Road surface friction sensor and road surface friction coefficient detector, and vehicle antilock braking device

Abstract

The road surface friction sensor of this invention comprises means for measuring the strain of the tire or around the wheel of a vehicle. By using this sensor, a vehicle antilock braking device can be constructed which is adapted to cyclically increase the pressure of brake fluid while the road surface frictional force increases in response to elevation of brake fluid pressure, decrease the brake fluid pressure when the road surface frictional force declines despite elevation of brake fluid pressure and increase the brake fluid pressure again when the road surface frictional force has declined in response to fall-off of brake fluid pressure. The output signal from the above road surface friction sensor can be subjected to mathematical operation to find a road surface friction coefficient. With such a road surface friction coefficient detector, there can be implemented a vehicle antilock braking device comprising brake control means adapted to cyclically increase the pressure of brake fluid while the road surface friction coefficient increases in response to elevation of brake fluid pressure, either relieve or release the brake fluid pressure when the rising velocity of road surface friction coeffi-

What is claimed is:  
     
         1 . A road surface friction sensor comprising means for measuring the strain of the tire or the strain around the wheel of a vehicle.  
     
     
         2 . A vehicle antilock braking device comprising brake control means adapted to detect a road surface frictional force and to cyclically increase the pressure of brake fluid while the road surface frictional force increases in response to elevation of the brake fluid pressure, decrease the brake fluid pressure when the road surface frictional force declines despite elevation of brake fluid pressure and increase the brake fluid pressure again when the road surface frictional force declines in response to fall-off of brake fluid pressure.  
     
     
         3 . A vehicle antilock braking device according to  claim 2  wherein the road surface frictional force is detected by means of the road surface friction sensor of  claim 1 .  
     
     
         4 . A road surface friction coefficient detector comprising a road surface friction sensor and a vertical load sensor, each equipped with means for measuring strain of the tire or the strain around the wheel of a vehicle, and means for calculating a road surface friction coefficient from signal outputs from said means.  
     
     
         5 . A vehicle antilock braking device comprising brake control means adapted to detect a road surface friction coefficient and to cyclically increase the pressure of brake fluid while said road surface friction coefficient increases in response to elevation of brake fluid pressure, either relieve or release the brake fluid pressure when the rising velocity of road surface friction coefficient has dropped below a preset value and increase the brake fluid pressure again when the road surface friction coefficient has declined below the set value.  
     
     
         6 . A vehicle antilock braking device according to  claim 5  wherein the road surface friction coefficient is detected by means of the road surface friction coefficient detector of claim  4 .