Tire air pressure monitoring system

Abstract

To provide a TPMS that can appropriately transmit electric waves from a sensor unit to an on-vehicle machine side.SOLUTION: A tire air pressure monitoring system comprises: sensor units 2a to 2d which are provided on a plurality of wheels 5a to 5d respectively; and an on-vehicle machine 3 which is provided on a vehicle body 6 of a vehicle 1, receives a frame from each sensor unit 2a to 2d at a prescribed reception period and detects a tire air pressure. The on-vehicle machine 3 includes: an antenna 31 for receiving the frame; a switch circuit 34 for switching directivity of the antenna 31; and an on-vehicle control part 33 for controlling the switch circuit 34. The on-vehicle control part 33 switches directivity of the antenna 31 by the switch circuit 34 when the frames transmitted from respective sensor units 2a to 2d cannot be received more than a certain number of times.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to tire pressure monitoring systems. [Background technology]

[0002] Conventionally, a tire pressure monitoring system (hereinafter referred to as TPMS) is known in which the on-board device intermittently receives radio waves in order to suppress dark current in the on-board device while the start switch is off (see, for example, Patent Document 1). TPMS is an abbreviation for Tire Pressure Monitoring System. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2023-102676 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when the vehicle is stopped or parked, the wheel rotation position may be in a so-called "NULL" position where radio waves from the sensor unit cannot reach the onboard device, and the onboard device cannot monitor the tire pressure.

[0005] The present disclosure aims to provide a TPMS that can appropriately transmit radio waves from a sensor unit to an in-vehicle device. [Means for solving the problem]

[0006] The invention described in claim 1 is A tire pressure monitoring system applied to a vehicle (1) having a plurality of wheels (5a to 5d) including tires, a plurality of sensor units (2a to 2d) provided on the plurality of wheels, each of which outputs a detection signal related to the tire pressure of the wheel, generates transmission data related to the tire pressure based on the detection signal, and transmits a frame containing the transmission data at a predetermined interval; an on-board device (3) provided on a body (6) of the vehicle, which receives the frames at a predetermined reception cycle and detects the tire pressure from the transmission data stored in the frames; The vehicle-mounted device is an antenna (31) for receiving the frame; a directivity switching unit (34) that switches the directivity of the antenna; an on-board control unit (33) that controls the directivity switching unit, When the vehicle-mounted control unit is unable to receive the frame transmitted from the sensor unit a predetermined number of times, the vehicle-mounted control unit switches the directivity of the antenna using the directivity switching unit.

[0007] This allows the in-vehicle control unit to switch the antenna directionality, thereby enabling the frames that were not received to be received properly. Therefore, the TPMS of the present disclosure allows the radio waves from the sensor unit to be transmitted properly to the in-vehicle device.

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

[0009] [Figure 1] 1 is a schematic configuration diagram of a TPMS according to a first embodiment. [Figure 2] FIG. 2 is a block diagram showing the configuration of a sensor unit. [Figure 3] FIG. 10 is an explanatory diagram for explaining a frame transmission interval in a sensor unit. [Figure 4] FIG. 2 is a block diagram showing the configuration of an in-vehicle device. [Figure 5] FIG. 2 is a schematic perspective view of an antenna of the vehicle-mounted device. [Figure 6] 10 is an explanatory diagram for explaining that radio waves from a sensor unit do not reach the vehicle-mounted device side. FIG. [Figure 7] FIG. 2 is an electrical circuit diagram of an antenna and a switch circuit. [Figure 8] FIG. 2 is an explanatory diagram for explaining a directivity pattern of an antenna. [Figure 9] 3 is a flowchart showing the flow of control processing executed by an in-vehicle device of the TPMS according to the first embodiment. [Figure 10] 10 is a flowchart showing the flow of a frame reception process executed by the vehicle-mounted device. [Figure 11] 4 is a flowchart showing the flow of parking TPMS processing executed by the in-vehicle device. [Figure 12] 10 is a flowchart showing a flow of a frame reception retry process executed by the vehicle-mounted device. [Figure 13] FIG. 10 is an explanatory diagram for explaining a retry process in the vehicle-mounted device. [Figure 14] 10 is a flowchart showing the flow of control processing executed by an in-vehicle device of a TPMS according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the following embodiments, parts that are the same as or equivalent to those described in the preceding embodiments will be given the same reference numerals, and their description may be omitted. Furthermore, in the embodiments, when only some of the components are described, the components described in the preceding embodiments can be applied to the remaining components. The following embodiments can be partially combined with each other, even if not specifically stated, as long as there is no particular problem with the combination.

[0011] (First embodiment) A first embodiment of the present disclosure will be described with reference to Figures 1 to 13. 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 top of the paper in Figure 1 is the front of the vehicle 1, the bottom is the rear of the vehicle 1, and the left and right of the paper are the left and right of the vehicle 1. Furthermore, when the four wheels 5a to 5d are to be distinguished from one another in the description, 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.

[0012] 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.

[0013] As shown in FIG. 1, the sensor units 2a to 2d are attached to wheels 5a to 5d of the vehicle 1 and detect the air pressure and temperature of the tires attached to the wheels 5a to 5d. The sensor units 2a to 2d store detection signal data indicating the detection results, such as tire air pressure, in a frame as transmission data and transmit the data. The in-vehicle device 3 is attached to the vehicle body 6 of the vehicle 1 and receives the frames transmitted from the sensor units 2a to 2d and detects the tire air pressure based on the transmission data stored therein. The sensor units 2a to 2d and the in-vehicle device 3 according to this embodiment are configured to enable communication from the sensor units 2a to 2d to the in-vehicle device 3. In the TPMS according to this embodiment, the sensor units 2a to 2d function as "transmitters," and the in-vehicle device 3 functions as a "receiver." The sensor units 2a to 2d and the in-vehicle device 3 may be configured to perform bidirectional communication, enabling communication not only from the sensor units 2a to 2d to the in-vehicle device 3 but also vice versa.

[0014] Hereinafter, the detailed configurations of the sensor units 2a to 2d and the vehicle-mounted device 3 that constitute the TPMS of this embodiment will be described with reference to FIGS.

[0015] As shown in Figure 2, the sensor units 2a to 2d are configured to include a detection section 21, a sensor control section 22, a sensor communication section 23, a battery 24, and an antenna 25, and each section is driven based on the power supply from the battery 24.

[0016] The detection 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 corresponding to the tire air pressure. The temperature sensor 21b outputs a detection signal corresponding to the internal tire temperature. The acceleration sensor 21c outputs a detection signal corresponding to the acceleration occurring with tire rotation, for example, the radial acceleration of each of the wheels 5a to 5d. The detection 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. Of these, the detection signals corresponding to the tire air pressure and the internal tire temperature are used to detect tire air pressure, and the detection signal corresponding to the acceleration is used to detect that the vehicle 1 is traveling.

[0017] The sensor control unit 22 is configured by a microcomputer equipped with a CPU, ROM, RAM, I / O, etc., and executes predetermined processing 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.

[0018] The sensor control unit 22 receives the detection signal output from the detection unit 21 and processes it as necessary. The sensor control unit 22 also stores data indicating the detection results of the tire pressure and internal tire temperature used for tire pressure detection in a frame together with ID information of each of the sensor units 2a to 2d. The sensor control unit 22 sends the frames to the sensor communication unit 23 at predetermined regular transmission intervals (e.g., 96 seconds), as shown in FIG. 3, for example. In the following description, the data indicating the detection results of the tire pressure and internal tire temperature will be referred to as detection data related to tire pressure.

[0019] The sensor communication unit 23 functions as an output unit that transmits the frame sent from the sensor control unit 22 as RF radio waves to the in-vehicle device 3 via the antenna 25. Here, the sensor communication 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.

[0020] The battery 24 supplies power to the detection unit 21, the sensor control unit 22, etc., and the power supplied from the battery 24 is used to collect data related to tire air pressure in the detection unit 21 and to perform various calculations in the sensor control unit 22.

[0021] The sensor units 2a to 2d configured in this manner are attached to the air injection valves of the wheels 5a to 5d, for example, and are arranged so that the detection 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 via the antennas 25 provided in the sensor units 2a to 2d.

[0022] Next, the onboard device 3 will be described. The onboard device 3 of this embodiment is configured as an integrated receiver that functions as part of the TPMS and also as part of the Smart Entry (registered trademark) system. The onboard device 3 has a function to receive frames transmitted from the sensor units 2a to 2d as well as a function to receive specific radio waves emitted by the electronic key. To avoid interference, the radio waves emitted by the sensor units 2a to 2d and the specific radio waves emitted by the electronic key have different frequencies. In the following, the specific signal emitted by the electronic key may also be referred to as a "smart signal."

[0023] Here, we will briefly explain the smart entry system. The smart entry system is a system that performs authentication via wireless communication between an electronic key owned by a legitimate user of vehicle 1 and an authentication ECU (not shown) via an in-vehicle device 3 when the electronic key enters the wireless communication area around vehicle 1. The authentication ECU determines whether the electronic key is present in the wireless communication area around vehicle 1, and if the electronic key is present in the wireless communication area, it certifies that the electronic key is owned by the legitimate user. Once the electronic key is authenticated, the authentication ECU performs various controls, including unlocking the doors.

[0024] Furthermore, when the start switch is in the off state, the authentication ECU intermittently activates the in-vehicle device 3 so that it can receive specific radio waves emitted by the electronic key. For example, while the start switch is in the off state, the authentication ECU switches the in-vehicle device 3 from sleep mode to wake mode at a predetermined cycle so that it can receive specific radio waves. The start switch is a switch for putting the vehicle 1 into a state where it can run. The start switch corresponds, for example, to an ignition switch (i.e., an IG switch) in a vehicle equipped with an engine, or a power switch in an electric vehicle.

[0025] 4, the in-vehicle device 3 includes an antenna 31, an in-vehicle communication unit 32, an in-vehicle control unit 33, and a switch circuit 34. The in-vehicle device 3 is driven by power supplied from a battery BT mounted on the vehicle 1.

[0026] The antenna 31 is provided on the vehicle body 6 and serves to receive frames transmitted from each of the sensor units 2a to 2d. For example, as shown in Fig. 5, the antenna 31 is configured by a loop antenna LA in which an annular element EL is arranged on a circuit board CB. This loop antenna LA is configured as a shared antenna that collectively performs communication with each of the sensor units 2a to 2d.

[0027] When the antenna 31 receives frames transmitted from the sensor units 2a to 2d or specific radio waves emitted by the electronic key, the in-vehicle communication unit 32 functions as an input unit that demodulates the frames and sends them to the in-vehicle control unit 33. The in-vehicle communication unit 32 is capable of changing the reception frequency so that it can receive the specific radio waves from the electronic key with priority over frames from the sensor units 2a to 2d.

[0028] The in-vehicle control unit 33 is configured by a microcomputer equipped with a CPU, memory M including ROM and RAM, I / O, etc., and executes various processes according to programs stored in the memory M. Specifically, the in-vehicle control unit 33 operates based on the power supply from the battery BT, and controls the reception of frames and specific radio waves in the in-vehicle communication unit 32, and executes various processes related to tire pressure detection.

[0029] For example, the on-board control unit 33 performs various processes related to tire pressure detection, such as alarm determination processing, as a standard process of the TPMS. In the alarm determination process, various signal processes and calculations are performed based on the detection data related to tire pressure stored in the frame received from the on-board communication unit 32, and an electrical signal corresponding to the tire pressure is output to the display device 4. For example, in the alarm determination process, the tire pressure is compared with a predetermined alarm threshold, and if it is detected that the tire pressure has dropped below the predetermined alarm threshold, a signal indicating this is output to the display device 4. Furthermore, if the sensor units 2a to 2d are detecting tire pressure, the display device 4 can be notified of the occurrence of a drop in tire pressure based on data indicating the occurrence of a drop in tire pressure included in the received frame.

[0030] Furthermore, once the on-board control unit 33 has determined the tire pressures for each of the four wheels 5a-5d, it can output the tire pressures to the display device 4 in association with each wheel 5a-5d. The memory M of the on-board control unit 33 stores ID information for the sensor units 2a-2d disposed on each wheel 5a-5d, associated with the position of each wheel 5a-5d. Therefore, by comparing the ID information stored in the frame, the on-board control unit 33 can recognize which of the wheels 5a-5d the sensor unit 2a-2d is attached to and identify the wheel 5a-5d whose tire pressure has dropped. Based on this, if a drop in tire pressure has occurred, the on-board control unit 33 can identify the wheel 5a-5d whose tire pressure has dropped and output it to the display device 4. Furthermore, even if a drop in tire pressure has not occurred, the determined tire pressures may be output to the display device 4 in association with each wheel 5a-5d.

[0031] In this way, the in-vehicle device 3 notifies the display device 4 that the tire pressure of any one of the four wheels 5a to 5d has dropped, or the tire pressures of each of the four wheels 5a to 5d.

[0032] When the activation switch is turned on, the in-vehicle control unit 33 enters an active operating mode and performs various processes related to frame reception and tire pressure detection at the in-vehicle communication unit 32. On the other hand, when the activation switch is turned off, the in-vehicle control unit 33 basically enters a sleep mode with low power consumption, and when a predetermined condition is met, it temporarily enters an active wake mode and receives frames and specific radio waves.

[0033] 1, the display device 4 is arranged in a location visible to the driver, and is configured, for example, as an alarm lamp or display installed in the instrument panel of the vehicle 1. When a signal indicating a drop in tire pressure is sent from the on-board control unit 33 of the on-board device 3, the display device 4 notifies the driver of the drop in tire pressure by displaying that information. Alternatively, when the on-board device 3 transmits the tire pressures of each of the four wheels 5a to 5d, the display device 4 displays the tire pressures corresponding to each wheel 5a to 5d.

[0034] In this embodiment, the display device 4 is used as a warning unit that warns the driver, but 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.

[0035] The vehicle-mounted device 3 configured as described above is connected to other vehicle-mounted devices including the DCM 7 via a communication network, such as a CAN, established in the vehicle 1. The DCM 7 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. The DCM 7 is also an abbreviation for Data Communication Module.

[0036] The vehicle-mounted device 3 can receive requests from an information terminal SD such as a tablet or smartphone owned by a user via a communication center, etc., using, for example, the DCM 7. The vehicle-mounted device 3 can also transmit detection data and abnormality data related to tire pressure to the information terminal SD.

[0037] In the TPMS configured as described above, information relating to tire pressure is notified by periodically transmitting frames from the sensor units 2a to 2d to the vehicle-mounted device 3. This notification is carried out regardless of whether the activation switch is on or off.

[0038] When the vehicle 1's start switch is turned on and the vehicle-mounted device 3 is in the on state, the vehicle-mounted device 3 receives frames in accordance with the frequency of frame transmission from the sensor units 2a to 2d so that it can receive frames from the sensor units 2a to 2d.

[0039] On the other hand, even when the activation switch of the vehicle 1 is in the OFF state, if the in-vehicle device 3 receives frames in accordance with the frequency of frame transmissions from the sensor units 2a to 2d, the dark current of the battery BT increases, which may prevent the vehicle 1 from starting. For this reason, in the TPMS of this embodiment, the frame reception cycle in the OFF state where the activation switch is turned off is set to be significantly longer than in the ON state where the activation switch is turned on.

[0040] Furthermore, when the vehicle is stopped or parked, the rotational positions of the wheels 5a to 5d may be in so-called "NULL" positions where it is difficult for radio waves from the sensor units 2a to 2d to reach the vehicle-mounted device 3.

[0041] 6, even if the rotational positions of the left front wheel FL, right front wheel FR, and left rear wheel RL are such that radio waves from the sensor units 2a to 2d can easily reach the in-vehicle device 3, the rotational position of the right rear wheel RR may be in the "NULL" position. In this case, radio waves from the sensor unit 2c attached to the right rear wheel RR cannot reach the in-vehicle device 3, making it impossible to monitor the tire pressure.

[0042] In particular, if the rotational positions of the wheels 5a to 5d are in the "NULL" position when the start switch is turned off, it will be impossible to monitor the tire pressure until the next time the start switch is turned on and driving begins.

[0043] Taking this into consideration, the vehicle-mounted device 3 is provided with a switch circuit 34 that switches the directivity of the antenna 31. In this embodiment, the switch circuit 34 constitutes a "directivity switching unit."

[0044] 7, the switch circuit 34 includes switch elements SW1 and SW2 and capacitors CN1 and CN2. The switch circuit 34 changes the connection state of the element EL of the antenna 31 to the ground GND by operating the switch elements SW1 and SW2, thereby switching the directivity of the antenna 31. The operation of the switch elements SW1 and SW2 of the switch circuit 34 is controlled in response to a control signal from the on-board controller 33.

[0045] When the in-vehicle control unit 33 fails to receive frames transmitted from the sensor units 2a to 2d a predetermined number of times, the in-vehicle control unit 33 switches the directivity of the antenna 31 by the switch circuit 34. The in-vehicle control unit 33 of this embodiment is configured to be able to set the directivity pattern of the antenna 31 to patterns A to D, as shown in FIG.

[0046] Pattern A is a pattern that is realized by connecting element EL to ground GND with switch element SW1 and setting switch element SW2 to the OFF position, and the directivity of antenna 31 becomes as shown in the upper left of FIG.

[0047] Pattern B is a pattern that is realized by connecting element EL to ground GND with switch element SW2 and setting switch element SW1 to the OFF position. Pattern B makes the electrical length of antenna 31 longer than in pattern A, and therefore the directivity of antenna 31 differs from that of pattern A, as shown in the upper right of Figure 8.

[0048] Pattern C is a pattern realized by connecting element EL to ground GND with switch element SW1, and also connecting element EL to ground GND via capacitor CN2 with switch element SW2. In pattern C, the amount of current in element EL is limited by the presence of capacitor CN2, and as a result, the directivity of antenna 31 becomes different from patterns A and B, as shown in the lower left of Figure 8.

[0049] Pattern D is a pattern realized by connecting element EL to ground GND with switch element SW2, and also connecting element EL to ground GND via capacitor CN1 with switch element SW1. In pattern D, the amount of current in element EL is limited by the presence of capacitor CN1, and as a result, the directivity of antenna 31 becomes different from patterns A to C, as shown in the lower right of FIG.

[0050] Next, a specific flow of control processing executed by the vehicle-mounted device 3 of this embodiment will be described with reference to Fig. 9 etc. The processing shown in Fig. 9 is executed periodically or irregularly by the vehicle-mounted control unit 33 of the vehicle-mounted device 3.

[0051] 9, in step S100, the in-vehicle control unit 33 determines whether the activation switch is turned on. If the activation switch is turned on, the in-vehicle control unit 33 proceeds to step S110, and if the activation switch is turned off, the in-vehicle control unit 33 proceeds to step S140.

[0052] If the activation switch is in the on state, in step S110, the in-vehicle control unit 33 sets the directivity of the antenna 31. Specifically, the in-vehicle control unit 33 maintains the directivity of the antenna 31 at a predetermined value, regardless of whether or not a frame can be received.

[0053] Next, in step S120, the on-board control unit 33 performs a reception process for frames periodically transmitted from each of the sensor units 2 a to 2 d. The on-board control unit 33 basically performs the reception process continuously so that it can receive frames from each of the sensor units 2 a to 2 d, for example.

[0054] Thereafter, when the on-board control unit 33 receives a frame from each of the sensor units 2a to 2d, the process proceeds to step S130, where the on-board control unit 33 performs the above-mentioned alarm determination and display on the display device 4 as the prescribed processing of the TPMS.

[0055] On the other hand, if the activation switch is in the OFF state, the in-vehicle control unit 33 determines in step S140 whether it is time for intermittent reception. Specifically, the in-vehicle control unit 33 determines whether the reception cycle for receiving frames from each of the sensor units 2a to 2d has arrived. If it is not time for intermittent reception, the in-vehicle control unit 33 exits this process.

[0056] If it is the timing for intermittent reception, the on-board control unit 33 proceeds to step S150 and performs reception processing of frames transmitted from each of the sensor units 2a to 2d. Details of the frame reception processing will be described with reference to FIG.

[0057] 10, the on-board control unit 33 first receives a frame in step S151. In order to receive frames from the four wheels 5a to 5d, the on-board control unit 33 maintains a state in which it can receive frames for a certain period of time (for example, about 100 seconds).

[0058] Next, in step S152, the on-vehicle control unit 33 checks the wheel positions of the wheels 5a to 5d that received the frame. Specifically, the on-vehicle control unit 33 checks to which of the wheels 5a to 5d the sensor unit 2a to 2d attached to the received frame is located, based on the ID information stored in the frame.

[0059] Next, in step S153, the on-board control unit 33 sets a flag (hereinafter also referred to as wheel position flag) for confirming the wheel position for which a frame has not been received. In this embodiment, the wheel position flag is a 4-bit flag, with the first bit from the left corresponding to the front left wheel FL, the second bit corresponding to the front right wheel FR, the third bit corresponding to the rear left wheel RL, and the fourth bit corresponding to the rear right wheel RR, and "1" is set to the bit indicating the wheel position for which reception of a frame has been confirmed. For example, if reception of frames has been confirmed for the front left wheel FL, the front right wheel FR, and the rear right wheel RR, but no frame has been received for the rear left wheel RL, the on-board control unit 33 sets the wheel position flag to "1101." Note that the wheel position flag may be configured with a flag different from the one described above.

[0060] Next, in step S154, the in-vehicle control unit 33 determines whether the wheel position flag is set to "1111". If the wheel position flag is set to "1111", the in-vehicle control unit 33 sets the number of wheels 5a to 5d for which frame reception has been confirmed (hereinafter also referred to as the number of received wheels) to four in step S155, and exits the frame reception process. Note that if the wheel position flag is not set to "1111", the in-vehicle control unit 33 skips step S155 and exits the frame reception process.

[0061] When this frame reception process is completed, the on-board controller 33 proceeds to step S160 in Fig. 9 and executes parking TPMS process, which will be described with reference to Fig. 11.

[0062] 11, in step S200, the on-board control unit 33 determines whether the number of wheels for which signals have been received is four. If the number of wheels for which signals have been received is not four, the on-board control unit 33 proceeds to step S205, and if the number of wheels for which signals have been received is four, the on-board control unit 33 proceeds to step S210.

[0063] In step S205, the in-vehicle control unit 33 determines whether the number of retries to receive the frame is less than a predetermined upper retry limit. As a result, if the number of retries is equal to or greater than the upper retry limit, the in-vehicle control unit 33 proceeds to step S210. That is, if the in-vehicle control unit 33 cannot receive the frame even after switching the directivity of the antenna 31 a predetermined number of times, the in-vehicle control unit 33 stops switching the directivity of the antenna 31.

[0064] In step S210, the on-board controller 33 executes a tire pressure monitoring process. In this monitoring process, for example, using information stored in the frame, it determines whether the tire pressure is greater than the warning threshold. If the tire pressure is equal to or less than the warning threshold, the on-board controller 33 transmits an abnormality signal indicating an abnormality in the tire pressure via the DCM 7 to an information terminal SD, such as a tablet or smartphone, owned by the user.

[0065] After performing the tire pressure monitoring process, the on-board control unit 33 resets the number of retries in step S215, and then resets the number of received wheels to a number other than four in step S220, and then exits this process.

[0066] On the other hand, if the number of retries is less than the upper limit, the in-vehicle controller 33 determines whether there is interference between the frame reception process and the smart process for receiving the specific radio waves from the electronic key. In this determination process, for example, if the electronic key is present in the wireless communication area around the vehicle 1 at the time the frame is received, it is determined that there is interference between the frame reception process and the smart process.

[0067] If there is no interference between the frame reception process and smart processing, it is highly likely that the rotation position of the wheel that is not receiving the frame is in the "NULL" position. Therefore, the in-vehicle control unit 33 changes the directivity of the antenna 31 and performs the frame reception process again.

[0068] Specifically, in step S230, the in-vehicle control unit 33 determines whether the current directivity pattern is any one of patterns A to D. If the current directivity pattern is pattern A, the in-vehicle control unit 33 proceeds to step S235, where it switches the directivity pattern to pattern B using the switch circuit 34. If the current directivity pattern is pattern B, the in-vehicle control unit 33 proceeds to step S240, where it switches the directivity pattern to pattern C using the switch circuit 34. If the current directivity pattern is pattern C, the in-vehicle control unit 33 proceeds to step S245, where it switches the directivity pattern to pattern D using the switch circuit 34. If the current directivity pattern is pattern D, the in-vehicle control unit 33 proceeds to step S250, where it switches the directivity pattern to pattern A using the switch circuit 34.

[0069] In this way, if there is no interference between the frame reception process and the smart process, the on-board control unit 33 changes the directivity pattern of the antenna 31. After changing the directivity pattern of the antenna 31, the on-board control unit 33 executes a retry process for frame reception in step S255.

[0070] On the other hand, if there is interference between the frame reception process and the smart process, it may be possible to receive the frame by delaying the frame reception. Therefore, if there is interference between the frame reception process and the smart process, the in-vehicle control unit 33 executes a retry process for frame reception in step S255 without changing the directivity of the antenna 31.

[0071] Here, the frame reception retry process executed by the in-vehicle control unit 33 will be described in detail with reference to Fig. 12. As shown in Fig. 12, in step S300, the in-vehicle control unit 33 executes a standby process in which it waits in sleep mode until a predetermined standby time (for example, about 5 minutes) has elapsed, and then transitions to wake mode. Note that the standby time at this time is set to a time that is sufficiently short compared to the frame reception cycle while the activation switch is off (for example, 1 hour), so as to increase the frequency of frame reception. The standby time corresponds to the time required to switch from sleep mode to wake mode.

[0072] Next, the on-board control unit 33 receives the frame in step S310. Specifically, the on-board control unit 33 maintains a state in which it can receive a frame for a certain period of time (for example, about 100 seconds).

[0073] Next, in step S320, the on-vehicle control unit 33 checks the wheel positions of the wheels 5a to 5d that received the frame. Specifically, the on-vehicle control unit 33 checks to which of the wheels 5a to 5d the sensor unit 2a to 2d attached to the received frame is located, based on the ID information stored in the frame.

[0074] Next, in step S330, the in-vehicle control unit 33 sets a wheel position flag. In this process, the wheel position flag is set only for wheel positions for which no frame has been received, and the wheel positions that have already been set are maintained as they were.

[0075] Next, in step S340, the on-board control unit 33 determines whether the wheel position flag is set to "1111." If the wheel position flag is set to "1111," the on-board control unit 33 sets the number of received wheels to four in step S350 and exits the frame reception retry process. Note that if the wheel position flag is not set to "1111," the on-board control unit 33 skips step S350 and exits the frame reception retry process.

[0076] When the retry process for frame reception is completed, the on-board control unit 33 proceeds to step S260 shown in Fig. 11 and increments the count of the number of retries by 1. Thereafter, the on-board control unit 33 returns to step S200 and again determines whether the number of wheels for which reception has been completed is four.

[0077] The TPMS described above is provided with a switch circuit 34 for switching the directivity of the antenna 31 for the on-board device 3. The on-board control unit 33 of the on-board device 3 switches the directivity of the antenna 31 by the switch circuit 34 when it is unable to receive a frame transmitted from the sensor units 2a to 2d more than a predetermined number of times (one time in this example).

[0078] As a result, even if the rotational positions of the wheels 5a to 5d are in the "NULL" position, it is possible to properly receive frames that have not been received by switching the directivity of the antenna 31 using the on-board control unit 33. Therefore, according to the TPMS of the present disclosure, radio waves from the sensor units 2a to 2d can be properly transmitted to the on-board device 3.

[0079] The TPMS of this embodiment has the following features.

[0080] (1) It is possible to switch the directivity of the antenna 31 by selectively using multiple antennas 31 with different directivities, but such a configuration may increase the number of parts on the vehicle-mounted device 3 side or make the configuration complex.

[0081] Taking this into consideration, in the TPMS of this embodiment, the directivity of the antenna 31 is switched by changing the connection state of the antenna 31 to the ground GND using the switch circuit 34. This allows the configuration of the in-vehicle device 3 to be simplified.

[0082] (2) While the vehicle 1 is moving, even if the rotational positions of the wheels 5a to 5d are in the “NULL” position at the timing of the current frame, there is a possibility that the rotational positions of the wheels 5a to 5d will not be in the “NULL” position at the timing of receiving the next frame.

[0083] On the other hand, when the activation switch is in the OFF state, if the rotational positions of the wheels 5a to 5d reach the "NULL" position at the timing of the current frame, the rotational positions of the wheels 5a to 5d will be maintained at the "NULL" position even at the timing of receiving the next frame. For this reason, it is desirable to switch the directivity of the antenna 31 in a situation where the rotational positions of the wheels 5a to 5d continue to be in the "NULL" position, as in the OFF state of the activation switch.

[0084] Taking these factors into consideration, the on-board control unit 33 of this embodiment is configured to switch the directivity of the antenna 31 using the switch circuit 34 when the vehicle 1's start switch is turned off and frames cannot be received more than a predetermined number of times (in this example, once).

[0085] (3) As shown in Fig. 13, the vehicle-mounted device 3 alternates between wake mode and sleep mode when the activation switch is in the off state, and performs intermittent operation of receiving frames in wake mode. If the vehicle-mounted control unit 33 is unable to receive frames a predetermined number of times when the activation switch is in the off state, it shortens the time required to switch from sleep mode to wake mode and increases the frequency of frame reception. This is expected to quickly improve the situation in which radio waves from the sensor units 2a to 2d are not transmitted to the vehicle-mounted device 3.

[0086] Here, if the frame cannot be received by smart processing, it is considered that there is no problem with the directivity of the antenna 31. For this reason, it is desirable that the on-board control unit 33 retry without switching the directivity of the antenna 31 when the frame cannot be received by smart processing.

[0087] (4) When the activation switch is in the on state, it is assumed that the wheels 5a to 5d will rotate as the vehicle moves. Therefore, even if the rotational positions of the wheels 5a to 5d are in the "NULL" position at the timing of the current frame, there is a possibility that the rotational positions of the wheels 5a to 5d will not be in the "NULL" position at the timing of receiving the next frame. For this reason, in a situation where the wheels 5a to 5d are expected to rotate, such as when the activation switch is in the on state, it is desirable to maintain the directivity of the antenna 31 at a predetermined value.

[0088] Taking this into consideration, the in-vehicle control unit 33 is configured to maintain the directivity of the antenna 31 at a predetermined value when the activation switch is turned on, regardless of whether or not a frame can be received.

[0089] (5) If frames can be received from all of the sensor units 2a to 2d, there is no need to change the directivity of the antenna 31 any further. In such a situation, it is desirable to maintain the directivity of the antenna 31 at a predetermined level. For this reason, the on-board control unit 33 of this embodiment is configured to stop switching the directivity of the antenna 31 when frames have been received from all of the sensor units 2a to 2d.

[0090] (6) If frames cannot be received even after switching the directivity of the antenna 31 a predetermined number of times, the on-board control unit 33 stops switching the directivity of the antenna 31. In this way, if the situation in which frames cannot be received continues even after switching the directivity of the antenna 31, it is desirable to stop switching the directivity of the antenna 31.

[0091] (Second embodiment) Next, a second embodiment will be described with reference to Fig. 14. In this embodiment, differences from the first embodiment will be mainly described.

[0092] In this embodiment, the on-board control unit 33 is configured to switch the directivity of the antenna 31 using the switch circuit 34 when frames cannot be received more than a predetermined number of times while the vehicle is stationary and the rotation of the wheels 5a to 5d has stopped for more than a predetermined time.

[0093] Details of the control process executed by the on-board control unit 33 of this embodiment will be described with reference to Fig. 14. The control process shown in Fig. 14 corresponds to the control process shown in Fig. 9 described in the first embodiment. Of the control process shown in Fig. 14, the processes of steps S100 to S160 are substantially the same as the processes of steps S100 to S160 shown in Fig. 9, and therefore description thereof will be omitted.

[0094] 14, after the frame reception process is completed in step S120, the in-vehicle control unit 33 determines in step S170 whether the number of wheels for which the frame has been received is four. If the number of wheels for which the frame has been received is four, the in-vehicle control unit 33 proceeds to step S130 and executes the TPMS-defined process.

[0095] On the other hand, if the number of wheels for which signals have been received is not four, the on-board control unit 33 proceeds to step S180 and determines whether the vehicle is in a temporary stop state in which the rotation of the wheels 5a to 5d has stopped for more than a predetermined time. As a result, if the vehicle is in a temporary stop state, the on-board control unit 33 switches the directivity of the antenna 31 in step S190 and then returns to step S120. If the vehicle is not in a temporary stop state, the on-board control unit 33 skips step S190 and returns to step S120. The switching of the directivity of the antenna 31 is performed in the same manner as described in the first embodiment.

[0096] The rest of the configuration is the same as that of the first embodiment. The TPMS of this embodiment can obtain the same effects as those of the first embodiment that are achieved by a configuration common to or equivalent to that of the first embodiment.

[0097] The TPMS of this embodiment also has the following features.

[0098] (1) As in this embodiment, when the rotational positions of the wheels 5a to 5d continue to be in the “NULL” position, such as when the vehicle is temporarily stopped, it is desirable to switch the directivity of the antenna 31.

[0099] (Other embodiments) Representative embodiments of the present disclosure have been described above, but the present disclosure is not limited to the above-described embodiments and can be modified in various ways, for example, as follows.

[0100] 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 the valve cap or on the tread inside the tire. Also, although an example has been shown in which the sensor units 2a to 2d are provided on all of the wheels 5a to 5d, the present disclosure can be applied to a TPMS provided on at least one of the wheels.

[0101] In the above-described embodiment, the vehicle-mounted device 3 is configured as an integrated receiver including part of a smart entry system, but the vehicle-mounted device 3 may also be configured as a receiver dedicated to TPMS.

[0102] The on-board control unit 33 may be configured to switch the directivity of the antenna 31 by the switch circuit 34 when frames transmitted from the sensor units 2a to 2d cannot be received multiple times.

[0103] The on-vehicle device 3 is configured to switch the directivity of the antenna 31 by changing the connection state of the antenna 31 to the ground GND using the switch circuit 34, but is not limited to this. For example, the on-vehicle device 3 may be configured to include multiple antennas 31 with different directivities and to switch the directivity of the antenna 31 by selectively using the multiple antennas 31 with different directivities.

[0104] The vehicle-mounted device 3 is configured to switch the directivity of the antenna 31 in a predetermined order, but is not limited to this. For example, the vehicle-mounted device 3 may be configured to switch the directivity of the antenna 31 so that frames successfully received from all wheels are given priority.

[0105] When the vehicle control unit 33 is unable to receive frames while the start switch is in the off state, it is desirable that the vehicle control unit 33 shortens the time required to switch from wake mode to sleep mode and increases the frequency of frame reception, but this is not a requirement.

[0106] If the in-vehicle control unit 33 is unable to receive a frame through smart processing, it is desirable that the in-vehicle control unit 33 retry without switching the directivity of the antenna 31, but this is not necessarily required.

[0107] It is desirable that the on-board control unit 33 maintains the directivity of the antenna 31 at a predetermined level when the start switch is turned on, regardless of whether frames can be received or not, but this is not necessarily required.

[0108] It is desirable that the on-board control unit 33 stops switching the directivity of the antenna 31 if it is unable to receive frames even after switching the directivity of the antenna 31 a predetermined number of times, but this is not a requirement.

[0109] In the above-described embodiment, the parts of the TPMS provided on the vehicle body 6 side are collectively referred to 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 communication unit 32 that perform the transmission and reception function and the on-board control unit 33 that performs the tire air pressure detection function may be provided in separate locations.

[0110] In the above-described embodiments, it goes without saying that the elements constituting the embodiments are not necessarily essential unless they are specifically stated as essential or are clearly considered essential in principle.

[0111] 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 they are expressly stated as being essential or are clearly limited to a specific number in principle.

[0112] In the above-described embodiments, when referring to the shapes, positional relationships, etc. of components, etc., the shapes, positional relationships, etc. are not limited to those unless otherwise specified or when they are limited in principle to specific shapes, positional relationships, etc. [Explanation of symbols]

[0113] 1 vehicle 2a~2d Sensor units 3 Onboard equipment 31 Antenna 33 On-board control unit 34 Switch circuit (directivity switching section) 5a~5d wheels 6. Body

Claims

1. A tire pressure monitoring system applied to a vehicle (1) having a plurality of wheels (5a-5d) including tires, a plurality of sensor units (2a to 2d) provided on the plurality of wheels, each of which outputs a detection signal related to the tire pressure of the wheel, generates transmission data related to the tire pressure based on the detection signal, and transmits a frame containing the transmission data at a predetermined interval; an on-board device (3) provided on a body (6) of the vehicle, which receives the frames at a predetermined reception cycle and detects the tire pressure from the transmission data stored in the frames; The vehicle-mounted device is an antenna (31) for receiving said frames; a directivity switching unit (34) for switching the directivity of the antenna; an in-vehicle control unit (33) that controls the directivity switching unit, The vehicle-mounted control unit switches the directivity of the antenna using the directivity switching unit when the frame transmitted from the sensor unit cannot be received a predetermined number of times.

2. The tire pressure monitoring system according to claim 1 , wherein the directivity switching unit switches the directivity of the antenna by changing a connection state of the antenna to the ground.

3. 3. The tire pressure monitoring system according to claim 1, wherein the on-board control unit switches the directivity of the antenna using the directivity switching unit when the frame cannot be received more than the predetermined number of times while the vehicle is in a stopped state in which rotation of the wheels has stopped for more than a predetermined time, or while the vehicle's start switch is in an off state in which the vehicle's start switch is turned off.

4. the on-board device alternately switches between a wake mode and a sleep mode in the off state, and performs an intermittent operation of receiving the frame in the wake mode; 4. The tire pressure monitoring system according to claim 3, wherein, when the vehicle control unit is unable to receive the frame more than the predetermined number of times in the off state, the vehicle control unit shortens the time required to switch from the sleep mode to the wake mode and increases the frequency of receiving the frame.

5. 4. The tire pressure monitoring system according to claim 3, wherein the on-board control unit maintains a predetermined directivity of the antenna when the activation switch is turned on, regardless of whether the frame is received or not.

6. 3. The tire pressure monitoring system according to claim 1, wherein the on-board control unit stops switching the directivity of the antenna when the frames are received from all of the sensor units.

7. 3. The tire pressure monitoring system according to claim 1, wherein the on-board control unit stops switching the directivity of the antenna when the frame cannot be received even after switching the directivity of the antenna a predetermined number of times.

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