Patent ID: 7868749
Filing Date: 2011-01-11
Classification: B60C

Abstract:
1. A method of detecting a decrease in a tire air pressure based on wheel rotation information obtained from tires by a rotation information detection means attached to a four-wheel vehicle for which a distribution of the front and rear driving torque is variable, comprising: a step of calculating wheel rotation information obtained from the respective wheel tires using a computer control unit; a judgment step judging a decrease in a tire air pressure by comparing a predetermined reference value with a decreased pressure judgment value that is calculated using a computer control unit based on the wheel rotation information and that shows a wheel speed ratio between the front and rear axes; an initialization step of storing a wheel speed ratio between the front and rear axes at a regular internal pressure using a computer control unit in order to obtain the predetermined reference value; and a step of determining whether a distribution of front and rear driving torque using a computer control unit is equidistribution or not, wherein the initialization step includes a step of obtaining, when the distribution of the front and rear driving torque is determined to be equidistribution, a first relation formula showing a correlation between the total of the driving torque and the decreased pressure judgment value and a step of calculating, when the distribution of the front and rear driving torque is determined not to be equidistribution, a second relation formula showing the correlation between a difference in the driving torque and the decreased pressure judgment value, and wherein the judgment step judges a decrease in a tire air pressure by comparing, when the distribution of the front and rear driving torque is determined to be equidistribution, a reference value obtained based on the first relation formula with the decreased pressure judgment value and by comparing, when the distribution of the front and rear driving torque is determined not to be equidistribution, the reference value obtained based on the second relation formula with the decreased pressure judgment value.