In-vehicle receiver, tire pressure monitoring system

Abstract

To provide an on-vehicle receiver and a tire air pressure monitoring system that, while suppressing an increase in a dark current during off-state of a starting switch, are able to receive both a frame including information on a tire air pressure and a specific radio wave transmitted by a portable machine.SOLUTION: An integrated receiver 3 includes: a radio wave receiving unit 31 that receives a frame including information on tire air pressure transmitted at a predetermined regular transmission cycle by a TPMS transmitter and also receives a specific radio wave emitted by a portable machine; and a TPMS control unit 33 that detects an occurrence of a tire air pressure reduction. While a starting switch SSW is off, the TPMS control unit 33 shifts to a SMART reception mode in which the radio wave reception unit 31 is caused to receive the specific radio wave at each predetermined first intermittent cycle, In addition, the TPMS control unit 33 shifts from the SMART reception mode or a power saving mode to a TPMS reception mode in which the radio wave reception unit 31 is caused to receive the frame at each predetermined second intermittent cycle to intermittently monitor a tire air pressure.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present disclosure relates to an in-vehicle receiver and a tire pressure monitoring system. [Background technology]

[0002] Conventionally, a tire pressure monitoring system has been known in which an on-board receiver receives frames transmitted from a transmitter not only when the vehicle starter switch is on but also when it is off, and analyzes the information in the frames to detect a drop in tire pressure (see, for example, Patent Document 1). Separately, a system is also known in which an on-board receiver receives frames transmitted from a transmitter attached to a tire while the starter switch is on, and receives specific radio waves emitted by a portable device such as an electronic key while the starter switch is off. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6331679 Summary of the Invention [Problem to be solved by the invention]

[0004] The inventors have investigated a tire pressure monitoring system in which an in-vehicle receiver receives a frame containing information about tire pressure in addition to a specific radio wave emitted by a portable device while the starter switch is off. This investigation revealed that if an attempt is made to simply receive the frame and the specific radio wave separately while the starter switch is off, the operating time of the in-vehicle receiver while the starter switch is off will increase, resulting in a significant increase in dark current in the in-vehicle receiver.

[0005] The present disclosure aims to provide an in-vehicle receiver and tire pressure monitoring system that can receive both a frame containing information about tire pressure and specific radio waves emitted by a portable device while suppressing an increase in dark current when the start switch is off. [Means for solving the problem]

[0006] The invention described in claim 1 is An on-board receiver included in a tire pressure monitoring system applied to a vehicle (1) having a plurality of wheels (10a to 10d) with tires, a radio wave receiving unit (31) for receiving frames containing information about tire pressures transmitted at a predetermined periodic transmission interval (T1) by transmitters (2a-2d) provided on the tires of each of the plurality of wheels, and specific radio waves emitted by the portable device (4); a control unit (33) that detects occurrence of a decrease in tire air pressure based on data related to tire air pressure included in the frame, While the vehicle start switch (SSW) is off, the control unit transitions to a specific mode in which the radio wave receiving unit receives specific radio waves at every predetermined first intermittent period (T5), and transitions from the specific mode or the power saving mode to a monitoring mode in which the radio wave receiving unit receives frames at every predetermined second intermittent period (T2) to intermittently monitor tire pressure.

[0007] The invention described in claim 6 is A tire pressure monitoring system applied to a vehicle (1) having a plurality of wheels (10a to 10d) with tires, a plurality of transmitters (2a to 2d) provided on tires of a plurality of wheels, each of which transmits a frame including information about tire pressure at a predetermined periodic transmission interval (T1); an in-vehicle receiver (3) provided on the vehicle body (11), The in-vehicle receiver is a radio wave receiving unit (31) for receiving specific radio waves emitted by the frame and the portable device (4); a control unit (33) that detects occurrence of a decrease in tire air pressure based on data related to tire air pressure included in the frame, While the vehicle start switch (SSW) is off, the control unit transitions to a specific mode in which the radio wave receiving unit receives specific radio waves at every predetermined first intermittent period (T5), and transitions from the specific mode or the power saving mode to a monitoring mode in which the radio wave receiving unit receives frames at every predetermined second intermittent period (T2) to intermittently monitor tire pressure.

[0008] With these features, the reception of specific radio waves and the monitoring of tire pressure are performed intermittently while the starter switch is off, which reduces the operating time of the in-vehicle receiver while the starter switch is off. This makes it possible to receive specific radio waves and monitor tire pressure while suppressing an increase in dark current in the in-vehicle receiver.

[0009] 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]

[0010] [Figure 1] 1 is a schematic diagram showing a schematic configuration of a tire pressure monitoring system according to a first embodiment. [Figure 2] FIG. 1 is a block diagram showing a TPMS transmitter. [Figure 3] 4 is a time chart for explaining the operation of the TPMS transmitter and the integrated receiver when the start switch is switched from on to off. [Figure 4] 6 is a time chart for explaining the operation mode of the integrated receiver while the start switch is off. [Figure 5] 4 is a time chart for explaining the frame transmission timing of the TPMS transmitter of each tire. [Figure 6] FIG. 1 is a block diagram illustrating an integrated receiver. [Figure 7] 10 is a flowchart illustrating an example of a reception process executed by the multifunction receiver while the start switch is off. [Figure 8]10 is a flowchart showing an example of a reception process executed by the multifunction receiver of the second embodiment while the start switch is off. [Figure 9] 10 is a time chart for explaining the frame transmission timing of the TPMS transmitter of each tire in the third embodiment. [Figure 10] 10 is a time chart for explaining the frame transmission timing of the TPMS transmitter of each tire in the fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] 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.

[0012] (First embodiment) This embodiment will be described with reference to Figures 1 to 7. Note that the terms "front", "rear", "right" and "left" shown in Figure 1 refer to the "front", "rear", "right side" and "left side" of a vehicle 1.

[0013] The tire pressure monitoring system is a system that monitors the tire pressure of tires attached to multiple wheels 10a to 10d. Tire pressure is the pressure inside the tire. For convenience, the tire pressure monitoring system may be referred to as "TPMS" below.

[0014] As shown in FIG. 1, the TPMS includes a plurality of TPMS transmitters 2a to 2d attached to tires of wheels 10a to 10d, respectively, and an integrated receiver 3 attached to the body 11 of the vehicle 1.

[0015] The TPMS transmitters 2a to 2d are transmitters that detect the tire pressure of the tire to which they are attached and transmit frames containing information about the tire pressure (for example, a tire pressure detection signal) at a predetermined regular transmission period T1. As shown in Fig. 2, the TPMS transmitters 2a to 2d each include a sensor unit 21, a sensor control unit 22, and a radio wave transmission unit 23.

[0016] The sensor unit 21 includes a pressure sensor 21a that detects the pressure inside the tire and a temperature sensor 21b that detects the temperature inside the tire. The sensor unit 21 outputs a detection signal from the pressure sensor 21a and a detection signal from the temperature sensor 21b to the sensor control unit 22.

[0017] The sensor control unit 22 is configured with a microcomputer including a processor and memory and its peripheral devices. The sensor control unit 22 executes transmission processing and the like in accordance with a program stored in the memory. The memory of the sensor control unit 22 stores ID information including transmitter-specific identification information for identifying each of the TPMS transmitters 2a to 2d and vehicle-specific identification information for identifying the vehicle 1. The memory is configured with a non-transitory physical storage medium.

[0018] When the sensor control unit 22 receives the detection signal output from the sensor unit 21, the sensor control unit 22 processes the detection signal and processes it as necessary, and stores the data indicating the detection result together with ID information in a frame. Then, the sensor control unit 22 sends the frame to the radio wave transmission unit 23.

[0019] The radio wave transmitting unit 23 has an output unit 231 and a transmitting antenna unit 232. The output unit 231 transmits the frame sent from the sensor control unit 22 to the integrated receiver 3 via the transmitting antenna unit 232 as radio waves in a predetermined frequency band (for example, RF radio waves).

[0020] The TPMS transmitters 2a to 2d are not provided with a function for receiving signals from an external source, and are therefore unable to determine whether the start switch SSW of the vehicle 1 is on or off. As shown in FIG. 3, the process of sending a signal from the sensor control unit 22 to the radio wave transmission unit 23 is executed at predetermined regular transmission intervals T1, regardless of whether the start switch SSW is on or off. That is, the TPMS transmitters 2a to 2d are configured to transmit frames at predetermined regular transmission intervals T1. The start switch SSW corresponds to, for example, an ignition switch in an engine-equipped vehicle, or a power switch in an EV vehicle.

[0021] In this embodiment, the TPMS transmitters 2a to 2d transmit frames multiple times at a transmission interval T4 that is shorter than the regular transmission cycle T1. For example, as shown in FIGS. 4 and 5, the TPMS transmitters 2a to 2d transmit frames at the regular transmission cycle T1, and then transmit frames at a predetermined transmission interval T4 from the transmission of the previous frame. In this embodiment, the transmission interval T4 is the same for each of the TPMS transmitters 2a to 2d. In the example shown in FIGS. 4 and 5, frames are transmitted twice per regular transmission cycle T1, but frames may be transmitted three or more times. When transmitting frames three or more times, for example, the transmission interval T4 between the first and second transmissions and the transmission interval T4 between the second and third transmissions may be the same or different. Alternatively, for example, the transmission interval T between the first and second transmissions may be a fixed interval, and the transmission interval T4 between the second and third transmissions may be random.

[0022] Here, the frame transmission timing of each TPMS transmitter 2a-2d is set so that the frame transmission and the timing when the output of the SMART request signal RCO, which will be described later, are unlikely to overlap. Each TPMS transmitter 2a-2d is set so that the frame transmission interval T4 does not coincide with an integral multiple of the first intermittent period T5, which will be described later. Specifically, the frame transmission interval T4 is set to a time interval shorter than the first intermittent period T5, which will be described later.

[0023] Furthermore, the periodic transmission cycle T1 of each TPMS transmitter 2a-2d can be changed within a predetermined reference range to avoid overlapping of frame transmission timing. For example, each TPMS transmitter 2a-2d calculates the periodic transmission cycle T1 by adding or subtracting a random value generated by a random number function or the like to a reference time, and transmits frames at each periodic transmission cycle T1. In this way, the periodic transmission cycle T1 is changed randomly each time. In the example shown in FIG. 5, the periodic transmission cycle T1a of the TPMS transmitter 2a of the left front tire FL is the shortest, and the periodic transmission cycle T1c of the TPMS transmitter 2c of the left rear tire RL is the longest. The periodic transmission cycle T1b of the TPMS transmitter 2b of the right front tire FR is shorter than the periodic transmission cycle T1d of the TPMS transmitter 2d of the right rear tire RR.

[0024] The TPMS transmitters 2a to 2d configured in this manner are attached to the air valves of the tires of the wheels 10a to 10d, respectively, so that the sensor units 21 are positioned in the interior spaces of the tires.

[0025] The integrated receiver 3 is an in-vehicle receiver attached to the vehicle body 11. The integrated receiver 3 constitutes part of the TPMS and also constitutes part of the Smart Entry (registered trademark) system. The integrated receiver 3 functions as a receiver that receives frames transmitted by the TPMS transmitters 2a to 2d, as well as a receiver that receives specific radio waves emitted by a portable device 4 such as an electronic key. To avoid interference, the radio waves emitted by the TPMS transmitters 2a to 2d and the specific radio waves emitted by the portable device 4 are set to different frequencies.

[0026] Here, the smart entry system is a system that performs authentication by wireless communication between the portable device 4 owned by a legitimate user of the vehicle 1 and the authentication ECU 5 via the integrated receiver 3 when the portable device 4 enters a wireless communication area around the vehicle 1. For convenience, the smart entry system may be referred to as "SMART" below.

[0027] The authentication ECU 5 performs control to check whether the portable device 4 is present in a wireless communication area around the vehicle 1. For example, as shown in FIG. 4, the authentication ECU 5 has a voltage signal terminal connected to the integrated receiver 3 while the start switch SSW is off. The authentication ECU 5 turns on a SMART request signal RCO, which is an output from the voltage signal terminal, at every predetermined first intermittent period T5 to switch the operation mode of the integrated receiver 3.

[0028] Specifically, when the SMART request signal RCO is turned on, the operation mode of the integrated receiver 3 transitions to a SMART reception mode in which specific radio waves can be received from the portable device 4. When the SMART request signal RCO is turned off, the operation mode of the integrated receiver 3 transitions to a power saving mode or a TPMS reception mode, which will be described later.

[0029] When the presence of the portable device 4 is confirmed, the authentication ECU 5 authenticates whether the portable device 4 is owned by a legitimate user. When authentication is successful, the authentication ECU 5 executes various controls such as unlocking the doors of the vehicle 1 and permitting the start of the drive source (e.g., the engine) of the vehicle 1.

[0030] Next, the main configuration of the integrated receiver 3 will be described with reference to Fig. 6. As shown in Fig. 6, the integrated receiver 3 includes a radio wave receiving unit 31, a power supply adjusting unit 32, and a TPMS control unit 33.

[0031] The radio wave receiving unit 31 has an input unit 311 and a receiving antenna unit 312. The input unit 311 receives frames sent from the TPMS transmitters 2a to 2d and specific radio waves emitted by the portable device 4 via the receiving antenna unit 312.

[0032] The radio wave receiving unit 31 is capable of changing the receiving frequency so that it can receive the specific radio wave emitted by the portable device 4 with priority over the radio waves emitted by the TPMS transmitters 2a to 2d. For example, while the SMART request signal RCO is on, the radio wave receiving unit 31 changes the receiving frequency to a frequency at which it can receive the specific radio wave emitted by the portable device 4 so that reception of the specific radio wave is given priority over reception of frames. Note that while the SMART request signal RCO is off, the radio wave receiving unit 31 changes the receiving frequency to a frequency at which it can receive the radio waves emitted by the TPMS transmitters 2a to 2d based on a control signal issued by the TPMS control unit 33.

[0033] When the radio wave receiving unit 31 receives the specific radio waves emitted by the portable device 4, it outputs data relating to door locking, unlocking, etc. contained in the specific radio waves to the authentication ECU 5. The radio wave receiving unit 31 also outputs frames emitted by the TPMS transmitters 2a to 2d to the TPMS control unit 33. Note that the above-described method of changing the receiving frequency of the input unit 311 is one example. The integrated receiver 3 may be configured to change the receiving frequency using a method different from that described above.

[0034] The power supply adjustment unit 32 generates power for driving the radio wave receiving unit 31 and the TPMS control unit 33 of the integrated receiver 3 from a predetermined voltage (+B) applied from the battery BT. The integrated receiver 3 operates based on the power generated by the power supply adjustment unit 32.

[0035] The TPMS control unit 33 is configured with a microcomputer including a processor and memory and its peripheral devices. The TPMS control unit 33 executes predetermined processes according to programs stored in the memory. The memory is configured as a non-transitory physical storage medium.

[0036] The TPMS control unit 33 is in an active operating mode while the start switch SSW is on, and various processes related to radio wave reception by the radio wave receiving unit 31 and tire pressure monitoring by the TPMS control unit 33 are executed as needed. In this embodiment, the TPMS control unit 33 constitutes a "control unit" that detects the occurrence of a drop in tire pressure based on data related to tire pressure included in frames transmitted from the TPMS transmitters 2a to 2d.

[0037] On the other hand, while the start switch SSW is off, the TPMS control unit 33 basically enters a power-saving mode with low power consumption, such as a sleep mode, but if a predetermined condition is met while the start switch SSW is off, it temporarily transitions to an active operating mode. Note that in the power-saving mode, the functions of the radio wave receiving unit 31 and the TPMS control unit 33 are limited, thereby suppressing dark current in the integrated receiver 3.

[0038] Since the tire pressure may fall below a predetermined warning threshold while the starter switch SSW is off, it is desirable to continue monitoring the tire pressure using the TPMS even while the starter switch SSW is off.

[0039] However, simply attempting to receive frames and specific radio waves separately while the start switch SSW is off increases the operating time of the integrated receiver 3 while the start switch SSW is off, resulting in a significant increase in dark current in the integrated receiver 3. Note that dark current is a standby current that constantly flows even while the start switch SSW is off.

[0040] Taking this into consideration, the TPMS control unit 33 transitions to SMART reception mode at every predetermined first intermittent period T5 while the start switch SSW is off, and transitions from SMART reception mode or power saving mode to TPMS reception mode at every predetermined second intermittent period T2.

[0041] The SMART reception mode is an operation mode in which the radio wave receiver 31 receives specific radio waves emitted by the portable device 4. For example, every time the SMART request signal RCO is turned on, the TPMS control unit 33 outputs a control signal indicating this to the radio wave receiver 31 and switches the reception frequency of the radio wave receiver 31 to a frequency at which the specific radio waves emitted by the portable device 4 can be received.

[0042] The TPMS reception mode is an operation mode in which tire pressures are monitored intermittently by causing the radio wave receiver 31 to receive frames. The TPMS control unit 33 outputs a control signal to the radio wave receiver 31 to instruct it to receive frames, for example, at every predetermined second intermittent period T2, and switches the reception frequency of the radio wave receiver 31 to a frequency at which it can receive radio waves emitted by the TPMS transmitters 2a to 2d.

[0043] In this way, the operating mode of the integrated receiver 3 while the start switch SSW is off can be switched between power saving mode, SMART reception mode, and TPMS reception mode. The SMART reception mode is a "specific mode" that causes the radio wave receiving unit 31 of the integrated receiver 3 to receive specific radio waves every predetermined first intermittent period T5. The TPMS reception mode is a "monitoring mode" that causes the radio wave receiving unit 31 of the integrated receiver 3 to receive frames every predetermined second intermittent period T2 to intermittently monitor tire pressure. The power saving mode is an operating mode that consumes less power than the SMART reception mode and the TPMS reception mode.

[0044] Upon receiving a frame from the radio wave receiver 31, the TPMS control unit 33 monitors for tire pressure drops based on the tire pressure data included in the received frame. Specifically, the TPMS control unit 33 calculates the tire pressure by performing various signal processing and calculations based on the tire pressure data stored in the frame. The monitoring control unit 331 then outputs an electrical signal corresponding to the calculated tire pressure to an external device 6, including an in-vehicle display, via a CAN or the like. For example, the monitoring control unit 331 compares the tire pressure with a predetermined alarm threshold, and if it detects that the tire pressure has dropped below the predetermined alarm threshold, it outputs a signal to that effect to the external device 6. The monitoring control unit 331 can also calculate the tire pressure for each of the four wheels 10a to 10d and display the tire pressure on the in-vehicle display in association with each wheel 10a to 10d.

[0045] The memory of the TPMS control unit 33 stores ID information for the TPMS transmitters 2a-2d installed on each of the wheels 10a-10d, associated with the position of each wheel 10a-10d. Therefore, by comparing the ID information stored in the frame, the TPMS control unit 33 can recognize which of the wheels 10a-10d the TPMS transmitter 2a-2d is attached to and identify the wheel with low tire pressure. Based on this, when a tire pressure drop occurs, the wheel with the low tire pressure is identified and displayed on the in-vehicle display.

[0046] Here, the shorter the cycle for monitoring tire pressure while the start switch SSW is off, the better the real-time performance, but the dark current of the integrated receiver 3 also increases. Therefore, the cycle for monitoring tire pressure while the start switch SSW is off is set longer than the cycle for receiving the specific radio waves emitted by the portable device 4. That is, the second intermittent cycle T2 is longer than the first intermittent cycle T5. It is desirable that the second intermittent cycle T2 be set to, for example, several hours. The first intermittent cycle T5 is set to, for example, one second or less. As a result, while the start switch SSW is off, a non-monitoring period in which the SMART reception mode and the power saving mode are alternately switched, and a monitoring period in which the SMART reception mode and the TPMS reception mode are alternately switched, are repeated.

[0047] Furthermore, the longer the monitoring time T3 for monitoring tire air pressure, the greater the increase in dark current, so it is desirable to set it to a small value. However, if it is too small, it becomes difficult to receive frames. For this reason, as shown in FIG. 3, the monitoring time T3 is set to a time longer than the periodic frame transmission cycle T1 of the TPMS transmitters 2a to 2d. Considering interference of frames from the TPMS transmitters 2a to 2d, it is desirable to set the monitoring time T3 to at least twice the periodic frame transmission cycle T1. Furthermore, considering the increase in dark current, the monitoring time T3 is set to be shorter than the second intermittent cycle T2.

[0048] The TPMS according to this embodiment is configured as described above. Next, the operation of the TPMS according to this embodiment will be described.

[0049] As shown in FIG. 3, while the start switch SSW is on, the TPMS receives frames transmitted from each of the TPMS transmitters 2a to 2d, and monitors the tire pressures described above based on the received frames.

[0050] On the other hand, while the start switch SSW is off, the TPMS receives specific radio waves emitted by the portable device 4 and intermittently receives frames transmitted from each of the TPMS transmitters 2a to 2d to monitor the tire pressure, as shown in Fig. 4. An example of control processing executed by the integrated receiver 3 while the start switch SSW is off will now be described with reference to Fig. 7. The control processing shown in Fig. 7 is periodically executed by the TPMS control unit 33 when the start switch SSW is turned off.

[0051] 7, in step S100, the integrated receiver 3 determines whether the second intermittent period T2 has elapsed. This determination process is performed based on the time measured by a timer built into the TPMS control unit 33.

[0052] If the time measured by the timer has not elapsed the second intermittent period T2, the multifunction receiver 3 determines in step S110 whether the SMART request signal RCO is off. Specifically, the multifunction receiver 3 determines that the SMART request signal RCO is off when the output of the voltage signal terminal is off. Also, the multifunction receiver 3 determines that the SMART request signal RCO is on when the output of the voltage signal terminal is on.

[0053] If the SMART request signal RCO is off, the multifunction receiver 3 goes to power saving mode in step S120 and turns off the reception function of the radio wave receiving unit 31 for frames and specific radio waves emitted by the portable device 4. The multifunction receiver 3 then exits this process. If the SMART request signal RCO is on, the multifunction receiver 3 goes to SMART reception mode in step S130 and turns on the reception function of the radio wave receiving unit 31 for specific radio waves. The multifunction receiver 3 then exits this process.

[0054] On the other hand, when the time measured by the timer has elapsed the second intermittent period T2, the multifunction receiver 3 determines in step S140 whether the SMART request signal RCO is OFF. Specifically, the multifunction receiver 3 determines that the SMART request signal RCO is OFF when the output of the voltage signal terminal is OFF. Furthermore, the multifunction receiver 3 determines that the SMART request signal RCO is ON when the output of the voltage signal terminal is ON.

[0055] If the SMART request signal RCO is ON, the integrated receiver 3 transitions to SMART reception mode in step S150 and turns on the specific radio wave reception function in the radio wave receiver 31. If the SMART request signal RCO is OFF, the integrated receiver 3 transitions to TPMS reception mode in step S160 and turns on the frame reception function in the radio wave receiver 31.

[0056] After setting the operation mode in steps S150 and S160, the integrated receiver 3 determines whether the monitoring time T3 has elapsed in step S170. This determination process is performed based on the time measured by a timer built into the TPMS control unit 33.

[0057] If the time measured by the timer has not elapsed the monitoring time T3, the multifunction receiver 3 returns to step S140 and again determines whether the SMART request signal RCO is off. On the other hand, if the time measured by the timer has elapsed the monitoring time T3, the multifunction receiver 3 resets the timer in step S180 and exits this process.

[0058] The TPMS integrated receiver 3 described above transitions to SMART reception mode at predetermined first intermittent cycles T5 while the start switch SSW is off, and transitions to TPMS reception mode at predetermined second intermittent cycles T2. This allows reception of specific radio waves and tire pressure monitoring to be performed intermittently while the start switch SSW is off, thereby reducing the operating time of the integrated receiver 3 while the start switch SSW is off. This makes it possible to receive specific radio waves and monitor tire pressure while suppressing an increase in dark current in the integrated receiver 3. The TPMS of this embodiment monitors tire pressure even while the start switch SSW is off, allowing for early notification of a drop in tire pressure to the user.

[0059] (1) The second intermittent period T2 is longer than the first intermittent period T5. While the start switch SSW is off, a non-monitoring period in which the SMART reception mode and the power saving mode alternate, and a monitoring period in which the SMART reception mode and the TPMS reception mode alternate are alternately repeated. This increases the time during which tire pressure is not monitored while the start switch SSW is off, thereby suppressing an increase in dark current in the integrated receiver 3 while the start switch SSW is off.

[0060] (2) The tire pressure monitoring time T3 in the TPMS reception mode is longer than the periodic frame transmission cycle T1. In this way, by making the monitoring time T3 longer than the periodic frame transmission cycle T1, it becomes easier for the integrated receiver 3 to properly receive frames.

[0061] (3) In this embodiment, the TPMS transmitters 2a to 2d transmit frames multiple times at transmission intervals T4 that are shorter than the regular transmission cycle T1. This allows the integrated receiver 3 to properly receive the frames transmitted by the TPMS transmitters 2a to 2d.

[0062] For example, for the right front tire FR shown in the top row of Figure 5, at time ta, the timing of frame transmission from the TPMS transmitter 2b overlaps with the timing when the SMART request signal RCO is turned on, so the frame cannot be received by the integrated receiver 3.

[0063] However, at time tc, which is a transmission interval T4 after time ta, the timing of the frame transmission from the TPMS transmitter 2b does not overlap with the timing when the SMART request signal RCO is turned on, so the frame can be received by the integrated receiver 3.

[0064] (4) The transmission interval T4 is a time interval that is different from an integer multiple of the first intermittent cycle T5. This prevents the frame transmission timing from consecutively overlapping with the timing when the SMART request signal RCO is turned on, making it easier for the integrated receiver 3 to properly receive the frames transmitted by the TPMS transmitters 2a to 2d.

[0065] (5) Specifically, the transmission interval T4 is set to a time interval shorter than the first intermittent cycle T5, which makes it easier for the integrated receiver 3 to receive frames transmitted by the TPMS transmitters 2a to 2d in a short period of time.

[0066] (6) The periodic transmission cycle T1 of each of the TPMS transmitters 2a to 2d can be changed within a predetermined reference range. This prevents the frames transmitted by each of the TPMS transmitters 2a to 2d from continuously arriving at the integrated receiver 3 at the same time, allowing the frames transmitted by the TPMS transmitters 2a to 2d to be properly received by the integrated receiver 3.

[0067] For example, as shown in the second and third rows from the top of Figure 5, at times tb and td, the frame transmission timings of the TPMS transmitter 2a of the left front tire FL and the TPMS transmitter 2d of the right rear tire RR overlap, making it impossible for the integrated receiver 3 to properly receive the frames.

[0068] However, the regular transmission cycle T1a of the TPMS transmitter 2a of the front left tire FL is shorter than the regular transmission cycle T1d of the TPMS transmitter 2d of the rear right tire RR.

[0069] As a result, at times tg and tj, which are the periodic transmission cycle T1a after times tb and td, the frame transmission timing of the TPMS transmitter 2a for the left front tire FL does not overlap with the frame transmission timing of the TPMS transmitter 2d for the right rear tire RR, and the integrated receiver 3 can receive the frame transmitted from the TPMS transmitter 2a for the left front tire FL.

[0070] Furthermore, at times ti and tl, which are the periodic transmission cycle T1d after times tb and td, the frame transmission timing of the TPMS transmitter 2a of the right rear tire RR does not overlap with the frame transmission timing of the TPMS transmitter 2d of the left front tire FL, so the integrated receiver 3 can receive the frame transmitted from the TPMS transmitter 2d of the right rear tire RR.

[0071] In the example shown in Fig. 5, the timing of frame transmission from the TPMS transmitter 2c of the rear left tire RL shown in the bottom row of Fig. 5 does not overlap with the timing of frame transmission from the other TPMS transmitters 2a, 2b, and 2d and the timing when the SMART request signal RCO is turned on. Therefore, at times te, tf, tm, and tn, the integrated receiver 3 can receive frames transmitted from the TPMS transmitter 2d of the rear right tire RR.

[0072] (Second embodiment) Next, a second embodiment will be described with reference to Fig. 8. In this embodiment, differences from the first embodiment will be mainly described.

[0073] Fig. 8 corresponds to the flowchart of Fig. 7 described in the first embodiment. The processes of steps S100 to S180 in Fig. 8 are the same as the processes of steps S100 to S180 in Fig. 7, and therefore their description will be omitted.

[0074] 8, if the multifunction receiver 3 determines in step S170 that the monitoring time T3 has not elapsed, the process proceeds to step S190. In step S190, the multifunction receiver 3 determines whether or not it has completed receiving frames from all of the TPMS transmitters 2a to 2d and has received the tire pressures of all of the tires.

[0075] If the tire pressures of all tires have not been received, the multifunction receiver 3 returns to step S140 and determines again whether the SMART request signal RCO is off. On the other hand, if the tire pressures of all tires have been received, the multifunction receiver 3 resets the timer in step S180 and exits this process.

[0076] The other points are the same as those in the first embodiment. The integrated receiver 3 of this embodiment can obtain the same effects as those in the first embodiment that are achieved by a configuration common to or equivalent to that of the first embodiment.

[0077] Furthermore, according to this embodiment, the following effects can be obtained.

[0078] (1) When the TPMS control unit 33 completes receiving frames from the TPMS transmitters 2a to 2d in the TPMS reception mode, it transitions to the power saving mode. This suppresses unnecessary operation of the integrated receiver 3 while the start switch SSW is off, and effectively suppresses an increase in dark current in the integrated receiver 3.

[0079] (Third embodiment) Next, a third embodiment will be described with reference to Fig. 9. In this embodiment, differences from the first embodiment will be mainly described.

[0080] In the TPMS of the first embodiment, the frame transmission interval T4 is the same for each of the TPMS transmitters 2a to 2d. In contrast, in the TPMS of this embodiment, the frame transmission interval T4 is variable within a predetermined range to prevent overlapping of frame transmission timing among the TPMS transmitters 2a to 2d. For example, each of the TPMS transmitters 2a to 2d calculates the transmission interval T4 by adding or subtracting a random number generated by a random number function or the like to a reference interval, and transmits frames at this transmission interval T4.

[0081] In this way, the frame transmission interval T4 is changed randomly each time. For example, in the example shown in Fig. 9, the transmission interval T4b of the TPMS transmitter 2b for the right front tire FR is the shortest, and the transmission interval T4d of the TPMS transmitter 2d for the right rear tire RR is the longest. Furthermore, the transmission interval T4a of the TPMS transmitter 2a for the left front tire FL is longer than the transmission interval T4c of the TPMS transmitter 2c for the left rear tire RL.

[0082] The other points are the same as those in the first embodiment. The integrated receiver 3 of this embodiment can obtain the same effects as those in the first embodiment that are achieved by a configuration common to or equivalent to that of the first embodiment.

[0083] Furthermore, according to this embodiment, the following effects can be obtained.

[0084] (1) Each of the TPMS transmitters 2a to 2d is able to change the frame transmission interval T4 within a predetermined range. This prevents the frames transmitted by each of the TPMS transmitters 2a to 2d from consecutively arriving at the integrated receiver 3 at the same time, allowing the integrated receiver 3 to properly receive the frames transmitted by the TPMS transmitters 2a to 2d.

[0085] For example, as shown in the second and third rows from the top of Figure 9, at time tb, the frame transmission timing of the TPMS transmitter 2a of the left front tire FL and the TPMS transmitter 2d of the right rear tire RR overlap, so the frame cannot be received by the integrated receiver 3.

[0086] However, the transmission interval T4a of the TPMS transmitter 2a of the front left tire FL is shorter than the transmission interval T4d of the TPMS transmitter 2d of the rear right tire RR.

[0087] As a result, at time td, which is a transmission interval T4a after time tb, the frame transmission timing of the TPMS transmitter 2a for the left front tire FL does not overlap with the frame transmission timing of the TPMS transmitter 2d for the right rear tire RR, and the integrated receiver 3 can receive the frame transmitted from the TPMS transmitter 2a for the left front tire FL.

[0088] At time te, which is a transmission interval T4d after time tb, the frame transmission timing of the TPMS transmitter 2a of the right rear tire RR does not overlap with the frame transmission timing of the TPMS transmitter 2d of the left front tire FL, so the integrated receiver 3 can receive the frame transmitted from the TPMS transmitter 2d of the right rear tire RR.

[0089] (Modification of the third embodiment) The TPMS may be configured such that, for example, one of the frame transmission interval T4 and the regular transmission cycle T1 in each of the TPMS transmitters 2a to 2d is changeable, and the other is not changeable.

[0090] (Fourth embodiment) Next, a fourth embodiment will be described with reference to Fig. 10. In this embodiment, differences from the first embodiment will be mainly described.

[0091] Each of the TPMS transmitters 2a to 2d in the first embodiment is configured to transmit a frame multiple times at a transmission interval T4 that is shorter than the regular transmission cycle T1. In contrast, each of the TPMS transmitters 2a to 2d in this embodiment is configured to transmit a frame multiple times in succession. For example, as shown in FIG. 10, each of the TPMS transmitters 2a to 2d is configured to transmit a frame three times in succession. Note that the number of consecutive frame transmissions is not limited to three, and may be two or four or more times.

[0092] The other points are the same as those in the first embodiment. The integrated receiver 3 of this embodiment can obtain the same effects as those in the first embodiment that are achieved by a configuration common to or equivalent to that of the first embodiment.

[0093] Furthermore, according to this embodiment, the following effects can be obtained.

[0094] (1) The multiple TPMS transmitters 2a to 2d transmit frames consecutively multiple times. This also makes it difficult for the frames transmitted by the multiple TPMS transmitters 2a to 2d to arrive at the integrated receiver 3 at the same time, making it easier for the integrated receiver 3 to properly receive the frames transmitted by each of the TPMS transmitters 2a to 2d.

[0095] (Fifth embodiment) Next, a fifth embodiment will be described, focusing on differences from the first embodiment.

[0096] Generally, punctures and other abnormalities are more likely to occur while the vehicle is moving rather than while it is stopped, so it is thought that tire air is more likely to change immediately after the start switch SSW is turned off.

[0097] Taking this into consideration, the TPMS control unit 33 is configured to change the time interval of the second intermittent period T2 within a predetermined range.

[0098] The other points are the same as those in the first embodiment. The integrated receiver 3 of this embodiment can obtain the same effects as those in the first embodiment that are achieved by a configuration common to or equivalent to that of the first embodiment.

[0099] (1) In the TPMS of this embodiment, the time interval of the second intermittent period T2 is changed within a predetermined range. This is expected to suppress unnecessary operations in the integrated receiver 3 and sufficiently suppress an increase in dark current in the integrated receiver 3.

[0100] (Modification of the fifth embodiment) For example, the TPMS control unit 33 may be configured to periodically or irregularly change the time interval of the second intermittent period T2 within a predetermined range.

[0101] (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.

[0102] As in the above embodiment, it is desirable that the second intermittent period T2 be longer than the first intermittent period T5, but this is not necessarily the case.

[0103] In the above embodiment, the monitoring time T3 is set to be longer than the regular transmission cycle T1, but the present invention is not limited to this. For example, the monitoring time T3 may be set to be shorter than the regular transmission cycle T1.

[0104] As in the above embodiment, it is desirable that the TPMS transmitters 2a to 2d transmit frames multiple times at transmission intervals T4 that are shorter than the regular transmission cycle T1, but this is not necessarily required.

[0105] As in the above embodiment, it is desirable that the transmission interval T4 be a time interval other than an integer multiple of the first intermittent cycle T5, but this is not required. Also, it is desirable that the transmission interval T4 be a time interval shorter than the first intermittent cycle T5, but this is not required.

[0106] As in the above-described embodiment, it is desirable that the transmission interval T4 of the TPMS transmitters 2a to 2d be changeable within a predetermined range, but this is not necessarily the case.

[0107] As in the above-described embodiment, it is desirable that the regular transmission cycle T1 of the TPMS transmitters 2a to 2d be changeable within a predetermined reference range, but this is not necessarily the case.

[0108] It is desirable that the integrated receiver 3 predicts the timing of frame transmission from the TPMS transmitters 2a to 2d based on the time of reception of the TPMS transmitters 2a to 2d, and adjusts the timing of monitoring the tire pressure using the prediction result.

[0109] Here, when the specific radio waves emitted by the portable device 4 are received, the operating time in SMART reception mode is longer than when the specific radio waves are not received. For this reason, it is desirable to set the transmission interval T4 to a time interval that is longer than the operating time in SMART reception mode when the specific radio waves emitted by the portable device 4 are received.

[0110] In the above embodiment, a TPMS applied to a vehicle 1 having four wheels 10a to 10d has been described, but the present disclosure is applicable to vehicles having three wheels and vehicles having five or more wheels.

[0111] 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.

[0112] 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 specifically stated as essential or are clearly limited to a specific number in principle.

[0113] 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 fundamentally limited to specific shapes, positional relationships, etc.

[0114] The controller and method of the present disclosure may be implemented on a special-purpose computer by configuring a processor and memory programmed to perform one or more functions embodied in a computer program. The controller and method of the present disclosure may be implemented on a special-purpose computer by configuring a processor with one or more dedicated hardware logic circuits. The controller and method of the present disclosure may be implemented on one or more special-purpose computers configured with a processor and memory programmed to perform one or more functions in combination with a processor configured with one or more hardware logic circuits. The computer program may also be stored on a computer-readable non-transitory tangible storage medium as instructions executed by a computer. [Explanation of symbols]

[0115] 1 vehicle 10a~10d wheels 11 Body 2a~2d TPMS transmitter (transmitter) 3 Integrated receiver (vehicle receiver) 31 Radio wave receiving unit 33 TPMS control unit (control unit) SSW Start switch

Claims

1. An in-vehicle receiver included in a tire pressure monitoring system applied to a vehicle (1) having a plurality of wheels (10a to 10d) with tires, a radio wave receiving unit (31) for receiving frames containing information about tire pressures transmitted at a predetermined periodic transmission interval (T1) by transmitters (2a to 2d) provided on the tires of each of the plurality of wheels and a specific radio wave emitted by a portable device (4); a control unit (33) that detects occurrence of a decrease in tire air pressure based on data related to tire air pressure included in the frame, The control unit, while the start switch (SSW) of the vehicle is off, transitions to a specific mode in which the radio wave receiving unit receives the specific radio waves at every predetermined first intermittent period (T5), and transitions from the specific mode or the power saving mode to a monitoring mode in which the radio wave receiving unit receives the frames at every predetermined second intermittent period (T2) to intermittently monitor tire pressure.

2. 2. The in-vehicle receiver according to claim 1, wherein the second intermittent period is longer than the first intermittent period so that, while the start switch is off, a non-monitoring period in which the specific mode and the power saving mode are alternately switched and a monitoring period in which the specific mode and the monitoring mode are alternately switched are repeated.

3. 3. The vehicle-mounted receiver according to claim 1, wherein a tire pressure monitoring time (T3) in the monitoring mode is longer than the periodic transmission cycle.

4. 4. The in-vehicle receiver according to claim 1, wherein the control unit transitions to the power saving mode when reception of the frames from all the transmitters is completed in the monitoring mode.

5. The in-vehicle receiver according to claim 1 , wherein the control unit changes the time interval of the second intermittent cycle within a predetermined range.

6. A tire pressure monitoring system applied to a vehicle (1) having a plurality of wheels (10a-10d) with tires, a plurality of transmitters (2a to 2d) provided on the tires of the plurality of wheels, respectively, for transmitting frames including information about tire pressures at a predetermined regular transmission cycle (T1); an in-vehicle receiver (3) provided on the vehicle body (11), The in-vehicle receiver includes: a radio wave receiving unit (31) for receiving specific radio waves emitted by the frame and the portable device (4); a control unit (33) that detects occurrence of a decrease in tire air pressure based on data related to tire air pressure included in the frame, The control unit, while the vehicle start switch (SSW) is off, transitions to a specific mode in which the radio wave receiving unit receives the specific radio waves at every predetermined first intermittent period (T5), and transitions from the specific mode or the power saving mode to a monitoring mode in which the radio wave receiving unit receives the frames at every predetermined second intermittent period (T2) to intermittently monitor tire pressure.

7. 7. The tire pressure monitoring system according to claim 6, wherein the plurality of transmitters transmit the frame a plurality of times at a transmission interval (T4) that is shorter than the regular transmission cycle.

8. 8. The tire pressure monitoring system according to claim 7, wherein the transmission interval is a time interval that is different from an integer multiple of the first intermittent period.

9. 9. The tire pressure monitoring system according to claim 8, wherein the transmission intervals of the plurality of transmitters are variable within a predetermined range.

10. 8. The tire pressure monitoring system according to claim 6, wherein the plurality of transmitters transmit the frame consecutively a plurality of times.

11. 11. The tire pressure monitoring system according to claim 6, wherein the periodic transmission interval of each of the plurality of transmitters is variable within a predetermined reference range.

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