Brake control apparatus for vehicle

Abstract

A characteristic changing device is adopted in the inventive brake control system for the vehicle. The characteristic changing device sets a differential pressure between a first brake hydraulic pressure which is applied to wheel cylinders and a second brake hydraulic pressure which is generated by a master cylinder so that the first brake hydraulic pressure is higher than the second hydraulic pressure when the second brake hydraulic pressure is reduced. Due to the differential pressure set as described above, the first brake hydraulic pressure enough to exhibit effective braking force is kept even if the second brake hydraulic pressure is reduced.

What is claimed is:  
     
         1 . A brake control apparatus for a vehicle, comprising: 
 a brake hydraulic pressure generating device having a hydraulic pressure generating source for generating brake hydraulic pressure;    a braking force generation member for providing braking force to wheels of the vehicle by receiving the brake hydraulic pressure from the brake hydraulic pressure generating device;    a conduit which connects the brake hydraulic pressure generating device with the braking force generation member; and    characteristic changing means disposed in the conduit, which differentiates a characteristic of pressure-reduction of the hydraulic pressure generating device from that of the brake hydraulic pressure applied to the braking force generation member by setting a differential pressure such that a first brake hydraulic pressure on a side of the braking force generation member is higher than a second brake hydraulic pressure on a side of the brake hydraulic pressure generating device when the brake hydraulic pressure generated by the brake hydraulic pressure generating device drops.    
     
     
         2 . A brake control apparatus for a vehicle, comprising: 
 a brake hydraulic pressure generating device having a hydraulic pressure generating source for generating brake hydraulic pressure;    a braking force generation member for providing braking force to wheels of the vehicle by receiving the brake hydraulic pressure from the brake hydraulic pressure generating device;    a conduit which connects the brake hydraulic pressure generating device with the braking force generation member;    characteristic changing means disposed in the conduit, which increases the brake hydraulic pressure applied to the braking force generation member in conformity with increase of the brake hydraulic pressure generated by the brake hydraulic pressure generating device and which differentiates a change in reduction of the brake hydraulic pressure generated by the brake hydraulic pressure generating device from that of the brake hydraulic pressure applied to the braking force generation member when the brake hydraulic pressure generated by the brake hydraulic pressure generating device drops.    
     
     
         3 . The brake control apparatus for a vehicle according to  claim 2 , wherein the characteristic changing means differentiates the characteristic of pressure-reduction of the brake hydraulic pressure generating device from that of the brake hydraulic pressure applied to the braking force generation member so that a first brake hydraulic pressure on a side of the braking force generation member in the conduit is kept higher than a second brake hydraulic pressure on a side of the brake hydraulic pressure generating device when the brake hydraulic pressure generated by the brake hydraulic pressure generating device drops in the conduit.  
     
     
         4 . The brake control apparatus for a vehicle according to  claim 1 , wherein the characteristic changing means differentiates the characteristic of pressure-reduction of the brake hydraulic pressure generating device from that of the brake hydraulic pressure applied to the braking force generating member by causing brake fluid on the side of the braking force generation member to flow to the side of the brake hydraulic pressure generating device while attenuating an amount of the brake fluid.  
     
     
         5 . The brake control apparatus for a vehicle according to  claim 1 , wherein the characteristic changing means controls flow resistance when brake fluid flows in the conduit from the braking force generation member to the brake hydraulic pressure generating device more than flow resistance when the brake fluid flows in the conduit from the brake hydraulic pressure generating device to the braking force generation member.  
     
     
         6 . The brake control apparatus for a vehicle according to  claim 1 , wherein the characteristic changing means has a proportional control valve for attenuating the brake hydraulic pressure with a predetermined attenuating ratio when brake fluid flows from the conduit on a side of the braking force generation member to the conduit on a side of the brake hydraulic pressure generating device through the proportional control valve.  
     
     
         7 . The brake control apparatus for a vehicle according to  claim 1 , wherein the brake hydraulic pressure generating device includes a brake pedal which is depressed by a driver to brake the vehicle, and 
 wherein the hydraulic pressure generating source generates the brake hydraulic pressure which is increased or reduced in response to variations of stroke of the brake pedal.    
     
     
         8 . The brake control apparatus for a vehicle according to  claim 7 , wherein the characteristic changing means delays a change in pressure-reduction of the brake hydraulic pressure applied to the braking force generation member rather than a change in pressure-reduction of brake hydraulic pressure in the hydraulic pressure generating source which is reduced in accordance with the decrease of the stroke of the brake pedal.  
     
     
         9 . The brake control apparatus for a vehicle according to  claim 1 , wherein the characteristic changing means equalizes the brake hydraulic pressure applied to the braking force generation member with the brake hydraulic pressure in the hydraulic pressure generating source when the brake hydraulic pressure in the hydraulic pressure generating source drops below a predetermined pressure.  
     
     
         10 . The brake control apparatus for a vehicle according to  claim 1 , wherein the characteristic changing means equalizes the brake hydraulic pressure applied to the braking force generation member with the brake hydraulic pressure in the hydraulic pressure generating source when the brake hydraulic pressure in the braking force generation member drops below a predetermined pressure.  
     
     
         11 . A brake control apparatus for a vehicle, comprising: 
 a braking force generation member for providing braking force to wheels of the vehicle in response to a command coming from the outside; and    characteristics changing means for change characteristics of the braking force provided to the wheel by the braking force generation member so that reduction of the braking force is executed with a delayed response than increase of the braking force in response to the command which orders to reduce/increase the braking force.    
     
     
         12 . A brake control apparatus for a vehicle, comprising: 
 an operating member to cause brake hydraulic pressure to generate;    a hydraulic pressure generating source for generating the brake hydraulic pressure in response to an operation of the operating member;    wheel braking force generation member for providing braking force to wheels of the vehicle by receiving the brake hydraulic pressure from the hydraulic pressure generating source;    a conduit which connects the hydraulic pressure generating source with the wheel braking force generation member; and    characteristic changing means for lessening variations of reduction of the brake hydraulic pressure applied to the wheel braking force generation member with respect to variations of the operating member when the operating member is operated so as to reduce the brake hydraulic pressure in the hydraulic pressure generating source.    
     
     
         13 . A brake control apparatus for a vehicle, comprising: 
 an operating member for causing brake hydraulic pressure to generate;    a hydraulic pressure generating source for generating the brake hydraulic pressure in response to an operation of the operating member;    a wheel braking force generation member for providing braking force to wheels of the vehicle by receiving the brake hydraulic pressure from the hydraulic pressure generating source;    a conduit which connects the hydraulic pressure generating source with the wheel braking force generation member; and    characteristic changing means for lessening a gradient of reduction of the brake hydraulic pressure applied to the wheel braking force generation member during a predetermined time from a start of the reduction of the brake hydraulic pressure applied to the wheel braking force generation member than that after the predetermined time when the operating member is operated so as to reduce the brake hydraulic pressure in the hydraulic pressure generating source.    
     
     
         14 . A brake control apparatus for a vehicle, comprising: 
 an operating member for causing brake hydraulic pressure to generate;    a hydraulic pressure generating source for generating the brake hydraulic pressure in response to an operation of the operating member;    a wheel braking force generation member for providing braking force to wheels of the vehicle by receiving the brake hydraulic pressure from the hydraulic pressure generating source;    a conduit which connects the hydraulic pressure generating source with the wheel braking force generation member; and    characteristic changing means for keeping the brake hydraulic pressure applied to the braking force generation member substantially during a predetermined period of time when the operating member is operated so as to reduce the brake hydraulic pressure in the hydraulic pressure generating source.    
     
     
         15 . A brake control apparatus for a vehicle, comprising: 
 an operating member for causing brake hydraulic pressure to generate;    a hydraulic pressure generating source for generating the brake hydraulic pressure in response to an operation of the operating member;    a wheel braking force generation member for providing braking force to wheels of the vehicle by receiving the brake hydraulic pressure from the hydraulic pressure generating source;    a conduit which connects the hydraulic pressure generating source with the wheel braking force generation member; and    characteristic changing means for executing reduction of brake hydraulic pressure applied to the wheel braking force generation member with a delay of time when the operating member is operated so as to reduce the brake hydraulic pressure in the hydraulic pressure generating source compared to increase of the brake hydraulic pressure applied to the wheel braking force generation member when the operating member is operated so as to increase the brake hydraulic pressure in the hydraulic pressure generating source.    
     
     
         16 . A brake control apparatus for a vehicle, comprising: 
 an operating member for causing brake hydraulic pressure to generate based on an operation of a driver;    a hydraulic pressure generating source for generating the brake hydraulic pressure in response to an operation of the operating member;    a wheel braking force generation member for providing braking force for wheels of the vehicle by receiving the brake hydraulic pressure from the hydraulic pressure generating source;    a conduit which connects the hydraulic pressure generating source with the wheel braking force generation member; and    characteristic changing means for executing reduction of the brake hydraulic pressure applied to the wheel braking force generation member with a first gradient of pressure-reduction in an initial stage of an operation of the operating member to reduce the brake hydraulic pressure and for executing reduction of the brake hydraulic pressure applied to the wheel braking force generation member with a second gradient of pressure-reduction which is greater than the first gradient of pressure-reduction after the initial stage of the operation of the operation member to reduce the brake hydraulic pressure when the driver operates the operating member so as to reduce the brake hydraulic pressure in the hydraulic pressure generating source.    
     
     
         17 . A brake control apparatus for a vehicle, comprising: 
 an operating member for causing brake hydraulic pressure to generate based on an operation of a driver;    a hydraulic pressure generating source for generating the brake hydraulic pressure in response to an operation of the operating member;    a wheel braking force generation member for providing braking force to wheels of the vehicle by receiving the brake hydraulic pressure from the hydraulic pressure generating source;    a conduit which connects the hydraulic pressure generating source with the wheel braking force generation member; and    characteristic changing means for keeping the brake hydraulic pressure applied to the wheel braking force generation member at a pressure of more than a predetermined value when the driver operates the operating member so as to reduce the brake hydraulic pressure in the hydraulic pressure generating source.    
     
     
         18 . The brake control apparatus for a vehicle according to  claim 12 , wherein the characteristic changing means includes a brake booster whose boosting rate is variably controlled.  
     
     
         19 . The brake control apparatus for a vehicle according to  claim 12 , wherein the characteristic changing means executes its function when deceleration of the vehicle is greater than a predetermined value.  
     
     
         20 . The brake control apparatus for a vehicle according to  claim 12 , wherein the operating member is a brake pedal which is operated by a driver, and the characteristic changing means executes its function when a pedal stroke of the brake pedal is greater than a predetermined value.  
     
     
         21 . The brake control apparatus for a vehicle according to  claim 12 , wherein the operating member is a brake pedal which is operated by a driver, and the characteristic changing means executes its function when depressing force to the brake pedal is greater than a predetermined value.  
     
     
         22 . The brake control apparatus for a vehicle according to  claim 12 , wherein the hydraulic pressure generating source includes a master cylinder, and the characteristic changing means executes its function when master cylinder pressure is greater than a predetermined value.  
     
     
         23 . The brake control apparatus for a vehicle according to  claim 12 , wherein the braking force generation member includes a wheel cylinder, and the characteristic changing means executes its function when wheel cylinder pressure is greater than a predetermined value.  
     
     
         24 . The brake control apparatus for the vehicle according to  claim 12 , wherein the characteristic changing means executes its function when deceleration of wheel is greater than a predetermined value.  
     
     
         25 . The brake control apparatus for a vehicle according to  claim 12 , further comprising; 
 an anti-skid control device which executes anti-skid control, wherein the characteristic changing means executes its function when anti-skid control is being carried out.    
     
     
         26 . A brake control apparatus for a vehicle, comprising: 
 an operating member for causing brake hydraulic pressure to generate based on an operation of a driver;    a brake hydraulic pressure generating device which generates the brake hydraulic pressure in response to an operation of the operating member;    a wheel braking force generation member for providing braking force to wheels of the vehicle by receiving the brake hydraulic pressure from the brake hydraulic pressure generating device;    a conduit which connects the brake hydraulic pressure generating device with the wheel braking force generation member; and    increasing means for increasing the brake hydraulic pressure applied to the wheel braking force generation member when the driver operates the operating member so as to reduce the brake hydraulic pressure in the brake hydraulic pressure generating device.    
     
     
         27 . The brake control apparatus for a vehicle according to  claim 26 , wherein the increasing means includes a brake booster whose boosting rate is variably controlled.  
     
     
         28 . The brake control apparatus for a vehicle according to  claim 26 , wherein the operating member is a brake pedal of which stroke is controlled by the driver.  
     
     
         29 . The brake control apparatus for a vehicle according to  claim 12 , wherein the wheel braking force generation member includes a wheel cylinder.  
     
     
         30 . The brake control apparatus for a vehicle according to  claim 26 , wherein the hydraulic pressure generating source includes a master cylinder.