Tire inflation pressure monitoring and location determining method and apparatus

A method for determining inflation pressures of tires and locations thereof on wheels of a vehicle, said method comprising the steps of:

• providing a wireless inflation pressure measuring device for each wheel of a vehicle, each of the wireless inflation pressure measuring devices has an antenna located toward an outer perimeter of a respective one of the wheels, wherein each of the wireless inflation pressure measuring devices transmits from its respective antenna a radio frequency signal comprising inflation pressure information of a tire mounted on the respective one of the wheels;
• providing an inflation pressure monitor having a radio frequency receiver adapted for receiving the radio frequency signals from each of the inflation pressure measuring devices, whereby an amplitude of each of the received radio frequency signals varies periodically with each rotation of the respective one of the wheels;
• determining rotation speeds of each of the vehicle wheels by detecting the periodic amplitude variations of each of the radio frequency signals as the respective ones of the vehicle wheels rotate;
• detecting a position of the vehicle front wheels relative to an axis along the length of the vehicle as viewed facing the front of the vehicle;
• determining relative wheel rotation speeds;
• and
• assigning a location to each of the wheels based on the relative wheel rotation speeds and the position of the vehicle front wheels relative to an axis along the length of the vehicle as viewed facing the front of the vehicle.

An apparatus for determining inflation pressures of tires and locations thereof on wheels of a vehicle, comprising:

• a wireless inflation pressure measuring device for each wheel of a vehicle, each of the wireless inflation pressure measuring devices has an antenna located toward an outer perimeter of a respective one of the wheels, wherein each of the wireless inflation pressure measuring devices transmits from its respective antenna a radio frequency signal comprising inflation pressure information of a tire mounted on the respective one of the wheels;
• an inflation pressure monitor having a radio frequency receiver adapted for receiving the radio frequency signals from each of the inflation pressure measuring devices, whereby an amplitude of each of the received radio frequency signals varies periodically with each rotation of the respective one of the vehicle wheels;
• a vehicle turn sensor for determining in which direction the vehicle is making a turn;
• a vehicle relative direction sensor for determining a relative direction in which the vehicle is moving;
• an amplitude demodulator circuit connected to the radio frequency receiver and adapted for detecting the periodic amplitude variations of each of the radio frequency signals as the respective ones of the vehicle wheels rotate, whereby rotation speeds of each of the wheels may be determined;
• and
• a logic circuit connected to the vehicle turn and relative direction sensors and the amplitude demodulator circuit, wherein the logic circuit determines wheel locations based on the relative wheel rotation speeds, the relative direction of the vehicle movement, and the direction the vehicle is making the turn;
• wherein when the vehicle is making a right turn and going forward
• the left front wheel has the fastest rotation speed,
• the left rear wheel has the second fastest rotation speed,
• the right front wheel has the third fastest rotation speed, and
• the right rear wheel has the slowest rotation speed;
• wherein when the vehicle is making a left turn and going forward
• the right front wheel has the fastest rotation speed,
• the right rear wheel has the second fastest rotation speed,
• the left front wheel has the third fastest rotation speed, and
• the left rear wheel has the slowest rotation speed;
• wherein when the vehicle is making a left turn and going backward:
• the left front wheel has the fastest rotation speed,
• the left rear wheel has the second fastest rotation speed,
• the right front wheel has the third fastest rotation speed, and
• the right rear wheel has the slowest rotation speed;
• and
• wherein when the vehicle is making a right turn and going backward
• the right front wheel has the fastest rotation speed,
• the right rear wheel has the second fastest rotation speed,
• the left front wheel has the third fastest rotation speed, and
• the left rear wheel has the slowest rotation speed.

An apparatus for determining inflation pressures of tires and locations thereof on wheels of a vehicle, comprising:

• a wireless inflation pressure measuring device for each wheel of a vehicle, each of the wireless inflation pressure measuring devices has an antenna located toward an outer perimeter of a respective one of the wheels, wherein each of the wireless tire inflation pressure measuring devices transmits from its respective antenna a radio frequency signal comprising inflation pressure information of a tire mounted on the respective one of the wheels;
• an inflation pressure monitor having a radio frequency receiver adapted for receiving the radio frequency signals from each of the inflation pressure measuring devices, whereby an amplitude of each of the received radio frequency signals varies periodically with each rotation of the respective one of the vehicle wheels;
• a vehicle front wheel position sensor for determining a position of the front wheels relative to an axis along the length of the vehicle as viewed facing the front of the vehicle;
• an amplitude demodulator circuit connected to the radio frequency receiver and adapted for detecting the periodic amplitude variations of each of the radio frequency signals as the respective ones of the vehicle wheels rotate, whereby wheel rotation speed of each of the wheels may be determined;
• and
• a logic circuit connected to the vehicle front wheel position sensor and the amplitude demodulator circuit, wherein the logic circuit determines relative wheel rotation speeds and assigns a wheel location to each of the wheels based on the relative wheel rotation speeds and the position of the vehicle front wheels determined by the vehicle front wheel position sensor;
• wherein when the position of the vehicle front wheels are to the right of the axis as viewed facing the front of the vehicle
• the left front wheel has the fastest rotation speed,
• the left rear wheel has the second fastest rotation speed,
• the right front wheel has the third fastest rotation speed, and
• the right rear wheel has the slowest rotation speed;
• and
• wherein when the position of the vehicle front wheels are to the left of the axis as viewed facing the front of the vehicle
• the right front wheel has the fastest rotation speed,
• the right rear wheel has the second fastest rotation speed,
• the left front wheel has the third fastest rotation speed, and
• the left rear wheel has the slowest rotation speed.