JP2007276643A - Tire pneumatic pressure monitoring device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tire pneumatic pressure monitoring device enabling the data transmitted by a transmission unit to be reliably received by a reception unit, and saving the power in the transmission unit. <P>SOLUTION: The delay time for transmitting the packet at the timing different for each transmitter 55 is set so that the timing of transmitting the packet by the transmitter 55 is not superposed on the timing of transmitting the packet by the other transmitter 55. A receiver 61 is in a sleep state in the set time after stopping each tire, and started for a predetermined time at every elapse of the interval time from the delay time of each transmission unit. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention belongs to a technical field of a tire pressure monitoring device that receives tire pressure information detected by a tire pressure sensor attached to a tire of a vehicle by a receiver attached to a vehicle body and monitors each tire pressure.

As this type of technology, the technology described in Patent Document 1 is disclosed. In this publication, when the vehicle speed is equal to or lower than the set vehicle speed, the receiving unit repeats activation and sleep at a predetermined interval. At this time, the data transmission time during which the transmission unit transmits data is set to be longer than the interval time at which the reception unit is activated.
JP 2005-153641 A

  In the above prior art, in order to save power of the transmission unit, the transmission unit transmits data when the vehicle speed is equal to or lower than the set vehicle speed. The interval at which data is transmitted when the vehicle speed is higher than the set vehicle speed. It is set long.

  In addition, although the receiving unit is always activated when the vehicle speed is higher than the set vehicle speed, when the vehicle speed is equal to or lower than the set vehicle speed, the receiving unit also saves power by repeating activation and sleep at a predetermined interval. I am trying.

  However, the data transmission time during which the transmission unit transmits data is set to be longer than the interval time during which the reception unit is activated, so the time during which the transmission unit is activated is also increased, and the power consumption of the transmission unit is increased. There was a problem that sometimes became larger.

  The present invention has been made paying attention to the above problems, and the object of the present invention is to ensure that the data transmitted by the transmission unit is received by the reception unit and to further save power in the transmission unit. An object of the present invention is to provide a tire pressure monitoring device.

  In order to achieve the above object, according to the present invention, a tire pressure detecting unit for detecting each tire pressure, a packet creating unit for creating a packet as a collection of data including at least tire pressure information, and transmitting the packet by a radio signal A transmission unit, a transmission unit attached to each of a plurality of tires mounted on the vehicle, a reception unit that receives a packet transmitted by a radio signal from the transmission unit, and a tire pressure included in the packet Tire pressure monitoring means comprising: tire pressure determining means for determining from the information that the tire air pressure has fallen below the set value; and notifying means for notifying the driver when the tire air pressure falls below the set value. In the apparatus, the transmission means includes a wheel stop state detection unit for detecting a stop state of each tire, and a transmission after each tire stop. A delay time setting unit that sets a delay time for different transmission timing for each transmission unit, and a transmission unit that transmits a packet so that the transmission timing of the packet does not overlap with the transmission timing of another transmission unit. An interval setting unit that sets an interval time from transmission to transmission of the next packet, and after each tire stop, a delay time measurement unit that measures a delay time for each transmission unit is provided, and the reception unit is The tires are put into a sleep state after a set time after the tires stop, and are activated for a predetermined time every interval time from the delay time of each transmitter.

  Therefore, since the delay time measuring unit measures the unit delay time, the receiving unit is activated in accordance with the measured delay time of the transmitting unit, and in other cases, it is possible to enter a sleep state. In addition, the number of packet transmissions of the transmission unit can be reduced. Therefore, the transmission time of the transmission unit can be shortened, the activation time of the reception unit can be shortened, and power saving of the transmission unit and the reception unit can be achieved.

  Hereinafter, the best mode for carrying out the present invention will be described based on the first embodiment.

  First, the configuration will be described.

  FIG. 1 is an overall system diagram showing a vehicle to which the tire pressure monitoring apparatus according to the first embodiment is applied. The tire pressure monitoring device includes a right front wheel tire 1, a left front wheel tire 2, a right rear wheel tire 3, and a left rear wheel tire 4. Each tire is provided with a transmission unit 5 that detects the tire pressure and transmits the detected tire pressure information in a packet. On the vehicle body side, a receiving unit 6 for receiving a packet transmitted by each transmitting unit 5 is provided.

  FIG. 2 is a block diagram showing the configuration of the transmission unit 5.

  The transmission unit (transmission means) 5 includes a centrifugal force switch (wheel stop state detection unit) 50, an air pressure sensor (tire pressure detection unit) 51, an interval timer 52, a delay time storage unit (delay time setting unit) 53, transmission data. A memory (packet creation unit) 54, a transmitter (transmission unit) 55, and a control device 56 are provided.

  The centrifugal force switch 50 determines whether the wheel is rotating or stopped from the centrifugal force generated by the rotation of the wheel. It is ON when the wheel is rotating, and OFF when the wheel is stopped, and outputs each signal to the control device 56.

  The air pressure sensor 51 detects the tire air pressure and outputs it to the control device 56 as tire air pressure information.

  The interval timer 52 controls the transmission interval (transmission interval) of the transmitter 55.

  The delay time storage unit 53 stores a delay time set so that the transmission timing of the transmitter 55 does not overlap with the transmission timing of the transmitter 55 provided in another tire. This delay time is set to a different time for each transmitter 55.

  The transmission data memory 54 stores information on packets transmitted from the transmitter 55.

The transmitter 55 transmits a packet as a radio signal based on a signal from the control device 56. The following information is put on the packet as a code.
Header: Bit information attached as a mark for notifying the beginning of a group of data in serial communication. A normal packet carries information such as a communication method and synchronization between the transmission side and the reception side.
Function: Information indicating that a normal pressure or an abnormal pressure has been detected in the air pressure sensor 51, wake-up, and a tire ID initialization request, which will be described later, are placed.
ID: Information on the unique code set for each transmitter 55 is placed.
・ Data: Tire pressure information is placed.
CS: A checksum provided for checking received data on the data receiving side.

  The control device 56 controls the transmitter 55 based on input information from each device.

  Next, the configuration of the receiving unit 6 will be described.

  FIG. 3 is a block diagram showing the configuration of the receiving unit 6.

  The receiving unit 6 includes a receiver (reception unit) 61, an interval time measurement unit 62, a delay time measurement unit (delay time measurement unit) 63, a determination unit (tire pressure determination unit) 64, a display unit (notification unit) 65, A control device 66 is provided.

  The receiver 61 receives the packet transmitted from the transmitter 55 and outputs tire pressure information of the Data code of the packet to the control device 66.

  The interval time measurement unit 62 starts measurement when receiving a packet from the transmitter 55 while the vehicle is stopped, and outputs the elapsed time to the control device 66.

  The delay time measuring unit 63 measures the delay time of the transmitter 55 attached to each tire 1 to 4 in a synchronization mode described later. The delay time is set according to the ID code provided in each transmitter 55. For this reason, when the ID code of the transmitter 55 is not recognized in advance, the delay time is measured from the transmission timing of each transmitter 55 in the synchronous mode. The measured delay time information is output to the control device 66.

  The determination unit 64 determines whether or not the tire air pressure is lower than a set value, and outputs this determination information to the control device 66. For the set value, a tire pressure suitable for vehicle travel is obtained in advance by experiment or calculation.

  When the tire pressure is lower than the set value, the display unit 65 notifies the driver that the tire pressure is decreasing.

  The control device 66 controls the receiver 61 and the display unit 65 based on input information from each device.

  Next, the operation will be described.

  In a tire air pressure monitoring apparatus such as the present invention, a transmission unit having an air pressure sensor and a transmitter is attached to each tire of a vehicle. Therefore, since the transmission unit rotates together with the tire, it is difficult to supply power from the vehicle battery. Therefore, an individual battery is provided in the transmission unit. However, since the transmission unit is mounted on the tire, a small volume is required and it is difficult to perform charging or the like. Therefore, power saving of the transmission unit is required.

  As a method for reducing the power consumption of the transmission unit, for example, a method is proposed in which the interval at which the transmitter transmits a packet is set to about several minutes while the vehicle is traveling, and is set to about several hours when the vehicle is stopped. ing. In addition, when the vehicle is stopped, packets are transmitted from the transmitter every few hours, so the receiver is activated only when packets are transmitted from the transmitter, and otherwise the sleep state is set. Also, the power saving of the receiving unit is planned.

  However, in order to perform the above operation, it is necessary to adjust the timing so that the receiver starts from the sleep state so that the receiver can reliably receive the packet from the transmitter.

  A conventional example of matching the packet transmission / reception timing between the transmitter and the receiver will be described with reference to FIG.

(Transmitter)
When the transmitter of the transmission unit attached to each tire detects that the tire has stopped, transmission is performed at intervals of several hours. After the interval, the packet transmission timing is randomly shifted for each transmitter, and the packet is transmitted a plurality of times (five times in FIG. 4).

(Receiving machine)
If the receiver cannot receive a packet from the transmitter even after a predetermined time has elapsed, the receiver enters a sleep state (time t1). Further, when a predetermined time elapses after entering the sleep state, it is activated again (time t3), and when a packet is received from the transmitter of each tire, the sleep state is again entered (time t5).

  Due to the action of the transmitter and the receiver, the success rate of successful transmission and reception of packets between the transmitter and the receiver is improved.

  For example, at time t2 in FIG. 4, the transmitter of the left rear wheel tire starts transmitting packet (A). At this time, since the receiver has not started yet, packet (A) cannot be received. However, it is possible to receive a packet (b) transmitted from the transmitter of the left rear wheel tire from the rear.

  Also, at time t4 in FIG. 4, the transmitter of the right front wheel tire starts transmitting the packet (c). At this time, the transmitter of the left rear wheel tire transmits the packet (d), so a collision occurs. Therefore, the receiver cannot correctly receive the packet (c). However, after the transmitter of the left rear wheel tire finishes transmitting the packet, the packet (e) transmitted by the transmitter of the right front wheel tire can be received.

  However, since the transmitter transmits a packet a plurality of times, the transmission time of the transmitter becomes long, and power consumption may increase. In addition, since each transmitter performs transmission at random, the receiver must continue to be activated until packets from all transmitters are received. As a result, power consumption may increase in the receiver.

  Therefore, in the first embodiment, the delay time is set in advance so that the packet transmission timing of the transmitter 55 does not overlap the packet transmission timing of the other transmitters 55.

  Further, the receiver 61 measures the delay time of each transmitter 55 in the synchronous mode. The receiver 61 is activated for a predetermined time according to the interval of the transmitter 55 and the measured delay time.

  FIG. 5 is a table showing the delay time of the transmitter 55. A unique ID is recorded on the transmitter 55 attached to each tire. A delay time is set for each ID of the transmitter 55. For example, the delay time of the transmission unit 5 with ID "0000" is 0 (zero) seconds, and the delay time of the transmission unit 5 with ID "0001" is 2 seconds. Is set as follows.

  In FIG. 5, the delay time of the transmission unit 5 for each ID is 2 seconds, but this is based on the sum of the variation in stopping the tires 1 to 4 and the timing error at which the centrifugal force switch 50 determines the tire stop. May be set to a large value. As a result, even if there is a deviation in the timing at which each centrifugal force switch 50 determines the stop of the tire, the transmission timing of each transmitter 55 does not overlap.

  FIG. 6 is a time chart showing an example of the operation of the tire pressure monitoring apparatus in the first embodiment.

(Transmitter)
The transmitter 55 transmits a packet after the delay time has elapsed after detecting the stop of each tire (time T1). Thereafter, each transmitter 55 transmits a packet for each preset interval.

  For example, since the ID of the transmitter 55 for the right front wheel tire is “0003”, the delay time is 6 seconds from Table 5. Therefore, the transmitter 55 for the right front wheel tire detects that the right front wheel tire has stopped, and transmits the packet (a) 6 seconds later (time T2). Similarly, the transmitters 55 of other tires also transmit packets after their respective delay times.

  Thereafter, the transmitter 55 for the right front wheel tire transmits the packet (b) after a preset interval has elapsed (time T7). Similarly, the transmitters 55 of other tires also transmit packets at intervals.

(Receiving machine)
The receiver 61 receives a packet transmitted from each transmitter 55 after each tire stops, and enters a sleep state when receiving packets from all the transmitters 55 to which the vehicle is attached (from time T3 to time T4: sleep). mode). In the delay time measuring unit 63, the delay of each transmitter 55 is determined from the packet transmission timing of each transmitter 55 during the time from when the tire stops until the receiver 61 enters the sleep state (from time T1 to time T3: synchronous mode). Measure time.

  Next, the receiver 61 is activated when the interval of each transmitter 55 elapses after each tire stops. In FIG. 6, the activation is performed slightly before (time T4) the time (time T5) when the interval of the left front wheel tire with the shortest delay time has elapsed. Since it is activated at time T4 in order to receive a packet more reliably, it may be activated at time T5. After restarting, the receiver 61 goes back to sleep again when a time sufficiently longer than the packet transmission time of the transmitter 55 has elapsed (time T6). After that, the transmitter 55 is activated before transmitting a packet in accordance with the delay time of each transmitter 55. When a time sufficiently longer than the packet transmission time of the transmitter 55 has elapsed (time T6), the sleep state is again entered. Repeat from time T4 to time T8 (restart mode).

  Thereafter, the receiver 61 repeats the sleep mode and the restart mode until the tire starts to rotate (the vehicle starts).

  As a result of the above operation, the delay time measuring unit 63 measures the delay time of each transmitter 55 in the synchronous mode. Therefore, the receiver 61 is activated according to the measured delay time of each transmitter 55 in the restart mode. In other cases, the sleep mode can be set.

  In addition, a delay time is provided so that the transmission timing of each transmitter 55 and the transmission timing of other transmitters 55 do not overlap with each other, and the receiver 61 is synchronized with the transmission timing of the transmitter 55. Should be sent once.

  Therefore, while ensuring the transmission / reception of packets between the transmitter 55 and the receiver 61 when the tire is stopped, the transmission time of the transmitter 55 is shortened and the start-up time of the receiver 61 is also shortened compared to the conventional example. It becomes possible to do.

  Next, the effect will be described.

  (1) An air pressure sensor 51 (tire pressure detector) and a transmission data memory 54 (packet creation) for storing packet data in a transmission unit 5 (transmission means) attached to each of a plurality of tires mounted on the vehicle Part), a transmitter 55 (transmission part) that transmits a packet by radio signal, a centrifugal force switch 50 (wheel stop state detection part) that detects a stop state of each tire, and a transmitter 55 that transmits the packet Interval timer 52 (interval setting unit) that sets an interval from when the next packet is transmitted, the timing at which the transmitter 55 transmits the packet, and the timing at which the other transmitter 55 transmits the packet do not overlap A delay time storage unit 53 (delay for setting a delay time for transmitting a packet at a different timing for each transmitter 55. Between setting section) was formed.

  In addition, the receiving unit 6 installed on the vehicle body side receives the packet transmitted from the transmitter 55 by radio signal, and the tire pressure falls below the set value from the tire pressure information. A determination unit 64 (tire air pressure determination unit) for determining the above, a display unit 65 (notification unit) for notifying the driver when the tire air pressure falls below a set value, and a transmitter 55 for each transmitter 55 after each tire stops. A delay time measuring unit 63 (delay time measuring means) for measuring the delay time is provided.

  The receiver 61 enters a sleep state after a set time after each tire stops, and is activated for a predetermined time every interval time from the delay time of each transmitter.

  Therefore, since the delay time measuring unit 63 measures the delay time of each transmitter 55 in the synchronous mode, the receiver 61 is activated according to the measured delay time of each transmitter 55 in the restart mode, and otherwise. In this case, the sleep state can be set. In addition, the number of packet transmissions of the transmitter 55 can be reduced. For this reason, the transmission time of the transmitter 55 can be shortened, the startup time of the receiver 61 can be shortened, and power savings of the transmitter 55 and the receiver 61 can be achieved.

(Other examples)
Although the best mode for carrying out the present invention has been described based on the first embodiment, the specific configuration of the present invention is not limited to the first embodiment.

  For example, when a keyless entry system is mounted on a vehicle, tire pressure information may be transmitted to the portable terminal when the driver goes out of the vehicle.

1 is an overall system diagram of a tire pressure monitoring system according to a first embodiment. 3 is a block diagram of a transmission unit according to Embodiment 1. FIG. 2 is a block diagram of a receiving unit according to Embodiment 1. FIG. It is a time chart of an effect | action of the transmitter and receiver of a prior art example. It is a figure which shows the setting of the delay time of Example 1. FIG. It is a time chart of an effect | action of the transmitter and receiver of Example 1. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Right front wheel tire 2 Left front wheel tire 3 Right rear wheel tire 4 Left rear wheel tire 5 Transmission unit 6 Reception unit 50 Centrifugal force switch 51 Air pressure sensor 52 Interval timer 53 Delay time memory | storage part 54 Transmission data memory 55 Transmitter 61 Receiver 63 Delay time measurement unit 64 Judgment unit 65 Display unit

Claims (1)

A tire pressure detector for detecting each tire pressure;
A packet creation unit for creating a packet as a collection of data including at least information on the tire pressure;
A transmitter for transmitting the packet by a radio signal;
A transmission means attached to each of a plurality of tires mounted on the vehicle,
Receiving means for receiving the packet transmitted by a radio signal from the transmitting means;
Tire pressure determining means for determining from the tire pressure information included in the packet that the tire pressure is below a set value;
When the tire pressure falls below a set value, notifying means for notifying the driver;
In a tire pressure monitoring device comprising:
The transmission means includes
A wheel stop state detector for detecting the stop state of each tire;
A delay for setting a delay time for making the transmission timing different for each transmission unit so that the timing at which the transmission unit transmits a packet and the timing at which another transmission unit transmits a packet do not overlap after each tire stop A time setting section;
An interval setting unit for setting an interval time from when the transmission unit transmits a packet until the next packet is transmitted;
Have
After each tire stop, provided a delay time measuring means for measuring the delay time for each transmission unit,
The tire pressure monitoring device, wherein the receiving unit is a unit that enters a sleep state after a set time after the tires stop and starts for a predetermined time every interval time from the delay time of each transmitter. .

Images