Patent Application
20060197655
Not Applicable.
Not Applicable.
1. Field of the Invention
This invention relates in to a tire pressure monitoring system, and more specifically, to a batteryless tire pressure sensor monitoring system.
2. Description of the Related Art
Tire pressure monitoring (TPM) systems include disposing pressure sensors on or within vehicle tires to sense the pressure within a respective tire and report low or high pressure conditions to a driver. Various systems have mounted sensors inside the tires on a portion of the rubber, the rim of the wheel, on a valve stem within a wheel, or on the valve stem outside of the wheel. TPM systems sense tire pressure within a tire and transmit a signal to a body-mounted receiving unit located external to the tire for processing tire pressure data. A power source is required to energize the sensor and other electrical components of the TPM system within the tire. Other electrical devices may include a transmitter if the data sensed is being wirelessly transmitted to a nearby receiver. Many TPM systems utilize a battery as the power source for energizing the electrical components within the TPM system. However, typical storage batteries have a finite life and require periodic replacement. The longer the activation time of a respective TPM to measure and report pressure values, the shorter the useful life of a respective battery. For TPM sensors located external to the tire, batteries may be easily replaced or recharged. However, TPM systems incorporating TPM systems external to tire are directly exposed to and affected by exterior environment conditions and road conditions.
For TPM systems located internally to the tire and utilizing a battery as the power source, these systems typically require dismounting the tire from the vehicle and removing the tire from the rim to access the TPM sensor for replacing or recharging the battery. This requires cost, time, and effort.
Systems utilizing T?M sensors internal to the tire typically place the TPM electronics into a dormant state when not in use and activate the TPM system only when needed so as to conserve energy and extend the life of the battery. However, this only extends the life of the finite power source and at some future point in time requires changing the battery. What would be useful is a maintenance free TPM system that includes a power source which requires neither replacement nor recharging.
The present invention has the advantage of mounting a batteryless tire pressure sensing device on a vehicle wheel and transmitting a microwave energy signal to the tire pressure sensing device for powering a sensor within the tire pressure sensing device for retrieving at least one pressure related parameter. A signal containing the sensed pressure related parameter portion is modulated with a portion of the received microwave energy signal and transmitted to a reading module disposed within the vehicle.
In one aspect of the present invention, a batteryless tire pressure sensing device is provided that includes a sensor disposed in a wheel for sensing at least one pressure-related parameter of a tire. An antenna is coupled to the sensor for receiving a modulated microwave energy signal. A control circuit coupled to the antenna and the sensor converts at least a portion of the modulated microwave energy signal to a supply voltage for providing power to the sensor. The sensor senses the at least one pressure related parameter of the tire in response to receiving the supply voltage from the control circuit.
Referring now to the Drawings and particularly to
To monitor the internal air pressure of an inflated tire without having to manually couple an air gauge measurement device to a valve stem of the wheel, a tire pressure sensor is coupled to a respective vehicle wheel for automatically measuring the internal air pressure of the respective tire. The tire pressure sensor monitors the respective vehicle tire for a high or low pressure condition. Other pressure related parameters such as temperature may also be monitored. The pressure related measurements are transmitted via a wireless signal to a receiving unit within the vehicle. The receiving unit receives the tire pressure measurements and when a low or high pressure condition is detected, a warning indicator is provided to the driver of the vehicle informing the driver of the respective condition.
A tire pressure sensing device 19 is affixed to the inside of a wheel 16 to monitor the inflation pressure of a tire 18. Various methods may be used to attach the tire pressure sensing device 19 to the wheel 16 of the vehicle 10 such as bolting the tire pressure sensing device 19 to the interior surface of the wheel 16, strapping the tire pressure sensing device 19 about the inside circumference of the wheel 16, or mounting the tire pressure sensing device 19 to a valve stem. Since the tire pressure sensing device 19 is sealingly contained within the rotating wheel 16 and tire 18, it is difficult to provide power a wireline from the fixedly-mounted reading module 22 via to the tire pressure sensing device 19. In the present embodiment, the reading module 22 provides power to the sensor 26 by transmitting a microwave energy signal to the tire pressure sensing device 19 disposed within the wheel 16.
The reading module 22 is mounted to the interior of the vehicle body 12 on an opposing side of a vehicle wheel well 23 for being in close proximity to tire pressure sensing device 19. Power level emissions of transmitted signals are limited as the Federal Communications Commission (FCC) maintains regulations on the maximum emission that may be generated by a respective transmitted signal for a respective application. As a result, it is advantageous to mount the reading module 22 in close proximity to the respective wheel so that a signal may be transmitted utilizing an optimum transmission power level in compliance with FCC regulations while minimizing the amount of energy dissipated during the energy signal transmission. The tire pressure sensing device 19 converts at least a portion of the microwave energy signal to a supply voltage that powers a sensor 26 within the tire pressure sensing device 19. Typically the sensor 26 operates on a voltage range of 1.7-5 volts; however, other sensors may be utilized which require voltages outside of the preferred operating range. The tire pressure sensing device 19 senses at least one pressure related-parameter. The sensed pressure related-parameter data is transmitted to the reading module 22. The reading module 22 demodulates the pressure related-parameter signal and provides pressure related-parameter data to an electronic control unit 24 for generating a control action in response to the pressure related-parameter data. Alternatively, the reading module 22 and the electronic control module 24 may be integrated into a single module. Preferably, the electronic control unit 24 is disposed in the interior portion of a door panel 25 or instrument panel (not shown). For complexity and cost reduction reasons, the electronic control unit 24 may be integrated with another control module such as a remote keyless entry module (not shown).
The tire pressure sensing device 19 includes an antenna 30 for receiving the transmittable energy signal (fc±fm), a control circuit 20 for transforming transmittable energy signal (fc±fm) to DC voltage, and the sensor 26 for measuring the pressure related parameters of a respective vehicle tire. The transmittable energy signal (fc±fm) is received via the antenna 30 at a power level of −12˜−2 dBm and is input to an envelope detector 32 such as a diode detector that forms a homo-dyne receiver. The envelope detector 32 includes an impedance matching device and diode with a resistor and capacitor connected in parallel from the input and output, respectively, to ground. Alternatively, a transceiver may be used for receiving the transmittable energy signal. The carrier signal (fc) is removed by the envelope detector and the microwave energy signal (fm) is then input to a voltage double rectifier 38 for converting the voltage of the microwave energy signal to a higher voltage level and for rectifying the microwave energy signal (fm) to a DC supply voltage. Alternatively, a separate rectifier and transformer may be used. In addition, only a rectifier may be required if the microwave energy signal (fm) received is of a voltage level that is sufficient to power the sensor 26 without having to boost the voltage level. The DC supply voltage is input to an energy storage device 42 but this is only necessary if the supply voltage output from the double voltage rectifier 38 is not sufficient to power the sensor 26. The sensor 26 is energized when the accumulated energy in the energy storage device 42 is sufficient to provide a continuous flow of energy to the sensor 26 for a predetermined duration of time to measure the pressure related parameters. When the sensor 26 is energized, the sensor 26 measures the pressure related parameters (e.g., pressure and temperature) of the pressurized air within the tire 18.
After the pressure and temperature parameters are measured by the sensor 26, the pressure related parameter data is digitized and is provided to a low pass filter 46. The sensor 26 is capable of generating high frequencies in the range of 10-20 kHz. The low pass filter 46 is required to filter the high frequencies generated by the sensor 26. Furthermore, the low pass filter 46 is used to block the 5.8 GHz signal generated by the mixer 44 from propagating to the sensor 26. In alternative embodiments, other sensors may be utilized which generate lower frequencies that do not require filtering or are not sensitive to high frequencies. The pressure related parameter data is then output to a mixer 44. The tire pressure sensing device 19 may include a second antenna 70 coupled to a first port 71 of the mixer 44 for receiving a portion of the transmittable energy signal (fc±fm) where it is then combined in the mixer 44 with the data signal (fs) input from a second port 72. Alternatively, a portion of the transmittable energy signal (fc±fm) received in antenna 30 may have been provided to the first port 71 of the mixer 44 for combining with the data signal (fs) as opposed to utilizing the second antenna 70. The combined data signal (fc±fm±fs) is then output from the mixer via port 73 and transmitted to the reading module 22 and is received by antenna 65. Alternatively, the reading module may utilize only one antenna receiving and transmitting incoming and outgoing signals, respectively. Furthermore, a 2-port mixer may be utilized where the energy received from a respective antenna is input to the mixer via a respective port and is then mixed with a data signal and output the same respective port for transmitting to the reading module. Alternatively, a transceiver may be used to transmit the signal to the reading module.
The combined data signal (fc±fm±fs) received by antenna 65 is input to a mixer (i.e., down converter). The coupler 64 directs the carrier signal (fc) to the mixer 66 for filtering the carrier signal (fc) from the received combined data signal (fc±fm±fs). The output of the mixer 66 (fm±fs) is input to a low pass filter 67 where the data signal (fs) is filtered from the output signal (fm±fs) of the mixer 66. The data signal (fs) is input to an amplifier 68 for increasing the signal strength and then transmitted to the electronic control module 24 (shown in
In step 64, the sensor is energized by the DC supply voltage. Pressure related parameter data, such as pressure and temperature within a respective vehicle tire, is measured. In step 65, the pressure related parameter data is input to a low pass filter for filtering high frequencies generated by the sensor. In step 66, pressure related parameter data is input to a mixer where it is mixed with the portion of the modulated microwave energy signal provided to the mixer. The modulated data signal is transmitted to the reading module. In step 67, the pressure related parameter data is demodulated from the received data signal. In step 68, the pressure related parameter data is amplified and is then output to the electronic control module for performing a control action in response to the pressure related parameter data.
From the foregoing description, one ordinarily skilled in the art can easily ascertain the essential characteristics of this invention and, without departing from the spirit and scope thereof, can make various changes and modifications to the invention to adapt it to various usages and conditions.
