JP2007283816A - Tire air pressure monitoring device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tire air pressure monitoring device capable of receiving certainly the data transmitted from a transmitter unit using a receiver unit and capable of saving the power consumed by the transmitter unit. <P>SOLUTION: The tire air pressure monitoring device is equipped with the transmitter unit 5 (transmitting means) having an air pressure sensor 51 (air pressure sensing part), a normal packet transmission data memory 54 and a low-consumption packet transmission data memory 55 (packet preparing part), and a transmitter 56 (transmission part) and attached to each tire, a receiver 61 (receiving means), a judgement part 63 (air pressure judging means) to judge that the tire air pressure has sunk below the set value, an indication part 64 (notifying means) to notify the driver of a drop of the tire air pressure, and a centrifugal switch 50 (stopped condition sensing means) to sense the vehicle running or being stopped, wherein the transmitter 56 transmits the normal packet while the vehicle is running and does the low-consumption packet having a smaller data amount than the normal packet while the vehicle is stopped. <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 is activated 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

  However, in the above prior art, since the data transmission time for the transmission unit to transmit data becomes longer, the time for which the transmission unit is activated also becomes longer, and the power consumption of the transmission unit may increase. There was a problem that there was.

  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 save power in the transmission unit. The object 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, when the vehicle is stopped, the stop state detection means for detecting the stop state of the vehicle and the packet creation unit Data amount of packets to be created, and to be smaller than the data amount of packets to be created when the vehicle is traveling.

  If there is no effect due to changes in tire pressure, such as when the vehicle is stopped, even if the information transmitted by the transmitter is insufficient, it does not immediately fall into a dangerous state. Only the data needs to be included in the packet. Therefore, in the present invention, the data amount of the packet to be transmitted when the transmission unit determines that there is no influence due to the change in tire air pressure in the running state, the packet data to be created when it is determined that there is an influence. Since it is smaller than the data amount, the transmission time can be reduced. Therefore, it is possible to save the power of the transmission means.

  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. The vehicle is provided with a receiving unit 6 that receives a packet transmitted by each transmitting unit 5.

  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 (stop state detection means) 50, an air pressure sensor (tire pressure detection section) 51, an interval timer 52, a switching section 53, and a normal packet transmission data memory (packet creation section) 54. A low-consumption packet transmission data memory (packet creation unit) 55, a transmitter (transmission unit) 56, and a control device 57 are provided.

  The centrifugal force switch 50 determines whether the vehicle is running or stopped from the centrifugal force generated by the rotation of the wheels, and is turned on while the vehicle is running and turned off when the vehicle is stopped. To 57.

  The air pressure sensor 51 detects the tire air pressure and outputs it to the control device 57 as tire air pressure information.

  The interval timer 52 receives the transmission start information of the transmitter 56 from the control device 57, measures the time from the transmission start of the transmitter, and outputs the measured time information to the control device 57.

  The switching unit 53 selects the type of packet to be transmitted by the transmitter 56 based on a signal from the control device 57. Packets to be transmitted are divided into normal packets that are transmitted mainly while the vehicle is running and low-consumption packets that are transmitted mainly when the vehicle is stopped. Normal packets are stored in the normal packet transmission data memory 54, and low-consumption packets are stored in the low-consumption packet transmission data memory 55.

  The transmitter 56 transmits the packet as a radio signal based on the signal from the control device 57.

  The control device 57 inputs ON / OFF signal information from the centrifugal switch 50, tire pressure information from the air pressure sensor 51, interval information from the interval timer 52, packet information from the switching unit 53, and the interval time transmitted by the transmitter 56. (Interval) and the type of packet to be transmitted are determined, and the transmitter 56 is controlled.

  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 is provided with a receiver (receiving means) 61, an interval time measuring unit 62, a determining unit (tire pressure determining unit) 63, and a display unit (notifying unit) 64.

  The receiver 61 receives the packet transmitted from the transmitter 56 and outputs tire pressure information in the packet to the determination unit 63.

  The interval time measurement unit 62 measures the interval of the transmitter 56 and outputs this measurement information to the determination unit 63.

  The determination unit 63 determines whether or not the tire air pressure is lower than a set value. This set value is obtained in advance by experiment or calculation of a tire pressure suitable for vehicle travel. When the tire air pressure is lower than the set value, the display unit 64 notifies the driver that the tire air pressure is decreasing.

  Next, the operation will be described.

  In the tire pressure monitoring apparatus as in the present invention, a transmission unit having a tire pressure sensor and a transmitter is attached to each tire of the 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.

  Next, consider the effect of tire pressure when the vehicle is running and when the vehicle is stopped. Changes in tire air pressure during vehicle travel have a significant effect on vehicle travel. On the other hand, even if the tire air pressure changes while the vehicle is stopped, the fact that the vehicle is stopped has little effect. Furthermore, there are differences such as a small change in tire air pressure when the vehicle is stopped and a small amount for identifying the unique code of the transmitter when the vehicle is stopped.

  Therefore, in the first embodiment, by deleting unnecessary data when the vehicle is stopped, the data amount of the low-consumption packet transmitted while the vehicle is stopped is smaller than the data amount of the normal packet transmitted while the vehicle is traveling. I tried to do it.

  Next, the difference between normal packets and low-consumption packets will be described in detail.

  4A and 4B are diagrams showing the contents of a packet. FIG. 4A shows a normal packet, and FIG. 4B shows a low consumption packet.

As shown in FIG. 4A, a normal packet is composed of the following contents.
・ Header (18 [bit])
・ Function (3 [bit])
・ ID (24 [bit])
・ Data (8 [bit])
・ CS (2 [bit])

  Header is bit information attached as a mark for notifying the beginning of a group of data in serial communication. In normal packets, the communication method, information for synchronizing the transmission side and the reception side, and the like are placed, and 18 bits are secured.

  Function indicates that the air pressure sensor 51 has detected normal pressure or abnormal pressure, wakes up, and a tire ID initialization request to be described later, and 3 [bit] is secured.

  The ID contains information on a unique code unique to the transmitter. In the normal packet, all 24 [bits] of the unique code unique to this transmitter are carried.

  Data contains tire pressure information. In this normal packet, the tire pressure can be set at 0.2 [psi] from 0 [psi] to 51 [psi]. In other words, 8 [bit] are reserved to put 256 kinds of information. Note that 1 [psi] = 0.145 [kPa].

  CS is a checksum provided for checking received data on the data receiving side.

  This normal packet is composed of 55 bits in total.

As shown in FIG. 4B, the low consumption packet is composed of the following contents.
・ Header (10 [bit])
・ ID (8 [bit])
・ Data (4 [bit])
・ CS (2 [bit])

  The header is reserved 18 [bit] for normal packets, but 10 [bit] for low-consumption packets. In the first embodiment, when the vehicle stops, the transmission unit 5 and the reception unit 6 are synchronized in advance, so information 8 [bit] for achieving this synchronization is reduced.

  In Function, information on a flag indicating an abnormal state of the tire air pressure or the like is placed in the normal packet. A low-consumption packet is used only in a normal state, and a normal packet is transmitted when an abnormal state occurs. Therefore, a function is not provided for a low-consumption packet.

  Since other vehicles that are close to the host vehicle change from time to time while the vehicle is running, it is necessary to identify the unique codes of a large number of transmitters. On the other hand, when the vehicle is stopped, the change in other vehicles that are close to the host vehicle is small compared to when the vehicle is running. Therefore, the lower 18 [bit] of the unique code of this transmitter is deleted and the lower 8 [bit] ] Minutes are secured.

  Data contains tire pressure information. Since the change in tire air pressure is smaller when the vehicle is stopped than when the vehicle is running, only the difference in tire air pressure from when the previous packet was transmitted is included in the low consumption packet as tire air pressure information. As the difference in tire pressure, information in every 0.2 [psi] from -1.6 [psi] to 1.4 [psi] can be placed. In other words, 4 [bits] are reserved for 16 types of information.

  Since CS is a checksum, 2 [bits] are reserved as with normal packets.

  This low-consumption packet is composed of 24 bits in total.

  Next, the operation of each of the transmission unit 5 and the reception unit 6 will be described while comparing the conventional example with the first embodiment.

  FIG. 5 is a time chart showing the operation of the transmitter and the receiver according to the conventional example and the first embodiment. FIG. 5A shows the conventional state and FIG.

(Transmission unit: Conventional example)
When the vehicle is running, the transmission unit 5 transmits normal packets at intervals of several minutes. On the other hand, when the vehicle is stopped, the transmission unit 5 transmits normal packets at intervals of several hours.

(Receiving unit: Conventional example)
When the vehicle is traveling, the receiving unit 6 always receives a packet transmitted from the transmitting unit 5. On the other hand, when the vehicle is stopped, the activation is performed in accordance with the interval of the transmission unit 5, but a longer activation time is set in advance so that the packet can be reliably received.

(Transmission unit: Example 1)
When the vehicle is traveling, the transmission unit 5 transmits normal packets at intervals of several minutes (normal mode). On the other hand, when the vehicle is stopped, the transmission unit 5 transmits normal packets several times at intervals of several hours (synchronous mode). After completion of the synchronous mode, the transmission unit 5 transmits a low consumption packet at intervals of several hours (low consumption mode).

(Receiving unit: Example 1)
When the vehicle is traveling, the receiving unit 6 always receives a packet transmitted from the transmitting unit 5 (normal mode). On the other hand, when the vehicle is stopped, the transmission unit 5 is synchronized. As a method of obtaining this synchronization, when there is a time during which the reception unit 6 is activated and no packet is received, the next activation time of the reception unit 6 is delayed by a predetermined set time. (Synchronous mode). After the end of the synchronous mode, the low consumption packet is received only when the transmission unit 5 is transmitting (low consumption mode).

  As shown in the above-described operation, since the data amount of packets transmitted while the vehicle is stopped is smaller in the first embodiment than in the conventional example, the packet transmission time of the transmission unit 5 while the vehicle is stopped can be reduced.

  Next, the effect will be described.

  (1) Tire pressure sensor 51 (tire pressure detector) for detecting each tire pressure, normal packet transmission data memory 54 and low-consumption packet transmission data memory 55 (packet creation unit) for storing packet data, vehicle side A transmitter 56 (transmission unit) that transmits a packet by radio signal, a transmission unit 5 (transmission means) that is attached to each of a plurality of tires, and a packet transmitted from the transmitter 56 Receiver 61 (receiving means) that receives the information, a judgment unit 63 (tire pressure judging means) that judges that the tire pressure is below the set value from the tire pressure information in the packet, and the tire pressure is below the set value In a tire pressure monitoring apparatus comprising a display unit 64 (notification means) for notifying the driver in some cases, A centrifugal force switch 50 (stop state detecting means) that detects whether the vehicle is traveling or stopped is provided so that a normal packet is transmitted from the transmitter 56 while the vehicle is traveling, and the amount of data is smaller than the normal packet when the vehicle is stopped. The consumption packet is transmitted from the transmitter 56.

  Accordingly, the transmitter 56 reduces the packet transmission time of the transmission unit 5 while the vehicle is stopped because the data amount of the low-consumption packets transmitted while the vehicle is stopped is smaller than the data amount of the normal packets transmitted while the vehicle is traveling. It becomes possible to do. Therefore, power saving of the transmission unit 5 can be achieved.

  (2) In the synchronous mode, when there is a time during which the reception unit 6 is activated and no packet is received, the next activation time of the reception unit 6 is delayed by a predetermined set time.

  Therefore, it is possible to delete data that synchronizes the transmission unit 5 and the reception unit 6 from the low-consumption packet that the transmitter 56 transmits while the vehicle is stopped. For this reason, it is possible to reduce the data amount of low-consumption packets and reduce the packet transmission time of the transmission unit 5 while the vehicle is stopped, so that power saving of the transmission unit 5 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. FIG. 3 is a diagram illustrating a packet configuration according to the first embodiment. 3 is a time chart of a transmission unit and a reception unit according to the first embodiment.

Explanation of symbols

1-4 Tire 5 Transmission unit 50 Centrifugal switch 51 Tire pressure sensor 54 Normal packet transmission data memory 55 Low-consumption packet transmission data memory 56 Transmitter 6 Reception unit 61 Receiver 63 Judgment unit 64 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, an informing means for informing the driver;
In a tire pressure monitoring device comprising:
Stop state detecting means for detecting the stop state of the vehicle;
The tire pressure monitor characterized in that the packet creation unit makes the data amount of the packet created when the vehicle is stopped smaller than the data amount of the packet created when the vehicle is running. apparatus.

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