Abstract: A method for detecting decrease in tire air-pressure including the steps of: detecting rotational information of the respective tires; storing rotational information; detecting whether the vehicle is running on a flat road or not; detecting whether the vehicle is accelerating or decelerating; comparing rotational information of both front wheels with rotational information of both rear wheels when it has been determined that the vehicle is running on a flat road and that the vehicle is neither accelerating nor decelerating; and judging simultaneous decompression of both front wheel tires or simultaneous decompression of both rear wheel tires on the basis of a relationship between a value obtained through comparison of the rotational information of both front wheels and both rear wheels and a specified threshold. It is possible to judge simultaneous decompression of both front wheel tires or both rear wheel tires when employing the present invention.

Abstract: A method for detecting decrease in tire air-pressure on the basis of rotational information obtained from tires attached to a vehicle. The method includes the steps of: detecting rotational information of the respective tires; storing the rotational information of the respective tires; obtaining an acceleration/deceleration of the vehicle; obtaining a slip rate when the acceleration/deceleration of the vehicle is within a specified range proximate to zero; comparing the slip rate with a slip rate which has been preliminarily obtained when the tire is under normal air pressure; and judging simultaneous decompression of both front wheel tires or simultaneous decompression of both rear wheel tires on the basis of a relationship between a value obtained through comparison of the two slip rates and a specified threshold. It is possible to judge simultaneous decompression of both front wheel tires or both rear wheel tires when employing the present invention.

Abstract: A method for detecting decrease in tire air-pressure in which decrease in internal pressure of a tire is detected on the basis of rotational information. The method includes the steps of: detecting rotational information of the tires; storing the rotational information; comparing rotational information of all left-sided wheels and rotational information of all right-sided wheels of the vehicle when the vehicle is performing straight-ahead running; and judging decompression on the basis of a relationship between a value obtained through comparison of the left-sided and right-sided rotational information and a specified threshold. It is possible to detect decompression of a single wheel tire while it is also possible to detect that two wheel tires on the left or right are simultaneously decreased.

Abstract: An apparatus for detecting a decrease in internal pressure of a tire based on rotational information obtainable from tires attached to a four-wheeled vehicle equipped with a limited slip differential device is presented. The apparatus includes a way of correcting a turning radius or a reciprocal of the turning radius of driving wheels by calculating a shift amount. The shift amount is a difference between turning radiuses or a difference between reciprocals of turning radiuses, which is obtainable from the rotational information of driving wheels and following wheels. An accurate turning radius can be calculated for the driving wheels, which is not affected by the limited slip differential. Consequently, a decrease in the internal tire pressure can be properly judged in a vehicle that has a limited slip differential.

Abstract: A method for detecting decrease in tire air-pressure for detecting decrease in internal pressure of a tire on the basis of rotational information obtained from tires attached to a vehicle. A threshold for judging decrease in air-pressure of following wheels is different from a threshold for judging decrease in air-pressure of driving wheels. Threshold for judging abnormalities in air-pressure are varied for judging abnormalities of tire air-pressures of following wheels and for judging abnormalities of tire air-pressure of driving wheels so that appropriate judgment of abnormalities in air-pressure can be performed.

Abstract: A method and apparatus for judging a decrease in internal pressure of a tire attached to a four-wheeled vehicle and for accordingly generating an alarm, wherein a threshold for judging decompression is set to be larger immediately after switching an ignition key ON when compared to a threshold for the vehicle in a normal running condition, and decompression is judged in a decompression judging time which is shorter than a time for the vehicle in a normal running condition. The threshold for judging decompression and the decompression judging time are returned to that for the normal running condition of the vehicle in the case no decompression is judged. It is thus possible to detect a condition in which a large decompressed condition exists at an early stage before running begins so that it is possible to improve the accuracy of detecting decompression.

Abstract: An apparatus for identifying between summer tires and winter tires based on rotational information obtained from tires attached to a four-wheeled vehicle equipped with a limited slip differential device. The apparatus comprises a rotational information detecting means for detecting rotational information of each of the tires, a memory means for storing rotational information of each of the tires, an arithmetic processing means for respectively calculating reciprocals of turning radiuses based on rotational information of tires attached to a driving shaft as well as judged value based on rotational information of each of the tires, and an identification means for identifying whether the tires attached to the driving shaft are summer tires or winter tires from a relationship between reciprocals of turning radiuses and the judged value. It is possible to accurately perform detection of decrease in tire air-pressure since alarm is generated upon identification of the tires.

Abstract: A method and an apparatus for detecting a decrease in tire air-pressure based on rotational information obtained from tires of a four-wheeled vehicle, wherein memories of isokinetic random access memory devices used for starting judgment of decompression from the beginning are cleared in case it is judged that a normal internal pressure has been assumed after a tire has been judged to be in a decompressed condition. It is prevented that the apparatus repeatedly but erroneously judges a decompressed condition to generate an alarm immediately after judging a normal internal pressure condition.

Abstract: A method for alarming decrease in tire air-pressure for judging a decrease in internal pressure of a tire attached to a four-wheeled vehicle and for accordingly generating alarm. A threshold for judging decompression is set to be larger immediately after switching an ignition key ON when compared to a threshold for the vehicle in a normal running condition, and decompression is judged in a decompression judging time which is shorter than a time for the vehicle in a normal running condition. The threshold for judging decompression and the decompression judging time are returned to those for the normal running condition of the vehicle in case no decompression is judged. An apparatus used for the method is also disclosed. It is possible to detect a condition in which a large decompressed condition exists at an early stage before starting running so that it is possible to improve the accuracy of detecting decompression.

Abstract: An apparatus for alarming decrease in tire air-pressure in which decrease in internal pressure of tires is alarmed based on rotational information obtained from tires attached to a four-wheeled vehicle. The apparatus comprises a rotational information detecting means for detecting rotational information of each tire, a memory means for storing the rotational information of each tire, a calculating means for calculating reciprocals of turning radiuses based on rotational information of tires attached to a driving shaft and judged values from the rotational information of each tire, and a determining means for determining decrease in internal pressure from a relationship between the reciprocals of the turning radiuses and judged values.

Abstract: A method for detecting decrease of tire air pressure includes detecting each angular velocity of rotation of four tires, judging as to whether the tire air pressure is decreased or not based on the detected angular velocity of rotation, and issuing an alarm. The method includes a judgement step for low velocity in which, when the angular velocity of rotation is detected, judgment is made as to whether the tire air pressure is decreased or not; and a judgement step for high velocity in which, when the angular velocity of rotation is detected, judgment is made as to whether the tire air pressure is decreased or not only when the vehicle velocity is higher than a predetermined threshold value and the vehicle is in driven condition.