Apparatus and method for alarming decrease in tire air-pressure

Abstract

An apparatus for alarming a decrease in tire air-pressure which alarms the decrease in inner pressure of the tire by using a judged value calculated based on wheel speed information obtained from tires fitted to a four-wheeled vehicle. The apparatus comprises calculating means for calculating the judged value based on the wheel speed information on each of the tires, the calculating means being connected to one of on-vehicle LANs, via which the wheel speed information on each of the tires is transmitted. The calculates means captures the wheel speed information on each of the tires via one of the on-vehicle LANs. The wheel speed information is converted into the digital data, which is then captured into the apparatus for alarming the decrease in tire air-pressure via the on-vehicle LAN, thus remarkably reducing the number of lines laid in the vehicle in comparison with the prior art.

What is claimed is:  
     
         1 . An apparatus for alarming a decrease in tire air-pressure which alarms the decrease in inner pressure of the tire by using a judged value calculated based on wheel speed information obtained from tires fitted to a four-wheeled vehicle, comprising calculating means for calculating the judged value based on the wheel speed information on each of the tires, the calculating means being connected to one of on-vehicle LANs, via which the wheel speed information on each of the tires is transmitted wherein the calculates means captures the wheel speed information on each of the tires via one of the on-vehicle LANs.  
     
     
         2 . The apparatus of  claim 1 , wherein the wheel speed information per wheel is 2 bytes, and wheel speed information for four wheels is captured via one transmission.  
     
     
         3 . The apparatus of  claim 1 , wherein the wheel speed information is one expressed by a combination of the number of pulses output in proportion to rotation of a wheel and a time corresponding to the number of pulses, and the number of pulses and the corresponding time are received in 1 byte and 2 bytes respectively.  
     
     
         4 . The apparatus of any one of  claims 1  to  3 , wherein an interval for capturing the data on the wheel speed information ranges from 10 ms to 100 ms.  
     
     
         5 . A method for alarming a decrease in tire air-pressure which alarms the decrease in inner pressure of the tire by using a judged value calculated based on wheel speed information obtained from tires fitted to a four-wheeled vehicle, comprising the step of capturing the wheel speed information on each of the tires into calculating means for calculating the judged value based on the wheel speed information on each of the tires via one of on-vehicle LANs.  
     
     
         6 . The method of  claim 5 , wherein the wheel speed information per wheel is 2 bytes, and wheel speed information for four wheels is captured via one transmission.  
     
     
         7 . The method of  claim 5 , wherein the wheel speed information is one expressed by a combination of the number of pulses output in proportion to rotation of a wheel and a time corresponding to the number of pulses, and the number of pulses and the corresponding time are received in 1 byte and 2 bytes respectively.  
     
     
         8 . The method of any one of  claims 5  to  7 , wherein an interval for capturing the data on the wheel speed information ranges from 10 ms to 100 ms.