Patent ID: 7760079

Claim:
A tire-pressure control apparatus comprising: an air pump capable of supplying compressed air to a tire air chamber of a wheel assembly; a mechanical control valve device disposed in an air passageway extending between the air pump and the tire air chamber and adapted to control a tire pressure within the tire air chamber, the control valve device being in a permission state where the control valve device permits supply of compressed air from the air pump to the tire air chamber during a period over which the tire pressure increases to an upper limit set value from a lower limit set value after having decreased to the lower limit set value, and being in a prohibition state where the control valve device prohibits supply of compressed air from the air pump to the tire air chamber during a period over which the tire pressure decreases to the lower limit set value from the upper limit set value after having increased to the upper limit set value; a value state detection sensor for detecting whether the control valve device is in the permission state or the prohibition state; time measurement means for measuring a pressure decreasing time, which is a time period starting when the control valve device enters the prohibition state and ending when the control valve device enters the permission state, and a pressure increasing time, which is a time period starting when the control valve device enters the permission state and ending when the control valve device enters the prohibition state; and discharged-air-flow-rate calculation means for calculating a flow rate of air discharged from the air pump to the tire air chamber from the pressure decreasing time and the pressure increasing time.