Brake control device improving driver's brake feeling

Abstract

A lower limit of a target value of a wheel cylinder pressure generated by a wheel cylinder is set as a first value PT1. Specifically, the first value PT1 is determined based on the application pressure generated by the wheel cylinder during an automatic brake control. Accordingly, the actual application pressure generated can be set to be equal to or more than the first value PT1. Thus, it is possible to prevent the application pressure from being decreased unintentionally when the automatic brake control is switched to a manual brake control, and thus, it is possible to maintain a deceleration speed of a vehicle at the level of a vehicle body deceleration generated during the automatic brake control. Accordingly, it is less likely that the driver will be caused to feel a sense of unease by weakening of the braking force.

1 . A vehicular brake control device for use in a vehicle, the brake control device performing an automatic brake control that generates braking force at a wheel by automatically applying pressure to a braking force generating unit entirely independently of a brake control member that is operated by a driver, and performing a manual brake control that generates braking force at the wheel by applying pressure to the braking force generating unit in accordance with operation of the brake control member by the driver, 
 wherein a target value of application pressure generated by the braking force generating unit for generating braking force at the wheel is set, and when the automatic brake control is switched to the manual brake control, a first value is set to a lower limit value of the target value based on application pressure generated by the braking force generating unit during the automatic brake control, and the braking force generating unit is caused to generate application pressure that is equal to or greater than the first value.    
   
   
       2 . The vehicular brake control device according to  claim 1 , wherein the first value is determined based on a relationship between a vehicle body deceleration generated by application pressure of the braking force generating unit during the automatic brake control and an effective braking force.  
   
   
       3 . The vehicular brake control device according to  claim 1 , wherein 
 a brake assist control for assisting application pressure of the braking force generating unit that is generated in accordance with operation of the brake control member by the driver is performed in the manual brake control;    the braking force generating unit comprises a wheel cylinder for generating application pressure based on a brake fluid pressure of a master cylinder that generates the brake fluid pressure in accordance with operation of the brake control member;    the brake fluid pressure generated by the master cylinder is detected by a pressure detection unit;    a frontal collision likelihood level indicating the likelihood that a collision with an obstacle in front of the vehicle will occur is detected by a frontal collision likelihood level detection unit, and an assist pressure is set in correspondence with the frontal collision likelihood level; and    a second value is set to a value calculated by adding the assist pressure to the brake fluid pressure of the master cylinder detected by the pressure detection unit, and the larger one of the first value and the second value is set to the target value.    
   
   
       4 . The vehicular brake control device according to  claim 2 , wherein 
 a brake assist control for assisting application pressure of the braking force generating unit that is generated in accordance with operation of the brake control member by the driver is performed in the manual brake control;    the braking force generating unit comprises a wheel cylinder for generating application pressure based on a brake fluid pressure of a master cylinder that generates the brake fluid pressure in accordance with operation of the brake control member;    the brake fluid pressure generated by the master cylinder is detected by a pressure detection unit;    a frontal collision likelihood level indicating the likelihood that a collision with an obstacle in front of the vehicle will occur is detected by a frontal collision likelihood level detection unit, and an assist pressure is set in correspondence with the frontal collision likelihood level; and    a second value is set to a value calculated by adding the assist pressure to the brake fluid pressure of the master cylinder detected by the pressure detection unit, and the larger one of the first value and the second value is set to the target value.    
   
   
       5 . The vehicular brake control device according to  claim 1 , wherein the braking force generating unit comprises a wheel cylinder for generating application pressure based on a brake fluid pressure of a master cylinder that generates the brake fluid pressure in accordance with control of the brake control member; and 
 when the first value is set to the lower limit value of the target value based on application pressure generated by the braking force generating unit during the automatic brake control, if the first value is smaller than the brake fluid pressure of the master cylinder detected by the pressure detection unit, the brake fluid pressure of the master cylinder is set to the lower limit value of the target value.    
   
   
       6 . The vehicular brake control device according to  claim 2 , wherein the braking force generating unit comprises a wheel cylinder for generating application pressure based on a brake fluid pressure of a master cylinder that generates the brake fluid pressure in accordance with control of the brake control member; and 
 when the first value is set to the lower limit value of the target value based on application pressure generated by the braking force generating unit during the automatic brake control, if the first value is smaller than the brake fluid pressure of the master cylinder detected by the pressure detection unit, the brake fluid pressure of the master cylinder is set to the lower limit value of the target value.    
   
   
       7 . The vehicular brake control device according to  claim 1 , wherein, when the automatic brake control is switched to the manual brake control, an upper limit value of the target value is set based on application pressure generated by the braking force generating unit during the automatic brake control, and the braking force generating unit is caused to generate application pressure that is equal to or less than the upper limit value.  
   
   
       8 . The vehicular brake control device according to  claim 2 , wherein, when the automatic brake control is switched to the manual brake control, an upper limit value of the target value is set based on application pressure generated by the braking force generating unit during the automatic brake control, and the braking force generating unit is caused to generate application pressure that is equal to or less than the upper limit value.  
   
   
       9 . The vehicular brake control device according to  claim 3 , wherein, when the automatic brake control is switched to the manual brake control, an upper limit value of the target value is set based on application pressure generated by the braking force generating unit during the automatic brake control, and the braking force generating unit is caused to generate application pressure that is equal to or less than the upper limit value.  
   
   
       10 . The vehicular brake control device according to  claim 4 , wherein, when the automatic brake control is switched to the manual brake control, an upper limit value of the target value is set based on application pressure generated by the braking force generating unit during the automatic brake control, and the braking force generating unit is caused to generate application pressure that is equal to or less than the upper limit value.  
   
   
       11 . The vehicular brake control device according to  claim 5 , wherein, when the automatic brake control is switched to the manual brake control, an upper limit value of the target value is set based on application pressure generated by the braking force generating unit during the automatic brake control, and the braking force generating unit is caused to generate application pressure that is equal to or less than the upper limit value.  
   
   
       12 . The vehicular brake control device according to  claim 6 , wherein, when the automatic brake control is switched to the manual brake control, an upper limit value of the target value is set based on application pressure generated by the braking force generating unit during the automatic brake control, and the braking force generating unit is caused to generate application pressure that is equal to or less than the upper limit value.  
   
   
       13 . The vehicular brake control device according to  claim 7 , wherein the upper limit value is calculated by adding the first value to an upper limit value of change in application pressure of the braking force generating unit that is determined based on an elapsed time from the start of the manual brake control.  
   
   
       14 . The vehicular brake control device according to  claim 8 , wherein the upper limit value is calculated by adding the first value to an upper limit value of change in application pressure of the braking force generating unit that is determined based on an elapsed time from the start of the manual brake control.  
   
   
       15 . The vehicular brake control device according to  claim 9 , wherein the upper limit value is calculated by adding the first value to an upper limit value of change in application pressure of the braking force generating unit that is determined based on an elapsed time from the start of the manual brake control.  
   
   
       16 . The vehicular brake control device according to  claim 11 , wherein the upper limit value is calculated by adding the first value to an upper limit value of change in application pressure of the braking force generating unit that is determined based on an elapsed time from the start of the manual brake control.  
   
   
       17 . The vehicular brake control device according to  claim 1 , wherein a brake assist control for assisting application pressure of the braking force generating unit that is generated in accordance with operation of the brake control member by the driver is performed in the manual brake control; 
 the braking force generating unit comprises a wheel cylinder for generating application pressure based on a brake fluid pressure of a master cylinder that generates the brake fluid pressure in accordance with the control of the brake control member;    the brake fluid pressure generated by the master cylinder is detected by the pressure detection unit;    a frontal collision likelihood level indicating the likelihood that a collision with an obstacle in front of the vehicle will occur is detected by a frontal collision likelihood level detection unit, and an assist pressure is set in correspondence with the frontal collision likelihood level;    a second value is set to a value calculated by adding the assist pressure to the brake fluid pressure of the master cylinder detected by the pressure detection unit; and    when the automatic brake control is switched to the manual brake control, an upper limit value of the target value is set based on application pressure generated by the braking force generating unit during the automatic brake control; and    the first value and a second value that is set to a value calculated by adding the assist pressure to the brake fluid pressure of the master cylinder detected by the pressure detection unit are compared with each other, and the larger one of the first value and the second value and the upper limit value are compared with each other and the smaller one of the values is set to the target value.    
   
   
       18 . The vehicular brake control device according to  claim 2 , wherein a brake assist control for assisting application pressure of the braking force generating unit that is generated in accordance with operation of the brake control member by the driver is performed in the manual brake control; 
 the braking force generating unit comprises a wheel cylinder for generating application pressure based on a brake fluid pressure of a master cylinder that generates the brake fluid pressure in accordance with the control of the brake control member;    the brake fluid pressure generated by the master cylinder is detected by the pressure detection unit;    a frontal collision likelihood level indicating the likelihood that a collision with an obstacle in front of the vehicle will occur is detected by a frontal collision likelihood level detection unit, and an assist pressure is set in correspondence with the frontal collision likelihood level;    a second value is set to a value calculated by adding the assist pressure to the brake fluid pressure of the master cylinder detected by the pressure detection unit; and    when the automatic brake control is switched to the manual brake control, an upper limit value of the target value is set based on application pressure generated by the braking force generating unit during the automatic brake control; and    the first value and a second value that is set to a value calculated by adding the assist pressure to the brake fluid pressure of the master cylinder detected by the pressure detection unit are compared with each other, and the larger one of the first value and the second value and the upper limit value are compared with each other and the smaller one of the values is set to the target value.    
   
   
       19 . A vehicular brake control device for use in a vehicle, the brake control device performing an automatic brake control that generates braking force at a wheel by automatically applying pressure to a braking force generating unit entirely independently of a brake control member that is operated by a driver, and performing a manual brake control that generates braking force at the wheel by applying pressure to the braking force generating unit in accordance with operation of the brake control member by the driver, 
 wherein, when the automatic brake control is switched to the manual brake control, an upper limit value of a target value is set based on application pressure generated by the braking force generating unit during the automatic brake control, and the braking force generating unit is caused to generate application pressure that is equal to or less than the upper limit value.    
   
   
       20 . The vehicular brake control device according to  claim 8 , wherein the upper limit value is calculated by adding the first value to an upper limit value of change in application pressure of the braking force generating unit that is determined based on an elapsed time from the start of the manual brake control.