Patent Application
20060206247
The present invention relates to a tire parameter sensing system for a vehicle and an associated method. More particularly, the present invention relates to a tire parameter sensing system in which a tire-based unit is responsive to a trigger signal from the vehicle-based unit for transmitting a parameter signal indicating sensed tire parameters and an associated method.
Tire parameter sensing systems for vehicles typically include multiple tire-based units and a single vehicle-based unit. Each tire-based unit has an associated tire of the vehicle and is operative to sense at least one parameter of the tire. The sensed parameter(s) may include temperature, pressure, etc. Each tire-based unit is also operative to transmit a parameter signal indicative of the sensed parameter(s) to the vehicle-based unit. The vehicle-based unit is connected to a display. In response to receiving a parameter signal from a tire-based unit, the vehicle-based unit outputs a signal to the display. The display is responsive to the signal for displaying the sensed tire parameter(s).
It is common for the tire-based units of a tire parameter sensing system to be battery powered. Battery powered tire-based units, however, have specific limitations, for example, a limited life, a limited current supply, and a limited operating temperature range. The design of a tire parameter sensing system using battery powered tire-based units must be mindful of these limitations. As a result, it is common for a battery powered tire-based unit to transmit parameter signals only in response to a determination that a sensed parameter is outside of a desired range. For example, if the desired pressure range is 32 to 36 pounds per square inch (“psi”), the battery powered tire-based unit may transmit a parameter signal to the vehicle-based unit only when the sensed tire pressure is determined to be below 32 psi or above 36 psi. By limiting the transmissions of the parameter signal, the battery life of the battery powered tire-based unit may be extended.
In some tire parameter sensing systems, the tire-based units do not include batteries. Tire-based units that do not include batteries receive energy via magnetic or electric field coupling of the tire-based unit with an associated energy transmitting component of the vehicle-based unit. The associated energy transmitting component of the vehicle-based unit is generally located near the tire-based unit, such as in the wheel well of the vehicle.
The tire-based unit generally includes a capacitor that is charged by magnetic or electric field coupling. The tire-based unit uses the energy stored in the capacitor for sensing the parameter(s) in the tire and for providing a parameter signal indicative of the sensed tire parameter(s). The tire-based unit may include signal transmission circuitry, including an oscillator, for transmitting a tire parameter signal to the vehicle-based unit. Alternatively, the tire-based unit may use the principal known as “backscatter modulation” to transfer a tire parameter signal to the vehicle-based unit.
It is common for the tire-based unit to be fixed for rotation with its associated tire. During the rotation of the tire relative to the vehicle, the tire-based unit moves relative to the associated energy transmitting component of the vehicle-based unit. During a portion of each rotation of the tire, the rim upon which the tire is mounted becomes interposed between the tire-based unit and associated energy transmitting component of the vehicle-based unit. When the rim is located between the tire-based unit and the associated energy transmitting component of the vehicle-based unit, the rim may block signal transmissions between the tire-based unit and the associated energy transmitting component of the vehicle-based unit. Additionally, when the tire-based unit is located at certain rotational positions relative to the vehicle, attenuation of the tire parameter signal may occur as the tire parameter signal passes through the structure of the tire. As a result, a signal to noise ratio of a tire parameter signal that is received by the vehicle-based unit may be too low for enabling the vehicle-based unit to accurately extract the sensed tire parameter(s).
A communication zone exists for each tire-based unit and its associated energy transmitting component of the vehicle-based unit. When the tire-based unit is located within the communication zone, communication between the tire-based unit and the associated energy transmitting component of the vehicle-based unit is likely to occur. The tire-based unit passes into and out of the communication zone during rotation.
The tire-based unit requires a certain amount of the energy stored in the capacitor for transmitting a tire parameter signal. When the tire-based unit transmits a tire parameter signal while outside of the communication zone, the energy used for transmitting the signal may be wasted as it is unlikely that the vehicle-based unit will receive the transmitted tire parameter signal. It is desirable to increase the success rate of communication from the tire-based unit to the vehicle-based unit. An increased success rate of the communication will enable the use of a smaller capacitor in the tire-based unit. As a result, the tire period necessary for charging the capacitor will be decreased and a response time for the system may be increased.
The present invention relates to a tire parameter sensing system for a vehicle. The system comprises a vehicle-based unit and a tire-based unit. The tire-based unit is associated with a tire of the vehicle and rotates with the tire. The tire-based unit is located in a communication zone for communicating with the vehicle-based unit through only a portion of each rotation of the tire. The tire-based unit senses at least one parameter of the tire and transmits locator signals at predetermined intervals. The vehicle-based unit receives a locator signal that is transmitted while the tire-based unit is located in the communication zone and, in response to receiving the locator signal, transmits a trigger signal to the tire-based unit. The tire-based unit is responsive to receipt of the trigger signal for transmitting a parameter signal indicative of the sensed at least one parameter.
According to another aspect, the present invention relates to a tire parameter sensing system for a vehicle. The system comprises a tire-based unit that is associated with a tire of the vehicle and that rotates with the tire. The system also comprises a vehicle-based unit having a reader portion that is mounted on the vehicle at a location adjacent the tire to which the tire-based unit is associated. The vehicle-based unit is configured to communicate with the tire-based unit when the tire-based unit is located in a communication zone with the reader portion. The tire-based unit is located in the communication zone with the reader portion through only a portion of each rotation of the tire. The tire-based unit includes a parameter sensing portion for sensing at least one parameter of the tire and a communication portion for communicating with the vehicle-based unit. The communication portion of the tire-based unit transmits locator signals at predetermined intervals. The vehicle-based unit is responsive to receipt of a locator signal for transmitting a trigger signal from the reader portion to the tire-based unit. The communication portion of the tire-based unit, in response to receiving the trigger signal, transmits to the vehicle-based unit a parameter signal indicative of the at least one parameter of the tire.
In accordance with yet another aspect, the present invention relates to a method of operating a tire parameter sensing system of a vehicle in which a tire-based unit is associated with a tire of the vehicle and rotates with the tire. The tire-based unit is located in a communication zone with a vehicle-based unit through only a portion of each rotation of the tire. The method comprises the steps of sensing, with the tire-based unit, at least one parameter of the tire; transmitting locator signals from the tire-based unit at predetermined intervals; transmitting a trigger signal from the vehicle-based unit to the tire-based unit in response to receipt of a locator signal at the vehicle-base unit, and transmitting a parameter signal indicative of the at least one parameter of the tire from the tire-based unit to the vehicle-based unit in response to receipt of the trigger signal at the tire-based unit.
The foregoing and other features 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:
The vehicle 10 has a front 24, a rear 26, and opposite left and right sides 28 and 30, respectively.
The tire parameter sensing system 12 includes four tire-based units 34, 36, 38, and 40. Each tire 16, 18, 20, and 22 of the vehicle 10 includes an associated tire-based unit 34, 36, 38, and 40, respectively, for sensing at least one parameter, e.g., pressure, temperature, etc., of the tire and for transmitting parameter signals 44, 46, 48, and 50, respectively. The parameter signals 44, 46, 48, and 50 are indicative of the sensed parameter(s) of the tires 16, 18, 20, and 22, respectively.
The tire parameter sensing system 12 also includes a vehicle-based unit 54. The vehicle-based unit 54 includes a central portion 56 and four reader portions 60, 62, 64, and 66. One of the reader portions 60, 62, 64, and 66 of the vehicle-based unit 54 is associated with each one of the tire locations of the vehicle 10. Preferably, each reader portion 60, 62, 64, and 66 is located in the wheel well at its associated tire location. Each reader portions 60, 62, 64, and 66 of the vehicle-based unit 54 is also associated with the tire-based unit 16, 18, 20, and 22 of the tire located in its associated tire location. With reference to
Each reader portion 60, 62, 64, and 66 of the vehicle-based unit 54 is coupled to the central portion 56 of the vehicle-based unit.
The central portion 56 of the vehicle-based unit 54 is preferably located within a housing 94. In the embodiment illustrated in
A memory 100 is operatively connected to the controller 96. Alternatively, the memory 100 may form a portion of the controller 96. The memory 100 is a non-volatile memory that includes a lookup table for associating each reader portion 60, 62, 64, and 66 to its associated tire location on the vehicle 10. The memory 100 also stores a tire parameter sensing algorithm that is performed by the controller 100 of the vehicle-based unit 54.
A display 102 is operatively connected to the controller 96. The display 96 is located in the occupant compartment of the vehicle 10 and is responsive to receipt of display signals from the controller 96 for providing an operator of the vehicle with indications of the sensed tire parameter(s) and, optionally, the associated tire locations. For example, the display 102 may provide an indication of the sensed tire temperatures and the sensed tire pressures for each of the tires 16, 18, 20, and 22 of the vehicle 10.
The central portion 56 of the vehicle-based unit 54 also includes a direct current (“DC”) to alternating current (“AC”) converter 104, such as an oscillator. The DC to AC converter 104 receives a direct current from the power source 90 and outputs electrical energy having an alternating current. The alternating current is received by transmit circuitry 106 of the vehicle-based unit 54. The transmit circuitry 106 includes a relay circuit (not shown) that is operatively coupled to the controller 96. The controller 96 controls the relay circuitry 106 for controlling the output of the alternating current to the reader portions 60, 62, 64, and 66 of the vehicle-based unit 54 via lines 70, 74, 80, and 84, respectively. The transmit circuitry 106 also includes a modulator (not shown). The modulator is responsive to signals from the controller 96 for modulating information onto the alternating current that is provided to the reader portions 60, 62, 64, and 66. The modulator may use any known modulation method, such as amplitude shift keying or frequency shift keying.
The central portion 56 of the vehicle-based unit 54 also includes receive circuitry 110. The receive circuitry 110 includes a demodulator (not shown) for demodulating the received parameter signals 44, 46, 48, and 50 and for outputting message packets received in the parameter signals to a controller 96. Each message packet includes the sensed tire parameter(s).
The antenna 116 of the reader portion 60 of the vehicle-based unit 54 is responsive to receipt of electric power for providing a signal 126 to couple the reader portion 60 to the tire-based unit 34 to which it is associated. Either magnetic field coupling or electric field coupling may be used for coupling the reader portion 60 to the tire-based unit 34. In an exemplary embodiment of the invention, the antenna 116 is a coil that is configured for providing a low frequency signal at approximately 125 kHz to create a magnetic field for inductively coupling the reader portion 60 and the tire-based unit 34. The antenna 116 is also configured to receive signals from the tire-based unit 34 and to transfer the received signals to the central portion 56 of the vehicle-based unit 54 so that the signals may be demodulated and sent to the controller 96.
The tire-based unit 34 also includes an energy supplying portion 132, a parameter sensing portion 134, and a communication portion 136. The energy supplying portion 132 includes rectifying and regulating circuitry 140. The rectifying and regulating circuitry 140 receives the electric energy from the antenna 130, converts the alternating current of the received electrical energy to direct current, and outputs electrical energy having a regulated direct current. The rectifying and regulating circuitry 140 provides the rectified and regulated electrical energy to an energy storage device 142, such as a capacitor, which provides the electrical energy for operation of the tire-based unit 34. The energy storage device 142 of the energy supplying portion 132 of the tire-based unit 34 supplies electrical energy to the components of the parameter sensing portion 134 and the communication portion 136 that require electrical energy for operation of the tire-based unit 34.
The parameter sensing portion 134 of the tire-based unit 34 includes one or more sensors operable for sensing one or more parameters of the tire 16. The parameter sensing portion 134 of the tire-based unit 34 illustrated in
The parameter sensing portion 134 of the tire-based unit 34 also includes a controller 158. The controller 158 is preferably a microcomputer. Alternatively, the controller 158 may be formed from discrete circuitry, an application-specific-integrated-circuit (“ASIC”), or any other type of control circuitry. The controller 158 is operatively coupled to the temperature sensor 150, the pressure sensor 152, and the other sensors 154 and receives the temperature signals, pressure signals, and other parameter signals, respectively. The controller 158 performs a tire parameter sensing algorithm and outputs a message packet that includes the sensed parameters of the tire 16. As shown schematically in
A memory 162 is operatively coupled to the controller 158. Alternatively, the memory 162 may form a portion of the controller 158. The memory 162 is a non-volatile memory in which the tire parameter sensing algorithm for the tire-based unit 34 is stored.
The controller 158 and the memory 162 also form a portion of the communication portion 136 of the tire-based unit 34. The communication portion 136 also includes receive circuitry 166 and transmit circuitry 168. The receive circuitry 166 is operatively coupled to the controller 158 and includes appropriate signal conditioning components (not shown), such as filters and amplifiers, and also includes a demodulator (not shown). The demodulator of the receive circuitry 166 is operable for removing message packets that may be modulated onto the signals received by the antenna 130 of the tire-based unit 34. The receive circuitry 166 provides the message packets to the controller 158.
The transmit circuitry 168 is also operatively coupled to the controller 158. The transmit circuitry 168 includes components for communicating message packets that include the sensed tire parameters to the reader portion 60. For example, when the tire-based unit 34 communicates with the reader portion 60 using backscatter modulation, the transmit circuitry 168 may include a shorting transistor that is applied across the antenna 130 and that has the effect of changing the reflectivity of the antenna. By changing the reflectivity of the antenna 130, a message packet provided by the controller 158 will be modulated onto energy that the antenna 130 reflects back toward the reader portion 60.
When the reader portion 60 of the vehicle-based unit 54 receives a signal, such as the parameter signal 44, from the tire-based unit 34, the received signal is passed through the received signal conditioning circuitry 120 of the reader portion 60 and is transferred to the receive circuitry 110 of the central portion 56 of the vehicle-based unit 54. The receive circuitry 110 demodulates the received signal and sends the message packet received from the signal to an associated input of the controller 96. The controller 96 associates the received message packet to the reader portion 60 from which the signal was received. As a result, the controller 96 of the vehicle-based unit 54 may associate the data regarding the sensed parameters of tire 16 with the location on the vehicle of reader portion 60. The controller 96 may include the sensed parameters and the associated tire location in a display signal that is provided to the display 102. The display 102 may then be responsive to receipt of the display signal for providing an indication of the sensed parameters and the associated tire location.
During rotation of the wheel assembly 176, the tire-based unit 34 periodically passes into and out of the communication zone 190. Communication of signals between the reader portion 60 of the vehicle-based unit 54 and the tire-based unit 34 is most probable when the tire-based unit 34 is located within the communication zone 190. Communication of signals between the reader portion 60 of the vehicle-based unit 54 and the tire-based unit 34 is less likely to occur when the tire-based unit 34 is located outside of the communication zone 190.
The tire-based unit 34 uses a predetermined amount of the electrical energy for transmitting a tire parameter signal 44. This electrical energy is supplied from the energy storage device 142. When the tire-based unit 34 transmits a tire parameter signal 44 that is not received by the reader portion 60 of the vehicle-based unit 54, the amount of electrical energy stored within the energy storage device 142 may be decreased below an amount necessary for providing another tire parameter signal 44. As a result, the energy storage device 142 may need to be recharged prior to the tire-based unit 34 transmitting another tire parameter signal 44 and the response time of the system to the occurrence of an undesirable tire parameter is lengthened.
The parameter sensing system 12 of the present invention is configured for ensuring that the tire-based unit 34 transmits the tire parameter signal 44 while the tire-based unit 34 is located within the communication zone 190. As a result, the reader portion 60 of the vehicle-based unit 54 is likely to receive the tire parameter signal 44 and a timely indication of the sensed parameters of the tire 16 occurs.
To ensure that the tire-based unit 34 transmits the tire parameter signal 44 while the tire-based unit 34 is located within the communication zone 190, the controller 158 of the tire-based unit 34 controls the tire-based unit 34 to transmit one or more locator signals. Each locator signal has a number of bits that is less than the number of bits of the parameter signal 44. As a result, the amount of electrical energy needed for transmitting the locator signal is less than the amount of electrical energy needed for transmitting the parameter signal 44. The tire-based unit 34 transmits the locator bits at spaced intervals.
The reader portion 60 of the vehicle-based unit 54 is configured to receive the locator signal and to transfer the locator signal to the central portion 56 of the vehicle-based unit. In the central portion 56 of the vehicle-based unit 54, the receive circuitry 110 demodulates the locator signal and sends a message packet indicating receipt of the locator signal to the controller 96. The controller 96 is responsive to the message packet indicating receipt of the locator signal for controlling the vehicle-based unit 54 to transmit a trigger signal to the tire-based unit 34. The trigger signal indicates to the tire-based unit 34 that the locator signal was received and that the tire-base unit is likely located within the communication zone 190.
The trigger signal is received by the antenna 130 of the tire-based unit 34 and is transferred to the receive circuitry 166. The receive circuitry 166 demodulates the trigger signal and provides a message packet indicative of the trigger signal to the controller 158 of the tire-based unit 34. The controller 158 of the tire-based unit 34 is responsive to receipt of the message packet indicating receipt of the trigger signal for controlling the tire-based unit 34 for transmitting the parameter signal 44.
As shown in
At step 306, the tire-based unit transmits a locator signal. At step 308, the tire-based unit activates its timer. The process 300 proceeds from step 308 to step 310 in which the tire-based unit listens for a trigger signal from its associated reader portion of the vehicle-based unit. At step 312, a determination is made as to whether a trigger signal has been received. When the determination at step 312 is negative, the process 300 proceeds to step 314. At step 314 a determination is made as to whether a predetermined amount of time, indicated as X in
When the determination at step 312 is affirmative and the tire-based unit has received a trigger signal, the process 300 proceeds to step 316. At step 316, the tire-based unit transmits its tire parameter signal indicating the sensed parameters of its associated tire. From step 316, the process 300 returns to step 304.
When a locator signal is received at the vehicle-based unit and the determination at step 410 is affirmative, the process 400 proceeds to step 416 in which the vehicle-based unit transmits a trigger signal. At step 418, the timer is reactivated and, at step 420, the vehicle-based unit listens for a parameter signal. From step 420, the process 400 proceeds to step 422 in which a determination is made as to whether a parameter signal has been received. When the determination at step 422 is negative, the process 400 proceeds to step 424 in which a determination is made as to whether a predetermined amount of time, indicated as Z in
When the determination at step 422 is affirmative and the vehicle-based system has received a parameter signal, the process 400 returns to step 404. During the process 400 of
The vehicle-based unit 54′ of
From the above description of the invention, those skilled in the art will perceive improvements, changes and modifications. Such improvements, changes and modifications within the skill of the art are intended to be covered by the appended claims.
