US20020084896A1

US20020084896A1 - Tire condition sensor communication with tire location provided via vehicle-mounted identification units

Info

Publication number: US20020084896A1
Application number: US09/753,290
Authority: US
Inventors: Rahul Dixit; Timothy DeZorzi
Original assignee: TRW Inc
Current assignee: Northrop Grumman Space and Mission Systems Corp
Priority date: 2001-01-02
Filing date: 2001-01-02
Publication date: 2002-07-04
Anticipated expiration: 2021-01-02
Also published as: US6441728B1

Abstract

A tire condition communication system (10) for a vehicle (12) that has a tire (e.g., 14A). A sensor (e.g., 74), associated with the tire (e.g., 14A), senses at least one tire condition. A memory (e.g., 70), associated with the tire (e.g., 14A), holds an identification. Transmitter components (e.g., 80 and 22), associated with the tire (e.g., 14A) and operatively connected to the sensor (74) and the memory (70), transmit a condition signal (e.g., 24A) that indicates the held identification and the sensed tire condition. A vehicle-based unit (28) receives the transmitted condition signal (e.g., 24A) indicative of the held identification and the sensed tire condition. An identification provision unit (e.g., 42A), located on the vehicle (12) adjacent to the tire (e.g., 14A) and having a location identification, transmits the location identification in response to a request. A communication portion (e.g., 48A) of the tire condition sensor unit (e.g., 18A) communicates a request to the identification provision unit (e.g., 42A) to transmit the location identification. The tire condition sensor unit (e.g., 18A) receives the requested location identification and updates the held identification.

Description

TECHNICAL FIELD

The present invention relates to a tire condition monitoring system for providing a tire operation parameter, such as tire inflation pressure, to a vehicle operator. The present invention relates specifically to a tire condition monitoring system that provides ready identification of a tire providing condition information and avoids misidentification regardless of previous tire position change due to tire position rotation or the like.

BACKGROUND OF THE INVENTION

Numerous tire condition monitoring systems have been developed in order to provide tire operation information to a vehicle operator. One example type of a tire condition monitor system is a tire pressure monitor system that detects when air pressure within a tire drops below a predetermined threshold pressure value.

There is an increasing need for the use of tire pressure monitoring systems due to the increasing use of “run-flat” tires for vehicles such as automobiles. A run-flat tire enables a vehicle to travel an extended distance after significant loss of air pressure within that tire. However, a vehicle operator may have difficulty recognizing the significant loss of air pressure within the tire because the loss of air pressure may cause little change in vehicle handling and visual appearance of the tire.

Typically, a tire pressure monitoring system includes a pressure sensing device, such as a pressure switch, an internal power source, and a communications link that provides the tire pressure information from a location at each tire to a central receiver. The central receiver is typically connected to an indicator or display located on a vehicle instrument panel.

The communications link between each tire and the central receiver is often a wireless link. In particular, radio frequency signals are utilized to transmit information from each of the tires to the central receiver. However, in order for the central receiver to be able to properly associate received tire pressure information with the tire associated with the transmission, some form of identification of the origin of the signal must be utilized. Such a need for identification of the origin of the transmitted tire information signal becomes especially important subsequent to a tire position change, such a routine maintenance tire position rotation.

SUMMARY OF THE INVENTION

In accordance with one aspect, the present invention provides a tire condition communication system for a vehicle that has a tire. A sensed condition signal that includes an identification is transmitted to a vehicle-based unit. The system includes a tire condition sensor unit, associated with the tire, that sends the sensed condition signal. The system also includes an identification tag, located on the vehicle adjacent to the tire, that sends the identification to the tire condition sensor unit for inclusion in the signal to the vehicle-based unit.

In accordance with another aspect, the present invention provides a tire condition communication system for a vehicle that has a tire. Sensor means, associated with the tire, senses at least one tire condition. Memory means, associated with the tire, holds an identification. Transmitter means, associated with the tire and operatively connected to the sensor means and the memory means, transmits a signal that indicates the held identification and the sensed tire condition. Receiver means, associated with the vehicle, receives the transmitted signal indicative of the held identification and the sensed tire condition. Location identification means, located on the vehicle adjacent to the tire and having a location identification, transmits the location identification in response to a request. Update request means communicates a request to the location identification means to transmit the location identification. Identification update means, associated with the tire and operatively connected to the memory, receives the requested location identification and provides the received location identification to the memory means to be held as the held identification.

In accordance with yet another aspect, the present invention provides a method of providing tire condition communication for a vehicle that has a tire. A tire condition sensor unit is associating with the tire. An identification tag is affixed to the vehicle adjacent to the tire. An identification is sent from the identification tag to the tire condition sensor unit. A sensed condition signal that includes the identification is sent from the tire condition sensor unit to a vehicle-based unit.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features and advantages of the present invention will become apparent to those skilled in the art to which the present invention relates upon reading the following description with reference to the accompanying drawings, in which: [0009]
FIG. 1 is a schematic block diagram of a vehicle that contains a tire condition communication system in accordance with the present invention, and with a plurality of tire condition sensor units and a plurality of identification provision units; [0010]
FIG. 2 is a schematic illustration of an example of relative locations for a tire condition sensor unit and an identification provision unit of the system of FIG. 1; [0011]
FIG. 3 is a representation of a signal message that coveys location identification from an identification provision unit within the system of FIG. 1; [0012]
FIG. 4 is a representation of a signal message packet that conveys location identification and sensed tire condition information from a tire condition sensor unit within the system of FIG. 1; [0013]
FIG. 5 is a function block diagram of a first embodiment of a tire condition sensor unit for the system of FIG. 1; [0014]
FIG. 6 is a function block diagram of a first embodiment of a vehicle-mounted identification provision unit for the system shown in FIG. 1; [0015]
FIG. 7 is a function block diagram of a second embodiment of a tire condition sensor unit for the system of FIG. 1; [0016]
FIG. 8 is a function block diagram of a second embodiment of a vehicle-mounted identification provision unit for the system of FIG. 1; [0017]
FIG. 9 is a flow chart for a first example process performed with a tire condition sensor unit of the system of FIG. 1; [0018]
FIG. 10 is a flow chart for a second example process performed with a tire condition sensor unit of the system of FIG. 1. [0019]

DESCRIPTION OF EXAMPLE EMBODIMENTS

A tire [0020] condition communication system 10 is schematically shown within an associated vehicle 12 in FIG. 1. The vehicle 12 has a plurality of inflatable tires (e.g., 14A). In the illustrated example, the vehicle 12 has four tires 14A-14D. It is to be appreciated that the vehicle 12 may have a different number of tires. For example, the vehicle 12 may include a fifth tire (not shown) that is stored as a spare tire.
The [0021] system 10 includes a plurality of tire condition sensor units (e.g., 18A) for sensing one or more tire conditions at the vehicle tires (e.g., 14A). Preferably, the number of tire condition sensor units 18A-18D is equal to the number of tires 14A-14D provided within the vehicle 12. In the illustrated example of FIG. 1, the tire condition sensor units 18A-18D have the same components. Identical components are identified with identical reference numerals, with different alphabetic suffixes. It is to be appreciated that, except as noted, the tire condition sensor units 18A-18D function in the same manner. For brevity, operation of one of the tire condition sensor units (e.g., 18A) is discussed in detail with the understanding that the discussion is generally applicable to the other tire condition sensor units (e.g., 18B-18D).
Each tire condition sensor unit (e.g., [0022] 18A) includes a power supply (e.g., a battery 20A) that provides electrical energy to various components within the respective sensor unit. The electrical energy enables the tire condition sensor unit (e.g., 18A) to energize a radio frequency antenna (e.g., 22A) to emit a radio frequency signal (e.g., 24A) that conveys one or more sensed conditions along with an identification to a central vehicle-based unit 28. Specifically, a radio frequency antenna 30 receives the signal (e.g., 24A) from the tire condition sensor unit (e.g., 18A) and the conveyed information is processed. In one example, the system 10 is designed to operate with the signals (e.g., 24A) in the FM portion of the radio frequency range. Hereinafter, the radio frequency signals (24A-24D) are referred to as condition signals.
A power supply (e.g., a vehicle battery) [0023] 34, which is operatively connected (e.g., through a vehicle ignition switch 36) to the vehicle-based unit 28, provides electrical energy to permit performance of the processing and the like. The vehicle-based unit 28 utilizes the processed information to provide information to a vehicle operator via an indicator device 38. In one example, the indicator device 38 may be a visual display that is located on an instrument panel of the vehicle 12. Accordingly, the vehicle operator is apprised of the sensed condition(s) at the tire (e.g., 14A).
It is to be noted that the sensed condition may be any condition at the tire (e.g., [0024] 14A). For example, the sensed condition may be inflation pressure of the tire (e.g., 14A), temperature of the tire, motion of the tire, or even a diagnostic condition of the tire condition sensor unit (e.g., 18A) itself.
It should be noted that only the [0025] single antenna 30 of the vehicle-based unit 28 receives all of the condition signals 24A-24D from a plurality of tire condition sensor units 18A-18D. In order for the vehicle-based unit 28 to accurately “know” which tire (e.g., 14A) is providing the condition signal (e.g., 24A), the identification conveyed via the condition signal is a location identification of the tire. Specifically, each of the condition signals 24A-24D conveys a location identification. The provision of location identifications via the condition signals 24A-24D from the tire condition sensor unit 18A-18D is accomplished by the system 10 including a plurality of identification provision units 42A-42D that provide location identifications to the tire condition sensor units.
Each identification provision unit (e.g., [0026] 42A) is associated with a respective tire mount location on the vehicle. Accordingly, each identification provision unit (e.g., 42A) is associated with a respective tire (e.g., 14A) and a respective tire condition sensor unit (e.g., 18A) associated with the respective tire.
Each identification provision unit (e.g., [0027] 42A) is fixedly mounted on the vehicle 12 at or adjacent to the area of attachment of the respective tire (e.g., 14A) to the vehicle. For example, the identification provision unit (e.g., 42A) is fixedly mounted (e.g., epoxy glued) within a wheel well 44 (FIG. 2) of the vehicle 12 that is provided for one of the ground-engaging tires (e.g., 14A).
Each identification provision unit (e.g., [0028] 42A) holds a location identification. In one embodiment, the identification is a fixed (i.e., non-changing) identification value. The identification is associated with the specific tire mounting location. Accordingly, when a tire (e.g., 14A) is located at the tire mounting location, that identification is considered to be associated with that tire.
Each identification provision unit (e.g., [0029] 42A, FIG. 1) communicates (e.g., signal 46A) with the associated tire condition sensor unit (e.g., 18A). Specifically, the identification provision unit (e.g., 42A) communicates (e.g., signal 46A) with a communication portion (e.g., 48A) of the associated tire condition sensor unit (e.g., 18A) to provide the location identification to the tire condition sensor unit. Thus, each identification provision unit (e.g., 42A) is an identification tag for that tire location.
FIG. 3 illustrates an example of a message that is conveyed via the signal (e.g., [0030] 46A) to the tire condition sensor unit (e.g., 18A). Hereinafter, the signals 46A-46D are referred to as identification providing signals.
The tire condition sensor unit (e.g., [0031] 18A) utilizes the provided location identification as the identification transmitted within its condition signal (e.g., 24A) sent to the vehicle-based unit 28. FIG. 4 illustrates an example of a message package that is sent via the condition signal (e.g., 24A) to the vehicle-based unit 28. The location identification is sent along with condition information, and other message portions (e.g., error checking bits).
The vehicle-based unit [0032] 28 (FIG. 1) is programmed (e.g., taught) or has learned to recognize the location identifications for the various tire mount locations on the vehicle 12. Accordingly, when the vehicle-based unit 28 receives a signal that contains a certain location identification, the vehicle-based unit 28 interprets the signal as originating from a tire (e.g., 14A) located at that vehicle mount location.
It is contemplated that the provision of the location identification to the associated tire condition sensor unit (e.g., [0033] 18A) may be accomplished via different communication methods, formats, etc. In the illustrated example of FIG. 1, the provision of the location identification is accomplished via an interrogation exchange. When the tire condition sensor unit (e.g., 18A) wishes to receive a location identification, the communication portion (e.g., 48A) of the tire condition sensor unit outputs an interrogation signal (e.g., 50A) intended for reception by the associated identification provision unit (e.g., 42A). Hereinafter, the interrogation signals 50A-50D are referred to as identification request signals.
In response to receipt of the identification request signal (e.g., [0034] 50A), the identification provision unit (e.g., 42A) outputs the identification providing signal (e.g., 46A) that conveys the location identification. Upon receipt of the identification providing signal (e.g., 46A) from the identification provision unit (e.g., 42A), the associated tire condition sensor unit (e.g., 18A) utilizes the provided location identification for subsequent condition signals to the vehicle-based unit 28.
The occurrence of the interrogation to receive the location identification may occur upon initial power-up of the tire condition sensor unit (e.g., [0035] 18A), may occur based upon a predetermined time schedule, or may occur as a response to a radio frequency condition request signal (e.g., 52A shown via a dashed line in FIG. 1) from the vehicle-based unit 28 to one or more tire condition sensor units (e.g., 18A). It is to be understood that the present invention is not to be limited by the communication technique utilized to cause the provision of the location identification to the tire condition sensor unit (e.g., 18A) for use in the transmitted condition signal (e.g., 24A).
FIGS. 5 and 6 illustrate first examples of a tire [0036] condition sensor unit 18′ and an identification provision unit 42′, respectively. Specifically, the first examples are provided for a communication scheme in which the identification request signal 50′ output from the tire condition sensor unit 18′ provides power to the identification provision unit 42′, in addition to requesting the location identification. It is to be noted that the tire condition sensor unit 18′ and the identification provision unit 42′ are indicated using reference numerals with primes, to signify that the examples are for a first specific discussion. Also, it is to noted that the tire condition sensor unit 18′ and the identification provision unit 42′ are indicated without use of alphabetic suffixes to signify that the examples are generic to all of the tire condition sensor units and all of the identification provision units, respectively.
Turning to the example of the tire [0037] condition sensor unit 18′ shown in FIG. 5, a magnetic interrogation emitter component 56 of the communication portion 48′0 is operatively connected 58 to a controller 60. The magnetic interrogation emitter component 56 may include a coil antenna or the like. Upon excitation control provided by the controller 60, the magnetic interrogation emitter component 56 outputs the identification request signal 50′ in the form of an electromagnetic field for reception by the associated identification provision unit 42′ (FIG. 6).
A radio frequency antenna [0038] 62 (FIG. 5) of the communication portion 48′0 is operatively connected 64 to radio frequency receive circuitry 66. In the shown example, the identification providing signal 46′ is in the form of a radio frequency for reception by the antenna 62. The RF receive circuitry 66 is, in turn, operatively connected 68 to the controller 60 such that the received location information is conveyed to the controller.
A [0039] location identification memory 70 is operatively connected 72 to the controller 60. When the controller 60 receives location information, the information is stored in the memory 70.
When the tire [0040] condition sensor unit 18′ is to output a condition signal 24 that conveys tire condition information, the controller 60 receives sensory information from one or more sensors 74 that are operatively connected 76 to the controller 60. The controller 60 also then accesses the location information from the memory 70. A message package that contains the location information and the sensory information is assembled. See for example, the message package of FIG. 4.
The controller [0041] 60 (FIG. 5) is operatively connected 78 to RF transmit circuitry 80, which is in turn operatively connected 82 to the antenna 22. When the controller 60 provides the message package to the RF transmit circuitry 80, the RF transmit circuitry stimulates the antenna 22 to cause emission of the condition signal 24 that conveys both the location and tire condition information.
Turning to FIG. 6, the [0042] identification provision unit 42′ includes a magnetic interrogation receive component 84. In one embodiment, the magnetic interrogation receive component 84 may include a coil antenna. When the identification request signal 50′ (i.e., the magnetic field) is imposed upon the magnetic interrogation receive component 84, the magnetic interrogation receive component outputs electrical energy. For example, the output of the magnetic interrogation receive component may be an electrical pulse.
A [0043] power storage component 86 is operatively connected 88 to the magnetic interrogation receive component 84. In one example, the power storage component 86 includes a capacitor. The electrical energy output from the magnetic interrogation receive component 84 is stored by the power storage component 86 for use by other components within the identification provision unit 42′.
A [0044] controller 90 is operatively connected 92 to the magnetic interrogation receive component 84. The output electrical energy from the magnetic interrogation receive component 84 is a stimulus to the controller 90 that a location identification is requested. In response to the stimulus and via power provided by the power storage component 86, the controller 90 accesses the location identification from a location identification memory 94 that is operatively connected 96 to the controller. The controller 90 then provides an identification message to RF transmit circuitry 98 that is operatively connected 100 to the controller 90. The RF transmit circuitry 98, via power provided by the power storage component 86, provides a stimulus to a RF transmit antenna 102 that is operatively connected 104 to the RF transmit circuitry 98. In response to the stimulus, the antenna 102 outputs the identification providing signal 46′ for reception by the associated tire condition sensor unit 18′. Thus, the identification provision unit 42′ is an identification tag for the tire location.
FIGS. 7 and 8 illustrate second examples of a tire [0045] condition sensor unit 18″ and an identification provision unit 42″, respectively. Specifically, the first examples are provided for a communication scheme in which the identification request signal 50″ provided by the tire condition sensor unit 18″ does not provide power to the identification provision unit 42″, but only requests the location identification. It is to be noted that the tire condition sensor unit 18″ and the identification provision unit 42″ are indicated using reference numerals with double primes, to signify that the examples are for a second specific discussion. Also, it is to noted that the tire condition sensor unit 18″ and the identification provision unit 42″ are indicated without use of alphabetic suffixes to signify that the examples are generic to all of the tire condition sensor units and all of the identification provision units, respectively.
Turning to FIG. 7, the [0046] communication portion 48″ of the tire condition sensor unit 18″ includes a RF interrogation component 110 that is operatively connected 112 to RF transceive circuitry 114. In turn, the RF transceive circuitry 114 is operatively connected 116 to a controller 118. When it is desired to receive a location identification, the controller 118 provides a control signal to the RF transceive circuitry 114. In turn, the RF transceive circuitry stimulates the RF interrogation component 110, to output the identification request signal 50″.
As a response to the [0047] identification request signal 50″, the RF interrogation component 110 receives the identification providing signal 46″ as a radio frequency signal. The RF interrogation component 110 provides an electrical signal to the RF transceive circuitry 114. In turn, the RF transceive circuitry 114 conveys the location identification information to the controller 118.
A [0048] location identification memory 122 is operatively connected 124 to the controller 118. Upon receipt of location information, the controller 118 stores the location information within the memory 122.
When the tire [0049] condition sensor unit 18″ is to provide a condition signal 24 to the vehicle-based unit 28, the controller 118 receives sensory information from one or more sensors 126 that are operatively connected 128 to the controller. The controller 118 also accesses the location identification from the memory 122.
The [0050] controller 118 is further operatively connected 130 to RF transmit circuitry 132. A message package that contains the sensory information and the location identification is assembled by the controller 118 and provided to the RF transmit circuitry 132. In response to the provided message packet, the RF transmit circuitry 132 provides an electrical stimulus signal 134 to the antenna 22 that causes the antenna to output the condition signal 24 that conveys the sensory information and the location identification.
In the example of FIG. 7, the [0051] communication portion 48″ is shown to be separate from the RF transmit circuitry 132 and the antenna 22. However, it is to be appreciated that the components may be combined in view the use of radio frequency signals for identification provision.
Turning to FIG. 8, the [0052] identification provision unit 42″ includes an application specific-integrated circuit (ASIC) chip 140. The ASIC chip 140 includes control, memory. and RF transceive components. Attached to the ASIC chip 140 are a radio frequency antenna 142 and a power supply 144, such as a battery.
In response to receipt of an [0053] identification request signal 50″ from the associated tire condition sensor unit 18″, the antenna 142 provides an electrical signal to the ASIC chip 140. The ASIC chip 140 interprets, via power provided by the power supply 144, the signal as a request for provision of the location identification. The ASIC chip 140, using power from the power supply 144, stimulates the antenna 142 to cause output of the location identification providing signal 46″. Thus, the identification provision unit 42″ is an identification tag for the tire location.
A first example of a [0054] process 200 performed within a tire condition sensor unit (e.g., 18A, FIG. 1)) is shown in FIG. 9. The process 200 is associated with an embodiment of the system 10 in which the vehicle-based unit 28 controls which of the tire condition sensor units (e.g., 18A) is to provide tire condition information. Specifically, the process 200 is associated with the vehicle-based unit 28 providing a condition request signal (e.g., 52A) for reception by the respective tire condition sensor unit (e.g., 18A).
The [0055] process 200 is initiated at step 202 and proceeds to step 204. At step 204, the tire condition sensor unit (e.g., 18A) is in a sleep mode in order to conserve battery power. At step 206, it is determined whether a condition request signal (e.g., 52A) has been received. If the determination at step 206 is negative (i.e., a condition request signal is not received), the tire condition sensor unit (e.g., 18A) remains in the sleep mode (i.e., the process 200 proceeds from step 206 to step 204).
If the determination at [0056] step 206 is affirmative (i.e., the condition request signal 52A is received), the process 200 proceeds from step 206 to step 208. At step 208, the tire condition sensor unit (e.g., 18A) interrogates the associated identification provision unit (e.g., 42A). At step 210, the tire condition sensor unit (18A) receives and stores the location identification provided from the associated identification provision unit (e.g., 42A).
At [0057] step 212, tire condition status is derived (e.g., sensed), a message package is assembled, and the condition signal (e.g., 24A) that conveys the sensory information and the location identification is sent. Upon completion of step 212, the process 200 proceeds to step 204 (sleep mode).
It is to be noted that the [0058] process 200 provides for the reception (updating) of the location identification from the identification provision unit based upon each requested tire condition update. Accordingly, the process is suitable for use in the embodiments shown in FIGS. 5 and 6, wherein the tire condition sensor unit provides power to the identification provision unit.
Turning to FIG. 10, another example of a [0059] process 300 that is performed within a tire condition sensor unit (e.g., 18A) is shown. The process 300 is initiated at step 302 and proceeds to step 304. At step 304, the tire condition sensor unit (e.g., 18A) interrogates the associated identification provision unit (e.g., 42A). At step 306, the tire condition sensor unit (e.g., 18A) receives and stores the location identification provided by the associated identification provision unit (e.g., 42A).
At [0060] step 308, the tire condition sensor unit (e.g., 18A) is in a sleep mode in order to conserve battery power. At step 310, it is determined whether the tire condition sensor unit (e.g., 18A) is to awake for the transmission of a condition signal (e.g., 24A). The waking of the tire condition sensor unit (e.g., 18A) may be the result of expiration of a predetermined timer period or via the condition request signal (e.g., 52A) from the vehicle-based unit 28. If the determination at step 310 is negative (i.e., no stimulus to wake), the process 300 goes from step 310 to step 308 wherein the sensor unit remains asleep.
If the determination at [0061] step 310 is affirmative (i.e., the sensor unit awakes), the process 300 proceeds from step 310 to step 312. At step 312, tire condition sensory information is derived, the message package that includes the sensory information and the location identification is assembled, and the condition signal (e.g., 24A) is transmitted.
At [0062] step 314, it is determined whether the location identification value stored within the tire condition sensor unit (e.g., 18A) is to be updated. Updating may be in response to an external stimulus, expiration of a timer period, etc. Upon a negative determination at step 314 (i.e., no need to update the currently stored location identification), the process 300 proceeds from step 314 to step 308 (i.e., sleep).
Upon an affirmative determination at step [0063] 314 (i.e., a need to update the location identification), the process 300 proceeds from step 314 to step 316. At step 316, the tire condition sensor unit (e.g., 18A) interrogates the associated identification provision unit (e.g., 42A). At step 318, the tire condition sensor unit (e.g., 18A) receives and stores the location identification provided by the associated identification provision unit (e.g., 42A). Upon completion of step 318, the process 300 proceeds from step 318 to step 308 (i.e., sleep).
From the above description of the invention, those skilled in the art will perceive improvements, changes and modifications. For example, the illustrated embodiments show that the request to provide a location identification is via a signal (e.g., [0064] 50A) from a tire condition sensor unit (e.g., 18A). However, it is contemplated that the provision of a location identification may be via other stimulus (e.g., a signal from a hand-held unit), or the provision a location identification may be via some other, non-stimulus, arrangement (e.g., predefined, periodic provision of the location identification). Such improvements, changes and modifications within the skill of the art are intended to be covered by the appended claims.

Claims

Having described the invention, the following is claimed:

1. A tire condition sensor unit for association with a tire of a vehicle and for communicating a tire condition to a vehicle-based unit, said tire condition sensor unit comprising:

sensor means for sensing the tire condition;

radio frequency transmitter means, operatively connected to said sensor means, for transmitting a radio frequency signal that indicates the sensed tire condition; and

low frequency receiver means, operatively connected to said radio frequency transmitter means, for receiving a low frequency initiation signal and for causing said radio frequency transmitter means to transmit the radio frequency signal indicative of the sensed tire condition in response to receipt of the low frequency initiation signal.

2. A tire condition sensor unit as set forth in claim 1, wherein said tire condition sensor unit and said vehicle-based unit are part of a tire condition communication system and said low frequency receiver means is a first part of communication means of said tire condition communication system, a low frequency transmitter means of said tire condition communication system is a second part of said communication means that is operatively connected to said vehicle-based unit and that is for transmitting the low frequency initiation signal, said communication means for communicating a request from said vehicle-based unit to said tire condition sensor unit via the low frequency initiation signal to cause the transmission of the radio frequency signal.

3. A tire condition sensor unit as set forth in claim 2, wherein said low frequency receiver means and said low frequency transmitter means include first and second magnetic induction antennas, respectively.

4. A tire condition sensor unit as set forth in claim 2, wherein said low frequency receiver means is also for receiving a signal such that said radio frequency transmitter means transmits a signal that indicates an identification to said vehicle-based unit.

5. A tire condition sensor unit as set forth in claim 4, wherein said vehicle-based unit includes means for storing the identification.

6. A tire condition sensor unit as set forth in claim 5, wherein said vehicle-based unit includes means for pairing the stored identification with a tire location.

7. A tire condition sensor unit as set forth in claim 2, wherein said vehicle-based unit includes means utilizing vehicle speed to vary rate of repeat occurrence of the transmission of the initiation signal.

8. A tire condition sensor unit as set forth in claim 1, including controller means, providing the operative connection between said sensor means, said radio frequency transmitter means, and said low frequency receiver means, for controlling operation of said tire condition sensor means.

9. A tire condition sensor unit as set forth in claim 1, including memory means for holding a fixed identification associated with the tire, said radio frequency transmitter means is operatively connected to said memory means, and said transmitted radio frequency signal also indicates the fixed identification associated with the tire.

10. A tire condition sensor unit as set forth in claim 9, including controller means, providing the operative connection between said sensor means, said radio frequency transmitter means, said low frequency receiver means and said memory means, for controlling operation of said tire condition sensor means.

11. A tire condition sensor unit as set forth in claim 9, wherein said memory means is capable of learning new identifications.

12. A tire condition sensor unit as set forth in claim 9, wherein said tire condition sensor unit and said vehicle-based unit are part of a tire condition communication system and said low frequency receiver means is a first part of communication means of said tire condition communication system, a low frequency transmitter means of said tire condition communication system is a second part of said communication means that is operatively connected to said vehicle-based unit and that is for transmitting the low frequency initiation signal, said communication means for communicating a request from said vehicle-based unit to said tire condition sensor unit via the low frequency initiation signal to cause the transmission of the radio frequency signal.

13. A tire condition sensor unit as set forth in claim 12, wherein said communication means does not convey identification information.

14. A tire condition sensor unit as set forth in claim 1, wherein said sensor means senses tire inflation pressure as the sensed tire condition.

15. A tire condition communication system for a vehicle, said system comprising:

sensor means, associated with a tire, for sensing at least one tire condition;

radio frequency transmitter means, associated with the tire and operatively connected to said sensor means, for transmitting a radio frequency signal that indicates the sensed tire condition; and

communication means, having a first portion associated with the tire and operatively connected to said radio frequency transmitter means and a second portion associated with the vehicle, for communicating a request from the vehicle to said radio frequency transmitter means to transmit the radio frequency signal that indicates the sensed tire condition.

16. A tire condition communication system as set forth in claim 15, wherein said first portion of said communication means includes low frequency receiver means for receiving a low frequency initiation signal and for causing said radio frequency transmitter means to transmit the radio frequency signal in response to receipt of the low frequency initiation signal.

17. A tire condition communication system as set forth in claim 16, wherein said communication means includes first and second magnetic induction antennas.

18. A tire condition communication system as set forth in claim 15, including radio frequency receiver means, associated with the vehicle, for receiving the radio frequency signal that indicates the sensed tire condition.

19. A tire condition communication system as set forth in claim 18, wherein said sensor means senses tire inflation pressure as the sensed tire condition.

20. A tire condition communication system as set forth in claim 18, including indicator means for providing an indication of sensed tire condition.

21. A tire condition communication system as set forth in claim 20, wherein said indicator means also for indicating tire location.

22. A tire condition communication system as set forth in claim 20, wherein said radio frequency transmitter means also for transmitting an identification, said system including means for using the identification to determine tire location, and said indicator means also for indicating tire location.

23. A tire condition communication system as set forth in claim 22, including means for storing identifications and associating identifications with respective tire locations.

24. A tire condition communication system as set forth in claim 23, including means for updating the stored identifications.

25. A tire condition communication system as set forth in claim 24, wherein said means for updating the stored identifications includes means for monitoring the number of times an identification is received.

26. A tire condition communication system as set forth in claim 15, including means utilizing vehicle speed to vary rate of operation of said communication means.

27. A tire condition communication system as set forth in claim 15, including memory means, associated with the tire, for holding a fixed identification associated with the tire, said radio frequency transmitter means also for transmitting the radio frequency signal to indicate the fixed identification.

28. A tire condition communication system as set forth in claim 27, including memory means, associated with the vehicle, for holding identification values for comparison with the fixed identification indicated by the received radio frequency signal.

29. A tire condition communication system as set forth in claim 27, wherein said memory means is capable of learning new identifications.

30. A tire condition communication system as set forth in claim 27, wherein said communication means does not convey identification information.

31. A tire condition communication system for a vehicle, said system comprising:

sensor means, associated with a tire, for sensing at least one tire condition;

memory means, associated with the tire, for holding a fixed identification associated with the tire;

radio frequency transmitter means, associated with the tire and operatively connected to said sensor means and said memory means, for transmitting a radio frequency signal that indicates the fixed identification and the sensed tire condition; and

communication means, having a first portion associated with the tire and operatively connected to said radio frequency transmitter means and a second portion associated with the vehicle, for communicating a request from the vehicle to said radio frequency transmitter means to transmit the radio frequency signal that indicates the fixed identification and the sensed tire condition.

32. A tire condition communication system as set forth in claim 31, wherein said first portion of said communication means includes low frequency receiver means for receiving a low frequency initiation signal and for causing said radio frequency transmitter means to transmit the radio frequency signal in response to receipt of the low frequency initiation signal.

33. A tire condition communication system as set forth in claim 32, wherein said communication means includes first and second magnetic induction antennas.

34. A tire condition communication system as set forth in claim 31, including radio frequency receiver means, associated with the vehicle, for receiving the radio frequency signal that indicates the fixed identification and the sensed tire condition, and memory means, associated with the vehicle, for holding identification values for comparison with the fixed identification indicated by the received radio frequency signal.

35. A tire condition communication system as set forth in claim 31, wherein said memory means is capable of learning new identifications.

36. A tire condition communication system as set forth in claim 35, including means for counting the number of receptions of an identification to determine whether to learn a new identification.

37. A tire condition communication system as set forth in claim 31, wherein said communication means does not convey identification information.

38. A tire condition communication system as set forth in claim 31, wherein said sensor means senses tire inflation pressure as the sensed tire condition.

39. A tire condition communication system as set forth in claim 31, including indicator means for providing an indication of sensed tire condition.

40. A tire condition communication system as set forth in claim 39, wherein said indicator means also for providing an indication of tire location with the indication of sensed tire condition.

41. A tire condition communication system as set forth in claim 39, including means for controlling said communication means responsive to a vehicle condition.

42. A tire condition communication system as set forth in claim 41, wherein the vehicle condition is vehicle speed.

43. A method of communicating tire condition information from a tire condition sensor unit to a vehicle-based unit, said method comprising:

outputting, in response to control from the vehicle-based unit, a low frequency initiation signal for reception by the tire condition sensor unit; and

outputting, in response to receipt of the low frequency initiation signal, a radio frequency response signal that conveys the tire condition information from the tire condition sensor unit for reception by the vehicle-based unit.

44. A method of communicating tire condition information from a tire condition sensor unit to a vehicle-based unit, said method comprising:

outputting, in response to control from the vehicle-based unit, a low frequency signal for reception by the tire condition sensor unit; and

outputting a radio frequency signal that conveys a fixed tire identification and the tire condition information from the tire condition sensor unit for reception by the vehicle-based unit.

45. A method as set forth in claim 44, including indicating the sensed condition and tire location to a vehicle operator.

46. A method as set forth in claim 44, including controlling the step of outputting the low frequency signal for reception by the tire condition sensor unit in response to a vehicle condition.

47. A method as set forth in claim 44, including comparing the conveyed tire identification with a stored identification at the vehicle.

48. A method as set forth in claim 47, including updating the stored identification at the vehicle via provision of a new identification from a tire condition sensor unit.

49. A method of communicating tire condition information from a plurality of tire condition sensor units to a vehicle-based unit, said method comprising:

sequentially outputting, in response to control from the vehicle-based unit, low frequency initiation signals, each low frequency initiation signal being for reception by a different tire condition sensor unit; and

each tire condition sensor unit outputting, in response to receipt of the respective low frequency initiation signal, a radio frequency response signal that conveys the tire condition information from that tire condition sensor unit for reception by the vehicle-based unit.

50. A method as set forth in claim 49, wherein said step of outputting the radio frequency response signals includes outputting the response signals to convey fixed tire identifications.

51. A method as set forth in claim 50, including indicating the sensed conditions and tire locations to a vehicle operator.

52. A method as set forth in claim 50, including comparing the conveyed tire identifications with stored identifications at the vehicle.

53. A method as set forth in claim 49, including updating a stored identification at the vehicle via provision of a new identification from a tire condition sensor unit.

54. A method as set forth in claim 49, including controlling the step of outputting the low frequency signals for reception by the tire condition sensor units in response to a vehicle condition.

55. A method of communicating tire condition information from a plurality of tire condition sensor units to a vehicle-based unit, said method comprising:

sequentially outputting, in response to control from the vehicle-based unit, low frequency signals, each low frequency signal being for reception by a different tire condition sensor unit; and

each tire condition sensor unit outputting a radio frequency signal that conveys a fixed tire identification and the tire condition information from that tire condition sensor unit for reception by the vehicle-based unit.

56. A method as set forth in claim 55, including indicating the sensed conditions and tire locations to a vehicle operator.