sensor units 2a to 2d to the vehicle-mounted device 3 when the sensor units 2a to 2d receive a response signal from the vehicle-mounted device 3. This makes it possible to suppress interference of frames from the sensor units 2a to 2d and to suppress unnecessary power consumption in the sensor units 2a to 2d.

[0074] In addition, the TPMS of this embodiment has the following features.

[0075] (1) Since the sensor units 2a to 2d are attached to the tires, the radio wave level of the signal transmitted from the sensor units 2a to 2d to the vehicle-mounted device 3 varies greatly depending on the wheel angle. The radio wave level of the signal transmitted from the vehicle-mounted device 3 to the sensor units 2a to 2d also varies similarly due to reversibility. For example, the radio wave level of the signal transmitted from the sensor unit 2a to the vehicle-mounted device 3 changes as shown by the solid line in FIG. 7. The angle in FIG. 7 indicates the angle at which the sensor unit 2a exists. In FIG. 7, the angle when the sensor unit 2a is located at the uppermost position is set to 0 degrees, and the existence angle is gradually increased counterclockwise from there. The dashed line in the figure indicates the reception sensitivity level at which the vehicle-mounted device 3 can receive the signal.

[0076] As shown in Fig. 7, when the sensor unit 2a rotates, the radio wave level of the signal received by the vehicle-mounted device 3 changes according to the angle. There are multiple angles at which the received power level is lower than the reception sensitivity level indicated by the dashed line, i.e., communication is not established. For example, assume that the vehicle-mounted device 3 receives a bidirectional command frame when the sensor unit 2a is at a position of 150 degrees. In this case, if the sensor unit 2a is at around 165 degrees or 210 degrees at the timing when the vehicle-mounted device 3 transmits a response signal, the sensor unit 2a may fail to receive the response signal.

[0077] On the other hand, if the wheel angle is such that the vehicle-mounted device 3 can receive the frame from the sensor unit 2a, it is considered that the sensor unit 2a can easily receive the signal from the vehicle-mounted device 3. Taking this into consideration, when the vehicle-mounted control unit 33 of this embodiment receives a frame indicating a bidirectional command, it stores the wheel angle of the tire to which the sensor unit 2a to 2d that transmitted the frame is attached as a reference angle in the memory M. Specifically, the vehicle-mounted control unit 33 identifies the sensor unit 2a to 2d that transmitted the frame from the ID information included in the frame, and stores the ID of the sensor unit 2a to 2d in the memory M in a state in which the ID and the reference angle are associated with each other. Then, the vehicle-mounted transmitting / receiving unit 32 transmits a response signal at a timing when the wheel angle of the tire to which the sensor unit 2a to 2d that transmitted the frame is attached becomes the reference angle again. This makes it easier for the sensor units 2a to 2d to receive the response signal transmitted from the vehicle-mounted device 3 after the vehicle-mounted device 3 is notified of an abnormality in the tire air pressure, and the frequency of frame transmission by the sensor units 2a to 2d can be appropriately reduced.

[0078] (2) When the in-vehicle control unit 33 receives a frame indicating a bidirectional command, it causes the in-vehicle transmitting / receiving unit 32 to transmit a response signal multiple times. In this way, if the response signal from the in-vehicle device 3 is transmitted multiple times to the sensor units 2a to 2d, the probability that the response signal will be received by the sensor units 2a to 2d can be increased.

[0079] (3) However, simply increasing the frequency of signal transmission from the vehicle-mounted device 3 would result in restrictions on reception of frames from each of the sensor units 2a to 2d at the vehicle-mounted device 3. If the frequency of signal transmission from the vehicle-mounted device 3 is low, it would become difficult for each of the sensor units 2a to 2d to receive signals from the vehicle-mounted device 3.

[0080] Taking these factors into consideration, the in-vehicle control unit 33 of this embodiment, as shown in Fig. 8, causes the in-vehicle transmitting / receiving unit 32 to transmit a response signal once when it is the first time that a frame indicating a bidirectional command is received from the sensor units 2a to 2d. When a frame indicating a bidirectional command is received two or more times from the same sensor unit 2a to 2d, it causes the in-vehicle transmitting / receiving unit 32 to transmit a response signal multiple times.

[0081] In this way, when receiving the first frame, it is desirable to transmit a response signal only once and quickly return to a receiving state so that it is easy to receive signals from other units. Also, when receiving a second or more frames from the same sensor units 2a to 2d, it is desirable to transmit a response signal multiple times in order to prioritize stopping the high-frequency transmission of the sensor units 2a to 2d as early as possible. This can increase the probability of receiving a response signal from the sensor units 2a to 2d.

[0082] (4) The appropriate tire pressure varies depending on the vehicle model, tire size, etc. For this reason, if it is attempted to determine whether the tire pressure is normal or abnormal based on the absolute tire pressure value, it is necessary to store a unique threshold value, etc. according to the vehicle model, tire size, etc. for each of the sensor units 2a to 2d. This is a factor that hinders mass production operation of the TPMS.

[0083] For this reason, it is desirable that the sensor units 2a to 2d are configured to determine that the tire pressure is normal when the amount of change in the tire pressure is within a predetermined amount of change, and to determine that the tire pressure is abnormal when the amount of change in the tire pressure exceeds the predetermined amount of change. In this way, it is not necessary to store unique threshold values, etc. according to the vehicle model, tire size, etc. for each sensor unit 2a to 2d, making it easier to mass-produce the TPMS.

[0084] (Modifications of the present disclosure) Although the present disclosure has been described based on the above-described embodiment, it is not limited to the embodiment, and includes various modifications and modifications within the equivalent range. In addition, various combinations and forms, and other combinations and forms including only one element, more than one element, or less than one element, are also within the scope and concept of the present disclosure.

[0085] [Sensor units 2a to 2d] In the above embodiment, each of the sensor units 2a to 2d transmits one frame at each predetermined period set as an abnormality interval in the high-frequency transmission mode, but is not limited thereto. Each of the sensor units 2a to 2d may transmit multiple frames at each predetermined period set as an abnormality interval in the high-frequency transmission mode, as shown in FIG. 9. In addition, each of the sensor units 2a to 2d may transmit multiple frames at each predetermined period set as an abnormality interval in the normal transmission mode.

[0086] In the above embodiment, each of the sensor units 2a to 2d is configured to transmit frames at an abnormal interval that is shorter than a normal interval in the high-frequency transmission mode, but is not limited to this. For example, each of the sensor units 2a to 2d may transmit a larger number of frames than in the normal transmission mode at each predetermined period set as a normal interval in the high-frequency transmission mode.

[0087] In the above embodiment, each of the sensor units 2a to 2d is in a waiting state to receive a response signal from the vehicle-mounted device 3 until a predetermined waiting time has elapsed after transmitting a frame indicating a bidirectional command, but this is not limited to the above. Each of the sensor units 2a to 2d can grasp its own rotational position based on the output of the acceleration sensor 21c. Therefore, each of the sensor units 2a to 2d may be configured to cancel the waiting state to receive a response signal based on the number of rotations of the sensor unit after transmitting a frame indicating a bidirectional command. For example, each of the sensor units 2a to 2d may continue the waiting state for at least one rotation after transmitting a frame indicating a bidirectional command, and cancel the waiting state if the response signal cannot be received even after two rotations.

[0088] As in the above embodiment, the sensor units 2a to 2d are preferably configured to determine that the tire pressure is normal when the amount of change in the tire pressure is within a specified amount of change, and to determine that the tire pressure is abnormal when the amount of change exceeds the specified amount, but are not limited thereto. The sensor units 2a to 2d may be configured to determine that the tire pressure is abnormal when the tire pressure is equal to or lower than the specified pressure.

[0089] In the above embodiment, the sensor units 2a to 2d are described as being attached to the air injection valve, but they may be provided in other locations. For example, they may be attached in place of a valve cap or on the tread on the inside of the tire.

[0090] In the above embodiment, an example was shown in which the sensor units 2a to 2d are provided on all of the wheels 5a to 5d, but the present disclosure can be applied to a TPMS provided on at least one of the wheels.

[0091] [About on-board device 3] As in the above embodiment, the vehicle-mounted control unit 33 is preferably configured to transmit a response signal at a timing when the wheel angle of the tire to which the sensor unit 2a-2d that transmitted the frame is attached becomes the reference angle, but is not limited to this. For example, the vehicle-mounted control unit 33 may transmit a response signal at a timing when a predetermined time has elapsed after receiving the frame, or at any timing after receiving the frame.

[0092] As in the vehicle-mounted device 3 of the above embodiment, it is preferable that the vehicle-mounted control unit 33 transmits a response signal once when it receives a frame indicating a bidirectional command for the first time, and transmits the response signal multiple times when it receives the frame two or more times, but is not limited to this. For example, as shown in Fig. 10, the vehicle-mounted device 3 may transmit the response signal multiple times even when it receives a frame indicating a bidirectional command for the first time.

[0093] In the above embodiment, the parts of the TPMS provided on the vehicle body 6 side are collectively described as the on-board device 3, but the on-board device 3 does not necessarily have to be a single component. For example, the antenna 31 and on-board transceiver unit 32 performing the transmission and reception function and the on-board control unit 33 performing the tire pressure detection function may be provided in separate locations.

[0094] [others] For example, in the above embodiment, when the tire pressure is normal, the unidirectional command is included in the frame, and when the tire pressure is abnormal, the bidirectional command is included in the frame. However, these commands do not necessarily need to be commands represented as data, and may be in a form in which each command is substantially indicated by not including data. For example, only one of the unidirectional command and the bidirectional command may be indicated by data, and when that command is not included in the frame, the vehicle-mounted device 3 may determine that the other command is indicated. Specifically, only the bidirectional command may be stored in the frame, and when the bidirectional command is not included in the frame, the vehicle-mounted device 3 may determine that the unidirectional command is indicated.

[0095] In the above-described embodiments, it goes without saying that the elements constituting the embodiments are not necessarily essential, except in cases where it is particularly expressly stated that they are essential or where they are clearly considered to be essential in principle.

[0096] In the above-described embodiments, when numerical values ​​such as the number, values, amounts, ranges, etc. of components of the embodiments are mentioned, they are not limited to the specific numbers unless it is specifically stated as required or unless it is clearly limited to a specific number in principle.

[0097] In the above-described embodiments, when referring to the shapes, positional relationships, etc. of components, etc., there is no limitation to those shapes, positional relationships, etc., unless specifically stated or in principle limited to a specific shape, positional relationship, etc.

[0098] The control unit and the method of the present disclosure may be implemented in a special-purpose computer provided by configuring a processor and a memory programmed to execute one or more functions embodied in a computer program. The control unit and the method of the present disclosure may be implemented in a special-purpose computer provided by configuring a processor with one or more dedicated hardware logic circuits. The control unit and the method of the present disclosure may be implemented in one or more special-purpose computers configured by a combination of a processor and a memory programmed to execute one or more functions and a processor configured with one or more hardware logic circuits. The computer program may also be stored in a computer-readable non-transitory tangible recording medium as instructions executed by a computer. [Explanation of symbols]

[0099] 1 vehicle 2a~2d Sensor unit 21a Pressure sensor 22 Sensor control unit (first control unit) 23 Sensor transmitter / receiver unit (first transmitter / receiver unit) 3 Onboard equipment 32 Vehicle-mounted transceiver unit (second transceiver unit) 33 In-vehicle control unit (second control unit) 5a~5d wheels 6. Body

Claims

1. A tire pressure monitoring system for monitoring tire pressure of a vehicle (1), comprising: a plurality of sensor units (2a to 2d) provided corresponding to a plurality of wheels (5a to 5d) including tires, An on-board device (3) provided on a vehicle body (6), Each of the plurality of sensor units includes a pressure sensor (21a) that outputs a detection signal indicating the tire pressure, a first control unit (22) that processes the detection signal indicating the tire pressure to create a frame that includes detection data related to the tire pressure and indicates one of a unidirectional command and a bidirectional command, and transmits the frame at a predetermined transmission interval, and a first transmitting / receiving unit (23) that transmits the frame and receives a response signal transmitted from the vehicle-mounted device, the vehicle-mounted device has a second transceiver unit (32) that receives the frame and transmits the response signal, and a second control unit (33) that detects the tire air pressure based on the detection data stored in the frame received by the second transceiver unit, the second control unit is configured to transmit the response signal from the second transceiver unit when the bidirectional command is indicated in the frame, The first control unit is when detecting an abnormality in the tire pressure based on the detection signal indicating the tire pressure while the vehicle is traveling, transitioning to a high frequency transmission mode in which the number of times the frame is transmitted per unit time is increased compared to when the tire pressure is normal, and causing the frame indicating the bidirectional command to be transmitted from the first transceiver; A tire pressure monitoring system, wherein when the first transceiver receives the response signal after transmitting the frame indicating the bidirectional command, the system transitions to a normal transmission mode in which the number of transmissions is smaller than that in the high frequency transmission mode.

2. 2. The tire pressure monitoring system according to claim 1, wherein, when the second control unit receives the frame indicating the bidirectional command, the second control unit stores the wheel angle of the tire to which the sensor unit that transmitted the frame is attached as a reference angle in a memory (M), and causes the second transceiver unit to transmit the response signal at a timing when the wheel angle of the tire to which the sensor unit that transmitted the frame is attached becomes the reference angle.

3. 3. The tire pressure monitoring system according to claim 1, wherein the second control unit, upon receiving the frame indicating the bidirectional command, causes the second transceiver unit to transmit the response signal a plurality of times.

4. When the first control unit transitions to the normal transmission mode, the first control unit causes the first transceiver unit to transmit the frame indicating the one-way command at a predetermined period; 3. The tire pressure monitoring system according to claim 1, wherein the second control unit causes the second transceiver unit to transmit the response signal a plurality of times when the second control unit receives the frame indicating the bidirectional command from the same sensor unit two or more times.

5. 3. The tire pressure monitoring system according to claim 1, wherein the sensor unit determines that the tire pressure is normal when an amount of change in the tire pressure is within a predetermined amount of change, and determines that the tire pressure is abnormal when an amount of change in the tire pressure exceeds the predetermined amount of change.

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