JP2003272080A - Method and device for specifying remote transmission unit of vehicular tire pressure monitoring system by using secondary modulation of wheel rotation - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an automatically controllable with improved reliability remote tire monitoring system. <P>SOLUTION: The remote tire monitoring system 10 includes a tire monitor 12 arranged in respective wheels of a vehicle V, and transmitting a radio signal modulated by tire data, and a modulating means arranged in the vicinal upper part of the tire monitor, and adding secondary modulation to the radio signal. A receiver 14 receives the radio signal, and restores the tire data 26 from the radio signal, and relates the tire monitor to the respective wheels of the vehicle by using the secondary modulation. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

BACKGROUND This invention relates to a central receiving unit program for identifying a sending unit, such as a radio frequency tire pressure sending unit, in a vehicle remote tire monitoring system.

US Pat. No. 5,600,301, assigned to the assignee of the present applicant, discloses a tire pressure monitoring system including a delivery unit provided for each tire of a vehicle and a central receiving unit. Is disclosed. Each of the delivery units includes a wireless transmitter that transmits a radio frequency (RF) signal. The RF signal includes both the identifier code and the tire pressure indicator. In addition, each of the delivery units includes a magnet sensor. The magnets are used to operate the delivery units of the vehicle in a predetermined order when the receiving unit is in the learning mode. The receiver learns the identifier associated with each tire based on the sequence of actuation of the delivery unit. Although this method is reliable in use, it requires the use of suitable magnets for the delivery unit.

In one patent application assigned to the assignee of the present applicant, a remote tire pressure monitoring system includes a delivery unit for each tire being monitored. The delivery unit sends an RF signal containing an identification and a pressure indicator. In the learning mode, the receiving unit associates a specific identification name with a vehicle or a specific tire. During the learning mode, the vehicle is driven at a speed greater than the threshold speed and the identifier is the vehicle or vehicle's Associated with each tire. In one example, the tires are inflated at different pressures according to a predetermined pattern and the pressure indicator of the received signal is used to associate the position of each tire with its respective delivery unit.

Other techniques for identifying the position of the transmitting tire monitor are known. US Pat. No. 5,4
No. 83,827 and No. 5,661,651, the transmit frequency is used to identify and distinguish the tire monitor transmitting it.

Another method of programming tire position information in the receiving unit is to manually enter the information. In this method, a keypad has been used to enter both tire monitor identification information and tire position information. Bar codes have also been used to read the tire monitor identification information directly from the tire monitor, but the tire position information was manually entered.

The methods described above are not fully automated. Therefore, there is a demand for an automation technique that has improved reliability and is convenient for users.

Overview As a prelude, the methods and apparatus described below use secondary modulation of the radio signals transmitted by each monitor to locate a tire monitor mounted on a vehicle. Each monitor performs a primary modulation on the signal it transmits using tire data related to tire pressure. In addition, other parts of the vehicle, such as a lump of metal near the wheels, provide a secondary modulation to the radio signal transmitted by the tire monitor. This secondary modulation is learned and decoded at the receiver to identify the position associated with the received signal. In addition, further components can be mounted near the wheels to modify and control the secondary modulation for later retrieval by the receiver.

The foregoing discussion of the preferred embodiment is provided only as a prelude. Every part of this section
It should not be construed as limiting the claims, which define the scope of the invention.

Detailed Description of the Presently Preferred Embodiment FIG. 1 is a schematic diagram of a vehicle V, which has four tires in this example. Vehicle V is a remote tire pressure monitoring system 1
0, which in this example includes four sending or tire monitors 12 and receiving units 14. Each of the plurality of delivery units is associated with a wheel arranged on the vehicle V. Tire monitor 1
Each of the two includes a radio frequency transmitter powered by a battery. It periodically transmits a radio frequency signal indicative of the corresponding tire pressure. In this example, the tire has T (1), T (2), T (3), T
Numbered (4), the corresponding tire pressures are identified as P (1), P (2), P (3), P (4). The receiving unit 14 receives the radio frequency signal from the sending unit 12, and when the displayed pressure of any of the tires deviates from a predetermined range, the operator is alerted.

The present invention may be used with the widest variety of delivery units or tire monitors 12 and receivers 14. For these reasons, a brief description of these components will be given here.

FIG. 2 is a block diagram of the delivery unit or tire monitor 12. Tire monitor 1
2 is a pressure sensor 16, a magnet sensor 18, a signal processor 20, a radio frequency (RF) transmitter 22,
And a motion switch or sensor 25 can be included. The battery 24 supplies operating power for the tire monitor 12. The pressure sensor 16 is configured to generate data representative of tire characteristics. In the illustrated embodiment, the pressure sensor 16 is a tire pressure sensor and the characteristic is the aerodynamic pressure of the tire. In another embodiment, the tire characteristic to be detected may be temperature, the number of rotations of the tire, or other characteristic. The pressure sensor 16 is a signal processor 20.
Sensor data or sensor signals representative of the tire characteristics for supply to the vehicle.

The magnet sensor 18 is used in the tire monitor 1.
A signal is provided to the signal processor 20 in response to an external magnetic action applied to the 2. For example, if the magnet sensor 18 is a reed switch (reed switch)
tch). The magnet sensor 18 is
In order to initialize the position of the tire monitor 12 on the vehicle V, the tire monitor 12 and the receiving unit 14 can be activated into a learning mode. The motion switch / sensor 25 can be adjusted or programmed to provide a signal to the signal processor 20 when the vehicle speed exceeds a certain threshold.

The signal processor 20 controls the operation of the tire monitor 12. In one embodiment, the signal processor 20 includes a microcontroller and memory that stores data and instructions for operating the tire monitor 12. As another example, the signal processor 20 may be an application specific integrated circuit (ASIC) that implements the circuitry necessary to perform the functions associated with the signal processor 20 on a single semiconductor chip. . Signal processor 20 specifically receives data and signals from pressure sensor 16, magnet sensor 18, motion switch / sensor 25 and formats this data as a message for transmission to a remote receiver. This message is
The identification information for the tire monitor 12 may be included. This message is given to the transmitting unit 22, and the radio signal is transmitted to the receiving unit at a remote place in cooperation with the antenna 23.

The transmitter 22 operates by modulating the carrier signal with the data provided by the signal processor. Any suitable modulation technique, such as amplitude modulation or frequency modulation, can also be used to transmit the data. Here, this modulation is applied to the tire monitor 12
Called the primary modulation of the radio signal transmitted by.

The tire monitor 12 thus constitutes tire monitoring means for individually and commonly arranged on the respective wheels of the vehicle V for transmitting radio signals modulated by tire data. Other tire monitoring means may be implemented using only some components of the tire monitor 12 illustrated in FIG. 4 or using additional components for implementing other functions. In general, the tire monitoring means includes a data sensor such as a pressure sensor and a temperature sensor, and a transmission circuit that transmits a wireless signal for transmitting the data collected by these data sensors.

In this example, the RF signal transmitted by the RF transmitter 22 may include tire data whose format is shown in FIG. As shown in FIG. 3, the tire data 26 includes two components. The tire data 26 includes an identification name 28 and a pressure indicator 30. The identification 28 in this embodiment includes a digital variable D (i), which is set to be the same as the identification code assigned to each delivery unit 12. Therefore, each tire monitor 12 of the vehicle V has a different identification 28. The pressure indicator 30 provides an indication of the pressure in each tire. The pressure indicator 30 is preferably in the form of a digital variable P (i) equal to a measure of pressure, although other techniques can be used. In this example, each sending unit 12 transmits tire data 26 of 8 frames per block, and one block of multiple frames is transmitted every minute while the vehicle is operating. Further, due to the operation of the magnet sensor 18, each transmission unit transmits 40 frames within a short time. However,
It is also possible to select other transmission formats and procedures.

As shown in FIG. 4, the receiving unit has an RF
It includes a receiver 34, a signal processor 36, a non-volatile memory 37, a learning mode switch 38, and a display 40. The RF receiver 34 operates to receive the radio signal transmitted by the transmitter unit or tire monitor 12. The structure and operation of the RF receiver 34 will be described in more detail later in connection with FIG. R
The data carried on the F signal and received by the RF receiver 34 is sent to the signal processor 36.
The signal processor controls the operation of the reception unit 14 based on the data and the instruction stored in the nonvolatile memory 37. The signal processor controls the display 40 to display the status of the tire monitoring system 10 (FIG. 1). For example, if the received signal is the tire T
If one of the (1), ..., T (4) indicates that the pressure deviates from the predetermined range,
The signal processor 36 can display automatically. The learning mode switch 38 is used to put the receiving unit 14 into the learning mode. In this mode, the receiving unit 14 has the sending unit 12 associated with the vehicle V.
Automatically associates each of the identifiers with the tire. In the learning mode, a specific learning signal or a function code indicating the learning mode is transmitted by the operating tire monitor.

Rotation of the wheel assembly including the tire monitor 12 induces an overall variation in the signal strength of the signal received at the receiver 14. This can be thought of as a secondary modulation of the signal. Other vehicle parts, such as the brake caliper, which is the most prominent mass of metal,
It produces a special modulation pattern. Thus, the secondary modulation conveys information about the structure surrounding the wheel and tire monitor.

FIG. 5 shows the received signal strength at the RF receiver 34 as a function of the circumferential position of the wheel for the wheel near the brake caliper. This received signal strength is shown as the relative displacement of the measured values from the center of the circle in FIG. The larger received signal strength is shown at a point farther from the center of the circle, and the smaller received signal strength is shown at a point closer to the center of the circle in the radial direction. As shown in FIG. 5, the data in FIG. 5 is experimentally obtained data for the left rear wheel of the vehicle with and without the brake caliper.

The characteristic pattern of FIG. 5 includes two nulls in the received signal strength as the position of the tire monitor on the wheel progresses clockwise. The relative position on the circumference of the tire monitor is indicated by the numbers on the circumference. The first null 502 occurs at an angular position of about 135 °. The second null 504 is 285 ° and 300
Shown in angular position between °. These nulls represent a temporary reduction or attenuation of the received signal strength, which is due to the presence of vehicle parts such as metal lumps such as brake calipers in the vicinity of tire monitors mounted on rotating wheels. to cause. In implementing previous monitoring systems, such variations in received signal strength were considered noise or interference. However, the inventor has recognized that such patterns or variations could be associated with individual tires to provide position information for vehicle tire monitoring.

In the receiving unit 14 of the system, the secondary variations characteristic of each particular tire monitor are:
Associated with a particular wheel position. In this way, the location information and identification information of the transmitting tire monitor can be associated with the transmitted tire data such as tire pressure. By detecting the secondary variation, the need to send the tire monitor identifier is avoided. This secondary variation is specific to each vehicle wheel position,
Accordingly, the position of the tire with which the transmitted tire data is associated is uniquely identified. Only the tire data would need to be transmitted with a mode signal or function code indicating learning mode or normal mode. This reduces the amount of data that needs to be sent,
Power consumption in the tire monitor is reduced and noise in the wireless environment of the system is also reduced.

The vehicle of the tire monitor that has transmitted it by storing data corresponding to the variation pattern of the received signal strength or other signal characteristic and then comparing this characteristic with that transmitted from the tire monitor. The position above can be determined. Generally, when the received data correlates to a pattern of stored data, the position of the wheels on the vehicle matches the position associated with that stored data. If the correlation is low, the positions do not match.

Generally, the position of the tire monitor 12 will need to be initialized at the receiving unit 14. This initialization is performed by, for example, the magnet sensor 18 of the tire monitor 12.
Magnetically activated to enter the learning mode. As another example, using radio frequency identification (RFID) tag technology, low frequency (eg 150
The initialization can also be performed by operating the (kHz) transponder. In response to this operation, the tire monitor makes a unique transmission indicating that it is in the learning mode and that the receiving unit 14 can update the stored position information for the operating tire monitor.

In addition to using variations in signal characteristics due to vehicle components and structures, it is also possible to place components and structures specific to each wheel position to further control signal transmission characteristics. For example, in the exemplary embodiment shown in FIG. 5, components may be placed that cause another null 506 in the received signal strength characteristic. further,
Other components may be placed in other locations that cause other nulls 508 in the received signal strength characteristics. When a signal is received at the receiving unit 14 of the tire monitoring system 10, the received signal strength has a repeating pattern of variations due to the movement of the tire monitor during transmission through a structure located near the wheels. These structures reflect the transmission signal strength, change the direction thereof, or absorb the transmission signal strength, so that the null 5 as shown in FIG.
02,504,506,508.

If specific structures are incorporated such that the secondary modulation patterns on the wheels are modified, these specific structures may be existing structures such as brake calipers, brake disc dust covers and the like. It is desirable to incorporate them so as to represent the characteristics of the parts. Alternatively, these additional structures may be additional components added to the wheel or strut assembly or other structure near the wheels. These structures may be as simple as a piece of reflective tape on a wheel sufficiently close to the tire monitor. Such structures, whether they are original parts of the vehicle, such as brake calipers, or added to the vehicle to create secondary variations,
A modulation means for adding secondary modulation to the radio signal transmitted by the tire monitor 12 is provided in the vicinity of the tire monitor 12.

FIG. 6 is a block diagram showing one structure of the receiving unit 34 of FIG. The receiving unit 34 constitutes a receiving unit for receiving the wireless signal transmitted by the tire monitor 12. The receiver 34 of the exemplary embodiment of FIG. 6 comprises a first demodulation circuit 56 and a second demodulation circuit 5.
Contains 8. The first demodulation circuit 56 includes a first filter 60, a demodulation unit 62, a data restoration circuit 64, and a local oscillator 66. The second demodulation circuit 58 has a second
The filter 68, the received signal strength instruction circuit 70, the second data restoration circuit 72, and the memory 74.

The first demodulation circuit 56 including the filter 60, the demodulation unit 62, the data restoration circuit 64, and the local oscillator 66 is
It is operative to receive signals of data transmitted by the monitor 12 at the wheels of the vehicle. First filter 60
Is usually a bypass filter having a passband centered on the transmit frequency used by the monitor. Signals outside this passband are considered noise and are attenuated. Demodulation unit 6
2 demodulates the filtered signal produced by filter 60 in response to the carrier signal produced by oscillator 66. Any suitable modulation and demodulation technique may be used in monitoring system 10. The demodulated data is given from the demodulation unit 62 to the first data restoration circuit 64. The data restoration circuit 64 includes a digital variable D (i) including an identification code assigned to each transmission unit.
And data containing a pressure variable P (i) containing a measure of pressure, which data is transmitted by the tire monitor 12 (FIG. 3).

Thus, in one embodiment, the demodulation unit 6
2 and the data restoration circuit 64 constitute demodulation means for restoring tire data from a radio signal. As aforementioned,
In the present embodiment, the identification code may not be transmitted, and the receiving unit 34 may identify the tire data by using the secondary variation or associate the tire data with the vehicle position. The recovered data is sent to the signal processor 36 of the receiving unit 14 including the receiving section 34.

The second demodulation circuit 58 includes a filter 68, a received signal strength indication (RSSI) circuit 70, and a second data restoration circuit 72. This circuit 58 demodulates secondary modulated data that defines the position data of the tire monitor 12 during transmission. The filter 68 acts as a low pass filter for attenuating signals above the low frequency pass band suitable for detecting secondary modulation information in the received signal. Since the frequency of this modulation is related to the speed of the vehicle wheels, this modulation information is received at a relatively low frequency.

The RSSI circuit 70 detects the relative signal strength of the signal passing through the filter 68. This signal has a signal strength similar to that shown in FIG. This signal is
It has a relatively high amplitude value corresponding to the portion of the circular movement of the tire monitor where the transmitted signal is not attenuated or reflected. Similarly, this signal is sent to the tire monitor 12
The signal is attenuated and absorbed during the orbital movement of
Alternatively, it has portions such as nulls 502, 504, 506, 508 (FIG. 5) that are reflected and limit reception by the received signal 34. Suitable received signal strength indication circuits are well known.

The RSSI circuit 70 includes a data restoration circuit 72.
Give a received signal strength indication to. In response to this signal, the data restoration circuit 72 detects the bit pattern or data pattern corresponding to the position data of the tire monitor 12 issuing the signal. In the illustrated embodiment, the data recovery circuit 72 compares the received position data with the positions stored in the memory 74. The stored position data has been previously learned and stored while the monitoring system 10 is operating in the learning mode. The data restoration circuit 72 compares the received position data with the position data. If they match, the receiving unit 14 has received tire data from a known tire monitor of the monitoring system 10. If there is no match, the position data received is either noisy or was sent from the tire monitor of another tire monitoring system on the nearby vehicle. Other data restoration methods can also be used.

Therefore, in one embodiment, the data recovery circuit 72 comprises an identification circuit responsive to a secondary variation in the received carrier signal, and based on this secondary variation the position of a particular wheel. Specify. In another embodiment, RSSI
The circuit 70 and the data recovery circuit 72 constitute decoding means for associating the tire data with the position of the wheels of the vehicle V in response to the secondary modulation of the radio signal received at the receiver.

In applications where metal or other components are placed in the vicinity of the tire monitor 12 to produce a unique pattern of secondary modulation in the transmitted signal from the tire monitor 12, the transmitted data is proportional. Appear as a series of data bits with different characteristics. The duration of these data bits is a direct function of wheel speed. That is, this duration is not an absolute value, it fluctuates over time and becomes shorter if the wheels and vehicle are moving faster,
Long durations if wheels and vehicles are moving slowly. Therefore, the data recovery circuit 72 may be implemented as a ratiometric decoder that detects data based on the relative size or duration of received data bits to distinguish between logical 0 bits and logical 1 bits. desirable.

From the above contents, for vehicles such as automobiles,
It is clear that an improved tire monitoring system has been described which transmits data from a wheel assembly on a motorway via radio frequency communication. By monitoring and controlling the secondary modulation of the transmitted signal, fluctuations in the signal, previously treated as noise or interference, can self-associate the tire movement during transmission with the physical wheel position in the vehicle. Used for. In this case, there is no need to modify the existing sensors and transmitters of the tire monitor. This is a great advantage as tire monitors are mostly cost sensitive articles.

While we have shown and described specific embodiments of the present invention, modifications are possible. For example, any suitable technique for deploying a tire monitoring system in a learning mode that initializes position data may be used with the method and apparatus according to the present invention. Accordingly, the appended claims are intended to cover within their scope all such changes and modifications as fall within the true spirit and scope of this invention.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a remote tire pressure monitoring system.

FIG. 2 is a block diagram of one of the delivery units of FIG.

3 is a block diagram of one of the RF signals generated by the sending unit of FIG.

FIG. 4 is a block diagram of the receiving unit of FIG.

5 is a block diagram illustrating secondary modulation of wireless signals and the remote tire monitoring system of FIG.

FIG. 6 is a block diagram of a receiving unit used in the receiving unit of FIG.

Continued front page    F term (reference) 2F073 AA36 BB01 BC02 CC01 CC20                       GG01 GG06

Claims (17)

[Claims] 1. A plurality of transmitter and receiver units associated with wheels disposed on a vehicle, at least one of the transmitter units transmitting a radio signal containing tire data relating to a tire corresponding to the transmitter unit. And a receiving unit configured to receive the radio signal and restore the tire data from the radio signal, the method comprising: operating a remote tire monitoring system, the method comprising: Detecting a significant variation and associating a particular secondary variation with a particular wheel position. 2. Detecting a primary modulation of the carrier signal transmitted by a particular delivery unit and detecting a secondary modulation of the carrier signal due to ambient variations associated with a particular wheel position. Detecting, The method of Claim 1 characterized by these. 3. The method of claim 2 further comprising detecting variations in the carrier signal associated with the rotational movement of a particular delivery unit passing through a structure near a particular wheel position. 4. Further comparing the secondary variation in the radio signal with the stored data, and when the specific secondary variation of the specific wheel position matches the stored data, the tire data is The method according to claim 1, characterized in that it is associated with the stored tire information of a particular delivery unit. 5. Further comparing the secondary variation of the radio signal with the stored data and using the specific secondary variation to correlate tire data with a specific delivery unit at a specific wheel position of the vehicle. The method of claim 1, wherein: 6. A plurality of tire monitors associated with the wheels of a vehicle and configured to transmit wireless signals that carry tire data, and a plurality of tire monitors configured to receive wireless signals resulting from movement of the plurality of tire monitors. A remote tire monitoring system comprising: a receiver including a circuit for detecting a secondary variation in a wireless signal; 7. The remote tire monitoring system of claim 6, further comprising one or more components that can be placed near each tire monitor to add secondary variations to the wireless signal. . 8. The one or more components may further be a metal positionable along a circumferential path of a tire monitor on a vehicle wheel for modifying a radio signal received by a receiver. 8. The remote tire monitoring system according to claim 7, including an element made from. 9. The receiver according to claim 6, further comprising an identification circuit that responds to the secondary fluctuation and identifies a specific wheel position based on the secondary fluctuation. Remote tire monitoring system. 10. The remote tire monitoring system according to claim 9, wherein the receiving unit further includes a decoder that detects position data in the secondary fluctuation. 11. The remote tire of claim 10, wherein the decoder further comprises a ratiometric decoder responsive to the relative duration of bits of duration data to decode position data. Monitoring system. 12. The remote tire monitoring system according to claim 9, wherein the reception unit further includes a demodulation unit that demodulates a radio signal to receive tire data. 13. Tire monitor means arranged at each wheel position of the vehicle for transmitting a radio signal modulated by tire data, and secondary modulation to the radio signal arranged in the vicinity of the tire monitor means. A receiving means for receiving the radio signal, the demodulating means for reconstructing the tire data from the radio signal, and the tire data for each wheel of the vehicle in response to the secondary modulation. A remote tire monitoring system, comprising: a decoding unit associated with a position. 14. The tire monitor means further comprises a plurality of remote tire monitors attached to respective wheels of the vehicle to monitor tire conditions and generate tire data. 14. The remote tire monitoring system according to claim 13, wherein the remote tire monitoring system transmits the wireless signal of. 15. The modulating means further comprises an arrangement of one or more parts that can be mounted near a path on the circumference of each tire monitor, each arrangement being transmitted by each tire monitor. 14. The remote tire monitoring system of claim 13, wherein the signal produces a unique secondary modulation. 16. The remote tire monitoring system according to claim 14, wherein the modulation means further comprises modification means adapted to selectively absorb or reflect radio signals. 17. The decoding means further comprises a ratiometric decoder for decoding position data as a function of the relative duration of the secondary modulation for associating the tire monitoring means with each wheel of the vehicle. 15. The remote tire monitoring system according to claim 14.